Effects of Ultrasonic Waves on Vapor-Liquid Equilibrium of an Azeotropic Mixture

Abstract

Azeotropic and extractive distillation techniques used to separate azeotropic mixtures are among the most challenging separation processes in the chemical industry. In this work, an innovative distillation technique which employed ultrasonic waves was proposed to intensify the conventional multi-column azeotropic distillation method into a single-column alternative. The effects of ultrasonic intensity on the vapor-liquid equilibrium (VLE) of methyl-tert-butyl-ether (MTBE)-methanol was investigated at 50, 100, 200, and 250 W/A·cm² and at a fixed frequency of 40 kHz. Studies were also done to examine the effects of ultrasonic frequency on the VLE data at 25 and 68 kHz frequencies. It was found that ultrasonic waves at 50 W/A·cm² intensity and 25 kHz frequency gave the highest relative volatility (α) at 2.654 and completely eliminated the MTBE-methanol azeotrope, thereby allowing highly pure MTBE to be recovered in just a single distillation column. The results revealed that ultrasonic waves had the potential to favorably manipulate α, and hence, the VLE of an azeotropic mixture.     

正丁醇-氯苯-苯乙酮三元体系等压汽液平衡的测定与关联

正丁醇-氯苯常压下存在最低共沸现象,首先应用汽液平衡法从6种备选溶剂中筛选出苯乙酮作为最佳萃取剂,然后分别测定了正丁醇-氯苯、正丁醇-苯乙酮、氯苯-苯乙酮3个二元体系以及正丁醇-氯苯-苯乙酮三元体系在101.33 kPa下的汽液平衡数据。所有实验数据都通过了Herington法和Van Ness法的热力学一致性检验,采用Wilson、NRTL和UNIQUAC 3种活度系数模型进行关联计算,其二元拟合数据与实验数据吻合较好。使用关联得到的二元交互参数推算三元汽液平衡数据,并与实验值进行对比,偏差在合理范围以内。结果表明,苯乙酮作为萃取剂可以有效地改变正丁醇与氯苯的相对挥发度,在溶剂质量比为1：1时能够使共沸现象消失。为工业上使用萃取精馏分离正丁醇-氯苯体系提供参考,也为汽液平衡数据库补充新的内容。     

An approximate model for binary azeotropic distillation design

A simple analytical model has been developed for representing vapor-liquid equilibrium data in binary azeotropic mixtures. The method treats the azeotrope as a new pure component and considers the mixture to be composed of two independent binary subsystems; component 1 + azeotrope and azeotrope + component 2. After suitable variable transformations, each subsystem can then be represented by a constant relative volatility type model. The resulting vapor-liquid equilibrium models have been used to derive design equations for binary azeotropic distillation columns.     

萃取精馏分离四氢呋喃-乙醇共沸物系

首先根据汽液平衡实验数据采用UNIFAC法进行VLE关联。然后通过定性判断、基团贡献法定量估算选择该二元物系的合适萃取剂为乙二醇。通过气液平衡实验对萃取剂的有效性进行验证．比较了不同溶剂比对四氢呋喃,乙醇相对挥发度的影响,当溶剂比为3时,相对挥发度为2．26。最后进行精馏实验验证过程的可行性。     

萃取精馏分离甲苯和甲基噻吩中萃取溶剂的选择

在一系列萃取溶剂存在下,通过测定常压气液平衡试验数据来计算甲苯与甲基噻吩的相对挥发度,并且以相对挥发度为评价指标,考察了单一萃取剂对甲苯与甲基噻吩分离过程的影响,从而研究分离纯化由焦化苯中得到的甲苯与甲基噻吩(2-甲基噻吩和3-甲基噻吩)时所需要的萃取溶剂.结果表明:以N-甲基吡咯烷酮为萃取剂且溶剂体积比为7时,甲苯与...     

