Preparation of Vanadium V Oxide

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. 

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Preparation of Vanadium(V) Oxide. Put 0.1-0.2 g of ammoniuni 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. 

The catalyst used in the production of maleic anhydride from butane is vanadium—phosphoms—oxide (VPO). Several routes may be used to prepare the catalyst (123), but the route favored by industry involves the reaction of vanadium(V) oxide [1314-62-1] and phosphoric acid [7664-38-2] to form vanadyl hydrogen phosphate, VOHPO O.5H2O. This material is then heated to eliminate water from the stmcture and irreversibly form vanadyl pyrophosphate, (V(123,124). Vanadyl pyrophosphate is befleved to be the catalyticaHy active phase required for the conversion of butane to maleic anhydride (125,126). 

Preparation of Vanadium by the Aluminothermic Process. Perform the experiment in the presence 0/ your instructor Wear eye protection or a protective mask Thoroughly dry vanadium oxide in a drying cabinet at 120-130 °C. Prepare a mixture of 10 g of vanadium(V) oxide with 6.5 g of aluminium in grains. Place the mixture into a chamotte crucible as shown in Fig. 120. 

Preparation of Sodium Vanadate. Put a thoroughly triturated mixture of 0.5 g of vanadium(V) oxide and 1 g of sodium carbonate into a crucible and place it into a crucible furnace. Raise the furnace temperature to 800 °C and control the course of the process. Lower the hot crucible into a beaker with water to separate the melt easily from the crucible walls. Crush the melt in a mortar and treat it with water while heating. Evaporate the solution until crystallization begins. Examine the crystals under a microscope. Write the equation of the reaction. 

Preparation of Vanadium Oxychloride and Studying of Its Properties. Preparation of Vanadium Oxychloride by Roasting a Mixture of Vanadium(V) Oxide with Charcoal in a Chlorine Stream. Prepare a fine mixture of 5 g of vanadium(V) oxide, 3 g of charcoal, and 5 g of dextrin. Add water dropwise to the mixture until a paste... 

The reaction apparently proceeds without difficulty with any quantity of vanadium (V) oxide if the specified ratio of reactants is maintained. Larger ratios of vanadium (V) oxide give large crystals or crystal aggregates of product in the reaction flask because the solubility of the product is exceeded. Vanadium (V) oxide prepared by decomposition of pure ammonium metavanadate at 250° gives higher yields of product but no increase in its purity. 

One hundred and fifty grams (1 mol) of vanadium(III) oxide, either the commercial powder or that prepared by hydrogen reduction of vanadium(V) oxide, is mixed with 684 g. (12 mols) of ammonium hydrogen fluoride. The excess ammonium hydrogen fluoride serves to ensure complete reaction of the vanadium(III) oxide. The mixture is heated in a graphite crucible of the approximate dimensions 5-in. o.d. X 6-in. height X i-in. thickness. After it... 

Pure anhydrous vanadium(III) sulfate can be prepared by the reduction of vanadium(V) oxide dissolved in sulfuric acid with elemental sulfur as the reducing agent.The procedure given below is an adaptation of this method. 

Vanadium(II) sulfate can be prepared by reduction of vanadium (V) oxide in sulfuric acid solution either electro-lytically or with sodium amalgam or with zinc, followed by evaporation of the solution in vacuo over phosphorus (V) oxide.It also may be prepared by the electrolytic reduction of vanadium(IV) oxide sulfate, VOSO4, which is the basis of this procedure. 

Until comparatively recently only vanadium had a significant coordination chemistry and even so the majority of its compounds are easily oxidized and must be prepared with air rigorously excluded. The usual methods are to use VCI3 as the starting material, or to reduce solutions of vanadium(V) or (IV) electrolytically. However, the reduction of pentahalides of Nb and Ta by Na amalgam or Mg, has facilitated the expansion of Nb " and Ta " chemistry particularly with S-and P-donor ligands. 

Vanadium phthalocyanine (PcVO) is prepared from vanadium(IIl) chloride in a melt of phthalonitrile228 to which sometimes ammonium vanadate137 or molybdate229 and urea are added. Also a reaction with vanadium(V) oxide and phthalonitrile in pen tan-1-ol has been performed.230 Besides these direct syntheses, transformation of PcH2 to PcVO in refluxing dimethylformamide with vanadyl sulfate (V0S04) has been carried out.231... 

The incorporation of vanadium(V) into the framework positions of silicalite-2 has been reported by Hari Prasad Rao and Ramaswamy . With this heterogeneons oxidation catalyst the aromatic hydroxylation of benzene to phenol and to a mixtnre of hydroqninone and catechol conld be promoted. A heterogeneons ZrS-1 catalyst, which has been prepared by incorporation of zirconinm into a silicalite framework and which catalyzes the aromatic oxidation of benzene to phenol with hydrogen peroxide, is known as well in the literature. However, activity and selectivity were lower than observed with the analogous TS-1 catalyst. 

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. 

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... 

Vanadium(V) oxide, V2O5, a yellow, amphoteric solid, may be obtained as an intermediate in the preparation of vanadium metal, as indi-... 

Vanadium(V) oxide is obtained on burning the finely divided metal in an excess of oxygen, although some quantities of lower oxides are also formed. The usual method of preparation is by heating ammonium metavanadate ... 

However, this reaction is very slow in the absence of a catalyst. One of the mysteries during early research on air pollution was how the sulfur dioxide produced from the combustion of sulfur-containing fuels is so rapidly converted to sulfur trioxide in the atmosphere. It is now known that dust and other particles can act as heterogeneous catalysts for this process (see Section 15.9). In the preparation of sulfur trioxide for the manufacture of sulfuric acid, either platinum metal or vanadium(V) oxide (V205) is used as a catalyst, and the reaction is carried out at approximately 500°C, even though this temperature decreases the value of the equilibrium constant for this exothermic reaction. 

