Correlation Of Vapor-liquid Equilibria Research Articles

Measurement and correlation of vapor-liquid equilibria for a binary system containing 1-butyl-3-methylimidazolium tridecafluorohexylsulfonate and carbon dioxide

Using a high-pressure variable-volume view cell, the vapor-liquid equilibria of the binary system CO2 and 1-butyl-3-methylimidazolium tridecafluorohexylsulfonate ([BMIM][TDfO]) were determined. The CO2 mole fraction ranged from 0.104 to 0.952 over a temperature range of 298.2-323.2 K. Both the Peng-Robinson and Soave-Redlich- Kwong equations of state were applied with two different mixing rules to correlate with the experimentally obtained results. Increasing the alkyl chain length in perfluorinated sulfonate anion mother structure from methyl to hexyl markedly increased the CO2 solubility. To investigate the effect of the number of fluorine atoms in the anion on the phase behavior of imidazolium-based ionic liquid, these experimental results were then compared with those reported in previous experimental studies of 1-alkyl-3-methylimidazolium cations-including ionic liquid+CO2 binary system.

Evaluation of different contribution methods over the performance of Peng–Robinson and CPA equation of state in the correlation of VLE of triglycerides, fatty esters and glycerol + CO2 and alcohol

The study of biodiesel production has been intensified over the last decades. The ability of predicting the several kinds of equilibrium involved in the process of biodiesel production is highly important in order to optimize and control the processes of production and purification. This work investigated the ability of the group contribution methods to predict critical properties and acentric factor and their effect on the performance of Peng–Robinson Equation of State (PR-EOS). This was done in order to select a reliable set of methods to be used in predicting vapor–liquid equilibrium (VLE) involving triglycerides, fatty esters and glycerol. The contribution methods tested to predict critical properties were: Joback and Reid (JRM); Constantinou and Gani (CGM) and Marrero and Gani (MGM). For the acentric factor the following methods were chosen: Ptizer (PM) and Kesler and Lee (KLM). The properties evaluated by these methods were used in the PR-EOS to predict the density, vapor pressure and VLE involving triolein, methyl oleate and glycerol. The PR-EOS with the inclusion of the associative term (CPA-PR-EOS) was tested in the VLE involving alcohols. Based on the results, a set of methods for each component was selected and used to evaluate the VLE of others triglycerides and fatty esters. The results showed that the choice of the predictive method used is highly important in the performance of the cubic equation. The set of methods chosen proofed to be reliable. The addition of the association term in the cubic equation (CPA-PR-EOS) improves the performance of PR-EOS in the correlation of VLE just in a few cases, especially when the temperature of the system is around or above the critical temperature of the associative molecule.

Measurement and Correlation of Vapor-Liquid Equilibrium for a Cyclohexene-Cyclohexanol Binary System at 101.3 kPa

Many by-products are generated in the process of oxidizing cyclohexene to produce 1,2-epoxycyclohexane by hydrogen peroxide, including cyclohexanol, cyclohexanone, etc. To obtain high-purity 1,2-epoxycyclohexane, the by-products and unreacted cyclohexene must be removed through rectification, in which the vapor-liquid equilibrium (VLE) data of the system are needed. In this study, the VLE data of cyclohexene-cyclohexanol system were studied at 101.3 kPa using an improved EC-2 VLE still. The thermodynamic consistency of the data was examined by Herington's method. The results obtained were exemplary. The VLE data were correlated by the Wilson equation. The difference between the calculated values and the experimental data is minor, indicating that the VLE data are suitable for engineering design.

Correlation of Vapor-Liquid Equilibria for Ethanol + Hydrocarbon Binary Systems Using Regular Solution Model with Exponent-Type Mixing Rule

The regular solution model (the Hildebrand–Scatchard equation) has been improved so that it can be applied to polar mixtures by introducing the exponent-type mixing rule and interaction parameters between unlike molecules. The applicability of the proposed regular solution model is examined by correlating vapor–liquid equilibria of several ethanol + hydrocarbon binary systems, and it is found that the proposed model can be adopted for polar mixtures. For calculations, solubility parameters and liquid molar volumes at given temperatures can be estimated from the molecular structures of constituent pure components by using additive methods.

Correlation of vapor-liquid equilibria for binary mixtures with free energy-based equation of state mixing rules: Carbon dioxide with alcohols, hydrocarbons, and several other compounds

The correlation of vapor-liquid equilibrium data for high-pressure carbon dioxide systems is of interest in a number of industrial applications, including supercritical extraction. Here, we consider the correlation of data for 12 binary systems of carbon dioxide separately with alcohols, with hydrocarbons, and with acetone, benzene, and water. The Wong-Sandler (W-S) and modified Huron — Vidal first order (MHV1) free energy-based equation of state mixing rules (the W-S and MHV1 models) were used in the calculations. Both combined equation of state+free energy models generally resulted in good correlations of the experimental data over wide ranges of temperature and pressure with temperature — independent parameters. However, for the carbon dioxide+water system, the W-S model produced an 11% average absolute deviation in pressure, while no parameter that resulted in an AAD in pressure of less than 20% could be found for the MHV1 model.

