PURIFICATION AND RECOVERY OF DICARBOXYLIC ACIDS USING MELT CRYSTALLIZATION

Abstract: Methods are disclosed for recovering dicarboxylic acids, particularly long chain dicarboxylic acids, from a feed containing at least one impurity. The methods utilize melt crystallization involving the steps of: (a) contacting the feed in a molten state with a crystallization surface, (b) cooling the crystallization surface to cause the formation of crystals comprising dicarboxylic acids and a mother liquor, (c) removing the mother liquor from the crystals, (d) heating the crystals to cause a partial melting of the crystals to form a sweat, (e) removing the sweat from the crystals, (f) melting the remaining crystals to form product, and (g) recovery of the product. The methods may be repeated as is necessary to obtain the desired purity. The purity of the dicarboxylic acids product obtained is generally greater than 96.0 weight % dicarboxylic acids based on the total weight of the product. Methods are also described for producing and recovering dicarboxylic acids by fermentation and melt crystallization.

Description: PURIFICATION AND RECOVERY OF DICARBOXYLIC ACIDS USING MELT CRYSTALLIZATION FIELD OF THE INVENTION The present invention relates to purification and recovery of dicarboxylic acids, and more particularly relates to methods for purification and recovery of dicarboxylic acids, particularly long chain dicarboxylic acids, from feeds by melt crystallization. BACKGROUND OF THE RELATED ART A variety of methods have been utilized for separating mixtures of dicarboxylic acids. One such method, solvent crystallization, typically involves dissolving the mixture of dicarboxylic acids in an organic solvent, cooling the solution to a temperature sufficient to form crystals, followed by filtering and washing the mixture to recover crystals containing a specific dicarboxylic acid. This method is inefficient and costly when performed on a commercial scale due to the effort required to recover the organic solvents and prevent their hazardous emissions. Distillation, chromatography, and membrane filtration of mixtures of dicarboxylic acids in conjunction with pH adjustment of the mixtures, have also been utilized to separate out a specific dicarboxylic acid from other dicarboxylic acids present in the mixture. Use of distillation to separate out a specific dicarboxylic acid is inefficient because the boiling point temperature of the dicarboxylic acid may be near the temperature at which decomposition of the dicarboxylic acid occurs, thus leading to low yields of the dicarboxylic acid. While the aforementioned methods have been utilized to separate specific dicarboxylic acids from mixtures containing a number of dicarboxylic acids, there are no known methods for separating dicarboxylic acids, particularly long chain fatty acids having eight or more carbon atoms, as a class from monocarboxylic acids and other impurities present in a feed on a large commercial scale, to yield a high quality product comprising dicarboxylic acids substantially free from the monocarboxylic acids and other impurities. Accordingly, a process for purification and recovery of dicarboxylic acids from feeds which also contain monocarboxylic acids and other impurities which yields a high quality product comprising dicarboxylic acids substantially free from such impurities is highly desired. SUMMARY OF THE INVENTION The present invention is directed to a novel method for recovering dicarboxylic acids, particularly mixtures of long chain dicarboxylic acids having eight or more carbon atoms, from feeds comprising dicarboxylic acids and at least one impurity, e.g.. monocarboxylic acids. The method of the present invention utilizes melt crystallization and involves the steps of (a) contacting the feed in a molten state with a crystallization surface, (b) cooling the crystallization surface to a crystallization temperature sufficient to cause the formation of crystals comprising dicarboxylic acids in a higher concentration than in the feed, and a mother liquor comprising dicarboxylic acids in a lower concentration than in the feed, (c) removing mother liquor from the crystals, (d) heating the crystals to a sweat temperature sufficient to cause melting of a portion of the crystals to form a sw eat, (e) removing the sweat from the crystals, (f) heating the crystals to a melt temperature sufficient to cause the crystals to form a product, and (g) recovering the product. The present invention is also directed to a method of producing and recovering dicarboxylic acids from a feed involving the steps of (a) providing a feed obtained by fermenting with a microorganism in a culture medium comprising a nitrogen source, an organic substrate and optionally a cosubstrate: (b) contacting the feed in a molten state with a crystallization surface; (c) cooling the crystallization surface to a crystallization temperature sufficient to cause the formation of crystals comprising dicarboxylic acids in a higher concentration than in the feed, and a mother liquor comprising dicarboxylic acids in a lower