Liquid Phase Activity Coefficients Research Articles

Solid-liquid equilibrium of triolein with fatty alcohols

Triacylglycerols and fatty alcohols are used in the formulation of cosmetic, pharmaceutical and food products. Although information about the phase transitions of these compounds and their mixtures is frequently required for design and optimization of processes and product formulation involving these substances, these data are still scarce in the literature. In the present study, the solid-liquid phase diagrams of two binary systems composed of triolein + 1-hexadecanol and triolein + 1-octadecanol were evaluated by differential scanning calorimetry (DSC) and optical microscopy. The experimental data were compared with predicted data by solving the phase equilibrium equations using an algorithm implemented in MATLAB. The liquid-phase activity coefficients were calculated using the Margules equation (two- and three-suffix) and the UNIFAC model (original and modified Dortmund model). The approaches used for calculating system equilibrium allowed an accurate prediction of the liquidus line with low deviations from the experimental data.

Flash points of partially miscible aqueous–organic mixtures predicted by UNIFAC group contribution methods

This work predicts the flash points of partially miscible aqueous–organic mixtures using the flash point prediction model of Liaw et al. (J. Chem. Eng. Data 55 (2010) 3451–3461) handling non-ideal behavior through liquid phase activity coefficients evaluated with UNIFAC-type models, which do not need experimentally regressed binary parameters. Validation of this entirely predictive model is conclusive with the experimental data over the entire flammable composition range for 10 aqueous–organic binary and ternary mixtures. Overall, the model describes the experimental data of flash point well when using UNIFAC-type models to estimate the activity coefficient. If the LLE UNIFAC parameters are not accessible, a model based upon the VLE UNIFAC parameters provides an acceptable means of predicting flash point for partially miscible aqueous–organic mixtures, as revealed by a comparison between predicted and experimental data.

Influence of Gas Impurities on Thermodynamics of Amine Solutions. 1. Aromatics

New parameters for improving the Electrolyte-NRTL model have been regressed for acidic gas-MDEA aqueous solution systems containing aromatics. Values of binary interaction parameters for liquid phase activity coefficients are estimated from regressions of experimental data. Aspen Plus has been used for regressions and thermodynamic modeling. The focus of the work is to have better predictions of VLE of aromatic compounds in amine systems for acidic gases purification.

Influence of Gas Impurities on Thermodynamics of Amine Solutions. 2. Mercaptans

New parameters for improving the Electrolyte-NRTL model have been regressed for acidic gas-MDEA aqueous solution systems containing mercaptans. Values of binary interaction parameters for liquid phase activity coefficients are estimated from regressions of experimental data. Aspen Plus has been used for regressions and thermodynamic modeling. The focus of the work is to have better predictions of VLE of mercaptans in amine solutions for acidic gases purification.

Isobaric Vapor–Liquid Equilibrium Data of 2-Methyl-propan-2-ol (1) + Heptan-1-ol (2), Methanol (1) + Heptan-1-ol (2), Ethanol (1) + Heptan-1-ol (2), and Propan-1-ol (1) + Heptan-1-ol (2) at 96.5 kPa

Isobaric vapor–liquid equilibrium data at a local atmospheric pressure of 96.5 kPa is reported for the four binary systems, namely, 2-methyl propan-2-ol (1) + heptan-1-ol (2), methanol (1) + heptan-1-ol (2), ethanol (1) + heptan-1-ol (2), and propan-1-ol (1) + heptan-1-ol (2). The experiments are done using a Swietoslawski-type ebulliometer. The liquid-phase activity coefficients are modeled using the well-established Wilson model and the universal functional (UNIFAC) group contribution method. The data are found to be thermodynamically consistent.

Solubility of salicylic acid in pure alcohols at different temperatures

This work focused on the experimental measurements and the numerical calculations of the solubility of salicylic acid in various alcohols. The solubility of salicylic acid in pure alcohols was determined using a (solid+liquid) equilibrium measurement apparatus at temperatures ranging from (278.15 to 318.15)K. Also, the melting temperature and fusion enthalpy of salicylic acid were determined by a differential scanning calorimeter (TA instrument Q100). The experimental results were correlated with the equation for solubility of a solid in a liquid with the nonrandom two liquid (NRTL), universal quasi-chemical (UNIQUAC) and Wilson models for liquid phase activity coefficients to validate the quality of the data taken. Adjustable interaction parameters were also provided. The experimental data fit appropriately with all three models for the pure alcohols studied.

