Binary Mixtures Of Carbon Dioxide Research Articles

Prediction of solid-liquid-gas equilibrium for binary mixtures of carbon dioxide + organic compounds from approaches based on the COSMO-SAC model

Six predictive approaches based on the Peng-Robinson (PR) equation of state (EOS), conductor-like screening model segment activity coefficient (COSMO-SAC), and mixing rules were applied to model solid-liquid-gas equilibrium for 21 binary mixtures of CO2 and an organic compound. The accuracy of these approaches in predicting equilibrium temperatures at given pressures (635 experimental data with T=220∼413.97K and P=0.05∼48.35MPa), liquid phase compositions, and liquid molar volumes was examined and compared to provide an overview on their performance. The recently developed PR+COSMO-SAC EOS was found to be most accurate, with deviations of 6.25K in temperature, 0.071 in liquid mole fraction, and 21% in liquid molar volume. The performance of these models can be very different for the solid containing different functional groups. Nevertheless, the PR+COSMO-SAC EOS could provide useful a priori predictions with only input of experimental heat of fusion and melting temperature of the solid.

Characterization of fluid mixtures at high pressures using frequency response of microcantilevers

The frequency response of ferromagnetic nickel microcantilevers immersed in binary mixtures of carbon dioxide (CO2) and nitrogen (N2) at 308K and pressures up to 23MPa was investigated. Experimental data were analyzed using the model developed by Sader for a clamped oscillatory beam immersed in a fluid and a very good agreement between the measured resonant frequencies and quality factors (Q-factors) and the theoretical predictions of the model with cantilever characteristic parameters regressed from experimental data was observed. This suggested that the data could be used to simultaneously measure the density and the viscosity of fluid mixtures over a wide range of pressures. Subsequently, density and viscosity of binary mixtures of CO2 and N2 were determined using N2 as the reference fluid and compared to the predictions of Gerg equation of state and Chung equation, respectively. For the studied fluids with different compositions, the average relative difference between the experimental density values and the values predicted using Gerg equation of state and NIST database ranged from 1.0 to 13%. The average relative difference between the experimental viscosity values and the values obtained using Chung equation and NIST database ranged from 2.4 to 15%. Since the resonant frequency and Q-factor were found to vary with composition at a fixed temperature and pressure, the technique can in principle also be used to measure the composition of a binary mixture at a fixed temperature and pressure. The study represents the first systematic attempt to use microcantilevers for the characterization of high-pressure fluid mixtures and paves the way for devising portable sensors for in-line monitoring of thermophysical properties and composition of fluid mixtures under a wide range of environmental conditions.

Description of the gas transport through dynamic liquid membrane

Abstract Recently we published a short communication about the gas separation by new type of membranes so called “dynamic liquid membranes” (DLM). The gas transport through water film was described by solution diffusion model commonly used for evaluation of the gas permeation through nonporous polymeric membranes; therefore this type of membranes is suitable for the separation of such systems where one of the components has high solubility in water. The separation ability of DLM based on thin water film for the binary mixtures of carbon dioxide and methane was investigated. Since direct measurement of permeate flux and its composition was not possible, we suggested three models for gas transport evaluation based on the use of simplifying assumptions. The obtained values of carbon dioxide permeate flux (permeance) from all models are very close, the highest difference is 6.3 mol % for feed composition 92 mol % CO2. Carbon dioxide flux is between 0.048 and 0.729 m3 m−2 h−1. The results of carbon dioxide permeation flux determined as difference between experimental values of the feed and retentate fluxes with permeate flux calculated using the Model 3 were in very good agreement.

