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

Abstract

AbstractHere the effect of HZSM‐5 acid‐properties on the reacting‐pathways 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 weak‐medium 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 side‐reaction. Our work may provide a theoretical guidance for improving the methanol alkylation‐efficiency in this reaction system.