Vapor+liquid equilibrium of water, carbon dioxide, and the binary system, water+carbon dioxide, from molecular simulation (original) (raw)
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The Journal of Physical Chemistry, 1995
We present a simple site-based intermolecular potential model for carbon dioxide (the EPM model). It uses point charges and Lennard-Jones interactions centered at each atom. The model predicts a coexistence curve and critical properties quite close to the experimental values. The EPM model predicts a critical temperature of 313.4 f 0.7 K compared with an experimental critical temperature of 304 K. By rescaling the potential parameters of the EPM model to obtain the model denoted as "EPMT', we more accurately reproduce the liquid-vapor coexistence curve. A flexible EPM model with rigid bonds, but a flexible angle exhibits identical coexistence properties to within the sensitivity of our calculations.
The Journal of Physical Chemistry B, 2002
The high-pressure phase equilibrium of the system carbon dioxide-methanol-water was studied by molecular simulation at temperatures near the critical temperature of carbon dioxide. The system was modeled by multisite Lennard-Jones plus Coulomb intermolecular potentials with common combining rules for unlike site interactions. Good agreement was observed between experimental and simulated phase equilibrium data. Reasonably accurate predictions were obtained for the two-phase liquid-liquid and three-phase liquid-liquidvapor coexistences.
Atomistic computer simulations for thermodynamic properties of carbon dioxide at low temperatures
Energy Conversion and Management, 2002
Investigation into the volumetric and energetic properties of two atomistic models mimicking carbon 9 dioxide geometry and quadrupole moment covered the liquid-vapor coexistence curve. Thermodynamic 10 integration over a polynomial path was used to calculate free energy. Computational results showed that 11 the model using GROMOS Lennard-Jones parameters was unsuitable for bulk or interface CO 2 simula-12 tions. On the other hand, the model with potential fitted to reproduce only the correct density-pressure 13 relationship in the supercritical region proved to yield the correct enthalpy of vaporization and free energy 14 of liquid CO 2 in the low temperature region. NPT molecular dynamics was used to estimate the water-CO 2 15 interfacial tension and solubilities at 276 K for a liquid-liquid system at 100 and 300 atm. Ó 2002 Pub-16 lished by Elsevier Science Ltd.
Fluid Phase Equilibria, 2018
Vapor-liquid equilibrium measurements for the binary system CO 2 +CO are reported at 253, 273, 283 and 298 K, with estimated standard uncertainties of maximum 9 mK in temperature, maximum 3 kPa in pressure, and maximum 0.001 in the mole fractions of the phases in the mixture critical regions, and 0.0003 in the mole fractions outside the critical regions. These measurements are compared with existing data. Although some data exist, there are little trustworthy literature data around critical conditions, and the measurements in the present work indicate a need to revise the parameters of existing models. The data in the present work have significantly less scatter than most of the literature data, and range from the vapor pressure of pure CO 2 to close to the mixture critical point pressure at all four temperatures. With the measurements in the present work, the data situation for the CO 2 +CO system is improved, enabling development of better equations of state for the system. A scaling law model is fitted to the critical region data of each isotherm, and high accuracy estimates for the critical composition and pressure are found. The Peng-Robinson EOS with the alpha correction by Mathias and Copeman, the mixing rules by Wong and Sandler, and the NRTL excess Gibbs energy model is fitted to the data in the present work.
The Journal of Chemical Physics, 2013
In this work the solid-fluid equilibrium for carbon dioxide (CO 2 ) has been evaluated using Monte Carlo simulations. In particular the melting curve of the solid phase denoted as I, or dry ice, was computed for pressures up to 1000 MPa. Four different models, widely used in computer simulations of CO 2 were considered in the calculations. All of them are rigid non-polarizable models consisting of three Lennard-Jones interaction sites located on the positions of the atoms of the molecule, plus three partial charges. It will be shown that although these models predict similar vapor-liquid equilibria their predictions for the fluid-solid equilibria are quite different. Thus the prediction of the entire phase diagram is a severe test for any potential model. It has been found that the Transferable Potentials for Phase Equilibria (TraPPE) model yields the best description of the triple point properties and melting curve of carbon dioxide. It is shown that the ability of a certain model to predict the melting curve of carbon dioxide is related to the value of the quadrupole moment of the model. Models with low quadrupole moment tend to yield melting temperatures too low, whereas the model with the highest quadrupole moment yields the best predictions. That reinforces the idea that not only is the quadrupole needed to provide a reasonable description of the properties in the fluid phase, but also it is absolutely necessary to describe the properties of the solid phase.
