US2477190A - Naphthenic acid production - Google Patents

Description

July 26, 1949. H. LINFORD ET AL NAPHTHENIC ACID PRODUCTION Filed July 9, 1945 will) .recovery end puriiioetion ofrioplitlisnloeold c boxylic acids.

also meant to include thefsynthetic oil-soluble5 acids produced by`.the, "oxidation .of naphtheriic be readily vrrroduce'd the,' liquid phasef c y peiroisllm Patented July 262 1949 'iloouer Liiiioril., yLos Angeles! uit@ .BaraL Long `Beach, Calif., assignm- Namjrnrrmo AomritopUGTION ffippucaa' my '9, isifseriai No.' sos-.ano

i .iaciaigaa l vThis invention .relates to e. process .for .the

Crude i.ieiphtlieiioeoits .Qbtoi @d flqlll e sludsesarising during therefiiiiug. of; Petroleum fractions. shale oil fractionsicoaltar and lits] iractions or obtained by synthesissuch asvby the Aoxidation of petroleumnaphthrenesLQontain im-l purities which. vtericl to .detreotiroui their mereiel velue- .Thereiore,..in oiiderto produce naphthenio eoids of. high marlietvalue it is I ieoessary to remoye these iniurities. therefrom.

Processes .erekiiowiiwliioliieleteto the iemoval of phenolsiromiiephthenio soidseitei ,both have Vbeen .liberated.simultaneously from.. the various alkaline residues er1 sing. in.. the ieiiriiiig vof petroleumfraotionshoweven. iu .dieser C# .esses 11o` rrouisioiis are madefior. the .removaiof .the impurties hereinafter mentioned .from -the phenol-.free nephtiieuioeoids- The. impurities which are oftentimesessooiated with .the nephtheuio .acids andwliioh impair-.their velue efe urisapoiiifablemeterials suoli es liiell .molecular weight'. hydrooarbou. oils, asphalt-like substenees suoli.. es loituiriens. asphalt. resins..

and Wag-like bodies, and Various gtherhydrocarboris contaminatesas Wellashigh molecular I weight fatty acids andirhydroxy acids.

lt is obvious that, all oftliese impurities are uotueoessarily present inmall naplithuenicL acids, however,

in general hydrocarbon impurities are preseritrinm substantiel quantities. In. any event no matter VWliioli one or ones of .the particular impurities are present theywillurilevoifebly iuiiueiiee the oommeroial ,desirability` of Vvthe l,I raplkitherlc acids.

' The .term riaphthenio acids as used herein is iuteildedto 15e Qssiieiioeiiiiubt limited to any" particular kind of Iiaphthenc (acids, derivedirom yany' particular crude oil or; ariy Aspr-:cie methods A o'fl. isolation therefrom. Neiilitlieiiit- .acids ere..eeii.ereily ouiisisleretito., be mono-carboxylic acidscontaining at leasthio-nev cycloparaftlri' ring. IfIoyyeyer, the term as used vhereinis meant to`include all 'ofi the naturally occurring` carboxylic acd'sffound in petroleum.

' Thisbroad interpretation is employed in'vorder to include fthe 'loyvjer Vmolznaci'ilar-' Weight naph--' Ythe'riicacids which are., thought bysome incestig'ators to be saturated operi branchedicham car- The term naphthenic 'acds' is tion of kerosene,

(cifrato, 14)

'.tfi sueur-iii.. iuilisgiorui'oi .their alkali llmetal soaps soaps@ are preferentially Solublei'n`the aqueouspha'se. and are separated L 'date by decantaton. w 1ca may ybef-'obtained us L extrayctsyby. aci.diiicationy with th dueto therettlitiorioi .urp oies Within the llesfofthe soap Further evidence' of the A eitff ntl'i"'I'i'aphthenate lcu "sie,"v 'indicated' by he aqueous" caustic o, ro solvents 'such es d0 riotie'tthere'moval of .r 1j.' Ao e caustic extracts solvents lis'fiiotfoartieubfuritis; such procn nfco'nriection 'l'i Plfl-dllfi'l' 0f 3 naphthenic acids. Solvents other than petroleum solvents such as alcohols and the like have also been employed, however by such means alone it has not been possible to obtain a naphthenic acid free of hydrocarbon oil. Other methods which have been employed for the removal of the impurities described .include steam distillation of the caustic extract to vaporize the hydrocarbon oil leaving an aqueous solution of soaps as a residue. This process has many disadvantages including the serious foaming ofthe still charge and the tendency for the sodium naphthenates to oxidize, decompose and/or polymerize during the heating period. Y

