Nonrandom Two-liquid Equation Research Articles

Solubility, Thermodynamic Parameters, and Dissolution Properties of 17-α Hydroxyprogesterone in 13 Pure Solvents.

The static gravimetric method was used to measure the solubility of 17-α hydroxyprogesterone (OHP) in 13 pure solvents ranging from 278.15 to 323.15 K. The results indicate that the experimental solubility of OHP increases with increasing temperature. The experimental solubility data were correlated by the selected van't Hoff model, λh model, modified Apelblat model, Yaws model, and nonrandom two-liquid (NRTL) model. The fitting results show that the Yaws model can give better correlation results by fitting 13 different pure solvent systems. Based on the NRTL equation, the thermodynamic analysis of solubility data showed that the mixing process was spontaneous. The Hansen solubility parameters (HSPs) and solvent effect were applied to explore these solubility characteristics. Finally, the thermodynamic properties ΔsolH°, ΔsolS°, ΔsolG°, %ξH, and %ξTS were calculated by the van't Hoff model equation. The results showed that ΔsolH°, ΔsolS°, and ΔsolG° are all positive values, indicating that the dissolution of OHP in the selected solvent is an endothermic reaction with increasing entropy.

Calculation of Component Activities for Se-Based Binary Systems by NRTL Equation

The interaction energy parameters of the Nonrandom two-liquid (NRTL) equation for the Bi–Se, Pb–Se, Sb–Se, and Tl–Se binary systems were determined. The difference in the goodness of fit between the systems was discussed for each system. The activities of components at corresponding temperatures for the four binary systems were calculated and discussed using the NRTL equation. The mixing enthalpies and Gibbs free energies of these systems were obtained. The calculations for the four binary systems are in agreement with the experimental data from the literature. It shows that the NRTL equation is reasonable and accurate based on the concept of local composition and two-fluid theory, especially for binary systems containing liquid–liquid equilibria. The results we obtained using the NRTL equation can be very useful in performing vacuum experiments for crude selenium.

Examination of eutectic phase change materials composed of diols and ionic liquids

This paper presents solid–liquid phase equilibrium studies of binary systems composed of pyridinium chloride monohydrates: hexadecylpyridinium chloride monohydrate, [PyC16][Cl] or dodecylpyridinium chloride monohydrate, [PyC12][Cl] with diols: 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol and 1,12-dodecanediol. These systems were selected to obtain eutectic mixtures with a high melting enthalpy and lower volatility (thus flammability) than pure diols. Ten eutectic Phase Change Materials (ePCMs) with melting points ranging from 265 K to 333 K (-8 °C to 60 °C) and enthalpies of melting from 125.9 to 212.8 J·g−1 were obtained. Experimental data were then correlated with the Non-Random Two-Liquid (NRTL) equation, and mixtures of eutectic composition were subjected to physicochemical characterisation. Using DSC, the latent heats of pure components and eutectic mixtures were determined, as well as the viscosity and the thermal conductivity of ePCMs was measured as a function of temperature. The final objective of the study was to increase the thermal conductivity of ePCMs by adding carbon nanotubes or expanded graphite, and to characterise the performance of such composite systems. The stability of nanofluids containing no less than 1 wt% SWCNTs and from about 10 wt% EG was confirmed under both isothermal and energy storage operating conditions, i.e. during a series of at least 1000 phase transformations. The addition of an inexpensive EG at 10 wt% increases the thermal conductivity by up to 200 % and reduces the probability of ePCM leakage as the material retains its shape even after melting.

