从纯组分蒸汽压方程计算混合物汽液平衡

本文运用双流体对应态方法,在常低压区,直接从纯组分蒸汽压方程计算混合物的汽液平衡.此法兼有状态方程法理论严密和活度系数法计算简便的优点.用vdW和Wong两种已有的混合法则配合此法计算,取得一定效果,但限于同系物体系,为此发展了一种新的能量混合法则,用一个调节参数,配合此法计算了大量非(弱)极性-非(弱)极性、极性-极性、极性-非(弱)极性各类体系的汽液平衡,精度相当于活度系数法,关联的参数值有一定规律.     

混合物临界性质的预测

本文基于Heidemann和Khalil的临界状态判别准则,对混合物临界性质进行了预测。为了扩展应用到极性混合物并提高预测质量(尤其是预测临界体积的准确度),本文应用了最近提出的立方型转子链(CCOR)状态方程及局部组成型的CCOR状态方程。按以上二模型及SRK和PR模型对十六组极性和非极性二元及三元混合物计算了临界性质。计算结果表明:CCOR模型应用于极性和非极性体系均能获得良好效果,尤其对临界体积(Vc)的预测,其准碓性较之SRK和PR模型有显著的提高。     

费托合成油品体系相关二元物系汽液平衡预测方法的评价

比较了基于不同α函数（BM、SRW）和不同混合规则（MHV2、WS、HG）的PR、RKS状态方程,SR-POLAR和PC-SAFT状态方程,以及UNIF-DMD和UNIF-HOC活度系数方程在费托合成油品体系预测汽液平衡的能力。结果表明：对于弱极性体系,各种计算方法结果接近,偏差均较小;对于非缔合极性体系,UNIF-DMD、RKS-MHV2和RKS-HG方程计算结果比较准确;对于含水缔合极性体系,RKS-MHV2方程和UNIF-HOC方程计算结果比较准确;含酸缔合体系,UNIF-HOC方程和SR-POLAR方程显示了最准确的预测能力;其他缔合极性体系,UNIF-HOC方程和SR-POLAR仍然显示了最高的计算精度,RKS-MHV2和RKS-HG次之;PC-SAFT缺少交互参数时,非均匀体系计算偏差较大。     

实用温度函数型PR方程及其在低碳醇混合物中的应用——(Ⅱ)混合物的汽液平衡

本文将前文(I)报中提出的实用温度函数型PR方程推广到了流体混合物.根据前人工作,提出了一个总括性的混合规则,针对不同体系可得到其简化形式.非极性-非极性,非极性-极性,极性-极性体系,尤其是含醇体系的低、高压下的二元及三元汽液相平衡计算表明,本文的模型有较广的适用性.此外还提出了处理超临界组分的方法,较准确地推算了含氢系统的汽液平衡.总之,本文提出的一套描述复杂体系汽液平衡的方法,可望用于指导低碳酸及其他工业实际体系的分离过程开发.     

实用温度函数型PR方程及其在低碳醇混合物中的应用——(Ⅱ)混合物的汽液平衡

本文将前文(I)报中提出的实用温度函数型PR方程推广到了流体混合物.根据前人工作,提出了一个总括性的混合规则,针对不同体系可得到其简化形式.非极性-非极性,非极性-极性,极性-极性体系,尤其是含醇体系的低、高压下的二元及三元汽液相平衡计算表明,本文的模型有较广的适用性.此外还提出了处理超临界组分的方法,较准确地推算了含氢系统的汽液平衡.总之,本文提出的一套描述复杂体系汽液平衡的方法,可望用于指导低碳酸及其他工业实际体系的分离过程开发.     

非极性混合物的假临界常数

以对应状态原理计算混合物的热力学性质是一较好的方法,为此必须计算混合物的假临界常数。本文利用统计力学基本关系式,作某些简化假设,给出了一种简便的非极性和微极性混合物假临界常数的计算方法。并与Lee-Kesler方法进行了详细比较。对一些实际混合气体的压缩因子进行了计算,与Lee-Kesler法和实验数据皆能很好地一致。     

香豆素-3-羧酸的制备及光谱性质研究

本文以水杨醛、丙二酸二乙酯为原料合成香豆素-3-羧酸乙酯,进而合成香豆素的重要衍生物香豆素-3-羧酸,对其结构进行了表征,并通过紫外光谱和荧光光谱研究了溶剂极性、溶液酸度及溶剂中甲醇含量所产生的影响,最后计算了荧光量子产率,得出香豆素-3-羧酸为弱荧光物质。     

