Petroleum and Coal - Analytical Chemistry (ACS Publications)

Anal. Chem. 1997, 69, 59R-93R

Petroleum and Coal Cliff T. Mansfield* and Bahajendra N. Barman

Texaco Fuels and Lubricants Technology Department, Box 1608, Port Arthur, Texas 77641 Jane V. Thomas

Wyoming Analytical Laboratories, 605 South Adams, Laramie, Wyoming 82070 Anil K. Mehrotra

Department of Chemical and Petroleum Engineering, The University of Calgary, Calgary, Alberta, Canada T2N 1N4 R. Paul Philp

School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019 Review Contents Coal (Jane V. Thomas) Oxidation Trace Elements Liquefaction Combustion NMR Swelling Geochemistry Environmental Sudies Waste Management Sulfur Chloride Reviews Crude Oil and Shale Oil (Anil K. Mehrotra) Hydrocarbon Identification and Characterization Gas Chromatography (GC) Gas Chromatography/Mass Spectrometry (GC/MS) High-Performance Liquid Chromatography (HPLC) Nuclear Magnetic Resonance Spectrometry (NMR) Other Analytical Techniques Trace Element Determination Trace Metals Sulfur Compounds Asphaltene Characterization Physical and Thermodynamic Properties Waxy (Paraffinic) Crude Oils Water -Oil Emulsions/Suspensions Miscellaneous Topics Heavy Oils (Natural and Refined) (Bhajendra N. Barman) General Reviews Chromatographic Techniques High-Performance Liquid Chromatography Thin-Layer Chromatography (TLC) Size Exclusion Chromatography Gas Chromatography Pyrolysis Gas Chromatography Supercritical Fluid Chromatography (SFC) Electrokinetic Chromatography and Related Techniques Extraction and Precipitation Methods S0003-2700(97)00006-1 CCC: $14.00

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© 1997 American Chemical Society

Spectroscopic Techniques Ultraviolet/Visible and Fluorescence Spectroscopy Infrared Spectroscopy and Fourier Transform Infrared Spectroscopy Nuclear Magnetic Resonance X-ray and Neutron Scattering Techniques Mass Spectrometry Miscellaneous Spectroscopic Techniques Thermal Techniques Miscellaneous Methods Viscosity API Gravity Microscopic Techniques Natural Gas and Refined Products (Cliff T. Mansfield) Natural Gas and Natural Gas Liquids Sulfur Content Trace Components Water and Dew Point Calorific Value Density Phase Equilibrium Hydrocarbons Sampling Reviews Gasoline Properties Composition Sulfur and Lead Middle Distillates Fuel Properties Hydrocarbon Composition Sulfur and Other Elements Dyes and Markers Jet Fuel Fuel Properties Thermal Stability Lubricants (Cliff T. Mansfield) Base Oils Chromatography Spectroscopy Other Additives Grease Spectroscopy Other

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Analytical Chemistry, Vol. 69, No. 12, June 15, 1997 59R

Surface Phenomena Oxidation DSC Other Physical Tests Used Lubricants On-Line FT-IR Atomic Spectroscopy Metals Related Chromatography Other Biodegradability Solid Lubricants Molybdenum Disulfide Other Inorganic Films Carbon Based Miscellaneous Reviews Source Rocks (R. Paul Philp) Applications United States/Canada U.K./North Sea/Europe Turkey/Middle East China/Japan Russia India Australia/New Zealand Central and South America Techniques Literature Cited

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This review is divided into six sections, each of which is reviewed by an individual knowledgeable in the subject area. The articles came from Chemical Abstracts published since the last review. All of the articles cited were written in or translated into English. Much of the published research on the analytical chemistry of coal during the last two years tended to be focused on coal liquefaction and on the environmental impact of coal processing and combustion. In all of these areas, elemental analysis for trace metals, sulfur, and chlorine played a major role. Several interesting applications of NMR for structural characterization were published. In the area of crude oil and shale oil, new techniques are reported in the characterization of hydrocarbons and asphaltenes in crude and shale oils. Also, new methods are reported for trace element analysis, including new applications of ICPMS. Differential scanning calorimetry has become an accepted method for wax determination, and a number of applications are reported. Heavy oil continues to be an important research area, as refineries move to operate at higher efficiencies and many new crude sources are heavier. Techniques such as GC/MS, LC/ MS, LC/ICPMS, and HTGC/MS played an important role in the characterization of these oils. Good progress was made in hightemperature GC, and this allowed the separation of compounds with boiling points as high as 700 °C. The GC atomic emission detector has also proven very useful in this area for speciation of metal complexes and compounds containing sulfur and nitrogen. NMR was an important technique for structural determinations and for hydrocarbon type analysis. In the area of natural gas and refined products, new methods and techniques were developed for on-line analysis and process 60R

Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

control. Part of this was driven by new regulations for products and emissions, and part was due to rapid developments in chemometrics and modeling techniques. Several good SFC methods are now available for hydrocarbon-type analysis of gasolines, kerosines, and middle distillates. The sensitivity of sulfur-specific detectors for GC use has been improved, and this has allowed progress in the speciation of sulfur compounds in these materials. Several areas in lubrication analysis showed good progress. There are now better methods available for base oil characterization and for rapid analysis of contaminants in used lubricants. The need for better lubricants for use in extreme environments pushed development of methods for analysis of solid lubricant composition and structure. More methods specifically for synthetic lubricants were also developed, as applications for these lubricants have expanded. In the literature dealing with source rocks, a large number of papers dealt with applications related to determining source rock characteristics that can be associated with oil and gas potential. Here, the author points out that a much higher percentage than in the past dealt with exploration activities outside the United States. Other papers dealt with analytical techniques and mathematical modeling that can relate source rocks to organic origin, development, and migration. COAL Oxidation. In a study of low-temperature oxidation, Keleman and Kwiatek (A1) used XPS for quantification of organic species on the surface of fresh and reacted Argonne Premium coals (Beulah Zap, Wyodak, Illinois No. 6, Blind Canyon, Pittsburgh No. 8, Lewiston-Stockton, Upper Freeport, Pocahontas); the coal fluidity and liquefaction behavior is believed to be influenced by coal weathering by changing the number and nature of surface oxygen species. Demir and others (A2) determined surface areas, pore volumes, and surface chemistry of eight coals in the Illinois Basin Coal Sample Program before and after exposing them for two months to air oxidation under ambient conditions; they found that the surface area and pore size distribution varied considerably among the coals, suggesting that these coals may respond differently to cleaning, conversion, and combustion processes. Surface areas were measured by CO2 adsorption, and all coals, but one showed an increase in surface area after exposure to air for the two months. Air oxidation also resulted in a decrease in volume of pores with diameters greater than 1800 Å as measured by mercury intrusion. Weitzsacker and Gardella (A3) used ESCA to analyze coals from four seams (Illinois No. 6, Kentucky No. 9, Upper Freeport, Pittsburgh) in raw, milled, and agglomerated forms; storage conditions (air, water, or nitrogen gas atmosphere) showed no detectable influence on surface concentrations of the elements in any of the coals, and no significant oxidation of these coals was detected by ESCA. Lacount and co-workers (A4) described the use of a multiple-sample, controlled-atmosphere, programmedtemperature oxidation (CAPTO) instrument for the characterization of raw and treated coals from the Argonne premium coal bank; samples subjected simultaneously to an oxidative treatment and a linear increase in temperature evolved combustion gases as a function of temperature.

In a study of the water vapor/oxidized coal interaction at 150, 60, and 30 °C, Fatnassi and others (A5) showed that the hydrolysis reaction previously identified at 150 °C persists near ambient temperatures, yielding the same products (CO2 and CO); H2O2 formed in the course of the interaction appears as a side product of the reaction. Trace Elements. Huggins and Huffman (A6) described the experimental aspects of X-ray absorption fine structure (XAFS) spectroscopy for determining the mode of occurrence of selected trace elements in coal; this method of determining elemental modes of occurrence provides information on element forms dispersed in the organic fraction of coal as well as on the mineralogiocal forms of the element. Palmer and Lyons (A7) isolated the four most abundant minerals generally found in Euroamerican bituminous coals (quartz, kaolinite, illite, pyrite) by density separation and handpicking from samples collected in the Ruhr Basin, Germany, and the Appalachian Basin, USA, and then used instrumental neutron activation analysis (INAA) to determine trace element concentrations of relatively pure separates of major minerals from these coals. Mass balance calculations for this study, which provided a direct and sensitive method of determining trace element relations with minerals in coal, indicated that the trace element content of coal can be explained mainly by three major minerals: pyrite, kaolinite, and illite. In an evaluation of leaching to determine modes of occurrence of trace elements in coal, Palmer and other co-workers (A8) determined the reproducibility and the reliability of leaching techniques on three samples using previously published methods, and duplicate and triplicate individual leaching experiments were conducted. Wong and Robertson (A9) utilized thick-target proton-induced γ-ray/X-ray emission analysis (PIGE/PIXE) to simultaneously determine the concentrations of 28 elements in eight Argonne Premium whole coal samples and oil shales, and activated carbon samples; they are also using these techniques to characterize over 400 samples of fly ashes from the Coolside coal desulfurization process and to study the effect of halogens on the corrosion process in boilers and ductwork in coal-fired power plants. Bloom and Prestbo (A10) developed a method for the determination of mercury in coal, based upon wet digestion, SnCl2 reduction, dual gold amalgamation, and cold vapor atomic fluorescence spectrometry (CVAFS). Using this method, which allows determination of mercury at the nanogram per gram (ppb) level, the authors surveyed coals being burned at power plants in the United States; analysis of the data indicated that U.S. mercury emissions from coals may be 50% lower than had been estimated from earlier data. Liquefaction. In a study of chemical dehydration of coals and its effect on coal liquefaction yields, Netzel and others (A11) compared the effects of thermal drying to chemical drying with 2,2-dimethoxypropane (DMP). They found that the chemical drying increased liquefaction conversion in all cases (one lignite, two subbituminous, three bituminous) but that thermal drying generally decreased conversions. They then used differential scanning calorimetry to show that some of the reaction product (methanol) from the chemical drying was incorporated into the coal pores. In another study of the effect of different drying methods on coal structure and reactivity toward liquefaction, Miknis and others (A12) investigated thermal and microwave drying at elevated temperatures and chemical drying at low

temperature; changes in coal structure brought about by the drying procedures were measured by solid-state NMR techniques, and it was concluded that chemical dehydration can be used as a pretreatment step to coal liquefaction. Gentzis and co-workers (A13) liquefied Black Thunder subbituminous or Illinois No. 6 bituminous coal and then examined the residues by optical microscopy; petrographic examination of the solid residues is discussed, and photomicrographs are presented. Intermolecular interactions for hydrocarbons on Wyodak coal surface were investigated by Glass and Stevenson (A14) by inverse GC; plots of isoteric adsorption heat vs molecular polarizability of the adsorbate were obtained for n-alkanes C1-C6, 1-alkenes C3-C7, cyclohexene, 1,3-cyclohexadiene, or benzene adsorbed on Wyodak coal samples heated to 150, 200, or 250 °C. Heating of the coal to 200 °C destroyed the specific interactions; for hydrocarbons adsorbed on the coal surface heated to 150 °C, results suggested two types of forces: nonspecific van der Waals dispersion force for n-alkanes and a stronger specific force for the unsaturated hydrocarbons, probably involving interaction of the double bond with ionic groups on the coal surface. Combustion. Crelling (A15) investigated coal combustion under conditions of blast furnace injection and reported that the semicokes from the lower rank coals should have a superior burnout rate in the tuyere and should survive in the raceway environment for a shorter time; these coals should have important advantages at high rates of injection that may overcome their slightly lower replacement rates. In a study of combustion reactivity of some world coals and their macerals, Hampartsoumian and others (A16) subjected a suite of five coals of different origin (Australia, Columbia, Germany, U.K., United States) and their maceral extracts to detailed optical and chemical characterization followed by laboratory-scale combustion tests using TGA and a high-temperature entrained flow reactor to determine reactivity. They found that classical petrographic classification needs to be supplemented with chemical data to account for the expected reactivity of a given coal. NMR. Netzel and co-workers (A17) used carbon-13 solid-state NMR in their investigation of coke deposits on spent CoMo-type catalysts used in coal liquifaction; results indicated that the aromatic cluster size of the coke on the used catalysts appeared to depend on the initial pore volume of the fresh catalyst and on the percentage of surface coating of the alumina support. The time-dependent swelling and deswelling of Illinois No. 6 coal by pyridine were measured by Hou and others (A18) by combined methods of nuclear magnetic resonance (NMR) and nuclear magnetic resonance imaging (NMRI); NMRI data indicated that coal swelling is anisotropic, with 13% greater swelling in a plane perpendicular to the bedding plane of the coal than that parallel to the coal-bedding plane; the process of deswelling was found to be almost isotropic. In an investigation of the alterations of nitrogen functional groups during peat and coal formation, Knicker and co-workers (A19) applied solid-state 15N NMR to a maturation series of undegraded plant material, plant composts, sediments, and coal samples. Up to the peat stage, most of the nitrogen occurs as amide nitrogen, which is derived from biogenic (presumably protein) precursors, but with increasing coalification, pyrollic N becomes the dominant form in the macromolecular coal network. Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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Swelling. The effect of swelling untreated and SO2-treated Black Thunder coals on coal liquefaction behavior was investigated by Brannan and co-workers (A20), who evaluated several catalyst precursors. Ding and others (A21) investigated the swelling behavior of O-alkylated Argonne Premium coals as examined by the EPR spin probe method; an increase in spin probe retention by the O-alkylated coals relative to the underivatized coals indicated a more open arrangement in the coal due to a decrease in attractive forces, confirming that microporosity increases with increasing rank. In an examination of change in coal gel structure due to solvent swelling, Hayashi and co-workers (A22) used size exclusion chromatography to evaluate the porous structure of Morwell (C ) 65 wt %, daf) and Pocahontas (C ) 91 wt %, daf) coals; each of the coals was packed in an inverse liquid chromatography column as the stationary phase, and either n-hexane or tetrahydrofuran was used as the mobile phase. Geochemistry. A series of recent peat samples from tropical, subtropical, and temperate locations were investigated by Dehmer (A23) using coal petrography and organic geochemistry techniques; maceral and biomarker compounds were examined for convergence or divergence from the known depositional environment of the peats. Warwick and Hook (A24) reported on the anomalous algae-rich coals in the middle part of the Claiborne Group (Eocene) of Webb County, TX; the petrography, geochemistry, and depositional setting of the San Pedro and the overlying Santo Tomas coal zones were discussed. Shearer and co-workers (A25) discussed the delineation of the distinctive nature of Tertiary coal beds. Stanton (A26) discussed the role of petrography in coal characterization: the characterization of coal using a combined microscopic technique involving reflected-light microscopy, fluorescence microscopy, and petrographic analysis of etched polished surfaces of coal as a means of obtaining information about the reactivity of coal macerals. Cody and co-workers (A27) used soft X-ray imaging and carbon near-edge absorption fine structure spectroscopy (C-NEXAFS) for the in situ analysis of sporinite in a rank-variable suite of organic-rich sediments extending up to high-volatile A bituminous coal. Stricker and Affolter (A28) analyzed statistics from the U.S. Geological Survey’s National Coal Resource Data System for Alaskan coals for heat of combustion and ash contents, paying particular attention to sulfur content and to elements of environmental concern (As, B, Cd, F, Hg, Pb, Se). Environmental Studies. To provide a general overview of the impact of coal switching on hazardous air pollutants emission, Oman and Finkelman (A29) calculated the input loads of 12 trace elements in the Clean Air Act Amendments and sulfur from six major coal-producing areas in the United States. In an investigation of air toxicities in coal, Crowley and Stanton (A30) examined the distribution and abundance of selected trace elements (As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, U) in coals from the Powder River Basin of Wyoming; elevated concentrations of the selected trace elements did not turn out to be restricted to samples having high ash contents. Ellis and co-workers (A31) discussed the distribution of hazardous air pollutant trace elements, total sulfur, and ash in coals from five tertiary basins in the Rocky Mountain region; arithmetic mean values of the contents of As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, U, and total sulfur were statistically compared on a whole-coal basis. 62R


Waste Management. In an evaluation of disposal and utilization options for advanced coal utilization wastes, Moretti (A32) identified potentially suitable practices for management of wastes from different clean coal processes: gas reburning with sorbent injection; pressurized fluidized-bed combustion; SOx, NOx, ROx, and BOX; coal reburning. Potential problems and possible alternative technologies were also identified. The effects of a Michelin [waste] tire tread and its various chemical components (butadiene-styrene rubber, cis-polybutadiene rubber, aromatic oils, carbon, sulfur, ZnO) on the free-radical intensities, N, of Blind Canyon coal using in situ ESR spectroscopy were reported from ambient temperature to 500 °C by Ibrahim and Seehra (A33); results supported the reported improved liquefaction of the coal with waste tire polymers. Sulfur. In an examination of sulfur forms in coal by direct pyrolysis and chemiluminescence, Xu and co-workers (A34) applied the high selectivity of a newly developed ozone-sulfur chemiluminescence detector coupled with controlled-temperature pyrolysis to the qualitative and semiquantitative determination of sulfur forms in coal. Louie and others (A35) described an improved method for extracting sulfate from bituminous coals using formic acid. Chloride. In a study of chlorine in coal and boiler corrosion, Chou and co-workers (A36) used both destructive temperatureprogrammed thermogravimetry with FT-IR (TGA/FT-IR) and nondestructive X-ray absorption near-edge structure (XANES) techniques to examine the thermal evolution characteristics and the forms of Cl in four Illinois and four British coals. Corrosion of superheaters in the United Kingdom has been attributed to the high level of Cl in coals, yet similar high-Cl Illinois coals have not caused boiler corrosion; analysis of the data from this study suggests that the way in which Cl ions are associated in Illinois coals is different from the way they are associated in British coals. Monroe and others (A37) measured corrosion rates of simulated water-well surfaces and superheater tubes during pilot-scale combustion of a high-Cl coal; surface corrosion was measured by probes which showed a change in electrical resistance. Reviews. New and improved analytical methods based on modern spectroscopic techniques were discussed in a review with five references by Dale and Riley (A38), providing more reliable data on the levels of environmentally significant elements in Australian bituminous thermal coals; elements of concern were As, Se, and Sb (by hydride generation from an Eschka fusion of raw coal), boron (by ICP-AES on the same Eschka solution), Be, Cr, Co, Cu, Mn, Ni, Pb, and Zn (by ICP-AES after fusion of the low-temperature ash with lithium borate), and Cd, U, and Th (by ICP-AES on a mixed acid digest of a low-temperature ash). It is anticipated that some of the methods will be eventually designated as Australian standard methods. Crelling (A39) discussed the petrology of resinite in American coals in a review with 29 references. Boni and others (A40) reviewed the surface and bulk techniques used to study fly ash particles, in particular, the applicability of PIGE/PIXE analysis in the study of the bulk composition of particulates produced during the combustion of fossil fuels. In a review with 74 references, Leszczynski (A41) discussed theoretical quantum mechanics in modeling of soot formation in combustion processes. An overview of global climate change and peatland carbon balance was presented by Wieder and others (A42). In a review with 10 references, Wertz (A43) discussed classical X-ray methods

