液上气相色谱法用于气-液平衡测定的研究

〕本文自行设计安装一套以减压法采样的液上采样装置,选择出在与气相色谱仪配套使用中的合适操作条件。并用两组文献中的气-液平衡数据检验了自制液上采样系统的可靠性。讨论了用液上气相色谱法测定溶液平衡总压的可行性。     

含盐混合溶剂气液平衡的线性关系

含盐混合溶剂气液平衡的线性关系刘文彬，王键吉，王彩兰，卢锦梭（河南师范大学化学系新乡４５３００２）１　引言纯物质的气液平衡规律早已被Ｃｌａｕｓｉｕｓ－Ｃｌａｐｅｙｒｏｎ方程所描述；两组分气液平衡的Ｔ－ｐ－ｘ关系也可从热力学理论导出。当少量的非挥发性溶...     

气液平衡相图绘制实验的改进

在环己烷-乙醇双液体系的气-液平衡相图实验中,现在使用的沸点测定仪存在着体系不易达到相平衡、取样困难以及不能得到分布均匀的相图等不足之处。改进后的实验装置及相应的实验方法在实际操作中可以避免上述问题,提高实验质量,获得良好的教学效果。     

氨基酸在甲醇—水混合溶剂中的气液平衡

采用改进的Ｒｏｓｅ釜测定了在３３３Ｋ和３３８Ｋ下，氨基乙酸、ＤＬ－氨基丙酸及Ｌ－氨基异戊酸在甲醇－水混合溶剂中的气液平衡数据。实验结果表明，当甲醇－水混合溶剂的相对组成固定时，体系的平衡压力与加入的氨基酸的浓度间存在线性关系，使已建立的含盐混合溶剂的“广义线性定理”进一步扩展到含有非挥发性物质的混合溶剂中。用热力学原理导出了线性方程的数学解析式；讨论了引入氨基酸对混合溶剂结构及性质的影响规律。     

顺丁烯二酸酐-癸二酸二丁酯二元体系等温气液平衡

利用改进的沸点仪测定了顺酐-癸二酸二丁酯二元体系在413.15, 433.15和453.15 K下的等温气液平衡数据以及纯癸二酸二丁酯和顺酐的饱和蒸气压数据. 通过与文献值对比, 验证了此方法的可靠性. 同时, 将实验数据回归得到了纯癸二酸二丁酯和顺酐的Antoine常数. 利用NRTL方程进行了气液平衡数据的关联推算, 得到了顺酐-癸二酸二丁酯二元体系的NRTL模型参数. 利用UNIFAC基团贡献法对实验数据进行了预测, 其结果与实验值及运用NRTL方程拟合的结果吻合较好.     

用二元交互作用函数预测高压下多组分体系的气液平衡

用和体系的状态有关且满足不变性条件的二元交互作用函数,结合F函数修改的立方状态--方程FRKS方程,预测高压下多组分体系的气液平衡.选择15个三元体系及其组分二元系来检验方法的可行性,这些体系覆盖了从简单的接近理想溶液行为的体系到高度非理想体系.计算结果表明,该方法不仅能相当精确地关联各种类型二元系的气液平衡,而且能在仅用组分二元系参数的条件下较准确地预测所考察的所有三元体系的气液平衡     

气液色谱法研究聚合物/溶剂体系气液平衡

 用气液色谱法测定了聚二甲基硅氧烷（PDMS）／溶剂、聚甲基丙烯酸甲酯（PMMA）／溶剂体系在不同温度下以质量分数表示的无限稀溶剂活度系数和Flory－Huggins相互作用参数。应用UNIFAC和UNIFAC－FV模型对PDMS／溶剂、PMMA／溶剂体系中以质量分数表示的无限稀溶剂活度系数进行了估算。结果表明,用这两个模型预测PDMS／溶剂、PMMA／溶剂体系中的无限稀溶剂活度系数有待修正或采用其它模型进行估算。     

