Regular Article

Dissociation against oxidation kinetics for the conversion of VOCs in non-thermal plasmas of atmospheric gases^*

Laboratoire de Physique des Gaz et des Plasmas, Université Paris-Sud, CNRS, Université Paris-Saclay, 91045 Orsay cedex, France

^a e-mail: stephane.pasquiers@u-psud.fr

Received: 24 November 2015
Revised: 18 January 2016
Accepted: 25 January 2016
Published online: 8 August 2016

Abstract

The kinetics of four volatile organic compounds (VOCs) (propene, propane, acetaldehyde, acetone) were studied in plasmas of atmospheric gases using a photo-triggered discharge (homogeneous plasma) or a dielectric barrier discharge (filamentary plasma). It was shown for the homogeneous plasma that quenchings of nitrogen metastable states, A³Ʃ⁺_u and the group of singlets a' ¹Ʃ^-_u, a ¹Π_g and w ¹∆_u, are important processes for the decomposition of such molecules. Recent measurements of the H₂ concentration produced in the N₂/C₃H₆ mixture emphasize that the hydrogen molecule can be an exit route for propene dissociation. It is also found that H₂ and CO molecules are efficiently produced following the dissociation of CH₃COCH₃ and the subsequent chemical reactivity induced by radicals coming from acetone. Addition of oxygen to a N₂/VOC mixture can change drastically the kinetics. However, the quenching processes of N₂ metastables by the VOC are always present and compete with oxidation reactions for the conversion of the pollutant. At low temperature, oxidations by O or by OH are not always sufficiently effective to induce an increase of the molecule decomposition when oxygen is added to the mixture. In particular, the presence of O₂ has a detrimental effect on the acetone removal. Also, as evidenced for acetaldehyde and propane, some kinetic analogies appear between filamentary and homogeneous plasmas.