Synthesis of MeOH and DME From CO₂ Hydrogenation Over Commercial and Modified Catalysts

Growing concern about climate change has been driving the search for solutions to mitigate greenhouse gas emissions. In this context, carbon capture and utilization (CCU) technologies have been proposed and developed as a way of giving CO₂ a sustainable and economically viable destination. An interesting approach is the conversion of CO₂ into valuable chemicals, such as methanol (MeOH) and dimethyl ether (DME), by means of catalytic hydrogenation on Cu-, Zn-, and Al-based catalysts. In this work, three catalysts were tested for the synthesis of MeOH and DME from CO₂ using a single fixed-bed reactor. The first one was a commercial CuO/γ-Al₂O₃; the second one was CuO-ZnO/γ-Al₂O₃, obtained via incipient wetness impregnation of the first catalyst with an aqueous solution of zinc acetate; and the third one was a CZA catalyst obtained by the coprecipitation method. The samples were characterized by XRD, XRF, and N₂ adsorption isotherms. The hydrogenation of CO₂ was performed at 25 bar, 230°C, with a H₂:CO₂ ratio of 3 and space velocity of 1,200 ml (g cat · h)^-1 in order to assess the potential of these catalysts in the conversion of CO₂ to methanol and dimethyl ether. The catalyst activity was correlated to the adsorption isotherms of each reactant. The main results show that the highest CO₂ conversion and the best yield of methanol are obtained with the CZACP catalyst, very likely due to its higher adsorption capacity of H₂. In addition, although the presence of zinc oxide reduces the textural properties of the porous catalyst, CZAWI showed higher CO₂ conversion than commercial catalyst CuO/γ-Al₂O₃.