Potassium pyrovanadate

Potassium Pyrovanadate, K4V207.4lI20, separates out in colourless, transparent crystals when one molecular proportion of vanadium pentoxide is dissolved in two molecular proportions of potassium hydroxide. These lose water when heated, melt, and leave a crystalline mass of the anhydrous salt K4Va07,5 which is deliquescent and melts at 910° C.6 A white, crystalline, xeadily soluble trihydrate, K4V207. SH20, has also been prepared.7... 

Basic Potassium Metavanadate, 5K20.4V20S.7H20 or K20. KV03. 7H20, separates in white crystals when a solution of potassium pyrovanadate, K4V207, is acidified with acetic acid and concentrated.4... 

An unstable double salt of potassium pyrovanadate and potassium cyanide, K4V207.4KCN.14H20, has been prepared,8 as well as a complex addition compound of sodium vanadyl cyanide and hexamethylenetetramine, Na3V0(CN)6.2C8H12N4.5Ha0.9... 

Sodium triperoxychromate Sodium peroxymolybdate Sodium peroxynickelate Sodium diperoxytungstate Potassium peroxyferrate Potassium peroxynickelate Potassium hyperoxytungstate Potassium peroxy pyrovanadate Calcium diperoxysulphate Calcium peroxychromate Zinc tetraaminoperoxydisulphate Ammonium peroxyborate Ammonium peroxymanganate Ammonium peroxychromate... 

Mg pyrovanadate (Mg2V207) was also found to be a selective catalyst for this reaction (30). A later study further showed that the catalytic performance of Mg2V207 was insensitive to the method of preparation, such that there were only minor differences whether or not the oxide contained small amounts of potassium (25). In contrast, the presence of K in Mg orthovanadate degraded its selectivity noticeably. Temperature-programmed reduction with H2 and electrical conductivity characterization in the presence of propane showed that Mg pyrovanadate could be reduced by both H2 and propane faster than Mg orthovanadate containing K (31). 

Ammonium Orthothiovanadate, (NH4)3VS4, is obtained in rhombic crystals by the action of ammonium hydrosulphide on potassium metavanadate or sodium pyrovanadate solution. It also separates out slowly from an ice-cold saturated solution of ammonium metavanadate in concentrated ammonium hydroxide which has been previously treated with hydrogen sulphide. 

The action of hydrogen sulphide at high temperatures on sodium pyrovanadate gives rise to sodium pentathiopyrovanadate, Na4V2Ss02, which is a hygroscopic substance very similar in its colour and lustre to potassium permanganate. 

Chaar, M.A., Patel, D., Kung, M.C., and Kung, H.H. Selective oxidative dehydrogenation of butane over V-Mg-O catalysts. J. Catal 1987,105, 483. Kung, M.C. and Kung, H.H. The effect of potassium in the preparation of magnesium orthovanadate and pyrovanadate on the oxidative dehydrogenation of propane and butane. J. Catal 1992, 134, 668. 

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