The absolute value of the hydroxyl radical was measured in the afterglow of an homogeneous photo-triggered discharge generated in N2/O2/H2O/C2H6 mixtures, using a UV absorption diagnostic synchronized with the discharge current pulse. Measurements show that OH is efficiently produced even in the absence of water vapour in the mixture, and that the radical production is closely linked to the degradation kinetic of the hydrocarbon. Experimental results for dry mixtures, both for OH and for the removal of ethane in the discharge volume, are compared with predictions of a self-consistent 0D discharge and the kinetic model. It appears that the oxidation reaction of the ethane molecule by O(3P) atoms plays a minor role. Dissociation of the hydrocarbon through quenching collisions of the nitrogen metastable states are of great importance for a low oxygen concentration value. Also, the oxidation of ethane by O(1D) cannot be neglected at high oxygen concentration. The most probable exit channel for N2 states quenching collisions by ethane is the production of ethene and hydrogen molecules. Afterwards C2H4 should be dissociated to produce H and H2. As previously suggested from the study of the OH density time evolution in relative value, the recombination of H and O atoms appears as a main process for the production of OH in transient low temperature plasmas generated in atmospheric gases at high pressure. Another important reaction is the reduction of the HO2 radical by O, this radical coming from the addition of H on the oxygen molecule. H atoms come from numerous kinetic processes, amongst which is the dissociation of ethene.
The kinetic of the hydroxyl radical is studied in N 2 /O 2 /H 2 O mixtures with small amounts of acetone or isopropyl alcohol (0.5 %). The radical density is measured in absolute value in the afterglow of a photo-triggered discharge, which generates an homogeneous transient nonequilibrium plasma, using a time resolved absorption measurement method. For dry mixtures, experimental results are compared to predictions of a self-consistent 0D discharge and kinetic model. It is shown that dissociation of the VOCs through quenching collisions of nitrogen metastable states plays an important role in the production of OH. Measurements can not be explained looking only at the oxidation of acetone or IPA by the oxygen atom. This result is reinforced by experimental results about the OH density in wet mixtures, with or without VOCs, compared to dry ones.
PACS:Plasma
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.