Partial Molar Excess Enthalpies Research Articles

Measurement of activity coefficient at infinite dilution for some bio-oil components in water and mass transfer study of bubbles in the dilutor

Activity coefficients at infinite dilution (γ∞) values are of great importance when designing separation processes like distillation, liquid–liquid extraction and gas stripping. In this study the γ∞ values were determined for four compounds in water that are present in bio-oil. Henry’s law constants (H12), Partial molar excess enthalpies at infinite dilution (H¯iE,∞) and air–water partition coefficients (Kaw) are also reported. The measurements were performed using inert gas stripping equipment (dilutor) in the 298–340K temperature range. Mass transfer study was also performed to investigate the equilibrium between the solution and the gas leaving the cell.

Solubilities of phosphoric acid, P,P′-1,4-phenylene P,P,P′,P′-tetraphenyl ester in the organic solvents

A phosphorous flame retardant of phosphoric acid, P,P′-1,4-phenylene P,P,P′,P′-tetraphenyl ester (PAPTE) was synthesized by diphenyl chlorophosphate and hydroquinone. The structural features of PAPTE were investigated with mass spectra (MS), infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and high-performance liquid chromatograph (HPLC) methods. The thermal behavior of PAPTE was analyzed with differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) instruments. A static analytic method was used to measure the solubilities of PAPTE in the several selected pure solvents, which are methanol, ethanol, acetone, ethyl acetate, acetonitrile, methyl acetate, toluene, ether, n-propanol, i-propanol, where the temperatures range is from 288.25 to 333.45K. The experiments were also performed in the binary mixed solvents of acetone and methanol. Several thermodynamic models were used to correlate the experimental solubility data, such as Wilson, nonrandom two-liquid (NRTL), UNIQUAC equations. The solubility data of PAPTE in binary solvents were correlated with the modified Wilson model. The calculated results showed that those models can excellently reproduce the experimental data and the UNIQUAC equation reveals the better ability in correlation. Using the Scatchard–Hildebrand methodology, the activity coefficients, solubility parameter of the solute and the partial molar excess enthalpies at infinite dilution were calculated.

Third derivative thermodynamic quantities of aqueous tetrahydrofuran at 25 °C

We measured the excess chemical potential, μΕTHF, the excess partial molar enthalpy and entropy of solute tetrahydrofuran (THF), HETHF and SETHF, in THF–H2O at 25°C. Using these second derivatives of G, we graphically evaluated the third derivative quantities; the enthalpic, entropic THF–THF interaction functions, HETHF–THF, and SETHF–THF. Using the literature density data, the effect of THF on the excess partial molar volume of THF, VETHF–THF, was also evaluated. Furthermore, we directly determined the partial molar entropy-volume cross fluctuation density of THF, δTHFSV, another third derivative quantity. By comparing the mole fraction dependence patterns of these third derivative quantities between the present THF–H2O with what we thought to be the weakest member of a hydrophobic mono-ol series, methanol (ME), we suggest that in spite of its larger non-polar surface area, THF is as amphiphilic as ME. A quantitative characterization and any difference between THF and ME ought to wait for characterization by the 1-propanol probing methodology developed by us [PCCP 15(2013) 14548-14565].

Thermo-physical properties of ammonium-based ionic liquid + N-methyl-2-pyrrolidone mixtures at 298.15 K

A systematic study of a series of room-temperature ionic liquids, belonging to the alkylammonium nitrate family (XAN), was carried out at 298.15K and 0.1MPa with the aim of investigating the effect of the cationic chain length on some thermo-physical properties and their behavior in the organic solvent N-methyl-2-pyrrolidone (NMP), over the whole concentration range. Experimental densities were used to calculate molar volumes, Vm, and excess molar volumes, VE. Complementary information was obtained by isothermal titration calorimetry that provided the values of the heat of mixing, HE, and the excess partial molar enthalpies of each component, H¯1E and H¯2E. The density values of neat XAN samples decreased as the alkyl chain length of the cation increases, whereas, the addition of the methoxy group to the considered smaller alkyl chain resulted in an increase of density. Negative VE and HE values were found for each XAN+NMP system, indicating the presence of strong attracting interactions between the constituents.

