Stability, carbon resistance, and reactivity toward autothermal reforming of nickel on ceria-based supports

'Full text:' Solid Oxide Fuel Cell (SOFC) normally requires a reformer unit, where the fuel such as natural gas, methane, methanol, or ethanol can be reformed to hydrogen before introducing to the main part of fuel cell. Nickel on commercial supports such as Al2O3, MgO, ZrO2 has been widely reported to be used as the reforming catalyst commercially. Carbon formation and catalyst deactivation are always the main problems of using this type of catalyst. It is well established that CeO2 and CeO2-ZrO2 have been applied as the catalysts in a wide variety of reactions involving oxidation or partial oxidation of hydrocarbons (e.g. automotive catalysis). In order to quantify the performance of nickel on CeO2 and CeO2-ZrO2 supports for reformer application, the stabilities toward methane steam reforming and the carbon formation resistance were studied. After 18 hours, nickel on CeO2-ZrO2 with the Ce/Zr ratio of 3/1 presented the best performance in term of stability and activity. It also provided excellent resistance toward carbon formation compared to commercial Ni/Al2O3. The autothermal reforming of methane over Ni catalyst on CeO2 and CeO2-ZrO2 supports were also investigated. Ni/Ce-ZrO2 with the Ce/ Zr ratio of 3/1 also showed the best performance. The kinetics of this reaction was also studied. In the temperature range of 750-900C, the reaction order in methane was always closed to 1. The catalyst showed a slight positive effect of hydrogen and a negative effect of steam on the steam reforming rate. The addition of oxygen increased the steam reforming rate. However, the productions of CO and H2 decreased with increasing oxygen partial pressure. (author)