Another method of purification of the naphthenic acids comprises the decomposition of the soaps With a. mineral acid to yield a Water-soluble alkali metal salt such as sodium sulphate, sodium chloride or the like, depending upon the mineral acid employed, Aand the free naphthenic 'acids containing the above-mentioned impurities. These crude naphthenic acids are subsequently treated'by extraction with a suitable solvent to effect the separation of the impurities from theacids. Solvents for this extraction are not particularly eiicient and, moreover, a great deal of difficulty is generally encountered in this method of treatment due to the formation of comparatively stable emulsions in the various stages of the process. Thus in the cracking-out of the alkali soap with the mineral acid thorough agitation is necessarywhich'often gives rise to a very stable emulsion. Similarly, the residual water remaining in the acid during subsequent stages of the treatment gives rise throughout to emulsion diiculties. y

Other refining processes have `included the steps of acidification o'f the caustic extracts, dilution of the crude acids thus obtained with light petroleum solvent, extraction of the diluted solution with caustic, separation of the aqueous soap solution, acidification of the soap solution to release the naphthenic acids and distillation of the released naphthenic acids. lThis process although apparently desirable in that it furnishes a de-oiling step has not been `connnercially feasible because of the formation of extremely stable jelly-like emulsions in the step of extracting the diluted crude na-phthenic acid solution with caustic solution. Emulsions obtained in this inanner have notb'een successfully broken with the various deemulsication agents available for such purposes and in fact the emulsions have been observed to remain stable over periods of several. Weeks. y

It is therefore an object of this invention to' separate naphthenio acid from crude naphthenic acid stocks containing any of the above named impurities, and in doing so to obtain a naphthenic acid product possessing improved characteristics with respect to color, odor, viscosity oil content and the like.

More specically itis an object of our invention to accomplish this purification or" naphthenic acids by a method which eliminates the normal emulsion diiculties incurred in such purication and at the same time eifects a greater degree of purification than normally accomplished.

Other objects and advantages of our invention Will become apparent to those skilled in the art as the description thereof proceeds.

We are able, by means ofthe process of our invention, to continuously recover and purify naphthenic acids as aresult ofthe fact that We have discovered a method whereby it is possible Cil to effect such purification in the absence of emulsion diiculties. The efliciency of our process depends upon the essential elements thereof. The first of these is the cracking of the naphthenate soaps, normally resulting from the treatment of naphthenic acid-containing fractions VWith a caustic solution, by treatment of these soaps with a mineral acid such as sulfuric acid, hydrochloric acid or the like to yield a naphthenic acid fraction. This is a necessary element of our invention inasmuch as we have found that the treatment of the alkali metal soaps themselves by the methods described is relatively ineiectual due to the retention in the soaps of the various impurities as above pointed out. The second and related element of our invention 'comprises the purication of these free acids under conditions of comparatively high temperatures and pressures which has the effect of preventing the formation of emulsions during the course of the purification and at the same time providing highly efficient removal of the undesirable constituents. It is therefore, understood that both of these elements are related and in combination with each other constitute the essence of our invention.

We have found that if purification of the crude naphthenic acids is carried out at temperatures in the range of from about F. to about .350 F. and at pressures in the range of about 166 pounds per square inch to about 250 pounds per square inch that emulsions are not formed in the various rening steps set forth hereinbelow. In most cases these pressures may be induced in closed systems by the temperatures employed in the operation due to the vapor pressures of water and other solvents employed but if it is desired to employ pressures in excess of the vapor pressure of the constituents at the temperatures of operation this added pressure may be created by the use of a relatively inert gas such as nitrogen or the like, or by the use of feed pumps and ba-ck-pressure valves as would be understood by those skilled in the art.

