Aug. 25, 1953 D. W. colleR 2,650,248 CONCENTRATION OF AQUEOUS. ACONITIC ACID SOLUTIONS Filed March 5, 1950

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INVENTOR. DONALD W, COLLER

SUD. eÖDOS BY hby Gaula 9. UDueuebe ATTORNEY. Patented Aug. 25, 1953 2,650,248

UNITED STATES PATENT office 2,650,248 CONCENTRATION OF ACUEOUS ACONTIC ACD SOLUTIONS Donald W. Collier, Philadelphia, Pa., assignor to The Sharples Corporation, a corporation of Delaware Application March 15, 1950, serial No. 149,864 6 Claims. (CI. 260-537) 2 This invention relates to a process and appara this method the blackstrap molasses of about 85 tus for the recovery of substances from relative Brix is suitably diluted with Water to about 50 ly dilute Solutions thereof. More Specifically, the Brix and is heated to about 50° C. Blackstrap invention relates to the recovery of aconitic acid mola SSes is the by-product of raW Sugar manu from relatively dilute aqueous Solutions contain- 5 facture. It is a heavy Wiscous liquid Separated ing impurities and foreign substances by contact- from the final low grade maSSecuite from which ing the aqueous solution with an organic Solvent no further Sugar can be crystallized by the usual to form two phases in which the aconitic acid is methods: The density of blackstrap molasses concentrated in the non-aqueous: phase, there- ranges from 85 to 92 Brix, containing total after adding hydrocarbon type solvent to the non-0 solids by drying of 77 to 84%. The SucroSeco aqueous phase which is miscible therewith and tent varies by Weight between 25 and 40% and the then contacting the mixed non-aqueous phase reducing Sugars from 30 to 12% With total Sugars with a small volume of water to form tWO phases about 50%. It contains anywhere from 0.5 to 5% in which the aconitic acid is concentrated in the on Brix of aconitic acid, and Small amounts of aqueous phase. other organic acids such as succinic acid and ox According to my invention I provide a system alic acid, and also substantial amounts of mineral and method for continuously recovering a sub- salts such as the chlorides, Sulfates and phOS stance, such as aconitic acid, without substantial phates of potassium, calcium, magnesium and loss of the organic solvents used by providing for Sodium. The molasses liquor is treated in a three the cyclic recovery of the solvents in my system 20 stage counter-current manner, for example, with and contacting the stream of aqueous Solution an anion exchange resin containing adsorbed Sul with a counter-current stream of a Substantially furic acid. This resin may be Ionac A-300, sold water-immiscible organic solvent in a plurality by American Cyanamid Company, New York, of stages. The concentration of the Substance, N.Y., which is an aliphatic amine phenol-formal Such as a conitic acid, is increased in a double ex- 25 dehyde resin. As an illustration, if the molasses traction system by virtue of the change in its dis- contains about 2.4% aconitic acid on Brix, the tribution tendency between Water and an organic dry base regenerated weight of the resin used is phase brought about by the addition of the hy- conveniently about 7% of the weight of the drocarbon type solvent to the organic phase con- diluted molasses. Line is added to the stage in taining the aconitic acid so that the final aqueous 30 which the anion exchanger first contacts the Solution issuing fronny System is of a greater molasses to adjust the pH Within a pH range concentration as compared with the untreated of about 4 to about 6 and preferably to about 5.0, aqueous solution fed to the system. the point, at Which the Selectivity of the ex Aconitic acid is found in substantial amounts changer for aconitic acid Over mineral acids is at in blackstrap molasses and Sorgo juices in 35 a maximum. Reference is made to co-pending amounts as high as 5% by Weight of solids. The application Serial No. 150,548, filed March 18, aconitic acid can be separated from the molasses 1950, by Hugh G. Bryce wherein such procedure by an anion-exchange material which is then is described and claimed. Each stage comprises treated to produce an aqueous solution of aconitic a steel treating tank with agitator which can be acid containing other impurities such as mineral 40 heated with live steam to maintain the tempera acids, organic substances, and coloring matters ture of about 50 C. Separation of molasses and derived from the molasses. According to my in anion, exchange resin between stages is accorn vention such solution of aconitic acid is extracted plished by the use of vibrating screens. The With a suitable organic Solvent, Such as