Effect of water density on methanol oxidation kinetics in supercritical water

Jeffrey T. Henrikson, Corey R. Grice, Phillip E. Savage

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

We oxidized methanol in supercritical water at 500°C to explore the influence of the water concentration (or density) on the kinetics. The rate increased as the water concentration increased from 1.8 to 5.7 mol/L. This effect of water density on the kinetics observed experimentally was quantitatively reproduced by a previously validated mechanism-based, detailed chemical kinetics model. In this model, reactions of OH radicals with methanol were the fastest methanol removal steps. The rates of these removal steps increased with water density at 500°C because the OH radical concentration increased. The OH radical concentration increased with density because the rates of the steps H + H 2O = OH + H 2 and CH 3 + H 2O = OH + CH 4, which produce OH radicals, increased. Thus, the main role of water in accelerating methanol oxidation kinetics at 500°C is as a hydrogen donor to a radical (R) in steps such as R + H 2O = OH + RH. This system provides a striking example of SCW being involved on the molecular level in the free-radical oxidation as a reactant in elementary steps.

Original languageEnglish (US)
Pages (from-to)3627-3632
Number of pages6
JournalJournal of Physical Chemistry A
Volume110
Issue number10
DOIs
StatePublished - Mar 16 2006

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Methanol
methyl alcohol
Oxidation
oxidation
Kinetics
Water
kinetics
water
methylidyne
Reaction kinetics
free radicals
Free Radicals
Hydrogen
reaction kinetics
hydrogen

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

Cite this

Henrikson, Jeffrey T. ; Grice, Corey R. ; Savage, Phillip E. / Effect of water density on methanol oxidation kinetics in supercritical water. In: Journal of Physical Chemistry A. 2006 ; Vol. 110, No. 10. pp. 3627-3632.
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Effect of water density on methanol oxidation kinetics in supercritical water. / Henrikson, Jeffrey T.; Grice, Corey R.; Savage, Phillip E.

In: Journal of Physical Chemistry A, Vol. 110, No. 10, 16.03.2006, p. 3627-3632.

Research output: Contribution to journalArticle

TY - JOUR

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AU - Henrikson, Jeffrey T.

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AU - Savage, Phillip E.

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N2 - We oxidized methanol in supercritical water at 500°C to explore the influence of the water concentration (or density) on the kinetics. The rate increased as the water concentration increased from 1.8 to 5.7 mol/L. This effect of water density on the kinetics observed experimentally was quantitatively reproduced by a previously validated mechanism-based, detailed chemical kinetics model. In this model, reactions of OH radicals with methanol were the fastest methanol removal steps. The rates of these removal steps increased with water density at 500°C because the OH radical concentration increased. The OH radical concentration increased with density because the rates of the steps H + H 2O = OH + H 2 and CH 3 + H 2O = OH + CH 4, which produce OH radicals, increased. Thus, the main role of water in accelerating methanol oxidation kinetics at 500°C is as a hydrogen donor to a radical (R) in steps such as R + H 2O = OH + RH. This system provides a striking example of SCW being involved on the molecular level in the free-radical oxidation as a reactant in elementary steps.

AB - We oxidized methanol in supercritical water at 500°C to explore the influence of the water concentration (or density) on the kinetics. The rate increased as the water concentration increased from 1.8 to 5.7 mol/L. This effect of water density on the kinetics observed experimentally was quantitatively reproduced by a previously validated mechanism-based, detailed chemical kinetics model. In this model, reactions of OH radicals with methanol were the fastest methanol removal steps. The rates of these removal steps increased with water density at 500°C because the OH radical concentration increased. The OH radical concentration increased with density because the rates of the steps H + H 2O = OH + H 2 and CH 3 + H 2O = OH + CH 4, which produce OH radicals, increased. Thus, the main role of water in accelerating methanol oxidation kinetics at 500°C is as a hydrogen donor to a radical (R) in steps such as R + H 2O = OH + RH. This system provides a striking example of SCW being involved on the molecular level in the free-radical oxidation as a reactant in elementary steps.

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