Coprocessing Reactions of Illinois No. 6 and Wyodak Coals with

Energy & Fuels 1994,8, 960-971

960

Coprocessing Reactions of Illinois No. 6 and Wyodak Coals with Lloydminster and Hondo Petroleum Resids in the Presence of Dideuterium under Severe Conditions Michael D. Ettinger and Leon M. Stock* Department of Chemistry, T h e University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637

John G. Gatsis Universal Oil Products Research Center, 25 E. Algonquin Rd., Des Plaines, Illinois 6001 7 Received January 11, 1994. Revised Manuscript Received April 4, 1994"

The molybdenum-catalyzed coprocessing reactions of Illinois No. 6 or Wyodak coal with Lloydminster or Hondo resid have been investigated by using dideuterium under severe conditions: 3000 psi at 420 "C, for 2 h. Asphaltene and coal conversions to lower molecular weight, less polar compounds exceed 70 and 90%, respectively, under these conditions. There are some differences in the product distributions for the four coal and resid mixtures, but these variations are rather modest. The product from Lloydminster resid and Illinois No. 6 coal yielded 10.2 5% gas, 75.1 % oil, 3.9 % resin, 8.5 % asphaltene, and 2.3 % insoluble material. The distribution of deuterium and hydrogen was measured in the gases, oils, resins, and asphaltenes. The deuterium contents of these products are large, near the statistical value dictated by the hydrogen/deuterium ratio in the starting materials. Evidence for modest selectivity is provided by the higher deuterium content at aromatic and reactive benzylic positions and the lower concentrations of this isotope at less reactive paraffinic sites. The purely paraffinic constituents in the oils, for example, experience only partial exchange, but the hydroaromatic molecules in the oils have abundant deuterium reflecting their origins in catalytic reduction reactions. The deuterium in the gaseous products suggests different origins for methane, ethane, and propane and butane. The results of this study and other recent work strongly infer that the success of the molybdenum-catalyzed reaction system depends upon the reduction of aromatic molecules, the facile deoxygenation of phenolic compounds, the removal of other heteroatoms via reductive chemistry, the fragmentation of large asphaltenes, especially the heteroatom-containing compounds, and the alkylation of aromatic molecules. These beneficial reactions occur simultaneously with other catalytic reactions that involve virtually all the molecules in the system. I t is evident that carbon-hydrogen bond cleavage proceeds rather readily on the catalyst. Fortunately, the catalytic addition of hydrogen to the intermediates on the catalyst surface is a favored process at high pressure, and fragmentation and coke formation are thereby minimized.

Introduction Recent advances in coprocessing of subbituminous and bituminous coals with petroleum resids were discussed in a recent review1and at the Denver meeting of the American Chemical Society.24 Generally, the coprocessing of these materials provides a remarkably high yield of pentanesoluble oils. Gatsis and co-workerspioneered work in this area, and they have extensively investigated coal and coprocessing t e c h n ~ l o g y . ~They , ~ established optimal reaction conditions for their process at a total pressure of 3000 psi, 420 OC, 2:l resid:coal, and 1 wt % of the @Abstractpublished in Advance ACS Abstracts, May 15, 1994. (1) Schobert, H. H.; Tomic, J. Inhibition of Retrogressive Reactions in CoallPetroleum Coprocessing,Final Report, DOE/PC/88935-T13,1993. (2) Parker, R. J.; Carmichael, M. H. Prep.-Am. Chem. Soc., Diu. Pet. Chem. 1993, 38, 314. Diu. Pet. Chem. (3) Chakma, A.; Zaman, J. Prepr.-Am. Chem. SOC., 1993, 38, 320. (4) Rahimi, P. M.; Fouda, S. A.; Kelly, J. F.; Liu, D.; Beaton, W. I.; Lenz, U. Prep.-Am. Chem. Soc., Diu. Pet. Chem. 1993,38, 329. (5) Fouda. S. A.: Rahimi. P. M.: Kellv. J. F.: Lenz. U.: Beaton, W. I. Prep;.-Am.' Chem. SOC., Diu. Pet. Che-6. 1993,38, 351.' (6)Louie, P. K. K.; Bottrell, S. H.; Steedman, W.; Kemp, W.; Bartle, Diu. Petr. Chem. 1993, 38, K. D.; Taylor, N. Prep.-Am. Chem. SOC., 363.

0887-0624/94/2508-0960$04.50/0

molybdenum-based Universal Oil Products (UOP) catalyst for the conversion of 89% of the coal to toluene-soluble products and 79 % of the asphaltenes to heptane-soluble p r o d ~ c t sRahimi . ~ ~ ~ and co-workers have also achieved high yields of desirable products under similar conditions by using an iron sulfide ~ a t a l y s t . ~The J requirement for effective catalysis is illustrated by the fact that coal conversion is limited to 67% in the thermal reaction compared to about 80 and 90% in the iron- and molybdenum-catalyzed reactions. Similarly, the heptane-soluble products account for only 21 % of the organic material in the thermal reaction, whereas about 60 and 80% of these products are obtained in the catalyzed processes. The effective utilization of dihydrogen during fossil fuel processing reactions is critical to the production of high yields of desirable products. It is necessary for the hydrogenation of thermally and catalytically produced radical fragments, heteroatom removal, and the hydro(7) Gatsis, J. G.; Nelson, B. J.; Lea, C. L.; Nafsis, D. A.; Humbach, M. J.; Davis, S. P. Continuous Bench-Scale Single Stage Catalyzed Coprocessing. Presented at the Contractor's Review Meeting, Pittsburgh, October 64,1987. (8)Nafsis, D. A.; Humbach, M. J.; Gatsis, J. G. Coal Liquefaction Coprocessing, Final Report, DOE/PC/70002-T6, 1988.

0 1994 American Chemical Society

Mo-Catalyzed Coprocessing Reactions of Coal

genation of aromatic structures. The chemistry involves hydrogen atom transfer reactions among the reactant molecules, hydrogen atom transfer from donor solvent molecules, as well as catalyzed hydrogen addition to unsaturated molecules from the dihydrogen atmosphere. While the petroleum resid may participate in hydrogen atom exchange and hydrogen shuttling reactions, the dihydrogen atmosphere is the predominant source of hydrogen atoms responsible for hydrogen addition since little carbon-rich coke is produced. Dihydrogen addition increases the hydrogen content of the coprocessing reactants by 2.4 to 2.9 w t This finding and the fact that dihydrogen may be the most expensive component in coprocessing make its efficient utilization an extremely important goal in any conversion reaction. This research was undertaken to identify the reaction pathways that involve hydrogen utilization to enhance efforts to optimize its effective and efficient use. The coprocessing reactions of Illinois No. 6 or Wyodak coal and Lloydminster or Hondo petroleum resid were carried out in a dideuterium atmosphere with a molybdenum catalyst to further this goal.

Energy & Fuels, Vol. 8, No. 4, 1994 961

i:

AUTOCUV PRODUCT

t-.

TOLUENE 5 / 1 UT. RATIO

SONIFICATION

t TOLUENE INSOLUBLES

I

I

If

ROTARY FUSH EVAPORATION RESIDUALS

ISOPENTANE 511 HT. RATIO

ROTARY FLASH EVAPORATION RESIDUALS

N-HEPTANE 511 W. RATIO N-HEPTANE SOLUBLE

SONIFICATION

CENTRIFUGATION

.

1

CENTRIFUGATION

EVAPORATION

RESINS OIL Figure 1. Solvent separation of coprocessing products into oil (pentane soluble), resin (heptane soluble/pentane insoluble), asphaltene (toluene soluble/heptane insoluble), and toluene insolubles.

