Electrolyte and reaction heat behavior in blended aqueous solutions of poly and mono alkanolamine for carbon capture processes: CO2–AEEA–DIPA–H2O system

Abstract

This study investigates the potential of complex amine reactions for minimizing solvent regeneration energy in CO2 capture processes. A thermodynamic framework, based on the electrolyte nonrandom two-liquid (electrolyte NRTL) model, was developed to rigorously characterize the vapor-liquid equilibrium (VLE) behavior of aqueous solutions of blended aminoethylethanolamine (AEEA) and diisopropanolamine (DIPA), representing poly and mono alkanolamines, respectively. The framework models CO2 solubility, cyclic capacity, liquid phase electrolyte speciation, heat of reaction, and heat of absorption. Model predictions of solubility were compared against experimental data. Furthermore, the heat of reaction for the individual amines and their blends was predicted and analyzed, investigating the effects of loading, temperature, amine blending ratio, and water content. A global sensitivity analysis was also conducted to identify the key thermodynamic parameters strongly affecting CO2 solubility and heat of absorption. Major contributors to heat of CO2 absorption in the AEEA:DIPA system include dissociation of protonated AEEA, protonated secondary AEEA carbamate, formation of primary AEEA carbamate, dissociation of protonated DIPA and DIPA carbamate, and CO2 dissolution. Among these, the dissociation of protonated secondary AEEA carbamate plays a significant role, particularly at higher CO2 loadings. The heat of absorption and cyclic capacities determined for the system demonstrate favorable performance when compared against values reported in the literature for other prominent amines. The thermodynamic behavior of blended amine system highlights the potential of AEEA:DIPA mixtures for reducing regeneration energy in CO2 capture applications.