Operating under the conditions as above described vve may purify the acids by various methods depending upon the degree of purity desired. The first of these methods involves the treatment of the acid fraction," obtained by acidification of the soaps, with Water at the high tem-- peratures and pressures mentioned to effect the removal therefrom of the residual mineral acid remaining after the acidification. The Water and naphthenic acid phases from this treatment may be then separated by conventional means such as settling orlcentrifuging to yieldl a crude naphthenic acid containing an appreciable Vquantity of residual impurities. If desired, this simple water extraction may be repeated one or more times to insure the complete removal of mineral acid without danger of emulsication. This process does not efiectthe removal oft the various hydrocarbon contaminates but results ina naphthenic acid free of mineral acid and may be simply accomplished, inthe absence of emulsion dif'culties, by carrying on the Water extraction under the conditions of temperature and pres- ;sure disclosed.

If more complete/purification is desired, another and more effective method may be employed which involvesthe dilution of Vthe acids, after splitting of the alkali metal soap, with alight gasoline or naphthafractionboiling below the boiling range of the'naphthenicV acids. Caustic extraction of the gasoline solution of the crude naphthenic acids results in theremoval of the naphthen-ic acids in the form of soaps' leaving a gasoline solution of the oilA kor unsaponiable material originally associated'with the crude' naphthenic acids. The soap phase contains small amounts of dissolved gasoline and extremely small proportions ofthe uns'aponiiia'bles originally present. The ratio'of gasoline to the higher boiling unsaponiable in the soap phase is similar to the corresponding ratio inthe gasoline solution of crude acids. Acidcation of these soaps with mineral acid, separating the aqueous phase containing the alkali metal salt thus formed from the released naphthenic acids andl removing residual salts and mineral acids from the' naphthenic acids by 'water washing results inthe production of a naphthenicacid containing low 'boiling hydrocarbon impurities' (gasoline solvent) which may be separated vtherefrom 'if desired by means of simple fractionaldistillation.

It is important that the dilution and subsequent extraction steps ou'tlined hereabove be carried out at elevated' temperatures and pressures in order to obtain highest eflic'iencies' and more particularly7 to avoid'the 'format-ion of stableemulsions. These operations carried out at ordinary tempera-tures andpressures invariably result in the formation of emulsions whichv fail to stratify even after-long periods of settling.

A third and vprefer-red method/of purification embodies lthe elements -offt'he'above described method With the addition thereto ofthe added step of acid-treating the gasoline diluentenaphthenic acidsolution to remove therefrom the resinous or Aasphaltic impurities'in 'the crude `naphthenic acid'thereby preventing any occlusion of these impurities 'uponY r'esa'ponication 'of the naphthenic acid.

The wide flexibility ofV our invention `may be appreciated from the foregoing description oi some of thetrnethods'of'procedurewhich'may be employed if the two primary elements of the inn vention-are adhered to, namely, the splitting of the alkaline naphthenate soaps' prior to purification andthe-operaton ofthesubsequent puri- ;cation at suii'iciently liigh Xtemperatures and pressures to 'prevent theformation'of diiiicultly separable emulsions vinthe process. Y'Over and above `the flexibility permissible in the 'purication according tothe 'present method Yother advantages 'accrue Twhich' serve to lemphasize the novelty and eifectivenes's 'of 'our' invention. Primary among A'these advantages'is the ability, in the absence' of emulsion diiicultiesjtooperatethe process on a continuouslbasiswhi'ch iscon'siderably more efficient thanbatch-wise methods of puricati'on. `Furthren'weihaveifouridthat we are able to obtain 'acids oi'ahigher degree 'of'purity than are ordinarily obtainable, 'by 'the conventional puricationmethods. Y

The process of this' invention may bemore'iully understood Yby Y'reference 'to v"the accompanying drawing which 'not .only"shows theelements of the invention 'but'f'urther 'illustrates theiiexibility of the process which is susceptible'of"considerable modification depending `upon the desired grade or purity of naphthenic acid.