Flash-Point Prediction of Binary Partially Miscible Aqueous-Organic Mixtures from UNIFAC Group Contribution Methods

Flash point is one of the most important variables used to characterize fire and explosion hazard of liquids. This paper predicts the flash point of binary partially miscible aqueous mixtures by using the flash point prediction model of Liaw et al. handling non-ideal behavior through liquid phase activity coefficients evaluated with UNIFAC-type models, which do not need experimentally regressed binary parameters. Validation of this entirely predictive model is conclusive with the experimental data over the entire flammable composition range. Overall, the proposed method predicted the experimental data very well. Potential application for this approach concerns the classification of flammable liquid mixtures in the implementation of GHS.

Product Separation after Chemical Interesterification of Vegetable Oils with Methyl Acetate. Part I: Vapor–Liquid Equilibrium

Chemical interesterification of triglycerides with methyl acetate yields biodiesel and triacetin. This reaction is highly reversible, which implies the presence of intermediate compounds such as diacetinmonoglycerides. In addition, the use of methanolic potassium methoxide as the catalyst causes the appearance of diacetin, monoacetin, and glycerol. Vacuum distillation becomes an interesting alternative for the separation of biodiesel and triacetin. Vapor–liquid equilibrium (VLE) determination requires information related to the vapor pressures of the different compounds and the nonideality of the liquid phase (activity coefficients). The lack of literature information for some compounds was supplemented with experimental data and predictive models for vapor pressure and activity coefficients (UNIFAC and UNIFAC Dortmund). The suitability of using vacuum distillation was evaluated using the Fenske equation and experimental results from a structured packed distillation column. According to the results, removal of diacetinmonoglycerides can be easily accomplished, unlike the elimination of diacetin, monoacetin, and glycerol, which form azeotropes with triacetin.

Isobaric vapor-liquid equilibrium for toluene, 3-methylthiophene and N-formylmorpholine at 101.33 kPa

Isobaric vapor-liquid equilibrium (VLE) data were measured for binary mixtures of toluene+N-formylmorpholine, toluene+3-methylthiophene and 3-methylthiophene+N-formylmorpholine at 101.33 kPa. The VLE data of the binary systems were found to be thermodynamically consistent. The saturated vapor pressure calculated by CSGC-PR equation of the pure component had higher accuracy than that calculated by Antoine equation. The liquid-phase activity coefficients of the binary systems were calculated by the Wilson, NRTL and UNIFAC models, and the binary interaction parameters of the three models were determined by the VLE data. The Wilson model was selected as the most suitable model to predict the VLE data of the ternary system of toluene+3-methylthiophene+Nformylmorpholine. The relative volatility between toluene and 3-methylthiophene was also calculated. Moreover, the effect of N-formylmorpholine as solvent was studied. When the molar ratio of solvent to feed (S/F) was 7, the relative volatility reached 1.904, which is almost twice the relative volatility without solvent. Therefore, N-formylmorpholine can be considered as an effective extracting agent for the separation of the close-boiling mixture of toluene+3-methylthiophene by extractive distillation.

Thermodynamic modeling of CO 2 and H 2S solubilities in aqueous DIPA solution, aqueous sulfolane–DIPA solution, and aqueous sulfolane–MDEA solution with electrolyte NRTL model

A thermodynamic model developed for CO 2 and H 2S solubilities in aqueous MDEA solution is extended to cover CO 2 and H 2S solubilities in aqueous DIPA solution, aqueous sulfolane–DIPA solution, and aqueous sulfolane–MDEA solution. The model makes use of the 2009 version of the electrolyte NRTL model for liquid phase activity coefficient calculations and the PC-SAFT equation of state for vapor phase fugacity coefficient calculations. The NRTL binary parameters for the molecule–electrolyte pairs required for the H 2O–DIPA–CO 2 ternary and the H 2O–sulfolane–DIPA–CO 2 quaternary are regressed against the solubility data of CO 2 in aqueous DIPA solution and aqueous sulfolane–DIPA solution, respectively. The NRTL binary parameters for the molecule–electrolyte pairs required for the H 2O–DIPA–H 2S ternary and the H 2O–sulfolane–DIPA–H 2S quaternary are regressed against the solubility data of H 2S in aqueous DIPA solution and aqueous sulfolane–DIPA solution simultaneously. The NRTL binary parameters for the electrolyte–electrolyte pairs involved in the H 2O–DIPA–CO 2–H 2S quaternary are regressed against the solubility data of the acid gas mixtures in aqueous DIPA solution. Likewise, the NRTL binary parameters for the sulfolane–electrolyte pairs required for the H 2O–sulfolane–MDEA–CO 2 quaternary and the H 2O–sulfolane–MDEA–H 2S quaternary are regressed against the solubility data of the acid gases in aqueous sulfolane–MDEA solution. The predicted enthalpies of acid gas absorption are compared favorably with the literature data available for the H 2O–DIPA–CO 2 system, the H 2O–DIPA–H 2S system, and the H 2O–sulfolane–MDEA–CO 2 system.