Vapor liquid equilibrium modeling of alkane systems with Equations of State: “Simplicity versus complexity”

Two types of Equations of State (EoS), which are characterized here as “simple” and “complex” EoS, are evaluated in this study. The “simple” type involves two versions of the Peng–Robinson (PR) EoS: the traditional one that utilizes the experimental critical properties and the acentric factor and the other, referred to as PR-fitted (PR-f), where these parameters are determined by fitting pure compound vapor pressure and saturated liquid volume data. As “complex” EoS in this study are characterized the EoS derived from statistical mechanics considerations and involve the Sanchez–Lacombe (SL) EoS and two versions of the Statistical Associating Fluid Theory (SAFT) EoS, the original and the Perturbed-Chain SAFT (PC-SAFT). The evaluation of these two types of EoS is carried out with respect to their performance in the prediction and correlation of vapor liquid equilibria in binary and multicomponent mixtures of methane or ethane with alkanes of various degree of asymmetry. It is concluded that for this kind of systems complexity offers no significant advantages over simplicity. Furthermore, the results obtained with the PR-f EoS, especially those for multicomponent systems that are encountered in practice, even with the use of zero binary interaction parameters, indicate that this EoS may become a powerful tool for reservoir fluid phase equilibria modeling.

05/01432 Measurement and correlation of vapor-liquid equilibria and excess enthalpies of binary systems containing ionic liquids and hydrocarbons: Kato, R. et al. Fluid Phase Equilibria, 2004, 224, (1), 47–54

05/01432 Measurement and correlation of vapor-liquid equilibria and excess enthalpies of binary systems containing ionic liquids and hydrocarbons: Kato, R. et al. Fluid Phase Equilibria, 2004, 224, (1), 47–54

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

AbstractIn 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 kij 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.

Simultaneous description of excess properties and vapor–liquid equilibria for associating mixtures by hydrogen-bonding lattice fluid equation of state

Since all residual thermodynamic properties can be calculated from an equation of state (EOS), an accurate EOS may also be used for the computation of excess properties and vapor–liquid equilibria (VLE) simultaneously. Cubic equations of state have been used with G E-mixing rules for associating mixtures. In the present study, the applicability of the hydrogen-bonding non-random lattice fluid model (NLF-HB) was investigated for the simultaneous correlation of VLE and excess properties of mixtures containing associating components. The optimized parameters for VLE and H E at room temperature gave reliable results for fitted properties. V E calculation showed large errors but the molar volume was accurate. The allowable range for the temperature extrapolation of the binary parameter was wider for VLE than for for H E.

Correlation of Vapor-Liquid Equilibria and Saturated Densities of Binary Mixtures by the Generalized Scott-Fuller-Soave-Redlich-Kwong Equation of State.

A new cubic type of Scott-Fuller-Soave-Redlich-Kwong equation of state (SFSRK EOS) has been proposed to calculate both vapor-liquid equilibria and saturated densities of vapor and liquid phases. The parameters of the proposed EOS are given for each pure substance. In this study, the parameters were generalized, based on the critical properties and the acentric factor, for several components representative of LNG. Furthermore, by adopting the exponent type mixing rules for the parameters, both the vapor-liquid equilibria and the saturated densities of vapor and liquid phases for binary mixtures were correlated using the SFSRK EOS. The calculated results show a good correlation with observations, especially for the liquid phase densities.

Prediction of phase equilibria in water/alcohol/alkane systems

The Cubic Plus Association Equation of State (CPA EoS) is applied to the prediction of Vapor–Liquid Equilibrium (VLE) and Liquid–Liquid Equilibrium (LLE) in ternary associating mixtures containing water, alcohols and alkanes. The appropriate set of combining rules for the cross-association energy and volume parameters of the EoS is identified by evaluating the performance of four such sets in the correlation of VLE and LLE for water/alcohol mixtures. Using only one interaction parameter per binary mixture, in the physical part of the EoS, CPA gives very satisfactory predictions of ternary VLE and LLE.

Modification of the Furter equation and correlation of the vapor–liquid equilibrium for mixed-solvent electrolyte systems

Isobaric vapor–liquid equilibrium values at 1 atm pressure were measured for the systems 1-propanol–water–potassium acetate and 2-propanol–water–potassium acetate under fixed salt mole fractions using a modified Othmer recirculation still. A modified Furter equation, ln( α s/ α)= k 1 z+ k 2 z 2, was proposed for correlating the effect of dissolved salts on vapor–liquid equilibrium (VLE). The modified equation contains two parameters that are applicable to the entire salt/solvent composition range. Correlation of VLE for 15 mixed-solvent electrolyte systems was made by means of the proposed modified equation with better results than those obtained from the original equation.

