Binary Mixtures Of CO2 Research Articles

Phase behavior measurement for the binary mixture of CO 2 + neopentyl glycol diacrylate and CO 2 + neopentyl glycol dimethacrylate systems at high pressure

In this work, the solubility curves for the CO 2 + neopentyl glycol diacrylate (NPGDA) and CO 2 + neopentyl glycol dimethacrylate (NPGDMA) systems are measured in static method at five temperatures of (313.2, 333.2, 353.2, 373.2 and 393.2) K and pressures up to 25.28 MPa. Both CO 2 + di(meth)acrylate systems have continuous critical mixture (locus) curves that exhibit maximums in pressure–temperature space between the critical temperatures of CO 2 and neopentyl glycol di(meth)acrylate. The solubility of CO 2 in the CO 2 + neopentyl glycol di(meth)acrylate mixture decreases as the temperature increases at a constant pressure. The CO 2 + NPGDA and CO 2 + NPGDMA systems exhibit type-I phase behavior. The experimental results for the CO 2 + NPGDA and CO 2 + NPGDMA systems are correlated with Peng–Robinson equation of state using a mixing rule including two adjustable parameters. The critical properties of NPGDA and NPGDMA are predicted with Joback–Lyderson and Lee–Kesler method.

Integration of CO2 and odorant signals in the mouse olfactory bulb

Carbon dioxide (CO2) is an important environmental cue for many animal species. In both vertebrates and invertebrates, CO2 is detected by a specialized subset of olfactory sensory neurons (OSNs) and mediates several stereotypical behaviors. It remains unknown how CO2 cues are integrated with other olfactory signals in the mammalian olfactory bulb, the first stage of central olfactory processing. By recording from the mouse olfactory bulb in vivo, we found that CO2-activating neurons also respond selectively to odorants, many of which are putative mouse pheromones and natural odorants. In addition, many odorant-responsive bulbar neurons are inhibited by CO2. For a substantial number of CO2-activating neurons, binary mixtures of CO2 and a specific odorant produce responses that are distinct from those evoked by either CO2 or the odorant alone. In addition, for a substantial number of CO2-inhibiting neurons, CO2 addition can completely block the action potential firing of the cells to the odorants. These results indicate strong interaction between CO2 signals and odorant signals in the olfactory bulb, suggesting important roles for the integration of these two signals in CO2-mediated behavioral responses.

Computational Study on Purification of CO2 from Natural Gas by C60 Intercalated Graphite

By combining grand canonical Monte Carlo (GCMC) simulations with adsorption theory, we perform a computational study on adsorption of CH4 and CO2 gases and purification of CO2 from the CH4−CO2 and N2−CO2 binary mixtures by the C60 intercalated graphite. The adsorption isotherms, isosteric heats and snapshots of pure gases have been examined extensively. It is found that the maximum excess uptakes at 298 K are relatively low, only giving 4.04 and 4.96 mmol/g for CH4 and CO2, respectively, due to a low porosity of 0.45 and a large crystal density of 1.57 g/cm3 of this material. It indicates that the pristine material is not suitable for gas storage. However, this material provides excellent selectivity for CO2, and the selectivity at ambient condition can reach 8 and 50 for the CH4−CO2 and N2−CO2 mixture, respectively. Furthermore, the selectivity of CO2 is almost independent of the bulk gas composition for P > 0.1 MPa. The dual-site Langmuir−Freundlich (DSLF) equation is used to fit the adsorption isotherm...

Vapor-liquid equilibria of carbon dioxide+n-propanol at elevated pressure

High-pressure vapor-liquid equilibrium data were measured for the binary mixtures of CO2+n-propanol at various isotherms (313.15–343.15 K). The vapor and liquid compositions and pressures were measured in a circulation-type apparatus. To facilitate easy equilibration, both vapor and liquid phases were circulated separately in the experimental apparatus and the equilibrium composition was analyzed by an on-line gas chromatograph. The experimental data were compared with literature results and correlated with the Peng-Robinson (PR) equations of state using the Wong-Sandler mixing rules. Calculated results with PR EOS showed good agreement with our experimental data.

High-pressure vapor-liquid equilibrium measurement for the binary mixtures of carbon dioxide+n-butanol

High-pressure vapor-liquid equilibrium data for the binary mixtures of CO2+n-butanol were measured at various isotherms of (313.15, 323.15, 333.15 and 343.15) K, respectively. The equilibrium compositions of vapor and liquid phases and pressures at each temperature were measured in a circulation-type equilibrium apparatus. To facilitate easy equilibration, both vapor and liquid phases were circulated separately in the experimental apparatus and the equilibrium composition was analyzed by an on-line gas chromatograph. The experimental data were compared with literature results and correlated with the Peng-Robinson (PR) equations of state using the Wong-Sandler mixing rules. Calculated results with the PR EOS showed good agreement with our experimental data.

