Catalytic combustion of methane over cerium-doped cobalt chromite catalysts

Cerium modified cobalt chromite catalysts were prepared via co-precipitation method and investigated for the catalytic combustion of methane. Characterization studies by X-ray diffraction (XRD), Raman spectroscopy, BET, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction mass spectroscopy (CH4 TPR-MS) and temperature-programmed desorption of oxygen (O2-TPD) were carried out. An improvement of the catalytic activity was observed over cerium-substituted cobalt chromite catalysts with appropriate cerium substitution degrees. The best result has been attained with 5% cerium modified catalyst, for which 5% chromium in CoCr2O4 was substituted by cerium, and the catalytic activity reached 90% of methane conversion at 465 °C. The characterization results indicated that cerium doping could deform the spinel structure and cause redistribution of metal ions with different oxidation states; consequently, they would increase crystal defects and oxygen vacancy concentration, which facilitate oxygen mobility and thus increase the catalytic performance of cerium modified cobalt chromite catalysts.