A combined experimental and computational investigation of excess molar enthalpies of (nitrobenzene + alkanol) mixtures

Excess molar enthalpies (HmE) for the binary mixtures of {(nitrobenzene+ethanol), 1-propanol, 2-propanol, 1-butanol and 2-butanol} have been measured over the entire composition range at ambient pressure (81.5kPa) and temperature 298K using a Parr 1455 solution calorimeter. From the experimental results, the excess partial molar enthalpies (HiE) and excess partial molar enthalpies at infinite dilution (HiE,∞) were calculated. The excess molar enthalpies (HmE) are positive for all {nitrobenzene (1)+alkanol (2)} mixtures over the entire composition range.A state-of-the-art computational strategy for the evaluation of excess partial molar enthalpies at infinite dilution was followed at the M05-2X/6-311++G∗∗ level of theory with the PCM model. The experimental excess partial molar enthalpies at infinite dilution have been compared to the computational data of the ab initio in liquid phase. Integrated experimental and computational results help to clarify the nature of the intermolecular interactions in {nitrobenzene (1)+alkanol (2)} mixtures. The experimental and computational work which was done in this study complements and extends the general research on the computation of excess partial molar enthalpy at infinite dilution of binary mixtures.

Framework for correlating the effect of temperature on nonelectrolyte and ionic liquid activity coefficients

A power‐law expression is proposed for correlating the temperature dependence of infinite‐dilution activity coefficients ( ) for nonelectrolyte solute–solvent binary pairs and for pairs including an ionic liquid: , where θij = 0 for Lewis–Randall ideal solutions, θij = 1 for classic enthalpy‐based Scatchard–Hildebrand regular solution and van Laar models, and −5 < θij < 5 for most real binaries. The exponent θij is a function of partial molar excess enthalpy ( ) and entropy ( ) such that . Real binaries are classified into seven types corresponding to distinct domains of and θij. The new method provides a framework for correlating phase‐equilibrium driven temperature effects for a wide variety of chemical and environmental applications. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3675–3690, 2014

Measurement and Correlation of Excess Molar Enthalpy of Binary Mixtures Containing Butyl Acetate + 1-Alkanols (C1–C6) at 298.15 K

Excess molar enthalpies, ∆H m E , for the binary mixtures of butyl acetate + 1-alkanols, namely (methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol), were measured over the whole range of composition at 298.15 K using a Parr 1455 solution calorimeter. The excess partial molar enthalpies, ∆H m, E , were calculated from the experimental excess molar enthalpies using the Redlich–Kister polynomial equation. The sign of ∆H m E for all systems are positive because of the disruption of hydrogen bonding and dipole–dipole interactions in the alkanols and esters, respectively. The magnitude of the ∆H m E values increases with increasing alkyl chain length. The behavior of ∆H m E was analyzed in terms of the length of the alkanol chain, the nature and type of intermolecular interactions and the balance between positive and negative effects on deviations from ideality. The experimental excess molar enthalpy data have also been correlated using the Redlich–Kister and SSF equations and two local composition models (UNIQUAC and NRTL).

Temperature dependence of limiting activity coefficients, Henry's law constants, and related infinite dilution properties of C4–C6 isomeric n-alkyl ethanoates/ethyl n-alkanoates in water. Measurement, critical compilation, correlation, and recommended data

Infinite dilution activity coefficients (γ1∞) of C4–C6 isomeric n-alkyl ethanoates/ethyl alkanoates, namely ethyl ethanoate, propyl ethanoate, ethyl propanoate, butyl ethanoate, ethyl butanoate in water were measured at several temperatures in the range from (273 to 361)K. Most measurements were carried out by the inert gas stripping method, although other three headspace gas chromatography techniques were also employed. A comprehensive critical review is further presented of literature data on γ1∞, infinite dilution partial molar excess enthalpies (H¯1E,∞) and heat capacities (C¯p,1E,∞) of these aqueous solutes. For each ester, the data measured in this work together with those reported previously in the literature were correlated with a suitable model equation providing adequate simultaneous description of the equilibrium measurements and the calorimetric information. As a result, a recommended temperature dependence of γ1∞ of superior accuracy was established. The consistency of recommended γ1∞(T) with literature data on mutual solubilities of esters and water was also demonstrated. Analogous recommendations were derived also for the temperature dependence of Henry's law constants (KH). The variation with temperature and ester molecular structure of γ1∞, KH, and related energetic functions of ester dissolution and hydration was overviewed and briefly discussed. Furthermore, the performance of five predictive approaches to estimate γ1∞(T) of the aqueous esters was tested.

