Structure and reactivity of titania-supported oxides. Part 1: vanadium oxide on titania in the sub- and super-monolayer regions

Abstract

P-25, 55 i3 m2gsy; 2-1 Vanadium oxid has been deposited gn TiO (washed anatase, 10 m g ; Degussa Eurotitania, 46 m g-l) gy aqueous impregnation of (NH) [VO(C 0) ] and by reaction with VOCl org&Pc sol3eEttP. VO(OR) (R=lBu) and VO(acac) in Single applications of tl?;! last taree reagents form no z more than a mon!layer of vanadium oxide VO,, a monolayer being defined as 0.10 wt.% V,O$ per m of surface. When less than about four monolayers of VD are pre ent, there is in most cases only a single TPR peak: T,,, valueg, which increase with V 0 content, are almost independent of the method used but varv slightly with t&e5support (P-25 < Eurotitania < washed anatase). The 995 cm-l hand, characteristic of V=O in V205, VOX is present. only appears when more than a monolayer of In the sub-monolayer region, VD is best formulated as an oxohydroxy species bonded to two surface oxygens. AsXthe V 0 content is increased, layers of disordered V 0 are formed on limited ar a of the surface, but crystalline $2 V 0 only oc&F?s, probably on top of the disordered V 0 ezcseds about four monolayers, $ 7' when the V O5 content and takes the form of c cular crysta s exposing P only planes perpendicular to the a and b axes. INTRODUCTION A number of recent papers from our two laboratories have concerned the preparation, characterisation and catalytic properties of monolayers of vanadium oxide (VOX) on Ti02, principally as anatase [l-5]. These have been made chiefly by specific reactions between the vanadium precursor and the OH groups on the Ti02 surface: precursors used include VO(acac)2 in solution [2,3] and VOC13 both as vapour 141 and in solution [5]. These methods can be applied to give not more than a monolayer of VOX, this designation beinq used to denote that the species formed are not well-defined, but are certainly not equivalent to crystalline V205. However by repetition of the procedure [Z],

The Effect of Acidic and Redox Properties of V2O5/CeO2–ZrO2 Catalysts in Selective Catalytic Reduction of NO by NH3

“…. Similarly, Baiker et al [21] also reported that titania supported vanadium oxide catalysts exhibited only one reduction peak as also reported by Bond et al [22] who found VO x monolayer species to be reduced in a single step from V 5? to V 3?…”

Preparation and characterization of VOx/TiO2 catalytic coatings on stainless steel plates for structured catalytic reactors

“…Bond et al [37,38] have demonstrated that, as the V loading increases, the formation of the polyvanadate monolayer is followed by the building of a disordered VO x phase in the one-to-four monolayers equivalent range, and (Table 5 and Figure 7), we observe indeed that V/Ti increases linearly up to 0.2 for V 2 O 5 /TiO 2 below 3.5 wt% , after which value the slope is far smaller.…”

Selective oxidation of methanol to form dimethoxymethane and methyl formate over a monolayer V2O5/TiO2 catalyst

“…It was found that vanadia on a titania surface forms different types of structures depending on the vanadia content and the preparation technique [27][28][29][30][31][32][33][34]. At vanadia content below 10 % of monolayer (ML), only a monomeric isolated structure exists, which has a tetrahedral coordination (VO 4 ) in dehydrated conditions [29,33].…”