Energy & Fuels 1991,5, 222-226
222
Liquid Fuel Analyses Using High-Performance Liquid Chromatography and Gas Chromatography-Mass Spectroscopy S. C. Lamey,* P. A. Hesbach, and K. D. White Morgantown Energy Technology Center, US.Department of Energy, Morgant ow n , West Virginia 2650 7- 0880
Received June 29, 1990. Revised Manuscript Received November 6, 1990 The potential of a coal- or shale-derived liquid fuel precursor to be upgraded to a fuel product can be assessed if the composition of the precursor is known. Herein is described a technique utilizing high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS) which provides sufficient compositional data to allow one to estimate fuel upgrading potential. Samples are first filtered and then subjected to a liquid-liquid extraction to remove solids and phenolics, which have deleterious effects on the HPLC separation. The liquids are then fractionated by using a semipreparative column into aliphatics and aromatics by ring size using HPLC and collected for off-line injection into the GC-MS, where further compositional information is obtained. Using this method, it is possible to quantitate the components present that are of most interest in assessing the potential of a fuel. These components include the various classes of aliphatics (such as straight chain, branched, cyclic, etc.) and the 1-,2-, and 3-ring aromatics. A discussion of the experimental details along with data from several samples is presented.
Introduction As the availability of petroleum feedstocks becomes uncertain, more and more interest has focused on converting other fossil fuel products into those materials currently derived from petroleum. Many of these other fossil-fuel-derived liquids appear to have compositions favorable for conversion to various usable fuel products.'S2 Liquids with a large abundance of aliphatic compounds should be readily converted with a minimum of processing. Those liquids with a great deal of aromatic character can be upgraded through hydr~genation.~~~ However, in order to predict potential fuel performance or estimate upgrading requirements, it is necessary to know the chemical properties of the fuel/fuel precursor.'t612 These chemical properties can then be related to the fuel properties through c ~ r r e l a t i o n s . ~ JOne ~ ' ~ possible application for the liquid fuel feedstocks is their use as high-energy, dense fuels (high Btu/volume) for jet aircraft.'J4JB It is, (1) Solash, J.; Taylor, R. F. Prepr. Pap-Am.
Chem. Soc., Diu. Fuel
Chem. 1976,21(6), 231-248. (2) Hollstein, E. J.; Janoski, E. J.; Scheibel, E. G.; Schneider, A.; Talbot, A. F. 'Conversion of Coal to Synthetic Gasoline and Other Distillate Fuels": NTIS PC AO9/MF A01: 1: DE 86002175: 1983. (3) Letorti M. Hydrocarbon Process. bet. Refin. 1962, 41(7), 83-88. (4) Hawk, C. 0.; Schleeinger, M. D.; Dobransky, P.; Hiteshue, R. W. 'US. Department of the Interior, Report of Investigation"; 1965, RI 6655, 1-31. (5) Hazlett, R. N.; Hall, J. M.; Solash, J. Prepr. Pap.-Am. Chem. SOC., Diu. Fuel Chem. 1976,21(6), 219-230. (6) Hunt, Jr., R. A. Ind. Eng. Chem. 1953,45, 602-606. (7) Siemssen, J. 0. Prepr.-Am. Chem. Soc., Diu. Pet. Chem. 1973,18, 87-98. (8)Lloyd, W. G.;Davenport, D. A. J. Chem. Educ. 1980,57, 56-60. (9) Affens, W. A.; Hall, J. M.; Holt, S.; Hazlett, R. N. Fuel 1984, 63, 543-547. (10) Cookson, D. J.; Lloyd, C. P.; Smith, B. E. Energy Fuels 1987, I, 438-447. (11) Niyogi, R. K.; Vaidya, U.; Duhaut, P.; Krishna, M. G. Pet. Hydrocarbons 1970,4, 151-158. (12) Cookson, D. J.: Latten, J. L.: Shew. I. M.: Smith. B. E. Fuel 1985. 64, 509-519. (13) Armstrong, G. T.; Fano, L.; Jessup, R. S.; Marantz, S.; Mears, T. W.; Walker, J. A. J. Chem. Eng. Data 1962, 7, 107-116. (14) Jenkins, C. I.; Walsh, R. P. Hydrocarbon Processing 1968,47(5), 161-166. (15) Cookson, D. J.; Smith, B. E.; Energy Fuels 1990, 4, 152-156.
