US2043389A - Solvent extraction of oil - Google Patents

Description

June 9, 1936.

D. RQMERRILL SOI-:VENT EXTRACTION 0F OIL Filed Aug. 26, 195s wE NS S5520 8 N mw Patented June 9, 1936 t UNITED STATES PATENT OFFICE SOLVENT EXTRACTIGN OF OIL David R. Merrill, Long Beach, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application August 26, 1933, Serial No. 686.941

20 Claims. (CL 19o-43) This invention relates to the fractionation oi referred to as the railinate, whereas, the fraction petroleum hydrocarbons by the use of solvents. dissolved in the solvent is known as the extract, Most crude oils are complex mixtures of hydroand may consist to a considerable extent of either carbons and contain varying proportions of unsaturated or aromatic hydrocarbons or a mixu parailin, naphthene, aromatic and unsaturated ture of these hydrocarbons. For convenience the hydrocarbons. In the production of lubricating raffinate fraction, or the fraction which is insoluoil for internal combustion motors it is desirable ble in the solvent, is called parailinic oil" and to produce a finished oil that exhibits a low temthe fraction which dissolves in the solvent is perature viscosity susceptibility, i. e., one which called "non-paraiilnic oil.

N shows a minimum change in physical character- In the conventional method of employing solistics for a given change in temperature. 'Ihe vents to separate paraiilnic and non-parafllnic hydrocarbons of highest hydrogen to carbon ratio fractions two oil fractions are produced; a railiare usually waxes, which because of their high nate fraction, or the portion insoluble in the solmelting point are not suitable for ordinary lubrivent and an extract fraction, or the oil fraction l* cation. The hydrocarbons of next highest hydrowhich is soluble in the solvent. Where oils are gen ratio are the so-called paraffinic lubricating extracted which are mixed base in character, or oils" from paraffin base crude. The parafilnic asphaltlc in character and which contain the oils are characterized by exhibiting a relatively intermediate group of hydrocarbons mentioned low temperature viscosity susceptibility, whereas, above, this group is either recovered in the railim the aromatic and highly unsaturated hydrocarnate or it is lost in the extract because modern 2O bons are characterized by exhibiting a relatively methods of refining with solvents will not permit high temperature viscosity susceptibility. these middle fractions to be produced as a sepa- In many crude oils, such as those produced rate entity. It is undesirable to permit this mldfrom the Mid-Continent fields, which are of a die oil to be recovered as a ralnate along with 3" mixed base character, and those of the California the parailnic fractions because the presence oi' fields, which are asphaltic in character to varythese middle oils tends to increase the temperaing extent, there are present three distinct types ture viscosity susceptibility of the raffinate. Furof oils. One group resembles the oils which are thermore, it is undesirable to permit these midpresent in parafn base crudes and exhibits a die oils to be recovered in the extract since the "o `low temperature viscosity susceptibility. A secintermediate oils are valuable lubricating oils for ond group is present which exhibits a very high purposes where temperature viscosity susceptibiltemperature viscosity susceptibility and a third ity is of minor importance. The extract is usually group is present which has a temperature visemployed for fuel or for cracking purposes or for cosity susceptibility intermediate between the the production of solvents which are aromatic in group having the low temperature viscosity suscharacter. These middle oils, therefore, act as ceptibility and the group having the high temcontaminants. The most desirable cracking perature viscosity susceptibility. stocks are composed mainly of hydrocarbons Recently a. number of solvents, such as aniline, which are aromatic in character and which are nitro-benzene, furfural, B B' dlchlorethyl ether, capable of producing. fuels having high antin methyl cellosolve, cellosolve acetate and sulphur knock value. Furthermore, where the extract dioxide, have been employed to separate a hydrois to be employed for a stock for producing highly carbon mixture into its respective parainic and aromatic solvents, it ls undesirable to have presnon-paratlnic constituents. If a hydrocarbon ent fractions which are intermediate between the mixture is mixed'with one of the foregoing solaromatic and paralnlc groups. 45 vents under the proper conditions of temperature, I have discovered that it is possible to separate the unsaturated aromatic hydrocarbons in the these middle oil fractions present in the crude mixture tend to be dissolved. and, furthermore, oils as a separate fraction by means of solvent exif this mixture of undissolved fractions and soltraction. By separating these middle oils as a vent containing the dissolved fractions is allowed separate fraction I am able to produce a paraillnic 50 to settle, the relatively light insoluble oil fracoil having a relatively low temperature viscosity tions rise to the top and form an upper liquid susceptibility which is not contaminated with phase and the solvent and dissolved fractions fractions ofarelatively high temperature viscosity which are relatively heavy settle out and form a susceptibility and/or an extract which is highly lowerliquid phase. The undissolved fraction aromatic in character. 55 "0 which is more paramnic in character is often In any system of solvent extraction it is highly desirable to employ a minimum quantity of solvent to obtain a maximum degree of refinement. This can only be carried out providing proper conditions of extraction have been determined. Successive extraction of a hydrocarbon mixture with a selective solvent at one temperature is only eapable of producing a rafllnate which is of limited paramnicity. The first one or two treatments of the oil with a solvent at one definite temperature will result in production of relatively high yields of extract, but thereafter the solvent becomes relatively ineifective and will not remove from the oil the remaining undesirable fractions present but the material extracted is of substantially the same composition as that remaining. Furthermore. it is undesirable to separate at relatively low temperatures because of the large quantity of solvent which is necessary to dissolve the non-paralilnic fractions present in the hydrocarbon mixture. Where high temperatures are employed in separating paramnic and non-parai'llnic fractions great care must be exercised in order that the temperature employed is below that at which the oil and solvent are completely miscible. The desirable method of separating paraillnic and non-paraillnic' fractions by solvent extraction is to extract the oil in stages operating at a temperature close to the point of complete miscibility between the oil and the solvent. Such a system of extraction results in the maximum yield of refined oil with a minimum quantity of solvent. By successively extracting a hydrocarbon mixture at successively higher temperatures with a selective solvent it is possible to obtain a maximum degree of refining with a minimum amount of solvent. As has been pointed out before, successive extraction of a hydrocarbon mixture at one temperature with the same solvent is open to criticism because after the first one or two extractions the solvent becomes relatively ineffective and is incapable of removing fractions which are present which are undesirable. However, where the extraction is carried out in stages operating at successively higher temperatures this fault is not present. The extraction at successively higher temperatures compensates for the increasingly limited ability of the solvent to remove the undesirable fractions present. At the higher temperatures the solvent power for the undesirable frgctions remaining in the oil becomes greater and they are thereby removed from the mixture.

