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Energy & Fuels 1996, 10, 216-219
Catalytic Activity of NiMo Sulfide Supported on a Particular Carbon Black of Hollow Microsphere in the Liquefaction of a Subbituminous Coal Kinya Sakanishi, Haru-umi Hasuo, Masahiro Kishino, and Isao Mochida* Institute of Advanced Material Study, Kyushu University, Kasuga, Fukuoka 816, Japan
Osamu Okuma Polymer and Chemical Technology Laboratory, Kobe Steel, Ltd., Kobe, Hyogo 651-22, Japan Received May 23, 1995X
The liquefaction of Wyoming coal (subbituminous coal) was investigated with an autoclave of 50 mL capacity, using Ketjen Black (KB)-supported NiMo catalyst, which has higher hydrogenation activity of 1-methylnaphtalene than a commercial NiMo/Al2O3. KB-supported NiMo catalyst gave the oil and oil plus asphaltene yield of 54 and 69% under reaction conditions of 440 °C, 60 min, and 13 MPa. These yields were much higher than those of a commercial NiMo/Al2O3 and synthesized FeS2 catalysts. The KB-supported NiMo catalyst was found to be recovered from the solid products using polar solvents such as THF because it is highly dispersed in liquid products due to its low specific gravity and the hydrophobic property of its surface. It was also found that KB-supported NiMo catalyst suffered the least deactivation by coke formation and mineral matter deposition because the recovered catalyst as THFI residue appeared to regenerate the activity to a level similar to the fresh catalyst.
Introduction Coal liquefaction has been rather extensively investigated for several decades in order to provide clean liquid fuel from coal to meet the increasing demand for transportation fuel expected in early next century.1,2 However, the cost of the liquid fuel is still too high for it to become a substitute for the petroleum products. Several breakthrough ideas on process simplification as well as a better catalyst are strongly desired to reduce the cost currently estimated. A large quantity of FeS2 derived from iron ore, dust, and natural pyrite is usually applied to the liquefaction as catalyst due to its low activity.3-6 Its cost and disposal cannot be overlooked. NiMo or CoMo on alumina which is applied in the ebulliating bed suffers deactivation from coke and mineral depositions and hence its turnover is limited, to force its purge with unreacted coal and minerals.7-10 X Abstract published in Advance ACS Abstracts, December 1, 1995. (1) Derbyshire, F. J.; Catalytic in Coal Liquefaction: New Directions for Research; IEA Coal Research: London, 1988. (2) Mochida, I.; Sakanishi, K. Advances in Catalysis; Academic Press: New York, 1994; Vol. 40, pp 39-85. (3) Farcasiu, M.; Smith, C.; Pradhan, V. R.; Wender, I. Fuel Process. Technol. 1991, 29, 199-210. (4) Montano, P. A.; Bommannavar, A. S.; Shah, V. Fuel 1981, 60, 703-709. (5) Schmid, B. K.; Jackson, D. M. Coal Processing Technology; AIChE: New York, 1978; Vol. IV, p 146. (6) Yokoyama, S.; Yoshida, R.; Narita, H.; Kodaira, K.; Maekawa, Y. Fuel 1986, 65, 164-170. (7) Groot, C. K.; de Beer, V. H. J.; Prins, R.; Stolarski, M.; Niedgwiedg, W. S. Ind. Eng. Chem. Prod. Res. Dev. 1986, 25, 522530. (8) Hillerova, E.; Vit, Z.; Zdrazil, M.; Shkuripat, S. A.; Bogdanets, E. N.; Startsev, A. N. Appl. Catal. 1991, 67, 231-236. (9) Louwer, S. P. A.; Prins, R. J. Catal. 1992, 133, 94-111.
