MODEL PUMICES SUPPORTED METAL-CATALYSTS .1. PREPARATION AND CHARACTERIZATION OF SUPPORTS AND SUPPORTED-PALLADIUM CATALYSTS

A series of aluminosilicates with similar silica/alumina ratios and si milar structural properties of natural pumice, but with differing amou nts of alkali ions in their framework, were prepared and characterized by different techniques such as IR, TG, physisorption, and XPS. The s ynthesis through the gel route yields quite homogeneous materials and, by varying the reaction mixture and the calcination parameters, allow s one to obtain supports closely resembling the natural pumice. The co rresponding palladium catalysts are prepared starting from two differe nt precursors, [Pd(NH3)(4)](NO3)(2) and Pd(C3H5)(2). The electronic pr operties, as obtained from photoelectron spectroscopy, and the structu ral parameters, obtained from X-ray diffraction techniques, are discus sed in terms of the alkali ions/Pd atomic ratio and also in terms of t he preparation methods. (C) 1997 Academic Press.