Molar Volume Of CO Research Articles

Assessments of molar volumes of Co-, Ni- and Ti- related bcc and fcc phases

In the present work, we modeled the molar volumes of the bcc phases in Co-X (X = Fe, Mo and Zr), Ni-X (X = Fe, Mo and V) and Ti-X (X = Fe, Mo, Nb, Ta and V) binary systems, as well as fcc phases in Co-X (X = Au, Fe, Ge, Hf, Ir, Mo, Nb, Ni, Os, Pd, Pt, Re, Rh, Ru, Sc, Sn, V, Zn and Zr), Ni-X (X = Al, Au, Cr, Cu, Fe, Ga, Ir, Mo, Nb, Os, Pd, Pt, Rh, Ru, Sb, Sn, Tc, Ti, V and Zn) and Ti-X (X = Au, Cu, Ni and Pd) binary systems, at room temperature and atmospheric pressure by using the CALPHAD method combined with first-principles calculations. The model parameters involve molar volumes of pure constituent elements in their stable, metastable or unstable bcc and fcc structures and excess molar volumes. Specifically, the molar volumes of the pure constituent elements in their stable or metastable bcc and fcc structures were directly adopted from the previous CALPHAD assessments or experimental measurements from the literature; for their unstable bcc and fcc structures, a new method of volume extrapolation was proposed, which avoids trial-and-error fitting. Once the molar volumes of pure constituent elements were fixed, the excess term was easily assessed according to the experimental measurements from the literature combined with the first-principles calculation results. The thus assessed model parameters can well reproduce most experimental data.

Prediction of molar volume and partial molar volume for CO 2/ionic liquid systems with heterosegmented statistical associating fluid theory

To design ionic liquids (ILs) as effective liquid absorbents for CO 2 separation from flue or synthesis gases, it is necessary to know the properties and phase equilibria of the CO 2/IL systems. The molar volumes of CO 2/IL mixtures are predicted with the heterosegmented statistical associating fluid theory equation of state. The comparison with the available experimental data shows that the model can be used to predict reliably the molar volumes of CO 2/IL mixtures from 293 to 413 K and pressures up to 160 bar. In addition, the partial molar volume of CO 2 in CO 2/IL mixtures and the partial molar volume of CO 2 at infinite dilution in an IL are also predicted.

The partial molar volume of carbon dioxide in peridotite partial melt at high pressure

The partial molar volume of CO 2 ( V ¯ C O 2 ) in silicate melt was determined for a komatiite composition using high pressure sink/float experiments in a multi-anvil press. The density of the experimental melt at pressure was determined by observing sinking and floating of pure forsterite (Fo100) and forsterite (Fo90) buoyancy markers. Values for V ¯ C O 2 were bracketed at 4.3 GPa (23.71 cm 3/mol) and at 5.5 GPa (22.06 cm 3/mol), normalized to 2123 K. Combining the current data with previous work we now more accurately constrain the compression curve of V ¯ C O 2 over the pressure range of 1.0 × 10 − 4 to 20 GPa. These data allow the calculation of density at pressure of carbonated silicate melts, such as kimberlite and silica undersaturated alkali basalts, and the determination of their buoyancy and eruptibility.

Density of carbonated peridotite magma at high pressure using an X-ray absorption method

The density of carbonated peridotite magma was measured up to 3.8 GPa and 2100 K using an X-ray absorption method. A fit of the pressure-density-temperature data to the high-temperature Birch-Murnaghan equation of state yielded the isothermal bulk modulus, K T0 = 22.9 ± 1.4 GPa, its pressure derivative, K 0 ′ = 7.4 ± 1.4, and the temperature derivative of the bulk modulus (∂K T /∂T) P = -0.006 ± 0.002 GPa/K at 1800 K. The bulk modulus of carbonated peridotite magma is larger than that of hydrous peridotite magma. The partial molar volume of CO 2 in magma under high pressure and temperature conditions was calculated and fit using the Vinet equation of state. The isothermal bulk modulus was K T0 = 8.1 ± 1.7GPa, and its pressure derivative was K 0 ′ = 7.2 ± 2.0 at 2000 K. Our results show that the partial molar volume of CO 2 is less compressible than that of H 2 O, suggesting that, on an equal molar basis, CO 2 is more effective than H 2 O in reducing peridotite melt density at high pressure.

