Paraffinic-based crude oil

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. 

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

Paraffinic-based crude oil. About 95% of the crude oil available is paraffinic-based, compared to about 5 % that is naphthenic-based. 

Fig. 4-5. Tnie-boiling-point evaluation curves of a 42.2 API paraffin-base crude oil.

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

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. 

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 problem to be solved for surfactant range alcohols based on n-paraffins is how to utilize all n-paraffins in crude oil, which have wide carbon number ranges, by finding effective applications of the products therefrom. 

It is a mixture of oils and waxes stabilised by a third component and is obtained from still residues of paraffin base crudes after fractionation. It does not leave an oily stain on paper as wax is the external phase and oil tile internal phase. It can be used as a grease. 

Motor Oils. Spark-ignition and diesel-engine oils differ primarily because the diesel oils must exhibit detergency properties to keep carbon from accumulating in the engine after a few hours of operation. Naphthene-base oils (low Viscosity Index) are somewhat satisfactory as diesel oils, but most heavy-duty oils are made by introducing a detergency additive to an oil manufactured from paraffin or mixed-base crude oils. 

In general, paraffin-base raw products are the most easily treated, and the others follow in the order mixed-base and naphthene-base. This applies to the light distillates such as gasoline, as well as to the heavy lubricating oils. Many naphthene-base oils contain more sulfur than mixed-base oils, and paraffin-base oils may contain scarcely any sulfur. Paraffin- and mixed-base crude oils contain troublesome wax. The fact that a true naphthene-base oil contains no wax simplifies the manufacture of lubricants. 

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. 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

Selecting the naphtha type can be an important processing procedure. For example, a paraffinic-base naphtha is a better feedstock for steam cracking units because paraffins are cracked at relatively lower temperatures than cycloparaffins. Alternately, a naphtha rich in cycloparaffins would be a better feedstock to catalytic reforming units because cyclo-paraffins are easily dehydrogenated to aromatic compounds. Table 2-5 is a typical analysis of naphtha from two crude oil types. 

Paraffin sulfonates, 24 146 Paraffin wax(es), 28 671 26 214—215 separation from crude oil, 26 216 as barrier coating, 28 125 in lubricating oil base stocks, 15 216—217 Paraffin wax vapor barriers, in finish removers, 28 80... 

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). 

Because the paraffin and mixed-base crudes yield lubricating oil fractions of high quality, means had to be devised in the early days of the petroleum industry to separate the wax from the oil. The removal of wax from petroleum fractions is one of the most important phases in the production of lubricating oils and fuel oils of low pour point, and has received the attention of many investigators. 

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 ... 

Mannich bases are present as auxiliaries and additives throughout the whole working process of the petroleum industry, from crude oil extraction up to the final products. Indeed, they are used as oleophilizers in drilling fluids- or in the treatment of cmde oil, such as desalting and prevention of paraffin deposits. Mannich bases and derivatives are, moreover, employed as antifoulants - in heat exchangers as well... 

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