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Abstract

A process for sweetening high mercaptan content gasoline or other liquid hydrocarbons is disclosed which utilizes aqueous caustic solution. A recycle stream is used to increase the conversion potential by reducing the relative mercaptan concentration of the untreated gasoline. Part of the treated gasoline effluent is recycled to the untreated feed. The treated gasoline has a low mercaptan concentration while the untreated gasoline is high in mercaptans. As the two streams combine, the feed to the unit becomes less concentrated in mercaptan compounds. In effect, the mercaptan concentration of the untreated gasoline has been diluted by the treated gasoline. Nitrogen inhibits the solubility of oxygen into gasoline. Nitrogen present in the recycle stream would create a system high in nitrogen and low in oxygen. By increasing the level of nitrogen, oxygen is limited in its ability to complete the sweetening reaction. In order to keep nitrogen from inhibiting oxygen, the gasoline effluent is sent to a low pressure separation vessel. in this vessel, nitrogen gas separates from the liquid gasoline. Part of this liquid gasoline stream is recycled to join with the untreated gasoline. The recycle gasoline is now free of nitrogen that would inhibit the solubility of oxygen.

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First Claim