摘要
利用ＣＯ_２－ＴＰＤ法考察了Ｌａ－Ｍｅ－Ｏ（Ｍｅ＝Ｍｇ，Ｃａ，Ｓｒ，Ｂａ）系催化剂的表面碱性，并用Ｏ_２－ＴＰＤ、ＣＨ_４－ＴＰＤ法对该体系的表面活性氧种进行了表征，并与催化性能相关联。结果表明，Ｌａ－Ｂａ－Ｏ催化剂由于表面强碱性中心数目多，产生活性氧种的数目也多，有利于甲烷的活化，因而具有最高的甲烷转化率和Ｃ_２烃选择性。脉冲反应表明，在无气相氧存在下，表面晶格氧参与了氧化偶联，而且是选择氧化的活性氧种。
CO2-TPD was used to study the surface basicity of La-Me-O mixed oxides and O2TPD, CH4-TPD were employed to study the surface active oxygen species. Comparing the CO2-TPD with O2-TPD, we can see that the basicity of catalyst is in parallel with the catalystic activity. The stronger basicity is more profitable for the catalyst to adsorb oxygen to form active oxygen species and to activate CH4 by breaking a C-H bond. By comparing the catalytic activity. the results showed that La-Ba-O(La/Ba=7/3) catalyst had the strongest basicity, and it gave the highest CH4 conversion and C2 selectivity. The results from the pulse reaction showed that the lattice oxygen participated in the OCM reaction without gas oxygen, and it was the selective oxygen species.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
1995年第3期432-436,共5页
Chemical Journal of Chinese Universities
基金
国家自然科学基金
关键词
甲烷
氧化偶联
催化剂
表面氧种
镧
碱土金属
Methane, Oxidation coupling, La-Me-O catalyst, Surface oxygen species
