Characteristics of Vanadium Complexes in Petroleum Before and After Hydrotreating

(NEt4)3[V6O2S4(edt)6]: a model for the adsorption of naked [VO]2+ units on vanadium sulfide surfaces

“…1 ORTEP representation at the 50% probability level for the anion of complex 2. Selected interatomic distances (A): V(l)-.-V(2), 2.852(4): V(l)**.V(4), 3.298(6); V (2). **V(3), 2.823(5); V(2)**-V(4), 3.279(5); V(3).…”

“…We do not believe the [VO]2+ groups are involved in the observed reduction or oxidation processes, for reasons stated earlier and because it seems highly unlikely that [V0]2+ groups would be oxidized in preference to VIII centres. The addition of the [VO]2+ and extra S2-units to the core of 3 thus results in the core being stabilized at a lower oxidation level (2) and all reductions becoming more facile (2.e. less negative potentials).…”

“…1 The formation of V sulfides (primarily V2S3 and V3S4) has deleterious consequences on the activity of the supported Mo HDS catalyst, although they are themselves good HDM catalysts, catalyzing the further conversion of vanadyl species into V sulfides. 2 The mechanism of this transformation is believed to involve initial Lewis acid-Lewis base interactions between the VO(por) (por = porphyrin) molecules and the V sulfide surface, followed by demetallation and subsequent reduction of the porphyrin ring to a chlorin.3--5 The liberated [VO]2+ entity becomes bound to surface S groups, as determined by EPR and EXAFS studies on used catalysts that indicate [VO]2+ groups in a VOS4 first-coordination sphere .2.697 This is summarized in Scheme 1. The surface-bound [VO]2+ groups subsequently get sulfided and reduced to form another layer of the growing V sulfide crystalline phase.…”

“…Thus, the crude oil V impurities catalyze their own removal (autocatalytic HDM activity). 2 We have for a long time sought a molecular system to model the surface-bound [VO]2+ units viz. a complex containing…”

MCM-41-supported vanadium catalysts structurally modified with Al or Zr for thiophene hydrodesulfurization

“…During HDT processes, the porphyrins are decomposed and the metal is deposited as a sulfide on the catalyst surface causing its permanent deactivation [1,4]. Although metal deposits are considered as one of the factors responsible for the catalysts deactivation, some authors have reported that these metal sulfides could act as catalytically active sites in the HDT processes [5,6]. Therefore, the development of vanadium-based catalysts to carry out HDT reactions is considered to be a research area of great interest.…”