UNSUPPORTED TRANSITION METAL SULFIDE CATALYSTS:RATIONAL DESIGN AND ACTIVITY - PROPERTY CORRELATIONS

摘要

Many works on the unsupported mixed Ni/Co - Mo/W and other transition metal sulfides were carried out during the recent years.Such catalysts might be promising from the point of view of specific mass or volume activity due to high contents of active sites in them.From the other hand,the properties of the unsupported sulfides are devoid of the support influence making them more suitable as model systems in the studies aimed on basic understanding of hydrotreating reactions mechanisms and building of the property-activity correlations.Despite considerable experimental effort and advanced theory background,available now,the Ni/Co-Mo/W supported catalysts remain the only widespreadly used hydrotreating catalysts up to date.In the present contribution,different classes of the unsupported mixed sulfides are considered on a common basis,such as Ni/Co-Mo/W bulk-like sulfides,Chevrel phases,thiospinels,or pentlandites.New approaches to the preparation of highly dispersed ternary sulfides and experimental difficulties of such studies are discussed.A tentative of comparison on a common basis of thiophene HDS activity is undertaken.