普遍化立方型状态方程中Wong-Sandler型混合规则的建立

<正>自70年代末期Huron和Vidal将过量Gibbs自由能模型引入状态方程的混合规则以来,状态方程新混合规则的研究引起了人们的高度重视并取得了重要成就,已成功地将状态方程推广到多种复杂体系的计算,其中近年来由Wong和Sandler等发展的Wong-San-dler（WS）混合规则模型受到了广泛的关注。他们工作的意义在于可以使用由低压汽液平衡数据得到的活度系数模型参数及二元交互作用参数直接推算高压汽液平衡。 但该模型的导出仅限于两参数的立方型状态方程,这样对于广泛应用WS型混合规则势必产生局限性,因此将此类型的混合规则推广到普遍化的立方型状态方程是十分必要的。本文报道了以五参数的Modified Kumar-Starling（MKS）立方型状态方程为工作方程,建立了将WS型混合规则推广到多参数立方型状态方程的途径。     

碳酸二甲酯-甲醇二元共沸物的分离方法

讨论了分离碳酸二甲酸－甲醇二元共沸物的各种方法，重点介绍了最有工业化前景的萃取精馏法，并对萃取剂的选择作了较为详细的讨论。     

碳酸二甲酯的合成及其共沸物的分离

介绍了目前国内外碳酸二甲酯的合成及碳酸二甲酯—甲醇二元共沸物的分离方法，并指出了各种方法的优缺点。甲醇气相氧化碳基化法合成碳酸二甲酯具有发展潜力，对于甲醇—碳酸二甲酯二元共沸物的分离建议使用物料自身压力加压精馏法。     

CO_2-C_2H_6共沸物分离的立方型状态方程选取

汽液平衡热力学模型的准确选取对CO_2-C_2H_6共沸物分离流程的设计和操作分析至关重要。在汽液平衡实验数据的基础上,依据逸度平衡原则,评估vdW、RK、SRK和PR立方型状态方程结合vdW、Margles和CVD混合规则预测CO_2纯物质、CO_2-C_2H_6共沸物和n-C_5H_(12)-CO_2-C_2H_6三元体系汽液平衡的可靠性,采用平均绝对误差的方法进行状态方程的选取。结果表明:SRK状态方程计算CO_2纯物质汽液平衡性质的精度最高;PR状态方程结合Margles混合规则可以准确计算CO_2-C_2H_6共沸体系汽液平衡特性;对于n-C_5H_(12)-CO_2-C_2H_6三元体系,SRK状态方程结合Margles混合规则计算精度明显优于vdW、RK和PR状态方程。通过试差迭代法优化CO_2-C_2H_6共沸体系和n-C_5H_(12)-CO_2-C_2H_6三元体系的二元交互作用参数,状态方程的计算精度得到明显提高。     

基于定量-构效关系预测含低碳酯二元共沸物的共沸温度

为了能够快速、准确地获取含低碳酯二元共沸物的共沸温度,以102种含低碳酯二元共沸物为研究样本,从分子角度出发,基于定量-构效关系原理对共沸温度与其分子结构信息之间的内在定量关系开展了理论研究,建立了多个共沸温度预测模型。通过对模型的拟合能力、显著性及标准误差进行比较和分析,得到最佳的共沸温度预测模型是由6个分子描述符所构建的模型;再利用留一交叉验证法、测试集及Williams图对该模型进行内部验证、外部验证及应用域分析,并将本文所建的模型与文献报道的同类模型及UNIFAC模型进行比较。研究结果显示:共沸温度预测模型具有稳定性好、预测精度高及泛化推广能力强等优点。     

甲醇-丙酮共沸物分离的研究进展

主要介绍了甲醇-丙酮共沸物系变压精馏和萃取精馏两种分离方法的研究进展。经过比较,萃取精馏方法在经济成本方面更具有显著优势。关于萃取精馏,首先阐述了萃取剂的选取以及近些年来萃取剂的研究,主要集中在3个方面:传统单一溶剂、各种盐类和离子液体。其次还介绍了各种萃取剂所对应的气液平衡模型的应用情况和操作条件的优化等方面,并对萃取精馏及其萃取剂的应用提出了展望。     