I

Experimental Section Materials. Illinois No. 6 coal was prepared by the Kentucky Center for Applied Energy Research (KCAER) and was used as received (Anal. % C, 68.60; % H, 4.51; % N, 1.39; % S, 3.04; % 0,9.65; % HzO, 3.15; % ash, 9.65). Wyodak coal was obtained from the Pennsylvania State University program and was prepared by KCAER, and was dried prior to use (Anal. % C, 63.01; % H, 4.50; % N, 0.90; % S, 1.08; % 0,16.73; % HzO, 1.78; % ash, 12.00). Lloydminster petroleum resid (Anal. % C, 83.6; % H, 10.3; % S, 4.77; % N, 0.59; % 0,0.54) and Hondo petroleum resid (Anal. % C, 82.17; % H, 9.57; % S, 5.50; % N, 1.37; % 0, 0.74) were obtained by UOP Research Center and used as is. The catalyst was a molybdenum-based UOP proprietary material. The triphenylmethane-d that was used as an NMR quantitative internal standard contained 82.1 atom % deuterium. The other chemicals were available commercially, and they were purified as necessary. Procedure. Lloydminster or Hondo petroleum resid (280 g) and Illinois No. 6 coal (165.4 g) or Wyodak coal (183 g) and the catalyst (0.2 wt % Mo) were added to an 1800-mL rocking autoclave. The autoclave was sealed and pressurized first with hydrogen sulfide and then with dideuterium to give a 10 vol % hydrogen sulfide and 90 vol % dideuterium such that a t the reaction temperature of 420 "C the desired total pressure of 3000 psi would be obtained. The autoclave was heated to 420 "C in about 120 min and then kept at that temperature for 2 h. During the reaction, dideuterium was added automatically so that the reaction pressure, 3000 psi a t 420 "C, was maintained. After the desired time-at-temperature, the autoclave was cooled to room temperature over a 2-h period and was then depressurized with the gas passing through a foam trap, caustic scrubbers, and metering system, and then a sample was collected for analysis. The material in the autoclave was purged with dinitrogen to remove residual gas from the reaction mixture. This gas also was passed through the foam trap, caustic scrubber, and metering system and analyzed. The gaseous products include methane, ethane, propane, butanes, pentanes, hexanes, carbon oxides, hydrogen sulfide, ammonia, and water. Products that were swept into the foam trap were recovered with toluene and added to the toluene rinse solution. The slurry product from the autoclave was decanted. The material that remained in the autoclave was removed by rinsing the vessel with toluene until the autoclave was clean. The combined slurry product was separated by using sonication and centrifugation into four fractions: oil (pentane soluble), resin (heptane soluble/pentane insoluble), asphaltene (toluene soluble/heptane insoluble), and toluene insolubles, Figure 1. Solvent removal was carried out with a flash rotary

TOLUENE

L

I

I

I

I

I

IO

8

6

4

2

0

PPm Figure 2. Deuterium NMR spectra of the solvent separated products from the coprocessing reaction of Illinois No. 6 coal and Lloydminster resid for 2.0 h a t 420 "C under 3000 psi of dideuterium. The oil is shown a t the bottom, the resin in the center, and the asphaltene a t the top. evaporator. Unfortunately, this procedure resulted in the loss of some volatile materials, including five to eight carbon atom alkanes and simple alkylbenzenes from the oil fraction. All solvent separated fraction yields and conversions are adjusted for 100% ash balance. Analysis. Elemental analyses of the starting coals, resids, and solvent separated products were carried out a t Universal Oil Products using a Leco elemental analyzer. Gas analyses for deuterated methanes, ethanes, propanes, butanes, butenes, benzenes, and toluenes were carried out a t the Institute of Gas Technology. Deuterium NMR spectra were obtained on a Varian XL 400MHz spectrometer. Two hundred fifty-six scans were acquired for each example using a 900 pulse and a 30 s delay between pulses. Two spectra were obtained for each sample with different amounts of triphenylmethane-d in dichloromethane, and an average of the quantitative values was taken. Figures 2 and 3 show representative deuterium NMR spectra of the coprocessing products. Quantitative determinations were made for the

Ettinger et al.

962 Energy & Fuels, Vol. 8, No. 4, 1994

Table 2. Aliphatic Deuterium Contents and Standard Deviations deuterium contents (mmoVg) fraction analvsis 1 analvsis 2 average std dev ( u ) Lloydminster and Illinois No. 6 oil 2.3 22.5 25.7 24.1 resin 0.4 14.8 14.3 14.6 0.0 asphaltene 11.9 11.9 11.9 Hondo and Illinois No. 6 oil 0.8 24.3 25.4 24.9 resin 0.4 15.8 15.2 15.5 12.0 12.2 12.1 0.1 asphaltene Lloydminster and Wyodak oil 0.5 27.3 26.6 27.0 resin 0.4 15.6 15.1 15.4 asphaltene 0.8 9.9 11.9 10.5 Hondo and Wyodak oil 0.9 27.9 29.2 28.6 0.4 resin 16.0 16.5 16.3 11.2 11.4 11.3 0.1 asphaltene

10

8

4

6

2

0

PPm Figure 3. Deuterium NMR spectra of the solvent separated products from the coprocessing reactions of Illinois No. 6 coal and Hondo petroleum resid for 2.0 h. a t 420 "C under 3000 psi dideuterium. The oil is shown at the bottom, the resin in the center, and the asphaltene a t the top. Table 1. Aromatic Deuterium Contents and Standard Deviations fraction oil resin asphaltene oil resin asphaltene oil resin asphaltene oil resin asphaltene

deuterium contents (mmol/g) analysis 1 analysis 2 average std dev (u) Lloydminster and Illinois No. 6 2.5 3.2 2.9 0.5 0.6 5.7 4.9 5.3 5.0 4.9 5.0 0.1 Hondo and Illinois No. 6 0.3 2.6 3.0 2.8 0.3 6.1 5.7 5.9 4.6 4.5 4.6 0.1 Lloydminster and Wyodak 0.0 3.1 3.1 3.1 5.3 5.0 5.2 0.2 0.7 2.9 3.9 3.4 Hondo and Wyodak 0.2 2.9 2.6 2.8 0.1 5.2 5.3 5.3 0.3 3.7 3.3 3.5

aromatic (10-6.3 ppm) and aliphatic (4.2-0.0 ppm) regions through comparison with the triphenylmethane-d resonance near 5.5 ppm. The dichloromethane natural abundance peak a t 5.32 ppm was used as the chemical shift reference. The aliphatic deuterium content was partitioned into alpha aliphatic (4.2-2.0 ppm), beta aliphatic (2.0-1.0 ppm), and gamma aliphatic (2.00.0 ppm) regions based upon the average of duplicate or replicate integration values. Typical results are presented in the next paragraph and the full suite of data are assembled in the next section. The aromatic and aliphatic deuterium contents for the solvent separated products are shown in Tables 1 and 2. The average values and standard deviations were determined. Errors arise from integration, the overlap of fossil and triphenylmethane-d resonances, and inherent differences in the line shapes of the different resonances of the solvent separated products. An average percent error was calculated from the standard deviations of the individual determinations to provide perspective concerning the errors associated with the NMR determinations. Separate evaluations of the errors were made for the aromatic and aliphatic deuterium contents, which were f 7 and f3%, respecti~ely.~ Proton spectra were obtained on the University of Chicago 500-MHz spectrometer. Two hundred fifty-six scans were

acquired for each sample using a 90" pulse and a 30 s delay between pulses. Tetrakis(trimethylsilyl)silane1°was used as a quantitative internal standard and deuterated chloroform as the solvent. The aliphatic region was restricted to the region from 4.2 to 0.5 ppm due to the internal standard, but virtually all of the aliphatic resonances in the proton spectra occurred in this region, and the proton resonances were narrower than the resonances for the deuterium nuclei. The hydrogen contents are shown in Table 3. One spectrum was obtained for each sample, although multiple integrations were often carried out. The D/(H + D) ratio was evaluated for the aromatic and aliphatic positions. The values are given in the next section. Since errors in the hydrogen and deuterium determinations were similar, standard practice adds the errors of each measurement to give the error of the D/(H + D) value. Therefore, the corresponding errors would be 14 and 6% for the aromatic and aliphatic % deuterium contents, respectively.

