萃取精馏中离子液体萃取剂的研究进展

离子液体的低熔点和不挥发等特点使其较传统的萃取精馏萃取剂具有先天的优势,具有广泛的应用前景。本文介绍了离子液体作为萃取精馏萃取剂的研究进展,综述了汽液平衡法、无限稀释活度系数法等筛选离子液体萃取剂方法的研究成果以及目前用于计算含离子液体体系的相平衡模型研究进展,分析了离子液体萃取剂用于实用仍存在的问题,并展望了今后的研究方向。     

水-乙酸-乙酸丁酯体系汽液平衡研究

用改进Rose釜测定了乙酸-乙酸丁酯、水-乙酸-乙酸丁酯(完全互溶区)体系在101.33 kPa下的汽液平衡数据。考虑乙酸的缔合效应,利用维里方程和Hayden-O'Connell(HOC)模型计算各组分的汽相逸度系数,校正汽相的非理想性,液相的非理想性全部归结到液相活度系数中予以校正。用NRTL,UNIQUAC模型对乙酸-乙酸丁酯的汽液平衡数据进行关联,并得到相应的模型参数、温度偏差和汽相组成偏差。比较二元体系的关联结果,用NRTL模型参数预测了三元汽液平衡数据,计算值与实验值吻合良好,预测精度较好,说明采用的模型参数是可靠的,能够为精馏的设计和模拟计算提供基础热力学数据。     

丁酮-水共沸物系的萃取分离

采用液液萃取进行丁酮-水共沸物系的分离。测定了三元体系丁酮-水-（1-乙基-3-甲基咪唑醋酸盐）的液液平衡,采用NRTL活度系数方程对液液平衡数据进行回归得到组分间的二元交互作用参数。利用流程模拟软件ChemCAD进行了以离子液体为萃取剂的液液萃取过程的模拟,研究了理论板数、溶剂比（萃取剂摩尔流量和原料摩尔流量的比值）对萃取过程的影响,通过灵敏度分析,获得了优化的操作参数。在最适宜操作条件下,丁酮的摩尔分数可达0.999 4,离子液体经过回收能够直接循环使用。     

含离子液体水-醋酸物系等压汽液平衡

在100 kPa下,用改进的Ellis双循环汽液平衡釜测定了含离子液体三乙基铵醋酸盐([N2,2,2,H][AC])质量分数分别为5%,10%,20%时水-醋酸体系的等压汽液平衡数据,并研究了离子液体对水-醋酸体系汽液平衡的影响。实验结果表明:当水-醋酸体系中[N2,2,2,H][AC]的质量分数为5%时水-醋酸二组分物系的汽液平衡线就开始偏离,但是偏离程度比较小;当[N2,2,2,H][AC]的质量分数增加为10%和20%时,偏离程度增大,[N2,2,2,H][AC]对水-醋酸体系表现出明显的盐效应,使水对醋酸的相对挥发度发生改变;随着离子液体[N2,2,2,H][AC]质量分数增大,水-醋酸体系的盐效应越明显,水对醋酸的相对挥发度也随着增加。[N2,2,2,H][AC]可以做为水-醋酸物系萃取精馏分离的有机盐,所测得的汽液平衡数据可为水-醋酸物系萃取精馏的工艺改进、模拟计算提供热力学基础数据。     

噻吩-正辛烷体系等压汽液相平衡研究

利用双循环汽液平衡釜测定101.3 kPa下噻吩-正辛烷体系的汽液相平衡数据.运用该实验结果,进一步获得组分的液相活度系数.实验数据经Herington方法检验,表明符合热力学一致性.采用二元体系UNIQUAC模型对该实验数据进行关联,采用最小二乘法拟合得到UNIQUAC模型参数.结果表明,噻吩在汽相组成的平均绝对偏差为0.0635,取得满意的效果.     

