US2301528A - Purification of naphthenic acids - Google Patents

Description

Nov. 10, 1942. 'F J. EyvlN'c;n

y PURIFIGATION OFVNAPHTHENIC ACIDS Filed July 2, 1955 Patented Nov. 10, 1942 UNITED STATES PATENT OFFICE PURIFICATION OF NAPHTHENIC ACIDS Frederick J. Ewing, Pasadena, Calif.,.assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application July 2, 1935,Serial No. 29,495

8 Claims. (C1. 26o- 514) This invention relates to a process for the purification of naphthenic acids.

Crude naphthenic acids, obtained from alkaline sludges arising during the reiining of petroleum fractions, shale oil fractions, coal tar and its fractions or those obtained by synthesis (for instance by oxidation of liquid, gaseous or solid hydrocarbons) all contain various constituents which tend to detract from their commercial value. Therefore, in order to produce naphthenic acids of high market value, it is necessary to remove these impurities therefrom.

Processes are known which relate to the removal of phenols from naphthenic acids after both have been liberated simultaneously from the various alkaline residues arising in the refining of petroleum fractions. However, in these no provisions are made for the removal of the impurities hereinafter mentioned from the phenol-free naphthenic acids.

Th'e impurities which are oftentimes associated with naphthenic acids and which impair their value are asphalt like substances such as carbonaceous materials, bitumens, asphalt; hydroxycarboxylic acids or other hydroxy-acids, wax and Wax-like bodies and various color-forming bodies of yet unknown composition and structure. It should be obvious that all of these impurities need not all be present in the impure naphthenic acids at any one time as the number and amounts thereof are usually in some manner related to the particular stock from which the naphthenic acids are produced and the manner of isolation thereof.

In any event, no matter which one or ones of the particular impurities are present in the naphn thenic acids, they will unfavorably influence their commercial desirability especially in regards to color, odor, viscosity or their use for the manufacture of driers, siccatives, cosmetics or the like.

The term naphthenic acids used herein is intended to be generic and not limited to any particular kind of naphthenic acids or to naphthenic acids derived from any particular crude material or by any specific methods of isolation from various media in which they are normally encountered.

I have discovered that naphthenic acids containing impurities such as the asphalt-like substances, exemplied by carbonaceous materials, bitumens and asphalts; hydroxy-acids, wax and Wax-like bodies, color forming bodies and the like or mixtures of these impurities, may be `separated therefrom by the use of certain diluent solvents in which the naphthenic acids are readily soluble but in Which the impurities are substantially insoluble. Hence, by commingling crude naphthenic acids with a suitable portion or suitable portions of a solvent in which the naphthenic acids are soluble but toward which the impurities show only a limited solubility, I am able to separate the various above enumerated impurities from the crude or impure naphthenic acids and obtain a product of desirable characteristics such as light color, bland odor, absence of cloudiness, high acid number etc,

The solvents which I may employ for the separation of the foregoing impurities from naphthenic acids include such materials as petroleum naphtha, petroleum ether (a light paraflinic petroleum distillate h'aving a specific gravity between 0.685 and 0.650) natural gasoline, liquid aliphatic hydrocarbon such as liquid ethane, liquid ethylene, liquid propane, liquid propylene, liquid butane, liquid isobutane, pentane, hexane or mixtures of these hydrocarbons which mayor may not include methane.

I prefer to use as a diluent solvent for the separation of the foregoing impurities fromcrude naphthenic acids, light hydrocarbons which are normally vaporous at ordinary temperatures and pressures. These hydrocarbons include methane, ethane, ethylene, propane, propylene, butane and isobutane or mixtures thereof. Excellent results are also obtainable when using a diluent solvent consisting substantially only of propane. This solvent is a liquid at a temperature of '72 F. when maintained under a pressure of about 125 lbs. It has a boiling point of approximately 40 F.

