Ferric tungstate

In this paper, we will discuss results of the oxidation of methanol over a series of molybdates including solid solutions of ferric, chromium and aluminum molybdates and also over a new ferric tungstate phase. The mixed molybdates of iron/chromium, iron/aluminum and chromlum/aluminum were made for the first time in pure well-characterized forms. Results are compared with our earlier work over commercial mixtures of ferric molybdate and molybdenum tri oxide and a number of pure molybdates. ... 

The preparation of the new ferric tungstate phase has been described previously(jJ. It is schematically shown in Figure 1. Catalyst Characterization... 

Figure 1. Preparation Steps of Ferric Tungstate Phase ...

The mechanism and rate of hydrogen peroxide decomposition depend on many factors, including temperature, pH, presence or absence of a catalyst (7—10), such as metal ions, oxides, and hydroxides etc. Some common metal ions that actively support homogeneous catalysis of the decomposition include ferrous, ferric, cuprous, cupric, chromate, dichromate, molybdate, tungstate, and vanadate. For combinations, such as iron and... 

The reaction of Mo(H20)63+ and nitrate in aqueous solutions results in the formation of Mo2Oi(H20)62+ and nitrite. Mo(III) coordinated to oxygen and nitrogen donor atoms of EDTA also reduces nitrate in aqueous solutions. The reduction of nitrate by a Mo(III)-EDTA complex results in the formation of nitrite and a Mo(V)-EDTA complex, as determined by chemical and spectrophotometric techniques. These reactions serve as models for biological nitrate reduction. In addition, molybdate coordinates to naturally produced phenolates. The molybdenum-coordinating phenolates also coordinate tungstate and ferric iron. Two of these phenolates contain threonine, glycine, alanine, and 2,3-dihydroxybenzoic acid. 

The physiological roles of the phenolates produced by B. thuringien-sis are not known. Neither the slow band nor the intermediate band serves as the molybdenum cofactor in the in vitro restoration of NADPH-nitrate reductase. It is reasonable nevertheless to posulate that these compounds are excreted by this organism in nature and that under the appropriate environmental conditions, these phenolates will coordinate tungstate, ferric iron, or molybdate. 

Volumetric methods are not as reliable as the gravimetric and are mainly serviceable for comparative purposes. In one method, WO3 is dissolved in excess of standard sodium hydroxide, and the excess titrated a similar method uses ethylamine to dissolve the WO3, the excess being then titrated with oxalic acid. Silica, tantalum, and columbium do not interfere with the latter method. An attempt to reduce tungsten to the blue oxide, then titrate back with ferric alum in the presence of thiocyanate, has not been successful. Somewhat more accurate results are obtained by precipitating a neutral solution of ammonium tungstate with an excess of lead acetate and titrating the excess lead by means of ammonium molybdate-4... 

Such oxidation reactions may be responsible in part for the enhancement of the chromate catalysis which is produced by Mn++, Co++, Cu++, Ce+++, Ni++ (120,121). Alternatively this promotion may arise from the reaction of these ions with perchromate compounds, and it is possible that chain reactions may occur similar to those in the ferric ion catalysis with the perchromate replacing the peroxide. Uri has suggested such a scheme for promotion in the molybdate and tungstate catalyses (see Sec. IX.3). However the data are too fragmentary for any definite conclusions to be drawn. 

In acid solution where the catalyses by molybdate and tungstate alone are slow, Fe+++, Cu++, Mn++, Co++, Ni++, and I cause a pronounced increase in rate. Konovalova (128) found similar kinetics for the ferric ion promoted tungstate reaction as for the tungstate alone, and also showed that ferric ion increases the rate of decomposition of the per tungstate WOa". Similar observations were made by Bogdanov... 

Resorcinol and its mono- and diacetates can be separated from one another and from hexachlorophene by TLC after extraction from dermatological preparations silica gel layers were used, prepared with 0.01 M aqueous sodium tungstate as complexing agent, benzene-dioxan-acetic acid (90 +10 + 2) as solvent and ferricyanide-ferric chloride (Rgt. No. Ill) for detection [64]. Hexyhesorcinol and hexachlorophene can be separated on silica gel G layers, using methyl isobutyl ketone [64]. A separation of dichlorophene and hexachlorophene has been possible with n-heptane,saturated with acetic acid,and layers of a hand prepared mixture of silica gel and starch binder [26]. Some of the components of tar oils and their TLC are also of pharmaceutical interest [130]. TLC-data for dithranol have also been described [15]. lodo-chlorhydroxyquin(5-chloro-8-hydroxy-7-iodoquinoline) has been separated from possible contaminants originating from its synthesis, by TLC in methanol on polyamide-calcium sulphate layers (5g polyamide + 3.5 g calcium srdphate + 10 ml water) [90]. 

This procedure revealed 0.5 y nitrate ion in the presence of 500 y of the following oxidants hydrogen peroxide, and ionic species nitrite, chlorate, bromate, ferricyanide, chromate, permanganate, vanadate, molybdate, tungstate, ferric, ceric. 

Ferric-manganese doped tungstated/ molybdenum nanoparticle Impregnation reaction followed by calcination at 600° C for 3 h Waste cooking oil in methanol (ratio 25 1)... 

Alhassan, F.H., Rashid, U., Taufiq-Yap, Y.H., 2015a. Biodiesel synthesis catalyzed by transition metal oxides ferric-manganese doped tungstated/molybdena nanoparticle catalyst. Journal of Oleo Science 64 (1), 91—99. Available at http //www.scopus.coni/inward/record.url eid=2-s2.0-84920123341 partnerID=tZOtx3yl (accessed 30.04.15.). 

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