US2093001A - Refining naphthenic acids - Google Patents

Description

Sept. 14; 1937. A. L. BLouNT 2,093,001

REFININGVNAPHTHENIC ACIDS Filed Nov. 25. 19:55

f ATTORNEY.

Patented sept. 14, 1937 UNITED STATES PATENT AOFFICE marraine NAPn'rnENrc Acms Arthur L. Blount, Palos Verdes Estates, Calif., as- -j signor to Union Oil Company of California, Los Angeles, Calif., a corporation of California ApplicationNovember 2 5, 1935,` Serial No. 51,500

20 Claims.

The present invention relates to naphthenic acids, and more particularly to a new process for refining naphthenic acids from alkali wastes obtained from the treatment of petroleum frac- 5 tions. J

Naphthenic acids, such as might be obtained from the alkali wastes arising from therefl'ning of petroleum or shale oil fractions constitute a complex vmixture of acidic compounds' pril0 marily containing carbon, hydrogen and oxygen.

'I'hey range from comparativelylow boilingfliquids to materials which are solid and semisolid at ordinary temperatures. Their viscosities as Well as the boiling points of these substances are directly proportional to the viscositiesf; and boiling points of the hydrocarbon fractions in which they are originally present.

Ordinarily, the alkali wastes containing-these naphthenic acids, although substantially unsuitable for further treatment of petroleum fractions, still contain a relatively small amount of caustic soda, being present in amounts substantially equal to about 0.1% by weight of the a'ikali wastes. In order to remove phenolic materials- 25 from said alkali wastes, it is ilrst necessary to neutralize the mixture so that it is neutral .to phenolphthalein. Until the present time "this neutralization was carried out by the addition of an inorganic acid such as sulfuric acid. wever, it was found very dilcult and even practically impossible to produce such a neutral xture by the addition of the inorganic acid, such as sulfuric acid, due to its sludging effect. Itwas therefore found necessary to add an excess of sulfuric acid and to follow this treatment by a neutralization with caustic soda or a similar alkali until the reaction of the mixture was neutral to phenolphthalein. Obviously, such a pro-- ent invention to obviate the 'above defects and to provide a method .which avoids the necessity of usinginorganic acids as Well as the subsequent neutralization of the thus acidiiled alkali wastes with an alkali.

The alkali wastes neutralized by the use of an acid comprises an aqueous solution of sodium naphthenates generally containing appreciable quantities of oil and free phenolic materials. Before the sodium naphthenates may be con.

(Cl. 2130-108) y verted into naphthenic acids by acidification, kit

is first .necessary to" remove these appreciable l quantities'of oil and phenolic materials. the present time this was carried out by batch distillation. Such a procedure, however, is detrimental to the quality of the final naphthenic acids obtained due to the. prolonged cooking of the naphthenate soaps as well as because of the generation of froth which prevents'proper distillation. y

It is therefore a further object of the present invention to, provide a method whereby the removal of the oils and phenolic bodies from the mixture-thereof with sodium naphthenate may be carried out without any of the above-mentioned defects and without the undesirablecooking of the naphthenate soaps.

After the above described deoiling and dephenolating, the soaps are then dissolved in water and the thus obtained soap solution is acidi- 'ed to produce the semi-refined naphthenic acids. This reaction produces a `quantity of water thereby necessitating the removalof the semi-refined naphthenic acids from the thus obtained'aqueous phase.

'I'he obtained naphthenic acids contain varying amounts of carbonaceous materials, there being asmuch as three to Ave per cent and even more 'of these undesirable materials present; 'lhemaior portion of these carbonaceous materials exists in a nely suspended or colloidal centrifuging. The naphthenic acids containing such materials have a dark and turbid color and an undesirable odor, thereby rendering them practically useless as a commercial product.

