利用二元体系的C H红外光谱推算汽液平衡数据

Prediction of vapor-liquid equilibrium （VLE） is extremely necessary to separate liquid mixture in chemical production, especially when the required experimental data are difficult to measure, or the measurement is not economical. The infinite dilution activities can be used to predict VLE. However, it needs both the ends of the activities that are difficult to obtain for many systems. In the present study, a new model is proposed for correlating the frequency shift of C-H stretching band of IR spectra over the whole concentration. Investigated mixtures in- clude water/2-propanol, water/N, N-dimethylformamide （DMF）, water/methanol, water/ethanol, water/1, 4-dioxane, and water/dimethylsulfoxide （DMSO） systems. Simultaneous correlations of C--H frequency shift and VLE data are made. Furthermore, the VLE data were predicted with satisfactory results by the parameters obtained from IR spectra coupled with one ot the intinite chlution activity coefficients.     

Calculation of infinite dilution activity coefficients by the NRTL and UNIQUAC models

Infinite dilution activity coefficients have been calculated for 42 binary systems using the NRTL and UNIQUAC models. Temperature dependent parameters of the models are used in the calculations. These parameters have been estimated by using excess Gibbs free energy and enthalpy of mixing data simultaneously. The calculated values are compared with experimental infinite dilution activity coefficients obtained by extrapolation of vapor-liquid equilibrium (VLE) data published in the literature. The agreement between the calculated and experimental values is poor for highly nonideal system. The selection of the best model is difficult and may be system dependent.     

An improved prediction result of entropic‐FV model for vapor–liquid equilibria of solvent–polymer systems

In this work, entropic expressions of UNIFAC‐FV and Entropic‐FV models were evaluated by using an extensive database of infinite dilution vapor–liquid equilibrium (VLE) data of athermal systems containing polypropylene, polyethylene, and polyisobutylene. For the infinite dilution athermal systems, performance of the Entropic‐FV model was better than that of the UNIFAC‐FV model. Then, finite concentration VLE data of non‐athermal systems that consisted of 16 polymers and 36 solvents containing a large variety of solvent–polymer systems ranging from nonpolar to polar substances were considered to optimized 46 pairs of group interaction parameters of the Entropic‐FV model. For systems containing polar solvents of three types of solvents studied, revised group interaction parameters gave significant improvements from 17.9 to 13.0% average absolute deviation (AAD) of solvent activities. For overall results, improvements were achieved from 15.1 to 12.4% AAD. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1145–1153, 2005     

由无限稀释活度系数预测汽液平衡数据的探讨

用内聚能密度法,通过一个无限稀释活度系数和纯物质的性质,预测了包括非极性、弱极性和极性的28个二元体系汽液平衡数据,并与文献值作了比较。为了评价内聚能密度法的适应性,也用单参数 Wilson 方程法对相同体系的数据作了预测。结果表明:用内聚能密度法预删汽液平衡除含氢键的体系外,大部分体系汽相组成的绝对平均偏差均小于0.02。     

Prediction of viscosity of alcohol+hydrocarbon systems by H NMR and activity coefficients at infinite dilution

Based on the concept of local composition (LC), the ¹H NMR chemical shift data of the OH proton over the whole concentration for alcohol+hydrocarbon systems were correlated with only one energy parameter by the LC model. Using this parameter and coupled with one activity coefficient at infinite dilution, the viscosities of some alcohol+hydrocarbon systems were predicted, and the prediction data and experimental one were in a good agreement. The prediction results were also compared with the prediction ones from vapor-liquid equilibria (VLE) data directly, and the former were much better than the latter. In this way, the spectroscopic information can be related to transport property.     

含N-甲酰吗啉溶液体系的相平衡模型研究

通过对N甲酰吗啉(NFM)官能团的分析,将其划分为CH2,CNH2,CHO和CH2OCH2四个官能团,根据N甲酰吗啉溶液体系的实验数据对官能团的相互作用参数进行了拟合,并预测了含NFM的三元体系的汽液平衡数据及四种烃类在NFM中的无限稀释活度系数,并将其与已公开发表的三种划分方法预测数据进行比较。结果表明,划分方法较为合理,且应用UNIFAC基团相互作用参数拟合的误差结果较为满意。     

基于无限稀释活度系数模型的状态方程

发展了一种从纯物质的性质参数预测混合物汽液平衡的方法,它是以立方状态方程的过量吉布斯自由能 g~E结合型混合规则和无限稀释活度系数 MOSCED模型为基础,由MOSCED模型预测得到活度系数方程的相互作用参数,从而得到混合规则中的g~E,使得状态方程能在较大温度和压力范围内预测汽液平衡.用此法预测了含极性组分体系常压到较高压力的汽液平衡,结果良好,与UNIFAC基团贡献状态方程的结果相当.     

Solvent extraction of aromatics from middle distillates: Equilibria prediction method by group contribution

This work describes a method of calculating liquid-liquid aromatics extraction of a middle distillate. The group contribution models of the ASOG and UNIFAC type are investigated. Four vapour liquid equilibrium (VLE), two solid-liquid equilibrium (SLE), three binary and six ternary liquid-liquid equilibrium (LLE) have been measured. The parameters of the models are based mainly on the data of the systems having 10–20 carbon number. VLE, SLE, and infinite dilution activity coefficient data (17–245°C) have been used for calculating interaction parameters between hydrocarbon groups and LLE data (20–80°C) for interaction parameters of dimethylformamide-hydrocarbon groups. Middle distillate representation is based on mass spectrometric and gas chromatographic analysis and on limited data of middle distillate-DMF liquid-liquid equilibrium. It is shown that the performance of ASOG and UNIFAC models are sufficiently valid in representation of data base and in extraction calculations. Considering the predictive character and the rapidi of its application this method can be useful in the preliminary study of extraction processes.     

含盐多元体系汽液相平衡数据测定及预测

对甲醇／乙醇/水／NH_4NO_3四元体系中的有关含盐二元汽液相平衡数据进行了测定及关联．提出用化学滴定──色谱分析联合法确定含盐液相组成．关联所得的最佳参数用于该体系三元及四元汽液相平衡数据的预测,并与实验值作了比较．结果表明,预测值与实验值符合良好．     

An IR study on ion-specific and solvent-specific swelling of poly(N-vinyl-2-pyrrolidone) gel

Swelling degrees of poly(N-vinyl-2-pyrrolidone) (PVP) gel were measured in aqueous salt solutions and in water/organic solvent mixtures to find marked ion- and solvent-specificities. In order to investigate any correlation of those specificities with hydration or solvation of PVP, IR spectra band of the CO group was monitored by means of ATR method both for PVP gel and the relevant solution systems. Dependence of the peak frequency on the swelling ratio suggested that hydration of PVP carbonyl group in deswollen gel systems is different from that in the corresponding solution systems. In the solution systems, PVP carbonyl band showed a high-wavenumber shift for deswollen systems, which can be well correlated with changes in water proton charge through ionic hydration and with Gutmann's acceptor number of organic solvents. In the deswollen gel systems, the CO band showed a low-wavenumber shift, suggesting a strong hydration or doubly hydrated state. This unexpected behavior was interpreted by assuming an intermolecular hydrogen bond of two carbonyl groups intermediated by water molecules.