Straight-run fractions

Use of a lower percentage of a straight run fraction or waxy distillates in a blend... 

Another application of the Platforming process has been to produce aromatic hydrocarbons. Of particular interest is the production of benzene. It has been shown (10) that yields up to 92% of theoretical based on methylcyclopentane and cyclohexane content can be obtained from light straight-run fractions. Similarly, toluene and xylenes are produced in high yields from the corresponding C7 and Cg fractions. 

The operating conditions for the three processes are very similar— only temperatures are somewhat dissimilar. The Shell Development system, employing a modified Friedel-Crafts system, operates at a lower temperature—150°-210°F vs. 250°-400°F for the other two processes. However, the equilibrium effects of the temperature differences are minimized as shown by the similarity in n-C4 and n-C5 yields shown in Table VI. Unleaded octane numbers for C5/C6 isomerate, obtained from a pure C5/C6 straight-run fraction, could not be found in the literature for the Shell process. However, pilot unit operations charging laboratory blends of n-C5, n-C6, and C6 naphthenes have been reported (26, 45). In the Shell process the use of antimony trichloride and hydrogen has considerably reduced the amount of side reactions for a Friedel-Crafts system so that the yield for this process is quite close to the yield structure for the other two processes. 

A light straight-run fraction, consisting primarily of C5 and C hydrocarbons. These also will contain any C4 and lighter gaseous hydrocarbons that are dissolved in the crude. 

Isomerization of n-paraffins in the C5-C6 range, such as those present in the LSR (light straight run) fraction, is industrially carried out to improve the octane number of the gasoline. Skeletal isomerization of n-paraffins is an acid-catalyzed reaction that is thermodynamically favored at lower temperatures. Therefore, acid catalysts with strong acidity have to be used in order to perform the reaction at temperatures as low as possible. The process is carried out in the presence of hydrogen and a bifunctional catalyst, which typically consists of a noble metal (Pt) supported on an acidic carrier. 

The data of Table VII suggest that under the nearly constant conditions tested, conversion to ethylene increases with boiling range of the straight run fraction ... 

Reforming processes are used to change the inherent chemical structures of the hydrocarbons that exist in distillation fractions crude oil into different compounds. Catal3dic reforming (Fig. 13.11) is one of the most important processes in a modern refinery, altering straight-run fraction or fractions from a catal d ic cracker into new compounds through a combination of heat and pressure in the presence of a catalyst. 

Kerosene, because of its use as burning oil, must be free of aromatic and unsaturated hydrocarbons as well as free of the more obnoxious sulfur compounds. The desirable constituents of kerosene are saturated hydrocarbons, and it is for this reason that kerosene is manufactured as a straight-run fraction, not by a cracking process. 

There are little or no olefins in crude oil or straight run (direct from crude distillation) products but they are found in refining products, particularly in the fractions coming from conversion of heavy fractions whether or not these processes are thermal or catalytic. The first few compounds of this family are very important raw materials for the petrochemical Industry e.g., ethylene, propylene, and butenes. 

Straight Run Asphalt. In cmde-oil refining, the crude oil at 340—400°C is injected into a fractionating column (5,6,19,20). The lighter fractions are separated as overhead products and the residuum is straight-reduced asphalt. 

In addition to straight run naphthas, 70—190°C cuts obtained by distillation from streams produced by cracking high boiling petroleum fractions can also be used as feed to reformers. Naphthas produced by hydrocracking are particularly suitable. 

Naphtha is a generic term normally used in the petroleum refining industry for the overhead liquid fraction obtained from atmospheric distillation units. The approximate boiling range of light straight-run naphtha (LSR) is 35-90°C, while it is about 80-200°C for heavy straight-run naphtha (HSR). ... 

Typical analyses of two straight-run naphtha fractions from two crude types... 

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... 

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. 

Selected Diesel Fuel Properties from Different German Co-LTFT-Derived Straight-Run Distillate Fractions and the German Sonder Diesel Kraftstoff (SDK) Specifications of the 1940s... 

A light diesel fuel was produced by distillate hydrotreating of the straight-run Fe-HTFT material, while the heavier fraction was hydrocracked over a dewaxing catalyst, which produced a heavy diesel (Table 18.10). Some diesel fuel was also produced by C3-C4 olefin oligomerization over solid phosphoric acid by recycling the naphtha thus produced. It has previously been pointed out that solid phosphoric acid is not well suited for distillate production,42 and the hydrogenated... 

Diesel production involved a straightforward design. The olefinic distillate from olefin oligomerization was combined with the straight-run HTFT distillate and hydrotreated. The hydrotreated Fischer-Tropsch-derived distillate was blended with the distillate fraction from the natural gas liquids to produce diesel fuel. In 2003 another hydrotreater (noble metal catalyst) was added to the refinery to convert part of the hydrotreated HTFT distillate into low aromatic distillate to serve a niche market.56... 

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