Thermodynamics and separation process for quaternary acrylic systems

Vapor‐liquid equilibrium (VLE) and liquid‐liquid equilibrium (LLE) data of binary and ternary acrylic systems were systematically measured. Subsequently, VLLE phase diagrams of binary systems, tridimensional VLE phase diagrams of methyl acrylate (MA)‐methanol (Me)‐H₂O ternary system, and quaternary LLE phase diagrams of MA‐Me‐H₂O‐methyl acetate (MeOAc) system were constructed. These diagrams clearly demonstrated the effects of temperature on phase equilibrium. The experimental data was fitted by the NRTL and UNIQUAC models, and the best‐fitted parameters were used to predict interaction properties of ternary and quaternary mixture. Therefore, the phase equilibrium data were provided as reference for the design of acrylic systems rectification or extraction process. Residue curve was mapped out for MA‐Me‐H₂O system through Aspen plus software. Finally, using thermodynamics and residue curve as theoretical basis, two novel separation processes were proposed and applied to the quaternary acrylic systems. © 2015 American Institute of Chemical Engineers AIChE J, 62: 228–240, 2016     

Ternary liquid-liquid phase behavior by decorated-uniquac

To investigate the applicability of the decorated-UNIQUAC model for multicomponent multiphase liquid mixtures, equilibrium calculations were carried out for a variety of model ternary systems, and some typical predictions were introduced. The predicted phase behavior was less limited and more complicated than that of UNIQUAC without disagreement with experimental observations on the progressional behavior of tie lines. The binodal predictions were found very sensitive with respect to the model parameters, as expected in condensed phases. The general features of nonisland type of ternary LLE were excellently reproduced by the decorated-UNIQUAC.     

Understanding phase behaviors of multicomponent polymer mixtures based on a molecular thermodynamic framework combined with molecular simulation

A new molecular thermodynamic model based on a closed-packed lattice model is developed for multicomponent systems. Based on Monte-Carlo (MC) simulation results, we introduce new universal functions to consider the chain length dependence of polymers, and are able to obtain more accurate critical volume fraction results in liquid–liquid equilibrium (LLE) calculations. In associated blend systems, specific interactions are used to characterize strongly interacting polymer mixtures with a secondary lattice. To minimize the number of adjustable model parameters, chain length parameters are calculated in a conventional way using molecular weight and specific volume. Our proposed model successfully describes binary LLE for polymer-solvent systems. Furthermore, the model parameters obtained from these binary systems are directly used to predict corresponding LLE ternary systems, and the results were in good agreement with experimental data.     

1-甲氧基-2-丙醇水癸烷的液液平衡

通过测定可作界面活性剂的 1 甲氧基 2 丙醇、癸烷和水的液液相平衡数据 ,考察 1 甲氧基 2 丙醇、癸烷以及水的混合液三元体系的相行为 ,并将实验结果和extendedUNIQUAC溶液模型的计算结果进行比较。结果表明 :在 2 98.15K时测得 1 甲氧基 2 丙醇、癸烷和水的相平衡数据和用extendedUNIQUAC模型推算结果相当吻合 ,extendedUNIQUAC模型成功地描述了 1 甲氧基 2 丙醇、癸烷和水混合溶液的液液相平衡。     

Phase Equilibria for Ternary Liquid Systems of (Water + Carboxylic Acid + 1‐Heptanol) at 293.15 K: Modelling Considerations

Liquid‐liquid equilibrium data of the solubility curves and tie‐line end compositions are presented for mixtures of [water (1) + formic acid, or acetic acid, or propanoic acid (2) + 1‐heptanol (3)] at T = 293.15 K and P = (101.3 ± 0.7) kPa. The properties and liquid‐liquid equilibria (LLE) of associated ternary systems have been correlated using a solvatochromic approach SERLAS. The tie‐lines were also predicted using the UNIFAC‐original model. The proposed model appears to be an improvement in data fit for the ternary systems yielding a mean error of 3.8% for all the systems considered.     

Calculations of complex phase equilibrium by equal‐area method

The equal‐area (EA) method is studied with respect to its applicability to a wide range of phase equilibrium scenarios for pure fluids and binary mixtures. The study covers vapor‐liquid equilibrium (VLE), liquid–liquid equilibrium (LLE), solid‐liquid equilibrium (SLE) and their crossover transitions. The thermodynamic models studied include equation of state, activity coefficient and solid solubility models and their combinations. The performance of the EA method for chain molecules, at very low temperature and nearby the critical point is also investigated. We conclude that the EA method is very reliable and efficient and has a number of advantages over the conventional method. Finally, we apply the EA method to the regression of the model parameters to demonstrate its attractive application. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

