Pd nanoparticles immobilized on sepiolite by ionic liquids: efficient catalysts for hydrogenation of alkenes and Heck reactions

Palladium-sepiolite catalysts were prepared by immobilizing Pd2+ on sepiolite using an ionic liquid containing a guanidine cation, followed by reduction with hydrogen at 150 degrees C. The resulting composites were characterized by different techniques. X-Ray photoelectron spectroscopy analysis showed that the loaded Pd existed mainly in the form of Pd-0, with a small amount of its oxides, and distributed uniformly on sepiolite with particle size about 5 nm, as confirmed by transmission electron microscopy examination. X-Ray diffraction analysis indicated that the sepiolite retained its original structure after deposition of Pd nanoparticles. The activities of the Pd-sepiolite catalysts for hydrogenations of some alkenes (e. g., cyclohexene and 1,3-cyclohexdiene) and Heck reactions were investigated. It was demonstrated that the as-prepared catalysts exhibited very high efficiency for these reactions.