iso- molasses Solution leaving the third stage is passed phorone, and the extracted solution is further 45 through a centrifuge to remove the calcium Sull treated to isolate substantially pure aconitic acid. fate which is formed during the treat. This Further features and advantages of my inven- calcium sulfate is dropped into a settling tank tion will be evident from the following illustra- filled with Water, to dissolve the adhering tive embodiment of my invention in connection 50 mola SSes from the Solid. The SWeet Water may with the accompanying drawing. A solution con be then used in diluting the treated molasses fur taining aconitic acid to be treated in accordance ther to prepare it for fermentation, if desired, with my invention may, for example, be produced While the solids are discarded through a valve in accordance. With the method disclosed in my in the botton of the tank, which is operated copending application, Serial No. 149,863, filed periodically. March 15, 1950. According to an embodiment of The exchange resin, having passed through the 2,650,248 3 4. three stages, is washed on a vibrating screen to and benzene separated in settling tank A is fed remove the adhering molasses and is dropped into by line 9 and mixed in line 9 with a similar the regeneration tank. The sweet water result mixture of benzene and isophorone and finally ing from the Wash is used in diluting the raW mixed in pump 21 and line 22 with the isopho molasses. The pH in the regeneration tank is role stream from column . The amount of ben maintained at about 0.9 and not exceeding 2.0, Zene used is regulated to be about 1.5 times the by continuous addition of H2SO4. The mixture volume of isophorone fiowing through line 4t, of resin and regenerant solution which now con to a centrifuge 23. The addition of benzene re tains most of the aconitic acid that was on the Sults in the formation of a small amount of a resin is separated on a vibrating screen and the O Second phase of tarry liquid which is conveyed exchange resin is Washed counter-currently in in the stream of isophorone and benzene and fed three stages on a vibrating screen to remove the to centrifuge 23. This separation may be a C remainder of the aconitic acid and some of the complished in a settling tank instead of a centri Sulfuric from the resin. The resin is now ready fuge. The tarry phase is separated by the cen to be reused in the counter-current adsorption trifuge and is fed by line 24 to a settling tank B train. The wash-water is used as make-up water through which a water stream flows supplied by in the regeneration tank. r line 8. The regenerant solution separated from the The aqueous phase from tank B, containing exchanger on a vibrating screen, is then sub Some Water-soluble impurities and a Small jected to purification and recovery in accordance 20 amount of aconitic acid is fed to line 25 to join with the procedure of the present invention. the stream in line. 2 fed from the storage tank Referring to the drawing, the raw aqueous so f). As the tarry phase fed to settling tank B lution containing Say about 2.3% aconitic acid contacts the water therein it solidifies and is and impurities, as produced for example in ac- - discharged periodically from the bottom of the cordance with the method previously described, 25 Settling tank B and is discarded. ... ' is stored in a storage tank 0 from which it is The main stream of clarified isophorone and fed at a controlled rate by pump and line 2 benzene coming from the centrifuge 23 is fed to the top of an extraction column , preferably by line 26 and pump 27 to the bottom of extrac of the type which is internally agitated and pro tion column 2 which is preferably a five plate vided with say ten plates. A stream of iso 30 internally agitated column. Water is fed to the phorone is fed by line 56 to the bottom of the top of column 2 by line 8' in counter-current extraction column f in counter-current flow, flow at a volume rate 42 of that of the organic preferably at a rate 0.3 that of the aqueous feed stream. The presence of benzene in the isopho rate. This treatment strips aconitic acid and rone now causes the aconitic acid to go back in Some inpurities from the aqueous solution, 35 to Solution in the Water and as a result of the leaving behind the stripped residual aqueous SO faWOrable distribution COnStants in both extracts lution containing some sulfuric acid, a small tions, the concentration of the aconitic acid is amount of isophorone and other impurities. The now Over 10% which represents an increase of stream of isophorone leaves the top of the extrac about 4.5 times the concentration in the original tion column through line 40 and enters line 40 solution. 