Hydrotreating processes in petroleum refining were introduced more than
50 years ago for the removal of sulfur and nitrogen. The sulfided
cobalt-molybdenum catalyst, together with its near relatives, is still
widely used. Two oil crises made it clear that pretroleum reserves are
not inexhaustible and we shall be compelled to exploid less satisfactory
sources with high sulfur and nitrogen making hydrotreating even more
important. This review is particularly timely for the reason that only
recently has a detailed understanding of process chemistry and catalyst
structure been obtained. The authors concentrate on the catalytic
chemistry of the processes, dealing in some detail with the structure of
the most important types of catalysts and the relationship of structure
to activity.