Crude ultimate analyses

No generally accepted method of classifying crude oil exists. What is termed ultimate crude oil analysis describes the composition as a percentage of carbon, hydrogen, nitrogen, oxygen, and sulfur. Also, a chemical analysis is performed which describes the composition as a percentage of paraffinic-, naphthenic-, and aromatic-type compounds. 

Sec. 1.7 Physical and Chemical Properties of Compounds and Mixtures 57 TABLE 1.8 Ultimate Analysis of Petroleum Crude... 

Based on 13C-NMR analysis, ultimate analysis and molecular weight determination (table 9.1), a model of the average molecule was built for native asphaltene (Fig. 9.4a) and asphaltene from visbreaking at 425°C and a residence time of 30 minutes (Fig. 9.4b). These figures show clearly that during the thermal treatment of crude oil residue, only the cracking of paraffinic chains can cause asphaltenes reactivity to yield coke. 

As early as 1833, Dumas (37) made the statement that, based on the results of the ultimate analyses of crudes, they consisted essentially of hydrocarbons, in spite of the fact that they had different sources. Mabery (107) after many years of arduous labor to determine the hydrocarbon composition of crude oils came to a similar conclusion in 1903. He concluded that petroleum from whatever source is one and the same substance, consisting of a mixture of a few series of hydrocarbons in variable proportions, and no matter what field the oil comes from, it only varies from oil from other fields in its content of these series of hydrocarbons, the members of the series varying from one crude to another. In the same paper, where Mabery summarized his work in 1903, he said in substance that he had been working with the financial assistance of the C. M. Warren Fund, but that lack of adequate money for research on the composition of petroleum was a serious handicap. He added that if 5,000 could be obtained from the Carnegie Institute, a really thorough analysis could be made. 

The early investigators, by repeated fractional distillation, were able to determine that crude petroleum consisted principally of hydrocarbons. Ultimate analyses had shown that relatively small proportions of sulfur, nitrogen, and oxygen were usually present, probably in the form of derivatives. They were able to identify a number of hydrocarbon types such as paraffins, cycloparaffins, and aromatics, and even to isolate some members of these series in a qualitative way. The state of the art was very well summed up by Hoefer (1888) (65) when he wrote in his book Das Erdol as follows It should be pointed out that up to the present no complete quantitative analysis has been carried out on any crude petroleum, that we must be content rather to discover which are the principal types of hydrocarbons present, which predominate and, qualitatively, to identify the individual members of such series. ... 

Whatever the interpretation placed on the interactions involved may ultimately be, in one respect the results are clear. That is, the simple idea of the additivity of conformational energies fails badly, even in this relatively simple case. Thus, although the idea of additivity of conformational energies has been widely used, it can be regarded as only a very crude approximation. Unfortunately for the bench chemist, this means that much of conformational analysis will have to be taken away from the man with the slide rule and given to the computer, if reliable and accurate results are required. 

The potential of ultr igh-resolution mass spectrometry for the analysis of complex chemical mixtures is particularly illustrated by FT-ICR-MS, which currently is the definite standard. Ultrahigh resolution was applied to separate several thousand components in crude oil [99,100], fuels [101,102], or explosion residues [103]. Actually, the attempts to analyze dissolved organic matter (DOM) and similar complex humic systems present another prominent field of application requiring the ultimate performance of FT-ICR instruments equipped with magnets of up to 15 T field strength [104]. 

A compilation of properties of several selected heavy crude oils is shown in Table 1.1. As can be seen, heavy crude oils exhibit a wide range of physical and chemical properties. Whereas the properties such as viscosity, density, boiling point, and color may vary widely, the ultimate or elemental analysis varies over a narrow range for a large number of samples. The carbon content is relatively constant, while the hydrogen and heteroatom contents are responsible for the major differences between petroleum. Nitrogen, oxygen, and sulfur can be present in only trace amounts in some heavy crude oils, which consist primarily of hydrocarbons. 

Ultimate or elemental analysis (C, H, O, N, S, metals, and ash contents). The higher the nitrogen and sulfur contents in crude oils, the higher sludge-formation tendencies. 

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