What is the chemical equation of refining oil?

The basic process of refining crude oil into products is a physical separation, not a chemical reaction. A distillation column (also called pipestill) separates different components in the crude oil based on their differences in boiling point. No chemical equation is appropriate because there is (almost) no chemical reaction i.e. there is no change to the chemical bonds.

I say 'almost' because there is a relatively small number of chemical reactions (e.g. chloride ions attacking steel pipework; thermal cracking of long-chain hydrocarbons). However, these chemical reactions are undesirable and are minimised as far as possible.