To produce a commercial product. it has been customary toy dlstlll the thus' dephenolated and deoiled semi-reilned naphthenic acids to remove the admixed carbonaceous material, and then to 'treat the overhead product to remove therefrom Until state and are diiilcultlyA removed by settling orthe dark color and foul odor. Such a procedure,

however, would not materially improve the color of the overhead product, since thepresence of carbon caused the fouling of the stills. To avoid this defect, it has been previously proposed to pre-treat the semi-refined acids,'prior to the distillation step, toremove therefrom these undesirable constitutents.

It has now been discovered that theabove and other objects may be attained by the use of certain steps described hereinbelow, some ot these stepsy being in the form oi' substitutions for known steps of operation, while othersconstitute or comknown method of refining crude naphthenic acids. Thus, it has been discovered that itis preferred to neutralize the alkali wastes with naphthenic acids themselves instead of the above described step 5 of neutralization with inorganic acids. One of the advantages obtained by such neutralization of the alkali wastes still containing a small percentage of free alkali or sodium phenolates resides in the fact that it is possible to obtain a solution neutral to phenolphthalein by the addition of the naphthenic acids alone without the necessity of following this operation by the addition of further quantities of alkali, as is necessary in the case of the use of inorganic acids. Such use of naphthenic l5 acids avoids the undesirable formation of salt cakes, such as sodium sulfate cakes. Also, the addition of naphthenic acids is not detrimental to the final product since one is dealing with naphthenic acids in the first place so that the naphthenic acids added to the crude naphthenate mixture will be again recovered as naphthenic acids at the end of the refining process. Furtherlmore, the use of naphthenic acids is advantageous in that it avoids the treatment of. highly corrosive mixtures, as is the case when sulfuric acids are employed.

It was further discovered .that the distillation of the mixture containing the sodium naphthenates, phenolic materials, oil and water may'be realized at `lower temperatures than ordinarily'I necessary for such evaporation, and without 'any cooking of the naphthenate soaps.4 This may be accomplished by passing the ,above-mentioned mixture through some means such as a heat exchanger or tubular still wherein all of the.` heat necessary to evaporate the phenols,oil and water is added to the mixture, followed by a flashing of the mixture in a ash chamber wherein the temperature is maintained below a predetermined 40 upper limit to prevent the undesirable cooking of the naphthenate soaps. It has been Afurther discovered that the temperature in the flashing chamber may be kept below the maximum limit by maintaining a body of distillate in said chamber, said distillate having a suitable distillation range consistent with the maximum temperature desired in said ashing chamber, as well as by the injection of superheated steam into the flashing chamber during the the introduction of the charging stock as well as during the evaporation therefrom of the undesirable oil, water and phenolic materials.

The naphthenat'e soaps thus produced must at the same time prevent such-undesirable local then be converted into naphthenic acids, as by water and acid treatment. These semi-refined naphthenic acids contain certain undesirable carbonaceous and color-producing bodies, as wellgas* hydroxy-acids of mediocre oil"sol ubility. Many methods have been proposed to refine the naphthenic acids to remove these undesirable substances. Thus,'the acids may be treated with a solvent, such as a liquefied normally gaseous hydrocarbon. The naphthenic acids being soluble in such a solvent, it is easy to obtain phase separation, and thus remove, as aprecipitate; any and;

therein, followed by the flashing of the thus heated mixture to evaporate said materials without undue cooking of the sodium naphthenates in said mixture. Y

The invention further resides in neutralizing 5 alkali wastes 'by adding rened or semi-refined naphthenic acids, imparting to such alkali wastes all of the heat necessary to evaporate the oil, water and phenolic materials contained therein followed by the flashing of the thus heated mixl0 ture to separate these materials without the necessity of using the undesirable high temperatures detrimental to the naphthenate soaps, and