41. In extraction columns, such as columns , The extracted Stream of mixed iSophorone and 2 and 3, a disengaging section is present in the benzene is now fed by line 28 to a still 39 where top of the column to allow the up-flowing or the benzene is stripped from it by a steam distill ganic phase to coagulate into a substantially lation. The still 30 may be of any Suitable con Water-free phase, so that it may be withdrawn struction. It may, for example, comprise a pot from the column as such. The water feed to and a three plate column. ... Sufficient Water is the top of the column is placed below the take added to keep the pot temperature at about 100° Off of the organic phase and as a result an inter C. to prevent deterioration of the isophorone face forms between the aqueous phase being fed Which occurs at high temperatures. The ben into the column and the coagulated organic 50 Zene separated from isophorone in the still is phase being withdrawn from the top of the col fed through line 3 to a condenser 50. The lig lumn. The aqueous stream is removed from the uid benzene decanted in decanter 75 from the bottom of the extraction column at such a Water which also condenses in condenser is can rate as to keep the level of the interface of the then be supplied through line 32, pump 5 and isophorone and water solution at a constant 55 line 29 to settling tank A. as previously described height above the bottom of the column. This where it again enters the system to start anoth Can be accomplished by causing the stream to er cycle. The water from decanter 75 may be foW through an external vented overflow line recycled to the still through line 76 to maintain f5, the height of which controls the height of the steam distillation. The hot isophol'One Sep the interface. The stripped residual aqueous 80 arated in the still 30 is fed by line 52 to a flash Solution is removed from the bottom of the ex still 54 which is maintained at a vacuum of about traction column through line 5 to a settling 10 mm. Hg by means of a steam injector 5. The -tank A. to separate out any isophorone present isophorone recovered from the botton of still in the Solution. The stripped residual aqueous 54 is fed by pump 55 and through line 56 back phase in Settling tank A is removed through line 65 to a tower 8 containing lump limestone which to the extraction column f for reuse in another neutralizes the sulfuric acid in the solution so cycle. A small amount of isophorone is vapor ... that the aqueous stream may be safely discarded. ized in the flash still and is fed through line 5, Benzene at a volume rate about 0.6 that of the to condenser 58. The condensed isophorone is aqueous stream is fed into pump 5 to mix with fed by pump 59 through line 6) to the extraction the stripped aqueous stream in line 29 where the column 3. The degree of Vacuum in the flash mixture is conducted to settling tank A to sep still is controlled through a regulated air bleed arate into two phases. The benzene serves to so that sufficient isophorone vaporizes to Supply remove any isophorone dissolved in the stripped the extraction column 3. Column 3 is supplied aqueous solution. The mixture of isophorone 75 with isophorone which has been distilled to en 2,650,248 5 6 sure that the isophorone being fed will contain went in Order to permit a concentration of a co no dissolved solids. raitic acid to be accomplished by a two-step ex The aqueous phase now containing about 10% traction process, such as illustrated. With isopho by weight of aconitic acid which is separated rOne and benzene, is relatively simple and can from extraction column 2 is fed through line. 35, be related to the distribution coefficients for a co pump 38 and line 39 to the top of extraction initic acid between the aqueous and tWO Organic column 3. As previously stated the distilled phases concerned. When a substance is dissolved stream of isophorone from the flash still 54 is in a system of two immiscible liquids, a and b, fed to the botton of the column 3, Which may it will distribute itself between the two phases be a spray type or packed column containing O and the ratio of the concentrations in the tWO three stages, by line 60 at a volume rate of 0.1 phases at equilibrium is defined as the distribu that of the aqueous feed in counter-current flow tion coefficient as follows: K-Ca/Cb. For rea to the aqueous stream. A large fraction of the sonably immiscible liquids this distribution coeffi remaining impurities in the aqueous stream is cient is relatively constant