adopted for quantitative analysis of raw, cleaned, and blended coals, carbon fibers made from coals, and liquefaction residues. Memories of an old researcher were presented in a review with five references by Miyazu (A44) in which he discusses a brief history of the technological developments in Japanese cokemaking from 1950 to the 1980s. CRUDE OIL AND SHALE OIL This year’s review on crude oil and shale oil has been prepared by classifying the references into the following main headings: Hydrocarbon Identification and Characterization, Trace Element Determination, Asphaltene Characterization, Physical and Thermodynamic Properties, and Miscellaneous Topics. New analytical methodologies and applications were reported for hydrocarbon and asphaltene characterization and trace element determination in crude oils and shale oils. Also included in this review are a number of references from several major conferences held in the two-year review period. HYDROCARBON IDENTIFICATION AND CHARACTERIZATION Kershaw and Fetzer presented a review with 59 references on room temperature fluorescence spectroscopy (including conventional fluorescence, synchronous scanning, and excitation-emission matrix) of petroleum and its processed fractions (B1). Miknis presented a review with 40 references on the methods of oil shale analysis (B2). Speight presented a review on spectroscopic techniques for structural characterization of crude oils (B3). Gas Chromatography (GC). Neer and Deo described a capillary GC procedure for simulated distillation of crude oils; the technique was demonstrated with high-resolution characterization of C5-C90 fractions of two Utah crude oils (B4). High-temperature, high-resolution GC coupled with MS was used for accurate characterization of paraffins, resins, and asphaltenes in crude oils (B5). Subramanian et al. described a high-temperature chromatographic technique to include a portion of high-boiling compounds in heavy oils (B6). Ali described a comparative study of the hydrocarbons in fractions of Saudi crude oils using a multicolumn valve-switching GC technique (B7). Lai and Song determined temperature-programmed retention indexes for over 150 pure compounds [alkanes, alkenes, naphthenes, polycyclic aromatic hydrocarbons (PAHs)] using two capillary columns with different stationary-phase polarities at three heating rates (B8). Jokuty et al. used GC/FID to analyze saturates, aromatics, resins, asphaltenes, and waxes in 30 crude oils (B9). They also developed a method to determine oil adhesion to a test surface. Sulkowski developed an extractable petroleum hydrocarbon (EPH) method for qualitative and quantitative data useful in hazardous waste site cleanup. The EPH method incorporates solvent extraction, and silica gel fractionation, followed by GC equipped with a flame ionization detector (FID) (B10). Wang et al. reported chemical characterization, involving GC/FID and GC/ MS analyses of aliphatic, PAH, and biomarker compounds, of weathered crude oil residues (B11, B12). Also included were pattern recognition plots for over 100 important crude oil components and component groupings. For studying hydropyrolysis and catalytic hydropyrolysis of oil shales, Ekinci et al. characterized the pyrolysis products by chromatography fractions, GC, GC/MS, and NMR (B13). Guo

and Ruan identified a large number of non-hydrocarbon, aromatic, alkanes and alkenes in Fushun and Maoming (China) oil shale fractions by use of GC and GC/MS (B14). On the basis of GC analysis and IR spectra, Brukner-Wein explained the variations in the organic matter in oil shale samples from different regions (B15). Gas Chromatography/Mass Spectrometry (GC/MS). Hwang et al. utilized the results of GC/MS analysis on crude oil samples extracted with supercritical CO2 to explain their compositional variations (B16). Carlson et al. isolated the major mono-, di-, and triaromatic products of cholestane (a steroid structure C27 tetracyclic naphthalene hydrocarbon) by HPLC and then characterized them using proton NMR and GC/MS analysis (B17). Sarpal et al. described two-dimensional heteronuclear shiftcorrelated and homonuclear spectroscopy techniques which, in combination with polarization enhancement spectral editing, allowed assignment of different resonances in the overlapping 1H and 13C NMR spectra of crude oils and mixtures (B18). Wang and Fingas developed a GC/MS method for differentiation and source identification of crude oils using isomeric methyldibenzothiophene (C1-DBT) compounds (B19). Varotsis and Guieze used GC/MS with a quadrupole mass analyzer to obtain compositional characterization data for crude oils (B20). GC/FIMS was reported to be a rapid quantitative characterization method for refined fuels; it was developed by retrofitting a GC/MS with field ionization (FI) source (B21). Wang et al. identified 58 alkylbenzene components in crude oils by GC/ MS in the selected ion monitoring (SIM) mode and used the quantitative measurements on BTEX to estimate the extent of crude oil weathering (B22, B23). A GC/MS method was used to analyze polycyclic alkanes, steranes, and terpanes, which had been isolated using hydrous pyrolysis of immature Vranje shale oil at 280-300 °C and 12-13 MPa for 48-96 h (B24). Audino et al. identified 13 of the 14 possible isomeric ethylmethylnaphthalenes (EMNs) by a combination of GC/MS, direct GC/FT-IR and molecular sieving techniques (B25). Karr et al. demonstrated the ability of an ion trap MS technique for analyzing crude oil fractions for the presence of sterane biomarkers (B26). Barakat determined the distribution of steranes and diasteranes in saturated fractions of a crude oil by metastable scanning (computerized) GC/MS (B27). Lin and Wilk identified several polymentanes in a gas condensate (from a 6800 m deep reservoir located in the U.S. Gulf Coast) by fullscan and selective ion monitoring GC/MS (B28). High-Performance Liquid Chromatography (HPLC). A HPLC method was developed for saturates, aromatics, and aromatic ring number distribution in gas oil fractions of crude oils using refractive index and UV detectors (B29). Bennett et al. described a technique for the separation of alkylphenols from crude oils and their analysis by reversed-phase HPLC, followed by a chemical derivitization as trimethylsilyl ethers which were analyzed by oxidative electrochemical detection, GC/FID or GC/ MS (B30). Nuclear Magnetic Resonance Spectrometry (NMR). Gautier and Quignard measured the hydrogen content of hydrocarbons and petroleum fractions using low-resolution pulsed proton NMR spectrometry (B31). Siskin et al. carried out detailed structural characterization of the hydrocarbon, oxygen, and nitrogen functionality in two oil shales using selective/nondestructive derivatizations followed by 13C and 29Si NMR analysis (B32). Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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Samples of Rundle and Stuart (Australia) oil shales were processed to produce a range of products which were characterized by high-resolution 1H and 13C NMR, molecular weight, and elemental analysis (B33). Using high-resolution solid-state 13C NMR spectroscopy, kerogen from Aleksinac (Serbia) oil shale was found to contain 79% long-chain aliphatic plus alicyclic structures and 9% aromatic structures (B34). A study was undertaken for the interactions between bitumen and kerogen/mineral matter in nine samples of Aleksinac oil shale (B35). Other Analytical Techniques. Olajire and Oderinde proposed a rating scheme for analytical techniques used in fingerprinting crude oils, which included digestion and enrichment of trace metals, coordination ion-exchange, and adsorption chromatography followed by UV absorption spectrophotometry, IR spectrophotometry, proton NMR spectrometry, X-ray fluorescence spectrometry, and GC (B36). Tjomsland et al. measured dielectric parameters for four fractions of North Sea crude oil and correlated them with IR spectra (B37). Ge et al. developed a method, based on using a mid-IR silver halide fiber optic as an evanescent wave spectroscopic sensor, for detecting and classifying petroleum samples (B38). Syunyaev investigated the disperse structure in crude oils by dielectric and optical fluorescence spectroscopy (B39). Andersson and Sielex presented a method for the determination of C2-substituted benzothiophenes in crude oils, which involved capillary GC with atomic emission or FID (B40). Carbognani et al. characterized Venezuelan crude oils by a combination of liquid extraction, gravimetry, solvent deasphalting and liquid chromatography, elemental analysis, X-ray diffraction, SEM, infrared, and NMR spectroscopy (B41). Lee characterized petroleum residuum components that were fractionated by highvacuum short-path distillation (DISTACT) and GPC (B42). GPC was used for determining the molecular weight distribution in high-boiling petroleum fractions (B43). Bharati et al. described calibration and standardization of the Iatroscan (TLC/FID) analytical technique with over 30 widely different crude oil samples (B44). Sludges from Bombay High (India) crude oil were solventextracted and characterized by FT-IR, NMR, VPO, elemental analysis, and urea adduction (B45). Three methods (VPO, GPC, viscosity measurement/correlation) were used for the number-average molecular weight of the potential lubricating oil products derived from the processing of Rundle shale oils (B46). The pyrolysis products of these shale oils were processed by distillation and solvent extraction to produce a low-viscosity (high-viscosity-index) product in the lubricating oil range (B47). Trisunaryanti et al. carried out structural analysis of Indonesian and Arabian deasphalted crude oils by chromatographic separation, followed by 1H and 13C NMR, and Currie point pyrolysis (B48). Li et al. compared analyses from the static headspace (HS) and the purge-and-trap methods for water-soluble organics from crude oils (B49). Also reported were results from microwaveassisted (MAP)-HS and GC/MS systems. Yang et al. analyzed chemical components in shale oils by means of gravimetry, CHN analysis, X-ray diffraction, ICP-AES, and IAS (B50). Oil fractions of Goeynuek (Turkey) shale oil, obtained by pyrolysis and supercritical water extractions followed by solvent extractions, were analyzed for molar mass distribution by SEC (B51). Koel et al. assessed the performance of evolving factor analysis (EFA) and heuristic evolving latent projection (HELP) methods using thermochromatographic (ThGC) data for 64R


oil shales (B52). Jeong et al. studied the dependence of shale oil HDN reaction kinetics on molecular weight using a KDT-4 laboratory short-path distillation apparatus (B53). Samples of Ethiopian oil shale were studied using selective leaching, pyrolysis, and chemical methods for steranes, terpenes, carbon preference indexes, and pristane/phytane ratios (B54). Graham and Robertson reported elemental composition of framboidal pyrite and associated maceral types of a Devonian oil shale by use of a microanalytical PIXE technique (B55). Fisher et al. used laser ablation Fourier transform ion cyclotron resonanceMS, FT-IR, and solid-state 13C NMR to study oil shales as possible fullerene precursors (B56). TRACE ELEMENT DETERMINATION Trace Metals. Musa et al. used instrumental neutron activation analysis for measuring 25 trace elements in Libyan crude oils (B57). Olsen carried out trace element analyses on a variety of crude oils by INAA and ICPMS techniques (B58). Ysambertt et al. isolated and characterized metalloporphyrins from a heavy crude oil by Soxhlet adsorption chromatography and HPLC/SEC (B59). Khuhawar and Lanjwani reported simultaneous HPLC determination of V, Ni, Fe, and Cu in crude oil using a complexing agent (B60). Al-Swaidan presented analyses of Pb, Ni, and V in Saudi Arabian crude oil by sequential injection analysis and ICPMS (B61). Developments were reported for a GC/MS-based technique that is useful for fingerprinting trace metal and biomarkers in crude oil spills (B62). Nuzzi used a mixture of acetonitrile with 10 vol % CH2Cl2 to selectively extract vanadyl compounds from the residuum of a crude oil, which after a further treatment was analyzed for VO2+ ions by differential pulse voltammetry (DPV) (B63). Thomaidis and Piperaki discussed the use of chemical modifiers in the determination of vanadium by electrothermal atomization atomic absorption spectrometry (B64). Lanjwani et al. developed a method for the formation and solvent extraction of Co, Cu, Fe, and V complexes, followed by their detection using reversed-phase HPLC (B65). Following a micropyrolysis study of Green River oil shale concentrates and kerogens, Reynolds and Burnham reported that kerogen isolation may not be necessary for deriving the kinetic parameters for shale oils (B66). In another study, porphyrins in the retorted oil shale were isolated by chromatography, demetalized, separated into etio and DPEP fractions by chromatography, and analyzed by MS (B67). Lee et al. retorted Green River oil shale using the hot recycle solids process and separated the pyrolysis products into nonpolar, polar, acidic, and residue by chromatography using hexane, CH2Cl2, and methanol (B68). Each fraction was analyzed by UV for porphyrins and metals (Ni, Fe, Ca, Mg). The vanadyl porphyrins, extracted and separated from Mexican crude oils, were identified and characterized by UV/ visible spectrophotometry, HPLC, and MS (B69). Rosell-Mele et al. prescribed a method based on HPLC/MS for analysis of porphyrin mixtures using an atmospheric pressure interface, which when operated in the chemical ionization mode gave more effective results (B70). Rankin et al. reported the Q-band excited resonance Raman (RR) spectra for a series of nickel complexes of petroporphyrins (B71). Wololwiec et al. presented one- and two-dimensional 1H NMR spectra of low-spin Fe(III) DPEP geoporphyrins (B72). Sulfur Compounds. Hoffmann et al. developed a method involving the use of liquid SO2 as a solvent for extracting polar

organosulfur compounds from crude oils (B73). Andari et al. discussed the distribution of sulfur compounds in naphtha and gas oil fractions in a Kuwaiti crude oil, which was measured by a capillary GC equipped with a sulfur chemiluminescence detector (B74). Kim et al. used a strain of sulfate-reducing bacterium to degrade model sulfur compounds for sulfur removal from crude oils and their fractions (B75). Williams and Nazzal described the analysis of pyrolytic oils, obtained from fluidized-bed processing of oil shale at 400-620 °C, for polycyclic/aromatic sulfur and nitrogen compounds (i.e., PAC, PAH, PASH, and PANH) (B76). ASPHALTENE CHARACTERIZATION Wiehe and Liang reviewed the complex phase equilibria involving asphaltenes, resins, and other petroleum macromolecules (B77). Takhar presented a thermodynamic model for identifying the crude oil reservoir pressure and temperature conditions for asphaltene deposition (B78). By studying physicochemical polydispersity of crude oil asphaltenes, Szewczyk et al. described the physical distribution of asphaltenes in solution with a Flory-type aggregation equilibrium (B79). Bardon et al. used several analytical methods to study chemical composition and structural characterization of asphaltenes and resins in crude oil suspensions to propose that the behavior of asphaltenes in solutions is governed by an aggregation equilibrium (B80). Analyses of SARA fractions of conventional and heavy crude oils were compared to explain their solid deposition tendency in production pipelines (B81). Afanasieva and Contreras correlated the results of X-ray diffraction on asphaltenes for structural characteristics with SEM analysis for their morphology (B82). Travalloni and Freire used size exclusion chromatography (SEC) for molecular weight distribution and polydispersity to characterize precipitated asphaltenes (B83). Teixeira developed a new approach for compositional data related to asphaltene aggregation using hydrogen index spectra and elemental analysis (B84). Based on small-angle X-ray and neutron scattering measurements and precipitation data, Dabir et al. proposed analytical equations for molecular weight distribution of asphaltene aggregates formed by the addition of n-C6, n-C7, and n-C10 (B85). Calemma et al. reported structural characterization of asphaltenes from several crude oils by NMR, FT-IR, and ESR spectra (B86). Galtsev et al. studied asphaltene association in a Russian Harjaga crude oil by electron-nuclear double-resonance spectroscopy (ENDOR) (B87). Anisimov et al. investigated the kinetics of asphaltene aggregation and flocculation in hydrocarbon solutions by photon correlation spectroscopy (B88). The transmission of infrared light through an oil mixture was used for detecting the formation of asphaltene particles for assessing the influence of solvents and asphaltene content on the flocculation threshold (B89). Based on a study of maltenes with HPLC and asphaltenes with VPO, Soldan et al. proposed that polymeric additives may enable the formation of hydrogen bonds to inhibit the association of asphaltene molecules (B90). Nali and Manclossi used SEC and VPO for the molecular weight determination of n-heptane-insoluble asphaltenes in Italian crude oils (B91). Andersen used 1H and 13C NMR to show that the hydrocarbon structure of n-heptaneinsoluble asphaltenes, precipitated from Kuwait crude oils, did not change much over temperatures from ambient to 80 °C (B92).

Fluorescence spectroscopy showed that more porphyrins remain in solution as the temperature is increased. Canel et al. characterized asphaltenes and pre-asphaltenes from Goeynuek oil shale by 1H and 13C NMR and GC (B93). PHYSICAL AND THERMODYNAMIC PROPERTIES Mehrotra et al. presented a review with 97 references on the prediction and correlation of the liquid-phase viscosity of pure components and their mixtures, including liquid hydrocarbons and petroleum mixtures (B94). The applicability and average deviations of practical viscosity calculation methods were discussed. Henderson described a test method and calculation algorithm for the “actual” true vapor pressure of crude oils (B95). A static apparatus was described for the determination of average molar mass of petroleum fractions by the vapor pressure depression method, also called tonometry (B96). Boduszynski et al. used a characterization approach for heavy oils to illustrate compositional changes with increasing atmospheric equivalent boiling point (AEBP) distribution (B97). A consistent calculation procedure was illustrated for the delumping of crude oil pseudocomponents that can be used for estimating infinite dilution K values (which are needed in phase equilibrium calculations) (B98). Twu and Coon described a consistent lumping scheme useful for determining characterization parameters and binary interaction parameters in predicting phase behavior of petroleum reservoir fluids (B99). Schneider discussed the application of supercritical extraction and chromatography along with high-pressure phase behavior in new separation processes and technologies (B100). Kok et al. presented the results of high-pressure TGSA analysis of crude oils (B101). Laux and Kopsch reported the vaporization enthaplies of higher boiling crude oil components by using thermogravimetry and DSC (B102). Riazi and Al-Sahhaf provided equations for calculating boiling point, density, refractive index, critical properties, acentric factor, surface tension, and solubility parameters of hydrocarbon groups in crude oil fractions (B103). Puskas et al. studied the properties of a solid hydrophobic paraffin derivative, containing polar end groups, from crude oils, which by X-ray analysis was shown to be an organocolloid of lamellar structure (B104). Srivastava et al. reported measurement and correlation of the PVT behavior and viscosity of heavy crude oils saturated with CO2 (B105). Grigg used a continuous phase equilibrium apparatus to measure dynamic phase composition, density, and viscosity of a synthetic West Texas crude oil being displaced by CO2 (B106). Matthews et al. reported VLE measurements for a Wyoming crude oil and its light fraction using a vapor-liquid double-recirculation apparatus (B107). Jaubert et al. utilized NMR analysis on aromatic and paraffin/naphthalene fractions of an Indonesian crude oil to assist in phase equilibrium calculations for estimating the properties of heavy fractions (B108). A viscosity-temperature equation, involving one parameter that can be predicted from molar mass, was developed for crude oil fractions (B109). Ismail et al. developed a back-propagation neural network method for correlating the viscosity of petroleum fractions (B110). Princen showed that some of the commonly encountered problems in spinning drop tensiometry are caused by inadequate maximum rotation and/or tube diameters and developed criteria for its optimal design and operation (B111). Wang and Gupta used a pendant drop IFT cell to measure the Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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interfacial tension of crude oil-brine system at high pressures and temperatures and reported that it varied with both pressure and temperature (B112). Waxy (Paraffinic) Crude Oils. Misra et al. presented a review with 56 references on topics related to crystallization and deposition of paraffin waxes (B113). Letoffe et al. determined the wax content of 29 crude oils by DSC and found it to be higher than that determined by GC (B114). The two methods differed in terms of the total amount of crystallized species (n-alkanes, isoalkanes, cyclohexanes, etc.) determined by DSC, but only n-alkanes by GC. They also determined a number of important properties of several paraffin-crude oil mixtures by thermomicroscopy and DSC (B115). Kok et al. measured the wax appearance temperature of 15 crude oils from several locations worldwide by DSC, thermomicroscopy, and viscometry and found these to agree well at a significant wax precipitation rate (B116). Kruka et al. described a cooled-surface method, along with thermal analysis, for determining the cloud point temperature of waxy crude oils (B117). Srivastava et al. determined phase transition temperatures and energies of Bombay High (India) crude oil waxes with and without a pour point additive by DSC (B118). They reported that, upon solidification, wax samples with the additive produced a very soft gel with a low yield stress. Khan et al. measured and correlated pour point and cloud point temperatures of prepared solutions of paraffins, derived from Bombay High crude oil, in different solvents (B119). In a correspondence, the measurements and mathematical treatment of Khan et al. were discussed and shown to have certain limitations (B120). Matveenko et al. reported the rheological behavior of paraffinic crude oils to be pseudoplastic with pronounced thixotropic properties (B121). Results from a model pipeline test to assist in the design of waxy oil transportation were discussed by Carniani and Merlini (B122). Zhang and Wang used IR spectroscopy to show that the addition of a pour point/viscosity depressant altered the crystallization behavior of waxes in Chinese crude oils (B123). Water-Oil Emulsions/Suspensions. A membrane filtration method was used to separate oil particulates from the surfactantwater phase of Orimulsion dispersions, which were analyzed using GC/MS and GC/FID (B124). Urdahl et al. demonstrated that dielectric spectroscopy can be utilized for on-line characterization of asphaltenes and resins in water-in-oil emulsions. Also discussed were the roles of asphaltenes and resins in emulsion stability (B125). Foerdedal et al. studied properties and stability of wateroil emulsions in high external electrical fields by means of dielectric time domain spectroscopy (B126). MISCELLANEOUS TOPICS A review with 164 references was published by Sato et al. on the structural analysis of kerogen, the properties and structure of oil shale, and its decomposition during retorting, partial combustion retorting, and upgrading (B127). Khaledi et al. proposed a methodology for computer generation of random heavy hydrocarbons in crude oil mixtures, which utilizes the mixture chemical characteristics in terms of elemental analysis and NMR data (B128). Nazzal and Williams studied the influence of pyrolysis temperature (400-620 °C) in a semicontinuous fluidized-bed reactor (B129). The oil yield increased with temperature over 400-520 °C, but decreased at higher temperatures due to an increase in 66R


