Insight and assessment of CO2 capture using diethylenetriamine/2-(diethylamino)ethanol/n-propanol water-lean biphasic solvent: Experimental and quantum chemical calculation

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-11, Vol.500, p.156834, Article 156834
• Main Authors: Zhang, Guangyao, Qian, Juan, Liu, Jiangsheng, Yu, Tong, Liu, Qixin
• Format: Article
• Language: English
• Subjects: Absorbent stability; Biphasic solvent; CO2 capture; DFT calculation; Mechanism analysis
• ISSN: 1385-8947
• DOI: 10.1016/j.cej.2024.156834

[Display omitted] •A highly efficient and stable alcohol-regulated DETA + DEEA + PrOH water-lean biphasic solvent was proposed for CO2 capture.•PrOH reacted with the amine-CO2 reaction product and converted it into propyl carbonate to indirectly absorb CO2.•Total desorption energy consumption (2.05 GJ·ton−1 CO2) is 46 % lower than 5 M MEA, and its corrosiveness to carbon steel is negligible.•Insight into the priority of amine functional groups involved in CO2 absorption within water-lean biphasic solvent.•Innovatively revealed the pathway of PrOH involved in CO2 absorption reactions through DFT calculations. Biphasic solvents hold immense promise for CO2 capture, but often struggle to maintain stable performance over long-term cyclic use. Alcohols possess low dielectric constants, which can provide protons for amine-CO2 reaction products, enhancing the regeneration performance of absorbents while maintaining stability. In this study, diethylenetriamine (DETA) + 2-(diethylamino)ethanol (DEEA) + H2O was used as the biphasic solvent, with n-propanol (PrOH) serving as the regulator to develop the DETA + DEEA + PrOH water-lean biphasic solvent. Replacing half of the water with PrOH improved the cyclic stability of the absorbent, reduced the rich phase ratio (46 %) and energy consumption (2.05 GJ·ton−1 CO2), while effectively enhanced corrosion resistance and thermal stability, confirming the feasibility of PrOH as the regulator. The detailed reaction mechanism of the absorbent for CO2 absorption was elucidated through 13C NMR and DFT calculations. Quantum chemical calculations have provided the first compelling evidence for PrOH’s involvement in the absorption reaction: PrOH stores the reaction products in the form of PrOCOOH/PrOCOO−. By regenerating DETA, it restores its CO2 absorption capacity. Through polarity and hydrogen bonding, the reaction products aggregate in one phase, enhancing CO2 loading. In summary, the PrOH regulated water-lean biphasic solvent presents a highly promising absorbent for industrial use.