over fairly large con removed from the solution along With only a 5 centration ranges of the Substance in the tWO Small fraction of the aconitic acid. The solvent given liquids. stream of isophorone containing the impurities For such systems, if the liquid binitially con is removed through line 36 and is fed into line 4 taining all of the substance to be extracted is Where it combines with the stream of isophorone counter-currently contacted with liquid d. it can containing aconitic acid coming from extraction 20 be shown that the Substance can be substantially column f, and the combined streams are mixed completely transferred into a if with benzene in pump 2 and fed to centrifuge 23 to remove any tarry phase as previously described. The aqueous phase separated from column 3 containing the concentrated Solution of aconitic 25 where A and B are the volume flows of liquids a acid is fed through line 65 to a mixer 66 where and b. Thus in any two-step extraction System it is mixed with a stream of benzene Supplied Such as described previously, aconitic acid at from the decanter 75, pump. 67 and line St. The Concentration Co in an aqueous solution is first volume of benzene is about 0.6 that of the aque contacted counter-currently. With a polar organic ous stream. The benzene dissolves any isopho 30 solvent with the respective flow rates being Wi. rOne in the aqueous solution. and P. The organic solvent now containing the The mixture is fed to a settling tank C where a conitic acid is mixed with a non-polar organic the benzene containing dissolved isophorone is Solvent at flow rate of N for said non-polar sol separated and fed through line 68, then through : vent, and this mixture is counter-currently con line 9 where it joins the stream of isophorone tacted in a second step. With water at fiow. rate and benzene from Settling tank A. The combined of Wg to produce a final aconitic acid concen Streams of isophorone, and benzene are fed by tration in W2 of Cf. If the acornitic acid is sub pump 2 through line 22 to centrifuge 23. stantially completely transferred in each of the The aqueous phase separated in settling tank two extractions then: C is passed through line 70 to a tower con 40 taining granular activated carbon where the re maining Small amounts of impurities in the solu C=C(A)(E)(i) (1) tion are removed from the stream, I may provide Furthermore, if the aconitic acid is to be sub tWO carbon towers. So that while One is is use stantially completely transferred in each of the the other may be recharged With fresh carbon. 4. two steps then at least: The aqueous stream is now completely puri KP W. awa fied and contains about 10% by weight of aco W =1 and K,(P+N) (2) Initic acid. The solution is fed by line T2 and is evaporated to a slurry of aconitic acid in water Where K1 and K2 are the distribution coefficients in an evaporator-crystallizer 73 operated at at for aconitic acid between water and the polar mospheric pressure. The slurry is then fed on and mixed polar-non-polar organic phases, re an atmospheric drum drier 4, yielding a dry Spectively, as follows: White piroduct of substantially pure aconitic acid. K1 = C?C. and KT Ca+/Ca (3) The operation of the process as described can Therefore, if a concentration of a coilitic acid be carried out with great efficiency and at com-o: is to occur by the process, it follows by substi paratively low cost because the organic solvents tuting (2) into (1) that: used are recovered and reused in the process. It will be noted that a suitable head is main K1( P tained in the Various columns and tanks by hav CIC-E(pl.)>1 (4) ing the outflow lines arranged in suitable re 40 According to Equation 4 if the distribution entrant or U-shaped courses vented at the top coefficient for aconitic acid from water into a to provide externai overflow lines, the height of mixture of polar and non-pola, Solweints de which controls the height of the interface of creases more rapidly With addition of the Oil the two phases in each adjacent column or tank, polar solvent than does the fraction of polar such as the line 5 adjacent extraction column , 35 Solvent in the mixture, a more concentrated Solu line adjacent settling tank A, line 35 adjacent tion of aconitic acid can be obtained in the extraction column 2 and line adjacent settling Second water extract than existed in the initial tank C. The system is simple to operate and aqueous solution by such a two-stage process. control at all points. All of the polar solvents previously mentioned Instead of benzene, I may employ hexane, tolu 70 fulfill the condition expressed by Equation 4. ene, carbon