Anal. Chem. 1999, 71, 81R-107R
Petroleum and Coal Cliff T. Mansfield* and Bhajendra N. Barman*
Westholow Technology Center, Equilon Enterprises LLC, P.O. Box 1380, Houston, Texas 77251-1380 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 James M. McCann
12 Partners Road, Wappingers Falls, New York 12590 Spectroscopic Techniques
Review Contents Coal (Jane V. Thomas) Elemental Composition Ash and Fly Ash Analysis Spontaneous Combustion Environmental Concerns Weathering Instrumental Methods Petrography Liquefaction Reviews Crude Oil and Shale Oil (Anil K. Mehrotra)
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Hydrocarbon Identification and Characterization Reviews Gas Chromatography/Mass Spectrometry Other Analytical Techniques Trace Elements Reviews Trace Metals Sulfur Compounds Other Elements Asphaltene Precipitation and Characterization Physical and Thermodynamic Properties Rheology/Viscosity Waxy (Paraffinic) Crude Oils Water-Oil Emulsions/Suspensions Thermal/Gravimetric Analysis Miscellaneous Topics Heavy Oils (Natural and Refined) (Bhajendra N. Barman) General Reviews Chromatographic Techniques Gas Chromatography Liquid Chromatography Thin-Layer Chromatography Size Exclusion Chromatography Supercritical Fluid Chromatography Supercritical Fluid Extraction Miscellaneous Extraction and Precipitation Methods Multitechnique Separations
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10.1021/a1990010b CCC: $18.00 Published on Web 04/28/1999
© 1999 American Chemical Society
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Ultraviolet-Visible and Fluorescence Spectroscopy Infrared and Fourier Transform Infrared Spectroscopy Nuclear Magnetic Resonance X-ray, Neutron, and Light-Scattering Techniques Mass Spectrometry
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Thermal Techniques Miscellaneous Methods Modeling and Predictive Methods Microscopy Natural Gas and Refined Products (James M. McCann) Natural Gas and Natural Gas Liquids Sulfur Components
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Hydrocarbons and Gas Sensors Trace Contaminants Sampling and On-Line Analyzers Properties and Gas Measurement Gasoline Properties
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Infrared and Near-Infrared Spectroscopy NMR Spectroscopy Composition by Gas Chromatography and Mass Spectrometry Sulfur, Lead, and Other Elements Water Detection Middle Distillates Fuel Properties Hydrocarbon Composition Sulfur and Other Elements Jet and Aviation Fuels Fuel Properties Compositional Analysis Thermal and Oxidation Stability Lubricants (Cliff T. Mansfield) Base Oils Modeling NMR Chromatography and Spectroscopy
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Additives Separation and Analysis Surface Analysis Elastohydrodynamic Lubrication Reviews Films Solid Lubricants Finished Lubricants Oxidation/Thermal Analysis Metal Working Fluids Tags Power Transformer Oils Grease In-Service Lubricants Elements Water TAN/TBN Portable Instrumentation In-Line Sensors Real-Time Measurements Modeling Fuel Soot Deposits Literature Cited
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This review is divided into five 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. There is no section on source rocks in this review as has been the case in the past. COAL ELEMENTAL COMPOSITION Mastalerz and Hower (A1) analyzed Botryococcus-derived alginites from western Kentucky for elemental composition and functional group distribution using an electron microprobe and micro-FT-IR. The major differences between alginites were in the ratios of CH2 and CH3 groups, and ratios between aromatic bands in the out-of-plane region. These differences suggested that the ancient Botryococcus undergoes molecular and some elemental changes through the rank equivalent of vitrinite reflectance of 0.50.85%. However and other co-workers (A2) investigated the concentration and distribution of potentially hazardous elements in two eastern Kentucky coal beds, with emphasis on arsenic and lead. Most of the arsenic and lead appear to be associated with the pyrite, of which the coarser particles have the potential to be removed with beneficiation. Huggins and Huffman (A3) 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 spectroscopic method of determining elemental modes of occurrence complemented electron microscope or microprobe methods because it provides information on element forms dispersed in the organic fraction of coal as well as on the mineralogical forms of the element. Huggins and other collaborators (A4) examined the mode of occurrence of various elements in a Kentucky coal by XAFS spectroscopic characterization of the elements in float and tailings fractions generated by different flotation tests and chemical leaching methods on the finely ground 82R
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coal. The elemental concentrations in the same fractions were determined by particle-induced X-ray emission (PIXE) spectroscopy, and evidence was presented for arsenic as arsenate being incorporated in the major pyrite oxidation product, jarosite. The authors indicated a useful synergy in studies such as this because the more fractions examined by XAFS spectroscopy, the better the mode of occurrence is determined, and conversely, the better the mode of occurrence is determined, the better the behavior of elements in flotation and leaching tests can be explained. Bettinelli and others (A5) presented a method for the determination of arsenic, selenium, and mercury in coals based on a partial solublization of the coal sample in a microwave oven with aqua regia and the subsequent determination of As, Se, and Hg by flow injection hydride generation inductively coupled plasma mass spectrometry (FI-HG-ICPMS); comparisons with other techniques are presented. The fate and control of mercury emissions from coal-fired systems were investigated by Zygarlicke and Pavlish (A6), who looked at the transformation and control of mercury during the combustion of low-rank coal. Three North Dakota lignites and a Powder River Basin (Wyoming) coal were evaluated in bench- and pilot-scale tests. Tests indicated that the mercury in the coal is mostly associated with the pyrite, that it is partitioned about 90% into the gas phase, that the mercury is primarily in the oxide form, and that lime and lignite-activated carbon can reduce the mercury emissions. Palmer and Lyons (A7) isolated quartz, kaolinite, illite, and pyrite (the four most abundant minerals in Euroamerican coals) by density separation and handpicking from bituminous coal samples collected in the Ruhr Basin (Germany) and the Appalachian Basins and then determined the trace element concentrations in relatively pure fractions by instrumental neutron activation analysis. Their mass balance calculations indicated that the trace element content of coal can be explained primarily by three major minerals: pyrite, kaolinite, and illite. This leads to the conclusion that the size and textural relationships of these major coal minerals may be a more important consideration in coal cleaning and removal of the most environmentally sensitive trace elements than the trace elements present. In a study to determine the reasons for low material balances at eight coal-fired power plants, Devito and Carlson (A8) addressed the difficulties experienced in sampling and measuring selenium at these power plants. ASH AND FLY ASH ANALYSIS Borsaru et al. (A9) developed a lightweight (2 kg), hand-held coal-face ash analyzer, based on a backscattered γ-γ technique, and tested it at two coal mines. The primary source of radiation is a 1.8-MBq 133Ba γ-ray source, with another 0.35-MBq 137Cs γ-ray source used for gain stabilization. Hatt (A10) described the correlation of the slagging of a utility boiler with coal ash chemistry; the work demonstrated the need for more analytical data than just the routine ash fusion temperatures. Gibb (A11) reported on the 3.5-year collaborative research program designed to address all aspects of slagging in bituminous coal-fired boilers. The program employed full-scale plant programs, rig and laboratory-scale tests; coal, fly ash, and deposit characterization by computer-controlled SEM; and the development of computer models.
