(658b) Enhancing the CO2 Hydrogenation to Higher Alcohols By Potassium Promotion of Cocu Catalysts

Carbon dioxide (CO₂) is a significant greenhouse gas that contributes to global warming and climate change. From another perspective, CO₂ also can be considered a valuable carbon resource for producing various chemicals and fuels such as CO, light olefins, aviation fuel, methanol, and higher alcohols. Therefore, the realization of CO₂ capture and utilization is conducive to a circular carbon economy and sustainable development. CO₂ hydrogenation to higher alcohols is a challenging route that suffers from low selectivity and activity due to complex reaction mechanisms.

In this work, a CoCu catalyst was prepared via co-precipitation of an oxalate precursor and promoted by potassium (K), which significantly enhances the selectivity to higher alcohols from CO₂ hydrogenation. The reaction conditions (temperature, pressure, WHSV) were investigated in detail. The role of K was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) and chemisorption methods. As to the catalytic performance, the alcohol selectivity increased substantially compared to pure CoCu, The K promoter is assumed to increase the reverse water gas shift activity towards CO (and H₂O). Successive reaction steps typically involve those known for the CO hydrogenation over CoCu, i.e. CO insertion into surface hydroxyl and alkoxy species forming surface formate or, respectively, carboxylate-type species which undergo hydrogenation to produce hydrocarbons and alcohols. The formation of these species is demonstrated by DRIFTS. In summary, this work provides insight into how to tune the product selectivity in CO₂ hydrogenation by careful alkali promotion of suitable catalyst formulations.