Petroleum R. W.
King
Sun Oil Co., Marcus Hook, Pa. 19061
This is the eleventh in a series of reviews of analytical chemistry in the petroleum industry (IA-IOA) sponsored by the Division of Petroleum Chemistry of the American Chemical Society. For the most part, the current material covers the years 1970 and 1971, or more specifically, the papers abstracted in Chemical Abstracts, in the American Petroleum Institute Refining Literature Abstracts, and in Analytical Abstracts (London) for the period from July 1970 through June 1972. All reference citations conform to the Chemical A b stracts “Guide for Abbreviating Periodical Titles.” As a further aid, in those cases where the referenced publication might not be readily available, the abstract journal reference has been appended to that for the original source. The abbreviations C.A., A.P.I.A., and B.A.A. are used to identify, in order, the abstract journals listed above. These abbreviations are followed by the volumenumber, the abstract number, and the year. The abstract searching was done by C. A. Simpson, Mobil Research and Development Corp., J. F. Hickerson, Exxon Co., U.S.A., and R. W. King, Sun Oil Company. The initial collection was intensively screened and organized by subjects that seemed to possess a community of interest. The subject classifications were in the main related to products, properties, or certain constituents. These smaller collections were further screened by the fifteen authors of the eleven subsections which follow. The existence of this review is due entirely to the generous assistance of these contributors.
Crude Oils F. C. Trusell Marathon Oil Co., Littleton, Colo.
Distillation Data. Wilckens and Perez (70B) have devised a quick method for estimating true boiling point data. Cut points are calculated by averaging the 90% ASTM point of one cut with the 10% ASTM point of the next heavier cut, both values being weighted for the volume per cent yields of the two cuts. A curve made by connecting all of the estimated cut points for the test-case crude from crude topping unit data agreed well with the experimentally determined T B P curve. Heintzsch et al. (27B) obtained boiling point data on 1 to 2% by weight fractions of a crude oil as well as on several of its main product fractions. From these data, they constructed a crude oil boiling point curve on which curves of the several fractions were superimposed. Other data obtained on the small fractions were used to develop n-d-M correlations for the crude oil and a model for optimizing laboratory crude oil distillations. Sokolova and coworkers (6IB) used gas chromatography to obtain distillation curves of fractions boiling below 400 “C. The results were comparable to those obtained by distillation through a 20-plate rectification column. O’Neal et al. developed a gas chromatographic method for examining crude oils which takes into account any nonvolatile residue (47B). The column temperature is programmed to 350 “C. The eluted material is oxidized to
COz by CuO before passing into the thermal conductivity detector. The slightly volatile material is back-flushed into the injection block where it is pjvrolyzed a t 700 ”C, first in the absence and then in the presence of oxygen. This second COz peak is then recorded. Three crude oils were analyzed and data comparing results from this method with those from a conventional distillation are given. A detailed description of the apparatus is also available (48B). Hydrocarbons. Kozlov et al. (32B) determined the distribution of the n-paraffins through C Z Sin three Rechitsa crudes by gas chromatography. Egiaxarov and coworkers (15B) determined the distribution of the n-paraffins through C30 in four samples of Ostashkov crudes. By plotting the amount of n-paraffin against carbon number, three zones were observed. In the C1 to Clo region, there was a maximum a t C7 and CS.In the C11 to C Z Oregion, the maximum was between C13 and CIS. In the Czl to C ~ O range, the amount decreased gradually with increasing carbon number. Sergienko et al. separated the n-paraffins from a group of eastern Casp an coast petroleums by urea adduction and determined their distribution by gas chromatography (53B). Szergenyi et al. (65B) separated the n-paraffins from a series of Romashkino oils by refluxing in isooctane over Molecular Sieve 5A. Recoveries of 90% or greater were achieved by desorbing with 8-9 treatments of hot n-hexane. The mass spectral parent peak method was used to determine their distribution by carbon number. Safonova and Bule’cova (49B) studied the c13-c32 n-paraffins from a group of geologically young Apsheron peninsula crudes and from a group of geologically older Prikumskii crudes. The paraffins were isolated from the respective saturate fractions by urea adduction and were examined by gas Chromatography. In the younger samples, the n-paraffin distribution is somewhat irregular, while in the older sample n-paraffin content decreased with increasing carbon number. Additionally, overall n-paraffin content increas ?d with increasing geological age and with depth of the oil bearing strata, while the average molecular weight decreased. Koons and Pancirov (31B) developed a combined GC/MS method for the analysis cf the c5-c21 isoprenoids and applied it to a study of six widely varied petroleum samples. The results were used to build a hypothesis for the biogenetic origin of the iuoprenoid hydrocarbons. Maksimov and Safonova (39B) ck aracterized genetic types of petroleums by measuring their isoprenoid and n-paraffin contents and taking appropriate ratios of members of these two groups. Didyk and McCarthy (12B) malyzed various Chilean crudes for n-paraffin distribution, isoparaffin content, isoprenoid hydrocarbons, and branched-cyclic hydrocarbons. From these data they deduced the samples studied were of predominately nonmarine origin. Krasavchenko and Zemskova identified and determined the concentrations of 37 monoriethyl-substituted alkanes using GLC (33B). The distribution of these compounds in three typical paraffin-base crudes was similar to that found in the reaction mixture after liquid phase isomerization of 1-alkenes in the presence of a silica-alumina cat-
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alyst. Sergienko et al. (58B) characterized the isop araffins and alkylcyclopentanes in ten fractions of crude oil boiling between 200 and 450 "C. The isoparaffins were long chains with mostly methyl or isopropyl substituents. Solodkov et al. (62B) examined the bicyclic Cs iIAd CQ naphthenes from three crude oils. They also examir cd the equilibrium mixtures from the isomerization of bicyclic naphthenes and concluded that in petroleum thesr compounds were not in equilibrium. Kuklinskii et al. an dyzed the isoparaffinic-naphthenic fractions of the 200-4C10 "C distillate from two crude oils and determined the irends for various types of compounds ( 3 4 B ) . Sergienko and Chelpanova (55B) made a similar, but less detailed, study of the fraction boiling above 350 "C from four difi'uent oils. Naphthalan petroleum, useful for medicinal purposes, was analyzed by Kuliev et a!. ( 3 7 B ) and was shown to contain large amounts of polycyclic saturated hydrccarbons such as terpenes and steranes. Slobodin and coworkers determined the adamantane content of several crude oils (GOB). Shimanskii and Bogomolov (59B) determined the r,itios of the aromatic hydrocarbons in the CS to CIO rei:jon, using these data to explain the mode of formation of these compounds out of the original organic mass. Kuklinskii et al. '(,?6B)studied 50 "C cuts between 200 and 450 "C from various depths in four wells. While the aromatic con,ont of the cuts increased with increasing temperature, the proportion of carbon atoms in aromatic rings decreatwd, and the proportion of carbon atoms in naphthenic rings and paraffinic chains increased. Brodskii et al. examiiied the aromatic part of the 350-450 "C fraction from live crude oils by mass spectroscopy ( 5 B ) . They determirutd the concentration of various hydrocarbons and sylfur coi,ipounds in the sample. Gas chromatography was employed to analyze for individual compounds boiling in the gasoline range (28B, 2911, 67B, 68B). Buchta and Forster (7B) used GC to examine the light oils from petroleum in an effort to correlate utiderground petroleum reservoirs. Marlanov et al. characterized the kerosine fraction fro III Balakhany heavy petroleum by conventional liquid chromatography ( 4 0 B ) . Farag et al. (20B) reported the resu1.t; of the analysis of six cuts of Ras-Amer crude oil boiling ul) to 300 "C. Zimina et al. (72B) made a detailed study of the composition of the 300-400 "C fraction of Anastas'ev petroleum. Semyachko et al. studied those compounds from the 200-450 "C fractions of two crude oils which form urea complexes, characterizing them by the n-d-M method and by such parameters as their cyclicity and asymme . try factors ( 5 2 B ) . Zimina et al. (71B) found a relationship between the structure of 3-5 fused ring alkyl naphthalenes and aromatics, their physical and chemical characteristics, and the oil deposit depths. A combination of IR, NMR, and mass spectroscopy was used in the study. Sulfur Compounds. Lerescu and Ivanescu (38B) determined the distribution of sulfur, mercaptans, sulfides, and disulfides in the 60-250 "C fraction of sulfurous crude oils. Obolentsev and Makova (45B) studied the mercaptans in high sulfur crudes, determining the position of the thiol group and the structure of the parent hydrocarbon. The mercaptans in the samples studied were about 5% primary, 75% secondary, and 20% tertiary. The contents of alkylthiols, cycloalkylthiols, and thiophenols were 67-74%, 20-2970, and 3-6%, respectively. Obolentsev et al. (44B) determined the distribution of sulfur compounds in 3% fractions of western Siberian petroleum. Brodskii et al. (GB)carried out mass spectral studies of the sulfur compounds extracted from the 150-250 "C kero170 R
ANALYTICAL CHEMISTRY, VOL. 45, NO.
sine of Arlanskii petroleum by 86% HzSO4. This extract was separated into sulfide and thiophene fractions for analysis. Nikitina et al. made similar determinations on the 150-250" and 190-360 "C fractions of Arlan crude ( 4 3 B ) . Gal'pern and Brodskii (23B) combined oxidationreduction techniques with mass spectroscopy to determine the structural group composition of the c21-c24 fractions of an aromatic sulfide concentrate from Rosmashkino crude. They demonstrated the presence of 21 different structures, principally cyclic sulfides and thiophenes. A similar study of the 200-400 "C fraction from South Uzbek petroleum is reported by Gal'pern and coworkers (22B). Eigenson and Ivchenko (17 B ) found some correlations between sulfur content, physical properties, and chemical composition for Ural and Volga crudes and their fractions and residues. Crudes richer in sulfur were of higher density, were richer in nitrogen and heavy metals, and gave lower total amounts of distillate. The same authors also developed a system for classifying crudes to determine the need for desulfurizing the kerosine or jet fuel fraction (16B). Asphalts and Residua. Gadzhi-Kasumov and Adamov (21B) studied the asphaltenes from various petroleums but found no relations between the asphaltene content and other properties. Bajor and Wehner (3B) examined natural asphalts from world-wide sources, determining carbon-hydrogen and other ratios, aromatic and saturate hydrocarbon contents, molecular weights, volatiles, and asphaltene contents. These data are tabulated and discussed with reference to the geologic origins of the asp halt s. Sergienko and coworkers have published a series of papers dealing with the chemical nature of the high molecular weight components of petroleum. The group types in the residue boiling above 350 "C from five Caspian east coast and two Bukhara crudes were determined (54B). The resins and asphaltenes of six of these crudes were separated and characterized (57B). The thermal stabilities of the seven residues were also investigated. Heating to 300 "C did not cause significant change, but heating to 350 "C started a conversion from hydrocarbons to resins, and then to asphaltenes, with light unsaturated hydrocarbons being formed as by-products ( 5 6 B ) . Metals and Salts. Mileshina e t al. (42B) determined the trace element composition of Mesozoic petroleums in the eastern cis-Caucasus by the last line method of semiquantitative spectral analysis. The ash bottoms contained Cu, Ni, Cr, V, Fe, Ti, Zr, Na, Ba, Ca, Al, Mg, Mn, and Si. A few samples contained Be, Ag, Zn, Co, and B. Abyzgil'din et al. ( I B ) determined the distribution of metals in three sulfur-containing crude oils and in their fractions. The metals found, in order of decreasing concentration, were V, Ni, Fe, Na, Ca, Cu, Mg, and Mn. Measurable amounts of nickel were found in the 350-400 "C fraction of high sulfur crudes and in the 400-450 "C fraction of low sulfur crudes. This led the authors to conclude that nickel porphyrin complexes in high sulfur crudes are more volatile and unstable than those in low sulfur crudes. Berkutpva et al. ( 4 B ) used neutron activation analysis to determine the concentration of cobalt and sodium in western cis-Caucasus petroleums. These metals are concentrated in the higher boiling fractions. They assert that in many cases crudes can be more adequately differentiated on the basis of their cobalt contents than by nickel and vanadium contents. Sugihara and coworkers (64B) have reviewed their work of characterizing metalloporphyrins from Boscan crude. A variety of separation techniques are described, and the spectroscopic methods of measurement are discussed. The
5, APRIL 1073
predominance of vanadium and nickel in petroleum, compared to other metals, is also examined. Golebiowski also determined the vanadium, nickel, and porphyrin content of two crude oils and of their various fractions ( 2 4 B ) . Cipric et al. (IOB) described a potentiometric titration apparatus and a conductivity apparatus suitable for the routine determination of salt in petroleum. Al’khovskii e t al. (2B)reported on an automated potentiometric titration for the determination of chloride in crude oil. The nonaqueous titration with AgNOB is performed without prior separation of the salt. Gorski and Loska (25B) designed and constructed a n apparatus for the continuous determination of NaCl and water in crude oil by neutron activation analysis. The range for salt is 0.01 to 6 g/l., and that for water is 0.1 to 1.6 g/l. Grubjesic-Kovacic and Meles describe the analytical methods used to monitor a desalting unit in a refinery (26B). They also discuss the hydrolysis of chlorides, the reactions of iron and HC1, and the effect of pH on corrosion. Nonroutine Characterization. Efendiev (14B) determined the thermal conductivity and heat capacity of 15 oils at atmospheric pressure and at temperatures between 223 and 273 OK. The heat capacity increased linearly with temperature, while the conductivity and density decreased. Khristoforov has reviewed progress in the use of ESR for studying crude oil and products, beginning with the first observation of unpaired electrons in 1956 (30B). Eldridge and Flaherty (18B) have proposed y-ray spectroscopy as a means of identifying crude oils following their irradiation. They applied the method to identifying the reservoir responsible for the oil spill into the Santa Barbara Channel. Mattson et al. (41B) propose differentiating crude oils from drilling leaks and from natural seepages based on carbonyl- and carbon monoxide-like bands measured by internal reflectance spectroscopy. Sattar-Zade et al. measured the optical activity of fractions of Kyursange (50B) and Bukhta Il’ich (51B) petroleums. They were able to make some correlation of optical activity with depth of burial and with some physical and chemical properties. Gel permeation chromatography continues to be applied to the solution of problems in petroleum chemistry. Coleman et al. (1IB) and Oelert et al. (46B) used the technique to separate and characterize the high boiling material from crude oil. Done and Reid (13B) obtained unique crude oil chromatograms from a GPC system. The elution time was less than 1 hr for 6-mg samples. The method is also applicable to gas oils, waxy distillates, oil pollution samples, and the like. Kuklinskii et al. examined a paraffinic distillate fraction of Mangyshlak petroleum, characterizing it by means of liquid chromatography and mass and infrared spectroscopy (35B). Routine Analytical Data. Wenger and Morris have reported data from analyses by the U.S. Bureau of Mines Correlation Index method performed on 67 Utah crudes (69B). Charbonnier et al. (8B) have reported results from 198 analyses done according to the U.S. Bureau of Mines Routine Method of Distillation. Thompson et al. (66B) have determined the general characteristics of Prudhoe Bay crude oil by the same method. In addition, they have characterized the 700-1000 O F cut by the API Research Project 60 method. Fallah e t al. have tabulated properties of 37 Iranian crudes and residues from 16 different fields (19B).The data are used to predict yields and properties of residues from unknown Iranian crudes if their density is known.
Cherednichenko et al. (9B) have determined the properties of Priluki and Rybal’sk crudes and their various fractions by conventional methods. Stevancevic et al. (63B) have done similar studies on nine Voivodina crude oils.
Fuels, Gaseous and Liquid K. L. Shull and J.
