Isobaric Thermal Expansion Coefficient Research Articles

Nature of the interactions in binary mixtures of 1-butyl-3-ethylimidazolium bromide ionic liquid with methanol and ethanol

Physicochemical properties and nature of the interactions in methanol and ethanol solutions of 1-butyl-3-ethylimidazolium bromide ionic liquid, [C4C2im]Br, have been investigated experimentally measuring density over the whole composition range at selected temperatures and atmospheric pressure. From the experimental densities, the excess properties and partial molar volumes of the components at infinite dilution were calculated, as well as the excess molar expansibility at infinite dilution and isobaric thermal expansion coefficients. Obtained negative values of excess molar volumes with pronounced minimum at xIL ≈ 0.3 indicate strong ion–alcohol interactions and better packing due to differences in the size and shape of the molecules. Results are compared with those obtained for aqueous solutions of investigated ionic liquid and discussed in terms of hydrogen bond formation. Also, apparent molar volumes for {[C4C2im]Br + alcohol} systems show more pronounced deviations comparing to aqueous solutions of [C4C2im]Br confirming stronger self-association of the water molecules.

Evaluation of High-Pressure Thermophysical Parameters of the Diacylglycerol (DAG) Oil Using Ultrasonic Waves

Modeling of high-pressure technological processes in the food industry requires knowledge of thermophysical parameters of processed foodstuffs in a broad range of pressures and temperatures. However, the high-pressure thermophysical parameters of foodstuffs are very rarely published in the literature. Therefore, further research is necessary to achieve a deeper insight into the biophysical and thermophysical phenomena under pressure to provide better control of technological processes and optimize the effects of pressure. The essential goal of this work is to evaluate the impact of high pressure and temperature on the thermophysical parameters of liquid foodstuffs on the example of diacylglycerol (DAG) oil (which attracted recently a considerable attention from research and industrial communities due to its remarkable benefits for health), using ultrasonic wave velocity and density measurements. Isotherms of adiabatic and isothermal compressibility, isobaric thermal expansion coefficient, internal pressure, and thermal pressure coefficient versus pressure were evaluated, based on the measurement of the compressional ultrasonic wave velocity and density of DAG oil at high pressures (up to 500 MPa) and at various temperatures. The adiabatic compressibility is affected mostly by the changes of pressure, i.e., it grows about four times when the pressure increases from the atmospheric pressure (0.1 MPa) to 400 MPa at a temperature of 50 °C. By contrast, the internal pressure is a pronounced function of the temperature, i.e., it increases six times when the temperature rises from 20 to 50 °C at a pressure of a 200 MPa. To perform numerical calculations, it was convenient to introduce a Tammann–Tait type equation of state to approximate the measured density isotherms of the investigated DAG oil. The results obtained in this paper can be applied in modeling and optimization of high-pressure technological processes and processing of foodstuffs. Evaluation of high-pressure isotherms of the considered thermophysical parameters of the DAG oil is an original authors’ contribution to the state-of-the-art.

High pressure densities and derived thermodynamic properties for the (n-heptane + n-octane + ethanol) ternary system

The density of the ternary system (n-heptane+n-octane+ethanol) at temperatures from (293.15 to 373.15)K and at pressures from (0.1 to 40)MPa was experimentally determined at twelve compositions and the results are presented here. Measurements were performed using high pressure U-tube cell DMA HP coupled with DMA 5000 vibrating density meter. To fit the experimental density values the modified Tammann-Tait equation was applied. Excess molar volumes were also calculated at all pressures and temperatures in order to explain to what extent the investigated mixtures deviate from ideal behaviour. Moreover, the influence of pressure and temperature on density was studied by calculating isothermal compressibility and isobaric thermal expansion coefficient. It was found that non-ideal behaviour of the ternary mixture is strongly influenced by pressure and temperature conditions.

Molecular dynamics simulations of pure methane and carbon dioxide hydrates: lattice constants and derivative properties

ABSTRACTWe report extensive molecular dynamics simulation results of pure methane and carbon dioxide hydrates at pressure and temperature conditions that are of interest to various practical applications. We focus on the calculation of the lattice constants of the two pure hydrates and their dependence on pressure and temperature. The calculated lattice constants are correlated using second order polynomials which are functions of either temperature or pressure. Finally, the obtained correlations are used in order to calculate two derivative properties, namely the isothermal compressibility and the isobaric thermal expansion coefficient. The current simulation results are also compared against reported experimental measurements and other simulation studies and good agreement is found for the case of isothermal compressibility. On the other hand, for the case of isobaric thermal expansion coefficient good agreement is found only with other simulation studies, while the simulation studies are in disagreement with experiments, particularly at low temperatures.

