Vanadium high concentrations

Asphaltenes have high concentrations of heteroelements sulfur, nitrogen, nickel and vanadium. Their content varies widely in petroleum oils (Table 1.5). They cause a number of problems throughout the petroleum industry. 

In aqueous solution both the tetramer and the pentamer have cyclical structures (Fig. 6) as shown by the narrow 51V NMR linewidths indicating high symmetry around vanadium (29). The relative amounts of the species are concentration dependent but under moderate concentrations the tetramer is the most important (Figs. 2 and 3). The hexamer [V60i8]6 is a very minor species under most conditions, but it becomes somewhat more prominent at high concentrations and high ionic strength (8, 10, 15, 32). Indications are that it has a cyclic structure in aqueous solution (10). 

ZSM-5 has been used successfully in commercial operations when processing high boiling range feedstock and resids. This is principally due to its ability to maintain activity despite the presence of a high concentration of feed metals. ZSM-5 s excellent metals tolerance has been demonstrated commercially at equilibrium catalyst metals levels up to 10,000 ppm nickel plus vanadium and 6,000 ppm sodium with very little detrimental effect. Laboratory tests show that ZSM-5 is far less affected by metals than Y-zeolite catalysts. Metals were introduced, as follows ... 

High concentration of vanadium in the blood of some tunicates has been a long-standing problem of biochemistry. That vanadium(III) ions are part of the respiratory pigment has been ruled out recently. The efficient mechanism used to concentrate vanadium from sea water is now understood but the utility of vanadium for these living organisms is still an intriguing question. 

The uses of the metal for the living creature have been the subject of much speculation but the possibility that vanadium(III) is involved in oxygen transport has been ruled out experimentally.352 The role of the high concentrations of vanadium in tunicates remains tantalizing. 

Peter Zubovic You mentioned a high concentration of vanadium in some of your rocks. Do you know whether this vanadium is associated with the mineral or organic matter ... 

Vanadium Ferrocyanides.—Solutions of vanadates, when treated with potassium ferrocyanide, yield a precipitate of doubtful composition.1 The compound is insoluble in mineral acids of high concentration, and a method involving its precipitation has recently been suggested for the estimation of vanadium in steels.2... 

Other metalloporphyrins can also be found in Nature, though they do not seem to perform any vital physiological function. For example, the copper(II) complex of uroporphyrin-III (Table 1) occurs in high concentrations in the wing feathers of Turacus indicus, and is the source of most commercial samples of uroporphyrin-III. Chlorophyll degradation products, as the nickel and vanadium complexes, are found in oil shales and as a troublesome contaminant in crude petroleum oils. 

The phylum Chordata, to which we ourselves belong, includes not only the vertebrates but also more primitive marine animals that have a spinal cord. Among these primitive species, which may be related to early ancestral forms, are the tunicates or sea squirts. They have a very high concentration of vanadium in their blood. 

Sometimes, deposits accumulate on the exterior of tubes. These deposits are unavoidable when heavy industrial fuel oil is fired.Such fuel oils contain high concentrations of vanadium, nickel, sodium, and iron (in that order of concentration). These metals deposit as an ash, on the exterior of both the radiant- and convective-section tubes. The ash will get very hot and will turn sections of tubes yellow, or even whitish silver. This is not an indication of tube overheating. If the deposits get thick enough, they will interfere with the rate of heat absorption by the tube. It is very difficult to distinguish between a real hot spot and glowing ash. Dirty fuel gas also leads to ash formation on the radiant surface of tubes. 

In addition to catalyst pore structure, catalytic metals content can also influence the distribution of deposited metals. Vanadium radial profile comparisons of aged catalysts demonstrated that a high concentration of Co + Mo increases the reaction rate relative to diffusion, lowering the effectiveness factor and the distribution parameter (Pazos et al., 1983). While minimizing the content of Co and Mo on the catalyst is effective for increasing the effectiveness factor for HDM, it may also reduce the reaction rate for the HDS reactions. Lower space velocity or larger reactors would then be needed to attain the same desulfurization severity. 

Vanadium chloroperoxidase (C. inaequalis) is a 67,488 Da protein that comprises 609 amino acid residues, as determined from deoxyribonucleic acid (DNA) sequence analysis [20], As isolated, V-CIPO may contain a variable content of vanadium, depending on the concentration of vanadate in the growth medium however, one vanadium(V) per subunit can be achieved by addition of excess vanadate to the growth medium or to the purified protein [3,71] Like V-BrPO, V-CIPO is stable in the presence of organic substrates, to elevated temperatures, and to the presence of high concentrations of strong oxidants (e.g., HOC1) [59],... 

Neither V0(02)+ nor V0(02)2 oxidizes bromide rather they associate to form the dinuclear (V0)2(02)3, which oxidizes bromide (Scheme 3) [76], The association constant for the dinuclear compound is rather small (K3 = 9 M at pH 0-2) this explains why it is not observed by 51V NMR at low concentrations of vanadium [73,76], The dinuclear compound has now been observed by 51V NMR at very high concentrations of vanadium [76], A complex of V202(02)3(HGly)2(H20)2 has been isolated in which a p-peroxo coordination of one peroxide is proposed [76],... 

Table II, the second example, shows the benefits of metals passivation at a FCCU in a refinery operating to maximize throughput. The FCC catalyst contained 490 ppm nickel and 1200 ppm vanadium, and the unit was operating against both its air blower and gas compressor limits. Hydrogen production was 92 SCF per barrel of FCCU feed with this amount of hydrogen in the gas to the compressor, it was difficult to maintain the compressor governor on control. The high concentration of hydrogen in the fuel gas also affected the steady state operation of the heat control of other processing units.

Examples of secondary metabolites from Ascidians are shown in Figure 3.10. Ascidians are noteworthy for the presence of vanadium (and related metals) together with high concentrations of sulphuric acid and tunichromes, which are unstable hydroquinoid compounds. A defensive role for these has been suspected,98 and it is noteworthy that gastropod molluscs (both prosobranch and opisthobranch) that feed upon tunicates often secrete large amounts of sulfuric acid, used in both... 

High degradation temperature is favored by low vanadium ion concentration (Rasmussen, 2005). The low V concentration minimizes inert (V04)3 formation as temperature rises. 

The influx of vanadate is a rapid (t1/2 = 57 s at 0°C), monophasic process85, but the rate of vanadate influx approaches a saturation limit at high concentrations of exogenous vanadate. Influx experiments with added EDTA (ethylenediamminetetraacetic acid) were carried out to eliminate exchange or adhesion of vanadate to the cell surface to account for the reduction of radiovanadium in the extracellular medium. The amount of vanadium accumulated in a typical influx experiment was independent of added EDTA, and raised the intracellular concentration by 2.5 mM. Therefore, there is a net uptake of vanadium into the intracellular volume of the vanadocytes in these experiments. 

High concentrations of selenium may occur in groundwater in semiarid or arid areas, near known mineral deposits containing sulfide minerals of uranium and vanadium. Irrigated agriculture may substantially increase concentrations in groundwater in areas with high selenium levels in soil. 

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