【作者】 陈振华；

【导师】 黄志明； 曹堃；

【作者基本信息】 浙江大学 ， 化学工程与技术， 2009， 博士

【摘要】 超临界流体具有气体和液体所没有的一些特殊物理化学性质。近几十年来,超临界流体技术的理论研究及实际应用一直是个热点。其中,超临界流体体系的相平衡问题是理论研究的基础部分,对超临界流体技术的实际应用起着重要的指导作用。本文在超临界流体相平衡的实验测量及理论计算方面进行了一些探索性研究。通过可视直接观察法测量了丙烯(乙烯)+氢气二元体系在低氢浓度范围的临界性质。结果表明,随着氢气的加入,体系的临界温度缓慢下降,临界压力迅速升高。采用PR状态方程并结合van der Waals单流体混合规则,分别选取了van der Waals-1、van der Waals-2.、Panagiotopoulos-Reid和Berthelot’s-Lorentz四种结合律对实验数据进行关联。结果表明,四种结合律均能很好地关联临界温度且关联结果基本相同;对于临界压力地预测,其中van der Waals-1和Berthelot’s-Lorentz的误差略大。此外,选用基团贡献状态方程PSRK也能得到较好的预测结果。通过PR状态方程结合Van der Waals单流体理论混合规则,对包括非极性、极性及缔合等代表性二元体系的临界性质进行关联及预测,系统考察了van derWaals-1、van der Waals-2.、Panagiotopoulos-Reid和Berthelot’s-Lorentz四种结合律对计算结果的影响。临界温度关联结果表明,四种结合律均适用。临界压力预测结果表明,van der Waals-1和Panagiotopoulos-Reid两者的误差相当,而vander Waals-2则与Berthelot’s-Lorentz类似。相对于非极性和极性体系,缔合体系临界压力的预测偏差较大,有待于寻求更为合适的混合规则和状态方程。对HVOS混合规则进行改进得到M-HVOS,对不同体系的高压气液相平衡的预测结果表明,改进后的M-HVOS提高了对非对称体系的预测精度,其结果要明显优于HVOS和MHV1混合规则。此外,提出了一个以低压为参考态的新型超额自由能混合规则(LPMR),将新混合规则结合SRK状态方程及UNIFAC活度系数模型得到一种改进的基团贡献状态方程(LPMR-SRK)。将LPMR-SRK用于不同体系的高压气液相平衡预测,并与PSRK、M-PSRK、VTPR及LCVM模型进行比较。结果表明,LPMR-SRK模型的通用性强,能够较好地预测从对称到非对称及极性体系的高压气液相平衡。通过压力衰退法测量了丙烯分别于75℃和95℃下在半结晶线性等规聚丙烯中的溶解度。结果表明,随着压力的升高,丙烯在聚丙烯中的溶解度升高;而温度的升高,则会降低丙烯在聚丙烯中的溶解度。当温度为95℃时,溶解度曲线在压力为50bar附近时斜率有着明显的突变,在此压力以上,溶解度随压力升高而增加的趋势渐小。采用SL状态方程对实验数据进行关联,结果表明在实验的温度及压力范围之内,SL方程能够得到满意的结果。通过对不同的超(亚)临界流体-聚合物体系相平衡的计算,系统地比较了CK-SAFT、PC-SAFT、SL及SWP状态方程。结果表明,当聚合物为无定形状态时,SL方程和PC-SAFT的计算结果最为准确,而对于含半结晶聚合物体系,PC-SAFT则要逊于SL和SWP方程。对于所考察的体系,CK-SAFT的关联精度普遍最差。更多还原

【Abstract】 Supercritical fluids possess special physico-chemical properties that are different to gas and liquid.In the recent years,the theoretical studies and the applications of supercritical fluids technology are prevalent.The phase-equilibrium engineering problem has always played a fundamental and crucial role in supercritical fluids studies and provided significant direction to the applications of supercritical fluids technology.In this work,the phase-equilibrium experimental measurement and theoretical calculation for the systems involving supercritical fluid have been investigated.The gas-liquid critical properties of propylene(ethylene) + hydrogen systems were measured in the olefin-rich region with visual observation.The critical temperature of both systems decreased slightly with the increasing concentration of hydrogen,whereas the critical pressure increased dramatically with the increase in the concentration of hydrogen.The PR equation of state coupled with van der Waals one-fluid mixing rule was used to correlate the experimental data and four combining rules including van der Waals-1,van der Waals-2,Panagiotopoulos-Reid and Berthelot’s-Lorentz combining rule were discussed.The correlation results of critical temperature showed that all combining rules were accurate and similar to each other. The prediction results of critical pressure obtained by van der Waals-1 and Berthelot’s-Lorentz combining rules were less accurate than the rest of two combining rules.Furthermore,the group contribution equation of state Predictive Soave-Redlich-Kwong(PSRK) was used to predict the critical points and the results agreed well with the experimental data.PR equation of state coupled with the van der Waals one-fluid mixing rule was used to calculate and predict the critical temperature and critical pressure of various classical binary mixtures including nonpolar,polar and associating systems, respectively.Four combining rules including van der Waals-1,van der Waals-2, Panagiotopoulos-Reid and Berthelot’s-Lorentz combining rule were investigated systematically and compared with each other.The calculation results of critical temperature demonstrated that all combining rules provide satisfactory performance. As indicated by the prediction results of critical pressure,the similar deviations were obtained using van der Waals-1 and Panagiotopoulos-Reid combining rules.On the other hand,the van der Waals-2 and Berthelot’s-Lorentz combining rules gave similar accuracy.The prediction of critical pressure for associating systems were less satisfactory when compared with nonpolar and polar systems and more suitable equations of state and mixing rules were expected.The modified HVOS mixing rule(M-HVOS) was proposed and the predicted results for high pressure vapor-liquid phase equilibrium of various systems indicated that the M-HVOS had improved performance for asymmetric systems and was better than HVOS and MHV1 mixing rules.A new excess free energy mixing rule that employs a low-pressure reference state was proposed.This new low-pressure mixing rule(LPMR),coupled with the original UNIFAC method and the SRK equation of state,led to an improved group contribution equation of state(LPMR-SRK).The LPMR-SRK was used to predict the high pressure vapor-liquid phase equilibrium of various systems and the results were compared with that of the PSRK,M-PSRK, VTPR and LCVM models.It was found that satisfactory simulation was obtained by LPMR-SRK model for vapor-liquid phase equilibrium of systems whose components can involve various degrees of nonideality and asymmetry.The solubilities of propylene in semicrystalline linear isotatic polypropylene at 75 and 95℃were measured by the pressure decay method.The experimental results showed the solubility of gas increased with increasing pressure and decreased with increasing temperature.At 95℃,the isothermal solubility curve reached an inflection point when the pressure was increased to about 50 bar and then increasing of solubility slowed down significantly when the pressure was above 50 bar.The experimental data were correlated with the SL equation of state and the fitting result was satisfactory.The solubilities of subcritical and supercritical fluids in various polymers were modeled by the CK-SAFT,PC-SAFT,SL and SWP equations of state.The comparisons between the four models indicated that PC-SAFT and SL EoS provide most satisfactory results for the amorphous polymer systems.With regard to semicrystalline polymer systems,the PC-SAFT showed a poorer performance compared with SL and SWP EoS.In most cases,the performance of the CK-SAFT was least satisfactory.更多还原