gas yield due to thermal cracking reactions. Landau et al. developed a laboratory-scale, three-stage catalytic system for medium-severity hydrotreating and hydrocracking of Israeli shale oil (B130). Bradhurst and Worner reported that microwave retorting of Australian oil shales yielded a greater proportion of light hydrocarbons and a lower nitrogen and sulfur content than a conventionally retorted oil (B131). Su and Yang reported kinetic parameters for pyrolysis of Fushan (China) oil shale based on nonisothermal thermogravimetric data (B132). Dung used a statistical technique to identify the importance of process variables in shale oil retorting (in descending order of significance): reactor temperature, solids residence time, steam concentration, char content, solids recycle ratio, recycle solids temperature, and ammonia pretreatment (B133). Taulbee used a reactor system to monitor adsorption, desorption, and/or cracking of vapor-phase hydrocarbons over processed oil shale with short contact times at 300-650 °C (B134). A first-order pyrolysis kinetics was reported for three Turkish oil shales at temperatures up to 400-700 °C under a (nonisothermal) heating rate of 20 K/min (B135). Salhi et al. reported the results of an experimental study for the pyrolysis of Timahdit (Morocco) shale oil (B136). Ballice et al. used IR spectroscopy to classify kerogens and reported pyrolysis kinetics of oil shale samples using nonisothermal thermogravimetry (B137). Thomas and Harnsberger evaluated the possible use of eastern shale oil (ESO) residue as an additive to reduce oxidative agehardening and moisture susceptibility (B138). Rose used FT-IR spectroscopy to monitor chemical modifications in organic and inorganic components of the Rundle shale during in situ pyrolysis and oxidation (B139). Coorognite and β-carotene, precursors to oil-rich kerogens, were shown to be potential sources of fullerenes. HEAVY OILS (NATURAL AND REFINED) This review surveys analytical methodologies applied or developed for the analysis of heavy oils that appeared in Chemical Abstracts between October 1994 and October 1996. Although only about one-third of the published work was accommodated, an effort has been made to highlight the most useful and important developments in the characterization of heavy oils and products such as asphalts, bitumens, tars, pitches, and high-boiling natural and refined oils including residua. As was done in the last review on this subject (C1), the discussion is focused on application of individual analytical techniques. Combined analytical techniques (such as LC/MS, GC/FT-IR, or HPLC/ICPMS) are included under the more emphasized subtechnique. There are studies describing multiple techniques applied to the characterization of specific sample types. These are discussed under general reviews. GENERAL REVIEWS Two books on asphaltenes were published in which some excellent reviews on the characterization of petroleum asphaltenes can be found. There, various aspects of asphaltenes including their composition, colloidal behavior, and microstructures were examined by multidisciplinary approaches utilizing instrumental techniques and theoretical models (C2, C3). A number of articles and reviews on chromatographic methods for class separation, preparative fractionation, and component identification of heavy

oils and related products appeared in two issues of the Journal of High Resolution Chromatography which were dedicated to the analysis of fossil and synthetic fuels (C4, C5). A report addressed advanced analytical techniques for the speciation of organic sulfur forms in heavy oils, petroleum source rocks, and coals (C6). A brief overview of the detection of large-molecular-mass materials in coal-derived liquids covered the application of SEC and MS using fast atom bombardment and laser desorption techniques (C7). An analysis of complex material such as syncrude obtained by direct liquefaction of coal, required deasphalting by ultrasonic extraction with hexane followed by fractionation by an extrographic procedure using eluents of different polarity. Each fraction was then analyzed by Fourier transform infrared spectroscopy (FT-IR), gas chromatography (GC), GC/MS, and highresolution MS. (C8). Compositional analysis of asphaltenes from Arabian crude oils was carried out by precipitating asphaltenes from a 370 °C + residue using different alkane solvents. The asphaltenes were then characterized by elemental analysis, IR, and NMR (C9). CHROMATOGRAPHIC TECHNIQUES High-Performance Liquid Chromatography. HPLC was used for both preparative separation and characterization of coal liquids (C10-C13). A dinitroaniline stationary-phase (DNAP) column was found to separate coal liquid fractions by ring number with good resolution. Results from conventional gravimetric determination of coal liquid ring fractions were in good agreement with the hydrocarbon-type data obtained by a low-resolution MS method (C10). Analysis of oil products from catalytic and noncatalytic coal liquefaction by normal-phase HPLC with diode array detection revealed that oils from the catalytic runs contain more phenolic compounds and more heavy components than those from noncatalytic runs. These results were supported by GC/MS data on HPLC fractions. GC/MS also revealed that there are significant amounts of long-chain (C11-C35) alkanes in the coal oils (C11). Normal-phase HPLC with a “charge-transfer” column and a diode array detector was also used on coal liquefaction streams to separate and quantify PAHs and their isomers and alkylated derivatives (C12). Polar materials from coal liquids were analyzed to identify and determine phenols by reversed-phase HPLC in tandem with 31P NMR spectroscopy of derivatized samples (C13). Open-column liquid chromatography and HPLC were used for the structural characterization of coal tar pitches and petroleum pitch. Results showed that an increasing heat treatment temperature resulted in a decrease in the content of unsubstituted planar cata-condensed compounds with a corresponding increase in the peri-condensed compounds and an increase in polycyclic aromatic structures. Petroleum pitch was found to contain higher proportion of substituted cata-condensed compounds (C14). Saturates in asphalts and related materials were determined by HPLC using µ-Bondapak (aminopropyl)methylsilyl-bonded column and refractive index (RI) detector (C15). HPLC with RI and UV detectors was also used to obtain total saturates, total aromatics, and aromatic ring number distribution in straight run gas oil fractions (250-370 °C) (C16). HPLC with evaporative light scattering detection was used to determine residues in heavy oils. The method provided rapid measurements of vacuum gas oils and residues, and the results were comparable to those obtained by GC-simulated distillation using internal standards (C17).

A combination of HPLC and adsorption chromatography on a Florisil microcolumn was used to isolate chlorinated hydrocarbons from petroleum hydrocarbons. GC equipped with an electron capture detector (ECD) and a FID were then used for the analysis of organochlorine and petroleum compounds respectively (C18). Polycyclic aromatic hydrocarbons were determined by HPLC with UV detection (C19-C22). Three UV wavelengths that were found to be optimum for the detection of PAHs under various circumstances are 220, 254, and 287 nm. (C19). Coronene in hydrocracked vacuum gas oils was determined by normal-phase HPLC on a column packed with 3,5-dinitrobenzamidopropyl (DNBAP)-silica gel and with UV detection at 305 nm (C20). A new eight-ring PAH, produced during catalytic hydrocracking of petroleum-derived oils, was isolated by reversed-phase HPLC (C21). A diode array detector and a shape-selective reversedphase column were used to identify several 7-10-ring PAHs in coal tar pitches (C22). HPLC/MS with atmospheric pressure chemical ionization (APCI) was used to characterize metalloporphyrins and free-base porphyrins from shale oil (C23). Simultaneous determination of cobalt, copper, iron, and vanadium in crude petroleum oils was carried out by the formation and solvent extraction of metal complexes of bis(acetylpivalylmethane)ethylenediamine in methyl isobutyl ketone, followed by separation on a reversed-phase HPLC column with a mixture of methanol-acetonitrile as solvent and a UV detector at 260 nm (C24). Thin-Layer Chromatography (TLC). TLC using quartz rods coated with sintered silica particles and flame ionization detection (TLC/FID) was applied for group-type analysis of petroleum heavy distillates (C25), coal tar pitches (C26-C28), and petroleum hydroconversion products (C29, C30). A TLC/FID procedure was presented by which hydrocarbon classes (saturates, aromatics, polars) can be baseline separated and accurately determined (C25). This unique technique was also shown to be effective in providing rapid determination of saturates, alkylaromatics, aromatic hydrocarbons, polar compounds, and an uneluted fraction of a deasphalted heavy oil and its hydrocracking products (C29). This technique and paper chromatography with densitometric evaluation were used for determining asphaltene solubility in naphtha (C31). Planar chromatography (on silica plates) was used to fractionate coal tar pitch for subsequent characterization by SEC, UVfluorescence emission spectroscopy, and mass spectrometry (C32, C33). Size Exclusion Chromatography. To enhance the accuracy of SEC for the determination of molecular mass distributions of coal liquefaction and hydrocracking products, 1-methyl-2-pyrrolidinone (NMP) was used as mobile phase instead of tetrahydrofuran (THF), which was found to lead to partial loss of sample due primarily to solubility limitations (C34, C35). A high-temperature SEC method for the molecular mass distribution of petroleum wax was described. The separation was carried out with toluene and dichlorobenzene coupled with RI and flame ionization detectors. Analysis of samples containing molecules with e138 carbons were possible by FID using toluene as solvent (C36). Preparative-scale SEC was used to separate residua into subfractions for their subsequent analysis by other techniques including 13C NMR (C37). Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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There are a number of reports on the characterization of asphaltenes (C38-C40) and asphalts (C41). Vapor pressure osmometry and SEC were used for the molecular mass distribution of asphaltenes. The number-average molecular weights obtained by these two methods were found to be different. It was suggested that an association of asphaltenes occurs in solution and that correlation exists between aromaticity measured by NMR and intermolecular association (C38). A discotic shape of asphaltenes was proposed on the basis of SEC results of polystyrene standards and octylated asphaltenes standards and asphaltenes (C40). Elemental sulfur in vacuum gas oils (as well as in gasoline range distillates) was determined by SEC where sulfur was found to elute beyond the total permeation limit of a SEC column. The pore diameter of the column was found to be the most important factor, and optimum results were achieved from a single 103 Å pore poly(styrene-divinylbenzene) column with THF as the SEC solvent (C42). Gas Chromatography. There were some significant advances in the application of GC to high-boiling materials. Simulated distillation of heavy oils, particularly crude oils, with a wide carbon number distribution (up to C90), was shown to be possible by hightemperature capillary GC utilizing two columns (C43). Waxes with carbon numbers greater than C40 were analyzed by hightemperature GC (C44). A short 5 m glass capillary column was used to elute compounds with boiling points as high as 700 °C (equivalent to C90) that are found in bitumen and bitumen-derived products (C45). High-temperature GC with inductively coupled plasma mass spectrometry (HTGC/ICPMS) was used to provide rapid metal fingerprinting of geoporphyrins fractions from shale oils. However, for quantitative data, HPLC/ICPMS and HPLC with UV detection were used (C46). GC coupled with mass spectrometry was applied for the characterization of tire pyrolysis oils (C47), coal oils (C48), bitumen (C49), shale oils (C50), coal tar pitch volatiles (C51), reservoir fluids (C52), and crude oils (C53). Shale oils with boiling points less than 350 °C were fractionated into four subgroups by open-column chromatography, and each fraction was then analyzed by GC/MS. As many as 974 compounds (480 nonhydrocarbons, 356 aromatics, 138 alkanes and alkenes) were identified from one of the shale oil samples (C50). A group of 16 environmentally important PAHs in coal tar pitch volatiles were identified and determined by GC/MS (C51). A GC/MS procedure with a quadrupole mass analyzer was developed for routine analysis of reservoir fluids for alkanes, isoalkanes, naphthenes and aromatics (C52). Similar carbon isotopic composition of hydrocarbons obtained by gas chromatography/isotope ratio mass spectrometry (GC/IRMS), was used to identify sources of some bitumens and oils (C49). GC/MS, GC/FID and HPLC were used to determine C0-C3 alkylphenols in crude oils. For both GC/MS and GC/FID, alkylphenols were analyzed as trimethylsilyl ethers. For their HPLC determination, alkylphenols were first isolated by solidphase extraction and then separated by reversed-phase HPLC combined with oxidative electrochemical detection (C52). Sulfur compound-type distribution in gas oil fractions was obtained by capillary GC equipped with a sulfur chemiluminescence detector (C54). GC/element-specific detections with a flame photometric detector (FPD), an atomic emission detector (AED), and a nitrogen-phosphorus detector (NPD) were applied 68R


to identify and determine heteroatomic species in coal liquids. With the unique capabilities of GC/AED, a number of dual heteroatomic (sulfur-oxygen, nitrogen-oxygen) compounds were also identified (C55). Nitrogenous compounds in distillates derived from two-stage coal liquefaction were analyzed by GC/ MS and GC/nitrogen selective detection to obtain information on ring structures and side chains on the aromatic rings (C56). Pyrolysis Gas Chromatography. Pyrolysis gas chromatography was shown to provide useful information on the composition of asphaltenes (C57-C59), hydrocracked products (C58, C60), vacuum residues (C58), oil shale (C61), kerogens (C59), and coal (C62). A whole asphaltene sample and its fractions separated by SEC were subjected to analysis by pyrolysis GC/MS. Information such as average side-chain length, aromaticity index, and relative amounts of sulfur vs aliphatic compounds could be derived (C57). Characterization of vacuum residues, asphaltenes, and resins from different crude oils by pyrolysis GC coupled with both FID and FPD revealed differences in the pyrograms and generation of new sulfur compounds during pyrolysis (C58). Kerogen and asphaltene fractions derived from oil shale were analyzed by pyrolysismethylation, and the chemical structures of the released products indicated that considerable amounts of functionalized compounds are bound to the macromolecular structure of asphaltenes and kerogens via ester and ether linkages (C59). Toluene-insoluble solids from hydrocracked bitumen products were analyzed by pyrolysis GC/MS. It was found that the toluene-insoluble solids obtained by hydrocracking at low reaction severity release alkanes and alkenes in addition to aromatic compounds, while those obtained from high-severity hydrocracking release mostly aromatic compounds (C60). Oil shale was pyrolyzed in a fluidizedbed reactor with nitrogen as fluidizing gas. The resulting pyrolyic shale oils were found to contain PAHs, sulfur aromatic heterocyclic compounds, and nitrogen aromatic heterocyclic compounds. Many of these compounds were identified by GC/MS. It was also found that the amounts of PAHs are increased with increasing reactor temperature and residence time (C61). The pyrolysis products from 12 different coal samples, obtained at 800 °C, were collected in traps on the basis of their volatility. A packed-column GC/MS, with a double-focusing magnetic mass spectrometer, was used for the analysis of volatile fractions of the pyrolyzate. A capillary column, coupled to a quadrupole analyzer, was also employed for the analysis of condensed fraction for the determination of different classes of compounds (C62). Supercritical Fluid Chromatography (SFC). Microcolumn SFC was applied to the analysis of the Environmental Protection Agency (EPA) priority PAHs in the isocratic and gradient elution modes with supercritical CO2 as the mobile phase and methanol as the modifier. This SFC system was also applied to the analysis of PAHs in coal liquids (C63). Electrokinetic Chromatography and Related Techniques. Electrokinetic chromatography and related techniques were applied to the characterization of PAHs and asphaltenes. PAHs and C60/C70 fullerene mixtures were separated with capillary columns packed with a reversed-phase packing using electrokinetic pumping. Nonaqueous mobile phases, such as acetonitrile modified with methylene chloride and tetrahydrofuran, were used for these experiments (C64). Asphaltenes were found to have elctrophoretic mobility in aqueous medium and in a nonaqueous solvent such as nitromethane. In aqueous medium, electrophoretic mobilities of fine asphaltene particles were determined

as functions of pH, ionic strength, and ionic composition (C65). The acid-base characteristics of the surface of mechanically treated and untreated asphaltenes were studied by zetametry in organic media. The ratio of acid surface groups to that of base groups of different asphaltenes was obtained from the ratio of the electron donor and acceptor numbers experimentally determined by electrokinetic measurements (C66). The electrical conductivity of asphaltenes was measured as a function of concentration in solvents of varying permittivity to show that asphaltenes exist as ion pairs, and have strong dipole-ion interactions (C67). Extraction and Precipitation Methods. The efficiency of conventional Soxhlet extraction was compared with that of a Soxtec apparatus for coal and coal-derived products (C68) and that of a high-temperature supercritical fluid extraction for geological sediments and samples (C69). Coal tar pitches were extracted in several organic solvents and analyzed by GC and IR (C70). Similar extraction of oil shale with 17 solvents was carried out. Toluene and chloroform were found to be the most efficient solvents for extraction of bitumen from oil shale (C71). A waxy petroleum residue was subjected to supercritical propane fractionation by increasing the pressure stepwise. In this manner, the residue could be fractionated in order of increasing molecular weights. It was found that saturates are easier to fractionate than the aromatics (C72). An oil shale was subjected to slow pyrolysis and flash pyrolysis, as well as to super- and subcritical fluid extraction with water. The yields and compositions of oils varied considerably depending on conditions used; products with highly aliphatic character and low carbon number were obtained by slow pyrolysis, while flash pyrolysis gave a higher yield with highly aromatic products. Supercritical water afforded the highest yield with oils containing a high proportion of asphaltenes and polar compounds (C73). n-Heptane-insoluble asphaltenes obtained at temperatures between ambient and 80 °C from crude oils were characterized by 1H and 13C NMR and fluorescence spectroscopy. The experimental data indicated that there was very little change in asphaltene structural features except for a molecular weight increase as more materials went in solution at an elevated temperature. At higher temperature, aromaticity increased and apparently, alkyl chains diminished (C74). Both temperature and solvent effects on asphaltene precipitation were also examined (C75). Precipitation of asphaltenes in crude oil was studied as functions of pressure and alkane solvent. The onset of precipitation was determined by the measurement of conductivity in a specially designed high-pressure cell. The onset of precipitation was shown to increase linearly as a function of n-alkane carbon number. A higher pressure provided a smaller but significant increase in the onset (C76). SPECTROSCOPIC TECHNIQUES Ultraviolet/Visible and Fluorescence Spectroscopy. The aromatic ring systems in asphaltenes were examined with emphasis on the presence of one- to three-ring moieties by fluorescence emission spectroscopy. Asphaltenes were found to have significantly low populations of low-ring-number aromatics (C77). Fractions of coal tar pitch obtained by TLC using successive developments in tetrahydrofuran, 4:1 chloroform-methanol, toluene, and pentane were characterized by UV/fluorescence emission spectroscopy and other methods such as SEC and direct solid-

