Dehydrogenation vanadium/chromium oxides

Alkane Dehydrogenation over Vanadium and Chromium Oxides... 

Ethylbenzene dehydrogenation is generally catalyzed by a potassium-promoted iron oxide catalyst. The most widely used catalysts are composed of iron oxide, potassium carbonate, and various metal oxide promoters. Examples of metal oxide promoters include chromium oxide, cerium oxide, molybdenum oxide, and vanadium oxide. " The potassium component substantially increases catalyst activity relative to an unpromoted iron oxide catalyst. Potassium has been shown to provide other benefits. In particular, it reduces the formation of carbonaceous deposits on the catalyst surface, which prolongs catalyst life. 

The efficiency of zinc-chromium and vanadium-magnesium oxide catalysts in the reaction of butanediol dehydrogenation has been established. The optimum reaction conditions in butadione synthesis providing high yields and selectivity have been found. Experimental substantiation of principles for the purposeful synthesis of the catalytic systems mentioned above is considered. The catalysts were prepared based on these principles. 

We have investigated a series of the dehydrogenating catalysts for this reaction. Our attention was focused on two of them. Further study of 2,3-butanediol dehydrogenation and oxidative dehydrogenation to butadione was performed using zinc-chromium oxide catalysts and vanadium-magnesium oxide catalysts as well. 

Catalysts based on other metals, such as gallium and vanadium oxides, can be also employed in DH processes [8, 9]. For example, silica-supported gallium oxide catalyst has been found to be moderately active, but quite selective in propane dehydrogenation (up to 80%) and results in much less coking, 1/10 of that using a silica-supported chromium oxide [8], There is an extensive research aimed to find new DH catalysts that will perform well at moderate temperatures, suffer less from coke deposition and maintain catalytic activity for long periods of time without regeneration. 

Karamullaoglu G, Dogu T (2007) Oxidative dehydrogenation of ethane over chromium — vanadium mixed oxide and chromium oxide catalysts. Ind Eng Chem Res 46 7079-7086... 

It has been shown that the activity of niobia for the oxidative dehydrogenation of propane can be increased by adding vanadium or chromium, while maintaining a high selectivity towards propylene. 

A classical example of the dehydrogenative formation of a carbon-carbon double bond conjugated with an aromatic ring is the dehydrogenation of ethylbenzene to styrene at 500-600 °C over a complex catalyst containing oxides of zinc and chromium [1090] or at 625 °C over vanadium pentoxide on alumina [478]. 

A study of the catalytic properties of the oxides of vanadium and chromium, widely used as dehydrogenation catalysts, has shown that these oxides will catalyze the reaction of hydrogenation. 

In particular it is reported here the reaction of hydrogenation in the presence of oxides of vanadium and chromium, well known as dehydrogenating catalysts. 

Coudurier, G., Decottignies, D., Loukah, M., and Vedrine, J. C., Vanadium and Chromium Based Phosphates as Catalysts for Oxidative Dehydrogenation of Ethane , presented at 13th North American Meeting at the Catalysis Society, Pittsburgh, 1993. 

As an example, the joint analysis of IR and Raman spectra provided evidence of the partial ordering of cations in a Fe-Cr corundum-type mixed sesquioxides, which are used industrially as high temperature water-gas shift catalysts, but are also active in olefin oxidative dehydrogenation. X-ray diffraction (XRD) patterns of these solids indicate the conmdum-type structure without any superstructure. This implies that iron and chromium ions are randomly distributed. IR and Raman spectra instead definitely show that cations are at least partially ordered in layers such as in the ilmenite-type superstructure. Similarly, XRD analysis shows a cubic (non-ferroelectric) structure of nanometric BaTi03, while vibrational spectroscopies reveal microscopic asymmetry of this structure. Similarly, IR spectroscopy allowed the determination of the state of vanadium in solid solution in Ti02 anatase catalysts, and the presence of Ti" + in the silicalite framework of TSl catalysts, " used for the selective oxidation of phenol and the ammoximation of cyclohexanone with hydrogen peroxide. 

KaramuUaoglu, G., Onen, S., and Dogu, T. Oxidative dehydrogenation of ethane and isohutane with chromium-vanadium-niohium mixed oxide catalysts. Ghent. Eng. Process. 2002, 41, 331. 

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