SELECTIVE CATALYTIC REDUCTION OF NO OVER M–Ag/ZSM۵ BIMETALLIC NANOCATALYSTS (M = Mn, Fe AND Ni). PHYSICOCHEMICAL PROPERTIES AND CATALYTIC PERFORMANCE

چکیده مقاله

Selective catalytic reduction of NO by ammonia in the presence of excess oxygen has been studied over monometallic Ag/ZSM5 and bimetallic M–Ag/ZSM5 (M = Mn, Fe and Ni) nanocatalysts. Ag/ZSM5 shows a good activity but low selectivity to N2 and produces N2O in considerable amounts. To improve selec tivity for N2 the Ag/ZSM5 catalyst was modified by adding different transition metals (Mn, Fe and Ni). The Fe–Ag/ZSM5 bimetallic nanocatalyst showed the highest activity (95% NO conversion and 73% selectivity to N2 at 300°C). Xray diffraction, transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), ammonia temperatureprogrammed desorption (NH3TPD), and Xray photoelectron spectroscopy were applied to characterize Ag/ZSM5 and M–Ag/ZSM5 nanocatalysts. TEM results revealed the presence of nanosized Ag/metal oxide species on the HZSM5 support in M–Ag/ZSM5 catalysts and highly dis persed Ag/metal oxide species in the Fe–Ag/ZSM5 catalyst. The NH3TPD measurements confirmed that compared to other catalysts the Fe–Ag/ZSM5 catalyst has an increased amount of strong acid sites and a higher NH3 storage capacity.