Kinetics of Wet Oxidation of Propionic and 3-Hydroxypropionic Acids

Abstract

Oxidation of aqueous solutions of 3-hydroxypropionic (3-HPA) and propionic acids (PA) was studied in a titanium high-pressure reactor at 280−310 °C using oxygen partial pressures between 10 and 45 bar. Oxidation of both acids was found to obey first-order kinetic with respect to their concentrations as well as to their lumped TOC concentrations. Oxidation rate revealed a half order dependence with respect to oxygen for oxidation of both acids. In the case of 3-HPA oxidation, the activation energy was found to be 135 kJ/mol, and it was 140 kJ/mol when lumped concentration TOC was used. The activation energy for PA oxidation is 150 kJ/mol, and it is slightly higher, 158 kJ/mol, for TOC reduction. Almost complete conversion of 3-HPA was achieved at 300 °C after 1 h, whereas 95% conversion of PA acid was obtained at 310 °C after 3 h. During oxidation of 3-HPA, 3-oxopropionic and acetic acids were identified as intermediate products. Oxidation of PA yielded acetic and formic acids as intermediates; at oxygen p...