NO reduction with propylene over Co/Al2O3 and Co-Sn/Al2O3 catalysts has bee
n investigated. For the Co/Al2O3 catalyst, a calcination temperature exceed
ing 800 degreesC led to a decrease of NO conversion. Calcination of the Co/
Al2O3 catalyst at 1000 degreesC resulted in the formation of alpha -Al2O3 a
nd Co3O4. The presence of 20% water vapor showed a significant shift for th
e maximum NO reduction temperature from 450 to 600 degreesC over Co/Al2O3.
It has been found that modification of 6 wt% Co/Al2O3 with 2 wt% Sn signifi
cantly enhanced the catalyst thermal stability and improved the inhibitory
effect of water on NO conversion and reaction temperature. The promotional
effect of Sn on the catalyst thermal stability was attributed to the suppre
ssion of the phase transformation from highly dispersed Co2+ species on gam
ma -Al2O3 to alpha -Al2O3 and Co3O4. The smaller influence of water vapor o
n NO reduction conversion and temperature over Co-Sn/Al2O3, compared to Co/
Al2O3, was attributed to the dispersion effect of Sn species on Co2+ specie
s as well as the involvement of Sn species in NO reduction at a relatively
lower temperature. The synergetic effect between the octahedral Co2+ specie
s and gamma -alumina plays a significant role in the catalysis of NO select
ive reduction by C3H6.