Naphthenic crudes

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

The viscosity of a paraffinic crude increases rapidly with decreasing temperature on the other hand, for the naphthenic crudes, the increase in viscosity is more gradual. 

A crude-oil assay always includes a whole crude API gravity and a TBP curve. As discussed by Nelson (op. cit., pp. 89-90) and as shown in Fig. 13-85, a reasonably consistent correlation (based on more than 350 distillation curves) exists between whole crude API gravity and the TBP distillation curve at 101.3 kPa (760 torr). Exceptions not correlated by Fig. 13-85 are highly paraffinic or naphthenic crude oils. 

Paraffinic crude oils are defined as those crude oils containing waxes, naphthenic crude oils as those con-... 

Figure 2-77 shows how the weight distributions of the different molecular types vary during the fractional distillation of a naphthenic crude oil. Saturated aliphatic hydrocarbons (i.e., paraffins and naphthenes) are the predominant constituents in the light gasoline fraction. As the boiling point is raised, the paraffin content decreases, and the NSO content increases continuously. About 75 wt% of tbe residuum is composed of aromatics and NSO compounds. 

A high-density fuel is preferred because it normally has the greatest heating value per unit volume of fuel. Jet fuels derived from paraffinic crudes have a slightly lower density but higher calorific value per equivalent mass than those refined from naphthenic crudes. 

It has been determined that certain nitrogen-, oxygen-, and sulfur-containing aromatic compounds contained in crude oil can lead to darkening of refined fuels and oils. Often, these compounds are found in fuels refined from naphthenic crude oil or asphaltic, high-sulfur crudes. Compounds such as indoles, quinolines, and naphthenobenzothiophenes can lead to darkening of fuel. 

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. 

Since the viscosity-temperature coefficient of lubricating oil is an important expression of its suitability, a convenient number to express this property is very useful, and hence, a viscosity index (ASTM D-2270) was derived. It is established that naphthenic oils have higher viscosity-temperature coefficients than do paraffinic oils at equal viscosity and temperatures. The Dean and Davis scale was based on the assignment of a zero value to a typical naphthenic crude oil and that of 100 to a typical paraffinic crude oil intermediate oils were rated by the formula ... 

A sample of black paraffinic crude oil (Fig. 3.5-15 a) gives a spectrum which is quite similar to that of a black naphthenic crude oil and to those of other similar samples. Its... 

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). 

The for crude oil and its fractions generally range between 10 (highly naphthenic crude) and 13 (highly paraffinic crude). For highly aromatic compounds to highly paraffinic compounds, the value of usually ranges between 10 and 15, respectively, and therefore, can be said to be a qualitative measure of either the aromaticity or the paraffinicity of a crude oil. 

Usually, steam is added to the preheat system, either as velocity steam or after the preheater as dilution steam to get deeper volatilization. Each product is steam stripped as in crude oil distillation. In the case of naphthenic crude oils, the bottom product may be directed to asphalt specialties rather than being treated to make lubricating oil base stock. 

Although the pour point test is still included in many specifications, it is not designated for high-boiling fuel oil (ASTM D 396). In fact, although the failure to flow at the pour point normally is attributed to the separation of wax from the fuel oil (in the case of waxy crude oil precursors), it also can be due to the effect of the viscosity of the fuel oil (in the case of naphthenic crude oil precursors). In addition, the pour point of fuel oil may be influenced by the previous thermal history of the fuel oil. Thus the usefulness of the pour point test in relation to fuel oil, especially residual fuel oil, may be open to question. 

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 ... 

Naphthenics are made from a more limited range of crude oils than paraffinics, and in smaller quantities, at a restricted number of refineries. Important characteristics of naphthenic base oils are their naturally low pour points, because they are wax-free, and excellent solvency powers. Their viscosity/temperature characteristics are inferior to paraffinics, i.e. they have low/medium VI, but they are used in a wide range of applications where this is not a problem. Since naphthenic crudes are free of wax, no de-waxing step is needed but solvent extraction or hydrotreatment is often used now to reduce aromatic content and especially to remove polycyclic aromatics which may present a health hazard in untreated oils. The main producers of naphthenics are in North and South America because most of the world s supply of naphthenic lubricant crudes are found there. 

Electrical oils Oils used in industrial transformers for electrical insulation and heat transfer must have low viscosity and very good low-temperature properties. They are produced either from naphthenic crudes or by urea/catalytic de-waxing from paraffinic crudes. 

Bicyclic naphthenes (C7 - C9) are usually used as an indication of a naphthenic crude oil. The following bicyclic naphthenic compounds were observed in different crude oils bicyclo[3,3,0]octane, bicyclo[3,2,l]octane, bicy-clo[2,2,2]octane, bicyclo[4,3,0]nonane, bicyclo[2,2,l]heptane and their isomers or substituted compounds. 

Solvent extraction is successful as a refining procedure only with stocks of paraffinic character. Raw stocks which have too much naphthenic character do not respond to solvent extraction. For some purposes the properties of naphthenic oils are desirable and there are procedures used specifically to obtain these special stocks from naphthenic crudes. Figure 16-2 is a schematic diagram of the refining of naphthenic oils. The final step in the modern process is hydrofinishing the older process used a sulfuric acid treatment instead to reduce the content of aromatic compounds. 

If the reformer is being operated for aromatics production, the proper fractions of selected naphthenic crudes are charged. Pressures are, in general, lower than in gasoline production since little hydrocracking is wanted. 

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. 

Fig. 4 Lower IR HC readings after Ftorisil for emulsions of two naphthenic crudes...

Lube crudes are generally paraffinic or naphthenic in composition. A paraffinic crude is characterized by a higher wax content. West Texas and Arab Light are good quality paraffinic crudes. Naphthenic crudes are characterized by their low wax content and they make base stocks with low viscosity index, e.g. Venezuelan and Californian. 

Naphthenic process oil is used in high volume in general-purpose rubber compounds. Naphthenic oils are usually derived from naphthenic crudes that are more limited in supply than paraffinic crudes. In the world only about 5% of all crude is naphthenic crude. Only certain regions have naphthenic crudes. Pennsylvania was one of these regions, but today much of the naphthenic crudes come from Venezuela. 

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