Analysis of Crude Oil

Crude oil is a particularly complex and difficult matrix, but GF AAS has been used quite frequently, at least to determine elements such as nickel and vanadium, which are present in crude oil in relatively high concentration, making possible a reasonably high dilution of the crude oil matrix. Nickel and vanadium are particularly important elements, as their concentration and the ratio of the two elements are actually borehole specific, and make it possible to identify the origin of a crude oil. In addition, nickel and vanadium are both serious catalyst poisons, and may cause undesirable side reactions in refinery operations. 

Vanadium in addition causes corrosion problems, e.g. in the combustion chamber of power plants, and inhalable dusts or aerosols of nickel that might be generated during combustion of oil are classified as hazardous substances owing to their carcinogenic and mutagenic effects. 

The authors found that up to 50 % of the nickel and 40 % of the vanadium present in crude oil might be lost at temperatures above 400 °C, a loss that cannot be detected by conventional LS AAS. It might therefore be suspected that much data reported in the literature using LS GF AAS are wrong because of this phenomenon. 

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Fractionation and Elemental Analysis of Crude Oils and Petroleum Cuts... 

Chaptar 2. FRACTIONATION AND ELEMENTAL ANALYSIS OF CRUDE OILS AND PETROLEUM CUTS... 

Amtzen B, Brown G, Harrison T, Trafton L (1995) Global Supply Chain Management at Digital Equipment Corporation. Interfaces 25 (1) 69-93 Asche F, Gjolberg O, Volker T (2003) Price relationships in the petroleum market an analysis of crude oil and refined product prices. Energy Economics 25 (3) 289-301... 

Veal, D.J. (1966) Nondestructive activation analysis of crude oils for arsenic to one part per billion, and simultaneous determination of five other trace elements. Analytical Chemistry, 38(8), 1080-83. 

Sulfur Isotope Data Analysis of Crude Oils from the Bolivar Coastal Fields (Venezuela)... 

Sulfur Isotope Data Analysis of Crude Oils... 

The second method I propose to determine MW is the crude characterization method. For the past six decades, we have relied on the standard ASTM D86 distillation test to characterize crude petroleum and its products [6], The next section includes excerpts from the ASTM4 program for crude oil characterization presented in the CD. Please note that there is a proposed MW equation on line 4690.1 find this equation to be reasonably accurate, 3% or less, for most every HC compound or HC pseudogroup above 120 MW. The ASTM4 printout in the next section, in Table 1.5, shows a run for a typical ASTM D86 lab analysis of crude oil. Use this program with caution, however, especially for compounds 100 MW or less. Errors here may exceed 10% in this region. 

Done and Reid [12] applied gel permeation chromatography to the identification of crude oils and products isolated from estuary and sea water, The technique, which appears more suited to the analysis of crude oils, is based on the separation of oil components in order of their molecular size, for practical purposes their molecular weight. 

The difference between AAS and ICP-AES for metal analysis of crude oils and lubricating oils after dilution is the compatibility of solvents. Solvents that are compatible with AAS may not be compatible with ICP-AES. Selection of the most suitable solvent for metal analysis using ICP-OES is important in terms of stability and reproducible measurements. Table 5.3 is a short comparative list of common solvents used in atomic spectroscopy and their behaviour using AAS and ICP-OES and the respective solvent. 

Kerosene is a good solvent for use with ICP-AES but is prone to noisy plasma. The solvent tetralin (1,2,3,4-tetrahydronaphthalene) has been used by workers involved in metal analysis of crude and lubricating oils with success. The solvent decalin (decahydronaphthalene) was also found to be a good solvent for metal analysis of crude oils but it is very expensive and not used extensively. The analytical performance of these solvents was studied for stability over an extended period of time to determine the effect of varying viscosities. The solvents toluene and xylene are also good solvents for dissolution but have high background to noise ratio and will not be discussed further. 

Acid digestion is recommended for the analysis of waste oils from of vehicles. A few jxL of the resulting aqueous leachates can then be pipetted onto Ag powder and the slurries dried and pressed into polyethylene slugs to produce pins that can eventually be submitted to GD-MS analysis for the assay of their Pb contents [658], Determinations can be performed by isotope dilution and concentrations as low as 3 pg/g Pb determined with a precision of better than 5%. GD-MS has also been used for the analysis of crude oils [659] and Cr, Cu, Fe. Mg, Na, Ni, Pb, Si, Sn and Ti can be determined in NIST SRMs, SPEX organometallic standard oils and refined oil composites. The method performs very well for limited amounts of sample, but the polyatomic interferences are a drawback. 

