Catalytic hydroconversion of simulated coal tars: III. Activity of sulphided NiMo on alumina-zeolite catalysts for the hydroconversion of model compounds

The activity of a hydrocracking Catalyst depends on the protective effect from coking that the hydrogenating function has on the acid one. Nickel and molybdenum were impregnated on alumina-zeolite supports in order to reduce the space between the hydrogenating sites and the acid sites. The amounts of nickel and molybdenum and the weight of zeolite in the support were varied so as to obtain different ratios (number of acid sites) / (number of hydrogenating sites). The hydroconversion of phenanthrene, alone or in the presence of carbazole and 1-naphthol, was chosen as a model reaction. The results obtained clearly indicate the existence of an optimal ratio (number of acid sites) / (number of hydrogenating sites) for which the acid sites are protected from coking: the corresponding Catalyst is more active for phenanthrene conversion, more selective for cracking and yields much less coke.