Integrated CO2 capture and conversion to methanol: A performance comparison of alcohol-amine solvents

An integrated CO 2 capture and conversion (ICCC) process has been proposed to reduce the high energy requirement of solvent regeneration and gas compression in conventional carbon capture and utilization (CCU) process. This is achieved by capturing CO 2 in a solvent and then directly reacting the solvent captured CO 2 with H 2 in reactors to synthesize chemical products. This work investigates mixtures of tertiary amines, glycols, and alcohols to perform the integrated CO 2 capture and conversion to methanol in a hydrogenation slurry reactor using a Cu/ZnO/Al 2 O 3 catalyst. The CO 2 capture performance and methanol formation activity were first evaluated via gas-loaded CO 2 hydrogenation for pure solvents and amine mixtures, where hexanol-triethylamine mixture showed enhanced conversion performance. The integrated reaction was then studied by hydrogenation of liquid-captured CO 2 to establish the impact of alcohol-triethylamine solvents on methanol formation. The impacts of reaction temperature, H 2 pressure, and reaction time were investigated for hexanol-triethylamine mixtures. The recycling performance was also evaluated for the spent solvent and catalyst. The highest methanol activity of 5.6 mmol MeOH g cat −1 h −1 was achieved at 250 °C and 5 MPa with 48 % CO 2 conversion and 80 % selectivity to methanol using the 10:1 hexanol-triethylamine mixture, while a stable catalyst recycling performance was achieved by the 5:1 hexanol-triethylamine mixture at 170 °C and 5 MPa.