Abstract The absorption and desorption isotherms of CO2 in the ionic liquid tetrabutylphosphonium acetate ([P4 4 4 4][OAc]) were experimentally determined at 343.2 K in the pressure range 0–15 bar. Analysed in a mass basis, the CO2 absorption capacity of [P4 4 4 4][OAc] is particularly competitive among that of phosphonium ionic liquids. A contribution of chemical absorption was evidenced from the shape of the isotherms, and a reaction scheme based on the abstraction of an acidic proton in the cation by the basic acetate anion, with a 1:2 (CO2 to ionic liquid) overall stoichiometry, was proposed. The investigation of the solid–liquid equilibria of the mixtures of [P4 4 4 4][OAc] with its homologous halides, namely [P4 4 4 4]Cl and [P4 4 4 4]Br, led to the identification of eutectic behaviours, with the eutectic compositions having melting temperatures below 308.2 K, remarkably lower than the melting temperature of pure [P4 4 4 4][OAc]. The CO2 absorption capacities of these eutectic compositions were then explored at 308.2 K, and also 343.2 K for comparative purposes. While advantageously allowing their utilisation as CO2-capturing solvents at lower temperatures, in comparison to pure [P4 4 4 4][OAc] the eutectic mixtures did not lead to a major loss in CO2 absorption capacity, with greater physisorption compensating for the reduction in chemisorption.

中文翻译：

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乙酸四丁基鏻及其与共阳离子卤化物的低共熔混合物作为二氧化碳捕获的溶剂

摘要 在 343.2 K、0-15 bar 的压力范围内，实验测定了离子液体醋酸四丁基鏻 ([P4 4 4 4][OAc]) 中 CO2 的吸收和解吸等温线。在质量基础上分析，[P4 4 4 4][OAc]的CO2吸收能力在鏻离子液体中特别具有竞争力。化学吸收的贡献由等温线的形状证明，并且基于通过碱性乙酸根阴离子提取阳离子中的酸性质子的反应方案，具有 1:2（CO2 与离子液体）的总化学计量比，是建议的。研究 [P4 4 4 4][OAc] 与其同系卤化物（即 [P4 4 4 4]Cl 和 [P4 4 4 4]Br）的混合物的固液平衡，从而确定了共晶行为, 共晶成分的熔化温度低于 308.2 K，明显低于纯 [P4 4 4 4][OAc] 的熔化温度。然后在 308.2 K 和 343.2 K 下探索这些共晶组合物的 CO2 吸收能力以进行比较。虽然有利地允许它们在较低温度下用作 CO2 捕获溶剂，但与纯 [P4 4 4 4][OAc] 相比，低共熔混合物不会导致 CO2 吸收能力的重大损失，更大的物理吸附补偿了化学吸附。