The use of highly polar additives to reduce the degradation of Cu/ZnO/Al2O3 catalysts during the gas phase hydrogenation of CO2 to methanol and CO

Abstract

The impact of catalyst deactivation due to sintering on the activity and properties of the Cu/ZnO/Al₂O₃ system in CO₂ hydrogenation to methanol was systematically investigated. Additionally, the effects of various additives on methanol yield and catalyst stability during CO₂/H₂ hydrogenation were evaluated. Additives such as methanol were confirmed to enhance catalytic activity, while components with high dipole moments exhibited a poisoning effect. Interestingly, despite their deactivating influence on activity, these polar additives significantly improved catalyst stability. It is presumed that highly polar species adsorb onto the catalyst surface, displacing water that would otherwise promote crystal growth of copper and zinc oxides, leading to deactivation. A combined additive strategy using methanol (to boost activity) and propylene carbonate (to enhance stability) offers a novel approach to significantly slow down Cu/ZnO/Al₂O₃ catalyst deactivation during gas-phase CO₂ hydrogenation, without compromising initial activity compared to conventional additive-free systems. Thus, catalyst stability can be effectively improved through the addition of appropriate components to the feed, without sacrificing reaction rate.