The refining process typically involves the following steps:

Distillation: Crude oil is heated to a high temperature, causing it to vaporize. The vapors are then condensed, and the resulting liquids are separated into different fractions based on their boiling points. 

Conversion: The different fractions are then subjected to various chemical reactions to convert them into more useful products. For example, gasoline is produced by converting the heavier fractions of crude oil into lighter hydrocarbons.

Treatment: The final step in the refining process is to treat the products to remove any remaining impurities. This may involve the use of chemicals, heat, or other techniques.