Vapour–Liquid Equilibrium for N,N-Dimethylformamide + Benzene + Thiophene via Gibbs Ensemble Molecular Simulation

The selection and design of an optimal solvent for extractive distillation require reliable vapour-liquid phase equilibrium data and knowledge of extraction mechanisms.Compared with time-consuming experiments,molecular simulation presents great potential in research on the properties of fluids.Therefore,in this work,Gibbs ensemble Monte Carlo was applied to successfully predict the vapour-liquid phase equilibrium data of binary and ternary systems containing benzene,thiophene and N,Ndimethylformamide(DMF) at P=101.3 kPa.The explicit hydrogen version of the transferable potentials for phase equilibria potential model was chosen for benzene and thiophene,whereas the OPLS potential model was selected for DMF.The predicted phase diagrams were compared with experimental data and the UNIQUAC thermodynamic model.A good agreement was obtained,which corroborated the validity of the potential models.In addition,the extraction mechanism was explored by radial distribution function(RDF) of the liquid-phase structure.The RDFs showed that thiophene and benzene shared a similar liquidphase structure because of the intermolecular interaction.The distinct difference between the RDFs of DMF/benzene and those of DMF/thiophene is that the oxygen atom of DMF is more associated with hydrogen atoms of thiophene than that of benzene,which may be responsible for the extraction effect of DMF.

Measurement and Correlation of Isobaric Vapor-Liquid Equilibrium of Three Binary Systems Containing Chlorobenzene at 50.00 and 101.33 kPa

Isobaric vapor-liquid equilibrium(VLE) data for three binary systems, chlorobenzene + N,N-dimethylformamide, chlorobenzene + furfural, and chlorobenzene + benzaldehyde, were measured at 50.00 and 101.33 kPa using a modified Rose-Williams still. Gas chromatography was used to analyze the compositions of the samples and no azeotropic behavior was found. All of the measured VLE values were checked by the semi-empirical method proposed by Herington and the point-to-point Van Ness test method modified by Fredenslund. The experimental data were correlated by using the Wilson, the non-random two-liquid and universal quasi-chemical activity coefficient models. The corresponding parameters for the three models were obtained.

Extrapolation of High Pressure VLE Data and Simultaneous Representation of Excess Enthalpies by Using NRTL Equation

The non-random two liquids (NRTL) equation together with the Pitzer/Curl Virial equation of state are used to investigate the simultaneous representation of excess enthalpies (hE) and vapour-liquid equilibria (VLB) and the VLE prediction from hE data. The calculation strategy for properly determining NRTL parameters and the effect of their temperature dependence on the simultaneous correlation of hE and VLE data and the VLE extrapolation are analysed in detail.

Extension of LCVM-type mixing rule to three-parameter equations of state for vapor-liquid equilibria of mixtures

In this paper, the LCVM mixing rule is extended to the multi-parameter equations of state by combining infi- nite-pressure and zero-pressure mixing rule models. The new LCVM-type mixing rule, coupled with Patel-Teja equation of state (EOS) is applied for vapor-liquid equilibria of different polar and non-polar systems in which the NRTL activity coefficient model is used to calculate the excess Gibbs free energy. The tested results agree well with existing experimental data within a wide range of temperatures and pressures. In comparison with the Van der Waals mixing rule, the new mixing rule gives much better corre- lations for the vapor-liquid equilibria of non-polar and polar systems.

乙二醇和1,2-丁二醇二元气液平衡体系的研究及模型预测

为了研究乙二醇-1,2-丁二醇在不同真空度下共沸组成的变化规律及差压精馏分离的可行性,使用改进的Othmer气液平衡釜测定了1~100 kPa下乙二醇-1,2-丁二醇二元体系的气液平衡数据,均通过了热力学一致性检验。分别采用Wilson、NRTL和UNIQUAC方程对不同压力下的气液平衡数据进行整体关联,结果表明,UNIQUAC方程计算精度更高,可适用于1~100kPa下的相平衡计算。采用UNIQUAC方程计算了不同压力下乙二醇-1,2-丁二醇的共沸组成,共沸组成中乙二醇的摩尔分数随压力的降低呈非线性增加。操作压力由100降低至1kPa时,共沸组成中乙二醇的摩尔分数的变化可达到12%,推断乙二醇-1,2-丁二醇具有差压精馏分离的可行性。

A New Excess Free Energy Mixing Rule for Representing Vapor-Liquid Equilibria of Mixed Refrigerants

A suitable mixing rule is important for vapor liquid equilibrium(VLE)investigations for mixed refrigerants.In this work,a new excess free energy mixing rule(MRv)was proposed at zero pressure based on the linear relationship between dimensionless parameter 1/(u-1)and a.MRv mixing rule was explicit adopted variable liquid molar volume.The applicable temperature range of MRv could be extended by means of an empirical method to estimate the liquid molar volume for components at high temperatures.Three mixing rules modified Huron-Vidal mixing rule(MHV1),Wong-Sandler mixing rule(WS),and MRv at two reference pressures were used to compare the VLE data in the calculation of 37 mixed refrigerants.Results demonstrated that MRv had a relatively similar accuracy to MHV1 and WS for component and pressure calculation.Moreover,the average excess Gibbs free energy using the MRv mixing rule for the 37 selected mixed refrigerants(0.0013)was much lower than those using the MHV1(0.0078)and WS(0.0809)mixing rules,which was very valuable for the design and optimization of thermodynamic systems using mixed refrigerants.

