Effect of Mg addition on the catalytic performance of V-based catalysts in oxidative dehydrogenation of propane

Abstract

The effect of magnesia addition on the physicochemical characteristics of vanadia catalysts supported on titania and alumina was investigated. The results were correlated with the catalytic performance in oxidative dehydrogenation of propane. The concentration of the acid sites was measured by FT-IR after pyridine sorption at 75 °C. It was found that the catalysts studied possess only Lewis acid sites except the vanadia on titania catalyst, where a few Brønsted acid sites were identified. The concentration of acid sites is affected by both the catalyst support and modifier added. The adsorption of propene at 100 °C followed by TPD was examined. The amount of propene adsorbed strongly depends on the presence of Mg while the extent of deep oxidation of adsorbed propene is related to the nature of the support and/or the surface concentration of active species. Testing of catalysts using 1/1 ratio of C 3H 8/O 2 as a function of temperature and W/ F, showed that the vanadia on titania catalyst exhibits much higher surface activity than the alumina supported and magnesia modified catalysts. The sequence in surface activity parallels the concentration of acid sites. A significant increase in selectivity was obtained with the Mg modified catalysts, especially with the vanadia supported on titania catalyst. The primary dehydrogenation reaction for propene formation is favored by the presence of Mg on the catalyst surface.