Asphalt, petroleum refining process

Petroleum refining, processing, and distribution are considered downstream activities and generally fall within the subject scope of the chemical engineer. Crude oil, transported from the ground to the refinery, is used to produce many products, including petrolenm gas, gasoline, kerosene, heavy oil (fuel oil), coke, asphalt, tar, and other byproducts. 

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. 

Asphalt is a bituminous substance that is found in natural deposits or as the residual of in petroleum or coal tar refining processes. It has a black or brownish-black color and pitchy luster. It is cement-like in... 

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). 

Residua are the dark-colored nearly solid or solid products of petroleum refining that are produced by atmospheric and vacuum distillation (Figure 11.1 Chapter 3). Asphalt is usually produced from a residuum and is a dark brown to black cementitious material obtained from petroleum processing that contains very high-molecular-weight molecular polar species called asphaltenes that are soluble in carbon disulfide, pyridine, aromatic hydrocarbons, and chlorinated hydrocarbons (Chapter 3) (Gruse and Stevens, 1960 Guthrie, 1967 Broome and Wadelin, 1973 Weissermel and Arpe, 1978 Hoffman, 1983 Austin, 1984 Chenier, 1992 Hoffman and McKetta, 1993). 

Bitumen describes a black or dark brown masticlike material that is thermoplastic in nature and softens upon heating. The sources of bitumen are petroleum or coal deposits. The natural product is commonly called gilsonite or pitch, a mineral formed by an old weathered petroleum flow at the surface of the earth that has left behind the larger molecules from the petroleum. A principal source in the past has been Lake Trinidad, a 445,000 m2 deposit on the island of Trinidad. Bitumen from petroleum or crude oil is called asphalt (qv). It is the material left behind after all the valuable compounds, eg, gasolines, have been distilled out of the cmde oil. The amount and quality of asphalt is dependent on the source of the crude oil used in the refining process. Some cmde oils have a higher content of asphaltic bitumen left after the distillation process. Bitumen from coal is coal-tar pitch. It remains after the valuable coal oils and tars have been distilled out of the coal tars produced by distractive distillation. Most industrial applications for bitumen products use asphalt or coal-tar pitch because the supply is more uniform and plentiful. 

Oil (also referred to as petroleum) is a complex liquid mixture of organic substances, principally of hydrocarbons containing five to sixteen carbon atoms. Most crude oil, once removed from a well, is sent by pipeline to a refinery, where it is distilled to separate it into gasoline, heating oil, diesel oil, and asphalt. The use of catalysts during the refining process increases the yield of gasoline. In 2001, 25.7 billion barrels of oil were used worldwide, with estimated reserves of 1.05 trillion barrels. (One barrel contains 159 liters.)... 

Mohammad Fabhat Ah, Ph.D., is Professor of Industrial and Petroleum Chemistry at King Fahd University of Petroleum Minerals in Saudi Arabia. An expert in characterization studies of heavy ends, residues, and asphalt, he is also knowledgeable about crude oils and products, refining process technology, waste oil recycling, and stabihty characteristics of jet fuels. 

ORIGIN/INDUSTRY SOURCES/USES from petroleum refining, shale oil processing, coal tar distilling, combustion of tobacco used to manufacture dyes, plastics insecticides and fungicide manufacturing constituent in asphalt... 

Chromatography is perhaps one of the most widely applied automated instruments in process analysis, particularly in the nonaqueous chemical and petrochemical industries [8]. In petroleum refining, for example, the crude petroleum, containing hundreds of chemicals from methane to asphalt, is converted to salable cuts by distillation. Further processing by catalytic reforming, distillation, and chemical reaction yields materials used for fuels, lubricants, petrochemical feedstock, and other applications. 

Asphalt is defined by ASTM as a dark to black cementitious material in which the predominating constituents are bitumens that occur in nature or are obtained in petroleum processing. Asphaltene occurs in native petroleum and is enriched in asphalt when the light fractions of petroleum are removed during the refining process. 

Asphalt is thought of as a colloidal system similar to petroleum, the difference being that the lighter molecules have been removed from asphalt during the refining process. Asphalt can be fractionated into four important fractions saturates, aromatics, resins, and asphaltenes by either the SARA method or the ASTM D4124 process (standard test method for separation of asphalt into four fractions). The fractionated part of saturates and aromatics is generally considered to be gas-oil. The polarity of these four fractions increases from saturates —> aromatics —> resins —> asphaltenes. 

Over the years, multilayers of tar-based waterproofers replaced the hot asphalt used in roofing. In early 1900, asphalt became available from petroleum refining, and it was followed by oxidized bitumen interlaid with roofing felt and then alternated with a mineral base sheet, l" Asphalt-based materials are used extensively as binders, sealants, and waterproof coatings in diverse applications because of their low cost, inherent cohesive nature, weather-resistant properties, and ease of processing in the molten state. 

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. 

The most outstanding development resulting from these investigations is the use of liquid propane for the selective precipitation of resins and asphalts. The development of the propane deasphalting process is a very important contribution to petroleum technology in the refining of residual oils and provides a method for substantially complete separation of lubricating oils from the asphaltic materials contained in the residua derived from any crude source. 

This process, while capable of eliminating the asphaltic materials present in heavy stocks, has not been applied solely for this purpose on a commercial scale. Possibly with, an increasing scarcity of crude petroleum, this type of hydrogenation will be incorporated into refining operations in future to convert asphaltic materials to more useful products. 

The changing pattern of the availability of conventional petroleum has focused the attention of refiners on heavy feedstocks and their economic use is a necessity (Dickenson et al., 1997). The move to process these less desirable feedstocks has led to legislation to control the amount of sulfur in the various grades of liquid fuels. This, in turn, has meant that processing facilities must be adjusted accordingly to effectively remove the sulfur from the feedstocks (or products) as an integral part of the processing sequence. Furthermore, the lack of use of residua can also create environmental problems due to disposal issues or result in the production of low-quality asphalt that has limited life span in service. 

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