To obtain a supported heterogeneous catalyst, laser ablation of metallic palladium in supercritical carbon dioxide was performed in the presence of a carrier, microparticles of γ-alumina. The influence of the ablation process conditions-including supercritical fluid density, ablation, mixing time of the mixture, and laser wavelength-on the completeness and efficiency of the deposition of palladium particles on the surface of the carrier was studied. The obtained composites were investigated by scanning and transmission electron microscopy using energy dispersive spectroscopy. We found that palladium particles were nanosized and had a narrow size distribution (2-8 nm). The synthesized composites revealed high activity as catalysts in the liquid-phase hydrogenation of diphenylacetylene.
Keywords: Pd catalysts; Pd nanoparticles; hydrogenation; laser ablation; supercritical carbon dioxide; supercritical fluid (SCF) colloids.