吸附树脂极性的高效液相色谱法测定及表征

建立了测定及表征吸附树脂极性的高效液相色谱法。DA-201极性树脂、AB-8弱极性树脂和D-101非极性树脂分别填充高效液相色谱柱,以去离子水为流动相,葡聚糖为示踪剂,流速1.0 mL/min,柱温30℃,测定树脂的极性。结果表明,正丁醇、乙醇均可作为单一探针分子,流出顺序可定性表征吸附树脂极性:DA-201极性树脂AB-8弱极性树脂D-101非极性树脂;采用乙醇/甲醇作为探针分子组,通过相对极性法计算,得到3种吸附树脂的定量极性值:DA-201极性树脂极性值100,AB-8弱极性树脂极性值18,D-101非极性树脂极性值0,相对标准偏差(RSD)均小于1.50%。方法稳定可靠,可以有效表达吸附树脂的极性。     

LCVM型混合规则扩展用于多参数状态方程以关联混合物汽液相平衡

基于两参数状态方程提出的LCVM混合规则是将以无穷压力为参考态的HV混合规则与以零压力为参考态的MHV1混合规则线性结合而得的,尽管没有理论基础,但对于计算非极性、极性体系给出了较好的结果.因而研究借鉴获得LCVM混合规则的思路将LCVM混合规则扩展到多参数状态方程中,即将HVOS混合规则与MHV1混合规则进行线性结合,并通过引入两个对比参数λ0,λ∞给出了适合多常数状态方程的新LCVM型混合规则.在新的LCVM型混合规则中,参数δ决定了MHV1和HVOS混合规则的相对贡献,该参数可由模型在高压和低压下拟合二元混合物的泡露点得到,通过拟合得到的值约为0.21;混合规则中的活度系数模型可以利用由低压区关联出的GE模型.采用该新混合规则模型,在较宽的温度与压力范围内,结合Harmens-Knapp(HK)方程对包括非极性体系、极性体系等在内的20种二元混合物进行了相平衡计算.计算的结果与实验数据吻合得很好.该模型与采用VDW混合规则模型的相平衡计算结果比较表明,该模型的关联精度有了很大的提高,可以在较大的温度与压力范围内关联多种体系的汽液相平衡数据.但是在混合规则中,参数b,c是依赖于经验获得,因此还有待于进一步的研究.     

MH状态方程使用DDLC混合规则计算混合物临界轨迹

<正>一、引 言状态方程能否精确地描述流体混合物热力学性质,建立合适的混合规则是一个重要因素.近十年来,许多研究者把局部组成概念引入立方型状态方程,建立了与密度有关的局部组成(DDLC)混合规则,将两类重要的热力学模型——状态方程和活度系数方程联系起来,大大地改善了状态方程应用于高密度区时的柔软性,改进了状态方程描述极性一非极性、含超临界组分等高度非对称体系的精确度.作者将局部组成概念引入多参数的MH状态方程,椎导了MH方程的DDLC混合规则,用于计算高压汽液平衡和二元混合物临界轨迹.本文将介绍后者的计算情况.     

Unified equation of state based on the lattice fluid theory for phase equilibria of complex mixtures part II. Application to complex mixtures

In part I of the present article [Yoo et al., 1995], new rigorous and simplified lattice-fluid equations of state (EOS) were derived and their characteristic features of the molecular thermodynamic foundation were discussed by applying to pure fluids. In this part II, both EOSs were extended to various phase equilibrium properties of mixtures. Comparison of the models with experimental mixture data ranges from density, to equilibria of vaporliquid, vapor-solid and liquid-liquid phases for nonpolar/nonpolar, nonpolar/polar, polar/polar mixtures. Both models were also applied to supercritical fluid phase equilibria and activities of solvents in polymer solutions. With two temperature dependent parameters for pure compounds and one temperature-independent binary interaction energy parameter for a binary mixtures, results obtained to date illustrated that both EOSs are quantitatively applicable to versatile phase equilibria of mixtures over a wide range of temperatures, pressures and compositions.     

基于PR立方型状态方程普遍化温度函数的研究与评价

用11类70种非极性、弱极性和极性物质的实验蒸汽压数据对适用于Peng-Robinson状态方程(PR EoS)的17种普遍化温度函数对蒸汽压的预测能力进行了评价。根据各类物质蒸汽压预测结果平均相对偏差评价普遍化温度函数的预测能力。结果表明,Robinson-Peng (1978)、汪萍(2004)和Li-Yang (2011)温度函数能够准确预测烷烃、芳烃、气体和卤代烃类物质的蒸汽压,但对弱极性和极性的醇、醚、酯、酸、水等物质的预测结果不如Forero (2016)温度函数准确。以偏心因子和极性因子普遍化的温度函数对醇、酸、水等极性物质蒸汽压的预测结果明显优于仅以偏心因子普遍化的温度函数。     

PRSV — An improved peng-Robinson equation of state with new mixing rules for strongly nonideal mixtures

Two new composition dependent mixing rules for cubic equations of state are proposed. Both mixing rules contain two adjustable binary parameters and reduce to the conventional one parameter mixing rule when the parameters are equal. Vapor-liquid equilibrium data for mixtures of polar (associated or not) compounds with saturated hydrocarbons and for systems water/alcohol have been used to test the new mixing rules applied to the PRSV cubic equation of state. For these highly nonideal systems, correlation of the data with a new mixing rule of the Van Laar type for the PRSV equation gives better results than those obtained using excess Gibbs energy functions like the Wilson equation, NRTL and UNIQUAC.     