Correlation of vapor-liquid equilibrium for systems of carbon dioxide + hydrocarbon by the corresponding-states principle

Abstract A combination of the corresponding-states principle with mixing rules is used to correlate vapor-liquid equilibrium data for systems of carbon dioxide + hydrocarbon. Good agreement with experimental data is obtained by a suitable choice of the equations of state up to medium asymmetric systems. Binary interaction parameters for the proposed method are given.

Simulation of binary refrigerant mixture vapor-liquid equilibria using a quasi-regular nonrandom fluid theory and local composition mixing rules

A new model and a novel approach are presented for correlation/prediction of refrigerant mixture phase equilibria. The excess Gibbs free energy in binary halogenated alkane mixtures is described by a recently proposed two-liquid theory with a regular solution reference for mixtures of nonpolar species. The single g E model parameter, obtained by correlating near-ambient binary vapor-liquid equilibria (VLE), is used in Wong-Sandler mixing rules in the Peng-Robinson-Stryjek-Vera equation of state to predict binary VLE at elevated temperatures. This model is applied to the tetrafluoromethane-chlorotrifluoromethane (R14-R13), tetrafluoromethane-trifluoromethane (R14-R23), and the trifluoromethane-chlorotrifluoromethane (R23-R13) binary systems. The one-parameter quasi-regular g E model provides good correlation of VLE for the binary systems at near ambient conditions. However, successful prediction of high temperature VLE depends on the accuracy of the g E model, the consistency of the EOS mixing rule model, and the method used to solve the model equations and associated material balances.

Measurement and correlation of vapor-liquid equilibria in polymer solutions containing polystyrene with polymer ASOG

A gas chromatographic method is used to measure the activities of solvents which have a range of finite concentrations in polymer solutions. Experimental data are presented for 8 binary solvent/polystyrene systems at 393.15 and 423.15 K. The polymer ASOG is proposed to be correlated with the activities of solvents in polymer solutions, and consists of the original ASOG and the empirical modification of free volume. For 8 binary solvent/polystyrene systems containing nonpolar and moderately polar solvents, the polymer ASOG was successful to correlate with experimental data within the range of 1% error.

摂動型状態方程式による塩化カルシウムを含む溶液の気液平衡の相関

摂動型状態方程式による塩化カルシウムを含む溶液の気液平衡の相関

Phase Equilibria for Polymer Systems.

Phase equilibria for polymer systems were reviewed. The authors briefly described such methods as barometric method, gravimetric method, gas chromatographic method, and permeation method used as experimental techniques to measure the vapor-liquid equilibria of polymer systems, i.e., solubilities of gases and vapors in polymers. Furthermore, the corresponding state principle, solution models, and equation of state for prediction and correlation of vapor-liquid equilibria were described. For liquid-liquid equilibria, the experimental results obtained using the cloud point method and the correlated results obtained using a solution model for cyclopentane-polystyrene system were shown as an example of binary systems. The experimental and correlated results for the aqueous two-phase systems were shown as an example of multicomponent systems. Finally, the results of correlation for the volume-phase transition of polymeric gels were presented.

Simultaneous correlation of vapor-liquid equilibrium and heat of mixing data for ternary systems

The heat of mixing (H E) and vapor-liquid equilibrium (VLE) data were correlated by means of various parameter estimation methods. The most elaborate one - the “Orthogonal Regression” enables the introduction of the estimated experimental errors for all measured variables into the computational process. The use of such complicated procedure is justified only in the case when the real experimental errors are well known and the equations used for representation of data are so flexible that they do not introduce further errors. When the knowledge of errors is poor, which is the case for most literature data, sufficient results can be obtained on much simpler way by means of “least square” method.

Correlation of vapor-liquid equilibria for the system ammonia-carbon dioxide-water

New parameters are given for a previously published correlation for calculating vapor-liquid equilibria in aqueous systems containing volatile weak electrolytes. Particular attention is given to ternary aqueous mixtures containing ammonia and carbon dioxide. When the new parameters are used, good agreement is obtained with recent experimental data.

Thermodynamics of associated solutions. Excess thermodynamic properties of liquid mixtures of some organic compounds with amines

The UNIQUAC associated-solution model reproduces successfully the vapor pressure isotherms of binary aliphatic amine-saturated hydrocarbon mixtures by use of smaller values of the association constant for aliphatic amines than those given by Brandani. In the correlation of vapor-liquid equilibrium and excess enthalpy data for amine-alcohol mixtures, two cases are studied for solvation equilibria between these two self-associating components (A, B). In vapor-liquid equilibrium data reduction, for aliphatic amine-alcohol mixtures, a single solvation model forming A i B j complexes gives better results than a multisolvation model forming copolymers such as (A i B j ) k , (A i B j ) k A l , A i (B j A k ) l B m , etc., and for aniline-alcohol mixtures the latter is better than the former. In excess enthalpy data reduction, both models give very similar results.