In separating .a hydrocarbon mixture with a selective solvent, such as dichlorethvl ether, near the temperature of complete miscibility it is possible, as has been described before. to produceA a ramnate which is highly parafiinic in character and whichv exhibits a low temperature viscosity susceptibility and an extract which contains all of the non-paramnic lfractions together with the middle oils. After the extract phase is withdrawn from the extraction system, it is cooled to a temperature considerably below the temperature of the rst extraction. At this low temperature a second rafdnate is produced which has temperature viscosity susceptibility characteristics of the intermediate oil present in the hydrocarbon mixture and an extract is produced from the second extraction at a lowered temperature whichY is highly non-paratllnic in character. v In producing the high grade railnate from the first extraction and the second raillnate by rejection from the extract nrst recovered from the primary extraction it is necessary that temperatures be employed which are very close to the point of complete miscibility of the solvent and oil. I have found that it is desirable to operate within 20 F. of the temperature of complete miscibility. These three grades of oil are best produced by the process shown in the figure.

lt is, therefore, an object of 1m' invention to extract oil with a selective solvent and to produce a first grade raffinate, a second grade raiinate and an extract.

It is another object of the invention to extract oli with a selective solvent near the temperature of complete miscibility between -the oil and the solvent and to separate a raillnate fraction and a fraction dissolved in the selective solvent at this temperature.

