Hydrocarbon paraffin-type

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. 

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. 

Most USTs contain petroleum products that are mixtures of four types of hydrocarbons paraffins, olefins, naphthalenes, and aromatics. 

So far in this chapter, you have focussed on gaseous hydrocarbons, such as methane and acetylene. You have examined their heats of combustion and various processes in which they are used. In your everyday life, you may have encountered another type of hydrocarbon paraffins. Paraffins are long chain hydrocarbons. They are semisolid or solid at room temperature. One type of paraffin has been a household item for centuries—paraffin wax, C25H52(s), better known as candle wax. (See Figure 14.25.)... 

Burning oil kerosene contains three main types of hydrocarbons— paraffinic, naphthenic, and aromatic— with a preponderance of the paraffinic type. This is in contrast to power kerosene, or tractor vaporizing oil, which has a comparatively high content of aromatics and naphthenes favorable for high octane rating. It may also contain slight amounts of sulfur in the form of a variety of organic compounds. 

Cannot be cut easily with a knife but is relatively easy to scratch, for example, with a knife. This material will dissolve in solvents such as toluene and chloroform but will not dissolve in aliphatic hydrocarbons (paraffin and white spirit). This material will swell in solvents such as alcohols and phenols and is plasticized by some ester-type plasticizers, for example, tritolyl phosphate and dibutyl phthalate. 

Naphthenes hydrocarbons containing one or more saturated rings of 5 or 6 carbon atoms in their molecules, to which paraffinic-type branches are attached (adjective napthenic). 

These reactions proceed essentially through a bifimctional mechanism involving two types of catalytic sites hydro-dehydrogenating sites and acidic sites. A saturated hydrocarbon (paraffin... 

The principal nonpolar-type adsorbent is activated carbon. Kquilihrium data have been reported on hydrocarbon systems, various organic compounds in water, and mixtures of organic compounds (11,15,16,46,47). With some exceptions, the least polar component of a mixture is selectively adsorbed eg, paraffins are adsorbed selectively relative to olefins of the same carbon number, but dicycUc aromatics are adsorbed selectively relative to monocyclic aromatics of the same carbon number (see Carbon, activated carbon). 

Separation of Norma/ and Isoparaffins. The recovery of normal paraffins from mixed refinery streams was one of the first commercial appHcations of molecular sieves. Using Type 5A molecular sieve, the / -paraffins can be adsorbed and the branched and cycHc hydrocarbons rejected. During the adsorption step, the effluent contains isoparaffins. During the desorption step, the / -paraffins are recovered. Isothermal operation is typical. 

Petroleum Waxes. Waxes derived from petroleum are hydrocarbons of three types paraffin [64742-43-4] (clay-treated) sernimicrocrystaUine or intermediate and microcrystalHne [64742-42-3] (clay-treated). SernimicrocrystaUine waxes are not generally marketed as such (7). Others include acid-treated, chemically neutrali2ed, and hydrotreated and paraffin and hydrocarbon waxes, untreated. The quaHty and quantity of the wax separated from the cmde oil depends on the source of the cmde oil and the degree of refining to which it has been subjected prior to wax separation. Petroleum waxes are produced in massive quantities throughout the world. Subject to the wax content in the cmde, paraffin and, to a substantially lesser degree, microcrystalHne wax are produced in almost all countries of the world that refine cmde oil. Production capacity in the United States and imports for the years 1990 to 1995 are Hsted in Table 2. Canada suppHes over 50% of the petroleum wax imported into the United States (3). 

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