Thermodynamics and activity coefficients at infinite dilution for organic solutes, water and diols in the ionic liquid choline bis(trifluoromethylsulfonyl)imide

The activity coefficients at infinite dilution, γ13∞, for 63 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, ketones, esters, aldehyde, acetonitrile, pyridine and 1-nitropropane and 6 diols in the ionic liquid (IL) choline bis(trifluoromethylsulfonyl)imide, [N1112OH][NTf2] were determined by (gas+liquid) chromatography at six temperatures in range of (318.15 to 368.15)K and at three temperatures for diols in the range of (388.15 to 418.15)K. The thermodynamic functions at infinite dilution as partial molar excess Gibbs free energy, ΔG1E,∞, enthalpy ΔH1E,∞, and entropy term TrefΔS1E,∞ were calculated from the experimental γ13∞ values obtained over the temperature range. The density of [N1112OH][NTf2] was measured within temperature range (313.15 to 353.15)K. The (gas+liquid) partition coefficient KL was calculated for all solutes. The values of selectivity and capacity for a few separation problems as hexane/benzene, cyclohexane/benzene, heptane/thiophene at T=328.15K were calculated from γ13∞ and compared to literature values for similar ionic liquids, N-methyl-2-pyrrolidinone (NMP), and sulfolane. In comparison with the former measured ammonium-based ILs and the morpholinium-based ILs, the [N1112OH][NTf2] shows average selectivity for the separation of aromatic hydrocarbons, or sulfur compound from aliphatic hydrocarbons, and very high selectivity for pyridine/heptane separation. New data show that [N1112OH][NTf2] IL may be proposed as an alternative solvent for the separation of sulfur or nitrogen compounds from alkanes.

Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-butyl-3-methylimidazolium methyl sulfate

Activity coefficients at infinite dilution (γi∞) and (gas+liquid) partition coefficients (KL) for organic solutes: alkanes, alkenes, alkyl benzenes, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, and chloromethanes in the ionic liquid (IL) 1-butyl-3-methylimidazolium methyl sulfate ([BMIM][CH3SO4]) have been measured by the (gas+liquid) chromatographic method in the temperature range of (313.15 to 363.15)K. The values of the partial molar excess enthalpies at infinite dilution (H‾iE,∞) were derived from the temperature dependence of the γi∞ values. The entropies (TrefS‾iE,∞) and Gibbs free energies (G‾iE,∞) of organic solutes in [BMIM][CH3SO4] at a reference temperature Tref=298.15K were also calculated from the γi∞ values. The solubility parameters of the IL [BMIM][CH3SO4] were also determined by the regular solution theory (RST). The linear free energy relationship (LFER) analysis of the results was performed to disclose molecular interactions operating between the IL and the individual solutes.

Excess enthalpies for pseudobinary mixtures containing vegetable oils at the temperatures 298.15 K, 353.15 K and 383.15 K

This paper presents excess enthalpies for the following systems containing refined vegetable oils: soybean oil+methanol (at 353.15K/722kPa), soybean oil+ethanol (at 353.15K/687kPa and 383.15K/653kPa), soybean oil+n-hexane (at 353.15K/722kPa and 383.15K/756kPa), soybean oil+propan-2-ol (at 298.15K/998kPa), sunflower oil+methanol (at 353.15K/791kPa), sunflower oil+ethanol (at 353.15K/894kPa and 383.15K/860kPa), sunflower oil+n-hexane (at 353.15K/756kPa and 383.15K/894kPa), sunflower oil+propan-2-ol (at 298.15K/929kPa), rapeseed oil+methanol (at 353.15K/963kPa), rapeseed oil+ethanol (at 353.15K/998kPa and 383.15K/1136kPa), and rapeseed oil+n-hexane (at 353.15K/894kPa and 383.15K/1136kPa). The measurements were carried out with a commercially available isothermal flow calorimeter. The experimental HE values have been correlated using the Redlich-Kister polynomial equation. The results for systems with propan-2-ol and some values of partial molar excess enthalpies at infinite dilution, HiE,∞, obtained in this study have been compared to those available in the literature. The results were also discussed in terms of molecular interactions.

Solubilities of 4-(Hydroxymethyl)-1-oxido-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane in Organic Solvents

A phosphorus flame retardant of 4-(hydroxymethyl)-1-oxido-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane (PEPA) was synthesized by pentaerythritol and phosphorus oxychloride at a certain condition. The structural features of PEPA were investigated with Fourier transform infrared spectroscopy and 1H NMR methods. The thermal behavior of PEPA was carried out with differential scanning calorimetry and thermogravimetric analysis instruments. A static analytic method was used to measure the solubilities of the PEPA in several organic solvents. The measurements were accurately acted in ethyl acetate, acetonitrile, isopropyl alcohol, ethanol, n-propyl alcohol, acetone, methanol, and chloroform at the temperature range from 292.75 K to 333.45 K. Using the Scatchard–Hildebrand methodology, the activity coefficients of the solute have been calculated, and the partial molar excess enthalpies at infinite dilution were also predicted.