- treating the thus obtained naphthenaie soaps to of allthe heat necessary to evaporate the oil, 2liv water and phenolic materials contained therein. and of flashing said mixture to evaporate saidmentioned materials at a temperature which is insufficient 'to ailectl undesirably the sodium naphthenates. This phase of operation may be 30 realized by passing the neutralized alkali wastes .containing sodium naphthenates, oil. water and free phenolic materials through a heat exchanger or tubular still wherein all the heat necessary to evaporate'all the volatile materials is imparted to 35 the mixture. The thus heated mass is then flashed into al chamber to separate all the substances thus volatilized. Such a procedure eliminates the unnecessary and detrimental'frothing y of the sodium naphthenates (said frothing being i0 an incident to the ordinary batch method of distillation) as well as the undesirable cooking of the sodium soaps at temperatures suiilciently high to affect the quality of the ilnal product; l To aid the evaporation of the oil, water and phenolic i5 materials from the neutralized alkali wastes it is frequently necessary to heat the flashing chamber. If such heating is carried out by the use of external heat, the quality of the naphthenic acids 'may be affected by local overheating. To elimi- 50 nate this it is proposed to provide in the flashing chamber a bath of material which may be maintained at the desired temperature and which will overheating of the naphthenate soaps. For this lili purpose it is possible to use a hydrocarbon fraction having an average boiling temperature ol.4 about the temperature necessary to evaporate the' materials being ashed. 'I'hese hydrocarbons will then be evaporated together with the oil, water l0" and phenolicI materials, ultimately leaving the sodium naphthenate soaps in a substantially pure y state. As an aid to the distillation and evaporation of these materials it is sometimes advisable' to employ superheated steam which may be ind8 jected into the. flashing chamber during the charging therefewith the heated neutralizedxalkali wastes as well as thereafter during the evaporation of the above mentioned materials. This addition of superheated steam also lprevents the undesirable cooking of the naphthenate vsoaps by permitting the use of lower temperatures as well as shorter distillation periods. Therefore, the invention maystill further reside in imparting to the neutralized alkali wastes the heat nry the injection of superheated steam to aid said distillation and evaporation.

It is to be noted that the use of naphthenic acids to neutralize the lalkalinity of the alkali wastes avoids the necessity of careful neutralization. 'I'his is due to the weak corrosive qualities of naphthenic acids. Thus, when inorganic acids,

such as sulfuric acid, are used for this neutralization it is necessary to obtain a mixture which shows a neutral reaction to phenolphthalein due to the highly corrosive action, i. e. strong acidity,

of these inorganic acids. On the other hand, the naphthenic acids having a considerably weaker corrosive action, substantially `no detrimental effeet would occurin using an excess thereof. 'Ihe present invention, therefore, alsocovers the use of naphthenic acids not only in quantities suflicient to neutralize the alkali wastes, but also in any other quantities, preferably at least sucient to neutralize the alkalinity of these wastes.

The invention is illustrated by way of example in the accompanying drawing which discloses diagrammatically a system of refining naphthenic acids according to the process constituting and including the objects of the present invention.

Referring more particularly to the drawing, the alkali wastes such as obtained from the caustic soda solution treatment of petroleum distillates of the type of kerosene, light gas-oil or even lubrieating oil distillates, are introduced through line I into a container'or tank II. These alkali wastes, although unsuitable for further treating of petroleum distillates, still contain a small percentage of caustic soda," the amount thereof being in the neighborhood of 0.1% by weight of the Waste alkali. These Waste alkalies are then conveyed through line I 2 into a tank I3 wherein they are thoroughly commingled with suitable naphthenic acids introduced through line I4. The quantity and rate of introduction of the naphthenic acids is such that the mixture leaving tank I3 through line I5 shows a substantially neutral reaction to phenolphthalein. This mixture consists of sodium naphthenate soaps containing an appreciable quantity of oil, free phenolic materials, water and possibly a small amount of naphthenic acids.

