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 similar structural properties of natural pumice, but with differing amounts of alkali ions in their framework, were prepared and characterized by different techniques such as IR, TG, physisorption, and XPS. The synthesis through the gel route yields quite homogeneous materials and, by varying the reaction mixture and the calcination parameters, allows one to obtain supports closely resembling the natural pumice. The corresponding palladium catalysts are prepared starting from two different precursors, [Pd(NH3)(4)](NO3)(2) and Pd(C3H5)(2). The electronic properties, as obtained from photoelectron spectroscopy, and the structural parameters, obtained from X-ray diffraction techniques, are discussed in terms of the alkali ions/Pd atomic ratio and also in terms of the preparation methods. (C) 1997 Academic Press.