Dry reforming kinetics over a bulk molybdenum carbide catalyst

A bulk molybdenum carbide catalyst was used to determine a rate expression for dry methane reforming at temperatures between 800 and 900 degrees C, with CH4 and CO2 partial pressures from 0.15 to 0.32 bar and from 0.11 to 0.23 bar, respectively. Intrinsic kinetic measurements were made possible by co-feeding CO along with reactants at a constant CO : CO2 feed ratio of 3.0 in order to prevent oxidation of the Mo2C catalyst to MoO2. Methane conversion data as a function of inverse methane space velocity were obtained under conditions of negligible gas-solid mass transfer resistance and subjected to differential analysis. Partial pressure and rate data from all experiments were agglomerated and fit to a power law rate expression, which gave reaction orders of 1.2 and 0.7 for CH4 and CO2, respectively. The activation energy obtained in this temperature range was 172kJ/mol, higher than reported values for supported nickel or noble metals for the same reaction. It is proposed that the rate data are consistent with a mechanism that involves a combination of carbidic carbon exchange and chemisorbed CO2, accounting for the high activation energy and the susceptibility of the catalyst to oxidation. (c) 2005 Elsevier Ltd. All rights reserved.