therefore, desirable to develop a technique to measure all the pertinent chemical composition properties of these fossil fuel liquids. The compound classes of greatest interest in assessing the upgrading potential of these liquids are the aliphatics (including straight chains, cyclics, etc.) and the 1-,2-, and 3-ring aromatics. We have previously reported an open-column separation technique for coal liquid products." This method gave a good separation of these materials into fractions and provided sufficient information about the chemical composition of the sample so that fuel potentials could be estimated. However, the technique required a great deal of preparation and several hours to complete the separation. The present HPLC separation requires about a half-hour to complete when no fractions are collected and less than an hour when sample collection is required. Previous studies of HPLC separations of fuels and fuel-related liquids have been r e p ~ r t e d . ~ ~Dorn J ~ and co-workers have reported HPLC separations of this type in conjunction with proton NMR for on-line detection. They have reported successful separations using a silicacyano phase column and chlorofluorocarbon solvents. The work reported herein utilizes the same type of solvent and column system with the ability to collect fractions from the HPLC for analysis by GC-MS. In addition, a number of preparative techniques were employed to allow very dense and highly viscous samples to be successfully separated.
Discussion This HPLC/GC-MS method has provided a satisfactory characterization of the components in a variety of fossil fuel liquids. The technique consists of a number of steps, the first of which was the removal of particulate matter (16) Sullivan, R. F. Proc., Symp. Stmct. Fkture Jet Fkels, Am. Chem. Soc., Diu. Pet. Chem. April, 1987, Denuer, CO; 1987, Appendix N ,81-94. (17) Lamey, S.; Hesbach, P.; Childers, E. Energy Fuels 1989, 3, 636-6 40. (18) Hayes, Jr., P. C.; Anderson, S. D. J. Chromatogr. 1987, 387, 336-346. (19) Haw, J. F.; Glass,T. E.; Dom, H. C. Anal. Chem. 1983,55,22-29.
This article not subject to US. Copyright. Published 1991 by the American Chemical Society
Energy & Fuels, Vol. 5, No. 1, 1991 223
Liquid Fuel Analyses Using HPLC and GCIMS and phenols from the liquids. The amount of particulates present varied greatly among the samples studied. A refined material such as kerosene has little or no particulate matter, while a raw coal tar can have a large quantity of particles. These particles were removed by dissolving the sample in a solvent such as methylene chloride or dimethylformamide and passing the sample through a 25-pm polyethylene filter. Phenols were removed after the filtration by liquid-liquid extraction with 0.4 N NaOH. The NaOH extract containing the phenols was then neutralized with HC1 and subsequently back-extracted into methylene chloride. The methylene chloride solvent was then allowed to evaporate, and the extracted phenols were weighed. Some samples such as kerosenes required little or no pretreatment and could be injected neat into the HPLC. Other light oils usually needed the methylene chloride solvent to render them sufficientlynonviscous for injection. Some heavy oils and tars were not completely soluble in methylene chloride, and it was found that N,N-dimethylformamide (DMF) was necessary to solubilizethese materials prior to injection. The HPLC solvent system employed was a mixture of 97.5% 1,1,2-trichlorotrifluoroethane and 2.5% chloroform. Two different flow rates through the HPLC column were used during the study. For quantitation, the flow through the column was 1.5 mL/min, which produced a satisfactory separation of compound classes while still providing peaks sharp enough for good quantitation. For fraction collection the flow was slowed to 0.50 mL/min to give a greater separation between fractions. For collection purposes the peak shape was not as critical. The time frame for collection of fractions was determined by the length and diameter of tubing from the detector outlet to the collection point. These dimensions fix the time difference between the detector signal and the arrival of the fraction at the collection point. In order to determine this time, the standard compound mixture was separated and samples were taken every 15 s. These samples were then analyzed on a GC and the time period for each fraction collection was determined by the appearance of the appropriate standard compound(s). In general, it was found that, under the conditions of the HPLC experiments, a separation of each peak by 1.5-2 min was adequate to give a sufficiently clean separation of each fraction for collection purposes. It was usually necessary to collect several milliliters of eluant to obtain an entire fraction, and the solvent was then reduced down for analysis. The HPLC gave a fractionation into aliphatics, 1-ring aromatics, 2-ring aromatics, and up to 5-ring aromatics for some coal-derivedmaterials. It was not possible to differentiate between the various types of aliphatic compounds with the column and solvents used. Compounds with a given number of aromatic rings were found exclusively in the appropriate fraction associated with that ring number. Components with an aromatic ring and a saturated ring such as tetralin usually appeared as a shoulder or a distinct peak within the broader aromatic ring number fraction (for example, tetralins elute soon after 1-ring aromatics in the same fraction) but did not have sufficient resolution for separate collection. Each fraction from the HPLC was injected into the GC-MS for identification and quantification. Since the object of this work was only to determine the classes of compounds present, the MS library was usually adequate for identifications. Also, it was only necessary to determine the relative amounts of compounds present and not absolute quantities. With this in mind, the relative areas acquired from ion counts were considered sufficient.