Alternative measurements of ash fusion temperatures based on shrinkage and electrical conductivity of heating samples were examined by Wall and others (A12) on laboratory ash prepared in crucibles at about 800 °C and on combustion ash sampled at power stations. Sensitive shrinkage measurements indicate temperatures of rapid change that correspond to the formation of liquid phases which can be identified on ternary phase diagrams. Hurst and colleagues (A13) employed a phase diagram approach to predict the melting temperatures of coal ash/flux mixtures and the viscosity vs temperature characteristics of the molten slags. They studied the fluxing action of calcium oxide on three Australian bituminous coal ashes covering a range of silica-toalumina ratios. This ultimately suggests that sensible estimates can be made of the amount of fluxing agent necessary for satisfactory slag tapping from the ash content and ash composition of the coal. Hower et al. (A14) used a combination of techniques to study the iron distribution among phases in high- and low-sulfur coal fly ash. Moessbauer spectroscopy, reflected-light optical microscopy, scanning electron microscopy, wet chemical analysis, and X-ray diffraction studies were conducted on six fly ash samples representing the combustion byproducts of coals with total sulfur contents of less than 2% to greater than 4%, and ranging from 17.6 to 32% Fe2O3 by XRF analysis. They found that the variation in the oxidation state of the iron follows the variation in the sulfur and, consequently the pyrite content of the coal.
used to calculate the release rates of natural radionuclides from the power plants.
SPONTANEOUS COMBUSTION Hull and co-workers (A15) investigated the role of oxygen and radiation on the spontaneous combustibility of a coal pile in confined storage. The importance of bed compaction in enhancing the safety of the coal pile was confirmed.
INSTRUMENTAL METHODS Padlo and co-workers (A23) developed a normal-phase highperformance liquid chromatography (HPLC) analytical method to separate coal-derived liquids into six compound classes: aliphatics, one-ring aromatics, two-ring aromatics, three-ring aromatics, four-ring aromatics, and polars. Three columns were used for the separation, a photodiode array detector was used for compound class identification, and an evaporative light-scattering detector was used for quantitative analysis of compounds with boiling points over 600 °F. The Argonne Premium coal samples were used by Winans and Tomczyk (A24) in their investigation of linkages between aromatic clusters and variations of these links with coal rank. They looked at extracts, model polymers, extracted coals, and modified coals with temperature-resolved high-resolution mass spectrometry and found evidence that strong bond cleavage may be very important for volatile release in pyrolysis of higher rank coals. Genetti and Fletcher (A25) developed a nonlinear correlation to predict the chemical structure parameters usually measured by 13C NMR and required for the compound model; the correlation worked well for determining total volatile yields for low- to high-rank coals. Xiong and Maciel (A26) investigated in situ variable-temperature high-resolution 1H NMR of coal samples between 25 and 230 °C based on combined rotation and multiple-pulse spectroscopy (CRAMPS) technique. This study provided detailed correlations of molecular dynamics with molecular structure for coals over the selected temperature range. Xiong and Maciel (A27) also used the CRAMPS technique to carry out a systematic in situ variable-temperature (25-180 °C) high-resolution proton NMR study of laboratory-frame and rotating-frame proton spin-lattice relaxation of coal samples.
ENVIRONMENTAL CONCERNS In a systematic investigation of the compositional variations in solid coal combustion waste products, Breit and 14 other collaborators (A16) determined the chemical and physical characteristics of feed coals and combustion waste solids from a coalburning power plant. They also determined the abundance and modes of occurrence of trace elements considered to be potentially hazardous air pollutants and application of the results in understanding of the behavior of the combustion wastes in disposal sites and the potential of the wastes for beneficial use. The measurement of organic air toxic emissions from coal firing was discussed by Nsakala and others (A17). Data from this study were used to determine whether air toxic emissions regulations for fossil fuel-fired electric utilities are necessary. In a study of the effect of atmospheric emissions from coal-fired power plants, Flores and Martins (A18) collected egg samples from unconfined hens over a 2-year period near two major power plants in the state of Rio Grande do Sul, Brazil. Cadmium, lead, and fluoride concentrations were determined in the yolks, albumen, and shells. A comparison with reference materials indicated that the yolks were enriched in cadmium and lead, and fluoride was preferentially concentrated in the shell. Antic et al. (A19) studied the radiation exposure to the public in the vicinity of selected coal-fired power plants near Belgrade. The contents of uranium, thorium, and potassium in the coals were
WEATHERING Surface areas, pore volumes, and surface chemical structures of eight coals in the Illinois Basin Coal Sample Program were determined by Demir and others (A20) before and after exposing them to air oxidization under ambient conditions for 2 months. They noticed 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. The surface areas of all coals but one increased after exposure to air for 2 months; however, the diffuse reflectance IR spectroscopy signals of the coals did not changesindicating that the surfaces of the eight coals contained similar hydrocarbon functional groups. Twenty-three British, one Spanish, and five American coals were analyzed by McCarthy and others (A21) for their total sulfate content and the ratio of 18O and 16O isotopes in the sulfate. The isotopic data covered a wide range of values, and the coals with higher sulfate contents showed some tendency toward more 18Odepleted values. Weathering of stockpiled coals and the resulting loss of calorific value were studied by Miranda et al. (A22). They investigated the roles of the most important variables in the oxidation and spontaneous heating processes, quality/reactivity of the coal, characteristics of the stockpile, and climatological conditions.
