Vapor-Liquid equilibria measurement of carbon dioxide+1-hexene and carbon dioxide+2-ethyl-1-butene systems at high pressure

Pressure-composition isotherms were obtained for the carbon dioxide+1-hexene system at 40, 60, 80, 100 and 120 ‡C and pressure up to 120 bar and for carbon dioxide+2-ethyl-1-butene system at 40, 75 and 100 ‡C and pressure up to 115 bar. The accuracy of the experimental apparatus was tested by comparing the measured phase equilibrium data of the carbon dioxide+ 1-hexene system at 40 ‡C and 60 ‡C with those of Wagner and Wichterle [1987], and Jennings and Teja [1989]. The solubility of 1-hexene and 2-ethyl-1-butene for the carbon dioxide + 1-hexene and carbon dioxide+2-ethyl-1-butene systems increases as the temperatures increases at constant pressure. These two carbon dioxide-polar solute systems exhibit type-I phase behavior, which is characterized by an uninterrupted critical mixture curve that has a maximum in pressure. The experimental data are modeled by using the Peng-Robinson equation of state. A good fit of the data is obtained with Peng-Robinson equation of state using two adjustable parameters for carbon dioxide+1-hexene and carbon dioxide+2-ethyl-1-butene systems.     

Vapor-liquid equilibria of carbon dioxide and nonionic surfactant system at elevated pressures

Aqueous solutions of the polyoxyethylene nonionic amphiphiles have been extensively investigated at atmospheric pressure, but only a few data of nonionic amphiphile — carbon dioxide system are available at elevated pressures. Isothermal vapor-liquid equilibrium data for the binary ethylene glycol propyl ether (C3E1) — carbon dioxide system at 313.15 K, 323.15 K were measured at elevated pressures. We used two-phase circulating type equipment with a view cell. Modeling of the experimental data has been performed using the Peng-Robinson equation of state, statistical associating fluid theory (SAFT) and Sanchez-Lacombe equation of state.     

VLE calculation of carbon dioxide+n-alkanes binary mixtures with MHV2 mixing rule

Vapor-liquid equilibria for binary and asymetric systems include carbon dioxide+C₁-C₈, C₁₀ are calculated by using the Peng-Robinson-Stryjek-Vera equation of state coupled with the modified MHV2 mixing rule. The modified UNIFAC model is used for determining activity coefficient and excess Gibbs free energy. Calculated equilibrium pressures and mole fractions in vapor phase are compared with the experimental data. The average absolute deviation percent (AAD%)s indicates that the error involved in the application of the MHV2 mixing rule by optimized q₁ and q₂ is less than WS and PRSK mixing rules in most cases.     

High pressure isothermal vapor-liquid equilibria for the binary system of carbon dioxide (CO<Subscript>2</Subscript>)+1,1,1-trifluoroethane (R-143a)

Isothermal vapor-liquid equilibrium data for the binary mixture of carbon dioxide (CO₂)+1,1,1-trifluoroethane (HFC-143a) were measured within the temperature range of 273.15–333.15 K. The data in the two-phase region were measured by using a circulation-type equilibrium apparatus in which both vapor and liquid phases are continuously recirculated. The experimental data were correlated with the Peng-Robinson equation of state (PR-EOS) using the Wong-Sandler mixing rules combined with the NRTL excess Gibbs free energy model. The values calculated by the PR EOS with the W-S mixing rules show good agreement with our experimental data.     

Thermodynamic modeling of vapor-liquid equilibria and excess properties of the binary systems containing diethers and n-alkanes by cubic equation of state

A comparison of the performances of two different approaches of cubic equations of state models, based on a classical van der Waals and mixing rules incorporating theG ^E equation, was carried out for correlation of Vapor-Liquid Equilibria (VLE), H^E and C _P ^E data alone, and simultaneous correlation of VLE+H^E, VLE+C _P ^E , H^E +C _P ^E and VLE+H^E +C _P ^E data for the diethers (1,4-dioxane or 1,3-dioxolane) with n-alkane systems. For all calculations the Peng-Robinson-Stryjek-Vera cubic equation of state (PRSV CEOS) was used. A family of mixing rules for the PRSV CEOS based on the Modified van der Waals one-fluid mixing rule (MvdW1) and two well-known CEOS/G^E mixing rules (MHV1 and MHV2), was considered. The NRTL equation, as the G^E model with linear or reciprocal temperature dependent parameters, was incorporated in the CEOS/G^E models. The results obtained by the CEOS/G^E models exhibit significant improvement in comparison to the MvdW1 models.     

