Petroleum elemental composition

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. 

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 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. 

Like conventional petroleum, of the data that are available the elemental composition of oil sand bitumen is generally constant and, like the data for petroleum, falls into a narrow range (Speight, 1999) ... 

Table 2-1 Elemental Composition and Ratios for a Petroleum, Heavy Oil, Bitumen, and Petroleum Products...

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 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 -...

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... 

Humic and fulvic acids are presumed to arise by two classical natural processes. Terrestrial humates are found in the following pathway plants soil humates peat — coal. Aquatic humates start with soil leachates or marine phytoplankton and go through a sequence sediments kerogen petroleum. There are conditions which mix the two processes as well. As a result, there are a host of names and symbols applied to these compounds, such as peat humic acid, coal fulvic acid, soil humic acid, and so on. Depending on their oxidation state, they may be heavily bound to metal ions. Within each class of humic acid, there are subclassifications, such as Podzol Bj, humic acid, lignite fulvic acid. Other types are classified by geological age, depth in a sediment, and type of aquatic environment. The following discussion will attempt to relate elemental composition to these broad classes of humates. 

Minerals are inorganic compounds that are found in nature and have both a well-defined composition and crystalline arrangement of atoms. Coal and petroleum hydrocarbons are organic and thus not minerals. Obsidian is not a mineral because it has neither crystalline structure nor a specific composition. Stones such as chert and flint, which are mainly silica, SiO, have a relatively precise composition but lack crystalline structure, so are not minerals. While copper is a mineral, brass and bronze do not occur in nature and do not have a fixed elemental composition, so they are not minerals. A synthetic material can be a mineral, however, as long as it is also found in nature. Hematite can be produced artificially by firing ceramics in an oxidizing environment, but it is still considered mineral because hematite can be found in nature. A synthetic ruby is likewise a mineral because rubies do occur in nature, but modem cubic zirconia is not. 

A compound with the elemental composition C2i// C>6 determined by mass spectrometry, was isolated from the light petroleum extract of the leaves of Senecio darwinii (Compositae, Hooker and Amolt) 43, a plant which grows in Tierra del Fuego (Chile). What structure can be derived from the set of NMR experiments 50 ... 

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). 

Hughey, C.A. Cooper, H.J. Rodgers, R.P. Marshall, A.G. Robbins, W.K. Qian, K. Resolution and identification of elemental compositions for more than 3000 crude acids in heavy petroleum by negative-ion microelectrospray high-field FT-ICR mass spectrometry. Energy Fuels 2001,15, 1505-1511. 

It is now becoming more obvious (Speight, 2007), and perhaps has been obvious to polymer scientists for some time, that large polynuclear aromatic systems are not necessary to produce high yields of thermal coke. It is not only the elemental composition but also the chanical configuration of the system which plays a role in coke/carbon formation not heretofore considered in coal and petroleum science. Thus, the concept of relatively small polynuclear aromatic systans in coal is not at all outlandish and may (considering the natural product origins of coal) be expected, or certainly preferable. 

In parallel the chemical analysis of the water from the sites of C. demersum growth was made to ensure the proper interpretation of the element composition and IR spectra of the aquatic plants from industrial regions. Chemical analysis was performed with the aid of a spectrofluorimeter Fluorat-02-Panorama and capillar electrophoresis system Kapel-105 (Lumex). Determination of the contents of inorganic anions, surfactants, petroleum products, and phenols in water was made in accordance with standard methods described in [11-14]. 

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