Petroleum hydrocarbons components

Knowledge of physical properties of fluids is essential to the process engineer because it enables him to specify, size or verify the operation of equipment in a production unit. The objective of this chapter is to present a collection of methods used in the calculation of physical properties of mixtures encountered in the petroleum industry, different kinds of hydrocarbon components, and some pure compounds. 

Tar Sands. Tar sands (qv) are considered to be sedimentary rocks having natural porosity where the pore volume is occupied by viscous, petroleum-like hydrocarbons. The terms oil sands, rock asphalts, asphaltic sandstones, and malthas or malthites have all been appHed to the same resource. The hydrocarbon component of tar sands is properly termed bitumen. 

Petroleum Gases and Naphtha. Methane is the main hydrocarbon component of petroleum gases. Lesser amounts of ethane, propane, butane, isobutane, and some 0 + light hydrocarbons also exist. Other gases such as hydrogen, carbon dioxide, hydrogen sulfide, and carbonyl sulfide are also present. 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Limited information about environmentally important physical and chemical properties is available for the mineral oil and water-in-oil emulsion hydraulic fluid products and components is presented in Tables 3-4, 3-5, and 3-7. Much of the available trade literature emphasizes properties desirable for the commercial end uses of the products as hydraulic fluids rather than the physical constants most useful in fate and transport analysis. Since the products are typically mixtures, the chief value of the trade literature is to identify specific chemical components, generally various petroleum hydrocarbons. Additional information on the properties of the various mineral oil formulations would make it easier to distinguish the toxicity and environmental effects and to trace the site contaminant s fate based on levels of distinguishing components. Improved information is especially needed on additives, some of which may be of more environmental and public health concern than the hydrocarbons that comprise the bulk of the mineral oil hydraulic fluids by weight. For the polyalphaolefin hydraulic fluids, basic physical and chemical properties related to assessing environmental fate and exposure risks are essentially unknown. Additional information for these types of hydraulic fluids is clearly needed. 

For some of the treatment profiles, the specific components that make up the total cost were not provided in the source materials, such as for capital or operation and maintenance activities. In other cases, the types of contaminants present at the sites, other than MTBE, were not identified in the source materials. Sites may have been contaminated with gasoline components such as petroleum hydrocarbons, as well as oxygenates, and the treatment costs reported are for cleanup of both the gasoline components and oxygenates. 

Environmental issues associated with the subsurface release of petroleum hydrocarbons and other organics fall into four areas (1) vapors (Figure 1.5), (2) impacted soils, (3) the presence of nonaqueous phase liquids (NAPLs), and (4) dissolved constituents (i.e., benzene, toluene, ethylbenzene, and xylenes (BTEX), and other components) in groundwater. 

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. 

An important feature of the analytical methods for the total petroleum hydrocarbons is the use of an equivalent carbon number index (EC). This index represents equivalent boiling points for hydrocarbons and is the physical characteristic that is the basis for separating petroleum (and other) components in chemical analysis. 

There are many recommended sampling protocols (Table 6.2). The sampling methods used for petroleum hydrocarbons are generally thought of as methods for determination of the total petroleum hydrocarbons. In part due to the complexity of the components of the total petroleum hydrocarbons fractions, little is known about their potential for health or environmental impacts. As gross measures of petroleum contamination, the total petroleum hydrocarbons data simply show that petroleum hydrocarbons are present in the sampled media. Measured total petroleum hydrocarbons values suggest the relative potential for human exposure and therefore the relative potential for human health effects. 

There are two noncolumn cleanup methods, one of which uses acid partition (EPA SW-846 3650) to separate the base/neutral and acid components by adjusting pH. This method is often used before alumina column cleanup to remove acid components. The other method (EPA SW-846 3660) is used for sulfur removal and uses copper, mercury, and tetrabutylammonium sulfite as desulfurization compounds. Sulfur is a common interfering compound for petroleum hydrocarbon analysis, particularly for sediments. Sulfur-containing compounds are very common in crude oil and heavy fuel oil. Elemental sulfur is often present in anaerobically biodegraded fuels. Thus, abnormally high levels of sulfur may be... 

The assessment of health effects due to exposure to the total petroleum hydrocarbons requires much more detailed information than what is provided by a single total petroleum hydrocarbon value. More detailed physical and chemical properties and analytical information on the total petroleum hydrocarbons fraction and its components are required. Indeed, a critical aspect of assessing the toxic effects of the total petroleum hydrocarbons is the measurement of the compounds, and the first task is to appreciate the origin of the various fractions (compounds) of the total petroleum hydrocarbons. Transport fractions are determined by several chemical and physical properties (i.e., solubility, vapor pressure, and propensity to bind with soil and organic particles). These properties are the basis of measures of teachability and volatility of individual hydrocarbons and transport fractions (Chapters 8, 9, and 10). 

Specific contaminants that are components of total petroleum hydrocarbons, such as BTEX (benzene, toluene, ethylbenzene, and xylene), n-hexane, jet fuels, fuel oils, and mineral-based crankcase oil have been studied and a number of toxicological profiles have been developed on individual constituents and petroleum products. However, the character of the total petroleum hydrocarbons has not been studied extensively and no profiles have been developed. Although several toxicological profiles have been developed for petroleum products and for specific chemicals found in petroleum, the total petroleum hydrocarbon test results have been too nonspecific to be of real value in the assessment of its potential health effects. 

