Petroleum hydrocarbons fractions

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. 

Rather than quantifying a complex total petroleum hydrocarbon mixture as a single number, petroleum hydrocarbon fraction methods break the mixture into discrete hydrocarbon fractions, thus providing data that can be used in a risk assessment and in characterizing product type and compositional changes such as may occur during weathering (oxidation). The fractionation methods can be used to measure both volatile and extractable hydrocarbons. 

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). 

Weisman, W. 1998. Analysis of Petroleum Hydrocarbons in Environmental Media. Total Petroleum Hydrocarbons Criteria Working Group Series, Vol. 1. Amherst Scientific Publishers, Amherst, MA.(See also Vol. 2, Composition of Petroleum Mixtures, 1998 Vol. 3, Selection of Representation Total Petroleum Hydrocarbons Fractions Based on Fate and Transport Considerations, 1997 Vol. 4, Development of Fraction-Specific Reference Doses and Reference Concentrations for Total Petroleum Hydrocarbons, 1997 and Vol. 5, Human Health Risk-Based Evaluation of Petroleum Contaminated Sites, Implementation of the Working Group Approach, 1999.)... 

An expl mixt is obtd by adding to granular AN 4—8% of a combustible liquid, esp a petroleum hydrocarbon fraction, such as gasoline, refined oil.or gas oil.)... 

MADEP. 2003. Updated petroleum hydrocarbon fraction toxicity values for the VPH/EPH/APH methodology. Boston (MA) Massachusetts Department of Environmental Protection. Available from http //www.mass.gov/dep/water/drinking/standards/pethydro.htm... 

The amount of TPH found in a sample is useful as a general indicator of petroleum contamination at that site. However, this TPH measurement or number tells us little about how the particular petroleum hydrocarbons in the sample may affect people, animals, and plants. By dividing TPH into groups of petroleum hydrocarbons that act alike in the soil or water, scientists can better know what happens to them. These groups are called petroleum hydrocarbon fractions. Each fraction contains many individual compounds. Much of the information in this profile talks about TPH fractions. See Chapter 2 for more information on what components make up TPH and how they are measured. 

For purposes of this section, the chemical-specific parameters for the petroleum hydrocarbon fractions are based on selecting a midpoint for the fraction, based on empirical data unified by equivalent carbon number (EC). The fractions labeled as C5-C7 and >C7-C8 are characterized by one compound only, benzene and toluene, respectively. Remaining fractions are characterized by multiple compounds, as described in TPHCWG (1997b). Representative physical parameters for TPH fractions are presented in Table 5-7. 

Noncarcinogenic Effects. These effects are assessed only if the carcinogenic indicator compounds are not detected or are below regulatory criteria. The following petroleum hydrocarbon fractions, minus the carcinogenic indicator compounds, were selected as representing compounds with similar transport properties. Toxicity values for constituents of the fraction or for a similar mixture were selected to represent the toxicity of the fraction. Aromatic and aliphatic hydrocarbons are considered separately and further subdivided on the basis of equivalent carbon number index (EC). This index is equivalent to the retention time of the compounds on a boiling point GC column (non-polar capillary column), normalized to the //-alkanes. Physical and chemical properties of hydrocarbons that are... 

ASTM Serviee Fluids are special fluids which are either non-petroleum or are compoimded from special petroleum hydrocarbon fractions. They... 

Crude petroleum is fractionated into around fifty cuts having a very narrow distillation intervals which allows them to be considered as ficticious pure hydrocarbons whose boiling points are equal to the arithmetic average of the initial and final boiling points, = (T, + Ty)/2, the other physical characteristics being average properties measured for each cut. 

Petroleum ether fractions free from aromatic hydrocarbons are marketed, as are also n-hexane and n-heptane from petroleum. 

Olefins are produced primarily by thermal cracking of a hydrocarbon feedstock which takes place at low residence time in the presence of steam in the tubes of a furnace. In the United States, natural gas Hquids derived from natural gas processing, primarily ethane [74-84-0] and propane [74-98-6] have been the dominant feedstock for olefins plants, accounting for about 50 to 70% of ethylene production. Most of the remainder has been based on cracking naphtha or gas oil hydrocarbon streams which are derived from cmde oil. Naphtha is a hydrocarbon fraction boiling between 40 and 170°C, whereas the gas oil fraction bods between about 310 and 490°C. These feedstocks, which have been used primarily by producers with refinery affiliations, account for most of the remainder of olefins production. In addition a substantial amount of propylene and a small amount of ethylene ate recovered from waste gases produced in petroleum refineries. 

In the wood rosin process, rosin is isolated from aged pine stumps that have been left in fields cleared for farming or lumbering operations. The stumps are cut and shredded to pieces the size of matchsticks. The wood chips are then extracted with an appropriate solvent, eg, aUphatic or aromatic petroleum hydrocarbons or ketones. The extract is fractionally separated into nonvolatile cmde rosin, volatile extractibles, and recovered solvent. The dark rosin is usually refined further to lighter-colored products using selective solvents or absorption. 

The equihbrium shown in equation 3 normally ties far to the left. Usually the water formed is removed by azeotropic distillation with excess alcohol or a suitable azeotroping solvent such as benzene, toluene, or various petroleum distillate fractions. The procedure used depends on the specific ester desired. Preparation of methyl borate and ethyl borate is compHcated by the formation of low boiling azeotropes (Table 1) which are the lowest boiling constituents in these systems. Consequently, the ester—alcohol azeotrope must be prepared and then separated in another step. Some of the methods that have been used to separate methyl borate from the azeotrope are extraction with sulfuric acid and distillation of the enriched phase (18), treatment with calcium chloride or lithium chloride (19,20), washing with a hydrocarbon and distillation (21), fractional distillation at 709 kPa (7 atmospheres) (22), and addition of a third component that will form a low boiling methanol azeotrope (23). 

With this mobile phase colour compounds and carotenoids separated with 15 ml of chloroform (first fraction) and the second fraction with 20ml chloroform contained total petroleum hydrocarbons. At the end Spectrofluorophotometry was employed for quantification of analytes. 

Liquefied Petroleum Gas (LPG) - Hydrocarbon fractions lighter than gasoline, such as ethane, propane, and butane, kept in a liquid state through compression and/or refrigeration, commonly referred to as "bottled... 

Pure M-hexane is widely used in laboratories as an extractant for nonpolar compounds and in calibrating instruments for analyses of volatile organic compounds (VOC) or total petroleum hydrocarbons (TPH) (Kanatharana et al. 1993). Since such analyses may require very high levels of purity, laboratories sometimes carry out their own fractional distillation or other pretreatment-purification procedures to remove petroleum hydrocarbon impurities found in commercially available grades of M-hexane (Kanatharana et al. 1993). See Chapter 6 for more information about testing for -hexane. 

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