THE OXIDATION OF N-BUTANE ON VANADYL PYROPHOSPHATE CATALYSTS - STUDY OF THE PRETREATMENT PROCESS

The results of the pretreatment behaviour and catalytic properties of sulfate-containing vanadyl pyrophosphate catalysts in the oxidation of n-butane to maleic anhydride (MA) are presented. It has been found that the increase in the MA selectivity during the pretreatment procedure of the fresh catalysts prepared by anaerobic calcination is mainly caused by the decrease in the catalytic activity for MA total oxidation. The change of the catalyst surface composition by oxidation of the surface layer and the site isolation resulting from surface termination in pyrophosphate groups as well as the change of the acidic properties during the pretreatment process using conventional butane/air mixtures are assumed to be the reasons for the above finding.