Effect of methylimidazolium-based ionic liquids on vapor–liquid equilibrium behavior of tert-butyl alcohol + water azeotropic mixture at 101.3 kPa

Three ionic liquids(ILs),1-ethyl-3-methylimidazolium bromine([EMIM]Br),1-butyl-3-methylimidazolium bromine([BMIM]Br),and 1-hexyl-3-methylimidazolium bromine([HMIM]Br),were used as the solvent for separation of {tert-butyl alcohol(TBA)+ water} azeotrope.Vapor–liquid equilibrium(VLE)data for {TBA + water + IL}ternary systems were measured at 101.3 k Pa.The results indicate that all the three ILs produce an obvious effect on the VLE behavior of {TBA + water} system and eliminate the azeotropy in the whole concentration range.[EMIM]Br is the best solvent for the separation of {TBA + water} system by extractive distillation among the three ILs.The experimental VLE data for the ternary systems are correlated with the NRTL model equation with good correlations.Explanations are given with activity coefficients of water and TBA,and the experimental VLE-temperature data for {TBA or water + IL} binary systems.     

Isobaric vapor–liquid equilibrium for binary system of aniline+methyl-N-phenyl carbamate

In this study,the quasi-static ebulliometric method was used to measure both of the vapor pressures of methyl N-phenyl carbamate(MPC),and the isobaric vapor–liquid equilibrium(VLE) data of the aniline and MPC binary system.The measured vapor pressure data of MPC,at different temperature ranging from 369.60 to 389.54 K,fitted well with the Antoine equation.The VLE data for the aniline and MPC system at(2.00,4.00,6.00,7.00 and 8.00) k Pa were correlated by both of nonrandom two-liquid(NRTL) and Wilson models.The parameters of the two models were obtained by regressing the experimental data,with the absolute temperature deviations of 0.54 K and 0.53 K,respectively.The relative volatility of the binary system calculated was all far more than 1,which gives the conclusion that the high purity MPC can be separated from aniline and MPC binary system by rectification or distillation technology.     

High pressure vapor–liquid equilibrium for the ternary system ethanol/(±)-menthol/carbon dioxide

In this work the phase behavior of the ternary system ethanol/(±)-menthol/CO₂ was studied at the temperatures of 313 and 323 K, in the pressure range 8–10 MPa. Experiments were performed using a high pressure phase equilibrium apparatus with a visual cell. CO₂ is more selective toward ethanol, separation factors ranging from 1.6 to 7.6 at the conditions tested. The pTxy data obtained were correlated with the Peng–Robinson equation of state combined with the Mathias–Klotz–Prausnitz mixing rule. The model gave a good fitting to the data, with a total average absolute deviation of 3.7%, and was able to predict the occurrence of a three-phase region observed experimentally at 313 K and 9 MPa.     

Measurements and correlation of liquid–liquid equilibrium data for the ternary(methyl tert-butyl ketone + o,m, p-benzenediol + water)system at(333.2, 343.2 and 353.2) K

In this work, liquid–liquid equilibria(LLE) data for the ternary system methyl tert-butyl ketone(MTBK) + o, m,p-benzenediol + water were investigated at 333.2 K, 343.2 K and 353.2 K under 101.3 kPa. The performance of MTBK to extract o, m, p-benzenediol from wastewaters was estimated by partition coefficients and separation factors. The Hand and Bachman equations were both applied to check the reliability of the experimental LLE data. Furthermore, the Non-Random Two-Liquid(NRTL) and Universal Quasi Chemical(UNIQUAC) models were applied to correlate the measured LLE data. The results showed a good agreement with the determined ternary LLE data with the root-mean-square error(RMSE) values below 0.71%. MTBK was proved to be a promising extracting agent in extracting benzenediols from effluents.     

