MgO助剂对甲烷部分氧化Ni/Al2O3催化剂结构和性能的影响

采用分步浸渍法制备了MgO改性的Ni／Al2O3催化剂，采用BET、XRD、H2-TPR、TEM和活性评价等研究方法，考察了MgO助剂对Ni／Al2O3催化剂物化性质和甲烷部分氧化制合成气反应性能的影响。实验结果表明，MgO助剂提高了催化剂镍物种的均一性，抑制了NiAl2O4尖晶石的形成，并且增强了镍物种与载体的相互作用，这与MgO、NiO形成固溶体及与Al2O3形成MgAl2O4有关。同时，适量的MgO助剂可以提高Ni物种在催化剂中分散度，并提高其有效利用率，改性后的催化剂在甲烷部分氧化反应中显示出较好的反应性能。过量的MgO助剂对催化剂的反应性能产生负面影响，MgO的碱性可以促进逆水煤气变换反应，从而导致H2选择性降低和CO选择性提高。

Effects of MgO promoter on properties of Ni/Al2O3 Catalysts for partial oxidation of methane to syngas

The effects of MgO promoter on the physico-chemical properties and the catalytic performance of Ni/ Al2O3 catalysts for partial oxidation of methane to syngas were studied by BET, XRD, HE-TPR, TEM and reaction activity evaluation. It was found that MgO promoter benefited to the uniformity of nickel species on the catalysts, inhibited the formation of NiAl2O4 spinel and improved the interaction between nickel species and the support. This result was related to the formation of NiO-MgO solid solution and MgAl2O4 spinel. Moreover, for the catalysts with proper amount of MgO promoter, the dispersion of nickel species was enhanced, and thus their catalytic performance for methane partial oxidation to syngas was improved. However, excessive MgO promoter exerted a negative effect on the catalyst performance. In addition, the basicity of MgO promoted the reverse watergas shift reaction, which led to the increase of CO selectivity and the decrease of HE selectivity. The suitable content of MgO promoter in Ni/Al2O3 catalyst was about 7%.