Exxon Research and Engineering Company

Laura E Black

Adrianus Welmers

Robert C Schucker

Mahmoud M Hafez

Heather A Boucher

Peter G Miasek

Wan-Kei Wan

Georges Adriaens

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phase which is recycled to the solvent extraction zone, preferably at a point below that at which the side stream was withdrawn.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

Interfacially polymerized, crosslinked membranes on microporous, organic solvent resistant ultrafiltration membrane backing are useful for the separation of organic mixtures under reverse osmosis conditions. The membranes are prepared by depositing an aqueous (or conversely non-aqueous) solution of a first component on the microporous backing, draining off the excess quantity of this first solution and then applying a second component in the form of a non-aqueous (or conversely aqueous) solution. The two components interact and polymerize at the interface between the aqueous phase and the non-aqueous phase to produce a highly crosslinked thin polymer layer on the microporous ultrafiltration support backing layer.

Interfacially polymerized membranes for the reverse osmosis separation

Membrane separation under perstraction conditions of a lube oil distillate is disclosed which produces a retentate rich in non-aromatics hydrocarbons and alkyl aromatic and a permeate rich in multi-ring aromatics. The recovered retentate is similar to a solvent extracted raffinate but possesses a higher concentration of alkyl-single ring aromatics. The membrane separation process is highly selective for removing multi-ring aromatics from the lube distillate.

Selective separation of multi-ring aromatic hydrocarbons from

Aromatic hydrocarbons are separated from mixtures of same with non-aromatics by permeation through a membrane of thermally crosslinked polyconjugated diene rubber containing from 15 to 50 wt % nitrile groups. Thermal crosslinking increases selectivity far beyond the level obtained when crosslinking is caused by other techniques. The separations are conducted under pervaporation or perstraction conditions.

Aromatics - non-armoatics separation by permeation through thermally

The ability of cellulose membranes to separate solutes from solvents under reverse osmosis conditions is significantly improved by subjecting the membrane prior to use to several cycles of drying and rewetting.

Reverse osmosis cellulose and cellulosic membranes prepared by repeated

Aromatic hydrocarbons present in a hydrocarbon feed stream containing a mixture of aromatic hydrocarbons and non-aromatic saturated organic components are separated from said hydrocarbon feed stream by selective permeation of the aromatic hydrocarbon through a regenerated cellulose or cellulose acetate membrane which has been impregnated with polyethylene glycol. The thus treated membrane possesses high selectivity for aromatic hydrocarbons at a high flux. The amount and type of polyethylene glycol impregnated into the membrane is carefully controlled in order to achieve high aromatic selectivity and high flux.

Selective permeation of aromatic hydrocarbons through polyethylene

Flux solvents and/or pitch neomesophase anti-solvents used in the generation of carbon fiber precursors from pitch are separated from mixtures of such solvent and uncoverted carbon fiber precursors by contacting said mixtures with asymmetric hydrophobic membranes under conditions of reverse osmosis. The membranes used in this separation are asymmetric polyimide membranes and asymmetric polyvinylidene fluoride membranes. Separation conditions include a contacting pressure sufficient to overcome the osmotic pressure of the solvent. The pressure is typically about 300 to 1000 psi. Contacting temperature is about 0.degree. to 100.degree. C., preferably about 20.degree. to 80.degree. C. The membrane of choice is an asymmetric polyimide membrane.

Membrane separation of uncoverted carbon fiber precursors from flux

In the production of alkylaromatics by the alkylation of aromatic hydrocarbons with alkylating agents such as olefins typically in the presence of a catalyst, the unconverted aromatic hydrocarbon remaining after completion of the alkylation process is separated from the alkylaromatic product and the terminal alkylaromatic isomers are separated from the mixture of alkylaromatic isomers produced in the alkylation process by the selective permeation of the aromatic hydrocarbon and the terminal isomers through a permselective membrane, preferably an asymmetric membrane producing a permeate rich in the terminal isomers and a retentate which is lean (i.e., depleated) in the terminal isomers. Permeation is under reverse osmosis conditions, that is, under a pressure sufficient to at least overcome the osmotic pressure of the aromatic hydrocarbon present in the mixture made up of the aromatic hydrocarbon, the olefin and the mixed isomer alkylaromatic product. Permeation is carried out at a pressure of about 100 to 800 psig, preferably a pressure of about 200 to 600 psig, more preferably a pressure of about 300 to 500 psig, at a temperature of about 0.degree. to 100.degree. C., preferably about 20.degree.-80.degree. C., most preferably about 20.degree. to 50.degree. C. The membrane of choice is an asymmetric polyimide membrane.

Process for separating alkylaromatics from aromatic solvents and the

The present invention is directed to a process for producing high quality aromatic solvents in the middle distillate range containing 95.sup.+ % aromatics by contacting the liquid feed with a perm selective membrane under pressure thereby selectively permeating the aromatic components as the high quality solvents. This separation can be performed by contacting the feed stream in combination with a low boiling light polar aromatics extraction solvent (such as acetonitrile) with the membrane. The middle distillate feed has a molecular weight range of about 120 to 250 g/mole and an aromatic content of 75 to 90 volume percent aromatics and preferably 80 to 90 volume percent aromatics. The membranes which can be employed to effect this separation are selected from the group of regenerated cellulose, cellulose acetate and polyimide membranes, preferably the polyimide membranes.

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Sarnia, Canada

Laura E Black