OXIDATIVE DEHYDROGENATION OF ETHANE ON VANADIUM MOLYBDENUM OXIDE AND VANADIUM NIOBIUM MOLYBDENUM OXIDE CATALYSTS

The oxidative dehydrogenation of ethane has been investigated on a range of mixed Mo/V/Nb oxide catalysts. A maximum in activity was observed for Mo/V oxide catalysts at ca. 70% Mo. Addition of niobium oxide to this mixed oxide resulted in a more active and selective catalyst. The orders of reaction with respect to the ethane and oxygen partial pressures have been determined and found to be close to first order in ethane pressure but almost independent of oxygen pressure, except at higher temperatures and lower oxygen pressures. The role of lattice oxygen in the reaction has been explored by examining the reducibility of the catalysts, the thermal desorption of oxygen, and the activity in pulse experiments in the absence of gas-phase oxygen. A correlation is observed between the ease of reduction of the catalyst and the activity and selectivity, with the most easily reduced catalyst being the most active and selective for the formation of ethene. Possible mechanisms to account for the results are discussed and the role of niobium is considered.