concentration than in the feed, (d) removing the mother liquor from the crystals, (e) heating the crystals to a sweat temperature sufficient to cause melting of a portion of the crystals to form a sweat, (f) removing the sweat from the crystals, (g) heating the crystals to a melt temperature sufficient to cause the crystals to form a product, and (h) recovering the product. The present invention is also directed to a composition of two or more dicarboxylic acids selected from the group consisting of octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, heptadecanedioic acid, octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid and analogous olefmically mono-and poly-unsaturated α, ω long chain dicarboxylic acids wherein the dicarboxylic acids comprise 96.0 weight % or greater of the composition. Quite advantageously, the method of the present invention does not require the use of organic soh'ents. Accordingly, this method eliminates the need for recovery of the solvents and prevention of their hazardous emissions. Quite surprisingly, the method described herein also achieves very high purities of dicarboxylic acids as a final product, e.g., 96.0% or higher based on the total weight of the product, even when impurities that are present in the feed, e.g., monocarboxylic acids, have properties which are very similar to dicarbox) lie acids. For example, the saturated C-18 monocarboxylic acid, stearic acid, and the unsaturated C-18 dicarboxylic acid, 9-octadccenedioic acid, have similar melting points, i.e., about 60°C. Accordingly, one skilled in the art would expect that when conducting melt crystallization of a feed including these two acids, both acids would crystallize at the same temperature. However, unexpectedly. 9-octadecenedioic acid crystallizes out from the feed preferentially to stearic acid. This advantage is particularly important in preparing polymer grade dicarboxylic acids which require a low concentration of residual monocarboxylic acids. Accordingly, the present method provides an efficient way of separating dicarboxylic acids as a class from a feed which also contains monocarboxylic acids. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically depicts a falling film melt crystallization system useful in the practice of the present invention. Figure 2 is a flow diagram of a live-stage sequential countercurrent crystallization process useful in the practice of the present invention. Figure 3 schematically depicts a multistage countercurrent cooling crystallization system useful in the practice of the present invention. DETAILED DESCRIPTION OF THE INVENTION Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about". Feeds comprising dicarboxylic acids, particularly long chain fatty acids having eight or more carbon atoms, may originate from a variety of sources which are well known to those skilled in the art, e.g., from a concentrated fermentation broth comprising dicarboxylic acids produced through fermentation by a microorganism, e.g. a yeast cell. For example. U.S. Patent Nos. 5,254,466, 5,648,247 and 5.620,878, the contents of each of which are incorporated by reference herein, describe procedures for production of dicarboxylic acids, particularly long chain dicarboxylic acids, through fermentation of monocarboxylic acids or alkanes. In particular, the aforementioned patents describe the use of genetically altered strains of the species, Candida Iropicalis, for the effective production of long chain dicarboxylic acids. Preferably, the microorganism is a partially or completely beta-oxidation blocked C. iropicalis cell, and more preferably the microorganism is a completely beta-oxidation blocked C. iropicalis cell wherein both copies of the chromosomal POX5 gene and the chromosomal POX4A and POX4B genes are disrupted, e.g., C tropicalis strain H5343 (ATCC 20962), as described in aforesaid U.S. Patent No. 5,254,466. Typically, such procedures involve fermentation with a microorganism, e.g., yeast in a culture medium which includes a nitrogen source, an organic substrate, and optionally a cosubstrate. The resulting fermentation broth will include dicarboxylic acids in combination with various impurities, e.g., biomass from spent microorganisms, proteins, amino acids, monocarboxylic acids, sugars, carbohydrates, esters, glycerides, lipids and the like. The whole fermentation broth can be further processed to remove water and impurities such as the spent biomass from microorganisms by. e.g.. centrifugation and filtration, pH adjustment of the fermentation broth, distillation, ion exchange, solvent extraction, etc., to obtain an intermediate composition containing dicarboxylic acids and a minimum amount of at least one impurity which can be used as a feed to the melt crystallization process of this invention. As is well-known to those skilled in the art, feeds comprising dicarboxylic acids may also originate from chemical synthesis of dicarboxylic acids. For example, U.S. Patent No. 5,420,316, the contents of which are incorporated by reference herein, describes the production of a dicarboxylic acid