Exxon Research and Engineering Company

Adrianus Welmers

Laura E Black

James D Eagan

Joseph P Boyle

John J Dugan

Recovering a relatively volatile component of a solution from a less

The present invention is directed to an improved selective solvent extraction process wherein a hydrocarbon feed stream containing a mixture of aromatics and non-aromatics is contacted with an aromatics selective solvent in an extraction zone to produce an aromatics rich extract phase and an aromatics lean raffinate phase, water in a carefully controlled amount is added to the recovered extract phase resulting in the separation of the extract phase into a hydrocarbon rich pseudo-raffinate which is recycled to the extraction zone for processing with fresh feed and an increased yield of raffinate of higher quality than is obtained without pseudo-raffinate recycle.

Solvent extraction of hydrocarbon oils producing an increased yield of

The solvent extraction of aromatics containing oil using a selective aromatics extraction solvent to produce an aromatics rich extract phase and an oil rich/aromatics lean raffinate is improved by the steps of subjecting the extract phase to a membrane separation step to produce a permeate phase and a retentate phase passing the retentate phase to a settling zone wherein the retentate phase spontaneously separates into two liquid phases, and recycling the upper phase to the extraction zone, either to the feed inlet or to the bottom of the extract reflux zone to thereby increase the raffinate oil recovered from the extraction tower. Alternatively or in addition to the above, a side stream can be taken from an intermediate zone of the extraction zone (e.g. extraction tower) and fed to a membrane separation to produce a solvent rich permeate and an oil rich retentate. The solvent rich permeate is recycled while the oil rich retentate is fed to a settling zone wherein it will spontaneously separate into an oil rich pseudo raffinate upper phase which is recovered and into a solvent rich pseudo extract bottoms phase which is recycled to the solvent extraction zone, preferably at a point below that at which the side stream was withdrawn. The membrane separation zone preferably employs interfacially polymerized membranes under reverse osmosis conditions.

Solvent extraction process involving membrane separation of extract

A distillation tower (1) has a plurality of liquid sidestream lines (5, 6, 7) and a multi-stage sidestream stripper (13) which includes a respective stripping section (14, 15, 16) for each sidestream line housed in a common, upright, cylindrical shell (28) which allows vapor to pass freely from each stage to the one above. Partial vaporization of each sidestream is achieved by applying a vacuum to the top of the stripper shell (point 21) and/or introducing strip gas at the bottom (point 20). Because the vapor passes serially through the stripping sections from the bottom of the stripper (13) to the top, the need to supply strip gas separately to the stripping sections and/or apply vacuum individually is avoided. The separation between the sidestream products is improved by including, in each stage, a rectification zone (22, 23, 24) positioned above the stripping section.

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Sarnia, Canada

Adrianus Welmers