La_(1-x)Ca_xMnO_(3+δ)钙钛矿催化剂制备及其甲烷催化燃烧性能研究  

La_(1-x)Ca_xMnO_(3+δ) Perovskite Catalysts Preparation and Their Catalytic Performance for Methane Combustion

作　　者：晏耀宗 郭谨玮 陈亚中[1] 王琪[1] 崔鹏[1] 

机构地区：[1]合肥工业大学化学与化工学院,可控化学与材料化工安徽省重点实验室,安徽合肥230009

出　　处：《分子催化》2015年第1期82-89,共8页Journal of Molecular Catalysis(China)

基　　金：国家自然科学基金项目(21106027)

摘　　要：采用柠檬酸配合法制备了系列La1-xCaxMn O3+δ(x=0,0.03,0.05,0.07,0.1,0.15,0.2)催化剂,采用低温N2物理吸附,氢程序升温还原(H2-TPR)、氧程序升温脱附(O2-TPD),X-射线衍射(XRD)和X-射线光电子能谱(XPS)研究了其物理化学性质,并考察了甲烷催化燃烧活性.结果表明,当Ca摩尔掺杂量为0.1时,催化活性最好.XRD和BET表征结果表明Ca可以进入钙钛矿结构中,Ca掺杂对催化剂的比表面积无显著影响.H2-TPR和XPS表征结果表明Ca掺杂增加了Mn4+的含量.O2-TPD表征结果表明适量Ca掺杂可以降低晶格氧脱出温度.Mn4+具有较强氧化性,因此提高了催化活性,但随着Ca掺杂量增加,催化剂表面吸附氧含量有所减少,表明气相中氧难以迅速补充消耗的晶格氧,Ca掺杂量继续增加又会使催化活性有所下降.依据反应机理,Ca掺杂一方面可以促进Mn4+含量增加,有利于催化活性;另一方面会使催化剂表面吸附氧含量有所下降,降低了催化活性.A series of perovskite-type La1- xCaxMn O3 + δ( x = 0、0. 03、0. 05、0. 07、0. 1、0. 15、0. 2) catalysts were prepared by citrate complexing method. The catalysts were characterized by low temperature N2 absorption,H2-temperature programmed reduction( H2-TPR),O2-temperature programmed desorption( O2-TPD),X-ray powder diffraction( XRD) and X-ray photoelectron spectroscopy( XPS),as well as catalytic performance measurement for methane combustion. The results showed that the catalyst gave best catalytic activity for when molar doping amount of Ca was 0. 1. The result of XRD and BET showed that Ca can be doped into perovskite structure without significant effect on specific surface area. H2-TPR and XPS showed that the Ca doping increased the content of Mn4 +in the catalyst and thus could improve catalytic activity for methane combustion. However,with continuous increase of Ca doping,the content of adsorbed surface oxygen species decreased. Therefore,the increase of Ca doping decreased catalytic activity. Thus,based upon the reaction mechanism for methane combustion over perovskite catalysts,on one hand,calcium doping increased Mn4 +content and improved activity; on the other hand,high content doping of calcium decreased the content of adsorbed oxygen species,which resulted in negative impact on catalytic activity.

关 键 词：钙钛矿 La1-xCaxMnO3+δ Ca掺杂 甲烷催化燃烧 

分 类 号：O643.36[理学—物理化学] O623.11[理学—化学]