含醇体系超额性质模型TDAM的导出和应用

本文针对含醇体系的特性,基于缔合溶液理论,导出了一个形式简单、物理意义明确的溶液模型——TDAM.由于TDAM模型中引入了较为合理的温度关系,仅需两套不同温度下的超额焓数据,即可进行其它温度下超额焓数据以及汽液平衡数据的推算.将TDAM模型对非极性、极性体系超额焓的关联结果与其它常见溶液模型(Wilson、W-C和QCSM等)进行了比较,以TDAM模型为最佳;对含醇体系汽液平衡数据也进行了同样的比较,TDAM模型关联结果优于或相当于其它溶液模型.将该模型用于超额焓和汽液平衡的推算,结果令人满意.     

纳他霉素在不同溶剂中溶解度的测定与关联

采用平衡法测定了纳他霉素在纯水(278.15 ～ 341.15 K)和异丙醇(278.15 ～ 318.15 K)、甲醇(278.15 ～313.15 K)溶液中的溶解度.在三种溶剂中的溶解度均随温度升高而增大,以在甲醇中溶解效果最好,异丙醇次之,纯水最差.分别用经验模型、理想溶解度方程和Apelblat方程对实验数据进行关联,关联效果令人满意,平均相对误差小于5%,获得了相关模型参数.相对而言,经验模型和Apelblat方程关联的效果较好.实验得到的溶解度数据和关联结果对纳他霉素结晶工艺的研究具有较大的指导意义.     

关联二元体系超额焓的改进模型

在已提出的二元体系超额焓分子热力学模型基础上,用体积分数表征溶液宏观组成以校正由于分子尺寸不同引起的分子之间特殊交互效应,推导出关联二元溶液超额焓的三参数改进模型.用近10年发表的有代表性的上百个二元非对称体系实验数据,主要是含不同分子尺寸、形状、结构组分的复杂体系实验数据,对所提超额焓改进模型进行了检验.结果表明,对含不同分子尺寸、形状、结构组分的非对称体系,改进模型的关联精度明显优于原模型.同时,在φ→0 或φ→1的极限条件下,改进模型同样成立.     

用双液理论局部组成模型关联缔合体系核磁共振化学位移

¹H NMR化学位移被广泛用于研究缔合体系溶液微观结构和溶液热力学性质.本文基于局部组成思想和双液理论,提出了一个半经验的缔合体系核磁共振化学位移关联模型,模型中含有两个代表分子间相互作用力的待定参数.利用新提出的模型,对不同的缔合体系进行了关联,包括自缔、交叉缔等缔合体系.关联的结果表明,该模型能很好地描述各种不同缔合形式的缔合体系¹H NMR化学位移随浓度的变化关系.同时利用模型参数中含有的温度关系,预测了同一体系在不同温度时的核磁共振化学位移,预测偏差和模型自身关联偏差基本在同一数量级上.     

乙醇/丙醇-水-复合溶剂体系汽液平衡研究

为研究复合萃取溶剂体系下醇-水的汽液平衡,分别选用盐质量浓度为0.2 g/mL的乙二醇+氯化锂、乙二醇+醋酸钾2种复合萃取溶剂,测定了101.3 kPa下不同溶剂体积比(0.5∶1,1∶1,2∶1)时乙醇-水和丙醇-水的汽液平衡数据。分别用W ilson和NRTL热力学模型对所测汽液平衡数据按拟三元体系进行了关联。利用工业规模的实验装置,对测定结果进行了验证。结果表明,复合萃取溶剂能使乙醇-水和丙醇-水体系的共沸点消失,大大改变了体系中醇与水的相对挥发度。关联结果表明,W ilson热力学模型较NRTL热力学模型更适于乙醇/丙醇-水复合萃取溶剂体系。工业规模生产数据验证了所测定数据的可靠性,乙醇产品纯度可达到99.85%。     

混合溶剂在高分子膜中的传递模型

以单溶剂在高分子膜中的蠕变传递模型为基础,通过考虑溶剂间的耦合作用对溶剂在高分子膜中传递过程的影响,建立了混合溶剂在高分子膜中传递的蠕变模型.对模型参数进行了数值模拟研究,并使用该模型关联了吸收实验曲线.计算结果显示模型具有一定的预测功能.     