An electrolyte CPA equation of state for mixed solvent electrolytes

Despite great efforts over the past decades, thermodynamic modeling of electrolytes in mixed solvents is still a challenge today. The existing modeling frameworks based on activity coefficient models are data‐driven and require expert knowledge to be parameterized. It has been suggested that the predictive capabilities could be improved through the development of an electrolyte equation of state. In this work, the Cubic Plus Association (CPA) Equation of State is extended to handle mixtures containing electrolytes by including the electrostatic contributions from the Debye–Hückel and Born terms using a self‐consistent model for the static permittivity. A simple scheme for parameterization of salts with a limited number of parameters is proposed and model parameters for a range of salts are determined from experimental data of activity and osmotic coefficients as well as freezing point depression. Finally, the model is applied to predict VLE, LLE, and SLE in aqueous salt mixtures as well as in mixed solvents. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2933–2950, 2015     

甲基丙烯酸甲酯-甲醇体系的双溶剂萃取

针对甲基丙烯酸甲酯（MMA）-甲醇共沸体系,常规精馏难以分离。提出采用己烷-水双溶剂体系萃取分离MMA的新工艺。测定了不同温度下MMA（1）+甲醇（2）+正己烷（3）+水（4）、MMA（1）+甲醇（2）+环己烷（3）+水（4）两个体系的相平衡数据,考察了不同温度下溶剂正己烷/环己烷、水的用量对萃取分配系数和选择性系数的影响。在实验数据的基础上,进一步采用UNIQUAC模型对该体系的相平衡进行了拟合,获得了模型参数。     

液液平衡和会溶现象

提出了液体混合的通用Gibbs自由能模型,据此建立了液液平衡的双节线、旋节线和临界点方程.这些方程不仅适用于小分子液体混合物,而且亦适用于高分子溶液.计算结果表明,它们能满意地描述各种类型的液液平衡及其会溶现象.     

Ternary phase equilibria of tetrahydrofuran-polystyrene-polytetrahydrofuran

Phase diagrams including tie lines for three ternary solvent-polymer-polymer systems consisting of tetrahydrofuran-polystyrene-polytetrahydrofuran at 30°C have been obtained using size exclusion chromatography. The effect of molecular weight on polymer-polymer compatibility has been investigated. A liquid-liquid equilibria (LLE) database has been used to compare UNIQUAC and a modified Flory-Huggins model with respect to their ability to correlate LLE data. Both models contain six adjustable parameters. As previously observed in the literature, the estimation of the UNIQUAC parameters is troublesome due to the model's complexity and the intercorrelation of the parameters. On the basis of better performance and ease of use, the Flory-Huggins model is recommended. The Flory-Huggins model is capable of accurately describing LLE of systems which exhibit quite complex tie line behavior. © 1993 John Wiley & Sons, Inc.     

局部组成模型的研究(Ⅰ)似化学局部组成的分子模型

本文以Guggenheim似化学关系式及单流体模型为基础,推导得出了似化学局部组成计算式及活度系数分子模型。它用于非极性流体,具有参数少、精度高的优点;但对于极性流体则不如UNIQUAC。本文采用Baxter粘性硬球模型和PY统计近似方法,得到了6组二元体系的超额Gibbs自由能的数值解,以此检验了Wilson、NRTL、UNIQUAC、汪-赵和本文模型。结果表明,对于分子大小相同的体系,本文模型的预测性最佳;对于分子大小不等的体系,UNIQUAC优于本模型。     

Measurement and correlation of liquid-liquid equilibrium for the ternary system (water + 1,2-dichloroethane + sulfolane) at 288.15, 298.15, and 308.15 K

Sulfolane is an important aprotic polar solvent. Liquid-liquid equilibrium(LLE) data for the ternary systems of water + 1,2-dichloroethane + sulfolane were measured at temperatures of 288.15, 298.15 and 308.15 K under the atmospheric pressure. The distribution coefficient and selectivity were determined from the measured LLE data, which showed that 1,2-dichloroethane is a suitable extractant for the recovery of sulfolane from its aqueous solution. The nonrandom two-liquid(NRTL) model and the uni...     

A new insight to validation of local composition models in binary mixtures using molecular dynamic simulation

A computational method based on molecular dynamics (MD) simulation is developed to predict the interaction parameters in local composition (LC) models such as Wilson, nonrandom two‐liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC) applicable in vapor‐liquid equilibrium calculations so that LC models are validated. The five binary mixtures of water‐acetonitrile, water‐isopropanol, methanol‐chloroform, acetone‐cyclohexane, and meta xylene‐benzene were simulated. The MD simulations are performed using the condensed phase optimized molecular potential for atomistic simulation studies force field and all ranges of radial distribution function (RDF) are considered. In addition, the interaction parameters are determined by optimization through experimental data and are compared with the MD results. The interaction parameters are calculated through RDF where the effective radius is investigated by experimental data. The present results demonstrate that interaction parameters are composition dependent which are best fitted by a third‐order polynomial relation. Based on the deviation in the activity coefficients, the results of the UNIQUAC model are more accurate than Wilson and NRTL models. © 2015 American Institute of Chemical Engineers AIChE J, 62: 275–286, 2016     

Liquid–liquid extraction of toluene from its mixtures with aliphatic hydrocarbons using an ionic liquid as the solvent

The knowledge of liquid–liquid equilibria (LLE) of the ternary systems (alkane/toluene/ionic liquid) is essential to develop thermodynamic models for liquid–liquid extraction of aromatics such as toluene from its mixtures with aliphatic hydrocarbons. In this study, new experimental LLE data for the ternary systems (hexane and heptane/toluene/1-methyl-3-octylimidazolium tetraflouroborate) are measured at T = 298.15 K and atmospheric pressure. The capability of ionic liquid for extracting toluene from its azeotropic mixture with aliphatic hydrocarbons (hexane and heptane) has been evaluated by the selectivity and solute distribution coefficients. The Othmer–Tobias equation has been applied to check the consistency of the experimental tie-lines. Finally, the obtained experimental LLE data are satisfactorily correlated by the nonrandom two-liquid model.     