Results and Discussion The elemental compositions of the familiar heteroatomrich coals that were used in this study are summarized in Table 4. Although the petroleum resids consist of molecules with high molecular weights and rather abundant heteroatoms and cannot be distilled at temperatures below 500 "C, they can be completely solubilized in toluene. They were separated as shown in Figure 1into oils (pentane soluble), resins (heptane soluble/pentane insoluble), asphaltenes (toluene soluble/ heptane insoluble), and insolubles (toluene insoluble). The oils, resins, and asphaltenes are complex mixtures, but they also have common characteristics. For example, the oil fraction, which is of the greatest interest, presumably consists of long-chain normal alkanes ranging from 8 to more than 30 carbon atoms, branched alkanes such as pristane and phytane, and a variety of alkylated and mono-, bi-, and tricyclic aromatic and hydroaromatic compounds. In general, the oils contain the relatively small, nonpolar, hydrogen-rich molecules with low heteroatom content. The resin and asphaltene fractions contain larger molecules with higher degrees of aromaticity and heteroatom content. These properties are consistent with the data in Table 5, which show the distribution of solvent-separated products from Lloydminster and Hondo petroleum resids, their (9) Ettinger, M. E. Reaction Pathways in CoallPetroleum Coprocessing, University of Chicago Libraries, 1993, p 225. (10)Muntean, J. V.; Stock, L. M.; Botto, R. E. J.Mag. Reson. 1988, 76, 540.

Energy & Fuels, Vol.8, No. 4,1994 963


Table 3. Aromatic and Aliphatic Hydrogen Content

fraction

aromatic (10.0-6.3 ppm)

oil resin asphaltene

14.2 15.3 15.3


7.7 13.1 12.5


10.5 14.2 14.7


14.1 15.4

hydrogen content (mmol/g) aliphatic alpha (4.2-0.0 ppm) (4.2-2.0 ppm) Lloydminster and Illinois No. 6 82.8 13.4 18.3 44.6 14.2 33.5 Hondo and Illinois No. 6 12.4 77.7 35.9 12.9 28.4 11.3 Lloydminster and Wyodak 85.1 14.8 40.8 16.3 30.5 12.9 Hondo and Wvodak 14.0 96.8 15.0 41.9 13.2 30.6

12.2

Table 4. Elemental Analyses (MAF) of Illinois No. 6 and Wyodak Coals. coal Illinois No. 6 Wyodak a

%C 78.9 71.0

%H 5.5 5.5

%O

%S

10.6 21.6

3.4 0.9

%N 1.6 1.0

H/C 0.84 0.93

we are indebted to KCAER for this information. Table 5. Elemental Analyses and Yields of Solvent-SeDarated Petroleum Resids.

fraction oil resin asphaltene oil resin asphaltene

yield(%) % C % H Lloydminster Resid 73.5 83.5 10.9 10.4 82.5 8.8 16.1 82.2 8.5 Hondo Resid 11.1 71.5 82.6 6.7 81.8 9.2 21.8 80.9 8.9

%S

%N

H/C

4.3 7.4 7.8

1.3 1.3 1.5

1.28

5.4 7.1 7.8

0.9 1.9 2.4

1.61 1.35 1.32

1.57 1.24

"The samples were not analyzed for oxygen. The results are normalized to 100% of the measured components.

elemental analyses, and atomic hydrogen to carbon ratios. Lloydminster and Hondo resids both have considerable solubilities in pentane of 73.5 and 71.5%. The asphaltene fraction accounts for 16.1and 21.8% in Lloydminster and Hondo resids, respectively. The atomic hydrogen to carbon ratios show that the degree of saturation decreases in the order oil > resin > asphaltene consistent with increasing aromatic character. The sulfur content is very significant in each fraction and along with nitrogen content increases in the order oil < resin < asphaltene. The high severity coprocessing reactions were relatively large scale reactions employing approximately 450 g of material in a 3000-mL rocking autoclave. Combinations of each resid with each coal in a 2:l wt 5% MAF ratio were heated to 420 "C for 2.0 h with a molybdenum catalyst under a 10 vol 5% hydrogen sulfide and 90 vol ?4 dideuterium atmosphere at a constant total pressure of 3000 psi. Hydrogen sulfide was employed to sulfide the molybdenum catalyst. The dideuterium consumption was measured. The reaction time at 420 "C did not include the heating or cooling periods each of approximately 2 h during which the temperature changed at 3.3 "C/min. When the autoclave was cooled,the products were collected and separated as shown in Figure 1. Conversion and Product Yields. Coal processing reactions always yield extremely complex mixtures of solid

beta (2.0-1.0 ppm)

gamma (1.0-0.0 ppm)

48.8 19.0 14.6

20.6 7.3 4.7

45.7 17.6 13.1

19.6 5.4 4.0

50.3 17.8 12.4

20.0 6.7 5.3

58.1 19.8 11.9

24.7 7.1 5.4

and liquid products with a wide range of molecular weights, aromaticity, polarity, and heteroatom content. The types of molecules that we have identified in the solid and liquid coprocessing products include large polycyclic aromatic structures, smaller mono-, bi-, and tricyclic aromatic and hydroaromatic molecules often with alkyl groups, and longchain straight and branched alkanes with 30 or more carbon atoms, to name a few. For convenience, these complex product mixtures were separated into oil, resin, asphaltene, and insoluble fractions. The gaseous products were also collected and analyzed as discussed later. The yields of the solvent-separated products were determined, and the values for coal and asphaltene conversion were calculated according to the following equations. All values in the

[

coal conversion = 1 - MAF MAF toluene starting insolubles] coal asphaltene conversion = asphaltene + MAF insolubles] - MAF coal + resid asphaltene

L1

equations are corrected for mineral and water content and, thus, account only for the organic constituents. In the asphaltene conversion equation, the starting asphaltene value is the sum of the asphaltene fraction of the petroleum resid and the entire organic portion of the starting coal. Considerable experience has been gained over the past decade in the handling and analyses of the products of coprocessing reactions in the UOP laboratory. Standardized procedures customarily enable mass balances at the 95% level for all starting materials. Furthermore, ash balances are routinely performed so that the conversion information for the asphaltenes and coals is very secure. Special problems arise in the definition of the product distribution for high-severity reactions because significant quantities of volatile hydrocarbons are formed, the gases are readily measured, but the oil yields are impacted by the product isolation procedure. Specifically, toluene is used to dissolve the reaction products and wash the reaction vessel. Its removal from the products necessarily leads to the loss of volatile liquid products, such as the pentanes, hexanes, heptanes, and small aromatic compounds. The observed oil yields, therefore, greatly underestimate the actual oil yields. We have addressed this problem by reporting the observed oil yields and the oil yields that were assessed by difference. Experience


Ettinger et al.