D. Beardsley
The Standard Oil Co. (Ohio),Cleveland, O d o
Errors occurring during impurity determinations in liquefied petroleum gas are discussed by Dick ( I 2 C ) . These errors are due to the distribution of the volatile impurity between the liquid and vapor phases. Equations are shown for correcting experimental reaults and recommendations given for minimizing sampling errors. Magri (26C) describes a rapid procedure for the determination of olefins in liquefied petroleum gas. The procedure is based on the double bond oxidation-hydration of the olefins to glycols with an aqueous sodium hydroxide solution of potassium permanganate. The Oil and Gas Journal (32C) reports that the U S . Air Force has a new method (QPL MIL-1-2501 7 C) for testing the performance of jet fuel rust inhihitors. They have recently prepared a list of ten approved inhibitors. This development may hasten the acceptance of rust inhibitors by commercial airlines and by the Navy, which generally do not permit any corrosion inhibitor:; in the jet fuels that they use. An experimental study of reaction3 between silver and sulfur compounds conducted by Build and Sanger (7C) has confirmed that hydrogen sulfide and elemental sulfur are both reactive toward silver, which is used as a coating on certain fuel pump components. They have developed a test of similar severity to I P 227, silver corrosion test for aviation turbine fuels, which has been approved by the UK Ministry of Technology as a specification test and adopted by the Institute. Papok et al. (34C) have developed a method for measuring the scale formation during (mombustion of fuels. This method uses the UNT-1 test apparatus with a smallscale gas turbine engine. A laboratory device has been develclped by Aksenov and Litvinov ( 4 C ) for studying the antiwear properties of jet fuels and the wear resistance of structural materials under various conditions of contact loads, temperatures, and speeds. The apparatus requires only 25 to 70 nil of sample and about 2 hr per test. Aksenov et al. (5C) have studied the effect of deoxygenation on the antiwear properties of jet fuels. A review by Rozhkov e t al. (37C) covers various methods and instruments for determining the antiwear properties of jet fuels. Aird and Forgham ( 3 C ) have developed a method to detect differences in the lubricating properties of aviation fuels. The “dwell test” measures the time required to destroy the fuel film on the surface of a rotating disk with a loaded pin sliding against it. A discussion by Suresh and Goel (43C) of work carried out a t the Indian Institute of Petroleum includes the development of a ball-and-cylinder apparatus and test procedures foI studying the lubricating effects of aviation fuels on fuel pump parts. Chernyshev (9C) has established a nomogram for determining the solubility of water within -10 to +SO “C in individual hydrocarbons, gasolines, jet fuels, and white oils. As a result of the 1969 monthly sample exchange program of the Jet Fuel Quality Protection Group, Nathan and Dulaney (31C) have concluded that because the Water Separometer Test (ASTM D 2550) is controlled by the adsorption of surfactants, it is very doubtful that the test
A N A L Y T I C A L CHEMISTRY, VOL. 45, NO. 5, .APRIL 1973
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can be substantially improved. I t appears that g .eat uncertainties in the effect caused by the surfactant at intermediate surfactant concentrations is an inherent iind inescapable part of the inhibited corrosion process. Caldwell (8C) has obtained a patent on a mixture for detecting free water in hydrocarbons. The mixture cwnsisting of methylene violet and a finely divided anhydi*ous solid is shaken with the sample, the solids are allowed to settle and their color is compared with that of standaids. The classical Karl Fischer method has been modifiec by Misra (29C) to make it suitable for determining free iind dissolved water in aviation fuels. The modified method employs a special ethylene glycol solvent mixture and ,inother water-saturated fuel sample as a blank. Gardner (17C) has improved his field method for Lhe determination of fuel system icing inhibitor (ethylene clycol monomethyl ether) by replacing the potassium dichromate color standards with permanent glass stand irds (Tintometer; Lovibond Code No. 4/43). The standcuds correspond to 0, 0.05, 0.10, and 0.15 vol % of icing inhibitor in the fuel sample. An infrared procedure has been developed by Ritchie and Kulawic (36C) to identify and determine icing inhibitors in hydrocarbon fuels. The me1 hod uses the OH stretching bands of the additives in dilute solution in carbon tetrachloride. Englin and Reznikov (14C) have made a study of the intensity of combustion flames (luminometer number!)) of individual hydrocarbons and jet fuels. The luminomcbter numbers were determined by a Soviet method with Sc viet equipment. A round-robin program has been conducted by Svkiirmer (39C) to estimate the precision of a static 5-ml b m b procedure for measuring the high temperature oxids tion stability of aviation turbine fuels. The need for uniformity in gas-liquid chromatographic analysis of fuels and fuel emissions to permit interlal: oratory comparison of data is emphasized by Hurn ( Z l C ) . Galtieri ( I C ) discusses gas chromatographic techni -pes and their applications to fuels and derivatives. Thin liiyer chromatography is used by Esposito (15C) to determine di-tert-butyl disulfide in diesel fuel. The Journal of the Institute of Petroleum (24C) has published a review of existing and potential method; for testing motor gasoline. This review gives brief descripl ions and the current status of such existing tests as specific gravity, distillation, vapor pressure, and knock chara :teristics and covers the possibilities of replacing them with new methods or calculations. The general and specifi:: requirements for a standardized gas-liquid chromatogr,iphy method are included. Adlard et al. ( I C ) describe an apparatus for the chiiiacterization of gasoline volatility by gas-liquid chromato,;raphy. The apparatus analyzes gasoline samples once t very 20 min and is thus capable of giving true boiling ]mint data in about the same time as that required for an ASTM distillation. Zabryanskii et al. (50C) describe a universal UIT unit for the determination of octane number in motor fuels. Either the Motor or Research methods can be run 011 the engine, the change from one method to the other trking 15 to 20 min. The octane data obtained are almost identical with those of conventional testing units. The modified Uniontown Road octane results have been correlated with AR (change of research octane) numbers by Protaska (352). The Coordinating Research Council (IOC) has revised the 1951 Modified Borderline and 1951 Moc ified Uniontown Methods for measuring Road octane numbers of motor fuels. These 1970 versions utilize the latest instrumentation, newer vehicle designs, and highly stailjar172 R
dized operating procedures. A new procedure for measuring cetane number of motor fuels has been developed by Sellschopp (40C). The procedure utilizes a modified BASF diesel test engine. Smith and Doelling (41C) describe a n apparatus which can be used to measure the concentration effect of carburetor detergency additives and to screen possible carburetor detergents. Deposits are accumulated on a replaceable stainless steel specimen screen located in the intake system of a single-cylinder laboratory engine. A reflectance meter measures the amount of light reflected off the screen. The liquid products in gasoline engine blow-by have been collected and separated into structural types by Vineyard and Coran (47C). These materials are highly nitrated and extremely reactive; they are primarily responsible for crankcase deposition. They (11C) found that the amount of sludge binder (the MezCO-soluble portion of sludge solids and varnish) correlates negatively with total sludge ratings and is an important factor in deposition. Taylor and Wallace (44C) have patented an apparatus for testing liquid hydrocarbons for their deposit-forming tendencies at high temperatures. Several procedures have been used by Henderson and Nixon (20C) to evaluate jet fuel deposits on coker tubes. The combustion and p-ray backscattering approaches appear the most promising. Englin et al. (13C) determine resinous compounds in jet fuels by adsorption on activated alumina, followed by desorption with glacial acetic acid, and a final wash with distilled water. A method for the quantitative evaluation of the coking tendency of petroleum products has been developed by Guenther and Kirmes (18C). Maljkovic et al. (27C) have tabulated chemical and physical-chemical methods for the determination of lead in gasoline. Results using four different procedures are compared. These procedures are: ASTM D 526-61, IP 116, the EDTA method of Milner (C.A., 48, 12397g), and a modified IP 116 in which the gravimetric finish is replaced by a titration with di-Na EDTA using Erio T as indicator. A combined gas chromatographic-flame photometric method for the separation and detection of lead alkyls has been developed by Mutsaars and VanSteen (30C). No treatment of the sample is necessary and interference by other compounds is almost completely eliminated. Marti (28C) used a polarographic technique to determine lead in gasoline a t the part per billion level. Cadmium is used as an internal standard. Ishii and Musha (22C) also use a polarographic technique; but they are analyzing a t the part per million level. The direct determination of lead in gasoline with a premix air-acetylene burner has been developed by Kashiki et al. (25C). The addition of iodine to the gasoline diluted in isobutyl methyl ketone eliminates the variation in absorption due to type of alkyllead compound and permits calibration with a single standard alkyllead compound. Steinke (42C) has obtained satisfactory determinations of trace lead (ca. 20 ppb) in light gasoline by atomic absorption spectroscopy of the lead in aqueous solution. The determination of lead by atomic absorption spectrophotometry as done by Johns (23C) consists of extracting the total lead from a solution of the sample in 2,2,4-trimethylpentane with aqueous iodine monochloride and aspirating the aqueous extract into a lean air-acetylene flame. Agrawal and Fish (2C) have determined microamounts of phosphorus in motor gasoline by selective extraction of the molybdophosphoric acid with butanol-chloroform and spectrophotometric measurement of the absorbance of the organic layer. The correlation between the vapor-liquid ratio (V/L) of
ANALYTICAL CHEMISTRY, VOL. 45, NO. 5, A:’RIL 1973
motor gasolines and the vapor locking tendency has been investigated by Uchinuma et al. (46C). The results suggest the necessity of two V/L values (high and low) in the control of vapor locking tendency of motor gasolines. Sadykhov e t al. (38C) have designed an apparatus for determining the saturated vapor pressure a t 80 "C of motor fuels according to GOST 1756-52. The performance of the apparatus has been checked against benzene and the experimental saturated vapor pressure found to be 766 m m in comparison to the literature value of 754 mm. The Institute of Petroleum has accepted the concept that the flash point needed most frequently is not a definitive result but merely confirmation that the sample does not flash a t a certain temperature; that is, a go-no-go principle. Two basic methods-(1) Rapid Flash Test by the Setaflash Tester and (2) Flash Test using any Standard Closed Cup Apparatus-have been examined fully by Bell ( 6 C ) and presented in I P Standard Method format. The methods can be used for the go-no-go principle but can also be used to give definitive values. Zrelov and Boiko (51C) have studied the composition of the solid phase formed in fuels a t temperatures below 0 "C. They propose a method for the qualitative and quantitative determination of precipitates in fuels below 0 "C. The flow properties of residual fuel oils a t -20 to +110 "C have been determined on a Brookfield viscometer by Wakana et al. (48C). They conclude that the Brookfield viscometer gives a better estimate of low temperature flow properties than either pour point or yield value. Heinemann et al. (19C) have made a critical evaluation of methods for testing the cold behavior of middle distillates. They recommend that the Cold Filter Plugging Point Test for diesel fuel, the similar Heating Oil Operability Test, and preliminary screening in a cold chamber (-40 "C) should be included because pour points and cloud points are not good indicators of low temperature serviceability. Yanagase (49C) uses radiation (La) from rhenium as a n internal standard to determine sulfur in fuel oil by X-ray fluorescence. Ono (33C) has modified IP 143 for the determination of asphaltenes in residual fuel oil to improve the procedure. The modification shortens the analysis time by two thirds, but the results are biased consistently high. Texaco, Inc. ( 4 5 C ) , has published a review of the basic used-oil tests for appearance, odor, water content, gravity, flash point, viscosity, insolubles, neutralization number, and ash content, and comments on the significance of these tests, and some causes and effects of contamination and oxidation.
Lubricants, Oils, and Greases F. M. Roberts Texaco Inc., Beacon, N. Y .
Oils. The determination of neutralization numbers of a variety of lubricants was discussed in several papers published during the period of this review. Caughley and Joblin ( 9 0 ) used high frequency titrations to determine the total base number of lubricating oils. Toida and Uchinuma ( 9 3 0 ) reported that a newly developed acetic acid back titration method gave more realistic values for base number than the standard perchloric-acetic acid method. A mathematical method was used by Ciuti and Mezzanotte ( 1 0 0 ) to locate the end point of a titration curve and determine total base number. Giddings and Barrett (280)reported that a method involving potentiometric titration with anhydrous perchloric acid (Method I P 27671T) was superior to ASTM D 664/IP 177 and recommended it as an international standard. Mostecky et al. ( 6 3 0 )
used a 0.1N solution of perchloric acid in acetic acid and the type SEAJ electrode for the potentiometric determination of base numbers of oils dissolved in chloroform and acetic acid. Glass (300) used a colorimetric indicator in a perchloric acid titration method for determining total basicity of used engine oil. Krueger ( 4 8 0 ) described a simple apparatus for determining neutralization number which exc1,udes carbon dioxide. The determination of the acid number of dark oils by direct titration using bromcresol purple indicator was reported by Ignatenko et al. (360). Jantzen ( 4 2 0 ) described a potentiomexic determination of acid numbers in aircraft turbine oilti using tetrabutylammonium hydroxide as the titrant and either chlorobenzene-dimethyl sulfoxide or toluene-dimethyl sulfoxide as the solvent. Filenko et al. (210) dissolved petroleum products in isopropyl alcohol-toluene and titrated them' potentiometrically using tetraethylammonium hydroxide as the titrant. Nakajima et al. (66D:t determined weak acids and very weak acids in petroleum products by potentiometric titration with tetramethylammonium hydroxide. A field testing kit to determine whether a lubricating oil contains more than a predetermined amount of ' acidity was patented by Krawetz and Tovrog ( 4 7 0 ) . Filenko e t al. ( 2 2 0 ) removed fatty acid!; from oxidized oils with ion-exchange resins and identified them by gas chromatogr aphy . Lubricant additives were identified and determined by various techniques. Coates ( 1 1 0 ) used thin layer chromatography to separate a variety of addilives. This technique was also used by Hirokiet al. ( 3 4 0 ) to analyze zinc dialkyl dithiophosphates. Dovgopolyi (151)) separated and determined antioxidants in oils by a lhin layer chromatographic method. Amos ( I D ) ,descrihed improved procedures for the determination of additives in oils by thin layer chromatography. The application of partition paper chromatography to the separation and identification of dithiocarbamates and dithiophosphates was described in two papers published by Shimizu ((310, 8 2 0 ) . Campi et al. ( 6 0 ) used a pseudocountercurrent extraction technique to separate zinc dithiophosphates. 1Stemberger ( 8 9 0 ) reported the use of physical methods of separation, combined with infrared spectrometry, for the separation and identification of various additives in oils and additive mixtures. The application of ion-exchange resins in nonaqueous media to separate petroleum additives was reported by Webster et al. (1000).Care1 ( 7 0 ) used a combination of dialysis and alumina chromatography to analyze for nitrogen containing polymeric dispersants. A paper by McHenry and Littig ( 5 5 0 ) described the use of infrared spectrometry for determining the additives in hydraulic oil. The determination of 2,6-di-teit-butyl-p-cresol in oils was made by Furlan ( 2 6 0 ) using a phosphomolybdic acid colorimetric method. Stoll and Vuillemier ( 9 0 0 ) used a gas chromatographic method, and 'I'ooke and Wilde ( 9 4 0 ) used infrared spectrometry for this additive. Tylich ( 9 7 0 ) described a volumetric titration and a spectrophotometric method for determining sodium nitrate in water miscible cutting fluids. A photometric method for determining bisphenols in oils and fuels was reported by Romantsev (770).
A few papers appeared describing methods for determining materials other than additives. The examination of oils for furfural was described in three papers. Anand et al. ( 3 0 ) used a photometric proccdure in which p-bromoaniline was the color developing reagent. Ismailov et al. ( 3 9 0 ) extracted the furfural with water and measured the refractive index. Soutar ( 8 5 0 ) usad thin layer chromatography for its detection. A portable system for determining water was described by O'Hara and Siegfriedt ( 7 0 0 ) . A
ANALYTICAL CHEMISTRY, VOL. 45,
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40-ml septum-covered vial is the titrating vessel. The sample is injected into the dried vial and titrated by injecting 0.05-ml increments of Karl Fischer reagent. liaines (330) reported a method using differential near itifrared spectrometry for monitoring water content of brak? fluid. The effectiveness of lubricant purification plants ran be monitored by a method described by Krasikov (46L).Particles suspended in a given volume of oil were cmnted under a microscope by use of the effect of light depolarization on double-refracting objects of unequal diaroeters. A gas chromatographic method carried out a t 1 mqi and 100 “C was reported by Shtern et a!. ( 8 4 0 ) for the determination of gases in transformer oils. A refractometric method for determining normal paraffins in transformer oil was reported by Sadykhov and Zhirova ( 7 8 0 ) . The method is based on refractive index measurements before and after removal of n-paraffins with urea. Muntean and Mosescu ( 6 5 0 ) identified aromat ~csby ultraviolet spectrometry. The FDA UV method was “ound by Catchpole et al. ( 8 0 ) to be the most reliable m?thod for determining 3,4-benzpyrene. Kolyadich et al. I 4 4 0 ) used spectral fluorescence on fractions separated by chromatography to determine 3,4-benzpyrene. Used crankcase oils were examined for ethylene glycol by a gas chromatographic method described by Espcsito and Jamison (200). The glycol was converted to thv trimethylsilyl derivative and 1,4-butanediol was the intomal standard. Esposito ( 1 8 0 ) also reported a field test fo: detecting ethylene glycol in which the glycol is oxidized with periodic acid and the resulting formaldehyde detected with chromatropic acid. Gellner ( 2 7 0 ) extracted ethylme glycol from oils with acetone-water and analyzed the extract on a Porapak column a t 200 “C. Habermas and Rlorasky ( 3 2 0 ) patented a procedure for detecting ethyene glycol in which the oil sample is extracted with a so1u;ion of sodium metavanadate and ammonium nitrate. The cxtract is placed on a chromatographic column contair ing ‘Schiff reagent as an indicator. A gas chromatograrhic method was used by Turner et al. ( 9 6 0 ) to determine iiiel contamination in aviation turbine oils. Lantos and Lantos ( 5 0 0 ) developed a simplified paper chromatograpliic method for determining free carbon and oxidized matter in used lubricating oils. Jackson ( 4 0 0 ) compared the results obtained from analyzing used diesel engine oils by atomic absorption and emission spectrometry and c m cluded the atomic absorption method had better pre :ision. The use of ion-exchange columns followed by s p t ~ trochemical or wet chemical determinations was describ?d by Langanke ( 4 9 0 ) for the determination of various elcments in fuel and lubricant residues. In a study by Nowilk et al. ( 6 9 0 ) infrared spectra of used oils showed that the aliphatic and naphthenic hydrocarbons undergo only slight changes with engine operation. Janssen ( 4 1 0 ) rvviewed the laboratory and field test methods being a])plied to used oil analysis. Neilson ( 6 7 0 ) presented a dill. cussion of the modern analytical methods which are rvplacing older empirical methods for examining used oil>;. Richard ( 7 6 0 ) presented a survey of methods used t 2 monitor engine lubrication. These include portable instruments for rapid determinations of viscosity, water, acidity, etc., as well as infrared, emission spectroscopy, and conventional laboratory inspection tests. McGreevy (530 1 found that differential infrared spectrometry, emissiorl spectrographic analysis for metals, and viscosity are thc best means for determining the condition of oils in natural gas engines, provided that trend analyses are made rathei than single tests. Column, gas, and thin layer chromatography for separations and infrared spectroscopy for identification were the techniques used by Mostert and Bohnes 174
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(640) for operation control of various lubricant types. A survey by Tarbell ( 9 1 0 ) covered the analysis of used refrigerator compressor oils, with emphasis on testing methods and their interpretation. Ishizawa ( 3 8 0 ) studied the deterioration of gear oils by measuring viscosity increase, amount of sludge, neutralization value, water content, and metal content. Spedding and Noel ( 8 6 0 ) studied piston lacquers with reflectance infrared spectrometry and obtained results which were in agreement with published mechanisms for lacquer formation. Shipulina and Reznikov ( 8 3 0 ) found that coking capacity of used oils could be related to the contamination level. Esposito ( 1 9 0 ) absorbed both new and used oils into porous glass fiber sheets and heated them to determine volatile matter. He also reported a gas chromatographic procedure for determining volatility of new and used oils (17 0 ) . The evaluation of lubricating oils by a variety of tests, both chemical and physical, was the subject of numerous publications. Noel ( 6 8 0 ) characterized oils by differential scanning calorimetry. The values obtained by this technique show some correlation with standard cloud and pour point determinations. Thermooxidative stability can also be determined. Macko ( 5 4 0 ) made polarographic analyses of intermediate oxidation products in transformer oils to investigate the kinetics of oxidation. Rates of oxygen absorption by lubricants can be measured in a closed system in a n apparatus described by Dotterer ( 1 4 0 ) . The gum forming properties of motor oils a t high temperatures were studied in a “sliding ring” device developed by Papok et al. (720). Francois and Corvaisier ( 2 4 0 ) developed a n oil spot test and a solubilization test for testing dispersant additives and oils. Lashkhi and Belyshkov ( 5 1 0 ) evaluated the antipitting properties of lubricants on a four-ball friction machine, using a new cup for each test to improve precision. Pike and Spillman ( 7 3 0 ) studied the effects of seizure delay on transition temperatures in the four-ball machine. A discussion of the development, features, modifications, uses, and validity of results of the modern fourball apparatus was presented by Brown ( 5 0 ) . A high speed wear tester, in which three hemispherical riders rub against a rotating disk, was used by Barry and Brinkelman ( 4 0 ) to evaluate hypoid gear oils. Marini and Foa ( 5 8 0 ) evaluated cutting oils by both the Falex-Faville machine and a cutting machine. The Falex-Faville results were comparable with those obtained on the cutting machine. Inman and Kohn ( 3 7 0 ) reported the use of electron transmission microscopy for the detailed evaluation of surfaces damaged in wear tests. The FZG machine was used by Giusti et al. ( 2 9 0 ) to evaluate the shear stability of oil soluble polymers. Maillard and Deluzarche ( 5 6 0 ) designed a concentric cylinder viscometer with exchangeable inner cylinders arranged to form 0.005- to 0.1-mm films to measure irreversible degradation of VI improvers in multigrade oils. Polinelli et al. ( 7 4 0 ) reproduced the viscosity losses of gear oils containing polymethacrylate and polyisobutylene, operating in a diesel or automobile engine, with a sonic vibrator. Kichkin and Zaskal’ko ( 4 3 0 ) used the UZDN-1 ultrasonic low frequency disperser to determine mechanical destruction of polymers in mineral lubricating oil solutions. LePera and Pigliacampi ( 5 2 0 ) used a kinetic dispersion mill as a laboratory test to predict mechanical shear stability of polymer thickened oils. The mechanical stability of polymeric additives was studied by Zaskal’ko e t al. (1030) in a n ultrasonic device with a 100-W generator at 18 kcps and 100 “C. The degree of destruction was evaluated from the reduction in viscosity. Crouse and Wilkins (130) carried out shearing tests on oils containing VI improvers using a motored engine, a sonic oscillator, and a power steering pump. The tests
A N A L Y T I C A L CHEMISTRY, VOL. 45, NO. 5, A P R I L 1973
showed results depended on the shearing action of the test instrument. Freund et al. ( 2 5 0 ) described a new method for bench-testing diesel oils which consists of measuring wear of the first cylinder ring and piston, the iron content of the crankcase oil, the alkalinity and acidity of fresh and used oil, and percentage of dispersed carbon black at 50-, 100-, 150-, and 200-hr intervals on a single cylinder, Chepel-Steyr D-3 diesel engine. Towle and Marciante (950) presented a critical survey of European test procedures for engine testing of lubricating oils. An ASTM Special Technical Publication ( 2 0 ) discusses single cylinder engine tests for evaluating the performance of crankcase lubricants. A test based on the panel coker was developed by Sharma et al. ( 8 0 0 ) as a bench tkst for the evaluation of crankcase oils. Forbes and Wood ( 2 3 0 ) patented a test for lubricating oil detergency which involves adding neutralized oxidized gasoline to the oil and exposing the mixture to NOz. Greases. Several papers appeared describing the use of infrared spectrometry for the analysis of lubricating grease. Putinier ( 7 5 0 ) used differential infrared of a slurry of grease in white oil for the quantitative analysis of the components of greases. Elliot and Harting ( 1 6 0 ) listed examples of problems in the use of infrared in grease analysis to illustrate the utility and limitations of infrared spectroscopy. Stanton ( 8 8 0 ) described the use of demountable cells for the quantitative analysis of greases having good absorption bands. The infrared spectra of 39 major grease types were recorded by Verdura ( 9 9 0 ) and limited absorption-structure correlations were determined for most cases. The library thus developed provides a means of identifying various types of greases. Sato ( 7 9 0 ) used infrared spectrometry to study the changes in composition of greases due to heating. Kramer ( 4 5 0 ) determined alkyl benzenes in greases by infrared, and Medvedeva et al. (Sou) used infrared to study the oxidizability of lithium greases. A variety of other techniques for analyzing lubricating greases were also described. Spengler et al. ( 8 7 0 ) determined soap-oil ratios by paper chromatography on cellulose or glass fiber paper using n-heptane as the developing solvent. Panidi et al. ( 7 1 0 ) described a n activation analysis technique for determining lithium in grease. The polarographic determination of zinc in hydrocarbon greases was found by Gulaeva et al. (310) to be preferable to complexometric titrations. Manjarez ( 5 7 0 ) saponified greases, prepared the methyl esters of the acids, and determined them by gas chromatography. The rheological properties of lubricating greases were studied by a variety of techniques. Verdura ( 9 8 0 ) described a strain-gauge load-cell to determine the low temperature viscous resistance of wheel bearing grease. Thelen et al. ( 9 2 0 ) compared rheology of lubricating greases and starting torque and concluded the dominant parameter a t low temperature starting torque is the apparent viscosity a t a shear rate of approximately 1 sec-I. Martera and Ciuti ( 5 9 0 ) found different apparent viscosity values a t -25 and -30 "C for a given shear rate when two capillary tubes were used. Tests showed the phenomena apparently due to interaction of the internal metal surface with layers of grease in contact with the surface. The relations between apparent viscosity and shear rate with the capillary pressure viscometer for several greases were discussed by Moniwa and Komatsuzaki ( 6 2 0 ) . Wyllie (1010) measured flow properties in an experimental pumping rig to provide a design for pipe systems to dispense greases. Mikheev and Kobzova ( 6 1 0 ) determined the thermal stability of plastic grease by direct testing under mechanicodynamic conditions. A new test unit, involving
a weighed piston pressing on a grease filled cylinder, was developed to measure bleeding of grease s in spring loaded grease cups by Wyllie (1020). Thermogravimetric analysis was used by House (350) to predict volatility characteristics of grease. The design and evaluation of a small-bearing test rig are described and the data obtained in a 12laboratory round-robin test are discussed in a Coordinating Research Council, Inc. report ( 1 2 0 ) .
