Metals, in crude oil

This method has a very general application range analysis for metals in crude oils, in their various distillation cuts, and in their residues as well as for metals contained in spent lubricating oils, water, lubricants, etc. 

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. 

Further indication of how much more chemical the analytical requirements of the petroleum industry have become is evident from the nature of the problems on which the Committee on Analytical Research of the American Petroleum Institute is engaged. These problems include precise determinations of oxygen, nitrogen, and trace metals in crude oils, charge stocks, and cracking catalysts. 

C. Hardaway, J. Sneddon, J. N. Beck, Determination of metals in crude oil by atomic spectroscopy, A mini-review, Anal. Lett., 37 (2004), 1-19. 

The metals in crude oils are partly in the form of inorganic salts suspended in the oil or dissolved in droplets of suspended water, and partly in the form of oil-soluble compounds. The chemical natures of the oil-... 

The presence of major and trace metals in crude oils and their products is of considerable interest to the oil industry. This interest derives from the association of metals with the geological origin of the cmde and the influence of contamination by metal in the refining or processing of petroleum products, or the effects of metals on the utilisation or performance... 

The list of metals detected in petroleum products is considerable and the most common detected are Fe, Na, Ni, V, Cr, Mg, and Si other metals at a lower concentration are Sb, Ar, Be, Cd, Co, Pb, Mn, Hg, Mo and Se. The elements Fe, Ni and V are the most important as they are present in all crudes at a higher concentration than other metals and, as expected, can be extracted from the earth s mineral source. The important requirement of knowledge of metals in crude oils and their products has resulted in a considerable effort to develop analytical methods for accurate measurements of the true concentration of all metals present. 

Both methods are used for the determination of the metal content. The determination of the concentrations of heavy metals in crude oil and its products is an important topic in environmental chemistry. Heavy metals are always present in crude oil, especially in the heavy fractions such as residual fuel. The control of the concentration of heavy metals in such fuels is very important for ecological monitoring in crude oil chemistry. More about the methods, techniques and modern research results made by atomic absorption spectroscopy and atomic emission spectroscopy can be found in references 80-82 shown at the end of this chapter. 

The x-ray fluorescence analysis is used by crude oil chemists as an express method for the determination of the metal contents in crude oil and its products. This is very important because the metals in crude oil are poisons for cracking catalysts, and are also undesired in the fuels, since they lead to environmental pollution. All the elements with atomic number greater than eleven in the periodic table can be analyzed by x-ray fluorescence spectrometry. An important task of this method in crude oil chemistry is the determination of heteroatoms such as sulfur, oxygen, and nitrogen. Frequently, x-ray fluorescence spectrometry is used to verify the presence of certain additives in oils. 

The heavy metals in crude oil residues are agglomerated, first of all, in asphaltenes in the form of porphyrin compounds. One example of this compound is presented in Figure 8.2 ... 

The limited information available indicates, however, that probably 90% of the metals in crude oil are retained in the distillate bottoms, residual... 

The largest percentage of metals in crude oil apparently collects in the asphalt fraction. This material is used primarily in road construction and for roofing. The available data on the metal contents of asphalt are shown in Table 7.6. The minimum and maximum amounts of metals per inch of asphalt per mile of two-lane highways are also shown in Table 7.6. 

KEYWORDS inductively coupled plasma mass spectrometry, organic solvents, microflow nebulizer, trace and ultra trace metals in crude oils, maltenes, and asphaltenes... 

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. 

Among the porphyrins encountered in the crude oils, etioporphyrins (etio) and dexophylloerithroetioporphyrin (DPEP), and their homologues are more frequently observed (Baker and Louda, 1988), (Barwise and Roberts, 1984). The complexity of porphyrin mixtures have made the isolation of these pigments difficult, but the improved chromatographic and spectroscopic techniques have made possible the separation and identification of a number of metalloporphyrins (Les Ebdon et al.,1994). The identification of Ni and V porphyrin was quite earlier (Treibs et al., 1936) but the organic forms of other metals in crude oils was achieved only later, with the advent of hyphenated techniques, e.g. HPLC or GC coupled to AAS or ICP-MS for elemental detection. The porphyrins of Co, Cr, Ti and Zn were identified in oil shales by HPLC-ICP-MS (Les Ebdon et al.,1994). 

Crude oil is a complex matrix of varying viscosities and mixed phases (organic, water and particulate matter) and therefore not an ideal matrix for analysis. The determination of the metals in crude oil requires pretreatment to the sample before presentation to the instrument. This is the stage where most of the errors occur and is time consuming. The selection of a particular procedure depends upon (1) analytical technique to be employed, (2) nature and the number of the samples to be analyzed, (3) desired degree of precision and... 

Lord, C.J., (1991), Determination of trace metals in crude oil by inductively coupled plasma mass spectrometry with micro-emulsion sample introduction. Anal. Chem., 63,1594-1599. 

Udoh, A.P., Thomas, S. A., Ekanem., (1992), Application of P-xylenesulphonic acid as ashing reagent in the determination of trace metals in crude oils, Talanta, 39,1591-1595. 

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