Nonhydrocarbons in petroleum

Sulfur compounds form the largest group of nonhydrocarbons in petroleum. Crude oils vary considerably in their sulfur content. Some have extremely low sulfur contents with less than 0.1 weight percent of sulfur. However, high sulfur crudes can contain as much as five to seven weight percent sulfur. Since the sulfur atom is only a small part of a large molecule, a crude oil with a sulfur content of five weight percent may actually have sulfur atoms as a part of more than half of the total molecules. 

Petroleums also contain compounds in which sulfur, oxygen, and/or nitrogen atoms are combined with carbon and hydrogen. These elements usually are combined with the complex ring structures that make up the larger molecules of petroleums. These larger nonhydrocarbon compounds form a class of chemicals generally called resins and asphal-tanes. The quantity of these compounds in petroleum is often very small however, as much as 50% of the total molecules in some heavy crude oils are resins and asphaltines. 

Equations and property data are included for 39 hydrocarbons, 10 nonhydrocarbons, and petroleum fractions. Petroleum properties are predicted by equations derived from correlations that are in the Technical Data Book of the American Petroleum Institute (1). 

The Role of Nonhydrocarbons in the Analysis of Virgin and Biodegraded Petroleum... 

A fundamental study of surface reactions of many organic structures and various adsorbents (e.g., aluminas, silicas) was done by L. R. Snyder in the 1958-1968 period. This provided an excellent evaluation of the relative elution of both hydrocarbons and nonhydrocarbons in numerous chromatographic systems. These studies were a necessary ingredient in the LEAC technique that he utilized on petroleum products. These studies indicated that carbazoles and benzocarbazoles are major nonhydrocarbon types in petroleum (6). With the advent of many selective isolation techniques for nonhydrocarbons since 1965 and high-pressure liquid chromatography technology, the correlations that he developed should now find numerous applications. 

Nonhydrocarbon Solvents, Although an asphaltene fraction can be removed from petroleum by using a wide variety of hydrocarbon liquids (14), the use of nonhydrocarbon solvents as deasphalting media and their influence on asphaltene dispersibility and compatibility has also been investigated. Dispersibility of asphaltenes in petroleum is suggested to be conveniently related to the surface tension of the system components (8, 20, 21, 22, 23). Obviously, asphaltene dispersion and compatibility is complex and is dependent on several factors and varies markedly with the character of the added liquid. 

Most nonhydrocarbon solvents, whether inorganic or organic, are pure substances. They include water, ethanol, and glycol ether. Most hydrocarbon solvents are mixtures including the complex mixtures of hydrocarbons present in petroleum distillates or the carefully engineered solvent blends used in automotive paints. These blends and mixtures are chosen to produce the desired solvency, evaporation rates, flash point, and other factors applicable to any process. A significant number of organic solvents are flammable. 

The petroleum industry, which is responsible for producing most of the energy used in modern society, has produced, as a byproduct over the past AO years, a broad base of thermodynamic data for the hydrocarbons it processes. Even though the petroleum Industry is mature, the data development and correlation effort has not slacked off, and indeed has accelerated in the last two decades. A similar, but more proprietary, effort has been carried on by the chemical industry for nonhydrocarbons. In view of these long-lived programs, the question arises,—does the new synthetic fuels industry, which promises to become important in the last quarter of the century, need specific data programs or are the present data systems adequate for its needs This paper looks at that question and attempts to outline areas where work is needed. 

Petroleum crude oil, gas condensate, and natural gas are generally complex mixtures of various hydrocarbons and nonhydrocarbons with diverse molecular weights. In order to analyze the contents of a petroleum fluid it is a general practice to separate it first into five basic fractions namely, volatiles, saturates, aromatics, resins, and asphaltenes [74, 77]. Volatiles consist of the low-boiling... 

On this basis, petroleum may have some value in the crude state but, when refined, provides fuel gas, petrochemical gas (methane, ethane, propane, and butane), fiansportation fuel (gasoline, diesel fuel, aviation fuel), solvents, lubricants, asphalt, and many other products. In addition to the hydrocarbon constituents, petroleum does contain heteroatomic (nonhydrocarbon) species, but they are in the minority compared to the number of carbon and hydrogen atoms. They do, nevertheless, impose a major influence on the behavior of petroleum and petroleum products as well as on the refining processes (Speight and Ozum, 2002). 