带共沸的乙醇/乙酸乙酯/2-丁酮三元物系变压精馏分离过程及其参数优化

提出了一种带两股循环的三塔变压精馏结构用于分离乙醇（C₂H₅OH）/乙酸乙酯（C₄H₈O₂-3）/2-丁酮（C₄H₈O-3）三元混合物。由该三元混合物的剩余曲线图（RCM）可知,在大气压下该混合物的每一对组元均形成二元最低共沸物,且乙醇/乙酸乙酯二元共沸物组成随压力变化敏感。三个最低共沸物的同时存在形成了精馏边界线夹紧点现象,而通常压力下的精馏塔无法跨越,以至于传统变压精馏无法应用。通过对精馏塔压力的最优化克服了这一困难,提出了新的分离流程,并对过程进行严格稳态模拟。针对初分塔（T1）塔压不同的6种流程,采用序贯迭代法对各塔的塔板数、进料板位置、回流比等参数进行了优化。通过对比6种流程的经济评价和比较,得到了T1塔的最优压力,并经过能量集成使得过程的年度总费用降低了14.88%。     

2—氯—2—氢六氟丙烷的制备及其与HF的共沸物

介绍了一种2,2－二氯六氟丙烷一元氢解生成2－氯－2－氢六氟丙烷的方法,其过程为：在有效量的负载于三价氧化铬上的钯催化剂及HZ型酸（Z为Cl或F）存在下,于150℃以下的高温下,将2,2－二氯六氟丙烷与氢气反应,生成2－氯－2－氢六氟丙烷,以转化掉的2,2－二氯六氟丙烷计,反应的选择性可达70％以上,还介绍了2－氯－2－氢六氟丙烷与HF形成的共沸物及生成该共沸物的工艺。     

立方型+缔合状态方程模拟离子液体的pVT性质和汽液平衡(英文)

Combining Peng-Robinson (PR) equation of state (EoS) with an association model derived from shield-sticky method (SSM) by Liu et al., a new cubic-plus-association (CPA) EoS is proposed to describe the ther-modynamic properties of pure ionic liquids (ILs) and their mixtures. The new molecular parameters for 25 ILs are obtained by fitting the experimental density data over a wide temperature and pressure range, and the overall aver-age deviation is 0.22%. The model parameter b for homologous ILs shows a good linear relationship with their mo-lecular mass, so the number of model parameters is reduced effectively. Using one temperature-independent binary adjustable parameter kij, satisfactory correlations of vapor-liquid equilibria (VLE) for binary mixtures of ILs + non-associating solvents and + associating solvents are obtained with the overall average deviation of vapor pressure 2.91% and 7.01%, respectively. In addition, VLE results for ILs + non-associating mixtures from CPA, lattice-fluid (LF) and square-well chain fluids with variable range (SWCF-VR) EoSs are compared.     

无机相变材料CaCl2·6H2O的过冷特性

CaCl₂·6H₂O作为一种常见的常温无机水合盐相变材料,由于成本低、易获取、蓄热强而受到广泛的关注。按无水CaCl₂与H₂O的质量比为1.027：1制备了CaCl₂·6H₂O,经X射线衍射（XRD）表征其晶体结构;通过添加成核剂SrCl2·6H₂O和Ba（OH）₂对CaCl₂·6H₂O改性,发现两者的联合作用可抑制过冷,10次熔化-冷却循环平均过冷度1.07℃。采用差示扫描量热仪（DSC）测定CaCl₂·6H₂O添加成核剂前后相变潜热,发现潜热由223.54 J·g^-1降至160.41 J·g^-1;为了扩大CaCl₂·6H₂O相变温度的范围,通过添加质量分数分别为5%、10%、15%、20%和25%的MgCl₂·6H₂O,发现相变温度随MgCl₂·6H₂O质量分数的升高呈线性降低,但不宜超过20%;选取CaCl₂·6H₂O-20% MgCl₂·6H₂O二元共晶盐相变储热体系为改性目标,通过添加1% SrCl2·6H₂O和0.5% CMC,过冷度降至0.57℃,相变潜热为141.09 J·g^-1,低于单独组成盐CaCl₂·6H₂O的潜热223.54 J·g^-1和MgCl₂·6H₂O的潜热163.35 J·g^-1。研究表明,CaCl₂·6H₂O作为无机相变材料具有显著的应用价值。     