It is another object of the invention to countercurrently extract oil with a selective solvent at successively higher temperatures.

It is another object of the invention to extract oil in a plurality of stages with a selective solvent at a temperature in each extraction stage about 20 F. lower than the temperature of complete miscibility between the oil and the solvent.

It is still another object of the invention to counter-currently extract oil with a selective solvent in a plurality of stages in which the temperature of extraction in each extraction stage is about 2G F. lower than the temperature of complete miscibility between the oil and the solvent.

My process will be more thoroughly understood by referring to the drawing. Referring more particularly to the drawing, the apparatus comprises two extraction columns A and B. 'Ihese extraction columns are divided into a plurality of extractionstages. 4I, 42, 43, 44, I5.

46, 41, 48, 49, and 50. Each of these extraction 3 'stages is divided into an agitating zone E and a settling zone F. After the solvent and oil have been thoroughly agitated in the agitating zone E they pass through the partition 5I in the direction indicated by the arrow into the settling zone F. Each of these extraction stages is provided with means'for introducing oil and solvent into the agitating zone E and means for withdrawing rafilnate and solvent containing dissolved fractions from the settling zone F. From the upper part of the column A raffinate is withdrawn through line 20 into the upper part of the column and selective solvent is introduced into line 3. From the lower zone of the column A extract and dissolved fractions are withdrawn through line ii. cooled in cooler i1, settled in separator C and that portion of the extract phase insoluble at the lowered temperature and forming the upper layer in cooler C is returned through line i9 into the agitating zone of extraction stage 41. The solvent and dissolved fractions forming the lower layer in cooler C are withdrawn through line 26 and pass through heat .exchangers 2i and 21 to cooler 3i where the tem perature of the solvent and dissolved fractions is lowered to a point where a further quantity of oil is separated as an insoluble fraction at this lowered temperature. The cooled mass then passes from cooler 3i into separator D where the heavy solvent containing the remaining dissolved fractions settles to the bottom of separator D and is removed through line 33, heat exchanger 2l and line 28. The insoluble oil fractions in separator D forming the upper layer are removed through line 34 and introduced into the agitatins or mixing zone E of stage I8 in extraction column B where it meets solvent and dissolved fractions introduced through line 35. Fresh solvent is introduced through line 39 and countercurrently extracts the fractions introduced through line 34 in extracting stages 4I, 4.9, and 50. From stage 50 there is removed an intermediatev raffinate through line 40. The solvent and dissolved fractions removed through line 29 from extracting' stage 4I pass through line 22 into feed line 24 and are mixed in the orifice mixer in line 23. This mixture then passes through line into stage 46. Thus it is seen that the oil introduced into feed line 23 is split into three fractions, i. e., first grade raffinate withdrawn from line 20, a second grade raffinate withdrawn through line 40, which I have designated on the drawing as an intermediate raffinate, and a final extract which is withdrawn from line 28 alone with solvent. The

three fractions withdrawn from the respectivelines 20, 40, and 28 are distilled to remove their respective content of solvent.

From the drawing it will be seen that the process is essentially a method of countercurrently extracting oil in a plurality of stages operating at successively higher temperatures. The oil to be extracted is introduced into an intermediate extraction zone and the raiiinate produced in this zone is successively extracted at successively higher temperatures and, preferably,r at a point near the temperature of complete miscibility between the oil and the solvent. The extract phase withdrawn from the settling zone of the stage in which the oil is introduced, i. e., stage 46, is passed to an extraction stage operating at a lower temperature than stage 46 where it is contacted with fractions which have been removed from stage 41 by cooling the extract phase withdrawn from stage 41 and obtaining a fraction insoluble at this lowered temperature. This insoluble fraction is passed back through line I9 and introduced into the agitating zone E of extraction stage 41 along with the solvent and dissolved fractions withdrawn from stage 46 through line I5.

