Kinetics and Products from o-Cresol Oxidation in Supercritical Water

Abstract

Dilute aqueous solutions of o-cresol(2-methylphenol) were oxidized in a tubular flow reactor at near-critical and supercritical conditions. The power-law rate expression that best correlates the kinetics of o-cresol disappearance is rate = 105.7 exp(-29700/RT)[o-creso11°~57[0210~22[H~011~44.The power-law rate expression that best correlates the experimental results for the conversion of organic carbon to C02 is rate = 106.8 exp(-34000/RT)[TOClo~34[O~lo~'3[H~O11~18. All concentrations are in moles per liter, the activation energy is in calories per mole, and the rate is in moles per liter per second. The most abundant products from o-cresol oxidation were typically phenol, 2-hydroxybenzaldehyde, 1,3-benzodioxole, indanone, CO, and C02. 2-Hydroxybenzaldehyde was the major primary product. A reanalysis of published kinetics data for the oxidation of two other ring-containing compounds (pyridine and 4-chlorophenol) in supercritical water revealed that the rate laws previously reported for these two compounds do not provide the best correlation of the experimental data. We report the new rate laws, which are similar to those for o-cresol, 2-chlorophenol, and phenol in that the global reaction orders are between 0.55 and 0.9 for the organic compounds and between 0.2 and 0.5 for oxygen.

Electrochemical treatment of phenolic waters in presence of chloride with boron-doped diamond (BDD) anodes: Experimental study and mathematical model

“…m-Cresol is classified by the US EPA as persistent, priority and toxic chemical [17]: biological degradation of cresols was achieved only at long retention times, usually in days [18]. Thermal decomposition of cresols at 460 • C resulted in the formation of toxic intermediates [19,20]. The Fenton process was successfully applied to the removal of cresols; short chain aliphatic acids were obtained as final products [17].…”

Water‐density effects on phenol oxidation in supercritical water

“…In yet another report, the oxidation rate was assumed to be independent of the water density Ž . Krajnc and Levec, 1996 . If the question of the effect of water concentration on SCWO rates is expanded to include other compounds, then the apparent conflict grows, for water has been reported to Ž increase Holgate and Tester, 1994;Li et al, 1993;Martino and Savage, 1997;Martino et al, 1995;Meyer et al, 1995; . Ž Rice et al, 1998;Smith, 1995 , decrease Dell' .…”

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

“…Corrected Values for the Conversion of o-Cresol for the SCWO Experiments Reported inMartino et al (1995) …”