Effects of Palladium Precursors on the Activity of Palladium Nanocatalysts for the Oxidation of Volatile Organic Components

To screen a suitable precursor, the effects of palladium salts on performance of Pd nanocatalysts for the oxidation of volatile organic components (VOCs) were investigated. A series of catalysts was prepared by impregnating Pd(NO3)2, PdCl2and Pd(NH3)4Cl2on alumina-coated cordierites. These catalysts were characterized by XRF, ICP-OES, XRD, N2adsorption-desorption, TEM, EDS, Raman spectroscopy, pulse-CO chemisorption, H2-TPR, NH3-TPD, and XPS. Pulse-CO chemisorption and TEM showed that Pd species formed by Pd(NO3)2have the highest metal dispersion (17.7%), while the other two were aggregating. For the same Pd loading, the higher the metal dispersion, the more the number of PdO species, so the number of PdO particles in the catalyst prepared from Pd (NO3)2is the largest. The catalytic oxidation activities of these catalysts were evaluated by ethane and propane. Based on a 99% conversion in the oxidation of ethane and propane at 598 K and 583 K, respectively, the catalyst prepared from Pd(NO3)2was considered to be the best performing catalyst. The chloride species in precursors can promote the aggregation of Pd species and poison the catalysts. The results show that Pd(NO3)2is more suitable as the precursor of VOC oxidation catalyst than PdCl2and Pd(NH3)4Cl2.Keywords:volatile organic components;palladium;catalytic oxidation;precursors