While I have shown that the solvent and dissolved fractions introduced into the agitating zone E of stage 41 can be washed or rectified with insoluble fractions obtained from cooler C through line I9 I do not propose to limit myself by the use of fractions for washing purposes or for rectification which have been obtained by cooling a selective solvent containing dissolved fractions. Other oils may be introduced through line I9 into agitating zone E to Wash or rectify the solvent and dissolved fractions introduced through line I5. For example, I may partially evaporate a selective solvent from the extract phase withdrawn through line I6, introduce the mass containing the remaining selective solvent in oil fractions into cooler C where an oil fraction will separate as an upper layer and can be removed through line I9 and introduced into the agitating zone E of stage 41. -This fraction which i is obtained by partially evaporating a solvent from the extract phase withdrawn from line I6 will have the same, function as fractions introduced through line'l obtained by cooling the extract phase as described above. I Amay also use other oils to wash or rectifyv the extract phase introduced through line I5 into stage 41, for example, liquid normally gaseous hydrocarbons, such as liquid propane, or I may use petroleum naphtha. These materials are introduced through line I9 and mixed with the extract phase introduced through line I5 in the same fashion as described above for mixing these extract phases with thefractions obtained by cooling or partial evaporation of the selective solvent from an extract phase containing solvent and dissolved fractions'.

The oils introduced through line I 9 into the agitating zone E of stage 41, as described above, are termed wash oils and are employed to remove valuable constituents of the low solubility paramnic type from the extract phase. These wash oils, to accomplish such removal of valuable constituents from the extract phase, should be leaner. in paraiiinic constituents than theI oil l0 feed to the column as explained above.A Preferably, the types of wash oil are: 1.'A fraction separated from the extract phase by cooling or partial evaporation of the solvent; 2. A portion of the whole extract recovered by evaporation of the solvent from the extract phase; 3. A suitable oil fraction from a different stage or operation provided only it is leaner in desirable fractions than thefeed to the column and will not contaminate the various extraction products; or 4. A diluent miscible with oil, such as propane or naphtha, which will reduce the viscosity of the oil phase and which has a greater affinity than the selective solvent for the parafilnic fractions,in the exact phase orwhich lowers the 25 solvent power of the selective solvent in the extract phase rand causes the most parailinic constituents present to be forced out of solution from the extract phase.

It is, therefore an object of this invention to y contact an extract phase comprising a selective solvent and dissolved fractions with a wash oil I capable-of removing from the extract phase those fractions present which are most parainic in character. V

As a specific example of the method of carrying out my process, an oil feed having a viscosityk gravity constant of .872 is introduced through line 23 where it meets solvent and dissolved fractions recovered from stage 48 through line 49 and line 22. This mixture passes to the orifice mixer operating at 90 F. After thorough mixing the mass then passes through line 25 into the agitating zone E of stage 4G. Dichlorethyl ether (350 weight per cent based on the feed charge) is introduced through line 3 into the agitating zone E of stage 4I operating at a temperature of about 136 F. The oil introduced into stage 46 is agitated with solvent and dissolved fractions introduced through line I3 from the settling zcne 50 of stage 45 along with the oil fractions introduced from stage 41 through line I4. After thorough mixing in the agitating zone E of stage 46 the mass then passes into settling zone F of stageil where it is allowed to settle. The raiiinate fraction of the upper layer in settling Zone F of stage 45 is withdrawn through line I2v and introduced into the agitating zone of stage 45 operating at about 105 F. where it meets solvent and dissolved fractions Irecovered from the settling zone F o f stage 44 withdrawn through line II. After thorough mixing in the agitating zone E the mass passes into settling zone F of stage 45 where the heavy extract phase is withdrawn through line I3 as described above and the light raflinate 6D fraction constituting the upper layer is withdrawn through line I0 and introduced into the agitating zone E of stage 44 operating at 115 F. where it is mixed with solvent and dissolved fractions withdrawn from stage 43 through line 9 after T0 which it passes into the settling zone F of stage 44. The solvent and dissolved fractions in settling zone F of stage 44 are removed through line II as described above and the raiiinate fraction of the upper insoluble layer in this settling zone is withdrawn through line s and introduced vinto the agitating zone E of stage 49 operating at 125 F. where it is mixed with solvent and dissolved fractions recovered from settling zone F of stage 42 through line 1. The mixture in agitating zone E of stage 49 passes into settling zone F oi stage 43 where the extract and dissolved fractions are removed through line 9 and the raillnate fraction is removed through line 9 into agitating zone E of stage 42 operating at 130 F. where lit is mixed with solvent and dissolved fractions recovered from stage 4l through line 4. After thorough mixing in agitating zone E of stage 42 it passes into the settling zone F of stage 42 where the solvent and dissolved fractions settle to the bottom and are removed through line 1 while the light raillnate fraction is withdrawn through line 5 and introduced into the agitating zone E of stage 4I along with fresh solvent introduced through line 3. This stage operates at a temperature of about 136 F. After thorough mixing in agitating zone E of stage 4I the agitated mass passes through the opening in partition 5I, indicated by the arrow, into 4the settling zone F of stage 4I where the solvent and dissolved fractions are removed through line 4 and the high grade rst raffinate is withdrawn through line 20.

