Gas oil fraction

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. 

Gas oil fractions (204—565°C) from coal Hquefaction show even greater differences in composition compared to petroleum-derived counterparts than do the naphtha fractions (128). The coal-gas oils consist mostly of aromatics (60%), polar heteroaromatics (25%), asphaltenes (8—15%), and saturated... 

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). 

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). 

Example 9-8 Heavy Gas-Oil Fractionation of a Crude Tower Usu Glitsch s Gempak (used by permission of Glitsch, Inc. Bulletin 5140)... 

The heavy naphtha-Ught gas oil fractionation zone of a crude tower has to be revamped to handle 25% more capacity. Because trays would be working at high percent flooding, Gempak structured packing is condensed (Figures 9-56A-D). 

Adsorption of n-paraffms (C10-C14) from a kerosine or a gas oil fraction can be achieved in a liquid or a vapor phase adsorption process. 

Type 225-540°C gas oil fraction 50% of nitrogen as neutral nitrogen compounds ... 

The separation of n-alkanes from a kerosene or gas oil fraction by a molecular sieve can be performed in a liquid phase or in a gas phase process. In the gas phase processes there are no problems of cleaning the loaded molecular sieve from adherent branched and cyclic hydrocarbons. However, the high reaction temperature of the gas phase processes leads to the development of coke-contaminated sieves, which have to be regenerated from time to time by a careful burning off of the coke deposits. 

Ishii, Y. Kozaki, S. Furuya, T., et al., Thermophilic Biodesulfurization of Various Heterocyclic Sulfur Compounds and Crude Straight-Run Light Gas Oil Fraction by a Newly Isolated Strain Mycobacterium phlei WU-0103. Current Microbiology, 2005. 50(2) pp. 63-70. 

Catalytic cracking When a mixture of alkanes from the gas oil fraction (C12 and higher) is heated at very high temperature (-500 °C) in the presence of a variety of catalysts, the molecules break apart and rearrange to smaller, more highly branched alkanes containing 5-10 carbon atoms. 

The feedstocks were prehydrogenated real gas oil fractions with different aromatic, sulphur and nitrogen contents from Hungarian and Russian crudes. Their important properties are summarized in Table 2. 

A gas oil fraction from the distillation of crude oil contains hydrocarbons in the C16 to C20 range. These hydrocarbons can be cracked by heating in the presence of a catalyst. 

Fluid catalytic cracking over an acid catalyst converts residual hydrocarbons from the vacuum gas oil fraction into valuable olefins, gasoline, and diesel products. The catalytic cracking proceeds... 

Refining crude oil by hydrodesulfurization. The crude oil contains varying amounts of sulfur that may range from 0.05 to about 5%. The sulfur-rich fractions, the coke-distillate and the gas-oil fractions of the crude oil are passed through a fixed-bed catalyst along with hydrogen. 

Naphthenic-aromatic compounds are formed by the condensation of an aromatic ring with a cycloparaffin. Examples of naphthenic-aromatics include indane and tetralin and their derivatives. These compounds are common constituents of distillate fuel and light gas oil fractions. 

Liquid products contain sulfur and nitrogen and must be hydroprocessed to improve quality. Separate hydroprocessing units for upgrading the naphtha, kerosene, and gas oil fractions can be used to optimize the overall process. Refined gas oil or diesel fuel is aromatic in character and contains more cycloparaffins than conventional crude oil. The resulting fuel is low in cetane number, high in density, and typically has very good low-temperature handling properties. 

Charlet, Lanneau, and Johnson (10) in 1951, relating to the types of aromatic compounds in the gas oil fraction of petroleum... 

Hydrocarbons Isolated from Gas, Gasoline, Kerosene, and Gas-Oil Fractions. 

API Research Project 6 has, by exhaustive fractionation from the gas, gasoline, kerosene, and gas-oil fractions of the large lot of the foregoing representative petroleum, separated 122 different hydrocarbon compounds, as of June 30, 1951. These compounds are listed in Table I, which gives the molecular formula, name, and type of the compound its normal boiling point the purity of the best sample of the given compound actually isolated in the work of the project and the estimated amount of the given compound in the crude petroleum. 

Discussion. In connection with the hydrocarbons isolated from the gas, gasoline, kerosene, and gas-oil fractions of the project s one representative petroleum, the following points are of interest ... 

The values given in Figure 4 for the relative amounts of the different types of hydrocarbons in the several broad fractions are more reliable for some of the fractions than for others. The data for the gasoline fraction, 40° to 180° C., are very reliable the data for the kerosene fraction, 180° to 230° C., are fairly reliable in the light gas-oil fraction, 230° to 300° C., the data for the n-paraffins and mononuclear and dinuclear aromatics are reliable, while the values for the branched paraffins and cycloparaffins are less reliable for the heavy gas-oil and light lubricant fraction, 300° to 400° C., the values are all interpolated from the values for the light gas-oil and the lubricant fraction for the lubricant fraction, all the values are reliable. 

Fig. 3. GC-AED profiles of gas oil fractions (12). Estimated percentages from LC analysis. Reproduced from Ref. /2, with permission.

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