Partial Molar Volume Of CO2 Research Articles

Photodecarboxylation of ketoprofen studied by transient absorption spectroscopy and transient grating method: Estimation of the partial molar volume of carbon dioxide

The photoreaction of ketoprofen, a widely used nonsteroidal anti-inflammatory drug (NSAID), was intensively investigated in methanol by transient absorption spectroscopy and transient grating (TG) method. From quantitative analyses of the transient absorption and of the TG signal due to CO2, we successfully determined the partial molar volume of CO2 to be 46 ± 2 cm3 mol−1. With the partial molar volume of CO2 obtained in this work, the reaction quantum yield of photodecarboxylation of other NSAIDs can be estimated from only the TG signal. The approach with the TG method would be a new tool for evaluating photoreactivity of NSAIDs.

Modeling solubility of CO2/hydrocarbon gas in ionic liquid ([emim][FAP]) using Aspen Plus simulations.

The Peng-Robinson equation of state with quadratic van der Waals (vdW) mixing rule model was chosen to perform the thermodynamic calculations in Flash3 column of Aspen Plus to predict the solubility of CO2 or any one of the hydrocarbons (HCs) among methane, ethane, propane, and butane in an ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([emim][FAP]). Bubble point pressure, solubility, bubble point temperature, fugacity, and partial molar volume at infinite dilution were obtained from the simulations, and enthalpy of absorption, Gibbs free energy of solvation, and entropy change of absorption were estimated by thermodynamic relations. Results show that carbon chain length has a significant effect on the bubble point pressure. Methane has the highest bubble point pressure among all the considered HCs and CO2. The bubble point pressure and fugacity variation with temperature is different for CO2 as compared to HCs for mole fractions above 0.2. Two different profiles are noticed for enthalpy of absorption when plotted as a function of mole fraction of gas soluble in IL. Partial molar volume of CO2 decreases with increase in temperature in [emim][FAP], while it is increased for HCs. Bubble point temperature decreases with increase in the mole fraction of the solute. Entropy of solvation increases with temperature till a particular value followed by a decrease with further increase in temperature. Gibbs free energy change of solvation showed that the process of solubility was spontaneous.

What Determines CO₂ Solubility in Ionic Liquids? A Molecular Simulation Study.

Molecular dynamics (MD) simulations of 10 different pure and CO2-saturated ionic liquids are performed to identify the factors that determine CO2 solubility. Imidazolium-based cations with varying alkyl chain length and functionalization are paired with anions of different hydrophobicity and size. Simulations are carried out with an empirical force field based on liquid-phase charges. The partial molar volume of CO2 in ionic liquids (ILs) varies from 30 to 40 cm(3)/mol. This indicates that slight ion displacements are necessary to enable CO2 insertions. However, the absorption of CO2 does not affect the overall organization of ions in the ILs as demonstrated by almost equal cation-anion radial distribution functions of pure ILs and ILs saturated with CO2. The solubility of CO2 in ILs is not influenced by direct CO2-ion interactions. Instead, a strong correlation between the ratio of unoccupied space in pure ILs and their ability to absorb CO2 is found. This preformed unoccupied space is regularly dispersed throughout the ILs and needs to be expanded by slight ion displacements to accommodate CO2. The amount of preformed unoccupied space is a good indicator for ion cohesion in ILs. Weak electrostatic cation-anion interaction densities in ILs, i.e., weak ion cohesion, leads to larger average distances between ions and hence to more unoccupied space. Weak ion cohesion facilitates ion displacement to enable an expansion of empty space to accommodate CO2. Moreover, it is demonstrated that the strength of ion cohesion is primarily determined by the ion density, which in turn is given by the ion sizes. Ion cohesion is influenced additionally to a smaller extent by local electrostatic interactions among ion moieties between which CO2 is inserted and which do not depend on the ion density. Overall, the factors that determine the solubility of CO2 in ILs are identified consistently across a large variety of constituting ions through MD simulations.

