Adjustment of the Al siting in MCM-22 zeolite and its effect on alkylation performance of ethylene with benzene

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 T-2 sites 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.