What process separates crude oil into useful products by heating it in a refinery?

The refinery process that separates crude oil into useful products by heating it is fractional distillation.

In a distillation unit, crude oil is heated until much of it vaporizes. The vapors rise through a fractionating column, where they cool and condense at different heights according to boiling range. Lighter fractions generally condense higher in the column, while heavier fractions remain lower or leave near the bottom.

The process produces streams such as refinery gases, naphtha, kerosene-range material, gas oils, and residue. These streams are not automatically finished consumer fuels; refineries usually process them further to meet product specifications and improve their value.

Fractional distillation separates hydrocarbons but does not primarily break their molecules apart. Catalytic cracking does that by converting larger molecules into smaller ones, while hydrodesulfurization removes sulfur with hydrogen and catalysts. These related operations are why a modern refinery is more than a single distillation tower.