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

Abstract

The effects of MgO promoter on the physicochemical properties and catalytic performance of Ni/Al2O3 catalysts for the partial oxidation of methane to syngas were studied by means of BET, XRD, H2-TPR, TEM and performance evaluation. It was found that the MgO promoter benefited from the uniformity of nickel species in the catalysts, inhibited the formation of NiAl2O4 spinel and improved the interaction between nickel species and support. These results were related to the formation of NiO-MgO solid solution and MgAl2O4 spinel. Moreover, for the catalysts with a proper amount of MgO promoter, the nickel dispersiveness was enhanced, therefore making their catalytic performance in methane partial oxidation improved. However, the excessive MgO promoter exerted a negative effect on the catalytic performance. Meanwhile, the basicity of MgO promoted the reversed water-gas shift reaction, which led to an increase in CO selectivity and a decrease in H2 selectivity. The suitable content of MgO promoter in Ni/Al2O3 catalyst was ∼7 wt-%.