Physical/Chemical Solubility and Chemical Equilibrium Analysis of Carbon Dioxide Absorption in a Potential and Novel Blended Amine Solution of 2‑Methylaminoethanol (MAE) and N,N-Diethylethanolamine (DEEA)

This study comprehensively reports the physical and chemical equilibrium solubility data, along with a detailed chemical equilibrium analysis, of carbon dioxide (CO₂) absorption into a blended amine solution consisting of 2-methylaminoethanol (MAE) and N,N-diethylethanolamine (DEEA). Four models were employed to analyze the CO₂ physical solubility using N₂O analogy, with the Artificial Neural Network (ANN) model exhibiting an average absolute relative deviation (AARD) of 2.78%. The CO₂ chemical solubilities were then analyzed experimentally at various temperatures (298–313 K), CO₂ partial pressures (8–100 kPa), and concentrations (1–5 mol/L). In addition, the heat of CO₂ absorption was estimated to be 46.96 kJ/mol using the Gibbs–Helmholtz equation, which is approximately half that of the benchmark amine, monoethanolamine (MEA). A rigorous ¹³C NMR investigation was conducted to identify and quantify the species formed during the absorption process across varying temperatures, CO₂ loadings, and MAE/DEEA molar ratios, to clarify the capture mechanisms and intricate role of MAE and DEEA in the capture process. As a result, at an MAE/DEEA ratio of 1:4, the carbamate concentration peaks at a CO₂ load of about 0.45 mol of CO₂ /mol of amine at about 0.6 mol/L, which is only one-third of the concentration at the higher ratio, which contributes to the reduction of energy consumption for CO₂ desorption.