US2603590A - Method of extracting lubricating oil fractions - Google Patents

Description

Patented July 15, 1952 James A. Anderson,

ward F. Wadley,

of Delaware 1 This-invention'relates to an improved method of refining-lubricating oils. Particularly, it relates to a solvent extraction process whereby the organic acid content of lubricating oils may be effectively reduced.

Lubricating oil distillates derived from naphthenicand mixed base crude petroleum oils frequently contain appreciable quantities of naturally occurring -organic acids. These organic acids-such as naphthenic acids, even if present in alubricating oil in relatively small concentrations, are corrosive to engine parts at the high temperatures-to which suchoil is usually subjected. It is-important, therefore, that motor lubricants not only have satisfactory viscosity index, color, pour and stability characteristics, but also contain organic acids in concentrations insufilcient to cause corrosion difiiculties under severe temperature conditions.

Inpresent commercial practice, it is customary to improve the viscosity index characteristics, of untreated lubricating oil distillates by treatment in, theliquid phase with a solvent that has a preferential selectivity dex naphthenicand aromatic-type (relatively less parafiinic-type) compounds as compared with-the-high viscosity index (relatively more parafiinic-type) compounds. Phenol, furiural, aniline, nitrobenzene and the like are typical solvents used for this purpose. Solvents, such as phenol, that do not react with organic acids also demonstrate a preferential selectivity for organic acids of the type usually found in lubricating oil distillates derived from naphthenic or mixed base crudes. In a solvent treating process, therefore, the organic acids tend to be separated from the paraflinic constituents. It has been observed, however,.that lubricating oil distillates containing? relativelyhigh,concentrations of. organic acids maybe treated with a selective solvent to produce a finished lubricating oil having satisfactoryviscosity index characteristics and yet reta "Qsuflicient organic acids to render the solvent treated oil corrosive to engine parts.

Experience has shown that motor lubricants derived from mixed base and naphthenic crudes should contain organic acids in amounts below, i. e; having a neutralization value below, an equivalent of 0.1 milligram KOH per gram of. oil to render said lubricant non-corrosive to engine parts. Experience also has shown that the liquid phase extraction of lubricant distillates containing organic acids in amounts below an equivone milligram KQH per gram of said alent of distillate with a solvent, such as phenol, genera ,for the low-viscosity ining equipment is non-corrosive amounts of organic acids.

fUNl-TED, Y STATES P EIN l I METHOD OF EXTRACTING LUBBICATING OIL FRACTIONS J1'., Clyde MJFloyd, and Ed- Baytown, Tex.,'assignors, by. mesne ass'ignments,;to Standard Oil Develop- I ment Company, Elizabeth, N. J.,

a corporation ally produces high yields of a finished lubricant having a high viscosity index and containing been found, for example, that lubricant distillates containing organic acids in amounts substantially. above an equivalent of one milligram. KOH per gram of said distillate require solvent extracting to a lower yield of finished lubricant having a higher viscosity .index than is normally required inorder to reduce the organic acid content of said lubricant to non-corrosive amounts. Sucha motor lubricant is said to be over. ex-, tracted; that is, one requirement imposed on, the finished lubricant is met at the expense of other requirements imposed thereon.

In order to effect a substantially complete .re-. moval of the organic acids from the high viscosity index paraflinic constituents, it is frequently necessary to increase the severity of the solvent treat, that is, increase the ratio of solvent to lubricating oil, above the normal required to produce an oil of desired viscosity index. Increasing the solvent treat decreases the. yield of finished lubricating oil obtainedin the. treating process. In addition, if the solvent treat-' operated at its maximum ca-. pacity, an incr'ease in solvent treat above nor; mal: necessitates decreasing the; amount of oil feed which maybeintroduced. Increasing the severity of the solvent treat also is disadvan-r tageous in that natural inhibitors present in certain types of lubricating" oil distillates and known to be beneficial to motor lubricants are remove from. the finished lubricant.