Very pure vanadium (V) oxide is prepared from the purified ammonium metavanadate by decomposition in oxygen, as described in the first paragraph of this procedure. (The checkers report 27.5 g. yield, 54.3%.)... 

Chromium(VI) oxide nitrate and vanadium(V) oxide nitrate were first prepared by Schmeisser and Lutzow by the reaction of chromium(VI) oxide and vanadium(V) oxide with nitrogen(V) oxide. The nitrogen(V) oxide was prepared in the solid state by dehydration of fuming nitric acid with phosphorus(V) oxide. The method described below simplifies the preparation of anhydrous nitrogen(V) oxide and shortens significantly the time required. The products obtained can be protected from hydrolysis by totally excluding water from the all-glass system. 

After the preparation of the nitrogen(V) oxide is complete, 18.2 g. (0.10 mol) of anhydrous vanadium(V) oxide is placed in the two-necked 300-ml. reaction vessel E. The flask is heated to 100° while the vacuum is maintained, in order to dry the metallic oxide before introducing the anhydrous nitrogen (V) oxide. When the 100° temperature is reached, the vacuum in E is released at stopcock b. The flask E is allowed to cool to room temperature and is then immersed in a Dry Ice-methanol bath. Stopcock 6 is changed to allow flow of the nitrogen(V) oxide into the reaction vessel E. Stopcocks e and / are opened to the outside and stopcocks c and d (to the vacuum pump) are closed. The Dry Ice-methanol baths are removed from traps A, C, and D, and under a flow rate of 0.06 standard cubic feet per minute (1.7 l./minute) of ozone the nitrogen (V) oxide is sublimed into the reaction vessel. To assure complete sublimation of the nitrogen(V) oxide, traps A, C, and D may be immersed in a water bath at 50°. 

Bi s (2,4-pentanedionato) oxovanadium (I V) [vanadium-(IV) oxy(acetylacetonate)] has been prepared by direct reaction of 2,4-pentanedione and vanadium(V) oxide. By using the same method, bis(4-imino-2-pentanonato)oxo-vanadium(IV) has been prepared by substituting acetyl-acetone imide (4-imino-2-pentanone) for acetylacetone. ... 

A. N. Volkova, A.A. Malygin, S.I. Koltsov, V.B.Aleskovskii, Method of Preparation of Vanadium Oxide Catalyst for Organic Compounds Oxidation, USSR Patent No. 42447 (1976). 

EPA. 1983. Reportable quantity document for vanadium(V) oxide (vanadium pentoxide). Prepared for U.S. Environmental Protection Agency, Office of Solid Waste by U.S. Environmental Protection Agency, Criteria and Assessment Office. Cincinnati, OFI ECAO-CIN-R224... 

Several other biomimetic approaches to the synthesis of cephalotaxine have also been reported. In 1977, Kupchan etal. (72,73) prepared tetrahy-droisoquinoline 214, which underwent intramolecular oxidative coupling to 215 by means of vanadium(V) oxytrifluoride and trifluoroacetic acid/ trifluoroacetic anhydride (Scheme 38). Treatment of 215 with 1 N sodium hydroxide in methanol yielded the ring-expanded product, imine 216, which was converted in five steps to amine 217. Transannular cyclization of 217... 

Vanadium(IV) oxy(acetylacetonate) has been prepared by direct reaction of acetylacetone (2,4-pentanedione) with either hydrous vanadium(IV) oxide or an aqueous solution of an oxovanadium(IV) salt.1-3 Procedure A is an adaptation of this approach. The facts that acetylacetone can reduce vanadium(V) oxide to vanadium(IV) oxide, react as an acid4,5 with the latter to give the desired product, and behave as a solvent for that product are combined in procedure B to give a synthesis based directly upon readily available starting materials. 

Martin and coworkers have demonstrated the use of cylindrical-pored templates for the preparation of tubes and fibers composed of metal oxides, metals and polymers [35,36]. Track-etching of polycarbonate films gives membranes with cylindrical pores that are randomly distributed across the membrane. The pore diameters are monodisperse and, in the example described here, are 600 nm. Lak-shmi et al. have used these membranes for the preparation of vanadium oxide fibers [36]. The pores of the organic filter were filled with vanadium(V) triiso-propoxy oxide in an argon atmosphere. Exposure to air at 60°C induces hydrolysis of the precursor before an oxygen plasma is used to remove the polycarbonate. The crystalline alpha phase vanadium oxide (V2O5) fibers obtained by this... 

The physico-chemical properties of the supports and vanadium oxide catalysts are listed in Table 2. The catalysts are labeled XVj/M, where X corresponds to the % by weight of vanadium, V to vanadium, p to the preparation method (imp=impregnation, graf=grafting) and M to the support. No marked effect of the deposition of titanium oxide on the specific surface area of the silica was detected in the case of the support TSm, while, in the case of the vanadium-based catalysts, a decrease in Sbet was observed. The vanadium surface densities are calculated as number of vanadium atoms per square nanometer of catalyst (V/nm oat) to facilitate a comparison of the samples prepared on different surface area supports [6]. The vanadium contents of the samples are quite smaller than the theoretical monovanadate monolayer coverage of 2.3 VO,/nm" [6]. 

Glasses of sodium vanadate-phosphates with various P/V ratios are prepared by melting mixtures of sodium metaphosphate (Graham s salt), vanadium (V) oxide, and sodium carbonate. 

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