Effects of Solvents and Added Amines on the Selective Hydrogenation of 2-Naphthol over Urushibara Nickel and Cobalt Catalysts

Abstract The selective hydrogenation of 2-naphthol (NL) was investigated with Ni (U-Ni-B, U-Ni-A, and R-Ni) and Co (U-Co-B, U-Co-A, and R-Co) catalysts in various solvents at elevated temperatures and pressure (50 kg/cm2). U-Ni-B and U-Ni-A exhibited a high selectivity for the formation of 1,2,3,4-tetrahydro-2-naphthol (ac-TL), expecially in alcoholic solvents, while the hydrogenation with R-Ni in Et2O, i-PrOH, and benzene solvents gave preferentially 5,6,7,8-tetrahydro-2-naphthol (ar-TL). The ar-TL formation over Ni catalysts decreased in the following order, irrespective of the catalysts. i-PrOH>EtOH>MeOH and Et2O> benzene. However, the selectivity over Co catalyst was influenced to a lesser extent by the solvents. The addition of amines promoted the hydrogenation of NL to ar-TL in the following order: prim->sec->tert-amine in EtOH over Ni and Co catalysts. In general, Ni catalysts are more susceptible to the effects of solvents and added amines than Co catalysts.