The liquefied normally gaseous hydrocarbons are preferable over ordinary low boiling petroleum `distillates such as benzine, ligroin or the like because they are capable of separating 'substantial amounts of impurities from crude naphthenic acids, not removable therefrom with the above mentioned low boiling petroleum distillates. It is entirely possible to obtain a substantially pure naphth'enic acid product by treating crude naphthenic acids with a liquefied normally gaseous hydrocarbon only, without further treatment,

while in the use of a low boiling petroleum distillate sufcient amounts of impurities are carried over into the refined naphthenic acids to require a subsequent chemical treatment thereof for the purpose of removing the eolorgiving bodies and other impurities which were not removed by the above mentioned petroleum distillates. ,l

Inl the separation of the foregoing impurities from crude naphthenic acid the crude stock is,V

commingled with one of the foregoing solvents and the naphthenic acids present in the crude stock dissolve in the solvent while the impurities remain undissolved. This mixture may then be settled, filtered or centrifuged to separate the solvent solution of naphthenic acids from the undissolved impurities.

When I employ liquefied normally gaseous hydrocarbons, such as propane, for the separation of impurities from crude naphthenic acid, I find that the best separation occurs when I employ about 1 to 3 volumes of the liquefied normally gaseous hydrocarbon to one volume of the crude naphthenic acids. For example, when one volume of the crude naphthenic acids is commingled with two volumes of liquid propane under pressure and at a temperature of about '70 F., I find that the naphthenic acids are soluble in the liquid propane but the impurities such as the asphalt-like substances comprising carbonaceous materials, bitumen, asphalt; hydroxy acids and color bodies are substantially insoluble therein. If this mixture of crude naphthenic acids with liquid propane is settled, filtered or centrifuged, I am able to separate the major portion of the impurities from the naphthenic acids dissolved in the'liquid propane.

As a means of further refining the acids after the initial separation of impurities with solvents, I may employ chemical reagents and I find that such a chemical treating step is much more effective and complete if carried out in the presence of' the cliluent which I employ for the initial separation of the impurities present in the crude naphthenic acids. For example, the crude naphthenic acids may be extracted with a liquefied normally gaseous hydrocarbon, such as propane, `for the separation of a major portion of the impurities present, in the manner above described, whereupon the naphthenic acids dissolved in the liquefied normally gaseous hydrocarbon may be further purified by means of a chemical treatment. This treatment may comprise the use of reagents such as sulphuric acid, chlorio acid, bromic acid, iodio acid, hydroiodic acid, nitric acid, chlorsulphonic acid, nitrosulphonio acid, phosphoric acid, decolorizing agents such as fullers earth or diatomaceous earth, acid activated decolorizing earths such as Filtrol (fullers earth activated with dilute sulphuric acid) or metallic halides such as aluminum chloride, zinc chloride or iron chloride. The result of such a chemical treat may be said to reside in further improving the odor and color of the naphthenic acids.

In some cases the crude naphthenic acids may not contain a sufiicient quantity of impurities to obtain an initial separation thereof with the above-mentioned solvents, in which caseit may only be necessary to employ the chemical treatment of the crude naphthenic acid stock in the presence of the solvent. For example, the crude naphthenic acid stock may be dissolved directly in one of the foregoing solvents, for example a liquefied normally gaseous hydrocarbon such as propane and directly treated with one or all of the foregoing reagents such as acid, clay or metallic halides or mixtures thereof. These reagents and their associated impurities may then be separated from the naphthenic acids dissolved in or diluted with the solvent by such means as settling, centrifuging or filtering.

In the foregoing description I have described the use of diluents at ordinary temperature for the separation of oarbonaceous material, bitumens, asphalts, hydroxy-acids and color bodies from crude naphthenic acids. In some cases I find that these impurities are more effectively separated from the crude naphthenic acids by the use of the foregoing solvents at low temperatures. For example, in some cases I may extract the crude naphthenic acid with cnc of these solvents within the temperature range of |l0 F. to 40 F. and at these lowered temperatures obtain a more complete separation of the impurities from the crude naphthenic acids.