The solvent and dissolved fractions in settling stage 46 are withdrawn through line l5 and introduced into the agitating zone E of stage 41 where they are mixed with fractions obtained by cooling the extract phase of stage 41 to a temperature of about F, and then allowing the insoluble oil fractions at this lowered temperature to be withdrawn as an upper layer from cooler C through line I9 as described above. When selective solvents are employed which are normally gaseous at ordinary temperatures and pressures, the coolingmay be obtained by vaporizing a portion of the solvent from the extract phase as explained above. The extract phase entering 5| is cooled by opening valve 52 and permitting a portion of the solvent to vaporize through line 53. The agitated mass in zone E of stage 41, operating at about F., then passes into settling zone F of stage 41 and the ramnate oil fractions in this stage are withdrawn through line I4 andA introduced into agitating zone E of stage 46.

The solvent and dissolved fractions in cooler C are withdrawn through line 26 into cooler 3| where the temperature is lowered to about 0 F. At this temperature a further quantity of the more paraflinic fractions in this extract phase are forced out of solution. The chilled mass then passes to separator D where the solvent containing the remaining dissolved fractions is withdrawn through line 33. The insoluble oil fractions in separator D forming the upper layer are withdrawn through line 34 and introduced into the agitating zone E of stage 48 operating at about 40 F. where these oil fractions are mixed with solvent and dissolved fractions withdrawn from stage 49 through line 35. After thorough mixing the mass in agitating zone E of stage 48 passes into the settling zone of this stage. From the upper part of this settling zone there is withdrawn a railinate phase through line 36 which is introduced into a stage 49 operating at about 60 F. From the lower part of the set- A through line 31 and mixed with the oil introduced into the mixing zone E of stage 49 with the oil introduced through line 38 at a temperature of about 60 F. From settling zone F of stage 49 solvent and dissolved fractions are withdrawn through line 35 and a raillnate is withdrawn through line y99 and introduced into agitating zone E of stage 59 where it is mixed with dichlorethyl ether at a temperature of 'about 78 F. The amount of dichlorethyl ether introduced through line 99 will be about 50% by weight based upon the oil charged to this stage. From the settling zone of stage 50 there is withdrawn an intermediate raffinate from line 40. y

When the process is carried out according to the manner just described and the temperatures in each successive extraction stage are malntained at the values indicated and the quantities of oil and solvent introduced into columns A and B are maintained at the volumes shown on the drawing and just previously described, I lam able to obtain from an oil having a viscosity gravity constant of .872 a high grade raffinate having viscosity gravity constant oi .810 representing 37% of the original oil charged to the extraction process, an intermediate raillnate having viscosity gravity constant of .843 representing 32% of the oil charged to the process and an extract having viscosity gravity constant of .97 and representing 31% of the oil charged to the process.

