Methane, Propene and Toluene Oxidation by Plasma-Pd/γ-Al2O3 Hybrid Reactor: Investigation of a Synergetic Effect

Abstract

The combination of a sub-microsecond pulsed dielectric barrier discharge with Pd/gamma-Al2O3 catalyst was investigated for the oxidation of low concentration of methane, propene, and toluene in air at atmospheric pressure. The systematic comparison of the plasma-catalysis with the thermal-catalysis and the plasma-alone have been made for temperature window of 20–400 C and energy deposition in the range 23–148 J L-1. To emphasis the reactivity of plasma produced species on the activation of the catalyst, two reactor configurations were used [in-plasma catalysis (IPC), and post-plasma catalysis (PPC)]. Fourier transform infrared spectrometer was used to follow the VOCs conversion and to quantify the mineralized products. The plasma-catalyst combination leads to higher VOCs conversion and decreases the catalyst activation temperature in both IPC and PPC configurations. For hybrid system, the light-off temperature is always lower than those observed for catalytic oxidation. In addition, the formation of the by-products such as formaldehyde, formic acid, and ozone was reduced significantly. A significant synergetic effect of hybrid plasma-catalytic system is not really observed in the presence of CH4 and C3H6. However, for C7H8 oxidation the synergetic effect was demonstrated at low temperature (\150 C) for the IPC configuration.