1D NMR Analysis of a Quaternary MEA–DEAB–CO₂–H₂O Amine System: Liquid Phase Speciation and Vapor–Liquid Equilibria at CO₂ Absorption and Solvent Regeneration Conditions

New procedures were developed for our recently developed 1D NMR calibration method for quantitative liquid phase speciation analysis of a complex quaternary CO₂ loaded blended amine solution such as MEA–DEAB–CO₂–H₂O at high and low temperatures respectively representing CO₂ stripping and absorption conditions. The ion speciation analyses were performed in conjunction with the corresponding vapor–liquid equilibrium (VLE) of the system to enable the estimation of possible CO₂ capture performance. Accurate speciations were performed for a quaternary amine system using four concentrations consisting of 5.0 M MEA blended with 0.5, 1.0, 1.5, and 1.25 M DEAB solutions with different CO₂ loadings at 24 °C, and for the first time, at higher temperatures using only the NMR calibration method. By comparison, the NMR calibration method with the new procedures was shown to be valid and perhaps the only approach for determining ion speciation for quaternary amine solutions at higher temperatures

¹³C NMR Spectroscopy of a Novel Amine Species in the DEAB–CO₂–H₂O system: VLE Model

In the present work, ion speciation studies in solutions of the novel amine 4-(diethylamine)-2-butanol (DEAB), at various CO₂ loadings (0–0.8 mol of CO₂/mol of amine) and amine concentrations (0.52–1.97 M), were determined by ¹³C nuclear magnetic resonance (NMR) spectroscopy. In addition, the dissociation constant <i>K</i> of DEABH⁺ was determined at 24.5, 35, and 45 °C using a pH meter. The ion speciation plot, which contains various sets of concentrations of DEAB, protonated DEAB, bicarbonate, and carbonate, was successfully generated. Because DEAB is a novel solvent, this is the first time that the ion speciation plots of the DEAB–CO₂–H₂O system have been developed. It is also the first time that the ¹³C NMR calibration technique was applied to develop the vapor–liquid equilibrium (VLE) model for an amine–CO₂–H₂O system. The results obtained from the present work can be a great help for the further analysis of the DEAB VLE model, as well as CO₂ absorption and kinetics studies. Furthermore, it was found that the novel ¹³C NMR calibration technique developed in this work provides higher accuracy than the conventional technique