probe MS. A progressive shift of UV/fluorescence spectral intensity and high molecular mass with decreasing mobility of the fractions on the TLC plate, indicated the presence of increasingly larger PAHs in the less displaced fractions (C32). Infrared Spectroscopy and Fourier Transform Infrared Spectroscopy. FT-IR was applied to obtain concentrations of several functionalities of coal tar pitches (C78). Diffuse reflectance IR spectroscopy (DRIFT) was applied for monitoring and semiquantitative evaluation of structural changes associated with mesophase formation in pitches (C79). FT-IR in combination with thermogravimetry (TG/FT-IR) was used to evaluate the behavior of sulfur compounds during coal pyrolysis by monitoring the evolution of SO2, COS, and H2S (C80). Nuclear Magnetic Resonance. Since NMR techniques are capable of providing structural differences due to carbon, hydrogen, and heteroatom environments, they have been found to be useful for unraveling complex structures and compositions of many heavy petroleum and coal products. One- and two-dimensional (2D) NMR were applied for the characterization of hydrocracked base stocks. 2D heteronuclear shift-correlated (HETCOR) and homonuclear spectroscopic techniques in combination with distortionless enhancement by polarization transfer (DEPT) spectral editing were used to identify and quantify a number of branched structures (C81). 1H 2D NMR was also used to determine PAHs in crude gas oil mixtures. Specifically, structural information was obtained by total correlation spectroscopy (TOCSY) 2D NMR (C82). Both 1H and 13C NMR were applied to monitor changes in carbon and hydrogen distributions in feedstock and products of delayed coking (C83, C84). 1H NMR was also shown to provide information on structural changes during hydrogenation upgrading of vacuum residue and its mixtures with coal and coal tars (C85). 1H NMR together with elemental analysis, FT-IR, and SEC revealed that wax recovered from a lignite tar contained longchain (∼C30) paraffins in addition to small amounts of long-chain fatty acids and esters and their unsaturated counterparts (C86). There are a few reports on the characterization of asphaltenes by NMR (C87) and by NMR and other techniques (C88, C89). By applying high-temperature NMR with gated decoupling and the DEPT pulse sequence, average aromatic structures of asphaltenes and preasphaltenes in liquefied coal products were determined. Aromatic carbons could also be subdivided into protonated and quaternary carbons, and the latter into outer and inner quaternary carbons (C87). A combined NMR and X-ray diffractometry (XRD) procedure was used to estimate the average size of structural units in bitumen-derived asphaltenes (C88). Asphaltenes from crude petroleums of different geological origin were analyzed by 13C NMR and a number of spectroscopic techniques including FT-IR and electron spin resonance (ESR). It was found that these asphaltenes differ in aromatic carbon and heteroatom contents, length of the alkyl groups, and molecular weight (C89). 1H NMR was applied to determine hydrogen content in coalderived heavy distillates, and the data were found to be consistent with those obtained by the combustion method (C90). Information on aliphatic and aromatic carbons in cokes, char, coal tar and biomass pitches was obtained by quantitative solid-state 13C NMR (C91, C92). 13C NMR provided protonated and nonprotonated carbons in heavy oils derived from coal liquefaction, and the data were used to estimate average aromatic structures and Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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alkyl groups (C93). A naphthalene pitch was studied by highresolution 13C solid-state dynamic nuclear polarization (DNP) (C94). 13C NMR spectroscopy using spin-lattice relaxation technique was applied to the characterization of coal, coal tar, tar residue, and char. Insights into the number of aromatic carbons per cluster and carbon aromaticity were obtained (C95). X-ray and Neutron Scattering Techniques. Small-angle X-ray scattering (SAXS) (C96, C97), small-angle neutron scattering (SANS) (C98, C99), and a combination of both (C100-C102) were applied to study aggregation behavior of asphaltenes, with an emphasis on the cluster size measured as radius of gyration and fractal dimension. The structures of asphaltenes were investigated in different solvents (C96, C98, C100). The behavior of asphaltenes was also studied as a function of temperature (C97, C99, C101, C102) and asphaltene concentration (C98). The application of X-ray near-edge structure (XANES) spectroscopy for sulfur and nitrogen molecular structures in asphaltenes and related materials was detailed in a review article (C103). Mass Spectrometry. Mass spectrometry was applied primarily for the molecular mass distributions of heavy oils and products. The molecular mass distributions of a number of bitumen samples were obtained by californium-252 (252Cf) plasma desorption mass spectrometry (PDMS). In general, these distributions agreed well with those measured by SEC and vapor pressure osmometry (C104). Molecular mass distributions were also obtained by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (C105-C108). This technique was applied to coal tar pitch fractions separated by planar chromatography (C105), coal tars and coal liquefaction extracts(C106), coal (C107), and coal-derived products (C107, C108). Several ionization techniques were applied to the analysis of coal and coal products. It was found that the ions present in the laser desorption (LD) and desorption/chemical ionization (DCI) modes are comparable, while LD and desorption/ionization (DEI) modes produce different ion distributions (C109). Mass spectrometry of porphyrin fraction of a demetalated shale oil showed homologous series of porphyrins (C110). Miscellaneous Spectroscopic Techniques. Electron spin resonance was applied to study free-radical reactions involved in low-temperature oxidation of bituminous coal. The roles of moisture and oxygen were also identified (C111). Photon correlation spectroscopy (PCS) was used to study asphaltene aggregation in toluene/n-heptane mixtures. The kinetics of asphaltene flocculation and the stability of asphaltene aggregates were shown to depend on the origin of asphaltenes, their concentration, and the toluene/n-heptane ratio (C112). Trace elements in heavy oil samples were determined by graphite furnace atomic absorption spectrometry (GFAAS) after acid (HNO3-H2SO4) digestion. Vanadium and nickel were also determined by ICP-AES, and the results were in good agreement with the GFAAS results (C113). THERMAL TECHNIQUES Thermal behavior of petroleum bitumen and their fractions was studied by thermogravimetry and differential scanning calorimetry (DSC) (C114) and by DSC alone (C115). Effect of total pressure on the combustion behavior of crude oil and kinetics of crude oil oxidation were explored by high-pressure thermogravimetry at 100, 200, and 300 psi (C116). Thermogravimetric analysis (TGA) and GC were used to examine how the thermal behavior and composition of pitches affect coke formation (C117). 70R


A rapid TGA method was described for the determination of carbon residue of heavy fuel oil. In this method, a high heating rate (>750 °C/min) in nitrogen was applied to pyrolyze the sample rapidly. The carbon residue was then burnt in the presence of oxygen (C118). Wax in crude oils was characterized by thermomicroscopy and DSC. Pour points were also determined; for crude containing >10 wt % of n-paraffins; the pour point was reached when ∼2 wt % of waxes had precipitated (C119). DSC, thermomicroscopy, and viscometry were used for the study of wax appearance temperatures of 15 different crude oils. The use of both DSC and thermomicroscopy was recommended for the determination of wax appearance temperature of crude oils (C120). MISCELLANEOUS METHODS Viscosity. Prediction of viscosity of heavy liquids or their mixtures with other products and solvents was an area of great interest. Both solubility and viscosity of bitumen samples in five different solvents including toluene and naphtha were examined, and naphtha was recommended as the most appropriate solvent for reducing viscosity of bitumen (C121). Using 300 experimental points, a generalized viscosity correlation was presented to predict viscosity-temperature relationship of bitumen-diluent mixtures with an average deviation between predicted and experimental values of 8.7% (C122). Using a group contribution approach, a model for the prediction of viscosity of coal-derived liquids was developed (C123) which provided values with average deviation of 12%. The viscosity of petroleum fractions was predicted (with 10-15% average deviations), using corresponding states, and applied to crude petroleum and petroleum fractions (C124, C125). An empirical correlation for prediction of viscosity of heavy petroleum fractions applicable to a wide range of viscosities (0.4260 mm/s) and temperatures (40-200 °C) was proposed. This correlation showed an overall average absolute deviation of 6.5% when tested on 296 data for medium and heavy petroleum fractions (C126). API Gravity. An analyzer for the measurement of specific gravity and American Petroleum Institute (API) gravity of tars and asphalts was described. The instrument is equipped with a high-pressure and high-temperature measuring cell, a heated interface, and a high-temperature bath. The method offers advantages such as rapid analysis, small sample size, and less solvent consumption. The total analysis time is ∼5 min including cleanup time (C127). Microscopic Techniques. Scanning tunneling microscopy (STM) was used to verify molecular structures of Maya asphaltenes derived from 1H and 13C NMR experiments. The sizes and structures of asphaltenes as obtained by STM are in reasonable agreement with those derived from NMR. Specifically, the largest dimension of STM asymmetric structures averages 10.4 Å ( 1.9 Å, compared to an NMR-based average dimension of 11.1 Å ( 1.4 Å (C128). The equilibrium asphaltene particle shape, size, and size distribution were studied by confocal scanning laser microscopy (CSLM). The asphaltene particles were found to be highly nonspherical. Using CSLM, it was found that freshly prepared asphaltene particles maintained a constant fluorescence intensity under dry nitrogen. These particles underwent chemical changes, possibly oxidation, when exposed to air, as evident from the quenching of their fluorescence intensity with time (C129).

NATURAL GAS AND REFINED PRODUCTS In this article, the section headers describe the petroleum product type, and the subcategories are arranged by analytical test. There were many more papers dealing with the analysis of fuels during the last two years than in previous years due to regulatory pressures. Chemometrics continues to play an important role in the prediction of both physical and chemical properties, especially as relates to refinery process control and blending of fuels. NATURAL GAS AND NATURAL GAS LIQUIDS Sulfur Content. Several articles dealt with the determination of total sulfur and hydrogen sulfide as related to operation of amine units for their removal. Vincent (D1) discussed methods for the determination of hydrogen sulfide and total sulfur, and Skinner et al. (D2) proposed the use of a continuous analyzer for the analysis of hydrogen sulfide and carbon dioxide to reduce the costs of amine unit operation. Kadnar and Rieder (D3) used ion chromatography to analyze the anions in amine solutions, as some cannot be heat stripped from solution, reducing the useful life of the solution. Machino (D4) used a dual-flame-mode FPD to continuously measure the sulfur content in natural gas, and Anderson and Dimmer (D5) reviewed the field analysis of trace sulfur compounds. In one study, Tuan and Cramers (D6) evaluated the performance of universal and selective detectors for use in GC analysis of sulfur components and found the SCD to be almost compound independent and preferred. In another study, Tuan et al. (D7) optimized sample pretreatment and chromatographic steps for the determination of sulfur compounds by GC/SCD. Trace Components. Several reviewers discussed the analysis of mercury in natural gas, including Ceccarelli’s (D8) review of the occurrence, measurement, and removal of mercury; Frech’s et al. (D9) review of methods for the analysis of mercury species in natural gas and NGL; McNamara’s and Wagner’s (D10) coverage of methods and sampling techniques for low levels of mercury in natural gas; and Lewis’ (D11) experiences determining mercury at ppb levels in natural gas streams. Frech et al. (D12) made a study on the use of noble metal collectors for the amalgamation of mercury from natural gas followed by thermal desorption and analysis by cold vapor atomic absorption spectrometry. Snell et al. (D13) described improvements in the determination of mercury species using an on-line amalgamation trap for trapping mercury species separated by capillary column GC with ultimate detection by microwave-induced plasma atomic emission. Schickling and Broekaert (D14) used an on-line HPLC and cold-vapor AA for the analysis of mercury species in gas condensates. Delgado-Morales (D15) described new analytical methods for the analysis of arsenic compounds in natural gas and for the examination of solid arsine sulfides. Delgado-Morales et al. (D16) used NMR and other methods in the analysis and characterization of arsenic-containing pipeline solids. Denkhaus et al. (D17) used a microwave-induced plasma emission spectrometer for the determination of nitrogen in natural gas. Wharry and Sung (D18) reviewed the analysis of trace contaminants in natural gas. Bland and Chiu (D19) developed a method for the analysis of the accumulation of 210Pb on particulate matter in LNG rail cars. Water and Dew Point. Bullion (D20) described an automated gas pipeline monitor that used the chilled mirror technique

to measure water and hydrocarbon dew points as well as the water content in pipelines. Le Noe et al. (D21) developed a mathematical correlation between water content and water dew point in natural gas. Kazin (D22) gives a method to calculate the water and gas dew points at a given water content. Le Noe et al. (D23) used a microwave method for measuring compressibility factor and water content of natural gas. Calorific Value. Many of the papers published during the last two years continued to stress the importance of gas chromatographic methods in estimating the heating value of natural gas and natural gas liquid. Kizer (D24, D25) gave two reviews of using on-line chromatography for Btu measurements. Cox (D26) and Browne (D27) presented reviews on the use of portable chromatographs in Btu determination. Beeson (D28) discussed approaches to the use of flow computers and chromatography to measure the energy content of natural gas. Demczak et al. (D29) reviewed problems in using chromatographic analyses to calculate physical and chemical properties of natural gas. Goodwin et al. (D30) used acoustic measurement techniques for determining the compression factor and isobaric heat capacity. Density. Valentine and Keilty (D31) published applications for Coriolis flow and density measurements in natural gas. Kato et al. (D32) used a technique for measuring saturated densities on vapor-liquid equilibrium measurements at high pressures. Phase Equilibrium. The discovery of the existence of large deposits of methane hydrate has resulted in the publication of a number of papers describing the conditions under which this material can exist. Many of these are beyond the scope of this review; however, a number of good papers on the nucleation, growth, and agglomeration rates of hydrates were published in the Proceedings from the 2nd International Conference on Gas Hydrates (D33). The formation of hydrates in pipelines is of more direct interest. Ashcroft et al. (D34) described a new apparatus for measuring high-pressure three-phase equilibria in (methane + methylcyclohexane + ethan-1,2-diol + water). The results are relevant to understanding the use of ethylene glycol to inhibit hydrate formation in pipeline gas. Urdahl et al. (D35) designed an experimental setup to study the possible inhibition of hydrate formation by chemical means. Tohidi et al. (D36) discussed equipment and numerical models for measuring and predicting the amount and composition of equilibrium phases in the presence of gas hydrates. Koh et al. (D37) used time-resolved X-ray synchrotron techniques to study the crystal structure dynamics of gas hydrates during formation in order to examine the effects of inhibitors. Voulgaris et al. (D38) developed a model that uses extended chromatographic analysis to predict the potential hydrocarbon liquid of natural gas, and the results were compared to field tests. This model (D39) was used to predict the amount of liquid formed in natural gas pipelines under transport conditions. Hydrocarbons. Gas chromatography was the major method for the analysis of hydrocarbons in natural gas and natural gas liquids. Collins (D40) and Renfrow (D41) reviewed the applications of GC to the analysis of natural gas liquids, and Cowper (D42) reviewed the chromatographic analysis of hydrocarbon gases. Schrock (D43) has discussed the use of an on-line gas chromatograph in the analysis of natural gas liquids for pipeline control. Varotsis and Pasadakis (D44) used an integrated gas chromatographic method for the analysis of natural gas and natural gas liquids. Canfield and Iwamoto (D45) reviewed the Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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use of extended GC for the analysis of heavy components in natural gas liquid and natural gas. Heath et al. (D46) applied hightemperature capillary GC to the analysis of the C30+ fraction of North Sea gas condensates. Yun and Lee (D47) used a PLOT column for fast GC analysis of light hydrocarbons and permanent gases. Cao et al. (D48) studied the response of a GC reduction gas detector to gaseous hydrocarbons and found it to be more sensitive to alkenes. Hakuli et al. (D49) used an FT-IR spectrometer for the analysis of up to 12 hydrocarbons in a gaseous mixture. Podvorec and Kephart (D50) reviewed the use of quadrupole mass spectrometers in natural gas processing. Sampling. Parrott (D51) reviewed the techniques for sampling natural gas, and Welker (D52) reviewed the sampling procedures for LPG. Hathaway (D53) discussed how changes in sampler types and techniques have been influenced by the change in emphasis from volume to heating value pricing. Reviews. In addition to some of the more specific reviews published during the last two years, there were several good reviews of a more general nature that were published. Gonzalez (D54) published a review on the use of portable gas chromatographs for natural gas applications. Lechner-Fish (D55) reviewed applications to multidimensional capillary GC for the analysis of NG mixtures to provide calorific value, source fingerprint, and calculation of physical properties. Chao and Attari reviewed methods for the characterization and measurement of NG trace constituents, with volume I (D56) dealing with arsenic and volume 2 (D57) dealing with other trace constituents. Gamez et al. (D58) published a review of emissions estimation, measurement, and control from glycol dehydrators. GASOLINE Much of the activity in the gasoline area was driven by new EPA regulations dealing with gasoline and reformulated gasoline (RFG). The need for better and faster methods for blending gasolines to given octane numbers and with specific properties such as oxygenate content or Reid vapor pressure was driven by these. I have chosen to divide this part of the review into three areassproperties, composition, and trace sulfur and lead. Properties. Many developments dealt with fast on-line or atline methods using either IR spectrometry, near-infrared (nearIR) spectrometry, or GC with some type of modeling technique in order to predict with good accuracy properties such as octane number, Reid vapor pressure, or other physicochemical property. Ranson et al. (D59) proposed using neural networks in conjunction with near-IR measurements to predict fuel properties. Lane and Davidson (D60) described a method for operating a near-IR for determination of properties such as octane number. Murray and Zetter (D61) described a calibration method for near-IR spectral measurement in the prediction of properties of gasoline. Le Febre and Lane (D62) used near-IR monitoring of properties for control of continuous blending, as did Lambert et al. (D63). Workman and McDermott (D64) developed a photodiode array near-IR for process gasoline analysis. Prufer and Mamma (D65) developed an acousto-optic tunable near-IR spectrometer for on-line analysis of octane number. Maggard et al. (D66) patented a sampling system for on-stream near-IR analysis of gasolines and diesel fuels. An experimental and computational protocol was established by Fodor et al. (D67) for the simultaneous determination of several key gasoline properties. Doyle (D68) compared the use of near72R


IR and mid-IR for process analysis. Andrade et al. (D69) developed a method for predicting octane numbers in FCC gasoline using FT/mid-IR and partial least squares. Lob et al. (D70) gave an FT-IR method for predicting RON of reformates and naphtha feeds during evaluation of reforming catalysts. Llinas et al. (D71) patented a method for using IR measurements for predicting properties such as octane number. Perry and Brown (D72) patented a nonlinear multivariate IR method for determination of RON and other properties. DeBakker and Fredericks (D73) used a fiber-optic FT-Raman spectrometer and partial leastsquares analysis to determine properties of gasoline. Cooper et al. (D74) also used FT-Raman and partial least squares to predict octane numbers and Reid vapor pressure. Van Leeuwen et al. (D75) used nonlinear regression techniques with GC analysis to predict octane numbers. Golombok et al. (D76) used a kinetically based NMR method to measure the blending octane number of olefin streams. NMR spectrometry was used by Hutter et al. (D77) to measure hydrocarbon type composition, benzene, MTBE, and ETBE content and to predict octane number. NMR was used by Meusinger (D78) to determine the amounts of MTBE, benzene and aromatics, and methanol, and octane number was calculated using multiple linear regression. Stanley and Ramamoorthy (D79) outline methods for continuous validation of on-line analyzers. Composition. Giarrocco (D80) reviewed GC methods for the analysis of RFG, and Clemons (D81) reviewed the use of process GC methods for on-line analysis of RFG. Pauls (D82) published a review with 202 references on chromatographic methods for the analysis of gasolines. Both Siroin and Verga (D83) and Goekeler (D84) published reviews on the use of the oxygensensitive O-FID for the analysis of petroleum and petroleumderived fuels. Durand et al. (D85) gave a review covering the detailed characterization of petroleum products using capillary column GC. Martines et al. (D86) described a GC method for the determination of BTEX in gasoline. Vatsala et al. (D87) described a simple method using two packed columns for the analysis of oxygenates in gasoline. Estel et al. (D88) developed a highresolution apolar fused-silica capillary column for the GC analysis of C4-C11 hydrocarbons. Berger (D89) developed an ultrahighresolution GC method for the detailed analysis of gasoline, which resulted in the resolution of up to 970 compounds. Diehl et al. described a method for the analysis of aromatics in gasoline (D90) by GC/FT-IR and a method for the analysis of oxygenated compounds in gasoline by GC/AED (D91). Nero and Drinkwater (D92) developed a fast GC/MS method for the analysis of both aromatics and oxygenates in RFG. Barman (D93) conducted a study comparing the use of multidimensional GC with the FIA and bromine number methods for estimation of hydrocarbon type composition of gasoline. Chen et al. (D94) conducted hydrocarbon group type analysis in the gasoline range using multidimensional SFC/capillary GC. Colaiocco and Lattanzio (D95) used SFC coupled to a light scattering detector and chemometrics to analyze additives in gasoline. Squicciarini (D96) used SFC for the PONA analysis of gasoline and JP-4 jet fuel. Dhole and Ghosal used both an HPLC method (D97) and a TLC method (D98) for the determination of adulteration of gasoline with kerosine. Orellana et al. (D99) constructed a reversible fiber-optic fluorosensing device for the analysis of lower alcohols in gasoline.

