Study On Partial Oxidation Of Methane To Syn-gas Over Cr₂O₃ And Ni/ZrO₂ Catalysts

Partial oxidation of methane (POM) to syngas is slightly exothermic and quick, the ratio of H2 to CO is 2, which is suitable for methanol and F-T synthesis. Ni-based catalyst possesses high reaction activity of POM, however, such a catalyst is prevented from commercialization due to the loss of Ni at high temperature and carbon deposition. The oxide catalysts are reverse in the situation. The main objectives of this work were to prepare Cr2O3 catalyst, explore the reason of carbon deposition over Ni/ZrO2-HT catalyst, and suppress the carbon deposition over Ni/ZrO2-HT in dual catalysts bed.The POM reactions were carried out in a flow-type fixed bed micro reactor (quartz tube) at atmospheric pressure, the catalysts were characterized by TPR, TGA, TEM, XRD, BET, XPS and methane pulse reaction.ZrO2-HT carrier was prepared by hydrothermal method and Ni/ZrO2-HT (loading 9%)catalysts were prepared by impregnation method. The catalytic performances and resistance to coking of Ni/ZrO2-HT catalysts were investigated. A part of syngas may be gotten by direct oxidation and the other part by steam and carbon dioxide reforming. Oxygen was rich in the upper catalyst bed and absent in the bottom catalysts bed. The oxygen rich area has good resistance to coking and the oxygen absent area carbon deposition was serious. Direct oxidation took palace in upper catalyst bed, and carbon dioxide reforming took palace in bottom catalyst bed.Effect of calcination of ZrO2-HT carrier, regeneration of coking Ni/ZrO2-HT catalyst and calcination of Ni/ZrO2-HT catalyst on catalytic performance and resistance to coking were investigated. Generally speaking, higher resistance to coking is due to smaller the size of Ni particles, but what we observed in experiment didn't agree to the common experience. We proposed that the major factor determining the resistance to coking of Ni based catalyst may be resistance to sintering in POM process. Good resistance to coking may be related to good resistance to sintering.The catalytic performance and the resistance to coking of dual catalysts in POM were investigated, the upper bed was filled with Cr2O3 and bottom with Ni/ZrO2-HT. The resistance to sintering of Ni/ZrO2-HT catalyst was improved, and then the resistance to coking was improved. The resistance to coking increased on the base to higher catalytic performance.