Low temperature complete combustion of methane over cobalt chromium oxides catalysts

摘要

Cobalt chromium oxides with different Co/Cr ratios were prepared via co-precipitation method and their catalytic performances on methane combustion were evaluated from 300 ℃ to 650 ℃ at a space velocity of 36,000 h~(-1). A significant improvement of activity was observed over the Co1Cr2 catalyst with a Co/Cr molar ratio of 1:2, and the methane conversion reached 90% at 464 ℃. The Co1 Cr2 catalyst also showed excellent resistance to water vapor poisoning. In addition, the catalytic activity was inhibited in the presence of water vapor at the entire temperature range, while catalytic activity decreased only at low temperature in the presence of sulfur dioxide. Based on BET, TPR, XRD and XPS results, the superior performance of ColCr2 would origin from the higher valence and coordination number of the metal ions. Both Cr~(3+) and Cr~(6+) species were observed on the surface of cobalt chromites, and Cr~(6+) causes disorders in the spinel structure of cobalt chromites, which would enhance the adsorption of chemisorbed oxygen species and thus improve the catalytic performance, especially at low temperature.