Isobaric Thermal Expansion Research Articles

Volumetric properties of n-hexadecane/ethyl octanoate mixtures from 293.15 K to 363.15 K and pressures up to 60 MPa

The densities of pure ethyl octanoate and n-hexadecane/ethyl octanoate mixtures were measured from 293.15 K to 363.15 K and up to 60 MPa using U-shape vibrating-tube densimeter. The results were correlated as Tait equation, the excess molar volumes, isothermal compressibilities, and isobaric thermal expansivities of the mixtures were calculated and analyzed. In addition, the parameters in the PC-SAFT equation for ethyl octanoate were obtained based on the high-pressure densities obtained in this work and the vapour pressure in the literatures. The densities of the mixtures were predicted by PC-SAFT equation, the absolute average deviations between the experimental results and those calculated were less than 0.52%.

Simultaneous viscosity and density measurements and modeling of 2-alcohols at temperatures between (291 and 353) K and pressures up to 50 MPa

Dynamic viscosity (η) and density (ρ) were simultaneously measured for pure 2-alcohols (2-propanol, 2-butanol, 2-pentanol, 2-hexanol, and 2-heptanol) in the temperature range from (291–349) K and pressures up to 50 MPa. The measurements were performed using a new coil capillary viscometer coupled with a vibrating tube densimeter with a relative expanded uncertainty (coverage factor k=2) of 1.6% for the dynamic viscosity and 0.3% for the density considering the impurities of the compounds. The reliability of the equipment used was verified by determining and comparing the dynamic viscosity and density of ethanol with the data published in the international literature, resulting a maximum deviation of 10 μPa s for viscosity and 0.40 kg m−3 for density. Experimental dynamic viscosity and density data were successfully represented by two empirical models, obtaining good results in agreement with the uncertainty (maximum deviation of 1.3% and 0.15% for dynamic viscosity and density, respectively). From the experimental density data, the isothermal compressibility and isobaric thermal expansivity were determined.

How Does the Guest—Host Hydrogen Bonding Affect the Thermal Properties of Clathrate Hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest-host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest-host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest-host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

A comprehensive study of the thermophysical properties of reline and hydrated reline

In this work, a physicochemical characterization of the Deep Eutectic Solvent, reline (formed by chloline chloride and urea in a molar ratio 1:2) and one of its aqueous mixtures (xreline = 0.645) has been made at atmospheric pressure (0.1 MPa) in a wide range of temperatures (288.15–338.15) K for reline and (278.15–338.15) K for the aqueous mixture. The measured properties were: density, speed of sound, refractive index, isobaric molar heat capacity, surface tension, kinematic and dynamic viscosity and electrical conductivity. Additionally, from these experimental results, some derivate properties such as isobaric thermal expansibility, isentropic compressibility, molar refraction, free volume and entropy and enthalpy of surface formation have been obtained. Taking into account the observed behaviour the introduction of water, at the considered composition, only modify drastically the dynamic viscosity and electrical conductivity.

Three-site and five-site fixed-charge water models compatible with AMOEBA force field.

In a typical biomolecular simulation using Atomic Multipole Optimized Energetics for Biomolecular Applications (AMOEBA) force field, the vast majority molecules in the simulation box consist of water, and these water molecules consume the most CPU power due to the explicit mutual induction effect. To improve the computational efficiency, we here develop two new nonpolarizable water models (with flexible bonds and fixed charges) that are compatible with AMOEBA solute: the 3-site AW3C and 5-site AW5C. To derive the force-field parameters for AW3C and AW5C, we fit to six experimental liquid thermodynamic properties: liquid density, enthalpy of vaporization, dielectric constant, isobaric heat capacity, isothermal compressibility and thermal expansion coefficient, at a broad range of temperatures from 261.15 to 353.15 K under 1.0 atm pressure. We further validate our AW3C and AW5C water models by showing that they can well reproduce the radial distribution function g(r), self-diffusion constant D, and hydration free energy from the AMOEBA03 water model and the experimental observations. Furthermore, we show that our AW3C and AW5C water models can greatly accelerate (>5 times) the bulk water as well as biomolecular simulations when compared to AMOEBA water. Specifically, we demonstrate that the applications of AW3C and AW5C water models to simulate a DNA duplex lead to a threefold acceleration, and in the meanwhile well maintain the structural properties as the fully polarizable AMOEBA water. We expect that our AW3C and AW5C water models hold great promise to be widely applied to simulate complex bio-molecules using the AMOEBA force field.