盐效分离作用理论预测

研究了盐效分离基本原理,采用选择性溶剂化模型,利用定标粒子理论计算盐在含水体系中的标准摩尔迁移自由能。提出了将迁移自由能与相平衡中盐效应的大小结合起来,用迁移自由能理论解释相平衡中的盐效应。文中计算了盐在6种含水体系的标准摩尔迁移自由能,并与其盐效应进行了对比,研究发现在含水体系中盐效应随盐的标准摩尔迁移自由能增大而增大,因此在盐效分离过程中可以采用标准摩尔迁移自由能模型选择有效的盐作分离剂。

甲缩醛-甲醇二元系汽液平衡数据的测定与关联

用改进的Rose平衡釜测定恒压下(99.9 k Pa)甲缩醛-甲醇二元系的汽液平衡数据。用Herrington检验法对实测数据进行了热力学一致性检验。对Wilson和NRTL活度系数模型进行了关联,回归得到模型参数与温度之间的关系。与实验数据相比较,用Wilson模型预测的汽相组成其相对平均偏差为7.99%,温度平均偏差为0.12 K;NRTL模型的偏差分别为7.66%和0.22 K。结果表明用两种模型参数预测二元系的泡点与实验值能很好地吻合。

苯和噻吩萃取精馏溶剂的筛选及汽液平衡数据的测定与关联

用气相色谱法测定了苯及噻吩在各种溶剂中无限稀释条件下的活度系数、选择性、溶解度和相对挥发度,综合比较,其中NMP(N-甲基吡咯烷酮)的性能较好。用改进的鼓泡平衡斧测定了苯-噻吩-NMP的二元和三元系等温汽液平衡数据,并通过热力学一致性检验。二元系数据用Wilson方程关联,三个二元系的汽相摩尔组成的总绝对平均偏差|△y|为0.0010,三元系的Wilson方程推算值与实测值的|△Y|为0.0064。

HFC混合物二元交互作用系数研究

目前国际上已商业化使用或提出的潜在的环保工质,大多数为氢氟烃(HFC)混合物,利用状态方程描述混合工质热力性质时,交互作用系数是重要参数之一。本文应用Peng-Robinson状态方程对多种HFC二元混合物的气液相平衡(vapor—liquid equilibrium,VLE)实验数据进行了回归,得到了相应混合物的交互作用系数。提出了交互作用系数新关联式,结果表明所得到的交互作用系数能很好的应用于描述HFC混合物气液相平衡性质,计算精度可以满足工程应用的需要。

辛烷-水二元部分互溶体系的相平衡

采用改进的Ｐａｒｔ釜测定了在０．１０１３ＭＰａ下，辛烷－水二元部分互溶体系的汽液相平衡数据，经热力学一致性检验表明，所测的数据是可靠的。采用等温法制定了５～７５℃范围内的液液相平衡数据。实验结果表明，辛烷在水中的溶解度仅为７．３×１０－５～７．５×１０－４，水在辛烷中的溶解度为３．８×１０－３～１．０×１０－１，该体系是互溶度极小的体系。

低温低压下H_2－N_2－Ar体系汽液平衡研究与应用

介绍了空气分离装置带精氩塔工艺流程中Ｈ２－Ｎ２－Ａｒ体系汽液相平衡计算的数学模型，根据实验数据，将Ｓｏａｖｅ方程中的参数ａＨ２进行了回归。经与大量实验数据比较，表明本文改进的Ｓｏａｖｅ方程对低温低压下Ｈ２－Ｎ２－Ａｒ体系汽液相平衡计算的精度较高，本文还用Ｓｏａｖｅ方程首次对精氩工艺流程、精氩塔的精馏工况及分凝器的热力参数等进行了计算，结果均较满意。

含水DMF溶剂对苯和噻吩相对挥发度的影响

含水ＤＭＦ溶剂对苯和噻吩相对挥发度的影响刘兵，郑英峨，赵维彭（南京化工大学，化学工程系）关键词苯；噻吩；相对挥发度；汽液平衡（ＶＬＥ）；萃取精馏１前言我国焦化苯所占比重较大［１］，焦化苯中硫化物（主要以噻吩形式存在）等杂质的含量普遍较高，限制了高质量...

