NO reduction by methane on the surface of iron and iron oxides

NO reduction by methane on the surface of iron and iron oxides was experimentally investigated in a one-dimensional temperature-programmed ceramic tubular reactor at 300~1 100℃ in both nitrogen and simulated flue gas atmospheres. To ensure that the residual methane after NO reduction and the intermediates (e.g. CO) formed during the NO reduction were completely burned out, a second furnace with a supply of O₂ was connected in series after the first furnace. The results indicated that methane can effectively reduce NO to N₂ over the surface of metallic iron and iron oxides. In N₂ atmosphere, more than 95% of NO is reduced by methane over metallic iron at a temperature above 900℃, which is very close to that for NO reduction over iron oxides. In the simulated flue gas atmosphere with an excessive air ratio being lower than 1.0, more than 90% of NO is reduced by methane over both metallic iron and iron oxides at a temperature above 900℃; there is little difference in NO reduction under both burnout or non-burnout conditions. NO is reduced simultaneously via two routes, i.e. the direct reduction by metallic iron and the reduction by reburning of methane. Iron oxides are reduced to metallic iron by methane through partial oxidation over iron oxides to maintain the sustainable reduction of NO by metallic iron. At the same time, the intermediate products during NO reduction by methane such as HCN/NH₃ are converted by iron oxides, which prevent the NO reduction efficiency from dropping after burnout. The present results then prove that methane can effectively reduce NO over iron or iron oxides under fuel rich condition.