On the role of external Co sites in NO oxidation and reduction by methane over Co-H-MFI catalysts.

Co–H-MFI and Co–silica–alumina catalysts were comparatively characterized and their activities in CH4-SCR and NO oxidation were compared. IR measurements evidence that Co sites distribute between internal cavities and external surface of Co–H-MFI; a large fraction of protonic sites are retained. Co–silica–alumina, unlike Co–H-MFI, is inactive in CH4-SCR and catalyzes only NO oxidation and methane combustion. The CH4-SCR activity is related to Co sites located in the zeolitic cavities. The role of NO2 gas as intermediate in the CH4-SCR reaction appears unlikely. The activity of zeolitic protons in NO oxidation seems negligible in the presence of cobalt.