'Ihe above mixture is conveyed by pipe I5 into.

a tubular still or heat exchanger II wherein the mixture is heated to a temperature suflicient to evaporate all of the'water, oil and phenols, but insuflicient to affect detrimentally the sodium naphthenate soaps. This heating may be carried out under any desired and preferred pressure. The thus heated mixture then passes through line I8 into a flashing chamber or still 20. In the preferred form this flashing chamber 20 contains a body of petroleum distillate introduced thereinto through line 2 I, said petroleum distillate having an average boiling temperature substantially equal to the temperature necessary for the evaporation of the oil, Water and phenolic materials from the heated waste alkalies introduced into said still through line I8. This petroleum distillate bath is`used primarily for the purpose of preventing local overheating of the sodium naphthenates. However, it also inhibits the foaming of these soaps. The petroleum distillate bath is Wateris introduced through line 3I.

maintained at its boiling point by the application of heat, preferably fromran external source (not shown in the drawing) to aid the removal of the oil, water and phenolic material vapors and to cover heat losses, and superheated steam may be introduced into the still 20 through line 23. 0bviously, the bath may be external to the still 20. The evolved vapors are removed through line 24, while the sodium naphthenate soaps remaining as the residue in still 20 are removed through line 26.

As shown in the drawing, the operation so far constitutes in effect a batch operation. Thus the waste alkalies neutralized in tank I3 and heated to the proper temperature in the coil I 'I are introduced into flashing chamber or still 20 until the latter is practically full. yThereafter the introduction of further quantities of heated alkali wastes is stopped and the mixture in the flashing chamber is allowed to boil or is steamed until only the naphthenate soaps remain in the still. The temperature inA said still or flashing chamber is maintained at the predetermined upper limit by the boiling of the aforesaid hydrocarbon fraction as well as by the injection of superheated steam both during the charging ofthe flashing chamber and the evaporation of all the constituents except the sodium naphthenate soaps. However, it is obvious that the operation may be made continuous by providing a plurality of ashing chambers so that the alkali wastes heatedin the heating coil I'I may be introduced into'one Aflashing chamber while another is in the stage of evaporation of the undesirable constituents. As a modification, a stripping column may be provided,v said column having means for a continuous removal of the SOapS.

till'ate bath not only prevents the undesirable overheating and cooking of the sodium naphthenate soaps but also the frothing thereof. In actual practice it has been found that a distillate having an approximate distillation range from 450 to 600 F. produced the desired results since with the injection of superheated steam it'was possible to maintain the temperature below 500 F. and still evaporate all the materials with the exception of the naphthenate soaps.

,The sodium naphthenate soaps removed from flashing chamber 20 through line 26 are dissolved in water in an injector 30 into which :olution thus obtained is then conveyed through line 32 into a container 33 wherein the solution is commingled with an inorganic acid such as render the naphthenic acids unsuitable for commercial use.V To eliminate these undesirable substances, according to the method shown in the drawing, the semi-rened naphthenic acids are conveyed from line 33 into a tank 39 wherein they are dissolved in four to ve volumes of a solvent ksuch as liqueed propane entering said tank through line 40. The solution is then chilled to The soap A atemperature of approximately F. by any of the well known methods of either internal or external refrigeration. Since the naphthenic acids are soluble in cold propane, they will remain in solution while the undesirable carbonaceous and asphaltic materials as well as other color and odor producing substances and hydroxy-acids will precipitate outof solution. These may be removed by any of the well known methods and means, such as centrifuging, filter- 'ing or simple decantation. In the diagrammatic drawing the solution of cold propane and naphthenic acids is removed through line 4i while the precipitated undesirable materials are withpressure of not exceeding 50 mm. of mercury.

The desired naphthenic acids having a clear color and a bland odor are removed as the overhead fraction through'line 40. After condensation these naphthenic acids are highly suitable for many commercial purposes since they have a light and'stable color and a bland odor. The darker color naphthenic acids having a high molecular lweight are withdrawn from the vacuum still 46 through line 49.