Isobaric Vapor–Liquid Equilibrium for Ethyl Acetate + Chloroform with Ionic Liquids [EMIM][OAc], [BMIM][OAc], and DMSO + [EMIM][OAc] as Entrainers at 101.3 kPa

Ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]), and a mixture of [EMIM][OAc] and dimethyl sulfoxide (DMSO) were used as solvents to separate the maximum boiling azeotropic mixture of ethyl acetate and chloroform. The ternary vapor–liquid equilibrium (VLE) data of ethyl acetate + chloroform + [EMIM][OAc] were measured at 101.3 kPa. The liquid phase is partially soluble when the concentration of ethyl acetate and [EMIM][OAc] is high in the ternary system, and DMSO is employed to enhance the solubility of [EMIM][OAc] in ethyl acetate. Different entrainers were compared by measuring the VLE of ethyl acetate + chloroform + DMSO, ethyl acetate + chloroform + [BMIM][OAc], and ethyl acetate + chloroform + [EMIM][OAc] + DMSO at 101.3 kPa. All of the entrainers can improve the relative volatility of ethyl acetate to chloroform. The salting-out effects of the ILs [EMIM][OAc] and [BMIM][OAc] are significantly greater than that of DMSO. Organic solvent DMSO can enhance the selectivity of [EMIM][OAc] at high ethyl acetate concentration. The effects of the entrainers were analyzed by sigma-profiles. The nonrandom two-liquid (NRTL) activity coefficient model was adopted to correlate the experimental data. The binary interaction parameters of the NRTL equation were obtained, and the correlation results agreed well with experimental results.

Thermodynamic Properties of {Diethyl Phosphate-Based Ionic Liquid (1) + Ethanol (2)} Systems, Experimental Data and Correlation

In this work, three solutions consisting of ionic liquid and ethanol were considered for forward-looking use in absorption refrigeration technology. It is proposed to use the following ionic liquids as absorbents: 1-ethyl-3-methylimidazolium diethyl phosphate (abbreviated as [EMIM][DEP]), 4-ethyl-4-methylmorpholinium diethyl phosphate ([EMMOR][DEP]), and 1-ethyl-1-methyl-pyrrolidinium diethyl phosphate ([EMPYR][DEP]). Since the thermodynamic and physicochemical properties of working fluids determine the efficiency of the refrigerator while looking for alternative operating fluids, it is crucial to perform their extensive characteristics. Therefore, in this work, (vapor + liquid) phase equilibria (VLE), liquid density (ρ), and dynamic viscosity (η) were determined for the ethanolic solution of the three mentioned diethyl phosphate-based ionic liquids. The isothermal VLE was measured by an ebulliometric method within a temperature range from T = (328.15 to 348.15) K with an increment of 10 K and pressures up to 90 kPa. Non-random two-liquid (NRTL) equation with temperature-dependence parameters was used to correlate experimental data. Physicochemical properties including liquid density and dynamic viscosity were determined at temperatures from (293.15 to 338.15) K at ambient pressure over the whole concentration range. These properties were correlated using empirical equations. From experimental density and viscosity data, the excess molar volumes and the deviations from additivity were determined and correlated using the Redlich–Kister-type equation. Two of the tested ILs, [EMMOR][DEP] and [EMPYR][DEP], were synthesized and characterized using NMR analysis. The thermophysical characterizations of pure compounds, including glass transition temperature (Tg) and heat capacity at the glass transition temperature (ΔgCp), have been determined using a differential scanning calorimetry technique (DSC) at atmospheric pressure. The work presented is a combination of basic studies on the effect of the cation structure of an ionic liquid on the properties of their solutions with ethanol, with the possibility of future application of the tested systems in a viable refrigeration system.