苯-噻吩-二甲基亚砜体系等压汽液相平衡研究

采用汽液双循环相平衡仪测定了101.33 k Pa下苯-噻吩、苯-二甲基亚砜及苯-噻吩-二甲基亚砜的等压汽液相平衡数据。两组二元体系实验数据均通过了Herington面积法的热力学一致性检验,分别采用NRTL和UNIQUAC活度系数模型对二元体系实验数据进行热力学关联,得到了相应的模型参数,温度偏差和汽相组成偏差,关联结果表明两种模型均能较好的关联实验数据,其中UNIQUAC模型的关联结果稍优于NRTL。利用二元体系UNIQUAC模型参数预测三元体系汽液平衡数据,预测值与实验值相比,平均温度偏差1.37 K,汽相各组分平均绝对偏差均在3%以内,获得了较优的预测结果,从而为工业上苯-噻吩萃取精馏分离过程提供可靠的热力学基础数据。     

甲乙酮-水-醋酸体系等压汽液平衡研究

用改进Rose釜测定了甲乙酮-醋酸、甲乙酮-水-醋酸体系在101.33kPa下的汽液平衡数据,其中二元体系汽液平衡数据均通过了热力学一致性检验.考虑醋酸的缔合效应,利用化学理论模型和Hayden-O'Connell(HOC)模型计算各组分的汽相逸度系数,校正汽相的非理想性,液相的非理想性全部归结到液相活度系数中予以校正.用NRTL、UNIQUAC模型对甲乙酮-醋酸的汽液平衡数据进行关联,并得到相应的模型参数、温度偏差和汽相组成偏差.用2组甲乙酮-水体系模型参数、5组水-醋酸体系模型参数结合本研究关联得到的甲乙酮-醋酸体系模型参数对甲乙酮-水-醋酸体系的汽液平衡数据进行了预测,通过比较预测偏差的大小筛选出了最优模型参数组合,用最优模型参数组合进行预测的结果为:温度的平均绝对偏差为0.51℃,甲乙酮、水、醋酸的汽相组成平均绝对偏差分别为0.0047、0.0065、0.0067.预测精度较好,说明采用的模型参数是可靠的,能够为精馏的设计和模拟计算提供基础热力学数据.     

甲醇-甲缩醛-聚甲醛二甲基醚体系汽液平衡

采用改进的Rose平衡釜首次测定了甲醇-DMM2,甲缩醛-DMM22组二元体系在101.3 k Pa条件下的等压汽液平衡数据。运用最大似然原理,借助Aspen Plus软件,采用Wilson,NRTL和UNIQUAC 3大活度系数模型对测定的2组二元汽液平衡数据进行了回归。关联得到了3个模型所对应的二元交互作用参数及汽液平衡数据的计算值,通过计算值与实验值的对比得到了2组数据关于平衡温度和汽相组成的平均绝对偏差∣ΔT∣,∣Δy∣,其平均绝对偏差均分别小于0.40 K和0.013 9。通过比较,结果表明用Wilson模型对2组测定数据进行关联最为适用。回归得到的二元交互作用参数能够应用于含甲醇-甲缩醛-DMM2体系的精馏设计。     

醋酸水体系共沸精馏过程的模拟研究

利用PRO/II软件对醋酸-水-醋酸丁酯体系的共沸精馏进行模拟计算,用Hayden-O’Connell方程计算气相逸度系数,用NRTL方程计算液相活度系数。用实验数据验证模拟结果,结果表明,模拟计算所得的沿塔温度和各组分浓度分布曲线与实验数据相吻合,醋酸-水-醋酸丁酯体系的精馏是一个汽-液-液三相共沸精馏,加料口以上为三相区,加料口附近为三相到两相的过渡区,加料口以下为两相区。     

应用分子聚集理论计算含羧酸体系的汽液平衡

本文论述了应用“分子聚集理论”对含羧酸体系的汽相进行非理想性校正的计算方法.在低压下,含羧酸体系的汽相由于缔合从而引起组分的汽相逸度系数偏离1较大,故对汽相非理想性的校正是不容忽视的.汽相应用“分子聚集理论”改进的维里方程而液相采用UNIQUAC活度系数方程对含羧酸体系的汽液平衡进行计算,取得较好的结果.     

