Aromatics Extraction Process

The UOP 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.

Fresh feed enters the extractor (1) and flows upward, counter current to a stream of lean solvent. As the feed flows through the extractor, aromatics are selectively dissolved in the solvent. A raffinate stream, very low in aromatics content, is withdrawn from the top of the extractor. The rich solvent, loaded with aromatics, exits the bottom of the extractor and enters the stripper (2). The lighter nonaromatics taken overhead are recycled to the extractor to displace higher molecular weight nonaromatics from the solvent.

The bottoms stream from the stripper, substantially free of nonaromatic impurities, is sent to the recovery column (3) where the aromatic product is separated from the solvent. Because of the large difference in boiling point between the solvent and the heaviest aromatic component, this separation is accomplished easily, with minimal energy input.

Lean solvent from the bottom of the recovery column is returned to the extractor. The extract is recovered overhead and sent on to distillation columns downstream for recovery of the individual benzene, toluene and xylene products. The raffinate stream exits the top of the extractor and is directed to the raffinate wash column (4). In the wash column, the raffinate is contacted with water to remove dissolved solvent.

The solvent-rich water is vaporized in the water stripper (5) and then used as stripping steam in the recovery column. The raffinate product exits the top of the raffinate wash column. The raffinate product is commonly used for gasoline blending or ethylene production.

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.

Licensor: UOP LLC, A Honeywell Company

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