Wax D. R. Cushman and J. W. Schick Mobil Research and Development Corp., Paulsboro, N.J.
Physical Tests. Barry and Grace ( 1 E ) studied the rheological properties of a white soft piraffin by continuous shear and creep viscometry. The flow curves showed the paraffin to be thixotropic except at 45 "C.Mozes et al. (15E) investigated rheological, properti.es of systems containing macro- and microcrystalline paraffins and of polyethylene. Tensile strength, compressive' strength, and specific impact value as a means of brittleness were determined as a function of composition. Sochevko and Lukashevich (20E) w e d a cone penetration method to measure residual shear stress (RSS)of paraffin wax and ceresin samples. Samples were melted before cooling to 25 "C and were tested in the 25 to 55 "C range. The ceresins were thermally more stable, with a flat slope of the RSS-temperature curve. Gryaznov et al. (7E)employed a dilatometric method to study phase alterations of paraffins. The temperature range of the phase transitions widened with increasing difference between melting temperatures of the component hydrocarbons. Szergenyi (21E) measured the conti,action of petroleum paraffins by an indirect refractometric method. Congcaling of macrocrystalline paraffins involves contraction of about 970,while phase transition causes 370 contraction. Contraction of ceresin on congealing is about the same as paraffin. Some fractions do not undei-go phase transition, but low molecular weight fractions s'now contraction due to phase transition about the same as macrocrystalline paraffins. In another article, the same author W E ) described essentially the same procedure. Washall et al. (24E) used a n improved molecular sieving procedure for the determination of total normal paraffins in microcrystalline wax. Normal paraffins are adsorbed on Linde 5A zeolite for 16 hr a t 180 "C from a dccalin solution. The new procedure avoids the usual inhibiting effect due to the highly substiuted monoaromatics in microcrystalline waxes. Flaherty (6E) characterized hydrlxarhon and natural waxes by differential scanning calorimetry. Melting, cooling, and remelting curves compared with corresponding curves of authentic waxes affords a valuable method for identification of many waxes, Heats of transition of many waxes are also given. Turner (23E) gave an extensive rzwiew of the physical behavior of normal alkanes in the pctroleum wax niolecular weight range. Subjects included glass formation, liquid crystals, crystal growth, the effects of chain length, impurities, and pressure on phase transition temperatures, and phase behavior of binary systems. Chemical Tests. Brink and Haasbroek ( 2 E ) reported on the analysis of oxidized waxes by determination of' ?isdroxyl number. The best results were obtained with a stearic anhydride reagent and direct determination of excess anhydride with morpholine. Sleveral other methods were compared.
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Brink and Kleynjan (3E) gave a procedure for determination of the urea-adduct-forming fraction of 11 lraffin waxes. An equation is given for calculating the cordent of nonnormal paraffins in the wax. The procedure is tsied for low melting waxes and, with modifications, for high melting waxes (congealing point 65 to 100 “C). The procedure is suitable for harder waxes which cannot be anal5ied by gas chromatography, mass spectrometry, or adsorp ;ion on molecular sieves. Kajdas (1OE) reported on the chemical charact ?cistics of aromatic hydrocarbons present in slack wax. Hydtocarbons not reacting with urea were separated by fra :tional distillation and fractions were separated by columIi chromatography. Saturated and aromatic hydrocarboIi:; and resins were eluted with solvents. Characteristics of the distillation and aromatic fractions are given. The same author (9E) gave data on seven slack waxes. Urca and thiourea clathrates extracted 43.2-86.3% of the waxes. A systematic general analytical scheme was providecl, and correlation of density and refractive index with Iioiling range was discussed. Seher and Lange (19E) covered a committee rerort of the DGF (Deutsche Gesellschaft Fur Fettwissenscheit) on uniform research methods for the fat and wax inclustry and analysis of waxes and wax products. New mtthods were given for dropping point determination and st ‘paration of iso- and n-paraffins by urea adduction. A mcthod for determining molecular weights of waxes us ng a steam-pressure osmometer was described. Markaryan and Kazakova (14E) studied the coniposition and structure of the hydrocarbon components in protective waxes used as antiozonants in the rubber indistry. Various boiling fractions were further separated by chromatography, urea complexing, and fractional crysta llization from solvent. Physical-chemical properties and s,ymmetry factors were determined. The products cont iined mainly isoparaffinic and naphthenic hydrocarbons with branched side chains in various proportions, which (icted as the protective agents. Chromatography. Dietsche ( 4 E ) described the separation of hydrocarbon waxes by thin layer chromatogrilphy on silica gel and on urea-impregnated silica gel. T h e effects of solvent polarity, solvent temperature, and hydrocarbon chain length and branching on the separations are discussed. The differing tendencies of the wax compormts to form inclusion compounds with urea improve the scparations on silica gel containing urea. Hillman (8E) used gel permeation chromatograph!I for the characterization and analysis of waxes. Chain leigth of major ingredients and overall carbon-number rang c‘ of waxes and polyethylene content of microcrystalline wixes were determined. Resolution of ingredients is infericr to gas chromatography but both high and low molecular weight ingredients are detectable in a single analysis. Rincker and Sucker (16E)studied the effect of chemical and physical data on the practical properties of petrnlatums. Petrolatums of various qualities were chromitographed on AgNOa-Si02 gel to separate paraffins, monoolefins, and higher unsaturated fractions. Normal fract ons were separated from isoparaffins and naphthenes on UI easilica gel columns. A large percentage of unsaturated f * x tions was noted. Spectrometric Methods. Esel’son and Lizogub ( 5 E ) reported on spectral control of the quality of paraffin ticcording to aromatic hydrocarbon content. The aromiitic hydrocarbon content and oil content were determined from the spectral absorption of solution and molten para Tin samples. Absorption coefficient ratios were constant and reliable for determining aromatic ring type. 176 R
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Kajdas and Berthold ( I I E ) studied the effect of average methyl group content and the length of the aliphatic chain on the properties of solid petroleum hydrocarbons. The chain branching (Me content) and chain length (aliphatic CH2 content) of the alkyl residues influence their solidification temperature, hardness, and plasticity. The Me and CH2 contents of petrolatums and fractionated microcrystalline waxes are determined by IR. Petrolatums have the highest Me content, and that of plastic waxes is higher than that of hard waxes. The solidification temperature of waxes increases linearly with aliphatic chain length. Kajdas et al. (12E) determined the structure of petroleum microcrystalline waxes by selected spectroscopic methods. Negative ion spectroscopy and IR spectrometry were used to study the compositions, saturated hydrocarbon structures, and physical properties of eight waxes. Molar mass and C-H ratio were determined by mass spectroscopy and the number of Me and naphthenic CH2 groups by IR. LeRoux (13E) used an improved infrared method to study branching and its effect on crystallinity of a Fischer-Tropsch wax and solvent extracted fractions of a “hard” wax. The Fisher-Tropsch wax showed low crystallinity, possibly due to low molecular weight or wide molecular weight distribution. The extract waxes showed a linear relationship between crystallinity and degree of branching. Waxes for Food (Packaging) Industry. Rotteri (17E) described the method officially adopted in Italy for analyzing paraffin waxes for polycyclic aromatic hydrocarbons suspected of having carcinogenic properties. Refinery techniques used to obtain the properties required for health protection are discussed. Rudakova and Germash (18E) described a wax treatment to reduce carcinogens. 3,4-Benzpyrene found in a Dolina residuum in amounts approximating 5 ppm was removed from the 280-450 “C fractions by treatment with sulfuric acid and from the 450-480 “C fractions with oleum (12%). The grade “A” treated paraffin contained 0.13-0.35 ppb of 3,4-benzpyrene.
Asphalt Herbert E. Schweyer Department of Chemical Engineering, University of Florida, Gaines ville, Fla.
The literature cited here applies for the most part to the work that has been done during the past several years on composition. Accordingly, the subdivisions will be based on composition followed by segregation of the other references according to the nature of the work cited. Gel Permeation. There are a large number of gel permeation citations in the recent literature wherein this technique was combined with other analytical techniques such as nuclear magnetic resonance, infrared and ultraviolet spectroscopy, etc. Dickson et al. (14F) studied Kuwait asphalts with this technique using nuclear magnetic resonance as did Haley (27F, 28F) on Kuwait and another Arabian residual. Hirsch (32F) used the same technique and included IR and certain other data to arrive a t possible structures. Albaugh et al. (2F) used GPC to separate various petroleum residuals including shale oil. Altgelt and Hirsch (3P) used GPC to separate asphalt into 30 different fractions and further studied the fractions by use of liquid chromatography in connection with elucidation of their structure. Dougan (17F) used GPC to study asphalt and the changes
ANALYTICAL CHEMISTRY, VOL. 45, NO. 5, APFliL 1973
of properties. Hayes et al. (29F) used GPC together with spectroscopic analysis including mass spectrometry for comparison of data on aromaticity as found by densimetric study. Liquid Chromatography. Barbour et al. (4F) used inverse gas-liquid chromatography methods and studied the parameters of the analysis technique. Dorrence and Petersen ( I 6 F ) employed inverse GLC including silylation for reaction effects. Gulerman (24F) employed a combination of X-ray diffraction with liquid chromatography for analysis of petroleum residues. Gulerman (25F) investigated the infrared and elemental analysis implications of various Russian residues. Knotnerus (35F) employed LC with infrared analysis to study the various materials that were present in asphalts as a result of the air-blowing process. Silina ( 5 I F ) proposed a high rate procedure for separating asphalts into oils and resins. Szpanier (54F) studied various Polish crude oils with gross separations and IR spectroscopy. Helm (30F) reported on the use of reversed phase partition and GLC with infrared spectrometry as the evaluating technique for comparisons. Miscellaneous Analyses. Bodan and Primak et al. (7F) discussed some aspects of NMR analysis with respect to signal intensity. The use of calorimetric measurements for paraffin wax determination was proposed by Giavarini e t al. (21F). Studies on certain chemical aspects of the components of bitumen as a result of oxidation were discussed by Glozman and Akhmetova (2287. Details on the use of infrared spectroscopy in studying the character of the chemical compounds present were reported by Gorelysheva and Rudenskaya (23F). The acidic nature of blown asphalts was studied by Nakajima (41F) using benzene-pyridine as solvents and potentiometric titration, Neutron activation has been studied by a number of investigators among whom is Rakovic (47F) who investigated the nickel content. Speight (52F) investigated the NMR spectra of Athabasca asphaltenes using proton magnetic resonance. Certain investigators have been studying asphalts using X-ray diffraction methods over a number of years. Among those reporting recently is Stefanescu (53F) who employed this technique for the study of cokes from various sources. Yen (59F) studied the chlorination of Kuwait resins by means of IR spectroscopy and X-ray diffraction. He also commented on the IR spectra of certain Libyan asphaltenes. The same author (60F) studied the asphaltene and petrolene fractions for specific electron acceptors. Electron spin resonance of a variety of bitumens and pyrobitumens was also reported by Yen and Sprang (61F) and they discussed the differences for asphaltenes and the T system from coal. Mass spectrometry has been used by Vogel (57F) for study of road surfacing materials. The petroporphyrin structures of asphaltenes have been reported by Vaughan et al. (56F) as a confirmation of information based on UV and NMR data. The properties of fractions and mixtures of fractions separated by the Rostler method from different asphalts were reported by White et al. (58F). They expressed the observation that with the exception of the asphaltenes, the components from different asphalts are sufficiently similar in properties to be interchangeable. These findings suggest that asphalt quality can be improved by blending to change the proportions of maltene components to desirable composition ratios. Rheological Properties. The glass transition temperatures were measured by differential calorimetry by Giavarini @OF). Bynum et al. (IOF) proposed a tension test for a n asphalt glass-bead mixture as an empirical control
test. Lefebvre (37F) proposed a modified penetration index based on viscosity a t 140 O F rather than softening point. A parallel plate type rheometer was p.:oposed by Marathe (39F)for studying asphalt deformation a t 25 "C. Noel (42F) and Noel and Corbett (43F)discussed ];he use of differential scanning calorimetry for glass trans ition measurements and the use of additives in affecting the properties of asphalts. Sakanoue (49F) proposed ar: equation to relate penetration with viscosity based on a load and a penetration time. A similar subject was discussed by Savu and Iorga (50F) and by Bazhenov and Bukhaev (6F). Evans and coworkers ( I 8 F ) presented a review and published data on synthetic blends and reported on the major influence of wax being present since it acts as a thinning agent a t high temperatures and a thickening agent a t low temperatures. Miscellaneous Studies. There were a number of papers relating to the change of the properties of asphalt or bitumen with time as measured by various techniques. Ajour ( I F ) investigated a number of asphdts for their differences in asphaltene, sulfur, oxygen, and acid contents after being aged. Traxler and Scrivner (55F) studied the change in viscosity of asphalts when exposed to ultraviolet radiation at 95 "F and related the relative hardening with the vanadium content. Fenijn (19F) reported results for the rolling thin film oven test, and Oliver and Gibson (44F) utilized tritium labeling for following the changes in water soluble parts of asphalt. Robertson and Moore (48F) used inverse GLC to study variations in the performance of asphalt from different crude sources. Bynum and Traxler (9F) used gel permeation chromatography to study the mdecular size distribution of asphalts when exposed to UV radiation. The same authors ( 8 F ) reported on similar techniques for study of hardening of asphalt in paveinents. Corbett and Lawson ( I 1 F ) studied changes in bitumen and its fractions in atmospheres of nitrogen, oxygen and ozone through changes in their IR spectra after various lengths of time. King and Corbett (33F), using a novel technique for exposing thin films to gases, studicd how the various fractions from asphalt differed in their ability to absorb oxygen. Knotnerus (36F) studied the a1)sorption of oxygen a t ambient temperatures for asphalts in toluene solution under fluorescent light. Results weie compared with weatherometer test.s and high tempel-ature rolling thin film tests using some additives. Petersen and coworkers (45F) discussed the identification of 8-quinolones and the value of 1.R spectrometry for identification of carbonyl functional groups. Poxon and Wright (46F) pyrolized several asphalt$#and gilsonite utilizing gas chromatography to evaluate the results. Bartashevich and Ermakova (5F) emploj.ed IR and NMR techniques to study the chloroform soluble bitumoid and its components from platform sediments, and reported mainly weakly branched, polycyclic aromatics and oxygen containing compounds. In two publications Corbett (12F, 1317) reported on the use of generic fractionations by extriiction and liquid chromatography. The densimetric procedure was used to evaluate the differences in the results dcpending upon the crude source in the first paper; and, in the second paper, it was shown that combinations of the fractions would explain the variations obtained in such properties as the temperature susceptibility and the rheological characteristics. Markova et al. (40F) reported on the interfacial tension of bitumen with air over the range of 125-250 "C. Heukelom and Wijga (31F) discussed the viscosity of disper-' sions as they relate to bituminous emulsions and other'
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mixtures. Jimenez (34F) discussed the durability of certain asphalt emulsions as used in certain pavement aFplications and related the results to viscosity. Dormon and Snashall (15F) studied the importanca of flow and fracture of bitumen in connection with service performance of various asphalt surfacings. In another ptiper by Lottman (383') the debonding of water saturated asphaltic concrete was studied in connection with c:n:lic stresses for roads in Idaho. Haines (26F)reported on the use of inverse gas-liquid chromatography to evaluate the effect of oxidation on petroleum asphalts and the intwactions of the asphalt and aggregates in pavements. Asphalt Technology. The reviews as reported h t iein have not attempted to cover the very large numbcr of publications that result from research on asphalt applications where asphalt is studied for its use in combintition with mineral aggregates. Among the rather large arecisof research are asphalt rheology, asphalt durability, asphalt emulsions, and asphaltic concrete pavements. Then, are available to the researcher in these areas certain very comprehensive surveys and summaries from the Highway Research Board of the National Academy of Sciewes. This organization provides a highway research abstract service (HRIS) that includes not only work that has been published but also, in some cases, a summary of work that is under current investigation. The cost of obtaining such information through a computer printout may be somewhat expensive if one is not a member of HRB.
Catalysts J. Free1 Gulf Research and Development Co., Pittsburgh, Pa.
