Vanadium sulfide transition

The transition metal trichalcogenides MX3 (M = Ti, Zr, Hf, Nb, Ta X = S, Se) have been studied in some detail. All the trichalcogenides contain anion-anion bonding and consequently a redox competition exists between electron transfer to the metal center and electron transfer to the anions. The situation is the converse of the deintercalation of the thallium vanadium sulfides, where the competition is between oxidation of T1+ cations and that of the metal sulfur framework. 

The class of layered transition metal dichalcogenides has been of great interest because of their varied electronic properties and chemical reactions. Most compounds of this class may be prepared by stoichiometric reactions of the elements above 500°. However, the highest vanadium sulfide that can be made in this manner is VjSg. An amorphous VS has been prepared by the metathetical reaction of LijS and VC. The method presented here allows preparation of polycrystalline VSj with the Cdiz structure. ... 

With other transition metal sulfides the mixed vanadium-silver cubane-like cluster, (Et4N)2[Ag2V2S4 S2CN(OC4H8)2 2(SPh)2] (166)1092 and [ y-C5Me5)WS3 2Ag3 (PPh3)3]N03 (167), have been reported.1093... 

In the first transition metal series, ions of vanadium, cobalt, nickel and copper became more available later as most sulfide was removed. 

This article is focused on HDN, the removal of nitrogen from compounds in oil fractions. Hydrodemetallization, the removal of nickel and vanadium, is not discussed, and HDS is discussed only as it is relevant to HDN. Section II is a discussion of HDN on sulfidic catalysts the emphasis is on the mechanisms of HDN and how nitrogen can be removed from specific molecules with the aid of sulfidic catalysts. Before the discussion of these mechanisms, Section II.A provides a brief description of the synthesis of the catalyst from the oxidic to the sulfidic form, followed by current ideas about the structure of the final, sulfidic catalyst and the catalytic sites. All this information is presented with the aim of improving our understanding of the catalytic mechanisms. Section II.B includes a discussion of HDN mechanisms on sulfidic catalysts to explain the reactions that take place in today s industrial HDN processes. Section II.C is a review of the role of phosphate and fluorine additives and current thinking about how they improve catalytic activity. Section II.D presents other possibilities for increasing the activity of the catalyst, such as by means of other transition-metal sulfides and the use of supports other than alumina. 

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