Studies of Volumetric and Transport Properties of Ionic Liquid–Water Mixtures and Its Viability To Be Used in Absorption Systems

Binary systems of two ionic liquids (ILs), 1-ethylpyridinium methanesulfonate [C2Py][MeSO3] and choline dihydrogen phosphate [Chol][H2PO4], and water have been experimentally studied. Density, viscosity, electrical conductivity and proton activity have been measured at several temperatures covering all the miscibility range. From density data, isobaric coefficient of thermal expansion was calculated to study the volumetric behavior of the mixtures. All volumetric data were fit using polynomial equations. The Vogel–Fulcher–Tamman (VFT) equation accurately describes the temperature dependence of viscosity for all systems. Systems based on [C2Py][MeSO3] are less dense and viscous than those involving [Chol][H2PO4], making [C2Py][MeSO3] more suitable for absorption systems where pumping cost has a significant importance. Electrical conductivity data were adjusted using the Casteel–Amis equation. Similar trends were found for both systems, although ionic conductivity is higher for [C2Py][MeSO3] + H2O mixtures....

Density and phase equilibrium of the binary system methane + n-decane under high temperatures and pressures

Densities of the binary system methane + n-decane have been determined through a vibrating tube densitometer from (278.15–463.15) K at pressures up to 140 MPa, and for methane mole fractions up to 0.8496. Negative excess volumes were found under the experimental conditions studied. Moreover isothermal compressibility values were obtained by differentiation from the Tammann-Tait correlation of the determined density values. Isobaric thermal expansion coefficients were also calculated based on differentiation from the isobaric fit of density data. We also measured the phase equilibrium of this binary system by using a variable volume cell with full visibility from (293.15–472.47) K for three mixtures with methane mole fractions of 0.4031, 0.6021 and 0.8496. Liquid fraction upon expansion below the saturation pressure has also been determined. Finally different equations of state were used to calculate the experimental density and excess volume data as well as the phase envelope data. No direct regression of the experimental data was involved in most of the calculation in order to provide a fair comparison of the performance of different models.

Flow reversals in Rayleigh–Bénard convection with non-Oberbeck–Boussinesq effects

Flow reversals in two-dimensional Rayleigh–Bénard convection led by non-Oberbeck–Boussinesq (NOB) effects due to large temperature differences are studied by direct numerical simulation. Perfect gas is chosen as the working fluid and the Prandtl number is 0.71 for the reference state. If NOB effects are included, the flow pattern $P_{11}$ with only one dominant roll often becomes unstable by the growth of the cold corner roll, which sometimes results in cession-led flow reversals. By exploiting the vorticity transport equation, it is found that the asymmetries of buoyancy and viscous forces are responsible for the growth of the cold corner roll because both such asymmetries cause an imbalance between the corner rolls and the large-scale circulation (LSC). The buoyancy force near the cold wall increases and decreases near the hot wall originating from the temperature-dependent isobaric thermal expansion coefficient ${\it\alpha}=1/T$ if NOB effects are included. Moreover, the decreased dissipation due to lower viscosity is favourable for the growth of the cold corner roll, while the increased viscosity further suppresses the growth of the hot corner roll. Finally, it is found that the boundary layer near the cold wall plays an important role in the mass transport from LSC to corner rolls subject to mass conservation.

Densities, Viscosities, and Refractive Indexes of Good’s Buffer Ionic Liquids

Good’s buffer ionic liquids (GB-ILs) have demonstrated their potential usefulness in the biotechnological field due to their advantageous properties of self-buffering and biocompatibility. To further investigate the applicability of these solvents in industrial process, the knowledge of the thermophysical properties of such solvents is of utmost importance. In this work, a series of GB-ILs prepared by the combination of the Good’s buffer anions MOPSO, BES, TAPSO, and CAPSO, with tetrabutylammonium, tetrabutylphosphonium, and cholinium cations were synthesized and characterized regarding the determination of the melting and decomposition temperatures. Additionally, the physical properties such as density, viscosity and refractive index were measured for these GB-ILs at atmospheric pressure and in the (288.15 to 353.15) K temperature range. Additional properties such as the isobaric thermal expansion coefficient and activation energy for viscous flow were also further derived from the temperature dependence...

