ON THE ACTIVE-ROLE OF WATER DURING PARTIAL OXIDATION OF N-BUTANE TO MALEIC-ANHYDRIDE OVER (VO)(2)P2O7 CATALYSTS

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 prod ucts. 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 struc ture-rupturing process leads to an easier reoxidation behaviour, neces sary to keep the catalyst in a reactive state to form maleic anhydride . (C) 1998 Elsevier Science B.V. All rights reserved.