Measurement of activity coefficients at infinite dilution for hydrocarbons in imidazolium-based ionic liquids and QSPR model

The separations of olefin/paraffin, aromatic/aliphatic hydrocarbons or olefin isomers using ionic liquids instead of volatile solvents have interested many researchers. Activity coefficients γ ^∞ at infinite dilution of a solute in ionic liquid are generally used in the selection of solvents for extraction or extractive distillation. In fact, the measurement of γ ⁻⁸ by gas-liquid chromatography is a speedy and cost-saving method. Activity coefficients at infinite dilution of hydrocarbon solutes, such as alkanes, hexenes, alkylbenzenes, styrene, in 1-allyl-3-methylimidazolium tetrafluoroborate ([AMIM][BF₄]) and 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF₆]), 1-isobutenyl-3-methylimidazolium tetrafluoroborate ([MPMIM][BF₄]) and [MPMIM][BF₄]-AgBF₄ have been determined by gas-liquid chromatography using ionic liquids as stationary phase. The measurements were carried out at different temperatures from 298 to 318 K. The separating effects of these ionic liquids for alkanes/hexane, aliphatic hydrocarbons/benzene and hexene isomers have been discussed. The hydrophobic parameter, dipole element, frontier molecular orbital energy gap and hydration energy of these hydrocarbons were calculated with the PM3 semi-empirical quantum chemistry method. The quantitative relations among the computed structure parameters and activity coefficients at infinite dilution were also developed. The experimental activity coefficient data are consistent with the correlated and predicted results using QSPR models.     

Extractive distillation with ionic liquids: A review

Extractive distillation is commonly used for the separation of azeotropic or close‐boiling mixtures in the chemical industry. During the past decade, the use of ionic liquids (ILs) as entrainers has received considerable attention due to their unique advantages when applied in extractive distillation. This work is devoted to providing an easy‐to‐read and comprehensive review on the recent progress made by chemical engineers, focusing on the issues of predictive thermodynamic models, structure‐property relations, separation mechanisms, and process simulation and optimization. This review spans from the molecular level to the industrial scale, to provide a theoretical insight into the molecular interactions between ILs and the components to be separated. Moreover, a comprehensive database on the vapor–liquid equilibria and activity coefficients at infinite dilution concerning ILs is provided as Supporting Information. Concluding remarks are made on the unsolved scientific issues with respect to this promising special distillation technology. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3312–3329, 2014     

A molecular design method based on the COSMO‐SAC model for solvent selection in ionic liquid extractive distillation

In this study, a molecular design method was used to select solvents for extractive distillation. A COSMO‐SAC model was used to screen for prospective solvents from a wide variety of ionic liquids for extractive distillation. Based on the COSMO‐SAC model, the σ‐profile database of ILs was established. Selectivity and solubility were used as the indexes for solvent screening. According to the molecular design method, three suitable extractive distillation solvents were determined for acetonitrile‐water and ethanol‐cyclohexane systems. Vapor ‐ liquid equilibrium experiment were used to test chosen ILs. This study showed that the experimental and design results were consistent with each other. Therefore, this method is effective and applicable to pick ILs solvents for extractive distillation, and the results could provide a theoretical foundation for industrial production. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2853–2869, 2016     

Application of a New Gibbs Energy Equation to Model a Distillation Tower for Production of Pure Ethanol

A steady‐state equilibrium‐stage model based on MESH equations was proposed to simulate saline extractive distillation columns. The interaction parameters between each component of water‐CaCl₂ and ethanol‐water were obtained from mean ionic activity coefficients and vapor‐liquid equilibrium (VLE) experimental data. Additionally, the interaction coefficients for the ethanol‐CaCl₂ pair were fitted to experimental VLE data which were reported by Nishi for the ethanol‐water‐CaCl₂ system. It should be noted that adjustable parameters between each pair were considered to be temperature dependent. The results confirmed that the proposed model could accurately predict the experimental vapor‐liquid equilibrium data for ethanol‐CaCl₂‐water systems. Finally, the validated model was coded using MATLAB software and was solved using the Wang‐Henke method, including the VLE and enthalpy models.     

离子液体在化工分离过程中的应用进展

综述了作为优良的绿色分离溶剂,有望替代传统的易挥发有机溶剂的离子液体在化工分离过程中的应用进展,包括生物制品、金属离子、芳香族化合物、燃油中的硫氮化合物的萃取分离,烟气脱硫、气体分离等吸收过程中的应用,简述了离子液体相平衡方面的基础研究进展.     