As a non-limiting example, a five gallon charge of alkali wastes obtained from the caustic alkali Vtreatment of kerosene distillates, wasA commingled with 330 grams of semi-refined naphthenic acids obtained from alkali wastes similar to the ones being treated. The addition of these naphthenic acids neutralized the alkalinity. of the wastes. The mixture was then passed through a heating coil ata rate of about 100 ml. per

45,5 minute, the mixture being heated in said coil to a temperature in the range of about 400 to 425 F. The thus heated mixture was then introduced into a flashing chamber which contained approximately 1500 ml. of kerosene extract bot- 50 toms having a distillation range of approximately 420 to 600 F. Superheated steam was injected into said dashing chamber both during the injection of the heated mixture and during the separation therein of the volatile substances from the naphthenate soaps. The temperature in the flashing chamber was maintained at between 300 and 425 F.

When all of the oil, water and free-phenolic materials were removed, the -remaining naphthenate soaps were dissolved in water to produce about seventeen liters of solution. After acidification of the solution with 30% sulfuric acid,

and then withdrawal of the aqueous phase, the

resulting serni-rened naphthenic acids had an uacid number of 278.

Although the drawing discloses a propane treatment of the semi-refined naphthenic acids acids had an acid number of 281 and'a 654 N. P. A. color, whichV constitutes a highly desirable naphthenic acid.

As another example, 600 ml. of semi-refined naphthenic acids produced according to the above described method of treatment from alkali `wastes obtained from the alkali treatment of gasvantageous, -it is obvious that other steps may besubstituted as'equivalents or may be added for further rening of the naphthenic acids. For example, it may be desirable to acid treat the naphthenic acids while they are dissolved inpropane and prior to the vacuum distillation of said naphthenic acids Also, it may be advantageous to distill the acids through decolorizing adsorbents such as clays, while said acids are in a vapor phase. Furthermore, the distillates obtained from the vacuum -distillation of the naphthenic acids may be clay treated or acid and clay treated or may be contacted with other adsorbent substances such as fullers earth, for the purpose of obtaining refined acids having a highlydesirable pale c olor and a bland odor.

It is obvious that the naphthenic acids employed for the purpose of neutralizing the alkalinity of the wastes may be taken from the same process; Thus, either the'semi-reiined naphthenic acids obtained from the acid treatment of the naphthenic soap solution, or the final refined product may be employed for this purpose.

'Ihe description of the drawing or of the examples, as well as other specic disclosures occurring herein, are not intended as limitations `upon the process constituting'the object of the present invention. As to the scope thereof, reference is made to the appended claims.

I claim: f

l. A method of refining alkali wastesobtained from petroleum and like fractions vto produce refined naphthenic acids, which comprises adding naphthenic acids to said alkali wastes to neutralize the alkalinity thereof, imparting to such neutralized alkali wastes all of the heat necessary to evaporate all of the constituents therein 'with the exception of naphthenate soaps, separating the thus vaporized volatile materials, and treating the naphthenate soaps to obtain therefrom the naphthenic acids.

2. In a 'method according to claim 1, wherein the quantity of naphthenic acids-added to the alkali wastes is only sufficient to neutralize the alkalinity of said wastes.

3. In a method according to claim 1, wherein the quantity of naphthenic acids added to the alkali wastes is in excess of the quantity necess ary to neutralize the alkalinity of said wastes.

4. In a method according to claim 1,' wherein the neutralized alkali wastes, containing naphthenatesoaps, oil, water and free-phenolic materials, are heated to impart thereto all the heat necessary to evaporate said oil, water and freephenolic materials, said heat being insufficient to aifect detrimentally the naphthenate. soaps.

5. In a method according to claim 1, wherein 6. In a method of refining alkali wastes ob- -f tained from petroleum and like fractions to remove therefrom naphthenic acids, the step of adding naphthenic acids to said alkali wastes. 7. In a method according to claimv 6, wherein the quantity of added naphthenic acids is suill cient to neutralize the alkalinity of the alkali wastes.

