硬模板法制备中孔LaMnO3+δ钙钛矿及其甲烷燃烧催化性能

摘要

Mesoporous LaMnO3+δ perovskite was synthesized by filling the La3+,Mn3+ citrate complex precursor into the pores of mesoporours material SBA-15,which was used as hard-template,followed by calcination and template removal.The sample was characterized by low temperature N2 absorption,oxygen temperature programmed desorption (O2-TPD),XRD,and XPS,and the catalytic performances for methane combustion were measured.Compared with the perovskite prepared by sol-gel method,the sample by hard-template method showed a higher surface area (45.2 m2/g) and typical mesoporous structure.The light-off temperature (T10) and the half-conversion (T50) were 318 ℃ and 480 ℃,while the corresponding temperatures for LaMnO3+δ prepared by sol-gel were 380 ℃ and 532 ℃,respectively.The O2-TPD and XPS characterization indicated that the presence of high valence manganese ions resulted in high non-stoichiometric oxygen in LaMnO3+δ prepared by hard template method,which were beneficial to high content of surface oxygen and high activity.%利用三维有序结构SBA-15分子筛为硬模板剂,在其孔道内填充La3+、Mn3+柠檬酸络合物,经过焙烧并去除模板剂得到中孔结构的LaMnO3+δ钙钛矿.采用低温氮气物理吸附、氧气-程序升温脱附(O2-TPD)、X射线衍射(XRD)、X射线光电子能谱(XPS)对LaMnO3+δ进行表征,考察了LaMnO3+δ甲烷燃烧催化性能,并与溶胶-凝胶法制备的LaMnO3+δ进行比较.结果表明,硬模板法制备的LaMnO3+δ具有更高的比表面积(45.2 m2/g),其甲烷起燃温度(T10)和半转化温度(T50)分别为318℃和480℃,而溶胶-凝胶法制备的LaMnO3+δ的T10和T50分别为380℃和532℃.O2-TPD和XPS表征结果表明,硬模板法制备的LaMnO3+δ存在更多的Mn4+和表面吸附氧物种,其非化学计量比氧更高,使得催化剂具有更好的活性.