such as nonanedioic acid, by ozonization of a monocarboxylic acid having at least one olefin bond, e.g., oleic acid. The resulting feed can then be utilized in the method described herein, or, alternatively, can be concentrated prior to its use in the instant method. For example, the feed can be concentrated, e.g., by fractional distillation, acid precipitation, etc., to separate dicarboxylic acids from solvents present in the feed. The concentration of dicarboxylic acids in the feed utilized in the present invention generally ranges from about 50 to about 95 weight % dicarboxylic acids, and preferably from about 70 to about 90 weight % dicarboxylic acids, based on the total weight of the feed. Examples of impurities that are present in the feed include, but are not limited to, monocarboxylic acids, mono- and diesters of dicarboxylic acids, esters of monocarboxylic acids, anhydrides, sugars, sugar esters, alcohols, glycerides, proteins, color bodies, amides, ami no acids, solvents and combinations thereof. The impurities are generally present in the feed at a concentration of about 5 to about 50 weight % impurity, and preferably from about 5 to about 30 weight % impurity, based on the total weight of the feed. The method (steps a-g) of the present invention comprises (a) contacting the feed in a molten state with a crystallization surface, and (b) cooling the crystallization surface to a crystallization temperature sufficient to cause the formation of crystals comprising dicarboxylic acids which are in a higher concentration than in the feed, and a mother liquor comprising dicarboxylic acids in a lower concentration than in the feed. The impurities, e.g., monocarboxylic acids, crystallize to a lower extent than the dicarboxylic acids onto the crystallization surface. Accordingly, the impurities concentrate in the mother liquor, which is (c) removed from the crystals. Typically, the crystallization surface is ramped down in temperature until about 40 to about 90% of the feed is crystallized on the crystallization surface to provide a layer of crystals of about 1 to about 20 millimeters on the crystallization surface. As used hereinafter, the "initial crystallization temperature" refers to the temperature at which the first crystals form on the crystallization surface and the "final crystallization temperature" refers to the temperature at which the crystallization cycle has ended and mother liquor is removed from the crystals. The time period for performing the crystallization step typically ranges from about 0.1 to about 20 hours and preferably from about 0.2 to about 3 hours. The desired crystallization temperature will vary with the composition of the feed, the purity of the dicarboxylic acids present in the feed, the carbon number of the dicarboxylic acids and the percentage of saturated \ ersus unsaturated dicarboxylic acids present in the feed. For example, the crystallization temperature of dicarboxylic acids having eight or more carbon atoms can range from about 30 to about 140°C, typically from about 40 to about 80°C for unsaturated dicarboxylic acids and from about 100 to about 140°C for saturated dicarboxylic acids. Subsequently, the crystals comprising dicarboxylic acids are (d) heated to a sweat temperature sufficient to cause melting of a portion of the crystals to form a sweat, which is (e) then removed from the crystals. As used hereinafter, the term "sweat" refers to a portion of the crystals comprising dicarboxylic acids which are melted to form droplets of liquid which appear on the surface of the remaining crystals. The sweat contains additional impurities that were entrapped in the crystals. Thus, the sweating process further increases the purity of the crystals. Typically, the sweat temperature ranges from about 0.1 to about 10°C, and preferably from about 0.1 to about 2°C above the final crystallization temperature. The portion of the crystals that melt to form a sweat generally ranges from about 1 to about 40% of the crystals formed and preferably from about 5 to about 25% of the crystals formed. The time period for performing the sweating step generally ranges from about 25% to about 90% and preferably from about 40% to about 80%, of the time required for the crystallization step. After the sweat is removed, the crystals arc (f) heated to a melt temperature sufficient to cause the crystals to melt and form a product, which is (g) recovered. The melt temperature can be the same as the sweat temperature which is maintained for a period of time, or a higher temperature than the sweat temperature, to melt the remaining crystals. The melt temperature, generally ranges from about 1 to about 50°C, and preferabl) from about 5 to about 25°C above the initial crystallization temperature. The time period for performing the melt step generally ranges from about 0. 