Supercritical Water Oxidation Kinetics, Products, and Pathways for CH3- and CHO-Substituted Phenols

Christopher J. Martino, Phillip E. Savage

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

Phenols bearing -CH3 and -CHO substituents were oxidized in supercritical water at 460°C and 250 atm. Experiments with each compound explored the effects of the reactor residence time and the concentrations of the phenolic compound and oxygen on the reaction rate. These experimental data were fit to global, power-law rate expressions. The resulting rate laws showed that the reactivity of the different isomers at 460°C was in the order of ortho > para > meta for both compounds. Moreover, the CHO-substituted phenol was more reactive than the analogous CH3-substituted phenol, and all of these substituted phenols were more reactive than phenol itself under supercritical water oxidation conditions. Identifying and quantifying the products of incomplete oxidation allowed us to assemble a general reaction network for the oxidation of cresols in supercritical water. This network comprises three parallel primary paths. One path leads to phenol, a second path leads to a hydroxybenzaldehyde, and the third path leads to ring-opening products. The hydroxybenzaldehyde reacts through two parallel paths, which lead to phenol and to ring-opening products. Phenol also reacts via two parallel paths, but these lead to phenol dimers and ring-opening products. The dimers are eventually converted to ring-opening products, and the ring-opening products are ultimately converted to CO2. The relative rates of the different paths in the reaction network are strong functions of the location of the substituent on the phenolic ring.

Original languageEnglish (US)
Pages (from-to)1391-1400
Number of pages10
JournalIndustrial and Engineering Chemistry Research
Volume36
Issue number5
StatePublished - May 1 1997

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Phenols
Phenol
phenol
oxidation
kinetics
Oxidation
Kinetics
Water
water
Dimers
Cresols
Bearings (structural)
Oxygen Compounds
product
Isomers
Reaction rates
phenolic compound
reaction rate
residence time
power law

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

Cite this

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abstract = "Phenols bearing -CH3 and -CHO substituents were oxidized in supercritical water at 460°C and 250 atm. Experiments with each compound explored the effects of the reactor residence time and the concentrations of the phenolic compound and oxygen on the reaction rate. These experimental data were fit to global, power-law rate expressions. The resulting rate laws showed that the reactivity of the different isomers at 460°C was in the order of ortho > para > meta for both compounds. Moreover, the CHO-substituted phenol was more reactive than the analogous CH3-substituted phenol, and all of these substituted phenols were more reactive than phenol itself under supercritical water oxidation conditions. Identifying and quantifying the products of incomplete oxidation allowed us to assemble a general reaction network for the oxidation of cresols in supercritical water. This network comprises three parallel primary paths. One path leads to phenol, a second path leads to a hydroxybenzaldehyde, and the third path leads to ring-opening products. The hydroxybenzaldehyde reacts through two parallel paths, which lead to phenol and to ring-opening products. Phenol also reacts via two parallel paths, but these lead to phenol dimers and ring-opening products. The dimers are eventually converted to ring-opening products, and the ring-opening products are ultimately converted to CO2. The relative rates of the different paths in the reaction network are strong functions of the location of the substituent on the phenolic ring.",
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Supercritical Water Oxidation Kinetics, Products, and Pathways for CH3- and CHO-Substituted Phenols. / Martino, Christopher J.; Savage, Phillip E.

In: Industrial and Engineering Chemistry Research, Vol. 36, No. 5, 01.05.1997, p. 1391-1400.

Research output: Contribution to journalArticle

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