Mechanisms of Decomposition of Organic Compounds by Water Plasmas at Atmospheric Pressure

Abstract

The decomposition of acetone, methanol, and ethanol by water plasmas at atmospheric pressure has been investigated using a direct current (DC) discharge. At torch powers of 910–1050 W and organic compound concentrations of 1–10 mol %, the decomposition rate of methanol was over 99.99%, while those of acetone and/or ethanol was 96–99%. The concentrations of H2 obtained were 65–71% in the effluent gas and the removal efficiencies of 90–95% for total organic carbon (TOC) were achieved in liquid effluent for any compounds by pyrolysis. Over 50 wt % carbon in acetone or ethanol fed as the plasma supporting gas was transformed into soot, while the soot formation was negligible during methanol decomposition. On the basis of the experimental results, the mechanisms of decomposition of organic compounds in water plasmas were proposed and the mechanism of soot formation was clarified for the first time.

Thermal Plasma Decomposition of Fluorinated Greenhouse Gases

“…Therefore, the water plasma system converts fluorinated compounds into environmentally benign and stable materials effectively with a high thermal efficiency of the torch and abundant radicals in the plasma flame. Furthermore, the water plasma torch has an advantage of direct use of a liquid waste as plasma supporting material instead of pure water [63][64][65]. For these reasons, the compact and energy efficient water plasma system can be effectively applied to treat a variety of waste including fluorinated compounds.…”

Characteristics of water thermal plasma for biomass utilization system

“…This is because decomposition energy of D-glucose was required in the case of D-glucose solution. Although the temperature was decreased with injection of D-glucose solution, the arc temperature was sufficiently high The time constant at D-glucose decomposition process was estimated to be on millisecond order (Narengerile, 2011). This estimation suggests that the influence of arc fluctuation on the D-glucose decomposition is negligible.…”

Decomposition of Glycerine by Water Plasmas at Atmospheric Pressure

“…The glycerine decomposition mechanisms as well as the intermediate behaviors were different from decomposition of organic compounds such as phenol [13] or acetone [18] by water plasmas. The negligible amount of soot generation from glycerine decomposition even at a low arc current indicated that a stronger oxidative atmosphere was formed which can enhance CH and CH 3 oxidation by OH radicals.…”

“…A simplified decomposition reaction mechanism of glycerine solution in water plasmas was proposed on the basis of the results of the experiment and information from the literature [13,14,18] , as shown in Fig. 9.…”

“…In contrast, a stronger reductive atmosphere was formed during decomposition of phenol and acetone, leading to incomplete oxidation of the intermediate organic species such as C 6 H 5 O, CH 3 , and CH 2 . Therefore, those intermediate species generated other by-products or soot in the low-temperature region [13,14,18] .…”