Petroleum distillation is the process by which crude derivatives are obtained by increasing the temperature to bring the crude oil to different boiling points. It is a unit operation whose definition is as follows: When a liquid containing two or more components is heated to its boiling temperature, the composition of the vapor will normally be different from that of the liquid. This difference in composition in the two phases at equilibrium is the basis for distillation and for this reason this operation is applicable to separate mixtures of compounds due to their different volatilities or their different vapor pressures.