Separation asphalt

One of the most used procedures, an ASTM standard, D4124, was developed by Corbett (61) and separates asphalt into four fractions. Asphaltenes are precipitated by heptane, and the remaining solution is divided into saturates, naphthene aromatics, and polar aromatics by a series of successively more polar solvents on an alumina column. Similar procedures produce fractions variously known as asphaltenes, resins, and oils or saturates, aromatics, resins, and asphaltenes, for example. Although similar, the methods are not identical and produce fractions that overlap those of other methods. 

O Donell, G. (1951). Separating Asphalt into Its Chemical Constituents. Anal Chem. 23 (6) 894. 

FIGURE 8.1 Typical cutaway view of cylindrical Leclanohd battery ( Eveready ) paste separator, asphalt seals. 

Simple conventional refining is based essentially on atmospheric distillation. The residue from the distillation constitutes heavy fuel, the quantity and qualities of which are mainly determined by the crude feedstock available without many ways to improve it. Manufacture of products like asphalt and lubricant bases requires supplementary operations, in particular separation operations and is possible only with a relatively narrow selection of crudes (crudes for lube oils, crudes for asphalts). The distillates are not normally directly usable processing must be done to improve them, either mild treatment such as hydrodesulfurization of middle distillates at low pressure, or deep treatment usually with partial conversion such as catalytic reforming. The conventional refinery thereby has rather limited flexibility and makes products the quality of which is closely linked to the nature of the crude oil used. 

Fabrics perform one or more function in each installation generally there is one primary function. The five basic primary functions have been identified as separation, stabili2ation, reinforcement, filtration, and drainage. When the geotextile is impregnated with an impermeable material such as an asphaltic... 

The vacuum residua or vacuum bottoms is the most complex fraction. Vacuum residua are used as asphalt and coker feed. In the bottoms, few molecules are free of heteroatoms molecular weights range from 400 to >2000, so high that characteri2ation of individual species is virtually impossible. Separations by group type become blurred by the sheer mass of substitution around a core stmcture and by the presence of multiple functionahties in a single molecules. Simultaneously, the traditional gc and ms techniques require the very volatiUty that this fraction lacks. 

The early developments of solvent processing were concerned with the lubricating oil end of the cmde. Solvent extraction processes are appHed to many usefiil separations in the purification of gasoline, kerosene, diesel fuel, and other oils. In addition, solvent extraction can replace fractionation in many separation processes in the refinery. For example, propane deasphalting (Fig. 7) has replaced, to some extent, vacuum distillation as a means of removing asphalt from reduced cmde oils. 

Liquefied petroleum gases precipitate asphaltic and resinous materials from cmde residues while the lubricating oil constituents remain in solution. Although all Hquefied gases possess this property to some extent, propane and butane are used to deasphalt residual lubricating oils because of their relative low cost and their ease of separation from lubricating oils. 

Straight Run Asphalt. In cmde-oil refining, the crude oil at 340—400°C is injected into a fractionating column (5,6,19,20). The lighter fractions are separated as overhead products and the residuum is straight-reduced asphalt. 

However, for the past 30 years fractional separation has been the basis for most asphalt composition analysis (Fig. 10). The separation methods that have been used divide asphalt into operationally defined fractions. Four types of asphalt separation procedures are now in use ( /) chemical precipitation in which / -pentane separation of asphaltenes is foUowed by chemical precipitation of other fractions with sulfuric acid of increasing concentration (ASTM D2006) (2) solvent fractionation separation of an "asphaltene" fraction by the use of 1-butanol foUowed by dissolution of the 1-butanol solubles in... 

The fractions obtained in these schemes are defined operationally or proceduraHy. The amount and type of asphaltenes in an asphalt are, for instance, defined by the solvent used for precipitating them. Fractional separation of asphalt does not provide well-defined chemical components. The materials separated should only be defined in terms of the particular test procedure. 

