Features of Zinc Modification of a Zeolite Catalyst for Dimethyl Ether Conversion to Synthetic Liquid Hydrocarbons

Abstract

Liquid hydrocarbons (HCs) with a low aromatic content have been synthesized from dimethyl ether (DME) in a hydrogen medium at a temperature of 340°C and a pressure of 10 MPa in the presence of catalysts based on Zn–HZSM-5 zeolites prepared by impregnation, ion exchange from an aqueous solution of zinc nitrate, and in situ synthesis. It has been shown that zinc modification of zeolite HZSM-5 leads to a decrease in the total number of acid sites with an increase in the fraction of strong Lewis acid sites in the total acidity spectrum. The introduction of Zn into zeolite HZSM-5 by the in situ method leads to an increase in the fraction of mesopores and thereby makes it possible to eliminate diffusion hindrances. These factors can provide a significant increase in the selectivity for liquid HCs and the isoalkane content in their composition and a substantial improvement in the on-stream stability of the in situ synthesized catalyst based on Zn–HZSM-5.