Universal Functional Activity Coefficient Research Articles

Phase Equilibrium of Binary Mixtures ofn-Hexane + Branched Chlorobutanes: Experimental Results and Group Contribution Predictions

In this work the study of the phase equilibrium (experimental and modeled) of three binary mixtures formed by n-hexane and a branched chlorobutane (2-chlorobutane, 1-chloro-2-methylpropane, or 2-chloro-2-methylpropane) is presented. New and consistent experimental vapor–liquid equilibrium data at isothermal conditions T = (288.15, 298.15, and 308.15) K have been obtained and correlated using the Wilson equation. In addition, two group contribution models, modified-UNIFAC (universal functional activity coefficient) and VTPR (volume-translated Peng–Robinson), have been used to predict the vapor–liquid equilibrium of the mixtures. The agreement between experimental results and predicted ones is not satisfactory.

Improvements in the Experimentation and the Representation of Thermodynamic Properties (iso-p VLE and yE) of Alkyl Propanoate + Alkane Binaries

This paper presents the experimental measurements of isobaric vapor–liquid equilibria (iso-p VLE) and excess volumes (vE) at several temperatures in the interval (288.15 to 328.15) K for six binary systems composed of two alkyl (methyl, ethyl) propanoates and three odd carbon alkanes (C5 to C9). The mixing processes were expansive, vE > 0, with (δvE/δT)p > 0, and endothermic. The installation used to measure the iso-p VLE was improved by controlling three of the variables involved in the experimentation with a PC. Experimental iso-101.32 VLE data showed a positive consistency with Fredenslund’s point-to-point method. Systems of methyl propanoate + heptane and ethyl propanoate + heptane presented azeotropes (xaz,Taz) at (0.844, 351.86) and (0.481, 366.61), respectively. Representations were obtained of pvE = φ(x,T) and hE = φ(x,T), using a model proposed previously [Ind. Eng. Chem. Res. 2010, 49, 406], and the behavior of the binary systems studied was interpreted. An adequate extended version of the same model was used to perform a stepwise correlation of the different properties according the following order (x,T,cpE)→(x,T,hE)→(x,T,gE), positively valuing the multiproperty correlation. The paper conducts a comparison with the results obtained by applying the nonrandom two-liquid (NRTL) model, which were acceptable with the exception of the inadequate reproduction of values of the second derivative of the Gibbs function. The universal functional activity coefficient (UNIFAC) group contribution model did not give a satisfactory representation of the properties for the binaries of this work.

Effect of mass fractions on evaporation of a multi-component droplet at dimethyl ether (DME)/n-heptane-fueled engine conditions

Two fuels with the compression–ignition property similar to conventional diesel–DME and n-heptane–are selected to analyze the evaporation performance of a two-component droplet at different internal combustion engine conditions. A multi-component evaporation model based on Universal Functional Activity Coefficient (UNIFAC) method and the non-equilibrium evaporation law is implemented to predict the evaporation characteristics of the DME/n-heptane droplets with different mass fractions. Generally, reducing the mass fractions of DME, increasing the ambient temperature or increasing the relative velocity between the droplet and the ambient air enhances the evaporation of a droplet. However, the variation of the ambient pressure does not affect much on the lifetime of a DME/n-heptane droplet. It is interesting to find that a relative constant and high evaporation rate of DME can last for a relative long time with an appropriate mass fraction of n-heptane. It proposes a way to change the evaporation rate of each component by altering the mass fractions in the DME/n-heptane mixture, in order to control the combustion of DME/n-heptane blended fuels.

Isobaric Vapor–Liquid Equilibrium for the Ternary System (Formaldehyde + 1,3-Dioxolane + Water) at 101.3 kPa

Isobaric vapor–liquid equilibria were measured at atmospheric pressure for the ternary system (formaldehyde + 1,3-dioxolane + water). The universal functional activity coefficient (UNIFAC) equation for the Gibbs excess energy was combined with the chemical reaction equilibria existing in this solution to represent the experimental results. The model parameters were determined from the corresponding data fits.

Liquid–Liquid Equilibria for Mixtures of (Water + Pyruvic Acid + Alcohol/Alamine). Modeling and Optimization of Extraction

Extraction equilibria of the systems (water + pyruvic acid + alcohol/Alamine 336) have been investigated at T = 293.2 K. The solvent mixture of 1-dodecanol/alamine yields the largest separation factors for the extraction of pyruvic acid. An analytical structure for optimum extraction has been developed as the locus of the proposed separation factors. The properties of extraction systems have been correlated by a solvation relation (SERLAS) with 5 and 10 parameters. The tie-lines of the present systems have been predicted by the universal functional activity coefficient (UNIFAC) original model. The reliability analysis of both models has been made statistically against the experimental extraction factors.