A comprehensive study of phase equilibria in binary mixtures of carbon dioxide + alcohols: Application of a hybrid intelligent model (CSA-LSSVM)

The phase equilibria of binary mixtures of CO2+alcohols are crucial for the design and optimization of supercritical fluid applications with recently growing reliance on CO2 as the primary solvent at its supercritical conditions. Essentially, alcohols, as cosolvent, contribute to the solvating characteristic of supercritical CO2, which is de facto required for (polar) compound extraction in different industries. However, the proposed, less time-consuming alternatives to experimentally measuring the vapor-liquid equilibrium (VLE) data have been successful in such non-ideal mixtures only to a certain extent. In particular, the observed high deviation in existing models from the experimental values in correlating VLE data necessitates developing an intelligent, self-learning, unique model with more accuracy as well as applicability to a notably broader range of conditions. To this end, we have employed a novel Least-Squares Support Vector Machine (LSSVM) approach as a problem-independent, general-purpose tool. In this research, the LSSVM model is optimized with a Coupled Simulated Annealing (CSA) optimization algorithm. The hybrid model is based on a comprehensive databank of 531 reliable experimental VLE data that cover binary systems of CO2+13 types of short to medium chained alcohols at temperature and pressure overall ranges of 293.15–432.45K and 5.2–213.91bar, respectively. The statistical and graphical error analyses vividly demonstrate the supremacy and robustness of the developed CSA-LSSVM model, particularly compared to the conventional SRK and PR equations of state. However, minor deviations in mixtures containing Pentanol and Hexanol are observed, despite the overall model accuracy that strongly satisfies engineering purposes. We hypothesize that uncertainty in the corresponding experimental data could be the cause; we prove this by applying a Leverage approach, while studying the validity and applicability domain of the model. Furthermore, detailed sensitivity analysis is conducted through a relevancy factor, which suggests that the CO2 mole fraction is the most influential parameter on the studied binary mixture bubble/dew point pressures.

Measurements of Decompression Wave Speed in Binary Mixtures of Carbon Dioxide and Impurities

Shock tube tests were conducted on a number of binary CO2 mixtures with N2, O2, CH4, H2, CO, and Ar impurities, from a range of initial pressures and temperatures. This paper provides examples of results from these tests. The resulting decompression wave speeds are compared with predictions made utilizing different equations of state (EOS). It was found that, for the most part (except for binaries with H2), the GERG-2008 EOS shows much better performance than the Peng–Robinson (PR) EOS. All binaries showed a very long plateau in the decompression wave speed curves. It was also shown that tangency of the fracture propagation speed curve would normally occur on the pressure plateau, and hence, the accuracy of the calculated arrest toughness for pipelines transporting these binary mixtures is highly dependent on the accuracy of the predicted plateau pressure. Again, for the most part, GERG-2008 predictions of the plateau are in good agreement with the measurements in binary mixtures with N2, O2, and CH4. An example of the determination of pipeline material toughness required to arrest ductile fracture is presented, which shows that prediction by GERG-2008 is generally more conservative and is therefore recommended. However, both GERG-2008 and PR EOS show much worse performance for the other three binaries: CO2 + H2, CO2 + CO, and CO2 + Ar, with CO2 + H2 being the worst. This is likely due to the lack of experimental data for these three binary mixtures that were used in the development of these EOS.

Effects of variable viscosity and periodic boundary conditions on natural convection double-diffusive flow past a vertical plate in a slip flow regime

This paper studies the effects of variable viscosity and periodic boundary conditions on natural convection double-diffusive flow past a vertical plate in a slip flow regime when suction velocity oscillates in time about a constant mean. The fluid viscosity is assumed to vary with temperature. The problem is governed by a nonlinear and coupled linear system of partial differential equations. Perturbation method is employed to solve the equations. The influence of flow parameters on fluid temperature, concentration and velocity, skin friction, and rate of heat transfer have been presented graphically. It is observed that increase in viscosity parameter for the binary mixture of carbon dioxide ( Sc = 0.94) in air ( Pr = 0.71) increase velocity near the plate. In addition, the mean skin friction increases with increase in viscosity parameter.

