Catalyst Oxidation and Dissolution in Supercritical Water

Jennifer N. Jocz, Levi T. Thompson, Phillip E. Savage

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We use thermodynamic models to predict catalyst oxidation and dissolution in supercritical water (SCW) and use experiments to assess the viability of the models for practical SCW reaction systems and provide relative rates for these mechanisms. We examined the oxidation and dissolution of noble and transition metals, metal oxide catalyst supports, and transition metal carbides and nitrides under SCW conditions. The materials were tested in batch reactors at 400 °C for 60 min, and the SCW density was varied from 0 to 0.5 g/mL to observe the influence of the solvent properties on stability. Oxidation and dissolution were determined by comparing the initial catalyst composition and structure with those of the catalysts recovered from the reactors after exposure to the SCW environment. The gas-phase recovered from the reactors was analyzed for H2 produced from oxidation. The aqueous phase was analyzed for metals from dissolution. The ΔGrxn for oxidation and the solubility of the catalysts in SCW at the experimental conditions were calculated for comparison. Overall, the thermodynamic calculations agreed with the experimentally observed oxidation and dissolution. We conclude that thermodynamic modeling is an effective tool for efficiently screening the stability of catalytic materials in SCW and for estimating long-term hydrothermal catalyst stability.

Original languageEnglish (US)
Pages (from-to)1218-1229
Number of pages12
JournalChemistry of Materials
Volume30
Issue number4
DOIs
StatePublished - Feb 27 2018

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Dissolution
Oxidation
Catalysts
Water
Thermodynamics
Transition metals
Metals
Batch reactors
Precious metals
Catalyst supports
Nitrides
Oxides
Carbides
Screening
Solubility
Gases
Chemical analysis
Experiments

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

Cite this

Jocz, Jennifer N. ; Thompson, Levi T. ; Savage, Phillip E. / Catalyst Oxidation and Dissolution in Supercritical Water. In: Chemistry of Materials. 2018 ; Vol. 30, No. 4. pp. 1218-1229.
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Catalyst Oxidation and Dissolution in Supercritical Water. / Jocz, Jennifer N.; Thompson, Levi T.; Savage, Phillip E.

In: Chemistry of Materials, Vol. 30, No. 4, 27.02.2018, p. 1218-1229.

Research output: Contribution to journalArticle

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AU - Jocz, Jennifer N.

AU - Thompson, Levi T.

AU - Savage, Phillip E.

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N2 - We use thermodynamic models to predict catalyst oxidation and dissolution in supercritical water (SCW) and use experiments to assess the viability of the models for practical SCW reaction systems and provide relative rates for these mechanisms. We examined the oxidation and dissolution of noble and transition metals, metal oxide catalyst supports, and transition metal carbides and nitrides under SCW conditions. The materials were tested in batch reactors at 400 °C for 60 min, and the SCW density was varied from 0 to 0.5 g/mL to observe the influence of the solvent properties on stability. Oxidation and dissolution were determined by comparing the initial catalyst composition and structure with those of the catalysts recovered from the reactors after exposure to the SCW environment. The gas-phase recovered from the reactors was analyzed for H2 produced from oxidation. The aqueous phase was analyzed for metals from dissolution. The ΔGrxn for oxidation and the solubility of the catalysts in SCW at the experimental conditions were calculated for comparison. Overall, the thermodynamic calculations agreed with the experimentally observed oxidation and dissolution. We conclude that thermodynamic modeling is an effective tool for efficiently screening the stability of catalytic materials in SCW and for estimating long-term hydrothermal catalyst stability.

AB - We use thermodynamic models to predict catalyst oxidation and dissolution in supercritical water (SCW) and use experiments to assess the viability of the models for practical SCW reaction systems and provide relative rates for these mechanisms. We examined the oxidation and dissolution of noble and transition metals, metal oxide catalyst supports, and transition metal carbides and nitrides under SCW conditions. The materials were tested in batch reactors at 400 °C for 60 min, and the SCW density was varied from 0 to 0.5 g/mL to observe the influence of the solvent properties on stability. Oxidation and dissolution were determined by comparing the initial catalyst composition and structure with those of the catalysts recovered from the reactors after exposure to the SCW environment. The gas-phase recovered from the reactors was analyzed for H2 produced from oxidation. The aqueous phase was analyzed for metals from dissolution. The ΔGrxn for oxidation and the solubility of the catalysts in SCW at the experimental conditions were calculated for comparison. Overall, the thermodynamic calculations agreed with the experimentally observed oxidation and dissolution. We conclude that thermodynamic modeling is an effective tool for efficiently screening the stability of catalytic materials in SCW and for estimating long-term hydrothermal catalyst stability.

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