Vanadium pentoxide ammonium salts

The ammonium salts of vanadic acid and vanadium pentoxide have been Hsted as toxic constituents in soHd wastes under the Resource Conservation and Recovery Act (27). 

Quinones can he prepared hy the oxidation of phenols, dihydroxy-henzenes, dimethoxyhenzenes and anilines. For example, 1,4-dihydroxy-henzene (hydroquinone) can he oxidized in good yield using sodium chlorate in dilute sulfuric acid in the presence of vanadium pentoxide and also hy manganese dioxide and sulfuric acid and hy chromic acid. Other reagents which convert hydroquinones to quinones include Fremy s salt [potassium nitrosodisulfonate, (KS03)2N0] and cerium(IV) ammonium nitrate [CAN, Ce(NH4)2(N03)J. 

To obtain a high yield, it is important to use the right catalyst and the right material for containing the catalyst. With vanadium pentoxide in pyrex tubes, the yield is only 25 percent of the input furfural, but with a vanadium pentoxide/molybdenum trioxide/iron molybdate catalyst in nickel tubes, the yield is in the order of 75 percent. Interestingly, the best yields are obtained when the catalyst, prepared from appropriate ammonium salts, is cured with air at 300 °C in situ, and when it is then used directly at the reaction temperature of 270 °C without allowing it to cool down. 

Vanadium raw materials are processed to produce vanadium chemicals, eg, the pentoxide and ammonium metavanadate (AMV) primary compounds, by salt roasting or acid leaching. Interlocking circuits, in which unfinished or scavenged material from one process is diverted to the other, are sometimes used. Such interlocking to enhance vanadium recovery and product grade became more feasible in the late 1950s with the advent of solvent extraction. 

For solvent extraction of pentavalent vanadium as a decavanadate anion, the leach solution is acidified to ca pH 3 by addition of sulfuric acid. Vanadium is extracted in about four countercurrent mixer—settler stages by a 3—5 wt % solution of a tertiary alkyl amine in kerosene. The organic solvent is stripped by a soda-ash or ammonium hydroxide solution, and addition of ammoniacal salts to the rich vanadium strip Hquor yields ammonium metavanadate. A small part of the metavanadate is marketed in that form and some is decomposed at a carefully controlled low temperature to make air-dried or fine granular pentoxide, but most is converted to fused pentoxide by thermal decomposition at ca 450°C, melting at 900°C, then chilling and flaking. 

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