Experimental densities and derived thermodynamic properties of pure p-cymene, α-pinene, limonene and citral under high pressure conditions

In order to reduce negative influence of fossil fuels on environment, use of various renewable resources is highly promoted. Terpenes, naturally occurring in plants, can be added to petroleum fuel as its substitute up to a certain share. Thermodynamic properties of a fuel under high pressure and moderate temperature conditions are of significant importance for engine efficiency. This work reports density measurements of pure p-cymene, α-pinene, limonene and citral at temperatures (293.15–413.15) K and pressures (0.1–60) MPa, applying an Anton Paar DMA HP measuring cell. Density data were fitted by modified Tammann-Tait equation where the absolute average percentage deviation between measured and calculated densities was about 0.010%. The obtained parameters were used to estimate the isothermal compressibility, the isobaric thermal expansion coefficient, the internal pressure, and the difference between specific heat capacity at constant pressure and at constant volume. For examined compounds, all thermodynamic properties, except the internal pressure, decrease with pressure rise along an isotherm and increase as temperature increases at a constant pressure. The intersection point of isotherms for the isobaric thermal expansion coefficient for pure citral was registered at pressure 47 MPa, while for other analyzed terpenes the intersection point is above 60 MPa, outside the measurements pressure range.

Measurement and correlation of thermophysical properties in aqueous solutions of some novel bio-based deep eutectic solvents (lactic acid/amino acids) at T = (298.15 to 313.15) K

Thermodynamic properties of novel bio-based deep eutectic solvents (DESs) and their mixture with other solvents is of great importance in extraction and pharmaceutical sciences. In the present study new class of these neoteric sustainable solvents composed of amino acids and lactic acid have been prepared, density and speed of sound data for neat lactic acid/alanine, lactic acid/glycine and lactic acid/histidine and their aqueous mixture have been measured over the entire composition range at T = (298.15, 303.15, 308.15 and 313.15) K. Based on these data, some of the thermodynamic properties including the excess molar volumes (VE), apparent molar volume (Vϕ), excess isobaric thermal expansion (αp,mE), the excess molar isentropic compressibility (κEs,m) and limiting apparent molar expansibility (ϕE,10) have been calculated. For all of the studied systems above, these important properties have been analysed based on various solute-solvent interactions, occurring between the components of the mixtures. Furthermore, it has been found that all the investigated DESs act as a structure-breaker in water over the whole temperature range using Hepler’s constant. The properties have been correlated by the Redlich-Kister type equations.

How does the guest—host hydrogen bonding affect the thermal properties of clathrate hydrates?

Herein, molecular dynamics simulations are performed to study the effect of the guest—host hydrogen bonding on the thermal properties, such as isothermal compressibility, isobaric thermal expansivity, and heat capacity, in the sI clathrate hydrate phases of trimethylene oxide (TMO), ethylene oxide (EO), and formaldehyde (FA) as polar guests. The results of these simulations are compared with those of nonpolar guests with analogous structures, cyclobutane (CB), cyclopropane (CP), and ethane (Et). Binary hydrates are constructed with the above guests in large 14-sided cages and methane placed in small 12-sided cages of the structure of sI clathrate hydrates. We present the temperature dependence of the lattice parameter and also the pressure dependence of the unit cell volume for variety guests with different sizes, polarity, and guest—host hydrogen bonding capability. The lattice parameters for some of the guest species obtained in this work are in good agreement with experimental values. The oxygen atom of the formaldehyde carbonyl group and the ether oxygen atoms of TMO and EO molecules can form hydrogen bonds with sI large cage water hydrogen atoms while CB, CP and Et molecules do not. The consequences of the guest—host hydrogen bonding on the isothermal compressibility, thermal expansivity, and heat capacity of the clathrate are discussed.

