Nickel in crude oils

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. 

Lewan M. D. (1984) Factors controlling the proportionality of vanadium to nickel in crude oils. Geochim. Cosmochim. Acta 48, 2231-2238. 

Vale et al. [143], analyzing nickel in crude oil using LSGFAAS, observed an unusual slight increase in sensitivity in the pyrolysis curves for pyrolysis temperatures below 1000 °C for crude oil, whereas no such increase was found for the calibration solutions, as shown in Figure 8.44. Originally this increase in sensitivity was interpreted as an arti-... 

The petroleum industry faces the need to analyze numerous elements which are either naturally present in crude oil as is particularly the case for nickel and vanadium or those elements that are added to petroleum products during refining. 

Other compounds which may be found in crude oil are metals such as vanadium, nickel, copper, zinc and iron, but these are usually of little consequence. Vanadium, if present, is often distilled from the feed stock of catalytic cracking processes, since it may spoil catalysis. The treatment of emulsion sludges by bio-treatment may lead to the concentration of metals and radioactive material, causing subsequent disposal problems. 

Many metals occur in crude oils. Some of the more abundant are sodium, calcium, magnesium, aluminium, iron, vanadium, and nickel. They are present either as inorganic salts, such as sodium and magnesium chlorides, or in the form of organometallic compounds, such as those of nickel and vanadium (as in porphyrins). Calcium and magnesium can form salts or soaps with carboxylic acids. These compounds act as emulsifiers, and their presence is undesirable. 

Metals, such as nickel, vanadium, and sodium, are present in crude oil. These metals are concentrated in the heavy boiling range of atmospheric bottoms or vacuum residue, unless they are carried over with the gas oil by entrainment. 

The chemical events described above are the basis for the removal of arsines (R3 As) in crude oil or in raw gas condensates, which are known to cause major environmental pollution, equipment corrosion and reduction of catalyst life time (including automotive converters). It was recently demonstrated that these compounds can be completely removed by feedstock hydrotreatment on nickel-based catalysts under FI2 at 160-200 °C [140]. 

Hodgson, G. W., 1954, Vanadium, Nickel and Iron Trace Metals in Crude Oils of Western Canada American Association of Petroleum Geologists Bulletin, Vol. 38, pp. 2537-2554. 

Generally, most resids and asphalt have 79 to 88% w/w carbon, 7 to 13% w/w hydrogen, trace to 8% w/w sulfur, 2 to 8% w/w oxygen, and trace to 3% w/w nitrogen. Trace metals such as iron, nickel, vanadium, calcium, titanium, magnesium, sodium, cobalt, copper, tin, and zinc occur in crude oils. Vanadium... 

Crude oil is composed primarily of hydrocarbon compounds. Organic and inorganic sulfur-, oxygen-, and nitrogen-containing species are also found in crude oil. Additionally, water, vanadium, nickel, sodium, and other metals may be present. 

Nickel and vanadium are the most abundant metals found in crude oil. Other metals, metalloids, and nonmetals including aluminum, arsenic, barium, calcium,... 

Two groups of elements appear in significant concentrations in the original crude oil, associated with well-defined types of compounds. Zinc, titanium, calcium, and magnesium appear in the form of organometallic soaps with surface-active properties, adsorbed in the water-oil interfaces, and act as emulsion stabilizers. However, vanadium, copper, nickel, and part of the iron found in crude oils seem to be in a different class and are present as oil-soluble compounds (Reynolds, 1997). These metals are capable of complexing with pyrrole pigment... 

In this paper, we present the results of an experimental study on the phase behavior of well-characterized binary mixtures which represent the more complex mixtures that arise in SCF extractions of petroleum residua and coal liquids. These binary mixtures consist of pentane and toluene with meso-tetraphenylporphyrin (TPP). Porphyrins occur naturally in crude oils (11,12) and represent an important class of high molecular-weight constituents of these oils, including those which contain heavy metals, such as nickel and vanadium. 

The uppgrading of heavy oil will continue to increase in importance as changes In crude oil availability causes a shift toward heavier crudes. Usually, for extra heavy crudes, the bottom resid fractions as well as its deasphalted oils may contain significant quantities of metals (i.e. nickel and vanadium). These pose a serious problem for refiners because metal contaminants accumulate on catalyst during hydroprocessing causing permanent deactivation. The use of HDM catalysts to protect downstream HDS catalysts is recommended. 

