Author Topic: Vanadiumcatalyst for gasphase oxidations  (Read 3069 times)

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ragnaroekk

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Vanadiumcatalyst for gasphase oxidations
« on: July 09, 2003, 03:41:00 PM »
Several times vanadiumpentoxide was mentioned over the the times as catalyst useful for oxidations mostly in the gasphase. One example is the oxidation of toluene to benzaldehyde. Also always was mentioned that vanadiumpentoxide is easy available at pottery supply houses. Thus maybe true but true is also that a successful reaction with this compound bought from a pottery supply is not very probable. It is the same as with manganesedioxide (MnO2) - the catalyst has to be fresh prepared for maximal activity - also bought catalyst from chemsupplyhouses equals not the properties of a freshly prepared one. (exemptions exist, TiO2 catalyst from DEGUSSA is told to beat everything else to buy or to prepare by oneself...)

Vanadium oxidation catalyst on silicagel:

Chemicals:

Silicagel ((SiO2)n), uncolored, granulated
Potassiumsulfate (K2SO4)
Ammoniummetavanadate (NH4VO3)

all of those should be available without hassle not at least as only small amounts are needed.

Preparation:

Prepare a hot saturated solution of 5gram ammoniummetavanadate and 1gram potassiumsulfate with about 50ml H2O. Mix with 50gram silicagel, evapourate under stirring and heating, dry until completeness in the oven at 130°C.
The catalyst has to be activated by heating in a stream of dry oxygen (air) at 450°C.
This forms the actual catalyst divanadiumpentaoxide (V2O5) from ammoniummetavanadate.
2 NH4VO3 -> V2O5 + 2 NH3 + H2O
Potassiumsulfate stays unchanged and functions as a promotor of the oxidation in the following catalysis.

The catalyst described is useful for SO2 -> SO3 and many other reactions. Of course exists a bunch of variations on amounts, cocatalysts and promotors, but te catalyst prepared afer this method will work for almost all gasphase reactions calling for a vanadiumcatalyst. The principle of the preparation stays the same anyways.

An interesting variation on preparations of this group of (oxidation) catalysts is the so called "preparation by ignition". A search at espacenet will unveal the related patents.
For the HIVE this is to "explosive"   ;)


for informational purposes only - don´t try this at home kids!
RagNaROEkk