Preparation Of Ce - Based Composite Oxide Supported Ni Catalyst And Study On Catalytic Performance Of Partial Oxidation Of Methane

Attributing to its sereval advantages with small reactor, mild exothermic, less energyconsumption, wide application of product, etc, synthesis gas (CO+H2) from methane partialoxidation (POM) has been become the focus study of natural gas chemistry, and study of catalystis the key technology for this process. This dissertation focuses on active component Ni andceria-based composite oxide supports for POM reaction. The effect of preparation methods on theperformance of catalyst had been firstly studied and the performance of Ni catalysts supported ondifferent composite oxides in POM reaction had been investigated afterwards. On this basis, BET,XRD, FT-IR, SEM, UV-Vis DRS, H2-TPR, NH3-TPD, TG, etc, were introduced to characterizethe physicochemical property of the fresh and reacted catalysts. The main contents of thisdissertation study were as follow:First, Ni/CeO2-Al2O3prepared by citric acid complex method exhibited the highest activityand good stability among all those prepared by different methods. The reason was that metalirons were freeze-framed in space grid during citric acid complex reaction, which caused gooddispersion for Ni, larger surface area, small particle, easy to be reduced and low carbondeposition rate for this catalyst. Investigations of technological conditions showed that thehighest activity was obtained for catalyst which was reduced in pure hydrogen for1h withtemperature programming to750°C and reacted at750°C with2of CH4/O2ratio,12000mL·h-1·g-1of gas hourly space velocity.Based on citric acid complex method, CeO2-ZrO2solid solution was modified by Cu, Ba andAl doping. It could be found that ternary composite solid solutions MxOy/CeO2-ZrO2with stablestructure were synthesized by this method, and catalytic performance was reduced after Nisupported on CuO/CeO2-ZrO2, but it was improved when Ni supported on BaO/CeO2-ZrO2andAl2O3/CeO2-ZrO2. Though H2spillover between Cu and Ni promoted the reduction of Ni,damage of textural structure and formation of CuNi alloy, which were the major reasons fordescend of its catalytic activity. However, Al doping slightly increased the surface acidity of thesupport, it also produced more obvious effects on the increase of surface area, decreased theparticle size of support and enhanced carbon deposition ability, which made its high activity andstability.Finally, series of CeO2-SiO2composite oxides synthesized by using a sol-gel process whichwere applied in Ni catalyst for POM reaction and good catalytic performance was obtained. Lowactivity and poor stability of Ni/SiO2catalyst was found, which was resulted from the strongmetal-support interaction, strong acidity and much deposited carbon. CeO2-SiO2compositesupports had large surface area and small particle size of cubic CeO2. After Ni loading, NiO existed high-dispersed state and easy to be reduced, catalyst surface acidity was weakened andcarbon deposition hard to be formed.10Ni/0.50CeO2-0.50SiO2-700catalyst with Ce/Si molarratio of1:1, Ni mass fraction of10%and calacined at700°C which exhibited good stability andthe highest CH4conversion (~84%), CO and H2selectivity (>87%) among these series ofcatalysts.