The role of fluorine, nickel and full sulfidation in the hydrodenitrogenation of o-toluidine over tungsten-based catalysts prepared from oxy- and thiosalts

The effects of preimpregnation of alumina with ammonium fluoride, incorpora tion of nickel and full sulfidation of tungsten catalysts on the catalytic performance of two series of tungsten catalysts, one made from ammonium met atungstate and the other from ammonium tetrathiotungstate (ATT), were inves tigated. The catalysts made from tetrathiotungstate had a much higher activ ity than the ones made from metatungstate, and fluoride addition substantia lly increased the catalytic activity in the hydrodenitrogenation (HDN) of o -toluidine. The elementary reactions involved in the HDN of o-toluidine wer e affected to different extents by full sulfidation, the fluorination of th e alumina support and the incorporation of nickel, proving that these react ions occur on different sites that were modified in different ways. The hyd rogenation of the phenyl ring and the C(sp(2))-N bond breaking improved mos t, while the hydrogenation of the alkene and the C(sp(3))-N bond breaking w ere affected to a lesser extent. (C) 2001 Elsevier Science B.V. All rights reserved.