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How does distillation separate crude oil into useful products?

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structures of common hydrocarbon compounds — hydrocarbon Structures assumed by hydrogen (H) and carbon (C) molecules in four common hydrocarbon compounds.

Fractional distillation is the primary process used to separate the hydrocarbon components of crude oil into useful products based on their boiling points.12

The process begins by heating desalted crude oil in a furnace to temperatures between 315 and 400 °C (600 and 750 °F). This mixture of vapor and unvaporized oil enters a tall fractionating column containing multiple trays. As the oil vapors rise, they cool and condense, while liquid reflux flows downward, contacting the rising vapors. This continuous interaction allows for the separation of constituents: lighter components with lower boiling points rise to the top, while heavier components with higher boiling points collect at the bottom.1

Intermediate products, or "sidestreams," are withdrawn at various points along the column, yielding specific products such as naphtha, kerosene, and gas oils. The remaining residue at the base can be used for industrial fuels or further processed into lubricating oils. These fractions are essential feedstocks for creating products ranging from gasoline and diesel fuel to asphalt.12