Effect of Mn doping to substitute Al on the structure and methane combustion activity of hexaaluminates catalysts K₂MnxAl_12-xO_19-δ

A series of K and Mn modified lanthanum hexaaluminates, K₂Mn_xAl_12-xO_19-δ(x=0， 1.0， 1.5， 2.0， 2.5， 3.0) as new catalysts for combustion of methane, were prepared by means of reverse microemulsionhydrolysis of metal alkoxide and high temperature calcination. The structure and properties of the catalysts were characterized by XRD, DTA-TG, TPR and methane catalytic combustion reaction. Effect of Mn doping to substitute Al on the structure and methane combustion activity of K₂Mn_xAl_12-xO_19-δ  catalysts was investigated. The results showed that the catalyst with good crystallinity was obtained after calcination in oxygen at 1200℃. At the same time all catalysts have high catalytic activity. The introduction of different content of Mn ion show great effect on the properties of catalysts. The K₂MnAl₁₁O_19-δ catalyst has higher activity with T10% at 458℃ and T90% at 676℃. Increased of Mn ions in precursor resulted in the formation of perovskite phase in the samples.