Optical Emission and Raman Spectroscopy Studies of Reactivity of Low-Pressure Glow Discharges in Ar–O2 and He–O2 Gas Mixtures with Coked Catalysts

Abstract

We demonstrate that low-pressure glow discharges in He–O2 gas mixture are effective in removing carbonaceous surface layers from coked catalysts. These discharges contain a number of reactive species including O, O3, and O2*, and all these could contribute in the decoking process. However, an evolving understanding is that the O atoms in the discharge have a predominant role in this. A working hypothesis is that the O atoms react with the coke to form CO, CO2 and other carbon complexes. Online measurements using emission spectra from O, H, and CO in the discharges are compared for the cases of He–O2 and Ar–O2 gas mixtures. Under the reported experimental conditions the estimated reactivity of the He–O2 discharges is considerably higher compared with discharges in the Ar–O2 gas mixture. Raman spectroscopy is used to confirm the removal of the coke from the surface of Pt/Alumina catalyst.