678
Energy & Fuels 1992,6, 678-679
C'ommuntcattons Large Rate Enhancement by Iron Catalysts in the Low-Temperature Hydrogasification of Brown Coal under Pressure Yasuo Ohtsuka,*?tKenji Asami,t Tetsuo Yamada,S and Tsuneyuki Hommat Research Center for Carbonaceous Resources, Institute for Chemical Reaction Science, Tohoku University, Katahira, Aoba-ku, Sendai 980, Japan, and Kitami Institute of Technology, Koen-cho, Kitami 090, Japan Received April 23, 1992. Revised Manuscript Received June 19, 1992 The direct conversion of coal into CHI with a catalyst is one of the most attractive of processes which utilize coal in an environmentally acceptable manner. Among the many gasification catalysts, nickel is more suitable for producing a high concentration of CH4 in one pass from low-rank coal and pressurized steam at around 850 K.' However, the use of expensive nickel would not be practical. Iron is promising as an alternative to nickel, and the iron chlorides and sulfates readily available as acid wastes from steel pickling and Ti02 production plants are the most desirable iron catalyst sources.2 We have recently found that FeCl3 can be successfully converted to a C1-free iron catalyst active for the steam gasification of low-rank However, the effectivenessis small at the low temperatures, 800-850 K, favorable for CH4 formation from coal and steam. The present study focuses on applying this iron to the hydrogasification reaction where CH4 is produced by the reaction of coal with H2, because an iron catalyst is more effective a t low temperatures in H2 than in steam.4 In this communication, the C1-free iron from FeCl3is found to show an exceptionally high catalytic activity in the lowtemperature, pressurized hydrogasification of brown coal. Loy Yang brown coal supplied from the Coal Corporation of Victoria, Australia, was crushed to 150-250 pm. The proximate analysis was ash, 0.5, volatile matter, 52.4, and fixed carbon, 47.1 wt % (dry), and the ultimate analysis was as follows: C, 66.7; H, 4.6; N, 0.5; S, 0.3;0,27.9 wt '3% (daf). Iron cations alone were incorporated into the coal from an aqueous solution of FeCl3 by using NH3; after a sufficient amount of NHdNH4Cl solution was added into the mixture of coal particles and FeC13 solution, the iron-bearing coal was separated from the solution by filtration, washed with deionized water, and then dried at 380 K in N2. The details of the procedure have been described e l s e ~ h e r e .Actual ~ iron loadings were 5 and 9 wt % . Since a higher equilibrium concentration of CHI
* Author to whom correspondence should be addressed.
Tohoku University. Kitami Institute of Technology. (1) Takarada, T.; Saaaki, J.; Ohtsuka, Y.; Tamai, Y.; Tomita, A. Ind. Eng. Chem. Rea. 1987,26,627-629. (2) HQttinger, K. J.; Adler, J.; Hermann, G. In Carbon and Coal Caaification;Figueiredo, J. L., Moulijn, J. A., Eds.; NATO AS1 Series; Martinua Nijhoff: Dordrecht, The Netherlands, 1986; pp 213-229. (3) Ohtauka, Y.; Asami, K. Ind. Eng. Chem.Rea. 1991,30,1921-1926. (4) Ohtauka, Y.; Tamai, Y.; Tomita, A. Energy Fuels 1987, I , 32-36. t f
Table I. Mdssbauer Parameters. iron species
IS,mm/s
present iron (5 wt %) present iron (9 wt % ) a-FeOOHb fine FeOOH'
0.39 0.39 0.57
QS,mm/s
H,kOe
0.97 0.97
0 0
0.40
380
0 "IS, isomer shift relative to a-Fe at room temperature; QS, quadrupole splitting; H,hyperfiie field. Commercial bulk compound (99.999% pure). Reference 7; FeOOH particles f i e l y 0.41
0.89-0.92
*
dispersed on brown coal.
is obtained at a lower temperature and higher pressure,6 the gasification run with a thermobalance (Shimadzu RT1HP) was carried out at temperature of
