US2248067A - Solvent extraction process - Google Patents

Description

I July 8, 1941. G. H; gums 2,248,067

SOLVENT EXTRACTION I PROCESS Filed July 6, 1938 F n/cn BOILING PAwArr/u Low BOILIN TRACT/ON Low BOILING AmnAr/c.

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F)! A c 110A! li/GIIJBOILING A no M4 Tic- INTERHEDI A TE TBA: 7) GA! 007457 Patented July 8, 1941 SOLVENT EXTRACTION PROCESS Garland 1:. a. nun. anube'ni. n. 1., "an" a,

Standard Oil Development Company, a corporation of Delaware Application July 0, 1m, semi N zi-1,062

(c1. roe-1s) 'lOlllml.

The present invention relates to the art of solvent treating mineral oils. It is particularly concorned with an improved process of solvent treating petroleum oils; as for example, lubricating oils, heating oils, and the like, and is particularly adapted for treating petroleum oils boiling in the naphtha, kerosene and gas oil ranges. The process of the present invention separates the feed oil into at least two fractions of different boiling ranges, introduces the respective fractions at different points in solvent treating equipment, then separates the rafllnate phase from the solvent extract phase and removes the solvent from the respective phases. The desolventized raillnate and extract phases may be further tractionated to secure narrow boiling cuts of highly aromatic and of highly parafllnic character.

It is well known in the art to treat mineral oils, particularly petroleum lubricating oils, with solvents which have the ability to segregate the relatively more aromatic fractions from the relatively more parafllnic fractions. In these processes it is usual to'employ solvents which have a preferential selectivity for the more aromatic type compounds, as for example, solvents of the class of phenol, cresol, aniline, nitro benzene, beta beta dichlor diethyl ether, furfural, and the like. Solvent mixtures of these substances are employed as well as mixtures containing materials of the class of liquefied normally gaseous hydrocarbons. Solvent modifying agents of the class of water, alcohols and glycols are also used.

In these processes it is the usual procedure to introduce the oil; as for example, the lubricating oil into the bottom of a solvent treating tower, since it is usually lighter than the solvent, and to introduce the solvent into the top of the tower. The oil being the lighter phase flows upwardly through the tower, intimately contacting the downfiowing solvent. A rafllnate phase completely saturated with solvent is removed from the upper part of the tower and a solvent extract phase is removed from the lower part of the tower. It is, of course, desirable to secure a ratflnate and extract phase having as high a concentratlon as possible of the paraflinic materials and aromatic materials respectively. The process of my invention is'a distinct improvement over the known processes in the art in that it is possible to secure a more concentrated aromatic fraction and a more concentrated paraffinic fraction than has heretofore been possible by known methods of operation. My invention is particularly applicable in the treatment of low boiling hydrocarbons for the production of highly aromatic fractions suitable for use as solvents and for high octane number fuels. The process of my invention at the same time produces a highly parafllnic material suitable for the production of superior Diesel fuels and high quality kerosene.

The process of my invention may be readily understood by reference to the attached drawing showing one modification of the same. For the purpose of illustrating the invention, it is assumed that the feed all is a petroleum oil boiling in the naphtha and gas oil range and that the solvent is of the class having a preferential selectivity for the more aromatic type compounds, and having suitable characteristics so that the solvent may be readily separated from the oil. The feed oil is introduced into fractionating tower I bymeans of feed line 2. The oil is separated into a low boiling fraction which is taken overhead by means of line 3 and introduced into tower I. The higher boiling fraction is withdrawn from tower i by means of line I and introduced .lnto tower l at a point somewhat below the point of introduction of the low boiling fraction. The respective fractions flow upwardly through tower I contacting downflowlng solvent which is introduced into tower l by means of feed solvent inlet line 8. A rafllnate Phase saturated with solvent is removed from tower 4 by means of line 1 and introduced into solvent separator l. The solvent is removed from solvent separator 8 by means of line 9 and the stripped rafllnate is removed by means of line i0 and subsequently introduced into still II. A low boiling highly concentrated parafllnic fraction is taken overhead from still II by means of line I! and a relatively high boiling, highly concentrated parafllnic fraction removed from still II by means of line l3. The solvent extract phase from tower 4 is removed by means of line I4 and introduced into solvent separator l5. Solvent is removed from solvent separator i5 by means of line It and stripped extract is removed from solvent separator l5 by means oi! line ll. The stripped extract is introduced into still i8 from which a low boiling, highly concentrated aromatic cut is removed by means of line H! and a high boiling highly aromatic cut removed from still I8 by means of line 20.

The process of my invention may vary widely. It is applicable in the treatment of any mineral oil, but it is particularly preferable in the treatment of petroleum oil boiling below about 700 F. l'he feed material may be fractionated into different boiling range fractions in any suitable manner. In general it is preferred to separate two fractions of approximately equal volume and to feed these respective fractions into the countor-current treating tower. The low boiling fraction is introduced into the countercurrent treating tower at a point intermediate the fresh solvent feed inlet and the point of introduction of the high boiling fraction. The high boiling fraction .is preferably introduced into the bottom of the solvent treater and the low boiling fraction introduced at a point somewhat near the center of the solvent treater.

