Sulfolane extraction

Aromatic Hydrocarbons. Sulfolane is used principally as a solvent for extraction of benzene, toluene, and xylene from mixtures containing aHphatic hydrocarbons (33—37). The sulfolane process was introduced in 1959 by SheU Development Company, and that process is Hcensed by Universal OH Products. A sulfolane extraction process is also Hcensed by the Atlantic Richfield Company. In 1994, worldwide consumption was estimated at ca 6974 t/yr of sulfolane for 137 sulfolane extraction units (see Bix processes Extraction, liquid-liquid Xylenes and ethylbenzene). 

In general, the sulfolane extraction unit consists of four basic parts extractor, extractive stripper, extract recovery column, and water—wash tower. The hydrocarbon feed is first contacted with sulfolane in the extractor, where the aromatics and some light nonaromatics dissolve in the sulfolane. The rich solvent then passes to the extractive stripper where the light nonaromatics are stripped. The bottom stream, which consists of sulfolane and aromatic components, and which at this point is essentiaHy free of nonaromatics, enters the recovery column where the aromatics are removed. The sulfolane is returned to the extractor. The non aromatic raffinate obtained initially from the extractor is contacted with water in the wash tower to remove dissolved sulfolane, which is subsequently recovered in the extract recovery column. Benzene and toluene recoveries in the process are routinely greater than 99%, and xylene recoveries exceed 95%. 

Fig. 7. Shell sulfolane extraction process. E, extraction ED, extractive distillation RC, recovery column.

FIGURE 1 Toluene or aromatics recovery by sulfolane extraction. 

The rotating disc contactor (B), developed in the Netherlands in 1951, uses the shearing action of a rapidly rotating disc to interdisperse the phases. These have been used in the petrochemical industry for furfural and SOj extraction, propane deasphalting, sulfolane extraction for the separation of aromatics from aliphatics, and caprolactam purification. Columns up to 4.3 m in diameter are in service. 

Sulfolane extraction process. (After Broughton and Asselin. )... 

Application The sulfolane extractive distillation (SED) process uses a complex solvent system composed of sulfolane (as the main solvent) and a co-solvent. The SED process can be used to recover high-purity benzene or benzene and toluene from hydrocarbon mixtures such as hydrogenated pyrolysis gasoline, reformate or coal tar oil. 

Also Meindersma Haan presented a conceptual process design for the separation of aliphatic/aromatic hydrocarbons, in which the authors concluded that ILs which show a high aromatic distribution coefficient, Danm = 0.6 m/m, with a reasonable aromatic/ aliphatic selectivity, Samm/aUf = 40, could reduce the investment costs of the aromatic/aliphatic separation to about M 25 to 30 and the annual costs to M 16 to 17 respect to total investment costs in the typically applied sulfolane extraction process (Meindersma de Haan, 2007). 

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