Separation techniques

Separation of aromatics

Benzene forms azeotropic mixtures with many C6 - C8 alkanes. This means that the mixture reaches a constant boiling point with a fixed proportion of benzene and the alkane in both the liquid and vapour. Benzene cannot therefore be separated from these alkanes by simple fractional distillation and various other techniques have to be employed.

These mostly involve using solvents that dissolve the aromatic components (mostly benzene, methylbenzene and dimethylbenzene) but not the alkanes. Very polar solvents are used for this technique, for example alcohols.

Separating benzene

The aromatic compounds, benzene, methylbenzene and dimethylbenzene, which are all dissolved in the solvent, can be separated using fractional distillation. The solvent recovered by this distillation is re-used. Any methylbenzene obtained is returned to the disproportionation unit.

















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