In case the crude naphthenic acids are extracted with a liquefied normally gaseous hydrocarbon, the lowered temperature may be obtained by vaporizing a portion thereof under reduced pressure from the mixture. For example, the crude naphthenic acids may be diluted with 3 to 5 volumes of a liquefied normally gaseous hydrocarbon, such as propane, and a portion of the propane may be vaporized under reduced pressure to chill the mixture. The propane solution of naphthenic acids may thus be separated from the undissolved impurities by settling, filtration or centrifuging. In case excessive amounts of the liquefied normally gaseous lhydrocarbon have been removed by vaporizing, I may add supplementary amounts of these hydrocarbons preferably pre-cooled to the desired temperature.

Furthermore, in some cases I find that the chemical treatment of the crude naphthenic acids may be effectively carired out at low temperatures. For example, the naphthenic acids diluted with one of the foregoing liquefied normally gaseous hydrocarbon solvents may be treated with such materials as sulphuric acid, hydrochloric acid, nitric acid, or any of the other acids enumerated above, or metallic halides at temperatures ranging from -}-l0 F. to 40 F. for the separation of the impurities present therein. Where chemical treatment is employed, the saturated aliphatic diluents such as propane should be used in preference to unsaturated aliphatics such as ethylene, as the latter tend to react with various chemicals such as sulphuric acid to form polymerized products which would hinder or counteract the purification of the dissolved naphthenic acids.

In the separation of the asphalt-like substances (carbonaceous material, bitumen, and asphalt) hydroxy-acids and color bodies from crude naphthenic acids, it may also be found advantageous to employ stage separation. For example, the crude naphthenic acids may be commingled at about Y0-80 F. with. a liquefied normally gaseous hydrocarbon and the hydrocarbon solution of naphthenic acids may then be separated from the undissolved impurities. This solution of naphthenic acids in the liquefied normally gaseous hydrocarbon may then be cooled in successive stages for the separation of a further quantity of impurities and the impurities separated at the lowered temperatures may then be removed from the cooled solution of naphthenic acids dissolved in the liquefied normally gaseous hydrocarbon.

In addition to the above-mentioned impurities, crude naphthenic acids may also contain solid, wax-like acids which tend, under normal conditions of temperature to crystallize out of the purified naphthenic acids unless steps are taken for their removal. The presence of these solid acids tends to raise the cloud point and pour point of the naphthenic acids. These wax-like acids are probably high molecular weight aliphatic acids, although I do not wish to be limited by any such theory. Their removal from naphthenic acids by chilling and filtering is tedious and wasteful due to the high viscosity and slimy quality of the naphthenic acids and waxy material at low temperatures. However, these solid acids may be readily removed from naphthenic acids containing them by dissolving the crude stock in a solvent such as a liquefied normally gaseous hydrocarbon and cooling the solution. They may then be removed in an expedient manner from the solvent solution of the naphthenic acids by iiltering, settling or centrifuging.

In want of a better term to designate these wax-like solid acids, I have chosen to call them wax although strictly speaking they are not analogous to or comparable with the solid parafn hydrocarbons usually designated by that name. I have also discovered that naphthenic acids may be separated from crude naphthenic acids containing asphalt-like impurities as carbonaceous material, asphalt, bitumen; hydroxyacids or color bodies, by leaching or extracting the crude stock at low temperature with light hydrocarbon solvents such as naphtha, casinghead gasoline, liquid propane, liquid ethane, liquid butane or mixtures thereof or mixtures of similar hydrocarbons. For example, I may commingle the crude naphthenic acid stock with liquid propane at a temperature ranging from F. to -40 F'. and at the lowered temperature the naphthenic acids dissolve in the solvent while the impurities remain undissolved. The solvent solution of naphthenic acids may then be separated from the undissolved impurities by filtering, settling or centriiuging, or by other conventional means.

It is therefore an object of this invention to separate naphthenic acids from crude naphthenic acid stock containing asphalt-like impurities such as carbonaceous materials, bitumens and asphalt; hydroxy-acids, color bodies or waxes or mixtures of these impurities, and in doing so obtain a naphthenic acid product possessing improved characteristics in regard to odor, color, viscosity and pour point.