An alternative method 0 acid content of motor lubricants is that of treating a topped crude or lubricating 'oil distillate with an alkaline material. For example, it is well known to the 'art to remove organic acid-s present in'petroleum oil fractions by distilling" a materials remaining in the residue is relatively high, the residue. may be unsatisfactory for asphalt manufacture or for use as a fuel oil.

In U. S, 2,451,025, issued October 12, 1948,11) Harold L. Ellendena method is described for removing organic acids from lubricating oil distillates in a process involving treating a lubricating oil distillate during distillation thereof with an'alkaline reagent, such as sodium hydrox lde,.followingwhich a fraction; boiling in the It hasf reducing the organic tion. This process is quite effective and allows the obtaining of a solvent rafiinate having the desired characteristics without requiring the lubricatingoil to be overextracted in the solvent extraction step to produce a product having the requisite low, neutralization value. It smite seen, however, that the aforesaid Ellenderpatent requires the addition of an alkaline reagentto the distillation Zone in which the .mineral' Oi].

lubricating fraction is being segregated from a.

topped crude petroleum. Thus, under some conditions the presence of the alkaline reagent in the distillation tower may be harmful, especially when long contact times are employed and excessive amounts of the alkaline reagent are necessary since the. presence of alkaline reagents, such as sodium hydroxide, may affect. deleteriously the ferrous metals employed in distillation towers. Itis well'known that sodium hydroxide may cause caustic embrittlement of'ferrous metals when in contact'therewith at high temperatures.

gIt is, therefore; the mainobject of the present invention to provide an improved process for refining mineral lubricating oils.

Another object of our invention is 'to provide an economical process wherein maximum, yields ofs'olvent extracted lubricating oils, meeting both viscosity index and organic acid contentrequirement's,may be produced from suitable mineral oils.

A still further object of our invention is to provide a selective solvent extraction process in which maximum quantities of oil and minimum quantities of solvent are circulated to produce lubricating oil of desired high viscosity index and low organic acid contentwithout overextracting the oils. v V I Still othe r objeots .and advantages willbe apparent to workers-skilled in the artgto which the present'invention relates. I In accordance with the-present invention, it has now been found that'lubricating-oil=fractions1ob tained from crude petr'oleums and m'ineral oil distillates may be "solvent extracted to obtain a solvent raffinate having thegrequired low neutrali'zation value without overextracting the oil.

,Thus, for example, in-accordanoewith the present invention, a lubricating oilfraction, such as a mineral'oil distillateboiling in the "lubricating oil boiling range and having'lubricating oil co nponents therein is subjected to extraction with phenol, such as anhydrous or aqueous phenol, containingfa small but. effective amount of an alkali metal phenolate which may bejformed in situ' by adding an alkali metal hydroxide to the phenol, under conditions to form an extract phase and a raffinate phase which are recovered separately. The reffinate phase, from which the undesirable components have 'been removed in the phenol, is subjectedtoia stripping operation-in' which the residualphenol is removed therefrom to allow recovery of the desirable motoroil'fractions which, by virtue'of the pres-f ence of the alkali metal hydroxide or phenolate during the extraction operation in the presence of phenol, allows the obtaining of a motor oil having the required low neutralization value.

7 Alternatively, dependi-ngcn the characteristics to the phenol priorto contact with the oil being extracted or to the solvent rafilnate containing the phenol. Addition of the alkali metal hydroxide converts a small amount of the phenol to the corresponding phenolate which; it is believed, by reaction with-the organic acids releases the alkali metal hydroxide which serves to neutralize the organic acids.

-Therefore,; it is within the purview of our inyen'tion to add alkali metal phenolates rather,

than alkali metal hydroxide to the phenol.

Therefore, the invention may be described briefly as involving maintaining alkali metal phenolate tro duced by line-|3 givenin more detail hereinafter.