Lopez-Anreus et al. (D100) determined benzene, toluene, and MTBE in gasoline using vapor generation and FT-IR. Cooper et al. (D101) compared FT-Raman, FT-IR, and near-IR spectroscopies for the determination of weight percent oxygen in gasolines. Kalsi et al. (D102) used 1H NMR for the rapid determination of oxygenates in gasoline. Alemany and Brown (D103) developed a method to identify C5-C6 dienes based on Diels-Alder derivatization with maleic anhydride followed by ultrahigh-resolution 13C NMR analysis. Sulfur and Lead. Robinson (D104) analyzed sulfur compounds in gasoline using GC and pulsed flame photometric detection (PFPD). Hutte (D105) reviewed the use of the sulfur chemiluminescence detector for the determination of sulfur species in petroleum products. Thomson et al. (D106) developed a scheme for distinguishing between sulfides and thiols in light fuel distillates by selective derivitization followed by GC and EIMS. Kubala et al. (D107) determined total sulfur in gasoline using sulfur-specific chemiluminescence detection. Bosilijkov and Ivovic (D108) used aqueous ion chromatography and atomic absorption spectrometry for determining lead alkyls in gasoline. Brenner et al. (D109) determined lead in gasoline directly by emulsification and ICP spectroscopy. Rajkovic et al. (D110) proposed using a lead-selective electrode for the potentiometric complexometric determination of lead in gasoline. MIDDLE DISTILLATES The last two years saw an increase in the development of chemometric-based on-line methods for the fast analysis of middle distillates and in the control of processes and blending. The topics are divided into fuel properties, hydrocarbon composition, and elemental analysis. Fuel Properties. Aaljoki et al. (D111) and Lambert et al. (D112) reviewed spectroscopic near-IR analyzers as applied to online monitoring. Tackett (D113) described near-IR measurements of physical properties of hydrocarbons using a computer-generated multivariate statistics-based calibration model. Sikora and Salacki (D114) used near-IR spectroscopy and chemometrics for the simultaneous estimation of viscosity, cetane number index, and density of diesel fuels and fractions. Sharma et al. (D115) developed a mathematical equation for predicting the diesel index of middle distillates from hydrocarbon composition. Ladommatos and Goacher (D116) tested 22 equations for predicting cetane number for diesel fuels for accuracy on over 500 fuels. Some linear relations between properties and composition were developed by Cookson et al. (D117) for jet fuels and diesel fuels of different boiling ranges. The properties investigated included smoke point, density, flash point, cloud point, hydrogen content, pour point, cetane number, and cetane index. Sharma et al. (D118) investigated sediment precursors in cracked middle distillate fuels through solvent extraction, derivitization, and FTIR, and the effects of additives on sediment formation were also studied. Combustion-relevant fuel properties such as stoichiometric oxygen demand, octane number, heating value, density, and other properties could be estimated using correlations with measurements made with small thermal flow microsensors developed by Boone (D119). Fonti et al. (D120) defined a particulate number, which is a measure of the fuel’s tendency to form particulates during engine combustion. The number was based on engine tests fueled by two reference fuels and the fuel to be tested, particulate emission measurements, and nitrogen

content of the tested fuel. McClain (D121) patented a spectrophotometric method for the detection of organic hydroperoxides in hydrocarbons that have been subjected to oxidative conditions. Marshman (D122) developed a rapid colorimetric test that can be used to predict the storage stability of middle distillate fuels. The test can be correlated with total sediment from ASTM D4625. Beal and Hardy (D123) used the quantitative gravimetric jet fuel total oxidation tester to rank diesel fuels according to their depositforming tendencies. Blondel-Telouk et al. (D124) constructed a static apparatus for the determination of the average molecular weight of petroleum cuts based on vapor pressure depression. Goossens (D125) developed a method for the prediction of the molecular weight of petroleum fractions based on the 50% true boiling point from simulated distillation data and the density at 20 °C. Hydrocarbon Composition. Chimenti and Halpern (D126) used an near-IR method to determine the weight percent of normal paraffins in an adsorber feed stream to control the removal of normal paraffins from kerosine. Lob et al. (D127) used FT-IR and partial least-squares regression analysis for hydrocarbon group analysis (PONA) of re-formate in a refinery. Neer and Deo (D128) used capillary GC for simulated distillation of oils with a wide carbon number distribution. Abbott (D129) reviewed advances in simulated distillation of petroleum and petroleum fractions. Huang et al. (D130) described a method using thermogravimetric analysis for the determination of the boiling range of a liquid fuel. Elizalde-Gonzalez et al. (D131) determined the retention indexes of 70 polynuclear aromatic hydrocarbons using a temperature-programmed GC with a methyl silicone capillary column as a means for identification in petroleum fractions. GC/ MS was used by Fafet and Magne-Drisch (D132) to analyze middle distillates in order to understand the hydrotreatment process mechanism. Guan et al. (D133) describe an all-glass heated inlet system interfaced to a dual-trap FT ion cyclotron resonance mass spectrometer for the analysis of aromatic hydrocarbons and aromatic compounds containing S, N, or O in petroleum distillates and refinery streams. Robert et al. (D134) coupled HPLC off-line with capillary GC to determine the aromatic content of middle distillates. Beens and Tijssen (D135) used an on-line-coupled HPLC/HRGC system for the analysis of oil fractions in the middle distillate range. Ma et al. (D136) separated visible fluorescence species existing in hydrodesulfirized diesel by HPLC and identified them by GC/MS. Korhammer and Benreuther (D137) reviewed the development of the hyphenation of HPLC and other chromatographic techniques, including SFC, GC, and GPC with NMR and considered some applications to fuel chemistry. Sarowha et al. (D138) developed an HPLC method to determine total saturates, aromatics, and aromatic ring number distribution on straight run gas oil fractions without prior separation. Sarowha et al. (D139) optimized HPLC separations to provide quantitative compositional data on hydrocarbon class types in products from the cracking of vacuum gas oils. Roberts (D140) reviewed petroleum applications of SFC. Nomura et al. (D141) provide applications for the analysis of kerosine and diesel fuel using SFC on ODS silica gel columns with fluorescence, UV absorption, and FID detectors. Lynch and Heyward (D142) describe the analysis of complex petroleum fractions with a coupled packed SFC and capillary GC. Li et al. (D143) made improvements in group-type separations of diesel fuels using packed capillary column SFC. The possibility of using SFC with Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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packed capillary columns for simulated distillation was investigated by Shariff and Bartle (D144). Bouigeon et al. (D145) investigated the use of long packed columns in SFC, including separation of complex oil samples. Doan et al. (D146) describe a new method for analyzing complex mixtures for polyaromatics using 1H 2D NMR. Gautier and Quignard (D147) reviewed the use of lowresolution 1H NMR in the determination of total hydrogen on a wide range of petroleum fractions. Sulfur and Other Elements. Tzanani and Amirav (D148) used a pulsed flame photometric detector for the simultaneous detection of compounds containing carbon, sulfur, phosphorus, or nitrogen atoms in gasoline and diesel fuel. Shearer (D149) described the simultaneous measurement of hydrocarbons and sulfur compounds in the analysis of diesel fuel, kerosine, and catalytic cracked product from a high-sulfur feed stock by using FID and sulfur chemiluminescence detection in GC. Abdillahi et al. (D150) compared Raney nickel, Houston Atlas, and GC with flame photometric detection in the determination of trace amounts of sulfur in naphthas. Zoccolillo et al. (D151) proposed determining sulfur in diesel with a computerized GC system with a flame photometric detector. Andari et al. (D152) established a database of 165 sulfur compounds to be used in the analysis of straight run gas oil. Botto and Zhu (D153) found that by using an ultrasonic nebulizer and a membrane desolvator for direct ICPAES analysis of trace elements, a universal calibration could be applied to a wide variety of petroleum fractions and fuel types. Mao et al. (D154) developed a procedure for the identification and characterization of nitrogen compounds in Brazilian diesel fuels by particle beam LC/MS. Dyes and Markers. Sweeny et al. (D155) described and evaluated methods for the determination of dyes in diesel fuels as required by IRS regulation. Henricsson and Westerholm (D156) developed an HPLC method to determine the dye Solvent Yellow 123, which is used as a marker in diesel fuel. Several fluorescing dyes were described for marking petroleum products (D157, D158). Smith and Desai (D159) developed a thymolphthalein marker and test method as a means of marking petroleum products. Weeks and Hebert (D160) developed a chemiluminescent material and method of test for marking petroleum products. An acid-extractable fuel marker and test method was described by Friswell et al. (D161). JET FUEL Major efforts continue in test methods to determine the thermal stability and storage stability of jet fuel. Although there were some interesting articles on the compositional analysis of jet fuel, many of the methods that apply to middle distillates can also be applied to jet fuels. Fuel Properties. Seinsche et al. (D162) used IR spectroscopic and GC data with multivariate regression analysis to predict properties of jet fuel, including flash point, viscosity, aniline point, and aromatics content for quality control. In a study by Garrigues et al. (D163), seven aircraft quality fuel properties were predicted using multivariate calculations and FT-IR. In another study, Minus (D164) used gas chromatography measurements as a basis to build models used to predict fuel-type classification and parameters. Thermal Stability. Pande and Hardy (D165) proposed an accelerated test method for predicting long-term storage stabilities of aviation turbine fuel, and then they used the jet fuel total 74R


oxidation tester (JFTOT) to study the effect of copper, MDA, and accelerated aging on jet fuel thermal stability (D166). Schulz and Gillman (D167) doped JP-8 fuel with thiols and thiophenols and analyzed the fuel after oxidation to determine their effect of oxidation of fuel components. In another study, Ali et al. (D168) used elemental analysis, FT-IR, and mass spectrometry to study sediments formed in tests in order to study the role of heteroatoms on jet fuel instability. Heneghan et al. (D169) examined the effects of oxygen scavenging on jet fuel stability using triphenylphosphine as a scavenging agent. The levels of triphenylphosphine were determined using a GC. Viilmpoc et al. (D170) integrated three techniques into a single instrument platform to allow simultaneous measurement in real-time of particle size and growth rate, surface mass deposition rate, and concentration of dissolved oxygen in thermally stressed jet fuel. Zabarnick et al. (D171) used a quartz crystal microbalance and pressure measurements for determination of jet fuel stability in a batch reactor. Rubey et al. (D172) used a dedicated in-line GC system for measuring trace levels of oxygen, methane, nitrogen, and other dissolved gases in thermally stressed jet fuel. Heneghan and Kauffman (D173) compared the results of thermal stability tests on 12 fuels with the analytical results of six separate tests to define the relationship between laboratory test data and thermal stability. Kamin et al. (D174) used a low-pressure reactor and an HPLC with an electrochemical detector for antioxidant determination for the diagnosis of storage stability problems of jet fuel. Morris et al. (D175) used light scattering photometry to monitor the formation of soluble deposit precursors in jet fuel. Gatlin et al. (D176) developed a method for the analysis of soluble Cu(I) and Cu(II) species in jet fuel by electrospray ionization mass spectrometry formed by exposure of jet fuel to copper surfaces. LUBRICANTS For this review, the material has been divided into sections dealing with base oils, additives, greases, oxidation, physical tests, used lubricants, biodegradability, solid lubricants, miscellaneous, and general reviews. This is a different approach from that used in the past, as there has been a change in focus in the analysis of lubricants. There has been more of a concern recently in the impact of disposal of used lubricants on the environment, so this has driven work on biodegradability of lubricants and to some extent analysis of used lubricants. There is also emphasis in the area of used lubricants in the savings that can be achieved through a good predictive maintenance program. Operation of equipment in extreme environments has driven both work on oxidation tests and development of synthetic base oils and solid lubricants. All of these changes are reflected in the literature reviewed for this article. There is a large body of lubricant work dealing strictly with tribometric research, and that was not included in this review. BASE OILS Chromatography. Hydrocarbon-type analysis has continued to be of importance in the design of lubricants for extended use. Many of the more classical methods such as the clay gel method are being replaced by more accurate chromatographic methods. Barman (E1) described the hydrocarbon-type analysis of base oils and other heavy distillates by rod thin-layer chromatography with FID detection (TLC/FID) and compared this to the clay gel method. The TLC/FID method was also applied to the determination of the base oil content of multigrade engine oils containing poly(butenyl succinimide) (PBS)-type dispersants (E2). HPLC

was also applied to the determination of base oil composition and dispersant content (PBS) (E3). In another study, an HPLC method was developed for the determination of saturated hydrocarbons, and mono-, di-, tri-, tetra-, and polyaromatics in base oils, and the method was correlated with mass spectrometric data and with a UV spectroscopic technique (E4). Supercritical fluid chromatography has been used for hydrocarbon-type analysis for petroleum-derived base oils; however, a method (E5) was developed that uses SFC with and FID for the analysis of polyol ester fluids. Through observation of the peak patterns obtained in the chromatograms, it was possible to gain knowledge of the carboxylic acids from which the esters were derived and other information. High-temperature GC simulated distillation of base stocks was compared to methods that used thermogravimetry/differential thermogravimetry (E6). The TG/DTG distillation temperatures were lower than HTGC for the 5 and 95% recoveries, and the distillation curves were almost parallel for 20-80% recoveries. Spectroscopy. Iob and others developed an FT-IR spectroscopic method that used partial least-squares regression for the hydrocarbon group analysis of re-formate (E7). Van den Ven et al. (E8) developed an FT-IR method based on correlation with 13C NMR to determine the aromatic content of mineral lubricant base oils. An IR method was also developed by Sastry et al. (E9) for the determination of aromatic, naphthenic, and paraffinic carbon contents of blended base oils. NMR spectrometry was also used for hydrocarbon-type analyses. An example was given by Sarpal et al. (E10) in the use of one- and two-dimensional NMR for hydrocarbon characterization of hydrocracked base stock. Singh and Singh (E11) estimated aromatic character of base oils using NMR spectroscopy and correlated this property to some other important parameters such as C/H ratio, KUOP, and CCR values. Sharma and others (E12) made correlations between NMR-derived structural parameters and a few physicochemical characteristics which play a critical role during their refining. A quick method for estimating the iodine number of fats, fatty oils, and their blends in mineral oils was developed based on 1H and 13C NMR spectroscopy (E13). A special mass spectrometric techniquesdirect-exposure probe chemical ionization mass spectrometry (E14)swas used for the analysis of the base oil compositions of biodegradable metalworking oils and hydraulic fluids. In another study, mass spectrometry was used to determine the chemical composition of base stock (E15), and a relationship was developed with the oxidation stability of blended turbine oils as determined by the RBOT. A simple multiple regression analysis of the data indicated that the tests could be used to predict the lifetime of the blended turbine oil, and a good correlation existed between the ASTM D943 oxidation test and the RBOT test. Stipanovic et al. (E16) characterized the chemical composition of re-refined base stocks from several sources using column chromatography coupled with mass spectrometry. The hydrocarbon-type distribution along with VI was used with statistical models to predict lubricant performance in the ASTM Sequence VE and IIIE Gasoline Engine Tests. Other. Firmstone et al. (E17) compared neural network and partial least-squares approaches in correlating base oil composition to lubricant performance in gasoline engine tests and industrial oil applications. Singhal and Mendiratta (E18) reviewed the the characterization of base stocks and finished lubricants through engine testing. Mattei et al. (E19) evaluated the influence of ester

and PAO synthetic lubricants on engine performance as well as their environmental consequences. Of a more general nature, Singh (E20) published a review with 10 references on the characterization of lube oil base stocks and its significance in lubricant formulations. Al-Banwan (E21) published a review with 13 references on the properties/characteristics of various base oils and their interaction with additives. Ramakumar et al. (E22) studied the effect of hydrocarbon composition of base oil on an optimized synergistic additive pair of overbased sulfonate and zinc dialkyl dithiophosphate in a a crankcase oil and found the paraffinic content to improve this synergism toward oxidation stability but worsen antiwear and detergency properties. Mohamed et al. (E23) examined the physicochemical characteristics of gas oils that affect their response toward lowtemperature additives as measured by pour point and cold filter plugging point depression. ADDITIVES Chromatographic methods continued to be important in the isolation and identification of additives from lubricants. Hiu and Rosset (E24) described a technique for isolation of PBS-type dispersants from monograde and multigrade lubricating oils by classical liquid adsorption chromatography on a Florisil column. Another procedure for the characterization of engine motor oil dispersants of the PBS type was developed (E25) that uses saponification, methylation, and size exclusion chromatography. An HPLC method was developed (E26) that can be used for the separation of zinc dialkyl dithiophosphates in lubricating oil additives. A direct solvent extraction/gas chromatographic method (E27) was developed for the determination of organophosphorus compounds as lubricating oil additives. Complex alilphatic polyamine mixtures used in the synthesis of PBS type lubricating oil dispersants could be identified by mild saponification followed by capillary column GC (E28). Taylor and Nasr-El-Din (E29) reviewed the determination of concentration and degree of hydrolysis of acrylamide copolymer additives. Raulf et al. (E30) developed a method for the isolation and determination of anionic surfactants in metal working fluids that involved separation on silica gel solid-phase extraction columns and potentiometric determination with an ion-sensitive electrode. Fernando (E31) used extraction, color development, and spectrophotometric determination to measure ethanolamines in lubricating emulsions. The microstructural parameters, such as comonomer sequence distribution, number-average sequence lengths, and run number, have been determined by 13C NMR spectroscopy for five commercial VI improvers in order to develop structure-performance relationships (E32). Work has continued on how additives interact with metal surfaces, especially antiwear and anticorrosion additives. In one study (E33), EXAFS was used as a tool to determine the local order in ZDDP reaction films generated on engine parts. Swift (E34) discussed the use of a variety of techniques such as XPS and static SIMS in the examination of the surface analysis of corrosion inhibitors on metal surfaces. FT-IR and AES were used to deduce the thickness of chemisorbed stearic acid layers on copper surfaces (E35). The tribological properties of conventional antiwear and extreme pressure additives in lubricated aluminumAnalytical Chemistry, Vol. 69, No. 12, June 15, 1997

