Energy & Fuels 1990,4, 585-588
585
Roles of Nondonor Solvent in the Hydrogen-Transferring Liquefaction of Australian Brown Coal Ryuji Sakata, Akihisa Takayama, Kinya Sakanishi, and Isao Mochida* Institute of Advanced Material Study, Kyushu University, Kasuga, Fukuoka 816, Japan Received April 27, 1990. Revised Manuscript Received July 10, 1990
Three kinds of polycondensed aromatic hydrocarbons, pyrene (Py), fluoranthene (FL) and anthracene (An), were examined in combination with tetrahydrofluoranthene (4HFL) in the hydrogen-transferring liquefaction of Australian brown coal to clarify their roles as nondonor solvents. The mixed solvent of 75% 4HFL and 25% Py in liquefaction at 450 "C for 10 min and a solvent/coal ratio of 2 provided oil and oil + asphaltene yields of 54 and 65 %, respectively, indicating favorable effects of the mixed solvent for the oil production compared with pure donor. The hydrogen consumption for the oil production indicated the highest hydrogen efficiency with the mixed solvent. Favorable effects of FL with 4HFL were observed at a higher solvent/coal ratio of 3.5. The mixed solvent of 4HFL and An failed to provide good yields. Roles of nondonor in hydrogen-transferring liquefaction are considered to design the optimum liquefaction solvent for the higher oil yield based on the depolymerization mechanisms of coal macromolecules.
Introduction Hydrogen transfer from donor solvent to solid coal is the first step to obtaining liquid hydrocarbon in coal liquealthough depolymerization can be designed according to the successive catalytic or separation step.4 In this step, the coal macromolecule is depolymerized through the spontaneous bond breakage, hydrogenationaccelerating pyrolysis, and hydrocracking by the most reactive hydrogen atoms according to the strength and type of the bonds to be Hence, the reactivity and amount of donor are of primary importance in this Nondonor solvent is necessary in this kind of liquefaction, because coal swelling, diffusion of donor into solid coal, and dissolution of coal-derived molecules assisted by the nondonor are important schemes for coal depolymerization. Pyrene (Py) has been reported as an excellent solvent to dissolve coal into quinoline-soluble substances under liquefaction c~nditions.'~J* Some aromatic hydrocarbons can pick up bimolecular hydrogens from the (1) Neuworth, M. B.; Moroni, E. C. In Proceedings of the IGT Symposium on Aduances in Coal Utilization Technology; Louisville.. KY,. May 1979; pp 354-364. (2) Mochida, I.; Moriguchi, Y.; Korai, Y.; Fujitau, H.; Takeshita, K. Fuel 1981. 60. 746-747. (3) Mochida, 1:; Otani, K.; Fujitsu, H. Chem. Lett. 1983, 1025-1028. (4) Mochida, I.; Sakanishi, K.; Korai, Y.; Fujitau, H. Fuel Process. Technol. 1986, 14, 113-124. (5) Mochida, I.; Sakata. R.; Sakanishi, K. Prepr. Pap-Am. Chem. SOC..Diu. Fuel Chem. 1989.34.601-608. (6)McMillen, D. F.; Ogier, W. C.; Chang, S.; Fleming, R. H.; Malhotra, R. Proc. Int. Conf. Coal Sci. 1983, 199-202. (7) McMillen, D. F.; Malhotra, R.; Hum, G. P.; Chang, S. J. Energy Fuels 1987, 1, 193-198. (8)Kamiya, Y.; Ohta, H.; Fukushima, A.; Aizawa, M.; Mizuki, T. Proc. Int. Conf. Coal Sci. 1983, 195-198. (9) Kamiya, Y.; Futamura, S.;Mizuki, T.; Kajioka, M.; Koshi, K. Fuel Process. Technol. 1986, 14, 79-90. (10) Curtis, C. W.; Guin, J. A.; Kwon, K. C. Fuel 1984,63,1404-1409. (11) Mochida, I.; Sakata, R.; Sakanishi, K. Fuel 1989, 68, 306-310. (12) Mochida, I.; Takarama, A.; Sakata. R.: Sakanishi. K. Enerav -Fuels 1990, 4, 81-84. (13) Mochida, I.; Takarabe, A.; Takeshita, K. Fuel 1979,58, 17-23. (14) Davies, G. 0.;Derbyshire, F. J.; Price, R. J. J. Inst. Fuel 1977,51, ~
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121-126.