Determination of individual compounds and quantitation were more difficult for the aliphatic fraction than for the fractions with aromatic components. The n-alkanes were easy to identify because they usually occurred in a series with a molecular weight difference of 14 amu and, also, usually provided a distinctive envelope of peaks in the ion chromatogram. However, distinguishing between branched alkanes, alkenes, and cyclic aliphatics in a mixture was somewhat more difficult. For these compounds, the MS library was not very reliable and more visual interpretation of the mass spectral data was required. This technique can be easily adapted for proton NMR characterization, since no protons are present in the HPLC elution solvent mixture. The fractions could then be analyzed directly by using NMR without solvent removal. This would be an attractive technique for characterization of the aromatic fractions and higher boiling components not recoverable from the GC column.
Experimental Section Solvents and Chemicals. The solvents used were HPLC grade 1,1,2-trichlorotrifluoroethaneand HPLC grade chloroform from Aldrich Chemical Co. The standard model compounds n-octane, cyclooctane, diethylbenzene, decalin, tetralin, naphthalene, and phenanthrene were purchased from Aldrich or Chem Services Co. and were used without further purification. Instrumentation. The HPLC system consisted of a PerkinElmer Series 410 pump, a Model LC-25 refractive index (RI) detector, and an LCI-100Laboratory Computing Integrator. The solvent mixture was run at flow rates ranging from 0.50 to 2.0 mL/min. The columns were two sizes of Whatman Partisil 10 PAC. A 250 mm X 4.6 mm column was used for initial studies and quantitation and a 500 mm X 9.4 mm column was employed when larger amounts of sample were required for fraction collection.
The GC-MS system was a Hewlett-Packard Model 5985B equipped with a library search program. The capillary GC column was of fused silica, 30 m X 0.32 mm i.d., 0.25 bm film thickness, RTX-5 from Restek Corp. (Port Matilda, PA). The GC oven was held at 20 O C for 3 min and then temperature programmed at 4 "C/min to a final temperature of 280 "C and held for 5 min. Splitless injection was utilized for all fractions. The gas chromatograph for establishing the fraction collection times was a Perkin-ElmerSigma 2000 with an LCI-100 integrator and 7500 computer. The GC was equipped with a splitlessinjector, a flame ionization detector, and a capillary column of fused silica, 30 m X 0.32 mm i.d., 0.25 pm film thickness, DB-5 from J&W (Folsom, California). Temperature programming was the same as with the GC-MS instrument. Sample Preparation. The kerosene sample used was a motor fuel kerosene purchased locally. The tar oil was a fixed-bed coal gasification condensate from the Great Plains, ND, facility. The shale oil was produced by Dravo Corp. from the retorting of eastern oil shale. The standard mixture of seven components represents the major classes of compounds of interest typically contained in fossil-fuel-derived liquids. It was prepared by weighing equal amounts of each and combining. A solvent was not necessary for the standard mixture. Quantitation. The relative percentages derived for each fraction required quantitation of both HPLC and GC-MS results. The use of an RI detector for the HPLC produces a different sensitivity for aliphatic and for various ring size aromatic compounds, since the response is a measure of the difference in refractive index between the eluent and the reference call material, which is typically the solvent. It is important to point out that an RI detector was used because it responds to both aliphatic and aromatic compounds, while a UV detector will not respond to nonaromatics without active chromophores. Response factors for each fraction were obtained by the use of naphthalene (with a response factor arbitrarily taken as 1.0) as an internal standard. The factors given in Table I are averages for the fractions from a number of fuels. These factors are similar to the empirical values used by Cookson and co-workersPzlfor kerosenes and diesel fuels.
