The formation of high CO2 loading solid phase from 1,4-butanediamine/ethylene glycol biphasic solvent: Phase-changing behavior and mechanism

• Published in: Separation and purification technology 2023-10, Vol.323, p.124397, Article 124397
• Main Authors: Wang, Cunshi, Xiao, Gongkui, Zhou, Xiaobin, Zhu, Qiuzi, Chen, Yuanyi, Gao, Zhimin, Liu, Chao, Zhu, Jianzhong
• Format: Article
• Language: English
• Subjects: Alkyl-carbonate; CO2 absorption; Liquid-solid phase change; Mechanism; Non-aqueous
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2023.124397

[Display omitted] •A novel biphasic solvent with a high CO2 loading in the solid phase was developed for CCUS.•The formation of H-bonding between EG and BDA was confirmed.•Particle self-aggregation induces the liquid–solid phase transition.•The interaction between the absorbed products was elucidated by ESP and IGMH analysis.•The phase-change mechanism of CO2 absorption into BDA/EG system was elucidated. Liquid-solid phase change absorption has been considered a promising strategy for CO2 capture. To achieve efficient and economic CO2 capture in industrial-scale applications, it is essential to understand the phase-change behaviors and mechanisms of the biphasic system. In this study, a blend of 1, 4-Butanediamine (BDA) and ethylene glycol (EG) was developed as a biphasic solvent that can form a high CO2 loading solid phase product (BESP) after absorption. The total solvent loading reached 0.9039 mol·mol−1, with 90.74% of the loading enriched in the solid phase, which only accounts for 51.01% of the total solvent mass. Based on the 13C NMR analysis and quantum chemical calculations, the reaction and phase change mechanism of CO2 capture was proposed. The BDA/EG system absorbs CO2 to generate carbamate species, protonated amines and alkyl-carbonates, which combine each other through hydrogen bonding or electrostatic attraction. The self-aggregation of zwitterions and the high polarity of the absorption products are considered to be the main reasons for the phase change. Alkyl-carbonate species are believed to co-precipitate through organic gelation via van der Waals force with the carbamate or protonated amine. Moreover, the viscosity, turbidity, solid-phase mass, and particle size distribution changes also demonstrate the growth and aggregation of particles during absorption. BESP, identified as a coupling product of carbamate and alkyl-carbonate ([2BDAH+COO-]·[EG‐OCO2-]), decomposes at a peak temperature of 127.4 °C. The calorimetric method determined regeneration heat to be approximately 3.17 GJ·ton-1 CO2, indicating its potential for alternative uses rather than direct heat regeneration. Such a biphasic solvent may provide unique solutions for industries to reduce CO2 emissions.