Any particular solvent may beused and will depend upon the feed material being treated and the quality and type of products desired. The solvent necessarily must have characteristics so that it may be readily separated from the oil by suitable means, as for example, by washing or by distillation. In general it is preferred to use solvents having boiling points substantially different from the boiling ranges of the feed material being treated in order to facilitate separation of the same. If a heavy gas oil is being treated. phenol, for example, would be entirely suitable as well as other solvents of this class having suitable boiling points. Particularly desirable solvents in the treatment of, petroleum oils, boiling in the range from 250 to 600 1''. are those solvents which are normally solid at normal temperatures and pressures, as for example, esters of phthalic acids, as for example, dimethyl phthalate, dibenzylphthalate and the like. Other solvents, as for example, sulfur dioxide, the ethylene glycols, particularly phenoxy alcohols, as for example, beta phenoxy ethyl alcohol, are also suitable.

If a solvent having a boiling point substantially different from the feed material being treated is utilized, it may be desirable, for example, to eliminate the solvent recovery units I and II and to recover a low boiling parafllnic fraction as the overhead in still ii, the high boiling paraflinic fraction as a side stream in still Ii and to remove the solvent as a bottom stream in still ii. This procedure could similarly be followed in regard to still l8.

The quantity of solvent used per volume of oil will, of course, depend upon the particular solvent or solvent mixture being used, the feed oil being treated and the quality of products desired.

In general it is preferred to use from about 0.5

to 4 volumes of solvent per volume ofoil being treated. It is preferred to solvent extract the materials under atmospheric pressure, although other pressures may be employed. The temperature of extraction will, of course, depend upon the solvent being used, the feed material being treated and will, of course, be below the complete miscibility temperature between the solvent and the oil. In general when treating low boiling petroleum oils, it is preferred to maintain a relatively low temperature somewhat above the solidification point of the particular solvent or i I Engral itispre to the ivt trons the r= phases bymeans of distillation. provided the respective boiling points are satisfactory. However. other means, as for example, re-extrsetion or washing may be also employed. The solvent free highly parailinic and highly aromatic rafilnateandestrectphasesrespeetivelymaybe fractionated into any suitable close out boiling fractions by any suitable means. as for example. y distillation In order to further illustrate the invention. the following example is given which is not to be construed as limiting the invention in any manner whatsoever.

Example A petroleum naphtha boiling in the range from about 200' to 000' 1'. may be separated into a low boiling fraction having an initial of about 200 1''. and a final of about 400 1''. and a high boilirv fraction having an initial of about 400 1''. and a final of about 000' 1''. These fractions are introduoed into a solvent treater in a manner in which the low boiling fraction is introduced into said treater between the point of introduction of the high boiling fraction and the point of introduction of the solvent. The respective fractions flow upwardly through the tower. intimately contacting ,downflowlng solvent having preferential selectivity for the more aromatic type compounds which is introduced into the top of the tower. A railinatephaseanda'nextractphaseareremoved from the tower and the respective phases desolventfled. By the process described it is found that the-extract phase removed fromthe bottom the tower is more aromatic and that the raiiinate phase, removed from the top of said tower, is more paraiiinic than if the feed material had been introduced directly into said tower.

The process of the present invention is not to be limited by any theoryv or mode of operation, but only by the following claims in which it is intended to claim all novelty insofar as the prior art permits.

I claim:

1. Process of producing from a particular mineral oil a more highly aromatic fraction and a more hishly paramic fraction, comprising separating said mineral feed oil into a low boiling fraction and into a high boiling fraction without effecting substantial segregation of the relatively more aromatic constituents from the relatively more paraflinic oonstituentsadirectly introducing said fractions into diiferent portions of a solvent. treating tower in a manner that said low boiling fraction is introduced into said tower at a point intermediate the point of introduction of the solvent and the point of introduction of said high boilingfraction and in which said fractions are extracted vwith a selective solvent, removing a railinate and extract phase. separating the solvent from the respective phases to produce said boiling in the gasoline and gas oil ranges comprising separating said petroleum oil into at least three boiling range fractions without eflecting substantial segregation of the relatively more aromatic constituents from the relatively more parafllnic constituents. discarding the intermediate boiling fraction, directly introducing the low boiling fraction and high boiling fraction into a solvent treating tower at different points in a manner in which said low boiling fraction is introduced into said tower at a point intermediate the point of introduction of the solvent and the point oi introduction of said high boiling fraction, contacting said fractions with a selective solvent having a preferential selectivity for the more aromatic type compounds, removing a rafflnatc phase and a solvent extract phase, then separating the solvent from the respective phases.

5. Process in accordance with claim 1 in which said selective solvent is phenol.

6. Improved process for the segregation of a petroleum oil boiling in the range from about 200 F. to 650 F. into its relatively more aromatic and into its relatively more parafllnic constituents, comprising distilling said petroleum oil under conditions adapted to segregate said oil into a relatively lower boiling fraction boiling in the range from about 200 F. to 400 F. and into a relatively higher boiling fraction boiling in the range from about 400 F. to 650 F. without eifecting substantial segregation of the relatively more aromatic constituents from the relatively more paraflinic constituents, directly introducing said low boiling fraction in the center section of a countercurrent treating tower, directly introducing said relatively high boiling fraction into the bottom section of said countercurrent treating tower, introducing a solvent selected from the class of solvents having a preferential selectivity for the more aromatic constituents as compared to the more parafilnic constituents into the top of said countercurrent treating tower, regulating conditions adapted to secure countercurrent flow between the oil and said solvent and adapted to produce a highly paraflinic raflinate phase and a highly aromatic solvent extract phase, separating the respective phases and removing the solvent therefrom.

- 7. Process in accordance with claim 6 in which said solvent is a phenol.

GARLAND H. B. DAVIS.

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