Investigation of the Destruction of Concentrated N-Containing Hydrocarbons by Supercritical Water Oxidation (SCWO)

摘要

This paper presents a preliminary investigation of the supercritical water oxidation (SCWO) of dimethyl formamide (DMF) under the thermodynamically sensitive conditions of 380 - 450°C and 25 MPa using 10mM DMF (equivalent to 60mM ambient concentration). Oxidant ratio was varied from 0.28 to 1.6 times the stoichiometric value (SR), and the initial organic concentration ranged from 5mM to 30mM under reaction conditions. Residence times ranged from 0.8 to 8s. Results were presented in terms of the % Yield of key intermediates (namely trimethyl- (TMA), dimethyl- (DMA), methyl-amine (MA), and ammonia) and products (CO, CO_2 and N_2O) as function of the investigated variable. At 25 MPa there was no product formation at 380°C then began to increase at T ≥ 400°C. Initial concentration had more prominent effect on ammonia production than the amines. Oxidant ratio was more effective in the range below the stoichiometric ratio (SR), while it was not advantageous for the values much above 1.1SR. In terms of the reaction pathway, TMA seemed to be the first intermediate, followed by DMA then MA. Ammonia followed subsequently. Hydrolysis seemed to be take place in the absence of oxygen. These intermediates help identifying the reaction pathway and the sequence of bond breakage. Nitrates were not detected as temperatures were too low for nitrate production. This preliminary study aims to lend insight for detailed investigation of the system kinetics, which is underway.