Catalytic behavior and nature of active sites in copper-on-zirconia catalysts for the decomposition of N2O

Cu-on-Zr catalysts prepd. by a sol-gel technique actively decompd. N2O comparable to Cu-ZSM-5, but were more stable at high N2O concns. ZrO2 promoted the activity of supported Cu species and played a catalytic role itself, but the tetragonal cryst. form of ZrO2 was a more effective promoter than the monoclinic form. Sample characterization by ESR, IR (CO chemisorption), and O thermodesorption suggested that during dehydroxylation of ZrO2 at 400-500°, Cu+ species formed which were stable against consecutive reoxidn., when the ZrO2 surface was not re-hydroxylated. It is suggested that the behavior of Cu-ZrO2 catalysts in N2O decompn. derives from stabilization of Cu+ species by the support. Water in the feed inhibits surface reactivity due to the modification of the redox properties of Cu ions and competition with N2O for chemisorption on Cu ions. [on SciFinder(R)]