Multiproperty Correlation of Experimental Data of the Binaries Propyl Ethanoate + Alkanes (Pentane to Decane). New Experimental Information for Vapor–Liquid Equilibrium and Mixing Properties

A thermodynamic study is carried out on binary systems composed of propyl ethanoate with six alkanes, from pentane to decane. Vapor pressures of the ester and the isobaric vapor–liquid equilibria of these six mixtures were measured at 101.32 kPa in a small-capacity ebulliometer and also the mixing properties yE = vE,hE over a range of temperatures and at atmospheric pressure. Adequate correlations are drawn for the surfaces yE = yE(x,T) with an interpretation on the behavior of the mixtures and also using cpE data from literature. The mixing processes are all endothermic with a change in the slope direction of the function hE = hE(T) for the binary systems, which all present expansive effects, with vE > 0 and also (∂vE/∂T)p > 0. The results of the different properties are analyzed within a general context of the behavior of ester + alkane systems. A parametric model is used that enables the simultaneous correlation of the experimental values of different thermodynamic properties for each of the systems considered, slightly improving on the representation obtained with the nonrandom two-liquid (NRTL) model. The representation of vapor–liquid equilibrium (VLE) and hE properties with the universal functional activity coefficient (UNIFAC) group contribution model is acceptable, although it does not reflect the change in enthalpies with varying temperature, resulting in an unacceptable estimation of cpE.

Adaptive Boosting with SVM Classifier for Moving Vehicle Classification

Abstract This study examines co-solvent modified supercritical carbon dioxide (SC-CO2) to extract the saturated fatty acids from palm oil. The applied pressure was ranging from 60 to 180 bar and the extraction temperatures were 313.15 and 353.15 K. The knowledge of the phase equilibrium is one of the most important factors to study the design of extraction processes controlled by the equilibrium. The objective of this work is the assessment of the feasibility studies of phase equilibrium mutual solubility process utilizing supercritical carbon dioxide. A thermodynamic model based on the universal functional activity coefficient (UNIFAC) used to predict the activity coefficients’ expression for the system carbon dioxide/fatty acid. The parameters such as adsorption, diffusion, solubility, and desorption were determined using mass transfer modeling.

Improved QSPR generalized interaction parameters for the nonrandom two-liquid activity coefficient model

Phase equilibrium properties are essential in developing and optimizing numerous processes. The objective of this work is the application of a theory-framed quantitative structure-property relationship (QSPR) modeling approach to provide a priori vapor–liquid equilibrium (VLE) predictions. For this purpose, we apply the nonrandom two-liquid (NRTL) activity coefficient model to describe the phase behavior, and then use the QSPR methodology to generalize the substance-specific parameters of the model. Generalizing the parameters of a proven phase behavior model, such as the NRTL, will minimize the need for acquiring costly VLE experimental data for the systems of interest.The newly developed generalized NRTL-QSPR activity coefficient model constitutes a significant improvement over our previous generalization of the NRTL model. Specifically, an internally consistent generalization is provided for the NRTL interaction parameters using a more extensive database involving 578 binary systems. A non-linear QSPR model was developed for the NRTL parameters, where evolutionary algorithms combined with artificial neural networks were used to perform molecular descriptor reduction. The model predicts pressure and temperature of a binary VLE system within 6% and 0.6% average absolute deviation (AAD), respectively. Further, the generalized NRTL phase behavior predictions show a significant improvement over to the group contribution method, Universal Functional Activity Coefficient model (UNIFAC), which resulted in 9% AAD for pressure predictions.

Application of the Conduct-like Screening Models for Real Solvent and Segment Activity Coefficient for the Predictions of Partition Coefficients and Vapor–Liquid and Liquid–Liquid Equilibria of Bio-oil-Related Mixtures