It is to be understood that the temperatures which I have employed above are merely illustrative of one set of conditions which may be employed in the process. 'I'hese temperatures obviously depend upon characteristics of the oil which is introduced into the process and the characteristics of the solvent used to separate the paralnic from the non-parafnic fractions. In

many cases it may be unnecessary to employ as many stages as shown. Furthermore, it may be found that a wider temperature range will be more advantageous than the range which I have just described, or in some cases it may be found necessary. to employ even a narrower range in order to obtain the optimum results. `These variations are within the knowledge of those skilled in the art.

The term viscosity gravity constant" is a means of expressing the temperature viscosity susceptibility of an oil, that is, the change in viscosity with a change in temperature. This constant is described in the Journal of Industrial and Engineering Chemistry, vol. 20, page 641 of 1928 by Hill and Coates. A high value represents a high degree of naphthenicity or a high temperature viscosity susceptibility While low values indicate relatively' greater paramnicity or a lower temperature viscosity susceptibility. Lubricating oils from natural crudes range from .903 for an extreme Gulf Coast type to .807 for an extreme Pennsylvania type.

I claim:

1. A process for the separation of paraiinic and non-paraiilnic fractions from an oil containing the same comprising extracting said oil with a selective solvent, separating a ralnate insoluble in said solvent, separating an extract dissolved in' said solvent, commingling the extract dissolved in said solvent with a wash oil comprising an insoluble fraction separated from said selective solvent solution of oil by cooling the solutiony and allowing said insoluble fraction to sepirate from said selective solvent solution.

2. A process for the solvent extraction of -oil which comprises commingling said oil with a selective solvent to separate a ramnate insoluble in said solvent from extract phase comprising said solvent and oil soluble therein. removing said raillnate from said extract phase, separating said extract phase into an oil traction insoluble therein and a further extract phase comprising said solvent and oil fractions remaining dissolved therein, removing said last mentioned insoluble oil fraction from said last mentioned extract phase, separating said extract phase comprising said solvent and oil fractions remaining dissolved therein into a second Aoil fraction insoluble therein and an extract phase, commingling said last mentioned insoluble fraction with a selective solvent to separate a raillnate from an extract phase and returning said last mentioned extract phase to said nrst mentioned extraction.

3. A process for the separation of oil into fractions -relatively more parailinic in character and relatively less paraiiinic in character than the original oil which comprises commingling said oil with a selective solvent in an extraction systeni and thereby forming a ratlinate phase comprising the more paraiilnic oil fractions and an extract phase comprising oil fractions dissolved in the selective solvent, separating said phases, recovering an oil fraction from said extract phase which is more parailnic in character than the remaining oil fractions dissolved in the selective solvent and returning said oil fraction recovered from said extract phase to said extraction system.

4. A process according to claim 3 in which the oil fraction is recovered from the extract phase by cooling the latter.

5. A process according to claim 3 in which the selective solvent employed is normally gaseous at ordinary temperature and pressure and the oil fraction is recovered from the extract phase by vaporizing a portion of the selective solvent under reduced pressure and thereby cooling the extract phase to cause separation of said oil fraction.

6. A process for the separation of oil into fractions in an extraction system with a selective solvent which comprises introducing said oil into the extraction system, introducing a selective solvent into said extraction system, withdrawing a nal railnate from said extraction system, withdrawing an extract phase from said extraction system. recovering an oil `fraction from said extract phase which is more parafiinic in character than the remaining oil fraction dissolved in the extract phase and returning said oil fraction to said extraction system at a point intermediatethe points of introduction of oil and withdrawal of the extract phase of said system.

1. A process according to claim 6 in which the oil fraction is recovered from the extract phase by cooling the latter.

8. A process according to claim 6 in which the selective solvent is normally gaseous at ordinary temperature and pressure and the oil fraction is separated from the extract phase by vaporizing a portion of the selective solvent under reduced pressure to cool the extract phase.