Modeling of Nitrogen and Carbon Dioxide Solubility in Alternative Fuels at High Pressures Using the Soave‐Redlich‐Kwong Equation of State

In this paper, the Soave‐Redlich‐Kwong equation of state with quadratic mixing rule has been tested for correlation of vapor‐liquid equilibria (VLE) at high pressures in the binary nitrogen + dimethyl ether, dimethyl ether + methanol, nitrogen + methanol, carbon dioxide + dimethyl ether and carbon dioxide + methanol systems. The interaction parameters k_ij were evaluated for each binary pair and used for prediction of VLE in the ternary nitrogen + dimethyl ether + methanol and carbon dioxide + dimethyl ether + methanol systems at high pressures. The results of correlation and prediction are discussed.     

On the application of GE models to high-pressure vapor—liquid equilibrium calculations

This paper demonstrates that the two excess Gibbs free energy G^E models with temperature-dependent parameters in the modified Huron—Vidal first-order (MHV1) mixing rule allow the Peng—Robinson equation of state modified by Stryjek and Vera (PRSV) to be used for calculation of vapor—liquid equilibria over wide ranges of temperature and pressure. Good results are obtained for strongly non-ideal binary and ternary systems.     

High pressure phase behavior for the binary mixture of pentafluoropropyl methacrylate and poly(pentafluoropropyl methacrylate) in supercritical carbon dioxide and dimethyl ether

Pressure-composition isotherm is obtained for the carbon dioxide+2,2,3,3,3-pentafluoropropyl methacrylate (PFPMA) using static apparatus with a variable volume view cell at temperature range from 40 °C to 120 °C and pressure up to 130 bar. This system exhibits type-I phase behavior with a continuous mixture-critical curve. The experimental result for carbon dioxide+PFPMA mixture was modeled using the Peng-Robinson (P-R) and multi-fluid nonrandom lattice fluid (MF-NLF) equation of state. Experimental cloud-point data of pressure up 470 bar and temperature to 182 °C were reported for the binary mixture of poly(2,2,3,3,3-pentafluoropropyl methacrylate) [Poly(PFPMA)] in supercritical carbon dioxide and dimethyl ether (DME). The Poly(PFPMA)+carbon dioxide and Poly(PFPMA)+DME systems showed LCST behavior.     

二氧化碳与丙酮,乙醚以及甲醇二元体系饱和液体密度的测定和关联

根据作者建立的一套实验装置,对二氧化碳-丙酮、二氧化碳-乙醚及二氧化碳-甲醇三个含极性混合物二元体系进行了饱和液体密度和泡点压力的测定,测定结果用立方型状态方程进行了关联。     

Separation of Alkanes and Aromatics with Supercritical Carbon Dioxide

Abstract

The separation of alkanes and aromatics with supercritical carbon dioxide has been studied by measuring vapour-liquid equilibria and selectivities in the model systems 2-methylnaphthalene/hexadecane/ carbon dioxide and 2-methylnaphthalene/dodecane/carbon dioxide. The results have been modelled with the Peng-Robinson equation of state. In both model systems supercritical carbon dioxide appeared selective for the component with the highest vapour pressure, 2-methylnaphthalene respectively dodecane. Consequently alkanes and aromatics will be separated by supercritical carbon dioxide on basis of their difference in vapour pressure instead of their difference in chemical structure.     