Elemental Analysis. Marsh et al. (38G) reviewed methods for elemental analysis in zeolite catalysts. They discussed volumetric and gravimetric techniques for aluminum and silicon, the determination of lanthano tis by X-ray fluorescence and wet chemical methods, and the flame photometric determination of sodium, pota: aium, and calcium. Dubinina and Berg ( I 7G) determined nickel, vanadium, iron, cobalt, and molybdenum in a singlt 0.5-g sample of spent cobalt-molybdenum-alumina ca ;(ilyst. The method involved a complex extraction procedura with spectrophotometric finishes, and the complete analysis required 5 days. A device for feeding powders directly into the flmne of an atomic absorption spectrophotometer was developed by Coudert and Vergnaud (13G). Various palladium-cc ntaining catalysts were diluted 100-fold with calcium car ,onate and analyzed in this way. Toma and Crisan (55G') described methods for the determination of iron, zinc, and sodium in alumina catalysts. After hydrochloric acid extraction, iron and zinc were determined by atomic i l~sorption, sodium by emission spectroscopy. No interfwences were found between the elements. The acid ext "action gave some aluminates which were difficult to disc ociate, but this effect was eliminated by adding excess strontium chloride. Liteanu et al. (34G) compared flame eiirission and atomic absorption spectroscopy for the determination of lithium in chromia-alumina catalysts. Lithium '7, as extracted with aqueous hydrochloric acid. The authors reported comparable accuracy for the two methods. Uribe (57G) used atomic absorption to analyze cracking c,italysts for iron, copper, nickel, vanadium, and chromium with fair accuracy. Using the iodide method, Lupert and Hozmar (36G) determined antimony and bismuth spectrophotometrically 178
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in alloy catalysts containing aluminum, silver, calcium, magnesium, zinc, antimony, and bismuth. The molar absorptivities of the two elements were measured a t two wavelengths, and various ratios of antimony and bismuth were determined a t concentrations >0.170with a n error of 0.8-2.3%. Neither silver nor lead interfered with the analysis. A spectrophotometric method for platinum in catalysts was described by Fisel and Simion (20G). Interfering elements were removed from a solution of the sample by treating with sodium hydroxide and sodium bicarbonate in the presence of nitrate ion. Addition of tin chloride produced a yellow complex which was extracted into butanol and determined spectrophotometrically a t 395 nm. Arroyo and Brune ( I C ) used neutron activation analysis to determine vanadium in oils and catalysts. The detection limit was 10 ppm in catalysts compared to 0.01 ppm in oils. Calistru et al. ( 1 I G ) used magnetic susceptibility data to determine nickel and cobalt oxides in catalysts. Susceptibility isotherms were measured between 100 and 300 " C for samples containing 1-1570 nickel or cobalt on alumina. A combusion method was used by Berg et al. ( 8 G ) to determine carbon and sulfur in catalysts. The combustion products were analyzed directly by gas chromatography. The authors report an analysis time of 10-15 min and cite 0.005 wt % carbon and 0.02 wt 70sulfur as their limits of detectability. A reductive coulometric method for sulfur was described by Svajgl (54G). Enterman et al. (18G) described an apparatus for the analysis of carbon and hydrogen in coked catalysts. Total carbon and hydrogen were calculated from the oxygen consumed during combustion a t 950 "C. Pressure drops after carbon dioxide and water absorption gave the carbon-hydrogen ratio. Analysis time was 5 min, and standard deviations of 0.01, 0.05, and 0.3% were found for hydrogen analysis, carbon analysis, and the carbon-hydrogen ratio determination, respectively. Surface Area Measurements. Hayes (23G) described a micro BET system suitable for low surface area solids. The adsorption cell and doser were a single unit comprised of three high vacuum valves and a thermistor. An inexpensive BET apparatus, for solids with surface areas in the 2-850 m2/g range, was developed by Benson and Garten (7G). A 0- to 800-Torr Bourdon gauge was used both to dose fixed amounts of nitrogen and to measure the pressure. Watanabe and Yamashina (59G) reported a rapid xenon adsorption method suitable for roughness factor determinations on evaporated films or foils. A new volumetric method applicable to samples of surface area >1 m2/g was described by Pommier et al. (46G). They compared this procedure with a chromatographic technique and showed that results from the two methods were in good agreement. The chromatographic method was also studied by Farey and Tucker (19G), who described a flow control system which minimized problems associated with gas blending and the effects of flow fluctuation on detector performance. A new procedure for calculating isotherms from peak area in the gas chromatographic method was given by Dollimore et al. (16G). Using a data logger and digital computer, the area under the peak was calculated from the top down, rather than vice versa. Heats of adsorption determined from such isotherms agreed better with values obtained by static adsorption methods than did previous chromatographic results. Burke and Ackerman (IOG) described a system for computerized data acquisition and surface area computation in the frontal analysis method. Karp and Lowell (30G) investigated the methods used to calibrate detectors for the flow techniqye. Their analysis showed that when nitrogen is injected into nitrogen/helium mixtures, the true volume responsible for the thermal
ANALYTICAL CHEMISTRY, VOL. 45, NO. 5, APRIL 1973
conductivity change is the volume of nitrogen introduced less the volume displaced. Pomeshchikov and Pozdeev (45G) measured krypton adsorption isotherms on various sorbents and compared the BET and DRK (Dubinin-Radushkevich-Kaganer) methods of estimating surface area from the isotherms. The monolayer volumes determined by the two methods were in good agreement provided that the BET equation gave a straight line. Naidu et al. (41G) compared mercury porosimetry with the BET method in mea’suring the surface areas of six different catalysts. For the samples studied, the cumulative surface areas obtained by porosimetry were in reasonable agreement with the B E T values. A critical discussion of surface area determinations by adsorption from the liquid phase was given by Schay and Nagy (52G). Adsorbate systems were recommended for determining the surface areas of both oxidic and carbonaceous adsorbents and the proper experimental conditions defined. The use of chemisorption to measure the specific surface area of metals on supports was discussed by Karnaukhov (29G). He distinguished between 2- and 3-dimensional metal accumulations and ascribed different adsorption properties to each. Methods were developed for calculating metal dispersion in either case. Hunt (25G) measured hydrogen chemisorption on supported platinum and palladium catalysts by a rapid thermal desorption method. Following hydrogen adsorption a t ambient temperature, the catalyst was heated from 21 to 370 “C in less than 1 min, and the hydrogen evolved swept into nitrogen carrier gas for chromatographic determination. Repeatability was 13%. Benesi et al. (6G) described a similar technique, except that 1% hydrogen in argon was used for both the adsorption and thermal desorption steps. For a series of platinum-silica catalysts, the data obtained were in good agreement with static volumetric measurements. Gruber’s pulse chromatographic method was also compared to static measurements of hydrogen chemisorption on platinum catalysts (21G). Again, the agreement between the two techniques was good. The chemisorption of hydrogen and oxygen on platinum catalysts was measured gravimetrically by Barbaux et al. (4G). The authors concluded that oxygen chemisorption on a hydrogen-saturated platinum surface provided the most sensitive measure of platinum dispersion. Wilson and Hall (60G) reexamined hydrogen chemisorption and hydrogen-oxygen titrations on platinum-alumina. Electron microscopy was used to provide an independent estimate of platinum particle size. They concluded that the stoichiometry of hydrogen chemisorption on platinum was reasonably constant as the platinum particle size was varied, but that the stoichiometry of oxygen chemisorption and the hydrogen-oxygen titration was not. Hydrogen chemisorption was, therefore, recommended for determining platinum dispersion on supports. Sermon (51G) described a new method for estimating palladium surface area which also involved the interaction of hydrogen and oxygen. The use of chemisorption to measure rhodium dispersion .on supports was studied by Wanke and Dougharty (58G), who investigated the adsorption of hydrogen, oxygen, and carbon monoxide on rhodium-alumina. The results obtained were significantly different from similar data for platinum-aluminas. Kirklin and Whyte (31G) examined small angle X-ray scattering as a means of determining platinum particle size in platinum-alumina catalysts. Interference scattering from the alumina micropores was eliminated by loading the pores with ethyl iodide. Both a mean size and the square root of the variance could be obtained assuming a
log-normal size distribution. Pore Structure Analysis. Unger (cF6G) reviewed the parameters used to describe pore structure and the methods used to determine them. The preparation of adsorbents with known pore structures was also discussed. Lard and Brown (33G) developed a rapid method for measuring the volume of catalyst pores in the 14-600 A range. Samples were equilibrated in flowing 96.7% nitrogen-3.3% helium a t atmospheric pressure and liquid nitrogen temperature. The volume of nitrogen desorbed on heating to 25 “C was then measured. Repeatability mas 15?0. A dynamic method for determining the size distribution of pores 15-300 A in diameter was described by Baresel and Gellert (5G). Nitrogen adsorption-desorption isotherms were measured a t liquid nitrogen temperature by varying the total pressure of a constant composition nitrogen-helium mixture. Dollimore and Heal (15G) compiired nine different methods of estimating the thickness o l the adsorbed layer from physical adsorption isotherms. Pore size distributions were computed for 36 silica a r d alumina samples using Dollimore’s method and assuming cylindrical, nonintersecting pores. DeBoer’s expression for the thickness t was recommended. Ione and Karnaukhov (26G) published a critical review of mercury porosimetry, which dealt mainly with the applicability of equations derived for cylindrical pores to real pore systems. Deviations caused hy the contraction of the sample, surface tension, and the contact angle of the mercury were also discussed. In a secclnd paper, Ione e t al. (27G) made a detailed study of errors arising from catalyst compression, and derived equations for correcting the pore volumes and pore radii obtained by mercury porosimetry. The same workers (28G) developed a modified electric dilatometer which reduced e-rors due to the partial filling of pores with mercury. A liquid-phase technique for the measurement of total pore volume was described by Bambrick and Geoghegan ( 3 G ) . Catalyst samples were wetted with known weights of 1%ammonium oxalate solution and their conductivities measured. Absorption of the solutioii into the pore structure caused a gradual increase in conductivity, with an abrupt rise in conductivity when the volume of electrolyte equaled the pore volume. A similar method was used to measure pore size distribution in construction materials by Astbury and Vyse (2G). An aqueous solution of 0.1M potassium sulfate was used as the electrolyte, and, in this case, information concerning the pore size distribution was developed by applying external pressure after the initial pore volume saturation. Miscellaneous. The use of gas chromatography in catalyst analysis was reviewed by Choud hary and Doraiswamy (12G). Subjects discussed included the measurement of specific and total surface areas, the analysis of pore structures, methods of measuring heat and mass transfer properties, and techniques for determining catalytic activity. Massoth (39G) reviewed appIications of the flow microbalance in catalyst studies, describing the use of both quartz spring and null beam balances in thermogravimetric analysis. Examples included the use of the flow microbalance in studying the dehydration of alumina, the coking and regeneration of silica-alumina cracking catalysts, and the adsorption of hydrocarbons on zeolites. An instrument for simultaneous DTA-TGA was described by Naidu et al. (40G). The authors discussed its utility as a quality control tool in catalyst development arid manufacture. Marcu et al. (37G) reported a semiautomatic apparatus for adsorption-desorption studies in which the electrical resistivity of the sample was measured.
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A simple method of determining the capacity of inolecular sieve catalysts for vapors was developed by Ro?lofsen (50G). Landolt (32G) also described a method for making this type of measurement. Okamoto et al. (43G) m e a u r e d the differential heats of n-butylamine adsorption or1 zeolite catalysts from n-butylamine-benzene solutions. The distribution of acid strength derived in this way differentiated a cation-dependent and cation-independent ac idity, the former being stronger. Catalyst acidity was also measured by Popowicz e t al. ( 4 7 G ) . Irreversible amiiionia chemisorption was determined by a chromatogruphic method, subsequent thermal desorption of the ammonia yielding a measure of acid strength distribution. Hirwhler (24G) extended his titration methods for measuring acid strength distribution by using a variety of amines with varying steric demand. The resulting data were U S ? ~to calculate the spacing of acid sites in catalyst surfaces. Bessonov et al. ( 9 G ) described a test of catalyst strength in which a hammer of variable mass was all3wed to fall onto the sample from different heights. Interpietation of the test results was discussed and illustrated with numerous examples. The measurement of diffusion cozfficients in porous catalysts was examined by Grachev p r a1 ( 2 2 G ) . By using a zero pressure drop method in whicl- two diffusing gas streams met inside the catalyst pellet, both the steady-state and nonsteady-state diffusion coeffic ents were determined in a single experiment. Richardson (49G) reported a method of analyzing rarbon concentration profiles in coked catalyst pellets. Coked catalyst spheres were regenerated under diffusion- r‘ontrolled conditions, measuring the carbon dioxide forr qed. Regeneration was stopped after various burning times, the spheres were sectioned, and the radius of the shell 01’removed carbon was measured. In a second paper, the s %me author (49G) described a chromatographic method for measuring the diffusivity of argon-helium mixtures in fouled catalysts. Diffusion occurred mainly in the l;id*ge pores of fresh Nalco 471 catalyst and was predominantly bulk diffusion. In contrast, diffusion in the coked cata yst was primarily Knudsen diffusion in micropores. The application of electron spin resonance spectrosc )py to catalyst analysis was reviewed by van Reijen (48G) ;ind Lunsford ( 3 5 G ) . Both authors discussed the spectra of adsorbed organic and inorganic radical ions on oxide surf; ces, lattice defect studies, and the application of ESR to systems containing suitable transition metal ions. Peanun (44G) used wide line nuclear magnetic resonance spectrcjscopy to distinguish between surface and bulk protons iii a transition alumina. The total hydroxyl content was gi\ t’n quantitatively. The fraction of hydroxyls in the surface was estimated from line width and found to be a function of B E T surface area. Ogilvie et al. (42G) discussed t h e analysis of catalyst structure by ESCA. They reviewed the theory, scope, and limitations of the new technique and described investigations of supported and unsupported divalent copper catalysts, zinc oxides, and various otk tlr metal oxide systems. The characterization of oxide catalysts by electr In probe mjcroanalysis was studied by Cormack et al. (14C’). Small amounts of magnesium, calcium, and nickel promoters in a n iron oxide catalyst were found to precipitate as ferrites. Schmidt et a1 (53G) used scanning electron microscopy, Auger spectroscopy, and sputtering tec 1niques to analyze rhodium-platinum gauze catalysts. Tlii: application of these modern instrumental methods to e i i applied catalyst problem was particularly fruitful in theii study, providing a correlation between catalytic activil y and catalyst structure. 180 R
Physical Properties W. A. Wright Sun Oil Co., Marcus Hook, Pa.
A comparison of the literature appearing since the 1971 review indicates that the topics of interest are about the same. There is evidence that it has not been as productive a period, even though the volume of papers has not decreased substantially. The areas of rheology, P-V-T relationships, and thermodynamic properties still exhibit the most activity. It is hoped that the work covered here represents a temporary period of lower activity rather than a retrenchment in effort. Most of the problems are still as demanding as ever. Rheology. There have not been many new viscometric techniques proposed, although Ray and Biswas (48H) studied the use of a vertically oscillating sphere on a spring mount. The frequency and amplitude were correlated to viscosity as long as the fluid flow was laminar. Hodgins and Beams (25H) disclosed a magnetic densitometer-viscometer which simultaneously measured density and viscosity on a 0.3-ml sample. A Zimm-Crothers type viscometer was improved by Scherr et al. (51H) including electronic timing. Lessnig (35H) automated Ubbelohde and Ostwald capillary viscometers and provided for digital print out. Smith et al. (53H) also automated the flow timing for a suspended-level viscometer. The torsional crystal was used by Collins and McLaughlin (10H) for viscosity measurements on light hydrocarbons under pressure up to 1750 kg/cm2. Fieggen (16H) derived a viscosity-temperature equation using four independent parameters based on an assumed quasicrystalline liquid structure. Good agreement was found for several compounds. The Walther viscosity-temperature equation for petroleum products was examined by Rumpf (50H). He devised a graphical method for determining the value of “c” which increases a t low viscosity and high temperatures. Rivkin and Levin (49H) derived a relationship between macroscopic compressibility of a liquid and its absolute temperature. The viscosity was also correlated to various thermal properties. Abbott et al. ( I H ) obtained a n improved correlation between the Watson characterization factor, specific gravity, and the viscosity-temperature behavior of petroleum fractions. van Velzen et al. (59H) related viscosities between the boiling and melting points to hypothetical alkanes having a 1 CPviscosity a t the temperature of the compound. Solov’ev and Egle (55H) related kinematic viscosity of petroleum products to temperature with a semilog equation. The equation includes the minimum viscosity possible for the particular liquid. Bazhenov and Bukhave ( 6 H ) correlated penetration of highway asphalts with temperatures over short ranges with a second power equation. Porokhov (43H) developed a formula and nomogram for pressure coefficients of viscosity and- related these to the operating characteristic of lubricating oils. Sodhi (54H) published a n extensive review of viscosity-temperature characteristics of lubricating oils. An equation for change of viscosity with shear rate for non-Newtonian flow was developed by Cross (11H). There seemed to be fewer publications on >on-Rewtonian lubricants during the period covered by this review. Liquid Density and Volume. Spencer and Danner (56H) modified the Rackett equation for hydrocarbons. It gave accurate predictions from the triple point to the critical point. Bagirzade ( 5 H ) studied the variation of density, refractive index, and viscosity of oils with temperature. Rastorguev (47H) related the density-temperature
A N A L Y T I C A L CHEMISTRY, VOL. 45, NO. 5, APRIL. 1973
corrections for paraffins, naphthenes, and aromatics to the inverse mole mass of fractions. A nomograph based on the ASTM-IP measurement tables was published (8H). Zanker (63H) prepared a density-temperature nomograph for oils and also one to permit calculation of the pour point of a mixture of two oils. A new sight glass and high pressure mercury seal suitable for P-V-T piezometer measurements up to 600 bars of pressure was developed by Akhundov et al. (4H). Hirsch (24H) studied the relations between molecular volume and structure of' hydrocarbons. A computer program was developed to aid in deriving the structure of petroleum fractions. Meisner (38H) related molar volume and thermal pressure coefficients to carbon number for homologous series using a corresponding states principle. The molar volumes of gases a t high pressures and low temperatures were measured by Haufe and Tannenberger (22H) in a n instrument consisting of two connected autoclaves. Yazgan (61H) used velocity of sound to determine adiabatic and isothermal compressibility up to 30,000 psi. Downer and Gardiner (12H) studied the isothermal compressibility of lubricating and crude oils up to 35 bar. The data were used to estimate errors in the API Standard 1101 compressibility tables. Density and bulk modulus of aviation instrument oil and its mixtures with 2methylbutane were measured by Houck and Heydemann (26H). The pressures ranged to 20 kilobars. The compressibility charts for gases by Nelson and Obert were converted to equations suitable for a computer by Bogomol'nyi and Stankevich ( 7 H ) . Distillation a n d Vaporization. Green (20H) described a n automatic gas chromatographic system which was related to the ASTM distillation curve for products boiling up to 540 "C. Ermolaev (15H) determined saturated vapor pressure of turbine oils by passing air over an oil sample and obtaining weight losses. Hientzsch et al. (23H) devised a more sophisticated Engler unit to develop boiling point curves for petroleum fractions. Johnston and Sargent (27H) derived an empirical equation to obtain vapor pressures of low viscosity lubricants from a modified ASTM D 86 distillation test. Results were obtained more rapidly and accurately than with the isoteniscope. Fowler and Trump (18H) described an automatic recording tensimeter. I t was also used to obtain decomposition temperature. Pestrikov et al. ( 4 2 m developed Antoine equations to calculate the effect of pressure on the boiling points of naphthenic acids. Gandbhir and Virk (19H) described a technique to interconvert ASTM and true boiling points of hydrocarbon mixtures by a special "probability" paper giving straight lines for cumulative volumes us. temperature. A nomograph to predict LPG vapor pressure was developed by Zanker (64H). Chernyshev ( 9 H ) also prepared a nomograph to obtain the heat of vaporization of liquids. The temperature scale represented the difference between the critical temperature and the temperature of interest. Mathur and Kuloor (37H) gave an equation to obtain latent heat from molecular weight of hydrocarbons. An equation to obtain latent heat of hydrocarbons from Raman frequencies was presented by Lielmezs (34H). King and Naylor (29H) prepared a nomograph for latent heat prediction from normal boiling point and molecular weight. Miscellaneous Thermal a n d Physical Properties. Frith (17H) gave a discussion on methods of computerizing calculations for critical values, specific heats, conductivity, latent heats of vaporization, etc. An additive group technique for calculation of gas heat capacities was developed by Ramalho and Thinh (44H). Liquid heat capacities were generalized by Yuan and Stiel (62H) using the Pitzer acentric factor and the Halm-Stiel fourth parame-
ter. Thinh and Duran (58H) used AI'I Research Project 44 data to develop four-term polynomid equations to predict heat capacities. Constants were ts bulated for over 400 compounds. A new equation for predicting critical volume was developed by Hall and Yarhorough (21H). Stein (57H) derived equations for obtaining the critical specific volume and derivatives of the thermal equation of state a t the critical point for pure fluids. Naziev et al. (60H) measured the thermal conductivity of ri -heptane at pressures up to 1000 atm and 300 "C. The pressure dependence of' conductivity decreased with rising pressure and decreasing temperature. Thermal conductivity of hydrocarbon mixtures was measured in a new de&e by Nurberdyev et al. (40H). The triple calorimeter was operated up to 1000 bars and 500 "C. Papadopoulos (4115') discussed the use of thermistors in measuring thermal conductivities. A relative method for thermal conductivi ;y using the temperature differences between two stainless steel concentric cylinders was developed by Kerimov et al. (28H).The instrument was first calibrated with known pure fluids. A formula relating density to heat conductivity was derived by Akhmedov (3H). A new method for measuring surface tension correlates the rate of decrear,e of a cavity with viscosity and surface tension as developed by Elmas (14H). Lielmezs and Watkinson (32H) del-ived a corresponding state equation for liquid surface tension. They (33H) also evaluated its application for high molecular weight liquids. The determination and prediction of flash points of multicomponent liquid mixtures was studied by Affens and McLaren ( 2 H ) . A compilation of combustion and physical properties related thereto was prepared by McCracken (36H). The qualitative relations between the structure of cyclic hydrocarbons and their auto-ignition temperatures were derived by Kurss e t al. (30H). Small additions of aromatics were recornmended to increase auto-ignition resistance in aviation fuels. Formulas for calculating flammability, ignition, jlash, and flame temperatures for hydrocarbons were b a e d on boiling .point and molecular weight by Shimy (52H). Rao and Kuloor (46H) prepared a nomogram relating heats of combustion to molecular weight. The chart WiiS based on API Research Project 44 data. Leffler (31" also prepared a nomogram to compare the equivalent fuel values of several selected hydrocarbons. New equations for gaseous diffusivity of binary systems were prepmiredby Ramamurthy and Narisimhan (45H). They were obtained by applying the theorem of corresponding states to the equations of Hirschfelder, Bird, and Spotz. Eaton (13E-I) developed melting point predictions for homologous series, based on observation that the product of the liquid-temperature range and the solid-temperature rmge was linear with molecular weight. Zanker (65H) reduced the UOP correlation index to a nomograph. Nongbri and Alpert (39H) presented a n equation and graph to otitain viscosities of' petroleum fractions from API gravities and sulfur contents. The viscosities were suitable for equiFment design.