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Anderson and co-workers (A28) investigated the porous structure of coal using 129Xe NMR with selective low-power presaturation and saturation transfer; this technique can be used to investigate pore connectivity in microporous materials of unknown pore structure. PETROGRAPHY Hower and Calder (A29) examined fractions from the Hardgrove grindability index test (ASTM D-409), analyzing them petrographically by a combined maceral/macrolithotype analysis. Padgett and Hower (A30) studied the Hardgrove grindability of Powder River Basin and Appalacian coal components in five coals representing four distinct coal sources blended at a midwestern power station. Hower and Trimble (A31) reported on the petrography and chemistry of sized fly ash from low-sulfur and highsulfur feed coals at a Kentucky power station. Sakuros (A32) presented a method for identifying interactions between coals in blends. The method assumes that the magnitude of the effect of an interaction between two coals in a blend of many coals is proportional to the product of the proportion of the two coals in the blend. Sakuros (A33) also presented direct evidence that the thermometric properties of blends are modified by interactions between the component coals. For an alternative to microscope-based petrographic analysis, Burragato et al. (A34) proposed a diffractometric method which characterizes coal as a “heterogeneous system”. A high-volatile bituminous coal was chemically and petrographically characterized and then demineralized and separated by density into its main organic fractions. The coal and the fractions were examined by energy-dispersive X-ray diffraction analysis, to which the radial distribution function was subsequently applied. LIQUEFACTION Burke and Winschel (A35) discussed the roles a processderived recycle oil can play as a vehicle to convey coal into the reactor, a medium for mass and heat transfer among reactants, and as a reactant itself. In addition to a short history and discussion of the development and importance of process oils in different coal liquefaction processes, they discussed current research trends to replace supported-catalyst systems with dispersed catalysts offering high selectivity and reactivity while avoiding capital costs and to incorporate solvent-mediated reactions as a part of a strategy to reduce process costs. Burke and other collaboators (A36) discussed recent advances and future prospects for direct coal liquefaction process development. Chadha and co-workers (A37) studied the activity of various ferric sulfide-based catalysts in model hydrogenation and cracking reactions under conditions typical of direct coal liquefaction; the performance of the catalysts was found to vary with the type of reaction, the initial ratio of nonstoichiometric FeSx to FeX2 (pyrrhotite to pyrite) found in the catalyst, and the catalyst age. REVIEWS Winkin and Garcia-Mallol (A38) reviewed anthracite firing in large utility arch-fired boilers (8 references). In a review with 23 references, Whaley (A39) discussed the development of low-NOx burners under the International Energy Agency coal combustion sciences agreement. Measures used to tackle environmental problems related to global warming and climate change were 84R
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discussed in a review with 8 references by Hoppe (A40). The release of nitrogen oxides during the combustion of chars is considered in relation to coal and char structural characteristics in a review with 104 references by Thomas (A41). The results available in the literature relating nitrogen oxide emissions to coal and char properties are discussed in terms of the mechanisms for production of nitrogen oxides and their reduction in the pores or on the surface of the char. Bonnett (A42) discussed recent developments in investigations of porphyrins in coal in a review with 43 references. The mercuryselenium interactions in the environment were discussed in a review with 44 references by Saroff and others (A43). Topics included health effects of both mercury and selenium, emissions and physical properties of mercury and selenium from coal combustion, and Hg-Se interactions. Lewitt and Lowe (A44) presented an overview of the principles, capabilities, and applications of proton magnetic resonance thermal analysis in a review with 21 references; potential applications of this technique are suggested. Diwekar and others (A45) describe recent developments in ongoing research to develop and demonstrate advanced computerbased methods for dealing with uncertainties that are critical to the design of advanced coal-based power systems. Laurila and Kehoe (A46) reviewed on-line monitoring of coal feedstock quality and its effect on boiler efficiency, discussing recent technological advances, on-line analytical capabilities, applications, and advantages of being able to monitor coal quality on-line. Process and quality control in coal preparation plants using on-line measuring devices were discussed in a review with 13 references by Bachmann (A47). Topics included current stateof-the-art and modern units, multichannel and bypass analyzers, variations in material composition, use of natural γ radiation, elemental analysis, and calibration. 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 elements; asphaltene precipitation and characterization; physical and thermodynamic properties; thermal/gravimetric analysis; and miscellaneous topics. Also included are nine review articles on various topics related to crude oil and shale oil that were published during the 1997-1998 review period. Compared to 139 references in the previous review on this topic (B1), this year’s review includes 100 references. HYDROCARBON IDENTIFICATION AND CHARACTERIZATION Reviews. Miknis presented a review with 128 references in the area of solid-state nuclear magnetic resonance (NMR) and its applications in oil shale research (B2). Long and Speight presented a review with a number of references on petroleum components and their analysis (B3). Speight reviewed the methods for characterization of petroleum feedstocks and products (B4). Leontaritis presented a review with 26 references on PARA (paraffin-aromatic-resin-asphaltene) characterization of crude oils (B5). Gas Chromatography/Mass Spectrometry (GC/MS). Zhang et al. analyzed carbazole-type compounds in different types of