" of the oil and therefore, the 'treating operations to;whichthe oil maybe subsequently subjected, the ;alkali metal hydroxide may be'added either in the phenol solvent and solvent extracting the lubricating oiliraction with the mixture ofa1- kali metal phenolate and phenol under condi! tions to form a raffinate phase and an extract phase, the two phases being separately recovered and processed for recovery of phenol and the hydrocarbons containedin the two phases.

In the foregoing briefdescription, it ;is seen that the essence of the present 'invention'resides in providing a process 'inwhich -a lubricating-oilfraction, such as a mineral oil -distillate,is sub jected to contact with phenol containing semen amount of an alkali metal phenolate -which'- n lay beformed in situ by adding to the phenol-a small buteffective amountof an =alkali=metal hydroxide. The presence of alkali metal phenolate in a small but effective amountiin the phenol causes the removal of the organic-acids and allows the obtaining of a 'soIVentraffinate having a neutralization value no greater -than 0. 1 milligram. KOH per gramwof oil without overextraction of the oil. [As mentioned befor'e,-'an alternative mode of thepresent invention involvs adding the alkali metal phenolateto the solvent rafilnate containing phenol or forming the alkali metal phenolate-in the solvent-rafiinate containing phenol to obtain amotor oil fraction having the-desired low organicacid content.

The invention will be better understood'by' contacting equipment such as bell captrays, pack ing, and the like to allow intimate contact be tween. the mineral oil distillate boiling inthe lubricatingpil boiling range and having lubri eating oil qualities which is introduced into zone H by line l2 and flows upwardly therein contacting the down-flowing phenol which is introduced into zone Ii byline 13. The phenol in-j may be sub amanyam hydrous phenolyxtl'iatia it may havefaph'enol content of approximately 100% for Zitf may be aqueous phenol containing -approXi lfrlalily 10%? of water. Thus, itis understood thatfphen'ol containing to phenoLmay .bejintro-l duced byline I 3 and,employedas a sollv'ent "n solvent extraction zone Ii. Conditionsare ad?- justedin extractionzonef Lil to produce a-Ifaf finate phase and ,an extract phase... ,"Such condi-tions'are well'knownto the art, but-will :be

4 The phenol, prior to introduction into .zone' I l has addedtoit by line 14 controlled by valve 15 a small but eiiective amount of sodium-hydroxide which is withdrawn from tank le'b pump 1". The amount of sodium hydroxidet'in troduced into the'phenol to cause the formation Kor per gram'of oill Usually,

o'iLff In. any valuegoi above about l'.0 milligramKO'I-Il per be the more aromatic and .ftheextent to which it isdesired toremovej'such acids. The mineralmotor'oifdistillate may have n organicflacidfcontent corresponding to 'aJneutralization value of approximately 3.5"mi'lligrams on however, the neutralization value will be somewhat lower and "mayb about 2 milligramsKQI-I per gram of event, oil'ha'ving' a neutralization grain] of; oil is generally 'too' high to allow the production of a ra'fiinate having the desired neutralization value no'greater than aboutO-J milligram KOI-I per; gram of oil'without overextract- 'ing hydroxide or sodium phenolate" introduce'dpor contained in the 'phenol'should usually at' least be the theoretical amount required to allow the Obtaining of a solvent rafilnate having a neutralization value of no greater than about 0.1 milligram KOH per gram of oil. In cases where it is not necessary to obtain extracted oils having such low neutralization values or in the event the oil to be extracted has a low neutralization value, such as below 1.0, and requires a light solvent treat, it may not benecessary to maintain the alkali metal hydroxide or phenolate content of the solvent at the theoretical amount. Generally, the amount of alkali metal phenolate maintained in the solvent should, on a; molar basis, be equivalent to from 0.2 to 3.0 times the theoretical amount of KOH required "to neutralize acidic bodies in the oil to be "extracted.

