UNIFAC Group Interaction Parameters Research Articles

Flash point prediction of tailor-made green diesel blends containing B5 palm oil biodiesel and alcohol

The flash point prediction accuracy of the Liaw model through UNIFAC-type models was evaluated and improved for B5 palm oil biodiesel–alcohol blends. The UNIFAC group interaction parameters of alcohol–alkyl chains (OH–CH2), alcohol–double bonded alkyl chains (OH–CC) and alcohol–esters group (OH–CCOO) were revised comprehensively to attend this improvement. The prediction accuracies (calculated as average absolute relative deviation (AARD)) were improved by solely revising the interaction parameters of OH–CH2 with similar AARD for all UNIFAC type models (from 7.0% and 5.8% to 1.1% for Original and NIST UNIFAC; from 6.6% and 6.2% to 1.3% for Modified UNIFAC (Dortmund) and NIST-Modified UNIFAC). The revised parameters were further validated using the test set data of B5-alcohol blends and B5-ethyl levulinate (EL)–butanol (BU) blends. Satisfactory improvements were obtained; but for B5–EL–BU blends, only the Original UNIFAC and NIST-UNIFAC model showed improvement. The presented study showed that by solely revising the interaction parameters of OH–CH3, a better flash point prediction is gained for the green diesel blends containing palm oil biodiesel and alcohol.

Solubility Model of Solid Solute in Supercritical Fluid Solvent Based on UNIFAC

A semitheoretical model based on UNIFAC was proposed to correlate the solubility of solid solute in supercritical fluid (SF) solvent simply and reliably, which does not need critical parameters for solid solutes. The interaction parameters aij between the SF solvents (such as carbon dioxide, ethylene, and ethane) and the functional groups of solutes were regressed, which is compatible with the vapor−liquid equilibrium (VLE) UNIFAC group-interaction parameters. More efforts and experimental data are needed to obtain a sufficiently large number of interaction parameters for extensive applications. The estimated power exponent of reduced density seems identical for the same solid solute in SF cosolvent homologues. This model could predict the solubility of a solid solute in supercritical CO2 with cosolvents successfully.

Liquid–liquid equilibrium for the quaternary system water + tetrahydrofuran + n-heptane + butyl acetate mixture at 25 °C and atmospheric pressure

Liquid–liquid equilibrium for the quaternary system water + tetrahydrofuran + n-heptane + butyl acetate mixture was measured at 25 °C and atmospheric pressure. Binodal curves, tie-lines, distribution, and selectivity for the quaternary system have been determined in order to investigate the effect of using binary solvents, n-heptane and butyl acetate, on extracting tetrahydrofuran from aqueous solution. In addition, these experimental tie-line data were also compared with the values predicted by the UNIFAC model. It is found that the UNIFAC group interaction parameters used for LLE could not provide a good prediction.

Liquid-liquid equilibrium for the quaternary system of o-xylene(1)+water(2)+butyric acid(3)+ethyl acetate(4) at 25 °C and atmospheric pressure

The liquid-liquid equilibrium for the quaternary system of o-xylene(1)+water(2)+butyric acid(3)+ethyl acetate(4) was measured at 25 °C and atmospheric pressure. Binodal curves, tie-lines, distribution, and selectivity for the quaternary system have been determined in order to investigate the effect of binary solvents, o-xylene and ethyl acetate, on extracting butyric acid from aqueous solution. In addition, these experimental tie line data were also compared with the values predicted by the UNIFAC model. It is found that UNIFAC group interaction parameters used for LLE could not provide a good prediction.

Liquid–Liquid Equilibrium for the Quaternary System Water + Tetrahydrofuran + Toluene + 1-Butanol Mixture at 25 °C and Atmospheric Pressure

Liquid–liquid equilibria (LLE) for the quaternary system water + tetrahydrofuran + toluene + 1-butanol mixture were measured at 25 °C and atmospheric pressure. Binodal curves, tie-lines, distribution, and selectivity for the quaternary system have been determined to investigate the effect of using binary solvents, toluene, and 1-butanol, on extracting tetrahydrofuran from aqueous solution. In addition, these experimental tie-line data were also compared with the values predicted by the UNIFAC model. It is found that the UNIFAC group interaction parameters used for LLE could not provide a good prediction.

