Thermal abatement of nitrogen-containing hydrocarbons by non-catalytic supercritical water oxidation (SCWO)

This work investigated the destruction of N-containing hydrocarbons namely DBU (1,8-diazobicyclo[ 5.4.0]undec-7-ene) and DMF (dimethyl formamide) by supercritical water oxidation (SCWO), using hydrogen peroxide as oxidant. Reactions were conducted under temperatures of (400–650 C), pressures of (50–250 bars), oxidant stoichiometric ratio SR (0.9–12), initial concentrations of organics (0.1–8.4 mM) and residence time s (6– 17 s). Reactions took place in a plug flow continuous reactor and the results were presented in terms of the % removal (of TOC and the organic compound), C-fraction and N-fraction; all plotted as function of the above system conditions. Also, GC-MS analysis for DMF was conducted. Percent removal increased with temperature and complete organic- and[90% TOC removal, was obtained at 500 and 600 C for DMF and DBU respectively. Conversion increased with the oxidant SR, residence time and initial organic concentration. Pressure affected conversion in the sub- and near-critical conditions but not in the supercritical region, yet an initial value of 150 bar was required to start the reaction. Pseudo first order-, integral power rate law-, and power law models successfully described the kinetic data; and the reaction constants for each model and energy of activation were evaluated.