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on-steel contact were evaluated using an Optimol SRV tester, the chemical reactivity of the additives with aluminum was investigated using a DSC, and XPS was used to determine the tribological reaction between additives and aluminum (E36). The novel surface analysis technique of multispectral Auger microscopy (MULSAM) was used to study simultaneously and at high resolution the chemical and topographical variations of antiwear films across wear scars (E37). The pressure effect on the frictional behavior of colloidal solutions of overbased calcium salts was examined (E38) using a surface force apparatus for low contact pressure and using tribometers supporting heavy loads for the analysis of the high-pressure domain. It was determined that the colloidal film does not flow above a critical pressure but forms a compacted mattress sliding on the surface plane and squeezing a molecular layer of lubricant. IR reflection absorption spectroscopy by Fourier transform and polarization modulatin techniques were used to study the adsorption of overbased calcium sulfonate on steel surfaces (E39). It was found that the adsorption leads to a preferential orientation of the carbonate, the c axis being perpendicular to the surface, and during friction, the sulfonate chains are ejected from the contact zone. Smeeth et al. (E40) found that some viscosity index improvers (VIIs) form boundary lubricating films of thickness 10-30 nm in contacts using ultrathin film interferometry. GREASE Spectroscopy. The use of FT-IR spectroscopy for the quantitative analysis of aluminum complex greases was examined (E41). The benzoic/stearic acid ratio could be determined fairly accurately for a given total acid/aluminum ratio, but more work needs to be done on other components. NMR was used as a tool to measure the diffusion coefficient of oil in a lubricating grease in order to determine the effect of the gelant on diffusion (E42). Other. Rizzo et al. (E43) developed a method for extracting, imaging, and measuring soap fibers in grease. The use of ferrographic analysis as applied to grease is increasing, and this was discussed by Maslach (E44). Rheological and physical studies were conducted on lubricating greases before and after use in bearings in order to determine changes that occur in the grease and to define mechanisms involved (E45). Surface Phenomena. XPS analysis was used to show that the antiwear and extreme pressure properties of CeF3 as an additive in grease could be attributed to the formation of a physically adherent film and a chemically reacted film on the metal surface (E46). Thermogravimetry showed that CeF3 acts as an agent for the slow release of fluorine. Lian et al. (E47) studied the antiwear and extreme pressure properties of rare earth trifluorides as additives in lithium grease. In another project (E48), a complex of lanthanum dialkyl dithiocarbamate and phenanthroline was synthesized, and its lubricating and antiwear behaviors as an antiwear additive in lithium grease were evaluated using a Timken tester with a SAE52100 steel ring sliding under a Al2024 block. The results of AES and XPS analyses indicated that the La complex forms a protective film containing lanthanum oxide, aluminum sulfide, and an organic compound containing sulfur and nitrogen on the rubbed aluminum surface. OXIDATION DSC. Trends in oxidation testing have been the development of tests that are faster and use smaller sample sizes than the more 76R


classical test methods such as ASTM D943 and D2272. Haglund and Enghag (E49) published a review with 13 references on the use of thermoanalytical methods for the characterization of lubricants used in the metalworking industry. Sealed-capsule DSC methodology has been described as a means of determining the oxidation stability of lubricating oils (E50). PDSC was used to investigate the thermal-oxidative degradation of biodegradable metalworking and hydraulic fluids (E51). A method that uses sealed-capsule differential scanning calorimetry was developed to determine the useful remaining life of industrial turbine oil (E52). DSC was used to evaluate the performance of an ester lubricant containing potassium trifluoroacetylacetonate in a study to evaluate its use as a synergist for arylamine antioxidant (E53). The ESR results indicated that the compound can reduce the free-radical content in the oxidized oil when arylamine antioxidants are present. The suitability of differential thermal analysis and principal component analysis for the assessment of service performance was studied using a total of 179 samples (E54). Other. In studies by Palekar et al. (E55), the Penn State microoxidation test was shown to have good correlation with ASTM III-D sequence engine tests and with heavy-duty diesel engine tests in the evaluation of a commercial mineral oil-based diesel engine lubricant and two experimental synthetic formulations. Miniaturized thermal oxidative techniques were used to study the metal-catalyzed thermal oxidative stability of PTPAE fluids (E56, E57). A new NIST thermogravimetric testing procedure was used to study the thermal and oxidative characteristics of several conventional, experimental, and high-temperature synthetic diesel lubricating oils (E58). Maleville et al. (E59) presented a study of the oxidation of mineral base stocks of petroleum origin and discussed the relationship between chemical composition, thickening, and oxidized degradation products. In order to study the effect of antioxidant in aged oils on preventing autooxidation (E60), solutions of antioxidant and model oxygen-containing compounds in hexadecane were used. Aldehyde was the most active species for reducing the antioxidation properties of ZDTP, DBPC, and PNA. Maduako et al. (E61) used a modified turbine oil oxidation stability test to determine the influence of soluble and elemental zinc, nickel, and aluminum on the oxidation of automotive crankcase oils. Chromatographic and spectroscopic techniques were used to investigate the degradation products from bulk oxidative and thermal stability testing of a substituted tricyclophosphazene high-temperature lubricant (E62). A study was made on deposit formation in the ASTM L-60 thermal oxidative stability test, and it was determined that additive effects dominate deposit formation, and base oil effects are secondary (E63). A laboratory-scale simulator was designed to develop a new laboratory oxidation stability testing method and to clarify factors relative to the viscosity increase of engine oil (E64). A novel thin-film oxidation technique was developed that is based on a sealed tube test for evaluation of oxidative stability of high-temperature liquid lubricating oils (E65). Hemsath (E66) designed an apparatus for the determination of the temperature at which residual rolling oils can be vaporized from cold-rolled strip without producing free carbon. An automated version of the Swift test, the Rancimat 679, can be used to determine the oxidation stability of plant-oil-based lubricants (E67).

PHYSICAL TESTS Three methods for the determination of molecular weight of base oils (vapor pressure osmometry, gel permeation chromatography, viscosity correlation) were studied for use on petroleumderived and shale oil-derived base oils by Stubington et al. (E68). For petroleum-derived base oils, the molecular weights by the three methods were similar; however, for the shale oil-derived base oils, the viscosity correlation method could not be used. Diaz et al. (E69) proposed a method for predicting the viscosity of multicomponent base lubricating oil mixtures based on Andrade’s equation and viscosity-temperature data of the components. Methodology was described by which the response of viscosity to both pressure and shear may be determined from measurements of elastohydrodynamic oil film thickness (E70). The methods were then applied to base oils and then base oils with additives. A high shear rate, high-pressure microviscometer was designed and used to examine the fluid film formed by the mechanism of elastohydrodynamic lubrication in the presence of an SAE 50 oil (E71). Williamson and Milton (E72) described the use of slit die rheometry to measure the viscoelasticity of several conventional multigrade oils at temperatures and shear rates close to that experienced by the lubricant in an automotive journal bearing. Suzuki et al. (E73) also constructed a viscometer in order to measure the effect of polymers and base oils on viscosity under high-shear conditions. Nakamura et al. (E74) developed techiques to use Brillouin scattering spectra to measure physical properties of lubricants under high pressure in a diamond anvil cell. In experiments designed to compare different base oil types, Kabuya and Bozet (E75) measured the viscosities and tribological properties (as measured by a Stribeck machine and a four-ball machine) of vegetable oils, a synthetic ester, and a mineral oil. USED LUBRICANTS Many of the developments in the analysis of used lubricants concerned instrumentation that could be used on-line or at-line for rapid determination of lubricant contaminants. This is needed in contaminant monitoring or predictive maintenance of critical equipment; however, accuracy/reliability should not be sacrificed for speed. Users are encouraged to conduct comparative testing with know methods prior to change. On-Line. Oil samples were taken from a steam turbine/ generator and analyzed off-line for contamination, and the data were used to design an system for monitoring contamination online (E76). As a result, a device using a filter blockage principle was developed and field tested. A gridlike capacitive sensor was developed that uses the lubricating oil as a dielectric medium was developed for use as a continuous on-board analyzer for diesel engine lubrication systems (E77). Van Schoiack and von der Porten (E78) developed an electric capacitance-based sensor for the detection and monitoring of trace water and glycol in lubricating oils. A conductive polymer-based sensor was developed, and its use as a sensor for measuring the presence of water and the buildup of acid species in lubricants was demonstrated (E79), and polymer-coated sensors were deveolped that can be used to measure the water content of synthetic lubricants (E80). A system using solid-state microsensors was developed for use on shipboard for monitoring the total residual base number in a diesel engine oil (E81). Kauffman (E82) has described the use of cyclic voltammetric method to determining the useful life of diesel engine oils, automotive engine oils, hydraulic fluids, and

greases. The equipment can also be used to quantify antioxidant levels in new fluids. A two-electrode ultramicroamperometry method was used to follow continuously the hydrolysis of triaryl phosphate esters which were proposed as fire-resistant substitute lubricating oils for primary pump motors in nuclear plants (E83). FT-IR. An on-site oil analyzer was developed which combines and FT-IR and an optical emission spectrometer for testing oil samples for water, trace metals, fuel dilution, viscosity, and soot (E84). An automated system for identifying different types of used lubricants has been developed that uses a spectrometer and a computer for data processing (E85). FT-IR/ATR using a gremanium crystal sample cell was used to directly test undiluted samples of aircraft fuels, hydraulic fluids, and dielectric coolants for monitoring purposes (E86). The feasibility of using two different thermal/FT-IR analytical methods in combination with advanced data analysis techniques to detect contamination in used turbine engine lubricants was demonstrated (E87). Atomic Spectroscopy. The analysis of wear metals and additive elements continues to be important in used oil analysis. Patel (E88) reviewed the determination of elemental compositions of base oils, lubricants, and additives by atomic spectroscopy. Hydraulic high-pressure nebulization was applied to the flame AAS/AES analysis of trace elements in fresh and used lubricating oils in order to eliminate viscosity effects and time-consuming dilution of oil samples (E89). Electrothermal vaporization was applied to the determination of metalloorganic compounds in lubricating oil by ICPMS (E90). A method for the rapid determination of the metal content (especially Li) in lubricating greases using xylene-HCl extraction, followed by AAS analysis was developed (E91). Metal complexes of 2,2-dimethyl-6,6,7,7,8,8,8heptafluoro-3,5-octanedione were developed for use as standards for the analysis of wear metals in perfluoro(polyalkyl ether) lubricating fluids (E92). Lanthanum and strontium were added to solutions of ashed unused lubricating oils for the determination of calcium, magnesium, and zinc by flame AAS as suppressors to overcome the interference of phosphate ion (E93). Wear metals and additive elements were extracted into aqueous solution by treatment of the oil sample with toluene/xylene, HCL, and H2O2 with ultrasonic agitation and magnetic stirring, and analysis of the aqueous solution was conducted with AAS and ICP-AES (F94). The extraction procedure recovered >95% of the metals. Anderau et al. (E95) described an analytical method for the determination of wear metals in engine lubricating oils by ICP-AES. Dobrinic et al. (E96) discussed the analysis of used motor oils by flame AAS as well as the impact on the environment because of the heavy metals that they determined the oils contained. Other techniques for wear metals analysis were used in addiltion to AES/AAS. Oil samples from UH-1H-type helicopter engines were collected, subjected to chemical pretreatment in order to reduce the high viscosity of the oil and to eliminate particle size effects, and analyzed by X-ray fluorescence spectrometry for wear metals (E97). A PIXE system was adapted for the analysis of liquid samples, and the analysis of a turbomolecular pump oil was used as an example (E98). Metals Related. In a related study, samples of used lubricants were taken and analyzed for a number of common contaminants during collection, transfer, and re-refining and recycling in order to determine the fate of these materials (E99). In a study on the disposal of used lubricants by combustion, the combustion gases from a furnace were analyzed for principal Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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contaminants, especially heavy metals (E100). The tests suggested that the levels would be too high to meet European Union emission levels. The use of analytical ferrography was suggested as an on-site method for the evaluation of the condition of used automobile parts such as the engine and transmission (E101). The use of a portable oil analyzer for monitoring moisture and wear particles in PAG and POE synthetic lubricants for compressors was investigated (E102). A method and apparatus was developed to prepare samples of viscous industrial fluids for analysis for the presence of magnetically responsive particle and other suspended solids (E103). Chromatography. In a unique HPLC method (E104), straightchain aliphatic aldehydes in used engine oils were selectively derivatized with 3-aminofluoranthene. The derivatives were separated by reversed-phase liquid chromatography and detected by monitoring the chemiluminescence emission from a postcolumn reaction with bis(2,4,6-trichlorophenyl) oxalate and hydrogen peroxide. A size exclusion LC method using refractive index and phodiode array detectors was developed for the detection of high molecular weight contaminants in a C15 linear paraffin-based cold rolling oil (E105). Other. Volumetric and coulometric Karl Fischer methods were compared in the determination of moisture in transformer oils (E106). When an oil is not completely dissolved in the titration vessel solution, a portion of the water is unavailable to react with the Karl Fischer reagent. The effect on water separation of three commercial steam turbine oils when contaminated with engine oil or a commercially available enhancement additive was investigated (E107). Linnersten (E108) presented a procedure for testing filters for removal of water from hydraulic fluids and, in addition, reviewed methods for water determination. An automatic coulometric titrator with a colorimetric indication was developed, and its use in acid number determination was demonstrated (E109). A method was developed that uses a nonazo-1,8-naphthalimide dye for the detection and quantitation of the total hydrogen ion activity in nonaqueous medium, and the method was applied to the determination of motor oil degradation (E110). BIODEGRADABILITY Disposal of used lubricants is a problem of global proportions. Some efforts are being directed at re-refining and reuse, and some analytical methods to support this effort are given under the Used Oil category. Other efforts are being made to develop lubricants that are biodegradable, and the methods to support those efforts are reviewed here. Voeltz et al. (E111) reviewed biodegradability tests for lubricant base stocks and fully formulated lubricants. Martelli et al. (E112) reviewed the development and use of biodegradable lubricants in a paper with 14 references. Biggen (E113) refers to the “science of life cycle analysis” in reviewing developments in the biodegradability of additives. Roehrs and Rossrucker (E114) discussed the ecological and toxicological characteristics of grease additives and their performance. Komarov et al. (E115) studied the effect of oil biocorrosion as a result of bidegradation on the tribological characteristics of the oil. Hund et al. (E116) investigated the formation of biomass during the biodegradation of ester base lubricants. 78R


SOLID LUBRICANTS Molybdenum Disulfide. Seitzman et al. (E117) studied the endurance of Ion beam assist deposited (IBAD) MoS2 using a ballon-disk tribometer and X-ray diffraction to study structure and orientation. They found that coatings with poor crystallinity exhibited good endurance and that the coating endurance decreases with increasing edge (1000) intensity. Seitzman et al. (E118) also used XRD to study the orientation of IBAD MoS2 coatings deposited under different ion/atom ratios and deposition temperatures. Another group studied the effects of atomic oxygen on the tribological properties and chemical composition of MoS2 film using the inclined plane method for static friction, the pinon-disk method for friction, atomic force microscopy for surface morphology, and XPS for chemical composition (E119). A number of tools, including electron diffraction, high-resolution transmission EM, and atomic force microscopy were used to study friction-induced crystal orientations in MoS2 thin films and their effects on friction coefficient (E120). Levy and Moser (E121) also examined the morphology and orientation of MoS2 films under different deposition temperatures and gas pressures, as well as the effect of crystal orientation and structure on friction coefficient. In a study of the effect of dopants on the chemistry and tribology of sputter-deposited MoS2 films, Zabinski et al. (E122) found that the presence of dopants caused film densification and affected crystallite size and caused a reduction in the mean and variance of the friction coefficient and an increase in wear life. Donnet et al. (E123) designed a AES/XPS ultrahigh vacuum tribometer coupled to a preparation chamber that allowed oxygen-free MoS2 coatings to be formed and friction tests to be carried out in various controlled atmospheres. Already published results, along with this study, indicate that super low friction behavior can be attributed to a combination of crystallographic orientations, surface chemistry, and absence of contaminant, allowing a strong decrease in the interfacial shear strength. Low-friction, high-endurance, IBD Pb-Mo-S coatings were studied using XRD and microRaman spectroscopy for structure and composition (E124). The wear resistance and low-friction properties were attributed to the combination of dense, adherent coatings, and the formation of easily sheared MoS2 containing surfaces. Other Inorganic Films. The chemistry and crystallinity of thin films of PbMoO4 were studied using XPS, and the friction coefficients and wear lives were measured using a ball-on-flat tribometer at room temperature and at 700 °C in order to determine the potential use of this material for a solid lubricant at elevated temperatures in oxidizing environments (E125). Prasad et al. (E126) examined the friction behavior of pulsed laserdeposited tungsten disulfide films, and the wear surfaces were characterized by SEM and Raman spectroscopy. In a study that examined the frictional interaction between tungsten carbide and chalcogens, a conclusion was made that surface layers of refractory metal carbides are activated mechanically, which results in transformation of carbides into chalcogenides with high frictional properties (E127). High-resolution electron microscopy imaging and electron and XRD were used to characterize the structure of low- and high-flux Au-20%Pd layers in Au-20%Pd/MoS2 multilayer solid lubricant films (E128). Carbon Based. The friction and wear properties of smooth diamond coatings sliding against a monocrystalline ruby ball were studied using a pin-on-disk tribometer, and a correlation of the film surface properties examined with different techniques, includ-

ing ATF, AES, Raman, and stylus prolilometry, and the tribological properties of the diamond films tested was established (E129). The effects of purity of fullerene films and ion implantation of the films with Ar ions on the friction and wear properties of sublimed fullerene films was reported. In this study, the increased amount of C70 and impurities in the film were determined using Raman and FT-IR (E130). Blanchet et al. (E131) demonstrated that extended duration high-temperature (>500 °C) lubrication of silicon nitride sliding and rolling contacts could be accomplished by solid carbon deposited and replinished via the decomposition of carbonaceous gas streams directed toward the surfaces. Studies were made to lubricate a nickel-based superalloy at 500 °C by using vaporized aryl phosphate ester at a concentration of 0.1% in air (E132). At first, it was impossible to form a good polymeric coating, and EDXA showed that this was due to minute quantities of aluminum in the alloy that migrated to the surface at this temperature and formed an oxide coating. A method of activation was achieved by electrodepositing the surface with a layer of iron oxide and then coating with the polymer. Wear inspection, XPS analysis of PTFE transfer film used as a lubricant, and bearing temperatures during firing were all used to evaluate the durability of cryogenic high-speed ball bearings on oxygen and hydrogen turbopumps of the LE-7 rocket engine (E133). Georges et al. (E134) used variations in the shear plane capacitance to determine the thickness of adsorbed layers of polyisoprene between two cobalt surfaces during friction measurements. MISCELLANEOUS Lee et al. (E135) added nonradioactive organic bromine or chlorine compounds to oil in small amounts and used a tunable dye laser spectrometer to measure HBr or HCl in the engine exhaust as a measure of oil consumption in the engine. Schram et al. (E136) also examined analytical methods to determine the fuel and lubricant contributions to particulate emissions from a diesel engine. Wong and Laurence (E137) studied the effect of lubricant and piston ring design on diesel engine particulate composition and emission rate. Radioactive tracer technology was used to study ring and bearing wear as a function of engine operating condition and lubricant characteristics on a real-time basis (FE38). Rhodes (E139) examined a number of multigrade oils that met SAE J300 low-temperature pumpability requirements but exhibited properties that made the low-temperature properties suspect. In this study, he used the two-day minirotatry viscometer (MRV) test as a reliable test for pumpability characteristics. REVIEWS Byers (E140) published a review with 33 references on the laboratory methods for evaluation of metalworking fluids. Cain et al. (E141) reviewed developments, performance measurements, and tests for industrial gear oil. Zareh (E142), in a review with 14 references, discussed industrial gas engines and their lubrication. Landman et al. (E143) published a review with 81 references dealing with advances in computer-based modeling and development of high-resolution experimental techniques that allow investigations of tribological phenomena at the atomic/molecular level. Singer (E144) presented a review with 52 references dealing with the mechanics and chemistry of solids in sliding contact.

