Selective Oxidation and Oxidative Dehydrogenation of Isobutane over Hydrothermally Synthesized Mo–V–O Mixed Oxide Catalysts

A series of Mo–V–O catalysts were prepared by calcining the orthorhombic (M1) Mo–V–O phase containing precursors under different conditions (T = 500 or 600 °C in atmosphere of N2 or air) and tested for the oxidation of isobutane and isobutene. Characterization results (BET, XRD, XPS, FTIR, and TPR) showed that their structure and properties depend on the composition of the calcined samples and the calcined conditions. Catalytic tests showed that relatively high isobutane conversion and desired product selectivity can be achieved over MoV0.3-500-N and MoV0.3-600-A catalysts. It is also found that both orthorhombic M1 phase and (V0.07M0.93)5O14 phase are active and selective for the selective oxidation of isobutane to methacrolein, whereas higher selectivity toward methacrolein (40.4%) can be achieved over the former phase at a moderate isobutane conversion (6.4%). Moreover, (Mo0.3V0.7)2O5 phase may be propitious to complete oxidation for the selective oxidation of isobutane. On the other hand, the presence of V affects the activity and selectivity, and a low surface V4+ concentration prefers selective oxidation products. In addition, specific surface areas of the catalysts appear to be little important in determining the catalytic activation.