Boiling oil fractions

Rossinskaja G., Dobele G., Domburg G. (1986) Thermocatalytic transformation of cellulose and lignin in the presence of phosphoric acid. 3. Characteristics of the higher - boiling oil fraction of carbohydrates pyrolysis. Khimija Drev., 6, 72-76. 

Hydrocarbons may be removed in oil scrubbers. However, the natural vapour pressure of these solvents sometimes requires the use of higher boiling oil fractions in the pre-absorber, which can then no longer be boiled out indirecdy with steam in a conventional heat regenerator, but can be heated to the boiling point only by means of live steam or in fired reboilers. 

If pure 3-bromo-4-aminotoluene is required, the crude base may be purified either by steam distillation or, more satisfactorily, by distillation under reduced pressure. The oil is dried with 5 g. of sodium hydroxide pellets, and distilled under reduced pressure from a Claisen fiask with a fractionating side arm a little p-tolui-dine may be present in the low boiling point fraction, and the pure substance is collected at 92-94°/3 inin. or at 120-122°/30 mm. The purified amine solidifies on cooling and melts at 17-18°. 

Olefins are produced primarily by thermal cracking of a hydrocarbon feedstock which takes place at low residence time in the presence of steam in the tubes of a furnace. In the United States, natural gas Hquids derived from natural gas processing, primarily ethane [74-84-0] and propane [74-98-6] have been the dominant feedstock for olefins plants, accounting for about 50 to 70% of ethylene production. Most of the remainder has been based on cracking naphtha or gas oil hydrocarbon streams which are derived from cmde oil. Naphtha is a hydrocarbon fraction boiling between 40 and 170°C, whereas the gas oil fraction bods between about 310 and 490°C. These feedstocks, which have been used primarily by producers with refinery affiliations, account for most of the remainder of olefins production. In addition a substantial amount of propylene and a small amount of ethylene ate recovered from waste gases produced in petroleum refineries. 

The feedstocks used ia the production of petroleum resias are obtaiaed mainly from the low pressure vapor-phase cracking (steam cracking) and subsequent fractionation of petroleum distillates ranging from light naphthas to gas oil fractions, which typically boil ia the 20—450°C range (16). Obtaiaed from this process are feedstreams composed of atiphatic, aromatic, and cycloatiphatic olefins and diolefins, which are subsequently polymerized to yield resias of various compositioas and physical properties. Typically, feedstocks are divided iato atiphatic, cycloatiphatic, and aromatic streams. Table 2 illustrates the predominant olefinic hydrocarbons obtained from steam cracking processes for petroleum resia synthesis (18). 

The bottoms, consisting of absorption oil, absorbed propane, and higher boiling hydrocarbons, are fed to the lean-oil fractionator. The LPG and the natural gas Hquids are removed as the overhead product from the absorption oil which is removed as a ketde-bottom product. 

The overhead product from the lean-oil fractionator, consisting of propane and heavier hydrocarbons, enters the depropanizer. The depropanizer overhead product is treated to remove sulfur and water to provide specification propane. The depropanizer bottoms, containing butane and higher boiling hydrocarbons, enters the debutanizer. Natural gasoHne is produced as a bottom product from the debutanizer. The debutanizer overhead product is mixed butanes, which are treated for removal of sulfur and water, then fed iato the butane spHtter. Isobutane is produced as an overhead product from the spHtter and / -butane is produced as a bottoms product. 

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. 

Cmde oil containing about 30% asphalt can be refined completely in an atmospheric unit to an asphalt product. However, most cmde oil cannot be distilled satisfactorily to an asphalt product at atmospheric pressure because of the presence of substantial proportions of high boiling gas oil fractions. Thus, as a supplement to the atmospheric process, a second fractionating tower (a vacuum tower) is added (Fig. 1). 

One of the most important operations in a refinery is the initial distillation of the crude oil into its various boiling point fractions. Distillation involves the heating, vaporization, fractionation, condensation, and cooling of feedstocks. This subsection discusses the atmospheric and vacuum distillation processes which when used in sequence result in lower costs and higher efficiencies. This subsection also discusses the important first step of desalting the crude oil prior to distillation. 

The complexity of oil fractions is not so much the number of different classes of compounds, but the total number of components that can be present. Even more challenging is the fact that, unlike the situation with other complex samples, in which only a few specific compounds have to be separated from the matrix, in oil fractions the components of the matrix itself are the analytes. Figure 14.1 presents an estimation (by extrapolation) of the total number of possible hydrocarbon isomers with up to twenty carbon atoms present in oil fractions. Although probably not all of these isomers are always present, these numbers are nevertheless somewhat overwhelming. This makes a complete compositional analysis using a single column separation of unsaturated fractions with boiling points above 100 °C utterly impossible. 

Secondary raw materials, or intermediates, are obtained from natural gas and crude oils through different processing schemes. The intermediates may be light hydrocarbon compounds such as methane and ethane, or heavier hydrocarbon mixtures such as naphtha or gas oil. Both naphtha and gas oil are crude oil fractions with different boiling ranges. The properties of these intermediates are discussed in Chapter 2. 

Approximate ASTM boiling point ranges for crude oil fractions... 

It is obtained by distn of high-boiling petroleum fractions, followed by purification. The latter operation consists of treatment with coned sulfuric acid, then coned Na hydroxide soln, and filtration thru decolorizing carbon. In order to reduce the solid paraffins, the oil is chilled aind filtered... 

In the thermal cracking methods, the higher-boiling petroleum fractions like heavy oils are subjected to high temperature and pressure by which the bigger hydrocarbon molecules break down to yield lower-boiling lighter fractions ... 

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