Studies on the extraction of aromatics with sulpholane and its combination with thiodiglycol

Liquid—liquid equilibria for the systems: toluene—heptane—sulpholane, toluene—heptane—sulpholane plus thiodiglycol at 40°C, and benzene—heptane—sulpholane plus thiodiglycol and benzene—heptane—sulpholane plus 9% water at 110°C have been studied. The results of the combined solvents have been compared with those obtained with sulpholane containing up to 9% water. Several advantages of combined solvents are discussed. The selectivities of the mixed solvents for different hydrocarbon types have been calculated from the limiting activity coefficients determined by gas chromatography.