Novel palladium catalysts supported on polyketone and on polyketone/silica: characterization and catalytic activity

Generally, metal nanoparticles catalysts are prepared in the presence of a stabilizing agents in order to prevent their agglomeration. The use of polymeric stabilizers has been widely investigated. These “quasi” homogeneous MNPs offer the advantage of high catalytic activity as the homogeneous ones, but, on the other side, they are not easily separable and recyclable as the heterogeneous ones. In order to overcome this drawback, they are generally supported on a solid inorganic carrier. On the contrary, the applications of polymers as supports have been less investigated. In particular, the use of polyketones has been almost neglected. They are high temperature melting materials, insoluble in the most common solvents. They might not only act as support, but also as stabilizer through MNP-keto groups interactions without encapsulating them with relatively strong bonds, which could inhibit catalysis as normally occurs with other stabilizers. Unfortunately, they show as drawback small surface areas and also low compatibility with hydroxylated media. A hybrid polyketones/(hydrophilic carrier) could overcome this problem. This prompted us to design a new support made of a polyketone grafted on high surface area silica. Here, we report the preparation of several Pd catalysts supported on polyketone, aerosil 380 and on polyketone-aerosil 380 with different Pd loading and polyketone/aerosil ratio, synthesized employing microwave irradiation. These systems were characterized by SEM, TEM, ICP, XPS, BET analysis and were tested in the selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde as probe reaction. The Pd/polyketone-aerosil 380 catalysts present a significantly higher activity than the Pd/polyketone and Pd/aerosil 380 systems.