0887-0624/96/2510-0216$12.00/0
Current approaches to solve the problem appear to apply fine particles and highly dispersed catalysts of high activity.11-15 So far, catalyst precursors and preparation methods are costly compared to their activity. Repeated use of the catalyst which is usually performed in the feasible process is the most promising way to reduce the cost. Bottom recycle with the catalyst has been proved effective, although it is limited by the amount of minerals in the bottom which contaminate the catalyst.16-18 Dow proposed very fine particles of molybdenum sulfide which was claimed to be recovered by liquid cyclone.19 The present authors proposed basic ideas to recover the catalysts by separating them from inorganic residue which originates from the feed coal.20-22 According to (10) Mochida, I.; Oishi, T.; Korai, Y.; Fujitsu, H. Ind. Eng. Chem. Prod. Res. Dev. 1984, 23, 203-205. (11) Suzuki, T.; Yamada, H.; Sears, P. L.; Watanabe, Y. Energy Fuels 1989, 3, 707. (12) Pradhan, V. R.; Tierney, J. W.; Wender, I.; Huffman, G. P. Energy Fuels 1991, 5, 497-507. (13) Hirschon, A. S.; Wilson Jr., R. B. Fuel 1992, 71, 1025. (14) Burgess, C. E.; Schobert, H. H. Fuel 1991, 70, 372. (15) Curtis, C. W.; Cahela, D. R. Energy Fuels 1989, 3, 168. (16) Paradhan, V. R.; Herrick, D. E.; Tierney, J. W.; Wender, I. Energy Fuels 1991, 5, 712-715. (17) Taunton, J. W.; Trachte, K. L.; Williams, R. D. Fuel 1981, 60, 788-795. (18) Rosenthal, J. W.; Dahlberg, A. J.; Kuehler, C. W.; Cash, D. R.; Freedman, W. Fuel 1982, 61, 1045-1052. (19) Whitehurst, D. D., Ed. Coal Liquefaction Fundamentals; ACS Symp. Ser.; American Chemical Society: Washington, DC, 1980; Vol. 139. (20) Mochida, I.; Sakanishi, K.; Sakata, R.; Honda, K.; Umezawa, T. Energy Fuels 1994, 8, 25-30. (21) Mochida, I.; Hasuo, H.; Sakanishi, K.; Taniguchi, H. Prepr. Pap.sAm. Chem. Soc., Div. Fuel Chem. 1995, 40(2), 329-337. (22) Sakanishi, K.; Hasuo, H.; Mochida, I.; Okuma, O. Prepr. Pap.sAm. Chem. Soc., Div. Fuel Chem. 1995, 40(2), 377-382.
© 1996 American Chemical Society
Catalytic Activity of NiMo Sulfide
Energy & Fuels, Vol. 10, No. 1, 1996 217
Table 1. Some Properties of Catalysts NiMo/Al2O3
NiMo/KB JD
400
1270 30 115 2 10
surface area (m2/g) particle size (nm) apparent density (g/L) Ni (wt %) Mo (wt %)
2.4 10
Table 2. Elemental Analysis of Wyoming Coal Wyoming coal a
Ca
Ha
Na
(O + S)a
ashb
66.8
4.9
1.0
27.3
4.9
b
In wt % (daf). In wt %.
the nature of inorganic residue, three approaches can be designed: (1) removal of inorganic residues such as carbonates and chlorides, (2) recovery of the ferromagnetic catalysts from the diamagnetic residue, and (3) gravimetric recovery of the catalysts supported on light materials of fine particles. The present authors have reported that NiMo supported on Ketjen Black (KB), which is one of the unique carbon blacks of hollow sphere, exhibited higher activity for the hydrogenation of 1-methylnaphthalene (1-MN) than a commercial NiMo supported on alumina.23 Its hollow sphere of the low gravity provides the possibility of its gravimetric recovery. In the present paper, the activities of KB-supported NiMo catalyst were studied for the liquefaction of Wyoming coal under certain conditions in terms of hydrogen pressure, reaction temperature, and heating rate. Several supporting procedures were also studied to find the best activity. The flotation separation scheme of KB-based catalyst was examined to utilize the low specific gravity and hydrophobic surface of KB. Experimental Section Catalyst. Some properties of Ketjen Black (KB) JD provided by Mitubishi Chemical Co. are summarized in Table 1. Ni and Mo salts were supported on KB JD by successive impregnating methods of Mo and Ni in this order using Mo dioxyacetylacetonate (MoO2-AA) and Ni(OAc)2 as metal salts in methanol. Other kinds of NiMo/KB catalysts were also prepared from the water-soluble metal salts such as (NH4)6Mo7O24 and Ni(NO3)2 by simultaneous or successive impregnating methods. The catalyst precursor was dried at 120 °C for 12 h in a vacuum and presulfided in a 5% H2S/H2 flow at 360 °C for 3 h prior to the reactions. A commercially available NiMo/Al2O3 (