Viscosity and Density of Aqueous Solutions of Carbon Dioxide at Temperatures from (274 to 449) K and at Pressures up to 100 MPa

The viscosity and density of aqueous solutions of carbon dioxide having mole fractions of CO2 of 0.0086, 0.0168, and 0.0271 are reported. The measurements were made in the single-phase compressed liquid region at temperatures between (294 and 449) K at pressures up to 100 MPa; additional density measurements were also made at T = 274 K in the same pressure range. The viscosity was measured with a vibrating-wire viscometer while the density was measured by means of a vibrating U-tube densimeter; both were calibrated with pure water and either vacuum or ambient air. The density data have an expanded relative uncertainty of 0.07 % with a coverage factor of 2. From the raw data, the partial molar volume of CO2 in aqueous solution has been determined and correlated as an empirical function of temperature and pressure. When combined with the IAPWS-95 equation of state of pure water, this correlation represents the measured densities of under-saturated solutions of CO2 in water within ± 0.04 %. The viscosity data have an expanded relative uncertainty of 1.4 % with a coverage factor of 2. A modified Vogel–Fulcher–Tamman equation was used to correlate the viscosity as a function of temperature, pressure, and mole fraction of CO2 with an absolute average relative deviation of 0.4 %. The viscosity and density of saturated aqueous solutions of CO2 may be calculated by combining the correlations presented in this work with a suitable model for the mole fraction of CO2 at saturation.

A new model for the density of saturated solutions of CO2–H2O–NaCl in saline aquifers

A new model is proposed to find the density of saturated ternary solutions of H2O–CO2–NaCl in the temperature range of 50–100°C and pressures up to 600bar. The model calculates the partial molar volume of dissolved CO2 from the density of saturated binary, H2O–CO2, solution and the corresponding mole fraction of dissolved CO2. The density of the saturated binary solution is determined as a function of temperature and pressure from a regression of experimental data. The mole fraction of dissolved CO2 is obtained from the Redlich–Kwong equation of state. The partial molar volume of CO2 obtained in his manner is then made to coincide with one solution branch of the Redlich–Kwong equation while retaining the other solution branch associated with the molar volume of the gas phase. This allows the simultaneous calculation of both the gas and the liquid molar volume with a single equation of state. The density of the saturated ternary solution predicted by the new model is found to be in good agreement with experimental data. The new model is then used to characterize the effects of temperature, pressure and salinity on the onset of buoyancy driven convection during CO2 sequestration.

CO2 absorption properties, densities, viscosities, and electrical conductivities of ethylimidazolium and 1-ethyl-3-methylimidazolium ionic liquids

We have focused on a protic ionic liquid, ethylimidazolium bis(trifluoromethanesulfonyl)amide ([eimH][Tf2N]), and the analogous aprotic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([emim][Tf2N]). Densities, viscosities, and electrical conductivities of the two ionic liquids have been measured over the temperature range T=(273.15–363.15)K at atmospheric pressure. The densities of [eimH][Tf2N] and [emim][Tf2N] decrease with increasing temperature. The protic ionic liquid has the higher density (the smaller molar volume) than the aprotic one. The transport properties of the two ionic liquids show ordinary temperature dependencies. [eimH][Tf2N] has the higher viscosities (smaller electrical conductivities) than [emim][Tf2N]. Empirical Walden products indicate that [eimH][Tf2N] shows smaller conductivities than [emim][Tf2N] at certain viscosities. To investigate CO2 absorption properties of the ionic liquids, binary phase equilibria in CO2+ionic liquid systems have been investigated under high pressures up to 6MPa at T=(298.15, 313.15, 333.15)K. The solubilities of CO2 in [eimH][Tf2N] and [emim][Tf2N] show typical pressure dependencies in both mole fraction and molarity scales as physical absorbents. The mole fraction of CO2 in [eimH][Tf2N] is slightly smaller than that in [emim][Tf2N] under the conditions investigated, while the molarity of CO2 in [eimH][Tf2N] is comparable to that in [emim][Tf2N]. The molar volumes in ionic liquid phase almost linearly decrease with the mole fraction of CO2 in the present systems. The partial molar volume of CO2 in [eimH][Tf2N] at infinite dilution is almost same as that in [emim][Tf2N].