用斜式沸点计测定二元气液平衡数据

改进了斜式沸点计的结构，使其更适用于气液平衡数据的分析测定和获得更精确的结果，在应用中取得了良好的效果。     

气液色谱法研究聚合物/溶剂体系气液平衡

用气液色谱法测定了聚二甲基硅氧烷（PDMS）／溶剂、聚甲基丙烯酸甲酯（PMMA）／溶剂体系在不同温度下以质量分数表示的无限稀溶剂活度系数和Flory－Huggins相互作用参数。应用UNIFAC和UNIFAC－FV模型对PDMS／溶剂、PMMA／溶剂体系中以质量分数表示的无限稀溶剂活度系数进行了估算。结果表明,用这两个模型预测PDMS／溶剂、PMMA／溶剂体系中的无限稀溶剂活度系数有待修正或采用其它模型进行估算。     

双液系气－液平衡相图绘制中有关问题的探讨

本文以物理化学实验“苯－乙醇气液平衡相图绘制”为研究对象，对其混合液的浓度调整以期达到再利用进行了探讨，提出了调整方法，进行了实验验证，取得了理想的效果。     

Prediction of vapor-liquid equilibrium from excess enthalpy data for binary ether +n-alkane or cyclohexane mixtures

Vapor liquid equilibrium (VLE) is successfully predicted from excess enthalpy H^E data for binary ether + n-alkane or cyclohexane mixtures. Parameters for the continuous linear association model (CLAM) and for the UNIQUAC Model for the excess Gibbs energy G^E were determined from H^E data measured at a low temperature (ambient temperature). These parameters are used to predict VLE data at low and high temperatures. The dependence of the accuracy of predictions on the set of H^E data chosen to evaluate the parameters and on the model for G^E are discussed.     

Excess molar volumes and isothermal vapor-liquid equilibrium in the binary system 1,1,1-trichloroethane with 1-chlorobutane and with pyridine at 25°C

Densities and vapor-liquid equilibrium were determined for 1-chlorobutane and pyridine with 1,1,1-trichloroethane at 25°C. From the experimental results, excess molal volumes and excess molar Gibbs energies were calculated. Information could be obtained about the possible interactions between the components of both binary systems. The Prigogine-Flory-Patterson theory was applied to calculate excess molar volumes. Liquid activity coefficients were calculated and correlated with different expressions existing in the literature.     

星型高分子共混体系的相平衡、相分离和相界面的 统计力学理论

在平均场近似下求得了星型高分子共混体系的混合自由能及其相分离动力学方程。本文的理论结果表明,型高分子共混体系与线型高分子共混体系相比具有更快的相分离速度。而且,因其相界面张力较低,体系较易形成更多的相界面,浓度涨落的临界波矢也更大。除此之外,由于在相同分子量的条件下星型高分子的尺寸要小,因此其相界面更窄,当星型高分子的臂数为1或2时,所有结果均合理地还原到熟知的线型高分子共混体系的结果。因此,本文的结果具有更大的普遍性。     

Isobaric vapor-liquid equilibrium for binary systems containing benzothiophene

Isobaric vapor-liquid equilibrium (VLE) of the following systems was measured with a recirculation still: benzothiophene + dodecane at 99.6 kPa, benzothiophene + 1-dodecene at 100.1 kPa, and benzothiophene + 1-octanol at 100 kPa. All systems studied exhibit positive deviation from Raoult's law. A minimum temperature azeotrope was found in the systems benzothiophene + dodecane (x₁ = 0.491, P = 99.6 kPa, T = 484.72 K) and benzothiophene + 1-dodecene (x₁ = 0.185, P = 100.1 kPa, T = 484.45 K). No azeotropic behavior was found in benzothiophene + 1-octanol system at 100 kPa. The experimental results were correlated with the Wilson model and compared to COSMO-SAC predictive model. Liquid and vapor phase compositions were determined with gas chromatography. All measured data sets passed the thermodynamic consistency tests. The activity coefficients at infinite dilution are also presented.     

