On the active role of water during partial oxidation of n-butane to maleic anhydride over (VO) 2P 2O 7 catalysts

Abstract

The role of water in the reaction of n-butane to maleic anhydride over vanadyl pyrophosphate prepared in aqueous solution was studied under vacuum conditions by transient experiments in the temporal-analysis-of-products reactor. Under the existing low surface coverage conditions, two main effects of water on the reaction could be identified. First, water prevents the non-reactive irreversible adsorption of butane on the V–P–O catalyst and it enhances the desorption of the reaction products. Secondly, it dissociatively adsorbs on V–P-oxide, breaking V–O–V, V–O–P or P–O–P bonds and forming V–OH and/or P–OH groups. This structure-rupturing process leads to an easier reoxidation behaviour, necessary to keep the catalyst in a reactive state to form maleic anhydride.