1993 Volume 72 Issue 2 Pages 98-103
Correlation between redox capacity and the activity for NO decomposition of various metallosilicates under excess oxygen conditions was studied. The redox capacity was measured by using thermogravimetric analyzer. The metallosilicates having a pentasil poreopening were prepared by the rapid crystallization method. Cu or Co ion-exchanged H-ZSM-5 (Cu/H-ZSM-5 or Co/H-ZSM-5) was used as the reference catalyst.
Cu/H-ZSM-5 showed a good correlation between the redox capacity and the activity of NO decomposition, assuming redox reactions occurred between Cu and CuO. Co/H-ZSM-5 also showed a good correlation between them, but the redox reactions occurred between Co2O3 and Co3O4.
On the other hand, in the case of metallosilicates, the active metal species were highly dispersed and tightly incorporated into the crystalline lattice, and therefore, the redox capacity did not exert explicitly, and reflecting this, the activity of NO decomposition was considerably low, however, stability of metallosilicates was higher than that of metal ion-exchanged ZSM-5, due to the small change in valency of metals in metallosilicates.