Chinese crude oils by use of GC and GC/MS (B6). Barakat et al. examined the distribution patterns of methyl homologues of naphthalene and phenanthrene in Egyptian crude oils using GC and GC/MS (B7). Warton et al. analyzed T-branched (monoalkyl) alkanes in crude oils by comparing their mass spectra and GC retention behavior results with those for synthesized reference compounds (B8). Li et al. used supercritical CO2 extraction followed by GC/MS analysis to study C6-C14 hydrocarbons in shale (and coal) samples (B9). El-Sabagh et al. reported the use of gas and liquid chromatography and NMR spectroscopy to characterize Arabian Gulf crude oils (B10). Fisher et al. described the application of GC/FT-IR as a complementary technique to GC/MS in the analysis of three coeluting dimethylphenanthrene (DMP) isomers (B11). Bastow et al. identified isodihydro-ar-curcumene in petroleum using GC/ MS by comparing its retention and mass spectrum with the same parameters from a reference compound (B12). Other Analytical Techniques. Varotsis and Pasadakis outlined an analytical method based on utilizing the HPLC/SEC size exclusion chromatography (SEC) fingerprints of crude oils derived from UV-DAD and IR detectors (B13). Herod et al. described experiments with matrix-assisted laser desorption/ionization timeof-flight mass spectrometry (MALDI-TOF-MS) for the characterization of fossil fuels and related materials, including kerogens (B14). The trends in the MALDI spectra agreed with those from SEC and UV fluorescence (UV-F) spectroscopy. Bastow et al. carried out a study involving the synthesis, characterization, and identification of isomeric pentamethylnaphthalenes (PMNs) in a number of crude oils (B15). Midttun et al. used diffuse reflectance FT-IR spectroscopy (DRIFT) to conduct a multivariate study of interfacially active resin fractions separated from crude oils (B16). Ovalles et al. isolated acid, base, and neutral fractions of Cerro Negro crude oil using ion-exchange chromatography, and characterized the fractions by spectroscopic methods (FT-IR, 1H NMR, 13C NMR), interfacial measurements, titration with KOH, and molecular weight measurements using vapor pressure osmometry (VPO) (B17). Carbognani developed methodologies based on SEC-evaporative light-scattering detection for rapid (7-20 min) monitoring of C20-C160 alkanes from crude oil deposits and asphalts (B18). Bharati et al. described the steps involved in preparing a standard (by remixing different fractions of a North Sea deasphaltened oil) for the calibration of thin-layer chromatography with flame ionization detection (TLC-FID) using Iatroscan that was employed for routine crude oil analysis (B19). Stasiuk and Snowdon recorded the fluorescence spectra of Canadian crude oils, which were synthesized as hydrocarbon fluid inclusions (HCFI) in NaCl crystals and correlated them with chemical analysis (B20). Melikhov et al. analyzed three Russian crude oils for the molecular weight distribution of olefinic compounds, and the measurements using 1H NMR showed that the olefin content within narrow distillate fractions increased linearly with the molecular weight (B21). Audino et al. identified 13 of the possible 14 isomeric ethylmethylnaphthalenes (EMNs) in crude oils using a combination of GC/MS, GC/FT-IR, and molecular sieving techniques (B22). Kabir et al. compared TLC-FID, liquid chromatography (LC), and TLC techniques for the analysis of crude
oil and condensate samples, and they found that the TLC-FID technique yielded more reliable data for low-molecular-weight organic compounds (B23). Sanchez et al. described a simple, rapid, and automated method for the determination of phenols in crude oils using HPLC with electrochemical detection (B24). Ralston et al. measured fluorescence quantum yields of crude oils and their dilute solutions for visible and UV excitation in the long-wavelength visible and the near-infrared (NIR) (B25). Bennett et al. described three methods for the isolation and determination of C0-C3 alkylphenols from crude oils (B26). The alkylphenol analysis involved reversed-phase (RP-) HPLC combined with oxidative electrochemical detection (ED), or by GC-FID and GC/ MS after chemical derivatization. A direct alkali extraction RPHPLC/ED approach was also described. Lee et al. identified the unusual presence of polymethylene in Stuart oil shale kerogen from Australia by NMR spectroscopy and X-ray diffraction (B27). Gillaizeau et al. examined the kerogens of Turkish oil shale by SEM and transmission electron microscopy, spectroscopy (FT-IR, solid-state 13C NMR), and pyrolysis (B28). TRACE ELEMENTS Reviews. Lobifiskia and Adams presented a review with 237 references on the topic of species-selective analysis by GC with plasma source spectrometric detection for organometallic and organometalloid compounds (B29). Various plasmas (inductively coupled, microwave induced, capacitatively coupled, dc and ac plasmas) were characterized and critically compared as sources of radiation (for AES) and ions (for MS). In a review with 125 references, Smagunova et al. identified X-ray spectrometry to be an efficient technique for elemental analysis of organic materials (B30). Solodukhin presented a review with 16 references on the use of nuclear-physical methods, including AA, XRF, and AESICP, for elemental analysis of crude and shale oils (B31). Trace Metals. Massoumi and Tavallali demonstrated the application of a sensitive kinetic spectrophotometric method, involving the indigo carmine-bromate reaction, for the determination of vanadium in crude oils (B32). For determining the concentrations of nickel and vanadium in crude oils, Molinero and Castillo performed ICP-AES measurements on prepared oil-inwater emulsions (B33). Verdizade and Kuliev reported that the presence of aminophenols provides improvements in the extraction and photometric determination of V(IV) in crude oils (B34). Lanjwani et al. developed a method for the simultaneous formation and solvent extraction of Co(II), Cu(II), Fe(II), and V(IV) complexes of H2APM2en from crude oils and their detection by eluting from a reversed-phase HPLC at 260 nm (B35). Khuhawar et al. reported a method for the determination of V(IV) in crude oils using fluorinated ketoamines as derivatizing reagents and capillary GC for separating the oxovanadium(IV) complexes of four tetradentate ligands from their Cu(II), Ni(II), and Pd(II) complexes (B36). Robert and Spinks developed a micellar electrokinetic capillary chromatography (MECC) technique for the separation of petroporphyrin compounds, including Ni(II) and V(IV)O etio-I- and octaethyl-type porphyrins (B37). They suggested that the MECC technique, while offering several advantages over HPLC, might prove to be extremely useful for metal speciation when coupled Analytical Chemistry, Vol. 71, No. 12, June 15, 1999
