Highly selective hydrogenation of phenol and derivatives over Pd catalysts supported on SiO2 and γ-Al2O3 in aqueous media

• Pd/Al2O3 with 3 nm Pd particles was prepared by the reduction at 273 K.
• It shows high activity and selectivity in phenol hydrogenation to cyclohexanone.
• 99% conversion and > 99% selectivity were achieved within 3 h in water.
• Similar results are obtained in hydrogenation of phenol derivatives over Pd/Al2O3.
• Phenol adsorbs through both interaction of hydroxyl and aromatic rings with Pd/Al2O3.

Pd/Al2O3 and Pd/SiO2 catalysts containing Pd nanoparticles in the size range of 3–13 nm were prepared and investigated in direct selective hydrogenation of phenol to cyclohexanone. Catalysts with 3 nm Pd nanoparticles present highly active and promoted the selective formation of cyclohexanone under atmospheric pressure of hydrogen in aqueous media without additives. Conversion of 99% and a selectivity higher than 99% were achieved within 3 h at 333 K. The generality of Pd/Al2O3 catalyst with 3 nm Pd nanoparticles for this reaction was demonstrated by selective hydrogenation of other hydroxylated aromatic compounds with similar performance.

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