Naphthenes

The petroleum oil which is found in the Caucasus in the region of the Black Sea and commonly known as Russian petroleum differs from American petroleum in that while the latter contains almost entirely hydrocarbons of the aliphatic series, the former contains hydrocarbons known as naphthenes which are hydrogenated benzene compounds. 

These naphthene hydrocarbons are the mother substances of important derivatives some of which have already been considered as direct derivatives of benzene but which may also be regarded as derivatives of the naphthenes. 

Quinone and Phloroglucinol.—Benzoquinone or quinone (p. 636) is considered a di-ketone derivative of benzene because of its relation to hydroquinol or para-di-hydroxy benzene. It may also be considered as an oxygen derivative of di-hydro benzene. 

Also phloroglucinol the 1-3-5-tri-hydroxy benzene may have the tautomeric constitution of a tri-ketone (p. 621) in which case it is a tri-oxy derivative of hexa-hydro benenze. 

A less complete oxidation of hexa-hydro benzene than that represented by the relationship of the tri-ketone compound above yields a series of cyclic secondary alcohols some of which are natural substances. Their relationship to hexa-hydro benzene is as follows  

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Dapalm The aluminium soap of naphthenic and palmitic acids used to gel gasoline. The thickened gasoline has been used for military flame throwers and incendiary bombs. See metallic soaps. 

It is produced from petroleum fractions rich in naphthenes by catalytic reforming in the presence of hydrogen (hydroforming) in this process dehydrogenation .nd dealkylation... 

Commercially, xylene is obtained by the catalytic reforming of naphthenes in the presence of hydrogen see toluene) or was formerly obtained from coal tar. The material so-produced is suitable for use as a solvent or gasoline ingredient, these uses accounting for a large part of xylene consumption. If xylene is required as a chemical, separation into the iso-... 

Or by a naphthenic ring which can also be substituted for two adjacent hydrogen atoms forming a naphthene aromatic such as tetralin or tetra.hydronaphthaiLene. ... 

Because of the differences existing between the quality of different distillation cuts and those resulting from their downstream processing, it is useful to group them according to a major characteristic. That is, they are grouped into the three principal chemical families which constitute them paraffins, naphthenes and aromatics. From a molecular point of view, their chemical reactivities follow this order ... 

Consider the molecule below. From an atomic point of view, an atom common to two structures, aromatic and naphthenic, or aromatic and paraffinic or still further naphthenic and paraffinic will be considered first of ill aromatic, then naphthenic, then paraffinic 2... 

As in the case of density or specific gravity, the refractive index, n, for hydrocarbons varies in relation to their chemical structures. The value of n follows the order n paraffins < n naphthenes < n aromatics and it increases with molecular weight. 

With the accumulation of results obtained from various and complex analyses of narrow cuts (Waterman method), correlations have been found f ctween refractive index, specific gravity and molecular weight on one hand, and percentages of paraffinic, naphthenic and aromatic carbon on the other. 

Separation of families by merely increasing the resolution evidently can not be used when the two chemical families have the same molecular formula. This is particularly true for naphthenes and olefins of the formula, C H2 , which also happen to have very similar fragmentation patterns. Resolution of these two molecular types is one of the problems not yet solved by mass spectrometry, despite the efforts of numerous laboratories motivated by the refiner s major interest in being able to make the distinction. Olefins are in fact abundantly present in the products from conversion processes. 

The naphthenic carbon percentage is the difference between 100 and the sum of the above concentrations. 

Starting from these methods, as we will see further on, nuclear magnetic resonance (NMR) of carbon has provided an absolute percentage of aromatic, paraffinic, and naphthenic carbons. 

Group the component in a petroleum fraction, which is possible if the normal boiling temperature and the standard specific gravity are known. This method gives correct results when the chemical structure is simple as in the case of a paraffin or naphthene. 

Generally speaking, paraffins, naphthenes, and aromatics have a potential for exploding under the following conditions 2 )... 

Naphthenes always have higher octane numbers —RON and MON— than their non-cyclic homologs for example, the RON of n-hexane is 24.8 while cyclohexane attains 83. 

The properties of straight run diesel fuels depend on both nature of the crude oil and selected distillation range. Thus the paraffinic crudes give cuts of satisfactory cetane number but poorer cold characteristics the opposite will be observed with naphthenic or aromatic crudes. The increasing demand for diesel fuel could lead the refiner to increase the distillation end point, but that will result in a deterioration of the cloud point. It is generally accepted that a weight gain in yield of 0.5% could increase the cloud point by 1°C. The compromise between quantity and quality is particularly difficult to reconcile. 

Hydrotreating the LCO increases its cetane number to around 40 (Table 5.16), but this technique needs large amounts of hydrogen for rather mediocre results, the aromatics being converted into naphthenes which are still not easily auto-ignited. That is why LCO is sent to the domestic heating oil pool. 

Feedstock Paraffinic crude Naphthenic crude Vacuum distillate Vacuum residue Deasphalted atmospheric residue... 

The smoke point corresponds to the maximum possible flame height (without smoke formation) from a standardized lamp (NF M 07-028). The values commonly obtained are between 10 and 40 mm and the specifications for TRO fix a minimum threshold of 25 mm. The smoke point is directly linked to the chemical structure of the fuel it is high, therefore satisfactory, for the linear paraffins, lower for branched paraffins and much lower still for naphthenes and aromatics. 

The level of injector fouling is most often illustrated in terms of residual flow (RF) expressed as a percentage of the flow under new conditions for a given needle lift. An RF on the order of 20% for a lift of 0.1 mm is a good compromise. This level may not be achieved with certain aromatic or naphthenic diesel fuels. The best recourse is then detergent additive addition. 

The most common liquid lubricants are mineral oils (usually naphthenic), esters (either diesters or complex esters), polyalpha olefins and polyalkylene glycols. 

The pour point is the lowest temperature at which an oil can still pour while it is cooled, without agitation, under standardized conditions. The pour point of paraffinic bases is linked to the crystallization of n-paraffins. The pour point of naphthenic bases is related to a significant viscosity increase at low temperatures. This property can be improved by additives. 

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