Syntheses of La₁₋xBaxMn₂Al₁₀O₁₉ Catalysts (x = 0, 0.05) in a Novel Microemulsion of Water/2-Propanol/1-Butanol and Their High Activities in Methane Combustion

In this work, a novel system of water/2-propanol/1-butanol (W/iP/nB) was developed to synthesize La 1- x Ba x Mn 2 Al 10 O 19 ( x = 0, 0.05) catalysts. These catalysts were also synthesized by the hydrolysis of the alkoxides in distilled water. The physicochemical properties of the catalysts were characterized by transmission electron microscopy, X-ray powder diffraction, and N 2 adsorption isotherm measurements. The effects of the reaction medium and drying method on the properties of the catalysts were investigated. The results showed that La 0.95 Ba 0.05 Mn 2 Al 10 O 19 catalyst synthesized in W/iP/nB had a higher activity in methane combustion ( T 10% = 425 °C; T 10% = the temperature at 10% methane conversion) than that prepared in distilled water ( T 10% = 515 °C). After the reaction was run at 700 °C for 100 h under the reaction conditions, La 0.95 Ba 0.05 Mn 2 Al 10 O 19 catalyst synthesized in W/iP/nB showed a higher stability than that prepared in distilled water. The LaMn 2 Al 10 O 19 synthesized by subcritical drying showed a higher activity ( T 10% = 440 °C) than that prepared by conventional oven drying. La 0.95 Ba 0.05 Mn 2 Al 10 O 19 catalyst showed a higher activity than LaMn 2 Al 10 O 19, which was ascribed to the partial substitution of Ba for La. Furthermore, the structure property of water in W/iP/nB was investigated by means of FT-IR, NMR, electric conductivity, and laser light scattering granulometry. It was proposed that a novel reverse microemulsion of W/iP/nB is formed by distilled water, 2-propanol, and 1-butanol. The hydrolysis of the alkoxides in W/iP/nB was controlled efficiently, just as in a conventional reverse microemulsion.