Adsorption of polymer-protected palladium nanoparticles on polyacrylamide gel and their catalysis

Adsorption of the palladium nanoparticles protected by poly(N-vinyl-2-pyrrolidone) (PVP) on polyacrylamide gel and its derivatives in dispersion medium [water-methanol (1:1, v/v)] was carried out. The PVP-protected palladium nanoparticles were adsorbed on aminoethylated polyacrylamide gel [G(PAA-AE)], but not adsorbed on polyacrylamide gel or carboxylated polyacrylamide gel. By using adsorption of the PVP-protected palladium nanoparticles on the G(PAA-AE) in the dispersion, we successfully separated PVP dissolved in free state (free PVP) in the dispersion medium. Thus, both the amount of PVP protecting palladium nanoparticles and the concentration of free PVP were determined. The palladium nanoparticles adsorbed onto G(PAA-AE) exhibited high activity and high selectivity as a catalyst for hydrogenation of 1,3-cyclooctadiene to cyclooctane. The palladium nanoparticles adsorbed onto G(PAA-AE) were easily separated from the reaction mixtures, and the initial activity and selectivity were maintained during repeated uses as catalyst.