In the drawingfthe naphtheniciacidecontaining petroleum fraction is juvlitlidrawnvv from storage tankl 0 by means of lin'ef-l Iffeontrolledbyfvalve l2 with the petroleum fraction, the mixture passing through mixing valve I9 into settler 2li. In this manner the naphthenic acids in the petroleum fraction are converted to their corresponding so dium soaps which settle to the bottom of settler 20 the hydrocarbon phases being removed from the upper portion of settler 2l) by means of line 2|. It is understood that the method of extrae'- tion is not a critical feature of our invention inasmuch as any method of recovering the naphthenic acids from fractions in which they are contained may be employed. y

The crude sodium naphthenate is withdrawn from the bottom of settler lill bymeans of'line 22. Sulfuric acid is withdrawn from storage tank 24 by means of line 25 controlled by valve 2t and is pumped by pump 2l into line 22 wherein'it contacts the crude sodium naphtlienate solution, the mixture passing therefrom through line 28 and mixing Valve 29 into heat interchanger Sil. In the interchanger 3B the mixture is heated 'by means of steam or other vapor or liquids introduced into the interchanger by line `3l and removed therefrom byline 32', to a temperature in the range of about 150 F. to 350 F.

The entire operation both prior to and subsequent to the point o heating is carried out under a pressure of from -to 250 pounds per square inch. However, such a-pressure in itself appears to be insufficient to prevent the formation vof emulsions in subsequent stages of the operation but if such pressures of operation are combined with the use of relative high temperaturesfthe emulsion difficulties are overcome.

The mineral acid-naphthenate mixture which at this point has atleast partially reacted-to form sodium sulfate, water and naphthenic 'acids is withdrawn from the interchanger 36 by means of line 33 and is introduced into settler 34 wherein the aqueous sodium sulfate settles to the 'bottom and is drawn ofi' by means of line 35 controlled by valve 3d. The naphthenic acid phase is Withdrawn Ifrom settler 34 by lmeans of line 3l controlled by valves 38 and 39.

Inthe preferred method of Yoperation valve 39 is `closed and the naphthenic acid passesfrom line El through valve 38 into line di?. A light gasoline fraction is withdrawn Yfrom storage'tank i2 by .means of line lcontrolled by yvalve i4 and is pumped by pump 45 into line i6 and is injected together with crude naphthenic acids into settler 46. This hydrocarbon diluent may -be any comparatively low boiling'naphtha such as one boiling below about 350? F. and preferablyvbelow about 300F. This low boiling naphtha has the effect upon solution oi the naphthenie acids therein of diluting the impurities which are contained in the naphthenic acids. Residual water `remaining with the naphthenic acids is Withdrawn from the bottom of settler do by'means of' line lll controlled by valveI 48.

The naphthenic acid-light hydrocarbon solution is Withdrawn from the Atop of settler 46 by means of line 49 controlled byvalve litiA passing therethrough into line 5l controlled* by valves 52 and'53. At this point alternativennethods of procedure may again be followed, in-onemethod the sulfuric acid refining oflthe gasoline-naphthenic acid solution is employed and in the other method the sulfuric acid refining step is bypassed. I-.f'valve 52 is closed the"gasoline-naplithentic acid solution is passed through valve 53 into line 54. sulfuricr acid is Ywithdrawn'jfror'n storage tanlrlf `bymeans'of line v7.51, controlled byivalyejdand -is-"pumped by pumpP-*Sllrthrough line=` lillv intolline 54 and is passed together with the gasolinenaphtenic acid solution into settler 62. The sulfuric acid employed in the initial phase of the process to acidify the sodium naphthenate soaps and the sulfuric acid employed at this point of the operation may be of the same or diierent concentrations; that is, the reiining process as carried out on the light hydrocarbon-naphthenic acid solution requires an acid of high concentration such as approximately 75 or higher, whereas, the acid employed in the cracking of the soaps may even be less concentrated such as in the range of 50% to 90% or higher.