1 to about 1.0 hours, and preferably from about 0.1 to about 0.3 hours. The aforementioned steps comprise one stage or cycle of the melt crystallization method, which may be repeated as man}- times as necessary on the product to achieve the desired purity, and also on the mother liquor and/or sweat to increase the overall yield of product. Preferably, multi-staging is carried out using a countercurrent crystallization process wherein the product from the first stage is pumped to the next higher purity stage, the mother liquor is pumped to the next lower purity stage, and the sweat is pumped either to the next lower purity stage or to the current feed stage depending on its composition, as described in detail below. Examples of dicarboxylic acids that are recovered as product include saturated and unsaturated, linear and branched dicarboxylic acids including, but not limited to, octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, hepladecanedioic acid, octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid, analogous olefmically mono- and poly-unsaturated α, ω long chain dicarboxylic acids and combinations thereof. Preferably, the dicarboxylic acids include, but are not limited to. nonanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, octadecenedioic acid and combinations thereof. Typically, the purity of the dicarboxylic acids recovered is substantially greater than the purity of the dicarboxylic acids present in the initial feed. After completion of one or more stages of the melt crystallization process, the product generally comprises greater than about 96.0 weight % dicarboxylic acids, preferably greater than about 99.0 weight % dicarboxylic acids, and more preferably greater than about 99.9 weight % dicarboxylic acids, based on the total weight of the product. The dicarboxylic acids, and particularly long chain dicarboxylic acids, are commercially important products utilized in the production of polymers, adhesives, perfumes, and antibiotics. The method described herein can be carried out using any type of crystallization system which is suitable for conducting melt crystallization. For example, a specific melt crystallization system has been designed for conducting the technique known as "falling film crystallization," as described herein by Jancic, "The Sulzer MWB Fractional Crystallization System," Tech. Rev. , Sulzer, Winterthur, Switz., 1986; Wynn, "Separate Organics by Melt Crystallization", Chemical Engineering Progress, Sulzer Brothers Limited, Winterthur. Switz, 1992; Fischer et al., "Crystallization Without Solvent," Sulzer Technical Review, Sulzer Brothers Limited, Winterthur, Switz., 1992; Mullin,"Cr) stallization Techniques and Equipment", Crystallization, pp. 318-319, Reed Educational and Professional Publishing Ltd.. 1993; and U.S. Patent No. 5,700,435, the contents of each of which are incorporated by reference herein. Various types of other melt crystallization systems are commercially available such as the batch crystallization systems manufactured by Sulzer Brothers Limited (Ontario. Canada) and Griffiths Chemicals and Metals (Atkinson. WI) as described e.g., by Meyer, "Using Crystallization For Organic Separations", Chemical Processing. January 1990. the contents of which are incorporated by reference herein; and the countercurrent cooling crystallization system developed by Tsukisliima Kikai Co., Ltd. (Tokyo. Japan), which is described in more detail below. In falling film crystallization, a film of melt flows downward over a cooled crystallization surface on which the crystals grow. Figure 1 schematically depicts a falling film melt crystallization system, as described, e.g.. in Mullin. supra. The system generally comprises a crystallizer 1. a collecting tank 2, a puirp 3 for circulating feed, a circulation system 4 for circulating the feed, heat exchange fluid lines 5, a jacket 6 surrounding crystallizer 1, residue line 7 and product line 8, residue and product storage tanks (not shown) and a heat exchanger (not shown). The interior of crystallizer 1 contains a crystallization surface, e.g., a group of vertical tubes, on which crystals are deposited. At the start of one stage or cycle, collecting tank 2 is filled with molten feed, and pump 3 circulates the feed in collecting tank 2 through circulation system 4 and downward onto the crystallization surface of the crystallizer 1. The temperature of the crystallization surface is lowered bj pumping chilled heat exchange fluid, e.g.. propylene glycol. through heat exchange fluid line 5 into jacket 6 surrounding crystallizer 1, preferably in a direction concurrent to the flow of the feed. The temperature of the crystallization surface is decreased until about 40 to about 90% of the feed is crystallized on the crystallization surface to provide a layer of crystals of about 1 to about 20 millimeters. The mother liquor remaining after the en stallization step is removed fiom collecting tank 2 through residue line 7 and is pumped into a residue storage tank or tank for the next lower purity stage as described below. After crystallization is completed, the circulation of the feed is discontinued, and a portion of the crystals formed on the crystallization surface is sweated by increasing the temperature of the crystallization surface b} pumping heated heat exchange fluid through line 5 into