Lamey et al.
224 Energy & Fuels, Vol. 5, No. 1, 1991
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F i g u r e 3. HPLC chromatogram of the tar oil.
F i g u r e 1. HPLC chromatogram of kerosene.
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F i g u r e 2. HPLC chromatogram of the standard component mixture. Due to the large variety of compounds possible and their varying relative amounta in each fraction of authentic samples, it is impractical to measure a response factor for each specific compound type, since detailed characterization of samples would be required before the appropriate response factor could be applied. The HPLC area counts for each fraction were multiplied by the average response factors obtained t o give a relative quantity of each fraction present. When each fraction was run on the GC-MS, the ion count total for each compound was obtained. After identifications had been made, the counts for all compounds of any further subfractions (e.g., n-alkanes,monocyclic aliphatics, decalins, tetralins, etc.) were added together. Since only relative quantities of one group to another were desired, it was not deemed necessary t o run internal or external standards. In order to calculate the quantity of each subfraction in the entire sample, the percent of a subfraction in each HPLC fraction as identified by GC/MS was multiplied by the area percent of the HPLC fraction in the entire sample. Repetitive separation of the same sample on the HPLC gave results within *1.0% for each fraction, while repetitive GC/MS analyses of the same sample gave a range of &2.0%for each fraction.
Results A representative HPLC analysis trace for the kerosene sample is shown in Figure 1. The prominent aliphatic peak is followed by the unresolved cluster of monoaromatics and then the single broad peak of diaromatics. The trace level of 3-ring aromatics eluting last is not evident on the scale of this chromatogram. The assignments for these classes are based on the elution behavior of the standard compounds, as shown in Figure 2. In contrast to this kerosene compound class distribution profile is the (20) Cookson, D.J.;Rix, C. J.; Shaw, J. M.; Smith, B.E.J. Chromatogr. 1984,312, 237-246. (21) Green, M.; Huane, S.;Strangio, V.; Reilly, J. Prepr. Pap-Am. Chem. SOC.,Diu. Fuel Chem. 1989,34(4) 1197-1205.
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F i g u r e 4. HPLC chromatogram of shale oil. Table 1. Refractive Index Response Factors for Different Compound Classes' fraction response factor aliphatics 3.5 1-ring aromatics 1.6 1.0 multi-ring aromatics (I
Relative to naphthalene taken as 1.0.
