La2O3 和CeO2对CH4-CO2重整Ni/MgO催化剂结构和性能的影响

采用共沉淀方法制备了NiO-MgO、NiO-La2O3-MgO、NiO-CeO2-MgO三种催化剂，用BET、XRD、TPR、XPS、TG及活性评价等方法考察了La2O3、CeO2助剂对NiO-MgO物化性质和CH4-CO2重整反应性能的影响.实验结果表明，三种催化剂中镍物种以镍镁固溶体形式存在.与NiO-MgO相比， NiO-La2O3-MgO、NiO-CeO2-MgO具有较高比表面积，且其镍物种可还原能力有所增强， NiO-CeO2-MgO尤为明显. La2O3、CeO2均在一定程度上改善了NiO-MgO的CH4-CO2重整反应性能，提高了镍晶粒的抗烧结能力.但二者的作用机制有所差异， La2O3和CeO2分别主要作为结构助剂和电子助剂发挥作用.

Influence of La2O3 and CeO2 Promoters on Physico-chemical Properties and Catalytic Performance of Ni/MgO Catalyst in Methane Reforming with Carbon Dioxide

Three catalysts, NiO-MgO, NiO-La2O3-MgO and NiO-CeO2-MgO containing 10％(w) Ni were prepared by the co-precipitation method. The effects of La2O3 and CeO2 on physico-chemical properties and catalytic performance of NiO-MgO catalysts were studied by means of BET, XRD, TPR, XPS, TG and reaction activity evaluation. It was found that NiO formed a nickel-magnesia solid solution with MgO, and La2O3 and CeO2 promoters improved the resistance to sintering of the nickel-magnesia solid solution, which was attributed to the higher specific surface area and smaller size of crystallites of the Nickel-magnesia solid solution. Besides, La2O3 and CeO2 could promote reduction of nickel species in nickel-magnesia solid solution, especially CeO2. Under reaction conditions of CH4/CO2=1(molar ratio), 0.1 MPa, 1023 K and 1073 K, 18 L•g-1•h-1, NiO-La2O3-MgO and NiO-CeO2-MgO showed higher activity than NiO-MgO. However, the three catalysts had similar activity at 1123 K because the reaction was close to the thermodynamic equilibrium under these reaction conditions. La2O3 and CeO2 act as a structural promoter and an electronic promoter respectively to improve the properties of NiO-MgO.