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

Two series of pumice-supported palladium catalysts (W washed, U = unwa shed) were prepared by the reaction of [Pd(C3H5)(2)] with the support, followed by reduction using H-2. W catalysts were washed before reduc tion 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 li ne broadening, and transmission electron microscopy (TEM). Line-broade ning analysis revealed the presence of lattice imperfections, such as growth stacking faults and microstrains in the fee structure of pallad ium. The average particle size values determined by SAXS were confirme d by TEM analysis and were employed to calculate the percentage of pal ladium exposed (catalyst dispersion). W catalysts showed well-disperse d spheroidal particles, whereas the U series displayed agglomerates. ( C) 1994 Academic Press, Inc.