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．     

应用PSRK状态方程预测高压汽液平衡

为预测高压汽液平衡,将过量吉布斯自由能混合规则和UNIFAC活度系数模型与SRK状态方程相结合,建立基团贡献状态方程PSRK。利用该状态方程对5个体系在不同压力和温度下的汽液平衡数据进行了关联实验测定的汽相压力和汽相组成与计算结果相比所得的相对平均偏差分别为2．16％和1．01％。结果表明,PSRK状态方程可以成功地预测高压下汽液平衡,其精度高于MHV1和MHV2模型。     

High pressure phase behavior for carbon dioxide-1-butanol and carbon dioxide-1-octanol systems

Pressure-composition isotherms are obtained for binary mixtures of carbon dioxide-1-butanol and carbon dioxide-1-octanol systems at 40, 60, 80, 100, and 120 °C and pressures up to 220 bar. The accuracy of the experimental apparatus was tested by comparing the measured phase equilibria data of the carbon dioxide-1-butanol system at 40 °C with those of Ishihara et al. [1996]. The solubility of 1-butanol and 1-octanol for the carbon dioxide-1-butanol and carbon dioxide-1-octanol systems increases as the temperature increases at constant pressure. The carbon dioxide-1-butanol and carbon dioxide-1-octanol systems have continuous critical mixture curves that exhibit maximums in pressure at temperatures between the critical temperatures of carbon dioxideand 1-butanol or 1-octanol. The carbon dioxide-1-butanol system exhibits type-I phase behavior, characterized by a continuous critical line from pure carbon dioxide, to the second component with a maximum in pressure. Also, the carbon dioxide-1-octanol system exhibits type-I curve at 60–120 °C, and shows liquid-liquid-vapor phase behavior at 40 oC. The experimental results for the carbon dioxide-1-butanol and carbon dioxide-1-octanol systems have been modeled by the Peng-Robinson equation of state. A good fit of the data is obtained with the Peng-Robinson equation by using two adjustable interaction parameters for the carbon dioxide-1-butanol system and a poor fit using two adjustable parameters for the carbon dioxide-1-octanol mixture.     

Measurement and modelling of the interfacial tension of triglyceride mixtures in contact with dense gases

The interfacial tension of various triglyceride mixtures in contact with carbon dioxide is compared. The interfacial tension of these triglyceride mixtures is similar. The interfacial tension in contact with carbon dioxide and nitrogen decreases with increasing pressure. Concerning the interfacial tension in contact with carbon dioxide, the interfacial tension increases at higher pressure with rising temperature. The interfacial tension of triglyceride mixtures and of many other liquids in contact with carbon dioxide can be described as a function of the carbon dioxide density.The modelling of the interfacial tension of triglycerides in contact with carbon dioxide or nitrogen using the density gradient theory (Macromolecules 14 (1981) 361) and the Sanchez-Lacombe equation of state (J. Phys. Chem. 80 (1976a/b) 2352 and 2568) is successful if one parameter for nitrogen and two parameters for carbon dioxide are employed. Nevertheless, an appropriate equation of state must be utilized for modelling the interfacial tension of a system. For complex systems, e.g. for triglyceride mixtures, it is indispensable to check the equation of state by means of experimental equilibrium data (e.g. density, volume, or mole fraction).     

Prediction of the infinite-dilution partial molar volumes of organic solutes in supercritical carbon dioxide using the Kirkwood-Buff fluctuation integral with the hard sphere expansion (HSE) theory

Two thermodynamic models were used to predict the infinite dilution partial molar volumes (PMVs) of organic solutes in supercritical carbon dioxide: (1) the Kirkwood Buff fluctuation integral with the hard sphere expansion (HSE) theory incorporated (KB-HSE fluctuation integral method) and (2) the Peng-Robinson equation of state with the classical mixing rule. While an equation of state only for pure supercritical carbon dioxide is needed in the KB-HSE fluctuation integral model, and thus, there is no need to know the critical properties of solutes, two molecular parameters (one size parameter σ₁₂ and one dimensionless parameter α₁₂) in the KB-HSE fluctuation integral model are determined to fit the experimental data published on the infinite dilution PMVs of solutes. The KB-HSE fluctuation integral method produced better results on the infinite dilution PMVs of eight organic solutes tested in this work than the Peng-Robinson equation of state with the classical mixing rule.     

