The promotion effects of Ba on manganese oxide for CH4 deep oxidation

A series of catalysts based on high specific surface area MnO2 precursor an d modified by various amount of Ba were prepared and applied in CH4 deep ox idation. The catalysts were characterized by means of N-2-BET, XRD, TG-DTA, H-2-TPR and CH4-TPR techniques. The catalytic evaluation results show that CH4 oxidation activity of the modified catalysts was enhanced, with the op timal Ba/Mn mol ratio being similar to0.1. Whereas, comparative study demon strates that CO oxidation activity of the modified catalysts was not improv ed. II was shown previously that the reactivity of the oxygen species in a catalyst is crucial for CO oxidation, but not critical for CH4 oxidation. I n this study, TPR results verify that the mobility and reactivity of the la ttice oxygen of Ba-modified catalysts is not improved, thus leading to no e nhancement of their CO oxidation activity. However, the addition of Ba into manganese oxides is supposed to improve the basicity of the lattice O2- of the prepared catalysts, which is favorable for the rupture of the first C- H bond in CH4, the rate-determining step of the reaction. It is thus conclu ded that the enhanced CH4 oxidation activity of the modified catalysts can be attributed to this modification effect of Ba.