Salt effect on the liquid–liquid equilibrium of the ternary (water + phenol + methyl isobutyl ketone) system: Experimental data and correlation

The effects of NaCl, KCl and Na_2SO_4 on the liquid–liquid equilibrium(LLE) data for the ternary system, water+ phenol + methyl isobutyl ketone, were determined at 0.101 MPa and 333.15 K and 343.15 K.The nonrandom two-liquid(NRTL) model was used to correlate the experimental data and to yield corresponding binary interaction parameters for these salt containing systems.The Hand and Othmer–Tobias equations were used to confirm the dependability of the determined LLE data in this work.Distribution coefficient and selectivity were used to evaluate the extraction performance of methyl isobutyl ketone with the existence of salt.The magnitude of salt effect on the water + phenol + methyl isobutyl ketone(MIBK) system is in the following order: Na_2SO_4NaClKCl.     

Studying the structure of the vapor–liquid equilibrium diagram of the butyl propionate–propionic acid–butyl butyrate–butyric acid system

This article deals with specific structural features of the vapor–liquid equilibrium diagram of the butyl propionate–propionic acid–butyl butyrate–butyric acid four-component system, which is of industrial importance and contains biazeotropic ester–acid constituents. The positions of some isomanifolds in the concentration tetrahedron and in its constituents are reported.     

Density,refractive index and liquid–liquid equilibrium data of polyethylene glycol 3000 + potassium formate + water at different pH values

New liquid–liquid equilibrium data for polyethylene glycol(PEG) 3000 + CHO_2K + H_2O systems were measured at 298.15 K and pH values of 7.95, 8.40 and 9.98. It was found that an increase in pH caused the binodal curve to be displaced downward and the two-phase region to expand. Accordingly, the binodal curve was adjusted to the Pirdashti equation and the tie-line compositions were correlated using the Othmer–Tobias, Bancroft and Hand equations. The study measured the refractive index and densities of several homogeneous binary and ternary solutions. The solutions were used for calibration within a range of 0% to 30% of the mass of the PEG and potassium formate. The density and refractive index data show a linear variation with the mass fraction of the polymer and the salt. The effect of pH on the binodal, tie-line lengths(TLL) and slope of the tie-line(STL) in the systems was examined. It was found that an increase in pH increased the TLL and decreased the STL. It was observed that the density of the aqueous two-phase system was influenced by the TLL. The difference in density between phases(Δρ) increased as the TLL and pH increased. It was found that the TLL and Δρ showed a linear relationship. The effective excluded volume(EEV) of the PEG was obtained and it was found that EEV also increased as the pH increased.     

Investigation of liquid–liquid equilibrium of the ternary system(water +1,6-diaminohexane + 2-methyl-1-propanol or 3-methyl-1-butanol) at different temperatures

In this study, the LLE data of ternary system (water+1,6-diaminohexane+2-methyl-1-propanol) and (water+1,6-diaminohexane+3-methyl-1-butanol) were measured at 293.15, 303.15 and 313.15 K under atmospheric pressure. Reliability of the experimental tie-line data was checked by empirical Hand, Othmer-Tobias and Bachman equations. Distribution coefficient (D) and selectivity (S) were calculated in order to investigate capability of the studied organic solvents for 1,6-diaminohexane extraction. The high values of separation factors demonstrated that 2-methyl-1-propanol and 3-methyl-1-butanol were applicable for this purpose. The experimental data were correlated by nonrandom two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models. The percent-root-mean-square deviation (RMSD) values for NRTL and UNIQUAC models were less than 0.15, which indicated that the experimental data have been sufficiently correlated.     

Liquid–liquid equilibrium extraction of ethanol with mixed solvent for bioethanol concentration

The extraction of ethanol with the solvents of aldehydes mixed with m-xylene was studied for the bioethanol concentration process.Furfural and benzaldehyde were selected as extraction solvents,with which the solubility of water is small,expecting large distribution coefficient of ethanol.The liquid–liquid two-phase region was the largest with m-xylene solvent,followed by benzaldehyde and furfural.The region of two liquid–liquid phase became larger with the mixed solvent of m-xylene and furfural than that with furfural solvent.The NRTL model was applied to the ethanol–water–furfural–m-xylene system,and the model could well express the liquid–liquid equilibrium of the system.For any solvent used in this study,the separation selectivity of ethanol relative to water decreased as the distribution coefficient of ethanol increased.The separation selectivity with m-xylene was the largest among the employed solvents,but the distribution coefficient was the smallest.The solvent mixture of furfural and m-xylene showed relatively high distribution coefficient of ethanol and separation selectivity,even in the higher mass fraction of m-xylene in the solvent phase.The ethanol extraction with a countercurrent multistage extractor by a continuous operation was simulated to evaluate the extraction performance.The ethanol content could be concentrated in the extract phase with relatively small number of extraction stages but low yield of ethanol was obtained.     