Table 6. Solvent-Separated Fraction Yields and Conversion of Coprocessed Products yields and conversions, w t % MAF Lloydminster and Hondo and Lloydminster and fraction Illinois No. 6 Illinois No. 6 Wyodak gases oil (observed) oil (by difference) resin asphaltene insoluble coal conversion asphaltene conversion

10.2 62.3 75.1 3.9 8.5 2.3 92.8 74.1

12.7 56.1 68.8 4.0 11.9 2.6 92.3 66.6

12.6 61.2 76.0 5.1 5.2 1.1 96.1 84.6

Table 7. Elemental Analyses of the Solvent-Separated Coprocessing Products Lloydminster and Hondo and Lloydminster and Illinois No. 6 Illinois No. 6 Wyodak oil fractions % carbon % hydrogen, isotopea 7% sulfur % nitrogen atomic [H + D/Clb resin fractions % carbon % hydrogen isotopesa % sulfur % nitrogen atomic [H + DI/Cb asphaltene fractions % carbon % hydrogen isotopes0 %sulfur % nitrogen atomic [H + DI/Cb

Hondo and Wyodak 12.2 56.9 76.6 5.0 4.9 1.3 96.2 85.6

Hondo and Wyodak

84.9 13.7 1.2 0.4 1.7

84.4 13.1 1.2 0.6 1.9

85.6 13.7 1.4 0.3 1.9

82.8 14.1 1.2 0.6 2.0

86.2 8.7 1.7 2.2 1.2

85.4 8.6 1.4 1.9 1.2

84.5 8.5 2.2 1.6 1.2

83.3 9.4 1.8 2.0 1.3

87.7 7.1 1.7 1.7 1.0

85.4 8.0 1.5 2.1 1.1

83.5 7.3

85.7 7.6 2.4 1.8 1.1

2.5 1.1

1.1

The observed weight percent for hydrogen and deuterium is reported. The atomic ratio is reported. The value is based upon the H/D ratio determined for each fraction by NMR spectroscopy. a

indicates that the by-difference values are much more accurate. The yields and conversions for coprocessed products are summarized in Table 6, and the elemental analyses of the oil, resin, and asphaltene fractions are presented in Table 7. High levels of coal conversions, over 90 % ,were achieved in all four reactions. Although increased coal conversion does not necessarily translate to increased oil production, it is a vital initial step. The coal conversions were essentially identical at 92.3 and 92.8% for the Illinois No. 6 coal and 96.1 and 96.2% for Wyodak. The resid apparently had no effect on the coal conversion in these experiments. This result is consistent with the idea that, under the severe conditions employed in these reactions, the coal conversions were maximum values essentially independent of the particular coal resid combination. Our other work on low severity coprocessing of Illinois No. 6 coal and Lloydminster resid confirmed that high coal conversions are achieved quite early in the reaction." Such extensive coal conversion allows the maximum amount of material to enter the catalyst-containing liquid phase during the reaction. Conversion of the coal and resid asphaltene molecules to oil, resin, and gas was most extensive when Wyodak coal was used. Indeed, asphaltene conversions averaging 85 % were realized when Wyodak coal was coprocessed with either Lloydminster or Hondo resid. This favorable result may be related to the fact that Wyodak coal is a subbituminous coal that is less mature and less aromatic than bituminous Illinois No. 6 coal. While asphaltene conversion appeared unrelated to the petroleum resid in the reactions with Wyodak coal, (11) Ettinger, M. E.; Stock, L. M. Energy Fuels 1994,8, 808.

the related values for Illinois No. 6 coal differed. When it was coprocessed with Lloydminster and Hondo resids, the asphaltene conversions were 74.1 and 66.6%, respectively. In a previous investigation of the underlying chemistry of these four fossil fuel materials, Illinois No. 6 coal was found to be the most effective hydrogen donor, a trait believed to inhibit its own conversion due to the premature termination of radical fragmentation reactions.12 This factor may render molecules in Illinois No. 6 coal more resistant to reactions responsible for asphaltene conversion. Hondo resid was less effective than Lloydminster resid for asphaltene conversion with Illinois No. 6 coal. The lower level of asphaltene conversion realized with Hondo resid may be the result of several factors. First, it has a higher nickel and vanadium content, 126 and 295 ppm, than Lloydminster resid, 82 and 126 ppm, respectively. Second, it has a larger quantity of asphaltene molecules than the Lloydminster resid. Although we did not investigate this feature of the reaction, it is known that the combination of high asphaltene content and high metal content may seriously impact catalyst effi~iency.~ The yields of the resin fractions were measured, but we focused most attention on the oils. Unfortunately, the oil yields are somewhat less certain than the yields of the resins and asphaltenes because volatile hydrocarbons were lost during toluene removal. Nevertheless, the oil yields do seem to depend on the petroleum resid. Reactions employing Lloydminster resid resulted in observed oil yields of approximately 62 % ,while reactions with Hondo resid produced oil yields of about 56%. We infer that the (12)Ceylan, K.; Stock, L. M. Energy Fuek 1991,5, 482.



differences in the behavior of the Lloydminster and Hondo resid are real. Direct comparison of the elemental analyses of the coprocessed products, Table 7, and that for the starting resid and coal, Tables 4 and 5, must take into account the observation that the hydrogen content values for the coprocessed products include both hydrogen and deuterium. When corrections are applied for the differences in the mass of these isotopes, the (H + D)/C atomic ratios in the table reveal quite unambiguously that the hydrogen to carbon ratios of all the oil fractions are higher than the corresponding ratios for the oil fractions of the original petroleum resids. The hydrogen to carbon ratio of the oils increases even though aromatic coal molecules are being converted to pentane-soluble molecules and some hydrogen-rich gas products are evolved. Conversely, the hydrogen to carbon ratios in the resin and asphaltene fractions decrease. Although the decreases are modest, the results are compatible with the idea that these fractions selectivelyretain aromatic compounds. The sulfur content significantly decreases in all of the product fractions, even though hydrogen sulfide gas was present. Other work shows that high levels of demetallation (V and Ni) are realized in c o p r o ~ e s s i n g . ~ ~ ~ Deuterium and Hydrogen Distribution. Previous work has shown that between 2.5 and 2.9 wt % dihydrogen are added to the products of coprocessing reacti0ns.~?8 Our results, which indicate that about 4 wt % dideuterium is added to the products, are consistent with the earlier work. The oils are clearly the principal beneficiary of this additional hydrogen. The finding that the resins and asphaltenes in the products have somewhat less hydrogen than the resins and asphaltenes in the original resid may be a consequence either of the conversion of intractable coal molecules into heptane- and toluene-soluble products, or of the processing of these substances. Hydrogen (deuterium) is used in heteroatom removal, in the formation of gaseous hydrocarbons and other fragmentation products, and in the reduction of aromatic compounds. Heteroatom removal is extensive under the conditions of the reaction with virtually all of the organic oxygen, 74% of the sulfur, and 42% of the nitrogen eliminated from the oils, resins, and asphaltenes produced from Illinois No. 6 coal and Lloydminster resid. The reaction system ,which contained 425 g of fossil fuel, had 1.95mol of heteroatoms, and their complete removal would have consumed about 3.3mol of dihydrogen. Uncertainties arise in this analysis because the distribution of the functional groups in these fossil materials has not been accurately established, and their hydrogen requirements differ, i.e., thiols comsume 1 mol of dihydrogen, sulfides consume 2 mol, and so forth. Our results suggest 1 5 2 0 % of the heteroatoms remain in the products, and, therefore, about 2.6 mol of dihydrogen were consumed in this way. The conversion of the large resid and coal molecules to gaseous hydrocarbons consumes another 1.4 mol of dihydrogen. In both cases, 50 % of the hydrogen is retained in the liquid products as illustrated in the equations. ArSAr + 2H, RCH,

