Study On Partial Oxidation Of Methane To Synsgas Over Ni-Ce_xZr_1-xO₂ Catalyst

The catalytic partial oxidation of methane (POM) to syngas is a promising approach for methane utilization, because it has many advantages such as less equipment investment, lower power cost, smaller volume reactor and H2/CO molar ratio of the syngas about 2.0, which is favorable to synthesis of methanol and F-T synthesis.In this work, the catalyst preparation, the process conditions and surface state of catalyst were investigated.Polyethylene glycol (PEG) was used as dispersant. Ceria and zirconia were chosen as first and second promoter respectively. The reparation conditions were studied by means of TG-MS and TPR. The optimized preparation conditions of catalyst were shown as followed: calcined at 500℃for 2h, reduced at 500℃for 1h in 10%H2 -90%N2 atmosphere, sintering at 1000℃for 1h in N2.The catalytic POM activity of Ni-Ce_xZr_1-xO₂ catalysts was investigated. The crystal phase structure and the surface properties of catalyst were researched by means of XRD and BET. The results showed that the zirconia and ceria was informed of the solid solution, which improved the storage capacity and mobility of oxygen. The Ni-Ce0.8Zr0.2O₂ catalyst showed the highest activity, the optimized process conditions for this catalyst were n(CH4)/n(O₂)=2.0mol/mol, reaction temperature 930℃and gas space velocity 1.4×105h-1. Under above conditions, the CH4 conversion was 98%, H2 selectivity was 93%, CO selectivity was 98%, and H2/CO molar ratio in product was 1.9.The effect of surface state of Ni, Ni-CeO₂ and Ni-Ce_xZr_1-xO₂ catalysts on the POM performance was studied by mean of TPSR-MS. The results showed that: the reduced Ni species were the active sites of CH4 dissociation, the promoter ceria and zriconia can evidently change the surface state of catalyst. The POM reaction could be influenced by the existence form and concentration of oxygen species, which were improved by the addition of promoters.