Curvature dependence of Henry's law constant and nonideality of gas equilibrium for curved vapor–liquid interfaces

Curved interfaces between coexisting vapor and liquid phases are ubiquitous in nature, and the question of whether the Henry's law is applicable for highly curved vapor/liquid interfaces remains unsolved. Using stable surface nanobubbles that have highly curved interfaces as examples, we investigate the viability of Henry's law with molecular simulations and thermodynamic analysis. We show that the prediction of Henry's law displays an increasingly deviation from the simulation results as nanobubble curvature increases. Such a curvature dependence of Henry's law constant is ascribed to the nonideality of gas in liquid phase because of the required gas supersaturation for stabilizing nanobubbles. Based on the effect, we develop a relationship for determining Henry's law constant from the level of gas supersaturation, as well as a robust relationship between gas supersaturation and nanobubble radius.     

常压下环己烯-环己醇汽液平衡的测定和关联

Many by-products are generated in the process of oxidizing cyclohexene to produce 1,2-epoxycyclohexane by hydrogen peroxide,including cyclohexanol,cyclohexanone,etc.To obtain high-purity 1,2-epoxycyclohexane, the by-products and unreacted cyclohexene must be removed through rectification,in which the vapor-liquid equilibrium(VLE)data of the system are needed.In this study,the VLE data of cyclohexene-cyclohexanol system were studied at 101.3 kPa using an improved EC-2 VLE still.The thermodynamic consistency of the data was examined by Herington’s method.The results obtained were exemplary.The VLE data were correlated by the Wilson equation. The difference between the calculated values and the experimental data is minor,indicating that the VLE data are suitable for engineering design.     

碳酸二甲酯-乙醇体系等压汽液相平衡

采用双循环汽液平衡釜测定了碳酸二甲酯-乙醇在100 kPa下的汽液平衡数据。实验数据经Herington面积积分法校验符合热力学一致性。运用M atlab中的非线性最小二乘法程序,对二元汽液平衡的W ilson模型进行参数计算,利用关联出的模型参数计算相应的汽相组成,并与实验值比较,其平均绝对偏差为0.002 8,表明二者符合良好,这为建立碳酸二甲酯和乙醇的精馏分离数学模型提供了基础数据。     

四氢呋喃-水-正己烷体系等压汽液平衡研究

用改进Rose釜测定了100 kPa下四氢呋喃-水、四氢呋喃-正己烷、四氢呋喃-水-正己烷体系(互溶区域)的等压汽液平衡数据。汽相非理想性通过逸度系数的计算进行校正,液相非理想性归结到活度系数中予以校正。用非线性最小二乘法关联了二元体系的汽液平衡数据,得到NRTL/UNIQUAC模型参数。利用得到的二元模型参数,结合部分三元汽液平衡数据,关联得到水-正己烷体系的模型参数。由关联得到的3对二元模型参数预测另一部分的三元汽液平衡数据,实验值与预测值基本吻合。     

含离子液体乙腈-正丙醇体系的等压汽液平衡

常压(101.3 kPa)下, 测定了如下体系的汽液平衡数据:乙腈-正丙醇-氯化1-苄基-3-甲基咪唑([BzMIM][Cl])、乙腈-正丙醇-溴化1-苄基-3-甲基咪唑([BzMIM][Br])、乙腈-正丙醇-溴化1-己基-3-甲基咪唑([HMIM][Br]), 考察了3种离子液体对乙腈-正丙醇体系相平衡行为的影响。实验结果表明, 3种离子液体都能够提高乙腈对正丙醇的相对挥发度, 3种离子液体提高相对挥发度的顺序为 [BzMIM][Cl] > [BzMIM][Br] > [HMIM][Br]。用NRTL模型对测得的汽液平衡数据进行了关联, 关联结果与实验结果具有良好的一致性。     