In situ nitrogen enriched carbon for carbon dioxide capture

In situ nitrogen enriched carbon was synthesized from locally available low cost soybean as the proteinaceous source. The material was synthesized by chemical activation using zinc chloride followed by physical activation using CO 2. The surface area of synthesized nitrogen enriched carbon was found to be 811 m 2/g which is comparable with commercially available activated carbon. The nitrogen enriched carbon was having a breakthrough adsorption capacity of 23 mg/g at 120 °C which was almost three times higher in comparison with the commercially available activated carbon for a gas mixture comprising 15% CO 2 balanced with helium. This high adsorption capacity was attributed to the presence of nitrogen group within the carbon matrix, which was estimated to be about 0.64% as determined using the Kjeldahl’s method. The presence of different nitrogen containing groups assisting the adsorption of CO 2 in the synthesized sample was also confirmed by infrared analysis. For checking the consistent performance of the synthesized carbon, multi-cycle adsorption–desorption studies were carried out at 30 and 75 °C in binary mixture of CO 2/N 2.

Diffusion Coefficients in CO2/n-Alkane Binary Liquid Mixtures by Molecular Simulation

The objective of this work was to determine Fick diffusion coefficients in CO2/n-alkane binary mixtures without experimental test. For doing so, Maxwell-Stefan (MS) diffusivity was calculated by molecular simulation. Simultaneously, a thermodynamic factor was estimated using the PC-SAFT (perturbed chain statistical associating fluid theory) equation of state (eos). The binary Fick diffusivities are calculated as the product of both quantities. The binary mixtures investigated contain CO2 and various n-alkanes (nC10, nC16, nC22, nC28, nC44), at their bubble pressure at varying temperatures between 298 and 373 K. The calculated values of Fick diffusivities were compared against the experimental ones for the systems where literature data exist. An average deviation of 26% was found for the CO2/n-decane and 15% for CO2/n-hexadecane mixtures. These results support that molecular simulation can be employed as a tool for the determination of Fick diffusivities in high pressure systems, like in oil reservoirs, without the need to construct a complicated and expensive experimental setup. This method only requires the phase behavior of the desired system, and it can be used for multicomponent mixtures. As an example, predictions of Fick diffusivities were done for CO2 binary mixtures with heavy n-alkanes (nC22, nC28, nC44).

Liquid−Vapor Equilibrium of the Systems Butylmethylimidazolium Nitrate−CO2 and Hydroxypropylmethylimidazolium Nitrate−CO2 at High Pressure: Influence of Water on the Phase Behavior

Ionic liquids (IL) are receiving increasing attention due to their potential as "green" solvents, especially when used in combination with SC-CO2. In this work liquid-vapor equilibria of binary mixtures of CO2 with two imidazolium-based ionic liquids (IL) with a nitrate anion have been experimentally determined: butylmethylimidazolium nitrate (BMImNO3) and hydroxypropylmethylimidazolium nitrate (HOPMImNO3), using a Cailletet apparatus that operates according to the synthetic method. CO2 concentrations from 5 up to 30 mol % were investigated. It was found that CO2 is substantially less soluble in HOPMImNO3 than in BMImNO3. Since these ILs are very hygroscopic, water easily can be a major contaminant, causing changes in the phase behavior. In case these Ils are to be used in practical applications, for instance, together with CO2 as a medium in supercritical enzymatic reactions, it is very important to have quantitative information on how the water content will affect the phase behavior. This work presents the first systematic study on the influence of water on the solubility of carbon dioxide in hygroscopic ILs. It was observed that the presence of water reduces the absolute solubility of CO2. However, at fixed ratios of CO2/IL, the bubble point pressure remains almost unchanged with increasing water content. In order to explain the experimental results, the densities of aqueous mixtures of both ILs were determined experimentally and the excess molar volumes calculated.