High - temperature and high-pressure (p, ρ, T) measurements and derived thermodynamic properties of 1-octyl-3-methylimidazolium hexafluorophosphate

Densities of ionic liquid (IL) 1-octyl-3-methylimidazolium hexafluorophosphate [OMIM][PF6] at high temperatures and high pressures were measured. The measurements were made along 10 isotherms over a temperature range T = 278.15 to 413.15 K, at pressures up to 140 MPa by means of an Anton Paar DMA HPM vibration tube densimeter (VTD). The combined expanded relative uncertainties of the density, pressure and temperature measurements at the 95 % confidence level with a coverage factor of k = 2 are estimated to be 0.03 to 0.08 % (depending on temperature and pressure ranges), 0.1 %, and 0.015 K, respectively. We have critically assessed all of the reported high-pressure densities for [OMIM][PF6], together with the presented results, in order to carefully select primary data for development of a reference wide-ranging equation of state. Values of ??T isobars curvatures, (?2?/?T2)?, were estimated using the present high-pressure ?-T measurements and they were pretty low (0.78?10-7 to 1.50??10-7 m3 kg-1 K-1), indicating that the heat capacity of [OMIM][PF6] very weakly depends on pressure, since (?Cp/?P)T ?(?2?/?T2)?. Density data were fitted to the modified Tammann?Tait equation and the multiparametric polynomial-type equation of state (EOS) for the IL was developed using the measured high-pressure and high-temperature (p, ?, T) data. This EOS, together with our previous measured heat capacity data at atmospheric pressure, was used to calculate high-pressure and high-temperature derived thermodynamic properties, such as isothermal compressibility,isentropic compressibility, isobaric thermal expansion coefficient, heat capacities,etc.

Thermophysical and volumetric properties of mixtures {carvacrol + ethanol} at several temperatures and atmospheric pressure

Experimental molar heat capacities at atmospheric pressure have been determined for the mixture {carvacrol + ethanol} every 10 K in the temperature interval (298.15–328.15) K and over the entire composition range with a Calvet type calorimeter. Densities, necessary for determining isobaric heat capacities, and ultrasonic speed of sound have been also measured at the same conditions. From these properties isobaric thermal expansivities, isentropic compressibilities, isothermal compressibilities, internal pressures and isochoric molar heat capacities have been calculated. Furthermore, in order to complete our thermophysical study the corresponding excess properties have been calculated and discussed in terms of molecular interactions. Finally, excess molar isobaric heat capacities have been calculated with COSMO-RS and compared to the experimental values.

Densities, speed of sound, and derived thermodynamic properties of toluene, tetradecane, and 1-chlorohexane in the compressed liquid region

The densities have been measured at temperatures from (273.65–473.15) K and pressures up to 140.1 MPa for toluene, at temperatures from (298.15–433.15) K and pressures up to 100.1 MPa for tetradecane, and 1-chlorohexane. The speeds of sound in liquid toluene and 1-chlorohexane have been measured over the temperature range from (298.15–433.15) K under pressures up to 100.1 MPa. The relative combined expanded uncertainty in the measurement of the density is 0.0003, and of the speed of sound is 0.001, both for 0.99 level of confidence. The values of the heat capacity at constant pressure and at constant volume, isobaric thermal expansivities, isothermal and isentropic compressibilities have been calculated at temperatures between 273.15 K and 473.15 K at pressures up to 140 MPa for toluene, at temperatures between 293.15 K and 433.15 K at pressures up to 100 MPa, for tetradecane, and at temperatures between 298.15 K and 433.15 K at pressures up to 100 MPa for 1-chlorohexane.

High-temperature and high-pressure thermophysical property measurements and thermodynamic modelling of an international oil standard: RAVENOL diesel rail injector calibration fluid

Presented here are the thermophysical characterization and thermodynamic modelling of RAVENOL Calibration Fluid 2.5 which is used for the calibration and preservation of diesel engine fuel injectors. Accurate knowledge of the standardized fluid properties is an important component for engineering modelling to deliver the correct dose of fuel into the combustion chamber of diesel engines while reducing the occurrence of cavitation phenomena. The liquid density and specific isobaric heat capacity measurements were carried out up to T = 423 K at ambient pressure. The speed of sound moving through the liquid was measured from T = (300 to 423) K from ambient pressure up to p = 200 MPa. This plays a crucial role in fuel injection timing. With the combination of these data with high pressure, it is possible to accurately calculate the liquid density, specific isobaric heat capacity, coefficient of isobaric thermal expansion and isothermal compressibility at elevated pressures. The data obtained at ambient pressure were used to confirm the accuracy of the high-pressure experimental data by comparing them with the predictions of the Fluctuation-Theory Equation-of-State. The calibration fluid has become the second ISO 4113 fluid to be characterized in this fashion.

