Catalytic behavior of AMoOx (A = Ba, Sr) in oxidation of 2-propanol

Perovskite-type oxides, BaMoO3 and SrMoO3, were prepared by reduction of scheelite-type oxides, BaMoO4 and SrMoO4, in H2 flow at 873 K and characterized by XRD, TG, SEM, TPR, NH3-TPD, UV–vis DRS and BET measurement. The catalytic activity of these alkaline-earth molybdenum oxide catalysts was tested for oxidation of 2-propanol with gaseous oxygen under atmospheric pressure. Dehydration to propylene was mainly promoted over the scheelite-type with Mo6+, while oxidative dehydrogenation to acetone was mainly promoted over the perovskite-type with Mo4+, and selectivity to acetone was much higher over BaMoO3 than over SrMoO3. Both perovskite-type oxide catalysts underwent oxidation to some degree during the catalytic reaction, so that they also contained some Mo6+. We concluded that the high selectivity to acetone resulting from oxidative dehydrogenation during 2-propanol conversion is related to the constantly changing oxidation state of the catalyst, resulting in coexistence of Mo6+ octahedra and Mo4+ octahedra on the AMoO3 oxides.