Evaluating cubic equations of state for calculation of vapor–liquid equilibrium of CO 2 and CO 2-mixtures for CO 2 capture and storage processes

Proper solution of vapor liquid equilibrium (VLE) is essential to the design and operation of CO 2 capture and storage system (CCS). According to the requirements of engineering applications, cubic equations of state (EOS) are preferable to predict VLE properties. This paper evaluates the reliabilities of five cubic EOSs, including PR, PT, RK, SRK and 3P1T for predicting VLE of CO 2 and binary CO 2-mixtures containing CH 4, H 2S, SO 2, Ar, N 2 or O 2, based on the comparisons with the collected experimental data. Results show that SRK is superior in the calculations about the saturated pressure of pure CO 2; while for the VLE properties of binary CO 2-mixtures, PR, PT and SRK are generally superior to RK and 3P1T. The impacts of binary interaction parameter k ij were also analyzed. k ij has very clear effects on the calculating accuracy of an EOS in the property calculations of CO 2-mixtures. In order to improve the calculation accuracy, the binary interaction parameter was calibrated for all of the studied EOSs regarding every binary CO 2-mixture.

High‐pressure viscosity and density of carbon dioxide + pentaerythritol ester mixtures: Measurements and modeling

AbstractThis article reports densities and viscosities up to 60 MPa and from 303.15 to 353.15 K on two binary mixtures of CO2 and lubricant pentaerythritol tetra‐2‐ethylhexanoate with 7.8% and 14.4% mass fraction of lubricant. Because CO2 and the lubricant are not in the same phase at atmospheric pressure and room temperature, a specially‐designed vibrating‐wire apparatus has been used. The experimental data, together with our previous data for six mixtures of CO2 and three polyolesters, have been used to test the predictive and correlation ability of several models: simple mixing laws, the self‐referencing method, and the hard‐sphere and free volume models. In general, it is not possible to predict the viscosity with deviations smaller than 10%. The hard‐sphere model and the self‐referencing model are the more adequate to represent the viscosity of these mixtures. Most of the models studied underestimate the viscosities over the investigated (T,p) range. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Prediction of Molar Volumes of CO2-Expanded Liquids Using a New Generalized Method

A new, easy-to-use generalized method is presented in this work for accurate computation of ν L , the molar volume of the carbon dioxide (CO 2 )-expanded liquids. This method calculates the liquid-phase compressibility factor, Z L , of the binary mixture of CO 2 and solvent. The uniqueness of this method is that it does not involve computation to solve a cubic equation, nor does it require any binary interaction constants and critical temperatures of the pure components, as in the case of the equation of state (EOS) method. Z L is obtained directly from a generalized correlation in terms of the pseudo-reduced pressure (P r ) with two system-specific constants. These two constants are simply dependent on the acentric factor of the solvent, ω 2 . The computation of υ L by this method has been validated for 17 CΟ 2 -solvent systems at temperatures in the range of 290.8-328.2 K and at pressures in the range of 4-96 bar with the experimental data available in the literature.

High-Pressure Vapor−Liquid Equilibria for the Binary Mixtures of Carbon Dioxide + Isopropanol (IPA)

Isothermal high-pressure vapor−liquid equilibrium data were measured for the binary mixtures of CO2 + isopropanol (IPA) at various temperatures [(323.15 ∼ 353.15) K]. The vapor and liquid compositions and pressures were measured in a circulation-type apparatus. To facilitate easy equilibration, both vapor and liquid phases were circulated separately in the experimental apparatus, and the equilibrium composition was analyzed by an on-line gas chromatograph. The experimental data were compared with literature results and correlated with the Peng−Robinson equations of state (PR EOS) combined with the Wong−Sandler mixing rules. Calculated results with the PR EOS showed good agreement with our experimental data.

Matrimid polyimide membranes for the separation of carbon dioxide from methane

AbstractThree types of polyimide membranes viz., Matrimid, Kapton and P84, were prepared by solution casting and solvent evaporation method to study the permeation of CO2 and CH4 gases. Barrier properties were investigated as a function of feed pressure for pure gases and feed composition for the binary mixtures of CO2 and CH4. Kapton polyimide, prepared by imidization of polyamic acid, showed an increase in permeability, but reduction in selectivity, due to the occurrence of plasticization at higher feed CO2 concentrations. Matrimid was found to exhibit the highest permeability and was studied in greater detail, due to the feasibility in its scale‐up into a hollow fiber modular configuration for commercial application. Matrimid was characterized by Fourier transform infrared (FTIR) spectroscopy and X‐ray diffractometry (XRD) to assess the intermolecular interactions and to understand the separation profiles. The effect of feed flow was evaluated by studying the permeation behavior of flat sheet membrane in dead‐end operation mode with the hollow fiber module operated in crossflow feed mode. For pure gases, Matrimid hollow fiber membrane exhibited a CO2 permeability of 12.7 Barrers with a CO2/CH4 selectivity of 40 at the feed pressure of 20 bar. At the same pressure, for binary mixture feed of 5 mol % CO2 in methane, the module gave a permeability of 7.4 Barrers with a selectivity of 21. The total binary mixture permeability was determined at the feed CO2 concentrations varying from 0 to 20 mol % to demonstrate the preferential sorption of CO2 in Matrimid membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Using a Fiber-Optic Probe for the Measurement of Volumetric Expansion of Liquids

