Characterization of copper-exchanged ZSM-5 and ETS-10 catalysts with low and high degrees of exchange

Abstract

Two different copper molecular sieve systems (Cu-ZSM-5 and Cu-ETS-10) have been prepared with different copper loadings from under- to overexchanged levels. The adsorption and surface properties have been studied using calorimetry of adsorbed NO, CO, C 2H 4 and NH 3 probe molecules. The respective numbers and strengths of CO and NO adsorption sites on the surface, which are related to the ratio of Cu(I) to Cu(II), depend on the matrix type, location of the metal ions, and degree of Cu exchange. Cu(I) was the prominent copper species in Cu-ETS-10, and the number of Cu(I) species increased as the level of copper loading increased. In overexchanged Cu-ZSM-5, the Cu(I) sites were less prominent but more stable, as shown by temperature programmed reduction (TPR) experiments. The catalytic activity for NO reduction by C 2H 4 in oxygen-rich atmosphere appeared to depend on the Cu(II)/Cu(I) ratio, but also on the adsorption properties towards the NO reactive gas. The samples presenting the best NO adsorption properties are the most active in the NOC 2H 4O 2 reaction.