+ H,

-

-

2ArH + H,S RH

+ CH,

Additional hydrogen is used for the reduction of aromatic hydrocarbons. The reaction system, as discussed subsequently, converts bi- and tricyclic aromatic compounds into cyclic compounds with single benzene rings. For

Oil

Resin

Asphaltene

I

f

AlA,A,

IO

8

6

4

2

010

PPm

8

6

4

2

010

PPm

8

6

4

2

0

ppm

Figure 4. (Upper) Hydrogen NMR spectra in CDCls. (Lower) Deuterium NMR spectra in CHzClz with triphenylmethane-dat 5.5 ppm of the oil, resin, and asphaltene fractions from Wyodak coal and Lloydminster resid coprocessed for 2.0 hat 420 O C under 3000 psi of dideuterium.

example, naphthalenes are reduced to tetralins, and phenanthrenes are reduced to di-, tetra-, and hexahydrophenanthrenes. These reduction reactions are accompanied by hydrogen-incorporating fragmentation reactions that also consume dihydrogen to produce higher quality oils, resins, and asphaltenes. ArCH,CH2CH,Ar

+ H,

-

ArCH,

+ ArCH,CH,

The inclusion of deuterium into the reaction system complicates the assessment of the mass balance, but the current work can be coupled with the previous work718on the same reaction systems to establish that the 425-g mixture of Illinois coal and Lloydminster resid consumes 1.4 mol of dihydrogen in gaseous hydrocarbon formation, 2.6 mol in heteroatom removal, and between 1 and 2 mol for reductive processes. As already mentioned, 50% of the hydrogen used in heteroatom removal and in the hydrocarbon formation of gaseous hydrocarbons are retained in the liquids. The distribution of deuterium in the coprocessed products was quantitatively investigated by deuterium magnetic resonance with triphenylmethane-d as an internal standard. Our procedure was based on the recommendations for quantitative NMR spectroscopyby Martin, Delpeuch, and Martin.13 Figures 4 and 5, which display representative deuterium and hydrogen NMR spectra of the oil, resin, and asphaltene products illustrate the many different and broad overlapping resonances that exist as a result of deuterium addition and hydrogen deuterium exchange. The deuterium content in the aromatic (106.3 ppm) and aliphatic (4.2-0.0 ppm) regions could be determined with very good accuracy. The distribution of deuterium among the aliphatic resonances was partitioned in the ranges of 4.2-2.0, 2.0-1.0, and 1.0-0.0 ppm to deuterium atoms alpha to aromatic rings, deuterium atoms beta to aromatic rings and in methylene and methine positions not alpha to aromatic rings, and deuterium atoms in methyl groups gamma or farther from aromatic rings, respectively. The resonances of the coprocessed substances in the aliphatic region often overlap, and the accuracy of the division of these resonances into discrete groups is somewhat arbitrary, but the data are very valuable for the definition of the reaction selectivity. Proton NMR work was carried out in parallel, with tetrakis(trimethylsily1)silane as an internal standard.lO (13) Martin, M. L.; Delpeuch, J. J.; Martin, G. J. Practical NMR Spectroscopy, Heyden: Philadelphia, 1980.

966 Energy & Fuels,

Ettinger et al.

Vol.8, No. 4,1994 Resin

Oil

Asphaltene

reduction of aromatic molecules. This feature is illustrated by the reduction of phenanthrene and naphthalene over molybdenum catalysts.'"'* Another feature that con-

d, ,d, ,L, D

IO

8

6

4

2

010

8

6

4

2

010

8

6

4

2

0

D

? ppm

PPm

PPm

Figure 5. (Upper)Hydrogen NMR spectra in CDC13. (Lower) Deuterium NMR spectra in CHzClzwith triphenylmethane-dat 5.5 ppm of the oil, resin, and asphaltene fractions from Wyodak coal and Hondo resid coprocessed for 2.0 h at 420 "C under 3000 psi of dideuterium.

The hydrogen and deuterium content of the aliphatic and aromatic molecules and the % deuteration, D/(H + D), for the three coprocessing products are presented in Table 8 and the distribution of deuterium among the aliphatic positions is shown in Table 9. The quantity of deuterium in these products greatly exceedsthe quantity of dideuterium that was catalytically added to the starting material through reduction reactions involving the addition of hydrogen to unsaturated molecules, the capping of thermally produced free radicals, deoxygenation, desulfurization, and so forth. Hydrogen deuterium exchange is clearly responsible for the abundance of deuterium in the products. The amount of deuterium in the oil fractions ranged from 24.1 mmol g1 for the reaction with Illinois coal and Lloydminster resid to 28.6 mmol g1for the reaction with Wyodak coal and Hondo resid. As already mentioned, aliphatic constituents decrease and aromatic elements increase from oil to resin to asphaltene. Aliphatic hydrogen and deuterium, both individually and combined, follow this trend with the aliphatic hydrogen and deuterium content in the oils about twice as large as in the resins and asphaltenes. The degree of deuteration of the aliphatic substances in the oils, resins, and asphaltenes lies in a very narrow range from about 23 to about 30 % in the 12 samples. The oils always have the lowest percentage of deuterium. This feature was examined in detail for the oil, resin, and asphaltene that were obtained in coprocessing Lloydminster resid and Illinois No. 6 coal, (Table 10). The degree of deuteration at the CY position is much greater than at the /3 and y positions in the oil and in the resin, but virtually equal in the asphaltene. The selectivity for the incorporation of deuterium at the a position of the oil and resin presumably arises from the facility with which the catalyst and thermal reactions accomplish exchange at these reactive positions, even though they account for only 26% of the aliphatic hydrogenldeuterium in the oil. The 0 and y hydrogen atoms in the oil, and presumably in the resin, are less reactive; and once paraffinic molecules are formed, they are less prone to bind and react on the catalyst surface and undergo exchange. In contrast, the deuterium contents at the CY and 0+ y positions of the asphaltenes are very similar. One factor that contributes to this result is the high abundance of deuterium atoms at /3 positions in these substances. We believe that the /3 deuterium atoms are located in hydroaromatic structures that are produced by the catalytic

D

tributes to the equilibration of deuterium in the asphaltenes is their sluggish degradation chemistry. The asphaltenes that remain after a severe coprocessing reaction must necessarily be the least readily fragmented constituents of the system, but they must also have been exposed to many thermal interactions as well as many interactions with the catalyst, and, therefore, have experienced numerous opportunities for exchange. Although there are some small differences, the deuterium distributions in the aromatic positions, Table 8, are essentially independent of the starting material. The results for the aliphatic positions are even more consistent, with little or no differences in the amounts of deuterium that have been incorporated in the three products. The amount of deuterium in the aromatic molecules of the resins always exceedsthe amount in the aromatic positions of the oils and asphaltenes, but there is no similar consistency in the results for the aromatic deuterium content of the oils and asphaltenes in these four experiments. We have emphasized the differences in selectivity in the previous paragraphs. However, the overriding feature of these spectroscopic observations is that the degree of deuteration is essentially statistical. While there are major differences in the amounts of deuterium in different positions ranging from 2.8 mmol g1in aromatic positions to 28.6 mmol g' aliphatic positions, the percentages of deuteration differ rather modestly, and are all close to the D/(H + D) ratio calculated for the total gases and organic materials charged to the autoclave, about 0.25 for the four experiments. As already mentioned, the amount of deuterium in the products greatly exceeds the amount of deuterium used in reduction and product improvement reactions. The results require that the molecules in the oils, resins, and asphaltenes contact the catalysts with high frequency to experience these high degrees of deuterium incorporation. Thermal reactions are certainly important, but our workgJ1shows that the catalyst is responsible for the addition of deuterium to aromatic compounds and for the deoxygenation of the coal molecules in these reaction systems. Gaseous Hydrocarbons. The economics of coprocessing like those of other coal conversion processes are adversely affected by the production of hydrogen-rich (14)Curtis, C. W.;Cassell, F. N. Energy Fuels 1988, 2, 1. (15)Curtis, C. W.;Chung, W. J. Energy Fuels 1989, 3, 148. (16)Curtis, C.W.;Pellegrino, J. L. Energy Fuels 1989,3, 160. (17)Kim, H.;Curtis, C. W. Energy Fuels 1990,4, 206. (18)Kim, H.; Curtis, C. W. Energy Fuels 1990, 4 , 214.


