Sulfolane

Sulfolane (tetramethylene sulfone) is produced by the reaction of butadiene and sulfur dioxide followed by hydrogenation:

Optimum temperature for highest sulfolene yield is approximately 75°C. At approximately 125°C, sulfolene decomposes to butadiene and SO₂. This simple method could be used to separate butadiene from a mixture of C₄ olefins because the olefins do not react with SO₂. Sulfolane is a water-soluble biodegradable and highly polar compound valued for its solvent properties. Approximately 20 million pounds of sulfolane are consumed annually in applications that include delignification of wood, polymerization and fiber spinning, and electroplating bathes.  It is a solvent for selectively extracting aromatics from reformates and coke oven products.