氧化镧催化剂上甲烷氧化偶联—不同制备方法的比较

本文研究了５种不同制法的Ｌａ＿２Ｏ＿３对甲烷氧化偶联的催化性能，其Ｃ＿２选择性和Ｃ＿２收率的相对顺序为：Ｌａ＿２Ｏ＿３（１）＞Ｌａ＿２Ｏ＿３（２）＞Ｌａ＿２Ｏ＿３（４）＞Ｌａ＿２Ｏ＿３（５）＞Ｌａ＿２Ｏ＿３（３）。并运用ＸＲＵ、ＸＰＳ、ＣＯ＿２－ＴＰＤ、ＮＨ＿３－ＴＰＤ和ＩＰＡ转化反应等技术分别对催化剂的体相结构和表面性质，表面酸碱性进行了测定。结果表明，由于制备方法的不同，导致了Ｌａ＿２Ｏ＿３晶体表面结构的差异，这是影响催化性能的主要原因。同时还发现，催化剂的活性和Ｃ＿２选择性与表面酸碱性存在着相依性，Ｌａ＿２Ｏ＿３表面的总碱位数与总酸位数的比值，与其催化性能有较好的直接对应关系。

OXIDATIVE COUPLING OF METHANE OVER La_2O_3 CATALYSTS A COMPARISON OF La_2O_3 CATALYSTS FROM DIFFERENT PREPARATION METHODS

The performance of La2O3 catalysts prepared by five different methods for oxidative coupling of methane was studied.The C2 selectivity and yield obtained on the catalysts are in the order of: La2O3(1)>La2O3(2)>La2O3(4)>La2O3(5)>La2O3(3). The bulk -phase and surface structure of the catalysts were determined by XRD and XPS respectively. The surface basicity and acidity were measured by TPD of CO2,NH3-TPD and IPA conversion reaction.Study results showed that the difference in lattice surface properties among five La2O3 catalysts, which influenced the performance of the catalysts, were caused by their prepared methods.The catalyst activity and selectivity depend on both the surface acidity and basicity.The correlation between the ratio of total basic sites to acidic sites and the C2 selectivity was observed.