Hydrocarbons T. J. Mayer Sun Oil Co., Marcus Hook, Pa.
Gas chromatography continues to be the most popular single technique for the analysis of' hydrocarbons and a large number of new applications, using either new column materials or various instrument modifications, continue to be reported in the literaturt:. An increasing preference for investigating capillary GC techniques was noticed in this review along with a renewed interest in preparative-scale gas chromatography.
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Research into the use of GC-MS and a new technique, Carbon-13 NMR spectroscopy, along with the more conventional MS and l H NMR techniques, provided the major portion of published spectroscopic methods. Apymently little work is being done with IR and UV. The trend in hydrocarbon analysis seems to be a-cvay from individual compound analysis and toward hydr0c:iirbon type or group analysis. Efforts continue toward ailtomation of instrumental techniques. Elemental Analysis. Glass and Cowell (671) descrikc! a precise combustion method for hydrogen that was deieloped for the rapid analysis of macrosamples of petroleum products boiling above 200 “C without risk of explosion. Hydrogen was determined by a macrocombustion over copper oxide in a nitrogen atmosphere to give close control of combustion rate. Typical analyses of pure hydrocarboiis, and of nonvolative liquid and waxy petroleum-based ]riaterials, gave a standard deviation for precision of O.O:::I% hydrogen. Liederman and Glass (1071) described tlizir patented torch analyzer used for the precise determiiration of hydrogen. On a routine basis, 12 to 15 sam1)les could be analyzed in 8 hr using this torch analyzer. Aliro, a n improved torch was described which used interchar .::eable metal parts when the dimensions were critical so that the need for highly skilled quartz working was eliminaicd. Smith et al. (1811) obtained microdeterminations of C, H, N, and 0 in petroleum samples using a n automatic ?lemental analyzer; the results were comparable to those obtained by conventional methods. This automated met iod was useful for analyzing petroleum samples contair ing 0.05 to 0.1% N. Liquid Chromatography. Liquid chromatograF ltic techniques have proved quite valuable for the analysi!; of higher boiling petroleum fractions. Haines e t al. (721) described the chromatographic separation scheme deve1o:ied by API Research Project 60 for the separation of high boiling petroleum distillates. Five ’crude oil fractions n we separated into acids, bases, neutral nitrogen compour.ds, saturates, and aromatic compounds for further M S clitiracterization. A second report by Jewell and cowor1:i:rs (891) described the separations in more detail. The scid and base fractions were, respectively, separated by 8~01umn chromatography on Amberlyst A-29 and Amber yst 15 anion- and cation-exchange resins; the neutral nitrogen fraction was obtained by coordination-complex formal ion with ferric chloride supported on a kaolin-Chromosorl: W column; and the remaining hydrocarbon and “nonpol sir” nonhydrocarbon compounds were separated into satui,ate and aromatic fractions by silica gel adsorption chromalography. A further separation of the aromatic concentriices into mono-, di-, tri-, and polyaromatic subfractions .,vas described by Jewell et aI. (881). The separation was done by gradient elution chromatography (GEC) on freshly .:alcined, water-free alumina using continuous on-line monitoring of the effluent stream with a UV detector. Alcyl substituted benzenes and benzenes containing up to tlii,ee cycloparaffin rings were included in the monoarom;itic fractions, but benzenes containing two or more isolated t e n zene rings or monobenzenes containing more than three (ondensed cycloparaffin rings appear in the diaromatic E-ilctions. Another method, reported by Hirsch et al. (771) used a single dual-packed column containing fully activated Ijilica gel in the top half and fully activated alumina in the bottom half to separate samples into saturates, monoilromatics, diaromatics, and other polyaromatics/polar cornpounds with three or more aromatic rings, which rriay contain heteroatoms. A gradient elution technique ,vas also used here. The concentrates prepared by this method 182 R
had only small amounts of cross-contamination, as shown by spectral adsorption and radiotracer examination. Popl and coworkers (1511) used gradient elution techniques to separate mono- and polycyclic aromatic hydrocarbon mixtures. In their first report, they used a programmed gradient of pentane-ethyl ether eluent on alumina columns containing 2% water which shortened the analytical time to about 2.5 hr and increased the sharpness of the separation. The method was applied to the qualitative and quantitative analysis of aromatic hydrocarbons in kerosene oils ranging from alkyl benzenes to benzanthracene. Spectrophotometric detection at 260 nm permitted determinations of 0.570 hydrocarbons in less than 1-mg samples. In the second paper (1491) the pentane-ethyl ether solvent was replaced by cyclopentaneether which improved the sensitivity and selectivity. This method was tested on a standard mixture of polycyclic aromatics and was also applied to the analysis of an extract of coal tar pitch. Popl et al. (1501) also reported using a 4-m column packed with alumina containing 0.5% water, n-pentane, and methylcyclohexane as eluents, and a UV spectrophotometer with a flow through cell as the detector for the analysis of alkyl benzenes. For n-alkyl benzenes, retention volumes increased with increasing chain length up to CS, then remained constant up to C11. Berthold et al. (191) described a chromatographic procedure for the quantitative structure type analysis of aromatic concentrates. Aromatic compounds were complexed with picric acid absorbed on activated silica gel and then single structural types such as monocyclics, bicyclics, tricyclics, tetracyclics, pentacyclics, and all other polycyclics were eluted with various solvents a t various temperatures. The resulting fractions were concentrated and analyzed by thin layer chromatography. Stejaru et al. (1881) described a gradient elution technique using alumina columns for the analysis of mineral oil components. The mineral oils were separated into a series of fractions containing alkanes plus cycloalkanes, mono-, bi-, tri-, tetra-, polycyclic aromatic hydrocarbons, and S-, 0-, and N-heterocyclic compounds. The purity of the separated fractions was determined by UV spectrophotometry and refractive index. The reproducibility was within rt0.570 and the recovery was greater than 99%. A liquid chromatographic method to determine the group composition of petroleum fractions with the speed and accuracy sufficient for a n automatic process was described by Ivanova et al. (841). Reproducible results were obtained in 60-70 min with a relative error of 10% or less in determining the saturated, monocyclic, and bicyclic aromatic portions of an extract from crude oil and a synthetic mixture. The column was packed with 150-200 mesh alumina gel, and isooctane was used as a liquid carrier. Martin e t al. (1201) described a group analysis of industrial mixtures of polynuclear aromatic hydrocarbons by rapid liquid phase chromatography. Short alumina columns were used with n-pentane or n-heptane as the mobile phase. Under these conditions, the hydrocarbons were separated by the nature of their aromatic characteristics such as number of rings, linkage of these rings, etc., while the elution time was more or less independent of the possible presence of alkyl chains or of the length of these chains. The FIA method for the analysis of hydrocarbon types, based on liquid displacement chromatography, is still undergoing some experimentation. Perry (1411) reported that the method could be accelerated considerably (from 1 hr to 5-10 min) by increasing the pressure applied a t the silica gel-packed column head from 1-5 psig to 20-35 psig, using a silica gel of pHq and injecting the sample a t the
A N A L Y T I C A L CHEMISTRY, VOL. 45, NO. 5, APRIL 1973
neck below the charger section of the standard FIA tube. The results obtained with this rapid method were in good agreement with those of internationally standardized methods and the precision was about the same as that of the ASTM/IP method. Perry also discussed the extension of the method to higher boiling samples such as gas oils and its use to obtain representative saturate fractions. Sinha and Venkatachalam (1 791) reported optimum experimental conditions for FIA analysis using anthracene as the indicator and N z 0 4 saturated silica gel as the visual marker for olefins. The best resolution was obtained on dry silica gel. These authors (1801) also reported FIA experiments using various aromatic compounds as indicators in benzene solution and on columns of silica gel dyed with Sudan red 111. They found that 2-methylanthracene and 9-methylanthracene gave the best results for aromatic fluorescence both in the presence and absence of olefins. Variations of standard chromatographic techniques have been reported by different authors in an attempt to further improve procedures for hydrocarbon analysis. Stevenson (1891)described a high pressure liquid chromatographic technique for the rapid separation of petroleum fuels by hydrocarbon type. The samples were injected directly into a high pressure system consisting of a stainless steel precolumn packed with 30% Carbowax 600 on silica and an analytical column packed with 10% Carbowax 600 on Bio-Si1 HA. A separation of gasoline or jet fuel into saturates, monoaromatics, and diaromatic hydrocarbons was accomplished in less than 10 min. Chromatography with a super critical mobile phase was discussed by Rijnders (1591). This report on fluid-solid chromatography covers theory, comparisons with gas-solid chromatography, the effects of pressures up to 50 atm, temperature, and the nature of mobile phases and column packings on the separations of various compound types and homologous series. Tanimura and coworkers (1951) developed a new technique which they named droplet countercurrent chromatography. This all-liquid separation technique was based on the partitioning of solute between a steady stream of droplets of moving phase and a column of surrounding stationary liquid phase. Using this technique, the author separated milligram quantities of dinitrophenyl (DNP) amino acids with an efficiency comparable to that of gas chromatography. Sheehan and Langer (1771) developed a method for rapidly screening potential liquid extraction solvents or solvent pairs for liquid-liquid chromatography using published gas-liquid chromatographic data. The basis of the method was experimental data for the C7 through Cs n-alkanes and 1alkenes, benzene, toluene, o-xylene, and rn-ethyltoluene on five stationary phases. Nomura and coworkers (1321) studied the adsorption chromatography of 38 benzene derivatives on various resins including Bio-Rad AG 50W and Dowex 50W (H+ and Na+ forms). Adsorption isotherms were discussed and the distribution coefficient and HETP values on the two resins cited were calculated and tabulated. Gel Permeation Chromatography. Oelert and Weber (1364 studied the separation of hydrocarbons and related compounds by gel permeation chromatography. Linear correlations between relative elution volume and carbon number, molecular weight, and molar volume were derived from semilogarithmic plots of GPC data for 79 paraffinic, cyclic, and aromatic hydrocarbons and sulfur, oxygen, and nitrogen compounds obtained with the Poragel A-l/methylene chloride system, and from published GPC data. For condensed aromatics, the relation of interaction volume and the number of x-bonded carbon atoms was shown, and was different for polyaromatics, kata-con-
densed aromatics, and peri-condensed aromatics. The separation of nonhydrocarbons depended on the basic structure and functional groups. Oelert 1.1341) also studied the elution behavior of 40 hydrocarbons from the polyvinylacetate gel Merckogel OR-500 using cyclohexane, methylene chloride or isopropanol. For application to crude oils and high boiling petroleum fractions, refractive indexes were correlated with elution volumes for 30-mg samples and methylene chloride eluent, on the assumption that naphthenes and aromatics predominate and the molecular weight is constant. The elution curves from vacuum gas oils and a diesel oil were characteristic and reproducible but could not be correlated to any specific property of these materials. Schulz (1731) predicted the GPC (elution behavior of branched alkanes in the C7-Cll range by use of a published correlation between the averagc? number of gauche arrangements the molecule can assumc? and physical properties related to the molecular voluines. The data confirmed that the gel permeation procws is one of volume exclusion and that for small nonpolar molecules the molecular volume alone (but not the molar volume) explains the elution behavior. Thin Layer Chromatography. The number of published applications of TLC for the analysis of hydrocarbons decreased considerably since the last rwiew in 1971. Martinu and Janak (1210 investigated the selective chromatographic separation of aromatic hydrocarbons and their hydrogenated derivatives on Porapak T in both TLC and LC applications. The differences in retention in the system Porapak T-nonpolar solvent were analytically significant and enabled substances that differed in structure by only one double bond to be separated. Peurifoy et al. (1451) studied the TLC separation of hydrocarbon types in heavy oils with the emphasis on separation of petroleum resins. A three-stage discontinuous layer .gradient plate, comprised of silica gel G, alumina G, and Florisil G with phosphor gave better separations .;ban the single adsorbent plates. An eluotropic series of nine developing solvents for the petroleum resin separation was given. Thielemann (1971) reported the separation of 11 polynuclear aromatic hydrocarbons by TLC on Silufol UV 254 plates by using hexane-chloroforra (95:5) as the developing solvent. The compounds wei’e detected by spraying with SbC16 in chloroform or UV i1:radiation. A new technique called “Drum TLC” was described by Saunders and Snyder (1681). This technique, which was developed for rapid, high efficiency separations of poorly-resolved bands, involved partial immersion of an adsorbent-coated drum in solvent; the drum was rotated at a speed sufficient to keep the bands stationary just above the solvent. A description of the drum apparams and procedure plus a discussion on the limitations and possible modifications of the method were included in the paper. Physical Properties. Instrumental methods for the determination of molecular weight continued to be reported. Holle e t al. (791) described a new apparatus for determining the molecular weight of petroleum products by vapor pressure osmometry. This method was 2-3 times faster than the cryoscopic method and was accurate to 1.112.90% (relative) for molecular aeights of 122-850. It was suitable for petroleum fractions having Reid vapor pressures 50.3 kg/cm2 a t 50 “C. Paul and Umbreit (1401) described an apparatus for determining molecular weights by gas chromatography. The apparatus, which uses two gas density balances and two different carrier gases, splits the sample into two reproducible portions. The molecular weight and the absolute weight of each component were calculated from the ratio of the two signals obtained. The
ANALYTICAL CHEMISTRY, VOL. 4 5 , NO. 5, A P R I L 1973
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system was applied to mixtures of hydrocarbons having molecular weights of 86-338. Ali (71) calculated mo:lerately accurate molecular weights of aromatic compounds containing only one basic aromatic system using the ratio of peripheral carbon atoms to the total number of a wmatic carbon atoms. This ratio was readily determined from NMR/IR and C-H analyses. The method was app.icable to compounds containing heteroatoms and can a LO be used for average molecular weights of mixtures. Simple contamination with nonaromatic hydrocarbons did r ot influence the calculated molecular weight. Ioffe and coworkers (831) described methods for determining hydrocarbon types in straight run gasolines b y refractive index methods. They first reported a dispersiometric method for determining the total content of aromatic hydrocarbons in straight run gasolines. Data on refrs ctive index of the fractions obtained a t two different Iiavelengths were used to determine the aromatics content within 0.4-0.5% of the results obtained by sulfonation and chromatographic methods. This method required only 10 min compared to 60-120 min for the others, and pre iminary fractionation of the sample was eliminated. 1’Eieir second method (811) determined naphthenes in the nonaromatic portions of straight run low sulfur gasolines by using a nomogram having as coordinates the spe-ific refraction, and n of paraffins and naphthenes in stantliud oil fractions with specified middle range boiling points. Data for the construction of the nomogram were supplied. Their final publication (820 combined these two procedures into one refractometric method for determining the hydrocarbon type composition of the straight run gz EOlines which required only the values of the refractive indexes a t the red (C) and the blue (F) hydrogen lines 2nd the density. The aromatic content and the concentrat on of naphthenic hydrocarbons were found from the two methods described above. The results agreed within &2.3% absolute with those calculated from analyses of standard samples, the mean absolute error in the determination of the aromatics being &0.5%. Gas Chromatography. New and different materids continue to be investigated as possible GC column packings for the separation of hydrocarbon mixtures. Mathews et a!. (1231, 1241) described the preparation and evaluition of isocyanate-based polyimides as liquid phases for gilj chromatography in two publications. The noncross-linked, organic solvent-soluble polyimides prepared by reactir E: C36 dimer diisocyanate with anhydride, formed homoge neous, tenacious films on siliceous and steel surfaces an3 were stable up to 325 “C. Good results were obtained wit i hydrocarbon samples on both packed and capillary columns. A cracked hydrocarbon wax in the C14-C36 rang? was successfully separated on a steel capillary column coated with PZ-117 polyimide and programmed from 130 to 300 “C. Uno and Okuda (2051) separated m- and p . chlorotoluene and m- and p-xylene using a GC columr packed with napthalene-l&diamine (20% on Chromosorl: W) operating at 80 to 95.5 “C with helium as a carrier gas. Liquid crystals have been used by some authors as GC packings for the separation of particularly difficult mixtures. Richmond (1581) studied the behavior of the ortho, meta, and para isomers of 25 disubstituted benzenes using one or more of three liquid crystal materials. Vigdergauz and Vigalok (2104 used p,p’-azoxyphenetole, which exists in a nematic phase a t 136-167 “C, for the GC separation of dimethylnaphthalene pairs. The authors also stated that complete separation of alkyl naphthalenes was possible on a binary sorbent consisting of p,p’-azoxyphenetole and polyethylene glycol 2000. They concluded that the control of selectivity in the analysis of complex 184 R
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mixtures could be improved markedly by using a binary liquid crystalline phase where the components form a eutectic mixture and as a result the sorptive properties no longer follow the additivity rule. Chow and Martire (331) used GLC to obtain infinite dilution activity coefficients and partial molar enthalpies and entropies of solution for 42 nonmesomorphic solutes including paraffins and haloderivates, alkenes, aromatics, etc. in both the nematic and isotropic liquid regions of p-azoxyanisole and 4,4’dihexoxyazoxybenzene. The authors found that with regard to chromatographic separation of isomers using liquid crystal stationary phases, the shape, size, flexibility, polarity, and polarization were all important in determining the relative solubilities of isomers. The use of GC packings with chemically-bonded stationary phases was illustrated by Little and Dark et al. (1101). They separated a premium gasoline on a programmed temperature (40-200 “C) column of a 400 mol wt polyethylene glycol bonded to Porasil S silica, all six Cq alkanes and alkenes on octane bonded to Porasil C, and ethane, ethylene, and acetylene on phenyl isocyanate bonded to Porasil C. Some controlled surface porosity supports with chemically bonded organic stationary phases suitable for both gas and liquid chromatography were described by Kirkland and DeStefano (924. These “permanent” stationary phases could be produced with a variety of functional groups resulting in chromatographic columns with widely diverse selectivity. GC packings made with these phases show extremely low vapor pressures a t high temperatures. Column life was excellent and the level of detector background noise due to stationary phase bleed was minimal. Grob and McGonigle (701) investigated the use of vanadium(II), manganese(II), and cobalt(I1) chlorides as GC packings to separate alkanes, alkenes, and alkynes. Compounds with K bonds were more strongly absorbed than those without; thus, hexane, hex1-ene, hex-1-yne were eluted in that order. Gil-Av and Schurig (651) investigated the use of rhodium coordination compounds as stationary phases for the GC separation of monoolefin mixtures. They found that a series of dicarbonylrhodium(1) p-diketonates interacted rapidly and reversibly with olefins. One complex was examined in detail using 27 C 2 - c ~ n-alkenes and 12 cyclic olefins and was found to interact far stronger than silver complexes. Janak et al. (851) investigated the use of olefin-silver ion complexes for the chromatographic separations of higher olefins in liquid-solid systems. Static and dynamic measurements of the adsorption of nonane, decene, and benzene were made on Porapak Q columns in the presence of propanol, water, and AgN03. The author stated that the K complex formation of olefins with Ag+ in the mobile phase altered their retention volumes and allowed their separation from other hydrocarbons. Rang and coworkers (1561) studied the GLC separation of the geometric isomers of straight-chain 2-alkenes and 3-alkenes on columns loaded with AgNOs-polyol stationary phases. They found that the optimum column performance was achieved with saturated AgN03 in the polyols and with liquid phase loadings of 40%. Both old and new materials have been investigated as stationary phases in gas-solid chromatographic applications. Cook and Givand (371) prepared Chromosorb Wsupported silver nitrate complexes from pyridine and from 2-, 3-, or 4-methylpyridine. These complexes preferentially absorbed olefins from their mixtures with alkanes and adsorbed 1,4-hexadiene more strongly than 1-hexene. A second report by Pflaum and Cook (1461) indicated that promising results were obtained with 58 pure organic compounds using nickel complexes as absorbents in GSC.
