How hexane is made

Heat the crude oil

Heat separates crude oil into its distillates, light hydrocarbons from heavy ones. Naphtha comes off as a light cut with a wide boiling range, 50 to 140 °C in one patent.

Cut the narrow fraction

Refiners fractionate again and keep only the slice boiling close to 69 °C. It still holds 3 to 15% aromatics, mainly benzene, which food use cannot accept.

boils at 65 to 70 °C

Hydrogenate out the benzene

One industry route runs the cut over a catalyst with hydrogen at raised temperature and pressure, which converts the benzene. Sulfur has to come out before this step. Other refiners use adsorption or catalytic distillation.

Or extract with solvent

Another route mixes the cut with a solvent such as sulfolane, which carries the aromatics away. One patent runs two extraction stages in a row, then washes the remaining hydrocarbon with water to remove carried-over solvent.

Check benzene and isomers

Food-grade limits have kept tightening, and one patent's process targets under 100 ppm of aromatics. The isomer mix varies with the oil it came from, with about 50 percent by weight usually straight-chain.