Elucidation of Ionic Interactions in the Protic Ionic Liquid Solutions by Isothermal Titration Calorimetry

The strong hydrogen-bonded network noted in protic ionic liquids (PILs) may lead to stronger interactions of the ionic entities of PILs with solvents (water, methanol, ethylene glycol, dimethylsulfoxide (DMSO), N,N'-dimethylformamide (DMF)) as compared with those of aprotic ionic liquids (APILs). The PILs used in this work are 1-methylimidazolium tetrafluoroborate, 2-methylpyridinium tetrafluoroborate, and N-methylpyrrolodinium tetrafluoroborate in comparison to 1-butyl-3-methylimidazolium tetrafluoroborate, which is classified as an APIL. In this work, the excess partial molar enthalpy, H(E)IL obtained from isothermal calorimetric titrations at 298.15 K is used to probe the nature of interactions of the PIL cations with solvent molecules against those present in APIL-solvent systems. This work also reports interesting flip-flopping in the thermal behavior of these PIL-solvent systems depending upon the structure of the cationic ring of a PIL. In some cases, these flip-flops are the specific fingerprints for specific PILs in a common solvent environment. The excess partial molar enthalpy at infinite dilution, H(E,∞)IL, of these PILs bears a critical dependence on the solvent properties. An analysis of relative apparent molar enthalpies, ϕL, of the PIL solutions by the ion interaction model of Pitzer yields important information on ionic interactions of these systems.

Experimental study on the calorimetric data of butylacetate with pentanol isomers as important biofuels and correlation treatment at T = 298.15 K

Excess molar enthalpies, , of binary mixtures of butylacetate (common component) + pentanol isomers as important biofuels, namely 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 2-methyl-2-butanol and 3-methyl-2-butanol, were measured over the whole range of the composition at T = 298.15 K and ambient pressure using a Parr 1455 solution calorimeter. The excess partial molar enthalpies, , were calculated according to experimental excess molar enthalpies and the Redlich–Kister polynomial equation. The extracted data were used to evaluated the so-called intermolecular interaction functions, and . The sign of for all systems are positive and show endothermic behaviour over the entire range of compositions. The values become more positive with the increasing of the branches and steric factors. The experimental excess molar enthalpy data have been also correlated using the Redlich–Kister and SSF equations and two thermodynamic models (Wilson and NRTL). The experimental data have been qualitatively discussed and interpreted on the basis of the polarity, size and shape of alkanols.

Excess molar volumes and excess molar enthalpies in binary systems N-alkyl-triethylammonium bis(trifluoromethylsulfonyl)imide + methanol

In the present paper, a study on the influence of the alkyl chain length in N-alkyl-triethylammonium bis(trifluoromethylsulfonyl)imide ionic liquids, [NR,222][Tf2N] (R=6, 8 or 12), on the excess molar enthalpy at 303.15K and excess molar volume within the temperature interval (283.15–338.15K) of ionic liquid+methanol mixtures is carried out. Small excess molar volumes with highly asymmetric curves (i.e. S-shape) as a function of mole fraction composition were obtained, with negative values showing in the methanol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the ammonium cation of the ionic liquid and decrease with temperature. The excess enthalpies of selected binary mixtures are positive over the whole composition range and increase slightly with the length of the alkyl side-chain of the cation on the ionic liquid. Both excess properties were subsequently correlated using a Redlich–Kister-type equation, as well as by using the ERAS model. From this semipredictive model the studied excess quantities could be obtained from its chemical and physical contribution. Finally, the COSMOThermX software has been used to evaluate its prediction capability on the excess enthalpy for investigated mixtures at 303.15K and 0.1MPa. From this work, it appears that COSMOThermX method predicts this property with good accuracy of approx. 10%, providing at the same time the correct order of magnitude of the partial molar excess enthalpies at infinite dilution for the studied ILs, H¯1E,∞, and methanol, H¯2E,∞.

Activity coefficients at infinite dilution of organic solutes in 1-hexyl-3-methylimidazolium trifluoroacetate and influence of interfacial adsorption using gas–liquid chromatography

Activity coefficients at infinite dilution for a series of organic solutes in the ionic liquid 1-hexyl-3-methylimidazolium trifluoroacetate ([HMIM][TFA]) have been determined by gas–liquid chromatography at the temperature range from (303.15 to 363.15)K. The contribution of interfacial adsorption to the retention mechanism was estimated by changing the loading of ionic liquid in stationary phase. The partial molar excess enthalpies at infinite dilution and the solubility parameters of ionic liquid were also calculated from the experimental values of activity coefficients at infinite dilution.