Thermophysical properties of 4-dimethylaminopyridine based ionic liquids

In this study, a molecular simulation (Gaussian03) was used to analyze the chemical structure of 4-dimethylaminopyridine (DMAP) to investigate its use for the synthesis of ionic liquids (ILs). Based on DMAP, a series of new ILs was prepared and characterized by fourier transform infrared spectroscopy (FT-IR), 1H nuclear magnetic resonance (1H-NMR), thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). The density data of the studied ILs were measured from 328.15 K to 358.15 K, p = 0.101 MPa. It is shown that density decreases with an increase in the temperature and the alkyl chain length of cations. And density is also affected by the anion type. Furthermore, the volume of ions, NBO charges, and the interactions of anions and cations were calculated by Gaussian03 to explain the obtained density results. The second-order polynomial equation was adopted to correlate the relationship of density and temperature. Then, an isobaric thermal expansion coefficient, molecular volume, and lattice potential energy were obtained from the density data. Viscosity was determined from 323.15 K to 368.15 K, p = 0.101 MPa. It is determined that the viscosity of ILs decreases with an increase in the temperature but increases with an increase in the alkyl chain length of cations. The temperature dependence of viscosity was described by the Vogel-Fulcher-Tamman (VFT) model, and the activation energy of viscous flow (Eη) was obtained. Furthermore, the decomposition temperature (Td), glass transition temperature (Tg), and melting temperature (Tm) of ILs were obtained from the results of TGA and DSC.

Development and Validation of a Virtual Gelatin Model Using Molecular Modeling Computational Tools

To successfully design and optimize the application of hydrogel matrices one has to effectively combine computational design tools with experimental methods. In this context, one of the most promising techniques is molecular modeling, which requires however accurate molecular models representing the investigated material. Although this method has been successfully used over the years for predicting the properties of polymers, its application to biopolymers, including gelatin, is limited. In this paper we provide a method for creating an atomistic representation of gelatin based on the modified FASTA codes of natural collagen. We show that the model created in this manner reproduces known experimental values of gelatin properties like density, glass-rubber transition temperature, WAXS profile and isobaric thermal expansion coefficient. We also present that molecular dynamics using the INTERFACE force field provides enough accuracy to track changes of density, fractional free volume and Hansen solubility coefficient over a narrow temperature regime (273–318 K) with 1 K accuracy. Thus we depict that using molecular dynamics one can predict properties of gelatin biopolymer as an efficient matrix for immobilization of various bioactive compounds, including enzymes.

(p,ρ,T) data of 1-butyl-3-methylimidazolium hexafluorophosphate

Herein, experimental pressure-density-temperature (p,ρ,T) data of 1-butyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], are reported over a wide range of temperatures T = (278.15 to 413.15) K and pressures p = (0.101 to 140) MPa. These measurements were carried out using an Anton Paar DMA HPM vibrating tube densimeter. (p,ρ,T) data of [BMIM][PF6] were correlated with a designed equation of state (EoS). After a thorough analysis of the validity of the constructed EoS, various thermophysical properties such as: isothermal compressibility, isobaric thermal expansivity, differences in isobaric and isochoric heat capacities, thermal pressure coefficient, internal pressure, heat capacities at constant pressure and volume, speed of sound and isentropic exponent were then calculated. Finally, the predictive capability of various models available in the literature was then tested by using the collected (p,ρ,T) data to highlight the best approach to be used to evaluate the volumetric properties of the selected ionic liquid.

The Widom Line and the Lennard-Jones Potential.

The phenomenological behavior of the Widom line above the vapor-liquid critical point for the Lennard-Jones (LJ) potential is investigated using four accurate equations of state (EoS) and a comparison with molecular dynamics (MD) simulation data. This involved calculating the supercritical maximum values of the isochoric heat capacity (CV), isobaric heat capacity (Cp), isothermal compressibility (βT), and thermal expansion coefficient (αp). All LJ EoS predict the pressure (p)-temperature (T) Widom line behavior. In contrast, the T-density (ρ) Widom line behavior, observed in MD simulations, is not predicted by any LJ EoS. The calculations highlight the important role of βT in determining the range of p and T for which Widom line behavior is observed. Analysis of MD data for the supercritical maximum/minimum of CV and Cp suggests the extension of a Clausius-Clapeyron-type relationship from the triple point to the supercritical region. This provides a new description of the Widom line as the near critical part of this larger curve for which other thermodynamic functions also have maximum values.

