Liquid-phase oxidative coupling of 2-naphthol by vanadium catalysts supported on MCM-41

The liquid-phase oxidative coupling reaction of 2-naphthol was carried out in dichloromethane solvent over vanadium catalysts supported on inorganic oxides such as MCM-41 using molecular oxygen as the oxidant. The main product was 1,1 '-bi-2-naphthol, the oxidative C-C coupling product of 2-naphthol. The yield of 1,1 '-bi-2-naphthol increased with the increasing amount of supported V, but leveled off when the amount of V was more than about 1 wt.%. The sterically bulky 1,1 '-bi-2-naphthol was suggested to be mainly produced in the mesopores of the MCM-41 support in comparison with the activity of the V catalyst supported on NaZSM-5 support which has only micropores. The active vanadium species for the oxidative coupling product was found to be the tetrahedral V5+ species based on the correlation between the yield of 1,1 '-bi-2-naphthol and the intensity of the tetrahedral V5+ species estimated by the DR spectra of the V/MCM-41 catalysts. (c) 2005 Elsevier B.V. All rights reserved.