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

作者：Wang, Cunshi; Xiao, Gongkui; Zhou, Xiaobin; Zhu, Qiuzi; Chen, Yuanyi; Gao, Zhimin; Liu, Chao; Zhu, Jianzhong^*

来源：SEPARATION AND PURIFICATION TECHNOLOGY, 2023, 323: 124397.

DOI：10.1016/j.seppur.2023.124397

• CO2 absorption
• Non-aqueous
• Liquid-solid phase change
• Alkyl-carbonate
• Mechanism

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 C-13 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 alkylcarbonates, which combine each other through hydrogen bonding or electrostatic attraction. The selfaggregation 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 degrees 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.

• 单位
  桂林理工大学; 河海大学