Thermodynamic model of aqueous CO 2–H 2O–NaCl solutions from −22 to 100 °C and from 0.1 to 100 MPa

Experimental measurements of the solubility of CO 2 in aqueous NaCl solutions have been assembled from 21 literature studies and tested for consistency using analytical and thermodynamic criteria. Of the 508 data compiled, 170 data (33%) were discarded and 36 were reserved to test the high-pressure dependency of the model. Possible reasons for the observed discrepancies between datasets are discussed. The 302 measurements that satisfy the acceptance criteria have been used to fit Pitzer parameters. These have been incorporated into a semi-empirical, γ– ϕ type thermodynamic model that builds upon published equations of state for the unary and binary subsystems. The accepted experimental solubilities are reproduced by the model with a precision of better than 1.6% (one standard deviation) over the entire P– T– x range considered. The new model provides a thermodynamically consistent description of numerous properties of the aqueous liquid in the ternary CO 2–H 2O–NaCl system, including: the activity coefficients, activities and partial molar volumes of CO 2(aq) and Na +Cl − (aq); the activity coefficient and osmotic coefficient of the solvent H 2O; the Setchenow coefficient; saturation indices of all four solid phases in the system (CO 2–clathrate–hydrate, ice, hydrohalite and halite); and the molar volume, excess molar volume and density of the bulk liquid. These properties can be calculated for any CO 2 concentration up to saturation, and for any NaCl concentration (whether stable or metastable). The model is available as a computer code at < www.geo.unibe.ch/ diamond>.

A New Correlation and Prediction Method for the Solubility of Metal Complexes in Supercritical Carbon Dioxide Using Regular Solution Theory with the COSMO-RS Method

A new correlation and prediction model for the solubility of metal complexes in supercritical carbon dioxide (scCO2) based on the regular solution theory was developed in this study and the solubilities were calculated for metal(III) acetylacetonates: chromium(III) acetylacetonate (Cr(acac)3), cobalt(III) acetylacetonate (Co(acac)3), iron(III) acetylacetonate (Fe(acac)3), and rhodium(III) acetylacetonate. The physical properties, enthalpies of vaporization, and molar volumes of the metal acetylacetonates that are required to obtain the solubility parameters were estimated using the COSMOtherm program based on the conductor-like screening model for real solvents (COSMO-RS) method. The predicted molar volumes of Co(acac)3 and Fe(acac)3 and the solubility parameter of Cr(acac)3 were in good agreement with the data from the material safety data sheets and the group contribution method, respectively. The binary interaction parameter was introduced into the cross-term of the solubility parameters to calculate solubility. Although some deviations were found in the low-pressure region where the solubility dramatically increased with increasing pressure, the correlated results reproduced the experimental data for all metal acetylacetonates investigated using the physical properties estimated from the COSMOtherm program.The relationship was nearly linear between the values of the interaction parameters optimized by correlation and the pseudo residual chemical potentials of the metal acetylacetonates obtained using the COSMO-RS method. Therefore, the prediction was carried out using the interaction parameters determined from the pseudo residual chemical potentials of the metal acetylacetonates. The predicted results deviated somewhat from the experimental data in the low-pressure region; however, the predicted results reproduced the experimental data in the high-pressure region.

Compressed Liquid Densities and Excess Molar Volumes of CO2 + Hexan-1-ol Mixtures from (313 to 363) K and Pressures up to 25 MPa

Compressed liquid densities of hexan-1-ol and of CO 2 (1) + hexan-1-ol (2) binary mixtures (at four different compositions, x 1 = 0.1413, 0.2289, 0.3610, and 0.6673) have been measured from (313 to 363) K and pressures up to 25 MPa. A vibrating-tube densimeter was used to measure the experimental densities. The densities of hexan-1-ol were correlated with a short explicit volume equation and the Benedict-Webb-Rubin-Starling equation of state (BWRS EoS). Excess molar volumes were calculated using density values calculated with the BWRS EoS and the Span-Wagner EoS for hexan-1-ol and CO 2 , respectively.

Why Is the Partial Molar Volume of CO2 So Small When Dissolved in a Room Temperature Ionic Liquid? Structure and Dynamics of CO2 Dissolved in [Bmim+] [PF6-

When supercritical CO2 is dissolved in an ionic liquid, its partial molar volume is much smaller than that observed in most other solvents. In this article we explore in atomistic detail and explain in an intuitive way the peculiar volumetric behavior experimentally observed when supercritical CO2 is dissolved in 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim+] [PF6(-)]). We also provide physical insight into the structure and dynamics occurring across the boundary of the CO2 ionic liquid interface. We find that the liquid structure of [Bmim+] [PF6(-)] in the presence of CO2 is nearly identical to that in the neat ionic liquid (IL) even at fairly large mole fractions of CO2. Our simulations indicate, in agreement with experiments, that partial miscibilities of one fluid into the other are very unsymmetrical, CO2 being highly soluble in the ionic liquid phase while the ionic liquid is highly insoluble in the CO2 phase. We interpret our results in terms of the size and shape of spontaneously forming cavities in the ionic liquid phase, and we propose that CO2 occupies extremely well-defined locations in the IL. Even though our accurate prediction of cavity sizes in the neat IL indicates that these cavities are small compared with the van der Waals radius of a single carbon or oxygen atom, CO2 appears to occupy a space that was for the most part a priori "empty".