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to an ICPMS detection system. Huseby et al. subjected samples of pre-extracted oil shale to hydrous pyrolysis at 225-350 °C, and the released porphyrins were analyzed using HPLC, and UVvisible, MS, and NMR spectroscopy (B38). El-Sabagh described a scheme for separating, identifying, and characterizing vanadyl porphyrins from the residual fractions of Saudi Arabian crude oils (B39). Rosell-Mele et al. described a method for HPLC/MS analysis of porphyrin mixtures using an atmospheric pressure interface, which can operate in two modes, pneumatically assisted electrospray and atmospheric pressure chemical ionization (APCI), with the most effective results obtained from the latter mode (B40). Zujovic et al. studied the influence of kerogen depyritization on NMR relaxation parameters from measurements on Aleksinac oil shale kerogen based on the parallel proton and crosspolarization magic-angle spinning (CPMAS) NMR relaxation technique (B41). Sulfur Compounds. Imashev et al. studied thiophene sulfur oxides in light fractions of west Siberian crude oils by use of resonance electron capture negative-ion mass spectrometry (RECNI-MS) in combination with low-voltage positive-ion mass spectrometry (PI-MS) (B42). In a followup paper, Imashev and coworkers applied the same technique to investigate the structure of (poly)sulfides in crude oils (B43). Schmid and Andersson tested three NIST standard reference materials (SRM), 1597 coal tar, 1582 crude oil, and 1580 shale oil, for determining the concentration and the coelution of polycyclic aromatic sulfur heterocycles using GC-AED (B44). Shen et al. developed a new GC-AED technique for the analysis and identification of organosulfur compounds in crude and light oils (B45). Peng et al. isolated pentacyclic lanostane sulfides from an immature Chinese crude oil using oxidation (with tetra-n-butylammonium periodate), reduction (with LiAlH4), and thiourea adduction and molecular distribution (B46). The position of the sulfide bridges was assigned by deuterium exchange and mass spectra of the corresponding sulfones. A GC method was described by Galdiga and Greibrokk for the simultaneous determination of trace amounts of sulfur hexafluoride (SF6) and cyclic perfluorocarbons (B47). Chakhmakhchev et al. analyzed the distribution of aromatic sulfur compounds (i.e., alkylated dibenzothiophenes) in aromatic fractions of 64 oil condensate samples using GC/FPD and GC/MS (B48). Mitra-Kirtley et al. separated the asphaltene, resin, and maltene fractions of crude oils to determine the chemical structures of sulfur compounds in each fraction (with thiophene, sulfide, and sulfoxide being the major ones) using X-ray absorption near-edge structure (XANES) spectroscopy (B49). Other Elements. Cam et al. reported multielement analysis of Saudi Arabian crude oils by a 14.6-MeV neutron activation technique (B50). Merdrignac et al. compared three techniques (liquid-solid extraction, liquid-liquid extraction, and deprotonation with a strong base followed by liquid-liquid extraction) for separating nitrogen compounds in crude oils (B51). Garwan et al. presented a preliminary study on the analysis of trace elements in crude oils using µ-PIXE (B52). 86R
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ASPHALTENE PRECIPITATION AND CHARACTERIZATION Hammami et al. used HPLC and TLC Iatroscan to characterize the saturate, aromatic, resin, and asphaltene fractions of an asphaltenic tank oil from the North Sea (B53). They also reported results for the onset of asphaltene precipitation with n-C5 at 25 °C and 690 kPa. Andersen et al. carried out an experimental investigation for the precipitation of asphaltenes from crude oil mixed with n-C7 at 40-200 °C and high pressure (B54). The precipitated asphaltenes were separated by filtration and analyzed using FT-IR, while the maltene-diluent filtrate was analyzed using GC. Wilt et al. described a faster method for quantitative determination of asphaltene content in crude oils by use of FT-IR spectroscopy (B55). Buckley et al. reported the use of refractive index measurement for detecting the onset of asphaltene precipitation from mixtures of crude oils and solvents/precipitants (B56). PHYSICAL AND THERMODYNAMIC PROPERTIES Friiso et al. reported the details of a new crude oil characterization method based on dielectric spectroscopy, which could be used for the determination of viscosity and interfacial properties (B57). Avaullee et al. presented a method for calculating the physical properties of crude oils from either the true boiling point distribution or an advanced chromatographic analysis (B58). The method, involving up to two parameters, was tested on a large database with more than 50 samples. A calculation method, based on the mean-field lattice-gas model, was proposed by Koch et al. for vapor-liquid equilibrium involving crude oils (B59). Maples proposed a simple correlation between volume midpercent and other properties (such as gravity and sulfur content) of true boiling point cuts or blends (B60). Daridon et al. performed ultrasonic speed measurements (under pressure) to characterize crude oils for predicting thermophysical properties (B61). Amin and Smith measured and correlated the interfacial tension (IFT) and spreading factor (as well as viscosity and density) of crude oil systems at pressures up to 26 MPa (B62). Mughal and Ahmad reported dielectric conductivity, free space attenuation, absorption coefficient, and refractive index for Pakistani petroleum samples (B63). Rheology/Viscosity. Burg et al. proposed a new classification for crude oils based on polarity in chromatography and on group composition (B64). Also reported were the five parameters in Abraham’s linear solvation energy relationship (LSER) equation to characterize 47 crude oils. In a subsequent paper, they presented an approach for predicting the kinematic viscosity of crude oils using the LSER equation along with GC data (B65). Selves et al. developed a calculation method for crude oil transport properties, which is based on characterizing the solvents in terms of their interactions with solutes and employing the LSER equation (B66). Secerov et al. studied the rheological properties of crude oils at 20-45 °C in terms of the effects of shear stress, shear rate, and pulsed electromagnetic fields (8-60 Hz) on viscosity (B67). Guo et al. developed a viscosity calculation method, based on equations of state, for hydrocarbon mixtures (including crude oils), which uses the similarity between the pressure-volume-temperature (P-V-T) and temperature-viscosity-pressure (T-µP) relationships (B68). Wakabayashi reported a correlation for the kinematic viscosity of crude oils and fractions in terms of specific gravity and molecular weight (B69). Miadonye and
