Catalytic activity of rare earth oxides in flameless methane combustion

The following rare earth oxides, which were prepared by the precipitation of hydroxides, were studied as catalysts for the reaction of complete methane oxidation: CeO2, a hydrated phase of La2O3, Pr6O11, Tb4O7, and Gd2O3. The catalytic activities of the oxides were compared in terms of first-order reaction rate constants per unit surface area of the catalyst. With consideration for data on the reduction of CeO2, Pr6O11, and Tb4O7, the previously proposed redox reaction mechanism on transition metal oxides was supported. The high activity of hydrated La2O3 was found, and it was hypothesized that, in this case, the process occurred by the mechanism of oxidative methane condensation followed by the rapid oxidation of the resulting intermediate products.