Vanadium in oil

Gastrointestinal Effects. Volunteers exposed acutely to vanadium pentoxide dusts had no gastrointestinal complaints (Zenz and Berg 1967). People who were exposed to vanadium in oil-burner ashes also did not show gastrointestinal symptoms (Sjoeberg 1950). One study found that workers exposed chronically to vanadium dusts in factories sometimes complained of nausea and vomiting (Levy et al. 1984), but these symptoms can have a number of causes (such as exposure to other substances) and cannot be directly attributed to the vanadium. These people probably also swallowed some of the dusts. 

Magnesium salts have been used to combat corrosion resulting from the presence of vanadium in oil fired equipment. High melting point magnesium sulphates and vanadates are produced [Matveevicheva 1969]. 

Sulfuric acid condenses below 4(X)°K. Fortunately, equilibrium conditions are not attained in conventional combustion processes. However, the presence of catalytically active matoi-al, such as vanadium in oil and iron pyrites in coal, can increase SO3 formation. In the absence of actual analytical data for specific cases, a rough estimate of the SO3 concentration expected in combustion gases from coal and oil may be obtained fiom Table 7-4, hidi presents data compiled by Pierce (1977). 

Sodium plus vanadium in the fuel in excess of 100 ppm can be expected to form fuel ashes corrosive to metals by fuel oil ashes. 

Flydrodemetallization reduces the amount of nickel and, to a lesser extent, vanadium in FCC feeds. Nickel dehydrogenates feed to molecular hydrogen and aromatics. Removing these metals allows heavier gas oil cut points. 

Furnace area and superheater slagging may occur at low furnace or superheater temperatures (below 450-500 °C) due to high vanadium content in fuel oil. These high levels of vanadium in the fuel reduce the eutectic temperature of the noncombustibles, creating a molten deposit that holds unbumed carbon and contributes to a thickening of the slag. The trapped carbon is unavailable for combustion, and this process consequently reduces the overall fuel combustion efficiency. 

Hoffman, D.J. 1979. Embryotoxic effects of crude oil containing nickel and vanadium in mallards. Bull. Environ. Contam. Toxicol. 23 203-206. 

It may be mentioned that starting with ash and soot from crude oil-fired stations, the resulting metals are the same, but the main leaching residue is carbon. This residue is initially burned and the ash is leached again to increase the total yield of vanadium. In the same operation, the concentration of iron is reduced by precipitation of jarosite. During leaching, the redox potential is controlled by SO2 addition to keep vanadium in its IV-valent state. 

Fly ash is a light material, which is carried out of the combustion chamber in the flue gas stream. The ash from fuel oil combustion is usually in the form of fly ash. The many elements that may appear in oil ash deposits include vanadium, sodium, and sulfur. 

Crude oil consists mainly of a mixture of paraffinic, naphthenic, and aromatic hydrocarbons with small amounts of metals-containing heterocyclic compounds. The most abundant metals found in oils are those contained in porphyrin or porphyrin-like complexes (nickel, copper, iron, and vanadium). These... 

Crown thioethers, coordination chemistry, 35 3 (CIO4), 43 226 Crude oil, vanadium in, 35 99 Crustaceans, arsenic in, 44 150, 167, 168, 170 Cryoscopic measurements, sulfuric acid and, 1 390-391... 

Nickel in snow from Montreal, Canada, was highly enriched compared with ambient air, ranging from 2 to 300 ppb (Landsberger et al. 1983). The nickel content of snow particulate matter was 100-500 ppb. Nickel concentrations were highly correlated with those of vanadium, suggesting oil combustion was a source. 

Kleinman, M. T., D. M. Bernstein and T. J. Kneip. An apparent affect of the oil embargo on total suspended particulate matter and vanadium in New York City air. Air Pollut. Contr. Assoc. 27 65-67 (1977). 

Vanadium in deposit Indicates presence of residual oil vanadium can combine with sodium, potassium or sulfur to form compounds which can cause severe corrosion of engine valves reaction takes place at temperatures >1,100°F (593.3°C)... 

Skinner, D. A., Chemical State of Vanadium in a Santa Maria Valley Crude Oil, presented... 