Compressed liquid densities of binary mixtures of difluoromethane (R32) and 2,3,3,3-tetrafluoroprop-1-Ene (R1234yf) at temperatures from (283 to 363) K and pressures up to 100 MPa

The compressed liquid densities of binary mixtures difluoromethane (R32) and 2,3,3,3-tetrafluoroprop-1-ene (R1234yf) were measured using a high pressure vibrating-tube densimeter over the temperatures from (283 to 363) K and pressures up to 100 MPa at five different compositions, xR32 = (0.189, 0.268, 0.500, 0.723, 0.904) in the present work. The combined expanded uncertainties of the temperature, pressure, mole fraction and the density with a level of confidence of 0.95 (k = 2) is estimated to be 16 mK, 0.062 MPa (p ≤ 60 MPa), 0.192 MPa (60 MPa < p < 100 MPa), 0.01 and up to 0.6 kg·m−3 depending on the temperature and pressure ranges, respectively. The experimental data were correlated using the modified Tait equation. The isothermal compressibility, κT, and the isobaric thermal expansivity, αp, were determined using liquid densities of mixtures and modified-Tait equation. Furthermore, the relative deviations of the experimental data with the equation of state (EOS) from Akasaka were lower than 1% from (283 to 363) K with the pressure up to 40 MPa.

Effect of temperature on molecular interaction of ethyl acetate with ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

The speeds of sound, u and densities, ρ, of the pure and their mixtures of Imadazolium based Ionioc liquid having cation 1-butyl-3-methylimidazolium ([BMIM]+) with the anion hexaflurophospate [PF6]− with Ethyl acetate (EtOAc) have been determined from 0 to 1 mol fraction range of ILs with interval 0.1 at (298.15–323.15) K at pressure 0.1 MPa. We used the measured data to assess the excess molar volumes, VmE., excess isentropic compressibility, κsE, excess speeds of sound, uE, excess molar isentropic compressibility, Ks,mE, excess isobaric thermal expansion, αpE, were calculated and fitted with Redlich-Kister polynomial equation. The excess partial molar volumes, V¯m,1E and V¯m,2E and excess partial molar isentropic compressibilities, K¯s,m,1E and K¯s,m,2E, excess partial molar volumes, V¯m,1oE and V¯m,2oE and excess partial molar isentropic compressibilities, K¯s,m,1oE and K¯s,m,2oE of the components at infinite dilution also been measured. The departure of measured properties has been explored in terms of intermolecular interactions.Simultaneously, the FTIR studies exhibited qualitative analysis of ion-pair formation, interactions of ion–dipole and hydrogen bonding between IL with the EtOAc.

Effect of alkyl chain length in cation on thermophysical properties of two homologous series: 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imides and 1-alkyl-3-methylimidazolium trifluoromethanesulfonates

The two homologous series of ionic liquids: 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imides [CnC1pyr][NTf2] (n = 3, 4, 6, and 8) and 1-alkyl-3-methylimidazolium trifluoromethanesulfonates [CnC1im][TFO] (n = 2, 4, 6, 8, and 10) were examined. The speed of sound, density, isobaric heat capacity, and surface tension were determined as a function of temperature at atmospheric pressure. From these experimental data, the isentropic compressibility, isobaric thermal expansion, isothermal compressibility, isochoric heat capacity, internal pressure, thermal conductivity as well as, the surface entropy and surface enthalpy were calculated. The minimum of the speed of sound dependence on the alkyl chain length in the cation u(n) is observed for [C6C1pyr][NTf2]. This effect is another confirmation of the presence of the minimum of u(n) dependence in ionic liquids with the large, weakly coordinating [NTf2]− anion. At the same time, the minimum of u(n) dependence for the series [CnC1im][TFO] was not observed.

Volumetric and acoustic study of 1,4-butanediol with 2-ethoxyethanol/2-butoxyethanol at various temperatures

The speeds of sound, u and densities, ρ, of the blends, 1,4-butanediol (1,4-BD) with 2-ethoxy ethanol (2-EE) and 2-butoxyethanol (2-BE), including those of pure liquids, have been determined from 0 to 1 mol fraction range of 1,4-BD with interval 0.1 at 303.15 K to 318.15 K at pressure 0.1 MPa. We used the measured values to assess the excess molar volumes, VmE, excess isentropic compressibility, κsE, excess speeds of sound, uE, excess molar isentropic compressibility, Ks,mE, excess isobaric thermal expansion αpE, and the results were fitted with Redlich-Kister equation. The excess partial molar volumes and isentropic compressibilities of the components at infinite dilution have also been measured. The departure of measured properties has been explored in terms of intermolecular interactions. Moreover, the theoretical ultrasonic speeds are computed based on the scaled particle theory and compared with the experimentally measured values.