AN EVIDENCE OF ACTIVE SURFACE MOOX OVER MGMOO4 FOR THE CATALYTIC OXIDATIVE DEHYDROGENATION OF PROPANE

In order to clarify whether MgMoxOy catalysts with slight excess of mo lybdenum relative to the stoichiometric MgMoO4 compound showed increas ed activities for propene formation in the propane oxidative dehydroge nation, we investigated the catalytic properties of MoO3 supported on MgMoO4 and of MgMoxOy catalysts treated with acid or base. Supporting MoO3 on magnesium-rich MgMo0.99Oy catalysts which are poorly active, o r treating them with acetic acid to remove excess magnesium, resulted in drastic activity increases. On the other hand, the ammonia treatmen t of molybdenum-rich MgMo1.05Oy, catalysts which are highly active tur ned out to give a remarkable decrease in activity, because surface MoO x dissolved in ammonia water. A clear correlation was observed between the catalytic activities for propane oxidation and the dehydration of 2-propanol to propene over the supported catalyst and the treated cat alysts. Since the bulk structures were unchanged by supporting or by t he treatments, the existence of MoOx clusters formed on the surface of MgMoO4 are responsible for the activities in the oxidative dehydrogen ation of propane.