Effect of preparation method of Co-promoted Pd/alumina for methane combustion

Abstract

Effect of preparation method of Co-promoted Pd/alumina for methane combustion was investigated. The addition of Co was carried out by two methods: co-impregnation of an aqueous solution of palladium nitrate and cobalt nitrate mixture, and sequential impregnation of an aqueous solution of cobalt nitrate to Pd/alumina. At the loading amount of 1–3wt%, the co-impregnated catalysts showed the higher activity than un-promoted Pd/alumina, while the sequentially impregnated catalysts showed the lower activity. XPS and IR spectra of adsorbed CO indicated that the oxidation state of Pd was not much affected by the preparation methods. Good dispersion of Co on the co-impregnated catalyst was demonstrated by HAADF-STEM images, while less interaction between Co and Pd was suggested on the sequentially impregnated catalysts. The profiles of temperature programmed reduction by methane indicated that the better dispersion of Co on Pd resulted in the better reducibility of Pd species, which is attributed to the higher methane oxidation activity of co-impregnated catalysts.