Study of thermophysical properties of the binary mixtures of ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate and 2-propoxyethanol from T = (298.15 to 328.15) K at atmospheric pressure

Experimental data for density (ρ), speed of sound (u) and refractive index (nD) for pure 1-ethyl-3-methylimidazolium ethyl sulfate ([Emim][EtSO4]), 2-propoxyethanol and their binary mixtures are measured over the whole composition range as a function of temperature between 298.15 and 328.15K at atmospheric pressure. Experimental values are used to calculate the excess molar volumes (VmE), excess partial molar volumes (V‾mE), partial molar volumes at infinite dilution (V‾mE,∞), excess/deviation values of isentropic compressibility (κsE), free length (LfE), acoustic impedance (ZE), speeds of sound (uE), refractive index (ΔϕnD) and isobaric thermal expansion coefficient (αPE) for the binary mixtures. These excess/deviation properties are fitted to the Redlich–Kister type equation to obtain the coefficients and the standard deviations. The negative values of excess properties such as VmE, κSE, LfE, αPE and positive values of ZE, uE, ΔϕnD indicate existence of strong interaction between studied components. A quantitative analysis of these parameters was further supported by IR spectroscopy analysis.

Densities and derived thermodynamic properties for the (n-heptane + n-octane), (n-heptane + ethanol) and (n-octane + ethanol) systems at high pressures

This work reports densities for the pure n-heptane, n-octane and ethanol at temperatures from (288.15 to 413.15)K and at pressures up to 60MPa. The same properties were determined for the binary mixtures n-heptane + n-octane, n-heptane + ethanol and n-octane + ethanol over the temperature range (293.15–373.15)K and at pressures ranging from (0.1 to 40)MPa. Highly precise densimeter DMA HP was used for density measurements. Experimental values of densities were fitted by the modified Tammann–Tait equation. Additionally, derived volumetric properties, e.g. excess molar volumes, isothermal compressibilities and isobaric thermal expansion coefficients were calculated. The effect of pressure and temperature on the measured and derived properties was discussed.

Volumetric and Refractive Properties of the Mixtures of 1,1,3,3-Tetramethyl-1,3-diphenyldisiloxane with Various Organosilicon Compounds at T = (308.15 to 328.15) K

The density and refractive index were determined for four binary mixtures of 1,1,3,3-tetramethyl-1,3-diphenyldisiloxane with 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane, and 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane at different temperatures (T = 308.15, 313.15, 318.15 323.15 and 328.15 K) and atmospheric pressure using a DMA4500/RXA170 combined system. The excess molar volume, partial excess volume at infinite dilution, isobaric coefficient of thermal expansion, excess refraction indices, Lorentz–Lorenz molar refraction, and the deviation in molar refraction have been calculated using these data. The results have been incorporated into the Redlich–Kister equation and used to estimate the binary interaction parameters and standard deviation. The values of partial excess volume at infinite dilution and excess refraction indices for the four binary systems at different temperatures were calculated using the adjustable parameters of the Redlich–Kister smoothing equation. The factors that affect these excess quantities have been discussed.

Lattice constants of pure methane and carbon dioxide hydrates at low temperatures. Implementing quantum corrections to classical molecular dynamics studies.

We introduce a simple correction to the calculation of the lattice constants of fully occupied structure sI methane or carbon dioxide pure hydrates that are obtained from classical molecular dynamics simulations using the TIP4PQ/2005 water force field. The obtained corrected lattice constants are subsequently used in order to obtain isobaric thermal expansion coefficients of the pure gas hydrates that exhibit a trend that is significantly closer to the experimental behavior than previously reported classical molecular dynamics studies.

