Effect of the Cu/Ni Ratio on the Activity of Zeolite Based Cu–Ni Bimetallic Catalysts for CO₂ Hydrogenation to Methanol

Abstract: Bimetallic zeolite based Cu/Ni catalysts having different molar ratio were synthesized by precipitation method. The synthesized catalysts were extensively characterized by different analytical techniques. X‑ray diffraction method was employed to investigate the crystalline nature of the catalysts. Morphology of synthesized catalysts was studied by scanning electron microscopy. Nitrogen adsorption–desorption studies revealed a promoting role of increasing Cu/Ni molar ratio on the BET surface area of the catalysts. The BET surface area was decreased from 330 to 239 m²/g by the introduction of Cu and Ni to the zeolite however it was increased to 279 m²/g by further Cu/Ni enrichment. The temperature programmed reduction was used to study the reduction behavior of the bimetallic catalysts. Activity studies of the catalysts exhibited that rate of methanol synthesis was increased by incrementing Cu/Ni molar ratio. The highest methanol synthesis rate of 475 g/(kg h) was recorded for catalyst with Cu/Ni molar ratio of 2. A linear relationship was found between the increasing Cu/Ni molar ratio and methanol selectivity.