Plasma-catalytic decomposition of nitrous oxide over Γ-alumina-supported metal oxides

This work investigated the decomposition of dilute N₂O from gas streams with various oxygen contents by using a plasma-catalytic process over metal oxide catalysts supported on γ-Al₂O₃. Among the metals explored (Ru, Co, Cu, V, etc.), Ru was found to be the best catalyst for the decomposition of N₂O in a plasma-catalytic reactor, and most of the experiments were conducted with alumina-supported Ru. The effects of applied voltage, reaction temperature, O₂ content, gas flow rate and initial N₂O content on the decomposition efficiency and byproducts formation were examined. Compared to the catalyst-alone case, the presence of plasma enhanced the decomposition efficiency by 30-50%, depending on the operating condition. The increase in the oxygen content from 0 to 20% largely decreased the catalytic decomposition efficiency, whereas in the presence of plasma N₂O could be successfully decomposed even at 20% O₂ content. The decomposition efficiency was not a strong function of the initial N₂O concentration in the range of 225-1800 ppm, exhibiting pseudo first-order reaction kinetics. Without O₂, there were negligible byproducts, but in the presence of O₂, NO and NO₂ were formed mainly due to the plasma-induced reactions between background molecules such as N₂ and O₂. The results obtained in this work showed the feasibility of plasma-catalytic process for the abatement of N₂O.