Effect of electric field and water on Pd-based catalyst for complete oxidation of methane: Study on promotion and deactivation

Abstract

Methane (CH4) is an important greenhouse gas, and its ability to cause greenhouse effect is 25 times of the same amount of CO2. Electric field is one of the effective ways to reduce the ignition temperature of CH4 catalytic oxidation. In this paper, a Pd-based catalyst with Ce0.75Zr0.25-γ-Al2O3 composite support was synthesized by impregnation and its activity and water resistance were evaluated. The effect of water and electric field on the properties of catalyst was investigated by XRD, XPS, BET, TEM, H2-TPR and in-situ DRIFT. The results showed high CH4 conversion was maintained in the presence of water because the aggregation of Pd specie was prevented by electric field. After 24 h operation in electric field, catalyst’s lattice structure remained stable, however, a loss of surface Pd active sites due to the strong metal-support interaction and the formation of Pd-OH were observed, and finally reduced its thermal activity. Pd-OH, the inhibited site in thermal reaction, can be used as active site to participate in CH4 oxidation process, which was the key factor in maintaining high activity of the catalyst in electric field.