As mentioned before, the' phenol containing the sodium phenolateeither added thereto or produced in situ contacts countercurrently' the ascending mineral motor oil distillate in extraction zone I] and by adjustment of conditions therein, causes the formation of raffmate and extract phases. The extract phase is withdrawn from zone II by line l8 and is discharged thereby into a stripping zone l9 which is provided with a heating means 20 which is illustrated by an internal coil which will be understood to embody any of the well known types of heating means available to the industry. Stripping zone I9 is provided with internal baffiing equipment to allow separation of the phenol from the hydrocarbon constituents contained therein which will naphthenic constituents as opposed to the more paraffinic constituents which will be found in the solvent raffinate, The phenol is removed from stripping zone [9 by line 2| for reuse in the process while the predominantly aromatic and naphthenic constituents removed from the mineral motor oil distillate as a solvent extract are discharged from stripping zone l9 by line 33 to be used as a cracking stock or in other uses as may be desired.

A solvent raffinate is removed from extraction zone II by line 22 and is discharged thereby into a stripping zone 23 which is similar to stripping zone I9 and is provided with a heating means illustrated :by coil 24 which may be any of the well known heating means available to the industry. Zone 23 is provided, like zone IS, with internal, contacting equipment to allow separation between the phenol and the predominantly paraffinic constituents found in the Conditions are adjusted in while solvent raflinate. stripper 23 to remove phenol by line 25 the oil. Therefore, the amount "of'sodium' be conne d; to; n 11 pi mp l and tank nd.albwinetheso y h fi introduction of sodium ,droxide to line 22, it, may be-desirable toyco'nthe desired motor 'oil components are removed from zone 23 by line 26. we

When sodium hydroxide or sodium phenolate is not. added to the phepqrhalternatiyely it [may be added to thesolvent raffinate inline22 5 When this is desired, valve 'I S-in line M-is closed and va ve 21;:11 li '28. is enema. low l e '28 o troduced into the solvent raffinate containing phenolto cause formation in situroi sodium phenolate andallow the obtaining. of arirafflnate having an organicacidcontent corresponding to a neutralization value no greater than 0.l milligram KO-H per grarnof oil. When thelatter 1 operation is; employed, it will be understood v that I a suitable incorporation means, not shown, will be provided in line 22to allow intimat' admixture of the solvent rafiinate with" Ithej sodium hydroxide or sodium phenolate introduced'thereto by line 28.

When the sodium ,phenolatesare .formedb'y phenolate or sodium hyftact the phenol-free oil, which may contain smallquantities of sodium phenolate's, with clay.

Therefore, a clay contacting zone. 29 is'provided wherein the oil containing small quantities of sodium phenolate 'may be contacted at'a rela- 'tively high temperaturesuch as in tlierangeof 350 to'450? F. with' afsiiitable contactlclay'such as illustrated by acid'treated natural clays or bentonite, and the like," When this operation is conducted valve 3i l'.'in line 26 will be opened, valve 3| in line 32 will'be'closed, and1valve33 jinline 34 will be, opened, allowing the oil to'be routed byline zfiltdclaycontacter zawhere it is intimately admixed withv cIay Which is subsequently removed from the oil by m'eans nolt shown;

zone 29 by line 34"into line 32, cooled in cooler 35 in line 32, and discharged thereby tosuitable storage facilities, not shown, from whencethe oil may be withdrawn for use as a commercial lubricating oil having 'a neutralization 'valuejfno 'greate'rthan; one milligram KOH per gramlof oil. s. V

When 1 the sodium hydroxidev or sodium phenolate is introduced into thephenol byline [4 connecting into line l3, the employment of clay contacting zone 29 may be dispensed with andthe oil may bypass this zonefbyi lclosing valve 30 in line 26 and valve 33 in linev34. Withvalve 3| in line 32 in the open position, the motor oil substantially free of phenol is routed 'by'line 2'6 and line 32 through cooler 35 to storage for use .as a commercial motor oil having the desired low neutralization value as mentioned before.

Although the inventionhas been described andillustrated above with respect to tank 6 containing sodium hydroxide, it will be apparent that this tank maycontain alkali metal hydroxide such as sodium hydroxide or an alkali metal phenolate. Thus, provision is made by line 1, controlled by valve 8, to introduce alkali metal hydroxide to tank 16 and provision is also made to introduce alkali metal phenolate thereto by line 9, controlled by valve In.