The 1-octanol/water partition coefficients (log P) at 298.15 K and the vapor-liquid and liquid-liquid equilibria (VLE and LLE) of biofuel-related mixtures have been predicted with four different thermodynamic models: conduct-like screening models for real solvent (COSMO-RS), conduct-like screening models for segment activity coefficient (COSMO-SAC) (2002 version), modified COSMO-SAC (2006 version), and universal functional activity coefficient (UNIFAC). The 2002 version of COSMO-SAC gives more reasonable predictions for log P for most investigated mixtures than the other two approaches when appropriate molecular geometries are chosen for the computation of the sigma profiles. However, the COSMO-RS model gives better predictions for VLE pressures and vapor-phase compositions for biofuel-related mixtures, as well as for the LLE of the 1-octanol + water and furfural + water mixtures. The accuracy of the models for the predictions of the partition coefficients and VLE may be improved by changing the molecular conformations used to generate the sigma profiles. Generally, the three COSMO-based models give better predictions than UNIFAC for log P and VLE of the investigated systems and can be applied to predict the thermodynamic properties of the biofuel-related mixtures especially when no experimental data are available

Ebulliometric Determination and Prediction of Vapor–Liquid Equilibria for Binary Mixtures of Ethanol and Ethyl Hexanoate

The objective of this study is to measure vapor–liquid equilibria (VLE) data for an ethanol + fatty acid ethyl ester (FAEE) system. VLE data for the binary system ethanol + ethyl hexanoate were determined at pressures of (40.00 to 101.3) kPa using an ebulliometer, which could compensate for vapor hold-up. The hold-up compensable ebulliometer was designed for this study, and the experimental apparatus and procedure were verified by measuring the VLE data for ethanol + p-xylene at pressures of (40.00 to 101.3) kPa. The densities at 298.15 K for pure components investigated in this study were also measured by a densimeter. The experimental VLE data of the two binary mixtures, ethanol + p-xylene and ethanol + ethyl hexanoate, were represented by the Wilson and nonrandom two-liquid (NRTL) models. The analytical solutions of groups (ASOG) and modified universal functional activity coefficient (UNIFAC, Dortmund) group contribution models were also used to predict the VLE behavior of these binary mixtures. The VL...

Phase Equilibria Involved in the Extractive Distillation of Cyclohexane + Cyclohexene Using Diethyl Carbonate as an Entrainer

Isobaric vapor–liquid equilibrium (VLE) data at 100 kPa have been measured for the ternary system cyclohexane + cyclohexene + diethyl carbonate and two constituent binary systems: cyclohexane + diethyl carbonate and cyclohexene + diethyl carbonate. Both binary systems show moderate positive deviations from ideal behavior and do not present an azeotrope. The VLE data have been correlated by the Wilson, universal quasichemical activity coefficient (UNIQUAC), and nonrandom two-liquid (NRTL) equations. The ternary system does not present an azeotrope and is well-estimated from binary interaction parameters. A prediction with the universal functional activity coefficient (UNIFAC)-Dortmund method has been also obtained.

Performance assessment of a liquid-phase separation refrigeration cycle

SUMMARY Absorption refrigeration cycles are alternatives to conventional vapor-compression cycles in which the energy required for refrigeration is provided by heat instead of mechanical work. In this paper, a novel refrigeration cycle utilizing the immiscible liquid-phase separation behavior is simulated and analyzed using Aspen simulator. The two conjugate liquids adopted in this work are triethylamine (solute) and water (solvent). This binary system has a low critical solution temperature of 18 °C. The thermophysical properties of the binary mixture are generated using the universal functional activity coefficient (UNIFAC) and the nonrandom two-liquid (NRTL) models. The phase splitting phenomenon at the generator temperature is predicted by both models. However, in comparison with the available experimental data for the same binary mixture, NRTL model gives better predictions for the flow rates and compositions of the material streams. Heat duties of the evaporator, absorber, and generator and the power consumption of the solution pump have been calculated using UNIFAC and NRTL models. The cycle COP that plays a major role in determining the cycle economical viability has been predicted for different operating conditions using the two models. Simulation results show that, for a waste heat reservoir at 60 °C and using NRTL model, the COP is about 2.0. Second law analysis conducted for all cycle components of the cycle shows that about 42% of the total exergy destructed occurs in the generator. Finally, the liquid-phase separation refrigeration cycle is predicted to be a promising cycle in the near future because of hardware and energy savings. Copyright © 2011 John Wiley & Sons, Ltd.

