摘要
采用XPS ,XRD和TEM对含氧气氛下钙钛矿LaCoO3 硫化活化过程中不同阶段的催化剂进行了表征分析 .在硫化初期 ,经SO2 预中毒后 ,吸附氧种不存在 ,Co 2 p3 / 2 结合能发生明显的位移 ,La 3d的XPS双峰变得不明显 ,同时出现不稳态的S4+ 物种 ,表明催化剂LaCoO3 被SO2 的强吸附所覆盖 ;催化剂LaCoO3 仍为钙钛结构并没有新的物相产生 ,SO2 中毒仅在催化剂表面进行 .在进一步的硫化活化过程中 ,出现吸附氧物种 ,Co出现三种价态 ,分别对应于LaCoO3 ,Co3 O4和CoSO4,La 3d的XPS双峰变得特别明显 ,同时催化剂表面出现S2 -物种和S6+ 物种 .可以认为 ,在含氧气氛下硫化LaCoO3 的过程中 ,SO2 预中毒为进一步硫化提供硫物种 ,吸附氧物种保证硫化过程中钙钛矿结构不会被完全破坏 .
It was found in our previous study that the process of activation sulfurization of LaCoO 3 plays a necessary role in the catalytic reduction of SO 2 with CO to element S in the presence of oxygen. In order to explain the phenomenon, the process of activation sulfurization of LaCoO 3 in the presence of oxygen was studied by XPS, XRD and TEM methods. The valence variety on LaCoO 3 surface in various processes of activation sulfurization was investigated. When LaCoO 3 was pre poisoned by SO 2, the adsorbed oxygen on its surface was absence, the chemical shift of binding energy of Co 2 p 3/2 was more than 1.0 eV, the La 3 d double peak turned unobvious, and at the same time the S 4+ appeared on the surface, indicating that the perovskite was overlapped by the strongly adsorbed SO 2 species. The results of XRD and TEM showed that after poisoned by SO 2 no new phase appeared on the surface of perovskite LaCoO 3. However, after activation sulfurization the surface adsorbed oxygen reappeared, corresponding to LaCoO 3, Co 3O 4 and CoSO 4, Co had three valence states, La 3 d double peak got clarity, S 2- and S 6+ appeared on the surface of LaCoO 3. During the activation sulfurization of LaCoO 3 in the presence of oxygen, the SO 2 poisoning on perovskite supplied S 2-species to sulfurize the perovskite LaCoO 3, and the surface adsorption oxygen made perovskite structure stable.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2004年第1期19-22,共4页
基金
国家自然科学基金重大计划资助项目(90 2 10 0 2 5 )
教育部重点资助
天津大学基金项目
南开大学基金项目
关键词
钙钛矿
钴酸镧
硫化
氧
二氧化硫
perovskite, lanthanum cobaltate,sulfurization,oxygen, sulfur dioxide
