Combustion induced synthesis of multicomponent Cu-based catalysts for autocatalytic CO hydrogenation to methanol in a three-phase reactor system

Abstract

Multicomponent Cu-based catalysts with ZnO/MgO were prepared by the solvent combustion method and the activity test was performed for CO hydrogenation to methanol in a slurry reactor. The promotional effect of ZnO and MgO on the physicochemical and structural properties and their correlation with the catalytic activity in the slurry reactor were analyzed. The space–time yield (STY) of the methanol synthesis revealed the relationship with the Cu⁰ surface area, particle size, and initial methanol concentration. The CuZnMg catalysts exhibited higher Cu⁰ surface area and Cu dispersion, and the promotional effect of MgO on Cu/ZnO results in a maximum STY of 527.23 g_MeOH kg_cat⁻¹ h⁻¹. The initial methanol concentration of 0.04% enhances the activity by 14.3% (615.8 g_MeOH kg_cat⁻¹ h⁻¹) of CuZnMg by an autocatalytic pathway of methanol synthesis, which illuminates the concept of the paradigm shift of the methanol synthesis mechanism. It was observed that incorporation of MgO further increases the defect sites and increases the activity. The synergistic effect of the ZnO and CuMgO highly active interface contributed to an increase in the catalytic performance of the CuZnMg catalyst. The time-on-stream (TOS) study for 30 h revealed the higher activity and stability of the CuZnMg catalyst while CuMg started to deactivate after 3 h revealing the synergistic effect of ZnO. Further DFT results confirmed the promotional role of MgO and ZnO in the catalytic activity and stability. The Cu binding on the ZnOMgO surface was found to be higher than those on CuZnO and CuMgO which further confirmed that the strong metal support interaction (SMSI) revealed the higher activity of CuZnMg.