PUMICE-SUPPORTED PALLADIUM CATALYSTS .1. CHEMICAL PREPARATION AND MICROSTRUCTURAL FEATURES

Two series of pumice-supported palladium catalysts (W washed, U = unwashed) were prepared by the reaction of [Pd(C3H5)(2)] with the support, followed by reduction using H-2. W catalysts were washed before reduction to eliminate unreacted [Pd(C3H5)(2)]. U catalysts did not undergo this treatment. Microstructural characterization of the catalysts was performed by small-angle X-ray scattering (SAXS), wide-angle X-ray line broadening, and transmission electron microscopy (TEM). Line-broadening analysis revealed the presence of lattice imperfections, such as growth stacking faults and microstrains in the fee structure of palladium. The average particle size values determined by SAXS were confirmed by TEM analysis and were employed to calculate the percentage of palladium exposed (catalyst dispersion). W catalysts showed well-dispersed spheroidal particles, whereas the U series displayed agglomerates. (C) 1994 Academic Press, Inc.