jacket 6. The sweat which contains impurities drains off and is removed thiough residue line 7 and pumped into a residue storage tank or tank for the next lower purity stage. Following sweating, the remaining crystals on the crystallization surface are completely melted to form the product, which is recovered through a product line 8 and is pumped into a product storage tank or tank for the next higher purity stage. As stated above, the resulting product initially may not be of the desired purity. Accordingly, the present melt crystallization method of lecovering dicarboxylic acids from a feed can further comprise multi-staging, wherein the melt crystallization method is repeated as many times as desired on the product to achieve the desired purity. In the "falling film crystallization" technique, as described above, the crystallization, sweating, and melting stages are usually performed using one crystallizer and a cascade of tanks in which each stages' product are pumped to the next higher purity stage tank, the mother liquor is pumped to the next lower purity stage tank, and the sweat is pumped either to the next lower purity stage tank or to the current feed stage tank. Figure 2 depicts a typical multi-stage sequential, countercurrent crystallization process. Each stage represents the sequential occurrence of the above- described method for recovering dicarboxylic acids from a feed comprising the steps of crystallizing, sweating, and melting. Essentially, melted product comprising dicarboxylic acids from the ions stage is fed to the next stage in the sequence, and combined with mother liquor and s eat originating from the subsequent stage in the sequence. As shown in Figure 2, feed containing dicarboxylic acids and at least one impurity is introduced to the Feed Stage along with the mother liquor and the crystal sweat from Enrich Stage 1, and the melted product from Strip Stage 1. This mixture undergoes one stage of the above- described method comprising the steps of crystallization, sweating, and melting. The melted product formed in the Feed Stage 1 is forwarded to Enrich Stage 1. In Strip Stage 1. the product from Strip Stage 2, and the mother liquor and sweat originating from the Feed Stage are combined and processed as described with reference to the Feed Stage. In Strip Stage 2, the mother liquor and sweat from Strip Stage 1 are processed as described above with reference to the Feed Stage. The melted product is forwarded to Strip Stage 1 and the mother liquor and sweat are removed as impurities. In Enrich Stage 1, the melted product from the Feed Stage is combined with the mother liquor and sweat from Enrich Stage 2, and the process is repeated, as described above with reference to the Feed Stage. In Enrich Stage 2, the melted product from Enrich Stage 1 is processed as described above with reference to the Feed Stage. The mother liquor and sweat from Enrich Stage 2 is forwarded to Enrich Stage 1. The melted product comprising dicarboxylic acids is then recovered as a product. Accordingly, as the product is processed through each stage, it becomes increasingly enriched with dicarboxylic acids. As the mother liquor and sweat are reprocessed through each stage, they become progressivel} stripped of any remaining dicarboxylic acids, to form a residue substantial!} free of dicarboxylic acids. Accordingly, the reprocessing of sweat and mother liquor enhances recovery of the product. Another example of a melt crystallization system useful for practicing the present invention is the countercurrent cooling crystallization (referred to as TSK 4C) system developed by Tsukishima Kikai Co.. Ltd. (Tokyo. Japan) as described, e.g., in Mullin, supra and Meyer, supra. This crystallization system utilizes several scraped surface crystallizcrs connected in series with a purifying column, which contains a melter at the bottom. Figure 3 schematically depicts a countercurrent cooling crystallization system having two cooling crystallizers connected in series represented as Stages 1 and 2, as described, e.g., in Mullin, supra. Each crystallizer possess a cooling jacket 1 and a rotating draft tube (not shown) having attached scrapers (not shown). The rotating tube mixes the contents of each crystallizer to provide a uniform slurry. Feed in a molten state containing dicarboxylic acids and at least one impurity flows through the crystallizer in Stage 1, where a portion of the feed crystallizes on the cooled en stallization surface and a mother liquor-crystal shiny is formed. The scraper blades continuously remove crystals from the cooled crystallization surface. The mother liquor-crystal slurry is then pumped to a hydroclone 2. which concentrates the crystal slurry, thereby separating out most of the mother liquor present in the slurry. The crystals fall into the purifying column 3 and form a packed bed of crystals which moves toward the bottom of the column. As the en stals move down the column the temperature of the cr) stals increases, and a portion of the crystals melt to form a sweat, which moves in a countercurrent direction from the