Measurement of activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-hexyl-1,4-diaza[2.2.2]bicyclooctanium bis(trifluoromethylsulfonyl)imide using gas–liquid chromatography

Based on gas–liquid chromatography (GLC) retention data, activity coefficients at infinite dilution of 39 different solutes in the ionic liquid 1-hexyl-1,4-diaza[2.2.2]bicyclooctanium bis(trifluoromethylsulfonyl)imide ([HDABCO][NTf2]) have been determined. Measurements covered a broad range of types of organic solutes including alkanes, alcohols, ketones, benzene derivatives and McReynold’s compounds. Activity coefficients were measured over the temperature range (331.15–363.15)K. The partial molar excess enthalpies of mixing at infinite dilution have been determined based on Gibbs–Helmholtz relationship. Selectivity at infinite dilution values have been also calculated for exemplary separation processes in the systems hexane/benzene and cyclohexane/benzene. The results obtained were analyzed in comparison to literature data for ionic liquids with the same [NTf2]− anion. The obtained results indicate the potential for the application of the investigated ionic liquid in separation problems.

Measurements of activity coefficients at infinite dilution in vegetable oils and capric acid using the dilutor technique

This paper reports experimental activity coefficients at infinite dilution, γi∞, for methanol, ethanol and n-hexane in three refined vegetable oils (soybean, sunflower, and rapeseed oils) measured using the dilutor technique (inert gas stripping method). The measurements were carried out in the temperature range between 313.15 and 353.15K. Furthermore, activity coefficients at infinite dilution for various solutes (acetone, methanol, ethanol, n-hexane, cyclohexane and toluene) were measured in capric (decanoic) acid using the same technique in the temperature range from 313.13 to 353.30K. The new data obtained for capric acid and soybean oil were compared with already published experimental data. Additionally, densities of the investigated vegetable oils were measured in the temperature range from 293.15 to 353.15K. Using the experimental γi∞ values obtained over the temperature range, the partial molar excess Gibbs energy (ΔGiE,∞), enthalpy (ΔHiE,∞) and entropy (ΔSiE,∞) at infinite dilution were determined. The relative error for the γi∞ measurements carried out using the dilutor technique is approximately ±2.5%. The measured γi∞ data in the investigated refined vegetable oils were also compared with the results of the group contribution methods original UNIFAC and modified UNIFAC (Dortmund) and an extension of the latter method to triacylglycerols was proposed.

Measurement of activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate at T = (308.15, 313.15, 323.15 and 333.15) K using gas + liquid chromatography

In this study, the interactions between volatile organic compounds and the ionic liquid (IL) 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate [EMIM]+[MDEGSO4]− were investigated using gas+liquid chromatography measurements. The activity coefficients at infinite dilution γ13∞ were determined for 28 polar and non-polar organic solutes (alkanes, cycloalkanes, alkenes, alkynes, aromatic compounds, alcohols, and ketones) in 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate at T=(308.15, 313.15, 323.15 and 333.15)K. Packed columns with phase loadings of 0.27 and 0.37 mass fraction of the IL in the stationary phase were employed to obtain γ13∞ values at each temperature. Density and refractive index values were also measured for the pure IL at P=0.1MPa and at the experimental temperatures. Partial molar excess enthalpies at infinite dilution ΔH1E,∞ were calculated for the solutes from the temperature dependency of the γ13∞ values. The uncertainties in the activity coefficient at infinite dilution were critically evaluated and estimated on average to be ±5.3%. Selectivity values at infinite dilution Sij∞ for the hexane/benzene separation were also calculated at T=308.15K. The selectivity Sij∞ value of the IL investigated in this study is approximately 3.7 times greater than that for NMP, 2.6 times greater than that for NFM, and 2.3 times greater than that for sulfolane. These results indicate the potential use of this IL in extractive separation processes.

Thermodynamics of (ketone + amine) mixtures. Part XI. Excess molar enthalpies at T = 298.15 K for the (1-propanol + N,N,N-triethylamine + 2-butanone) system

Molar excess enthalpies, HmE, measured by means of a Tian-Calvet microcalorimeter, for the ternary system {1-propanol+N,N,N-triethylamine (TEA)+2-butanone} at T=298.15K are reported. Values of HmE for the constituent binaries are available in the literature. The data are interpreted in terms of different interactional contributions to HmE. The coefficients of the corresponding fittings of binary and ternary HmE values have been used to determine the partial molar excess enthalpies of each component. It is concluded that 1-propanol and TEA molecules can participate in interactions between unlike molecules, and that 2-butanone is mainly a breaker of interactions between like molecules. The DISQUAC model is applied, using binary parameters only, for the HmE prediction of the ternary mixture investigated. Large differences between experimental values and theoretical results show the existence of ternary interactions.