Volatilization of petroleum

One of the main properties of petroleum that serves to indicate the comparative ease with which a material evaporates after a spill is its volatility. Investigation of the volatility of petroleum is usually carried out under standard conditions in which petroleum or the product is subdivided by distillation into a variety of... 

These examples indicate that aggregation and pore-size distribution parameters affect volatilization of petroleum products from a contaminated subsurface. Fine and Yaron (1993) report that kerosene volatilization depends on the type of soil. Tests on four soils with a clay content increasing from 0.3% to 74.4%, and organic matter... 

Toluene is released into the atmosphere principally from the volatilization of petroleum fuels and toluene-based solvents and thinners and in motor vehicle exhaust. It is also present in emissions from volcanoes, forest fires and crude oil. It has been detected at low levels in surface water, groundwater, drinking-water and soil samples (United States National Library of Medicine, 1997). 

Distillation, as a means of determining the boiling range (hence the volatility) of petroleum and petroleum products, has been in use since the beginning of the petroleum industry and is an important aspect of product specifications. 

The pyrolysis/devolatilization kinetics determined for the relatively volatile petroleum coke can be compared to those for Black Thunder subbituminous coal, and Pittsburgh 8 bituminous coal. This comparison is shown in Table 2.4. Note the higher pre-exponential constant. A, and activation energy, E, associated with the petroleum coke, relative to the reference coals. The kinetic parameters shown above are consistent with the lower maximum volatility of petroleum coke. 

A residuum, often shortened to resid, is the residue obtained from petroleum after nondestmctive distillation has removed all the volatile materials. The temperature of the distillation is usually below 345°C because the rate of thermal decomposition of petroleum constituents is substantial above 350°C. Temperatures as high as 425°C can be employed in vacuum distillation. When such temperatures are employed and thermal decomposition occurs, the residuum is usually referred to as pitch. By inference, the name is used in the same manner as when it refers to the nonvolatile residue from the thermal decomposition of coal tar (3). 

Petroleum coke. In order to eliminate excess volatile matter, petroleum coke is calcined at temperatures of 1475 to 1525 K. This is a sensitive material, and temperature control is difficult to maintain. 

Vacuum Distillation - Heavier fractions from the atmospheric distillation unit that cannot be distilled without cracking under its pressure and temperature conditions are vacuum distilled. Vacuum distillation is simply the distillation of petroleum fractions at a very low pressure (0.2 to 0.7 psia) to increase volatilization and separation. In most systems, the vacuum inside the fractionator is maintained with steam ejectors and vacuum pumps, barometric condensers, or surface condensers. 

These are semisolid or solid substances formed in nature from crude oils after the volatile components have evaporated and the remainder has undergone oxidation and polymerization. They are also referred to as bitumens, waxes, and pitch. These materials are believed to consist of mixtures of complex organic molecules of high molecular weight. As with crude oils, which contain thousands of different chemical compounds, an exact chemical analysis for identification and composition is impractical to perform on the solid deposits of petroleum. 

The procedure for determination of neutral oils in AOS measures petroleum spirit-extractable material from an aqueous alcoholic solution. Normally a solution of 1 1 ethanol/water is used as to dissolve the sample prior to extraction. For higher molecular weight materials 2 1 propan-2-ol/water is preferred. The petroleum ether is removed on a steambath and finally under vacuum. The amount of neutral oil is then determined gravimetrically. Due to the slight volatility of alkenes, alkanes, and alcohols, especially in the C,2 materials, the neutral oil tends to be underestimated by these procedures. 

The oil used should be of a volatile type, as the more volatile oils gives the greatest sensitivity. However, the use of petroleum fractions with too low a flash point is hazardous. The choice is, therefore, usually made of a fuel oil similar to those used for diesel engines. It is common practice to add a proportion of dyestuff to the oil, partly to make adequate mixing of the explosive immediately visible, and partly to assist the user in seeing proper loading of boreholes, particularly in salt and other white materials. 

VRDS Isomax [Vacuum residua desulphurization] A hydrodesulfurization process adapted for processing the residues from the vacuum distillation of the least volatile fraction of petroleum. An extension of the RDS Isomax process, developed and piloted by Chevron Research Company in the early 1970s. In 1988, one unit was under construction and one was being engineered. 

Vapor Pressure (VP) - The pressure, measured in psia, exerted by a volatile liquid as determined by ASTM D 323, Standard Method of Test for Vapor Pressure of Petroleum Products (Reid method). 

Chemical name NA Molecular weight NA Formula Mixture of petroleum fractions Density 0.820-0.869 g ml 1 Volatility None... 

Current EPA analytical methods do not allow for the complete speciation of the various hydrocarbon compounds. EPA Methods 418.1 and 8015 provide the total amount of petroleum hydrocarbons present. However, only concentrations within a limited hydrocarbon range are applicable to those particular methods. Volatile compounds are usually lost, and samples are typically quantitated against a known hydrocarbon mixture and not the specific hydrocarbon compounds of concern or the petroleum product released. By conducting EPA Method 8015 (Modified) using a gas chromatograph fitted with a capillary column instead of the standard, hand-packed column, additional separation of various fuel-ranged hydrocarbons can be achieved. 

Yang, W. P, 1981, Volatilization, Leaching and Degradation of Petroleum Oils in Sand and Soil Systems Ph.D. thesis, Department of Civil Engineering, North Carolina State University. 

Fractionation of petroleum by volatility, informative as it might be, does not give any indication of the physical nature of petroleum. This is more often achieved by subdivision of the petroleum into bulk fractions that are separated by a variety of solvent and adsorption methods. 

A further aspect of volatility that receives considerable attention is the vapor pressure of petroleum and its constituent fractions. The vapor pressure is the force exerted on the walls of a closed container by the vaporized portion of a liquid. Conversely, it is the force that must be exerted on the liquid to prevent it from vaporizing further (ASTM D323). The vapor pressure increases with temperature for any given gasoline, liquefied pefioleum gas, or other product. The temperature at which the vapor pressure of a liquid, either a pure compound or a mixture of many compounds, equals 1 atm pressure (14.7 psi, absolute) is designated as the boiling point of the liquid. 

Another approach is to consider petroleum constituents in terms of transportable materials, the character of which is 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. Thus, petroleum transport fractions can be considered by equivalent carbon number to be grouped into 13 different fractions. The analytical fractions are then set to match these transport... 

Cracking the thermal processes by which the constituents of petroleum are converted to lower-molecular-weight products a process whereby the relative proportion of lighter or more volatile components of crude oil is increased by changing the chemical structure of the constituent hydrocarbons. 

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