Binary mixtures of supercritical carbon dioxide with methanol. A molecular dynamics simulation study
Chemical Physics Letters, 2003
Molecular dynamics simulations were performed on supercritical mixtures of MeOH in CO 2 with MeOH mole fractions in the range 0.0939-0.1173 at 323.15 K and pressure from 9.952 to 16.96 MPa. It is found that the EPM2 model of CO 2 with the J2 model of MeOH predicts the experimental pVT relationship of the fluid in this region quite good. Furthermore, the structural and hydrogen-bonding data obtained reveal the existence of MeOH type aggregates in the mixed fluid. The latter finding was found to be in agreement with conclusions from previous experimental studies on this system.
Fluid Phase Equilibria, 1999
High-pressure vapor-liquid equilibria for the binary carbon dioxide-2-methyl-1-butanol and carbon dioxide-2-methyl-2-butanol systems were measured at 313.2 K. The phase equilibrium apparatus used in this work is of the circulation type in which the coexisting phases are recirculated, on-line sampled, and analyzed. The critical pressure and corresponding mole fraction of carbon dioxide for the binary carbon dioxide-2-methyl-1-butanol system at 313.2 K were found to be 8.36 MPa and 0.980, respectively. The critical point of the binary carbon dioxide-2-methyl-2-butanol was also found 8.15 MPa and 0.970 mole fraction of carbon dioxide. In addition, the phase equilibria of the ternary carbon dioxide-2-methyl-1-butanol-water and carbon dioxide-2-methyl-2butanol-water systems were measured at 313.2 K and several pressures. These ternary systems showed the liquid-liquid-vapor phase behavior over the range of pressure up to their critical point. The binary equilibrium Ž. Ž. data were all reasonably well correlated with the Redlich-Kwong RK , Soave-Redlich-Kwong SRK , Ž. Ž. Peng-Robinson PR , and Patel-Teja PT equations of state with eight different mixing rules the van der Ž. Waals, Panagiotopoulos-Reid P & R , and six Huron-Vidal type mixing rules with UNIQUAC parameters.
Journal of Molecular Liquids, 2018
The structural and thermodynamic properties of Na +-Clion-pair association in water-CO2 binary mixtures in supercritical conditions for infinitely dilute solutions are studied using constrained molecular dynamics simulations over a wide range of compositions. It is found that solvation structure varies dramatically with the solvent composition. Contact ion pairs (CIPs) are found to be more stable than all other configurations as seen from the potentials of mean force (PMFs). PMFs of the NaCl ion pair in pure CO2 look almost like the pair potential between the ion pair. Stabilities of CIPs increase with increase in the mole fraction of CO2. An increment in the average number of hydrogen bonds with an increase in the mole fraction of H2O in the bulk as well as in the solvation shell of the ions is observed. Ion-pair association in aqueous CO2 mixtures in supercritical conditions is found to be endothermic and driven by entropy. Preferential solvation analysis shows that both Na + and Clions are preferentially solvated by water and even a small percentage of water in the mixture prevents CO2 molecules from entering the first solvation shell of ions due to the strong hydrophilicity of the ions.
Fluid Phase Equilibria, 2016
Accurate thermophysical data for the CO 2-rich mixtures relevant for carbon capture, transport and storage (CCS) are essential for the development of the accurate equations of state (EOS) and models needed for the design and operation of the processes within CCS. Vapor-liquid equilibrium measurements for the binary system CO 2 +O 2 are reported at 218, 233, 253, 273, 288 and 298 K, with estimated standard uncertainties of maximum 8 mK in temperature, maximum 3 kPa in pressure, and maximum 0.0031 in the mole fractions of the phases in the mixture critical regions, and 0.0005 in the mole fractions outside the critical regions. These measurements are compared with existing data. Although some data exists, there are little trustworthy literature data around critical conditions, and the measurements in the present work indicate a need to revise the parameters of existing models. The data in the present work has significantly less scatter than most of the literature data, and range from the vapor pressure of pure CO 2 to close to the mixture critical point pressure at all six temperatures. With the measurements in the present work, the data situation for the CO 2 +O 2 system is significantly improved, forming the basis to develop better equations of state for the system. A scaling law model is fitted to the critical region data of each isotherm, and high accuracy estimates for the critical composition and pressure are found. The Peng-Robinson EOS with the alpha correction by Mathias and Copeman, the mixing rules by Wong and Sandler, and the NRTL excess Gibbs energy model is fitted to the data in the present work, with a maximum absolute average deviation of 0.01 in mole fraction.