Effect of Mn content in CuO/MnCeOx catalysts on CO2 hydrogenation for methanol synthesis

Abstract

Controlling metal–support interaction is critical when constructing a highly efficient catalytic system. Herein, different Cu–CeO_x interactions are realized by preparing a sequence of CuO/MnCeO_x catalysts with varying Mn content. The impact of Mn content on the behavior of CuO/MnCeO_x catalysts during the hydrogenation of CO₂ to CH₃OH is analyzed to determine the optimum Mn content. The catalyst with 20% Mn content (CuO/Mn_0.2CeO_x) exhibits optimal catalytic behavior with a methanol space–time yield of 0.25 g_CH3OH g_cat⁻¹ h⁻¹ at 260 °C. The CuO/Mn_0.2CeO_x sample exhibits the highest catalytic activity as it has the highest concentration of oxygen vacancies and Cu⁰ as well as medium-to-strong basic sites, which are generated by the strongest metal–support interactions between CuO and MnCeO_x solid solution. In situ diffuse reflectance infrared Fourier-transform spectroscopy evidence indicates that the CO₂ methanolization over CuO/MnCeO_x catalysts proceeds via a formate mechanism. The results obtained herein are highly significant for controlling oxygen vacancies and surface basic sites by rationally altering the metal–support interaction to develop new, highly efficient CO₂ hydrogenation catalysts.