The different catalytic behaviour in the propane total oxidation of cobalt and manganese oxides prepared by a wet combustion procedure

Abstract

Cobalt oxide and manganese oxide catalysts have been prepared through aqueous synthesis using a wet combustion procedure. These materials have been tested as catalysts for the total oxidation of propane. It has been observed a different catalytic behaviour between cobalt and manganese oxides although for both oxides a very high catalytic activity has been obtained. Cobalt oxides prepared by the wet combustion procedure are less reactive than a simple cobalt oxide prepared without the addition of organic acids. However, in the case of manganese oxide the use of organic acids highly increases the catalytic activity. The different catalytic behaviour has been related to the variation of the surface characteristics and also to the crystalline phases formed. The activity of Co catalysts has been observed to be mainly determined by the surface area as the specific activity of all cobalt oxide catalysts is comparable. This fact has been related to the similar bulk and surface redox catalyst characteristics. In the case of manganese oxide the specific reaction rate is remarkably higher in those catalysts prepared by wet combustion and this has been linked to the presence of a reduced phase and surface. The most active manganese oxide catalysts are those that present the best redox properties and the highest oxygen mobility.