Partial Oxidation of CH4 over Ni/SrTiO3 Catalysts Prepared by a Solid-Phase Crystallization Method

Abstract

Supported Ni catalysts on perovskite-type CaTiO3, SrTiO3, and BaTiO3 oxides were prepared by the solid-phase crystallization (spc) method and tested for the partial oxidation of CH4 to synthesis gas. The impregnation (imp) method was used for comparison. spc-Ni/SrTiO3 showed the highest activity as well as the highest sustainability against both coke formation and reoxidation of Ni metal, followed by spc-Ni/BaTiO3, spc-Ni/CaTiO3, and then imp-Ni/SrTiO3. The order of the activity was clearly confirmed in the reaction at high space velocity. Both transmission electron microscopy and temperature-programmed reduction showed the presence of finely dispersed and stable Ni metal particles on the catalysts and their amount correlated well with the order of the catalytic activity. It is suggested that incorporation of Ni is enhanced in SrTiO3, followed by BaTiO3, and much less in CaTiO3, resulting in the higher dispersion of Ni metal particles on SrTiO3. Less heat was generated over spc-Ni/SrTiO3 during CH4 oxidation, suggesting that the heating of the catalyst bed by CH4 combustion must be quickly compensated for by endothermic reforming reactions. Oxygen mobility was highest over spc-Ni/SrTiO3 as judged from CO2 pulse measurements. The high sustainability against coke formation may be due to the high activity of finely dispersed nickel metal particles for the reforming reactions partly assisted by the mobile oxygen on the catalyst.