Chemical composition of petroleum

The main constituents of petroleum can be subdivided into five main groups  

Many naphthenes contain the biogenic isoprene structure (see below) which can be used as biogenic markers for identifying petroleum origin. 

Pristane and phytane are the most abundant isoprenoids in petroleum. 

Multiple ring aromatic compounds are commonly referred to as polynuclear aromatic hydrocarbons or PAHs. The most common PAH is naphthalene. Naphthalene is a two-ringed unit. Three, four or more fused ring compounds also exist. 

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The chemical composition of petroleum also varies over a wide range. A broad functional definition of petroleum hydrocarbons is that hydrocarbons are composed primarily of many organic compounds of natural origin and low water solubility. 

Most investigations involving petrolenm hydrocarbons are regulated by various agencies that may require methodologies, action levels, and cleanup criteria that are different. Indeed, the complex chemical composition of petroleum and petroleum products can make it extremely difficult to select the most appropriate analytical test methods for evaluating environmental samples and to interpret and use the data accurately. 

As already noted, the chemical composition of petroleum and petroleum products is complex and may change over time following release into the environment. These factors make it essential that the most appropriate analytical methods are selected from a comprehensive hst of methods and techniques that are used for the analysis of environmental samples (Dean, 1998 Miller, 2000 Budde, 2001 Sunahara et al., 2002 Nelson, 2003 Smith and Cresset, 2003). But once a method is selected, it may not be the ultimate answer to solving the problem of identification and, hence, behavior (Patnaik, 2004). There are a significant number of petroleum hydrocarbon-affected sites, and evaluation and remediation of these sites may be difficult because of the complexity of the issues (analytical, scientific, and regulatory not to mention economic) regarding water and soil affected. 

Specific gravity is influenced by the chemical composition of petroleum, but quantitative correlation is difficult to establish. Nevertheless, it is generally recognized that increased amounts of aromatic compounds result in an increase... 

Many questions concerning the nature of petroleum asphaltenes remain unresolved (1) What is the chemical composition of petroleum asphaltenes (2) What are the molecular weights of asphaltene components (3) Why are asphaltenes precipitated from solution in petroleum by the addition of a hydrocarbon solvent such as n-pentane In this chapter we attempt to answer these questions. In addition, we suggest that asphaltene formation is a general phenomenon that is pertinent to the chemistry of coals, tar sand bitumens, shale oil, and other complex solutions of organic compounds. 

Even though the chemical composition of petroleum varies, almost all the hydrocarbons found in petroleum do not include alkenes. On the other hand, many oils with high amounts of paraffinic or naphthenic compounds or arenes are known. 

It is necessary to make a chemical classification of petroleum since chemical properties are very crucial in selecting the right method for processing the oil. There are many classifications with regard to fractions and chemical compositions of petroleum. In this chapter we will present the basis for these classification methods. 

Jones, H.O. and H.A. Wootton, The Chemical Composition of Petroleum from Borneo , Journal of the Chemical Society. Transactions, 91 (2), (1907), 1146-1149. 

Petroleum consists of a complex hydrocarbon mixture. The physical and chemical compositions of petroleum can change with location, age and depth. Beside carbon and hydrogen, the organic portion of petroleum contains compounds combined with sulphur, oxygen and nitrogen, as well as metals such as nickel, vanadium, iron, and copper. 

Considering the composition of petroleum and petroleum products (Speight, 1994, 1999), it is not surprising that petroleum and petroleum-derived chemicals are environmental pollutants (Loeher, 1992 Olschewsky and Megna, 1992). The world s economy is highly dependent on petroleum for energy production, and widespread use has led to enormous releases to the environment of petroleum, petroleum products, exhaust from internal combustion engines, emissions from oil-fired power plants, and industrial emissions where fuel oil is employed. 

In addition, a method of petroleum classification based on other properties as well as the density of selective fractions has been developed. The method consists of a preliminary examination of the aromatic content of the fraction boiling up to 145°C (295°F), as well as that of the asphaltene content, followed by a more detailed examination of the chemical composition of the naphtha (bp < 200°C < 390°F). For this examination a graph is nsed that is a composite of cnrves expressing the relation among the percentage distillate from the naphtha. 

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. 

Petroleum products themselves are the source of the many components but do not adequately define total petroleum hydrocarbons. However, the composition of petroleum products assist in understanding the hydrocarbons that become environmental contaminants, but any ultimate exposure is also determined by how the product changes with use, by the nature of the release, and by the hydrocarbon s environmental fate. When petroleum products are released into the environment, changes occur that affect their potential effects significantly. Physical, chemical, and biological processes change the location and concentration of hydrocarbons at any particular site. 

Changes in the chemical composition of the kerosene during volatilization also affect the physical properties of this petroleum product. Table 16.8 summarizes the effect of volatilization on kerosene viscosity, surface tension, and density when 20%, 40%, and 60% of the initial amount has been removed by the partial transfer of light hydrocarbon fractions to the atmosphere. Only the liquid viscosity is affected, with volatilization having a negligible effect on the density and surface tension of the kerosene. 

The chemical composition of vapors and fumes from asphalt products is variable and depends on the crude petroleum source, type of asphalt, temperature, and extent of mixing. Therefore, the adverse effects from asphalt may also vary considerably depending on the source of exposure. 

Quality control standards have been developed for the new petroleum weed killers and laboratory techniques have been worked out tor testing and establishing the suitability of a given petroleum fraction for a specific herbicidal use. Although attempts to correlate herbicidal action with physical and chemical tests have not been entirely successful, the use of additional specific t ts to determine the chemical composition of the fraction has served as an indicator of toxicity in the specific composition under study. 

GEOCHEMISTRY. The study of the chemical composition of the earth in terms of the physicochemical and geological processes and principles thai produce and modify minerals and rocks. Of practical importance in discovering and establishing the limits of ore deposils, petroleum, lar sands, salt, sulfur, and other valuable resources,... 

In Section II, the nature of the metal compounds in petroleum oils is discussed to establish a basic understanding of the targeted reactants. The chemical composition of the host petroleum and residuum is described, including a discussion of the two classes of metal compounds (1) metal-loporphyrins and (2) nonporphyrin metals. The troublesome asphaltenes will also be described. Comparison is made between the characteristics of vanadium and nickel complexes and their distribution in residua. 

The chemical composition of heavy oils and residua is, in spite of the large volume of work performed in this area, largely speculative (Thompson et al., 1976 Altgelt and Boduszynski, 1994 Speight, 1999). Indeed, the simpler crude oils are extremely complex mixtures of organic compounds. In fact, the composition of petroleum can vary with the location and age of the field in addition to any variations that occur with the depth of the individual well. Two adjacent wells are more than likely to produce petroleum with very different characteristics. 

Table 1.4 General chemical compositions of selected biomass components and petroleum (Pun et ah, 2007)...

Chemical composition of waste plastic cracking products depends on shares of the individual polymers (PE, PP, PS) in the feed and process parameters. This fact decides the technological application of the final products. Important products of the cracking process, both petroleum fractions and waste plastics, are coke residues. Coke residue yield increases considerably, up to 10 wt%, in cracking of municipal and industrial waste plastics since they contain various inorganic impurities and additives. It can be applied as solid fuel, like brown coal. In the fluid cracking the solid residue is continuously removed from the process by combustion in a regenerator section. 

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