Seed-assisted synthesis of Cu-(Mn)-UZM-9 zeolite as excellent NO removal and N2O inhibition catalysts in wider temperature window

In this paper, acid-treated seeds have been adopted to improve the yield of UZM-9 zeolite, which could reach 50% for the first time within only two days. When applied as NH3-SCR catalysts after ion exchange, Cu-Mn-UZM-9 catalysts exhibited high NO conversion and excellent N-2 selectivity in a wider temperature region. The ICP, H-2-TPR and XPS results further revealed that the Cu species in the catalysts mainly existed as isolated Cu2+ located in the interval parts of crystals, while Mn species mainly existed as Mn4+ in the outer parts. That means, the co-exchange of Mn cation could actually play an adverse role in the direct interaction between Cu2+ and NH3 to produce N2O. Finally, the NH3-TPD and in situ FTIR results proved that the addition of Mn cation could introduce extra BrOnsted acid sites into the catalysts, which could capture NH3 in NH3-SCR reaction and suppress its nonselective oxidation as well as the N2O formation.