Boiling point petroleum fractions

Diluent A low-boiling-point petroleum fraction, such as naphtha, that is added to a more viscous high-boiling-point petroleum liquid or oil-continuous emulsion. The diluent is usually added to reduce viscosity. 

Distillation of petroleum separates alkanes into fractions with similar boiling points. These fractions are suited for different uses based on their physical properties, such as volatility and viscosity. 

Parameters Determining Selectivity. We believe that the peculiar selectivity of Pt-H-mordenite for hydrocracking normal and near-normal paraflSns in high-boiling feedstocks could not have been predicted from the known adsorption and diffusion properties of mordenites loc. cit.). However, extensive catalytic studies on the preparation of low-pour-point petroleum fractions have suggested to us that catalyst selectivity depends... 

The usual first step in the railing, or processing, of petroleum is to separate it into fractions on the basis of boiling point. The fractions commonly taken are shown in Table 25.3 T. Because gasoline is the most commercially important of tiiese fractions, various processes are used to maximize its yield. 

A number of fractions (components) are obtained from the distillation of petroleum. Distillation is defined as the separation of the various fractions in a mixture by individual boiling points. Hydrocarbon fractions obtained from petroleum include straight-run gasoline, kerosene, heating oil, diesel, jet fuel, lubricating oil, paraffin wax, asphalt, and tar (Figure 13-10). Additional processes can be applied to these different fractions to create other products. 

Those checking the reference from where this technique was developed will find mention that it should only be applied to pure hydrocarbons and narrow-boiling range petroleum fractions. However this restriction applies primarily to the conversion between the true normal boiling point (Ti,) and the boiling point corrected to a Watson K of 12 (T ). The procedure for calculating PCT does not involve this conversion and experience shows that the resulting formula works well. 

The procedure applies to stabilized, i.e., debutanized, crudes, but can be applied to any petroleum mixture with the exception of liquefied petroleum gas, very light naphtha, and those fractions having boiling points over 400°C. 

D 2887, applies to products and petroleum fractions whose final boiling points are equal to or below 538°C (1000°F), and have boiling points above 38°C (100°F). The results obtained are equivalent to those obtained from the TBP distillation, ASTM D 2892. 

D 3710, applies to products and petroleum fractions whose final boiling points are equal to or less than 260°C (500°F). 

To extend the applicability of the characterization factor to the complex mixtures of hydrocarbons found in petroleum fractions, it was necessary to introduce the concept of a mean average boiling point temperature to a petroleum cut. This is calculated from the distillation curves, either ASTM or TBP. The volume average boiling point (VABP) is derived from the cut point temperatures for 10, 20, 50, 80 or 90% for the sample in question. In the above formula, VABP replaces the boiling point for the pure component. 

One has seen that the number of individual components in a hydrocarbon cut increases rapidly with its boiling point. It is thereby out of the question to resolve such a cut to its individual components instead of the analysis by family given by mass spectrometry, one may prefer a distribution by type of carbon. This can be done by infrared absorption spectrometry which also has other applications in the petroleum industry. Another distribution is possible which describes a cut in tei ns of a set of structural patterns using nuclear magnetic resonance of hydrogen (or carbon) this can thus describe the average molecule in the fraction under study. 

The current calculation methods are based on the hypothesis that each mixture whose properties are sought can be characterized by a set of pure components and petroleum fractions of a narrow boiling point range and by a composition expressed in mass fractions. 

We will use the term petroleum fraction to designate a mixture of hydrocarbons whose boiling points fall within a narrow temperature range, typically as follows ... 

It is common that a mixture of hydrocarbons whose boiling points are far enough apart petroleum cut) is characterized by a distillation curve and an average standard specific gravity. It is then necessary to calculate the standard specific gravity of each fraction composing the cut by using the relation below [4.8] ... 

The molecular weight can be also estimated for petroleum fractions whose boiling point is not known precisely starting with a relation using the viscosities at 100 and 210°F ... 

As seen in Chapter 2, mixtures of hydrocarbons and petroleum fractions are analyzed in the laboratory using precise standards published by ASTM (American Society for Testing and Materials) and incorporated for the most part into international (ISO), European (EN) and national (NF) collections. We wiil recall below the methods utilizing a classification by boiling point ... 

Maxwell and Bonnel (1955) proposed a method to calculate the vapor pressure of pure hydrocarbons or petroleum fractions whose normal boiling point and specific gravity are known. It is iterative if the boiling point is greater than 366.5 K ... 

Crude petroleum is fractionated into around fifty cuts having a very narrow distillation intervals which allows them to be considered as ficticious pure hydrocarbons whose boiling points are equal to the arithmetic average of the initial and final boiling points, = (T, + Ty)/2, the other physical characteristics being average properties measured for each cut. 

Naphthenic acids occur ia a wide boiling range of cmde oil fractions, with acid content increa sing with boiling point to a maximum ia the gas oil fraction (ca 325°C). Jet fuel, kerosene, and diesel fractions are the source of most commercial naphthenic acid. The acid number of the naphthenic acids decreases as heavier petroleum fractions are isolated, ranging from 255 mg KOH/g for acids recovered from kerosene and 170 from diesel, to 108 from heavy fuel oil (19). The amount of unsaturation as indicated by iodine number also increases in the high molecular weight acids recovered from heavier distillation cuts. 

Methylphenol. y -Cresol is produced synthetically from toluene. Toluene is chlorinated and the resulting chlorotoluene is hydrolyzed to a mixture of methylphenols. Purification by distillation gives a mixture of 3-methylphenol and 4-methylphenol since they have nearly identical boiling points. Reaction of this mixture with isobutylene under acid catalysis forms 2,6-di-/ f2 -butyl-4-methylphenol and 2,4-di-/ f2 -butyl-5-methylphenol, which can then be separated by fractional distillation and debutylated to give the corresponding 3- and 4-methylphenols. A mixture of 3- and 4-methylphenols is also derived from petroleum cmde and coal tars. 

The second category differs from those discussed above in that it relates, in the main, to those situations for which no data or only characterizing data exist. In such cases, this small set of characterizing data or, in its absence, stmcture data are used to estimate a set of parameters of the type requited by point generation routines. One notable specific example of this type of facihty is the creation of data sets for petroleum boiling fractions from information on average boiling point and density. 

Crude oil is the source for over. 1,(1(1() petroleum-based products for both industrial and consumer applications. The technique of distillation, the first stage processing of petroleum, exploits the different boiling points of the various petroleum fractions to separate out and isolate for use the different portions of the crude. The type and proportions of hydrocarbons present in each fraction depends upon the type of crude oil used and the range of temperatures employed. The major products produced directly... 

Petroleum refining begins by fractional distillation of crude oil into three principal cuts according to boiling point (bp) straight-run gasoline (bp 30-200 °C), kerosene (bp 175-300 °C), and heating oil, or diesel fuel (bp 275-400 °C). Further distillation under reduced pressure then yields... 

Petroleum distillation, (a) A distillation tower at a petroleum refinery, (b) A diagram showing the boiling points of the petroleum fractions separated by distillation. 

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