Hydrogenation of Phenol by the Pd/Mg and Pd/Fe Bimetallic Systems under Mild Reaction Conditions

Three palladium-catalyzed zerovalent metal systems were found to be able to hydrogenate phenol to cyclohexanol and cyclohexanone under room temperature and pressure conditions. Exposure of 5.0 mM aqueous phenol solutions to Pd (2.6 ppt m/m)/Mg (1.00 g 20 mesh) and to 0.53 g of 1 / 8 in. Pd (0.5%)/alumina in contact with 1.00 g 20 mesh Mg results in 74% and 24% destruction of the reactant after 6 h of reaction time. The latter system was found to be greatly enhanced in the presence of 2% (v/v) glacial acetic acid, resulting in an 84% reduction of phenol with a carbon balance of 93%. Palladized iron and unmodified metals systems were much less effective at hydrogenating phenol. The advantage of the 1 / 8 in. Pd/alumina/20 mesh Mg system is that it gives a readily recoverable form of the catalysts when compared to the bimetallic systems.