This paper offers potential explanations for the inhibition and acceleration by water of phenol supercritical water oxidation rates. We report new experimental data at 380-465 °C that reveals the effect of water density on the oxidation reaction. At 380 and 400 °C, increasing the water density increases phenol conversion. At 442 and 465 °C, the phenol conversion decreases as water concentration increases from 2 to 9 mol/L. At 420 °C, the phenol conversion decreases as water density increases from 2 to 8 mol/L, but conversion increases as water density increases from 8 to 13 mol/L. We present new data and analyses showing that ion-ion reactions are not responsible for the observed effects. These effects are, however, quantitatively consistent with a model based on the existence of two competing rate-determining steps. In one possible scenario, one step has an increase in polarity along the reaction coordinate and the other has a decrease. It is also plausible that diffusion limitations at high temperatures and the increase in the dissociation of phenol into phenolate ions may play a part in water's effect on phenol SCWO kinetics.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering