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In the present work, ion speciation studies in solutions of the novel amine 4-(diethylamine)-2-butanol (DEAB), at various CO 2 loadings (0−0.8 mol of CO 2 /mol of amine) and amine concentrations (0.52−1.97 M), were determined by 13 C nuclear magnetic resonance (NMR) spectroscopy. In addition, the dissociation constant K 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−CO 2 −H 2 O system have been developed. It is also the first time that the 13 C NMR calibration technique was applied to develop the vapor−liquid equilibrium (VLE) model for an amine−CO 2 −H 2 O 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 CO 2 absorption and kinetics studies. Furthermore, it was found that the novel 13 C NMR calibration technique developed in this work provides higher accuracy than the conventional technique.

The mass transfer performance of the absorption of CO 2 in an aqueous solution of monoethanolamine was evaluated experimentally in a lab-scale absorber packed with high efficiency DX structured packing and compared with that of methyldiethanolamine (MDEA) as well as that of a newly developed tertiary amino alcohol, 4-diethylamino-2-butanol (DEAB). The absorption experiments were conducted at atmospheric pressure, using a feed gas mixture containing 14.9% CO 2 and 85.1% nitrogen in an absorption column containing DX structured packing. The absorption performance was presented in terms of the CO 2 removal efficiency, absorber height requirement, effective interfacial area for mass transfer, and overall mass-transfer coefficient (K G a v ). In particular, the effects of parameters such as inert gas flow rate and liquid flow rate were compared for both DEAB and MDEA. The results show that the DEAB has a much higher removal efficiency for CO 2 along the height of the column than MDEA. Also, the K G a v of DEAB was much higher than that for MDEA. For all the solvents, the K G a v increased as the liquid flow rate was increased. An empirical correlation for the mass transfer coefficient for the CO 2 -DEAB system has been developed as a function of the process parameters. In terms of comparison, the results show that the DEAB system provided an excellent overall mass transfer coefficient, which is higher than that of the MDEA system but less than that of MEA.

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.

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