Partial molar volume and compressibility of dissolved CO2 in glasses with magmatic compositions

Carbon dioxide is the second most abundant magmatic volatile and strongly affects the chemical and physical properties of melts. However, the volumetric properties of CO2-bearing silicate melts and glasses are still poorly constrained. In this study, the density, acoustic velocities and elastic properties of CO2-bearing basaltic, phonolitic and rhyolitic glasses have been determined by the sink/float method and Brillouin scattering spectroscopy to constrain the effect of magma composition on the partial molar volume and compressibility of dissolved CO2. The glasses were synthesized at elevated pressure to achieve high CO2 contents, up to 3.9wt.%, and subsequently annealed at room pressure to relax the pressure-induced densification. The relaxation times indicate that CO2 lowers the viscosity of basaltic melts, while that of rhyolitic and phonolitic melts remains unchanged. The partial molar volume of CO2 depends on the silicate composition with V¯CO2=26.6±1.8, 22.1±0.6 and 25.4±0.9cm3/mol, in basaltic, phonolitic and rhyolitic glasses, respectively, but is not a simple function of the CO2/CO32− speciation. In addition, our data indicate a strong compositionally dependent partial molar adiabatic compressibility with βs¯CO2=−10±11, 6.7±2.2 and 3.6±0.9 10−2GPa−1 for basaltic, phonolitic and rhyolitic glasses, respectively. A plausible compositional dependence of the partial molar volume and compressibility of dissolved CO2 in magmatic liquids may need to be considered in density models for CO2-bearing magmas.

Phase equilibria of (CO2 + H2O + NaCl) and (CO2 + H2O + KCl): Measurements and modeling

We report experimental measurements of the phase behavior of (CO2+H2O+NaCl) and (CO2+H2O+KCl) at temperatures from 323.15K to 423.15K, pressure up to 18.0MPa, and molalities of 2.5 and 4.0molkg−1. The present study was made using an analytical apparatus and is the first in which coexisting vapor- and liquid-phase composition data are provided. The new measurements are compared with the available literature data for the solubility of CO2 in brines, many of which were measured with the synthetic method. Some literature data show large deviations from our results.The asymmetric (γ–φ) approach is used to model the phase behavior of the two systems, with the Peng–Robinson equation of state to describe the vapor phase, and the electrolyte NRTL solution model to describe the liquid phase. The model describes the mixtures in a way that preserves from our previous work on (CO2+H2O) the values of the Henry's law constant and the partial molar volume of CO2 at infinite dilution Hou et al. [22]. The activity coefficients of CO2 in the aqueous phase are provided. Additionally, the correlation of Duan et al. [14] for the solubility of CO2 in brines is tested against our liquid-phase data.

Manometric Sorption Measurements of CO2 on Moisture-Equilibrated Bituminous Coal

Gas sorption isotherms have been measured on dry and wet Tupton coal at 318.15 K up to a pressure of 160 bar with the manometric method. The aim of this paper is to determine the relevance of the presence of water for CO2 sorption on coal. The manometric method requires an accurate equation of state (EoS). Experimental measurements conducted with a density meter show that the density of the CO2–H2O mixture in the gas phase can be calculated using the Span and Wagner EoS for pure CO2 gas. The density of the CO2–H2O mixture in the aqueous phase can be described by a Peng–Robinson–Stryjek–Vera (PRSV) EoS optimized for the CO2–water system. For the interpretation of the coal experiments, we also measured the adsorption of CO2 in a wet unconsolidated sand sample. We show that adsorption experiments follow the computations with the PRSV EoS. These experiments also allows us to determine the partial molar volume of CO2 in water, which agrees well with the literature data. Given the small amount of water in the c...

CO2 sorption and transport behavior of ODPA-based polyetherimide polymer films

Plasticization phenomena can significantly reduce the performance of polymeric membranes in high-pressure applications. Polyetherimides (PEIs) are a promising group of membrane materials that combine relatively high CO2/CH4 selectivities with high chemical and thermal stability. In this work sorption, swelling, and mixed gas separation performance of 3,3′,4,4′-oxydiphthalic dianhydride (ODPA)-based PEI polymers, with 1, 2 or 3 para-aryloxy substitutions in the diamine moeiety, is investigated under conditions where commercial membranes suffer from plasticization. Particular focus is on the influence of the amount of para-aryloxy substitutions and the film thickness. Results are compared with those of commercially available polymeric membrane materials (sulphonated PEEK, a segmented block-co-polymer PEBAX and the polyimide Matrimid).The glassy polymers display increasing CO2 sorption with increasing Tg. The larger extent of sorption results from a larger non-equilibrium excess free volume. Swelling of the polymers is induced by sorption of CO2 molecules in the non-equilibrium free volume as well as from molecules dissolved in the matrix. Dilation of the polymer is similar for each molecule sorbed. Correspondingly, the partial molar volume of CO2 is similar for molecules present in both regions.Mixed gas separation experiments with a 50/50% CO2/CH4 feed gas mixture showed high CO2/CH4 selectivities for the ODPA PEI films at elevated pressure. This shows that these materials could potentially be interesting for high-pressure gas separation applications, although additional gas permeation experiments using different feed gas compositions and thin films are required.