Phase Behaviour of 1‐Ethyl‐3‐methylimidazolium Thiocyanate Ionic Liquid with Catalytic Deactivated Compounds and Water at Several Temperatures: Experiments and Theoretical Predictions

Density, surface tension and refractive index were determined for the binary mixture of catalytic deactivated compounds with 1‐ethyl‐3‐methylimidazolium thiocyanate {[EMIM][SCN]} at temperature of (298.15 to 323.15) K. For all the compounds with ILs, the densities varied linearly in the entire mole fraction with increasing temperature. From the obtained data, the excess molar volume and deviation of surface tension and refractive index have been calculated. A strong interaction was found between similar (cation‐thiophene or cation‐pyrrole) compounds. The interaction of IL with dissimilar compounds such as indoline and quinoline and other multiple ring compounds was found to strongly depend on the composition of IL at any temperatures. For the mixtures, the surface tension decreases in the order of: thiophene > quinoline > pyridine > indoline > pyrrole > water. In general from the excess volume studies, the IL‐sulphur/nitrogen mixture has stronger interaction as compared to IL‐IL, thiophene‐thiophene or pyrrole‐pyrrole interaction. The deviation of surface tension was found to be inversely proportional to deviation of refractive index. The quantum chemical based COSMO‐RS was used to predict the non‐ideal liquid phase activity coefficient for all mixtures. It indicated an inverse relation between activity coefficient and excess molar volumes.

Prediction of miscible mixtures flash-point from UNIFAC group contribution methods

Flash point is one of the most important variables used to characterize fire and explosion hazard of liquids. This paper predicts the flash point of miscible mixtures by using the flash point prediction model of Liaw and Chiu (J. Hazard. Mater. 137 (2006) 38–46) handling non-ideal behavior through liquid phase activity coefficients evaluated with UNIFAC-type models, which do not need experimentally regressed binary parameters. Validation of this entirely predictive model is conclusive with the experimental data over the entire flammable composition range for twenty four flammable solvents and aqueous–organic binary and ternary mixtures, ideal mixtures as well as Raoult's law negative or positive deviation mixtures. All the binary-mixture types, which are known to date, have been included in the validated samples. It is also noticed that the greater the deviation from Raoult's law, the higher the probability for a mixture to exhibit extreme (minimum or maximum) flash point behavior, provided that the pure compound flash point difference is not too large. Overall, the modified UNIFAC-Dortmund 93 is recommended, due to its good predictive capability and more completed database of binary interaction parameters. Potential application for this approach concerns the classification of flammable liquid mixtures in the implementation of GHS.

Isobaric vapour–liquid equilibria and physical properties for isopropyl acetate + isopropanol + 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide mixtures

Experimental densities, refractive indices and dynamic viscosities of binary and ternary mixtures of isopropyl acetate, isopropanol and 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C 4mim][NTf 2]) have been determined at 298.15 K and atmospheric pressure. The excess molar volumes as well as molar refraction and viscosity changes of mixing have been calculated and adequately fitted to the Redlich–Kister equation. The adjustable parameters and the standard deviations between experimental and calculated values are reported. Vapour–liquid equilibrium (VLE) data have been obtained for these binary and ternary systems at 101.32 kPa and were adequately correlated by means of NRTL and UNIQUAC equations for the liquid phase activity coefficient.

Bubble point measurements of binary mixtures formed by 1-hexanol with selected nitro-compounds and substituted benzenes at 95.6 kPa

Bubble point measurements (at 95.6 kPa) over the entire composition range are carried out for the binary mixtures formed by 1-hexanol with the: nitro-compounds (acetonitrile, acrylonitrile N, N-dimethyl formamide and aniline) and substituted benzenes ( o-xylene, chlorobenzene, and nitrobenzene), employing a Swietoslawski type ebulliometer. Wilson model is found to represent the measured liquid phase composition versus bubble point temperature data well. Computed values of the vapor phase mole fractions and liquid phase activity coefficients are tabulated and briefly discussed.

Isobaric vapor–liquid equilibria for the n-heptane + ethylene glycol monopropyl ether and n-octane + ethylene glycol monopropyl ether systems

Vapor–liquid equilibria (VLE) for the n-heptane + ethylene glycol monopropyl ether and n-octane + ethylene glycol monopropyl ether systems were measured. Isobaric VLE measurements of the associating fluid mixtures were conducted at several pressures (60 kPa, 80 kPa and 100 kPa) using Fischer VLE 602 equipment. The experimental data were correlated using a two-term virial equation for vapor-phase fugacity coefficients and the three suffix Margules equation, Wilson, NRTL, and UNIQUAC models for liquid-phase activity coefficients. The results show good agreement with the variety of models.

