Copper vanadates

Chemically pure vanadium pentoxide is alternatively prepared by precipitating insoluble mercurous vanadate, HgV03, from a neutral solution of a vanadate, and distilling off the mercury, or by ignition of vanadium salts of volatile acids, for example, vanadium oxytrichloride, VOCl3. The oxide also results from the oxidation of any of the lower oxides, or by the electrolysis of a solution of sodium vanadate or copper vanadate, using a divided cell the last method yields a product of 98 per cent, purity.2... 

The yellow, amorphous variety is unstable and its identity is a little doubtful. It is stated to be obtained sometimes from the red, amorphous form by evaporation of a solution of the latter in hydrochloric acid, and it may also result from the ignition of ammonium meta-vanadate or from the decomposition of vanadates by acids. According to Bleecker it is most conveniently prepared by the electrolytic decomposition of copper vanadate.5 It becomes brick red on being heated, and is similar to the red variety in its general properties, except that it appears to be less hygroscopic and less soluble its saturated aqueous solution contains between 300 and 400 mgm. per litre.6... 

Yoshida et alP2 observed that oxygen within a layer of 20 A thickness of the surface of copper vanadate catalysts takes part both in reduction by CO and in CO oxidation. The Cu ions are also very mobile in this layer and surface enrichment of these ions occurs upon 02 treatment after reduction at 200°C. 

Yoshida et a/.110 concluded from experiments with copper vanadate that the NO reduction on a pre-reduced catalyst proceeds by a mechanism involving adsorbed NO, adsorbed NH3, and adsorbed 02. Shikada et al.nl have shown that by using a complex Si02 —Ti02 oxide as carrier a very active and stable catalyst is obtained which is highly resistant to S02 for long periods. 

The high soot oxidation activity in loose contact of catafytic sterns containing an alkali metal chloride (KCl or CsCl or LiCl) and CUM0O4 (or CUWO4 or copper vanadates) can be ascribed to the formation of volatile copper chlorides. 

The significant difference between the TOP and selectivity of bulk metal molybdates and vanadates compared with pure metal oxides was a key factor in uncovering the true surface composition of those bulk catalysts. Table 11.3 and Table 11.4 show the number of surface active sites, redox TOP, and selectivity toward methanol selective oxidation products of bulk metal vanadates and the corresponding metal oxide, respectively. Similar results were obtained for bulk metal molybdates. Bulk metal vanadates possess a high selectivity to formaldehyde with some selectivity to dimethoxy methane (nickel vanadate), dimethyl ether (niobium, chromium, and aluminum vanadates), methyl formate (magnesium, chromium, and copper vanadates), and CO2 (niobium and silver vanadates). 

Nord and Tronner (1998) have identified a yellow copper vanadate in various green samples from Swedish mediaeval paintings. 

Oxides Vanadates) bismuth vanadate (BiV04) chnobisvanite (BiV04) copper vanadate dreyerite (BiV04) lead vanadate (Pb5(V04)3Cl) pucherite (BiV04) vanadinite (Pb5(V04)3Cl). 

Vanadium Oxides with Group Copper vanadate... 

We could not detect any metallic Mn or V element in XRD measurement, which is not in agreement with the results of Takeda et al. [19] who pointed out the displacement of Cu by lithium in copper vanadate. This means that the interpretation of this high capacity of MnVgOa must be interpreted by another mechanism for Li insertion. 

Rearrangement of dehydrolinalool (4) using vanadate catalysts produces citral (5), an intermediate for Vitamin A synthesis as well as an important flavor and fragrance material (37). Isomerization of the dehydrolinalyl acetate (6) in the presence of copper salts in acetic acid followed by saponification of the acetate also gives citral (38,39). Further improvement in the catalyst system has greatly improved the yield to 85—90% (40,41). 

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. 

While it is convenient to write the charges on the copper and vanadate layers as 2+12- per formula unit, this conceals a more accurate and valuable way of describing the formal charge and understanding the stmcture. To understand why this... 

