Step-change performance enhancement of ethylene aromatization on Ga-ZSM-5 through steaming treatment

Abstract

In continuation of our two-step process development for the conversion of ethane to aromatics, this work focuses on catalyst performance improvement for ethylene aromatization. The approach is to apply steaming dealumination method to tailor ZSM-5 acidity to optimize its catalytic performance. Our results indicate that applying steaming treatment for the base Ga-ZSM-5 catalyst at specified conditions could reduce the total acid amount from 0.46 to 0.15–0.25 mmol/g, with 46–67% acidity loss, accompanied with the decrease of the acid strength for the strong acid sites. As a result, the catalyst prepared in this way exhibited a step-change performance enhancement in terms of cycle lifetime, target product yield/capacity, byproduct, coke formation and so on. Through examining the reaction mechanism and acid strength requirements for individual steps involved in ethylene aromatization, we conclude that steps that require strong acid strength – such as cracking and aromatics alkylation (both leading to catalyst deactivation) are effectively suppressed due to the lower acid amount/strength obtained after steaming treatment. The findings and this zeolite acidity tailoring technique will provide insights and solutions for zeolite-based acidic catalyst design.