Catalytic combustion of methane over La2TM_(0.3)Zr_(1.7)O_(7-δ) (TM = Mn, Fe, and Co) pyrochlore oxides

摘要

La2Zr2O7 and La2TM_(0.3)Zr_(1.7)O_(7-δ) (TM = Fe, Mn, and Co) pyrochlores were investigated as catalysts for methane combustion at moderate-high temperatures. They were prepared by the coprecipitation method and characterized by XRD, DSC, H2-TPR, IR, and N2 adsorption/desorption techniques. The introduction of transition metals strongly influences the Zr-0 bond strength, the temperature of pyrochlore phase formation, the redox properties, and crystallite size of pyrochlores. Among the catalysts tested, La2Fe_(0.3)Zr_(1.7)O_(7-δ) gives the highest catalytic activity. The catalytic activities of La2TM_(0.3)Zr_(1.7)O_(7-δ) pyrochlore oxides for methane combustion were mainly dependent on the textural properties (BET area, crystallite size).