Table 11. Compound Class Identification by RI/HPLC Fractionation for Various Fuels % aromatics sample % aliphatics I-ring 2-ring 3-ring kerosene 87.8 11.3 0.9 trace tar oil 35.0 19.5 21.7 4.5 shale oil 58.7 28.5 11.2 0.1
HPLC trace for the tar oil sample shown in Figure 3. In this latter chromatogram, the 1- and 2-ring aromatic species appear to dominate the trace, with a significant amount of higher ring compounds present. The shale oil chromatogram (Figure 4) shows the least resolution between the aliphatic and l-ring aromatic peaks. Also, the shale oil 2-ring aromatic region is less clearly defined than in the other traces. The application of the appropriate response factors from Table I to the peak areas from refractive index detection of components resulted in the compound class distribution found in Table 11. When this correction for the different refractive indices of component classes is made, the expected predominance of aliphatics in kerosene is clearly demonstrated. The same treatment of the tar oil data reveals the more even class distribution of this material. In addition, almost 20% of the tar oil sample was phenolic-type components. As previously explained, these compounds were removed prior to injection into the HPLC. The shale oil data in Table I1 indicates
Liquid Fuel Analyses Using HPLC and GCIMS
Energy & Fuels, Vol. 5, No. 1, 1991 225
Table 111. (a) Quantitation of Aliphatic Fraction Absolute Percentage Values of the Entire Sample and (b) Relative Percentage Distribution of Aliphatic Subclasses a total 1-ring multi-ring branched aliphatics cyclics cyc1ics n-alkanes alkenes ahhatics kerosene 87.8 11.3 2.4 27.3 5.2 41.6 tar oil 35.0 4.7 0 18.3 6.7 5.3 shale oil 58.7 4.0 0 24.4 23.0 7.3 b
kerosene tar oil shale oil
1-ring cyclics 12.8 13.4 6.8
multi-ring cyclics 2.7 0 0
Table IV. Kerosene Fraction 1 re1 % n-C10 1.82 C16 cycloaliphatic C11 branched aliphatic 1.02 C15 branched aliphatics decalin 0.75 n-C14 C11 cycloaliphatics 2.45 C15 alkene C1-decalins 1.94 C16 branched aliphatic n-C11 4.10 C15 cvcloaliuhatics C12 branched aliphatic 1.30 n-CG C2-decalin 1.84 C17 cycloaliphatics 1.24 C13 alkene C18 branched aliphatic n-C12 C18 alkene 6.12 C13 branched aliphatic 2.31 C17 branched aliphatics C13 cycloaliphatic 1.48 n-Cl7 1.84 C19 branched aliphatic C14 cycloaliphatic n-C18 C14 branched aliphatic 2.19 6.38 Cl8 cycloaliphatic n-C13 1.56 n-C19 C14 alkene n-C20 n-C21
re1 % 3.15 2.49 6.23 1.67 3.34
n-alkanes 31.1 52.3 41.5
alkenes 5.9 19.1 39.3
Table VII. Kerosene Fraction 4 re1 % phenanthrene 36.31 C1 phenanthrene
4.22
0.98 3.24 2.47
1.48
Table V. Kerosene Fraction 2 re1 % C2-benzenes 2.77 C1-tetralins 9.97 C3-benzenes C2-indan C4-benzenes 10.22 C2-tetralins C5-benzenes 17.11 C7-benzenes C1-dihydroindenes 3.36 C3-tetralins C2-dihydroindenes 4.30 C8-benzene C6-benzenes 10.24 C4-indanone
re1 70 10.86 1.50 9.28 4.92 8.95 4.84 1.69
Table VI. Kerosene Fraction 3 re1 % naphthalene 2.64 C3-naphthalenes C1-naphthalenes 16.57 C4-naphthalenes biphenyl 1.31 C2-biphenyls C2-naphthalenes 27.44 C3-biphenyls C1-biphenyls 7.50 C5-naphthalenes
re1 % 25.89 7.37 1.86 7.20 2.22
the high proportion of 1-ring aromatics in this material, as well as a substantial amount of aliphatic species. A determination of the constituents found in the aliphatic fraction is very important to any evaluation of the potential fuel quality of a liquid fuel precursor. Therefore, the kerosene, tar oil, and shale oil (aliphatic and aromatic fractions) were analyzed by GC-MS, whereby all significant components were identified and quantified. The aliphatic fraction quantitation by subclass for the samples is given in Table IIIa as a percentage of the total sample. The relative distribution of the aliphatic subclasses is given in Table IVb. The kerosene aliphatics consist more of branched compounds and less of n-alkanes than the tar oil or shale oil. The lower alkene content for the kerosene fraction is probably due to a fuel refinement step. The high alkene contribution to the shale oil aliphatics is clearly shown, as are the low-branched aliphatics and intermediate n-alkane contents of this material. The monocyclic ali-
