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Liquefaction of Australian Brown Coal with Mixed Solvents of Different Qualities and Reactivities of Transferable Hydrogens Isao Mochida,* Akihisa Takayama, Ryuji Sakata, and Kinya Sakanishi Institute of Advanced Material Study, Kyushu University 86, Kasuga, Fukuoka 816, Japan Received February 7,1990. Revised Manuscript Received May 31, 1990 The liquefaction ability of a mixed donor of 4HFL (tetrahydrofluoranthene) and 8HAn (octahydroanthracene) was examined to reveal the roles of donors with different qualities and reactivities of transferable hydrogens, the components being applied in the same pot at once (single stage) or consecutively (two stages). Two donors competed for the radical fragments from the coal when mixed in the same pot (solvent/coal = 2,450 OC/lO min), and the yields of oil and asphaltene were 37 and 2070, respectively, which were much the same as the averages of the values obtained by their single use. A series use of a donor with eight donable hydrogens of less reactivity (8HAn) in the first stage (8HAn/coal= 1/1,450 OC/lO min) and another donor with four hydrogens of higher reactivity (4HFL) provided high yields of oil and asphaltene (41 and 19%, respectively) at less consumption of donors. 4HFL converted a larger amount of the heavier fraction in HI (hexane-insoluble fraction), which was obtained in the first-stage reaction of 450 OC/lO min using 8HAn (8HAn/coal = l / l ) , into the lighter fractions (oil 26%) in the second-stage liquefaction of 450 OC/lO min at 4HFL/HI = 1.5/1, while 8HAn provided a lesser amount (oil 13%) with larger amounts of residue and preasphaltene. Thus, two donors of different reactivities can share the roles in the depolymerization of coal molecules in the two-stage reaction according to their reactivities, giving high yields of oil and asphaltene. The mechanisms of fragment stabilization and hydrogen-assisting bond fission may explain these results which contribute according to the reactivities of donors as well as coal molecules.
Introduction It has been widely recognized that hydrogen transfer is most effective to depolymerize the coal macromolecule of solid form or high viscosity in the initial stage of liqueThe present authors have proved the high liquefaction ability of tetrahydrofluoranthene (4HFL) against Australian brown coal.44 However, a fairly large amount of solvent, a solvent/coal ratio at least above 1.5 is necessary,' because of the limited amount of transferable hydrogens in one molecule, enlarging the reactor volume. Donors of more hydrogens such as octahydroanthracene are effective to stabilize the radical fragments produced thermally from the coal macromolecules. However, the oil yields are restricted because they fail to depolymerizethe macromolecules through their hydrogenation or hydrocracking, which the former donors can p e r f ~ r m . ~ In the present study, the liquefaction ability of a mixed donor of 4HFL and 8% was examined to reveal the roles of donors with different quality and reactivity of transferable hydrogens. The components of the solvent could be applied in the same pot at once (in a single stage) or consecutively (in two stages), where different types of reactions between coal macromolecules and donors are expected. (1) Mochida, I.; Moriguchi, Y.; Korai, Y.; Fujitsu, H.; Takeshita, K. Fuel 1981,60,746-747. (2)Mochida, 1.; Otani, K.; Korai, Y.; Fujitsu, H. Chem. Lett. 1983, 1025-1028.
(3) Neuworth, M. B.; Moroni, E. C. In Proceedings of the IGT Symposium Advances in Coal Utilization Technology, Louisuille, KY,May
1979; New York, 1979; pp 354-364. (4) Mochida, I.; Yufu, A.; Sakanishi, K.; Korai, Y.; Shimohara, T. J. Fuel Soc. Jpn. 1986,65, 1020-1026. (5) Mochida, I.; Yufu, A.; Sakanishi, K.; Korai, Y. Fuel 1988, 67, 114-118. (6) Mochida, I.; Sakata, R.; Sakanishi, K. Fuel 1989, 68, 306-310. (7) Mochida, I.; Takayama, A.; Sakata, R.; Sakanishi, K. Energy Fuels 1990, 4, 81-84.
