CuZnAl embedded silicoaluminate catalyst promotion for the hydrogenation of carbon dioxide to dimethyl ether

The resource utilization of CO₂ serves as a feasible method for emission reduction and the establishment of an artificial carbon cycle. This study primarily focuses on the direct synthesis of dimethyl ether (DME) from the hydrogenation of CO₂. We have prepared bifunctional catalysts with metal oxides embedded in amorphous silicon-aluminum by an improved Stöber method. By precisely adjusting the Si/Al molar ratio and the CTAB/Si molar ratio in the synthesis precursor solution, structural characteristics and acid properties of the catalyst could be effectively regulated. The results indicated that compared to Cu/ZnO/Al₂O₃, the catalyst significantly enhanced the selectivity of DME and methanol (MeOH), reduced the selectivity of CO with a moderate conversion rate of CO₂. The highest DME selectivity of 37.94 % was achieved at an Si/Al ratio of 8, with the total selectivity for methanol and DME reaching 52.96 %. The addition of cetyltrimethylammonium bromide (CTAB) increased the proportion of Brønsted acid sites and medium-strong acid sites, thereby enhancing methanol dehydration and suppressing the reverse water-gas shift reaction. The optimal selectivity for DME of 43 % was obtained over catalyst prepared with a CTAB/Si molar ratio of 0.1. This study provides a new strategy for the structural design of bifunctional catalysts for CO₂ hydrogenation.