It is another object of this invention to separate impurities contained in crude naphthenic acids by means of solvents in which the naphthenic acids are soluble and in which the impurities are substantially insoluble.

It is another object of this invention to extract crude naphthenic acids containing impurities with solvents in which the naphthenic acids are substantially soluble and in which the impurities are substantially insoluble, separate the solvent solution of naphthenic acids from the bulk of the insoluble impurities and further reiine the solvent solution of naphthenic acids with reagents such as mineral acids, decolorizing clay or metallic halides or with -mixtures of these reagents.

Other objects of my invention will be apparent from the description covering the various features of my process.

The process of this invention may be more fully understood by reference to the accompanying ligure which represents a preferred embodiment thereof. Referring to the drawing, crude naphthenic acid stock in tank I is withdrawn through valve 2 and passed by means of pump 3 through line 4 where it is commingled with liquid propane containing a small amount of dissolved naphthenic acids. The mixture in line 4 then passes to mixer or agitator 5 where thorough mixing of the crude naphthenic acid and liquid propane takes place. The mixture in agitator 5 then passes via line 6 to decanter 'l where it is settled.

The insoluble impurities ln decanter 1 settle to 75 the bottom thereof and are withdrawn through valve 8 and line 9 to agitator or mixing coil I0 where the insoluble impurities are commingled with liquid propane Withdrawn from tank I5 through valve I6, pump I1 and line I8. After thorough agitation of the mixture in agitating coil I0 it passes into separator II where the insoluble impurities such as carbonaceous material, asphalt, bitumens (asphalt-like substances), hydroxy-acids or color bodies or mixtures of these impurities settle to the bottom of the decanter and are withdrawn through valve I2 and line I3. The overflow from decanter II consisting of liquid propane and a small quantity of dissolved naphthenic acid is withdrawn through line I4 and returned to line 4 as explained above.

The overflow from decanter 1 consisting of naphthenic acids dissolved in the liquid propane is withdrawn through line I9, provided with pump 20.

In case the naphthenic acids contain impurities which are not eliminated by the preceding treatment, it may be further reiined for the removal of the remainder of the impurities. For example, the overiiow from decanter 'I which is withdrawn through line I9 may be passed by pump 20 through line 24 to mixing coil 58 where it is mixed with a rening agent such as sulphuric acid, nitric acid, phosphoric acid, chlcric acid, iodio acid, bromic acid, stored in tank 2| and withdrawn through valve 22, pump 23 and line 6I into mixing coil 58. The refining agent introduced into mixing coil 58 may also comprise such materials 'as aluminum chloride, zinc chloride, iron chloride or decolorizing clay such as fullers earth or diatomaceous earth, Filtrol or the like.

The mixture in mixing coil 58 comprising the refining agent commingled with the propane solution of naphthenic acid, then passes to decanter 25 where the rening agent and its associated impurities settle to the bottom of the decanter and are removed through valve 26 and line 21. The chemically treated naphthenic acids dissolved in the liquid propane and free from the refining agent and associated impurities are Withdrawn from the top of the decanter 25 through valve 28 and line 29.

In case the crude naphthenic acid contains Wax or wax-like bodies the treatment which has been so far described. with respect to the gure, will not completely remove these waxes or wax-like bodies. For the removal of the Wax, the propane solution of naphthenic acids in line 29 passes by means of pump 30, line 33 and valves 55 and 69 into chiller 34 Where the temperature of the pro-v pane solution may be reduced to a suiiicient degree to cause the wax present in the propane solution to precipitate. The cooling of the propane solution in chiller 34 may be produced by means of cooling coils inserted in Chiller 34 (not indicated in the drawing) but is most conveniently produced by allowing a, portion of the propane to vaporize under reduced pressure from chiller 34 by opening valve 35. The degree of cooling necessary in chiller 34 will depend upon the stock being treated and any temperature from -{-l0 F. to 40 F. may be attained by merely opening valve 35 and allowing the propane to evaporate from the solution under reduced pressure. If desired, additional liquid propane may be introduced into chiller 34 to supply the necessary reirigeration and the proper dilution of the chilled mass in chiller 34 for eicient separation of the wax from the propane solution of naphthenic acid. The introduction of this make up propane is more or less optional and the means forl doing this have not been indicated in the drawing.

rThe propane vapors removed from chiller 34 through valve 35 pass through line 36 to compressor 31 where they are compressed and then pass via line 38 to cooler or condenser 60 where they are liqueed and thence to storage tank I5, via line 62 and valve 63.

