Preparation of Mn substituted La-hexaaluminate catalysts by using supercritical drying

LaMnxAl12−xO19 catalysts were prepared from NH4OH and metal nitrates solutions. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods on properties of the catalysts were investigated by means of TEM, N2-adsorption, thermogravimetry (TG)–differential thermal analysis (DTA) and X-ray diffraction. SCD method is beneficial to maintain high surface area and improving catalytic activity for methane combustion of the catalyst. The specific surface area and pore volume of LaMn1Al11O19 catalyst prepared by SCD method are 28 m2/g and 0.23 cm3/g, respectively, and the ignition of methane could be carried out at 450 °C. However, those of the CD catalyst prepared from the same precursor are 15 m2/g, 0.11 cm3/g and 530 °C, respectively. Suitable Mn content (0≤x≤2) could promote the formation of LaMnAl11O19 hexaaluminate, while further addition of Mn (2