crystals. At the bottom of the column, the remaining cr) stals melt to form product comprising dicarboxylic acids. A portion of the melt product is withdrawn, and the remaining melted product flows upward in a countercurr.nt direction from the crystals. The countercuπent stream of sweat and melted product washes the crystals and carries impurities. The melted product and sweat then combine with the mother liquor which was separated from the crystals by hydroclone 2 and the combined mixture flows back 4 to Stage 1. A portion of the mother liquor from Stage 1 overflows 5 to the crystallizer in Stage 2. and because of even lower temperatures on the second crystallization surface, a portion of the mother liquor forms crystals on the crystallization surface. The mother liquor-crystal slurry is then pumped to a hydroclone 6, and then to the crystallizer in Stage 1. Another aspect of the present invention is directed to a method for producing and recovering dicarboxylic acids from a feed comprising the steps of providing a feed obtained by fermenting with a microorganism in a culture medium comprising a nitrogen source, an organic substrate and optionally a cosubstrate. The feed can be further processed to remoλ e biomass and water as described above. The feed in a molten state is then subjected to the same melt crystallization method as the melt crystallization method utilized to recover dicarboxylic acids as described aboλ e. The microorganisms which are preferably utilized in the fermentation step are the same as those that can be utilized in the melt crystallization method as described above. Preferably, the dicarboxylic acids are selected from the group consisting of octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, heptadecanedioic acid. I I octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid, analogous olefmically mono- and poly-unsaturated σ, ω long chain dicarboxylic acids and combinations thereof. More preferably, the dicarboxylic acids include octadecenedioic acid. Another aspect of the present invention is directed to a composition of two or more dicarboxylic acids selected from the group consisting of octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pcntadecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, heptadecanedioic acid, octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid, and analogous olefmically mono- and poly-unsaturated α. ω long chain dicarbox} lie acids wherein the dicarboxylic acids comprise 96.0% or greater of the composition. Preferably, the two or more dicarbox} lie acids are selected from the group consisting of nonanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid and octadecenedioic acid. Preferably the dicarboxylic acids comprise at least about 99.0 weight % or greater of the composition, and more preferably at least about 99.9 weight % of the composition. Preferably, the dicarbox) lie acids include greater than 60 weight % octadecenedioic acid. The practice of the present invention is not limited to the use of the above- mentioned crystallization systems, but also contemplates the use of any other suitable melt crystallization systems which are well-known to those skilled in the art. The following examples are meant to illustrate but not to limit the invention. EXAMPLE RECOVERY OF DICARBOXYLIC ACIDS BY MELT CRYSTALLIZATION A laboratory falling film crystallizer is used to recover dicarboxylic acids from a concentrated broth containing dicarboxylic acids and at least one impurity. The concentrated broth was produced by fermenting C. tropicalis strain H5343 (ATCC 20962) according to the procedure as described, e.g., in aforesaid U.S. Patent 5,254,466. Fermentation of oleic acid with strain H5343 under standard fermentation conditions produced a broth comprising 100-140g/l dicarboxylic acids which corresponded to 10-14 weight % dicarboxylic acids based on the total weight of the feed. The remaining impurity was 5-25 g/1 monocarboxylic acids, which corresponded to a yield of 85-95% monocarboxylic acids based on the total w eight of the monocarboxylic acid feed. The amount of dicarboxylic acids and impurities in the above-described fennentation broth and the concentrated liquid broth described below was measured by gas chromatographic analysis. The resulting fermentation broth is put into an insulated, open top tank with overhead stirrer. It is heated to 80°C with an immersion steam coil and acidified with -2.2 N H 2 S0 4 to pH 1.5. The mixer is then shut off and the acidified broth is then allowed to settle. The biomass sinks to the bottom and an organic layer fonns on the top. The surface is skimmed off through a hose into an evacuated, jacketed tank. The mixer in the open top tank is then turned back on to stir up the biomass phase. The mixer is again turned off and the mixture allowed to settle. The organic layer is once again skimmed off to the evacuated, jacketed tank. The mix/settle/skim process is repeated until no more organic layer forms. The vacuum in the evacuated, jacketed tank is then broken with N 2 . A volume of deionized water equal to the