The cooled lmass in `chiller 34 is withdrawn through valve 64 into line 40 and sent by means of pump 4I and line l2 through lter 43 where the precipitated wax is removed from the propane solution of naphthenic aci-d. The wax is withdrawn from lter 43 through line 4.1 and valve 55 and the propane solution of dewaxed naph'thenic acids pas-ses from the lter through line 45, valve 46, line 41 to pump 48 which forces this solution through line 49 into evaporator 50 where the liquid propane is removed from the naphthenio acid. Evaporator 50 is supplied with heating coils I which vaporize the propane. The propane vapors are withdrawn from evaporator dal through valve 55 and pass via line 56 to compressor 5l Where the vapors are compressed and pass via line 38 to cooler SII where they are liqueed and are returned to storage tank I5. The wax recovered from lter 4'3 is relatively free from asphalt-like bodies as these impurities have been eliminated by the prior solvent treatment and/or chemical treatment.

The purified naphthenic acids are Withdrawn from evaporator 50 through valve 52 and line 53 into rened naphthenic storage 54.

In some cases I find that the Wax may be more readily separated from the naphthenic acids by the use of iilter aid. The lter aid may be introduced into the propane solution of naphthenic acids containing wax by means of line 3| and valve 32 into line 33. After the solution of naphthenic acids containing the lter aid in Chiller 3:1 has been cooled sufliciently to precipitate the wax, the chilled mass in chiller 34 is then passed through Iilter 43 for removal of the wax and filter aid from the propane solution of naphthenic acid. As filter aids I may use keiselguhr, sawdust, diatomaceous earth, fullers earth or clay.

As has been explained above, I find that many naphthenic acid stocks contain wax which separates from the acid in solid form at ordinary temperature or slightly reduced temperature after certain of the impurities present in the crude naphthenic acid have been removed. Thus, if the solvent treatment and/or chemical treatment has removed substantially all of the impurities in the crude naphthenic acids other than the Wax, the latter will separate from the naphthenic acid without any substantial reduction in temperature.

Where the solvent treatment and/or chemical treatment has removed suicient of the impurities to permit separation or precipitation of the wax from the naphthenic acid at ordinary ternperature, chiller 3J. may be eliminated or employed only to produce a slight reduction in the temperature of the solution to cause separation of the Wax from the naphthenic acids.

Furthermore, as has been explained above, my process may be operated in such a manner that the wax may be removed simultaneously with any or all of the other impurities mentioned herein. In such instances the crude naphthenic acid stock in tank I is commingled with .liquid propane from tank I-5 at ordinary temperatures while the temperature in mixing coils 5 and. I0 and in decanters 'I and I I is maintained at suiiciently low temperature (for instance between +10 F. and -40 F.) to cause 'the wax to be separated together with the other impurities present in the crude naphthenic acids. These low temperatures may be created by surrounding mixing coils 5 and It] with cooling jackets through which cooled brine is allowed to circulate or into which liqueed propane may be introduced and allowed to evaporate. I may also provide cooling of the mixture of crude naphthenic acids and propane (or similar liqueed normally gaseous hydrocarbon) by allowing a portion of the propane present in decanter I to vaporize, the vapors escaping through line 61 provided with valve 65. The vapors in line 61 are passed into the suction side of compressor 68 which compresses them and causes their introduction into line 38 Where they are commingled with the propane vapors already present therein and pass into cooler 6E! and subsequently into propane storage I5. The Wax will then be eliminated along with the other impurities from4 decanter III through line I3 provided with valve I2. If desired, the wax which is acidic in nature may be separated from the asphaltic materials precipitated therewith by extraction with an alkaline material such as sodium hydroxide which will selec-tively remove the wax (in the form of salts) from the asphaltic materials. The acids contained in the wax may be liberated from these salts by means of aninorganic acid.