Isobaric (vapour + liquid) equilibria for the (1-pentanol + propionic acid) binary mixture at (53.3 and 91.3) kPa

Isobaric (vapour + liquid) equilibrium measurements have been reported for the binary mixture of (1-pentanol + propionic acid) at (53.3 and 91.3) kPa. Liquid phase activity coefficients were calculated from the equilibrium data. The thermodynamic consistency of the experimental results was checked using the area test and direct test methods. According to these criteria, the measured (vapour + liquid) equilibrium results were found to be consistent thermodynamically. The obtained results showed a maximum boiling temperature azeotrope at both pressures studied. The measured equilibrium results were satisfactorily correlated by the models of Wilson, UNIQUAC, and NRTL activity coefficients. The results obtained indicate that the performance of the NRTL model is superior to the Wilson and UNIQUAC models for correlating the measured isobaric (vapour + liquid) equilibrium data.

Vapor−Liquid Equilibria of Binary Mixtures Formed by Hexan-1-ol with Chloroethanes and Chloroethenes at 95.6 kPa

Bubble-point temperatures (at 95.6 kPa) over the entire composition range are measured for the binary mixtures formed by hexan-1-ol with 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, trichloroethene, and tetrachloroehene, employing a Swietoslawski type ebulliometer. Both Wilson and nonrandom two-liquid (NRTL) models are found to represent the measured liquid-phase composition versus bubble-point temperature data well. The computed values of the vapor-phase mole fractions, liquid-phase activity coefficients, and excess Gibbs energies are tabulated and briefly discussed.

CACHAÇA PRODUCTION IN A LAB‐SCALE ALEMBIC: MODELING AND COMPUTATIONAL SIMULATION

ABSTRACT This work presents the application of a differential distillation model for the simulation of cachaça production in a pot still (alembic). The vapor–liquid equilibria of the multicomponent mixture were described in a rigorous way, using the nonrandom two‐liquid model for the liquid phase activity coefficients and the virial equation with the chemical theory for the vapor phase fugacity coefficients. Two experimental trials were performed in order to validate the simulation results. The boiling points of the wine and the ethanol concentration of the distillate were measured at fixed time intervals. The concentrations of acetaldehyde, ethyl acetate, methanol, n‐propanol, isobutanol and isoamyl alcohol, and the volatile acidity were analyzed in the head, heart and tail fractions of the distillate. In general, a good agreement was achieved between the experimental and the simulation results, in terms of the temperature and the alcoholic graduation profiles, and also a satisfactory similitude in terms of the concentrations of the main congeners.PRACTICAL APPLICATIONSSpirit's sensorial quality depends on the ethanol and main congener concentrations, which should be controlled by dividing the distillate in appropriate cuts (head, heart and tail fractions) during the distillation. A correct simulation procedure of the pot still distillation allows improving the policy of distillate cuts, considering the product quality, the maximal recovery of ethanol in the heart fraction (spirit) and the energy consumption. It can as well help to define a policy of distillate cuts more appropriate to different types of wine, i.e., wines containing, for instance, larger concentrations of light components (acetaldehyde, methanol, etc.), or of those containing larger contents of heavy compounds, such as acetic acid. So this work goal was to indicate that computational simulation, based on a careful modeling of the system, could be an important tool to investigate the effect of processing variables in the final product quality, also in terms of minor compounds.

Physical properties and phase equilibria of the system isopropyl acetate + isopropanol + 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide

Densities, refractive indices and dynamic viscosities of binary and ternary mixtures composed of isopropyl acetate, isopropanol, 1-octyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C 8mim][NTf 2]) have been determined at 298.15 K and atmospheric pressure. The excess molar volumes and dynamic viscosity changes of mixing have been calculated and correlated using the Redlich–Kister polynomial equation. Isobaric vapour–liquid equilibrium (VLE) data have been determined experimentally for these binary and ternary systems at 101.32 kPa. The equilibrium data have been adequately correlated by means of Wilson, NRTL, and UNIQUAC equations for the liquid phase activity coefficient.

Vapor pressures and flash points for binary mixtures of tricyclo [5.2.1.0 2.6] decane and dimethyl carbonate

Bubble-point vapor pressures, equilibrium temperatures and flash points for binary mixtures of a high energy density hydrocarbon fuel, tricyclo [5.2.1.0 2.6] decane (JP-10), and dimethyl carbonate (DMC) were measured. Correlation between vapor pressures and equilibrium temperatures for each mixture was given by the Antoine equation. The binary system of JP-10 and DMC appears with very large positive deviations of vapor pressure from the Raoult's law. The experimental vapor pressures are correlated and the flash points are then predicted using Scatchard-Hildeband, Van Laar and Wilson models of liquid phase activity coefficients with satisfactory results.