IN-SITU GENERATION OF PALLADIUM NANOPARTICLES IN SMECTITE CLAYS

A novel synthetic route has been developed for the preparation of clay intercalated palladium catalysts, Liquid sorption and X-ray diffracti on measurements on ethanol(1)-toluene(2)/hexadecylammonium montmorillo nite dispersions indicated that a toluene-rich bulk liquid phase was e quilibrated with a swollen, ethanol-rich interlamellar phase having a volume of about 0.9 cm(3)/g organoclay. Introduction of palladium(II) acetate into the organoclay suspension led to the generation and depos ition of a metallic palladium dispersion in the interlamellar space. T his system behaved as a versatile nanophase reactor, wherein the ethan ol functioned as both solvent and reducing agent. The progress of the Pd2+ --> Pd-0 reaction was monitored spectrophotometrically. The ethan olic reduction afforded Pd particles 2 to 14 nm in diameter, depending on the experimental conditions, deposited on clay particle defect sit es, Organoclays loaded up to 10 mass% Pd were synthesized and characte rized by BET surface area analysis, transmission electron microscopy, low-shear rheology, X-ray diffraction, and small-angle Xray scattering measurements, The Pd-organoclay samples proved to be catalytically ac tive in olefin hydrogenation in the liquid phase. (C) 1996 Academic Pr ess, Inc.