Zubeir Lawien F, Lacroix Mark H M, Kroon Maaike C
Separation Technology Group, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology , Den Dolech 2, 5600 MB Eindhoven, The Netherlands.
J Phys Chem B. 2014 Dec 11;118(49):14429-41. doi: 10.1021/jp5089004. Epub 2014 Dec 1.
The potential of three newly discovered low transition temperature mixtures (LTTMs) is explored as sustainable substituents for the traditional carbon dioxide (CO2) absorbents. LTTMs are mixtures of two solid compounds, a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA), which form liquids upon mixing with melting points far below those of the individual compounds. In this work the HBD is lactic acid and the HBAs are tetramethylammonium chloride, tetraethylammonium chloride, and tetrabutylammonium chloride. These compounds were found to form LTTMs for the first time at molar ratios of HBD:HBA = 2:1. First, the LTTMs were characterized by determining the thermal operating window (e.g., decomposition temperature and glass transition temperature) and the physical properties (e.g., density and viscosity). Thereafter, the phase behavior of CO2 with the LTTMs has been measured using a gravimetric magnetic suspension balance operating in the static mode at 308 and 318 K and pressures up to 2 MPa. The CO2 solubility increased with increasing chain length, increasing pressure, and decreasing temperature. The Peng-Robinson equation of state was applied to correlate the phase equilibria. From the solubility data, thermodynamic parameters were determined (e.g., Henry's law coefficient and enthalpy of absorption). The heat of absorption was found to be similar to that in conventional physical solvents (-11.21 to -14.87 kJ·mol(-1)). Furthermore, the kinetics in terms of the diffusion coefficient of CO2 in all LTTMs were determined (10(-11)-10(-10) m(2)·s(-1)). Even though the CO2 solubilities in the studied LTTMs were found to be slightly lower than those in thoroughly studied conventional physical solvents, LTTMs are a promising new class of absorbents due to their low cost, their environmentally friendly character, and their easy tunability, allowing further optimization for carbon capture.
探索了三种新发现的低转变温度混合物（LTTMs）作为传统二氧化碳（CO₂）吸收剂的可持续替代物的潜力。LTTMs是两种固体化合物的混合物，一种是氢键供体（HBD），另一种是氢键受体（HBA），它们混合后形成液体，其熔点远低于各组分化合物的熔点。在这项工作中，HBD是乳酸，HBA是四甲基氯化铵、四乙基氯化铵和四丁基氯化铵。首次发现这些化合物在HBD:HBA = 2:1的摩尔比下形成LTTMs。首先，通过确定热操作窗口（如分解温度和玻璃化转变温度）和物理性质（如密度和粘度）对LTTMs进行表征。此后，使用在308 K和318 K的静态模式下运行且压力高达2 MPa的重量磁悬浮天平测量了CO₂与LTTMs的相行为。CO₂溶解度随链长增加、压力增加和温度降低而增加。应用彭 - 罗宾逊状态方程关联相平衡。根据溶解度数据确定了热力学参数（如亨利定律系数和吸收焓）。发现吸收热与传统物理溶剂中的吸收热相似（-11.21至-14.87 kJ·mol⁻¹）。此外，还测定了所有LTTMs中CO₂扩散系数方面的动力学（10⁻¹¹ - 10⁻¹⁰ m²·s⁻¹）。尽管在所研究的LTTMs中发现CO₂溶解度略低于深入研究的传统物理溶剂中的溶解度，但由于其低成本。环境友好特性以及易于调节性，LTTMs是一类有前途的新型吸收剂，可用于进一步优化碳捕获。