Sorption and Swelling of Poly(D,L‐lactic acid) and Poly(lactic‐co‐glycolic acid) in Supercritical CO2

AbstractSummary: The equilibrium sorption and swelling behavior in supercritical CO2 of poly(D,L‐lactic acid) and poly(lactic‐co‐glycolic acid) has been studied at a temperature of 35 °C and at pressures up to 200 bar. Sorption was measured through a gravimetric technique and swelling by visualization. From these data, the behavior of the different polymers can be compared. In terms of partial molar volume of CO2 in the polymer matrix, all the polymers exhibit a behavior typical of rubbery systems. The experimental results have been modeled using the Sanchez‐Lacombe equation of state, which is able to represent the actual behavior of the polymer‐CO2 systems with reasonable accuracy.

Sorption and swelling of semicrystalline polymers in supercritical CO2

AbstractThe equilibrium sorption and swelling behavior of four different polymers—poly(methyl methacrylate), poly(tetrafluoroethylene), poly(vinylidene fluoride), and the random copolymer tetrafluoroethylene–perfluoromethylvinylether–in supercritical CO2—are studied at different temperatures (from 40 to 80 °C) and pressures (up to 200 bar). Swelling is measured by visualization, and sorption through a gravimetric technique. From these data, the behavior of amorphous and semicrystalline polymers can be compared, particularly in terms of partial molar volume of CO2 in the polymer matrix. Both poly(methyl methacrylate) and the copolymer of tetrafluoroethylene exhibit a behavior typical of rubbery systems. On the contrary, polymers with a considerable degree of crystallinity, such as poly(tetrafluoroethylene) and poly (vinylidene fluoride), show larger values of partial molar volume. These can be related to the limited mobility of the polymer chains in a semicrystalline matrix, which causes the structure to “freeze” during the sorption process into a nonequilibrium state that can differ significantly from the actual thermodynamic equilibrium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1531–1546, 2006

Effect of penetrant-induced isothermal glass transition on sorption, dilation, and diffusion behavior of polybenzylmethacrylate/CO2

The effect of a penetrant-induced isothermal glass transition on sorption, dilation, and diffusion behavior was studied in a single experimental run for CO2 in cast polybenzylmethacrylate films. The dual-mode type sorption isotherms below the glass transition temperature of the polymer changed to linear ones above a certain concentration. Meanwhile, partial molar volume of CO2 determined from the dilation of the films above the concentration gave a value very close to the one reported for rubbery polymers, and diffusion coefficients became less concentration-dependent. The results were conformable to the concept of unrelaxed volume in glassy polymers. © 1996 John Wiley & Sons, Inc.

Gas sorption‐induced dilation of poly(4‐methyl‐1‐pentene)

Sorption and volume dilation isotherms of semicrystalline poly(4-methyl-1-pentene) (PMP) were measured using CO2 and C3H8 as penetrants, which have sieving diameters of 3.3 and 4.3 Å, respectively. On the other hand, the PMP crystal has a void width of approximately 4 Å as estimated by X-ray diffraction, so it was anticipated that CO2 would be able to sorb into the PMP crystal while C3H8 would not. The data show that C3H8 has a constant partial molar volume of approximately 87 cc/mol, just above the value reported in other rubbery polymers, and are consistent with the hypothesis that the C3H8 molecules are too large to sorb into the PMP crystals. The partial molar volume of CO2 was found to be 39 cc/mol for CO2 weight fractions of up to 0.03. Since the typical partial molar volume of CO2 in rubbery materials is 46 cc/mol, the lower values in this study were attributed to CO2 sorption into crystalline regions of the polymer, which provided no dilation. Application of a two-phase model using the assumption of Henry's law sorption showed that apparently all C3H8 sorption was occurring in the amorphous region but approximately 16% of CO2 sorption occurred in the crystalline regions. © 1996 John Wiley & Sons, Inc.