辣椒碱在不同溶剂中溶解度的测定与关联

应用平衡法,以辣椒碱晶体(含辣椒碱50.4%,二氢辣椒碱37.1%,降二氢辣椒碱7.9%)为原料,在262~333 K温度下测定了辣椒碱在甲醇、乙醇、正丁醇等9种溶剂中的溶解度曲线,分别采用理想溶液模型、Apelblat模型和多项式经验方程对实验数据进行关联. 结果表明,9种溶剂中,辣椒碱的溶解度均随温度升高而增大,辣椒碱在正丁醇中的溶解度最大,在水中的溶解度最小. 计算表明,乙醚适合作为辣椒碱的冷却结晶溶剂,产率为51.23%. 模型关联结果为理想溶液模型的误差较大,多项式经验方程的误差最小.     

间苯二甲腈在四种溶剂中溶解度的测定及关联

采用平衡法分别测定了间苯二甲腈在甲醇、甲苯、二甲苯和苯胺四种溶剂中的溶解度,温度范围为293.15~318.15 K,并分别采用λ-h方程、Apelblat模型和Yaws模型对实验数据进行了关联。根据实验数据可以看出间苯二甲腈的溶解度在4种溶剂中均随着温度的升高而升高,并且间苯二甲腈在不同溶剂中的溶解度差别较大。通过4个体系的24个数据点的实验值与计算值相比较,三种模型的总的平均相对误差分别为5.92%、3.90%、3.86%。结果表明λ-h方程、Apelblat模型和Yaws模型都可以较好地关联间苯二甲腈在四种溶剂中的溶解度数据。     

氯唑沙宗在不同溶剂中溶解度的测定与关联

氯唑沙宗是一种口服有效的中枢性骨骼肌松弛剂,通过固液相平衡实验可为其合成及纯化工艺中溶剂的选择提供基础数据。采用动态平衡法测定了288.15—318.15 K温度范围内氯唑沙宗在甲醇、乙醇、正丙醇、二氧六环、乙酸乙酯、四氢呋喃和乙腈中的溶解度。结果表明:氯唑沙宗在这7种溶剂中的溶解度均随温度的升高而增大,其中在四氢呋喃中的溶解度最大、乙腈中最小。采用Apelblat方程、λh方程、NRTL和Wilson模型对溶解度数据进行了关联,数据表明实验中的二元体系的关联结果都较好地与实验值相吻合,对比平均相对标准偏差,Wilson模型(平均RSD=0.69%)的关联结果是4种模型中最佳的。     

电解质NRTL模型的研究进展及应用

电解质NRTL模型是重要的热力学局部组成模型。本文阐述了电解质NRTL模型的研究进展过程,包括模型的提出、修正、改进和扩展,同时指出了不同模型的适用范围。介绍了模型在各种复杂电解质溶液体系关联计算中的应用,可以为一些工业生产过程的模拟、设计和优化提供理论指导。电解质NRTL模型的主要优势是适用的温度和浓度范围宽,不需二元以上高阶参数;但模型自身也存在缺陷,如参数的回归工作量大、在溶液体系临界点处的预测精度较差等,故模型仍需进一步完善。     

GAS CHROMATOGRAPHIC DETERMINATION AND CORRELATION OF WEIGHT-FRACTION HENRY'S CONSTANTS FOR HYDROCARBON GASES AND VAPORS IN MOLTEN POLYMERS

In the polymer industry, separation equipment is required to separate unreacted monomers and solvents from polymers. In order to design such equipments, solubilities of gases and vapors in molten polymers are needed as fundamental data. It is very helpful if the weight-fraction Henry's constant, which gives solubilities of a solute at concentrated regions of a polymer, can be estimated by a predictive method.

