Vacuum and Azeotropic distillation:

Vacuum distillation is actually distillation under decrease pressure. It is used to separate high boiling mixtures or liquids in which decompose below their normal boiling points. Low pressure reduces the boiling point.

Steam distillation is employed to separate a component from a nonvolatile impurity. The boiling temperature of the mixture is reduced by vaporizing it in a stream of carrier vapour say steam that upon condensation is immiscible with the original mixture. And thus, a separation can be readily achieved.

Azeotropic distillation is used for separating components of a mixture that boil extremely close to each other. The associative volatility of the components of the mixture is altered by adding another substance. This declaration will give you an idea about the different ways the distillation can be carried out for different types of mixtures.