The detection of vanadium, nickel, and porphyrins in crude oils were analyzed by high-temperature gas chromatography-atomic emission spectroscopy (HT-GC-AES), presenting characteristic metal distribu-... 

Tungsten alloyed with nickel, cobalt, or rhodium in thin layers on alumina supports, also sulfided, is used on an industrial scale as a catalyst in crude oil processing (hydrotreating, hydrocracking, reforming, hydrodesulfurization, and hydrodenitrogenation), as well as in Fischer-Tropsch synthesis (alcohol formation from CO + H2). 

PAR was applied in the determination of Ni in crude oil [30], and steel [93,94]. PAN was used for determining Ni in drinking water [95] and in sewage [96]. Nickel in the presence of Zn and Cu was determined by derivative spectrophotometry [97]. DDTC was used for determining Ni in natural waters [98]. Nickel was determined in iron and aluminium alloys by the derivative spectrophotometry with the use of the cyanide complexes [99]. The thiocyanate complex was applied in determination of Ni by the FIA method [100]. 

Crude oils — Petroleum in its natural form before it is subjected to any refining process such as fractional distillation or catalytic cracking. The main elements in crude oils are hydrogen and carbon as they are composed of mixtures of hydrocarbon compounds. Crude oils also contain varying amounts of sulphur, nitrogen, oxygen, and sometimes mineral salts, as well as trace metals such as nickel, vanadium, and chromium. 

Because the sulfur contained in crude oil is concentrated in the residue material, residual fuel sulfur levels naturally vary from less than 1 to over 6%. The sulfur level is not a critical factor for the combustion process as long as the flue gases do not impinge on cool surfaces. However, residual fuels may contain large quantities of heavy metals such as nickel and vanadium these produce ash upon burning and can foul the burner systems. Such contaminants are not easily removed and usually lead to lower market prices for fuel oils with high metal contents. 

Heated vaporization atomic absorption (HVAA) has been described extensively. HVAA differs from conventional atomic absorption in that an electrically heated device replaces the flame. The characteristics of HVAA are microliter sample consumption, sensitivity down to picogram quantities, and applicability to a wide variety of solutions. These characteristics have led to its widespread use. In petroleum analyses, this technique has been used to determine relatively high levels (ppm) of lead in gasoline, metals in used oils, and nickel and vanadium in crude oils (18). The Trace Metals Project has extended application of this technique to the determination of Be, Cd, Co, Cr, Mn, Mo, Sb, and V at the 10-ng/g level. 

Vanadium, nickel and iron are indigenous in crude oil but sodium occurs in a brine phase. The silicon and calcium are present as a result of the oil refining process. 

Nickel and vanadium in crude oils have been studied extensively because of the presence of Ni and... 

The porphyrin metallo complexes in crude oils, asphaltenes and other natural bitumens are chiefly those of vanadium and nickel although copper, iron and even uranium have been suggested. Recently in a Precambrian shale, porphins were found to chelate with iron, zinc and copper in addition to vanadium and nickel.The origin of these complexes is still uncertain, although several theories have been advanced. Some of these theories could be verified or possibly even disproved if the porphyrin type bound to each metal was known. Furthermore, since these heavy metals are harmful to both health and catalysts, a systematic study of demetallation of metalloporphyrins should prove useful. 

Elemental speciation using mass spectrometry in conjunction with ICPAES is a latest advance in atomic spectroscopy, which is becoming popular in analytical research labs. Mason et al. ExxonMobil Research and Engineering) show how linking ICP-MS to various liquid chromatographic techniques has enabled determination of ppm levels of metals in hydrocarbons to ppb level measurements in refinery effluent streams. Hyphenated ICP-MS techniques were used to provide speciation information on nickel and vanadium in crude oils and assist in development of bioremediation options for selenium removal in wastewater treatment plants. Similar ICP-MS technique without sample demineralization was used by Lienemann, et al. Institut Francais du Petrole) to determine the trace and ultra-trace amounts of metals in crude oils and fractions. 

The use of natural gas condensates, cheaper and easier to obtain than naphta, is growing. These raw materials are often contaminated by mercury and arsenic compounds. The presence of arsenic or mercury in crude oil can cause not only environmental pollution and equipment corrosion, but also reduction of metallic catalysts life time [1]. For example, in the case of steam reforming or methanation reactions, the presence of arsenic causes severe poisoning of the nickel catalysts [2]. 

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