Hydrogenation of CO2 into aromatics over ZnZrO-Zn/HZSM-5 composite catalysts derived from ZIF-8

The direct conversion of CO2 to aromatics is of great strategic significance for the realization of carbon capture, utilization, and storage. However, the efficient conversion of CO2 is still challenging due to its thermodynamic stability and chemical inertness. Herein, we report a ZnZrO solid solution prepared via direct calcination using ZIF-8 and Zr(NO3)(4)center dot 5H(2)O as precursors. Zn-Modified nano-hierarchical-pore HZSM-5 zeolite (Zn/Z5) was prepared via steam-assisted crystallization using ZIF-8 as a sacrificial template and Zn source. The ZnZrO-Zn/Z5 composite catalyst was prepared by the physical mixing of the two components, which was used to catalyze the hydrogenation of CO2 to aromatics. The physical and chemical properties of the catalysts were investigated using XRD, SEM, TEM, N-2 adsorption-desorption, ICP-OES, EDX, NH3-TPD, Py-IR, H-2-TPR, XPS, CO2-TPD and other characterization methods. The effects of the ZnZrO calcination temperature, different Zn/Zr ratios, reaction conditions and the spatial distance between the ZnZrO and the Zn/Z5 zeolite on the catalytic performance of the catalytic hydrogenation of CO2 to aromatics were investigated. The generalized gradient approximation (GGA) of density functional theory (DFT) simulation results showed that the adsorption and activation capacity of ZnZrO for CO2 can be significantly improved with the increase of oxygen vacancies. Finally, the reaction mechanism was investigated by in situ DRIFTS. Under the optimal reaction conditions, a CO2 conversion of 15.2% and aromatic selectivity of 63.9% can be achieved over the ZnZr8O(350)-Zn/Z5 composite catalyst, and excellent catalytic stability was demonstrated.

Automated summary

In this study, a ZnZrO solid solution and Zn/Z5 composite catalyst were synthesized and characterized for the hydrogenation of CO2 to aromatics, resulting in improved efficiency and selectivity. Various reaction conditions and catalyst properties were investigated, leading to insights on enhancing the catalytic performance.