摘要
考察了用不同来源Ｌｉ（ＬｉＮＯ３和ＬｉＳＯ４）制备的催化剂催化的甲烷氧化偶联（ＯＣＭ）反应的特点，探讨了以ＬｉＮＯ３为锂源制备的催化剂的高温反应失活机理。ＸＲＤ、ＩＲ、ＸＰＳ和ＢＥＴ等方法的研究结果表明，以ＬｉＮＯ３为锂源制备的催化剂具有反应活性高、空速大的特点，而以Ｌｉ２ＳＯ４为锂源制备的催化剂具有Ｃ２选择性高、活性低、空速小等特点。由ＬｉＮＯ３制得的催化剂的失活原因是：在较高的反应温度下由于表面Ｌｉ的流失，使体相晶格中的Ｌｉ向表相扩散进而导致含Ｌｉ活性相ＬａＴｉ１－ｙＬｉｙＯ３－λ的分解（或部分分解），从而减少了体相和表相中氧空位的数量，导致催化剂的活性降低。设计了ＮＨ：（ＳＯ４）２浸渍法来固定表面锂。
The mixed lithium-lanthnum-titanium oxide catalysts have been prepared fromdifferent Li-containing compounds(LiNO3, Li2SO4)for oxidative coupling of methane, TheXRD, IR, XPS, and BET resuIts showed that LiLa0.5 Ti0.5 O2+λ catalysts prepared fromLiNO3 pos:essed a higher activity and space velocity, while those from LizSO4 possessed amuch higher C2 selectivity, but lower activity and space velocity. The deactivation of LILa 0.5Ti0. 5O2+λ catalysts prepared from LiNO3 is mainly caused by the loss of surface lithium. Inthe course of the coupling reaction the bulk lithium diffuses to the surface, leading to the de-composition of active phase containing lithium and lowering the amount of oxygen vacancies. In order to combine the advantages of both catalysts prepared from LiNO3 and Li2SO4 and tofix the surface lithium a novel preparation method with impregnation in(NH4)2SO4 is pro-posed.
出处
《应用化学》
CAS
CSCD
北大核心
1994年第6期32-36,共5页
Chinese Journal of Applied Chemistry
基金
国家自然科学基金资助项目
关键词
甲烷
氧化偶联反应
催化剂
锂镧钛系氧化物
methane, oxidative coupling, lithium-lanthanum-titanium mixed oxide, deactiva-tion