In settler 62 a phase separation takes place between the sulfuric acid sludge and the hydrocarbon solution of naphthenic acids. The acid sludge phase will contain the resinous and asphaltic impurities originally contained in the naphthenic acid leaving in the gasoline solution only the high boiling hydrocarbon impurities. The acid sludge is removed from the bottom of settler 62 by means of line 63 controlled by valve 65. The acid-treated gasoline-naphthenic acid solution is withdrawn from the top of settler E2 by means of line E5 :controlled by valve Se and is passed via line $1 into centrifuge 68. In

centrifuge 68 the residual sludge is separated from the hydrocarbon-naphthenic acid solution and is removed from the centrifuge by means of line 69.

The centrifuged naphthenic acid-hydrocarbon solution is withdrawn from centrifuge 88 by means of line l controlled by valve and is passed into line 12. It is at this point in the process that the eiuent from settler 46 may be introduced if it is desired to bypass the sulfuric acid refining step. This is accomplished by closing valve 53 and opening valve 52 allowing the hydrocarbon-naphthemc acid solution from settler 46 to pass via line 13 controlled by valve 1d into line T2. Irrespective of which of these streams is to he treated caustic is withdrawn from tank I5 by means of line 15 controlled by valve 76 and is pumped by pump `i`| Via line 18 and is commingled with the hydrocarbon-naphthenic acid solution in line 'I9 passing into settler 83. At this point the naphthenic acids are resaponiied and the impurities retained in the soap solution :constitute essentially light hydrocarbons which have replaced the major proportion of the heavier hydrocarbon impurities. The light hydrocarbon phase containing the major proportion of heavier hydrocarbon impurities originally present in the naphthentic acid is withdrawn from the top of settler 8i) by means of line 8| controlled by valve 82 and is passed via line 83 back to the light gasoline storage tank 42. Because of the relatively small amount of heavier hydrocarbons in the naphthenic acid as compared to the amount of diiuent employed and consequently the relatively small amount in the light diluent it may be reemployed in the process with only occasional redistillation to effect the removal of accumulated heavy hydrocarbons.

The naphthenic soaps, containing as impurities predominately light hydrocarbons are withdrawn from the bottom of settler 89 by means of line 8d and are passed Vinto line 89. Sulfuric acid is withdrawn from storage tank 24 by means of line controlled by valve Se and is pumped by 1 p E? via line S8 into line 39 mixing therein the naphthenate soaps from settler 80. This mixture is passed into settler 9i) wherein, as in settler 3d, the aqueous sodium-sulfate solution separates from the naphtenic acid phase and is withdrawn from the bottom of the settler by means of line 9 |,controlled by valve 92.

The naphthenic acids are lWithdrawn from the settler 98 by means of line 93 controlled by Valves 94, 95 and 95. It is at this point in the process that the crude naphthenic acids taken overhead from settler 34 may be introduced, thereby bypassing the treatment with light hydrocarbon, sulfuric acid refining, resaponilcation, and acidiioation of the resaponied soaps. Of this bypassing is employed the process is considerably simplified but the purity of the final product is reduced.

Two alternative procedures are again available at this stage of the operation. In the simplest of these the naphthenic acids may be passed directly through valve 96 via line 98 through valve 99 and via line |00 into centrifuge |98. Alternatively the acids may be passed through valve 94 via line |0| into interchanger |02 to increase the temperature thereof7 from interchanger |02 into line |05 wherein water is introduced into the acids by means ,of line |66. This water-acid mixture is passed from line |5 through valve |01 into centrifuge |08. The combination of the addition of water to the acids and the heating thereof in the interchanger may be substituted by the direct addition of steam into the acid accomplishing both purposes simultaneously. The water wash at this point is designed to insure the'complete removal of mineral acid employed in the resapunification.

In centrifuge |08 the acids are separated from residual Water and mineral acid Which are removed from the centrifuge by line W9.

