Selective propene formation in periodic flow reactor: reducibility and catalytic activity of Ni-Mo-O system

Oxidative dehydrogenation (ODH) of propane with lattice oxygen of alpha-, a lpha'- and beta-NiMoO4 phases has been studied. Reduction tests of the diff erent phases were performed by TG analysis under hydrogen at different temp eratures. Under isothermal conditions lattice-oxygen-consumption rate was f ound to be higher on the beta-phase with respect to the alpha- and alpha'-p hases. TG analyses showed the existence of different sources of lattice oxy gen in the catalyst, depending on the NiMoO4 phase. Catalytic activity was measured under steady state conditions, using a periodic flow reactor and i t was then correlated to the reduction curve. It was found that the activat ion energy for ODH reaction over NiMoO4 of 54.3-62.7 kJ/mol is nearly ident ical to that obtained for the catalyst reduction under hydrogen (46-50.2 kJ /mol). The correlation between the activation energy of the reaction in a p eriodic operating system (POS) and that of solid reduction under hydrogen s uggests that the reaction obeys a red-ox mechanism.