What is extraction distillation?
fractional distillation, which is commonly referred to as distillation or simple distillation, is a common method for separating volatile compounds based on boiling points (BP). Some mixtures are not separable by distillation. In many of these cases, mining distillation is used. In this process, a high cooking solvent is added to the feed, which changes the relative volatility of the compounds of feed. The solvent is then obtained in a separate distillation column and recycled. If one substance is cooked at a higher temperature than another, then the lower boiling substance will tend to evaporate first and condense at a higher point in the column. Fraction distillation will not separate mixtures whose compounds have similar BPS, especially if their chemical structures are similar.
Some liquid compounds form a special mixture called azeotrophe when there are present ratios. Azeotropy are a mixture of two, but sometimes three, separate compounds that behave as if they were the only compound with the only onethe point of boiling. Azeotropy cannot be divided into their components by fractional distillation. In the mining distillation, the solvent enters the distillation column above the supply. The solvent used is less volatile than any of the compounds to be separated.
The construction of the mining distillation column is often simple. The solvent must have a higher boiling point than the least volatile substance. The solvent concentration throughout the column must be high enough to have a widely separated volatility, but low enough to form two phases. The phase results in two layers of liquids, such as oil and water that do not dissolve each other. The solvent may be introduced into the column as a steam to prevent a sudden change in the solvent concentration at the feed point.
Extraction distillation examples include toluene separation (BP 110.8