What role does Sulfolane play in the separation of aromatics (BTX)?

Sulfolane plays the role of a selective solvent in the separation of aromatics (benzene, toluene, and xylenes - BTX) from non-aromatics in a process called solvent extraction. Solvent extraction is a separation technique that relies on the differing solubilities of components in a mixture. Sulfolane (tetrahydrothiophene 1,1-dioxide) is a polar aprotic solvent, meaning it has a high dipole moment but does not readily donate protons. It has a strong affinity for aromatic hydrocarbons (BTX) compared to aliphatic hydrocarbons (paraffins and naphthenes). In the solvent extraction process, the feed stream containing both aromatics and non-aromatics is contacted with Sulfolane in an extraction column. The Sulfolane selectively dissolves the aromatics, forming a Sulfolane-rich extract phase. The non-aromatics remain largely undissolved and form a raffinate phase. These two phases are then separated. The Sulfolane is then recovered from the aromatic-rich extract phase through distillation or stripping, allowing the purified aromatics to be obtained and the Sulfolane to be recycled back to the extraction column. Sulfolane's high selectivity for aromatics, its high boiling point (which facilitates its recovery), and its chemical stability make it an effective and widely used solvent in aromatics extraction units.