Phase equilibrium data for binary mixtures of carbon dioxide with {1,1,2,3,3,3-hexafluoro-1-propene or 2,2,3-trifluoro-3-(trifluoromethyl)oxirane} at temperatures between (233 and 273) K

Isothermal vapour-liquid equilibrium data were measured for binary mixtures of carbon dioxide with either hexafluoropropylene or hexafluoropropylene oxide at five temperatures in the (233–273) K range. The experimental data presented in this manuscript supplement data which were previously measured at temperatures of 273 K and above. The data is required for the assessment of the operating conditions for a purification process for the production of high purity hexafluoropropylene oxide from a mixture of hexafluoropropylene and hexafluoropropylene oxide. The experimental P-x-y data were measured using an apparatus based on the “static-analytic” method. The experimental data were satisfactorily correlated using the Peng-Robinson Equation of State with the Mathias-Copeman alpha function.

Effective permeability of binary mixture of carbon dioxide and methane and pre-dried raw biogas in supported ionic liquid membranes

Abstract The influence of the temperature and stage cut on permeation of CO 2 and CH 4 through two different supported ionic liquid membranes were studied. The measurements were performed with binary mixture of CH 4 and CO 2 and with real pre-dried biogas collected in sewage plant. The influence of temperature on permeability followed the Arrhenius behavior in agreement with solution diffusion model of transport. The influence of stage cut was also very small, what helped to confirm that the membrane was operated under optimal conditions. The results obtained with real pre-dried biogas were very close to those obtained with the binary mixture. This was caused by the fact that the amount of trace compounds present in real pre-dried biogas was very small (less than 1 vol.%). The results showed that supported ionic liquid membranes (SILMs) can be used for biogas upgrading. It can be also concluded that the use of model mixture instead of real biogas for measurements brings relevant results.

Adsorption equilibrium of binary mixtures of carbon dioxide and nitrogen on zeolites ZSM-5 and 13X

An investigation of the adsorption equilibrium of carbon dioxide (CO2) and nitrogen (N2) and their mixtures on zeolites ZSM-5 and 13X is presented. Pure component isotherms are measured at five different temperatures in the range of 25 °C and pressures up to 10 bar, and the resulting data are described with an appropriate isotherm equation. Adsorption equilibrium of CO2/N2 mixtures was measured at two temperatures (25 °C and 45 °C) and three pressure levels (1.2 bar, 3 bar and 10 bar) using three feed gas compositions on both materials tested. The isotherms obtained from the pure component measurements are used to predict the binary data using two approaches: An empirical extension of the Sips isotherm and the application of ideal adsorbed solution theory (IAST). In the context of the binary CO2/N2 adsorption, it was found that for ZSM-5 the system behaves close to ideal over the whole range of pressure and temperature investigated here and thus is well described by the IAST prediction. On the other hand, our results demonstrate non-ideal behavior in the adsorbed phase with increasing pressure for zeolite 13X, thus motivating the use of real adsorbed solution theory (RAST) to accurately describe the binary adsorption data.

РАВНОВЕСИЕ ЖИДКОСТЬ–ПАР В БИНАРНЫХ СМЕСЯХ ДИОКСИДА УГЛЕРОДА С ОСНОВНЫМИ КОМПОНЕНТАМИ ВОЗДУХА

Compiled equations describing the experimental data of the liquid-vapor phase equilibrium in three binary mixtures of carbon dioxide with nitrogen, oxygen and argon. Equations describe the dependence of liquid or vapor pressure from temperature and composition. At their compiling were automatic selected the most significant coefficients of equation. Standard deviations of the experimental values of the pressure from calculated for different mixtures are equal from 4,2 to 5,4 %. Equations permits also to determine the composition or temperature of phases at given values of other parameters of the phase equilibrium

Molecular dynamics simulation of CO2 hydrates: Prediction of three phase coexistence line.