While the invention has been described and illustrated with respect to employment of sodium phenolate or sodium hydroxide, it is to be understood that the phenolates or hydroxides oi the other alkali metals, such as lithium and potassium phenolates or hydroxides, may be employed in lieu of sodium hydroxide or sodium and the clay-treated oil discharged" from encased phenolate, =but that the latter are ito'be preferred by virtue of their ability? r r a V In thepresentinvention it will be obvious to those skilled in the art that 'the critical quantity o'f-alk ali metal hydroxide or alkali metal-phenolate introducedinto the solvent extraction sysoheapness and avail- :tem will depend on the'concentration of organic acids contained-in the lubricating oil fractions subjected'to the process of the present invention. The organic acidcontent of the lubricating oil distillate must be reduced 'sufiiciently to permit obtaining the highest possible yield of solvent extracted lubricating oil meeting viscosity index and acid content requirements.- On the other hand; the quantity'of alkali metal hydroxide or alkalimetal phenolate introduced into the extraction system should be sufiicient to react with the" organic acid content of the motor oil fraction without providing such an excess amount that the phenol will be reacted with and cause loss of the valuable solvent. In general, it is preferred to employ an amount of alkali metal hydroxide orpheno late in either the solvent or 'rafilnate phase that is about theoretically equivalent to the amount of KOH required to neutralize acidsjin either the oil charge or remaining in the flraifinate'phase; however, on a molar basis, as ilittleas 0.2 mol alkaline material per mol of KOH (determined from theneutralization value) may be used wherethe treating conditions are such that the phenol solvent issufficiently selective to'removemo'st of the acids. '"On the other hand, as" much as 3 mols alkaline material per mol of KOH .required to jneutralize the acids may be used under extreme conditions 'where substantially complete removal of th'e organic acids from the .oil is desired and where the acids are difii cult to extract. s 'Ihe conditions employed in the solvent extraction zone I l mayvary with the composition of the feedstock charged. Inthe case of treating Ewample' II solvent used in the extraction step andthegneu- Example I.

traliz'a'tion value 01. the oil charge, is equivalent on a molar basis to 1.1 times the theoretical amount 7 of KOH required to neutralize organic acidsinthe oil treated. The tower temperature conditions were the same as those employed in The yield of solvent rafiinate in this operation was 56% by volume of the motor oil charged and had a viscosity index of 61. The

neutralization value of raffinate was 0.059 milligram KOH per gram of oil, which is well below the specification requirementin this particular case.

Ezzzample III In this particular operation; the same ratio of Oil to solvent and the same temperature conditions were used in the treating step thatwere used in Example II. A 56% yield of rafflnate having a viscosity index of "61 was obtainedgjIn this operation, howeverjsodium hydroxide was notadded to theanhydrous'plhenol prior ,to the extractionstep, and the neutralization value of the .rafiinate was 0.308 milligram-KOH per gram of oil, which isgreatly in excess of the specification figure and of the neutralization value of the raifinate produced in Example II.

It will be observed fromthe foregoingexamples that thepresent' invention allows vastly improved distillates derived from coastal crudes, oil to solvent ratios inthe range from 120.5 to about 1 :3.0, treating temperatures in the" range from about to 250 F., and essentially atmospheric pressures are generally satisfactory. As mentioned before, the phenol may be'substantially anhy+ 'drous or may contain up to about 10% by volume of water. i

In order to demonstrate the invention further, the following examples are given whichshould notbe construed as limiting the invention in anymanner.