A N A L Y T I C A L CHEMISTRY, VOL. 45, NO. 5, APRIL 1973
Fifteen C5-Clo aliphatic, alicyclic, and aromatic hydrocarbons were included in tests made a t 50, 85, and 125 "C on four different nickel complex columns. Vernon (2081) studied GSC on modified alumina stationary phases. Alkylated benzenes were separated on NaCl-impregnated, NaOH modified A1203 stationary phases. He reported that symmetrical peaks were obtained even for hydrocarbons with boiling points up to 350 "C. Surface modified alumina was used by Neumann and Hertl (1311) for hydrocarbon separations in a parallel IR/GC study. The electron accepting alumina sites, which are the most active on the alumina surface and lead to severe tailing and excessive retention times, were effectively removed by treatment with pyridine or acetic anhydride. Compared with untreated alumina, the pyridine- or anhydride-treated alumina gave greatly improved resolution as illustrated by the separation of a commercial gasoline. Seide and coworkers (1751) discussed a procedure for modifying silica gel for use as a GC phase in the separation of aliphatic and aromatic hydrocarbon mixtures. This column has the advantage over more conventional columns of heat stability (to 800 "C) and indefinite life in programmed temperature operation. Ross and Jefferson (1661) discussed the advantages of using in situ-formed open-pore polyurethene as a chromatographic support. The polyurethene was easily prepared to uniform structures in columns of 0.06-2.25-in. i.d., adhered to the column walls thus preventing channeling, and could be used as support in gas-solid, gas-liquid, and liquid-liquid separations and TLC. Good separation was demonstrated for several n-alkane mixtures and for gasoline components under various conditions. Dunlop and Pollard (471) designed a GC injection system for light hydrocarbons, to improve on the durability of commercially available sample introduction systems using indium tubing, to be intrinsically safer than high pressure liquid sampling valves, and to have much better reproducibility than syringe sampling. Applications included the routine analysis of c 2 - C ~hydrocarbon streams, of Cs and heavier hydrocarbons, and of oxygenated compounds in Cq hydrocarbons. Applications of gas chromatography to petroleum chemistry were reviewed by Berezkin and Nametkin (141). The discussion covered the combination of GC with physical and chemical analytical methods, reaction chromatography, and the use of computer and rapid GC data processing along with the usual topics of stationary phases, separation efficiencies, and faster analysis times. Churacek et al. (34I) used three columns in various combinations to separate 21 components of a mixture of rare gases, permanent gases, and lower saturated and unsaturated hydrocarbons. Column A was packed with 20% bis(2-methyloxyethyl) adipate on Chromosorb P, Column B was 1 m of Porapak Q operated at 20 "C, and Column C was 5 m of Porapak Q operated a t -78 "C. As combination of A and C separated the permanent gases and the C1 to CS hydrocarbons; a combination of B and C separated the rare gases and the permanent gases. A threecolumn system was also used by Deans et al. (411) for the isothermal GC analysis of light gases. This system consisted of a primary column packed with Porapak T connected in series to two columns in parallel, one containing Porapak S and the other 13X molecular sieves. Column temperatures ranged from 35 to 100 "C. Preparation of the apparatus and its operation, including column switching and back-flushing, were described. Malan and Brink (1181) also used a three-column configuration for the analysis of some inorganic gases and light hydrocarbons. Their system was compiled from three columns packed with
DC-200, dibutyl maleate, and Porapak Q. This system was ideally suited for computer link-up because no negative peaks or base-line upsets were observed. Marchio (1190 described a dual-channel GC technique for analyzing mixtures of permanent gases and G-Cz hydrocarbons. His instrument comprised two complete units maintained a t 50 "C and provided with individual gas sampling valves and thermal conductivitj detectors. The first channel, which measured hydrogen with nitrogen as a carrier, consisted of a single column; the second channel, which determined the remaining CZ and higher components with helium as carrier, consisted of two columns in series. This technique permitted sariples to be analyzed in 16-18 min. Some authors have investigated alumina as a stationary phase for the GC separation of light gases. Duerbeck (451) investigated the quantitative simultaneous determination of hydrogen, methane, ethane, and ethylene by GC using a column packed with neutral, 60-8C1 mesh alumina, deactivated with 5 ml of water and treated for 60 min a t 160 "C in carrier gas. A single determination of the quantitative calibration factors was sufficieiit for calculating the concentrations of the four componerlts in less than 10 min with a standard deviation of +=1.5%. Paterok and Wandzik (1391) examined the usefulness of four kinds of alumina and 13 liquid stationary phases for the separation of CI-CS hydrocarbons by GC. The best results were obtained using Alcoa Type F-1 alumina with 1,2,3-tris(2cyanoeth0xy)propane as the stationary phase. Additional data on this column packing were reported by Paterok and Kotowski (1381) showing that temperature dependence and variations of the ratio of liquid phase to alumina affected the separation of 19 comi3ounds. Packed columns continue to be used for the GC analysis of hydrocarbon mixtures. Akopova et al. (41) determined C2-C5 hydrocarbons in straight run unstabilized naphtha by cooling the sample to -15 "C, changing the direction of the helium or hydrogen carrier giis flow after the n-pentane peak was eluted, obtaining ii single peak for the Ce and higher hydrocarbons, and interpreting quantitatively by the method of internal standardization. Toader and coworkers (1981) analyzed gasoline cuts boiling from 50 to 140 "C by combined molecular sieves adsorption and chromatography. The n-alkanes were separated in a column containing 5A molecular sieves s t 180 to 220 "C and the n-alkane-free sample was analyzed by column chromatography over dioctyl sebacate on Chromosorb P using temperature programming. The olefins were removed from the sample before analysis by adsol-ption on alumina or on mercuric perchlorate. Peterson and Rodgers (1420 analyzed cyclic hydrocarbons and normal and isoparaffins by carbon number in naphthas by gas-solid chromatography. A combination of 5A and 13X molecular sieve columns was used. Aromatics, and other unsaturated compounds if present, were hydrogenated in A precolumn immediately after injection. Satisfactory sepwation of the hexane and heptane isomers present in a 14-component mixture of saturated .linear, branched, and cyclic Ce-C7 hydrocarbons was achieved by Vollert and Mautsch (2114 using columns packed with 20% N,N-dimethyl-1-naphthylamine or N,N-diethyl-1-naphthylamincton kieselguhr. Gawlik and coworkers (621) developed a method for the determination of small amounts, of hydrocarbon impurities in Clo-Cls n-paraffinic fractions using 5A molecular sieves. The method consisted of two stages. First, the sample with a n internal reference standard added was analyzed in a separating column. The second stage was analogous, with the use of an additional precolumn
ANALYTICAL CHEMISTRY, VOL. 45, NO. 5, APRIL 1973
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packed with molecular sieves which adsorbed n-para1finic hydrocarbons. The content of impurities in the sariples was obtained by comparing the results of the two-jtage analysis. For wide boiling range fractions, the impu pities a t a level of 0.4-10.0 wt % could be determined with tatisfactory accuracy. Bernardini (161) described three GC methods for the determination of n-paraffins in mi tldle distillates: (1) Separation of unsaturated hydrocarbons by silica gel followed by GC determination of the saturnted hydrocarbons. (2) Separation of the n-paraffins by their affinity for urea followed by GC. (3) Removal of n-paiaffins by molecular sieves followed by capillary column GC with differential analysis. Method 3 could be used for all middle distillates, while methods 1 and 2 were preferible for light distillates below Clz. In addition to the traditional silver nitrate coluni ns, other GLC systems are being used for the analysis of slefins in hydrocarbon mixtures. Kugucheva and Alekseuva' (1011) studied the use of molecular sieves for the GC anal. pore ysis of olefins. All types of Ca+ zeolites and 4-5 A size granulated silica were studied. All the zeolites caused cis-trans isomerization and double bond shift in the isoolefins. A part of the branched C&S olefins were iireversibly absorbed on zeolites. Retention of n-olefins by he zeolites was incomplete, some 3 to 5% passing throu,:h. Silica grains pass up to 70% of the normal hydrocarbms and cause isomerization of normal and branched olefi,is. The authors (1021) also developed a method for the identification of acetylenes and conjugated dienes in pyrolyjis and cracked products which contained paraffins, monoo P fins, and naphthenes. The acetylenes and dienes were t e lectively reduced on Pd catalyst and the acetylenes were absorbed by saturated silver nitrate solution on Chromosorb. The dienes were separated by a modified maleic a i hydride method. Fourteen acetylenes and dienes we-u identified using a packed column with a flame ionizatic~i detector, McDonough and George (1151) described a procedure for the GC determination of the cis-trans isomw content of olefins, The method involved epoxidation of tl-c olefin followed by reduction and acetylation of epoxidized alcohol. Samples were then injected onto GC columns packed with 5% of various stationary phases. An improved silver nitrate GLC column was used bq Schmitt and Jonassen (1711) to separate high boiling cyclic diolefins. Fourteen different columns were evaluated for the separation of some cyclic diolefins and their iso. mers in the C ~ and O CS series. A 20% loading of silver ni trate-Carbowax 20M or AgNOs-Carbowax 1540 gave thv best separations. Zlatkis et al. (2211) used carbon molecu lar sieve columns for the trace analysis of impurities in ethylene. These columns could also be used in the determination of N oxides, HzS, and S02. Jaworski and Szewczyk (861) described a method for the GC determination of impurities in a propylene fraction. The column was packed with 25% formamide on a fire resistant brick GS-22 which completely separated methylacetylene, butadiene, and propadiene. For acetylene separation, a packing of 15% dimethylsulfolene on Celite must be used. A rapid two-stage GC method for determining aromatic hydrocarbons in gasolines was proposed by Vigalok and coworkers (2091). The first-stage column retained paraffinic and aromatic hydrocarbons a t 80-140 "C on 1,2,3,4tetrakis(P-cyanoeth0xy)neopentaneas a fixed phase. The second-stage column had 10% p,p'-azoxyphenetole as a fixed phase and was operated a t 140 "C. Duerbeck (461) separated isomeric C&lo aromatics using packed columns and Bentone-34 modified with silicone oil and lanolin. For maximum resolution, the proportions of the modi186
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fying agents were important. Retention data and chromatograms for 23 aromatic hydrocarbons obtained with two different column types were given. A method for the GC determination of polycyclic hydrocarbons which might be adapted to the analysis of airborne particulates and petroleum distillates was reported by Bhatia (214. Separation of benzo(a)pyrene, benzo(e)pyrene, benzo(k)fluoranthene, and perylene from each other and other polycyclic aromatic hydrocarbons was obtained using temperature programmed GC on columns packed with OV-7-coated glass beads. Column performance was strongly influenced by the column preparation method. Since the number of possible isomers makes the identification of individual components highly impractical in higher boiling petroleum fractions, even with the separating power of gas chromatography, more attention has been given to the quick analysis of hydrocarbon types in these fractions. Dorokhov et al. (441) described a system for the two-stage GC analysis of unstable catalytic reformate. The instrument consisted of two chromatographs connected in series by means of a six-way stopcock. The first chromatograph was used for the analysis of aromatic hydrocarbons and for the separation of the c 2 - C ~paraffinic fraction which was then analyzed in the second chromatograph. This procedure shortened the analysis time to 1 hr. A hydrocarbon-type analysis of olefinic gasolines using through a column packed with N,N'-bis(2-cyanoethyl)formamide on Chromosorb W to remove aromatics; these of Brunnock and Luke described in the 1971 Petroleum Reviews. ThB sample, in hydrogen carrier gas, was passed through a column packed with N,N'-bis(2-cyanoethyl)formamide on Chromosorb W to remove aromatics; these were backflushed and determined as a total with the flame ionization detector. The rest of the sample was passed over a platinum-alumina catalyst in a small oven to hydrogenate the olefins and then into a 13X molecular sieve column to determine paraffins and naphthenes. In a second run, the sample was passed through a small precolumn containing mercuric perchlorate to remove olefins and aromatics and then through the 13X molecular sieve column. Paraffins, olefins, cycloparaffins, and cycloolefins up to Cll were determined with sufficient accuracy and good reproducibility in three cracked naphthas boiling in the 45 to 180 "C range. A complete analysis required a time period of three hours. The analysis of hydrocarbon types-saturates, aromatics, and olefins-by selective chemical absorption and flame ionization detection can be done in 5 min on samples boiling up to 220 "C using the technique developed by Soulages and Brieva (1851). A special accessory was installed directly in the GC oven in place of the column without further modification. A 2 . 5 ~ 1injected sample is split into three parallel flows so that the different hydrocarbon types reach the detector in the order: saturated hydrocarbons from the first branch (in which aromatics and olefins are retained by mercuric perchlorate/perchloric acid absorbent), the total sample from a branch containing no absorbent, and saturated and aromatic hydrocarbons from the third branch (in which olefins are retained by mercuric sulfate/sulfuric acid absorbent). Commercial and synthetic gasolines and other hydrocarbon mixtures were successfully analyzed. Hydrocarbons were automatically analyzed in an apparatus patented by Mator (1251) in which two GLC columns were arranged to permit backflushing and isolation of components within the system. Aromatics were isolated in the first column and the second column separated n-alkanes from naphthenes. Total paraffin equalled n-alkanes times an ex-
A N A L Y T I C A L CHEMISTRY, VOL. 45, NO. 5, A P R I L 1873
perimental factor and the naphthenes were determined by difference. Finally, a completely automated GC system for the PNA (paraffin-napthene-aromatic) analysis of naphthas was described in two papers by Boer and Van Arkel (221, 231). This automatic analyzer, devised for straight run as well as processed streams in the boiling fange of 0 to 200 "C gives per cent paraffins, naphthenes, and aromatics per carbon number during 2 hr of unattended operation. The separation between paraffinic and naphthenic bands of equal carbon number is quantitative through Cg, nearly quantitative for Cl0, and still useful for C11. Following injection of the naphtha sample, the instrument performs a sequence of separations on a polar, a nonpolar, and a 13X molecular sieve column, using flow switching and hold up of fractions of the sample. To obtain accurate analysis, all separations must be carried out on a single sample in a closed system and the components measured with a single detector. A module matching the analyzer allows additional differentiation between 5- and 6-ring naphthenes as well as n- and isoparaffins. The authors state that the PONA analysis of olefinic naphthas is under investigation. Capillary Gas Chromatography. Petroleum chemists who are developing GC methods for the analysis of hydrocarbon mixtures are now favoring capillary columns over packed columns, judging from the increased number of references using the former technique. Petrovic and Vitrovic (1441) used an Apiezon L-coated, 50 m long by 0.1-mm diameter steel capillary column for the direct GC determination of Cg-C14 rz-paraffins in kerosene fractions. Quantitative results were obtained by comparing n-paraffin peak heights in the sample to those 'on a reference standard chromatogram. The method, which was faster than the molecular sieve paraffin adsorption procedure, showed a coefficient of variation of 1-270 and a relative error rt2-3%. A versatile short IO-m by 0.010-in. capillary column coated with OV-101 was described by Gouw and coworkers (691). The column was used to analyze petroleum fractions with end points >lo00 "F and high boiling waxes up to n-C5s, yet it could easily resolve isobutane from n-butane at lower temperatures. A surprising quality was its exceptional ability to resolve isomers of high molecular weight compounds. Another application of this column was its use for simulated distillation of wideboiling range mixtures. Lindeman (1080 used a 1000-ft X 0.01-in. squalanecoated capillary column in the analysis of naphthas for C9- and Clo-alkylcyclohexenes. All of the nongeminally substituted Cs-alkylcyclohexenes and all but six of the nongeminally substituted Clo-alkylcyclohexanes were prepared by hydrogenating the corresponding alkylbenzenes. GC-MS was used to identify the products of these hydrogenations. GC relative retention times and Kovats retention indexes were then calculated for all the isomers and these data plus available data for geminally substituted cyclohexanes were used to identify 20 products from the isomerization of n-propylcyclohexane over AlC13. A selective capillary coating made from a mixture of nhexadecane, n-hexadecene, and KEL was used by Petrovic and Kapor (1430 for the analysis of straight run gasolines and reformates. The composition of C&8 hydrocarbons in straight run gasolines, the c 5 - C ~hydrocarbons in the nonaromatic fraction, and the C&g hydrocarbons in the aromatic fraction of the reformates was determined. The capillary GC procedure was accurate within 2% for components present in concentrations greater than 1%, to within 5% for components in concentration 0.1-1.0% and to within 10% for components in concentrations 0.01-0.1%.
