Phase transformation and catalytic activity of hexaaluminates upon high temperature pretreatment

Both hexaaluminates powder have been synthesized with the co-precipitation method. High temperature pretreatment catalysts are characterized by X-ray diffraction (XRD) and BET method. The catalytic activity in methane combustion also is reported.The hexaaluminate structure is formed and retains the surface area of 20–30 m2/g upon calcinations at 1200 °C for both SLMA (Sr0.8La0.2MnAl11O19) and SBLMA (Sr0.3Ba0.5La0.2MnAl11O19). The surface area of SBLMA is larger than that of SLMA upon temperature higher than 1200 °C illustrating the superior thermal stability of the barium hexaaluminate. Partial replacement of Sr2+ ion with Ba2+ ion improves the thermal stability of the Ba-containing system. Also, the high surface area for SBLMA can be understood from the microstructural change of pore size. The SBLMA possesses larger pore than the SLMA to resist sintering under high temperature aged and shows a good activity in methane combustion.