The naphthenic acids are Withdrawn from the centrifuge |68 by means of line ||0 and may be passed directly through valve ||2, line H3, valve Hd, and line 5 into storage tank ||6. If this procedure is employed the finished acids will contain as impurities small amounts of light hydrocarbons. However, still further purification may be effected by passing the acids from line through valve into preheater from which they are passed via line I8 into fractionator |20. In fractionator |28 the light hydrocarbon impurities are distilled overhead being withdrawn from the fractionator by means 4of line |2| controlled by valve |22 and are passed into storage tank |24. Naphthenic acids, freed of the light hydrocarbon are obtained as a side cut in the distillation being withdrawn from the column by means of line controlled by valve |26 passing through line ||5 into a finished acid storage tank IIB. The bottoms from the distillation consisting of polymeric substances and high molecular Weight acidic fractions are withdrawn by means of line |21 controlled by valve |28. Alternatively this fractionation may be effected in such a manner that gasoline is obtained as the overhead distillate and the naphthenic acids as the bottoms fraction.

The following specific examples are presented to further illustrate our invention but are not to be considered as limiting the broader aspects of the invention:

Example I acid in a closed system at a pressure of 100 pounds per square inch, the mixture was heated to about 200- F. and passed intoI a settler maintained at the same pressurein Which-the crude naphthenic acidsfwere separated; from the aqueous sodium sulfate solution. The naphthenic acidphase was washed with watertoremove. mineral acid and again settled to separate the Water. The crude acids thus produced-had an acid number of about 175 mg. KOH/g.

In order to determine the quantity of oil or unsaponiable. matterassociatedwithA the naphthenic acids in the crude acid mixture, a 20-gram sample of the crude acids was converted into sodium soaps by neutralization to the phenolphthalein end. point With 2% NaOH solution and the dilute soap solution thus obtained was extracted Withtwo 50;-ml. portions. of ethyl ether. The ether extractedV soap solution was acidiiied withV sulfuric acid and the resulting naphthenic acids Washed with Water. These acids which Were substantially free from unsaponiable material had an acid number of 235 mg. KQH/g. The proportion of unsaponiable material in the original crude acids calculated from the increase inA acid number after. deoilingwas 25.5%.

For purposes of comparison a second ZO-grani sample. of theY crude acids Was neutralized with 2% caustic solution and the resulting,r dilute soap solution Was extracted-with two 50 mi. portions of a petroleum naphtha boiling in the range of about 150 F. to 250 Fr andthe extracted soap solution was acidied toV .obtain thev naphthenic acids. These acids, after Water Washing to remove mineral acid and water soluble salts, had an acid number of 200 mg. KOH/g. Extraction of soap solution with the petroleum naphtha removed approximately 12;5%.byweight oan unsaponiable material or about 49 %fby Weight .of the unsaponiliable material originally presentl as calculated from the acid number increase obtained by ethyl ether extraction.

Another sample of the crude acids` was distilled to produce an overhead amounting to` 5% by Weight of the crude acids of an oilhaving an acid number of mg. KOH/g. and a bottoms fraction amounting to 95% by- Weight of the crude acids 45 having an acid number of l1783 lmg.V KOH/g.

Example II A portion of the crude naphthenic acids described in Example I was diluted with six volumes of a petroleum naphtha boiling in the range of about 150 F. to about250 F. and the diluted acids, under a pressure of about 100 pounds per square inch and ata temperature of about 225 F., Were contacted With a dilute caustic solution containing about 2% by Weight of NaOH. The resulting soap solution being maintained under a pressure of 100 poundsper squareV inch was heated to 225 F., acidied With 80% sulfuric acid to 30 liberate the naphthenic acids-and the mixture allowed to separate. The liberated naphthenic acids were Washed with hot WaterY to remove mineral acid and centrifuged to remove substantially all of the Water. These acids had an acid number 65 of 180 mg. KOH/g. A portion ofthe acids thus produced was vdistilledto produce as overhead distillate a naphtha fraction amounting to 21.5% by Weight of the distillation charge having an acid numbergof l1.5. mg. KOH/g. and a bottoms 70 fraction having an acid number of 229 Ing. KOH/g. Calculations based on acid number determinations indicated that the naphthenic acids produced in this manner contained approximately 2.5% by Weight of unsaponiable matter.