In the method (ASTM D287), the API gravity is determined using a glass hydrometer for petroleum and petroleum products that are normally handled as liquids and that have a Reid vapor pressure of 26 psi (180 kPa) or less. The API gravity is determined at 15.6°C (60°F), or converted to values at 60°F, by means of standard tables. These tables are not applicable to nonhydrocarbons or essentially pure hydrocarbons such as the aromatics. 

Black oil should be a pure petroleum product free from fatty oils, fatty acids, resins, soaps, or other nonhydrocarbons. Sediment and sludge, insoluble in paraffin naphtha, should not exceed 12% when determined by the methods of the American Association of State Highway Officials. The product should be a distilled or fractionated oil, and should contain no oil-well water or residue therefrom. The product should be free of or contain no more than traces of naphthenic acids, naphthenes, mercaptans, soluble sulfide, and volatile sulfur derivatives. The oil should flow freely from the tank car at temperatures above 32 F. 

This paper presents a survey of our present knowledge of the composition of petroleum. Included in the presentation is a brief discussion of the nonhydrocarbon constituents of petroleum, covering sulfur, nitrogen, oxygen, and metallic constituents, together with more detailed information regarding the hydrocarbon constituents which comprise the bulk of crude petroleum. In addition to a discussion of the hydrocarbon compounds and types of hydrocarbon compounds occurring in one representative petroleum, the problem is considered of how different crude petroleums differ in their composition with respect to the hydrocarbon components. 

Nitrogen, carbon dioxide, and hydrogen sulfide are common nonhydrocarbon constituents of petroleum. All three are light molecules and mainly are part of the gas at the surface. Hydrogen and helium are found in some natural gases. Table 1-1 shows the quantities of these nonhydrocarbons typically found in naturally occurring petroleum gases. 

Effect of Petroleum Fuel Properties. Three primary requirements must be met by practical fuels for aircraft turbojets. These requirements are They must be available in large quantities at low cost, they must produce satisfactory performance in all types of engines, and they must be suitable for aircraft fuel systems. Petroleum fuels vary in volatility, chemical composition, and concentrations of minor nonhydrocarbon compo-... 

Sulfur compounds are perhaps the most important nonhydrocarbon constituents of petroleum and occur as a variety of structures (Table 3-3). During the refining sequences involved to convert crude oils to salable products, a great number of the sulfur compounds that occur in any particular petroleum are concentrated in the residua and other heavy fractions. 

Petroleum A generic term applied to oil and oil products in all forms, such as crude oil, lease condensate, unfinished oils, refined petroleum products, natural gas plants and liquids, and nonhydrocarbon compounds blended into finished petroleum products. 

Natural gas is an odorless and colorless naturally occurring mixture of hydrocarbon and nonhydrocarbon gases found in porous geologic formations beneath the earth s surface, often in association with petroleum or coal. The principal constituent is methane (CH4) and its composition is regionally dependent. Table 2.2 summarizes the composition of natural gas by region.8... 

Scope of the Problem. Petroleum hydrocarbons are the principal components in a wide variety of commercial products (e.g., gasoline, fuel oils, lubricating oils, solvents, mineral spirits, mineral oils, and crude oil). Because of widespread use, disposal, and spills, environmental contamination is relatively common. It is important to understand that petroleum products are complex mixtures, typically containing hundreds of compounds. These include various amounts of aliphatic compounds (straight-chain, branched-chain, and cyclic alkanes and alkenes) and aromatic compounds (benzene and alkyl benzenes, naphthalenes, and PAHs). In addition, many petroleum products contain nonhydrocarbon additives such as alcohols, ethers, metals, and other chemicals that may affect the toxicity of the mixture. 

Additional limitations to the use of health effects data for whole petroleum products include the variable composition of each type of petroleum product due to differences in the crude oil from which it was refined, in the refining processes used, and in the formulation of the final product. Also, nonhydrocarbon additives and contaminants, many of which have significant toxicity, are often included in these whole products (e.g., methyl-/e/7-butyl ether (MTBE) or lead in gasoline). Finally, the identity of the originally released material may not be known or more than one such product may have been released. 

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