The three phase equilibrium line (hydrate-liquid water-liquid carbon dioxide) has been estimated for the water + carbon dioxide binary mixture using molecular dynamics simulation and the direct coexistence technique. Both molecules have been represented using rigid nonpolarizable models. TIP4P/2005 and TIP4P/Ice were used for the case of water, while carbon dioxide was considered as a three center linear molecule with the parameterizations of MSM, EPM2, TraPPE, and ZD. The influence of the initial guest occupancy fraction on the hydrate stability has been analyzed first in order to determine the optimal starting configuration for the simulations, paying attention to the influence of the two different cells existing in the sI hydrate structure. The three phase coexistence temperature was then determined for a pressure range from 2 to 500 MPa. The qualitative shape of the equilibrium curve estimated is correct, including the high pressure temperature maximum that determines the hydrate re-entrant behaviour. However, in order to obtain quantitative agreement with experimental results, a positive deviation from the classical Lorentz-Berthelot combining rules must be considered.

Demixing pressures of hydroxy-terminated poly(dimethylsiloxane)–carbon dioxide binary mixtures at 313.2 K, 323.2 K and 333.2 K

The phase behavior of PDMS(OH)–CO2 binary mixtures was investigated. Two different molecular weight PDMS(OH) were utilized and the demixing pressures were determined at three temperatures for a wide composition range. Both of these polymers were found to form miscible mixtures with CO2 at all compositions at pressures lower than 31MPa in the temperature range 313.2–333.2K. Depending on the composition of the binary mixtures, two types of phase separation was observed during depressurization; the bubble point and the cloud point. In addition, at specific weight fractions a color change was also observed which was attributed to the mixture critical point. The demixing pressures were observed to increase with temperature and decrease with increasing polymer weight fraction. In addition, higher demixing pressures were obtained for the higher molecular weight polymer mixtures. The bubble point data were modeled by using Sanchez–Lacombe equation of state (SLEoS) and the binary interaction parameters were regressed at the studied temperatures. It was observed that the binary interaction parameters decreased with increasing temperature.

Use of Equations of State and Coarse Grained Simulations to Complement Experiments: Describing the Interfacial Properties of Carbon Dioxide + Decane and Carbon Dioxide + Eicosane Mixtures

We report surface tension measurements, coexisting densities, concentration profiles along the interfacial region, surface activities, and relative Gibbs adsorption isotherms for binary mixtures of carbon dioxide (CO2) + n-decane (n-C10H22) at 344.15 K and carbon dioxide (CO2) + n-eicosane (n-C20H42) at 323.15 K over a pressure range from 0.1 MPa to 10.35 MPa. The results are obtained by employing a broad approach that integrates experiments with both theory and molecular simulations to gain an enhanced multiscale description of the interfacial region. Measurements are based on the use of a high-pressure pendant drop tensiometer coupled to a high-pressure densimeter. Theoretical modeling is carried out using the Square Gradient Theory based on a version of the Statistical Associated Fluid Theory (SAFT-VR Mie) equation of state. At the molecular level, Molecular Dynamics is employed and molecules are represented by the SAFT-γ coarse-grained force field. The novelty here is that both the theory and the simulations uniquely share the same underlying intermolecular potentials, hence the experimental data are employed to verify and inform in the same way both the theory and simulations. Reassuringly, theory, experiments, and molecular simulations agree with each other in the description of the bulk phase equilibria and interfacial tension. It is observed that for both mixtures, the interfacial tension decreases as the pressure (or the liquid mole fraction of CO2) increases. Furthermore, there is quantitative agreement between the theoretical predictions and the results obtained from the molecular simulations of surface activities, concentration profiles along the interfacial region, and relative Gibbs adsorption isotherms at the interfaces. A remarkable high excess adsorption of CO2, larger in eicosane than in decane, is detected along the interface.

