Vanadium pentoxide

 

Vanadium pentoxide

Chemical formula	V2O5
OTP appearance	yellow solid
Molar Mass(g/mol)	181.880
Density(g/cc)	3.357
Melting Point(°C)	690
Boiling Point(°C)	1750(decomp to V2O4)
Solubility in water(g/L)	0.8
NFPA 704	0 3 0

Uses

Primary

• Vanadium pentoxide is a key catalyst in the production of sulfur trioxide via the contact process for the making of sulfuric acid, phthalic anhydride, and others.

Natural occurrence

• does occur naturally as the very rare minerals shcherbinaite. and navajoite

Production

Extraction

from ores not containing iron or uranium

This would include vanadinite, patronite, roscoelite:

... vanadium-bearing ores or slags are crushed, ground, screened, and mixed with a sodium salt such as sodium chloride or sodium carbonate. This charge is then roasted at about 850° C (1,550° F) to convert the oxides to sodium metavanadate, which can be leached in hot water. With the acidulation of the leachate with sulfuric acid, the vanadium is precipitated as sodium hexavanadate. This compound, known as red cake, can be fused at 700° C (1,300° F) to yield technical-grade vanadium pentoxide (at least 86 percent V2O5, or it can be further purified by dissolving it in an aqueous solution of sodium carbonate. In the latter case, the iron, aluminum, and silicon impurities in the red cake precipitate from solution upon adjustment of the acidity. The vanadium is precipitated as ammonium metavanadate by adding ammonium chloride. After filtration, the precipitate is calcined to produce V2O5 of a purity greater than 99.8 percent.

Roughly:

1. Fuse ore with sodium chloride, producing sodium metavanadate(NaVO₃)

   Pb₅(VO₄)₃Cl + 2 NaCl + O₂

   {

   →

   850°C}

   3 NaVO₃ + insoluble dross

   4 VS₄ + 2 Na₂CO₃ + 21 O₂

   {

   →

   850°C}

   4 NaVO₃ + insoluble dross

2. Leach with water and evaporate to dryness
3. Combine with sulfuric acid precipiating red cake
4. Calcine red cake at 700°C producing crude vanadium pentoxide

Synthesis

Thermally decompose ammonium metavanadate at 200°C

2 NH₄VO₃

{

→

200°C}

V₂O₅ + 2 NH₃ + H₂O