As a modication of the wax removal process above described, I may commingle the crude naphthenic acids with a solvent at a temperature suiciently low to prevent solution of the wax and thus simultaneously remove the wax and other impurities which are insoluble in the solvent employed. For example, I may cool the liquid propane or other solvent in lines I4 and/or I8 to a suitable low temperature (-I-10 F. to 40 F.) before com-mingling it with the crude naphthenic acids withdrawn from tank I. In such instance, the decantate in line I9 will be substantially wax-free as the wax Will have been eliminated from the bottom of decanter II through valve I2 and line I3. The naphthenic acids dissolved in the solvent present in line I9 may be further puried with chemical reagents in the remaining stages of the process. The Wax removal after the chemical treatment or treatment with the adsorbent materials or after a combination of these two treatments, may be eliminated if desired, as most of the wax has been removed in decanter I I In case it is desirable to carry out the chemical treatment at a reduced temperature (not sufficiently low to cause Wax separation) I may vaporize only suiiicient propane from decanter 'I to create such a temperature without causing wax separation, or I may altogether eliminate the vaporization in decanter 'I and provide suitable heat exchangers in line I9 (not indicated in the drawing).

It has been found preferable in most instances to subject the dissolved naphthenic acids to a treatment with an absorbent material subsequent to the chemical treatment thereof, previously described. Referring to the drawing, this adsorbent treatment may be carried out by providing an adsorbent storage tank IIJ capable of discharging suitable amounts of the adsorbent via line 12, screw conveyor 82, line 83 and valve 'Il into the amounts of the chemicals remaining in the naph-l thenic acids after chemical treatment, are removed from the bottom of agitator via line 8S and valve 1S. Small amounts of the solvent adhering to the spent adsorbent'I may be recovered by heating it in a heating vessel (not shown)v and: passing the vapors so liberated to one of the Vapor gathering lines 61, 38, 36 or 55.

i The decantate from agitator l5 (after the agitation has stopped) passesfvia line 'H and valve 18 intol Chiller 34 whereupon it may be chilled for dewaxing purposes in the manner previously described. .If small amounts of adsorbentv are carried over into chiller 34 they will serve as de# waxing aids during the dewaxing operations. Suitable settling means (notshown) in which any adsorbent carried over from agitator 15 may be removed, may be provided 'in line 11, if so desired. Valve 'i8 will remain closed in those operations in which the adsorbentv treatment after chemical treatment is not being used. The adsorbent Will tend to act as a coking agent in those instances Where sludge forming acidssuch as concentrated sulphuric acid areused. When used in sui'licient amounts, it will operate in such a manner as to decolorize and deodorize the naphthenic acids and in any event will supplement the action of the chemical reagent.

The equipment used in the process ofv my inventicnis preferably constructed out of material showing little or no corrosion in thel presence of naphthenic acids. Acid resistant steel orl steel alloys and aluminum lined equipmentv or other non-corrosive steels or alloys recentlyl put on the market have been found to'be suitable; Evaporator 58 and heating coil 5| should'preferab'ly be constructed out of acid resistant materials in Viewv of the increased temperature' prevailing therein. I' have, however, found that Where propane orI similar liqueied normally gaseous hydrocarbonsare used'in my process that the corrosion problem has been materially reduced andthat the conventional iron or steel equipment may be employed.

Itshould'be obvious to anyone thatinvie'w'of the use of` liquid normally gaseous diluents, the system will have' to operate under pressure and the equipment used in my process Will have to be constructed in cases Where diluents such as propane are used towithstand pressures as high as 150 to 200 pounds or greater. The equipment used for heating or cooling should preferably be insulated against temperature loss.