0887-0624/90/2504-0585$02.50/0
Table I. Elemental Analysis of S a m p l e Coal w t % (daf) ~~
Morwell I Morwell I1
~
C
H
N
O+S
61.4 63.7
4.9 4.9
0.7 0.9
33.1 30.5
ash,wt% 2.3 2.3
donor present in the process, providing a new donor of higher reactivity, (hydrogen shuttling).'"lg Derbyshire et al." reported that Py is an excellent shbttler to give a higher conversion of THF-soluble product in the liquefaction with tetralin. In the present study, three kinds of polycondensed aromatic hydrocarbons, pyrene, fluoranthene, and anthracene, were examined in the hydrogen-transferring liquefaction of Australian brown coal with tetrahydrofluoranthene (4HFL) as a nondonor solvent. The present authors have reported that too much donor decreases the oil yield.20 It accelerates the dealkylation and promotes the formation of hydrocarbon gas. The best mixing ratio of donor and nondonor provided the best yield of oil and asphaltene, the feed for the successive catalytic step. Hence, the present study will facilitate the design of the best solvent for the most efficient liquefaction in the first step. Experimental Section Materials. T h e ultimate analysis of Morwell brown coal I1 (the second lot in our series of study) is summarized in Table I. The carbon content of the coal appears reasonable in comparison with the data in t h e literature.20v21 1,2,3,10b-Tetrahydrofluoranthene (4HFL) was prepared b y catalytic hydrogenation (15) Derbyshire, F. J.; Whitehurst, D. D. Fuel 1981, 60, 655-662. (16) Derbyshire, F. J.; Whitehurst, D. D. High Temp-High Pressures 1981, 13, 177-183. (17) Derbyshire, F. J.; Varghese, P.; Whitehurst, D. D. Fuel 1982,61, 859-864. (18) Cassidy, P. J.; Grint, A.; Jackson, W. R.; Larkins, F. P.; Louey, M. B.; Rash, D.; Watkins, I. D. Proc. Int. Conf. Coal Sci. 1987,223-226. (19) Kwon, K. C. Fuel 1985, 64, 747-753. (20) Mochida, I.; Yufu, A,; Sakanishi, K.; Korai, Y. Fuel 1988, 67, 114-118. (21) Okuma, 0.; Mae, K.; Hirano, T. Fuel Process. Technol. 1988,19, 165-178.
0 1 9 9 0 A m e r i c a n Chemical Society
586 Energy & Fuels, Vol. 4, No. 5, 1990
Sakata et al.
-a
-
b
Figure 2. Influence of 4HFL concentration in the mixed solvent of 4HFL and FL on liquefaction yields (450 "C, 20 min, solvent/coal ratio = 3, 3.5). Solvent/coal ratio = (a, b) 3 and (c, d) 3.5. Solvent composition: (a, c) 100% 4HFL; (b, d) 75% 4HFL. 0,oil; m, asphaltene; n, preasphaltene; ,. residue; 8 , gas. Figure 1. Influence of 4HFL concentration in the mixed solvent of 4HFL and FL on liquefaction yields (450 "C, 10 min, soloil ,+ asphaltene; o, oil; @, preasphaltene; vent/coal ratio = 2): . a, residue; 0, gas. of commercial fluoranthene (FL) using a commercial Ni-Mo catalyst. 4HFL was identified by 'H and 13CNMR, quantified by gc, and purified by recrystallization with n-hexane, removing perhydrofluoranthenes (PHFL). 1,2,3,4,5,6,7,8-0ctahydroanthracene (8HAn),9,lO-dihydroanthracene(2HAn),anthracene (An), pyrene (Py), and fluoranthene (FL) were commercially available. Liquefaction Procedure. Liquefaction was carried out in a tube bomb (volume 20 mL). The coal (2.0 g) and the mixed solvent (3.0,4.0,6.0,or 7.0 g) were transferred to the bomb. The bomb was then pressurized with nitrogen gas to 1.0 MPa at room temperature, immersed in a molten tin bath at the prescribed temperature, and agitated axially during the reaction time. After the reactor was cooled in water, the products remaining in the bomb were recovered by washing with THF and extracted subsequently with THF, benzene, and hexane. The hexane-soluble (HS), hexane-insolublebut benzene-soluble (HI-BS), benzene-insoluble but THF-soluble (BI-THFS),and THF-insoluble (THFI) substances were defined as oil, asphaltene, preasphaltene, and residue, respectively. The oil yield was calculated as the difference between the recovered HS and solvent-derived products identified by GC. A small amount (
