低浓度甲烷催化燃烧La0.8Ca0.2FeO3/MgO蜂窝催化剂

La_(0.8)Ca_(0.2)FeO_3/MgO honeycombs for catalytic lean burn of methane

开发了以MgO为第二载体的La0.8Ca0.2FeO3钙钛矿整体催化剂,用于低浓度甲烷(φ(CH4)=0.5%)的催化燃烧。首先用共沉淀法制备了不同比例Ca掺杂的钙钛矿粉体,然后在程序升温反应-质谱仪中对催化剂进行筛选,并用XRD、TPR、BET对粉末进行表征。在此基础上,选择La0.8Ca0.2FeO3并确定800℃为焙烧温度,采用浆料涂覆法将粉末La0.8Ca0.2FeO3涂覆在α-Al2O3蜂窝陶瓷基体上制成整体催化剂,在空速40 000h-1下进行催化燃烧反应试验。考察了引入MgO作为第二载体的效果以及在MgO中引入少量Al2O3的影响,对MgO的焙烧温度、负载量进行了优化。结果表明,MgO对活性组分有隔离保护和高温下的分散稳定作用,而MgO与La0.8Ca0.2FeO3之间的相互作用是导致La0.8Ca0.2FeO3整体催化剂的活性比粉末催化剂高了1倍左右的主要原因。

La0.8Ca0.2FeO3/MgO perovskite monolithic honeycomb catalysts were developed for catalytic lean burn of methane（0.5% by volume in air）.Firstly,the calcium doped La1-xCaxFeO3（x =0,0.1,0.2,0.3,0.4） powder catalysts were prepared by coprecipitation,then screened in the Temperature-Programmed Reactions-Mass Chromatograph（TPRs-MS） reactor,and characterized by XRD,TPR and BET.Based on above studies,the La0.8Ca0.2FeO3 calcined at 800℃ was picked out for preparation of the honeycomb catalysts by washcoating La0.8Ca0.2FeO3 on an α-Al2O3 ceramic honeycomb substrate and methane combustion on the honeycomb catalysts was tested under GHSV of 40 000h-1.The effects of introducing MgO as the second support and adding a small amount of Al2O3 into MgO were investigated,and MgO calcination temperature and loading amount were optimized.The results indicated that MgO performed the functions of isolating the active catalyst from the Al2O3 substrate as well as stabilizing and dispersing the active catalyst at high temperature,and the interaction of MgO with the active catalyst was the key factor that the reaction activity of the La0.8Ca0.2FeO3/MgO perovskite monolithic honeycomb catalyst was twice as high as that of the La0.8Ca0.2FeO3 powder.