1oM Example H1.

A portion of the crude naphthenic `acids described in Example I" were diluted With six volumes of a` petroleum naphtha boiling in the range of about 150' F. to. 250' F. and the diluted acids, under a pressure of about 100 pounds per square inch and at a temperature of about 18.0k F., were contacted with 10% by weight, based on the crude naphthenic acids,v of 85% of H2504 and the mixture passed to a settler Where the acid sludge phase produced bythe acid contacting was separated from the treated gasoline solution of acids. The treated. solution was passed to a centrifuge WhereI Vsubstantially all of the remaining sludge was removed and the centriiuged gasoline solution of` treated acids at a temperature of 200 F; and under a pressure ci 100 pounds per square inch was contacted With a dilute caustic solution. containing about 2% by weight of NaOH to convelftthe acids into their sodium soaps. The resulting soap solution being maintained under a pressure of 10.0. pounds Y per square inch was heated to 225 F. and acidifled with sulfuric acid to liberate naphthenic acids. The liberated naphthenic acids were Washed with hotl Water to remove mineral acid and water-soluble salts and then centrifuged to remove substantially all of the water. These naphthenic acids had` an acid number of mg. KOH/g. A portion. of the acids thus produced was distilled to produce as overhead distillate a naphthenic fraction. amounting to 21.0% by Weight of the distillation charge having an acid number of 2 mg. KOH/g, and a bottoms fraction having an acid number. of 234. mg. KOH/g.

In order to determnethe proportion of urlsaponiable..material present in. the acids produced in the above process. a 2li-gram sample of the reiined acids. having an acid-number of 234 mg. KOH/g. was converted'into sodium naphthenate by neutralization to, thephenolphthalein end point with 2% NaOHof solution and the dilute soap solution. thus obtained Was extracted with two 50 ml. portionsoi. ethyl ether. The ether extracted soap solution was acidified with sulfuric acid and theresulting naphthenic acids Washed with Water to remove mineral acid and 50 water soluble salts and finally dried. The puriiied acids had an acidnumbei` of 238mg. KOH/g. On the basis of acid number increasethe refined acids were indicated to contain1.75% by Weight of unsaponifiable material. Y

Having described and illustrated the essential elements' of our invention Y and realizing that many modifications may occur to those skilled in the art without .departing from the principal elements thereof which comprise essentially the recovery and puriiicationv of naphthenic acid fractions at elevated temperatures and pressures, We claim: v-

1. A method of recovering naphthenic acids comprising the steps of (1) contacting a petroleum fraction containing said naphthenic acids with an aqueous solution ofV a basic alkali metal compound thereby forming the alkali metal soap of said naphthenic acid; (2) separating the aqueous soap solution from said. petroleum fraction, (3) acidifying .said soap solution fwith a suiiicient quantity of a vminerai acid to convert said soap into naphthenic acids, (4) separating said naphthenic acids from the aqueous salt solution formed in the acidification step, (5) diluting said naphthenic acids with a hydrocarbon solvent,

(6) contacting said hydrocarbon solvent solution of naphthenic acid with an aqueous solution of a basic alkali metal compound thereby reforming the alkali metal soap of said naphthenic acids, (7) separating the aqueous soap solution from said petroleum fraction, (8) acidifying said soap solution with a suicient quantity of a mineral acid to convert said soaps into naphthenic acids and (9) separating said naphthenic acids from the aqueous salt solution formed in the acidification step, said aforesaid steps 3 to 9 inclusive being eiected in a continuous manner at a pressure greater than about 100 pounds per square inch and at a temperature above about 150 F.

2. A method of recovering naphthenic acids according to claim 1 in which steps 3 to 9 inclusive are carried out at a temperature in the range of about 150 F. to about 350 F. and at a pressure in the range of about 100 pounds to about 250 .pounds per square inch.

3. A method of recovering naphthenic acids according to claim 1 in which the basic alkali metal compounds is sodium hydroxide.

4. A method of recovering naphthenic acids according to claim 1 in which the hydrocarbon solvent boils in the range of about 100 F. to about 400 F.

