Abstract:

As a green solvent, organic superbase proton-type ionic liquids show unique advantages in the field of CO₂ capture. In this work, we investigated the organic super base dual-cation protic ionic liquid [DBUH]₂[NtBuDEA], synthesized via the reaction between 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and N-tert-butyl-diethanolamine (NtBuDEA). The microstructure, action mechanism and absorption process between the [DBUH]₂[NtBuDEA] and CO₂ were analyzed by density functional theory (DFT) and molecular dynamics (MD) simulation. The results demonstrated that the anion [NtBuDEA]^2- is critical for CO₂ absorption, engaging in chemical bonding with CO₂ to form the alkyl carbonate [NtBuDEACOO]^2-. Additionally, CO₂ molecules diffuse rapidly from the gas phase to the surface of absorbent and accumulate at the gas/absorbent interface. The amount of absorbed CO₂ fluctuates around the average value after reaching maximum absorption. Temperature and pressure are key factors influencing CO₂ uptake and it is favorable for CO₂ capture through decreasing the reaction temperature and increasing the CO₂ partial pressure. Although the existence of water reduces the interaction energy between the absorbent and CO₂, it enhances CO₂ transfer performance, particularly under high pressure conditions, where the CO₂ absorption capacity per molar ionic liquid in water-containing ionic liquids surpasses that in pure ionic liquids.

Key words: CO₂ capture, ionic liquids, density functional theory, molecular dynamics, microcosmic mechanism

摘要：

有机超强碱质子离子液体作为一种绿色溶剂，在CO₂捕集领域展现出独特优势。选择由1，8-二氮杂双环[5.4.0]十一碳-7-烯（DBU）和N-叔丁基二乙醇胺（NtBuDEA）反应生成的有机超强碱双阳离子质子型离子液体[DBUH]₂[NtBuDEA]为吸收剂，通过密度泛函理论和分子动力学模拟分析其与CO₂之间的微观结构、作用机理及吸收过程。研究发现，阴离子[NtBuDEA]^2-的烷基氧负离子在CO₂吸收过程中发挥关键作用，与CO₂发生化学键合作用，生成烷基碳酸盐[NtBuDEACOO]^2-。CO₂分子从气相扩散到吸收剂表面并在气/液界面处聚集，其吸收量在达到最大值后围绕平均值波动。温度和压力是影响CO₂吸收的关键因素，降低吸收温度和提高CO₂分压有利于CO₂的捕集。水的存在虽降低了吸收剂与CO₂的相互作用能，却提高了CO₂的传输性能。

关键词: 碳捕集, 离子液体, 密度泛函理论, 分子动力学, 微观机理