re1 % 63.69
Table VIII. Tar Oil Fraction 1 re1
re1
%
2.71
5.54 6.80 2.89 1.38 5.02 4.86 3.24
branched aliphatics 47.4 15.1 12.4
C10 alkene n-C10 C10 cycloaliphatic C11 alkene n-C11 n-Cl2 C13 branched aliphatic C11 cyclic aliphatic C13 alkene n-C13 C15 branched aliphatic C15 alkene n-C14 C14 cyclic aliphatics C16 branched aliphatic C16 alkenes n-C15 C15 cyclic aliphatics C16 cyclic aliphatics n-C16 C18 branched aliphatic n-Cl7 C19 branched aliphatic C17 alkenes n-C18 C20 branched aliphatic C18 alkenes
0.48 0.52 0.11 0.55 1.20 1.59 0.70 0.40 1.26 2.24 0.91 1.65 2.76 4.33 1.86 2.25 2.84 3.47 1.65 2.70 1.36 3.02 2.72 6.59 2.75 1.00 2.71
%
n-Cl9 n-C20 C18 alkenes n-C21 C21 branched aliphatic n-C22 n-C23 C22 alkene n-C24 C26 branched ailphatic n-C25 C27 branched aliphatic n-C26 n-C27 C28 branched aliphatic n-C28 C30 branched aliphatic n-C29 n-C30 C30 cyclic aliphatic n-C31 C33 branched aliphatic n-C32 C31 cyclic aliphatic n-C33 C32 cyclic aliphatic
Table IX. Tar Oil Fraction 2 re1 % C2-benzenes 16.23 tetralin C2-thiophene 0.54 C2-tetralin C3-benzenes 34.44 C3-tetralin C4-benzenes 12.65 C4-dihydroindene dihydroindene 7.03 C8-benzene Table
re1 % 7.46 4.30 4.60 10.16 2.63
X. Tar Oil Fraction 3 re1
re1
%
naphthalene C1-naphthalene biphenyl CPhnaphthalenes acenaphthene C1-biphenyl
3.27 3.14 2.88 3.31 0.39 2.95 3.11 0.57 3.76 0.46 3.49 1.54 2.55 2.42 1.40 1.74 0.71 1.55 1.20 0.95 1.04 0.90 1.18 0.77 0.60 0.50
31.62 25.28 3.74 13.63 1.47 5.80
%
C3-naphthalene fluorene C2-biphenyls C1-fluorenes C4-naphthalene
Table XI. Tar Oil Fraction 4 re1 % phenanthrene 9.88 C2-phenanthrenes C1-phenanthrenes 40.65 pyrene phenylnaphthalene 9.93
5.62 4.23 4.46 3.33 0.81
re1 % 28.31 11.23
Lamey et al.
226 Energy & Fuels, Vol. 5,No. I , 1991 Table XII. Shale Oil Fraction 1 re1
re1
%
%
C12 alkene 0.47 C19 branched aliphatic 1.54 n-C11 1.18 C18 alkene 1.57 C13 alkene 0.29 n-C20 2.98 0.48 C19 alkene 1.43 n-C12 C14 alkenes 4.39 n-C21 2.60 C12 branched aliphatic 1.54 n-C22 2.38 2.51 n-C23 2.02 n-C13 C15 alkenes 2.20 n-C24 1.77 C14 cyclic aliphatics 1.76 n-C25 1.51 3.74 n-C26 1.26 n-Cl4 C15 cyclic aliphatics 1.03 n-C27 1.12 C15 branched aliphatics 9.87 n-C28 0.88 3.87 n-C29 0.71 n-C15 C16 alkenes 6.97 n-C30 0.56 C16 cyclic aliphatic 1.51 C31 alkene 0.38 4.10 n-C31 0.41 n-C16 C17 alkenes 15.42 C32 alkene 0.33 4.09 n-C32 0.21 n-Cl7 C17 cyclic aliphatics 1.54 C33 alkene 0.16 3.50 C33 branched aliphatics 0.33 n-C18 C18 branched aliphatic 1.82 n-C33 0.08 n-C19 3.53
Table XIII. Shale Oil Fraction 2 C2-benzenes C3-thiophene C3-benzenes C4-benzenes C2-dihydroindenes
re1 % 10.52 0.31 7.88 20.72 15.63
C5-benzene C2-tetralins C3-indan C4-dihydroindene C3-tetralin C3-dihydroindenone
re1 % 6.28 8.52 5.17 4.96 15.46 4.56
Table XIV. Shale Oil Fraction 3
naphthalene benzothiophene C1-naphthalenes C1-benzothiophene biphenyl C2-benzothiophenes C2-naphthalenes
re1 70 8.39 2.29 15.77 0.69 0.67 4.25 19.82
C3-benzothiophenes C3-naphthalenes C1-biphenyl C4-naphthalenes C2-biphenyls C3-biphenyl carbazole
re1 70 9.32 17.30 2.18 12.07 5.88 1.82 1.73
Table XV. Shale Oil Fraction 4 phenanthrene carbazole C1-phenanthrenes
re1 % 5.43 37.66 38.76
C2-phenanthrenes C3-phenanthrenes
re1 % 14.62 3.53
