新基团贡献型状态方程VDW—GC应用于超临界流体萃取过程的相平衡计算

本文将新开发的基团贡献型范德华方程应用于超临界流体萃取过程涉及的气-固、气-液两相平衡及气-固-固和气-液-液三相平衡的预测计算,取得了较为满意的结果。     

基团贡献状态方程的开发与热力学模型参数的理论预测

热力学模型是研究流体相行为和热力学性质的重要工具。理论模型的有效应用离不开模型参数的确定。为赋予热力学模型的预测功能,目前的策略一是建立基团贡献(GC)状态方程(EOS),二是探索热力学模型参数的理论预测方法。围绕先前开发的变阱宽方阱链流体状态方程(SWCF-VR),采用基团贡献法思路获得了不同基团对模型参数的贡献值,建立了GC-SWCF方程,证实GC-SWCF方程能满意预测纯物质的密度。进一步将似导体屏蔽模型(COSMO)与SWCF结合,基于COSMO方法获得了192种有机化合物的SWCF方程的模型参数,这是一种不依赖实验数据确定模型参数的理论方法。发现COSMO+SWCF能较好地预测纯物质的密度。引入一个与温度无关的二元交互作用可调参数后,GC-SWCF与COSMO+SWCF都可应用于二元混合物密度与气液相平衡的计算中。     

高分子体系基团贡献法研究进展

介绍了高分子溶液中基团贡献活度系数模型、基团贡献状态方程、高分子密度计算的基团贡献法以及它们的最新进展。     

基团贡献法确定简化空穴理论状态方程的分子参数

本文对作者开发的简化空穴理论状态方程的纯物质参数做了基团贡献处理，得到了１４个基团参数，可以比较好地预测正构烷烃、异构烷烃、环烷烃、芳香烃及部分聚合物的热力学性质。     

UNIFAC基团贡献法估算甲醇-碳酸二甲酯的汽液相平衡

以甲醇-碳酸二甲酯为实验物系，在考虑了汽、液混合物非理想性的情况下，用UNIFAC基团贡献法估算了液相活度系数，用维里方程求算了汽相逸度系数。并最终给出了此二元物系在不同压力下的汽液相平衡数据，结果表明其共沸组成(甲醇摩尔分数)随压力的增高而增大，当压力从0．1MPa增至1．5MPa时，共沸组成由0．890增加到0．960。最后将常压下的相平衡数据与实验值进行了对比，二者的最大偏差为9．4％。     

一个修正的多参数状态方程

从统计热力学的观点出发，结合经验的状态方程，对方程参数作出适当的修正，得到一个改进的适用范围广的多参数状态方程。结果表明，修正的状态方程精度较高。     

汽液平衡计算与立方型状态方程

本文综述应用于汽液平衡计算的立方型状态方程的发展和研究动向。     

基团贡献法推算有机混合液体表面张力

本文在作者曾经提出的推算液体混合物表面张力计算方法的基础上,考查了不同纯组分摩尔表面积的计算公式对液体混合物表面张力推算精度的影响.通过对100个二元体系、10个三元体系和2个四元体系的推算,找到了合适的计算公式.二元体系、多元体系的推算偏差分别为2.45%和4.42%,对于非含一元醇-水体系,式(3)为好,其偏差为2.45%,对含一元醇-水体系式(6)有明显的改善,其推算偏差为6.98%.     

基团贡献法预测含极性基团离子液体对气体的溶解选择性

室温离子液体是一种“绿色溶剂”,具有独特的气体溶解选择性.基于正规溶液理论,根据文献发表的常规咪唑盐离子液体对不同气体的溶解度数据,结合基团贡献法预测了常压下CO2、CH4、N2、CO在含氰基、醚键等极性基团的咪唑盐离子液体中的亨利系数,进而得到不同气体在该类离子液体中的溶解选择性.结果表明,极性基团的引入有助于提高咪...     

立方型状态方程含过量自由焓模型的新混合规则

提出了在参考压力下将过量自由焓(g~E)模型引入状态方程的修正Huron-Vidal混合规则,由g~E模型确定状态方程中混合物的参数,以SRK方程和Wilson模型为例,取大气压为参考压力,计算了16个体系50组汽液平衡,结果表明本文建议的混合规则可直接使用现有文献报道的常压g~E模型参数由立方型状态方程预测常压汽液平衡,并对直接外推预测高压汽液平衡作了尝试.     

PREDICTION OF PHASE EQUILIBRIA IN BINARY MIXTURES USING AN IMPROVED EQUATION OF STATE AND A THEORETICALLY CONSISTENT MIXING RULE

Prediction of thermodynamic properties and phase equilibria in fluid mixtures using a simple cubic equation of state is still a challenging problem. In this paper, we have predicted vapor/ liquid phase equilibria of several binary fluid mixtures using our previously developed improved Peng-Robinson equation of state and a theoretically consistent mixing rule. Our mixing rule combines the mixing rule of Wong-Sandier with a physically based combination rule. Mixtures are composed of nonpolar, nonassociating polar and associating polar fluids. Comparisons of theoretical predictions with experimental data show a very good performance of our approach in describing vapor/liquid phase equilibria of several mixtures, namely, carbon dioxide/ propane, ethane/hexane, butane/methanol, benzene/methanol, acetone/methanol, methanol/ ethanol, methanol/1-butanol, methanol/water and ethanol/water.     