Mechanism analysis of solvent selectivity and energy-saving optimization in vapor recompression-assisted extractive distillation for separation of binary azeotrope

Octane and p-xylene are common components in crude gasoline, so their separation process is very important in petroleum industry. The azeotrope and near azeotrope are often separated by extractive distillation in industry, which can realize the recovery and utilization of resources. In this work, the vapor–liquid equilibrium experiment was used to obtain the vapor–liquid equilibrium properties of the difficult separation system, and on this basis, the solvent extraction mechanism was studied. The mechanism of solvent separation plays a guiding role in selecting suitable solvents for industrial separation. The interaction energy, bond length and charge density distribution of p-xylene with solvent are calculated by quantum chemistry method. The quantum chemistry calculation results and experiment results showed that N-formylmorpholine is the best solvent among the alternative solvents in the work. This work provides an effective and complete solvent screening process from phase equilibrium experiments to quantum chemical calculation. An extractive distillation simulation process with N-formylmorpholine as solvent is designed to separate octane and p-xylene. In addition, the feasibility and effectiveness of the intensified vapor recompression assisted extraction distillation are also discussed. In the extractive distillation process, the vapor recompression-assisted extraction distillation process is globally optimal. Compared with basic process, the total annual cost can be reduced by 43.2%. This study provides theoretical guidance for extractive distillation separation technology and solvent selection.     

甲醇-乙酸-丙酸多元体系汽液平衡

用新型泵式沸点仪测定了在100kPa下甲醇-乙酸、甲醇-丙酸、乙酸-丙酸3个二元体系以及甲醇-乙酸-丙酸三元系在不同液相组成时的沸点,并用间接法T-p-x(温度、压力和液相摩尔分数)推算了3个二元体系的汽相平衡组成。3个二元体系活度系数分别用Wilson模型、NRTL模型、Margules模型和van Laar模型进行关联,用最小二乘法求出了它们的液相活度系数模型参数,同时,用这些模型参数来计算它们的汽相摩尔分数。所得的液相活度系数来计算3个二元体系的过量吉布斯自由能函数,且所研究的所有体系中各组分之间不存在共沸点。用3个二元体系Wilson模型参数对所测的三元体系数据进行关联,建立该系统汽液平衡的热力学模型并计算平衡时的汽相摩尔分数和泡点温度。由面积积分法检验这些模型参数计算的3个二元体系相平衡数据,得到很好的热力学一致性。     

Salt effect in distillation: A literature review II

A salt dissolved in a mixed solvent is capable, through preferential association or other structure-related effects in the liquid phase, of altering the composition of the equilibrium vapor phase. Hence salt effect on vapor-liquid equilibrium relationships provides a potential technique of extractive distillation for difficult separations. The literature pertaining to salt effect in vapor-liquid equilibrium and in extractive distillation over the period 1966-present is reviewed, and also the remainder of work up to 1966 not covered in the Part I review.     

Measurement of Activity Coefficients from Unsteady State Evaporation and Growth of Microdroplets

Techniques are presented for determination of activity coefficients of binary systems from unsteady state evaporation and growth of single microdroplets in controlled environments. A high-precision light scattering method based on resonances observed in light scattering by microdroplets was used to determine the size and composition of a microdroplet as functions of time. The techniques were validated through data on growth of glycerol microdroplets in slowly developing water vapor concentration fields and evaporation of microdroplets, containing volatile dimethylphthalate (DMP) and nonvolatile dioctylphthalate (DOP), in vapor-free atmospheres. When the water vapor concentration in the surrounding gas changes slowly a glycerol droplet maintains a dynamic equilibrium with the water vapor; thus the activity coefficient of water was determined from knowledge of the droplet composition and the water vapor saturation ratio in the gas phase. The activity coefficients of DMP were determined on the basis that the instantaneous evaporation rate of a DMP-DOP microdroplet in a vapor-free atmosphere is equal to the product of the activity of DMP and the evaporation rate of a pure DMP droplet. The activity coefficient values obtained from microdroplet experiments are highly reproducible and agree with data available in the literature.