摘要
通过物理混合法制得ZnO/HZSM-5分子筛催化剂,采用XRD、BET、NH3-TPD和Py-IR等方法对分子筛催化剂进行表征,考察了引入Zn的含量对ZnO/HZSM-5上甲醇芳构化性能的影响.结果表明,Zn的引入减少了HZSM-5表面的B酸,增加了L酸;Zn的引入量存在一个最佳值:随着Zn含量的增加,ZnO/HZSM-5分子筛上芳烃选择性先增加后降低,Zn含量为5%时甲醇芳构化性能最优.ZnO/HZSM-5分子筛催化剂上的B酸和Zn-L酸中心形成一种协同催化作用,其中Zn物种起着脱氢作用,B酸中心起裂解和氢转移作用,只有B酸和Zn-L酸这两种作用协调发挥,才能得到较好的芳构化效果.
ZnO/HZSM-5 zeolites were prepared by physical mixing with ZnO and characterized by means of XRD, BET, NH3-TPD and Py-IR. The influence of Zn content on the performance of ZnO/HZSM-5 zeolites in methanol-to-aromatics（MTA） was investigated in a fixed-bed reactor. The results indicated that Lewis acid sites of zinc species（ZnOH＋） were formed by introducing zinc into HZSM-5, at the expense of the silanol hydroxyl and proton acid sites. The catalytic performance of Zn/ZSM-5 in MTA was significantly influenced by the content of introducing zinc. The catalytic performance showed the selectivity of aromatics firstly increased and then decreased slowly with increasing Zn content, and the optimal Zn content was about 5%. The introduction of zinc could enhance the dehydrogenation of alkanes and alkenes to form aromatics and B acid sites catalysed hydride transfer to lead to the formation of alkanes. The contact synergy between B acid sites and Zn-L acid sites improved the aromatization of methanol in ZnO/HZSM-5 zeolites.
出处
《晋中学院学报》
2016年第3期42-46,77,共6页
Journal of Jinzhong University