超临界二氧化碳和醇类体系的相平衡计算

应用Peng-Robinson(P-R)状态方程对超临界CO2系统进行了相平衡模拟。对超临界CO2和醇类二元系统进行了汽液相平衡计算,结果表明,P-R状态方程模拟高压下CO2系统的相平衡具有较高的精度。     

Prediction of Solubility of Cholesterol in Supercritical Solvents

In this study the solubility of cholesterol was calculated in two supercritical pure solvents (carbon dioxide and ethane) as binary systems, and four supercritical solvent/co-solvent systems as ternary systems (cholesterol/carbon dioxide/methanol, cholesterol/ethane/acetone, cholesterol/ethane/hexane, cholesterol/ethane/propane) in various temperatures by SRK, PR, and SAFT equations of state. Pure molecular parameters of SAFT equation of state were obtained by fitting vapor pressure and liquid density data. Also the molecular parameters of cholesterol were obtained by fitting the solubility data of binary systems in one temperature, then they were used for the same system in other temperatures and for ternary systems with the same solvent. Results show that the SAFT equation of state can predict the trend and amount solubility of cholesterol in supercritical solvents much better than the other equations of state.     

Phase behavior measurement for the ethylene glycol dimethacrylate in supercritical carbon dioxide at temperatures between (313.2 and 393.2) K and pressures from (5.8 to 22) MPa

High pressure experimental data are presented on the phase equilibrium of ethylene glycol dimethacrylate in supercritical carbon dioxide. Pressure-composition (P-x) isotherms were measured in static method at five temperatures of (313.2, 333.2, 353.2, 373.2 and 393.2) K and at pressures up to 22.0MPa. This (carbon dioxide+ethylene glycol dimethacrylate) system has continuous critical mixture curves that exhibit maximums in pressure at temperatures between the critical temperatures of carbon dioxide and ethylene glycol dimethacrylate. At a fixed pressure, the solubility of ethylene glycol dimethacrylate for the (carbon dioxide+ethylene glycol dimethacrylate) system increases with increasing temperature. The (carbon dioxide+ethylene glycol dimethacrylate) system exhibits type-I phase behavior. The experimental result for the (carbon dioxide+ethylene glycol dimethacrylate) system is correlated with Peng-Robinson equation of state using mixing rule including two adjustable parameters. The critical property of ethylene glycol dimethacrylate is predicted with Joback and Lee-Kesler method.     

Experimental measurement and correlation of phase behavior for the CO2+heptafluorobutyl acrylate and CO2+heptafluorobutyl methacrylate systems at high pressure

Experimental data of high pressure phase behavior from 313.2 to 393.2 K and pressures up to about 14.3 MPa were reported for binary mixture of 2,2,3,3,4,4,4-heptafluorobutyl acrylate (HFBA) and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (HFBMA) in supercritical carbon dioxide. The high pressure experiment was performed by static method using variable-volume view cell apparatus. The CO₂+HFBA and CO₂+HFBMA systems are correlated with the Peng-Robinson equation of state using a van der Waals one-fluid mixing rule. The CO₂+HFBA and CO₂+HFBMA systems exhibit type-I phase behavior with continuous critical mixture curves.     

Diffusion coefficients of l-menthone and l-carvone in mixtures of carbon dioxide and ethanol

The molecular diffusion coefficients of l-menthone and l-carvone in supercritical carbon dioxide (SCCO₂) and carbon dioxide containing 5 and 10 mol% ethanol as a modifier were measured by the Taylor-Aris chromatographic peak broadening (CPB) method over the ranges of temperature from 308.15 to 338.15 K and pressure from 15 to 30 MPa. It was found that the correlation relationships between diffusion coefficients and the temperature, pressure, viscosity, and density, such as the linear correlation between the D₁₂ and ρ, and between the D₁₂ and T/η, which were valid in binary systems, were also suitable for ternary systems of carbon dioxide containing modifier. The diffusion coefficients in modified SCCO₂ decreased with increasing the ethanol mole fraction due to the chemical association between the two solutes and ethanol. Of several models used to predict experimental data in pure carbon dioxide, the two models of Funazukuri-Ishiwata-Wakao and He-Yu-1998 were the best with the AAD less than 3.2%. Furthermore, the models of modified Wilke-Chang, Scheibel, Reddy-Doraiswamy, Lusis-Ratcliff, Hayduck-Minhas, Tyn-Calus, and Lai-Tan overestimated the diffusion coefficient in ethanol modified SCCO₂ with the AAD values increaseing with the percentage of ethanol, which were probably due to the increase of the volume of solvaton sphere as a true diffusion unit with the percentage of ethanol. Moreover, the free volume model of Dymond is good for predicting the experimental data in pure carbon dioxide and ethanol modified SCCO₂ with the AAD values range from 3.21 to 1.90%.