Insight into the Alkylation‐Efficiency of Methanol with Toluene over HZSM‐5 Zeolite II: Acidic Properties also Significantly Affects Reacting‐Pathways

Abstract

Here the effect of HZSM-5 acid-properties on the reactingpathways in the reaction system of toluene alkylation with methanol was studied detailedly, from the aspects of acidic type (Brönsted/Lewis), density, strength and location. A reasonable acid-properties as following is an indispensable support to achieve a high methanol alkylation-efficiency: not only the relatively high ratios of both Brönsted/Lewis and external/ internal acid-amount, but also both modest density and weakmedium strength. Firstly, because alone Lewis acidity is almost inactive to aromatic alkylation, meaning Brönsted acid-sites are indispensable. Secondly, an extremalization in either acidic density or strength is disadvantageous to aromatic alkylation, but encourages the conversion of methanol to olefins (MTO). Besides, the external acid-sites in a relatively relaxed microenvironment are more favorable to catalyze aromatic-alkylation than those inside channel where the strong diffusion/space restriction to aromatic-molecules but foments MTO sidereaction. Our work may provide a theoretical guidance for improving the methanol alkylation-efficiency in this reaction system.