The GC behavior of tricyclic saturated hydrocarbons was studied by Vanek and coworkers (2071) on polar (Carbowax 20M) and nonpolar (SE-30) stationary phases in capillary columns. The Kovats retention indextbs for various tricyclanes were successfully correlated with the homomorphic factors, the differences between the retention indexes on the two sorbents and the chemical (or stereochemical) structure. The authors claimed that the correlaticms could be used for differentiating between stereoisomeric mixtures of two or more hydrocarbons, predicting the rvtention indexes for individual stereoisomers, and determining the configurations of unknown stereoisomers. ZlatKis and de Andrade (2201) studied several silver nitrate substrates on capillary columns for the analysis of olefins. The columns were tested for temperature stability and their ability to separate alkenes. Best results were obtained with 1,2-bis(2cyanoethoxy)ethane as stationary phase (1 ml) containing AgN03 ( 2 g) with operation a t 60 "C or with temperature programming. Such a column was caiJable of separating a number of alkenes including several pairs of cis-trans isomers. Lulova et al. (1131) studied the composition of individual c5-cS hydrocarbons and cracked gasolines using a 120-m long by 0.25-mm i.d. copper c:%pillarycolumn coated with squalane. More than 90 individual compounds consisting of c 5 - C ~hydrocarbons of p and y olefin type with one methyl group and n-olefins with one double bond in the p and y position were identified along with 5-carbon cyclic olefins, isoparaffins, and 5-carbon naphthenes. Prior to the capillary GC analyses, the catalytic cracked gasoline fractions had been separated by silica gel into paraffin-naphthene, olefin, and aromatic fractions. Sojak et al. (1831) determined the optimum conditions for separation, on a 200-m squalane column, of the olefins and aromatics in the dehydrogenation prcducts of C&lo n-alkanes. A complete analysis of a 60-component mixture at 115 "C took about 160 min. Dec-1-erie and trans-dec-4-ene could not be separated. The data obtained in this study were used by Sojak et al. (1841) to identify all nine straight chain undecenes in a m i x t x e obtained from the dehydrogenation of n-undecane. The relative amounts of individual positional undecanes found were about 1:4:4:3:3 for the 1-, 2-, 3-, 4-, and 5-isomers and abput a 2: 1ratio for the trans and cis isomers of the last four. Correlations of retention data on two different capillary columns were used to identify alkylbenzenes in hydrocarbon mixtures in two different laboiatories. Krupcik et al. (1001) examined the validity of relations between the structure and GC retention data of C&lo alkylbenzenes on capillary polyethylene glycol 2 nd squalane columns. They proposed a relationship bet%een the linear correlation of free energies and the differcnces of the Kovats' indexes in the two liquid phases. The relation was demonstrated experimentally and then used to identify Cll alkylbenzenes from GC data. Aliev and coworkers (61) studied the effect of the boiling points of C&12 alkylbenzenes on retention volumes in capillary columns coated with dialkylnaphthalenes and bis(1-phenylethy1)glutarate as stationary phases. They found a strict linear dependence existed between the logarithm of the retention volume and the boiling temperature of the homologous aromatic hydrocarbons. Data for 42 Cs-C1z alkylbenzenes were reported using these two capillary columns. Stuckey (1900 used two capillary columns in series to identify 23 aromatic compounds in the 375-435 OF fraction of crude oil. The first column (300-ft X 0.01-in.) was coated with 1,2,3-tris(2-cyanoethoxy)propane(TCEP) and the second (150-ft x 0.01-in) was coated with silicone DC-550. The first column separated the saturated compounds
ANALYTICAL CHEMISTRY, VOL. 45, NO. 5, APRIL 1973
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from the aromatics, and the second column separated 38 aromatic compounds eluted after tridecane. Tho GC retention parameters of methyl- and dimethyltetralim on Apiezon-L and pentaerythritol tetrabenzoate werc reported by Vaisberg and Gizitdinova (2061). The retention volumes relative to tetralin and the Kovats retentio;i indexes were determined for 21 tetralin hydrocarbons. ;1Iostecky et al. (1291) determined C12 alkylnaphthalenes and niethylbiphenyls in aromatic fractions using three different capillary GC columns. Identification of 18 dimeihylnaphthalenes, ethylnaphthalenes, and methylbiphenyls in the 250-280 "C pyrolysis oil from naphtha cracking and in a 130-160 "C black coal tar cut was achieved by comparing the retention times, relative to naphthalene, of the hydrocarbon compound types on Apiezon-L a t 180 "C, mbis(m-phenyoxyphen0xy)benzene a t 200 "C, and polyethyleneglycol adipate a t 190 "C. UV spectrometry was used to determine 2,6- and 2,7-dimethylnaphthalenes, which were not separable chromatographically. Tomii e t al. (1991) found capillary columns to be much more efficient than packed columns for the analysis of heavy aromatic by-products from hydrodealkylation processes. A prior distillation of the circulation-tower Iiottoms residue from a Hydeal benzene unit permitted the identification of 122 components which comprised >'W% of the total residue. When direct-packed columns u ere used, only 22 components could be identified. The mrijor components found were naphthalene, biphenyl, 3-methylbiphenyl, fluorene, and phenanthrene. Kozeiko et al. (971) used a dialkylnaphthalene (DAN) with two c24 alkyl groups to separate isomeric alkylaromatic hydrocarbon mixtures on a 45-m X 0.25-mm dianeter capillary column. According to the authors, DAN knd 8, 10, and 40 times the polarity of Apiezon-L, tricresyl phosphate, and polyethyleneglycol adipate, respectively, in tests with benzene and n-heptane. Pollock (1481) found that GC capillary columns coatcd with Dexsil 400-GC in its capped (end groups covercd with trimethylsilyl groups) or uncapped (free hydro:::$ end groups) form exhibited small base-line drifts whtm operated a t greater than 325 "C or greater than 225 "C, I T spectively, and could be used for short periods of time sit 350-400 "C or 225-300 "C, respectively. Separations of C1o-CZo saturated hydrocarbons on the Dexsil 400-GC columns were demonstrated. Cramers et al. (391) demonstrated the potentialities of micropacked columns for applications in petroleum chernistry. Columns of 0.6- to 0.8-mm diameter and up to 15 111 long with very homogeneous packing densities and up to 50,000 theoretical plates were prepared by packing tli,? coiled column with carefully sieved support under pressure and vibration. All types of support precoated with any stationary phase were used. Several hydrocarbcn mixtures containing low-boiling alkanes, alkenes, and al.kyldienes up to c8, benzene, neopentane, and methylcycloalkanes were successfully separated a t 70 and 150 "C o n micropacked columns with various packings. High ten.perature GC separations using glass capillary columns and carborane stationary phases were reported by Novotny and coworkers (1331). The constituents of petroleum frat tions containing hydrocarbons up to CSOand other compounds of up to 800 mol wt were separated with good efficiency at up to 350 "C on phases such as Dexsil 300-GC and Carborane polymers 700-8-73 and 700-8-95C applied to 0.3-mm i.d. by 28-35 m long silylated glass capil1ar:r columns. Krajnovic and Osterman (991) determined the concen. trations of Cs through C7 hydrocarbons in crude oil bjr 188 R
ANALYTICAL CHEMISTRY,
GLC without preliminary distillation. The apparatus included a precolumn packed with 0.17- to 0.25-mm Chromosorb supporting 20% of Apiezon-L operating at 120 "C and fitted with a backflushing device, connected by a gas sampling valve to a support-coated open-tubular capillary column (squalane as stationary phase) operated a t 40, 65, or 80 "C. Forty-two components in two crude oils were determined and were compared with results obtained by distillation. For components present in concentrations less than 0.01%, more accurate results were obtained by analyzing the gasoline fraction rather than the crude oil. A method for the rapid hydrocarbon-type analysis of gasoline by dual column GC was reported by Robinson et ul. (1641). The saturates, olefins, and aromatics content of gasoline were determined using an uncoated open tubular column a t 250 "C connected in series to a N,N'-bis(2-cyanoethy1)formamide coated column operated at 50 "C. After elution of the saturates from the coated column, the olefins were adsorbed on Chromosorb P containing 40 wt % Hg(C104)Z and 15 wt % of 70% HC104, and the aromatics were backflushed through the coated column for rapid detection. The average relative error was 1.6% for determining the hydrocarbon types in a synthetic blend. The advantages of a dual column (packed and capillary columns in series) for GC analysis was demonstrated by Walker and Wolf (2121). Complex C1-Czo hydrocarbon mixtures were resolved by GC, without subambient temperature programming or backflushing, by using a dual capillary column consisting of a short (5 ft) capillary column packed with Porasil B followed by an open tubular capillary column (50 ft long) coated with polydimethyl silicone (OV-101). The column separated the hydrocarbons produced by the pyrolysis of phytane. GC Peak Identity. The use of the Kovats retention indexes, or some variation of this system, seems to have become the most popular method for correlating GC retention times. Takacs and Szita (1921) developed a method to calculate retention indexes of paraffin hydrocarbons on the basis of their molecular structure. The method, based on the Kovats system, calculated the retention index of a saturated aliphatic hydrocarbon by treating it as the sum of the molecular index contribution (which equals the atomic index and the bond index contributions) and an index of interaction with the stationary phase. Retention indexes on squalane calculated for 16 C&10 isomeric alkanes were in excellent agreement with the experimental values. Martynov and Vigdergauz (1221) studied the relationship between the retention index of Cs-Clo alkanes and their structure and physical chemical constants. They found that rectilinear correlation of retention index with boiling point for isomeric alkanes existed only over a narrow range of working temperature; for c s alkanes the optimum range was 20 to 30 "C. The possibility of determining density, boiling point, and other constants of the alkanes from measured retention index values was shown. Louis (1121) calculated the Kovats index tables for 195 commercially available C4-C12 hydrocarbons boiling from 20 to 220 "C. The data for nine rz-paraffins, 66 isoparaffins, 74 cycloparaffins, and 46 aromatic hydrocarbons were obtained in GC columns containing bis(2-ethylhexy1)sebacate, silicone DC 550, and Apiezon-L as stationary phases. Hala et al. (731) studied the relationship between structure and retention values on three stationary phases for 31 adamantanoid hydrocarbons. By plotting the retention indexes on two different stationary phases, a graph was obtained from which the number of methyl and ethyl groups a t the bridgehead carbon atoms could be determined unambiguously. Cook and Raushel (381) calculated the
VOL. 45, NO. 5, APRIL 1973
Kovats retention indexes for the benzene ring and 27 individual substituent groups from new experimental GC data obtained a t several temperatures on Apiezon-L, SE-30, and squalane. The generally good agreement between the measured values for di- and trisubstituted benzene derivatives and the values predicted by adding the contributions of the individual substituent values established the validity of the method. Wallaert (2134 published an equation for calculating the Kovats retention indexes of alkylbenzenes on Carbowax 1540 capillary columns from the alkylbenzene boiling point, column temperature, and the ratio of the number of aromatic C atoms to the total number of C atoms in the alkylbenzene molecule. The equation permitted identification of unknown GC peaks and optimization of the column temperature. Bach et al. (111) derived a new parameter, the “retention boiling point,” which they used to supplement the Kovats identification system. Based on the thermodynamic relation between retention time and vapor pressure of a substance, a retention boiling point was introduced which, with suitable selection of the working conditions, approximates very closely the true boiling point. Robinson and Ode11 (1631) devised a system of standard retention indexes ‘for the characterization of stationary phases and prediction of retention times. An equation was given from which a “standard retention index” could be calculated for a hydrocarbon using its boiling point and those of two reference n-alkanes. Experimental retention indexes were determined for 39 hydrocarbons in seven different classes on four stationary phases. Stationary phases could be characterized by the difference between the standard and experimental values of retention index for each of the seven classes of hydrocarbons. Schomburg ( I 721) reported the application of retention index values and their structural increments to the identification of the components of isomeric hydrocarbon mixtures by combined methods. Methods were described for the identification, via retention index increments, of isomeric hydrocarbons separated by gas chromatography. The procedure of deducing structural information from the retention behavior in combined systems (reaction GC, GC-MS, etc.) of components separated by GC was explained by means of flow diagrams. Finally, a Fortran IV computer program was developed by Castello and Parodi (301) for the automatic calculation of GC retention indexes. Either normal paraffins or other homologous series can be used as reference substances, and data from isothermal and temperature programmed analyses can be processed. The program was designed to be easily used by any gas chromatographer without need of particular knowledge of programming languages. Berezkin and Tatarinskii (151) developed a method for the identification of chromatographic peaks based on the combination of elemental analysis for C, H, N, and 0 and the data on the retention values. Rezl et al. (1571) identified organic substances by means of the direct coupling of GC with elemental analysis. A conventional gas chromatograph fitted with a katharometer detector was coupled directly to a previously developed carbon-hydrogen analyzer to determine C and H on a submicro scale with a precision of better than &0.3% absolute. Umstead and coworkers (2021) studied the response characteristics of the catalytic ionization detector to organic compounds of varied molecular structure. The degree of ionization on platinum catalyst in oxygen a t 400 to 900 “C depended strongly on the structure of the compound. Many petroleum analysts are now using GC retention
times for the prediction of various other properties of hydrocarbons. Weingaertner et al. (2161) calculated the boiling points of hydrocarbons from their retention times, t ~ , using the formula log t~ = log A m(1og bp). The empirical constants A and m were calculated from t~ and bp’s of two homologous n-paraffins selected as reference substances. The A and m values were valid for all hydrocarbon peaks between the two reference peaks. The authors then used these calculated boiling PO nts to identify unknown mixtures of saturated and aromatic hydrocarbons. Boiling points were calculated from CiC data for the CIO hydrocarbons of the cis-bicyclo(3.3.0)octane series by Makushina et al. (11 71). Thirty-four stereo isomers of 1,2-, 1,3-,3,7-,2,7-, and 2,8-dimethylbicyclo(3.3.0)octaneswere synthesized, their spatial configuration was determined, and a methylenation technique and capillary GLC were used to determine their ‘elution sequence and retention times. Shevchuk et al. (1231) studied the relationship between the chromatographic retention indexes and the thermodynamic characteristics of paraffins, cycloalkanes, and olefins. They showed that the heats of solution of isomeric alkanes and cycloalkanes in nonpolar solvents decrease with increasing number of geminal hydrogen-atom pairs on the molecule. The relationship between the retention indexes of olefins on squalane and their heat of formation was represented as a series of straight lines corresponding to the number of substituents a t the unsaturated bond in the olefin molecule. The estimation of errors in the determination of‘ heats of evaporation by gas chromatography was determined by Dondi et al. (431) using a statistical analysis based on more than 900 retention volume measurements. The computer-assisted analyses yielded criteria which could be used to estimate the error in retention volume and AH as well as the precision and reliability of 1(1H)values derived either from AH or directly Yrom relative retention parameters. Lodi and Costa (1111) evaluated the thermodynamic functions calculated froin GC determinations. The relative retention times of C S - C n-paraffins, ~~ Cz-C? n-alcohols, and c 6 - C ~2-methyl paraffins were correlated with their absolute entropy, free tmergy, enthalpy of formation, and specific heat, and conditions were determined for the validity of linear correlations between these properties. Bezukhanova and Diniitrov (201) determined the heats of adsorption of 31 moccel dialkylbenzenes on B silica-alumina catalyst of the Houdry type by gas adsorption chromatography. They found a dependence between the heats and the length, structure, and mutual position of the substituents in the benzene ring. A correlation was found between the adsorption and the reactivity of the dialkylbenzenes on the silica-alumina catalyst. Wicarova et al. (2170 studied the reliabilit-7 of the excess enthalpies calculated from GLC retention data. A statistical analysis of the infinite dilution activity coefficients and partial molar excess ‘enthalpies determined from high precision GC retention data showed that the enthalpy values were as precise as calorimetric ones for values over 500 cal/ mole. A rapid and simple GC technique for determining the infinite dilution relative volatilities of a pair of solutes in a higher boiling solvent W ~ Sdeveloped by Tassios (1961). The results obtained by this method for five hydrocarbon pairs with phenol and other solvents compared favorably with those obtained from equilibrium-still measurements. Preparative Scale GC. A slightly revived interest in preparative scale chromatograohy was apparent during the period of this review. Carei et al. (281) described the construction and operation of B gas chromatograph utiliz-
+
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ing sectional 1-ft diameter columns. The apparatus was similar to that described previously which used columns of 4- to 6-in. 0.d. The columns consisted of connectini: tubes 2-ft long X 1-ft0.d. The fractionation of 1.5 1. of a mixture of c6, and c7, and CS alkanes on an 8-ft column waii illustrated. The quantitative recovery of hydrocarbons in preparative gas chromatography was reported by Postnov and Lulova (1521). Good results were obtained in the collection of n-heptane in a trap by use of carbon dioxide as carricr gas after which calcium chloride tubes were attached i o the ends of the trap, and the carbon dioxide was evapo.xted. Similar success was obtained with a CS-CIS mixture of liquid paraffins. Khurana et al. (911)used preparative ?;tale GC for the analysis of individual aromatic compounds boiling up to 195" in a petroleum fraction. Preparative G(: was effected using TCEP as the stationary phase, and the separated compounds were identified using IR spectroscopy. Over the boiling range 185 to 217 "C, GLC separation was poor but tentative assignments for most of the pcaks could be made by resubjecting the trapped fractior L; to GC on an analytical Apiezon-L column. Gelpi and coworkers (631, 641) pioneered in the app:ication of GLC techniques to separations which required the use of highly efficient small-bore columns. Their first report described the evaluation of chromatographic techniques for the preparative separation of steranes and 1)riterpanes from Green River formation oil shale. Their objective was the isolation of milligram amounts of high purity terpenoid hydrocarbons. Partial separations were obtained by liquid adsorption and gel filtration chromatography. However, because of the complexities of hhe mixtures, the nonpolar character of these compounds, 2 lid the relatively small differences in boiling points and molecular size, they concluded that gas chromatography vus more suitable for these separations. A second repo;t (letailed their milligram-scale automated preparative GLC technique. A complex mixture extracted from Green Rixw oil shale was treated with thiourea to yield two fractiotis enriched in 5a-steranes and triterpanes, respectively. Milligram amounts of these were isolated on an automatic preparative unit which was modified for operation with an 3lytical size columns. It was possible to collect compounds with a purity of 99%. Chromatographic Component Identification. Tke rapid development of GC-MS and GC-IR instrument2 tion has made the on-line techniques much more popular than the off-line for the identification of chromatographically separated components. Some refinements in off-linl? trapping techniques were reported, however. Cronin (4011 developed a simple quantitative method for trapping ant1 transfer of low concentration GC fractions, suitable for ust! with some small diameter glass column systems. Results, showed the trapping system to be 100% efficient a t 2 to 1 E ml/min and 99.8% at 20 ml/min of carrier gas flow. Bus and Liefkens (270 developed a system for the collection of microgram GLC fractions for IR analysis. The fraction was trapped in an 18-cm Ag capillary tubing immersed in a Dewar flask containing liquid N. After several intermediate steps, the trap contents were transferred using a Hamilton syringe into an IR microcavity cell and the IR spectrum was scanned. The method was suitable for compounds with boiling points between 35 and 250 "C. Primavesi (1541) developed a GC apparatus for concentrating, and subsequently either detecting or trapping for spectroscopic examination, trace impurities which emerge after the main GC peak. Three different separating columns were used with a microkatharometer and FID detectors. 190
The system was demonstrated by determining trace compounds in purified toluene. Osborne (1371) reported a simple technique for isomer identification using GC coupled with infrared spectroscopy. A Minipress (Wilks Scientific) was held at the exit of the GC unit flush with the chromatograph housing and a KBR disk was prepared rapidly in situ as the peak emerged from the column. The technique was illustrated by the unequivocal identification of 8-methylquinoline and 2,4,8-trimethylquinoline in a reaction mixture. This technique required a sample size of a t least 0.5 p1 and the sample should have a boiling point greater than 150 "C. Brown and Warren (251) built a rapid scan IR spectrophotometer for operation with support-coated open-tubular or packed GC columns. The double beam instrument, with scan rates of 5-20 sec over the 3700-750 cm-1 spectral range, had sufficient resolution to identify components in chromatographic fractions of a 20-pg sample. An apparatus for combining a gas chromatograph with a spectrophotofluorometer and other devices by means of a flowing liquid surface was patented by Beroza and Bowman (170. The two instruments were combined so that the substances which were separated in the gas chromatograph were absorbed in a flowing stream of solvent and monitored in a flow cell of the spectophotofluorometer or in another instrument, depending on the property of the solute being determined. Chromatograms were obtained for five polynuclear hydrocarbons using a glass column. Less than 1 ng of some of the compounds was detectable based on noise level of 0.01 relative intensity. Burchfield et al. (260 developed a gas phase fluorescence detector for the gas chromatography of polynuclear arenes which permitted the analysis of pairs of compounds, such as perylene and benzo(a)pyrene, that could not be separated on currently available GC columns. Gallegos (611) demonstrated the power of combined GC-MS by identifying 36 individual components in the saturated fraction of Green River shale. Included in these identifications were two tetracyclic and 11 tricyclic terpanes, two 5-@-steranes,Fj-a-pregnane, and some branched paraffins. A capillary column (150-ft X 0.02-in. i.d.) coated with 7% OV 17 was used for the separations. Aleksandrov et al. (51) used GC-MS to analyze paraffin and naphthene hydrocarbons with the same retention time. The method was based on evaluation of the sums of the intensities of the mass spectrometric peaks of the characteristic ions. It was used for the qualitative and quantitative determination of c6-c9 hydrocarbons in a petroleum fraction boiling from 62 to 105 "C. New computer evaluation techniques were devised by Hites and Biemann ( 781) to monitor continuously scanned mass spectra of GC effluents. One of the most useful was the display of the change of an abundance of certain ions during the gas chromatogram (called "mass chromatogram"). This technique permitted detection of the presence or absence of homologous series of compounds as well as the specific substances of known or predictable mass spectra. Application of this technique to the analysis of oil shale for organic acids not volatile in steam was described. Reaction Gas Chromatography. New methods of reaction gas chromatography continue to be developed for the analysis of certain hydrocarbon and functional group mixtures. Franc (571) patented a method for the identification of alkyl groups in organic compounds by destructive cleavage. A 60:40 mixture of silica-alumina was impregnated with 4.5% by weight of a mixture of Wo3 and Moo3 in a quartz tube. A sample was fed to the column using hydrogen carrier gas and the decomposition prod-
R * ANALYTICAL CHEMISTRY, VOL. 45, NO. 5 , APRIL 1373