The removal of the naphthenic acids from the diluent solvent may be accomplished by means other than heating, although the latter appears to be the most economical. For instance, I may extract the solution of the purified naphthenic acids with an alkaline reagent such as sodium hydroxide, potassium hydroxideJ calcium hydroxide or the like, and separate the naphthenic acid soaps so produced from the solvent. These soaps may then be extracted, if desired, With suitable amounts of solvents such as naphtha, petroleum ether, gasoline or the like, to remove any heavy hydrocarbon fractionscarried over into the soaps and the free naphthenic acids may then be obtained by commingling the soaps with an inorganic acid, preferably sulphuric acid. Y

I- may also nally distill the' naphthenic acids after completion of the other purifying steps t0 produce a finished product which is light in color and does not darken on standing.

Crude naphthenic acids contain impurities which are unstable andY tend to darken when exposed to light. When such crude naphthenic acids are distilled, these unstable bodies are carriedl over in the distillate fractions and due to their instability soon darken the distillate. If, however, the crude naphthenic acids are first eX- tractedwith a liqueed normally gaseousY hydrocarbon, suchl as liquid propane, and the propane soluble portion recovered from the crude naphthenic acid is distilled, preferably by vacuum distillation, the distillates so produced' are'free from these unstable bodies and'have a very pronounced color stability. The impuritiesy which cause the darkening of the distillates are substantially irrsoluble in liqueed normally gaseous hydrocarbons, such as ethane, propane, butane and mixturesth'ereof. Thereforefby first extracting the crude naphthenic acids With a liquefied normally gaseous hydrocarbon-andthen distilling' the por'- tion which isV soluble in` thev liquefied' normally gaseous hydrocarbon, distillate fractions are recovered Whichh'avea high color stability.

Furthermore', I1 may' also extract the crude naphthenic acidsv With a liquefied normally gaseous hydrocarbon, treat the portion whichis soluble in the' liquefied normally gaseous hydrocarbon'A with' niineral acidsv such a's` sulphuricI acid; hydrochloric acid, chloric/ acid, bromic'acid-,fiodic acid, hydroiodic' acid; phosphoric acid, chlorsulphonic acid, nitrosulphonic afcid either iii the presence` or absence of the" liquefied normally gaseous hydrocarbon andthen distillthe extractedand ac idtreat'edfnaphthenic acids into frac tions. Furthermore, I mayl extract' the crude naphthenic acids with a liquefied normally' gaseous hydrocarbon according tothefn'i'ethodsl s'et forth above; treat the extracted acidswith'ariy ofv the above 'mentioned' mineral acids, ytreat"`the acidi treatedy naphthenic" acids 'with decolorizing clay (such asfullers'earth) and'then distill'the acidl and -clay treated naphthenic" acids into fra'c-y tions or I may' omit the mineral `acid` treatment of the extracted acids'andftr'e'at the'liqueiiednor, mally gaseous hydrocarb'onextract' of'tle crude naphthenic acids with" c'la'y" al'onefandthen dis` tillfthe clay treated naphthenicY` acids into fractions.' The clayl treatment maybe' carried out on the naphthenic acid commingled-or dissolved in the liquefied normally gaseous hydrocarbonor Imay remove' the liquefied normally' gaseous .hydrocarbon-'from' the extract prior to* the clay treatment. By the term extract I mean those fractions contained in the crude naphthenic acid Which are soluble in the liqueed normally gaseous hydrocarbon.

It is therefore an object of the present invention to commingle crude naphthenic acids with a liquefied normally gaseous hydrocarbon solvent to separate naphthenic acids dissolved in the liquefied normally gaseous hydrocarbon solvent from impurities insoluble in the light hydrocarbon solvent, recover the naphthenic acids dissolved in the light liquefied normally gaseous hydrocarbon solvent as an extract and distill this extract into fractions. The ydistillation is for the purpose of separating the naphthenic acids into distillates of substantially pure form from the remaining impurities therein which are left as bottoms or residues in the still. Furthermore, it is an object of this invention to acid and/or clay treat the liquefied normally gaseous extract obtained from the crude naphthenic acids prior to the distillation.

The general effect of the purification process herein described is to transform crude naphthenic acids into a product having alight color, a bland odor, a high acid number (number of milligrams of KOH necessary to neutralize 1 gram of substance) as well as a substantial freedom from wax-like, solid acids, asphalt-like substances and other undesirable impurities whose exact composition has not yet been determined.

