No abstract

No abstract

The oxidative dehydrogenation of propane (ODHP) over NiO-Bi 2 O 3 -ZrO 2 catalyst was carried out with a fixed-bed flow reactor at 400°C under atmospheric pressure. NiO-Bi 2 O 3 -ZrO 2 prepared by the co-precipitation method afforded moderate propane conversion of 18.6% and propylene selectivity of 56.1% at 400°C. From XPS analyses of the used catalysts, NiO/ZrO 2 prepared by the impregnation method exhibited reduced metallic Ni species after the ODHP for 1 h. On the other hand, NiO-ZrO 2 and NiO-Bi 2 O 3 -ZrO 2 prepared by the co-precipitation method exhibited predominantly NiO and Ni 2 O 3 together with a minor amount of metallic Ni. From TPR and TPO, it was suggested that propylene was formed by the reaction with adsorbed oxygen species on NiO x , in contrast, metallic Ni promoted complete oxidation of propane to decrease propylene selectivity. Thus, to maintain Ni species in the oxidized state was crucial for the high selectivity to propylene. The additive effect of Bi 2 O 3 is ascribed to have kept NiO in the solid solution less reducible state. In addition, once metallic Ni was formed, it could easily be oxidized to NiO or Ni 2 O 3 .

No abstract