AN IMPROVED PENG-ROBINSON EQUATION OF STATE WITH A NEW TEMPERATURE DEPENDENT ATTRACTIVE TERM

An improved form of the Peng-Robinson cubic equation of state has been proposed. The temperature dependence of the attractive term has been modified so as to accurately represent vapor pressures of several fluids with large acentric factors from triple point to close to the critical point. The prediction of saturated liquid volume is also improved by introducing volume translation term in the equation of state. Comparisons of theoretical results with experimental data are made for the vapor/liquid phase equilibria of 44 pure fluids including nonpolar, polar and associating fluids. Our results show that the modified Peng-Robinson equation of state can represent accurately saturated vapor pressures of the fluids investigated in this paper, and it is more accurate than the Peng-Robinson equation of state and its earlier modifications due to Stryjek and Vera (1986) and Twu et al. (1995rpar;. Incorporation of the volume translation term in the equation of state has been found to improve the accuracy of saturated liquid volume significantly.     

A CUBIC EQUATION OF STATE BASED ON A SIMPLIFIED HARD-CORE MODEL

The Redlich-Kwong (RK) equation of state introduced in 1949 has been considered the most accurate two-constant-parameter cubic equation of state. The other cubic equations which are more accurate than the RK equation contain either three, or more, parameters and/or their parameters are temperature- dependent. A New two-constant-parameter cubic equation of state, $ is introduced using a simplified molecular theory of hard-sphere fluids for its repulsive term. This two-constant-parameter cubic equation of state appreciably increases the accuracy of thermodynamic property predictions and phase equilibria of pure fluids and flluid mixtures over the equations of this category.     

一种新的WS型混合法则

立方形状态方程被广泛应用于相平衡计算中．绝大多数状态方程是结合简单的van der Waals混合法则来进行VLE数据关联的．然而对于应用这些方程关联高度非理想混合物的复杂的相行为,仅用van der waals单维流体混合法则是不够的．甚至在van der Waals混合法则引入另外一个参数都不能够精确地关联含有极性物质的混合物．     

M-H-EOS的理论基础

根据virialEOS的推导方式 ,从具有分子体积的准理想气体模型出发 ,利用巨正则分布和势能函数 ,从理论上推导了M -H -EOS ,并探讨了M -H -EOS的理论基础。结果表明 ,M -H -EOS与virialEOS具有相同的理论基础 ,只是在考虑实际气体对理想气体在分子体积和分子间相互作用的偏差上做了不同的近似。M -H -EOS为了计算简便 ,在实验的基础上对分子间相互作用做了合理的近似 ,从而避免了高阶virial系数求解困难的问题 ,因此在实用中取得成功。了解M -H -EOS的理论基础 ,对进一步发展和改进M -H -EOS的应用领域和计算准确度具有一定的意义     

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.     

方型状态方程在高压相平衡中的研究及应用

对近年来状态方程的研究及其在高压相平衡计算中的应用状况作了综述分析。以ＰＲＳＶ方程为基础，通过实际计算考察和评价不同混合规则在复杂体高压汽液平衡、超临界流体／固体体系相平衡计算中的性能     

VAPOR-LIQUID EQUILIBRIA BY EXTENDED SOAVE EQUATION OF STATE

The Soave[1]equation of state is extensively accepted because of its accuracy andsimplicity.In 1988,Tan et al.[2]suggested a modification by introducing atemperature-dependent factor to parameter"b"on the basis of statistical meaning,anda good accuracy was obtained for supercritical fluids as well as fluids approaching criti-cal conditions but not for mixtures.In the previous work,an extended Soave equa-tion of state[3]has been proposed to improve the prediction of liquid density.In thispaper,the extended equation is used to calculate vapor-liquid equilibria of mixtures atsubcritical conditions.     

VAPOUR LIQUID EQUILIBRIA IN STRONG ELECTROLYTE SOLUTIONS BY THE CORGC EQUATION OF STATE

The capability of chain-of-rotalor group contribution equation of state (CORGC EOS) in prediction of vapour-liquid equilibria for electrolyte solutions is discussed. A new approach is considered in which salt is considered as a single component and therefore, there is no ion in the solution. The interaction parameters between water and 50 salts are determined and reported. The parameters are temperature dependent and thus, vapour-liquid equilibria calculations can be achieved at moderate temperature. The percent average absolute deviation for prediction of vapour pressure and osmotic coefficient for 50 aqueous solutions are equal to 0.89 and 16.7, respectively. Comparison between the calculated results and experimental data has been performed.