Solid–Liquid Equilibrium of Binary Mixtures Containing Fatty Acids and Triacylglycerols

Solid–liquid phase diagrams of the following systems were measured using differential scanning calorimetry (DSC): tristearin (2,3-di(octadecanoyloxy)propyl octadecanoate) + tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate), tristearin (2,3-di(octadecanoyloxy)propyl octadecanoate) + palmitic acid (n-hexadecanoic acid), tristearin (2,3-di(octadecanoyloxy)propyl octadecanoate) + linoleic acid (cis-9,cis-12-octadecadienoic acid), tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate) + triolein (2,3-bis[[(Z)-octadec-9-enoyl]oxy]propyl (Z)-octadec-9-enoate), and tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate) + commercial oleic acid (commercial (Z)-octadec-9-enoic acid). The eutectic point was observed for two systems, tristearin with tripalmitin or with palmitic acid. Polarized optical microscopy was employed to investigate the solid phase of the systems and confirmed the occurrence of a solid solution at the extreme of the phase diagram rich in the component with a higher melting temperature. Margules-2-suffix, Margules-3-suffix, nonrandom two-liquid (NRTL), and universal quasichemical functional group activity coefficient (UNIFAC) models were employed to describe the liquidus line of the studied systems, except for the system formed by tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate) + commercial oleic acid (commercial (Z)-octadec-9-enoic acid) which is a pseudobinary system that was well-described by the UNIFAC model. The best results for the other systems were obtained when employing the Margules-3-suffix and NRTL models.

Liquid−Liquid and Vapor−Liquid−Liquid Equilibrium of the 2-Butanone + 2-Butanol + Water System

Liquid−liquid phase equilibrium (LLE) data have been measured for the ternary system 2-butanone + 2-butanol + water at (293.25, 313.15, 323.15, and 333.15) K. Experimental results show the extreme phase sensitivity of this system to temperature. At (293.15 and 313.15) K the ternary system has two separate biphasic regions, while at (323.15 and 333.15) K the system has only one region of immiscibility. The nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) models were applied to correlate the ternary system at (323.15 and 333.15) K; the interaction parameters obtained from both models successfully correlated the equilibrium compositions. Moreover, isobaric vapor−liquid−liquid equilibrium (VLLE) is measured for this ternary mixture at 101.3 kPa. The experimental data were compared with the estimation from LLE binary interaction parameters using NRTL and UNIQUAC models and with the prediction of universal functional activity coefficient (UNIFAC) model.

A Local-Composition Model for the Prediction of Mixture Dielectric Constants

A local composition model is developed for mixture dielectric constants based on the nonrandom two-liquid (NRTL) model commonly used for correlating activity coefficients in vapor−liquid equilibrium (VLE) data regression. In this model the NRTL local compositions, which represent an effective local molecular structure, are the counterpart of the Kirkwood factor g, which in dielectric constant theory characterizes local molecular orientations and their effect on the static dielectric constant. The resultant model requires values for the pure-component dielectric constant and binary NRTL model parameters available from VLE data compilations or predicted from the universal functional activity coefficient model (UNIFAC). It is predictive in that no mixture dielectric constant data are used and there are no adjustable parameters. Predictions made on 16 binary and six ternary systems at various compositions and temperatures compare favorably with extant correlations that require experimental values to fit an adjustable parameter in the mixing rule and are significantly improved over values predicted by Oster's equation that also has no adjustable parameters.

De-emulsification of mixtures containing glycerin and fatty acid methyl ester promoted by dimethyl ether co-solvent

Transesterification in a homogeneous mixture with the volatile co-solvent dimethyl ether (DME) has been proposed as a new fatty acid methyl ester (FAME) processing technique. Ternary feed mixtures of triolein, methanol and DME form a homogeneous solution, but the product mixtures of FAME, glycerin and DME form an emulsion after transesterification. In order to obtain FAME only, the glycerin phase mush be separated out from their mixtures by a centrifuge or settler. Therefore, we investigated the de-emulsification process at different methanol compositions in the feed mixtures, either with or without DME co-solvent. The rate of de-emulsification of the product mixture increased as the methanol content in the feed mixture increased; moreover, the rate of de-emulsification with DME co-solvent was 3–5 times faster than that without DME. The rate of de-emulsification was evaluated as a function of the molar ratio of dispersed glycerin phases in the product mixture. When the molar ratio of dispersed glycerin phases increased in the product mixture, the coagulation of the dispersed glycerin phases accelerated according to the Smoluchowski model. The de-emulsification was measured by UV spectroscopy as a function of time, and the relative transmissivity measured by UV spectroscopy was fit to the simple Smoluchowski equation, and the rate of de-emulsification was considered with respect to the molar ratio of dispersed glycerin phases, as calculated from the liquid–liquid equilibrium using the universal functional activity coefficient (UNIFAC) model.