tetrachloride or other Similar non When the non-polar Solvent is benzene and the polar Organic compounds which are miscible with effect of the other non-polar solvents specified is the aforenamed polar organic compound and are Substantially the same. relatively immiscible with Water. The miscibility limits for water and the or The criterion of selection of polar organic sol 75 ganic Solvents, as long as two phases are formed 2,650,248 upon contacting, is dependent upon commercial ing a stream of Said isophorone-benzene mixture rather than technical factors. Rather arbi to a second extraction stage, continuously feed trarily one might set a maximum solubility for ing a counter-current stream of water to said the polar solvent in Water at 30% and the non Second extraction stage to Strip the aconitic polar solvent at 1% at room temperature. acid from said isophorone-benzene mixture and My invention is particularly useful in obtain form an aqueous solution thereof, separating the ing relatively pure aconitic acid from dilute solu last-mentioned aqueous solution from the iso tions thereof at relatively low cost. The Solvents phO'one-benzene phase, continuously feeding a used in my process are continuously recycled stream of said last-mentioned aqueous solution to and reused. The aconitic acid Cain be coCens O a third extraction stage, continuously feeding a trated from its aqueous solutions at relatively COUntercurrent stream of isophorone to said third low temperatures without requiring boiling of di eXtraction stage to dissolve therein impurities in lute aconitic acid solutions, thereby avoiding der Said aqueous Solution, separating said last-men composition of the aconitic acid. Ina SEXuch as tioned aqueous Solution from said isophorone, the aconitic acid is extracted by the solvent from 5 then contacting said aqueous solution with ben an aqueous solution containing inorganic acids, Zene to dissolve isophorone therefrom, separating the further processing of the aconitic acid can Said last-mentioned benzene from said aqueous be carried out in equipment which need not be Solution, thereafter passing said aqueous solu acid resistant to inorganic acids. -Iffy proceSS tion through a bed of activated carbon and there also permits the recovery of the acoritic acid 20 after evaporating said solution to obtain solid from the Organic solvents without evaporating acOnitic acid. the polar organic solvent, thereby preventing any 5. A continuous process for recovering aconitic Substantial decomposition or losses of the pola. acid from a relatively dilute aqueous solution de Solvent. rived from molasses by anionic exchange which It is to be understood that the invention is not 25 Comprises continuously feeding a stream of said limited to the specific materials and Solvents Ol' aqueous Solution to an extraction stage, continu conditions utilized in the foregoing illustrative ously feeding a counter-current stream of iso embodiment of my invention except as Specified phorone to said extraction stage in proportion of in the appended claims, and that Elodifications about 0.3 by volume to strip the aconitic acid and variations may be adopted utilizing tié 30 from Said Solution, separating the mixed streams essential features of my invention which are into two phases, then contacting the stripped intended to be included in the appended claii)S. aqueous phase With benzene to dissolve isophorone I claim: therefrom, separating the benzene from said 1. A process for purifying and concentiating aqueous phase and adding said benzene in amount aconitic acid which comprises intinately coin 35 of about 0.6 by Volume to the isophorone phase tacting an aqueous solution of a COInitic acid COin and Separating a tarry phase therefron, then taining impurities with isophorone with the for feeding a stream of Said isophorone-benzene mix nation of the two phases, separating said phaSeS, ture to a second extraction stage, continuously intimately contacting the separated a gueois feeding a counter-current stream of Water in phase with a non-polar organic solvent. With the 40 proportion of about 0.5 by volume to said second formation of two phases, said non-polar Organié extraction stage to strip the aconitic acid from solvent being miscible with isophorone but sta Said isophorone-benzene mixture and form an stantially completely iminiscible with Water, aqueous Solution thereof, separating the said separating said last-mentioned phases, intimately aqueous Solution from the isophorone-benzene contacting the separated isophoroine phase with 45 phase, continuously feeding a stream of said the separated