Kinetics of Methanol Oxidation over Mesoporous Perovskite Catalysts

Abstract

AbstractBy using the nanocasting method, a series of mixed metal perovskite oxides with general formula LaBO3 (B=Mn, Co, Fe) were synthesized with use of ordered mesoporous KIT‐6 silica as a hard template. Even though the resulting materials were not found to be the exact replica of the template, extremely high values of Brunauer–Emmett–Teller specific surface areas (110–155 m2 g−1) were obtained for the materials. The redox properties of nanocast mesoporous perovskites were determined by performing temperature‐programmed reduction and temperature‐programmed desorption of oxygen. Catalytic activity was monitored by using methanol oxidation as a model reaction over mesoporous LaMnO3, and the first kinetic model was developed for the same. Nanocast mesoporous LaMnO3 catalysts were found to show the highest conversion efficiency for methanol under steady‐state conditions as compared with both LaCoO3 and LaFeO3 nanocasts and with LaMnO3 samples prepared by using other methods. This result is clearly associated with the higher specific surface area of this nanocast perovskite. Furthermore, these materials were found to be stable under conditions prevailing in the reactor. Reaction rates obtained from the experimental conversions at various space velocities (19 500–78 200 h−1) for nanocast LaMnO3 were found to follow a rate equation that depends on the partial pressure of methanol. Using the rate constants obtained, the value of activation energy and pre‐exponential factor were determined from the Arrhenius plot. The calculated values of conversions from the rates modified with surface areas were found to agree with the experimental conversions, which in turn reflect the proportionality of rates to the specific surface area.