' Example I A motor oil distillate having a Saybolt Universal viscosity of approximately-950 seconds at 100 F., a viscosity index of 24, and a neutralization value of 1.25 milligrams KOH per gram of.

oil was extracted-with 100% phenol using an "oil tosolvent ratio of 1:15; The extraction was carried out in a towerhaving 'five theoretical stages'with a top tower temperature of F. and a bottom temperature of 100 F. 1 5.43% 'yield, based onthe charge, of raflinate having a viscosity index of 68 and a neutralization value of 0.085 milligram KOH per gram of oil was'produced during the extraction operation. Inthis particularoperation it was desired to produce a solvent rafiinate meeting a viscosity index specification of 60 and a neutralization value specification df-less-than 0.1 milligram KOH per gram 1 of'oil, but it was necessary to overextract the oil tomeet the'neutrali'zation value specification.

results both in yield and quality of finished product without resorting 'to' overextraction thereof.

It isfurther noted that the-invention permits employing much lower solvent treats than are conventionally permitted to obtain a product having a lowneutralization value by employinga small amount of sodium hydroxide or sodium phenolate in the solvent instead of a relatively large amount of solvent to remove acidic bodies'from the oil;

It should be mentioned that anhydrous phenol was employed in the foregoing examples, and, therefore, the yields of finished rafiinate were somewhat lower than would be obtained-byusing aqueous phenol. For example, a distillate similar to that used in the Examples but having a 1.5 neutralization value may be treated at a temperature of F. with a mixture comprising 96% phenol and water (oil to solvent ratio of '1 :15) to obtain a 63% yield of r-afiinate having a viscosity index of 68 and a neutralization value of 0.08 milligram KOH per gram of oil. By adding a small amount ofan alkali-metal hydroxide tas neutralization value specifications. Since anhydrous phenol is somewhat more selective to acidic bodies in the oilthan is the aqueous phenol, it'is generally necessary to use a slightly higher amount of alkali metal hydroxide or phenolate based on the acidic bodies and/or a higher solvent treat when using the latter material as com- ;pared to the anhydrous phenol.

It is, therefore, seen that by practicing the present invention, it is possible to remove acidic bodies from lubricating oil distillates by a modified solvent which comprises phenol and a'small amount of an alkali metal hydroxide or phenolate which has a greatly improved selectivity for the acidic constituents. It is possible to obtain an extracted oil meeting both neutralization value and viscosity index requirements without resorting to overextraction which causes the loss of valuable lubricating oil constituents. Such high viscosity index constituents where overextraction occurs are lost in the solvent extract and, therefore, are degraded to cracking stocks whereas in the practice of the present invention, these valuable constituents may be used as lubricating oil components.

The nature and objects ofthe present inven' tion having been completely described and illus trated, what wewish to claim as new and useful and to secure by Letters Patent is:

1. A method for solvent extracting a mineral lubricating oil distillate fraction which contains small quantities of naturally occurring naphthenic acids, has a neutralization value in the range from about 1 to about 3.5 milligrams KOH per gram of oil and would be over extracted if extracted with phenol alone in such an amount as to reduce its acid neutralization value below .1 milligram KOH per gram of oil, which comprises the steps of intimately contacting said fraction with a phenol solvent containing no more than 10% water and a small but effective amount of an alkali metal phenolate equivalent to from 0.2 to 3.0 times the theoretical amount of KOH required to neutralize acidic bodies in said fraction under conditions including a temperature in the range between 100 and 250 F. and substantially atmospheric pressure to form a rafiinate phase and an extract phase andseparately recovering said phases. 1

2. A method in accordance with claim 1 in which the phenolate is formed in situ by adding to said phenol solvent an alkali metal hydroxide in an amount in the range from .2 to 3.0 times the theoretical amount of KOH required to neutralize acidic bodies in said fraction.

