Reaction pathway and kinetics for uncatalyzed partial oxidation of p-xylene in sub- and supercritical water

Abstract

In sub- and supercritical water, partial oxidation of p-xylene was performed by the batch reactor without a catalyst at the conditions of 240-400 degreesC and 220-300 bar. The loaded amount of hydrogen peroxide was set to 21-100% of the stoichiometric requirements for oxygen. Conversion of p-xylene was reached over about 89.02% (in subcritical conditions) and over 99% (in supercritical conditions) within 20 min. In sub- and supercritical water, we proposed a simplified reaction pathway in parallel and the possible reaction mechanism from major products that consist of p-tolualdehyde, p-toluic acid, terephthalic acid, 4-carboxybenzaldehyde, toluene, and benzaldehyde. The yield of major products in subcritical condition was higher than that of major products in supercritical condition. The values of rate constants and activation energy were determined. The overall rates of p-xylene were divided into two equations. Also, the kinetic constants obtained from a simplified reaction pathway showed good agreement with experimental results.