Excess properties and spectroscopic studies for binary system of polyethylene glycol 600 + 1,2-ethanediamine at T = (298.15, 303.15, 308.15, 313.15, and 318.15) K

Density (ρ) and viscosity (η) data for the binary system of polyethylene glycol 600 (PEG)+1,2-ethanediamine (EDA) over the entire concentration range at a number of temperatures T=(298.15, 303.15, 308.15, 313.15, and 318.15) K as a function of composition were measured under atmospheric pressure. On the basis of experimental density and viscosity data, the excess properties of PEG (1)+EDA (2) mixtures, including excess molar volumes (VmE), viscosity deviations (∆η), excess free energies of activation (∆G*E), apparent molar volumes (Vϕ,1 and Vϕ,2), partial molar volumes (V1̅and V2̅), and isobaric thermal expansion coefficient (αp), were calculated. Meanwhile, the values of VmE, ∆η, and ∆G*E were fitted with the Redlich–Kister equation to derive coefficients and to evaluate the standard deviations (σ) between the experimental and calculated values. Moreover, on the basis of FTIR and UV–vis spectral data of PEG (1)+EDA (2) mixtures with various concentrations, the intermolecular interaction of PEG with EDA was discussed.

The study of molecular interactions in 1-ethyl-3-methylimidazolium trifluoromethanesulfonate + 1-pentanol from density, speed of sound and refractive index measurements

A molecular interaction study is carried out between the ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-pentanol using the experimental values of density, speed of sound and refractive index measurements over the whole composition range as a function of temperature between (298.15 and 328.15)K at atmospheric pressure. The excess/deviation properties, such as molar volumes (VmE), partial molar volumes (V‾mE), partial molar volumes at infinite dilution (V‾mE,∞), isentropic compressibility (κsE), free length (LfE), speeds of sound (uE), refractive index (ΔϕnD) and isobaric thermal expansion coefficient (αPE) obtained from the experimental values are fitted into the Redlich–Kister type equation to obtain the binary coefficients and the standard deviations. The negative values of excess properties such as VmE,κSE,LfE,αPE and the positive values of uE, ΔϕnD clearly indicated the existence of strong molecular interactions between the studied components. The values of ∂VmE∂TP and ∂HmE∂PT are also calculated to support the existing interactions. A quantitative analysis of these parameters is further supported by IR spectroscopic analysis.

Partial molar volumes, isentropic compressibilities, and partial molar expansibilities of N-Methylglycine and d-Glucose in aqueous environments at temperatures between (298.15 and 323.15) K

The apparent molar volumes, isentropic compressibility coefficient, and partial molar expansibilities of N-Methylglycine and d-Glucose in aqueous environments from measurements of the densities, speeds of sound and refractive indices at different temperatures from (298.15 to 323.15) K are reported. The experimental results of thermophysical properties are obtained in a mole fraction range from (0.0018 to 0.0189) for N-Methylglycine and of (0.0037, 0.0075, 0.0115, and 0.0157) for d-Glucose solutions.The refractive indices data were analyzed based on the Lorentz–Lorenz equation. The standard isentropic compressibility and standard partial molar volumes were determined by extrapolation to infinite dilution. From the temperature dependence of solutes partial molar volumes, the partial molar expansivity, the isobaric thermal expansion coefficient, and the Hepler constant values as second derivative of infinite dilution of partial molar volume with temperature have been estimated. The variations of these thermophysical properties with concentration and temperature suggest the effects of N-Methylglycine and d-Glucose in aqueous mixtures by solute–solvent interactions.

Study of molecular interactions in binary liquid mixtures of [Emim][BF4] with 2-methoxyethanol using thermo acoustic, volumetric and optical properties

Physical properties, such as density (ρ), speed of sound (u) and refractive index (nD) for pure [Emim][BF4], 2-methoxyethanol and their binary mixtures are measured over the whole composition range as a function of temperature between (298.15–328.15)K at atmospheric pressure. Experimental values were used to calculate the excess values of molar volumes (VmE), partial molar volumes (V¯mE), partial molar volumes at infinite dilution (V¯mE,∞), excess/deviation values of isentropic compressibility (κsE), acoustic impedance (ZE), free length (LfE), speeds of sound (uE), refractive index (ΔϕnD) and isobaric thermal expansion coefficient (αPE) for the binary mixtures. These excess/deviation properties are fitted to the Redlich–Kister type equation to obtain the binary coefficients and the standard deviations. A qualitative analysis of these parameters indicates strong intermolecular interactions between the liquids in study. This was further supported by IR spectroscopy.