Evaluation of the adequacy of phase equilibria modeling based on various sets of experimental data

Objectives. The purpose of the paper is to compare the adequacy of mathematical models of vapor–liquid equilibrium (VLE) and their ability to reproduce the phase behavior of the ternary system benzene–cyclohexane–chlorobenzene using different experimental data sets to evaluate binary interaction parameters.Methods. The research methodologies were mathematical modeling of VLE in the Aspen Plus V.10.0 software package using activity coefficient models (Non-Random Two-Liquid (NRTL), Wilson) and the Universal quasichemical Functional-group Activity Coefficients (UNIFAC) group model, which allows for independent information. For the benzene–cyclohexane–chlorobenzene ternary system, the use of the NRTL equation is warranted because it provides a better description of the VLE experimental data.Results. The diagram construction of the constant volatility of cyclohexane relative to benzene lines revealed three topological structures. Only one of them can be considered reliable because it corresponds to the experimental data and coincides with the UNIFAC model diagram constructed based on independent UNIFAC model data. The results indicate that to study systems containing components with similar properties, it is necessary to improve the description quality of the available data sets (the relative error should not exceed 1.5%).Conclusions. The reproduction of the thermodynamic features of various manifolds in the composition simplex obtained by processing direct VLE data can be used to supplement the adequacy of the model. For the cyclohexane–benzene–chlorobenzene system, the best NRTL equation parameters are those regressed from the extensive experimental VLE data available in the literature for the ternary system as a whole.

Solubilities of Flame Retardant Trifluoroiodomethane (R13I1) in Polyol Ester and Polyvinyl Ether Lubricant Oil in the Temperature from 283.15 to 353.15 K

Experimental solubilities of trifluoroiodomethane (R13I1) in polyol ester (POE) and polyvinyl ether (PVE) lubricant oils were measured at a temperatures range from 283.15 to 353.15 K and pressure from 0.15 to 0.76 MPa. The solubility data were obtained by an experimental system based on the isochoric saturation method. During the experiment, no stratification, no sediment generation, and no color change were observed in both the R13I1 + POE32 lubricant oil system and the R13I1 + PVE32 lubricant oil system. Moreover, the experimental data were correlated by the nonrandom two-liquid (NRTL) equation. From the correlated results, the absolute average deviation for R13I1 in POE and PVE lubricant oil were 1.63 and 1.75%, respectively. Moreover, the maximum relative pressure deviation of the mixtures (R13I1 + POE32 lubricant oil and R13I1 + PVE32 lubricant oil) between experimental data and correlated values were 4.15 and 5.16%, respectively. It shows that the experimental results fit well with the NRTL model. In this work, R13I1 dissolved more in POE lubricant oil than in PVE lubricant oil. Thus, POE lubricant oil is more soluble than PVE lubricant oil.

Fluctuation in diethylene glycol diethyl ether/water mixtures near the lower critical solution temperature studied by small- and wide-angle x-ray scattering and thermodynamic calculation

We studied local structure of diethylene glycol diethyl ether (DEGDEE)-water mixtures near the lower critical solution temperature (LCST) by means of simultaneous small- and wide-angle x-ray scattering measurement and thermodynamic calculation based on the activity coefficient model. Long-wavelength limits of structure factors SNN(0), SCC(0), and SNC(0), which respectively represent mean square fluctuations in the particle number, the concentration, and their cross correlation, are determined from scattering intensity extrapolated to the zero scattering vector and thermodynamic quantities according to the Bhatia and Thornton formula. SNN(0) and SCC(0) exhibit maxima near critical concentration. We found that difference between partial molar volumes of water and DEGDEE essentially results in SNN(0) values being one order of magnitude larger than SCC(0) values. Further, we determined Kirkwood-Buff (KB) integrals to clarify a mixing state of the solution from a mesoscopic point of view. The KB integrals also exhibit extrema near critical concentration. These results demonstrate self-segregations of both DEGDEE and water in a nanometer length scale even at homogeneous solution states, which can be regarded as a precursor of the macroscopic phase separation. Concentration dependence of the wide-angle scattering curve suggests that the short-range structure, whose length scale is sub-nanometer, moderately changes between the intrinsic bulk structures of DEGDEE and water. Comparison of the KB integrals with those determined by the activity coefficient model using non-random two-liquid equation is presented and effects of the fluctuation on the phase behavior are discussed.

