Selective CO2 Hydrogenation to Light Aromatics over the Cu-Modified Fe-Based/ZSM-5 Catalyst System

Direct CO2 hydrogenation to value-added chemicals not only decreases carbon emissions but also provides an alternative way for fossil fuels. Even though some outstanding results were obtained, the high productivity of the target product is still hard to achieve. In this work, we fabricated a bifunctional catalyst comprising a Cu-modified Fe-based catalyst and ZSM-5 for selective CO2 hydrogenation to aromatics with the help of XRD, H2-TPR, CO2-TPD, SEM, TEM and N2 adsorption and desorption techniques for the catalytic mechanism of the prepared catalysts. The results show that the Cu promoter can improve the carbon-chain growth, suppress methane formation over the Fe-based catalyst, and then increase the aromatic selectivity over the bifunctional catalyst, suggesting that heavy olefin-based intermediates are more prone to aromatization than light intermediates. By lengthening the straight channel length of zeolites in the direction of the b-axis, a STYtoluene of 14.8 gCH2·kgcat–1·h–1 is obtained. The relevant mechanism may be attributed to the increase in the b-axis length, which restricts the diffusion of products on the straight channel, forcing the product to diffuse from the sinusoidal channel in the ZSM-5 zeolite. This work provides insights for designing a bifunctional catalyst that achieves high productivity of high value-added aromatics.