ON THE NIMOO4 OXIDATIVE DEHYDROGENATION OF PROPANE TO PROPENE - SOME PHYSICAL CORRELATIONS WITH THE CATALYTIC ACTIVITY

The alpha- and beta-phases of NiMoO4 have been investigated with different techniques (X-ray diffraction, electrical conductivity, IR spectroscopy) in order to tentatively rationalise the different catalytic activities observed in the oxidative dehydrogenation of propane to propene. XRD analyses have shown that at 595-degrees-C, the beta-phase is already present but a temperature of approximately 700-degrees-C is required to obtain a full conversion into a pure beta-phase. Electrical conductivity showed the presence of anionic vacancies. It is proposed that propene is formed by the reaction of propane with surface O2- anions. The beta-phase is almost twice more selective in propene formation than the alpha-phase for comparable conversion at identical temperatures. This could derive from different oxygen environments on the active catalytic site.