A hybrid polyketone–SiO2 support for palladium catalysts and their applications in cinnamaldehyde hydrogenation and in 1-phenylethanol oxidation

An organic-inorganic hybrid material, PK-SiO2 (PK = polyketone), was employed as support for Pd catalysts. Their synthesis was carried out by MW irradiation of an ethanol solution of Pd(OAc)(2) in the presence of the support. The obtained systems were characterized by solid state NMR, SEM, TEM, ICP, XPS, BET, gas porosimetry and tested in two probe reactions: the selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde carried out in decalin and the oxidation of 1-phenylethanol to acetophenone in water. For comparison, Pd/PK and Pd/SiO2 catalysts were also prepared by using the same procedure, characterized and tested in the same reactions. On the hybrid support the Pd nanoparticles resulted significantly smaller and with a more homogeneous size distribution compared to those on bare SiO2 or PK. The catalysts on the hybrid support allowed a higher performance and could be recycled up to five.times without loss of activity and metal leaching. These results were related to the improved surface area of the hybrid material (compared to the low surface area of bare PK) ascribable to silica introduction, combined with the stabilizing effect of the polymeric counterpart against Pd nanoparticles agglomeration