Liquid−liquid equilibrium data in binary systems γ-valerolactone + hydrocarbon (n-heptane, n-decane, n-dodecane, cyclohexane, and 2,4,4-trimethyl-1-penetene) were determined by direct analytical and cloud-point methods. The experimental data were smoothed by the extended scaling law equation which respects nonclassical behavior of fluid mixtures in critical loci. The nonrandom two-liquid equation's parameters were evaluated from the data obtained, as well. Since the molecule of γ-valerolactone retains a quite high dipole moment, the acquired experimental data on liquid−liquid equilibrium were used for the testing of predictive capabilities of the perturbed-chain polar SAFT equation of state (PCP-SAFT) in comparison to the original PC-SAFT model. Vapor pressures of γ-valerolactone in the temperature range from 264 K to 313 K and its liquid densities at temperatures from 288 K to 363 K were measured and utilized for evaluation of the PCP-SAFT and PC-SAFT parameters. It was found that prediction of liquid−liquid equilibrium performed by the polar PCP-SAFT equation with pure component parameters can be classified as relatively successful. ■ INTRODUCTIONγ-Valerolactone (GVL) is a natural compound which can be found for example in fruits. Recently this compound has gained attention as a versatile sustainable liquid which can be efficiently produced from biomass, preferentially from lignocellulose. The versatility of GVL is very wide. GVL can be utilized as liquid fuel, green solvent, and food additive or as an organic intermediate in the syntheses of other chemicals. To produce GVL from biomass, different technologies are studied. A pioneering technology suggested by Horvath et. al 1 involves a high pressure hydrogenation step which is rather costly for large-scale production of GVL. Romań et al. 2 devised a less expensive method to synthesize the key biofuel component, which could make its industrial production much more costeffective. From this point of view the utilization of GVL as fuel, fuel additive, or fuel precursor seems to be very promising. GVL can be converted to lower molecular weight valerate esters (methyl-, ethyl-, and propyl valerate) suitable for use as a gasoline additive and higher esters (butyl and pentyl valerate) that could be used directly as a diesel fuel or as a diesel additive. 3 Alternatively GVL can be converted to butane molecules which can be further combined to yield longer hydrocarbon chains for diesel or jet fuels. 4 A comparison of GVL with absolute ethanol as a gasoline additive was done by Horvath et al. 5 It was found that most of the data for GVL are comparable with that of ethanol. The lower vapor pressure of GVL even leads to improved performance. According to experiments carried out by Bereczky et al., 6 the addition of GVL to diesel fuels had relatively little effect on engine performance and NO x emission, but it significantly reduced the exhaust concentration of CO, unburned fuel, and smoke. The use of GVL as direct additive to gasoline can be restricted however because of t...

Liquid−liquid equilibrium and excess enthalpies were studied for the two binary systems:  methylcyclohexane + methanol and methylcyclohexane + N,N-dimethylformamide. Points of the binodal curve in the vicinity of the critical point were established in both of the systems by means of the cloud-point method. Equilibrium compositions were determined at different temperatures using the direct analytical method and the volume method. Excess enthalpies as functions of composition were determined at 298.15 K and 313.15 K using a Hart 4410 microcalorimeter with continuous-flow mixing cells. The results were correlated by the modified Wilson equation. A prediction of the liquid−liquid equilibrium and the excess enthalpy by the modified UNIFAC contribution method (Dortmund) was compared to the experimental values.

Isothermal vapor−liquid equilibrium data were measured for two binary systems, ethanol + 2,4,4-trimethyl-1-pentene and 2-propanol + 2,4,4-trimethyl-1-pentene, at 343 K. The measurements were made with a circulation still. The composition of liquid and condensed vapor phase was determined with a gas chromatograph. Excess molar enthalpy data were measured for the same binary systems at 298 K. Both systems indicate positive deviations from Raoult's law and exhibit azeotropic behavior.

A refined flow microcalorimetric setup with a fully automatic control of the entire experimental sequence has been designed for accurate measurement of mixing enthalpies of highly dilute aqueous solutions as a function of composition and, in turn, for reliable determination of the solute's infinite dilution dissolution enthalpies (Δsol ). The instrument and procedure were extensively tested, and their performance was verified using various microcalorimetric standards and further test reactions that involved the dissolutions of 1-propanol at eight temperatures from (283.15 to 318.15) K, of 1-butanol at 298.15 K, of 2-hexanol at five temperatures from (288.15 to 318.15) K and the dilutions of 10 % mass fraction aqueous 1-propanol and 2 mol·kg-1 sucrose solutions at 298.15 K. It was found that even for viscous solute media (viscosity 7 mPa·s) of limited aqueous solubility (mole fraction 0.002), Δsol could be determined with a combined standard uncertainty of 1 % or lower. The microcalorimeter was employed to determine Δsol for further oxygenated solutes for which these data are lacking or insufficient, namely, for 2-pentanol, 3-methyl-1-butanol, and 3-methyl-2-butanol at 298.15 K, for 1-methoxy-2-propanol at four temperatures from (288.15 to 318.15) K, for diethyl ether at five temperatures from (283.15 to 303.15) K, and for dimethoxymethane at seven temperatures from (288.15 to 318.15) K. The measurements of Δsol as a function of temperature enabled us to derive reliable values of infinite dilution dissolution heat capacities.

The present work deals with the precise experimental determination of the gas–liquid chromatography (GLC) retention factors (k) in a sufficiently large temperature range to allow the calculation of the thermodynamic quantities associated with the sorption process. Once isothermal retention factors of three homologous series members of the type H-(CH2) n -Y (Y = CH3, OH, CN) were measured over a temperature range of about 110 K on a low-polar PDMS (HP-1) capillary column and checked for accuracy and precision by “arc plot” representation, the data were analyzed by applying different forms of the van’t Hoff relationship. We compared the linear versus nonlinear van’t Hoff plots representing situations characterized by Δsolv C p ° = 0, Δsolv C p °≠ 0 = constant, and Δsolv C p ° = f(T), respectively (Δsolv C p ° represents the difference in isobaric heat capacity associated with movement of the analyte between the mobile and the stationary phase). The “logarithmic” and “quadratic” nonlinear van ‘t Hoff equations were shown to be more appropriate than the linear van‘t Hoff equation for determining enthalpy and entropy of solvation. Special attention was devoted to the fitting performance and extrapolation capability of models with nonzero Δsolv C p °. By several metrics, the quadratic model exhibits better behavior in extrapolations yielding reasonable accuracy for retention time and/or enthalpy of solvation predictions at temperatures located below the experimental range.

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A flow mixing microcalorimetric system we developed recently was appended in this work with a vibrating tube densimeter into a tandem flow arrangement. This new combined apparatus (calo/densimeter) allows simultaneous automatic measurement of mixing enthalpies and densities of highly dilute solutions as a function of composition and, in turn, reliable determination of the solute's infinite dilution partial molar excess enthalpies H _

Liquid-liquid equilibrium and excess enthalpies were measured for the binary system 2-methylpentane + N,N-dimethylformamide. Equilibrium data were obtained at different temperatures by the direct analytical and volume methods; points of the binodal curve in the vicinity of the upper critical solution temperature of this system were acquired by means of the cloud-point method. Excess enthalpies were measured at 298.15 K and 313.15 K. Binary data were correlated by the modified Wilson equation. To estimate the critical composition and the upper critical solution temperature, the liquid-phase behavior data were also described by the extended scaling-law equation proposed by Ewing et al. 5 The liquidliquid equilibrium and excess enthalpies in the binary system were predicted by the modified UNIFAC (Dortmund) model so that the prediction could be compared to the experimentally achieved data.