A new four-parameter cubic equation of state for mixtures. Vapor–liquid equilibrium calculations

A new four-parameter cubic equation of state has been recently developed and has accurately reproduced the thermodynamic properties of pure substances including polar fluids. In this work we apply the equation to vapor-liquid equilibrium calculations through the introduction of different mixing rules. Various classes of mixtures are investigated at low pressures as well as at high pressures. The calculated results show that the equation with the Huron-Vidal mixing rules offers better correlations for all types of systems over a wide range of temperature and pressure.     

An evaluation of multiple binary interaction parameters in cubic equations of state

Three cubic equations of state are utilized in regressing a large vapour-liquid equilibrium data bank using single and multiple binary interaction parameters. A second binary interaction parameter is shown to be both physically significant and useful in improving the match of experimental data, particularly in polar systems. The use of a third binary interaction parameter in the Trebble-Bishnoi equation of state is found to be of value in systems with large molecular size differences.     

Prediction of ethane and CO2 solubilities in heavy norma paraffins using generalized-parameter soave and peng-robinson equations of state

A study was made of the abilities of the Soave and Peng-Robinson equations to represent the phase behavior of ethane + n-paraffin and CO₂ + n-paraffin systems. These equations are capable of describing the phase behavior of such systems; however, the level of precision obtained varies with the degree of complexity used in representing the interaction parameters in the mixing rules employed. For ethane/C0₂ with n-paraffins extending from C₃ to n-C₄₄, an uncertainty of about 1 % is obtained for bubble point pressures (or about 0.005 mole fraction for solubilities) when two system-specific interaction parameters per isotherm are used. Simple generalized correlations are presented for the equation-of-state interaction parameters which allow prediction of the bubble point pressures with an expected uncertainty of about 5.7% (0.014 in mole fraction).     

Vapour—liquid equilibrium of H2S-Hydrocarbon mixtures using a generalized cubic equation of state

A generalized cubic equation of state proposed by one of the authors has been applied to the calculation of vapour-liquid equilibrium (VLE) of hydrogen sulfide-containing systems. Experimental VLE data for hydrogen sulfide + hydrocarbons, taken from the literature, have been systematically studied using the generalized equation and conventional van der Waals's mixing rules. The interaction parameter required in the mixing rules was obtained for thirteen systems at different temperatures, and a correlation for the interaction parameter as a function of the reduced temperature of the hydrocarbon solvent is proposed. The correlation for the interaction parameter is recommended for predicting VLE in processes in which hydrogen sulfide mixtures are involved.     

A systematic approach for the efficient estimation of interaction parameters in equations of state using binary vle data

A systematic and computationally efficient approach for the estimation of the interaction parameters in equations of state using binary vapor liquid equilibrium (VLE) data is presented. Initially, the best set of interaction parameters is estimated by implicit least squares. Subsequently, the VLE calculations are performed using these parameters. Based on the quality of the fit it is decided whether these estimates suffice or implicit maximum likelihood estimation should be performed to obtain the statistically best values. Estimation subject to the liquid phase stability constraint is performed when erroneous phase behavior is computed. The approach is illustrated with typical examples.     

Efficient separation scheme for binary mixture of CO2 and H2S using aromatic components

Separating a mixture of CO₂ and H₂S into two products through distillation is both difficult and complicated because of similar relative volatility between the two gasses, particularly when a CO₂ concentration exceeds 80%. Therefore, the separation process can involve many separating stages. However, adding a solvent (agent) to the distillation column during the separation process makes this procedure easier.

