Sulfolane process

Sulfolane and sulfones Sulfolane process Sulfolane-W 3-Sulfolene [77-79-2]... 

UOP s Parex Process UOP Sulfolane process UOP Udex Process Upilex UpilexR... 

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). 

Ethylbenzene is separated from mixed xylenes by fractionation using 360 trays and a high reflux ratio. Ethylbenzene is separated from the closest isomer paraxylene whose normal boiling point is only 3.90°F higher. The average relative volatility between ethylbenzene and paraxylene in the fractionation is about 1.06. The fractionator feed is entirely Cg aromatics which are prepared by the extraction of powerformate by the sulfolane process and by fractionation of the aromatic extract. 

The sulfolane process is a versatile extractant for producing high purity BTX aromatics (benzene, toluene, and xylenes). It also extracts aromatics from kerosines to produce low-aromatic jet fuels. 

Use of reflux is most effective with Type II systems since then essentially pure products on a solvent-free basis can be made. In contrast to distillation, however, extraction with reflux rarely is beneficial, and few if any practical examples are known. A related kind of process employs a second solvent to wash the extract countercurrently. The requirements for this solvent are that it be only slighly soluble in the extract and easily removable from the extract and raffinate. The sulfolane process is of this type it is described, for example, by Treybal (1980) and in more detail by Lo et al. (1983, pp. 541-545). 

Application The Sulfolane process recovers high-purity C6-C9 aromatics from hydrocarbon mixtures, such as reformed petroleum naphtha (reformate), pyrolysis gasoline (pygas), or coke oven light oil (COLO), by extractive distillation with or without liquid-liquid extraction. 

The solvent used in the Sulfolane process was developed by Shell Oil Co. in the early 1960s and is still the most efficient solvent available for recovery of aromatics. 

Commercial plants In 1962, Shell commercialized the Sulfolane process in its refineries in England and Italy. The success of the Sulfolane process led to an agreement in 1965 whereby UOP became the exclusive licensor of the Sulfolane process. Many of the process improvements incorporated in modern Sulfolane units are based on design features and operating techniques developed by UOP. UOP has licensed a total of 134 Sulfolane units throughout the world. 

Application The Sulfolane process recovers high-purity aromatics from hydrocarbon mixtures by extractive distillation (ED) with liquid-liquid extraction or with extractive distillation (ED). Typically, if just benzene or toluene is the desired product, then ED without liquid-liquid extraction is the more suitable option. 

Economics The solvent used in the Sulfolane process exhibits higher selectivity and capacity for aromatics than any other commercial solvent. Using the Sulfalane process minimizes concern about trace nitrogen contamination that occurs with nitrogen-based solvents. Estimated inside battery limits (ISBL) costs based on a unit processing 158,000 mtpy of BT reformate feedstock with 68 LV% aromatics (US Gulf Coast site in 2003). 

UOP/Shell BTX, purification Reformate, pyrolysis gasoline Shell Sulfolane process liquid extraction and/or extractive distillation with sulfolane solvent 123 1998... 

Example 5 Simplified Sulfolane Process—Extraction of Toluene from n-Heptane. 15-56... 

PRACTICAL EXAMPLES OF EXTRACTION WITH REFLUX. There are few, if any, practical examples of reflux in the simple manner shown in Fig. 20.14. For systems such as aniline-heptane-methylcyclohexane (Fig. 20.11), the ratio of MCH to heptane in the extract is only modestly greater than in the raffinate, so a great many stages would he needed for high-purity products. Furthermore, the low solubility of both solutes in aniline would mean a very large flow of solvent to be handled. However, a modification of the reflux concept has been applied in several industrial processes for extraetive separation. Enrichment of the extract is accomplished by countercurrent washing with another liquid, chosen so that the small amounts of this liquid that dissolve in the extract can be easily removed. The Sulfolane process for extraction of aromatics is an example of this type. 

Sulfolane process. A flow sheet for the Sulfolane process is shown in Fig. 20.15. The hydrocarbon feed is introduced near the middle of the extractor and the heavy solvent is fed at the top. In the top section, nearly all the aromatics are extracted from the raffinate, but the solvent at this point also contains a few percent paraffins and naphthenes. The boiling point ranges overlap, so preparation of pure aromatics by distillation of this material is not practical. Also, Sulfolane and the... 

The backwash stream is sometimes called countersolvent or reflux, but the term reflux" should be reserved for streams having the same composition as the product. The backwash need not be a low-molecular-weight material in one version of the Sulfolane process, the backwash is a heavy paraffinic fraction, which is easily removed from both extract and raffinate. 

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