Puttagunta developed a viscosity-temperature correlation for Nigerian crude oils (B70). Waxy (Paraffinic) Crude Oils. Philp et al. evaluated the use of high-temperature GC for the characterization of C40+ waxes in petroleum and asphaltene fractions (B71). Ferworn et al. described an experimental study for the effect of solvents on controlling wax deposition from three different crude oils (B72). Cross-polarization microscopy (CPM) and mechanical spectrometry (RMS 800) techniques were used for the paraffin crystal habit and/or morphology, the wax dissolution temperature (WDT), and the pour point. Ruffier-Meray et al. developed a low-resolution pulsed NMR spectroscopy method for quantifying the crystallized fraction of waxy crude oils as a function of temperature below their wax appearance temperature (WAT) (B73). Chang et al. used a controlled stress rheometer to study the yielding of statically cooled waxy crude oils by means of a controlled stress test, a creep-recovery test, and an oscillatory test (B74). El-Gamal and Gad measured and correlated the lowtemperature flow properties and rheological parameters of treated and untreated Umbarka waxy crude oil (B75). Pan et al. measured the cloud point temperature (CPT) and wax precipitation at liveoil conditions for four waxy crude oils (B76). The data and model predictions showed that the CPT increases with pressure and decreases upon dilution with C1-C7. Adewusi presented a mathematical model for the wax deposition potential, requiring as input the crude oil viscosity-pressure-temperature data (B77). Secerov et al. measured the density of crude oils, with the pour point ranging from -30 to +38 °C, by use of low-frequency pulsed electromagnetic field (PEMF) (B78). Water-Oil Emulsions/Suspensions. Sjoeblom et al. presented a review with 40 references on colloidal chemistry related to water-oil emulsions in offshore crude oil production and transportation, including spectroscopic techniques applied to characterize the emulsified systems (B79). Harpur et al. reported the influence of a 50-Hz sinusoidal electrical field on the destabilization of water-in-oil emulsions under flowing conditions (B80). Also studied was the coalescence of water droplets by image analysis using an image processor. Bailes et al. developed an in-line coalescing apparatus based on a pulsed dc electrical field for promoting electrical induced droplet coalescence from water-in-oil emulsions (B81). Bhardwaj and Hartland measured dynamic IFT and dilational modulus of water-inoil emulsions using a microprocessor-controlled drop-volume IFT measurement apparatus and microvideography (B82). Laux et al. investigated the influence of different factors on the stability of colloid disperse crude oil systems by determining the flocculation point (B83). Mouraille et al. tested the stability of water-in-oil emulsions by means of separation/sedimentation and high-voltage stabilization tests (B84). They also analyzed the role of naturally occurring waxes and/or asphaltenes on the emulsion stability. THERMAL/GRAVIMETRIC ANALYSIS Berkovich et al. used TG/DTA and differential scanning calorimetry (DSC) techniques for thermal analysis of Australian oil shales (B85). In a subsequent paper, they reported enthalpy change and mass loss of oil shales at temperatures relevant for the drying/preheating and retorting applications (B86). Yue and
Watkinson used the thermogravimetric analysis (TGA) technique to study the kinetics of thermal pyrolysis of petroleum pitches from two upgrading processes (B87). Skala et al. investigated the pyrolysis and oxidation of oil shale kerogen concentrates using DSC and TG analysis (B88). Dogan and Uysal used the TGA technique to determine the overall pyrolysis kinetics of three Turkish oil shales (B89). Koek et al. reported improved oxidation kinetics data on Turkish crude oils when the SARA fractions were tested individually using thermogravimetric (TG/DTG) analysis (B90). Karacan and Kok investigated the pyrolysis behavior of crude oils and their fractions using DSC and thermogravimetry (B91). In a related study, Kok and Okandan developed a weighted-mean activation energy approach for use in TG/DTG kinetic analysis of crude oils (B92). MISCELLANEOUS TOPICS Hsu et al. reported that, of the MS techniques evaluated for the characterization of naphthenic acids, a method based on negative-ion atmospheric pressure chemical ionization using acetonitrile as a solvent and mobile phase gave the cleanest spectra (B93). Smirnov and Frolov described a precision 1H NMR spectroscopy method for the proton chemical shift calculations of petroleum methylcarbazoles (B94). Rolfes and Andersson outlined a method for the derivatization of phenols and alcohols with ferrocenecarboxylic acid chloride to the corresponding esters, which were separated by capillary GC and detected by atomic emission in the iron-selective mode (B95). Reiss et al. identified several series of hopanoid triterpenes by the synthesis of actual compounds; the hopanoid triterpenes were formed by oxidation of Messel shale kerogen using RuO4 (B96). Vayisoglu et al. carried out room-temperature extraction of two Turkish oil shales with a mixture of N-methylpyrrolidone and CS2 and analyzed the extractants by chromatography and spectroscopy (B97). Fisher et al. employed laser-ablation Fourier transform ion cyclotron resonance mass spectrometry, FT-IR, and solid-state 13C NMR techniques to study oil shales to confirm their usefulness as fullerene precursors (B98). In studying the kinetics of petroleum generation and cracking of Toarcian shales by programmed-temperature closed-system pyrolysis, Dieckmann et al. used single-step on-line GC for analyzing all pyrolysates (B99). Rose et al. used IR emission spectroscopy to monitor chemical modifications during the oxidation of different samples of Australian oil shales (B100). HEAVY OILS (NATURAL AND REFINED) Analytical methodologies applied as well as developed within the last two years for the characterization of heavy oils and related products are covered in this section. The discussion is focused primarily on three major analytical areas: chromatography, spectroscopy and thermal techniques. GENERAL REVIEWS Since the publication of the last application review (C1), there have been some surveys on analytical techniques that relate to the analyses of high-boiling heavy oils and related materials. Fundamental reviews covering recent developments and selected applications of major analytical methods such as SEC (C2), planar chromatography (C3), and supercritical fluid chromatography Analytical Chemistry, Vol. 71, No. 12, June 15, 1999
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(SFC) (C4) appeared in Analytical Chemistry. A book was published in 1998 dealing with composition, analysis, and refining processes of petroleum and related products that include crude oils, heavy oil fractions, and asphalts (C5). A review with 132 references on the analysis of petroleum hydrocarbons in oils, petroleum products, and oil-spill-related environmental samples highlighted methodologies used for chemical fingerprinting by GC to determine the source of an oil spill, degree of weathering, and biodegradation (C6). Separation techniques utilizing coupled chromatographic systems such as GC/GC, SEC/GC, and LC/ LC/GC were surveyed and were shown to be very effective for the analysis of complex petroleum fractions including heavy oils (C7). CHROMATOGRAPHIC TECHNIQUES Gas Chromatography. High-temperature GC simulated distillation has been applied widely for the characterization of heavy oil fractions (C8-C14). The coupling of simulated distillation with MS provided boiling range distributions as well as hydrocarbon type distributions of products obtained by hydroconversion of a deasphalted oil (C8). Catalytic upgrading of atmospheric and vacuum residues was monitored by hightemperature simulated distillation (C9, C14). Hydroprocessed vacuum residues were subjected to simulated distillation, simulated distillation coupled with MS, and other techniques including UV spectroscopy, 