Ba、Mn对Al2O3热稳定性和甲烷催化燃烧活性的影响

采用溶胶-凝胶法制备BaO?6Al2O3系列催化剂.考察了Ba、Mn的引入对Al2O3的热稳定性及甲烷催化燃烧性能的影响.结果表明, Ba在高温下与Al2O3首先生成BaAl2O4，然后进一步与Al2O3反应生成具有β-Al2O3结构的BaAl12O19六铝酸盐，抑制了Al2O3进一步的烧结，提高了催化剂的热稳定性. Mn的引入也能够促进六铝酸盐的生成并提高催化剂的甲烷燃烧活性.采用超临界干燥法可抑制干燥过程中因毛细收缩引起的比表面积降低.所制备的BaMnAl11O19催化剂经1200 ℃焙烧4 h后，比表面积为35.1 m2?g－1，在空速40000 h－1条件下，10％甲烷转化温度(T10％)为500 ℃，催化活性明显高于常规干燥法制备的相应催化剂.

Effect of Introduction of Ba, Mn on Thermal Stability andCatalytic Activity to Methane Combustion of Al2O3

A sol-gel method was employed to prepare Mn-substituted barium hexaaluminate catalysts for methane combustion. Supercritical drying (SCD) and conventional oven drying (CD) methods were used to extract the water in the hydrogel. The effects of drying methods, as well as the incorporation of Ba, Mn, on properties of the catalysts were investigated by means of N2 adsorption, TG－DTA and X-ray diffraction. The supercritical drying method could maintain a higher specific surface area of the samples and suppress the transformation into α-Al2O3 at elevated temperatures. The introduction of Mn oxides could promote the transformation into hex aluminates during calcinations. BaMnAl11O19 catalyst dried by SCD method has a specific surface area of 35.1 m2?g－1 and an activity with T10％ (temperature for 10％ methane conversion) of 500 ℃ under the condition of 0.1 MPa and 40000 h－1 GHSV.