Adjustment of the Al siting in MCM-22 zeolite and its effect on alkylation performance of ethylene with benzene
Adjustment of the Al siting in MCM-22 zeolite and its effect on alkylation performance of ethylene with benzene
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DOI：
10.1016/j.cattod.2018.02.040
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发表时间：
2018-10
期刊：
影响因子：
5.3
通讯作者：
Yanan Wang;Yang Gao;Sujuan Xie;Shenglin Liu;Fucun Chen;Wenjie Xin;Xiangxue Zhu;Xiujie Li;Nanzhe Jiang;Longya Xu
中科院分区：
文献类型：
--
作者：
Yanan Wang;Yang Gao;Sujuan Xie;Shenglin Liu;Fucun Chen;Wenjie Xin;Xiangxue Zhu;Xiujie Li;Nanzhe Jiang;Longya Xu
由于苯与乙烯的液相烷基化反应主要发生在MCM-22分子筛表面口袋和超笼中的酸性中心，因此，在合成过程中调节Al的位置可能是提高MCM-22分子筛烷基化性能的重要途径。在水热合成MCM-22的过程中，以哌啶为结构导向剂，通过引入阴离子成功地调节了Al的位置。考察了合成前体中添加阴离子对MCM-22分子筛物化性能，特别是Al的位置和烷基化性能的影响。当Cl-、PO 43-或SO 42-存在于合成凝胶中时，产物的形貌趋向于不规则的层状结构。虽然H-MCM-22-PO 43-和H-MCM-22-SO 42-的酸中心浓度低于H-MCM-22，但它们的乙烯转化率明显高于H-MCM-22。这可能是由于在合成凝胶中PO 43-或SO 42-的存在，更多的Al物种被定向到位于口袋或超笼中的T2位点。这种新的合成方法为改性MCM-22乃至其它分子筛的性能提供了一种新的途径。
It may be an important route to improve the alkylation performance of MCM-22 zeolite by regulating the Al siting during the synthesis, as the liquid alkylation of benzene with ethylene mainly occur on the acid sites in the surface pockets and supercages of MCM-22. Here, the Al siting has been successfully adjusted by introducing additional anion in the hydrothermal synthesis of MCM-22 using piperidine as the structure directing agent. The effect of the additional anion in the synthesis precursor on the physiochemical property, especially the Al siting, and alkylation performance of MCM-22 zeolite was investigated. The morphology of products tends to be irregular lamellar structure when Cl−, PO43−, or SO42−are present in the synthesis gel. Although H-MCM-22-PO43−and H-MCM-22-SO42−show less acid site concentration than H-MCM-22, they exhibit obviously higher conversion of ethylene than H-MCM-22. This can be attributed to that more Al species are oriented to T2sites located in the pockets or supercages by virtue of the presence of PO43−or SO42−in the synthesis gel. The novel synthesis strategy may provide an alternative way to modify the performances of MCM-22 and even other zeolites.