CH4 deep oxidation on Ag promoted manganese oxide catalysts

Manganese oxide modified by various amounts of Ag was prepared and used for CH4 deep oxidation. The most active catalysts are those with a Ag/Mn mol r atio around 0.10. In these samples, XRD and TG-DTA showed the coexistence o f alpha -Mn2O3 and Ag2Mn8O16. In the lattice of Ag2Mn8O16, the electron tra nsfer between Mn3+ and Mn4+, the possible redox couple under reaction condi tions, becomes easier since it can happen without changing the lattice stru cture. alpha -Mn2O3 possibly functions as Mn3+ provider since in Ag2Mn8O16, the Mn3+/Mn4+ atomic ratio is 2/6. Additional Mn3+ could be helpful for ef fective electron transfer between Mn3+ and Mn4+. Moreover, CH4-TPR demonstr ated the formation of bigger amounts of more active oxygen species in Ag-Mn binary catalysts. Indeed, these factors are believed to be the main causes leading to the enhanced CH4 oxidation activity of Ag-Mn binary oxide catal ysts.