La1-xSrxMnAl11O19-δ催化剂的甲烷燃烧性能研究

摘要

A series of La,Sr and Mn modified lanthanum hexaaluminates, La1-xSrx MnAl11O19-δ(x＝0. 2,0. 4,0. 5,0. 6,0. 8) as new catalysts for combustion of methane, were prepared by reverse microemulsion-co-precipitation method and calcined at high temperature. The structure and properties of these samples were characterized by XRD,BET and methane catalytic combustion. Effect of La/Sr molar ratio on the structure and methane combustion activity of La1-xSrxMnAl11O19-δ catalysts is investigated. The results show that the catalyst with good crystallinity is obtained after calcination under oxygen at 1200℃. At the same time all catalysts have the high catalytic activity. The introduction of different content of La/Sr ion show great effect on the properties of catalysts. The La0.5 Sr0.5 MnAl11O19-δ catalyst has higher activity with T10％ as 502℃ and T90％ as 683℃. Kinetic analysis indicates that La1-xSrxMnAl11O19-δ catalysts for methane catalytic combustion are first order reactions, and reaction rate is controlled by intrinsic properties of catalyst surfaces.%采用反相微乳液-共沉淀法制备了一系列以La、Sr作为镜面阳离子、锰离子作为活性组分的六铝酸盐催化剂La1-xSrxMnAl11O19-δ(x=0.2、0.4、0.5、0.6、0.8).利用X射线衍射、比表面积分析等分析方法及甲烷燃烧对催化剂的结构和性质进行了考察,主要考察了不同含量的La和Sr离子的掺杂量对催化剂结构及对甲烷催化燃烧活性的影响.结果表明,La和Sr同时作为镜面阳离子,不但可以形成完整的六铝酸盐,而且所制备的催化剂具有较高的催化活性.不同含量的La和Sr离子掺杂对于催化剂的特性有较大影响.当x=0.5时,所制备的催化剂La0.5-Sr0.5MnAl11O19-δ具有较高的催化活性,起燃温度T10%=502℃,至683℃甲烷完全转化.催化剂在低转化率下的宏观动力学实验结果表明,甲烷催化燃烧在La1-xSrxMnAl11O9-δ催化剂上为一级动力学反应,反应速率受催化剂固有性质控制.