Excess thermodynamic properties and vapor-liquid equilibrium data for then-butylamine+p-dioxane system at 25°C

Excess values of molar volumes, viscosities, molar enthalpies, Gibbs molar energies, surface tensions and molar diamagnetic susceptibilities were calculated at 25°C for then-butylamine+p-dioxane system. The observed deviations from the ideality were explained on the basis of intermolecular interactions. Van Laar's equations were the best in predicting activity coefficients for this system.     

Novel bare-bones particle swarm optimization and its performance for modeling vapor-liquid equilibrium data

Parameter estimation in models plays a significant role in developing mathematical models which are used for understanding and analyzing physical, chemical and biological systems. Parameter estimation problems for vapor-liquid equilibrium (VLE) data modeling are very challenging due to the high non-linearity of thermodynamic models. Recently, stochastic global optimizations and their applications to these problems have attracted greater interest. Of the many stochastic global optimization methods, Bare-bones particle swarm optimization (BBPSO) is attractive since it has no parameters to be tuned by the user. In this study, modifications are introduced to the original BBPSO using mutation and crossover operators of differential evolution algorithm to update certain particles in the population. The performance of the resulting algorithm is tested on 10 benchmark functions and applied to 16 VLE problems. The performance of the proposed BBPSO for VLE modeling is compared with that of other stochastic algorithms, namely, differential evolution (DE), DE with tabu list, genetic algorithm and simulated annealing in order to identify their relative strengths for VLE data modeling. The proposed BBPSO is shown to be better than or comparable to the other stochastic global optimization algorithms tested for parameter estimation in modeling VLE data.     

Trial wave functions induced by the minimum mean deviation from statistical equilibrium

The ground state of an atom is studied by introducing a trial function whose unknown coefficients, taken as variational parameters, are determined by minimizing the mean energy of the respective quantum system. There is no clear methodology about how to choose such trial functions. Using techniques from information theory and statistical inference, this study deals with the construction of trial wave functions by minimizing the mean deviation from statistical equilibrium. The formalism is applied to the ground state of the helium and lithium atoms with surprisingly good numerical results even when only a few variational parameters are used. Details about the effective computation are also given. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 175–190, 1998     

On the phase equilibrium Stockmayer fluids

The fluid phase equilibrium of the Stockmayer fluid is investigated using a thermodynamic perturbation theory approach. The reference and the perturbation potential are the Lennard–Jones potential and the dipolar–dipolar interactions, respectively. They are assumed to be represented by the modified Benedict–Webb–Rubin equation of state [J.K. Johnson, J.A. Zollweg, K.E. Gubbins, Mol. Phys. 78 (1993) 591–618] and the Padé approximant [G. Stell, J.C. Rasaiah, H. Narang, Mol. Phys. 27 (1974) 1393–1414], respectively. The asymmetry found in an analogous study [M.E. van Leeuwen, B. Smit, E.M. Hendriks, Mol. Phys. 78 (1993) 271–283] based on the BWR equation of state [J.J. Nicolas, K.E. Gubbins, W.B. Streett, D.J. Tildesley, Mol. Phys. 37 (1979) 1429–1454] is now not observed on the vapour–liquid equilibrium coexistence curves of Stockmayer fluids with dipolar strength of μ^*2 = 1, 2, 3, and 4. Results agree with computer simulations for dipolar strength of μ^*2 = 1; however as strength dipole increases, liquid densities are over-estimated.     

Investigation of the surface tension of methane and n-alkane mixtures by perturbed-chain statistical associating fluid theory combined with density-gradient theory

The perturbed-chain statistical associating fluid theory (PC-SAFT) and density-gradient theory are used to construct an equation of state to describe the phase behavior of binary methane–n-alkane mixtures. With the molecular parameters and influence parameters regressed from bulk properties and surface tensions of pure fluids, respectively as input, both the bulk and interfacial properties are investigated. The surface tension of the binary systems methane–propane, methane–pentane, methane–heptane and methane–decane are predicted, and the results are satisfactory compared with the experimental data. Our results show that PC-SAFT combined with density-gradient theory is able to describe the interfacial properties of binary methane–n-alkane mixtures in wide temperature and pressure ranges, and illustrate the influence of the equilibrium bulk properties and chain length of n-alkane molecule on the interfacial properties.