Synthesis of tetramethylbenzene from CO2 hydrogenation over ZnZrO/ZSM-11 tandem catalyst

Abstract

The synthesis of aromatics via CO2 hydrogenation is receiving an increasing attention. However, the direct conversion of CO2 to a single aromatic product with high selectivity is very challenging. Herein, we report a synthesis of tetramethylbenzene(TeMB) on a tandem catalyst consisting of ZnZrO and hierarchical ZSM-11 zeolite, the selectivity of TeMB up to 79 % in aromatics is achieved while maintaining 76 % total aromatic selectivity. Uniform mesopores of ZSM-11 created with mixed TPAOH and NaOH organic-inorganic base are found to be responsible for the increased selectivity of aromatics and TeMB. Based on the acidic property of the catalyst, the increase of TeMB selectivity is attributed to the increase in the amount of the external BrØnsted acid which is increased with the external surface area of ZSM-11 zeolite. More BrØnsted acid on the external surface promotes the alkylation of low-carbon aromatics such as xylene, therefore increases the selectivity of TeMB.