Catalytic role of different pore systems in MCM-49 zeolite for liquid alkylation of benzene with ethylene

The properties of three types of pore systems in MCM-49 zeolite have been investigated by precoking to block the supercages and poisoning the surface pockets. Most Lewis acid sites (ca. 73%) are located within the supercages, while 38% of Brönsted acid sites are located in the surface pockets, 28% in the sinusoidal pores and only 34% in the supercages, respectively. Alkylation of benzene with ethylene mainly occurs in the surface pockets, and the contribution from the sinusoidal pores is limited. The generation of heavy aromatics in supercages results in the deactivation of MCM-49 at the early reaction stage. A moderate alkali-treatment process has been demonstrated to enlarge the opening of supercages without affecting the sinusoidal pores, resulting in improved diffusion of big molecules and hence better catalytic performance for liquid alkylation of benzene with ethylene.

Graphical abstractSurface pockets of MCM-49 are the main place for the liquid alkylation of benzene with ethylene. The generation of heavy aromatics within the supercage system is the main reason for the deactivation of MCM-49 catalyst at the early reaction stage.Figure optionsDownload full-size imageDownload high-quality image (81 K)Download as PowerPoint slideHighlights► Liquid alkylation of benzene with ethylene over MCM-49 zeolite was studied. ► Ethylbenzene was mainly produced in the surface pockets. ► Distributions of acidic sites within different pore system were determined. ► Possible reactions within different pores were proposed. ► Effects of alkali-treatment on catalytic performances of MCM-49 were studied.