Experimental and modelling studies of carbon dioxide adsorption by porous biomass derived activated carbon

The goal of the study was to produce a low-cost activated carbon from agricultural residues via single stage carbon dioxide (CO2) activation and to investigate its applicability in capturing CO2 flue gas. The performance of the activated carbon was characterized in terms of the chemical composition, surface morphology as well as textural characteristics. The adsorption capacity was investigated at three temperatures of 25, 50 and 100 °C for different types of adsorbate, such as purified carbon dioxide and binary mixture of carbon dioxide and nitrogen. The purified CO2 adsorption study showed that the greatest adsorption capacity of the optimized activated carbon of 1.79 mmol g−1 was obtained at the lowest operating temperature. In addition, the adsorption study proved that the adsorption capacity for binary mixtures was lower due to the reduction in partial pressure. The experimental values of the purified CO2 adsorption were modelled by the Lagergren pseudo-first-order model, pseudo-second-order model, and intra-particle diffusion model. Based on the analysis, it inferred that the adsorption of CO2 followed the pseudo-second-order model with regression coefficient value higher than 0.995. In addition, the adsorption study was governed by both film diffusion and intra-particle diffusion. The activation energy that was lesser than 25 kJ mol−1 implied that physical adsorption (physisorption) occurred.

Thermodynamic Properties of Supercritical Mixtures of Carbon Dioxide and Methane: A Molecular Simulation Study

Volumetric and second-derivative thermodynamic properties of binary mixtures of carbon dioxide and methane were calculated under supercritical conditions at pressures up to 99.93 MPa and temperatures between (323.15 and 573.15) K using molecular dynamics simulations with the multistate Bennett acceptance ratio technique. Eleven compositions were studied, ranging from pure methane to pure carbon dioxide in 0.10 increments in carbon dioxide mole fraction. The molecular simulations utilized the TraPPE and SAFT-γ force fields to model methane and carbon dioxide. Because of the unavailability of experimental data, the results were compared against the extended range estimation and extrapolation of the GERG-2008 equation for the calculation of volume expansivity, isothermal compressibility, isobaric and isochoric heat capacities, Joule–Thomson coefficient, and speed of sound of the binary mixtures. The agreement between the simulation results and those obtained through the extrapolation of the GERG-2008 equation beyond its stated range of validity is quite good, suggesting that the force field representation of the binary mixture is accurate, especially when compared with the extrapolation of traditional cubic equations of state. Although more computationally expensive, molecular simulations relying upon only a few physically meaningful parameters are able to give similar results to those obtained with the semiempirical multiparameter GERG-2008 model.

Biohydrogen purification using a commercial polyimide membrane module: Studying the effects of some process variables

In this work the purification of biohydrogen was attempted in mixed gas measurements using a commercial polyimide membrane module. The impact of several process variables (gas composition, temperature, ratio of retentate and feed flows) on the real separation efficiency was statistically studied applying a 3-level full-factorial experimental design. The results showed that all the factors examined could significantly affect the achievable selectivity and it was observed that the theoretical and real separation factors were remarkably different. It was also found that – in comparison with other commercially available membranes – the module reflected potential for hydrogen enrichment. Considering the design boundaries, the highest H2/CO2 gas selectivity (1.62) could be achieved at feed pressure, separation temperature and recovery value of ∼2.2 bar, 55 °C and 0.6, respectively, using a 65 vol% hydrogen/35 vol% carbon-dioxide binary mixture.

Adsorption of CO2, CH4, and H2O in Zeolite ZSM-5 Studied Using In Situ ATR-FTIR Spectroscopy