Determination of chlorzoxazone crystal growth kinetics and size distribution under controlled supersaturation at 293.15 K

Background: Chlorzoxazone (CHZ) is a water-insoluble drug having bioavailability problems. The absorption rate of such drugs can be improved by reducing their particle size. In this work, the crystal growth kinetics of CHZ–ethanol for different degrees of supersaturation (SS) has been studied. Method: The equilibrium solubility data of CHZ in ethanol is determined by the shake-flask method within the 283.15–313.15 K temperature range. The mole fraction solubility of CHZ is calculated and correlated with the modified Apelblat equation, λh equation, van’t Hoff equation, Wilson, and non-random two liquid (NRTL) equation. Batch crystallization experiments are performed on three different degrees of SS-1.16, 1.18, and 1.20 at 293.15 K as a function of time. Results: The maximum root mean square difference (RMSD) and relative average deviation (RAD) values of 169.24 x10-6 and 0.699 x10-2, respectively, are observed in the NRTL equation model. The dissolution properties such as standard enthalpy, standard entropy, and Gibbs free energy are predicted using van’t Hoff equation. Using a simple integral technique, the average crystal growth rate constant KG is calculated as 1.58 (μm/min) (mg/ml)-1 and the order n=1 for CHZ–ethanol at 293.15 K. Conclusion: The obtained result concludes that the crystals growth size is found to be varied at different SS ratio in batch crystallization. The particle size control in batch crystallization can be achieved by optimizing the operating conditions to get the desired size crystals.

Determination and correlation of solubility of 4,4′-difluorobenzophenone in pure and binary mixed solvents and thermodynamic properties of solution

The target of this study was to determine and correlate the solubility of 4,4′-difluorobenzophenone in various solvents from 293.15 K to 333.15 K by gravimetric method at 0.1 MPa, and at the same time got the thermodynamic parameters. In this work, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethyl acetate, methyl acetate, acetone, acetonitrile pure solvents and ethanol + n-propanol mixed solvents were selected as the experimental solvents. The results showed that the solubility of 4,4′-difluorobenzophenone in selected solvents increased with increasing temperature within the investigated temperature range. The effect of solvent properties on 4,4′-difluorobenzophenone solubility behaviors was discussed by solvent polarity, hydrogen bonding donor and acceptor propensity, and cohesive energy density. Furthermore, the dissolution behavior was explained using the Hansen solubility parameter (HSP). In pure solvents, the modified Apelblat equation, van't Hoff equation, λh equation, nonrandom two-liquid (NRTL) equation, Wilson equation and universal quasichemical (UNIQUAC) equation were used to correlate the experimental solubility of 4,4′-difluorobenzophenone. While the solubility in ethanol + n-propanol mixed solvents was correlated by the modified Apelblat equation, van't Hoff equation, λh equation, NRTL model, Wilson model, Jouyban-Acree and the modified Jouyban-Acree model. The results indicated that the calculated values of all selected equations were in good agreement with the experimental data. Furthermore, the thermodynamic properties (∆H°sol, ∆S°sol, ∆G°sol, %ξH and %ξTS) were measured by Van't Hoff analysis. In a word, the physicochemical data of 4,4′-difluorobenzophenone obtained in this work will be helpful for the purification, crystallization, recrystallization and designing a new synthetic route of 4,4′-difluorobenzophenone.

Comparison of extractive distillation flowsheets for methanol–tetrahydrofuran–water mixtures