离子液体对乙腈-水共沸物系汽液平衡的影响

选择离子液体1-丁基-3-甲基咪唑氯盐（Bmin[Cl]）作为分离乙腈-水共沸物系的溶剂。在0.101MPa下测定了在离子液体Bmin[Cl]含量为10%、20%和30%时乙腈-水物系的汽液平衡数据。实验结果表明,离子液体Bmin[Cl] 可以提高乙腈对水的相对挥发度,离子液体Bmin[Cl]含量在20%以上时可以消除乙腈-水物系的共沸点。离子液体Bmin[Cl]可以用作分离乙腈-水物系的萃取剂。用改进的Furter方程对数据进行了关联,得到了离子液体Bmin[Cl]对乙腈-水物系的盐效应参数。     

醋酸-水萃取精馏溶剂的筛选

采用平衡组分分析法对醋酸-水萃取精馏的溶剂进行了筛选.首先,对醋酸-水体系的常压气液平衡(VLE)数据进行了测定,并与文献值比较,同时采用Herington面积法对数据进行热力学一致性的检验,从而考察了气液平衡数据测定装置的稳定性及可靠性.然后,测定加入不同溶剂后体系的VLE数据,比较不同溶剂对体系的选择度,初步筛选出选择度最大的N-甲基乙酰胺(NMA)为醋酸-水萃取精馏的较优溶剂.     

THE VAPOR-LIQUID EQUILIBRIUM OF ETHANOL-WATER MIXTURE IN THE PRESENCE OF BENZYLTRIETHYLAMMONIUM CHLORIDE SALT AT ATMOSPHERIC PRESSURE

The phase transfer catalysis reaction is gaining more and more attention in chemical industry. Usually, the chemicals used as phase transfer catalyst are organic salts. Unfortunately, the effect of an organic salt on the vapor-liquid equilibrium (VLE) of a mixture has hardly been reported in literature. In this study, the effect of the benzyltriethylammonium chloride organic salt on the VLE of ethanol-water mixture was obtained experimentally. It is observed that this organic salt can shift and even break away the azeotrope of ethanol -water mixture as an inorganic salt does. The experimental data were correlated with the models or Tan (1987, 1990) and Ohe (1991). The results were not satisfactory probably due to the complicated interactions among ions and molecules and the big different particle sizes or ion, solvent molecule, and salt molecule.

The vapor pressures of benzyltriethylammonium chloride-ethanol mixtures needed in this study for determining solvent-salt interaction parameters in the correlation model were also measured and regressed by the Patil model (1990).     

乙酸异丙酯-异丙醇-DMSO的等压汽液相平衡和萃取精馏模拟

在101.3 kPa压力下,采用汽液平衡釜测定了二元物系异丙醇+二甲基亚砜（DMSO）、乙酸异丙酯+DMSO和三元物系异丙醇+乙酸异丙酯+DMSO的汽液平衡数据。利用Van Ness点校验法检验以上气液平衡数据,结果表明,数据符合热力学一致性。采用NRTL、Wilson和UNIQUAC活度系数模型对二元数据进行了拟合,并进行了三元物系汽液相平衡数据预测,结果表明,回归数据和实验数据吻合良好。Wilson模型的预测结果优于NRTL和UNIQUAC模型。一定量DMSO的加入可消除异丙醇和乙酸异丙酯的共沸点,因此,DMSO可作为一种有效的萃取剂来萃取精馏分离此二元物系。然后,通过流程模拟软件Aspen Plus,使用获得的二元交互作用参数对三元系统的萃取精馏进行了模拟。讨论了在不同的操作条件（塔板数、进料位置、溶剂比和回流比）下,异丙醇和乙酸异丙酯分离的情况,得到了最适宜的操作条件。     

萃取精馏分离丙酮-四氢呋喃的研究

为了分离丙酮-四氢呋喃共沸混合物,研究了萃取精馏在丙酮-四氢呋喃物系中的应用。通过溶剂选择原理初选出乙苯作为萃取精馏分离此共沸物系的溶剂,同时采用NRTL模型对常压下丙酮-四氢呋喃物系和加入溶剂乙苯后的汽液平衡进行模拟和实验验证,模拟结果与实验数据吻合较好。然后进行了间歇萃取精馏分离此共沸物的实验研究来进一步考察所选萃取剂的效果。结果表明:乙苯能够消除丙酮-四氢呋喃共沸物系的共沸点,采用有40块理论板的填料塔,回流比为5,溶剂摩尔比为2.5∶1时塔顶可以得到质量分数为99.34%的丙酮产品,说明采用乙苯作萃取剂分离丙酮-四氢呋喃共沸物是可行的。最后又对连续和间歇萃取精馏分离丙酮-四氢呋喃共沸物的流程进行了模拟,得到的工艺参数将为进一步的工业应用提供了理论依据。     