Biogas and natural gas are interesting fuels with high H/C ratio. However, these gases frequently contain carbon dioxide and water which lowers the heat value of the gas and may induce corrosion. Therefore, the development of more efficient processes, such as membrane processes and improved adsorbents, for the separation of carbon dioxide and water from biogas and natural gas is of great importance. Zeolite ZSM-5 membranes are promising for this separation which is controlled by the adsorption and diffusion of the different species in the zeolite. Multicomponent adsorption data are therefore required for development of new membrane and adsorption processes. In the present work, the adsorption of water, carbon dioxide, and methane in a Na-ZSM-5 zeolite film at various temperatures was studied by in situ Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy for the first time. Adsorption isotherms were retrieved from the experimental data and the Langmuir model fitted the isotherms very well. Limiting heat of adsorption was determined from the Henrýs law regime and the values determined agreed well with previously reported data. A few experiments were conducted with multicomponent mixtures and the experimentally determined amounts adsorbed were compared with values predicted by the Ideal Adsorbed Solution Theory (IAST). It was found that for the binary mixture of carbon dioxide and methane there was good agreement between the experimental values and those predicted by the IAST. However, when water was also introduced, the IAST could not fully capture the adsorption behavior of the multicomponent mixture, probably because the adsorbed phase is not ideal. These findings are in line with previous reports for adsorption in zeolites. The multicomponent adsorption behavior of this system will be further investigated in forthcoming work.

초임계 이산화탄소에서 소르비탄 모노팔미테이트 계면활성제의 상거동에 관한 연구

Phase behavior of carbon dioxide + surfactant binary system and carbon dioxide + surfactant + water ternary system was investigated at the temperatures from 318 K to 348 K by using high pressure vapor liquid equilibrium apparatus containing variable-volume view cell. Sorbitan monopalmitate was used as the surfactant. The cloud point pressures for the binary mixture of carbon dioxide + sorbitan monopalmitate increased with an increasing of system temperatures and the maximum cloud point pressure was observed at the composition of 0.226 wt% of sorbitan monopalmitate. On the other hand, as the temperatures and compositions of water increased, the cloud point pressures for ternary system containing 0.1 wt% of sorbitan monopalmitate in- creased significantly. For the ternary system of constant 0.2 wt% of water, the cloud point pressure curves show relatively flat according to the change of compositions of surfactant. The cloud point pressures increased when the temperatures and composi- tions of water increased.

Bubble point pressures and densities of hexamethyldisiloxane–carbon dioxide binary mixture using a constant volume view cell

The phase behavior of hexamethyldisiloxane (HMDS)–carbon dioxide (CO2) binary mixture was investigated using a constant volume view cell. The accuracy of the measurement technique was inspected against the bubble point pressure data in the literature for ethanol (C2H5OH)–carbon dioxide (CO2) binary mixture. The bubble point pressures for C2H5OH–CO2 agreed well with the literature values. The bubble point pressures of HMDS–CO2 binary mixture were determined at five different temperatures (T=298.2K, 308.2K, 313.2K, 323.2K, 333.2K) and at various compositions. The bubble point pressures increased with increasing temperature and CO2 mole fraction in the binary mixture. The phase behavior of the binary mixture was modeled using the Peng–Robinson Stryjek–Vera equation of state (PRSVEoS). The binary interaction parameters were regressed from experimental bubble point pressures at each temperature and were found to exhibit a linear dependency on temperature. The HMDS–CO2 binary mixture was also found to exhibit Type II phase behavior. Additionally, P–T–ρ measurements for the same binary system were conducted and excess molar volumes were calculated.

Pressure–Density–Temperature Measurements of Binary Mixtures Rich in CO2 for Pipeline Transportation in the CCS Process

Often, power plants and industrial production plants—large point sources of CO2—are situated at long distances from storage locations; thus the transportation of the resulting CO2-rich streams, containing small amounts of impurities, is required from the point of capture to the storage site, making it very important to understand the thermodynamic properties of CO2-rich mixtures. The range of conditions studied in this work are of great interest for carbon capture and storage applications, in particular for pipeline transportation of CO2-mixtures. Pressure–density–temperature measurements were taken for binary mixtures of carbon dioxide with nitrogen, oxygen, or argon. Density was measured for all of the binary systems for temperatures between 273.15 K and 293.15 K and pressures between 1 MPa and 20 MPa, using a vibrating tube densimeter, Anton Paar DMA 512-HPM. The molar CO2 concentration was greater than 85 % for all mixtures tested.