Time dependence of ethylene decomposition and byproducts formation in a continuous flow dielectric-packed plasma reactor

This work investigated the decomposition of ethylene in a continuous flow dielectric-packed bed plasma reactor filled with various packing materials at atmospheric pressure and room temperature. When compared to the case without any packing material, the reactor filled with packing materials remarkably facilitated the plasma-induced decomposition of ethylene in the order of α-alumina > silica > zirconia > glass wool (GW). Under identical condition, the increase in the decomposition efficiency (DE) with increasing the specific energy input was more rapid in the plasma reactor filled with the packing materials than in the blank plasma reactor. In the early stage, almost complete decomposition of ethylene was observed with the α-alumina, but after a certain period of time, the DE decreased with time. Unlike the α-alumina, the other packing materials examined did not show any significant deterioration in the decomposition over time during 10-h operation. After the regeneration of the used packing materials by using the plasma in the presence of oxygen, the original decomposition performance was nearly recovered. The decrease in the BET surface area due to the formation of polymer deposits was observed in the used α-alumina and silica; however the surface area was almost regained by the regeneration. While no other byproducts except carbon oxides and N2O were detected with the α-alumina and silica, methane, acetylene, formaldehyde and N2O were identified in the effluent gas with the zirconia and GW packing materials.

► Effectiveness of packing materials was in order of α-Al2O3 > SiO2 > ZrO2 > glass wool.
► The decomposition efficiency and the BET surface area were deteriorated over time.
► FTIR spectra evidenced the accumulation of polymer-like deposits in the reactor.
► Plasma-mediated regeneration restored the used packing materials to the former states.