Freon-extractable material is reported as total organic material from which polar components may be removed by treatment with silica gel, and the material remaining, as determined by infrared (IR) spectrometry, is defined as total recoverable petroleum hydrocarbons (TRPHs, or total petroleum hydrocarbons-IR). A number of modifications of these methods exist, but one particular method (EPA 418.1 see also EPA 8000 and 8100) has been one of the most widely used for the determination of total petroleum hydrocarbons in soils. Many states use or permit the use of this method (EPA 418.1) for identification of petroleum products and during remediation of sites. This method is subject to limitations, such as interlaboratory variations and inherent inaccuracies. In addition, methods that use Preon-113 as the extraction solvent are being phased out and the method is being replaced by a more recent method (EPA 1664) in which n-hexane is used as the solvent and the n-hexane extractable material (HEM) is treated with silica gel to yield the total petroleum hydrocarbons. 

Few analytical methods are available for the determination of total petroleum hydrocarbons in biological samples, but analytical methods for several important hydrocarbon components of total petroleum hydrocarbons may be modified. Most involve solvent extraction and saponification of lipids, followed by separation into aliphatic and aromatic fractions on adsorption columns. Hydrocarbon groups or target compounds are determined by gas chromatography-flame ionization or... 

Petroleum refining also produces substantial amounts of carbon dioxide, which with hydrogen sulfide, corrode refining equipment, harm catalysts, pollute the atmosphere, and prevent the use of hydrocarbon components in petrochemical manufacture. When the amount of hydrogen sulfide is high, it may be removed from a gas stream and converted to sulfur or sulfuric acid. Some natural gases contain sufficient carbon dioxide to warrant recovery as dry ice. 

Fig. 8.13 Concentration of selected petroleum hydrocarbons (mL / 100 g soil) during volatilization of kerosene from air dry vertisol. Reprinted from FineP, Yaron B (1993) Outdoor experiments on enhanced volatilization by venting of kerosene components from soil. J Contam Hydrol 12 335-374. Copyright 1994 with permission of Elsevier...

Once reaching a water system, the components of a crude oil or a petroleum hydrocarbon are truly dissolved at a molecular level or apparently soluble at a colloidal level when droplets characterized by radii of tens to hundreds of microns are formed. The apparent solubility of polycyclic aromatic hydrocarbons from oil in an aquatic system is reported by Sterling et al. (2003), who consider that the colloidal concentration of a given hydrocarbon contaminant in aqueous phase, C, is described by the equation... 

Heath JS, and Koblis K. 1993. Review of chemical physical and toxicological properties of components of total petroleum hydrocarbons. Journal of Soil Contamination 2(1) 125. 

Turpentine is a mixture of CioHie volatile terpenes (hydrocarbons made of isoprene units). There are actually four different types and methods of making turpentine, including steam distillation of wood. The two pinenes, a and P, are major components of turpentine. Other compounds found in abundant amounts are camphene, dipentene, terpinolene, and A -carene. Although it has been replaced by petroleum hydrocarbons as paint thinners (lower price, less odor), turpentine is still a good solvent and thinner in many specialty applications. The use pattern for turpentine is as follows synthetic... 

Biosolids-enhanced remediation (BER) is an ex situ bioremediation technology used to treat soils contaminated with petroleum hydrocarbons and polycychc aromatic hydrocarbons. The BER technology was developed by isolating particular microorganisms with the ability to degrade the specific components of petroleum products. The technology has been applied full scale and is commercially available. 

The low-temperature thermal aeration (ETTA) technology is a thermal desorption process that separates chlorinated hydrocarbons, volatile organic compounds (VOCs), semivolatile organic compounds (S VOCs), pesticides, and petroleum hydrocarbons from soils at temperatures of 300 to 800° F. This technology uses hot air to desorb contaminants from soil into a contained airstream and treats the airstream before discharging it to the atmosphere. The system is transportable and consists of six major components assembled on flat-bed trailers. The entire system and support areas require approximately 10,000 ft of operating space. 

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. 

In the period since 1920, the important investigations dealing with the hydrocarbon components of petroleum have included the following, in addition to the work of API Research Project 6 begun in 1927 ... 

The results obtained by API Research Project 6 from the exhaustive fractionation of the gasoline fraction of one representative petroleum serve to indicate what hydrocarbon compounds are in the gasoline fraction of petroleum and the amounts which may be expected to be present in a petroleum of intermediate type. In order to obtain information as to how the amounts of the hydrocarbon components vary in petroleums of appreciably different type, an investigation has been made of the hydrocarbons in the gasoline fraction of seven representative petroleums. The present status of the work of API Research Project 6 is summarized here, including the results of earlier investigations plus some unpublished results 46). 

Different crude petroleums may vary greatly with regard to the abundance of the hydrocarbon components as a function of the number of carbon atoms per molecule or in boiling range—that is, some petroleums may have a preponderance of the more volatile fractions while others may have a large amount of the less volatile lubricant fractions. 

A schematic for the fractional distillation of petroleum into its useful hydrocarbon components. 

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