Application of the UMR-PRU model to multicomponent systems: Prediction of the phase behavior of synthetic natural gas and oil systems

The applicability of the recently developed UMR-PRU EoS/ G E model is extended in this work by evaluating new gas containing UNIFAC group interaction parameters. Satisfactory prediction of various types of VLE data (dew and bubble point pressures, equilibrium ratios, liquid drop out, etc.) of multi-component systems, including gas condensates and oil mixtures, is obtained, and it is comparable or better than that of the other two EoS/ G E models considered, the LCVM and the PSRK. It is concluded that the UMR-PRU model is a powerful tool for phase equilibrium predictions in mixtures of interest to the gas and oil industry.

A method for prediction of UNIFAC group interaction parameters

AbstractGroup‐contribution‐based property estimation methods are suitable for obtaining quick evaluations of phase equilibrium under different conditions of temperature, pressure and composition. One of the best known and successful group‐contribution (GC) based methods for prediction of liquid‐phase‐activity coefficients in mixtures of organic compounds is the UNIFAC method. One of the principal limitation of the UNIFAC method and all other GC based methods is that groups or group‐interaction parameters needed for a specific property estimation problem may not be available. The method presented, is to be called the CI‐UNIFAC (Connectivity Index – UNIFAC) method, to predict the missing UNIFAC group‐interaction parameters for the calculation of vapor‐liquid equilibrium (VLE). The method is described as the CI‐UNIFAC for predicting missing group interaction parameters, as well as re‐estimating known group interaction parameters, using a set of atom connectivities and their regressed CI interaction parameters. The performance of the CI‐UNIFAC method with experimental data is compared, with a reference UNIFAC method, as well as cases where the CI‐UNIFAC method is used only for the missing UNIFAC group interaction parameters. © 2007 American Institute of Chemical Engineers AIChE J, 2007

Physicochemical properties of selected polybrominated diphenyl ethers and extension of the UNIFAC model to brominated aromatic compounds

The aqueous solubilities (S(w)) at various temperatures from 283 K to 308 K and 1-octanol/water partition coefficients (K(ow)) for four polybrominated diphenyl ethers (PBDEs: 4,4'-dibromodiphenyl ether (BDE-15), 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), and 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153)) were measured by the generator column method. The S(w) and K(ow) data revealed the effect of bromine substitution and basic structure on S(w) and K(ow). To estimate the infinite dilution activity coefficients (gamma(i)(w,infinity)) of the PBDEs in water from the S(w) data, enthalpies of fusion and melting points for those compounds were measured with a differential scanning calorimeter. Henry's Law constants (H(w)) of the PBDEs were derived from the determined gamma(i)(w,infinity) and literature vapor pressure data. Some physicochemical characteristics of PBDEs were also suggested by comparing the present property data with that of polychlorinated dibenzo-p-dioxins, brominated phenols and brominated benzenes in past studies. Furthermore, in order to represent different phase equilibria including solubility and partition equilibrium for other brominated aromatic compounds using the UNIFAC model, a pair of UNIFAC group interaction parameters between the bromine and water group were determined from the S(w) and K(ow) data of PBDEs and brominated benzenes. The ability of the determined parameters to represent both properties of brominated aromatics was evaluated.

(Liquid + liquid) equilibria of (water + butyric acid + isoamyl alcohol) ternary system

(Liquid + liquid) equilibrium (LLE) data for the ternary system (water + butyric acid + isoamyl alcohol) have been determined experimentally at T = (298.15, 308.15 and 318.15) K. Complete phase diagrams were obtained by determining solubility and the tie-line data. Tie-line compositions were correlated by Othmer–Tobias method. The UNIFAC method was used to predict the phase equilibrium in the system using the interaction parameters determined from experimental data between groups CH 3, CH 2, CH, COOH, OH and H 2O. It is found that UNIFAC group interaction parameters used for LLE could not provide a good prediction. Distribution coefficients and separation factors were evaluated for the immiscibility region.

