摘要
以六亚甲基亚胺为模板剂,乙醇为有机辅助剂,采用动态水热法合成了一系列 MCM-22分子筛,利用 X 射线衍射(XRD)、氨程序升温脱附(NH_3-TPD)、傅里叶变换红外光谱(FT-IR)和电子扫描显微镜(SEM)等表征手段考察了乙醇辅助剂对 MCM-22分子筛的结构及酸性的影响。结果表明,添加适量的乙醇可以有效调控分子筛结构性能和结晶度,分子筛的强酸位的强度适度增强,弱酸位的强度减弱,总酸量和 B 酸中心数增大,而L酸中心数减少,且晶粒尺寸减小,比表面积增加,但过量的乙醇会导致ZSM-5分子筛的生成。以苯和丙烯烷基化合成异丙苯为模型反应,评价对所制备的分子筛催化性能,发现添加合适的乙醇得到的 MCM-22分子筛具有更高的催化活性和选择性。
A series of MCM-22 zeolite samples were synthesized by dynamic hydrothermal crystallization method, taking alcohol as organic auxiliary chemical and hexamethyleneimine as template. The effects of alcohol on the textural property and acidity of MCM-22 zeolite catalyst were investigated based on the characterization of X-ray diffraction （XRD）, ammonia temperatureprogramme desorption （NH3-TPD）, fourier transform infrared （FT-IR） and scanning electron microscopy （SEM）. The results showed that the proper amount of alcohol could effectively adjust the textural property and acidity of MCM-22 zeolite. The crystallinity of MCM-22 synthesized with alcohol was slightly higher than those synthesized without alcohol. With the increasing of molar ratio of alcohol to SiO2, the strength of weak acid decreased gradually while strong acid increased, total acid and Bronsted acid increased while Lewis acid decreased. And the lamellas of high crystallization could be seen from the SEM images and their sizes were smaller than those synthesized without alcohol. However, excessive alcohol introducing would lead to form ZSM-5 zeolite. It could be predicted that such adjustment of textural property would definitely influence the catalytic performance of MCM-22 zeolite. Taking the alkylation of benzene with propylene to form cumene as a model reaction, the catalytic performance of MCM-22 zeolite synthesized was experimentally evaluated. The results showed that when the molar ratio of alcohol to SiO2 was 0.5 -- 1.0, significant increasing of initial activity of MCM-22 and cumene selectivity could be obtained.
出处
《化学反应工程与工艺》
EI
CAS
CSCD
北大核心
2008年第3期234-239,共6页
Chemical Reaction Engineering and Technology
基金
国家自然科学基金(20576012)
中国石油化工股份有限公司资助(X505016)
