Light hydrocarbons conversion in a pulsed DBD: effect of the temperature Olivier Aubry, Vanessa Sarron, Ahmed Khacef and Jean-Marie Cormier GREMI, Polytech’Orléans, Université d’Orléans - CNRS (UMR6606), GDR n°2495, France Abstract: Enhancement of light hydrocarbon conversion in diluting air can be easily per- formed using a Dielectric Barrier Discharges reactor at atmospheric pressure with a moderate heating. A heating (up to 800 K) leads to a decrease of the energetic cost keeping a high con- version rate. This paper presents results obtained for ethane or propane diluted with air. Main produced species are CO and CO 2 . Keywords: DBD, atmospheric pressure, volatile organic compounds, temperature, ethane, propane. 1. Introduction Non-thermal plasma (NTP) discharges are extensively studied for the removal of volatile organic compounds (VOCs') contained in air at low concentration levels [1-3]. We showed in previous papers [4,5] that a non-combined NTP process can be very interesting to promote VOCs' treatment. Conversion was performed using a heated DBD reactor which can lead to a decreasing of the total energy cost in comparison to a DBD treatment at 300 K because thermal energy added to the plasma treatment. Thus, the total power to achieve a high conversion rate (close to 100%) expressed from the sum “added thermal power + DBD electrical power” is moved towards lower values than the alone DBD energy density injected at room temperature to convert efficiently pollutant. This paper presents results on light hydrocarbons decomposition (ethane and propane) using a pulsed high voltage Dielectric Barrier Discharges (DBD) reactor. Experiments have been carried out on in diluting air at atmospheric pressure. Effects of the plasma and the temperature are clearly identified on the pollutant conversion and on produced species. An increase of the temperature leads to different kinetic pathways. Temperature can be adjusted to modify produced species. Plasma produces active species (O-atom, OH radical) which are efficient to convert VOCs’ [4]. 2. Experimental The experimental plasma reactor used is a wire to cylinder DBD type [4-7]. The active volume plasma is about 16 cm 3 . The DBD reactor is set in an oven which allows a heating up to 800 K in this study. The pulsed voltage generator used delivers high voltages (up to 30 kV) into 80 ns (FWHM) and short rise time (40 ns) from charging voltage, U ch (5 kV). Pulse repetition rates range, f, studied is varying between 15 and 200 Hz. The inlet gas mixtures are ethane and propane diluted in dry air (synthetic mixture of N 2 and O 2 ) at atmospheric pressure. Gas mixtures are injected through mass flow controllers with a total flow rate, Q, maintained at 1000 sccm. Energy density, Ed, injected in the plasma reactor is expressed from: Ed=((½.C.Uch²).f)/Q; with C the capacitor values of the Blumlein line high voltage generator. A Fourier Transform Infra Red spectrometer (FTIR, Nicolet Magna IR 550 Series II) is used to detect and measure outlet gas from the plasma reactor. Outlet quantified species are C 2 H 6 , C 3 H 8 , CO, CO 2 , CH 4 , C 2 H 4 . 3. Results and discussion 3.1. Ethane conversion at 300 K: effect of the inlet con- centration We report in figure 1, ethane conversion as a function of Ed for inlet ethane concentrations, [C 2 H 6 ] i , in air between 500 and 1660 ppm. Fig. 1 Ethane conversion rate as a function of the en- ergy density at 300 K. In all cases, an increase of Ed leads to a rise of the conversion rate. A light concentration effect can be ob- served: conversion rate is lightly enhanced for the lowest ethane inlet concentration at a given Ed. Main carbon produced species are mainly CO and CO 2 . In figures 2, CO and CO 2 concentrations are dis- played as functions of Ed for various [C 2 H 6 ] i . For low C 2 H 6 concentrations (500 ppm), outlet CO and CO 2 con- centrations increase when Ed rises. On the other hand, for [C 2 H 6 ] i higher, we observe that [CO] reaches a maximum level then decreases when Ed increases. This has been also observed previously when C 3 H 8 was diluted with air [4-6]. CO seems to be oxidized or less produced to the advantage of CO 2 production. This latter increases when 0 10 20 30 40 50 60 70 80 90 100 0 150 300 450 600 750 900 1050 1200 Energy Density (J.L -1 ) conversion (%) C2H6i = 1600ppm C2H6i = 1100ppm C2H6i = 500ppm