Regulation of acidity properties of ZSM-5 and proximity between metal oxide and zeolite on bifunctional catalysts for enhanced CO2 hydrogenation to aromatics

Abstract

Herein, Ga-ZnZrOx&ZSM-5 bifunctional catalysts were designed for CO2 thermal hydrogenation to aromatics, particularly, aiming to enhance the selectivity of high-value BTX (i.e., benzene, toluene, and xylene). It was evident that the exterior surface properties and acidity of ZSM-5 can be effectively tailored by in-situ silicon deposition originating from the rice husk template. Catalytic performance assessments demonstrate an optimized catalyst achieving 88.1 % aromatics selectivity (exclusive CO) in a single pass, with a notable 45.2 % BTX selectivity within total aromatics and a low CO selectivity of 23.6 %. This superior performance is attributed to the in-situ silicon deposition on ZSM-5 during one-pot synthesis and the optimized spacing between Ga-ZnZrOx and ZSM-5 facilitated by the rice husk platform. Furthermore, in-situ DRIFTS analysis identifies key reaction intermediates. This study offers an effective strategy for tuning zeolite acidity using rice husks, while modulating metal oxide-zeolite proximity on the bio-SiO2 platform, thus boosting CO2 conversion to aromatics.