Conversion of chlorophenols into cyclohexane by a recyclable Pd-Rh catalyst

In the presence of a silica sol-gel entrapped catalyst composed of metallic palladium and [Rh(cod)(μ-Cl)]2 under 27.6 bar H2 at 120 °C mono-, di-, tri- and tetrachlorophenols undergo exhaustive hydrogenation to give cyclohexane in >95% yield. The main isolated intermediates in this process, which can be isolated at lower temperatures are phenol, cyclohexanone and cyclohexanol. The combined entrapped catalyst is leach-proof and recyclable without loss in catalytic activity in three to six runs.