Elemental composition of petroleum

In terms of the elemental composition of petroleum, the carbon content is relatively constant it is the hydrogen and heteroatom contents that are responsible for the major differences. Nitrogen, oxygen, and sulfur are present in only trace amounts in some petroleum, which thus consists primarily of hydrocarbons. On the other hand, a crude oil containing 9.5% heteroatoms may contain essentially no true hydrocarbon constituents insofar as the constituents contain at least one or more nitrogen, oxygen, and/or sulfur atoms within the molecular structures. 

The ultimate analysis (elemental composition) of petroleum is not reported to the same extent as it is for coal (Speight, 1994). Nevertheless, there are ASTM procedures (ASTM, 1995) for the ultimate analysis of petroleum and petroleum products but many such methods may have been designed for other materials. 

The availability of high flux thermal neutron irradiation facilities and high resolution intrinsic Ge and lithium drifted germanium (Ge(Li)) or silicon (Si(Li)) detectors has made neutron activation a very attractive tool for determining trace elemental composition of petroleum and petroleum products. This analytical technique is generally referred to as instrumental neutron activation analysis (INAA) to distinguish it from neutron activation followed by radiochemical separations. INAA can be used as a multi-elemental method with high sensitivity for many trace elements (Table 3.IV), and it has been applied to various petroleum materials in recent years (45-55). In some instances as many as 30 trace elements have been identified and measured in crude oils by this technique (56, 57). 

The determination of the elemental composition of a petroleum cut is of prime importance because it provides a quick means of finding out the quality of a given cut or determining the efficiency of a refining process. In fact, the quality of a cut generally increases with the H/C ratio and in all cases, with a decrease in hetero-element (nitrogen, sulfur, and metals) content. 

Elemental Composition of Natural Petroleum (Percentage by Weight) [55,56,57]... 

In modern terms, asphaltene is conceptually defined as the normal-pentane-insoluble and benzene-soluble fraction whether it is derived from coal or from petroleum. The generalized concept has been extended to fractions derived from other carbonaceous sources, such as coal and oil shale (8,9). With this extension there has been much effort to define asphaltenes in terms of chemical structure and elemental analysis as well as by the carbonaceous source. It was demonstrated that the elemental compositions of asphaltene fractions precipitated by different solvents from various sources of petroleum vary considerably (see Table I). Figure 1 presents hypothetical structures for asphaltenes derived from oils produced in different regions of the world. Other investigators (10,11) based on a number of analytical methods, such as NMR, GPC, etc., have suggested the hypothetical structure shown in Figure 2. 

The elemental composition of petrolenm varies greatly from crude oil to crude oil. Most compounds in petrolenm (nsnally more than 75%) are types of hydrocarbons, and the majority of the chemical components in petroleum are made... 

An understanding of the chemical types (or composition) in petroleum can lead to an understanding of the chemical aspects of petroleum behavior. Indeed, this is not only a matter of knowing the elemental composition of a feedstock it is also a matter of understanding the bulk properties as they relate to the chemical or physical composition of the material. For example, it is difficult to understand, a priori, the behavior of petroleum and petroleum products from the elemental composition alone, and more information is necessary to understand environmental behavior. 

Of the data that are available (Speight, 1999), the ultimate composition of petroleum and heavy oil vary over fairly narrow limits of elemental distribution ... 

Table III shows elemental composition of typical sour petroleum, coal syncrudes or shale oils. Compared with typical sour petroleum, the coal syncrude is lower in sulfur content but significantly higher in nitrogen. Compared with shale oil, coal syncrude is lower boiling and contains only about one half the nitrogen. A major difference between the two liquids is the highly aromatic structure of coal liquids and the absence of long paraffinic structures. Shale oil is more aromatic than petroleum but significantly less aromatic than coal liquids. This is mirrored by the hydrogen contents which were shown in Table I.

Bio-oil from rapid pyrolysis is usually a dark brown, free-flowing liquid having a distinctive smoky odor. It has significantly different physical and chemical properties compared to the liquid from slow pyrolysis processes, which is more like a tar. Bio-oils are multicomponent mixtures comprised of different size molecules derived primarily from depolymerization and fragmentation reactions of the three key biomass building blocks cellulose, hemicellulose, and lignin. Therefore, the elemental composition of biooil resembles that of biomass rather than that of petroleum oils. Basic properties of biooils are shown in Table 33.7. More detail on fuel-related characteristics is provided in the literature.571... 

In Table I, a comparison is made of the elemental composition of typical asphaltenes from petroleum and coal liquids. This table shows the typical lower H/C ratio and higher oxygen content for the coal asphaltenes. Furthermore, the GPC molecular-weight distributions shown in Figure 7 illustrate the higher molecular-weight of petroleum asphaltenes as well as the wider molecular-weight distribution. 

Proximate analysis as well as generic and elemental compositions of the sieved bagasse feedstock are presented in Table 2. Some physico-chemical properties of the petroleum residue are also presented in Table 2. 

TABLE VII. TRACE ELEMENT COMPOSITION OF AN EASTERN SHALE OIL (CHATTANOOGA), A WESTERN SHALE OIL, AND TWO PETROLEUM CRUDES... 

The precise chemical composition of bitumen is, despite the large volume of work performed in this area, largely speculative. In very general terms (and as observed from elemental analyses), tar sand bitumen is an extremely complex mixture of 1) hydrocarbons 2) nitrogen compoimds 3) oxygen compounds 4) sulfur compounds and 5) metallic constituents. However, this general definition is not adequate to describe the composition of petroleum as it relates to the behavior of the feedstocks. 

The element specificity of atomic absorption spectrometry has also been used in conjunction with gas chromatography to separate and determine organo-metallic compounds of similar chemical composition, e.g. alkyl leads in petroleum here lead is determined by AAS for each compound as it passes from the gas chromatograph.75... 

Why Do We Need to Know This Material All life on Earth is based on carbon so is the fuel we burn, our food, and the clothes we wear. Therefore, to understand a major part of the everyday world, we need to be familiar with the chemistry of this extraordinary element. Compounds of carbon and hydrogen are the foundation of the petrochemical industry petroleum products are used to generate electricity and to heat our homes. They are also used to make the flexible, strong polymeric and composite materials that make modern communication and transportation possible. 

The elemental composition (ultimate analysis) of petroleum, no matter what the origin of the particular petroleum, varies only slightly over very narrow limits (Chapter 1) ... 

Table IV lists the elemental composition and the BTU value of various fractions. The SO2 solubles are virtually free of mineral matter and have a higher BTU content than the starting material. The deoxygenation of SO2 solubles could raise the BTU level to that of petroleum crude. The THF extracts of the SC -...

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