Ammonium vanadate, preparation

The vanadium pentoxide catalyst Is prepared as follows Suspend 5 g. of pure ammonium vanadate in 50 ml. of water and add slowly 7 5 ml. of pure concentrated hydrochloric acid. Allow the reddish-brown, semi-colloidal precipitate to settle (preferably overnight), decant the supernatant solution, and wash the precipitate several times by decantation. Finally, suspend the precipitate in 76 ml. of water and allow it to stand for 3 days. This treatment renders the precipitate granular and easy to 6lter. Filter the precipitate with suction, wash it several times with cold 5 p>er cent, sodium chloride solution to remove hydrochloric acid. Dry the product at 120° for 12 hours, grind it in a mortar to a fine powder, and heat again at 120° for 12 hours. The yield of catalyst is about 3 - 5 g. 

Vanadium Carbide. Vanadium pentoxide [1314-62-17, V2O5, or vanadium trioxide [1314-34-7] VO3, are the most satisfactory oxides for the preparation of VC. Vanadium pentoxide is best prepared by igniting chemically pure ammonium vanadate [7803-55-6] NH VO, in the presence of moist oxygen to avoid reaction with nitrogen V2O3 is obtained by reduction of V2O3 with hydrogen (see Vanadium compounds). 

Prepare a series of standards from potassium dihydrogenphosphate covering the range 0-2 mg phosphorus per 100 mL and containing the same concentration of acid, ammonium vanadate, and ammonium molybdate as the previous solution. Construct a calibration curve and use it to calculate the concentration of phosphorus in the sample. 

Phthalocyanine 2 can be prepared from 3-phenylphthalic acid (1) and vanadium(III) chloride in the presence of urea and ammonium vanadate at high temperature in a melt.401... 

Anthrapyrimidine and its substituted derivatives are obtained by condensation of 1-aminoanthraquinone (or its derivatives) with formamide or aqueous form-aldehyde/ammonia in the presence of an oxidant, such as ammonium vanadate or m-nitrobenzosulfonic acid. A newly developed, more simple route proceeds via formamidinium chloride, which is prepared from 1-aminoanthraquinone with di-methylformamide and thionyl chloride or phosphorus oxychloride. Cyclization in a solvent in the presence of ammonium acetate affords the desired product ... 

L — maltolate the coordination environment of the vanadium in K[V02(malt)2] H2O is approximately octahedral, the two 0x0 ligands being in cis positions. [K(H20)e] units link adjacent vanadium(V) complex anions to give a chain structure 166). The main products of aerobic oxidation of [V O(dmpp)2l in aqueous solution are [V02(dmpp)] and [VOo(dmpp)2]. High pH favors these V products, whereas at low pH V species predominate 171). Vanadium(V) also forms a VO(OR)(malt)2 series, readily prepared from ammonium vanadate, maltol, and the appropriate alcohol in a water-alcohol-dichloromethane medium 172), and 3-hydroxy-4-pyridinonate analogues V0(0R)L2 on oxidation of their oxovanadium(IV) precursors in solution in the appropriate alcohol ROH 168). 

AIPO4-5 molecular sieve (BET surface area, 299 m g ) used in this study was prepared by the method of Wilson et al. [1j. VjOg/AIPO -S samples were prepared by impregnating with aqueous solutions of ammonium vanadate after removing templating agent in the AIPO -S by calcining at 530°C. The samples were dried at 110 C for 24 h then calcined in air at 550°C for 2 h. VAPO -S was prepared from gel mixture of phosphoric acid, pseudoboehmite, vanadium pentoxide, tri-propylamine and water (1.3 PrjN x AljOj PjOj 40 HjO) by crystallization at 165°C for 3 - 7 days [7. ... 

Preparation of Vanadium(V) Oxide. Weigh 0.5 g of ammonium vanadate in a crucible. Roast the crucible with its contents up to a constant mass in a crucible furnace at 300-400 °C. Roast in an atmosphere of dry oxygen or air, feeding it into the furnace from a gas meter. Why is the substance roasted in an oxygen atmosphere Write the equation of the reaction. 

Preparation of Vanadium Oxychloride by Reacting Vanadium(V) Oxide with Thionyl Chloride. Place 16 g of ammonium vanadate into a porcelain crucible. Roast the substance up to a constant mass at 500-550 °C in a crucible furnace, passing oxygen into the latter via a glass tube from a gas meter. 

Preparation of Ammonium riuovanadate(III). Assemble an apparatus as shown in Fig. 115. Put a porcelain boat with 5 g of ammonium vanadate into quartz tube 5. Check the tightness of the... 

For vanadium(III) /8-diketonates the recommended preparation is reduction with the dithionite of compounds such as oxovanadium(IV) sulfate, vanadium(V) oxide or ammonium vanadate followed by the addition of the /3-diketone in alcohol.240... 

Bring together in a liter flask 1 g. of ammonium phosphate, 15 g. of ammonium tungstate, 3 g. of ammonium vanadate, 20 cc. of ammonium hydroxide, and 700 cc. of water. The ammonium tungstate and vanadate may be prepared from the corresponding anhydrides WO3 and VAX, which are more available. 

Mandelin s Test Prepare the reagent by dissolving 0.5 g of ammonium vanadate in 1.5 mL of water and diluting to 100 mL with sulfuric acid. When dipyridamole is reacted with this reagent, the resulting solution has a violet color. 

Color/Stop Solution While stirring, add 250 mL of Ammonium Vanadate Solution to 250 mL of Ammonium Heptamolybdate Solution. Slowly add 165 mL of 65% nitric acid. Cool to ambient temperature. Quantitatively transfer the mixture to a 1000-mL volumetric flask, dilute to volume with water, and mix. Prepare fresh daily. 

Preparation of Vanadium(V) Oxide. Put 0.1-0.2 g of ammonium vanadate onto the lid of a crucible. Heat the lid with the flame of a burner through an asbestos gauze. What do you observe Write the equation of the reaction. 

MgO-supported vanadium catalyst (with a 10 wt% of V-atoms Sbet= 108 m g ) has been prepared by impregnation of MgO with an aqueous ammonium vanadate solution [1,2] and calcined at the same conditions indicated above. It will be referred as V/MgO. 

Kotter et al. [79] prepared V and Ti-containing catalysts by dissolving appropriate amounts of ammonium vanadate in a titanium oxychloride solution followed by hydrolysis and evaporation. The 20 wt.-% V2O5 catalyst thus formed showed a decrease in BET specific surface area from 85 to 20 m g after heating the sample at 713 K for 100 h. 

In an efficient procedure for the preparation of 2,5-bis[2-carboxyanilino]-l,4-benzoquinone, Braun and Mecke used sodium chlorate as oxidant, catalyzed by ammonium vanadate. 

Impregnated catalysts (IPV) were prepared by mixing of ammonium vanadate aqueous solution and orthophosphoric acid with aerosil suspension at the presence of oxalic acid followed by heating under stirring and ftuther calcination of the solids at 600 C for 2-3 h (fp=0.6). 

---