In the present study, a new expression for the free volume term has been derived and is coupled with the UNIFAC model. The present UNIFAC-FV model was applied to common polymer systems. The weight-fraction Henry's constants were calculated for several volatile hydrocarbons and the calculated results were compared with the experimental data determined by a gas chromatographic technique.

The present UNIFAC-FV model with a new free volume expression was found to be helpful in predicting the weight-fraction Henry's constants of hydrocarbon solutes in molten polystyrene, in polypropylene, and in low-density polyethylene. It is advantageous that our model is applicable both supercritical gases and subcritical vapors with no adjustable parameters.     

PSRK模型的修正混合规则及其应用于聚合物溶液汽液平衡的预测

To extend the PSRK(predictive Soave-Redlich-Kwong equation of state)model to vapor-liquid equilibria of polymer solutions,a new EOS-gE mixing rule is applied in which the term ∑ xi ln(b/bi)in the PSRK mixing rule for the parameter a,and the combinatorial part in the original universal functional activity coefficient(UNIFAC)model are cancelled.To take into account the free volume contribution to the excess Gibbs energy in polymer solution,a quadratic mixing rule for the cross co-volume bij with an exponent equals to 1/2 is applied [b1/2 ij= 1/2(b1/2 i b1/2 j)].The literature reported Soave-Redlich-Kwong equation of state(SRK EOS)parameters of pure polymer are employed.The PSRK model with the modified mixing rule is used to predict the vapor-liquid equilibrium(VLE)of 37 solvent-polymer systems over a large range of temperature and pressure with satisfactory results.     

A modified entropic expression for the analysis of swelling behavior of polymeric membranes in solutions

The linear mixed relation for mixed molar volume and free-volume were modified to derive our new activity expression attributed to the combined combinatorial and free volume contributions. The validity and applicability of this expression were demonstrated by calculating the solvent activity in polymer solutions and analyzing the swelling behaviors for polymeric membranes. The average absolute deviation (AAD) of these calculated results from the experimental values of solvent activities for polymer solutions was employed for comparison. It is shown that the modified model can yield better results than the original one for most of the systems considered. The swelling behavior of poly vinyl alcohol (PVA) membranes in water/glycol (EG) mixture over a wide range of concentrations was analyzed. The activity of solvents in the liquid and the membrane was calculated by the UNIQUAC model and this present modified model, respectively. The estimations are consistent with experimental data roughly at temperatures of 333 and 343 K. It is found that the modified model is a suitable alternative to the Flory-Huggins equation for the analysis of the swelling behaviors of polymeric membranes in solutions.     

Optimization of polymer-solvent interaction in a multisolvent system by the UNIFAC group-contribution method

The solubility parameter scheme is an exceptionally useful tool for predicting the solubility behavior of simple polymer systems. However, this scheme is unable to handle well enough complicated systems, such as those involving donor-acceptor interactions and those containing more than two solvents. More advanced thermodynamic treatments and computer techniques, such as UNIFAC, can be a key to solving these kinds of problems. The UNIFAC group-contribution method utilizes a volume parameter and a surface-area parameter for each structural group and a pair of interaction-energy parameters for each pair of groups, which can be deduced from experimental activity data. The method was originally derived for mixtures of ordinary liquids and has been extended to polymer solutions by adding a free-volume correction. The modified UNIFAC method can be used to estimate the activities of solvents in a polymer solution, even when no experimental data are available for the mixture. In the present study, the UNIFAC method was applied to optimize polymer-solvent interactions in three-solvent systems. A three-dimensional plot, displaying polymer activity as a function of the solvent composition, was constructed for each polymer system. The minimum in polymer activity was used as the criterion for maximum polymer-solvent interaction. Dissolution rate and solution clarity were used to test the polymer-solvent interaction experimentally. Comparison of theoretical predictions with experimental results indicated that a better agreement could be obtained by using the UNIFAC method rather than the solubility parameter method.     

