Enhanced performance and stability of Cu/ZnO catalyst by introducing MgO for low-temperature methanol synthesis using methanol itself as catalytic promoter

Catalytic conversion of CO₂-containing syngas to methanol is one of important processes in industry. However, realizing high space time yield (STY) of methanol at low reaction temperature remains a challenge. Herein, ternary Cu/ZnO/MgO catalysts were prepared via co-precipitation and tested for low-temperature methanol synthesis via autocatalysis of methanol. The effects of Mg²⁺ ion and MgO content on the formation and composition of the precipitated precursors, as well as on the physicochemical properties of the calcined and the reduced catalysts were systemically investigated and discussed. The structure–activity relationships were disclosed by detailed catalysts characterization. Compared to Cu/ZnO, the total carbon turnover frequency (TOF) and space time yield (STY) of methanol on Cu/ZnO/MgO remarkably increased from 17.8 to 20.0 h⁻¹ and from 425.2 to 538.3 g/kg∙h⁻¹, respectively. Besides, Cu/ZnO/MgO kept its activity for 180 h without deactivation, which was much more stable than Cu/ZnO. In comparison with commercial Cu/ZnO/Al₂O₃ and other Cu-based catalysts reported in the literatures for methanol synthesis from syngas, Cu/ZnO/MgO catalyst with Cu/Zn/Mg molar ratio of 1:1:0.05 displayed much higher space time yield (STY) of methanol. In addition, the reaction conducted in the presence of methanol promoter exhibited much lower apparent activation energy than that of the reaction carried out without methanol promoter, indicating a catalytic and promotional role of methanol during low-temperature methanol synthesis reaction. The current work provided not only a hopeful strategy for enhancing activity and stability of Cu/ZnO catalyst, but also a sustainable low-temperature methanol synthesis route using methanol itself as catalytic promoter.