A new process for fuel ethanol dehydration based on modeling the phase equilibria of the anhydrous MgCl2 + ethanol + water system

The use of ethanol as a fuel for motor engines has attracted significant attention because of its possible environmental and economic advantages over fossil fuel. However, the energy demand for the ethanol dehydration process significantly impacts its production cost. A new and energy efficient process is developed on the basis of salt extractive distillation, which uses recycled MgCl₂ granules as a separating agent. Vapor‐liquor‐equilibria (VLE) data for the ternary MgCl₂ + ethanol + water system, and the three constituent binary systems were measured at 30, 60, 90, and 101.3 kPa. A large enhancement of relative volatility of the ethanol + water system in the presence of MgCl₂ is observed throughout the entire ethanol concentration range, which completely broke the azeotrope. The salt effect of MgCl₂ is thought to be the result of energetic interactions and the hydration equilibrium reaction of the Mg²⁺ ion with water molecules. The calculation results by the mixed‐solvent electrolyte model embedded in the OLI platform equipped with new model interaction parameters and equilibrium constant (obtained via the regression of experimental VLE data), provided for a satisfactory means of simulating the MgCl₂ salt extractive distillation process. Finally, the process was proven feasible at the laboratory‐scale resulting in large granules of recovered MgCl₂ and a product of 99.5 wt % ethanol. © 2014 American Institute of Chemical Engineers AIChE J, 61: 664–676, 2015     

Measurement and correlation of vapor-liquid equilibria for hexamethyl disiloxane + vinyl acetate system at 101.3 kPa简

Vapor-liquid equilibrium data of hexamethyl disiloxane ＋ vinyl acetate system at 101.3kPa were meas- ured by using double circulating vapor-liquid equilibrium still. The thermodynamic consistency of the VLE data was examined by Herrington method. Experimental data was correlated by non-random two-liquid （NRTL）, Wilson and universal quasichemical （UNIQUAC） parameter models. All the models satisfactorily correlated with the VLE data. The result showed that the NRTL model was the most suitable one to represent experimental data satisfactorily. The system had a minimum temperature azeotrope at 345.71 K and the mole azeotropic composition was 0.0541.     

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。     

三正丁胺络合萃取精馏分离醋酸和水

A new separation method, reactive extractive distillation, was put forward for separating water and acetic acid. The separation mechanism was analyzed through infrared spectra technique. Isobaric vapor-liquid equilibrium (VLE) data at 101.33 kPa for the binary or ternary systems consisting of water, acetic acid and tributylamine were measured. The activity coefficients were correlated by using Wilson, NRTL, and UNIQUAC Equations.The VLE experiment showed that tributylamine could enhance the relative volatility of water to acetic acid. An extractive distillation experiment was carried out and proved that tributylamine was a good extractive solvent.     

萃取精馏分离碳酸二甲酯和甲醇共沸物

通过气液平衡实验和Aspen Plus模拟软件对萃取精馏分离碳酸二甲酯和甲醇共沸体系的可行性进行了研究。实验和模拟结果表明:乙二醇作为溶剂能有效地改变体系的相对挥发度,UNIFAC模型能够对萃取精馏混合物系相平衡行为进行较准确的描述;通过改变原料进料位置、溶剂比、回流比和溶剂进料位置等操作参数对该体系的分离进行了模拟,得到了可行的分离条件:理论塔板数为30,原料进料位置为第20块塔板,溶剂进料位置为第3块塔板,溶剂比为1.5,回流比为2。实验值与模拟值吻合良好,说明了模拟的可靠性。     