Mo- Catalyzed Coprocessing Reactions of Coal

oil resin asphaltene oil resin asphaltene oil resin asphaltene oil resin asphaltene

Table 8. Hydrogen Content, Deuterium Content and 9% Deuteration of the Coprocessed Products hydrogen (mmol gl) deuterium (mmol g-1) deuteration aromatic aliphatic aromatic aliphatic aromatic aliphatic (6.3-10 ppm) (4.2-0.5ppm) (6.3-10ppm) (4.2-0PPm) (6.3-10 ppm) (4.2-0ppm) Lloydminster + Illinois No. 6 14.2 82.8 2.9 24.1 17.0 22.5 44.6 5.3 14.6 25.7 24.7 15.3 15.3 33.5 5.0 11.9 24.6 26.2 Hondo + Illinois No. 6 26.7 24.3 77.7 2.8 24.9 7.7 31.1 30.2 35.9 5.9 15.5 13.1 26.9 29.9 28.4 4.6 12.1 12.5 Lloydminster + Wyodak 10.5 85.1 3.1 27.0 22.8 24.1 14.2 40.8 5.2 15.4 26.8 27.4 14.7 30.5 3.4 10.5 18.8 25.6 Hondo + Wyodak 12.2 96.8 2.8 28.6 18.7 22.8 41.9 5.3 16.3 27.3 28.0 14.1 30.6 3.5 11.3 18.5 27.0 15.4

Table 9. Aliphatic Deuterium Content in Solvent-Separated Coprocessing Products aliphatic-D alpha-D beta-D solvent-separated (4.2-0.0ppm) (4.2-2.0ppm) (2.0-1.0 ppm) (mmol g-l) (mmol g-1) fraction (mmol g-1) oil resin asphaltene

24.1 14.6 11.9


24.9 15.5 12.1


27.0 15.4 10.5


28.6 16.3 11.3

Lloydminster+ Illinois No. 6 6.2 7.5 5.9 Hondo + Illinois No. 6 6.3 7.7 5.5 Lloydminster + Wyodak 7.0 7.4 4.8 Hondo + Wyodak 7.0 7.8 5.3

Table 10. Deuterium Distribution in the Aliphatic Positions of the Products of Illinois No. 6 Coal and Lloydminster Resid fraction % alpha-D % beta and gamma-D oil 31.6 17.3 resin 29.1 18.4 asphaltene 29.4 27.6

methane, ethane, propane, and butane under severe conditions. The reaction of Illinois No. 6 coal and Lloydminster resid provided deuterated methane, ethane, propane, butane, butene, benzene, and toluene. The amounts of butene, benzene, and toluene were so small that the experimental uncertainties became very large, and we have elected not to report these data. The results for the other substances are shown in Table 11and Figures 6-9. Deuterated methane was the most abundant gaseous product in every reaction. The yields of the products consistently decreased in the order, methane > ethane > propane > butane, with values ranging from 63 mol % methane to 5 mol % butane in the reaction with Illinois coal and Lloydminster resid. The % deuteration was similar amongthe products of the four reactions indicating that the deuterium content did not depend on the types of coal and resid, but the % deuteration varied considerably in the gaseous hydrocarbons. Methane and ethane contained 33 and 17% deuterium respectively,but propane and butane each contained 26% deuterium. The large differences in the deuterium content suggest that these

CW

gamma-D (1.04.0ppm) (mmol g-1)

15.6 6.0 4.8

2.3 1.1 1.2

16.1 6.1 4.7

2.5 1.7 1.9

17.0 6.7 4.4

3.0 1.3 1.3

18.5 7.2 4.5

3.1 1.3 1.5

OCHlD3

e CH?.D2

81 CHjDl

CH4

30.0

Lloyd & ll No.6

Hmdo & n No.6

Lkyd & Wyodak

Hondo & Wycdak

Figure 6. Distribution of deuterated methane products from the coprocessing reactions of Illinois No. 6 and Wyodak coals with Lloydminsterand Hondo petroleum resids for 2.0 h at 420 "C under 3000 psi of dideuterium.

substances originate in different ways. The origins of gaseous hydrocarbons during coal liquifaction or coprocessing have not been thoroughly studied, but this area has been extensively studied in the context of coal pyrolysis.1g-26Indeed, the relative yields of methane, (19)Calkins, W.H.; Tyler, R. J. Fuel 1984,63,1113. (20)Calkins, W.H.;Hagaman, E.; Zeldes, H. Fuel 1984,63,1119. (21)Calkins, W.H.Fuel 1984,63,1125. (22)Calkins, W.H.;Hovsepian, B. K.; Dyrkacz, G. R.; Bloomquist, C. A.; Ruscic, L. Fuel 1984,63,1226. (23)Juntgen, H.Fuel 1984,63,731.


Ettinger et al.

60.0 -r 50.0

I

40.0 % 30.0 20.0 10.0 0.0

Lloyd & D No 6

H&

Lloyd & WyodaL

& ll No 6

Hondo & Wyodak

Figure 7. Distribution of deuterated ethane products from the coprocessing reactions of Illinois No. 6 and Wyodak coals with Lloydminster and Hondo petroleum resids for 2.0 h at 420 "C

in the final stage of the reaction on the catalyst as for the other simplemolecules. The low deuterium incorporation in ethane suggests that it arises from a reaction within the coal or the resid that does not require the intervention of molybdenum catalyzed deuterium addition, but rather involves selective hydrogen abstraction from the fossil fuel by an incipient ethyl radical. Insofar as we are aware, this feature of the chemistry has not been uncovered previously. Our results imply that about 50% of the unlabeled ethane may arise in this way. Potentially reactive diarylpropane structural fragments, which have been postulated to account for the unusual product distributions in the oxidation reactions of bituminous may be responsible for this observation. Bulky CH,CH,CH(Ar),

under 3000 psi of dideuterium.

ethane, propane, and butane in these catalyzed coprocessing reactions are very similar to those in uncatalyzed pyrolysis. During pyrolysis, methane is believed to originate from several different precursors such as methoxy groups and aromatic methyl groups, and from thermal decomposition of paraffinic materials. However, methoxy groups are not present in Illinois No. 6 or Wyodak coal, ipso substitution reactions that yield methyl radicals are slow even during pyrolysis of coal, and thermal decomposition pathways of paraffins do not favor methane formation. These considerations and the high level of deuterium in the product imply methane arises indirectly from deuterium-rich aryl methyl groups. The pathways by which they arise may be lengthy, and we favor an interpretationthat centers on the reduction of the aromatic compound prior to dealkylation as illustrated for methylnaphthalene and naphthalene. CD2H