9. A process for the separation of oil into fractions which comprises introducing oil and selective solvent into an extraction system and thereby forming a final rainate phase comprising the more paraiiinic fractions of the oil and an extract phase comprising oil fractions dissolved in the selective solvent, separating said phases, cooling the extract phase and thereby separating an intermediate rainate and contacting the extract phase in said extraction system with said intermediate raillnate.

10. A process for the separation of oil into fractions with a selective solvent which comprises introducing' said oil and selective solvent 5 into a primary extraction stage and thereby forming a rannate phase and an extract phase, separating said phases, removing the rai'llnate phase from said primary extraction stage, passing the extract phase from said primary extrac- 10 tion stage to a secondary extraction stage, introducing railinate from said secondary stage 4into said primary stage, separately removing extract phase from said secondary stage, cooling the extract phase removed from said secondary 15 stage and thereby forming an intermediate raffinate phase and a nal extract phase, separating said intermediate railinate phase from said nal extract phase, introducing said intermediate raffinate phase into said secondary extraction stage, and commingling said extract phase and intermediate railinate phase in said secondary stage and thereby forming a ratlinate phase in said secondary stage.

l1. A process for the separation of oil into 25 fractions with a selective solvent which comprises-introducing selective solvent into a primary extraction stage, introducing said oil into a secondary extraction stage, introducing railinate from the secondary extraction stage into 30 the primary extraction stage, removing raiinate from the primary extraction stage, introducing extract phase from the primary stage into the secondary stage, introducing rafnate from a tertiary stage into said secondary stage, introduc- 35 ing extract phase from the secondary stage into the tertiary stage, withdrawing an extract phase from said tertiary extraction stage, cooling the extract phase withdrawnl from said tertiary extraction stage and thereby separating 40 an oil fraction insoluble in the extract phase at the lowered temperature. recovering said insoluble oil fraction, passing the insoluble oil fraction recovered from the extract phase by cooling the latter to the tertiary extraction stage 45 and commingling said insoluble oil fraction with the extract phase in said tertiary extraction stage and thereby forming a rainate in said tertiary stage.

12. A process according to claim 11 in which 50 the primary, secondary and tertiary extraction stages are operated at progressively lower temperatures.

13. A process according to claim 10 in which the primary extraction stage is operated at a 55 higher temperature than the secondary stage.

14. A process for the separation of oil into fractions with a selective solvent which cornprises introducing the selective solvent into a primary extraction stage, introducing said oil into a secondary extraction stage, passing raffinate from the secondary extraction stage to the primary extraction stage. extracting the railinate passed to said primary extraction stage with the selective solvent and thereby forming a rainate 65 and an extract phase in said primary extraction stage, passing the extract phase formed in said primary extraction stage to said secondary extraction stage. extracting the oil introduced into said secondary stage with the extract phase in- 70 troduced from the primary stage into said secondary stage and thereby forming a raifmate and extract phase in said secondary extraction stage. passing the extract phase formed in said secondary extraction stage to a tertiary extraction 75 stage. passing raffinate phase from said tertiary extraction stage to said secondary extraction stage, withdrawing extract phase from said tertiary extraction stage. cooling the extract phase and thereby forming a ramnate phase and an extract phase, separating said phases, separating said extract phase into a phase containing the relatively more paraiilnic oil fractions ot said exwithdrawn from said tertiary stage and theretract phase and a phase containing the relatively 5 by forming an oil fraction insoluble in said exless paramnic oil fractions of said extract phase tract phase. recovering said insoluble oil fracand contacting the extract phase in said extraction, passing said insoluble oil fraction to said tion system with said phase containing the reltertiary extraction stage, contacting the extract atively more paramnic oil fractions recovered 10 phase present in said tertiary extraction stage from said extract phase. 10 with said insoluble oil fraction and thereby 18. A process as claimed in claim 1'1 in which forming a rafiinate phase and an extract phase the extract phase is separated into-a phase conin said tertiary extraction stage. taining the relatively more paraiilnic oil frac- 15. A process according to claim 14 in which tions and a phase containing the relatively less 15 the primary stage is operated at a higher temparamnic oil fractions by cooling said extract l5 perature than the secondary stage. phase.

