A novel microwave assisted process for the synthesis of nanostructured ruthenium catalysts active in the hydrogenation of phenol to cyclohexanone

The synthesis of ruthenium nanocatalysts has been performed by adopting a novel microwave assisted process, which involves the use of an applicator working in a glass vessel out of the oven. Ru/γ-Al 2O 3 nanosystems, prepared in situ by irradiation of a glycol solution of the metal precursor in the presence of the support, showed interesting performances in the selective hydrogenation of phenol to cyclohexanone. ▪ An efficient, cheap and safe process for the solvothermal synthesis of ruthenium nanocatalysts has been developed: it involves the innovative use of a microwave (MW) applicator for the in situ activation of the reaction in a stirred glass vessel without resorting to an oven. The synthesis was carried out by direct MW irradiation of an alcohol or glycol solution of the metal precursor RuCl 3 nH 2O, in the presence of PVP (poly- N-vinyl-2-pyrrolidone) as stabilizing agent and eventually of γ-Al 2O 3 as support. The addition of PVP appears not to be necessary for the in situ preparation of the supported systems. The synthesized nanocatalysts were characterized by UV–Vis, TEM and XPS measurements: colloidal and supported nanoparticles with an average diameter about 2 nm and a narrow distribution of sizes were obtained. The supported systems showed interesting performances in the selective hydrogenation of phenol to cyclohexanone.