Characterization of Pd-mordenite Catalysts for NO Decomposition

Abstract

The aim of this study was to characterize Pd catalysts supported on three different mordenite zeolites (a commercial sample and two laboratory preparations) previously tested for the NO decomposition reaction. H2 chemisorption, TPR, FTIR spectroscopy of adsorbed CO and NO, DRS UV-vis and TPD of NO were used to characterize the catalysts. After reduction at 573 K a large fraction of Pdo particles and some Pd2+ ions were found in the commercial sample and one laboratory preparation. In contrast a sample prepared with a mordenite synthetized using a natural clay was found to exhibit mainly ionic Pd. The amount of Pdo (PdO) relative to Pd2+ depends on the oxidation temperature and the metal loading. The catalysts exhibited similar levels of activity for the NO decomposition reaction at 673 K but a different selectivity to N2O. This behavior was related to differences in metal dispersion and other surface conditions that influence the formation of PdO particles.