Studies of Ionic and Free Radical Reactions in Supercritical Water
Abstract
The goal of this project was to study the kinetics of fundamental free radical and ionic reactions in supercritical water (SCW). The first finding is that true diffusion controlled reactions are not impeded or enhanced by density inhomogeneities. This is based on a study of anthracene triplet-triplet annihilation in SCW at temperatures to 450 deg C. A second finding, based on a study of the reaction of xanthenium cations with amylamine, is that the rates of ion-neutral reactions in subcritical water follow simple Arrhenius behavior and can be easily extrapolated from ambient temperature measurements. The third finding is that the rate of hydroxyl radical addition to an aromatic ring in subcritical and supercritical water is well below the diffusion controlled limit and it is decidedly non-Arrhenius, with a rapid increase at temperatures above 300 deg C. This was determined by a pulse radiolysis study of the addition of hydroxyl radical to nitrobenzene at 250 bar and temperatures between 25 deg C and 390 deg C. We have been able to model this unusual behavior with a three-step mechanism that successfully predicts the rapid increase in the rate at supercritical temperatures. These studies provide fundamental kinetics upon which one can base modeling of supercritical water oxidation processes with elementary reactions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 26, 2001
- Accession Number
- ADA395438
Entities
People
- Joan F. Brennecke
Organizations
- University of Notre Dame