(Liquid + liquid) equilibria of (water + butyric acid + cyclohexyl acetate) ternary system

(Liquid + liquid) equilibrium (LLE) data for the ternary system (water + butyric acid + cyclohexyl acetate) have been determined experimentally at T = (298.15, 308.15 and 318.15) K. Complete phase diagrams were obtained by determining solubility and the tie-line data. Tie-line compositions were correlated by the Othmer–Tobias method. The UNIFAC method was used to predict the phase equilibrium in the system using the interaction parameters determined from experimental data between CH, CH 2, CH 3, COOH, CH 3COO and H 2O groups. It is found that UNIFAC group interaction parameters used for LLE could not provide a good prediction. Distribution coefficients and separation factors were evaluated for the immiscibility region.

Revision of UNIFAC group interaction parameters of group contribution models to improve prediction results of vapor–liquid equilibria for solvent–polymer systems

The objective of this work was to improve the accuracy of group contribution models for prediction of solvent activities in polymer solutions by revising UNIFAC group interaction parameters using a wide range of vapor–liquid equilibrium (VLE) data of solvent–polymer systems. The group contribution models considered in this work were UNIFAC-FV, Entropic-FV, GK-FV and UNIFAC-ZM models. A total of 142 systems that consisted of 16 polymers and 36 solvents containing a large variety of solvent–polymer systems ranging from non-polar to polar substances were considered to optimize 46 pairs of group interaction parameters. Data considered were split up into systems containing alkane and cycloalkane, aromatic, and polar solvents. For athermal systems, the UNIFAC-FV model gave the best results. Therefore, the model was used in optimizing the group parameters. Revised group interaction parameters were found to improve the reliability of VLE predictions in solvent–polymer systems. A significant improvement of prediction results was achieved by UNIFAC-FV model from 20.0 to 10.8% absolute average deviation (AAD) in solvent activities for systems containing polar solvents and from 16.7 to 10.9% AAD for all systems. The prediction results of GK-FV and UNIFAC-ZM models were also improved.

Liquid-Liquid equilibria of the water-acetic acid-butyl acetate system

Experimental liquid-liquid equilibria of the water-acetic acid-butyl acetate system were studied at temperatures of 298.15± 0.20, 303.15± 0.20 and 308.15± 0.20 K. Complete phase diagrams were obtained by determining solubility and tie-line data. The reliability of the experimental tie-line data was ascertained by using the Othmer and Tobias correlation. The UNIFAC group contribution method was used to predict the observed ternary liquid-liquid equilibrium (LLE) data. It was found that UNIFAC group interaction parameters used for LLE did not provide a good prediction. Distribution coefficients and separation factors were evaluated for the immiscibility region.

Vapor–liquid equilibria and excess molar volumes of diethylamine(1) + acetone(2) and diethylamine(1) + acetonitrile(2) binary systems

Isothermal vapor–liquid equilibrium (VLE) data for diethylamine(1)+acetone(2) and diethylamine(1)+acetonitrile(2) binary systems were obtained at 323.15 K by dynamic method. Excess molar volumes at 298.15 K for these systems were measured by a dilution dilatometer. VLE data have been checked for thermodynamic consistency and correlated by Wilson, NRTL and UNIQUAC equations. UNIFAC group interaction parameters for CH 2NHCH 3CO and CH 2NHCH 3CN pairs are also obtained from the experimental VLE data.

Contributions of additional group interaction parameters through limiting activity coefficient measurements on aliphatic alcohols, aromatic hydrocarbons, ketones and an ester in tetrahydroxyethylethylenediamine and tetraethylene pentamine

Gas chromatographic method has been used to measure the limiting activity coefficient of some aliphatic alcohols (ethanol, 1-propanol, 1-butanol and 1-pentanol), aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene and p-xylene), ketones (acetone and methylisobutylketone), ethylacetate and chlorobenzene in tetrahydroxyethylethylenediamine (THEEDA) and tetraethylpentamine (TEPA). The measurements involving THEEDA have been used to derive UNIFAC group interaction parameters for seven new pairs, while ten pairs of new group interaction parameters have been derived from the measurements on TEPA.

