A KINETIC AND IN-SITU XRD STUDY OF CARBON REACTIONS CATALYZED BY NICKEL, COBALT, MOLYBDENUM, AND THEIR MIXTURES

The kinetics of oxidation and hydrogenation of ground charcoal in the presence of nickel, cobalt, and molybdenum catalysts have been studied using a microbalance and ill situ X-ray diffraction to identify the p hases present during the reactions. Nickel and cobalt were found to be better catalysts than molybdenum for the oxidation of carbon, However , addition of molybdenum to the other metals resulted in increased cat alytic activity, probably because; of decreased crystal growth or sint ering of the active phases. The promoting effect of molybdenum was les s clear in the case of carbon hydrogenation, which took place in two d istinct temperature ranges (between 773 and 973 K and above 1023 K) wi th nickel catalysts. Possible mechanisms of the catalyzed reactions ar e discussed. (C) 1997 Academic Press.