萃取精馏分离乙腈-正丙醇的研究

采用萃取精馏的方法分离乙腈-正丙醇的共沸物系。首先利用溶剂选择原理和UNIFAC基团贡献法选出N-甲基吡咯烷酮作为萃取精馏的萃取剂,同时采用NRTL模型对常压下乙腈-正丙醇物系和加入萃取剂N-甲基吡咯烷酮后的汽液平衡进行模拟和实验验证,模拟结果与实验数据吻合较好。然后通过间歇萃取精馏实验进一步考察所选萃取剂的分离效果。结果表明,N-甲基吡咯烷酮能够打破共沸,有效分离乙腈-正丙醇共沸物系。采用有28块理论板的填料塔,萃取剂进料位置为第4块板,溶剂比为1.0,回流比为3,可以从塔顶得到质量分数为98.6%的乙腈产品。最后,用Aspen Plus软件对乙腈-正丙醇物系的连续萃取精馏流程进行了模拟,得出的参数为进一步的工业应用奠定基础。     

萃取精馏提取高纯度三甲苯的模拟研究

采用单级汽液平衡釜测定加氢裂解C9芳烃与溶剂之间的汽液平衡数据,计算各组分与茚满的相对挥发度,筛选出邻苯二甲酸二甲酯(DMP)为最佳溶剂。采用Aspen P lus流程模拟软件模拟加氢裂解C9芳烃萃取分离结果,模拟结果与实验结果相对误差小于1%。考察了萃取段理论板数、溶剂比(原料与溶剂的质量比)、回流比等因素对分离效果的影响。模拟结果表明,萃取精馏塔的最佳工艺条件:萃取段理论塔板数35,溶剂比0.5,回流比5。此时,三甲苯质量分数和收率分别达到99.87%和96.20%。     

动态法辅助筛选萃取精馏分离环己烷-苯混合物的溶剂

采用基于UNIFAC模型(改进UNIFAC模型)的较严谨的"动态法"替代传统的"静态法",以FORTRAN语言开发了萃取精馏法分离沸点接近液体混合物(含共沸物)的萃取剂筛选和多元气液平衡预测程序. 经文献中的乙醇-水体系气液平衡实验数据验证,UNIFAC模型和改进UNIFAC模型的平衡气相组成预测结果平均相对误差分别为3.26%和1.74%,表明所开发的程序具有良好的可靠性和适用性. 采用基于改进UNIFAC模型的"动态法"对萃取精馏法分离环己烷-苯混合物的萃取剂进行了计算机高通量筛选,根据适宜萃取剂选取原则和计算结果,经综合考虑选出较好的萃取剂为二氯甲烷和1,2,3-三氯丙烷. 选取二氯甲烷做实验验证,测定了环己烷-苯-二氯甲烷分离体系的部分气液平衡实验数据,结果表明实验值与计算值吻合良好. 以二氯甲烷作为萃取剂具有能耗低、待分离体系热稳定性好和有效能损失小的优点.     

苯-烯烃-N-甲基吡咯烷酮汽液平衡的研究

N-甲基吡咯烷酮(NMP)作为优良的萃取剂,广泛地被用于芳烃的抽提中,但其与苯及C6～C8烯烃之间的汽液平衡基础数据却极为贫乏.采用CE-2型汽液平衡数据测定仪,测定了常压下苯-1-己烯-NMP、苯-1-庚烯-NMP、苯-1-辛烯-NMP三组三元汽液平衡数据;对三组三元体系,分别以实测数据用Wilson、NRTL和UNIQUAC模型进行了关联,所得三元体系汽相组成计算值和实测值的平均偏差均较小(分别小于0.00839,0.00926和0.00802).研究结果补充了苯-烯烃-N-甲基吡咯烷酮的三元汽液平衡数据,为实际工程应用提供了基础数据.     

EXTRACTIVE DISTILLATION WITH AQUEOUS SOLUTIONS OF HYDROTROPES

The effect of hydrotropes on vapor-liquid equilibrium of a mixture provides a potential technique of extractive distillation for systems which are difficult or impossible to separate by normal rectification. Various hydrotropes, such as sodium toluate, sodium toluence sulfonate, sodium cymcnc sulfonate, sodium mesitylene sulfonate and sodium salicylate, in aqueous solutions have been tested for the separation of close-boiling point mixtures, such as p-cresol/2,6-xylenol, isopropanol/ fm-butanol, and wc-butanol/rert-butanol. The changes in the relative volatility increase with the concentration of hydrotrope and with the hydrotrope to solute ratio.