Synthesis and characterization of perovskites LaMnO3 and γ-alumina as catalysts for methane combustion reaction

ABSTRACT Perovskite-type Catalysts, LaMnO3, were synthesized by citrate and coprecipitation methods. Some of these materials was supported on γ-alumina or impregnated with Pd and/or Sn by wet impregnation, in 1% mass concentration. The catalysts were evaluated in the reaction of methane total combustion, and its activity measured by temperature programmed surface reaction (TPSR). The samples were heated to 800°C at a rate of 10°C / min under a flow rate of 50 mL / min of a mixture containing CH4, O2 and N2 at molar concentrations of 4%, 1% and 95 %, and He (50mL / min).As a standard of comparison, was synthesized also a reference sample PdO /γ-Al2O3. The samples were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD) and had its surface area measured by BET. The samples containing palladium were further analyzed in temperature programmed oxidation reaction (TPO) in order to determine the stability of PdO phases present in these materials. All samples were active to the methane combustion reaction, and the materials from citrate route higher than the coprecipitated material. The addition of palladium, even in low concentrations, was positive for catalytic activity, unlike tin, that resulted in a reduction in the final methane conversion for these materials.