SURFACE TENSION OF POLAR LIQUIDS AND MIXTURES

The simple principle of corresponding states for surface tension, has been generalized to include polar compounds (including those exhibiting hydrogen bond) and their mixtures, by introducing an additional parameter to characterize molecular polarity. In addition the statistical tool of factor analysis has been used to correlate this parameter. For mixtures a binary interaction parameter is also needed, which has also been correlated with easily available properties. Good agreement has been obtained for a wide range of pure liquids and mixtures.     

A FOUR PARAMETER PITZER-CURL TYPE CORRELATION OF SECOND VIRIAL COEFFICIENTS

The Pitzer-Curl ( 1957) correlation of second virial coefficients is slightly modified to accommodate high temperature data ( TT₄ 4.0) of He and H₂ and extended successfully to “ nonstandard” fluids as defined by Tarakad and Danner (1977), by introducing a fourth parameter per compound. The new version improves results at the high temperature limit while it gives comparable results with the previous versions presented by Pitzer and Curl ( 1957) and Tsonopoulos ( 1974) at lower temperatures. The present approach enhances the applicability of the method for polar and associating compounds by introducing a correcting term for 129 such fluids. The extension of the correlation to mixtures requires an additional parameter per binary. Successful results were obtained for thirty nine binary systems investigated in this work     

Factors affecting the electrical resistivity of soybean oil

The electrical resistivity of soybean oil that had been purified to remove polar constituents was determined, and the effect of measuring conditions and the addition of polar constituents (free fatty acids, phospholipids, monoglyceride, α-to-copherol, β-sitosterol, β-carotene, peroxides, and water) on resistivity was investigated. For reproducible resistivity measurements, voltages in excess of 50 volts and charging times greater than 120 s were necessary. As temperature was increased linearly, the resistivity of the oil decreased logarithmically. For making comparisons, a temperature of 24°C, a potential of 50 volts, and 120 s charging times were chosen. All polar constituents decreased the resistivity of the purified soybean oil, but water, phospholipids, and monoglycerides had the greatest effects. Water increased the resistivity-lowering effects of all other constituents except for free fatty acids, which were affected by water only slightly. The synergistic effect of water was much greater for phospholipids and monoglyceride than for other constituents.     

High pressure fugacity coefficients from equilibria of simple gases and polar liquids

An equation of state for mixtures proposed by De Santis, Breedveld and Prausnitz was used to predict the fugacity coefficients in binary gaseous mixtures containing a polar and a simple component. The model has been shown to be sufficiently valid by comparison with experimental fugacity coefficients derived from gas-liquid water equilibria. Special attention has been given to the possibility of systematic experimental errors and their relevance to the validation of the equations.     

SURFACE TENSION OF POLAR LIQUIDS AND MIXTURES

The simple principle of corresponding states for surface tension, has been generalized to include polar compounds (including those exhibiting hydrogen bond) and their mixtures, by introducing an additional parameter to characterize molecular polarity. In addition the statistical tool of factor analysis has been used to correlate this parameter. For mixtures a binary interaction parameter is also needed, which has also been correlated with easily available properties. Good agreement has been obtained for a wide range of pure liquids and mixtures.     

Characterization of soapstock and deodorizer distillates of vegetable oils using gas chromatography

Soapstock and deodorizer distillates are complex lipid mixtures that are produced in significant amounts by the vegetable oil refining process. These mixtures contain components such as fatty acids, sterols, squalene and tocopherols that have important commercial value and therefore their characterization and quantification are of interest. We describe here the development of a simple gas chromatography (GC) method based on a silylation derivatization technique coupled with the use of a medium polar column to separate the different classes of fatty compounds in these waste streams. This method is suitable for GC coupled with either a flame ionization detector or a mass spectrometer.     

AN EMPIRICAL VIRIAL-LIKE CUBIC EQUATION OF STATE FOR PHASE EQUILIBRIUM CALCULATIONS

An empirical cubic equation of state(EOS) was obtained by truncating the virial expansion in reciprocal of molar volume after the third term. The constants of the EOS was generalized in terms of critical temperature, critical pressure and Pitzer's acentric factor.

In pure component applications the EOS exhibited a performance comparable to Peng-Robinson (1976) EOS in the reduced temperature range of 0.5 to 1. The present EOS tends to predict better saturation liquid volumes at reduced temperatures below 0.8, and better estimations for second virial coefficient at high reduced temperatures.

The EOS was successfully employed for vapor liquid equilibrium calculations for some mixtures of normal or slightly polar fluids with traditional one binary parameter mixing rule at moderately high pressures. At low reduced temperatures, where conventional one adjustable parameter applications of the cubic equations compare unfavorably with dual methods based on excess Gibbs energy functions for the liquid phase, a new two constant mixing rule introduced by Stryjek and Vera (1986) was employed for the present equation of state.