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

Adsorption of the palladium nanoparticles protected by poly(N-vinyl-2-pyrrolidone) (PVP) was carried out on polystyrene gel beads (PSt-TA) having trimethylammonium groups in methanol dispersion. The palladium nanoparticles protected by PVP were adsorbed on a highly porous type of PSt-TA (PSt-HPA, average pore size 140 nm), but not adsorbed on a gel type of PSt-TA. The effect of average molecular weight of PVP ((M) over bar(w): 6000, 25000, 175000, and 574000) on the adsorption of PVP-protected palladium nanoparticles on PSt-HPA was investigated. The amount of PVP-protected palladium nanoparticles adsorbed on PSt-HPA decreased with increasing (M) over bar(w) of PVP. The diameter of palladium nanoparticles including adsorbed layer of PVP was determined by the use of the sedimentation coefficient of the PVP-protected palladium nanoparticle by ultracentrifugation. The diameter increased with increasing (M) over bar(w) of PVP. The PVP-protected palladium nanoparticles adsorbed on PSt-HPA, as a catalyst for hydrogenation of 1,3-cyclooctadiene to cyclooctane, were easily separated from the reaction mixtures. The nanoparticles maintained the initial activity and selectivity during repeated uses.