Production of hydroxyl radicals and removal of acetaldehyde in a photo-triggered discharge in N₂/O₂/CH₃CHO mixtures

Abstract

The evolution of the OH radical density was measured in the afterglow of a pulsed homogeneous discharge using time-resolved laser induced fluorescence, and the acetaldehyde removal was quantified using chromatography for N2/O2/CH3CHO mixtures at 460 mbar with 5% oxygen and an acetaldehyde concentration between 250 and 5000 ppm. It is shown that the radical density rapidly increases shortly after the discharge for all mixture compositions studied, although it does not contain water molecules. Afterwards this density decreases with a characteristic time much longer than the one estimated from the known reactivity of OH with CH3CHO. This emphasizes that processes other than oxidation of acetaldehyde by O-atoms play a significant role in OH radical production.