Titanium vanadate

Cr(II) may be used to carry out all the reactions of Ti(III), but usually under milder conditions. Applications of Cr(II) as a reductant have been reviewed. The applications include Sn(IV) chloride in the presence of catalysts such as Sb(V) or Bi(III), Sb(V) in 20% HCl at elevated temperatures, Cu(II), silver, gold, mercury, bismuth, iron, cobalt, molybdenum, tungsten, uranium, dichromate, vanadate, titanium, thallium, hydrogen peroxide, oxygen in water and gases, as well as organic compounds such as azo, nitro, and nitroso compounds and quinones. Excess Cr(II) in sulfuric acid solution reduces nitrate to ammonium ion. The reduction is catalyzed by Ti(IV), which is rapidly reduced to Ti(III). 

The colour sequence already described, for the reduction of van-adium(V) to vanadium(II) by zinc and acid, gives a very characteristic test for vanadium. Addition of a few drops of hydrogen peroxide to a vanadate V) gives a red colour (formation of a peroxo-complex) (cf. titanium, which gives an orange-yellow colour). 

The recovery of vanadium from these slags is of commercial interest because of the depletion of easily accessible ores and the comparatively low concentrations (ranging from less than 100 ppm to 500 ppm) of vanadium in natural deposits (147,148). In the LILCO appHcations the total ash contained up to 36% 20 (147). Vanadium is of value in the manufacture of high strength steels and specialized titanium alloys used in the aerospace industry (148,149). Magnesium vanadates allow the recovery of vanadium as a significant by-product of fuel use by electric utiUties (see Recycling, nonferrous LffiTALS). 

The production of acetic acid from n-butene mixture is a vapor-phase catalytic process. The oxidation reaction occurs at approximately 270°C over a titanium vanadate catalyst. A 70% acetic acid yield has been reported. The major by-products are carbon oxides (25%) and maleic anhydride (3%) ... 

H. 8-Hydroxyquinaldine (XI). The reactions of 8-hydroxyquinaldine are, in general, similar to 8-hydroxyquinoline described under (C) above, but unlike the latter it does not produce an insoluble complex with aluminium. In acetic acid-acetate solution precipitates are formed with bismuth, cadmium, copper, iron(II) and iron(III), chromium, manganese, nickel, silver, zinc, titanium (Ti02 + ), molybdate, tungstate, and vanadate. The same ions are precipitated in ammoniacal solution with the exception of molybdate, tungstate, and vanadate, but with the addition of lead, calcium, strontium, and magnesium aluminium is not precipitated, but tartrate must be added to prevent the separation of aluminium hydroxide. 

Lithium aluminum hydride reduced )J-azidoethylbenzene to j8-aminoethyl-benzene in 89% yield [600], The azido group was also reduced with aluminum amalgam (yields 71-86%) [149], with titanium trichloride (yields 54-83%) [601], with vanadous chloride (yields 70-95%) [217] Procedure 40, p. 215), with hydrogen sulfide (yield 90%) [247], with sodium hydrosulfite (yield 90%) [259], with hydrogen bromide in acetic acid (yields 84-97%) [232], and with 1,3-propanedithiol (yields 84-100%) [602]. Unsaturated azides were reduced to unsaturated amines with aluminum amalgam [149] and with 1,3-propane-dithiol [602]. 

Colorimetric Methods are used only for the estimation of very small percentages of vanadium, e.g. in vanadium steels and alloys. The most important depend on the intensity of the reddish-brown colour produced by the action of hydrogen peroxide on an acid vanadate solution.3 If chromium is present, an equal amount must be introduced into the standard vanadium solution under the same conditions of temperature, acid concentration, etc. Phosphoric acid is added to destroy any yellow colour due to ferric iron, and either hydrofluoric acid or ammonium fluoride to destroy any colour produced by titanium.4 A colorimetric method for the simultaneous estimation of small quantities of titanium and vanadium has also been worked out.5 Other colorimetric processes are based on (a) the formation of a yellow to black coloration, due to aniline black, in the presence of aniline hydrochloride and potassium chlorate or other oxidising agent,6 and (b) the orange coloration finally produced when an acid solution of a vanadate is brought into contact with strychnine sulphate.7... 

Bellobono, I.R., P.L. Pinacci, G. Riva, and C. Lagrasta (1998). Pilot-plant photomineralization of. v-triazincs in aqueous solution, by pho-tocatalytic membranes immobilising titanium dioxide and trialkyl vanadates photocatalysts. Fresenius Environ. Bull., 7 277-288. Beltran, F.J., G. Ovejero, and B. Acedo (1993). Oxidation of atrazine in water by ultraviolet radiation combined with hydrogen peroxide. Wat. Res., 27 1013-1021. 

Bismuth vanadate shows a sharp increase in reflection at 450 nm and considerably higher chroma than iron yellow or nickel titanium yellow. It has very good weather resistance both in full shade and in combination with Ti02. General pigment properties are ... 

Transition metal catalysts not only increase the reaction rate but may also affect the outcome of the oxidation, especially the stereochemistry of the products. Whereas hydrogen peroxide alone in acetonitrile oxidizes alkenes to epoxides [729], osmic acid catalyzes syn hydroxylation [736], and tungstic acid catalyzes anti hydroxylation [737]. The most frequently used catalysts are titanium trichloride [732], vanadium pentoxide [733,134], sodium vanadate [735], selenium dioxide [725], chromium trioxide [134], ammonium molybdate [736], tungsten trioxide [737], tungstic acid [737],... 

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