Compressed liquid densities and excess volumes of CO 2 + thiophene binary mixtures from 313 to 363 K and pressures up to 25 MPa

Experimental densities for the CO 2 (1) + thiophene (2) binary mixtures are reported from 313 to 363 K and up to 25 MPa. Densities were measured for thiophene and for binary mixtures at five different compositions, x 1 = 0.1990, 0.3818, 0.5661, 0.6996, and 0.9217. Densities of thiophene were correlated by four different models, the Benedict–Webb–Rubin–Starling equation of state (BWRS EoS), the Tait equation (TE), the Toscani and Szwarc (TS) model, and a proposed modification for this last model (MTS). These models represent densities of thiophene with a percent standard deviation of 3.90 × 10 −3, 1.97 × 10 −2, 2.76 × 10 −2, and 5.54 × 10 −3, respectively. The excess molar volumes were determined using densities for thiophene calculated from the BWRS EoS and densities for CO 2 calculated from the Span–Wagner EoS. The volumetric behavior and excess molar volumes of CO 2 + thiophene mixtures were modeled using the PC-SAFT EoS.

Structural dynamics of distal histidine replaced mutants of myoglobin accompanied with the photodissociation reaction of the ligand.

Protein dynamics observed by the transient grating (TG) method are studied for some site-directed mutants at the distal histidine of myoglobin (H64L, H64Q, H64V). The time profiles of the TG signals are very sensitive to the amino acid residue of the 64 position. It was found that the sensitivity is mostly caused by the different rates of the ligand escape from the protein to solvent and the magnitude of the molecular volume change. Several molecular origins of the volume difference between MbCO and Mb, such as the electrostatic interaction in the distal pocket, movement of helices, and distal water, are proposed. Interestingly, the volume difference between the CO-trapped Mb inside the protein interior and Mb is similar to that of the partial molar volume of CO in organic solvent. The effect of mutation on the nature of the CO trapped site is discussed.

On the amount of free volume in gas–polymer mixtures

Using sorption and dilatation data, the molar volumes of CO 2 and CH 4 that are inaccessible for diffusion were determined for silicone rubber. These values were used to calculate the mobile gas concentration for CO 2 and CH 4 in glassy polycarbonate assuming that an iso-free-volume state exists below the T g . The analysis presented here suggests an alternative view of the concept of partial immobilization that is independent of the dual mode sorption model. Those molecules that contribute to maintaining the iso-free-volume glassy state are mobile while those that do not are completely immobile

Revised densities of { xCO 2 + (1 − x)H 2O} with x < 0.014 at supercritical conditions Molar volumes, partial molar volumes of CO 2 at infinite dilution, and excess molar volumes

This communication revises the published (Crovetto et al. J. Chem. Thermodynamics 1990, 22, 231) differences in densities between water and dilute {xCO2 + (1 − x)H2O}, with 0.001 < x < 0.014, measured at temperatures from 651.1 K to 725.5 K at (28.0, 33.0, and 38.0) MPa. From the new densities the infinite-dilution partial molar volumes and the excess molar volumes are calculated. The mixtures, although dilute, are very non-ideal because of the proximity of the critical point. The integral of the indirect pair-correlation function Cδ1 2 is a simple function of pure-water density ρ*. The values of Cδ1 2 for CO2, Ar, Xe, and C2H4 at the same ρ* are approximately equal. Krichevskii's A-parameter calculated from the results is now in good agreement with the value calculated from the slope of the critical line.

Densities of { xCO 2 + (1 − x)H 2O} with x < 0.014 at supercritical conditions molar volumes, partial molar volumes of CO 2 at infinite dilution, and excess molar volumes

Using an improved vibrating-tube densitometer developed in our laboratory, differences in density between H 2O and { xCO 2 + (1 − x)H 2O} for (0.001 < x < 0.015) have been measured at temperatures from 651.1 to 725.5 K at 28.0, 33.0, and 38.0 MPa. At least three different values of x were measured for each temperature. From the measurements, excess molar volumes and partial molar volumes of CO 2 at infinite dilution were calculated. The partial molar volumes of CO 2 at infinite dilution were very large and positive. Results showed that the mixtures, although dilute, were very non-ideal. These effects were found when the solvent compressiblity was very large in the neighborhood of the solvent critical point. The integral of the indirect pair-correlation function was nearly constant for these measurements and for similar measurements on aqueous argon, xenon, and ethene near the critical point of water.