Oxidative Degradation Kinetics of Acetic Acid in the Supercritical Water

Acetic acid was selected as the model compound for the experiments since it has been known as a key or a rate-controlling byproduct in the supercritical water oxidation of organic compounds. Acetic acid oxidation in supercritical water was examined at 380~420℃ and 24~30MPa,at reaction residence times up to 143 s, initial total organic carbon (TOC) from 873.5~2783.5moLL-1. The observed effects of the concentrations of TOC and oxygen on the global disappearance rates for TOC were correlated by using power-law rate expressions. Under the range of conditions studied, the reaction order of acetic acid oxidation is globally 1.28 order to concentration TOC of acetic acid and 0.4 order to oxygen and the reaction has an activation energy of 144.8kJmol-1 and a frequency factor of 5.09×1010. The results show that acetic acid can be oxidative-decomposed effectively in supercritical water, and with the increase of reaction temperature, concentration of acetate acid or oxygen excessive rate and decrease of mass-flow rate the decomposition rate of acetic acid increases and it may reach as high as 99%.