Selective and Stable Pt Catalysts for the Catalytic Conversion of Captured CO ₂ to Methanol in an Advanced Water-Lean Postcombustion Solvent

We have successfully combined CO2 capture and conversion, which eliminates the need for the energy-intensive steps of sorbent regeneration, CO2 compression, and transportation. The exothermic conversion process regenerates the sorbent for further capture and conversion cycles. In this study, we evaluated supported Pt catalysts (over TiO2, ZrO2, or MoO3) for converting CO2 captured in a single-component, water-lean postcombustion solvent (EEMPA) into methanol. Pt supported on MoO3 and ZrO2 showed the highest methanol productivity and selectivity, respectively, among the catalysts evaluated. This study introduces a catalyst system that substantially reduces degradation in amine carbon capture solvents and demonstrates stable catalytic performance, marking a significant advancement over previous findings. Solvent durability was best with Pt/MoO3, attributed to the lack of detectable acidic or basic sites on its surface. Both Pt/MoO3 and Pt/ZrO2 catalysts maintained stable performance over 100 h of continuous operation. The higher methanol productivity with Pt/MoO3 is likely due to the significantly high H2 spillover under reaction conditions, which promotes the formation of oxygen vacancies. However, further mechanistic investigation is necessary to conclusively establish this relationship. The higher methanol selectivity (>99%) of Pt/ZrO2 is believed to be due to its strong basic sites, which reduce methanol adsorption and suppress methane formation. Our findings emphasize the importance of modulating acidic and basic sites on the catalyst surface to enhance methanol selectivity while preserving the integrity of the capture solvent.