The foremnner of the modern methods of asphalt fractionation was first described in 1916 (50) and the procedure was later modified by use of fuller s earth (attapulgite [1337-76-4]) to remove the resinous components (51). Further modifications and preferences led to the development of a variety of fractionation methods (52—58). Thus, because of the nature and varieties of fractions possible and the large number of precipitants or adsorbents, a great number of methods can be devised to determine the composition of asphalts (5,6,44,45). Fractions have also been separated by thermal diffusion (59), by dialysis (60), by electrolytic methods (61), and by repeated solvent fractionations (62,63). 

In the cathodic protection of storage tanks, potentials should be measured in at least three places, i.e., at each end and at the top of the cover [16]. Widely different polarized areas arise due to the small distance which is normally the case between the impressed current anodes and the tank. Since such tanks are often buried under asphalt, it is recommended that permanent reference electrodes or fixed measuring points (plastic tubes under valve boxes) be installed. These should be located in areas not easily accessible to the cathodic protection current, for example between two tanks or between the tank wall and foundations. Since storage tanks usually have several anodes located near the tank, equalizing currents can flow between the differently loaded anodes on switching off the protection system and thus falsify the potential measurement. In such cases the anodes should be separated. 

There is a wide range of conversion levels. The term maximum conversion type has no precise definition but is often used to describe a level of conversion, where there is no net fuel oil manufactured. A fuel products refinery with specialities may manufacture lubricating oils, asphalts, greases, solvents, waxes and chemical feed stocks in addition to the primary fuel products. The number and diversity of products will naturally vary from one refinery to another. Refineries produce chemical feed stocks for sale to the chemical affiliates and do not have responsibility for the manufacture of chemical products directly. Both operations may be carried out at the same physical location but the corporate product responsibilities are usually separate. 

Solvent separation, using the propane deasphalting process, is another procedure by which asphalts of the straight reduced type may be manufactured. This is a physical separation process used to recover high viscosity lube fractions from a given vacuum residuum. When mixed with the residuum, the solvent preferentially dissolves the oil and precipitates the asphalt. 

Teer-asphalt, m. tar asphalt, coal-tar pitch, -ausscheider, m. tar separator, -ausschlag, m. tar rash, -band, n. tarred tape, -baum,... 

Liquid propane is a selective hydrocarbon solvent used to separate paraffinic constituents in lube oil base stocks from harmful asphaltic materials. It is also a refrigerant for liquefying natural gas and used for the recovery of condensable hydrocarbons from natural gas. 

Residues containing high levels of heavy metals are not suitable for catalytic cracking units. These feedstocks may be subjected to a demetallization process to reduce their metal contents. For example, the metal content of vacuum residues could be substantially reduced by using a selective organic solvent such as pentane or hexane, which separates the residue into an oil (with a low metal and asphaltene content) and asphalt (with high metal content). Demetallized oils could be processed by direct hydrocatalysis. 

On the other hand, liquid propane also has a high affinity for paraffinic hydrocarbons. Propane deasphalting removes asphaltic materials from heavy lube oil base stocks. These materials reduce the viscosity index of lube oils. In this process, liquid propane dissolves mainly paraffinic hydrocarbons and leaves out asphaltic materials. Higher extraction temperatures favor better separation of the asphaltic components. Deasphalted oil is stripped to recover propane, which is recycled. 

Solvent extraction may also be used to reduce asphaltenes and metals from heavy fractions and residues before using them in catalytic cracking. The organic solvent separates the resids into demetallized oil with lower metal and asphaltene content than the feed, and asphalt with high metal content. Figure 3-2 shows the IFP deasphalting process and Table 3-2 shows the analysis of feed before and after solvent treatment. Solvent extraction is used extensively in the petroleum refining industry. Each process uses its selective solvent, but, the basic principle is the same as above. 

Drying the separated, sulfonated asphalt by passing it through a drum dryer... 

Dispersants for Asphalts. Asphalt and asphaltene components can produce difficulties in various processes in recovering crude petroleum oils and preparing them for transportation through pipelines or in refining separation. 

Asphaltene precipitation, in many instances, carries from the well tubing to the flow lines, production separators, and other downstream equipment. It has also been reported (19) that asphaltic bitumen granules occured in the oil and gas separator with oil being produced from certain oil fields. 

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