Integrated Capture and Conversion of CO2 to Methanol in a Post-Combustion Capture Solvent: Heterogeneous Catalysts for Selective C-N Bond Cleavage

Abstract

An efficient and selective heterogeneous catalyst is identified for the condensed-phase hydrogenation of captured CO2 in the presence of an advanced water-lean post-combustion capture solvent, (N-(2-EthoxyEthyl)-3-MorpholinoPropan-1-Amine), 2-EEMPA. The catalysts commonly used for gas-phase CO2 hydrogenation (e.g., Cu/Zn/Al2O3) cause deactivation of amine promoters via N-methylation by C-O cleavage of formamide intermediates. A heterogeneous catalyst system that suppresses N-methylation of amine solvents is identified, demonstrating how Pt, supported by reducible metal oxides CeO2 or TiO2, can be selective for C-N cleavage to produce methanol. This is the first known demonstration of integrated low-temperature thermocatalytic capture and conversion of CO2 to methanol in an economically viable CO2 capture solvent. Technoeconomic analyses performed on the state-of-technology suggest that methanol can be produced with a minimum selling price of $4.4/gallon ($1,460/metric ton) when using CO2 captured from a 650 MW natural gas combined cycle plant. Ultimately, a road map of how realistic and achievable improvements to space velocity and methanol selectivity of this integrated process can enable near cost parity to fossil-derived methanol, with a selling price of ≈$1.4/gal ($470/metric ton), is presented.