Fugacity coefficients for free radicals in dense fluids: HO<sub>2</sub> in supercritical water

Mizan, Tahmid I.; Savage, Phillip E.; Ziff, Robert M.

doi:10.1002/aic.690430517

Cited by 13 publications

(15 citation statements)

References 49 publications

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“…First, it is a simple model that is easily implemented. Second, the TJE model is the only flexible model that has been tested extensively for simulating SCW [29][30][31][32][33][34] and for which the critical point has been determined. 29 The TJE model describes the interaction between water molecules as a sum of electrostatic and Lennard-Jones interactions:…”

Section: Methodsmentioning

confidence: 99%

“…The Lennard-Jones parameters for H 2 O 2 and OH were taken from the values used in a previous molecular dynamics simulation of HO 2 in SCW. 30 We used the Lorentz-Berthelot combining rules for Lennard-Jones parameters of dissimilar atom types. We used a weighted nonlinear regression routine to fit eq 8 to the DFT interaction energies of the various configurations of both H 2 O 2 -water and OH-water dimers.…”

Section: Potential Energy Surfacementioning

confidence: 99%

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Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium

Akiya

Savage

2000

J. Phys. Chem. A

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Recent experiments showed that the rate of dissociation of H 2 O 2 in supercritical water (SCW) is density dependent and faster than its high-pressure limit rate in the gas phase. These observations suggest that water molecules play a role in this reaction in SCW. We performed density functional theory (DFT) calculations and molecular dynamics simulations to investigate the role of water in H 2 O 2 dissociation. We generated the potential energy surface for H 2 O 2 -water and OH-water complexes by DFT calculations to determine the parameters in an analytical intermolecular potential model, which was subsequently employed in the molecular dynamics simulations. These simulations were performed at different water densities. They provided the structural properties (pair correlation functions) of dilute mixtures of H 2 O 2 and OH in SCW, from which we were able to calculate the number of excess solvent molecules and partial molar volumes for each solute. We used the partial molar volumes for H 2 O 2 and OH to calculate the reaction volume for H 2 O 2 ) 2OH and thereby determined the density dependence of the equilibrium constant for this reaction. The results show that at the reduced temperature of T r ) 1.15 (695 K) the equilibrium constant for H 2 O 2 dissociation is a function of the water density. The mean value of the equilibrium constant changes by less than 5% between 0.25 < F r < 1, but it decreases by an order of magnitude between 1 < F r < 2.75. Knowing the density dependence of the equilibrium constant for this reaction will allow more accurate mechanism-based models of supercritical water oxidation chemistry to be developed. The computational approach applied herein for H 2 O 2 dissociation is general and can be profitably employed to discern the density dependence of the equilibrium constant of any elementary reaction in SCW. There is currently no experimental approach that will provide this information for reactions involving free radicals.

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Section: Methodsmentioning

confidence: 99%

Section: Potential Energy Surfacementioning

confidence: 99%

Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium

Akiya

Savage

2000

J. Phys. Chem. A

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“…In general, as p→0, →1, therefore, the fugacity coefficient can be set to 1 at low pressures. However, it differs from unity when the pressure increases [48].…”

Section: Supercritical Conversion Of Biomass 197mentioning

confidence: 96%

“…In a closed vessel, the solubility of gases increases after reaching a minimum point at higher temperatures and the gases become completely miscible with water under the supercritical conditions. Sabirzyanov et al [48] describe the solubility behaviour of carbon dioxide with increasing temperature and pressure (Figure 9.1). The solubility decreases with increasing temperature at first, but carbon dioxide starts to become more soluble at higher temperatures, especially at higher pressures.…”

Section: The Solubilities Of Gases In the Supercritical Watermentioning

confidence: 99%

Supercritical Conversion of Biomass

Akgül

2014

Transformation of Biomass

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“…The computational studies of oxidation kinetics in supercritical water had been published. − Traditional force fields are not well suited to describe the process of chemical bond breaking and forming, and ab initio molecular dynamics (MD) based on density functional theory (DFT) methods are typically used for those purposes . However, ab initio MD is computationally expensive, and significant effort was extended to develop force field alternatives.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Study of Combustion Reactions in a Supercritical Environment. Part 1: Carbon Dioxide and Water Force Field Parameters Refitting and Critical Isotherms of Binary Mixtures

2016

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The oxy-fuel–carbon dioxide combustion process is expected to drastically increase the energy efficiency and enable easy carbon sequestration. In this technology, the combustion products (carbon dioxide and water) are used to control the temperature and nitrogen is excluded from the combustion chamber, so that nitrogen oxide pollutants do not form. Therefore, in oxy-combustion, carbon dioxide and water are present in large concentrations in their transcritical state and may play an important role in kinetics. The computational chemistry methods may assist in understanding these effects, and molecular dynamics with a reactive force field (ReaxFF) seems to be a suitable tool for such a study. Here, we investigate applicability of the ReaxFF to describe the critical phenomena in carbon dioxide and water and find that several non-bonding parameters need adjustment. We report the new parameter set, capable of reproducing the critical temperatures and pressures. The critical isotherms of CO2/H2O binary mixtures are computationally studied here for the first time, and their critical parameters are reported.

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Fugacity coefficients for free radicals in dense fluids: HO₂ in supercritical water

Cited by 13 publications

References 49 publications

Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium

Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium

Supercritical Conversion of Biomass

Molecular Dynamics Study of Combustion Reactions in a Supercritical Environment. Part 1: Carbon Dioxide and Water Force Field Parameters Refitting and Critical Isotherms of Binary Mixtures

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Fugacity coefficients for free radicals in dense fluids: HO2 in supercritical water

Cited by 13 publications

References 49 publications

Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium

Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium

Supercritical Conversion of Biomass

Molecular Dynamics Study of Combustion Reactions in a Supercritical Environment. Part 1: Carbon Dioxide and Water Force Field Parameters Refitting and Critical Isotherms of Binary Mixtures

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Fugacity coefficients for free radicals in dense fluids: HO₂ in supercritical water