Hydrogenation of phenol over Urushibara Ni catalysts reduced by zinc powder

Urushibara nickel catalysts were prepared from aqueous NiCl₂ solution with zinc powder as a reducing agent and used in phenol hydrogenation. The effects of zinc powder amount, reduction temperature and pretreatment-activation method on the catalytic performance of Urushibara nickel in phenol hydrogenation was investigated. To inhibit the magnetic agglomeration of the pure nickel catalyst, γ-Al₂O₃, CaCO₃ and MgO were added as a support. The results indicated that the nickel catalysts obtained by zinc reduction can be pretreated and activated by NaOH or acetic acid solution, though the former is superior to the latter. The catalytic activity of Urushibara nickel is related to the amount of zinc used for the reduction. The nickel catalyst reduced at 100 ℃ with an n(Zn)/n(NiCl₂·6H₂O) ratio of 4.5 exhibits the highest hydrogenation activity. γ-Al₂O₃ as a support can promote the dispersion and sediment of the reduced nickel and alleviate the magnetic agglomeration. The Urushibara nickel catalysts are active for phenol hydrogenation at 120~160 ℃, with cyclohexanol and cyclohexanone as the main products; the conversion of phenol reaches 53%~66%, with the selectivity of 95.0%~96.0% to cyclohexanol.