Metallurgical Residue-Derived Cu-ZnO-Based Catalyst for CO2 Hydrogenation to Methanol: An Insight on the Effect of the Preparation Method

Valorization of residual materials in the development of catalytic materials has an appealing potential from the perspective of a sustainable development. For the first time, Fe/Mg-containing metal-lurgical waste (UGSO) was utilized as a support for the development of innovative catalysts for CO, hydrogenation into methanol. A series of different CuZn/UGSO catalysts were developed by conventional and modified deposition-coprecipitation methods. The addition of Cu/Zn into the structure of Fe3O4/MgxFeyOx was found to improve Cu2+ and Zn2+ dispersion, while the presence of MgO favors methanol selectivity. Compared to 10Cu7.5Zn/UGSO (10 wt % Cu, 7.5 wt % Zn), the higher methanol yield obtained over 10Cu7.5Zn/UGSO-EtOH (10 wt % Cu, 7.5 wt % Zn, ethanol addition after coprecipitation) is a result of both higher CO2 conversion [attributed to (i) finer particle sizes of CuO and ZnO, (ii) a higher Cu-0/Cu+ percentage, and (iii) higher oxygen vacancies and number of strong basic sites on the catalyst surface] and higher methanol selectivity [assigned to (i) the stronger interaction of Cu and ZnO and (ii) a higher number of medium basic sites] in comparison with its counterpart. This residue-based catalyst offers a 150% higher methanol yield than a commercial Cu-based methanol synthesis catalyst at 260 degrees C and 20 bar. These promising results can open a window to the utilization of this residue as a catalytic support in other CO2 hydrogenation processes.