Selective heterogeneous catalytic hydrogenation by recyclable poly(allylamine) gel-supported palladium(0) nanoparticles

The synthesis and stabilization of metallic Pd(0) nanoparticles incorporated hydrogel bearing coordinating amine groups and the use of these nanoparticles for the highly selective hydrogenation of a variety of hydrophilic substrates were analyzed. Cross-linked poly(allylamine) (cl-PAA) was used as the polymer matrix since it readily binds Pd(II) by coordination to the amine groups. It was found that by using in situ reduction the gel color changed from brown to black and the transparent crystals of Na2PdC14 were replaced by black Pd(0) nanoparticles homogeneously distributed inside the polymer matrix. It was also found that in the chloroform medium, Pd(0), gave 100% conversion and essentially 100% selectivity. The results shows that selectivity is lower with a more cross-linked hydrogel and the catalyst system is easy to recycle without loss of selectivity and activity.