Experimental Study Toward Integrated Capture and Conversion of CO 2 to Methanol: Mechanistic Insights into the Competition Between Amine Reactivity and Methanol Production

High Resolution Image Download MS PowerPoint Slide Carbon capture and utilization represents a promising strategy to mitigate anthropogenic CO 2 emissions; however, the energy-intensive stripping and compression steps render the process economically challenging. To decrease the overall energy consumption, the concept of integrated capture and conversion of CO 2 to methanol (IC 3 M) was introduced, in which the carbamate arising from carbon capture is directly hydrogenated toward methanol. In this work, the hydrogenation of the equilibrium-loaded amine is investigated using dipropylamine (DPA) as the carbon capture amine and several noble-metal catalysts supported on γ-Al 2 O 3, at a total pressure of 40 bar, temperatures between 125 and 175 °C and varying residence times. Besides trace amounts of methanol, 1-propanol, propylamine, tripropylamine, and N, N -dipropylformamide are identified as major reaction products, revealing complex amine reactivity under hydrogenation conditions. N, N -dipropylformamide is established as the key intermediate, undergoing either C–N bond cleavage to methanol or C–O bond cleavage to N -methyldipropylamine, with selectivity strongly dependent on reaction temperature, hydrogen partial pressure, and residence time. Additional amine-derived products originate from a Schiff-base-type transformation of carbamate species. The results demonstrate that methanol formation from captured CO 2 is mechanistically viable within integrated systems while highlighting intrinsic competition with amine reactivity, providing a foundation for a two-step process with enhanced methanol productivity.