Saba and Centers (E145) published a review with 54 references on advances in aerospace lubricant and wear metal analysis. SOURCE ROCKS Source rocks are the organic-rich rocks responsible for the production of oil or natural gas. Such rocks generally have relatively high total organic carbon (TOC) contents and may be at varying levels of thermal maturity. The nature of the organic material, along with the level of maturity, will determine whether the rock produces predominantly oil, gas, or a mixture of the two components. A source rock can be divided into two main parts, namely, the organic fraction and the inorganic, or mineral, matrix. The organic fraction can be further divided into a solventextractable fraction and solvent-insoluble, or kerogen, fraction. The kerogen fraction of any organic-rich rock contains the bulk of the organic carbon and can be thought of as that fraction remaining after the soluble organic material has been removed by extraction and the insoluble mineral matrix has been removed by dissolution with various acids. The literature covered for this year’s review does not contain as many references to specific compounds, or biomarkers, as in previous reviews. This may reflect the papers abstracted for the review, or more likely, it reflects the fact that biomarkers are now an accepted part of most source rock characterization studies and hence do not receive as much detailed attention as they have in the past. In addition, much more emphasis is placed on the application of source rock characteristics in an exploration sense rather than the type of study designed to unravel the basic fundamentals behind such characteristics. It should also be noted that this review contains a much larger percentage of papers concerned with exploration activities in basins outside of the United States than in previous years. The first part of the review will for the most part be concerned with papers that have discussed source rock characteristics in terms of their ability to source oil and/or gas. The second part will be concerned with a number of papers related to techniques, some novel, designed to improve our knowledge of source rock characteristics. Finally, it should be mentioned that a new book entitled Petroleum Geochemistry and Geology by John Hunt was published in 1995 (F1), and this is a completely rewritten version of his earlier book. It contains a great deal of information on source rocks as well as geochemical applications to petroleum exploration and as such it is certainly a book that any reader of this review should examine in detail. While this section is concerned with source rocks, it is important to mention that applications of geochemistry to reservoir and production problems have increased severalfold in the past few years. Although this topic will not be reviewed herein, there is one monograph published recently that serves as a good introduction to the topic which contains reservoir geochemistry papers by authors such as Mason et al. (F2) Stoddart et al. (F3), and Karlsen and others (F4). APPLICATIONS United States/Canada. Price and others (F5) have used numerical models in an attempt to constrain the thermal history of the Precambrian Nonesuch Formation, Michigan U.S.A. basin. Modeling indicates that maximum temperatures of 110-125 °C were obtained ∼1075Myr coincident with a burial depth of ∼6 km. A comprehensive study of organic and lithostratigraphic facies variations in a known hydrocarbon source rock interval of Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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the Triassic Shublik Formation on the North Slope of Alaska has been reported by Robinson and others (F6). Oils from the Big Horn Basin were analyzed to determine possible differences in oil types, their thermal maturity, and extent of oil alteration (F7). It was proposed that the geochemical characteristics of these oils were very similar, suggesting they all were derived from the same or very similar source rocks which now lie mostly to the west and outside of the basin, namely, the Permian Phosphoria Formation. Dahl and others (F8) used the biomarker analyses of the Aspen Shale, Skully’s Gap, Wyoming, to show that vital source rock properties may be indirectly, yet quantitatively, predicted from the biomarker properties of the oils. The method, as described, will probably be of most use for many deltaic and nearshore marine source rocks that were deposited after the evolution of vascular plants. Prediction of source rock properties from oils in vertically drained basins could be most useful to explorationists seeking to identify most oil-prone regions in areas such as the U.S. Gulf Coast, North Sea, Beaufort Sea, and the Mahakam and Niger deltas. In a related paper, McCaffrey and others (F9) applied this approach to a case study using Tertiaryreservoired Beaufort Sea oils. Two members of the Green River Formation in the Washakie Basin have been characterized using organic geochemical and organic petrographic techniques and the results placed in a sequence stratigraphic framework (F10). Both of the members had the potential to generate waxy oils, but the member deposited in the alkaline lake was clearly more prolific. Saller and others (F11) have studied the cycle stratigraphy and porosity in Pennsylvanian and Lower Permian shelf limestones, eastern Central Basin platform, Texas, and delineated 63 cycles and four general lithofacies, namely, fossiliferous wackestones and packstones, grainstones, phylloid algal bound stones, and shales. Variations in porosity resulting from variations in duration of aerial exposures were discussed in detail. Geochemical characterization of sediment samples from Hole 893A, Santa Barbara Basin, offshore California, by Hinrichs et al. (F12) showed a signature typical of a biodegraded petroleum. It was concluded that these compounds were derived from eroded Monterey Formation petroleum source rocks or related oil seeps. This problem is not unique to sediments from the Santa Barbara basin, and one must be aware of the potential of contamination of recent sediments by hydrocarbons derived from more mature hydrocarbon-bearing rocks particularly in petroleum provinces. A comparative study between oil shales and source rocks from Colorado, the South Eastern part of the Korean Peninsula, and the Paris Basin has been undertaken by Yang et al. (F13). Using techniques such as gravimetry, CHN analyses, X-ray diffraction, ICP, and atomic absorption spectrometry it was concluded that the Colorado shales were type I kerogens and all the others were type II kerogens. The Triassic outcrops of Bjornoya were used by Isaksen (F14) as an important reference sequence for the regional characterization of potential source rocks in the southwestern Barents Sea. These rocks are currently at a maturity level that would suggest they have gone through the oil window and also expelled some gas during the Late Cretaceous to Early Tertiary. Bitumen stains were characterized by tricyclic terpanes in the C21-C46 range. Variability in the lithology, TOC, and petrophysical properties of the Egret member of the Jeanne d’Arc Basin, off northeastern Canada were examined in detail, and it was concluded that there was a correlation between low sedimentation rates and high TOC values reflecting the deposition of the organic-rich samples during 80R


high sea level stands and warmer periods (F15). Huang and Williamson (16) also used an artificial neural network approach to establish detailed and accurate geochemical characterizations in oil source intervals using well logs and noisy information from cuttings in this same basin. Thermal maturity variations of Lower Paleozoic sediments in Arctic Canada have been studied using graptolite reflectance values (F17). It was proposed that liquid hydrocarbons could be expected in areas with graptolite reflectance values less than 1.7% and gaseous hydrocarbons in areas where the reflectance exceeds 2.0%. Variations in depth of burial of the sediments was the main cause of the significant variations in the graptolite reflectance values over the basin. Mukhopadhyay and others (F18) have undertaken source rock characterization, oil/oil, and oil/source rock correlations of selected organic-rich shales and selected oils and condensates from Jurassic and Cretaceous formations of the Scotian Basin. Two families of oils were revealed using multiple linear regression and cluster analyses of aromatic hydrocarbon ratios. The types of organic materials responsible for sourcing these oil types are also discussed. U.K./North Sea/Europe. Bitumens are often known to be associated with Mississippi Valley-type mineralizations and Ewbank et al. (F19) recently reported such an occurrence in samples from the South Pennine Orefield in England. These bitumens were characterized by standard geochemical techniques and compared with various suspected source rocks. Lower Namurian mudstones with type II kerogens from the Edale Gulf were proposed as the most likely source with other minor contributions from within the Dinantian limestone. Simple geochemical methods, consistent with recent sequence stratigraphic interpretation suggested a late Carboniferous age for hydrocarbon generation where the geothermal gradients were slightly higher than present day. Three types of fluid inclusions were also observed although none of them contained any hydrocarbons. Thus it was concluded that the main phases of hydrocarbon generation and mineralization appeared to be unrelated in this area. Aromatic hydrocarbons from the Kimmeridge Clay in Yorkshire showed early thermal evolution of the organic matter as determined from the distribution of various organic maturity parameters (F20). It was proposed that generation was occurring at maturity levels around 0.5% Ro with most of the organic material being of algal origin. Ramanampisoa and Disnar (F21) also showed that anoxia in the Kimmeridge clay resulted from high organic matter preservation resulting in turn from high primary production. Boussafir and others (F22) proposed that microcycle variations observed in the Kimmeridge clay could be explained by variations in TOC and HI, and these were controlled by interrelationships between primary productivity, sulfate reduction, and lipid vulcanization. Carboniferous rocks in the north Solway onshore outcrop have been shown to contain evidence of hydrocarbon migration (F23). It was proposed that the oil was emplaced in the sandstones after dissolution of the dolomite, calcite, and clay cements. Hydrocarbon source rocks were identified further east in a more complete succession exposed in the Esk Valley along with further oil residues. Time-temperature modeling suggested that the oil was generated from Lower Carboniferous source rocks during the Permo-Triassic. Chemical age dating of uranite in bitumen yielded early Jurassic ages which may reflect the time of hydrocarbon migration along the North Solway Fault system and may also be related to a mid-Jurassic episode of regional uplift.

Evaporitic source rocks occur in many areas of the world. In order to obtain a better understanding of sedimentary history of evaporated source rocks and related hydrocarbons, Benali et al. (F24)) undertook a detailed geochemical study of sediments from the Lorca Basin in southeastern Spain where the sediments had been deposited under a variety of salinity conditions, which in turn affected the type and quality of the organic matter. A series of papers have resulted from an extensive study of a Messinian evaporitic sequence (Vena del Gesso, Italy), all of which are concerned with various aspects of using molecular indicators to monitor palaeoenvironmental changes in these types of environments (F25-F29) Source rocks rich in sulfur are known to generate oils at relatively low levels of maturity, and di Primio (F30) found that the maturity of a Triassic to late Miocene carbonate sequence in Italy did not exceed 0.5% Ro. As previously discussed, this is attributed to the fact that cleavage of carbonsulfur bonds can occur at lower levels of thermal stress than cleavage of carbon-carbon bonds. Thermal evolution of extractable alkyldibenzothiophenes in the Posidonia Shale (Toarcian) source rocks has been described by Radke and Willsch (F31). Results from the study of 125 rock samples were reported covering a vitrinite reflectance range of 04.0-1.5%. Source rock analyses and numerical modeling techniques were used by Sachsenhofer (F32) to evaluate the petroleum potential of the Styrian Basin, Austria. Oil and gas-prone sediments were found to occur in the lower Miocene section (Ottnangian and Carpatian levels) with the hydrocarbons having been generated at higher temperatures within a narrower temperature interval from Ottnangian sediments rather than Carpatian sediments. Organic matter in organic-rich Cretaceous carbonates from the Outer Dinarides, South Croatia, was found to vary from thin laminas to thicker layers, uniformly dispersed in the mineral matrix, and fissures and cavities were found to be filled with bitumen or bituminous coatings. The kerogens were identified as type I-II in fine-grained laminated limestones with high generative potential. The source rock extracts and bitumens in the fissures were found to be very similar, suggesting short migration phenomena (F33). Palyonfacies, macerals, type of organic matter, and the organic geochemical characteristics of organic-rich samples from the Upper Santoian-late Campanian laminated limestones of Hvar Island, Croatia, were described by Jerinic and others (F34). These limestones were found to contain type II-S kerogen, which was observed to be marginally mature and oil prone. Low-maturity, sulfur-rich carbonate source rock sequences in Italy were found to be at maturity levels below 0.5% Ro and to have generated sulfur-rich oils. As with other situations like this, the effect was explained by the preferential cleavage of the carbon-sulfur bonds at low levels of thermal stress. Rich source rocks in the Ionian basin of Greece have also been described in detail by Karakitsios and Rigakis (F35) along with information on maturity levels and biomarker-based oil/source rock correlations. Oligocene menilite black shales and mudstones in the Carpathian Overthrust region of southeastern Poland have excellent source rock potential on the basis of TOC, Rock Eval data, and petrographic data. Kruge and others (F36) undertook a detailed geochemical study of samples from the region and were able to genetically link menilite kerogens with the Carpathian oils. Bakarat and Rullkotter (F37) examined bound and free fatty acids from five lacustrine sulfur-rich sediments in the Noerdlinger Ries,

southern Germany. The results obtained from a comparison of these acids supported previous suggestions of a broad similarity between the structures of asphaltenes and kerogen derived from the same source rock, along with the extremely mild thermal history of the Noerdlinger Ries sediments. 31 oil and condensate samples from the Haltenbanken region of the North Sea were characterized geochemically to determine genetic relationships. These samples could be divided into three genetic groups which also showed a dependence on the geographic location of the fields. One group was proposed to be sourced from a distal marine anoxic facies of the Spekk Formation, the second group was from a more terrestrially influenced proximal marine (partly dysaerobic) isotopically heavier shales of the Spekk Formation, and the third group was a mixture of both source rock facies. The Spekk Formation was proposed to be heterogeneous with significant geochemical variations both laterally and vertically. Petersen and others (F38) combined geochemistry and sequence stratigraphy plus multivariate data analysis to show a positive correlation between Rock Eval S1 + S2 peaks, selected macerals, and TOC values. It was proposed that such multivariate modeling may make it possible to better define the location of coals with the highest generative potential. Gormly and others (F39) analyzed nearly 100 oils from the North Viking Graben of the North Sea and identified three hydrocarbon populations based on geochemical parameters. One was proposed to be derived from the marine shales of the Draupne Formation, the second was from the marine shales of the Heather Formation, which also contain land plant material, and the third was from a mixture of these two sources. It was noted that variations in the properties of hydrocarbons in the North Viking Graben petroleum system are very complex due to the interplay of organic source material, maturity, migration, pressure distribution, and biodegradation. The Upper Cambrian Alum shale of Scandinavia has not generally been regarded as a significant potential source rock for oil generation. However Bharati (F40) has used a number of chemical and optical techniques to estimate the true petroleum potential of this formation and model the composition of the oil that may be generated from the shale under appropriate conditions of maturity. Turkey/Middle East. Ozcelik and Altunsoy (F41) in a very general study of the Bozbel Formation in the eastern Sivas Basin of Turkey, described the mineralogy of this formation and the TOC content of the major suspected source facies in the region, dominated by type III kerogens; however, it was concluded that the low content of organic matter would probably lead to gas production rather than oil. Abdullah and Kinghorn (F42) undertook a similar type of study with the Lower and Middle Cretaceous Thamama and Wasia Groups in Kuwait and concluded that the Sulaiy and Minagish Formations were the major sources of oils in the region. Cretaceous source rocks in the Zagros Foothills of Iran have been described by Bordenave and Huc (F43). The impact of these various source rocks was evaluated in relation to petroleum prospecting in these areas. A sequence stratigraphy study of Miocene limestones, marl, and siliclastic source rocks in eastern Tunisia was undertaken to define biostratigraphic and lithostratigraphic subdivisions. It was concluded that basin subsidence in response to the Alpine/Atlassic orogeny permitted the maturation of the Miocene source rocks, oil generation, and formation of oil traps, stratigraphic pinchouts, and structural enclosures on the flanks of folds and on the borders of grabens (F44) Beauchamp et al. (F45) studied reflection seismic data, Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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geochemical data, and surface geology and proposed that a Cretaceous rift basin exists beneath the thrusted allocthonous sedimentary sequence of the Masirah graben, Oman. A number of oils collected and analyzed from the Infracambrian sedimentary rocks penetrated by these wells suggested an origin from a Mesozoic source rock in the region. A detailed study to determine the most likely candidate for the source of the Paleozoic oils in Saudi Arabia has been reported by Cole and others (F46). On the basis of detailed geochemical analyses and other data, it was concluded that there were no other potential source rocks in the area that had the vertical or lateral regional persistence of the Silurian basal Qusaiba shales. In a separate report, Cole and others (F47) reconstructed the burial history and thermal maturity evolution of the Qusaiba source in Saudi Arabia. Several migration pathways for the expelled hydrocarbons were also determined using present day structural configurations for the basal Qusaiba shale. Potential source rocks, extent of hydrocarbon kitchens, and characterization of hydrocarbons in the Midyan and Jaizan Basins of the Red Sea Saudia Arabia have been studied in detail by Cole and others (F48). Source rocks in the Midyan basin were found to be oil to gas mature and may be sources for the gas and/or condensate accumulations although the mature Maqna sediments may have sourced black oil accumulations. In the Jaizan Basin, the Maqna and Burqan sediments were found to be high oil maturity to thermally spent due to high geothermal conditions and excessive burial. Source rock potential of the Miocene shales of the Eastern Nile Delta were evaluated by Felesteen (E49), based on organic matter type, concentration, and thermal maturity. The samples had fairly high TOC values in the range 0.82-2.26% and contained predominantly type III or mixed type II-III kerogens. It was concluded on the basis of the organic matter type that these shales were most likely to produce gas and gas condensate when exposed to the appropriate levels of maturity. Organic facies variations for presalt freshwater lacustrine source rocks in northern Gabon have been characterized by integrating their geochemical and geological data (F50). It was predicted that lower wax, better quality oils were to be expected to occur to the southwest of the study area where shales are more mature. The Sirite Basin, Libya, is a major petroleum basin on a world scale, and Baric et al. (F51) undertook a geochemical study to characterize sediments from the Zelten platform (concession block NC-157) in this basin. On the basis of the geochemical data, a source rock sequence 475m was identified and represented by the limey marls Kalash and shales of the Sirte formation. The organic facies of these sediments was dominated by the presence of the hydrogen-rich type II kerogens. Minor variations in the generative ability of this source rock facies could be attributed to differences in environmental and depositional conditions and to specific properties of the source material precursors. A total of 250 core samples from stratigraphically selected horizons and several outcrop samples from the eastern and western parts of the Dilbi oil shales from Ethiopia were geochemically characterized using selective leaching (extraction), pyrolysis, and chemical methods. From the distributions of various classes of biomarkers the oil shales were characterized as algal-rich fluvial-lacustrine sediments with fair to good source rock capabilities. The geological evidence suggested that these oil shales occur within the regionally extending rift zone of southwestern Ethiopia and warrant further exploration work for 82R


hydrocarbons (F52). Barakat (F53) analyzed an oil from the Lower Cretaceous Alamein oilfield. GC/MS/MS was utilized to determine the distribution of steranes in the oil and it was noted that the predominance of the C29 regular and rearranged steranes provided evidence for the presence of terrigenous land plant material in the source of the Alamein crude oils. The relatively low concentration of diasteranes compared to the regular steranes also suggested that the oils were generated from a source rock low in clay minerals. However, some caution needs to be exercised with this interpretation since relatively low concentrations of diasteranes may also reflect the oxicity of the depositional environment. Beach-stranded tars from the Seychelles were characterized by a variety of geochemical techniques, and a precursor source rock was characterized. It was suggested by Plummer (F54) that the source rocks for these tars were extensively developed to the west and south of the Seychelles islands. Three wells in the Seychelles offshore have indicated the existence of four potential source rock intervals with the Mesozoic succession (F55). The source rocks were dominated by terrestrial organic matter, and although TOC values were generally good, potential hydrocarbon yields were generally only poor to fair. The youngest source rock was immature while the oldest was in the gas window. The Jurassic/Cretaceous source rocks lie within the oil window and may be responsible for at least some the beach-stranded tarballs described in the preceding paper and nonbiodegraded oils in the same reservoir. China/Japan. The possibility of coal as a source for oil has been discussed for many years. A study by He et al. (F56) of more than 300 coals from northwest China suggested subernite in the coal macerals is not a substantial oil-generating maceral. Wang and others (F57) described the organic petrological characteristics of carbonate source rocks from the Tarim, Ordos, and Sichuan Basin. Maceral, submaceral, and submicromaceral contents of the whole rock and kerogen concentrates were described and classified. Source rocks of the Futan Group located in the west margin of Cenozoic Xiamen-Penghu fault depression contain nearly 5000 m thick Tertiary deposits of terrestrial-neritic facies. It was noted that when the vitrinite reflectance of the source rock in the Futan Group reaches 0.3% Ro, the resinite and alginite contained in the source rocks may form light crude oil or natural gas. Simulation studies have been undertaken by Dai et al. (F58) to study hydrocarbon expulsion from coals in the Turpan-Hami Basin. It was concluded that geochromatography caused changes in the expelled oil to the extent that it was not possible to undertake correlations based on comparisons of oil and extract fingerprints. Dong (F59) characterized oils and source rocks from the Liaodong Gulf area but provided little in the way of data or information on the way in which the correlations were actually made. In the Tarim Basin, the Yakela convex block was studied extensively by Fu and Ling (F60). However, despite the fact that it would appear a significant amount of work was undertaken in this study, few specific details concerning generation, migration, and accumulation were provided. Sun and others (F61) have studied characteristics of biomarker assemblages and their significance in immature source rocks from the Eastern Depression of the Liaohe Basin in China. Numerous biomarkers characteristic of the input of terrestrial organic matter plus specific freshwater dinoflagellate input were described. Tricyclic terpanes found in Precambrian bituminous sandstones from the eastern

