Letter Selective catalytic reduction of NO with methane over Ag-alumina catalysts

Silver-alumina catalysts prepared by a single-step co-gelation technique are reported in this letter as highly active and stable for the selective catalytic reduction of NO with methane (CH4–SCR). This type catalyst is active over a wide-temperature range (450–650C), and for a relatively wide range of Ag loading (1–7 wt.%). Excess O2 in the feed gas favors the SCR reaction. Catalysts capable of high conversions of NOx by CH4 in excess O2-containing gas streams would be an attractive alternative to high temperature NH3–SCR, which is commercially practised for NOx reduction in gas turbine exhausts at>500C. The structural stability of Ag was studied in reduction-oxidation cycles from 25–600C by UV–VIS diffuse reflectance spectroscopy. Totally reversible structures were observed. The catalyst is active both for CH4–SCR as well as for the complete oxidation of CH4. This bifunctionality appears to be related to the coexistence of highly dispersed silver clusters and silver nanoparticles in the alumina matrix. The catalyst activity/stability remained high under demanding reactio