Prediction of vapor–liquid equilibria in mixed-solvent electrolyte systems using the group contribution concept

The LIQUAC model is widely used to predict reliably vapor–liquid equilibria (VLE), osmotic coefficients and mean ion activity coefficients for electrolyte systems. It consists of a Debye–Hückel term, the UNIQUAC term and the osmotic virial equation for the middle-range contribution. The aim of this work is to provide a model based on the group contribution concept that can be used to predict phase equilibria in mixed-solvent electrolyte systems. Therefore, in the LIQUAC model the UNIQUAC equation has been substituted by the original UNIFAC equation and group interaction parameters have been introduced into the middle-range term. With the help of a large data base, 234 group interaction parameters for seven solvent groups, 13 cations and seven anions have been fitted. The model parameters have been used to calculate the VLE behavior, osmotic coefficients and mean ion activity coefficients for a large number of systems with high accuracy.

Modification of parameters in group contribution method to distinguish isomers based on information by Monte Carlo simulation

The solubility of xylenol isomers, dimethylnaphthalene isomers, naphthol isomers, and anthracene and phenanthrene in supercritical carbon dioxide is calculated by the Predictive Soave–Redlich–Kwong (PSRK) equation of state proposed by Holderbaum and Gmehling. The UNIFAC group interaction parameters used in this model are modified to distinguish solubility of the isomers using radial distribution functions, g mn ( r), of supercritical carbon dioxide around the sites of the isomers calculated from Monte Carlo simulation. The calculated solubility of isomers is improved by using the modified parameters.

Contributions of additional group interaction parameters through limiting activity coefficient measurements on aliphatic alcohols, aromatic hydrocarbons, ketones and an ester in organic phosphates

Gas chromatographic technique is used to measure the limiting activity coefficients of some aliphatic alcohols (ethanol, 1-propanol, 1-butanol, 1-pentanol), aromatic hydrocarbons (benzene, toluene, o-xylene, p-xylene, ethylbenzene), ketones (acetone, methylisibutylketone), and an ester (ethylacetate) and chlorobenzene in three organic phosphates (tricresylphosphate, trixylolphosphate, tributylphosphate). The limiting activity coefficient are used to derive the UNIFAC group interaction parameters for 13 new pairs.

Liquid–liquid equilibria of ternary systems containing alkane, methanol, and ether

Tie-line data of eight type I ternary systems consisting of alkane (heptane, octane, nonane or decane), methanol, and ethers (methyl tertiary butyl ether or diisopropyl ether) are reported at 25°C. The UNIFAC group contribution method is used to predict or correlate the observed ternary liquid–liquid equilibrium (LLE) data. It is found that the UNIFAC with original group-interaction parameters developed for LLE could not provide a good prediction. Therefore, the UNIFAC group-interaction parameters were adjusted to give better correlation performance.

UNIFAC Prediction of Aqueous and Nonaqueous Solubilities of Chemicals with Environmental Interest

The aqueous and nonaqueous solubilities of a vast number of chemicals with significant environmental roles have been predicted using the latest version of UNIFAC group interaction parameters. A few critical measurements to test specific UNIFAC calculations of nonaqueous solubilities are also reported. The chemicals included in the calculation have aqueous solubilities that span 11 orders of magnitude. Good agreement was observed between the UNIFAC-predicted and literature-reported aqueous solubilities for 11 groups of compounds, i.e., short-chain alkanes, alkenes, alcohols, chlorinated alkanes, alkyl benzenes, chlorinated benzenes, PAHs, PCBs, anilines, phenols, and organohalide insecticides (DDT and lindane). Similarly, UNIFAC successfully predicts the co-solvency of PCB in methanol/water solutions. The error between predicted and literature-reported aqueous solubilities was larger for three groups of chemicals: long-chain alkanes, phthalates, and chlorinated alkenes. The average absolute error in UNIFA...

Measurement and correlation of liquid-liquid equilibria of methanol+alkane+ether ternary systems

Liquid-liquid equilibrium (LLE) data at 25°C are reported for eight ternary systems consisting of methanol, alkane (heptane, octane, nonane or decane), and ether (diethyl ether or dibutyl ether). The UNIFAC group contribution method was used to predict or correlate the ternary LLE data obtained. The predicted results shows the discrepancy from the experiments. Therefore, the UNIFAC group interaction parameters were adjusted to give better correlation performance.