Yanshan region, North China, were proposed by Wang and Simoneit (F62) to be derived from microbial sources of organic material. Retene was found by Jiang and others (F63) in Precambrian and Lower Paleozoic marine sediments in the Lower Yangzte Valley area. There was no evidence for any higher plant material in the Sinian and Lower Paleozoic carbonate formations although it was still proposed that even in this situation the retene was still probably produced from abietic acid precursors. However, the authors did not propose an alternative source for these abietic precursors in the absence of higher plant precursors. A detailed study of the petroleum potential and history of the Yitong Basin, China, was reported by Chen and others (F64). The source rocks were mainly type IIb or III with abundant nonfluorescent amorphous organic matter. In the basin, it was proposed that oil generation began at 1900-2200 m and condensate was formed below 4000 m. In the Neogene Tsugaru basin, northern Honshu, Japan, 150 mudstones from seven transects were evaluated on the basis of organic-richness, organic maturity, and organic type. Ujiie (F65) was not able to identify an effective source rock but suggested that a possible source may exist off the west coast of Honshu and in the eastern part of the Tsugaru peninsula. The samples examined in this study were either too immature or if at sufficient levels of maturity for oil generation did not contain sufficient quantities of organic matter. Outcrop samples from the Middle Miocene Onnagawa diatomaceous sediments in the Aomori and Akita Prefectures in Japan were examined for the distribution of their major and minor elements. Watanabe et al. (F66) noted that good source rocks require an ample supply of biogenic materials, small level of dilution by terrigenous detritus, and anoxic bottom water conditions. It was observed that source facies developed in the central part of the basin which was kept stagnant by restricted circulation of the seawater. The Neogene sedimentary basins in the Akita and Niigata area of Japan were proposed to be typical of marine oil-producing sedimentary basins in Japan. Source rocks from the two basins were characterized geochemically by Suzuki and others (F67), and it was shown that the differences between the source rocks in these two basins result from differences in the oxic-anoxic conditions and primary productivity at the time of deposition, consumption of H2S by terrigenous iron at the sediment water interface, and the abundance of clay minerals which can act as catalysts for the isomerization of regular steranes to form diasteranes during diagenesis. The subsurface geology of the Onnagawa Formation in the Akita-Yamagata basin, Northern Honshu, Japan, was studied using well logs and geochemical data and it was observed that source rocks with lower γ-ray log values tended to have higher organic carbon contents. Reservoir rocks with low γ-ray values and high resistivity on the logs also had high potential as source rocks and occur mainly in the middle part of the Onnagawa Formation in areas where the formation is relatively thick and contains less amount of tuff. The geochemical characteristics of 31 Miocene through Eocene petroleum/seeps, an Eocene coal, and an Eocene resin from central Myanmar Basin system were studied by Curiale and others (F68), and it was proposed that variations in the oil characteristics are caused by varying levels of biodegradation superimposed upon a single genetic family of crude oils. Russia. Biomarkers in oils and source rocks from the Mesozoic sediments of the Jamal peninsula, West Siberia, were

analyzed and two possible source rocks revealed, namely, Jurassic and Lower Cretaceous (F69). On the basis of the biomarker data, it was concluded that the oils of the Jurassic-Cretaceous reservoirs were derived from Jurassic source rocks. Maturity levels of Devonian source rocks in the Buzuluk depression, Russia, were found to control the phase state and compositional variations of the hydrocarbons found in the region. A number of maturity parameters based on methyldibenzothiophenes were found to work well over a wide range of catagenesis and showed no reversal at advanced levels of thermal evolution and could be used to discriminate mature petroleums (F70). Oils from seven basins in Kazakhstan, Russia, were characterized by GC and GC/MS (F71). Variations in relative concentrations of sulfur compounds could be related to type of source material, and this observation was used to divide the oils into three groups on the basis of lithology, biomarker distributions and relative abundance of aromatic sulfur compounds. A total of 36 oils from the northern Timan-Pechora Basin were characterized geochemically by Requejo et al. (EF2) and divided into four groups. Two groups were distinguished on the basis of their sulfur content, a third on its alkane distributions, which closely resembled the classic Ordovician-sourced oils from other Paleozoic basins worldwide. The overall conclusion suggested that these Timan-Pechora oils were generated from Paleozoic carbonate or calcareous shale source rocks, at least one of which appears to be of Ordovician age. Margulis and others (F73) presented an overview on the oils and hydrocarbon source rocks of the Baltic syneclise. A number of different types of source rocks at different levels of maturity were proposed to be responsible for the oils and no single source could be identified. India. Pyrolysis studies were undertaken on 16 Paleogene rock samples containing type III organic matter from the Cambay Basin, India (F74). Kinetic parameters for hydrocarbon generation were obtained by mathematical optimization of pyrolysis curves, assuming a discrete distribution of activation energies with a constant preexponential function. Balan et al. (F75) studied the Krishna Godavari Basin in India to model the major hydrocarbon generation centers in the source rocks. Migration directions and possible accumulation locations in the reservoir units could also be identified using this model. Samples from selected wells in the Krishna-Godvari Basin and Cauvey and Andaman Basins, India, have been examined in an attempt to integrate palaeontological and geochemical parameters (F76). By using this combined approach, it was possible to establish a casual relationship between the paleobathymetry and organic matter enrichment and location of potential source rocks. In addition oil prone vs gas prone occurrences of source rocks could also be evaluated. Miocene sediments of the Patharia structure in Bangladesh were found to contain an abundance of alkanes indicative of higher plant contributions to the sediments (F77). Based on various biomarker parameters, it was proposed that these sediments were in an immature to early stage of thermal evolution. Australia/New Zealand. Luo and others (F78) have analyzed a number of oils from New Zealand, but despite advances in understanding conditions of oil accumulations in this area, several problems remain, including nature of the source materials and temperatures necessary for generation and expulsion. Geochemical characterization of the oils have suggested that the source rocks for the majority of the oils were deposited in terrestrial and paralic environments. Heavier crude oils form at Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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low levels of maturity, and lighter oils are probably formed from kerogen at greater depths rather than by fractionation of migrating oil. Armstrong and others (F79) reevaluated the present-day thermal state of the Taranaki Basin, New Zealand, and used these data to reconstruct complete thermal and petroleum generation and maturation histories for several areas within the basin. A geochemical appraisal of oil generation in the Taranaki Basin was presented by Killops et al. (F80). It was noted that most of the oils were source from terrestrial source materials, and it was possible to recognize varying contributions from source rocks within the Paleogene Kapuni Group and Late Cretaceous Pakawaau Group. The presence of bicadinanes, previously associated with angiosperms, in Jurassic sediments from the Eromanga Basin, Australia, has been suggested by Armanios et al. (F81) to indicate an early evolution of flowering plants in this particular basin. Geochemical tools for evaluating the Middle Proterozoic sediments of the McArthur Basin, Australia, have been discussed by Summons et al. (F82). Methylphenanthrene indexes, limitations of vitrinite reflectance, and pyrolysis analysis were discussed. HI and Tmax parameters were found to correlate with other maturation parameters but were not sufficiently sensitive, nor were they universally applicable for these old sediments. Taylor and others (F83) showed that, within these Middle Proterozoic sediments of the McArthur Basin, there was considerable variation in the nature of the depositional environment as manifested by variations in the C to S ratio and trace metal contents. However the source material was fairly uniform and appeared to be algaland H-rich. Most petroleum generation in the basin was proposed to have followed significant folding and faulting of the Roper Group. GC/IR/MS has also been used by Murray and others (F84) to study the isotopic composition of the n-alkanes for 29 late Cretaceous/Tertiary oils from SE Asia, China, Papua New Guinea, New Zealand, and the United States (Uinta Basin). Six kinds of depositional environments were observed, and it was proposed that the depositional setting was the primary control on the shape of the n-alkane isotopic profile. This in turn was probably related to bacterial reworking of higher plant material in certain environmental types and not others. Central and South America. Geochemical characteristics of lithofacies and organic facies in Cretaceous organic-rich source rocks from Trinidad, East Venezuelan Basin, have been described by Requejo and others (F85). A number of different organic facies could be recognized within the system on the basis of the biomarker distributions. Cerqueria and Ferreira (F86) noted that many of the oils in the productive offshore Campos Basin, Brazil, were biodegraded during the early stages of migration. However, since the source rocks are still generating oils in the basin, many reservoirs contain mixtures of degraded and nonbiodegraded oils in the same reservoir. A complete study of the geochemical source rock data for the Bolivian foothills and foreland (SubAndean Zone, Chaco, and Madre de Dios Basins) was undertaken by Moretti et al. (F87) in order to quantify the petroleum potential of the area. In addition to the classical mid-Devonian source rocks already described in the areas, a number of late Devonian and Late Cretaceous-early Permian Formation were also classified as possible source formations in the region on the basis of the geochemical data. Biodegradation can affect the validity of oil/ source rock correlation studies, and Jenisch et al. (F88) undertook laboratory simulation studies to investigate the possibility of microbial alteration of geomacromolecules in the oil. Various 84R


changes were observed, including the introduction of functional groups, such as ketones and hydroxyl groups, during the biodegradation process. Littke et al. (F89) examined deep sea sediments from the Chile continental margin and found that the organic matter in these wells have been influenced by high geothermal heat flows to the extent that they had generated hydrocarbons with a petroleum-like distribution at site 859. TECHNIQUES The evolution of the microstructure of shaley source rocks occurring during petroleum generation has been studied by smallangle neutron and X-ray scattering. A series of samples of increasing maturity was studied, and it was proposed that hydrocarbons were generated from the macerals and concentrated on grain boundaries. When the maturity reaches the oil generation window, the small grains crack and release oil into the microfractures, whereas the intergranular macerals produce oil and also wet the interface forming an oil-wet network of conduits for primary migration (F90). Kerogen maturity of the Neogene sediments in the Drmno depression (Kostolac, Serbia) has been studied by optical methods (vitrinite reflectance), by present day temperatures, and modeled using TTI models. The results have been used to reconstruct the geothermal history of the Drmno depression and to predict the position of potential source rocks and time of hydrocarbon generation (F91). Artificial maturation has been widely used in the past to study oil generation from immature source rocks and precursor-type materials. Kruge et al. (F92) undertook confined pyrolysis experiments on Botryococcus-related alginite and associated organic ground mass isolated from two torbanite samples. The alginite showed peak oil generation at 375 °C and the ground mass at 350 °C. It was proposed that such a multicomponent study of the torbanite components would provide an improved picture of oil generation from torbanites and related source rocks in sedimentary basins. Cheng and others (F93) noted that vitrinite-like macerals were widely distributed in highly overmature source rocks of the Lower Paleozoic in China. Thermal simulation experiments showed that these vitrinite-like macerals responded to heating in a manner similar to vitrinite and as such may be used as a possible maturity index for highly overmatured Lower Paleozoic source rocks. A qualitative and quantitative link between organically bound sulfur, and more specifically organic polysulfides, and the low-temperature evolution of soluble petroleum-like products was established by Nelson et al. (F94) on the basis of hydrous pyrolysis experiments using the Monterey Shale. Three different temperature ranges were noted where the type and amount of sulfur in the analyzed fractions underwent transformations. Reynolds and others (F95) also performed micropyrolysis experiments to determine laboratory pyrolysis kinetics. Results from the high S-content kerogens used suggested that laboratory decomposition kinetics of high-sulfur kerogens and, in particular, Monterey kerogens appear not to be governed by organic sulfur content alone. Reynolds and Burnham (F96) characterized shales and kerogen concentrates from the Green River, Rundle, Ohio, Draupne, and Phosphoria Formations using Pyromat II micropyrolysis. The shales and corresponding kerogens exhibited very similar kinetic parameters, suggesting that it may not always be necessary to isolate kerogen concentrates to derive valid kinetic parameters. Crighton and others (F97) presented a review on atomic spectrometry and its use in the analysis and characteriza-

tion of a wide variety of samples, including metals, chemicals, and advanced materials. Of particular importance to the current article is the discussion concerned with the use of ICPMS for oil-source rock correlations based on the presence of a wide range of elements in the oils and source rock extracts. Kowalewski et al. (F98) developed a chemical model of asphaltenes isolated from the Boscan crude oil, Venezuela, sourced from a marine source rock. The model is developed using various structure elucidation programs in conjunction with molecular simulation programs. It is proposed that only a few stable conformations are possible due to the high reticulation of the model of the asphaltene unit obtained. The use of supercritical fluid extraction to obtain source rock extracts has been discussed in a number of papers in recent years. In this paper, Shen et al. (F99) again make a comparison between the use of SFE and Soxhlet extraction for this purpose and the effects of adding 1% 2-propanol as an additive. Greenwood et al. (F100) have used a combination of laser desorption and electron impact to study a variety of source rocks. Data obtained directly from LD-EI without GC demonstrated that the technique provides a rapid method for characterization of preserved organic material in source rocks. Kuo (F101) combined SEM, digital image analysis, and fractal geostatistical analyses, and a renormalization algorithm was developed to determine the 3D geometrical properties defined as organic matter connectivity factor of hydrocarbon expulsion pathways in source rocks. The connectivity of the organic matter networks was affected by both the amount and distribution of organic matter in the source rocks. It was proposed that the method could be used to quantify geological models and average geological properties over a wide range of scales and, thereby, provide reliable geometric parameters for basin modeling using a numerical technique. 13C NMR is another technique that has been used extensively in the past to characterize insoluble organic matter in source rocks. In this paper, various macerals were analyzed in this manner and then the data from the individual macerals could be used to determine the oil or gas potential of different source rocks on the basis of their maceral composition. Li and others (F102) provided a general review discussing the advantages of whole rock analyses over conventional kerogen analyses in the study of terrestrial hydrocarbon source rocks. Qiu and others (E103) used ESR to study maturity of kerogens and mudstones as hydrocarbon source rocks. Paleoheat flows could be obtained from a single well although more wells are required to determine heat flow for the whole basin. SEM was used by Tricart (F104) to undertake X-ray mapping to characterize pore space, mineralogy, and texture. The transformation of smectite to illite has been used in many studies to determine the time at which source rocks became thermally mature enough to form oil and gas. Elliot and Matisoff (F105) recently evaluated three different models designed to model the kinetics of this transformation. A review on applications of TG/FT-IR to hydrocarbon fuels and resources has been prepared by Serio et al. (F106). TG/ FT-IR can provide information on the characteristics of adsorbent potential and combustion reactivity of solids as well as kinetic information for model validation or extrapolation. Borrego and others (F107) noted that the presence of mineral matter delays hydrocarbon generation from oil shales during thermal heating.

It was proposed that thermogravimetric analysis of the kerogen concentrates was in better agreement with the petrographic composition than results obtained by analyzing the raw oil shales. Additional problems were also observed, depending on the mineral type and the amount of hydrocarbon adsorption to the different minerals during the heating process. In a slightly different type of study, Bishop and Philp (F108) noted that a mechanism for amorphous kerogen formation could be proposed to occur via adsorption of organic material on mineral surfaces. Barker (F109) discussed a comparative study between vitirnite reflectance measurements made on whole rock vs dispersed organic matter concentrates. It was noted that measurements on whole rock samples are a few tenths of a percent lower and a slightly higher standard deviation. However, whole rock mounts were found to have the advantage in identification of first cycle vitirnite and differentiation of solid bitumen from vitrinite. Changes in the color of conodonts have long been used to assess thermal maturity, and in this paper, an attempt has been made to show a preliminary relationship between the spectral reflectance of conodonts to the conodont alteration index, the latter being somewhat of a subjective scale, and the in situ alteration temperature [Deaton et al. (F110)]. Swamay et al. (F111) have proposed a novel approach for the characterization of organic matter types in source rocks. The approach combines fluorescence techniques coupled with TAI values for maturation and superimposition of section maps of OM types, TOC, maturation, and paleoenvironments and has resulted in locating source potential of the basin in space and time. Ghiselli (F112) has described a method for separating and analyzing heavy hydrocarbons contained in source rocks. The method involves extraction of the sample with heated solvents, followed by evaporation and condensation of the solvent. Log responses to TOC contents in the Upper and Middle Velkerri Formation of the McArthur Basin have been discussed by Lin and Salisch (F113). The formation can be divided into three categories which showed significant differences in their well log properties. HI/OI plots prepared from inertinite-rich samples from the northwest shelf of Australia have been used to show that these samples contain significant amounts of oil-prone kerogens in source rocks previously evaluated as being gas prone, thus in turn upgrading the oil potential of the area [Horstman (F114)]. Alkylphenols in oils and source rock extracts have not been studied in detail previously but Ioppolo-Armanios et al. (F115) showed their distributions in crude oils to be dominated by orthoand para-substituted compounds. It was proposed on the basis of laboratory studies that alkylation of cresols can occur in the source rocks to produce alkylated phenols with distributions similar to those observed in crude oils. Bitumens are often retained by mineral matrices or kerogens during solvent extraction, and Yadav and Vig (F116) have analyzed a number of coals from sedimentary basins to study this retention behavior. Samples were extracted and mineral matrices dissolved, and then the samples were re-extracted to produced significant amounts of additional extract that had been weakly bound to the kerogen matrix. The quantity and composition of this so-called bitumen-2 was found to be dependent on the structure of the source rock kerogen and type of mineral matrix. Philp and Bishop (F117) reviewed many of the developments in both source rock and reservoir geochemistry, particularly the techniques available Analytical Chemistry, Vol. 69, No. 12, June 15, 1997

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for the characterization of the higher molecular weight hydrocarbons which are present in a wide variety of oils, not only those derived from sediments dominated by terrestrial source materials as previously proposed. Hughes and others (F118) examined 75 crude oils and 41 known source rocks and observed that the ratios of dibenzothiophene to phenanthrene and pristane to phytane could be used as indicators of depositional environments and lithology of petroleum source rocks. The classification scheme is based on the premise that these ratios reflect different Eh/ph regimes resulting from the significant microbial and chemical processes that occur during deposition and early diagenesis of sediments. GC/IR/MS was used in conjunction with sequential degradation techniques by Love and others (F119) to show that significant isotopic fractionation occurs between aliphatic constituents in the free bitumen vs those covalently bound into the kerogen network. Isotopic similarities in the aliphatics released by pyrolysis was proposed to support selective preservation as an important mechanism in kerogen formation. Cliff T. Mansfield is currently a Technical Consultant in Product Quality Assurance at Texaco Fuels and Lubricants Technology Division. Prior to this year, he was Manager of the Analytical Chemistry Section at Texaco’s FLTD Laboratory at Port Arthur, TX. He received his B.S. degree in chemistry from Mississippi College, Clinton, MS, and his Ph.D. in analytical chemistry from the University of Florida, Gainesville, FL. He was Assistant Professor of Chemistry at Millsaps College from 1963 to 1967. In 1967, he joined the R&D Department at RJR Nabisco where he worked until 1987. From 1987 to 1989, he was a Postdoctoral Fellow at the School of Medicine, University of Alabama, Birmingham, AL. In 1989, he joined Texaco. Jane V. Thomas, analytical chemist and President of Wyoming Analytical Laboratories, Inc., has been working with coal analysis since her first job in the coal laboratory at the Illinois State Geological Survey in 1963. She has a B.S. degree in chemistry and in biology from Murray State University (1962, Murray, KY) and a Master’s degree in chemistry from the University of Wyoming (1971, Laramie, WY). She has been an active participant with ASTM Committee D-5 on Coal and Coke since 1974, serving as secretary for subcommittees dealing with trace element analysis and chairing task groups working toward accreditation standards. Anil K. Mehrotra is a professor in the Department of Chemical and Petroleum Engineering at the University of Calgary. His current research interests include transport and thermophysical properties and phase equilibria of heavy oils, bitumens, and paraffinic crude oils, asphaltene/ wax deposition kinetics, and soil remediation. He is a registered professional engineer with APEGGA and a member of CIC, CSChE, and AIChE. He received a B.E. in chemical engineering from B.I.T.S. (Pilani, India, 1972), an M.Eng. in environmental engineering from A.I.T. (Bangkok, Thailand, 1972), and a Ph.D. in chemical engineering from the University of Calgary (Calgary, Canada, 1980). Bhajendra N. Barman received his B.Sc. and M.Sc. degrees from Rajshahi University, Bangladesh, and a Ph.D. in analytical chemistry from Georgetown University, Washington, DC. His major areas of interest have been chromatography, field-flow fractionation, and spectroscopy. Before he joined Texaco in early 1991, he was an Assistant Professor at Rajshahi University, postdoctoral research associate with the late Professor J. Calvin Giddings at the University of Utah, and a staff scientist at FFFactionation, Inc. at Salt Lake City, UT. He is currently a Technical Coordinator at Texaco’s Fuels and Lubricants Technology Department at Port Arthur, TX. Richard Paul Philp is a professor of petroleum geochemistry in the School of Geology and Geophysics at the University of Oklahoma in Norman. He received his B.Sc. in chemistry from the University of Aberdeen, Scotland, and his Ph.D. in organic chemistry in 1972 from the University of Sydney, Australia. His research has been directed at the application of organic and analytical chemistry to fossil fuel research, in particular, determination of compounds known as biological markers present in oils, coals, and oil shales. A second area of research has been the characterization of source rocks, coals, and oil shales using microscale pyrolysis techniques combined directly with gas chromatography/mass spectrometry.

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