A fiber-optic probe is developed for the fast, in-situ measurement of volumetric expansion of multiphase and multicomponent systems. An experiment with the binary mixtures of CO2−toluene and CO2−ethanol was conducted to demonstrate the usefulness of the fiber-optic probe in accurately tracking the isothermal volumetric expansion as a function of pressure. In the 1-L autoclave that has been used, the probe was shown to detect the liquid level height within a precision of 0.35% of the total height of the vessel. The results for the volumetric expansion of toluene and ethanol with CO2 correlate well with those found in the literature. The probe itself can be used up to pressures of 140 barg and temperatures of 120 °C.

Molecular dynamics simulations of transport and separation of supercritical carbon dioxide-alkane mixtures in supported membranes

The results of extensive nonequilibrium molecular dynamics (MD) simulations of flow and transport of several binary mixtures of CO 2 and an n -alkane chain, from CH 4 to C 4 H 10 , through a model porous membrane composed of three pores in series with significantly different sizes and in the presence of an external pressure gradient, are reported. The technique that we use for the simulations is a combination of the configurational-bias Monte Carlo method (used for efficient generation of molecular models of n -alkane chains) and the dual control-volume grand-canonical MD method. The selectivity of the membrane changes qualitatively as the length of the alkane chain increases, resulting in high separation factors in favor of the alkanes. Moreover, we find that, under supercritical conditions, unusual phenomena occur that give rise to direction- and pressure-dependent permeabilities for the fluids. The results, which are also in agreement with a continuum formulation of the problem, indicate that the composite nature of the membrane gives rise to the direction-dependent permeabilities. Hence, modeling flow and transport of supercritical fluid mixtures in porous materials with the type of morphology considered in this paper (such as supported porous membranes) would require using effective permeabilities that depend on both the external pressure drop and the direction along which it is applied to the materials.

Measurement and thermodynamic modeling of solid–liquid–gas equilibrium of some organic compounds in the presence of CO 2

Solid–liquid–gas (SLG) phase equilibrium measurements have been performed in a view cell apparatus, using the “first melting point” method. SLG data are presented for five binary mixtures of CO 2 with naphthalene, phenanthrene, benzoic acid, palmitic acid and stearic acid. The experimental data are correlated with the cubic Peng–Robinson EoS coupled with the conventional van der Waals one fluid mixing rules. Two different approaches for the calculation of the solid phase fugacity are examined. In the first the solid vapor pressure is used as the reference solid fugacity and in the second the so-called subcooled liquid reference state is used. The comparison of the two approaches indicates that the latter gives much better results than the former. Finally, the recently developed Universal-Mixing-Rule Peng–Robinson-Unifac (UMR-PRU) model is applied for the prediction of the SLG equilbrium curves of the CO 2/naphthalene and CO 2/phenanthrene systems, yielding satisfactory results, especially when coupled with the subcooled liquid reference state approach.

Modeling Phase Equilibrium of H2 + n-Alkane and CO2 + n-Alkane Binary Mixtures Using a Group Contribution Statistical Association Fluid Theory Equation of State (GC−SAFT−EOS) with a kij Group Contribution Method

A group contribution (GC) method combined with a SAFT equation of state (EOS) [Tamouza et al., Fluid Phase Equilib. 2004, 222−223, 67 and 2005, 228−229, 409] is extended here to model vapor−liquid phase equilibria of binary mixtures of H2 + n-alkanes and CO2 + n-alkanes. Modeling these systems requires binary interaction parameters kij that are estimated here in the same spirit as pure compound GC−SAFT parameters, i.e., through a specific group contribution method. Molecule−group interaction parameters (kH2,CH2, kH2,CH3, kCO2,CH2, and kCO2,CH3) are used rather than molecule−molecule interaction parameters. Two versions of SAFT are tested here: the Perturbed-Chain SAFT (PC−SAFT) [Gross and Sadowski, Ind. Eng. Chem. Res. 2000, 40, 1244] and Variable-Range SAFT (VR−SAFT) [Gil-Villegas et al., J. Chem. Phys. 1997, 106, 4168]. The results are very encouraging, particularly for predicting binary mixtures of CO2 and heavy n-alkanes. Mixtures that contain H2 are modeled here with deviations that compare well with those of the classically used Grayson−Streed model.

