Narrow boiling range

Their production in a refinery begins with base stocks having narrow boiling ranges and high octane numbers iso C5 cuts (used in small concentrations because of their high volatility) or alkylates are sought for such formulations. 

Other than fuel, the largest volume appHcation for hexane is in extraction of oil from seeds, eg, soybeans, cottonseed, safflower seed, peanuts, rapeseed, etc. Hexane has been found ideal for these appHcations because of its high solvency for oil, low boiling point, and low cost. Its narrow boiling range minimises losses, and its low benzene content minimises toxicity. These same properties also make hexane a desirable solvent and reaction medium in the manufacture of polyolefins, synthetic mbbers, and some pharmaceuticals. The solvent serves as catalyst carrier and, in some systems, assists in molecular weight regulation by precipitation of the polymer as it reaches a certain molecular size. However, most solution polymerization processes are fairly old it is likely that those processes will be replaced by more efficient nonsolvent processes in time. 

Extractive distillation, using similar solvents to those used in extraction, may be employed to recover aromatics from reformates which have been prefractionated to a narrow boiling range. Extractive distillation is also used to recover a mixed ben2ene—toluene stream from which high quaUty benzene can be produced by postfractionation in this case, the toluene product is less pure, but is stiU acceptable as a feedstock for dealkylation or gasoline blending. Extractive distillation processes for aromatics recovery include those Hsted in Table 4. 

Atmospheric distillation separates the crude oil complex mixture into different fractions with relatively narrow boiling ranges. In general, separation of a mixture into fractions is based primarily on the difference in the boiling points of the components. In atmospheric distillation units, one or more fractionating columns are used. 

When the condensation process is not exactly isothermal but the temperature change is small such as where there is a significant change in pressure, or where a narrow boiling range multicomponent mixture is being condensed the logarithmic temperature difference can still be used but the temperature correction factor will be needed for multipass condensers. The appropriate terminal temperatures should be used in the calculation. 

This fraction typically contains 5-7 mol% of cyclohexane as measured by NMR. Collection of a narrower boiling range can yield product with less cyclohexane but at lower recovery. 

Aviation gasoline, now usually found in use in light aircraft and older civil aircraft, has a narrower boiling range than conventional (automobile) gasoline, that is, 38 to 170°C (100 to 340°F) compared to approximately... 

A side stream product of narrow boiling range, which after passing through the stripper may be suitable for the aliphatic solvent Varsol ... 

Gray, J. A., et al., "Selected Physical, Chemical, and Thermodynamic Properties of Narrow Boiling Range Coal Liquids," paper presented to the AIChE Fall 1981 Annual Meeting, New Orleans, Nov. (1981). 

Taking this into consideration, specifications (as in the U.S.S.R.) require a fairly narrow boiling range for xylene, for example, 95% of the product should distil between 136.5-140°C or 136.5-141.5°C. 

Narrow boiling ranges, nessure < 2 MNAn abs, "SH,rnBxm 750 - 3 000 IxIO -SxlO ... 

Medium oiganics Narrow boiling range, pressure < 2 MN r abs, 1000 - 3300 Ixl0 -3xl0 ... 

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