Asphalt-base crude

Cresylic acid is a commercial mixture of phenolic compounds including phenol, cresols, and xylenols. This mixture varies widely according to its source. Properties of phenol, cresols, and xylenols are shown in Table 4-5 Cresylic acid constitutes part of the oxygen compounds found in crudes that are concentrated in the naphtha fraction obtained principally from naphthenic and asphaltic-based crudes. Phenolic compounds, which are weak acids, are extracted with relatively strong aqueous caustic solutions. 

The composition of crude oil may vary with the location and age of an oil field, and may even be depth dependent within an individual well or reservoir. Crudes are commonly classified according to their respective distillation residue, which reflects the relative contents of three basic hydrocarbon structural types paraffins, naphthenes, and aromatics. About 85% of all crude oils can be classified as either asphalt based, paraffin based, or mixed based. Asphalt-based crudes contain little paraffin wax and an asphaltic residue (predominantly condensed aromatics). Sulfur, oxygen, and nitrogen contents are often relatively higher in asphalt-based crude in comparison with paraffin-based crudes, which contain little to no asphaltic materials. Mixed-based crude contains considerable amounts of both wax and asphalt. Representative crude oils and their respective composition in respect to paraffins, naphthenes, and aromatics are shown in Figure 4.1. 

The presence of paraffin wax is usually reflected in the paraffinic nature of the constituent fractions, and a high asphaltic content corresponds with the naphthenic properties of the fractions. As a result, the misconception has arisen that paraffin-base crude oils consist mainly of paraffins and asphalt-base crude oils mainly of cyclic (or naphthenic) hydrocarbons. In addition to paraffin- and asphalt-base oils, a mixed base had to be introduced for those oils that leave a mixture of bitumen and paraffin wax as a residue by nondestructive distillation. 

All types of crudes have been used in the production of spray oils. On the West Coast the asphaltic base crudes occurring locally have been generally used, while oils derived from mixed base stocks are now most commonly used east of the Rockies. 

Petroleum crude oils, which are divided for the purposes of conventional classification into three main types—asphalt (or naphthenic)-base, paraffin-base, and mixed-base—contain varying amounts of hydrocarbons which readily solidify and are identified as wax. The asphalt-base crudes may contain only a trace of wax, while the wax content of the paraffin-base crudes and the mixed-base crudes may be as high as 15% or higher (73). Crude oils with a wax content as high as 35% are known. 

A widely used classification of petroleum distinguishes between crude oils either on a paraffin base or on an asphalt base and arose because paraffin wax separates from some crude oils on cooling, whereas other oils show no separation of paraffin wax on cooling. The terms paraffin base and asphalt base were introduced and have remained in common use (van Nes and van Westen, 1951). 

Large amt of asphalt used in the US is artifical. It is obtained as the residue from distillation of asphaltic and mixed base crude petroleum oils... 

Activities in the propane deasphalting (PDA) unit submatrix represent the operations on vacuum tower bottoms from the base crude mix and from the incremental crudes. The de-asphalter overhead streams from all activities enter one stream balance row with common properties. Each deasphalter bottoms enter a separate row for No. 6 fuel oil blending. 

Paraffin-Base Crude Oil Crude oil containing little or no asphalt, yielding at the refinery a high percentage of paraffin, lubricating oil and kerosene. 

For the low-temperature experiment the rate of extension apparatus, as described by Hajek (25) and Haas (26), was used to determine the stiffness of test specimen of SA binder based concrete mixes at — 10° and — 25°C. The asphalt cements chosen were 40-50, 85-100, and 300-400 penetration grade to cover the entire range as well as to ensure that if a difference in properties did exist, it would be noticeable. The other test variables included temperature susceptibility (obtained by using asphalts based on crude oils from various sources), SA ratio, and binder content. 

If the residue which remains after distillation is a waxlike solid consisting largely of paraffin hydrocarbons the crude is designated as paraffin base. If the residue is a black pitchlike solid the crude is called asphalt base, Pennsylvania crude has a paraffin base whereas California oils are for the most part asphalt base. Often a clear-cut distinction cannot be made and the crude is described as being mixed base oil. Most Mid-Continent crudes are of this tyrpe. 

Define (a) isomer, (f ) diolefln, (c) cyclic hydrocarbon, (d) unsaturated hydrocarbon, (e) wet gas, (/) parafim base crude, (g) asphalt. 

The first step in the manufacture of asphalt-based coatings consists of the distillation of crude petroleum, which results in distillate fractions (gasoline, naptha, kerosene, diesel fuel, and gas oil). The fraction of crude oil that boils above approximately 300 C is not distilled, but is withdrawn from the bottom of the distillation... 

Bituminous binders are a crude type of hydrocarbon resin, generally produced as a by-product during distillation of crude oil or coal. Bituminous resins, based on their chemical composition, are categorized as asphalt-based and coal-tar pitch-based products. We will briefly discuss some important bituminous binders used in coatings and related industries. 

Asphalt can be generally classified as natural or artificial. Natural asphalts include bituminous materials laid down in natural deposits, such as those in Trinidad, and as gilsonites and grahamite bitumens, which are completely soluble in carbon disulfide. Artificial asphalt includes mainly petroleum-derived asphalts and, to a lesser extent, coal tar, water-gas tars, and their pitches. There are types of asphalt products obtained from straight-run asphalt (refined naphtha-based crude oils) hot, cutback, and emulsion asphalt. 

The evaluation of a paraffin-base crude oil is particularly simple because the oil contains no asphalt. Only a true-boiling-point distillation, con-... 

Although distillation and elemental analysis of the fractions provide a good evaluation of the qualities of a crude oil, they are nevertheless insufficient. Indeed, the numerous uses of petroleum demand a detailed molecular analysis. This is true for all distillation fractions, certain crude oils being valued essentially for their light fractions used in motor fuels, others because they make quality lubricating oils and still others because they make excellent base stocks for paving asphalt. 

Vacuum distillation of the atmospheric residue complements primary distillation, enabli r.ecoyery of heavy distillate cuts from atmospheric residue that will un r o further conversion or will serve as lube oil bases. The vacuum residue containing most of the crude contaminants (metals, salts, sediments, sulfur, nitrogen, asphaltenes, Conradson carbon, etc.) is used in asphalt manufacture, for heavy fuel-oil, or for feed for others conversion processes. 

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. 

Three broad classes of crude petroleum exist the paraffin types, the asphaltic types, and the mixed-base types. The paraffin types are composed of molecules in which the number of hydrogen atoms is always two more than twice the number of carbon atoms. The characteristic molecules in the asphaltic types are naphthenes, composed of twice as many hydrogen atoms as carbon atoms. In the mixed-base group are both paraffin hydrocarbons and naphthenes. 

All crudes are a variation of the hydrocarbon base CH2. The ultimate composition shows 84 to 86% carbon, 10 to 14% hydrogen, and small percentages of sulfur (0.06 to 2%), nitrogen (2 %), and oxygen (0.1 to 2%). The sulfur content is usually below 1.0% but may be as high as 5.0%. Physically crude oil may be water-white, clear yellowish, green, brown, or black, heavy and thick like tar or asphalt. 

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