phatic content for the kerosene and tar oil is proportional to their total aliphatic content, while the shale oil monocyclics are disproportionately low by comparison with the other samples. Complete listings of the compounds found by GC-MS analyses in the kerosene, tar oil, and shale oil HPLC fractions can be seen in Tables IV-XV. In each table the relative percent of each component present is given. This allows determination of the principal components and those present in trace amounts. Notably absent in the tar oil and shale oil data are multi-ring cyclic aliphatics, with two and larger ring species only existing as aromatic compounds. The kerosene sample was pre-
viously separated by using open-column chromatography. A comparison of the results of that separation" with the present data shows a very close agreement with respect to the species present in each fraction and the relative amounts of each fraction present. This is the only sample analyzed by both techniques. The clean class separations by HPLC are evident from the GC-MS data. The fraction 1 compound lists indicate the less-refined natures of the tar oil and shale oil. The aliphatics in these samples extend to tritriacontane (C-33), whereas the longest n-alkane kerosene component is heneicosane (C-21). The longer paraffinic waxes found in the former samples would probably have to be cracked to smaller chains or be removed for aircraft applications, due to their high freezing points. The alkenes, especially high in the shale oil, are a concern for any applications involving long-term storage. Polycyclic aliphatics, especially the decalins, would be desirable due to their high energy density.3~5J6~22~23 The 1-ring aromatic dicyclic species such as the tetralins and hydroindenes found in each sample are an asset for the same reason, but only in moderation because of considerations of efficient and clean combustion.6,7J1,24The larger number of hydrogenated rings in the shale oil fraction 2 probably caused the spreading of this HPLC peak compared to that of the tar oil. The shale oil has a greater variety of aromatic species as well, including heteroatom compounds (e.g., thiophenes), which may have broadened the later eluting HPLC peaks. The carbazole and thiophene content of the shale oil would need to be addressed in an upgrading step prior to the use of this material as a fuel. The various two and larger aromatic species found in these samples, although high in energy density are otherwise possessors of unfavorable physical and combustion properties. Hydrogenation upgrading would appear warranted €or any extensive use of this tar oil and this shale oil as transportation fuels.
Conclusions The methodology discussed in this paper has been used successfully to fractionate a wide range of fossil fuel products. The examples presented represent a finished fuel product, a coal-derived fuel precursor, and a shalederived fuel precursor. Although the fractions obtained and the individual components in the fractions differed for each sample, this separation produced clean fractions in all cases. The method is relatively rapid and provides a characterization with sufficient detail to assess the fuel potential of a fossil fuel liquid. The experimental conditions described produce a sufficient HPLC separation of the various fractions so that samples may be collected for off-line analysis by mass spectroscopy, NMR, or other instrumentation. Separation of the aliphatic fraction to a greater extent is currently being pursued in our laboratories. (22) Perry, M.B.; Pukanic, G. W.; Reuther, J. A. Prepr. Pap.-Am. Chem. Soc., Diu. Fuel Chem. 1989,34(4) 1206-1217. (23) Hazlett, R. N.; Dorn, H. C.; Glass,T. E. Introduction, Advanced Topics and Applicatiom to Fossil Energy. In Magnetic Resonance; NATO AS1 Series 124C;Kluwer: Dordrecht, The Netherlands, 1984; pp 709-720. (24) Cookson, D. J.; Smith, B. E.; Shaw, I. M. Fuel 1987,66,758-765.