Gas sorption-induced dilation of poly(4-methyl-1-pentene)

Sorption and volume dilation isotherms of semicrystalline poly(4-methyl-1-pentene) (PMP) were measured using CO2 and C3H8 as penetrants, which have sieving diameters of 3.3 and 4.3 Å, respectively. On the other hand, the PMP crystal has a void width of approximately 4 Å as estimated by X-ray diffraction, so it was anticipated that CO2 would be able to sorb into the PMP crystal while C3H8 would not. The data show that C3H8 has a constant partial molar volume of approximately 87 cc/mol, just above the value reported in other rubbery polymers, and are consistent with the hypothesis that the C3H8 molecules are too large to sorb into the PMP crystals. The partial molar volume of CO2 was found to be 39 cc/mol for CO2 weight fractions of up to 0.03. Since the typical partial molar volume of CO2 in rubbery materials is 46 cc/mol, the lower values in this study were attributed to CO2 sorption into crystalline regions of the polymer, which provided no dilation. Application of a two-phase model using the assumption of Henry's law sorption showed that apparently all C3H8 sorption was occurring in the amorphous region but approximately 16% of CO2 sorption occurred in the crystalline regions. © 1996 John Wiley & Sons, Inc.

Sorption and dilation properties of poly(p‐phenylene sulfide) under high‐pressure carbon dioxide

AbstractSorption and dilation properties of the system poly(p‐phenylene sulfide) (PPS) and carbon dioxide have been investigated at pressures up to 50 atm over the temperature range 25–85°C. The shapes of the sorption isotherms are in agreement with those predicted by the dual‐mode theory. Analysis of the sorption and dilation isotherms confirms the occurrence of an isothermal glass transition. This occurrence and its corresponding disappearance in the range investigated is discussed. Values of the partial molar volume of CO2 sorbed in PPS are calculated below and above the isothermal transition. Compared with sorption by other polymers, these values were about the same in the glassy state, but were smaller in the rubbery state. Under 50 atm CO2 at 85°C crystallization of amorphous PPS was observed. The crystallinity estimated from the solubility before and after crystallization is about 20%.

Dilation of polyethylene by sorption of carbon dioxide

AbstractThe dilation of low‐density polyethylene accompanied by the sorption of CO2 was measured by microscopy under pressures up to 50 atm at temperatures from 25 to 55°C. The dilatometry measurement, which is also applied to the determination of the thermal expansion coefficient, is directly performed by a cathetometer. The dilation of LDPE by sorbed CO2 is linear with concentration. The buoyancy correction is described for the CO2 sorption isotherms in LDPE. The partial molar volume of CO2 in LDPE, calculated from the dilation and the sorption isotherms, is almost independent of temperature.

Dilation of polycarbonate by carbon dioxide

AbstractA new technique is described for dilatometry under high pressure. The technique is based on optical interferometry and is analogous to measuring the thickness of thin, nonabsorbing films and coatings. The procedure is demonstrated for the well‐characterized system of n‐pentane sorption by polyisobutylene, and then results for the dilation of polycarbonate by the sorption of carbon dioxide are presented. The dilation of polycarbonate by CO2 is nearly linear with concentration; the partial molar volume of CO2 decreases slightly with increasing pressure. This result indicates that all sorbed CO2 molecules contribute equally to the dilation of the polymer matrix and that none reside in microvoids or in preexisting free‐volume elements which do not contribute to volume expansion of the polymer.

Dilation and plasticization of polystyrene by carbon dioxide

AbstractWe have used an optical interference technique to measure the dilation of polystyrene films in the presence of carbon dioxide or helium at pressures up to 20 atm. Dilation isotherms (plots of dilation versus gas pressure at constant temperature) were obtained for three samples of polystyrene which had widely differing molecular weights. The dilation isotherms have the same general shape as sorption isotherms, which means that all of the sorbed gas molecules contribute to volume dilation and non can be thought of as occupying molecular‐sized voids in the polymer. Using sorption results from the literature we show that the partial molar volume of CO2 at 35°C is about 39 cm3 mol−1 and appears to be independent of polystyrene molecular weight. For a polystyrene sample with Mn = 3600, the partial molar volume of sorbed CO2 increases to 44 and 50 cm3 mol−1 at 45 and 55°C, respectively. The sorption of CO2 in polystyrene is shown to depress the glass transition temperature of the mixture, consistent with theoretical predictions. The shape of the dilation and sorption isotherms are consistent with the depression of the glass transition temperature.