Approximate contents of 14 minor and trace elements in oils produced from three coals by the catalytic hydrogenation process of Gulf Research and Development Co. were determined by emission spectroscopy. The results were compared with corresponding data for the original coals and the solid residues from the process. The contents of ash, sulfur, vanadium, lead, and copper are near or below the limits specified for an oil to be fired directly in a gas turbine while sodium and probably calcium are too high. Titanium appears to be somewhat enriched in the oils analyzed relative to other elements, suggesting its presence in organo-metallic complexes. 

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. 

Nickel and vanadium in petroleum exist as soluble organometallic complexes that fall into two categories metal porphyrins and nonporphyrin metal complexes. Both the porphyrins and the nonporphyrins may be distributed over a wide boiling range (350-650°C+), reflecting significant variations in molecular weight, structure, and polarity. Metal porphyrins and nonporphyrin metal complexes also tend to precipitate as part of the asphaltene materia] to an extent that varies with the source of the crude oil. 

Intrinsic reactivity patterns of the different porphyrins are reflected in their metal deposition profiles, which serve as fingerprints marking the reaction sequence. Vanadium profiles (Fig. 25) from pure VO-etiopor-phyrin in oil demetallation experiments are steeper with less deposit in the pellets center than the nickel profiles (Fig. 26) from the analogous experiment with pure nickel porphyrin. Pure compound intrinsic reactivity data revealed that vanadium was more reactive than nickel at most temperatures of interest. However, a reduction in VO-porphyrin diffusion by stronger adsorption interactions would also contribute to a steepening of the metal deposition profiles. Metal profiles have not been examined from demetallating model oils containing both Ni- and VO-porphyrins. 

A receptor model analysis in western Germany separated nitrate-rich from sulphate-rich secondary aerosols, with the latter being accompanied with vanadium and nickel [7]. Such factor composition pinpoints to heavy oil combustion sources which can be found, e.g. in oil refineries, off-shore platforms and overseas ships. In addition, trans-boundary pollution from eastern European countries is a significant source. 

The presence of vanadium and nickel in crude oils, especially as metal porphyrin complexes, has focused much attention in the petroleum refining industry on the occurrence of these metals in feedstocks (Reynolds, 1997). Only a part of the total nickel and vanadium in crude oil is recognized to occur in porphyrin structures (Table 3-5). In general, it is assumed that about 10% w/w of the total metal in a crude oil is accommodated as porphyrin complexes although as much as 40% of the vanadium and nickel may be present as metal porphyrin complexes in petroleum. 

A study of the vanadium catalyzed dehydrogenation reaction showed antimony interacts with vanadium and decreases its dehydrogenation activity. Cracking catalyst was contaminated with vanadium in the laboratory, A portion of this contaminated catalyst was then treated with an antimony containing compound to passivate vanadium. The catalysts were evaluated by cracking gas oil. The yield of hydrogen for passivated catalyst averaged fifteen percent less than for the unpassivated catalyst. 

Vanadium is present in crudes mainly in the +4 state (58). In fact, up to 50% of the total vanadium in crude oil can be found as V02+ in organometallic compounds such as porphyrins and naphthenates (59-63). During the cracking reaction in a FCCU, these compounds deposit V (probably in the form of VO+2 cations) on the catalyst surface. Then, after steam-stripping and catalyst regeneration, formation of V+5 surface phases occur. The effects of vanadium on FCC properties are more severe than any of the other metals present in petroleum feedstocks. In fact, vanadium causes an irreversible loss of cracking activity which is the result of a decrease in crystallinity, pore volume and surface area of the catalyst, Figure 5. 

Although metal ions are generally not very soluble in hydrocarbons, vanadium occurs at high levels in some crude oil products. What is there about vanadium in crude oil that enables this to occur ... 

E.p.r. studies459 indicate the formation of sandwich-type dimer complexes of V02+ and etioporphyrin (EP) in light petroleum at 77 K the e.p.r. data are consistent with an EP-EP plane distance of ca. 3.5 A. A planar ligand local environment for Vlv, possibly provided by a phthalocyanine- or porphyrin-type ligand, has been proposed460 to account for the axial microsymmetry of the V17 centre and the absence of zero-field splitting indicated by e.p.r. studies of vanadium in mineral oil. 

---