PARTIAL OXIDATION OF METHANE TO SYNTHESIS GAS OVER (CA,SR)(TI,NI) OXIDES

Ni catalysts supported on perovskite were in situ prepared from Ca1-xSrxTi1-yNiyO precursors and were tested in the oxidation of CH4 by increasing reaction temperature from room temperature to 800 degrees C. NiO originally separated from the perovskite structure under sol-gel preparation conditions was reduced to Ni metal during the CH4 oxidation and thus formed Ni metal supported on perovskite showed high activity for synthesis gas production at 800 degrees C. This process involves first the oxidation of a part of CH4 to H2O and CO2 followed by the reforming reaction of CH4 with H2O and CO2. When the catalyst of y = 0.2 was used, high Sr contents afforded high activity for the CH4 oxidation and the highest activity to synthesis gas was obtained with x = 0.2. In the catalysts of x = 0.2, those of y greater than or equal to 0.1 showed high activity for the synthesis gas production, that of y = 0.05 required pretreatment with CH4 for acquiring the activity and a further decrease in the Ni content resulted in no activity. Ni catalyst prepared by impregnation over the perovskite carrier showed a high activity, while those prepared by mixing metal oxides were not active. It is thus most likely that perovskite structure possesses an important role as the carrier in Ni catalysts.