咪唑类离子液体吸收低压苯蒸汽的热力学研究

南京大学学报(自然科学版) ›› 2015, Vol. 51 ›› Issue (4): 700–706.

咪唑类离子液体吸收低压苯蒸汽的热力学研究

李长浩¹，巫先坤²，王志祥¹*，张锋²*，张志炳²

出版日期:2015-07-07 发布日期:2015-07-07
作者简介:(1. 中国药科大学工学院,南京,210009;2. 南京大学化学化工学院,南京210093)
基金资助:
基金项目：国家自然科学基金(21306078)

Thermodynamic Study on absorption of low-pressure benzene vapor in imidazolium-based ionic liquids

Li Changhao¹, Wu Xiankun², Wang Zhixiang¹,*, Zhang Feng²,*, Zhang Zhibing²

Online:2015-07-07 Published:2015-07-07
About author:(1. School of Engineering, China Pharmaceutical University, Nanjing, 210009, China; 2. School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210093, China)

摘要/Abstract

摘要： 在303.2 ~ 333.2 K范围内，首先考察了低压苯蒸汽在5种咪唑离子液体中的溶解性能。然后采用NRTL活度系数模型关联二元体系的等温汽液平衡，关联误差在2%以内。最后，基于关联数据，获得了苯蒸汽在离子液体中的无限稀释活度系数和亨利系数，评价了体系的热力学变化：吸收焓、吸收熵与偏摩尔过量焓。结果表明，亨利系数随温度增大而增大，离子液体吸收苯蒸汽属于物理吸收。相同阳离子，当阴离子由[BF^-₄]、[PF^-₆]变为[Tf₂N^-]，无限稀释活度系数逐渐降低，混合溶液由正偏差溶液变为负偏差溶液，溶解度增大；阴离子相同时，延长阳离子烷基侧链长度，可降低无限稀释活度系数。热力学分析表明离子液体吸收苯蒸汽由体系的吸收熵控制。[hmim][Tf2N]吸收熵变值最大，与苯混合物的热力学稳定性高，分子间作用力较强，对苯蒸汽的溶解性能强。苯的溶解度由阴离子决定，且按如下顺序递增：[BF^-₄] < [PF^-₆] < [Tf₂N^-]。

Abstract: Low vapor-liquid equilibria (VLE) of benzene in the selected five imidazole ionic liquids (ILs) was studied. VLE measurements were conducted over extremely low concentration range and at temperature varying from 303.2 K to 333.2 K. Based on the VLE data, Infinite Dilution activity coefficient (γ∞) and Henry’s constant (H) were derived and described formally by using NRTL activity coefficient model, with the deviation being less than 2%. In addition, the partial molar excess enthalpies at infinite dilution (Hi^E,∞) have been derived from the temperature dependence of the limiting activity coefficients, and partial molar enthalpies and entropies at infinite dilution have also been obtained from the temperature dependence of the Henry’s constants. The experimental results indicated that Henry’s constants increase with a rise in temperature, indicating that absorption of benzene in ILs is a typical physical absorption. When changing anion species of ILs from [BF^-₄] to [PF^-₆] or [Tf₂N^-], the γ∞ gradually decreases, and the behavior of benzene vapor dissolved in ILs gradually changes from positive deviation from Raoult’s law to negative deviation. The length of the alkyl chain slightly enhances the solubility of benzene. From analysis of thermodynamic properties, it is found that the absorption of benzene in imidazolium-based ILs is dominated by entropy. The [hmim][Tf2N] possesses the greatest entropy, leading to better absorption capability and thermodynamical stability. The anion of ionic liquids play a more important role in the solubility of benzene than cation, and the effect increases following the sequence [BF^-₄] < [PF^-₆] < [Tf₂N^-]

李长浩¹，巫先坤²，王志祥¹*，张锋²*，张志炳². 咪唑类离子液体吸收低压苯蒸汽的热力学研究[J]. 南京大学学报(自然科学版), 2015, 51(4): 700–706.

Li Changhao¹, Wu Xiankun², Wang Zhixiang¹,*, Zhang Feng²,*, Zhang Zhibing². Thermodynamic Study on absorption of low-pressure benzene vapor in imidazolium-based ionic liquids[J]. Journal of Nanjing University(Natural Sciences), 2015, 51(4): 700–706.

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