13C NMR spectrometry, TLC/FID and VPO (C13). Simulated distillation revealed a bimodal distribution of n-paraffins in sludge wax from a crude oil storage tank. The paraffins with even carbon number homologues between C56 and C66 were present at a higher ratio (C10). Wax samples were also characterized by high-temperature GC to correlate GC data with various physical properties such as needle penetration, refractive index, melting point, and kinematic viscosity (C11). GC/MS was found to be useful for the differentiation of similar viscosity grade white mineral oils obtained by different processes (C15). Wax separated from blown bitumens and straight-run bitumens were examined by GC/MS, and it was found that these wax samples contain n-alkanes of carbon number ranging from C21 to C39 . It was also found that wax from blown bitumens is composed of n-alkanes with longer chains as compared to that from straight-run bitumens (C16). Polycyclic aromatic hydrocarbons (PAHs) and fused-ring heterocyclic compounds (FHCs) from coal tar pitch, ranging from C12 to C45, were analyzed by a combination of mass spectroscopic methods. Semivolatile PAHs and FHCs were analyzed by GC/MS. Nonvolatiles, heavier PAHs, and FHCs up to C45 in coal tar pitch were analyzed by liquid ionization MS (LI-MS) by detecting their MH+ ions. Methanol was added to the ion source and was found to be effective to distinguish between PAHs and FHCs. Most LI-MS spectral peaks were identified by the molecular map constructed on the basis of the regularity of the increment of molecular weights that can be observed by adding six-membered rings to the known PAHs and FHCs (C17). Many linear, branched, and naphthenic compounds from the saturated fractions of asphalts (derived from vacuum residues), weathered asphalts, and their parent crude petroleums were identified by GC/MS. Hopanes, norhopanes, and steranes were selected to characterize and differentiate aliphatic structures of original and weathered asphalts as well as their parent crude 88R
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oils (C18). GC/MS was used as a tool to identify reaction intermediates in an effort to develop a mechanistic picture of the hydrodemetallization reaction of vanadyl and nickel tetraphenylporphyrins (C19). GC with atomic emission detection (GC-AED) and LC/field ionization mass spectrometry were used to assess relative desulfurization reactivity of thiophenes in vacuum gas oils (C20). GCAED, in the carbon- and sulfur-selective modes, was also used to determine the concentrations of polycyclic aromatic sulfur heterocycles in three standard reference materials: SRMs 1597 coal tar, 1582 crude oil, and 1580 shale oil, supplied by National Institute of Standards and Technology (C21). High-resolution GC-sulfur chemiluminescence detection (SCD) was used to obtain retention data for about 165 sulfur compounds. These data were used for the identification of individual sulfur compounds in a sample of straight-run gas oil. From the total sulfur determined by the Coulomax method and the sum of individual sulfur compounds determined by GC-SCD, the concentration of different sulfur compounds in straight-run gas oil was obtained (C22). Pyrolysis GC (Py-GC) has been applied to unravel structures of many heavy oil products including asphaltenes and coal tars. An increase in the pyrolysis temperature from 300 to 500 °C was found to cause the cracking of aliphatic hydrocarbons. High yields of pyrolysis products, as revealed by GC/MS, can be obtained at temperature above 359 °C (C23). Based on a kerogen-generated hydrocarbon model, a new method to calculate hydrocarbon yields for coals and related samples was put forward by means of pyrolysis techniques. It was suggested that the relative compositions of the three ranges of C1-C5 total hydrocarbons, C6-C14 n-alkanes plus n-alkenes, and C15+ n-alkanes plus n-alkenes from pyrolysates can be effectively used to distinguish the coalgenerated hydrocarbons types (C24). Eight coals from peat to anthracite were investigated by Py-GC and pyrolysis Fourier transform infrared (Py-FT-IR) to rank them according to polymerized carbon compounds in the tar (C25). The effects of reaction conditions on the yields and compositions of products from secondary pyrolysis of coal tar carried out with a flow reactor at 700-900 °C for 5-22 s were investigated. The variations in the compositions of light fractions obtained by solvent extraction of pyrolysates were observed by glass capillary column GC with flame ionization detection (C26). The thermal decomposition behavior and molecular structure of asphaltenes were studied by thermogravimetry (C27) and Py-GC/MS (C27, C28). Liquid Chromatography. Open-column liquid chromatography was applied for rapid fractionation of sediment, rock, and coal extracts as well as crude oils into compound classes based on combined polarity and affinity chromatography of soluble organic matters. Five well-defined heterocompound fractions were obtained in addition to the saturated and aromatic hydrocarbon fractions (C29). Sulfur aromatics and sulfur-containing PAHs from a PAH fraction (preseparated from a vacuum petroleum distillate) were separated by complexation chromatography using silica gel with 5% PdCl2 and a mixture of n-hexane and chloroform as a mobile phase (C30). Vacuum gas oils derived from crude oils of diverse API gravities were separated into acids and bases by anionand cation-exchange resins. Neutral nitrogenous compounds were also removed by using ferric chloride on cellulose. Saturates were
separated from aromatics by silica-alumina gel chromatography. The separated fractions were subjected to NMR analyses to elucidate average molecular parameters and average molecular structures (C31). Nitrogen-containing compounds in vacuum residues were separated by adsorption chromatography on basic and acidic alumina columns into strongly basic, weakly basic, and nonbasic fractions. The IR spectra showed that predominant nonbasic nitrogen compounds were pyrrole-type and amide-type compounds (C32). HPLC with refractive index and UV detectors was used to determine saturates and aromatics and aromatic ring number distribution in 250-370 °C straight-run gas oil fractions (C33) and lubricating base oil stocks (C34). The absolute concentrations of each hydrocarbon type are determined from peak area percentages by applying appropriate response factors. The UV detector provided better results for monoaromatics at 210 nm (compared to 254 nm) due to enhanced response (C34). HPLC was applied to obtain saturates, aromatics, olefins, and polars in products from cracking of vacuum gas oil. The class separation was achieved using an amino column, a backflush device, and n-hexane as the mobile phase. A refractive index detector was used to obtain saturates and aromatics, and a UV detector at 200 nm was used to estimate olefins and aromatic hydrocarbons by ring number. For quantitative data, external standards were used (C35). Vacuum gas oil, coker gas oil, and heavy cycle oil were