CHD2

I

I

D

D

CHD2

Calkins and his co-workers demonstrated a direct relationship between the quantities of paraffinic material in coal and the quantities of ethane, propane, and butane products after pyrolysis, and ethane, propane, and butane may form in a similar way during coprocessing.1g-22The data for propane and butane are compatible with an interpretation that invokes the molybdenum catalyst in such chemistry as sketched in the equation. alkane

MODz

RCHCHDCHDCHDCH3

I

Mo 02

surface RCH=CHD

+ CHD$HDCH3

I

surface

The results for ethane are not in accord with these suggestions because all such interpretations require the surface bound ethene or the ethyl radical to add deuterium (24) Suuberg, E. M.; Peters, W. A.; Howard, J. B. Ind. Eng. Chem. Process Des. Dev. 1978,17,3729. (25) Solomon, P. R.;Hamblen, D. G. In Chemistry of Coal Conversion, Schlosberg, R.H., Ed.; Plenum: New York, 1985, p 121. (26) Stock, L. M. Acc. Chem. Res. 1989,22,427.

substances of this kind might experiencesteric hindrance to adsorption on the catalyst surface and present a special case for selective thermally induced decomposition in a hydrogen-rich environment. Reaction Pathways. Several research groups have studied the distribution of coal and resid molecules among the products of coprocessing reactions by stable carbon and hydrogen isotope analysis.6s2g33This method exploits the differences in the natural abundances of 13C, which varies according to geological origin of carbonaceous materials. The different geological origins of coal and petroleum result in l3C to 1% ratios different enough so that coprocessed products can be analyzed for the percentages of their respective carbon contents originating from either the coal or the resid. Winschel and Burke employed this method to characterize the coprocessing products produced from the reactions of Lloydminster petroleum resid with either Illinois No. 6 or Wyodak coal.wl The liquid productswere separated into distillable and nondistillable fractions. Under conditions that are comparable with the conditions that were used in our study, Winschel and Burke found that the yield of distillable products increased from 32.2%a t 413 "C to 49.8%a t 431 "C and that the fraction of the coal carbon in the distillate increased from 33.6% to 49.6% of the available organic material in the coal. The reactions of Wyodak coal provided a somewhat greater yield of distillable products and more coal carbon. It is clear that many intractable coal molecules are converted into desirable products during coprocessing. Bartle and co-workers have carried out similar analyses of coprocessing p r o d u ~ t s . ~ sThey ~ ~ s used ~ ~ different fossil fuels and different conditions, but the results are consistent with the data of Winschel and Burke. Bartle and his associates isolated the dicholoromethane-solubleproducts and separated them into hexane-insoluble products (asphaltenes) and hexane-soluble products. The hexane (27) Wang, S. H.; Stock, L. M. Fuel 1986,65, 1552. (28) Steer, J. G.; Ohuchi, T.; Muehlenbachs, K. In Rolduc Symposia on Coal Science Coal Characterization for Conversion Process; Moulijn, J. A., Kapteijn, F., Eds.; Elsevier: Amsterdam, 1986; p 429. (29) Winschel, R.A.; Burke, F. P. In Coal and Petroleum Reactiom in CoallOil Coprocessing,1987Internutionul Conferenceon Coal Science, Rolduc, The Netherlands; Moulijn, J. A., Kapteijn, F., Eds., Elsevier: Amsterdam, 1987, p 383. (30) Winschel, R.A.; Burke, F. P.; Lancet, M. S. Proc. Int. Conf.Coal Sci., Tokyo, Jpn. 1989, 775. (31) Lancet, M. S.; Winschel, R. A.; Burke, F. P. Prepr. Pap-Am. Chem. SOC.,Diu. Fuel Chem. 1991,36,1266. (32) Bottrell, S . H.; Louie, P. K. K.; Bartle, K. D.; Taylor, N.; Wallace, S.; Kemp, W.; Steedman, W. Fuel 1990,69,1332. (33) Bottrell, S. H.; Bartle, K. D.; Louie, P. K. K.; Taylor, N.; Kemp, W.; Steedman, W.; Wallace, S. Fuel 1991, 70,442.



Table 11. Distribution of Deuterium in the Gaseous Products Hondo and Lloydminster and Lloydminster and Wyodak Illinois No. 6 Illinois No. 6 methanes yield (mmol) deuterated products (mol % ) CD4 CHlD3 CH2D2 CHID1 CH4 wtav%D ethanes yield (mmol) deuterated products (mol % ) C2D6 C2HlD6 C2H2D4 C2H3D3 C2H4D2 C2HSD1 C2H6 wtav%D propanes yield (mmol) deuterated products (mol % ) C3D8 C3HlD7 C3H2D6 C3H3D6 C3H4D4 C3H6D3 C3H6D2 C3H7D1 C3H8 wtav%D butanes yield (mmol) deuterated products (mol %) C4D10 C4HlD9 C4H2D8 C4H3D7 C4H4D6 C4H6D6 C4H6D4 C4H7D3 C4HD2 C4H9D1 C4H10 wtav%D total yield (mmol)

c1+c2 + c3 + c4 w C3D8 C3H632

7C3H1D7 C3H7D1

349.1

404.6

439.5

358.1

1.9 10.9 27.8 34.1 25.2 32.5

1.6 10.3 27.8 34.7 25.6 31.9

2.2 11.4 26.7 32.9 26.9 32.3

2.5 12.6 28.5 32.0 24.3 34.2

126.2

181.2

211.1

132.5

0.1 0.9 3.3 8.6 15.2 24.4 47.5 16.5

0.1 0.9 3.4 8.8 15.5 24.6 46.6 16.8

0.2 1.3 4.4 9.8 14.4 24.7 45.3 18.0

0.2 1.3 4.5 10.1 15.3 23.0 45.6 18.2

51.7

113.9

155.9

73.1

0.0 0.4 2.0 4.4 10.4 16.0 19.3 37.1 10.5 25.3

0.0 0.2 1.0 3.2 9.3 16.9 21.5 38.1 9.8 24.2

0.0 0.3 1.1 3.4 9.2 15.7 20.1 37.7 12.6 24.0

0.1 0.9 3.2 6.0 12.8 18.0 17.2 34.5 7.4 29.3

26.6

54.5

65.0

35.1

0.0 0.1 0.4 1.6 3.6 8.6 14.3 19.9 22.3 18.9 10.4 25.9

0.0 0.1 0.4 1.4 3.9 9.1 14.4 19.2 21.5 18.1 11.9 25.9

0.0 0.2 0.9 2.7 5.4 9.4 13.6 17.6 20.3 18.8 11.1 27.4

0.0 0.1 0.7 2.3 5.0 9.9 14.0 17.5 18.3 15.0 17.2 26.2

754

554 C3H2D6

C3H3DS

Hondo and Wyodak

C3H4D4

6 C3WD3

872 uC4DlO

C3H8

C4H6D4

599

OC4HlD9 HC4H2D8 MC4H3D7 e C 4 H 4 D 6 6C4H5DS

E C4H7D3

C4H8D2

C4H9D1

C4H10

40.0 .. T 3S.O

20.0

30.0

8 25.0

15.0 R,

20.0

10.0

1s.o

10.0 5.0

s.0 0.0 Lloyd & Il No.6

Hondo & Il No. 6

Lloyd & Wyodak

Hondo & WyodaL

Figure 8. Distribution of deuterated propane products from the coprocessing reactions of Illinois No. 6 and Wyodak coals with Lloydminster and Hondo petroleum resids for 2.0 h a t 420 "C under 3000 psi of dideuterium.

soluble products were further separated into saturated, aromatic, and polar classes on an activated silica-alumina column. The soluble products accounted for more than

0.0 Lloyd 8 11 No.6

Hondo & 11 No. 6

Lloyd & Wycdak

Hondo & Wyodal:

Figure 9. Distribution of deuterated butane products from the coprocessing reactions of Illinois No. 6 and Wyodak coals with Lloydminster and Hondo petroleum resids for 2.0 h a t 420 "C under 3000 psi of dideuterium.

