Plasma/catalyst system for reduction of NO_x in lean condition

A plasma/catalyst (Ag/Al₂O₃) system in rich oxygen similar to a lean-burn engine exhaust was used to study the NO_x conversion to N₂. Ag/Al₂O₃ significantly enhanced NO_x conversion in the lower temperature range under 400°C. At 300°-500°C, HC (C₁ base)/NO_x ratio of around 3:1, and 10% O₂, the NO_x conversion of the catalyst system was 40-50%, with over 96% selectivity to N₂. When assisted by plasma, Ag/Al₂O₃ exhibited better performance than Al₂O₃. Helium was utilized as balance gas to measure N₂ formation by GC. NO_x conversion was measured using a chemiluminescence NO_x analyzer in N₂ and He balances. NO_x conversion in N₂ balance gas was similar to that in He balance gas, proving that the plasma effect obtained in He balance gas could be consistent with that of N₂ balance gas, which is the largest component of the real exhaust gas. At 300°C, the largest enhancement by plasma was observed. Original is an abstract.