Steam gasification of carbon: Catalyst properties. Final report, September 15, 1988--October 31, 1992

Abstract

Coal gasification by steam is of critical importance in converting coal to gaseous products (CO, H{sub 2}, CO{sub 2}, CH{sub 4}) that can then be further converted to synthetic natural gas and higher hydrocarbon fuels. Alkali and alkaline earth metals (present as oxides) catalyze coal gasification reactions and cause them to occur at significantly lower temperatures. A more fundamental understanding of the mechanism of the steam gasification reaction and catalyst utilization may well lead to better production techniques, increased gasification rates, greater yields, and less waste. We are studying the gasification of carbon by steam in the presence of alkali and alkaline earth oxides, using carbonates as the starting materials. Carbon dioxide gasification (CO{sub 2} + C --> 2CO) has been studied in some detail recently, but much less has been done on the actual steam gasification reaction, which is the main thrust of our work. In particular, the form of the active catalyst compound during reaction is still questioned and the dependence of the concentration of active sites on reaction parameters is not known. Until recently, no measurements of active site concentrations during reaction had been made. We have recently used transient isotope tracing to determine active site concentration during CO{sub 2} gasification. We are investigating the mechanism and the concentration of active sites for steam gasification with transient isotopic tracing. For this technique, the reactant feed is switched from H{sub 2}0 to isotopically-labeled water at the same concentration and tow rate. We can then directly measure, at reaction the concentration of active catalytic sites, their kinetic rate constants, and the presence of more than one rate constant. This procedure allows us to obtain transient kinetic data without perturbing the steady-state surface reactions.