Simultaneous removal of hydrocarbon and CO using a nonthermal plasma-catalytic hybrid reactor system

Combined removal of n-heptane and CO using a catalytic reactor coupled with dielectric barrier discharge plasma was investigated over several metal oxide catalysts including bare γ-Al2O3, Ag2O/γ-Al2O3, MnO/γ-Al2O3, RuO2/γ-Al2O3 and PdO/γ-Al2O3. In order to effectively utilize the heat generated during plasma discharge for enhancing catalytic reactions, the plasma-catalytic reactor was thermally insulated by covering it with a glass wool jacket. Plasma propagated radially outward from the central high-voltage electrode with gradually increasing the applied voltage, and the temperature decreased with the radial distance due to the decreased plasma intensity, exhibiting a volcanic temperature distribution. The increased reactor temperature could improve the removal of CO and the selectivity toward CO2. The results obtained from separate experiments of n-heptane and CO removal showed that the PdO/γ-Al2O3 was the best for the simultaneous removal purpose. The effects of specific input energy (SIE), oxygen content, reaction temperature and PdO loading on the simultaneous removal of n-heptane and CO and the formation of byproducts were examined. The removal efficiencies of n-heptane obtained with different catalysts were similar to one another, whereas the removal of CO strongly depended on the type of catalyst. The catalytic activity for the oxidation of CO followed the order: MnO/γ-Al2O3 < Ag2O/γ-Al2O3 < RuO2/γ-Al2O3 < PdO/γ-Al2O3. In the present plasma-catalytic hybrid reactor, the mixture of n-heptane and CO was mainly converted into CO2, and under an optimized condition, the selectivity toward CO2 reached 100%.