The study of solute–solvent interactions in 1-ethyl-3-methylimidazolium ethylsulfate + 2-ethoxyethanol from density, speed of sound and refractive index measurements

Physical properties, such as density (ρ), speed of sound (u) and refractive index (nD) for pure [Emim][EtSO4], 2-ethoxyethanol and their binary mixtures are measured using Anton Paar vibrating tube density, sound velocity meter (DSA 5000M) and automatic refract meter over the whole composition range as a function of temperature between (298.15–328.15)K at atmospheric pressure. Experimental values were used to calculate the excess molar volumes (VmE), excess values of partial molar volumes (V̅mE), partial molar volumes at infinite dilution (V̅mE,∞), excess/deviation values of isentropic compressibility (κsE), isothermal compressibility (κTE), free length (LfE), speed of sound (uE), refractive index (ΔϕnD), internal pressure (πiE), free volume (VfE) and isobaric thermal expansion coefficient (αPE) for the binary mixtures. These excess/deviation properties were fitted to the Redlich–Kister type equation to obtain the binary coefficients and the standard deviations. A qualitative analysis of these parameters indicates strong intermolecular interactions between the liquids in study. This was further supported by IR spectroscopy.

Volumetric and viscosimetric properties of [bmim][DCA] + γ-butyrolactone binary mixtures

In this paper experimental densities and dynamic viscosities of pure 1-butyl-3-methylimidazolium dicyanamide ionic liquid, [bmim][DCA], and its binary liquid mixtures with γ-butyrolactone (GBL) are reported. All measurements were performed in the temperature range from (273.15 to 323.15)K at the pressure of 0.1MPa for the various mixture compositions. From the experimental density the related volumetric parameters were calculated and fitted using Redlich–Kister’s polynomial equation. Obtained values are compared to those previously obtained for GBL mixtures with imidazolium and pyrrolidinium based ionic liquids containing bis(trifluoromethylsulfonyl)imide and dicyanamide anions. Other volumetric properties, such as isobaric thermal expansion coefficients, partial molar volumes and partial molar volumes at infinite dilution were also calculated, in order to obtain information about the interactions between GBL and the studied ionic liquid. From the viscosity results, the Angell strength parameter was calculated and found to be 3.75 indicating that [bmim][DCA] is a “fragile” liquid.

The physicochemical properties of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane with various aromatic hydrocarbons at T = (308.15 to 323.15) K

The density and refractive index were determined for four binary mixtures of 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane with nitrobenzene, ethylbenzene, anisole and tert-butylbenzene at different temperatures T=(308.15, 313.15, 318.15 and 323.15)K and atmospheric pressure using a DMA4500/RXA170 combined system. The excess molar volume, partial excess volume at infinite dilution, isobaric coefficient of thermal expansion, excess refraction indices, Lorentz–Lorenz molar refraction and the deviation in molar refraction have been calculated using these data. The results have been incorporated into the Redlich–Kister equation and used to estimate the binary interaction parameters and standard deviations. The values of partial excess volume at infinite dilution and excess refraction indices for the four binary systems at different temperatures were calculated using the adjustable parameters of the Redlich–Kister smoothing equation. The factors that affect these excess quantities have been discussed.

The group contribution method (GC) versus the critical point-based approach (CP): Predicting thermodynamic properties of weakly- and non-associated oxygenated compounds by GC-PPC-SAFT and CP-PC-SAFT

In this study GC-PPC-SAFT and the CP-PC-SAFT Equations of State have been implemented for estimating thermodynamic properties of weakly-associated and non-associated oxygenated compounds, while the primarily attention has been paid to the elevated pressure data. The analysis indicates that the polar contribution of GC-PPC-SAFT has a negligibly small impact on predicting the high pressure data. Apparently, in the cases of the weakly- and non-associating compounds a major factor responsible for accuracy of the models at elevated pressures is the curvature of the dispersion contribution. At the same pressures CP-PC-SAFT tends to predict the lower values of densities and higher values of sound velocities. These predictions of CP-PC-SAFT are particularly accurate in the cases of slightly polar compounds with reliable values of the critical constants. Both models are capable of yielding only raw estimations of CP. Although CP-PC-SAFT has a clear advantage in predicting the available compressibility data, GC-PPC-SAFT is superior in qualitative estimating the isobaric thermal expansion coefficients. However the major advantage of GC-PPC-SAFT is the more accurate estimation of the vapor pressures away from the critical points.