Alkali-treatment of template-containing MCM-22 zeolite and its application in alkylation and transalkylation reactions

摘要

The effects of alkali-treatment on the compositions, acidities, texture properties and pore structures of template-containing MCM-22 zeolite were studied by Py-IR, N2 adsorption-desorption, o-xylene adsorption, XRD and ~(29)Si NMR. When template-containing MCM-22 zeolite was alkali-treated, desilication mainly occurred in the Al-poor regions, which broke the crystal sheets into smaller ones. The alkali-treatment process under the moderate conditions had little influence on the microporous properties and crystal structures of MCM-22 zeolite, but improved the diffusion conditions for aromatics mainly by reducing the crystal size. With the preserved framework Al species, the alkali-treated template-containing MCM-22 samples had higher ratio of Bronsted to Lewis acid sites, and exhibited improved catalytic performances in alkylation and transalkylation processes.