Molecular beam mass spectrometer equipped with a catalytic wall reactor for in situ studies in high temperature catalysis research

A newly developed apparatus combining a molecular beam mass spectrometer and a catalytic wall reactor is described. The setup has been developed for in situ studies of high temperature catalytic reactions (>1000°C), which involve besides surface reactions also gas phase reactions in their mechanism. The goal is to identify gas phase radicals by threshold ionization. A tubular reactor, made from the catalytic material, is positioned in a vacuum chamber. Expansion of the gas through a 100μm sampling orifice in the reactor wall into differentially pumped nozzle, skimmer, and collimator chambers leads to the formation of a molecular beam. A quadrupole mass spectrometer with electron impact ion source designed for molecular beam inlet and threshold ionization measurements is used as the analyzer. The sampling time from nozzle to detector is estimated to be less than 10ms. A detection time resolution of up to 20ms can be reached. The temperature of the reactor is measured by pyrometry. Besides a detailed description of the setup components and the physical background of the method, this article presents measurements showing the performance of the apparatus. After deriving the shape and width of the energy spread of the ionizing electrons from measurements on N2 and He we estimated the detection limit in threshold ionization measurements using binary mixtures of CO in N2 to be in the range of several hundreds of ppm. Mass spectra and threshold ionization measurements recorded during catalytic partial oxidation of methane at 1250°C on a Pt catalyst are presented. The detection of CH3∙ radicals is successfully demonstrated.

Vapor–liquid equilibria for CO2–fermentation alcohol mixtures: Application of a new group contribution equation of state to isomeric compounds

This study provides vapor–liquid equilibrium data that can be used for the separation of trace components from fermentation alcohol with supercritical CO2. C4 and C5 alcohols were selected as key components among the trace components of fermentation alcohols because these are impurities that can be produced during the process and separation is necessary from alcohol aqueous solutions. Vapor–liquid equilibrium data were measured for the systems of CO2–1,3-butanediol, CO2–1,2-butanediol, CO2–iso-amylalcohol, CO2–2-methylbutanol, and CO2–iso-butanol at 313.2 and 333.2K at pressures from 4 to 15MPa. The experimental results demonstrated that the isomers exhibited a slightly different phase behavior for the binary mixtures of CO2 at the range studied. The group contribution equation of state (GC-EOS) proposed by Skjold-Jorgensen [S. Skjold-Jorgensen, Fluid Phase Equilib. 16 (1984) 317–351] was modified to allow application to isomers by considering the contact surface area between molecular pairs. The new model could predict the phase behavior of the binary mixtures of CO2 and C4/C5 alcohols contained in fermentation alcohols.

Effects of Fluid Density on a Poly(dimethylsiloxane)-Based Junction in Pure and Methanol-Modified Carbon Dioxide

We report on the behavior of a three-armed, poly(dimethylsiloxane) (PDMS)-based junction that is site-selectively labeled with a single fluorescent dansyl reporter group (dansyl junction, DJ) in (i) pure CO2 at 308 K as a function of CO2 density and (ii) a binary mixture of CO2 and 3 mol % methanol at 313 K as a function of mixture density. The DJ results are compared to those of dansylpropylsulfonamide (DPSA)a dansyl reporter molecule without any PDMS segments. In pure CO2 at low fluid densities, the local microenvironment sensed by the dansyl residue in DJ appears to be rich in PDMS, indicating that the solvent quality is poor and the PDMS segments interact strongly with the dansyl residue. Increasing the CO2 density increases the solvent quality, and PDMS segments become better solvated by the CO2. At the highest CO2 densities studied, the solvent quality begins to decrease again, resulting in a local increase in the PDMS composition around the average dansyl residue. Results from steady-state anisotropy measurements suggest the presence of DJ aggregates in the fluid phase at low CO2 densities. As the CO2 density is increased, these aggregates are disrupted, and isolated DJ molecules appear to be the major species in the fluid phase above a reduced CO2 density of ∼1.5 and up to ∼1.9. DJ aggregates are present in the CO2/methanol mixture at all fluid densities studied. At low mixture densities there is enrichment in the local methanol concentration surrounding the dansyl residue in DJ in comparison to isolated DPSA molecules under equivalent mixture densities. Thus, it appears as if the PDMS segments in DJ augment/enhance the methanol concentration surrounding the dansyl reporter group in DJ. Together these results demonstrate the dramatic role fluid density and composition can play in tuning the local microenvironment that surrounds a polymeric junction point.