In this study, different solvents (ethylbenzene, o-xylene, m-xylene, and toluene) and operating conditions (temperature, pressure, and reflux ratio) for separating CO₂ from H₂S have been simulated through distillation using Aspen HYSYS software. Furthermore, four different aromatic compounds (solvents) for different concentrations (from 0 to 40 mol%) have been evaluated to increase the CO₂/H₂S relative volatility, reducing the quantity of the solvent required and energy consumption.

m-xylene was found to be the best solvent for separating CO₂ from H₂S because of the significant effect on relative volatility, the low quantity required for high CO₂ recovery, and the low energy for generating the solvent.     

CO2混合工质的气液相平衡的混合规则对比与预测研究

CO₂混合工质兼顾高效和环境友好的特点,在新一代热功转化循环中受到广泛关注。混合工质气液相平衡性质是循环分析与计算的基础。为了提高CO₂混合工质气液相平衡数据的计算精度,采用PR状态方程结合三种混合规则（vdW、MHV1、WS）,对7种CO₂+HFCs/HFOs及4种CO₂+HCs混合工质的气液相平衡性质进行了计算。结果表明,对CO₂+HCs混合工质,vdW混合规则可达较好的结果;对CO₂+HFCs/HFOs混合工质,在亚临界区三者计算精度相近,但在超临界区,WS混合规则对计算精度提升明显。最后,提出了一种差值模型预测CO₂混合工质气液相平衡性质,预测的AARD(p)值为2.03%,AAD(y)值为0.0120,预测精度较高。     

SRK方程结合超额Gibbs自由能规则预测汽液平衡

SRK方程结合范德华混合规则应用于极性体系会产生较大误差,而结合超额Gibbs自由能(GE)型混合规则能得较好的结果。Wong-Sandler(WS型)混合规则是基于无穷大压力的GE型混合规则,文中对提出一种基于常压的改进型WS(MWS型)混合规则,利用SRK方程分别结合WS型和MWS型混合规则对多个二元极性体系汽液平衡进行预测。比较结果表明,采用SRK方程结合MWS型混合规则预测汽液平衡结果一般优于WS型混合规则。     

汽液相平衡计算混合法则中协体积项b的改进

混合物汽液相平衡通常需要引入合适的混合法则才能更好地进行关联。针对目前混合法则中协体积项b的改进提出了一种新的修正协体积项b的方法。该方法以Mie势能理论、London色散力理论为基础,同时引入Leach等分子形状系数进行修正,这样协体积项b中的交互作用参数l_ij形式上是纯组分分子形状系数θ和φ及临界参数的函数,无需实验数据拟合得到,从而真实反映了二元混合物的实际混合情况。将修正的协体积项b运用于MHV1、LCVM及HV混合法则并结合PR NRTL模型对不同种类的16个体系汽液相平衡进行了计算,并与采用b ∑x_ib_i的MHV1、LCVM及HV混合法则结合PR NRTL模型计算的结果进行比较,结果表明运用修正的协体积项b的混合法则+PR+NRTL模型所得的计算结果精度优于采用b ∑x_ib_i的MHV1、LCVM及HV混合法则 PR NRTL模型的计算结果。     

Phase behavior of mixture of supercritical CO2 + ionic liquid: Thermodynamic consistency test of experimental data

Various models have been applied composed of the Peng‐Robinson equation of state (PR‐EoS) and the Soave‐Redlich‐Kwong equation of state (SRK‐EoS) associated with three mixing rules including the following: Wong‐Sandler (WS), van der Waals one (vdW1), and van der Waals two (vdW2) for phase behavior modeling of mixtures of supercritical CO₂ + different ionic liquids in vapor–liquid equilibrium (VLE) region. It has been found that the PR EoS implying the WS mixing rule can be used as a reliable thermodynamic model to perform a thermodynamic consistency test on the experimental data of phase behaviors of the supercritical CO₂ + ionic liquid systems (19 commonly‐used ionic liquids have been studied). The results show that 40% of the experimental data seem to be thermodynamically consistent, 55.5% seem to be thermodynamically inconsistent, and 4.5% seem to be not fully consistent. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3892–3913, 2013