Physicochemical and catalytic properties of micro-mesoporous zeolite materials

Abstract

Micro-mesoporous zeolite materials differing in their content of micro- and mesopores are obtained by the recrystallization of modernite zeolite. Using physicochemical methods such as scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction analysis, small-angle X-ray scattering analysis, low-temperature adsorption of nitrogen, temperature-programmed desorption of NH3, and IR spectroscopy, it is shown that recrystallization leads first to the formation of mesopores with sizes of 20–30 A in zeolite crystals, then to the appearance of zeolite/MCM-41 nanocomposite, and finally to the complete conversion of zeolite into mesoporous MCM-41. During this process, the concentration of strong Bronsted acid sites accessible to pyridine bases first increases then drops. The catalytic properties of the synthesized materials are studied in the reaction of alkylation of benzene by dodecene-1. It is shown that the creation of transport pores and the increase in the accessibility of acid sites due to recrystallization under soft conditions facilitate the alkylation reaction.