Heterogeneous oxidation kinetics of acetic acid in supercritical water

The potential catalytic effect by reactor surface has been noted in a number of studies of supercritical water oxidation (SCWO) of organic compounds. In the present study, acetic acid was tested to investigate the catalytic effect of the reactor surface on its SCWO kinetics. Batch experiments were carried out over the temperature range of 400-460 degrees C at a supercritical water (SCW) density of 0.25 g/mL. The acetic acid oxidation kinetics increased with the surface to volume ratio and was affected by the oxidation state of the reactor surface. A power law rate equation was determined as follows: r = 10(9.8+/-0.7) exp[-(148.5+/-9.4)/RT][CH3COOH](1.23+/-0.03) [O-2](0.23+/-0.01). Also, the observed kinetics was consistent with a proposed heterogeneous rate model assuming a rate control by the surface reaction between adsorbed oxygen and unadsorbed acetic acid. The results of this study show that the destruction performance by SCWO may significantly vary depending upon the type and state of reactor material. Therefore, potential heterogeneous characteristics of any reaction of interest should be sufficiently taken into consideration to maintain the desired performance of the SCWO process.