The role of CO2 over different binary catalysts in methanol synthesis

A small amount of CO2 in syngas (CO/H2) is beneficial to methanol synthesis over Cu-based catalysts. To obtain more information on the CO2 effect, a series of binary Cu-based catalysts including Cu/ZnO and Cu/MgO were prepared and evaluated under feed gas (CO/H2/Ar) with or without CO2. Evaluation results show that when CO2 was added, the CO conversion of Cu0.6ZnO0.3 catalyst jumped from -4% to -68%, while the activity of Cu/MgO catalyst decreased from -15% to -0% (230 degrees C, 4 MPa, 8000 h-1 with 78.5% H2, 12.75% CO, 1.75% CO2 and 7% Ar). In situ X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were employed to examine the states of catalysts under different treatment conditions. The migration and transformation of metal species on the catalysts surface should be a reason that caused the opposite change of catalysts activity with and without CO2.