ucts were analyzed by gas chromatography. A procedure for the identification of alkanes by pyrolysis GC was published by Brown (241). After pyrolysis of the sample a t 500 "C, the products were analyzed on a 2% Apiezon-L column for compounds boiling greater than 100 "C or on a column coated with octadec-1-ene for C1-CT compounds. N-Alkanes were detected as 1-olefins in the pyrolysate. Most of the C6-C8 alkanes were identified and the principal skeletal structures were indicated. Diskina et al. (421) determined 6-carbon naphthenes in several dearomatized heavy naphtha fractions by reaction gas chromatography. The hydrogenation catalyst comprised 19.6% by weight of platinum and 2.8% by weight of iron on Chromosorb W. A maximum relative deviation of 7.4% was observed between this procedure and ordinary analytical dehydrogenation. Moore and Brown (1281) used ozonolysis followed by GC for the microscale structure determinations of terpenes. Dry ozonized 0 was passed through the sample of terpene or similar unsaturated compound in CS2 or ethyl acetate a t -70 "C or a t room temperature, and the ozonolosis mixture was treated by one of three methods according to the nature of the fragments expected and then subjected to GLC. Useful structural information was obtained with 10 mg of material. Takeuchi (1931) used hydrogenation gas chromatography to determine acenaphthylene and acenaphthene. A precolumn packed with platinum on Diasolid L was used in conjunction with an analytical column packed with 5% Apiezon-L on Celite 545. By the use of proper operating temperatures in the precolumn, acenaphthylene could be reduced to various reduction products and then analyzed in the analytical column. The hydrogenation products were identified by retention data and IR spectra. The advantages of using laser pyrolysis for the GC analysis of petroleum products was demonstrated by Folmer and Azarrage (551). The authors postulated that fewer secondary reactions should occur with the laser owing to the extremely rapid heating and cooling of the sample. Thus, in general, laser pyrolysis chromatograms show similar peak patterns and allow greater distinction to be made between pairs of similar substances than either filament or tube-furnace pyrolysis. Examples of several pairs of substances readily distinguished by laser pyrolysis were shown. Ristau and Vanderborgh (1601) also used laser pyrolysis for the analysis of various petroleum products. GC determination of the products, and the study of the fragmentation patterns, of various solid hydrocarbons, including biphenyl, durene, paraffin wax, and the heat transfer media o-, m-, and p-terphenyl showed that laser-induced degradation gives characteristic reproducible pyrograms. Here, again, the fragmentation patterns were simpler than those obtained with older thermal degradation techniques. IR and UV Spectroscopy. Powell and coworkers (1531) determined total hydrogen bonded to carbon by near infrared analysis. The determination was based on the integrated absorption of the first overtone of the C-H stretching band a t 1680 to 1785 nm, which is rectilinearly related to concentration of C-H for the six hydrocarbons studied. Precisions for various mixtures of three hydrocarbons were given, and the authors considered that this method should be applicable to polluted river water. Pushkina and Kuklinskii (1551) developed a n IR absorption method for the quantitative determination of methyl groups in isolated isopropyl and methyl branches of saturated hydrocarbons. An equation for calculating the percentage by weight of methyl groups in these two structures based on the coefficients of extinction a t the maxima of 1171 and 1156 cm-1
bands was derived. An IR method for determining the purity of durene was reported by Kozlova (981). The time for one determination was 2 to 3 hr including calibration and the relative error was 1 2 % . Using the 366-cm-1 band prevented interference by the six other compounds in the durene crystals, while seven other compounds were left in the fractions from which the durene was crystallized. Luther and Oelert (1141) used a combination of IR and NMR spectroscopy to obtain structural group analyses of mineral oils. The fractions (CA and Cp) of aromatic and paraffinic carbon were determined in over 80 petroleum fractions with mol wts of 250-630 from the IR spectra a t 650-910 cm-1 (paraffins) and 1610 c n - 1 (aromatics). Results agreed with those determined by the classical n-d-M method. The fractions of H atoms bound to aromatic and paraffinic C were determined by NPAR. NMR also gave information on the molecular structures in the fractions. Muntean et al. (1301) determined aromatic hydrocarbons in transformer oils by UV absorption spectrophotometry. A direct and rapid method was developed for determining mono-, di-, and tricyclic aromatic hydrocarbons in chromatographically separated fractions of the transformer oils which may be applied to all mineral oils containing aromatics with less than three condensed rings. Proton NMR Spectroscopy. A comprehensive discussion of NMR analyses of organic compounds, including many applications to petroleum andyses, was published by Trogolo (2000. The structural analysis of hydrocarbons and small fractions derived from petroleum; the analysis of aromatics and of polycycloparalfins; studies relatin'g to the distribution and structure of paraffinic side chains in cyclic hydrocarbons separated Yrom lubricating oils; the analysis of fractions containing oxygen, nitrogen, and sulfur; the structural analysis of ar,phalts; and quantitative analysis of mixtures were some of the topics discussed. Robinson and Truitt (1620 developed quantitative olefin analyses using NMR. The meth8)d was based on quantitative NMR spectroscopy with the use of spin decoupling to condense and simplify the spectra. It was applicable to analyses for mono-substitur.ed, 2,2-di-substituted, 1,l-di-substituted, and, under certain conditions, 1,1,2tri-substituted ethylenes. A complete determination took less than 30 min. An NMR method for determining aromatic carbons in complex mixtures was described by Esparza and coworkers (521). The proportions of aromatic carbons in monocyclic compounds were determined by integration of the benzene ring protons and the protons in alkyl groups cy, p, and y to the ring. The method was verified with synthetic mixtures and was used for the analysis of various fractions and by-products from the synthesis of aromatic hydrocarbons. Some methods to change chelr ical shifts of hydrocarbons were reported. Foster and Twiselton (561) measured the NMR chemical shifts of molecular complexes of various aromatic hydrocarbons with aldehydes, ketones, and some nitroaromatics. Wasylishen et al. (2151) reported the proton chemical shifts of 99 polysubstituted benzmes in cyclohexane and in benzene-de and discussed substituent effect additivity, solvent shift, and dipole-moment correlation and steric effects. Chenon et al. (321) &died solvent effects on NMR by analyzing new and published NMR data for various solutes, including n-hexane iind rt-heptane, cyclohexane, 1,3,5-trimethylcyclohexane,and benzene, in a large number of polar and nonpolar solvmts. Mengenhauser (1271) proposed an NMR method for determining the aromaticity of hydrocarbon fuels. The
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method utilized NMR spectroscopy to measure complexing of acceptor molecules by aromatic hydrocarbon donors in the fuel. CHzClz and MeNOz were satisfactory acceptors for this purpose. For any unknown fuel, the acceptor shift is a precise, reproducible quantity that can be converted to volume per cent aromatics by means of a si *iiple equation. The method was applicable to any liquid hydrocarbon fuel and, like many existing methods, was iinaffected by olefins, dyes, and fluorescence compounds. The precision of the shift measurement was typically 0 . ~Hz which corresponded to 0.2-0.5% aromatics. The analysis of mixtures of isomeric polynuclear hydrocarbons by h lvlR was reported by Keefer et al. (901). A method suitable for detecting alkyl aromatic carcinogens in natural environments, based on relative chemical shifts and values of methyl chemical shifts a t infinite dilution in a specified solvent system, was used to characterize some amber petrolatum and paving grade asphalt fractions. Chemical shift data were also obtained for monomethyl derivatives of anthracene, benz(a)anthracene, benzo(c)phenanthrwe, and pyrene. Cryoscopic purity measurements were improved by Herington and Lawrensen (741) who developed a new method called NMR cryoscopy in which the fixction of substance present in the liquid state at any given temperature was detected by NMR. Since the NMR jignal of a solid is 104 times stronger than that of a liqiiid, the NMR spectrometer can be regulated easily to detcct only the liquid signal in a mixture of solid and liquid. Tor measurement of impurity, the NMR spectrum is measured just below the melting point of the substance. Carbon-13 NMR Spectroscopy. The emergence of I : C NMR methods for the qualitative analysis of hydrocarbons and simple mixtures may be the most exciting new technique covered in the period of this review. The abilhy to look directly a t the bonded carbon atoms, instead of the protons attached to the carbon atoms, makes Liis technique look extremely promising for obtaining detailed structural information about hydrocarbon isomers, particularly those which are highly branched. A review published by Casu (311) covers the assignment of I3C reronance signals; correlations between 13C NMR spectra aiid the structures of linear and branched paraffins, cyclop: 1 affins, olefins, acetylenic hydrocarbons, and aromatic bydrocarbons. The author also compared 13C resonance spectroscopy to proton resonance spectroscopy. Lindeman and Adams (1090 published the I3C chelrical shifts for all Cs to CS paraffin isomers and many of tlie CS isomers. A correlation chart was presented which r?lates chemical shifts to paraffin molecular structure, th#tt is, to the presence of primary, secondary, tertiary, ar tl quaternary carbon atoms. The effect of magnetic nonequiyialents on the shifts was also discussed. These authois (34 published additional 13C NMR data for 35 alkylcyclw pentanes and alkylcyclohexanes as part of a report shon ing the use of 13C NMR to characterize cycloparaffins i i two crude oil fractions. The 13C NMR technique based 0 1 the structural features of "neighborhoods" was used wit,i MS and GC data to characterize the 60-300 "F and 300400 "F cuts of a naphthenic (California) and paraffini: (Sumatra) crude. Yamazaki et al. (2181) reported l3C NMR spectra of branched paraffins, alicyclic compounds, and alkylbenzenes along with a procedure for the 13(' NMR analysis of paraffin oils. The number of C atoms in n-paraffin oil and isoparaffin oil was determined by mea suring the chemical shifts of 13C resonance lines and using a plot of the C number us. signal intensity. Clutter e t al (351, 361) discussed the application of I3C NMR to the characterization of petroleum fractions in 192 R
two papers. They first described their modification of a commercial spectrometer so as to obtain 13C NMR spectra a t 15 Hz using 12-mm spinning samples and by incorporating a means for heteronuclear spin decoupling. The much greater sensitivity of 13C chemical shifts to chemical environment and the much more detailed composition information obtainable, as compared with proton magnetic resonance, were demonstrated by application to hydrocarbon mixtures. The authors claimed that the true aromaticity value of the sample can be determined by simple integration of the 13C spectrum. Methods for calculating average molecular parameters using both proton and 13C NMR data were reported in the second paper. An analysis of the results of the characterization of aromatic fractions from several fluid catalytic-cracking charge stocks pointed out the best method for determining aromaticity according to the accuracy desired and the best methods to determine several average parameters of the aromatic fraction, such as molecular weight, carbon atoms per alkyl substituent, number of aromatic and naphthenic rings per molecule, etc. Mass Spectrometry. Mass spectrometry continues to be the method of choice for obtaining hydrocarbon-type analyses of higher boiling petroleum fractions. Wallaert (2141) has discussed the applications of mass spectrometry to the analysis of hydrocarbons and sulfur compounds in hydrocarbon distillate fractions boiling below 400 "C. For fractions boiling below 150 "C, the analysis was based on measurement of fragment peaks characteristic of each of the hydrocarbon types, and calibration was very important. Fractions boiling above 200 "C were first separated using silica gel columns and then analyzed according to the Hood and O'Neal method. The advantages of mass spectrometry for these types of analyses were compared with those of GC. Unger et al. (2031) developed a mathematical method for calculating the group composition of hydrocarbon mixtures based on their mass spectra. Tests were carried out on synthetic mixtures but the leastsquares technique resulted in deviations up to 200Y0, and it was not possible to calculate groups not present in the synthetic mixtures. A second method was developed by Unger et al. (2041) to determine isoprenoid alkanes in petroleums. A study of seven C14-Czo isoprenoid hydrocarbons showed that ions with masses of 113+, 183+, and 253+ were characteristic in the mass spectra of isoprenoids and could be used in analytical identification. An MS method with 5-6% sensitivity and k6Yo relative error for determining the total content of isoprenoids in narrow fractions within the 200-400 "C boiling range was developed. A mass spectrometric method for determining the isomeric composition of paraffin hydrocarbons in saturated petroleum fractions was described by Medvedev et al. (1260. The method makes it possible to separate normal and branched paraffins in complex hydrocarbon mixtures and to determine the fractional composition of hydrocarbons and the molecular weight distribution of normal hydrocarbons. It may be used for paraffin fractions boiling from 200 to 500 "C. The sensitivity was 0.1 to 0.5% with a precision of 2-10 mole %. Hippe and Beckey (764 discussed the use of a field-ion mass spectrometer for the quantitative group analyses of gasoline mixtures. Field-ionization mass spectra have large molecular ion and small fragment ion sensitivities so that they provide a rapid survey of the molecular weight distribution of mixtures but generally do not distinguish satisfactorily between isomeric compounds. The spectra of gasoline-like hydrocarbon mixtures do not appear as linear
* ANALYTICAL CHEMISTRY, VOL. 45, NO. 5, APRIL 1973
superpositions of the spectra of their components; therefore, the sensitivity coefficients for a mixture must be obtained from a reference mixture. Graphs and tables were included showing sensitivity coefficients of different hydrocarbon types and other data needed for this type of analysis. Robinson (1611) developed a new low-resolution MS procedure to determine up to 25 saturated and aromatic compound types in petroleum fractions boiling in the 200-1100 O F range without need for prior physical separations. A base-line technique resolved the mass spectrum into saturates and aromatics spectra. The entire composition was accounted for in terms of four saturate hydrocarbon types, twelve aromatic types, three thiophenic types, and six unidentified aromatic groups. Kuras and Hala (1041, 1051, 1061) described the results of the M S analysis of petroleum middle distillates in three publications. In the first, 11 hydrocarbon groups were identified using the method of Fitzgerald, but this method was not applicable to fractions with high olefin contents. The second described the LIV analysis of aromatic concentrates separated from a kerosene of Romashkino crude and two liquid pyrolysis products. In the third article, the MS method of Hood and O'Neal was used to determine alkanes, mono-, di-, tri-, tetra-, penta-, and hexacyclic naphthenes and monocyclic aromatics in dearomatized oil fractions from two different crudes. Fisher e t al. (541) determined optimum conditions for the LIV analysis of aromatic petroleum distillates. They found that the best compromise between fragmentation and sensitivity was obtained a t 7.4 eV ionizing voltage. The optimum ionizing current was 20 mA. Sensitivities were determined for pure aromatic compounds. Repeatability and reproducibility of the sensitivities for individual compounds were approximately 2% and those for synthetic blends were 7%. Some authors have developed high resolution, low voltage M S techniques for the analysis of complex hydrocarbon mixtures. Juguin and Boulet (871) analyzed the 375400 "C fractions of different crude oils a t a resolution of 4500 with an ionizing potential of 12 eV. Isobaric mixtures of aromatic and sulfur compounds which were not resolved under these conditions were resolved by removing the sulfur compounds by oxidation and noting the subsequent depression in molecular-ion peak heights. Published sensitivities for aromatic compounds were used along with estimated sensitivities for the sulfur compounds. Aczel et al. (21) used this technique to characterize the aromatic products of coal liquefaction. They found that separation of aromatic nuclei of the same general formula but of different structure present in a given series was possible as the appearance of a new nucleus was associated with a maximum in the C number distribution. Thus, 6 or more nuclei were detected in the CnHzn-l~series and other hydrocarbon series also contained more than one nucleus. Types determined in individual samples ranged from 40 to 99, components from 100 to 500. Included were polyaromatic systems containing 6 to 8 rings and associated with 1-2 0 atoms and as many as 20 carbon atoms in side chains. Another publication by Aczel et al. (14 detailed the computer techniques used in their high resolution, low voltage MS methods. An IBM model 1801 was used for converting from analog to digital data. Steps in the data storage process included the determination of areas, precise masses, formulas, and homologous series of all the parent peaks present in the spectrum. The authors stated that the method was applicable to all materials derived from petroleum boiling below 1100 O F regardless of origin, pretreatment, or width of boiling range. A compound
classifier based on computer analysis of low resolution MS data was described by Smith (1821) The method relied on computer analysis of sets of standard spectra, reducing these large data sets to a much smaller correlation set. The correlation set, consisting of ion-series spectra of each class, was used in subsequent automatic computer classification of mass spectra. According to Smith, this approach is particularly important in analysis of data from coupled GC-MS systems where large numbers of spectra of separated components of complex mixtures can be classified rapidly and further structurd information elicited based on this classification. Combined Methods. Combining chromatographic separation methods with spectral or 01 her identifying procedures is now being used to characterize hydrocarbon types in petroleum fractions as well as individual components. Runge et al. (1671) has devised a complex analytical method for the characterization of hydrocarbon mixtures in the 160-250 "C boiling range. Column, gas, and thin layer chromatography were combined with IR spectroscopy in a way similar to the analytic21 separation scheme in inorganic chemistry. Thus, the aromatic hydrocarbons were separated from aliphatic hydrocarbons by partition chromatography on silica gel B, while the alkanes were separated from the alkenes by dis xibution chromatography using aniline-impregnated Supergel. IR spectrophotometry was used to identify CH3, CHz, and CH groups and quaternary C atoms. Arich et al. (90 combined liquid-liquid partition chromatography with gas-liquid chromatography to separate a gas oil fraction into more than 400 components, identifiable a t concentrations above 0.02%. Approximately 35 components present in concentrations greater than 1% (8 n-paraffins, 10 alkylbenzenes, 12 alkylnaphthalenes, and 5 alkylthionaphthenes) were determined quantitatively. Spasov (1861), in a review on modern methods of determining hydrocarbon composition of medium petroleum fractions, advocated combining adsorption chromatography with molecular sieves, followed by MS, to establish the total group hydrocarbon composition of average petroleum fraction3. With the aid of adsorption chromatography, urea dewaxing, GLC, and molecular spectroscopy, detailed structural analysis could be accomplished and, even to a large degree, the individual hydrocarbon content could be quant fied. Hinds ( 751) has described a preliminary analytical separation scheme for characterizing the heavy ends of crude oils. Gasoline and lighter materials were removed by isothermal distillation or other mean!, which did not expose the residues to high temperatures. A gas-oil fraction (boiling less than or equal to 700 "F) was removed in a vacuum still and the heavy ends were repa;sed a t lower pressures and higher temperatures to remove cuts boiling at 7001000 OF and 1000-1250 OF. The separated fractions were chromatographed over ion-exchange resins, supported FeC13, silica gel, and A1203, and offer the basis for a procedure for characterizing the heavy ends. The development and application of a structural group analysis of high boiling hydrocarbon mixtures and petroleum fractions based on IR and NMR spectroscopy and elemental analysis was reported by Oelert (1351). Eight experimental parameters obtained from the IR and NMR spectra of a sample, and from elemental analysis and determinations of molecular weight, were used to derive, on a statistical basis, 35 items of information. The reliability of the method was demonsti*ated for a series of oils and the results from two oils were comparecl to the results obtained by other methods. Gas chromatography followed by UV and MS analysis
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were used by Il'in et ~ l (801) . to analyze acetylenic hydrocarbons in cracked gases. The acetylenic hydrocarbons were determined in 40 min with an error of less than 5% by UV and M S analysis of components separated on a 2-m X 4-mm diameter GC column packed with dinorryl phthalate and &P'-oxydipropionitrile. Berthold I ild coworkers (181) patented a method for the complex structural groups were determined using a combination of riolecular weight, elemental analysis, high resolution NhTR, and chromatography. Aromatic rings, C and H atoiris, naphthenic rings, aromatic C rings, and Me and CEIz groups directly and indirectly bonded to an aromatic group were determined directly. CH2, Me, and C atoms in substituted aromatic, condensed aromatic, and satural chd structures were determined indirectly. The separation and characterization of methylethylnaplithalene isomers using instrumental methods was ~ 2 ported by Duswalt and Mayer (481). The individual iwmers were separated and purified from synthetic mixtu 1':s using preparative GC. Isomer structures were determincd from IR and NMR spectra. Thirteen out of a possilile fourteen methylethylnaphthalene isomers were identificd but 1-methyl-8-ethylnaphthalene was not found. The data and techniques reported in this investigation were then used by the authors (491) to characterize the dinuclear (iromatics in the 275-295 "C fraction of a catalytic gas-oil cycle stock. The cycle stock was solvent extracted to give a 95-98% dinuclear aromatic concentrate which was distilled into 34 fractions and analyzed by a combination of MS, NMR, IR, and GLC. The compounds isolated inclttled 32 C13- and C14-alkylnaphthalenes, four CIS- and C I alkylbiphenyls, acenaphthene, four Cis-alkylacenay lithenes, perinaphthane, 4,5-benzindan, fluorene, a tid dibenzofuran. The identification and estimation of polynuclear ai'omatic hydrocarbons in petroleum and related products was the topic of a review by Gupta and Kumar (711). -4 study of techniques for determining carcinogenic poly( yclic hydrocarbons in petroleum covered the use of chiomatographic and solvent extraction techniques for sample concentration, chromatographic separation methods, a id the identification and quantitative estimation of individual compounds by GC, UV, and spectrophotofluorometi y. Sear1 et d. (1741) used GC and UV to develop an analytical method for polynuclear aromatic compounds in coke ovsn effluents. The procedure, which is suitable for routine use in a plant laboratory, permits the quantitative measui t:ment of fluoranthene, pyrene, benz(a)anthracene, chi ysene, benzo(a)pyrene, and benzo(e)pyrene. Good cro:ii>checks of the method were obtained by mass spectrometry and fluorescence analysis. Chemical Methods. A renewed interest in chemic 211 separation methods, such as urea adduction, has appear ?d especially in the European laboratories. A series of papcis by Kisielow et al. was concerned with the determination of normal paraffin hydrocarbons in petroleum frac,tio [I s using urea and molecular sieves. They first (941) reportl?d the determination of normal paraffins in narrow fractiorts;. For fractions boiling a t 180-240 "C and 350-450 "C, adsorption was effected on 5A molecular sieves without aiiiS after removal of aromatic and sulfur compounds, respectively. Normal paraffins in the fraction boiling a t 240-3 50 "C may be determined by either method. The second paper (931) discussed the choice of methods for n-parrlfin hydrocarbon determination in typical petroleum fractions. Fractions boiling below 240 "C required the moleciilar sieve method, whereas those boiling a t 240-360 ' ( 2 194
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could be determined both by the molecular sieve and the urea method. For fractions boiling a t 300-450 "C, correct results could be obtained by the molecular sieve method only if a prior removal of polar substances from the sample was effected. The third paper (951) reported attempts made to determine optimum conditions for the quantitative adsorption of normal paraffins from heavy petroleum fractions using 5A molecular sieves. The adsorption from isooctane solutions a t 100 "C was measured by the weight or volume method. The authors concluded that the volumetric method was unsuitable for hydrocarbons boiling a t
