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

Naoko Akiya, Phillip E. Savage

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Recent experiments showed that the rate of dissociation of H2O2 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 H2O2 dissociation. We generated the potential energy surface for H2O2-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 H2O2 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 H2O2 and OH to calculate the reaction volume for H2O2 = 2OH and thereby determined the density dependence of the equilibrium constant for this reaction. The results show that at the reduced temperature of Tr = 1.15 (695 K) the equilibrium constant for H2O2 dissociation is a function of the water density. The mean value of the equilibrium constant changes by less than 5% between 0.25 < ρr < 1, but it decreases by an order of magnitude between 1 < pr < 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 H2O2 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.

Original languageEnglish (US)
Pages (from-to)4433-4440
Number of pages8
JournalJournal of Physical Chemistry A
Volume104
Issue number19
DOIs
StatePublished - Jan 1 2000

Fingerprint

hydrogen peroxide
Hydrogen Peroxide
dissociation
Water
Equilibrium constants
water
Density (specific gravity)
Density functional theory
Molecular dynamics
Free radical reactions
molecular dynamics
density functional theory
Potential energy surfaces
Molecules
simulation
Computer simulation
free radicals
Structural properties
molecules
solutes

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

Cite this

@article{18d65fee6e5c4ee2b3f080c2162ef815,
title = "Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium",
abstract = "Recent experiments showed that the rate of dissociation of H2O2 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 H2O2 dissociation. We generated the potential energy surface for H2O2-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 H2O2 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 H2O2 and OH to calculate the reaction volume for H2O2 = 2OH and thereby determined the density dependence of the equilibrium constant for this reaction. The results show that at the reduced temperature of Tr = 1.15 (695 K) the equilibrium constant for H2O2 dissociation is a function of the water density. The mean value of the equilibrium constant changes by less than 5{\%} between 0.25 < ρr < 1, but it decreases by an order of magnitude between 1 < pr < 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 H2O2 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.",
author = "Naoko Akiya and Savage, {Phillip E.}",
year = "2000",
month = "1",
day = "1",
doi = "10.1021/jp9920996",
language = "English (US)",
volume = "104",
pages = "4433--4440",
journal = "Journal of Physical Chemistry A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "19",

}

Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium. / Akiya, Naoko; Savage, Phillip E.

In: Journal of Physical Chemistry A, Vol. 104, No. 19, 01.01.2000, p. 4433-4440.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Effect of Water Density on Hydrogen Peroxide Dissociation in Supercritical Water. 1. Reaction Equilibrium

AU - Akiya, Naoko

AU - Savage, Phillip E.

PY - 2000/1/1

Y1 - 2000/1/1

N2 - Recent experiments showed that the rate of dissociation of H2O2 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 H2O2 dissociation. We generated the potential energy surface for H2O2-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 H2O2 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 H2O2 and OH to calculate the reaction volume for H2O2 = 2OH and thereby determined the density dependence of the equilibrium constant for this reaction. The results show that at the reduced temperature of Tr = 1.15 (695 K) the equilibrium constant for H2O2 dissociation is a function of the water density. The mean value of the equilibrium constant changes by less than 5% between 0.25 < ρr < 1, but it decreases by an order of magnitude between 1 < pr < 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 H2O2 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.

AB - Recent experiments showed that the rate of dissociation of H2O2 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 H2O2 dissociation. We generated the potential energy surface for H2O2-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 H2O2 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 H2O2 and OH to calculate the reaction volume for H2O2 = 2OH and thereby determined the density dependence of the equilibrium constant for this reaction. The results show that at the reduced temperature of Tr = 1.15 (695 K) the equilibrium constant for H2O2 dissociation is a function of the water density. The mean value of the equilibrium constant changes by less than 5% between 0.25 < ρr < 1, but it decreases by an order of magnitude between 1 < pr < 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 H2O2 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.

UR - http://www.scopus.com/inward/record.url?scp=0000650041&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000650041&partnerID=8YFLogxK

U2 - 10.1021/jp9920996

DO - 10.1021/jp9920996

M3 - Article

AN - SCOPUS:0000650041

VL - 104

SP - 4433

EP - 4440

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 19

ER -