Effects of alkaline-earth strontium on the performance of Co/Al2O3 catalyst for methane partial oxidation

Abstract

A series of Sr-Co/Al2O3 catalysts were prepared by co-impregnation method using γ-Al2O3 as the support. The effect of strontium promoter on the catalytic performance of Co/Al2O3 catalyst for partial oxidation of methane (POM) to synthesis gas was studied. The catalysts were characterized by some physicochemical characterizations such as N2 physical adsorption, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR) and thermogravime try (TG). The results show that both Co/Al2O3 calcined at 700°C and Sr-Co/Al2O3 calcined at 800°C exhibit low activity and deactivate at the initial stage of POM reaction. The addition of above 2% mass fraction of strontium will greatly enhance the activity and stability of Co/Al2O3. Two types of Co species were identified on the fresh calcined catalysts. One is Co3O4 which weakly interacts with Al2O3 (easily reduced by H2) and the other is the spinel CoAl2O4 (non-catalytic performance) which strongly interacts with the support. During the course of calcination, strontium can react with Al2O3 to form Sr4Al14O25 which will restrain the generation of the CoAl2O4 species and promote the stability and activity of catalysts. Without strontium promoter, CoAl2O4 is easy to be formed over Co/Al2O3 in the POM reaction. However, the formation of CoAl2O4 cannot be avoided with the addition of limited strontium when the calcination temperature is over 800°C.