Vanadium phosphorus oxide catalyst

Complex vanadium-phosphorus-oxide catalysts are the most successful industrial catalysts for the selective oxidation of /i-butane to maleic anhydride (MA) with uses in tetrahydrofurans (THE) and polyurethane intermediates. A schematic diagram of the reaction is shown in figure 3.21(a). These catalysts have been studied extensively (e.g. Centi et al 1993, Bordes 1987). In the selective catalysation of a-butane to MA, the best active phase in the V-P-0 system is identified as the vanadyl pyrophosphate, (VO)2P207 (hereafter... 

SELECTIVE OXIDATION OF METHYL ETHYL KETONE TO DIACETYL OVER VANADIUM PHOSPHORUS OXIDE CATALYSTS. 

Selective oxidation of methyl ethyl ketone to diacetyl has been studied by passing a mixture of the ketone in artificial air over vanadium phosphorus oxide catalysts in the temperature range 200-350 C. Products observed included diacetyl, methyl vinyl ketone, acetaldehyde, acetic acid and carbon dioxide. C4 products were favoured at low temperatures and at low or zero oxygen partial pressures. These results are rationalised in terms of two pathways for C2 products, namely oxidation of the double bond in the enol form of methyl ethyl ketone to yield acetic acid and acetaldehyde, and acid catalysed hydration of the keto form to yield acetaldehyde only. The C4 products are envisaged to go through a common intermediate, namely, CH3COCHOHCH3, formed by interaction between methyl ethyl ketone and lattice oxygen. 

C for 2 hours in air yielding a vanadium phosphorus oxide catalyst with a nominal P V atomic ratio of 1.2 1. The final product was dark green in colour. This catalyst will be identified below as 1.2PV(dir). 

Grasselli, R.K. and Sleight, A.W. (1991) Key Structure-Activity Relationships in the Vanadium Phosphorus Oxide Catalyst System, Elsevier, Amsterdam. 

Understanding the microstructural transformation mechanism which takes place during the activation of vanadium phosphorus oxide catalysts... 

Coupled Vanadyl Centres in Vanadium Phosphorus Oxide Catalysts Essential Structural Units for Effective Catalytic Performance in the Ammoxidation of Methylaromatics... 

Literature descriptions of active sites on oxide catalysts are often speculative and very often just generate a picture of the surface active site by extrapolation of the bulk structure. In general they envisage approach of the starting material to the active site in a preferred orientation without any indication of how the preferred orientation is established. In addition, the description of the active site is usually restricted to a small number of molecules. For example, the vanadium phosphorus oxide catalysts used for n-butane oxidation to maleic anhydride is based on the vanadyl pyrophosphate structure and an active site architecture is... 

B.K.Hodnett, Vanadium-phosphorus oxide catalysts for the selective oxidation of C4... 

J. R. Ebner and M. J. Thompson, An active site hypothesis for well-crystallized vanadium phosphorus oxide catalysts systems . Catalysis Today, 16, 51-60 (1993). 

G. J. Hutchings, Effect of promoters and reacting concentration on the selective oxidation of n-butane to maleic anhydride using vanadium phosphorus oxide catalysts. Applied Catalysis, 72,1-32 (1991). 

Vanadium Phosphorus Oxide Catalysts for n-Butane Oxidation. Vanadium phosphates have been extensively studied since Bergmann and Frisch (189) found them to be effective catalysts in the oxidation of n-butane to maleic anhydride ... 

Vanadium-Phosphorus Oxide Catalyst for /t-Butane Selective Oxidation From Catalyst Synthesis to the Industrial Process... 

Vanadium-Phosphorus Oxide Catalyst forn-Butane Selective Oxidation... 

Hodnett B.K. and Dehnon B. (1984). Influence of calcination conditions on the phase composition of vanadium-phosphorus oxide eatalysts, A/rp/. Catal., 9, 203-211. Hodnett B.K. (1985). Vanadium-Phosphorus Oxide Catalysts for the Selective Oxidation of C4 Hydrocarbons to Maleic Anhydride Catal. Rev.-Sci. Eng., 27, pp. 373 24. 

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