A spectroscopic study of ethylene destruction and by-product generation using a three-stage atmospheric packed-bed plasma reactor

Using a three-stage dielectric packed-bed plasma reactor at p $=$ 1 bar the destruction of C$_{2}$H$_{4}$ and the generation of major by-products have been studied by FTIR spectroscopy. As test gas mixture air containing 0.12{\%} humidity with 0.1{\%} ethylene admixture was used. In addition to the fragmentation of the precursor gas, the evolution of the concentration of ten stable reaction products, CO, CO$_{2}$ O$_{3}$, NO$_{2}$, N$_{2}$O, HCN, H$_{2}$O, HNO$_{3}$, CH$_{2}$O and CH$_{2}$O$_{2}$ has been monitored. Applying three sequentially working discharge cells (f $=$ 4 kHz, U $=$ 9 - 12 kV) a nearly complete decomposition of C$_{2}$H$_{4}$ could be achieved. In maximum the specific energy deposition was about 900 Jl$^{-1}$. The value of the specific energy $\beta $, characterizing the energy efficiency of the ethylene destruction in the used reactor, was 330 Jl$^{-1}$. The carbon balance of the plasma chemical conversion of ethylene has been analyzed. As a main result of the study, the application of three reactor stages suppresses essentially the production of harmful by-products as formaldehyde, formic acid and NO$_{2}$ compared to the use of only one or two stages.