0887-0624/90/2504-0398$02.50/0
Table I. Elemental Analysis of Morwell Coal and HI" wt ?% (daf) C H N O+S ash Morwell 63.7 4.9 0.6 30.8 2.3 HI 81.2 5.4 0.9 12.5 5.2 a Hexane-insoluble fraction in the product obtained from the liquefaction of Morwell coal at 450 OC/10 min (8HAn/coal = l/l).
Experimental Section Materials. The ultimate analyses of Morwell coal and ita hexane-insoluble (HI) product are summarized in Table I. 1,2,3,4,5,6,7,8-0ctahydroanthracene (8HAn) was commercially (4HFL) was prepared available. 1,2,3,1Ob-Tetrahydrofluoranthene by catalytic hydrogenation of commercially available fluoranthene (FL) using a commercial Ni-Mo ~ a t a l y s t . ~ Liquefaction Procedures. Liquefaction was carried out in a tube bomb (20-mL volume). The mixture of coal (2 g) and solvent (2,3, or 4 g) was transferred to the bomb. The bomb was then pressurized with nitrogen gas to 1.0 MPa a t room temperature, immersed in a molten tin bath kept a t the prescribed temperature, and agitated axially. Figure 1 illustrates the liquefaction procedures examined. Single-stage liquefaction with mixed solvents (see (1))was carried out at the solvent/coal ratio of 1.5/1 (3 g/2 g) or 2/1 (4 g/2 g) and 450 OC/lO min or 450 OC/20 min. Two types of two-stage liquefaction were examined in the present study. In the first case (2), the first-stage liquefaction was carried out at the solvent/coal ratio = 1 (2 g/2 g) and 450 "C/10min, and the second stage was consecutively carried out at 450 OC/lO min in the same pot after the addition of donor (1 or 2 g) without removing the solvent used in the first stage. In the second case (3),the hexane-insoluble fraction (HI), which was obtained from the liquefaction at the ratio of 8HAn/coal = 1 (2 g/2 g) and 450 OC/lO min, was consecutively reacted with the solvent (solvent/HI (3 g/2 g) = 1.5) a t 450 OC/lO min. Analyses of t h e Products. The liquid and solid products recovered from the bomb were subsequently extracted with THF, benzene, and hexane. The hexane-soluble (HS), hexane-insoluble but benzene-soluble (HI-BS), benzene-insoluble but THF-soluble 0 1990 American Chemical Society
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Liquefaction of Australian Brown Coal
Table 11. Hydrogen Consumption of Donors' under Various Liquefaction Conditions conversion, % reaction conditions 4HFL FL 8HAn 4HAn An HCb OYc single stagee 4HFL/coal = 2/1 21 13 28 430 4HFL/coal = 1.5/1 3 97 28 290 8HAn/coal = 2/1 56 40 4 21 320 8HAnlcoal = 1.5/1 46 46 8 20 320 4HFL/8HAn/coal = 1/1/1 17 83 64 34 2 24 310 two stagd first 49 18 18 130 (8HAn/coal = 1/1) (33 second 37 6 21 350 58 8HAn (29) added (S/C = 2/11 58 I 21 410 41 59 35 4HFL (2 g) added (S/C = 2/1) 49 10 22 320 41 8HAn (1 g) added (S/C = 1.5/1) 63 9 25 380 18 82 28 4HFL (1 g) added (S/C = 1.5/1) two stagd first 45 21 18 180 (8HAn/coal = 1/1) (34 second 51 8 24 410 53 41 41 4HFL (2 g) added (S/C = 2/1) 48 10 21 420 30 IO 44 4HFL (1 g) added (S/C = 1.5/1)
OY/HCd 15
10 16 16 15 10)
17 15 14 15 10) 20 20
Oil yield (mg/g of coal). mg of oil/mmol of 4HAn, 1,2,3,4-tetrahydroanthracene; An, anthracene. Hydrogen consumption ("01). H. '450 OC/lO min. !First and second, 450 "C/10 min. #First, 430 OC/lO min; second, 450 OC/lO min. (I
(BI-THFS), and THF-insoluble (THFI) substances were defined
as oil, asphaltene, preasphaltene, and residue, respectively. The oil yield was calculated after identification of solvent-derived products in HS by GC. A small amount (
