Naphthenic crude petroleum

The major part of the sulfur contained in crude petroleum is distributed between the heavy cuts and residues (Table 8.10) in the form of sulfur compounds of the naphthenophenanthrene or naphthenoanthracene type, or in the form of benzothiophenes, that is, molecules having one or several naphthenic and aromatic rings that usually contain a single sulfur atom. 

Hydrocarbons are segmented into a variety of categories. Each category possesses a distinct molecular profile and, in turn, set of chemical and physical properties. Each class of hydrocarbons therefore has historically served different markets. Crude petroleum is composed of four major hydrocarbon groups paraffins, olefins, naphthenes, and aromatics. 

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. 

Naphthenic acid from petroleum continues to be of interest as a material for making copper naphthenate and wood preservatives for use in greenhouses and the like. Naphthenic acids occur naturally to the highest extent in naphthenic crude oils, certain of which are stated to contain over 1% total naphthenic acid. As yet these meterials have not reached wide acceptance in agricultural pest control. 

Naphthenic acid corrosion has been a problem in petroleum-refining operations since the early 1990s. Refineries processing highly naphthenic crudes must use steel alloys 316 stainless steel is the material of choice. Conversely, naphthenic acid derivatives find use as corrosion inhibitors in oil-well and petroleum refinery applications. 

The commercial production of naphthenic acid from petroleum is based on the formation of sodium naphthenate. Naphthenic acids are recovered by caustic extraction uf petroleum distillates rather than from crude petroleum. Crude naphthenic acid is obtained by acidulating the sodium naphthenate, and can be further refined to remove impurities. 

Naphtha is divided into two main types, aliphatic and aromatic. Aliphatic naphtha is composed of paraffinic hydrocarbons and cycloparaffins (naphthenes), and may be obtained directly from crude petroleum by distillation. Aromatic naphtha contains aromatics, usually alkyl-substituted benzene, and is very rarely, if at all, obtained from petroleum as straight-run materials often reforming is necessary (Fig. 2). 

Shale oil is not a uniquely hydrogen deficient feedstock vis-a-vis petroleum crudes. As can be seen from the representative data presented in Table II, its atomic hydrogen to carbon ratio is within the range of some mid-continent crude oils. Its atomic H/C ratio is that of a naphthenic base petroleum crude. 

Other factors, such as the Watson characterization factor, are also used. A highly paraffinic crude oil can have a characterization factor as high as 13, whereas a highly naphthenic crude oil can be as low as 10.5, and the breakpoint between the two types of crude oil is approximately 12. Sulfur content, the carbon residue, and distillation data are also valuable in petroleum evaluation (Speight, 2001). 

Crude Oil. Crude petroleum consists essentially of mixtures of paraffinic, naphthenic, and aromatic hydrocarbons containing from 1 to over 70 carbon atoms per molecule and may contain dissolved gases or solids. The naphthenic hydrocarbons are based on cyclopentane or cyclohexane or on fused C5 and Ce rings. There is no evidence of the existence of C3, C4, C7, or C7+ cycloparaffins in crude oil. Olefins, diolefins, and acetylenes are absent. The aromatics are mainly benzene derivatives naphthalene, tetralin, and their substituted derivatives have been isolated in a few cases. 

Petroleum base lubricating oils are present in the atmospheric residuum (boiling above 370°C/698°F) of selected paraffinic and naphthenic crude oils. The production of lubricating oils is well established (Sequeira, 1992 Speight, 2000) and consists of five basic procedures ... 

Naphthenes. A term used in petroleum chemistry to denore certain saturated hydrocarbons, specifically five-and six-carbon cycloparaffins and their alkyl derivatives, Tound in crude petroleum. Sometimes used to include polycyclic members found in the higher-boiling fractions. 

NA (North American) number. Used only for shipments within Canada and the United States, naphthenic. A type of petroleum fluid delivered from naphthenic crude oil, thus containing a high proportion of closed ring methylene groups. National Institute of Occupational Safety and Health (NIOSH). The U.S. agency that is responsible for investigating the toxicity of workroom environments and all other matters relating to safe industrial practice. 

Naphthenes naf- thens (1884) n, C H2 . Found in certain types of crude petroleum. Known also as cycloparaffins or hydrogenated benzenes. 

The precise composition of crude petroleum varies widely from one source to another, but the principal components are always hydrocarbon paraffins (40-75%), cycloparaffins or naphthenes (mainly cyclopentane and cyclohexane derivatives) (20—50%) and aromatic hydrocarbons (5-20%). The first step in petroleum refining is distillation into broad fractions, which typically have the boiling ranges and compositions given in Table 2.1. None of these distillates contain significant amounts of olefins. The lower olefins, ethylene, propylene and butenes are produced principally by subsequent cracking operations. 

The first driers were based on fatty acids or rosin, which were subsequently replaced by naphthenic acid, a material obtained from crude petroleum. Due to scarcity of naphthenic acid, in modern driers it has been replaced by branched chain synthetic acids such as 2-ethylhexanoic acid and neodecanoic acid. 

Cycloparaffins - par-o-f3n n (1900) Ring compounds of saturated hydrocarbon type based on groupings of methylene radicals (CH2). Typical cycloparafflns are cyclopropane, cyclobutane, cyclopheptane, etc. The cycloparafflns have very good solvent properties, and are constituents of crude petroleum s. Known also as Naphthenes. 

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