Oxidation stability of MO2C catalysts under fuel reforming conditions

The oxidation stability of a low surface area Mo2C catalyst has been studied in the presence of gases associated with the steam and dry (CO) reforming of methane, at temperatures up to 850degreesC and pressures to 8 bar. The oxidation onset temperatures were found to be about 600degreesC when the carbide was exposed to either steam or CO2. There appears to be two distinct mechanisms for Mo2C oxidation: direct oxidation at temperatures below 750degreesC and thermal decomposition followed by oxidation of the Mo metal at temperatures above 750degreesC. Although onset temperatures were similar, CO2 was a stronger oxidant than steam at the higher temperatures. Both H-2 and CO were found to inhibit oxidation and the effect can be explained by their influence on the reactions governing carburization and oxidation. The water gas shift reaction readily occurred over the catalyst and it was found that a carburizing ratio, defined as the ratio of carburizing gases to oxidizing gases, was able to predict stability, with oxidation occurring at ratios of 0.8 or lower. The effect of pressure on the onset temperature of CO2 oxidation of the carbide was found to be negligible, even when inhibited by CO. (C) 2003 Elsevier B.V. All rights reserved.