Experimental Study and Kinetic Modeling for Ethanol Treatment by Air Dielectric Barrier Discharges

This paper deals with the ethanol (EtOH) removal in both dry and humid air fed dielectric barrier discharges. The experimental results were compared to the predictions of a zero dimension kinetic model to elucidate the main chemical routes occurring in the plasma phase. This comparison shows that both the dissociative quenching of the nitrogen metastables and the oxidation reactions by the oxygen atom or the hydroxyl radical should be taken into account to explain the EtOH abatement in these kinds of discharges. The CH3CHOH radical seems to be the main product of the nitrogen dissociative collisions, whereas radicals issued from the alpha- and beta-H atom cleavage are the dominant ethanol oxidation by-products. These radicals account for the production of acetaldehyde, the main by-product of the ethanol/air fed discharges investigated here. Apart the complete oxidation products, i.e. carbon oxides and water, aldehydes containing up to six carbon atoms, ketones, carboxylic acids, ozone, nitrogen oxides, nitric acid and organic nitrates were found in the exhaust gas. A kinetic pathway is proposed to explain the formation of the detected by-products. Water vapour addition to the feeding gas slightly improves the EtOH removal and promotes further oxidation of the main by-products, thus enhancing the CO2 selectivity. This behaviour could be ascribed to the higher amount of hydroxyl radicals, which could boost the production of the direct precursors of CO2.