5. A method of recovering naphthenic acids comprising the steps of (1) contacting a petroleum fraction containing said naphthenic acids with an aqueous solution of a basic alkali metal compound thereby forming the alkali metal soap of said naphthenic acids, (2) separating the aqueous soap solution from said petroleum fraction, (3) .acidifying said soap solution with a sumcient quantity of a mineral acid to convert said soaps into naphthenic acids, (4) separating said naphthenic acids from the aqueous salt solution formed in the acidification step, (5) diluting said separated naphthenic acids with a major proportion of a hydrocarbon solvent, (6) treating the resultant hydrocarbon solvent solution of naphthenic acid with sulfuric acid, (7) separating the acid sludge from said solution of naphthenic acid, (8) contacting said solution of naphthenic acid with an aqueous solution of a basic alkali metal compound thereby reforming the alkali metal soap of said naphthenic acid, (9) separating the aqueous soap solution from the hydrocarbon solvent, (10) acidifying said soap solution with a sufficient quantity of a mineral acid to convert said soaps into naphthenic acids, and (11) separating said naphthenic acids from the aqueous salt solution formed in the acidication step, said aforesaid steps 3 to 11 inclusive being effected in a continuous manner at a pressure greater than about 100 pounds per inch and at a temperature above about 6. A method of recovering naphthenic acids according to claim 5 in which steps 3 to 11 inclusive are carried out at a temperature in the range of about 150 F. to about 350 F. and at a pressure in the range of about 100 pounds to about 250 pounds per square inch.

7. A methodof recovering naphthenic acids according to claim 5 in which the basic alkali metal salt is sodium hydroxide.

8. A method of recovering naphthenic acids according to claim 5 in which the hydrocarbon solvent boils in the range of about 100 F. to about 400 F.

9. A method of recovering naphthenic acids comprising the steps of (1) contacting a petroleum fraction containing said napthenic acids with an aqueous solution of a basic alkali metal compound thereby forming the alkali metal soap of said naphthenic acids, (2) separating the aqueous soap solution from said petroleum fraction, (3) acidifying said soap solution with a suicient quantity of a mineral acid to convert said soaps into naphthenic acids, (4) separating said naphthenic acids from the aqueous salt solution formed in the acidification step, (5) diluting said separated naphthenic acids with a hydrocarbon solvent, (6) treating the resultant hydrocarbon solvent-naphthenic acid solution with sulfuric acid, (7) separating the acid sludge from said hydrocarbon solvent-naphthenic acid solution, (8) contacting said hydrocarbon solvent-naphthenic acid solution with an aqueous solution of a basic alkali metal compound thereby reforming the alkali metal soap of said naphthenic acid, (9) separating the aqueous soap solution from the hydrocarbon solvent, (10) acidifying said soap solution With a sufficient quantity of a mineral acid to convert said soaps into naphthenic acids, (11) separating said naphthenic acids from the aqueous salt solution formed in the acidification step, said aforesaid steps 3 to 11 inclusive being effected in a continuous manner at a pressure greater than about 100 pounds per square inch and at a temperature above about 150 F. and thereafter heating said naphthenic acids to remove therefrom residual light hydrocarbon solvent.

10. A method of recovering naphthenic acids according to claim 9 in which steps 3 to 11 inclusive are carried out at a temperature in the range of about 150 F. to about 350 F. and at a pressure in the range of about pounds to about 250 pounds per square inch.

l1. A method of recovering naphthenic acids according to claim 9 in which the basic alkali metal salt is sodium hydroxide.

12. A method of recovering napl'lthenic acids according to claim 9 in which the hydrocarbon solvent boils in the range of about 100 F. to about 400 F.

HOOPER LINFORD. WILLIAM J. BARAL.

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

UNITED STATES PA'I'ENTs OTHER REFERENCES Kalichevsky- Stagner, Cheml Refining of Petroleum, ACS Monograph #63 (1942), page 166.

Koetschau, Chem. Abst., vol. 13, pages 2757- 2753 (1919). (Copies in Scientific Library.)

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