溶剂加盐对醇水汽液平衡的影响

讨论了溶剂加盐对乙醇 -水、叔丁醇 -水、异丙醇 -水 3种醇水体系的影响。常压下汽液平衡的实验结果表明溶剂加盐能够有效地提高醇对水的相对挥发度 ,在恒沸点处 3种醇水体系的相对挥发度分别是 2 56、2 68、2 67。所加的最优盐是CaCl2 和KAc。溶剂加盐的作用机理是溶剂和盐对醇水分子的双重作用 ,且作用力大小不同。

N-甲酰吗啉与苯的二元等压汽液平衡

The extraction of aromatics with N-formylmorpholine (NFM) has been widely used in petrochemical and coal tar industries.However, the vapor-liquid equilibrium (VLE) data of N-formylmorpholine-aromatics systems are very limited, and no isobaric VLE data can be found in literature.The VLE data of benzene-NFM system were determined by using an improved VLE equipment EC-2.The experimental VLE data were correlated with the thermodynamic models NRTL and UNIQUAC, and the corresponding binary interaction parameters for these two models were obtained.The results showed that the VLE data agreed well with the two models, and passed the thermodynamic consistency test of Herington.By comparison with these models from literature, it is found that these two models are more suitable for VLE prediction for NFM systems above 80℃.The VLE data and model parameters obtained are essential for the engineering design of N-formylmorpholine-aromatics distillation processes.

缔合体系汽-液平衡数据的热力学一致性检验

以"化学"理论和Hayden-O’Connell(HOC)方法为基础,完整地推导出缔合体系的真实汽相组成及相平衡计算通式,并在常减压下简化,建立缔合体系热力学一致性检验方法。关联常减压下水+甲酸、水+醋酸、水+丙酸体系的等压汽-液相平衡实验数据。结果表明,简化相平衡模型的计算值与文献值相吻合,计算简单准确,需要基础物性数据少。最后以醋酸+N,N-二甲基甲酰胺体系汽-液相平衡数据为例,用建立的缔合体系热力学一致性检验方法,结合Herington面积法和点检验法,进行了热力学一致性检验。

26.67kPa下醋酸-水-N-甲基吡咯烷酮体系汽液相平衡的研究

在26.67 kPa下,采用改进的Rose汽液相平衡釜测定醋酸-N-甲基吡咯烷酮、水-N-甲基吡咯烷酮、醋酸-水-N-甲基吡咯烷酮的等压汽液相平衡数据。实验数据通过了Herington面积法和点检验法的热力学一致性检验。考虑醋酸在汽相中的缔合效应,以"化学"理论和Hayden-O’Connell(HOC)方法为基础,采用NRTL模型关联水-醋酸、醋酸-N-甲基吡咯烷酮、水-N-甲基吡咯烷酮体系的汽液平衡数据,得到相应的二元体系模型参数和关联偏差。用关联的二元体系NRTL模型参数,推算出醋酸-水-N-甲基吡咯烷酮三元体系的汽液相平衡数据,温度平均偏差绝对值为1.36 K,水汽相摩尔分数的平均偏差绝对值为0.0102,醋酸汽相摩尔分数的平均偏差绝对值为0.0072。

伴有平衡反应的分离过程的数学模拟(Ⅰ)板式反应精馏塔的模拟计算

本文提出了相平衡和化学平衡同时存在的多相复杂可逆反应的反应精馏计算方法。模型方程由物料衡算方程,化学平衡方程,相平衡方程,归一方程,焓衡算方程组成。模型分三层迭代求解。该算法可适用于非理想系统、反应动力学未知的快速可逆反应过程。并且对不同操作条件下的计算均能稳定收敛,可以进行操作条件的调优。应用该算法模拟计算未达到平衡的反应过程,可以预测各板上的最大转化率和各板组成。

深化物理化学实验教学,培养学生科研能力——关于双液系气液平衡最低恒沸点的确定

通过物理化学实验教学和指导学生实验,发现教材和实验报告中很少有关于双液系气液平衡最低恒沸点确定的具体方法,但这是该实验的基本目的和关键点。本文分析并探讨了最低恒沸点确定的具体方法和实验中遇到的其他问题,并提出了解决方案,以促进学生对物理化学实验的理解和对气液平衡、相图、相律等基本概念的掌握,提高学生对数据的分析处理能力,为其今后的科学研究和学术思想交流打下基础,也有利于学生科学研究能力的培养。

乙二醇、二甘醇对醇-水萃取精馏影响的数模计算与验证

应用多元汽液相平衡原理进行了乙二醇、二甘醇对醇-水萃取精馏影响的数模计算,并予以实验验证。模型计算值与实验值的最大误差△Y≤0.030,认为Wilson模型对醇-水物系是合宜的;乙二醇、二甘醇是醇-水萃取精馏分离的两种较好的萃取剂。