New experimental densities are reported for squalane and for branched pentaerythritol tetra(2ethylhexanoate), PEB8, in the compressed liquid state over the temperature range from (278.15 to 353.15) K and for pressures up to 45 MPa. The reliability of the technique and the procedure up to 25 MPa has been verified in our previous works, and in the present work they were checked up to 45 MPa by comparing our experimental densities for heptane with literature data. A total of 297 density values have been measured with a high-pressure vibrating tube densimeter. The correction factor for density due to the sample viscosity has been considered. This factor ranges from 1 × 10 -4 to 1 × 10 -3 g‚cm -3 for PEB8 and from 4 × 10 -5 to 6 × 10 -4 g‚cm -3 for squalane over the entire Tp interval. The pressure and temperature dependencies of squalane and PEB8 densities could be accurately represented by the Tammann-Tait equation with standard deviations of 3 × 10 -5 g‚cm -3 for squalane and 9 × 10 -5 g‚cm -3 for PEB8. These density data were used to analyze the isothermal compressibility, the isobaric thermal expansivity, and the internal pressure of squalane and PEB8.

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Knowledge of proper lubricant selection and its handling can substantially influence the reliability of a refrigeration system. In this sense the awareness of several thermophysical properties of refrigerants, lubricants, and their mixtures under different conditions of pressure and temperature is highly important for designing refrigeration systems. Polyol ester oils have been proposed as lubricant candidates for refrigeration systems. In this work, we have studied the density of two polyol esters, pentaerythritol tetraheptanoate and pentaerythritol tetranonanoate, in the range 278.15 ¡ T/K ¡ 353.15 and 0.1 ¡ p/MPa ¡ 45. In addition, the behaviour of two other essential volumetric properties, namely the thermal expansion coefficient and the isothermal compressibility coefficient, as well as the internal pressure have been analysed.

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New experimental densities in the compressed liquid state are reported for pentaerythritol tetrapentanoate (PEC5) over the temperature range of 278.15−353.15 K and for pressures up to 45 MPa. Density values (99 experimental data) have been measured with a high-pressure vibrating tube densimeter. A correction factor that was due to the viscosity of the sample was applied to the experimental density values. These data were used to determine isothermal compressibilities, isobaric thermal expansion coefficients, and internal pressures for this compound. Furthermore, the density data corresponding to the homologous series:  dialkyl sebacates, 1,10-decanediol diesters, triglycerides, trimethyolethane triesters, pentaerythritol tetraesters, and linear oligomer esters of poly(hexamethylene sebacate) were predicted using the Sako−Wu−Prausnitz (SWP) equation of state (EoS), which is linked to the group contribution approach of Elvassore et al. [Ind. Eng. Chem. Res. 1999, 38, 2110] and compared with experimental data in the literature. In addition, other two EoSthe Soave−Redlich−Kwong (SRK) and Peng−Robinson (PR) equationswere used to predict the densities of some pentaerythritol tetraesters, for which the critical constants and acentric factors have been published in the literature.

We measured the densities of 1-alkyl-3-methylimidazolium (C(n)mim, n = 2,4,6) tris(pentafluoroethyl)trifluorophosphate ionic liquids (eFAP) as a function of temperature and pressure and their viscosities as a function of temperature. These ionic liquids are less viscous than those based in the same cations but with other anions such as bis(trifluoromethylsulfonyl)imide. The ionic liquids studied are only partially miscible with water, their solubility increasing with the size of the alkyl side-chain of the cation and with temperature (from x(H(2)O) = 0.20 ± 0.03 for [C(4)mim][eFAP] at 303.10 K to x(H(2)O) = 0.49 ± 0.07 for [C(6)mim][eFAP] at 315.10 K). The solubility of carbon dioxide, nitrous oxide, ethane, and nitrogen in the three ionic liquids was measured as a function of temperature and at pressures close to atmospheric. Carbon dioxide and nitrous oxide are the more soluble gases with mole fraction solubilities of the order of 3 × 10(-2) at 303 K. The solubility of these gases does not increase linearly with the size of the alkyl-side chain of the cation. The solubilities of ethane and nitrogen are much lower than those of carbon dioxide and nitrous oxide (mole fractions 60% and 90% lower, respectively). The higher solubility of CO(2) and N(2)O can be explained by more favorable interactions between the solutes and the polar region of the ionic liquids as shown by the enthalpies of solvation determined experimentally and by the calculation of the site-site solute-solvent radial distribution functions using molecular simulation.

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Vapor-liquid equilibrium data are reported for the binary systems (CO2 + H2) and (CO2 + N2) at temperatures between (218.15 and 303.15) K at pressures ranging from the vapor pressure of CO2 to approximately 15 MPa. These data were measured in a new analytical apparatus which is described in detail. The results are supported by a rigorous assessment of uncertainties and careful validation measurements. The new data help to resolve discrepancies between previous studies, especially for the (CO2 + H2) system. Experimental measurements of the three-phase solid-liquid-vapor locus are also reported for both binary systems.The vapor-liquid equilibrium data are modelled with the Peng-Robinson (PR) equation of state with two binary interaction parameters: one, a linear function of inverse temperature, applied to the unlike term in the PR attractive-energy parameter; and the other, taken to be constant, applied to the unlike term in the PR co-volume parameter. This model is able to fit the experimental data in a satisfactory way except in the critical region. We also report alternative binary parameter sets optimized for improved performance at either temperatures below 243 K or temperatures above 273 K. A simple predictive model for the three-phase locus is also presented and compared with the experimental data.