甲基二氯硅烷-甲基三氯硅烷-苯三元体系等压汽液平衡

利用新型泵式沸点仪,在101.3 kPa下测定了甲基二氯硅烷-甲基三氯硅烷-苯体系以及3个二元体系在不同液相组成时的沸点;对所测的二元系数据,采用间接法由TPx推算了与之平衡的汽相组成,再用最小二乘法分别求出了二元体系的Wilson、NRTL、Margules和van Laar 4种模型的最佳配偶液相活度系数模型参数,并由二元最佳配偶参数推算了甲基二氯硅烷-甲基三氯硅烷-苯三元体系的气相组成和泡点温度,与实验测得的温度值进行了比较,其拟合精度良好,关联结果令人满意.     

二甲基硫醚-二硫化碳-甲醇体系等压汽液平衡

用泵式沸点仪测定了100 kPa下二甲基硫醚-二硫化碳、二甲基硫醚-甲醇2个二元系以及二甲基硫醚-二硫化碳-甲醇三元系在不同液相组成时的汽液平衡数据,用Wilson、NRTL、Margules和van Laar模型分别对2个二元系活度系数进行关联,用最小二乘法求出其液相活度系数模型参数,用这些模型参数来计算其汽相组成y,根据过量Gibbs自由能函数Q(GE/RT),采用间接法由Tpx推算了2个二元系的汽相平衡组成。用所得的液相活度系数计算2个二元系的过量吉布斯自由能函数GE/RT,并由2个二元系与三元系回归出二硫化碳-甲醇二元系的NRTL模型参数。用3个二元系NRTL模型参数对所测的三元系数据进行关联,建立三元系汽液平衡的热力学模型并计算平衡时的汽相组成y和泡点温度。分别由Herington法和McDermott-Ellis法对2个二元系和三元系进行热力学一致性检验,结果表明这些相平衡数据满足热力学一致性。     

正丙醇-水-复合溶剂体系等压汽液平衡研究

采用新型双循环沸点仪,测定了100 kPa下正丙醇-水-复合溶剂体系的等压汽液平衡数据。实验结果表明:乙二醇与醋酸钾组成的复合溶剂可消除正丙醇-水的共沸点,并显著提高正丙醇-水的相对挥发度;随着复合溶剂质量分数的增加,正丙醇对水的相对挥发度增大;此复合溶剂可作为萃取精馏正丙醇-水体系的溶剂,适宜的质量分数约为60%。用有序双液(NRTL)方程对实验数据进行了关联,关联结果良好,温度标准偏差为0.45 K,气相组成标准偏差为0.008 7。     

柑青醛与新铃兰醛体系等压汽液相平衡研究

采用静态法,利用Rose釜分别测定了柑青醛在368.65-409.35 K和新铃兰醛在391.85-416.35 K的饱和蒸气压,并用Antoine方程关联,得到柑青醛的3个参数A=-4.159,B=2 494.037,C=-626.842和新铃兰醛的3个参数A=10.701,B=558.048,C=-296.730....     

含离子液体乙醇-水物系等压汽液平衡数据的测定

用Ellis双循环汽液平衡釜测定了101.32 kPa下乙醇 水 三乙基铵硫酸氢盐(N-2,2,2,H］HSO4)的等压汽液平衡数据。实验结果表明,当［N-2,2,2,H］HSO4的摩尔分数为5%时乙醇 水二组分物系的汽液平衡线就开始偏离,［N-2,2,2,H］HSO4摩尔分数为10%、20%时,偏离程度增大;［N-2,2,2,H］HSO4表现出盐效应,使乙醇对水的相对挥发度发生改变,消除了乙醇 水物系的共沸点;含量越大,盐效应越明显。随着［N-2,2,2,H］HSO4含量的增加,乙醇对水的相对挥发度也随着增加;与其他离子液体相比较,［N-2,2,2,H］HSO4具有低成本、高效率的优点,可以作为乙醇-水物系萃取精馏分离的有机盐。用NRTL模型对数据进行了关联,关联的结果和实验计算值相当,符合实验趋势。