Objectives. Synthesis and comparative analysis of the extractive distillation flowsheets for aqueous mixtures of solvents utilized in pharmaceutical industries using the example of a methanol−tetrahydrofuran−water system with various compositions. The ternary system contains two minimally boiling azeotropes that exist in a vapor–liquid phase equilibrium. To evaluate the selective effect of glycerol, the phase equilibria of the methanol–tetrahydrofuran–water and methanol–tetrahydrofuran–water–glycerol systems at 101.32 kPa were studied.Methods. The calculations were carried out in the Aspen Plus V.9.0 software package. The vapor–liquid equilibria were simulated using the non-random two-liquid (NRTL) equation with the binary interaction parameters of the software package database. To account for the non-ideal behavior of the vapor phase, the Redlich–Kwong equation of state was used. The calculations of the extractive distillation schemes were carried out at 101.32 kPa.Results. The conceptual flowsheets of extractive distillation are proposed. The flowsheets consist of three (schemes I–III) or four (scheme IV) distillation columns operating at atmospheric pressure. In schemes I and II, the extractive distillation of the mixtures is carried out with tetrahydrofuran isolation occurring in the distillate stream. Further separation in the schemes differs in the order of glycerol isolation: in the third column for scheme I (traditional extractive distillation complex) or in the second column for scheme II (two-column extractive distillation complex + methanol/water separation column). Sсheme III caters to the complete dehydration of the basic ternary mixtures, followed by the extractive distillation of the azeotropic methanol–tetrahydrofuran system, also with glycerol. Sсheme IV includes a preconcentration column (for the partial removal of water) and a traditional extractive distillation complex.Conclusions. According to the criterion of least energy consumption for separation (the total load of the reboilers of distillation columns), sсheme I (a traditional complex of extractive distillation) is recommended. Additionally, the energy expended for the separation of the basic equimolar mixture using glycerol as the extractive agent was compared with that expended using another selective agent: 1,2-ethanediol. Glycerol is an effective extractive agent because it reduces energy consumption, in comparison with 1,2-ethanediol, by more than 5%.

Formation of glassy phases and polymorphism in deep eutectic solvents

Deep eutectic solvents (DESs) are a class of eutectic mixtures that have very low melting temperature at the eutectic point, which limits crystallization or lead to formation of metastable polymorphs. This can produce a false estimate of the actual melting temperature of the mixture. The present work focuses on the formation of metastable phases in eutectic systems containing l-menthol. Differential scanning calorimetry (DSC) was applied to measure the solid–liquid equilibria (SLE) of the eutectic mixtures. Two sample-preparation methods were employed, namely annealing and in situ crystallization during the DSC run. We found that the eutectic temperature of the stable mixture is much higher than the observed glass-transition temperature of the mixture. Moreover, the eutectic temperature of a mixture with a stable polymorph is different from that of a metastable polymorph. The measured SLE data were correlated through non-ideality modeling using the non-random two-liquid (NRTL) equation. Our results show that SLE modeling is a useful tool for predicting the melting temperatures of stable mixtures without the need for time-consuming annealing methods. This work serves as a guide for reporting stable mixture properties when dealing with eutectic mixtures that form metastable phases.

Solubility, thermodynamic parameters, and dissolution properties of gliclazide in seventeen pure solvents at temperatures from 278.15 to 318.15 K

The solubility of gliclazide in seventeen pure solvents, i.e. methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, acetone, cyclohexanone, ethyl formate, methyl acetate, ethyl acetate, acetonitrile, tetrahydrofuran, N, N-dimethylformamide, chloroform and toluene was determined using a gravimetric method over a temperature range from 278.15 to 318.15 K at atmospheric pressure. The obtained solubility was corrected by the modified Apelblat equation, λh equation, non-random two-liquid (NRTL) equation, and the Wilson equation. The mixing properties, such as the dissolution Gibbs energy, enthalpy and entropy of gliclazide, were calculated based on the Wilson equation. The solubility data, thermodynamic parameters and dissolution properties would be useful for the development and optimization of the crystallization processes for gliclazide in industry.

