Main-Product

Sulfolane is a colorless, odorless, polar aprotic organic compound classified as a sulfone. Its chemical name is tetrahydrothiophene-1,1-dioxide, and its molecular formula is C₄H₈O₂S. Structurally, sulfolane consists of a five-membered saturated heterocyclic ring containing four carbon atoms and one sulfur atom; the sulfur is oxidized to form a sulfonyl group (SO₂).

Sulfolene Production

Sulfolane is produced industrially primarily through a two-step process involving:

1. Formation of sulfolene: A conjugated diene such as 1,3-butadiene reacts with sulfur dioxide (SO₂) at elevated temperatures, typically in the absence of solvent, to form 3-sulfolene (2,5-dihydrothiophene-1,1-dioxide), an intermediate cyclic sulfone compound.
2. Hydrogenation of sulfolene to sulfolane: The sulfolene intermediate is then hydrogenated using a catalyst such as Raney nickel or more recently Ni-B/MgO, under controlled temperature and hydrogen pressure, converting it into sulfolane (tetrahydrothiophene-1,1-dioxide).

Applications

• Solvent for extraction: Primarily used in industry to selectively extract aromatic hydrocarbons (such as benzene, toluene, and xylenes) from petroleum streams due to its high polarity and selectivity.
• Chemical synthesis: Serves as a polar aprotic solvent in organic reactions where stability and high boiling point are required.
• Other uses: Can be found in polymer processing and as a reaction medium in specialized syntheses.

Safety and Environmental Impact

• Sulfolane is considered stable under normal conditions but may degrade at elevated temperatures or in the presence of acids and oxidizing agents.
• It is miscible with water and many organic solvents, and although it has low volatility, it is persistent if released to the environment, requiring careful management, especially in groundwater protection.

References

• PubChem—Sulfolane (C₄H₈O₂S) chemical data
• Alaska Department of Environmental Conservation. Sulfolane Technical Assistance and Evaluation Report (2010)
• US Patent US5290953A (1994): Process for producing sulfolane compounds by reaction of 1,3-butadiene and sulfur dioxide followed by hydrogenation with Raney nickel catalyst.
• US Patent US3622598A (1971): Improved process involving removal of sulfur dioxide from sulfolene and conversion to sulfolane with corrosion control.
• Amkumar et al., Oklahoma State University Thesis (2015): Detailed sulfolane synthesis including process modeling, reaction steps, purification, and waste treatment.
• ChemicalBook (2022): Description of sulfolane synthesis including catalyst improvements and oxidation alternatives.