Kinetic analysis for decomposition of 2,4-dichlorophenol by supercritical water oxidation

Abstract

2,4-Dichlorophenol (2,4-DCP), as a halogenated model pollutant, was decomposed by using superscriptical water oxidation (SCWO) in a batch reactor made of Hastelloy C-276. SCWO experiments for 2,4-DCP decomposition were performed in the range of 380-420 degrees C, 230-280 bar and 0.074+-0.221 mol/L H2O2. The effect of oixidant concentration in the SCWO process decreased with an increase in tempoerature of 380 degrees C. However, the role of the oxidant concentration in the SCWO process decreased with an increase in temperature; also excess oxidant played a key role in quite significantly decreasing the activiation energy of 2,4-DCP oxidation. Variation of thereaction rate by the change of pressure was negligible even at a near critical temperature. The kinetic rate for the decomposition of 2,4-DCP in the SCWO process was well described by a simple first order kinetic and global reaction rate model. From the SCWO experiments, the various intermediates identified with a GC/MS implied that the first reaction pathway for 2,4-DCP decomposition led to dimers such as dichlorophenoxyphenols, and the second led to single-ring and ring-opening products.