The simultaneous selective catalytic reduction of N2O and NOX with CH4 on Co- and Ni-exchanged mordenite

Abstract Co- or Ni-exchanged Na-MOR (Si/Al = 9.2) prepared by ion-exchange method were characterized by in situ UV–vis DRS and FTIR. We studied the selective catalytic reduction with CH 4 in the presence of O 2 (CH 4 -SCR) for the simultaneous abatement of NO and N 2 O (CH 4 -SCR sim ) and the related reactions: (i) abatement of N 2 O ( CH 4 − SC R N 2 O ) , (ii) abatement of NO (CH 4 -SCR NO ), (iii) N 2 O decomposition, and (iv) CH 4 combustion. The catalytic measurements were performed in a flow apparatus with GC analysis of reactants and products. FTIR characterization with CO of Ni-MOR identified isolated Ni 2+ and [Ni 2+ O Ni 2+ ] dimers, both mainly located in α-sites. In Ni-MOR, the amount of isolated Ni 2+ and of dimers was comparable, whereas in Co-MOR isolated Co 2+ were more abundant than [Co 2+ O Co 2+ ]. Transition metal ion (tmi) dimers were easily reduced by CO to [tmi + □ tmi + ] yielding CO 2 . In situ UV–vis DRS characterization indicated that by heating in N 2 O, Co 2+ oxidized to Co 3+ O − , whereas Ni 2+ did not. Catalytic results for CH 4 -SCR sim showed that Co-MOR was active, whereas Ni-MOR was ineffective, because it did not abate N 2 O. Both catalysts were active for CH 4 − SC R N 2 O and for CH 4 -SCR NO . Whereas Co-MOR was highly active for N 2 O decomposition and poorly active for CH 4 combustion, Ni-MOR was inactive for N 2 O decomposition and active for CH 4 combustion. The NO abatement in CH 4 -SCR sim on both Co-MOR and Ni-MOR occurred via CH 4 -SCR NO , and the active sites were isolated tmi 2+ in α-sites. The N 2 O abatement in CH 4 -SCR sim on Co-MOR occurred in β-sites via N 2 O decomposition, and the active sites were isolated Co 2+ , that formed Co 3+ O − intermediate (UV–vis DRS evidence). The N 2 O abatement in CH 4 -SCR sim on Ni-MOR did not occur, because Ni 2+ , that formed no Ni 3+ O − , were inactive in N 2 O decomposition. Redox behavior of [Ni 2+ O Ni 2+ ] accounted for Ni-MOR activity in CH 4 − SC R N 2 O and CH 4 combustion.