The use of NMR for the compositional analysis of crude oils and fractionated products is routine in industrial production. Common analyses include the determination of saturated and aromatic hydrocarbon content, average structural parameters such as the percentages of n-paraffins, / 6>-paraffins, cyclo-paraffins, mono-, di-, and poly aromatics. These data are used for the development of correlations between the compositions and their characteristics.Spectral editing such as DEPT is routinely used for the unambiguous assignments of resonances in complex mixtures, and recent trends indicate the utility of 2D-correlation techniques for such purpose. " In addition, NMR is used to determine additive constituents... 

The study of the analysis of crude oil products is incomplete without some mention of instability and incompatibility. Both result in formation and appearance of degradation products or other undesirable changes in the original properties of petroleum products. 

ASTM D-5708). The second method provides an alternate method for analysis of crude oils and residuum (ASTM D-5863).The sensitivity range is 3.0-10 ppm for iron, 0.5-100 ppm for nickel, 0.1-20 ppm for sodium, and 0.5-500 ppm for vanadium. Higher concentrations may be determined after dilution. 

Four fractions of pseudo-compounds are obtained by solution analysis of crude oil residue or its cracked product. During solution analysis of the cracking product from thermal treatment of vacuum residue or mixtures of vacuum residue and plastics (such mixtures were used in our investigation), a first step of solution analysis is soxhlet extraction. In the soxhlet extractor, the liquid/solid product is extracted with fresh warm solvent (THF) that does not contain the extract. This can increase the extraction rate, as the sample is contacting fresh warm solvent. The sample is placed inside a cellulose thimble and placed in the extractor. The extractor is connected to a flask containing the extraction solvent, and a condenser is connected above the extractor. The solvent is boiled, and the extractor has a bypass arm that the vapor passes through to reach the condenser, where it condenses and drips into the sample in the thimble. Once the solvent reaches the top of the siphon arm, the solvent and extract are siphoned back into the lower flask. The solvent reboils, and the cycle is repeated until the sample is completely extracted, and the extract is in the lower flask. 

The described example of solution analysis was shown for the analysis of crude oil vacuum residue, but this method can be successfully applied for different kinds of feed. In our investigation, we used this method for the analysis of mixtures of vacuum residue and plastics, and pure plastics. In the case of the plastic or product of its cracking analysis, one has to consider that what is left behind after soxhlet extraction is the heavy plastic fraction or non-cracked plastic. 

Figure 8.10 shows the general scheme for coagulation analysis that was used for analysis of crude oil vacuum residue in our investigation. 

A variety of techniques are available for the determination of trace elements in crude oils, and chemical methods of analysis have been summarized by Milner and McCoy. Most geochemical studies of metals in petroleum have used emission spectrography of petroleum ashes because of the multielement nature of the method. " In recent years techniques such as polarograplWfcolorimetric analysis, X-r fluorescence, ESR, flame atomic absorption, and flameless atomic absorption have been used for the analysis of crude oils. Many of the techniques require preconcentration of the metals, usually by ashing techniques and consequently involve the risk of loss of volatile compounds or contamination by reagents. For many elements at very low concentrations (<1 ug/g) the risk of contamination is very high. Most of the applications cited above involve the determination of one or a few specific elements and are not suitable for multielement analysis. 

Analysis of Crude Oil and Its Fractions, Total Mass Balance (TMB) and Repeatability of Oil Fractionation... 

To meet the objectives of the EPA/API/NPRA project, measuring the sum of dissolved volatile, dissolved non-volatile, and suspended mercury compoimds is important as each type enters the refinery in crude oil. The newly developed procedures for sample homogenization, for retrieving representative liquid aliquots, and for preservation of volatile components are thought to eliminate a major portion of the negative bias that can exist in routine sampling and analysis of crude oil for determination of total mercury content. 

Filby, R. H. and Shah, K. R., Neutron Activation Methods for Trace Metal Analysis of Crude Oil, The Role of Trace Metals in Petroleum, T. F. Yen, Ed., Ann Arbor Science... 

The boat inlet design of the NIC Combustion-CVAAS instrument system precludes the addition of an auto-sampler. Due to the necessity of minimizing the residence time of the sample in the boat prior to the analysis, an auto-sampler may not be a practical accessory for the analysis of crude oil. 

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