GAS CHROMATOGRAPHIC DETERMINATION AND CORRELATION OF WEIGHT-FRACTION HENRY'S CONSTANTS FOR HYDROCARBON GASES AND VAPORS IN MOLTEN POLYMERS

In the polymer industry, separation equipment is required to separate unreacted monomers and solvents from polymers. In order to design such equipments, solubilities of gases and vapors in molten polymers are needed as fundamental data. It is very helpful if the weight-fraction Henry's constant, which gives solubilities of a solute at concentrated regions of a polymer, can be estimated by a predictive method.

In the present study, a new expression for the free volume term has been derived and is coupled with the UNIFAC model. The present UNIFAC-FV model was applied to common polymer systems. The weight-fraction Henry's constants were calculated for several volatile hydrocarbons and the calculated results were compared with the experimental data determined by a gas chromatographic technique.

The present UNIFAC-FV model with a new free volume expression was found to be helpful in predicting the weight-fraction Henry's constants of hydrocarbon solutes in molten polystyrene, in polypropylene, and in low-density polyethylene. It is advantageous that our model is applicable both supercritical gases and subcritical vapors with no adjustable parameters.     

用活度系数模型和PCOR状态方程预测聚合物溶液中的亨利常数（英文）

In this paper, the polymer chain of rotator (PCOR) equation of state (EOS) was used together with an EOS/GE mixing rule (MHV1) and the Wilson's equation as an excess-Gibbs-energy model in the proposed approach to extend the capability and improve the accuracy of the PCOR EOS for predicting the Henry's constant of solutions containing polymers. The results of the proposed method compared with two equation of state (van der Waals and GC-Flory) and three activity coefficient models (UNIFAC, UNIFAC-FV and Entropic-FV) indicated that the PCOR EOS/Wilson's equation provided more accurate results. The interaction parameters of Wilson's equation were fitted with Henry's constant experimental data and the property parameters of PCOR, a and b, were fitted with experimental volume data (Tait equation). As a result, the present work provided a simple and useful model for prediction of Henry's constant for polymer solutions.     

Correlation for volume phase transition of polymeric gel (vinyl alcohol-sodium acrylate copolymer) in alcohol-water solutions

A thermodynamic model was proposed to correlate the phase behavior of a swelling polymeric gel (vinyl alcohol-sodium acrylate copolymer) and the volume phase transition in alcohol (methanol, ethanol or propanol)-water solutions. The model is based on the Flory-Huggins formula for polymer solution coupled with the osmotic pressure by rubber elasticity proposed by Flory. The volume change behavior and the equilibrium concentrations inside and outside the gel were successfully correlated using the present model.     

Effects of thermodynamic models on the predictions of free volume diffusion theory for concentrated polymer solutions

Three thermodynamic models were used to demonstrate the effects of model choice on solvent–polymer binary diffusion coefficients predicted by free volume theory. Poly(vinyl acetate) and four solvents were used as typical solutions for these calculations. Thermodynamic models affect the predictions the most at high solvent weight fractions and for solutions which exhibit positive enthalpic interactions. For solutions dilute in solvent where Henry's law might describe phase equilibria, diffusion coefficients can be estimated without reference to thermodynamic data.     

The lower critical solution temperature (LCST) of non-polar polymer solutions: An introduction

The phase behavior at high temperatures of non-polar polymer solutions is discussed in a qualitative way in terms of the free volume theory of liquids developed by Prigogine, Patterson and Flory. This theory is necessary to explain the existence of a Lower Critical Solution Temperature (LCST) in non-polar polymer solutions and the related exothermic heats of mixing. The classical theory of polymer solutions and its limits is first reviewed.