. 8. In-a method according to claim 6, wherein the quantity of naphthenic acids added to the alkali wastes is in excess of the quantity neces-A sary to neutralize the alkalinity of said wastes.

9. In a method of rening alkali wastes obtained from petroleum and like fractions to remove therefrom the naphthenic acids, the steps of neutralizing the alkalinity of said alkali wastes by the addition of naphthenic acids thereto, imparting to said neutralized wastes all of the heat necessaryto evaporate therefrom all of the constituents with the exception of the naphthenate soaps, and separating the thus vaporized volatile materials. t

10. In a method according to claim 9, wherein the neutralized alkali wastes, after imparting thereto the heat necessary to evaporate the volatile materials, are introduced into a body maintained at a temperature which prevents any detrimental cooking of the naphthenate soaps contained in the alkali wastes. 11. In a method of rening alkali wastes obtained frompetroleum and like fractions to.re

move therefrom naphthenic acids, the steps ofadding a naphthenic acid to said wastes to neutralize their alkalinity, imparting to said wastes, containing oil, water, free-phenolic materials and naphthenate soaps, all of the heat necessary'to evaporate said oil, water and free-phenolic materials, butinsuicient to aect detrimentally said naphthenate soaps, flashing said mixture to separate the vaporized materials, and removing the thus separated materials from the naphthenate soaps. i D

12. In a method according to claim 11, wherein the heated materials are ilashed into a body maintained at a temperature suflcient to remove all of the volatile materials, but insuiilcient to aect detrimentally the naphthenate soaps.

13. In a method according to claim A11, wherein the heated alkali wastes are ashed into a hydrocarbon' fraction maintained ata temperature whereby all of the volatile constituents will be evaporated without any detrimental eiIect on the naphthenate s'oaps.

14. In a method according to claiml1, wherein the heated alkali wastesare flashed into a` 5 hydrocarbon fraction having an average boiling temperature of substantially the temperature necessary to evaporate the volatile materials ing, said alkali wastes.

l5. Ina method according to claim 11, where- 10 in Vsteamislintroduced into the flashed heated alkali wastes to aid in the separation of 'the volatilzed materials from the naphthenate soaps.

16. In a method. according to claim 11, where-v in the heated alkali wastes are flashed intoa bath l5 maintained at substantially the temperature, necessary to. evaporate the volatile materials, and wherein steam is introduced into said flashed wastes to aid in the separation of the volatilized` materials without anydetrimental effect on the 20 naphthenatesoaps. y

17. A method for refining alkali wastes obtained from petroleum and like fractions to proi duce naphthenic acids, which comprises adding naphthenic acids to said alkali wastes to neu- 25 tralize the alkalinity thereof, imparting to such neutralized alkali wastes all of the heat fnecessary to evaporate substantially all of the constituents therein with the exceptionof naphthenate soaps, separating the' thus vaporized '30 volatile materials, treating the naphthenate soaps to obtain therefrom semi-rened naphthenic acids, and subsequently refining said naphthenic acids to obtain acids having a clear color and a bland odor.

18. In a method according to claim 17, wherein the semi-rened naphthenic acids are dis-'- solved in a solvent having a preferential solubility for the naphthenic acids, whereby the carbonaceous. asphaltic and color and 'odor produco ing bodies may be separated from said acids.

19. In a method according to claim 17, where-f in the semi-rened naphthenic acids are solvent extracted to separate the carbonaceous, asphaltic and color and odor producing bodies, and where- 45 in the thus treated naphthenic acids are distilled to produce naphthenic acids having adesired g acid number, clear 'color and a bland odor.

20. In a method according to'claim 1'?, wherein the semi-rened naphthenic acids are Adis- 50 solved in propane under conditions whereby the carbonaceous, asphaltic and color and odor producing bodies may be separated from said acids.

ARTHUR. L. BLoUNr. .55

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