Theory of chromatography of linear and cyclic polymers with functional groups

We discuss the chromatographic behavior of linear polymers and rings having specific (functional) adsorption-active groups. Functionalized eight-shaped, daisy-like and theta-shaped macromolecules are considered as well. By using a model of an ideal chain with point-type defects in a slit-like pore we derive equations for the distribution coefficient covering all modes of chromatography of functionalized polymers of any molar mass in both narrow and wide pores. Additionally simple approximate formulae are obtained for a number of important modes of chromatography; chromatograms are simulated for model mixtures of polydisperse non-functional and functional polymers. By using the theory we analyze separation of polymers by molar mass, functionality and topology. Although there is a principal possibility to use adsorption chromatography or size-exclusion chromatography (SEC), we conclude that the liquid chromatography at the critical condition (LCCC) is especially efficient for separation of polydisperse polymers by both functionality and topology. The theory predicts that functionalized linear and cyclic polymers can be separated from each others by LCCC even better than non-functionalized ones. The LCCC behavior of some other types of polymers such as comb-like and semicyclic ones is discussed as well.     

Measurements and thermodynamic modeling of liquid–liquid equilibria in ternary system 2-methoxy-2-methylpropane+p-cresol+water

Liquid–liquid equilibrium(LLE)data for the ternary system 2-methoxy-2-methylpropane(methyl tert-butyl ether)+ p-cresol + water was measured at atmospheric pressure and temperatures of 298.15 K and 313.15 K.From the distribution coefficients and selectivity,it was found that 2-methoxy-2-methylpropane is an efficient solvent to extract p-cresol from wastewater.The consistency of the experimental tie-line data was verified with the Hand and Bachman equations.These data were also correlated with the non-random two liquid(NRTL)and universal quasi-chemical correlation activity coefficient(UNIQUAC)models to yield binary interaction parameters for p-cresol extraction process evaluation.Both models agreed with experiments very well,yet the NRTL model showed even smaller average deviation than the UNIQUAC model.     

Isobaric Vapor-Liquid-Liquid Equilibria for 1-Butanol + Water + 2,3-Butanediol at 101.3 kPa

Vapor-liquid-liquid equilibria (VLLE) data were determined for the ternary system 1-butanol + water + 2,3-butanediol at 101.3 kPa. A binary heterogeneous minimum boiling azeotrope was found at 365.95 K with mass fractions of 0.526 and 0.474 for 1-butanol and water, respectively. A modified UNIQUAC model was used to predict VLLE by using experimental data, including VLE of 1-butanol + 2,3-butanediol, VLE of water + 2,3-butanediol, LLE of 1-butanol + water, and one LLE tie-line of 1-butanol + water + 2,3-butanediol. The experimental data were compared with the calculated values. The absolute average relative deviations (AARD) are 1.65%, 1.72%, and 2.22% for organic liquid phase, aqueous liquid phase, and vapor phase, respectively. It demonstrates an appropriate fit of the modified UNIQUAC model.     

一个非局部组成型活度系数方程

根据前文提出的液体混合的通用Gibbs自由能模型,导得了一个两参数非局部组成型活度系数方程.它适用于各种小分子液体混合物和高分子溶液,并能由二元参数预测多元系汽液平衡.对小分子液体混合物的泡点计算结果表明,除了醇/烃系统外,计算准确度不逊于局部组成型活度系数方程.它对高分子溶液的适用性则明显地优于UNIQUAC等方程.     

An ionic liquid proposed as solvent in aromatic hydrocarbon separation by liquid extraction

Liquid–liquid extraction is the most common method for extraction of aromatics from their mixtures with aliphatic hydrocarbons. An ionic liquid (IL) 1‐butyl‐1‐methylpyrrolidinium bis (trifluoromethylsulfonyl) imide [BMpyr][NTf₂] was tested as solvent for this separation. The liquid–liquid equilibria (LLE) of the ternary mixtures heptane + benzene, or toluene, or ethylbenzene + [BMpyr][NTf₂] were carried out at 298.15 K. The solvent ability of the IL was evaluated in terms of solute distribution ratio and selectivity. The results were compared with those previously reported for the extraction of aromatics from its mixtures with heptane by using ILs. The conventional process using sulfolane as solvent was discussed. The experimental LLE data were correlated by non‐random two liquid equation. A proposal of extraction process with this IL as solvent is simulated by conventional software and the results are shown. © 2009 American Institute of Chemical Engineers AIChE J, 2010