As examples of some water-soluble salts, mention may be made of potassium chloride, copper sulfate, and sodium vanadate. As examples of some water-insoluble salts, mention may be made of some typical ones such as lead chloride, silver chloride, lead sulfate, and calcium sulfate. The solubilities of most salts increases with increasing temperature. Some salts possess solubilities that vary very little with temperature or even decline. An interesting example is provided by ferrous sulfate, the water solubility of which increases as temperature is raised from room temperature, remains fairly constant between 57 and 67 °C, and decreases at higher temperatures to below 12 g l-1 at 120 °C. Table 5.2 presents the different types of dissolution reactions in aqueous solutions, and Table 5.3 in an indicative way presents the wide and varied types of raw materials that different leaching systems treat. It will be relevant to have a look at Table 5.4 which captures some of the essential and desirable features for a successful leaching system. 

Aniline black (Cl Oxidation Base 1) is a complex polymeric phenazine that can be produced on cotton fabric by impregnation with aniline hydrochloride and suitable inorganic oxidants, such as sodium chlorate, ammonium vanadate and copper hexacyanoferrate(II). Aniline black is also made directly for use as a pigment (Cl Pigment Black 1). 

Under FCCU operating conditions, almost 100% of the metal contaminants in the feed (such as nickel, vanadium, iron and copper porphyrins) are decomposed and deposited on the catalyst (2). The most harmful of these contaminants are vanadium and nickel. The deleterious effect of the deposited vanadium on catalyst performance and the manner in which vanadium is deposited on the cracking catalyst differ from those of nickel. The effect of vanadium on the catalyst performance is primarily a decrease in catalyst activity while the major effect of nickel is a selectivity change reflected in increased coke and gas yields (3). Recent laboratory studies (3-6) show that nickel distributes homogeneously over the catalyst surface while vanadium preferentially deposits on and reacts destructively with the zeolite. A mechanism for vanadium poisoning involving volatile vanadic acid as the... 

IV. In the oxidised upper levels of certain veins of lead and copper. This class is numerous and widely distributed, and includes the various vanadates of lead, copper, zinc, etc. They may have been formed by... 

V. In sedimentary rocks. These minerals also contain oxidised vanadium, and consist of vanadates of iron, aluminium, lead, copper, etc. The carnotite deposits of Colorado are of this type. 

B. Wet Processes.—These vary considerably in detail according to the nature and amount of constituents other than vanadium in the ore. An outline of the operations involved in the case of patronite is as follows The ore is roasted with common salt or sodium carbonate and then extracted either (a) with water to give an alkaline solution of sodium vanadate and soluble vanadates of other metals, any lead, zinc, copper, etc., being left in the residue or (b) with sulphuric acid to produce a solution of vanadyl sulphate. Acid extraction is usually employed when the vanadium content of the material is low. The alkaline extract from (a) is treated with excess of sodium carbonate in order to precipitate calcium and aluminium, after removal of which,... 

Thiovanadates ana Oxythiovanadates.—A series of crystalline salts is known which resemble the ortho- and pyro-vanadates in composition, except that the oxygen is either wholly or partially replaced by sulphur. Copper orthothiovanadate, Cu3(VS4)2, occurs naturally as sulvanite (see p. 11). The following tliio- and oxythio-compounds have been prepared.3... 

The analysis of vanadium steels is effected by the application of one of the foregoing methods. Blank determinations on a steel free from vanadium but otherwise of the same approximate composition are used as a control. Iron and molybdenum are removed from hydrochloric acid solution by Kothe s ether separation method 1 chromium, nickel, copper, etc., are then precipitated as hydroxides by caustic soda, the filtrate containing the vanadium as vanadate.2 The method is modified for the simultaneous estimation of both vanadium and chromium in a vanadium-chromium steel.3... 

Silver, copper and other oxosalts have been extensively studied as cathodes in laboratory cells commercial power sources, principally for pacemakers, using silver chromate were manufactured until the 1980s, and silver vanadate or silver vanadium oxide (Ag2V4On), first reported by workers at Wilson Greatbatch Ltd, is currently used as cathode in implantable cardiac defibrillator batteries. 

In the presence of a ferric/ferrous (Fe +/Fe2+) couple, and that of tetraammine copper (II) Cu(NH3)42+ ion, the measured Us values also shifted. The redox potential for the ferric/ferrous couple, both in equal concentrations, is +0.5 V (vs SCE) in a low pH region, and that for the tetraammine copper (II)/(HI) couple is 0 to —0.2 V, depending on the concentration of ammonia. In the presence of a vanadate/vanadite (V +/V2+) couple at pH < 3, whose formal redox potential is very highly negative (—0.5 V (SCE)), the Us shifted very little and was the onset potential for the cathodic current. 

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