Naphthenes fraction

The hydrocarbon composition of gasoline produced from different raw materials under the same process conditions may essentially differ individually as well as in groups. The main differences are observed in the composition of the paraffin-naphthene fraction of gasoline, and aromatics are represented basically by the toluene-xylene fraction. As a result of the transformation of hydrocarbon feedstocks over H-ZSM-5/AI2O3 catalyst, hydrocarbon and fraction composition of liquid products widen which leads to an increase of the end boiling point of the catalysate. Simultaneously, the formation of Ci - C4 hydrocarbons and of a small amount of H2 (not more than 3-4 wt % in the gas phase) occurs. The composition of the gaseous products obtained (P>5 MPa) differs only slightly. 

The nonnormal fraction can be separated further into an isoparaffin and cycloparaffin (naphthene) fraction. The nonnormal paraffin chromatogram is shown again in Figure 5b for comparison purposes. The... 

Furfural is a solvent that is widely used to extract raw lubricating feed stock to give a refined grade of lubricating oil. The solvency of furfural allows separation of undesirable aromatic and olefinic components from the desirable paraffinic and naphthenic fractions. A countercurrent extraction column gives the furfural extract which contains the undesirable fractions. A distillation step recovers the furfural for reuse in the process [4]. Furfural is used as an extractive distillation solvent in the purification of butadiene and isoprene. The presence of furfural in the process alters the relative volatility of the hydrocarbons enough so that a distillation separation is possible [5]. 

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

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. 

It is worthwhile to mention that the distribution of naphthenic acids is not uniform in a crude oil since a maximum value is observed in the fractions distilled between 400 and 450°C and whose average specific gravity is 0.950 (Figure 8.2). 

A key process in the production of gasoline, catalytic reforming is used to increase the octane number of light crude fractions having high paraffin and naphthene contents (C7-C8-C9) by converting them to aromatics. 

The principal class of reactions in the FCC process converts high boiling, low octane normal paraffins to lower boiling, higher octane olefins, naphthenes (cycloparaffins), and aromatics. FCC naphtha is almost always fractionated into two or three streams. Typical properties are shown in Table 5. Properties of specific streams depend on the catalyst, design and operating conditions of the unit, and the cmde properties. 

The term naphthenic acid, as commonly used in the petroleum industry, refers collectively to all of the carboxyUc acids present in cmde oil. Naphthenic acids [1338-24-5] are classified as monobasic carboxyUc acids of the general formula RCOOH, where R represents the naphthene moiety consisting of cyclopentane and cyclohexane derivatives. Naphthenic acids are composed predorninandy of aLkyl-substituted cycloaUphatic carboxyUc acids, with smaller amounts of acycHc aUphatic (paraffinic or fatty) acids. Aromatic, olefinic, hydroxy, and dibasic acids are considered to be minor components. Commercial naphthenic acids also contain varying amounts of unsaponifiable hydrocarbons, phenoHc compounds, sulfur compounds, and water. The complex mixture of acids is derived from straight-mn distillates of petroleum, mosdy from kerosene and diesel fractions (see Petroleum). 

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. 

In the other market areas, lead naphthenates are used on a limited basis in extreme pressure additives for lubricating oils and greases. Sodium and potassium naphthenates are used in emulsiftable oils, where they have the advantage over fatty acid soaps of having improved disinfectant properties. Catalyst uses include cobalt naphthenate as a cross-linking catalyst in adhesives (52) and manganese naphthenate as an oxidation catalyst (35). Metal naphthenates are also being used in the hydroconversion of heavy petroleum fractions (53,54) and bitumens (55). 

Toluene, Benzene, and BTX Reeoveiy. The composition of aromatics centers on the C - and Cg-fraction, depending somewhat on the boihng range of the feedstock used. Most catalytic reformate is used directiy in gasoline. That part which is converted to benzene, toluene, and xylenes for commercial sale is separated from the unreacted paraffins and cycloparaffins or naphthenes by hquid—hquid extraction or by extractive distillation. It is impossible to separate commercial purity aromatic products from reformates by distillation only because of the presence of azeotropes, although comphcated further by the closeness in boihng points of the aromatics, t/o-paraffin, and unreacted C -, C -, and Cg-paraffins. 

Gas turbine fuels can contain natural surfactants if the cmde fraction is high in organic acids, eg, naphthenic (cycloparaffinic) acids of 200—400 mol wt. These acids readily form salts that are water-soluble and surface-active. Older treating processes for sulfur removal can leave sulfonate residues which are even more powerful surfactants. Refineries have installed processes for surfactant removal. Clay beds to adsorb these trace materials are widely used, and salt towers to reduce water levels also remove water-soluble surfactants. In the field, clay filters designed as cartridges mounted in vertical vessels are also used extensively to remove surfactants picked up in fuel pipelines, in contaminated tankers, or in barges. 

Only a small fraction of reactant is iavolved ia this step. When naphthenes are iavolved, diradicals are produced. Eor aromatics with side chains, H radicals are produced. 

Solvents are recovered from the oil stream through distillation and steam stripping in a fractionator. The stream extracted from the solvent contains high concentrations of hydrogen sulfide, aromatics, naphthenes and other hydrocarbons, and is often fed to the hydrocracking unit. 

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