Solid-Liquid Equilibrium of Xylose in Water and Ethanol/Water Mixture

This work deals with the study of thermodynamical models for the solid-liquid equilibrium (SLE) and comparing its performance with experimental data. The xylose solubility in the xylose-water and xylose-water-ethanol systems has been measured using a variant of the isothermal method. A total of 12 experiments were performed in a 100 mL glass jacketed crystallizer with helix-type agitator by changing the temperature from 0 to 60°C. The solution was mixed during 72 h with an IKA Labortechnic, RW 20.n agitator at 450 rpm. Later, the experimental and reported results were fitted using the prediction models based on the vapor-liquid-equilibrium (UNIFAC (Universal Functional Activity Coefficient), ASOG (Analytical Solutions of Groups) and GSP (Group Solubility Parameter); semi-empirical models based on the vapor-liquid-equilibrium (VLE) (UNIQUAC (Universal Quasi Chemical), Wilson and NRTL (Non Randon Two Liquid)) on the solid-liquid-equilibrium, and empirical model with fitted parameters (Nývlt, λh, Margules with 1 and 2 parameters). The results showed that the UNIQUAC model with fitted parameters can describe the SLE with reasonable accuracy (1.28 and 3.36% for binary and ternary systems, respectively). The average deviation was the arithmetic mean of the deviations. On the other hand, the other methods resulted in poor agreement with the system’s behavior presenting systematic deviations from the experimental data.

Solubility, Solubility Modeling, and Precipitation of Naproxen from Subcritical Water Solutions

In this paper, the solubility of naproxen in subcritical water (SBCW) between 130 and 170 °C is measured. The solubility of naproxen in SBCW was correlated to temperature using a Modified Universal Functional Activity Coefficient (M-UNIFAC) model. Errors in the model were minimized by optimizing the water−carboxylic acid interaction parameter, as other side groups were already optimized. The micronization of naproxen via processes that used the tunable solvent power of SBCW was conducted. Two precipitation techniques were developed. In the first technique, the temperature of a SBCW solution containing naproxen was rapidly quenched by injection into cold water solutions. The quenching media were either pure water or 1% w/v solution of lactose in water. Variations in SBCW−naproxen solution injection temperature and supersaturation ratios in pure water were examined. Product morphology was robust toward changes in operating conditions and consisted of flaky crystals with a particle size distribution ranging ...

The solubility and solubility modelling of budesonide in pure and modified subcritical water solutions

In this article, the solubility behaviour of budesonide in pure and alcohol-modified subcritical water (SBCW) solutions between 25 °C and 200 °C is reported. Methanol and ethanol were selected as modifiers. In the presence of ethanol, the solubility of budesonide in SBCW increased up to 10 times. In all reported cases, the solubility of budesonide was directly dependant on the dielectric constant of the solvent mixture. A correlation between the budesonide solubility data and the dielectric constant of SBCW was developed. The correlation parameters were altered to improve the accuracy of the outputs of the solubility model for 9-anthracenemethanol in SBCW. The model was able to predict budesonide solubility in SBCW and SBCW–alcohol solutions with an average error of 3%. The model is applicable to all the budesonide–SBCW–alcohol systems investigated in this work and is valid for a broad range of SBCW ternary systems. The solubility of budesonide was also modelled using the Modified Universal Functional Activity Coefficient (M-UNIFAC) model. Corrections were made to the interaction parameters so that the M-UNIFAC model was able to reproduce the solubility of budesonide in SBCW within 5% of experimental values. In order to check the validity of the parameter correction, the solubility of 9-anthracenemethanol in SBCW was established and modelled.

Vapor−Liquid Equilibrium for Binary Systems of Cyclohexane + Cyclohexanone and + Cyclohexanol at Temperatures from (414.0 to 433.7) K

In this work, the vapor−liquid equilibrium (VLE) data for binary systems of cyclohexane + cyclohexanone and cyclohexane + cyclohexanol were measured using a static-analytical apparatus at temperatures from (414.0 to 433.7) K. To avoid the disturbance of pressure drop during the sampling process, a stopcock was designed inside the autoclave to block out a part of vapor-phase space quickly before sampling. The measured VLE data were correlated by the Soave−Redlich−Kwong state equation (SRK) and Wilson activity coefficient models. The Redlich−Kwong (RK) and Hayden−O’Connell (HOC) equations were used to modify the vapor ideality in the Wilson models. The fitted Wilson model with the HOC equation (Wilson-HOC) was also compared against predictive universal functional activity coefficient (UNIFAC) models (standard UNIFAC and Dortmund modified UNIFAC). By error analysis, the Wilson-HOC model gave the best fit.