Activity and Selectivity Variations in the Oxidative Dehydrogenation of Ethane Over a Molybdenum - Vanadium - Niobium Mixed Oxide Catalyst

A single pellet reactor was used to investigate the activity and selectivity variations with time in the oxidative dehydrogenation of ethane with a mixed oxide catalyst having a composition of Mo0.71V0.2Nb0.09. Experiments conducted at 450°C in the absence of oxygen showed rapid deactivation. In these experiments very high selectivities, reaching to unity, were observed at fractional conversions of 0.1 or less. An increase in conversion and a decrease in selectivity was observed with a decrease in catalyst porosity and also with an increase in pellet length, indicating the significance of diffusion time. This effect is found to be especially significant at the initial stages of reaction (fresh catalyst). In the absence of oxygen a large amount of CO was produced during the first couple of minutes of the reaction. On the other hand, in the presence of oxygen, the major side product is CO2. It was also concluded that gas phase oxidation of ethane to CO2 is not significant.