Isothermal Vapor-Liquid Equilibrium Measurement of Isobutanol + Isooctane/N-Heptane Binary Mixtures at Temperatures Range of 303.15-323.15 K

The addition of alcohol as an oxygenated compound in gasoline blends may increase the vapor pressure of gasoline mixture. As a result, the study of vapor-liquid equilibrium for gasoline component and alcohol is necessary. In this study, the vapor-liquid equilibrium of isobutanol – isooctane/n-heptane blends were obtained experimentally at temperatures in the range 303.15 to 323.15 K using modified simple quasi-static ebulliometer. The apparatus was validated by comparing the vapor pressure of pure isobutanol, isooctane, and n-heptane with the published data and giving average absolute deviation (AAD) between experimental and calculated ones with magnitude less than 1.0%. The addition of isobutanol with the mole fraction range from 0.2 to 0.6 would increase the vapor pressure of the isooctane and n-heptane up to 12% and 14% respectively. The vapor pressure of binary mixtures was correlated with the Wilson, Non-random two-liquid (NRTL), and Universal quasi-chemical (UNIQUAC) equations with AAD 1.6%, 1.5%, and 1.7%, respectively for isobutanol + isooctane system and 1.8%, 1.7%, and 2.0%, respectively for isobutanol + n-heptane system. The systems studied show positive deviation from Raoult’s Law.

Measurement and Modeling of the Solubility of N,N-Dibenzylhydroxylamine in 17 Solvents from T = 273.15 to 323.35 K and Thermodynamic Properties of Solution

In this work, the solubility of N,N-dibenzylhydroxylamine (DBHA) in 17 pure solvents, including methanol, ethanol, n-propanol, n-butanol, acetone, ethyl acetate, dichloromethane, acetonitrile, isopropanol, n-octanol, cyclohexanone, 1,2-dichlorobenzene, toluene, isobutanol, n-pentanol, 1,2,4-trichlorobenzene, and tetrahydrofuran, was determined by a static gravimetric method with the temperature ranging from 273.15 to 323.35 K under atmospheric pressure. The solubility of DBHA was positively related to temperature in all selected solvents. Besides, the experimental solubility data were correlated with four thermodynamic models, i.e., the modified Apelblat equation, λh equation, nonrandom two-liquid (NRTL) equation, and the Wilson equation. The results indicated that all of the models could give satisfactory results and the NRTL equation provided the best fitting result. Furthermore, the dissolution thermodynamic parameters in the used solvents, including the Gibbs energy (ΔdisG), molar enthalpy (ΔdisH), and molar entropy (ΔdisS), were calculated according to the Wilson model, and it turned out that the dissolution process of DBHA was endothermic.

Measurement and correlation of solubility of flunarizine hydrochloride in ten pure and ethanol + n-propanol mixed solvents at temperatures within 293.15–333.15 K

The objective of this work is to obtain the solubility data for flunarizine hydrochloride, the parameters of its correlation equations,and the thermodynamic parameters involved in its dissolution process. The solubility was determined in ten pure solvents, includ-ing methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol,ethyl acetate, methyl acetate, acetone and acetonitrile, and binary mixed solvents of ethanol and n-propanol at 293.15–333.15 K using the gravimetric method under atmospheric pressure. The results revealed that the solubility increased with increasing temperature forall the selected solvents. In addition, Hansen solubility parameters (HSP) were used to explain and predict the solubility behavior. The experimental solubility in the mono solvents was correlated by the modified Apelblat equation，van't Hoff equation, λh equation, nonrandom two-liquid (NRTL) equation and Wilson model, respectively.While the solubility in the binary mixed solvents was correlated with the above methods as well as the Jouyban-Acree model and modified Jouyban-Acree model. The results showed that the solubility is in good agreement with the fitted values. In addition, the thermodynamic parameters including the enthalpy of dissolution (∆H°sol), entropy of dissolution (∆S°sol), Gibbs free energy (ΔG°sol) and the respective contributions of enthalpy and entropy were calculated. Consequently, the experimental solubility and correlation equations can be used as the essential data and simulation models in the purification and separation of flunarizine hydrochloride.