separated into saturates, monoaromatics, diaromatics, polyaromatics, and resins by preparative liquid chromatography and synchronous fluorescence spectrometry. The analysis of aromatics by GC and MS confirmed that there were little cross-contamination between fractions. The order of monoaromatic contents of the three samples were vacuum gas oil > coker gas oil > heavy cycle oil while the polyaromatic contents followed a reverse order (C36). A vacuum gas oil and its desulfurized product were analyzed by HPLC. Each oil was separated into seven fractions on the basis of aromaticity. Six fractions (excluding the polar one) were subjected to field ionization mass spectrometry. A lower yield of heavy distillate with relatively lighter oil, and a decrease in the amount of polycyclic aromatic compounds (PACs) due to hydrodesulfurization of vacuum gas oil, were attributed to transformation of polycyclic aromatic thiophenes into hydrocarbons containing fewer aromatic rings and hydrogenation of aromatic rings (C37). Quantitative measurements of both mass and distribution of aromatic rings in heavy distillates were obtained by HPLC with an evaporative light-scattering detector (ELSD) and a diode array UV detector. Saturates, one- to four-ring aromatics and polars were separated from oils using solvent gradients on coupled columns. Separation efficiencies were verified by alternate separations and mass spectrometry. The aromaticities derived from UV spectra were validated with 13C NMR, and the mass percent results were verified by weighing isolated fractions from multiple runs (C38). HPLC with thermospray ionization technique was used to obtain compound type and molecular weight distributions of high-boiling petroleum fractions (C39). Sulfur compounds in the nonpolar fraction of a vacuum gas oil were analyzed by sulfur-selective ligand-exchange chromatography combined with HPLC separation based on the number of aromatic rings. Subsequently, capillary GC/MS was used for compound identification. Quantitative data were obtained by
independent HPLC separation followed by capillary GC with a sulfur-selective flame photometric detector. The structures and concentrations of more than 100 sulfur compounds were determined (C40). HPLC was used to separate coal-derived liquids into six compound classes: saturates, one- to four-ring aromatics, and polars. The HPLC system consisted of three normal-phase HPLC columns and pentane and methylene chloride as solvents. A UV detector was used for compound class identification and an ELSD was used for quantitative analysis of compounds boiling above 600 °F (C41). Fourteen PAHs in pitch samples (used as binder for anodes for aluminum electrowinning) were determined by HPLC using a fluorescence detector and optimized wavelength selection (C42). Toluene-soluble fractions of pitches were analyzed by HPLC. Four different elution ranges were observed, three of cata-condensed compounds and one of peri-condensed compounds. This analytical approach was useful for distinguishing pitches of different origin and nature (C43). Ring number distribution of coal tars during secondary pyrolysis was investigated. For this, tar samples were fractionated by gravity flow column chromatography and the PACs in the toluene fraction were analyzed by HPLC. During the early stages of secondary pyrolysis, the measured ring number distributions reflect prominent features of the parent coal, but the influence of original coal structure on the ring number distributions diminishes with more severe pyrolysis conditions (C44). Polycyclic aromatic nitrogen heterocycles (PANHs) and PAHs in solvent-refined coal heavy distillates were isolated by opencolumn liquid chromatography for their characterization by HPLC. Using normal-phase liquid chromatography on a dimethylaminopropylsilica stationary phase, and backflush technique, the PANH fraction was separated into acridine-type and carbazole-type PANHs. A number of three- to five-ring acridines and carbazoles were subsequently identified with GC-electron impact MS, and quantified by GC-nitrogen-phosphorus detection. PAHs were determined from the PAH fraction by coupled LC/GC-FID (C45). Cobalt, copper, iron, and vanadium in crude petroleum oils were determined by HPLC. To achieve this, a method was developed for the simultaneous formation and solvent extraction of Co(II), Cu(II), Fe(II), and V(IV) complexes of bis(acetylpivalylmethane)ethylenediamine in methyl isobutyl ketone. The complexes were then eluted from a reversed-phase column with a mixture of methanol-water-acetonitrile and detected at 260 nm (C46). Thin-Layer Chromatography. Fractions of a coal liquefaction extract were obtained by planar chromatography for characterization by Moessbauer spectroscopy, SEC, and UV fluorescence spectroscopy in an attempt to distinguish between forms and chemical environments of iron found in the coal extract (C47). Preparative TLC was used to obtain saturated hydrocarbons, aromatic hydrocarbons, and polars from a deasphalted oil on a large scale to use their mixtures as standards for calibration and for monitoring responses of the individual group types in TLCFID (C48). Quantitative hydrocarbon group type analysis of petroleum residues was performed by TLC-FID on thin silica-coated quartz rods. The separation of hydrocarbons was achieved by three-stage development using n-hexane, toluene, and dichloromethane Analytical Chemistry, Vol. 71, No. 12, June 15, 1999
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(95%)-methanol (5%) (C49). Similar quantitative determinations of hydrocarbon types were carried out for petroleum asphaltenes and coal tar pitch, heavy oil and its hydrocracked products, coal extracts, and coal hydroliquefaction products. Various aspects of calibration procedures and response factors for different hydrocarbon types in relation to TLC-FID were also discussed (C50, C51). Heavy products from catalytic liquefaction of coal were analyzed by TLC-FID. The results showed that coal liquefaction products, under certain conditions, have a composition similar to that of petroleum-derived highway asphalts, but significantly different from that of coal tar pitch, paraffinic petroleum residue, and building asphalt (C52). TLC-FID was applied to assess the efficiency of the separation of hydrocarbon types by the ASTM D2007 clay-gel open-column chromatography method and to characterize polycyclic aromatics (PCAs) and non-PCAs obtained by the IP 346 liquid-liquid extraction method. Different fractions were analyzed by TLCFID. It was reported that the clay-gel method suffers adversely from cross-contamination of hydrocarbon types as well as from incomplete recovery of materials from the adsorbents. PCAs fractionated by the IP 346 method were found to contain nonPCAs and vice versa (C53). It was also observed that contaminants in both PCAs and non-PCAs could offset each other in some cases. However, the bias was significant for samples with both low and high PCAs, providing overestimation of PCAs at low concentration (