75% of the fossil materials. Their results, which are summarized in Table 12, imply that coal molecules are distributed in all the fractions. Both investigations


Ettinger et al.

Table 12. Product Distribution in Coprocessing Observed by Bartle and Co-workers coal carbon fraction

yield, %

%

wt.

dichloromethane asphaltenes saturated oils aromatic oils polar oils

76.9 16.2 45.1 29.3 9.5

15 18 30 70

12.2 8.1 8.8 6.6

Chart 1. Hydrogen Utilization in Molybdenum Sulfide Catalyzed Reactions of Hydrocarbons and heterocycle^^^-^^

~

"

i

-

~

1,2,3,4-tetrahydrophenanthrenein low severity coprocessing reactions in the presence of the UOP ~atalyst.l',3~ Under these conditions, 2-naphthol is rapidly converted to tetralin. Several lines of argument imply that reduction of the activated ring precedes dehydration. It was also established that, when phenol was incorporated into a coprocessing reaction, it underwent alkylation rather readily to form 2- and 4-methyl-, 2- and 4-ethyl-, and 2and 4-propylphenol as well as 2,4-dimethylphen01.'~93~ Thus, simultaneous alkylation, deoxygenation, and ring reduction enables the conversion of rather polar oxygencontaining aromatic compounds into oil-soluble substances. Lstudies are ~ These providing a clearer picture of the way in which the complex coal molecules are converted into oil molecules in the molybdenum-catalyzed reactions. In summary, many aromatic hydrocarbons are reduced even under low-severity conditions to molecules with isolated benzene rings, such as tetralin, octahydrophenanthrene, and biphenyl. The phenols and ethers also react very readily to produce hydrocarbons that contain no more than one benzene ring. Heterocyclic substances are transformed to less polar oillike substances under typical coprocessing conditions. These hydrogen-consuming reactions are accompanied by alkylation reactions, as illustrated in the equation. As already mentioned, an array

3blt3Ha

W*O"AoN indicate that deep-seated transformations occur in coal molecules to render them into oillike substances. In one of the first attempts to establish the molecular basis for these successful coal conversions, Curtis and her co-workers investigated the reduction reactions of several representative hydrocarbons and heterocyclic compounds in the presence of an unpromoted molybdenum sulfide catalyst in an inert solvent, Chart 1.'"18 They established that the reduction of naphthalene and indene predominantly occurred to form tetralin and indan. Decalin was detected, but in very low yield, and no cleavage products were formed. In agreement with Rahimi and co-workers, Curtis pointed out that the production of hydrogen donating hydroaromatic compounds would beneficially influence the coprocessing chemistry. Several heterocyclic compounds underwent facile hydrogenolysis, and two distinct pathways were observed in which saturation of the aromatic rings occurred either prior to or following heteroatom removal. Direct hydrogenolysis prior to hydrogenation was the favored pathway in the reactions of benzothiophene and benzofuran, while the reverse was true for quinoline. When two or more of the compounds were reacted, nitrogen compounds deactivated the catalyst for hydrogenation as well as for nitrogen and oxygen removal. However, they did not effect sulfur removal, and excess elemental sulfur reduced the deactivation by nitrogen compounds. These observations are consistent with the finding that molybdenum catalysts often require sulfidation to achieve high activity. All of these reactions assist in the conversion of aromatic and heterocyclic compounds of coal into oil soluble substances under typical coprocessing conditions. Related work in our laboratory has established that phenanthrene is reduced to 9,lO-dihydrophenanthreneand

of alkylated phenols were detected in a parallel study, and we infer from Curtis's work and our work that the alkylated phenols are subsequently converted, as shown,into oxygenfree molecules. We also infer that other reactive coal molecules also experience alkylation during molybdenumcatalyzed coprocessing. These reactions are certainly desirable inasmuch as alkylation will enhance hexane solubility and deoxygenation will enhance both hexane solubility and volatility. Finally, we have considered the consequences of this chemistry by applying it to describe the outcome of coprocessing Illinois No. 6 coal. For this exercise, we adopted the structure of Illinois No. 6 coal, Figure 10A, that was proposed in 1984 by Shinn.35It should be noted that recent contributions by Winans36 and Hatcher37JE and their co-workers suggest that this relatively low rank coal has a structure that is more lignin-like than the Shinn structure with fewer aliphatic oxygen atoms and, even more importantly, many fewer polycyclic structural elements. The consequences of removing all the oxygen,80 5% of the sulfur, and 40 ?6 of the nitrogen are shown in Figure 10B, and the changes that occur as the consequence of fragmentation reactions that are enhanced by the oxygen heteroatoms, the cleavage of 1,3-diarylpropanes, and the reduction of polycyclic aromatic molecules that further degrade the complex coal matrix are shown in Figure 1OC. It is evident that the chemical processes that have been identified in the past few years would dramatically transform a bituminous coal with this structure into much (34) Ettinger, M. D.;Stock, L. M.; Gatais, J. G. Prepr. Pap.-Am. Chem. Soc., Diu.Fuel Chem. 1992, 38(2),359. (35) Shinn, J. Fuel 1984, 63, 1187. (36) Winans, R.E.In Aduances in Coal Spectroscopy, Meuzelaar, H. L. C., Ed., Plenum Press: New York, 1992, p 255. (37)Hatcher, P. G. Eurth Miner. Sci. 1992, 61, No. 1. (38) Hatcher, P. G. Energeia 1993, 4, No. 5.



Figure 10. (A, top left) The Shinn structure of Illinois No. 6 coal. (B, top, right) The Shinn structure after the removal of 100% of the oxygen atoms, 80% of the sulfur atoms (dibenzothiophenes retained), and 40% of the nitrogen atoms (pyridines retained). (C, bottom) The Shinn structure after reduction of polycyclic aromatic components and the cleavage of activated alkane fragments (those that were ortho or para to oxygen substituents and other diarylpropano fragments which were susceptible to thermal cleavage). The isolated single lines that remain represent ethane and other small molecules, connecting links to other parts of the structure and so forth. No attempt was made to force coincidence between the chemistry of this structure and our experimental observations.

less polar, much more volatile, more oil-solublesubstances. It should also be noted that the structure shown in panel C would be subject to a variety of other fragmentation reactions including the rupture of ethano bridges and the cleavage of cyclic and acyclic side chains to produce small and large alkanes. Although many features remain unsettled, the results that have been obtained in the investigations of catalyzed coprocessing provide a reasonable basis for the discussion of the conversion of coal molecules in these reactions.

Acknowledgment. We are indebted to the coal sample programs at the Kentucky Center for Applied Energy Research and The Pennsylvania State University for starting materials. We also gratefully acknowledge the special efforts of the analytical group at Universal Oil Products and the Institute of Gas Technology, who analyzed the gaseous samples. Irene Fox of the Analytical Chemistry Laboratory a t Argonne National Laboratory provided insight concerning the interpretation of the H/D analyses that were obtained by LECO equipment.

Coprocessing Reactions of Illinois No. 6 and Wyodak Coals with

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