This work has investigated CO2 absorption using 3-(diethylamino)propylamine (DEAPA), a diamine that contains one primary and one tertiary amine in the same molecule. The results are compared with those for the blended amine system of monoethanolamine and methyldiethanolamine (MEA–MDEA), a mixed amine solvent with an equal number of moles of primary and tertiary amine. The 2 M DEAPA, 2 M MEA, and 4 M MEA–MDEA (1:1 mole ratio) were tested for their CO2 absorption performance. The experimental results show that the intramolecular tertiary amino group of DEAPA can promote the CO2 absorption rate of the intramolecular primary amino group and enhance its CO2 absorption capacity. The results using 13C nuclear magnetic resonance also showed that the intermolecular tertiary amine in the MEA–MDEA system was more favored for the promotion of the primary amine in the blend to form bicarbonate at an earlier CO2 equivalent loading stage and produced less carbamate than the intramolecular tertiary amino group of DEAPA did with respect to its primary amine. Furthermore, the CO2 equilibrium solubility of DEAPA was measured at different temperatures with various CO2 partial pressures, and then an empirical model based on these experimental data was developed. The results predicted by this model were fitted well with the experimental results. The Gibbs–Helmholtz equation was used to estimate the CO2 absorption heat of the DEAPA system, and the results showed that DEAPA has a CO2 absorption heat (−36.4 kJ/mol) lower than those of MEA, MDEA, and DEA. The results demonstrate that DEAPA has the potential to be an alternative solvent with a high absorption rate, a high CO2 capacity, and a low heat of absorption in CO2 capture processes.
Bin Zhao,Yujing Liu,Bo Zhou,Peidong Zuo,Liping Chang,Jiawei Zhong,Zhenyi Du,Mengmeng Wu,Zhifeng Qin
Understanding the structure-property-performance relationship of mixed amine solvents is essential for developing high-efficiency Carbonyl sulfur (COS) removal technologies. In this work, the thermophysical properties, intermolecular interactions, and COS capture performance of monoethanolamine (MEA) and N-methyldiethanolamine (MDEA) binary aqueous systems were systematically investigated. The density ( ρ ) and viscosity ( ν ) of MEA - MDEA mixtures were measured over a temperature range of 293.15–318.15 K with varying MDEA mole fractions. Key thermodynamic parameters, including viscosity deviation (Δ η ), excess molar volume ( V m E ), and excess Gibbs free energy of activation (Δ G *E ), were subsequently calculated. The results reveal that within an MDEA mole fraction range of 0.35–0.60, Δ η reaches a maximum while V m E remains negative, indicating stronger intermolecular attraction and denser molecular packing. Spectroscopic characterizations combined with quantum chemical calculations further confirm the formation of directional O—N–H hydrogen bonds between the hydroxyl groups of MDEA and the amino nitrogen of MEA, which stabilize the solvent microstructure. Based on these findings, COS absorption-desorption experiments were conducted. Notably, the mixed amine systems with MDEA mole fractions of 0.3852 and 0.5446 exhibited a significant synergistic effect, maintaining over 95 % COS removal efficiency throughout the 120 min absorption process, along with excellent regeneration performance characterized by higher and more stable desorption rates during the 60 min regeneration phase. This work establishes a clear structure-property-reaction correlation, providing valuable molecular-level insights for the rational design of efficient amine-based absorbents for industrial COS capture.
Yuqi Zhang,Yaxuan Zhen,Chunying Zhu,Taotao Fu,Youguang Ma
Chemical absorption has become the most mature and widely used CO 2 capture technology to address CO 2 emissions. Phase change absorbents based on mixed amines combine the advantages of individual amines and reduce regeneration energy consumption. A novel phase change absorbent system based on mixed amine was developed in this study and its CO 2 capture and desorption performance was investigated. The system comprises monoethanolamine (MEA), N-methyldiethanolamine (MDEA), n-butanol and water. Gas-liquid absorption experiments in the microchannel revealed that the flow patterns of the rich phase changed successively through homogeneous flow, irregular droplet flow, tubular-droplet flow and liquid slug flow as the gas-liquid ratio was increased. This transition was influenced by internal circulation, phase change and viscosity, causing the absorption rate to rise initially, then increase slowly before eventually declining. The desorption performance of the saturated rich phase in the MEA-MDEA-n-butanol-H 2 O system was significantly superior to that of the 30 wt% MEA aqueous solution. Comprehensively, the optimal mass ratio of MEA-MDEA-n-butanol-H 2 O was identified as 1.2:1.8:4:3, achieving a higher desorption rate and lower energy consumption. Desorption efficiency and cyclic capacity were 1.8 times those of the 30 wt% MEA aqueous solution, indicating promising application potential.
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