It will be noted from the above description that the process may be operated in such a manner as to obtain two separations of wax from the naphthenic acid stock. For example a portion of the wax may be removed by separator Il during the solvent treatment; in which other impurities are also removed from the naphthenic acid stock and a further quantity of wax may be removed from the partially purified stock by lter 43. By chilling the solvent solution of naphthenic acids discharged from Idecanter l through lines I3, 29 and 33 into chiller 34, a further quantityof wax precipitates which may be removed by filter 43 from the naphthenic acids dissolved in thesolvent. Furthermore, if the overflow in line I9 is chemically treated the remaining wax usually precipitates from the solution at ordinary temperature or at slightly reduced temperature and this wax may be removed by lter 43. The chemical treatment removes certain bodies present which tend to hold the wax in solution. Therefore by removing the impurities from the solution of naphthenic acids recovered in line I9 by chemical treatment prior to the dewaxing step in filter 43, a more complete separation of wax may be obtained from the naphthenic acid. The degree of cooling of the chemically treated solution of naphthenic acids entering chiller 34 varies with the stock. In most instances only slight or moderate chilling is necessary to cause separation of the wax from the chemically treat-v ed solution; however I find that in some instances it is desirable to lower the temperature of the chemically treated stock in Chiller 34 from 0 F. to 40 F. to obtain substantially complete precipitation of the wax present.

The description of the drawing as well as other specic descriptions occurring herein, are not intended as limitations upon myprocess. As to the scope thereof, reference is made tothe appended claims.

I claim:

1. A method for purifying crude naphthenic acids containing wax which comprises commin- Cil giingv said acids with a iow boiling hydrocarbon diluent adapted to dissolve the naphthenic acids and the wax at elevated temperature and to selectively precipitate the wax upon cooling, cooling the solution so obtained to precipitate wax, and separating the precipitated wax from the naphthenic acids dissolved in the said diluent.

2. A method as dened in claim 1 wherein the diluent is a liquefied normally gaseous hydrocarbon.

3. A method as defined in claim 1 wherein the diluent used is a liquefied normally gaseous hydrocarbon and the chilling of the solution of naphthenic acids in said liquefied normally gaseous hydrocarbon is produced by evaporating a portion thereof.

4. A method of purifying crude naphthenic acids which comprises commingling said acids with a light petroleum hydrocarbon. diluent to dissolve the acids and wax and precipitate the asphalt-like bodies, removing the asphalt-like bodies from the solution of naphthenic acids and wax, chilling said solution to precipitate wax and removing the Wax from the naphthenic acids and light petroleum hydrocarbon diluent.

5. A method of purifying crude naphthenic acids which comprises commingling said acids with a liquefied normally gaseous hydrocarbon to dissolve the acids and wax and precipitate the asphalt-like bodies, removing the asphalt-like bodies from the solution of naphthenic acids and waX, chilling said solution to precipitate wax and removing the wax from the naphthenic acids and liquefied normally gaseous hydrocarbon diluent.

6. A method of purifying crude naphthenic acids which comprises commingling said acids with a liquefied normally gaseous hydrocarbon diluent to dissolve the acids and wax and precipitate the asphalt-like bodies, removing the asphalt-like bodies from the solution of naphthenic acids and wax, chilling said solution to precipitate wax by evaporating a portion o the liqueed normally gaseous hydrocarbon and removing the precipitated wax from the naphthenic acids and remaining liquefied normally gaseous hydrocarbon diluent.

7. A method of purifying crude naphthenic acids which comprises diluting said acids with a liquid hydrocarbon diluent having a substantially lower boiling point than that of said acids and contacting the diluted acids with clay.

8. A method of purifying crude naphthenic acids which comprises contacting said acids with clay in the presence of a hydrocarbon diluent oi substantially lower boiling point than the naphthenic acids being treated, separating the treated acids from the clay and separating the clay treated acids into fractions by distillation.

FREDERICK J. EWING.

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