Reactivity of surface isocyanate species with NO, O2 and NO+O2 in selective reduction of NOχ over Ag/Al2O3 and Al2O3 catalysts

Abstract

Reactivity of surface isocyanate (NCO(a)) species with NO, O2 and NO+O2 in selective reduction of NOχ over Ag/Al2O3 and Al2O3 catalysts was studied by a pulse reaction technique and an in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The NCO(a) species on Ag/Al2O3 reacted with O2 or NO+O2 mixture gas to produce N2 effectively above 200°C, while the reaction of NCO(a) with NO hardly produced N2 even at 350°C. In the case of Al2O3 alone, less N2 was detected in the reaction of NCO(a) with NO+O2, indicating that silver plays an important role in the N2 formation from NCO(a). These behaviors of the reactivity of NCO(a) species with reactant gases were in good agreement with the changes in NCO(a) bands shown by in situ DRIFT measurements. Based on these findings, the role of NCO(a) species in the selective reduction of NOχ on Ag/Al2O3 and Al2O3 catalysts is discussed.