Guiding the Selection of Novel Amines for CO₂ Capture Using a Molecular-Based and Multicriteria Modeling Approach

Given the variety of novel amines as potential next-generation solvents for CO₂ capture, knowledge of their thermodynamic properties is imperative to guiding their selection. In this work, 37 alternative amines belonging to different molecular families are investigated using the soft-statistical associating fluid theory (soft-SAFT) molecular equation of state (EoS). Limited experimental data of density, vapor pressure, and viscosity were used in parametrizing the molecular models, relying on the transferability of parameters related to their functional groups, yielding a modeling accuracy of within 10% of available data. The physical basis of soft-SAFT allowed determining the role of carbon chain length, molecular geometry, and degree of functionalization on key properties for CO₂ capture including density, vapor pressure, heat capacity, heat of vaporization, and viscosity, identifying short-chain molecules with cyclic/branched structures and secondary or tertiary amine functional groups as more preferred. pK_a values were obtained from COSMO-RS as a measure of the affinity for CO₂, establishing the imperative role of functionalization with primary and secondary amine groups. The cost and flammability of the alternative solvents were also included as additional criteria for their final selection. In addition to quantifying the role of the molecular structure on the performance of the solvents, the methodology of this work allowed us to identify morpholine (Morph) and ethylenediamine (EDA) as potential next-generation CO₂ capture solvents, with superior performance to the current ones, to be further investigated for large-scale validation. This work showcases the relevance of using molecular modeling for systematic screening of novel solvents for CO₂ capture, even in the absence of experimental data.