3. A method in accordance with claim which the alkali metal is sodium.

4. A method in accordance with claim 1 in which the alkali metal is potassium.

5. A method in accordance with claim 1 in which the alkali metal is lithium.

6. A method for solvent extracting amineral lubricating oil distillate fraction which contains small quantities of naturally occurring naphthenic acids, has a neutralization value in the range from about 1 to about 3.5 milligrams KOI-I per gram of oil and would be over extracted if extracted with phenol alone in such an amount as to reduce its acid neutralization value below .1 milligram KOH per gram of oil, which comprises the steps of forming a first stream of said lubricating oil fraction, forming a second stream of phenol containing no more than water, adding to said second stream an amount of an alkali metal hydroxide equivalent to from 0.2 to 3.0 times the theoretical amount of KOH required lin to neutralize acidic bodies in said oil, contacting said first stream with said second stream under conditions including a temperature in the range from about to 250 F. and substantially atmospheric pressure to form a raffinate phase and an extract phase, separating said phases, separately removing phenol from said separated phases, and recovering from said rafiinate phase a motor oil fraction having a neutralization value less than 0.1 milligram of KOI-I per gram of oil.

7. A method for solvent extracting a mineral lubricating oil distillate fraction which contains small quantities of naturally occurring naphthenic acids, has a neutralization value in the range from about 1 to about 3.5 milligrams KOH per gram of oil and would be over extracted if extracted with phenol alone in such an amount as to reduce its acid neutralization value below .1 milligram KOH. per gram of oil, which comprises the steps of contacting said distillate with phenol solvent containing no more than 10% Water under conditions including a temperature in the range between 100 and 200 F. and substantially atmospheric pressure to form a rafiinate phase and an extract phase, separating said phases,

maintaining in said rafi'mate phase a small but effective amount of an alkali metal phenolate equivalent to from 0.2 to 3.0 times the theoretical amount of KOI-I required to neutralize acidic bodies in said fraction, separating phenol from said raffinate phase, and recovering from said raffinate phase a lubricating oil fraction substantially free of said acidic bodies.

8. A method in accordance with claim 7 in which said lubricating oil fraction substantially free of said acidic bodies is treated to remove sodium phenolate therefrom.

9. A method in accordance withclaim 7 in which said phenolateis formed in situ by adding to said solvent raffinate an alkali metal hydroxide in an amount equivalent to from 0.2 to 3.0-times the theoretical amount of KOH required to neutralize acidic bodies in said rafiinate phase to obtain a motor oil having a neutralization value less than 0.1 milligram KOI-I per gram of oil.

10. A method in accordance with claim 'I in which the alkali metal is sodium.

11. A method in accordance with claim '7 in which the alkali metal is potassium.

12. A method in accordance with claim 7 in which the alkali metal is lithium.

JAMES A. ANDERSON, JR. CLYDE M. FLOYD. EDWARD F. WADLEY.

REFERENCES CITED The following references are of; record in the fileof this patent:

UNITED STATES PATENTS

Claims (1)

1. A METHOD FOR SOLVENT EXTRACTING A MINERAL LUBRICATING OIL DISTILLATE FRACTION WHICH CONTAINS SMALL QUANTITIES OF NATURALLY OCCURRING NAPHTHENIC ACIDS, HAS A NEUTRALIZATION VALUE IN THE RANGE FROM ABOUT 1 TO ABOUT 3.5 MILLIGRAMS KOH PER GRAM OF OIL AND WOULD BE OVER EXTRACTED IF EXTRACTED WITH PHENOL ALONE IN SUCH AN AMOUNT AS TTO REDUCE ITS ACID NEUTRALIZATION VALUE BELOW 1. MILLIGRAM KOH PER GRAM OF OIL, WHICH COMPRISES THE STEPS OF INTIMATELY CONTACTING SAID FRACTION WITH A PHENOL SOLVENT CONTAINING NO MORE THAN 10% WATER AND A SMALL BUT EFFECTIVE AMOUNT OF AN ALKALI METAL PHENOLATE EQUIVALENT TO FORM 0.2 TO 3.0 TIMES THE THEORETICAL AMOUNT OF KOH REQUIRED TO NEUTRALIZE ACIDIC BODIES IN SAID FRACTION UNDER CONDITIONS INCLUDING A TEMPERATURE IN THE RANGE BETWEEN 100* AND 250* F. AND SUBSTANTIALLY

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