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

• Alkali-treated template-containing MCM-22 zeolites are studied.
• Alkali-treated template-containing MCM-22 has smaller crystal size.
• Diffusion conditions are improved in the smaller crystals.
• Ratio between different acid sites is changed.
• The alkali-treated samples show higher catalytic activity.

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 29Si 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 Brönsted to Lewis acid sites, and exhibited improved catalytic performances in alkylation and transalkylation processes.

Be different from the alkali-treated template-free (MCM-22-C) MCM-22, the framework of the template-containing (MCM-22-P) MCM-22 zeolites will experience a different evolution in NaOH solutions.Figure optionsDownload high-quality image (211 K)Download as PowerPoint slide