16. A process according to claim 14 in which 19. A process according to claim 6 in which the primary. secondary and tertiary stages are the selective solvent is one o! .the members seoperated at successively lower temperatures and lected from the group consisting .ofsulphur dithe temperature employed to separate the insoloxide, furiural, B B' dichlorethyl ether. nitro- 20 uble oil fraction from the tertiary extract phase benzine and aniline. is lower than the temperature employed in said 20. A process according to claim 9 in which tertiary extraction stage. the selective solvent is one of the members se- 17. A process for the separation of oil into lected from the group consisting of sulphur difractions with a selective solvent in an extraction oxide, iurfural, B B' dichlorethyl ether. nitro- 25 system which comprises contacting said oil and benzine and aniline. said selective solvent in said extraction system DAVID R. MERREL.

CERTIFICATE OF CORRECTION.

Patent No. 2,043,589, June 9, 1936,

DAVID R. MERRILL,

it is hereby certified that error appears in the printed specification of the above numbered patent requiring Correction as follows: Page 3, second column, line 25, for the word "exact" read extract; and that the said Letters Patent should be read with this correction .therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of February, A. D. 195'?.

Leslie Frazer (Seal) Acting Commissioner of Patents.

stage. passing raffinate phase from said tertiary extraction stage to said secondary extraction stage, withdrawing extract phase from said tertiary extraction stage. cooling the extract phase and thereby forming a ramnate phase and an extract phase, separating said phases, separating said extract phase into a phase containing the relatively more paraiilnic oil fractions ot said exwithdrawn from said tertiary stage and theretract phase and a phase containing the relatively 5 by forming an oil fraction insoluble in said exless paramnic oil fractions of said extract phase tract phase. recovering said insoluble oil fracand contacting the extract phase in said extraction, passing said insoluble oil fraction to said tion system with said phase containing the reltertiary extraction stage, contacting the extract atively more paramnic oil fractions recovered 10 phase present in said tertiary extraction stage from said extract phase. 10 with said insoluble oil fraction and thereby 18. A process as claimed in claim 1'1 in which forming a rafiinate phase and an extract phase the extract phase is separated into-a phase conin said tertiary extraction stage. taining the relatively more paraiilnic oil frac- 15. A process according to claim 14 in which tions and a phase containing the relatively less 15 the primary stage is operated at a higher temparamnic oil fractions by cooling said extract l5 perature than the secondary stage. phase.

16. A process according to claim 14 in which 19. A process according to claim 6 in which the primary. secondary and tertiary stages are the selective solvent is one o! .the members seoperated at successively lower temperatures and lected from the group consisting .ofsulphur dithe temperature employed to separate the insoloxide, furiural, B B' dichlorethyl ether. nitro- 20 uble oil fraction from the tertiary extract phase benzine and aniline. is lower than the temperature employed in said 20. A process according to claim 9 in which tertiary extraction stage. the selective solvent is one of the members se- 17. A process for the separation of oil into lected from the group consisting of sulphur difractions with a selective solvent in an extraction oxide, iurfural, B B' dichlorethyl ether. nitro- 25 system which comprises contacting said oil and benzine and aniline. said selective solvent in said extraction system DAVID R. MERREL.

CERTIFICATE OF CORRECTION.

Patent No. 2,043,589, June 9, 1936,

DAVID R. MERRILL,

it is hereby certified that error appears in the printed specification of the above numbered patent requiring Correction as follows: Page 3, second column, line 25, for the word "exact" read extract; and that the said Letters Patent should be read with this correction .therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2nd day of February, A. D. 195'?.

Leslie Frazer (Seal) Acting Commissioner of Patents.

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