Tuning the siting of aluminum in ZSM-11 zeolite and regulating its catalytic performance in the conversion of methanol to olefins
Tuning the siting of aluminum in ZSM-11 zeolite and regulating its catalytic performance in the conversion of methanol to olefins
复制标题
调整ZSM-11沸石中铝的位置并调节其在甲醇转化为烯烃中的催化性能
DOI：
10.1016/j.jcat.2019.07.028
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发表时间：
2019
影响因子：
7.3
通讯作者：
Wang Jianguo
中科院分区：
文献类型：
--
作者：
Wang Sen;Zhang Li;Li Shiying;Qin Zhangfeng;Shi Dezhi;He Shipei;Yuan Kai;Wang Pengfei;Zhao Tian-Sheng;Fan Subing;Dong Mei;Li Junfen;Fan Weibin;Wang Jianguo
酸性沸石在甲醇制烯烃（MTO）转化中的催化性能与铝（Al）在晶格位点的位置密切相关；然而，微调骨架Al的位置并有目的地调节沸石催化剂的性能仍然是一个巨大的挑战。本工作通过在合成凝胶中添加适当的碱金属离子来改变ZSM-11沸石中的Al位点，并研究Al位点对ZSM-11在MTO中的催化性能的影响。结果表明，合成凝胶中添加Na+和/或Li+可以提高ZSM-11交叉腔内Al的含量，而在无碱金属离子合成体系中，Si/Al比的增加导致交叉腔内Al的减少更为显着，直通道内Al的相对富集。 Al位点的变化对ZSM-11在MTO中的催化性能有显着影响，这可以通过双循环烃池（HCP）机制得到很好的解释。更多的Al原子位于直通道中可以增强烯烃循环，产生更多的丙烯和丁烯；相反，增加交叉腔中Al的含量可以促进芳烃基循环并促进乙烯和芳烃的形成。这项工作提供了一种有效的方法来微调Al在ZSM-11沸石晶格中的位置并可控地调节其在MTO中的催化性能；此外，这项工作所展示的见解也有助于更好地理解铝位点/酸位点分布与沸石催化剂性能之间的关系。
The catalytic performance of acid zeolite in the conversion of methanol to olefins (MTO) is closely related to the location of aluminum (Al) in the lattice sites; however, it is still a great challenge to finely tune the siting of framework Al and thereon purposefully regulate the performance of zeolite catalyst. In this work, adding proper alkali metal ions in the synthesis gel was used to alter the Al siting in ZSM-11 zeolite and the effect of Al siting on the catalytic performance of ZSM-11 in MTO was then investigated. The results indicate that the addition of Na+and/or Li+in the synthesis gel can elevate the fraction of Al sited in the intersection cavity of ZSM-11, whereas in the alkali metal ions free synthesis system, an increase in the Si/Al ratio leads to a more prominent decrease of Al sited in the intersection cavity and a relative enrichment of Al distributed in the straight channel. The variation of Al siting has a significant influence on the catalytic performance of ZSM-11 in MTO, which can be well explained by the dual-cycle hydrocarbons pool (HCP) mechanism. More Al atoms located in the straight channel can enhance the alkene-based cycle that produces more propene and butene; in contrast, an increase in the fraction of Al in the intersection cavity can then promote the aromatic-based cycle and facilitate the formation of ethene and aromatics. This work provides an efficient method to finely tune the siting of Al in ZSM-11 zeolite lattices and controllably regulate its catalytic performance in MTO; moreover, the insight shown in this work is also helpful for a better understanding on the relationship between the Al siting/acid sites distribution and the performance of a zeolite catalyst.