Green methanol synthesis by catalytic CO₂ hydrogenation, deciphering the role of metal-metal interaction

The current work deals with the synthesis, characterization and activity studies of zeolite based Ag–Cu bimetallic catalysts for CO₂ hydrogenation to methanol. To probe the effect of Ag–Cu weight ratio, Ag–Cu with 1:9, 2:8, 4:6 and 1:1 wt ratios were synthesized by impregnation method. Thermo-gravimetric analysis revealed that catalysts stability was improved by Ag enrichment to the zeolite based Ag–Cu bimetallic catalysts. X-ray diffraction studies showed that zeolite structure has been modified by the incorporation of Ag–Cu metals to the bare zeolite. Nitrogen adsorption desorption studies manifested that BET surface area, pore size and pore volume were less affected by variation in Ag–Cu weight ratio. Formation of nano-sized Ag–Cu bimetallic catalysts with high dispersion was illuminated by Field Emission Electron Microscopy (FESEM). X-ray Photoelectron Spectroscopy (XPS) findings revealed greater metal-metal chemical interaction as a consequent of Ag addition to the zeolite based Ag–Cu bimetallic catalysts. Activity studies of zeolite based Ag–Cu bimetallic catalysts exhibited the promoting role of Ag in CO₂ hydrogenation to methanol. The structure activity studies observed Ag–Cu metal-metal chemical interaction as the key factor controlling the rate of methanol synthesis.