non-polar organic solvent phase aqueous Solution to a third extraction stage, con With the formation of two phases, separating Sail tinuously feeding a counter-current stream of last-nientioned phases, one of Said ia,3t-niel isophorone in proportion of about 0.1 by volume tioned phases being a mixture of isophCTORs 35. to said third extraction stage to dissolve therein non-polar organic solvent having aconitis a Sid 50 impurities in Said aqueous solution, separating dissolved therein, intinately contacting Said last the aqueous Solution from said isophorone, then mentioned phase With water with the for nation contacting said aqueous solution with benzene to of two phases, and separating said last-Ileil dissolve isophorone: therefrom, separating the tioned phases to obtain an aqueous Solution 30)- benzene from Said aqueous solution, passing said taining aconitic acid in greater concentration an aqueous Solution through a bed of activated car. purity than in said original agueous Solution. bon, and thereafter evaporating said solution to 2. The process of claim 1 wherein the non obtain Solid aconitic acid. polar organic solvent is selected from the group 6. A continuous process for recovering aconitic consisting of benzene, hexane, toluene and car acid from a relatively dilute aqueous solution de On tetrachloride. O rived from mola SSes by anionic exchange which 3. The process of claim 2 wherein the non Comprises continuously feeding a stream of said polar organic Solvent is benzene, aqueous Solution to an extraction stage, con 4. A continuous process for recovering a conitic tinuously feeding a counter-current stream of acid from a relatively dilute aqueous Solution isophorone to said extraction stage to strip the derived from molasses by anionic exchange which 65 aconitic acid from Said solution, separating the comprises continuously feeding a strean of Said mixed streams into an aqueous phase and a non aqueous solution to an extraction. Stage, Con aqueous phase comprising isophorone having tinuously feeding a counter-current Stream of aconitic acid dissolved therein, then contacting isophorone to said extraction stage to Strip the the Stripped aqueous phase with benzene to dis aconitic acid from said solution, Separating the 70 Solve isophorone therefrom, separating the ben mixed streams into two phases, then contacting Zene from Said aqueous phase, thereafter neu the stripped aqueous phase with benzene to dis tralizing acid in the aqueous phase and discard solve isophorone therefrom, separating the ben ing same, adding said separated benzene to the Zene from said aqueous phase, adding Said Sepa Separated isophorone phase and separating a rated benzene to the isophorone phase and then tarry phase therefrom, then feeding a stream of separating a tarry phase therefrom, then feed the resulting isophorone benzene phase to a sec 2,650,248 9 10 Ond extraction stage, continuously feeding a benzene to dissolve isophorone therefrom, sepa Counter-current stream of water to said Second rating said last-mentioned benzene from said extraction stage to strip out the aconitic acid last-mentioned aqueous solution and feeding said from said isophorone-benzene phase and form last-mentioned benzene into said isophorone an aqueous solution thereof, separating the last benzene phase, and passing said last-named mentioned aqueous Solution from the isophorone aqueous Solution through a bed of activated car benzene phase, thereafter distilling Said isopho bon and evaporating Said solution to recover rone-benzene phase to separate the isophorone acOnitic acid. and benzene, feeding the last-mentioned sepa DONALD W. COLLIER. rated isophorone to Said first extraction stage O and feeding the last-mentioned separated ben References Cited in the file of this patent Zene to the aqueous phase flowing from the Said first extraction stage, continuously feeding a UNITED STATES PATENS stream of the aqueous phase from the Second Nurnber Naine Date extraction stage to a third extraction stage, con 5 1952,845 Dreyfus ------Mar. 27, 1934 tinuously feeding a counter-current stream of 2,076,126 Guinot ------Apr. 6, 1937 isophorone to said third extraction stage to dise 2,165,438 Allquist ------July 11, 1939 solve impurities from said aqueous Solution, Sep 2,526,508 Scheeline et al. - Oct. 17, 1950 arating said last-mentioned isophorone from the OTHER REFERENCES aqueous phase and feeding said last-mentioned 20 Separated iSOphOrOne into Said isophorone-ben McClure: “Chem. Eng. News,' vol. 22, pp. 416-- Zene phase, then contacting the aqueous phase 421 (1944). separated from the third extraction stage with