Solubility Measurement and Thermodynamic Modeling for o-Toluenesulfonamide in 16 Solvents from T = 273.15 to 323.85 K

The solid–liquid equilibrium data of o-toluenesulfonamide in 16 pure organic solvents, including methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, acetone, ethyl acetate, acetonitrile, cyclohexanone, cyclopentanone, methyl acetate, ethyl formate, and dichloromethane, were measured by a static gravimetric method with the temperature ranging from 273.15 to 323.85 K under atmospheric pressure. The results showed that the solubility of o-toluenesulfonamide increased with the increasing temperature in all the solvents studied. The experimental solubility data were correlated by the modified Apelblat equation, λh equation, nonrandom two-liquid (NRTL) equation, and Wilson equation. All the models could be well employed, and the NRTL model gave the best fitting results.

Extraction of Carboxylic Acids from Aqueous Solutions by Using [BMim][NTf2] and Salting-out Agents

Levulinic and lactic acids are important feedstock in a wide range of different industries such as polymer, pharmaceutical, or food manufacture. In this work, a study about levulinic acid and lactic acid recovery from their aqueous solutions was carried out using the hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonil)imide, [BMim][NTf2]. Liquid–liquid equilibria data for the ternary systems water + levulinic acid or lactic acid + IL were determined. The obtained experimental data were correlated by using the nonrandom two-liquid (NRTL) equation. An analysis of the influence of the acid structure and the addition of salting-out agents (potassium phosphate, ammonium sulfate, and saccharose) on the phase equilibria, was also carried out. [BMim][NTf2] was found to be a good extractant for the recovery of levulinic acid and the extraction process was improved by the addition ammonium sulfate.

New Predictive Nonrandom Two Liquid Equation for Solid–Liquid Phase Equilibrium in n-Alkanes Mixture with Multiple Solid Solutions

In this work, a predictive nonrandom two-liquid (NRTL) equation analyzed from binary experimental data is proposed to model the solid–liquid equilibrium in the n-alkanes mixture. The predictive NRT...

Solubility and solution thermodynamics of p-toluenesulfonamide in 16 solvents from T = 273.15 to 324.75 K

The solid-liquid equilibrium data and solution thermodynamics of chemicals are indispensable for the synthesis and purification of crystalline products in industry. The selection of a solvent directly influences the yield and purity of a product. In this work, the solubility of p-toluenesulfonamide (p-TSA) in 16 pure solvents, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, acetone, ethyl acetate, acetonitrile, cyclohexanone, cyclopentanone, methyl acetate, ethyl formate and dichloromethane, was determined by a static gravimetric method at temperatures ranging from 273.15 to 324.75 K under atmospheric pressure. The results indicate that the mole fraction solubility of p-TSA increased with increasing temperature in all 16 solvents. The solubility value in the selected alcohols ranks in the following order: methanol > ethanol >n-propanol > isopropanol >n-butanol >n-pentanol > isopentanol > isobutanol, and the polarity of a solvent seems to be an important factor influencing the solubility of p-TSA in alcohols. In the other eight solvents, the solubility sequence is cyclopentanone > acetone > cyclohexanone > (acetonitrile, methyl acetate) > ethyl acetate > ethyl formate > dichloromethane, which strongly deviates from the order of solvent polarities. Then, the measured solubility data were correlated with four thermodynamic models, i.e., the modified Apelblat equation, λh equation, non-random two-liquid (NRTL) equation and the Wilson equation. Overall, the NRTL model provided the most satisfactory fitting results. Furthermore, the dissolution thermodynamic parameters, Gibbs energy (△disG), molar enthalpy (△disH) and molar entropy (△disS) were calculated according to the Wilson model. The values of △disH and △disS are positive in all selected solvents, showing that the dissolution process of p-TSA in the selected solvents is endothermic and entropy-driven. The △disG values are negative in all selected solvents and decrease with increasing temperature, which demonstrates that dissolution of p-TSA in the selected solvents is favorable and spontaneous.