A route to selectively increase the microporous structure of zeolite and its optimization in the ethanol to butadiene reaction

Abstract

Ethanol is introduced into aqueous amine solution and the attractions between species of buffer solution lead to its limited etching capacity, which could selectively increase the micropore structure of zeolite.Control over the pore structure of zeolite is very important, so researchers are trying to regulate the pore structure of zeolite through various methods to endow it with better performance in industrial applications. Here, a confined etching route that could selectively increase the microporous structure of zeolite is developed using ethanol/amine buffer solution. Ethanol is introduced into an aqueous amine solution, where it could decrease the migration rate and concentration of hydroxyl ions which can etch the framework atoms of zeolite to fabricate various porous structures, consequently developing a confined etching route that could selectively increase the microporous structure of zeolite, unlike conventional approaches that generally increase mesoporous and macroporous architectures. In addition, ethanol enhances the solubility of amine in water, and a buffer solution (ethanol/amine) is formed, which is able to release hydroxyl ions continuously. Based on the above confined etching route, a micropore-increased beta crystal is synthesized and when used as a carrier in ZnLaY/beta catalysts, it achieves excellent ethanol conversion of 96.04% and butadiene selectivity of 64.22% in 20 h time-on-stream in an ethanol to butadiene reaction.