skimmed organic material is then added and the agitator turned on for five minutes. The agitator is turned off, the phases allowed to settle for two hours, and the denser water layer decanted off. The deionized water addition/mix/settle decant step is repeated five times or until no haze forms in a liter sample of the decant water upon addition of 10 drops of 2 N BaCU solution. Residual water is then stripped from the organic phase by turning on the agitator, heating the tank to 105°C b) applying steam to the jacket, and reducing the pressure to 35 mm Hg. The dicarboxylic acid purity in the stripped organic phase is typically about 70 to about 90 weight %. thereby making it suitable as a melt crystallization feed. The laboratory falling film crystallizer comprises, a crystallizer kettle possessing a heating element, a jacketed vertical tube, an outlet for recycling mother liquor, a recycle heater, a feed pump, a film distributor and a cooling system for the jacketed portion of the vertical tube. Approximately 20 kg of the concentrated molten feed containing dicarboxylic acids and at least one impurity is fed to the crystallizer kettle, followed by heating the kettle to a temperature of 70°C. Subsequently, the molten feed is passed through the outlet, and is circulated by the feed pump and the film distributor spreads this flow along the inside surface of the crystallizer. The molten feed then flows down back to the kettle. The crystallizer is cooled to a crystallization temperature of about 60 to about 63°C by decreasing the temperature of the heat exchange fluid, e.g., glycols, that are circulating through the jacket, until a layer of crystals forms on the inside walls of the crystallizer. The temperature of the cooling fluid is then decreased until about 25% of the remaining feed, i.e.. mother liquor, is left in the kettle. After crystallization, the mother liquor is removed, and the temperature of the heat exchange fluid is gradually increased to a sweat temperature of about 65°C until a portion of the crystals melt to form a sweat. The sweat is then removed through the outlet, and the remaining crystals are melted at a melt temperature of about 70°C to form product which is collected in the kettle. Approximately 12 kg of melted product is obtained comprising 90 weight % dicarboxylic acids based on the total weight of the product. The mother liquor (5 kg) comprises 56 weight % dicarboxylic acids based on the total weight of the mother liquor. The sweat (3 kg) comprises 80 weight % dicarboxylic acids based on the total weight of the sweat. It will be understood that various modifications may be made to the embodiments disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims: WHAT IS CLAIMED: 1 . A method for recovering dicarbox) lie acids from a feed comprising dicarboxylic acids and at least one impurity, the method comprising: (a) contacting the feed in a molten state with a crystallization surface; (b) cooling the crystallization surface to a crystallization temperature sufficient to cause the formation of crystals comprising dicarboxylic acids in a higher concentration than in the feed, and a mother liquor comprising dicarboxylic acids in a lower concentration than in the feed; (c) ing mother liquor from the crystals; (d) heating the crystals to a sweat temperature sufficient to cause melting of a portion of the crystals to form a sweat; (e) removing the sweat from the crystals; (f) heating the crystals to a melt temperature sufficient to cause the crystals to form a product; and (g) recovering the product. 2. The method of claim 1 wherein the dicarboxylic acids have eight or more carbon atoms. 3. The method of claim 1 wherein the feed is obtained by fermenting with a microorganism in a culture medium comprising a nitrogen source, an organic substrate and optionally a cosubstrate. 4. The method of claim 1 wherein the product comprises dicarboxylic acids selected from the group consisting of octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, hexadecene ioic acid, heptadecanedioic acid, octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid, analogous olefmically mono- and poly-unsaturated α, ω long chain dicarboxylic acids and combinations thereof. 5. The method of claim 4 wherein the product comprises dicarboxylic acids selected from the group consisting of nonanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, octadecenedioic acid and combinations thereof. 6. The method of claim 1 wherein the concentration of dicarboxylic acids in the feed is from about 50 to about 95 weight % dicarboxylic acids based on the total weight of the liquid feed. 7. The method of claim 1 wherein the impurities are selected from the group consisting of monocarboxylic acids, mono- and diesters of dicarboxylic acids, esters of monocarboxylic acids, anhydrides, sugars, sugar esters, alcohols, glycerides, proteins, color bodies, amides, amino acids, solvents and combinations thereof. 8. The method of claim 1 wherein the crystallization temperature ranges from about 30 to about 140°C. 9. The method of claim 1 wherein the sweat temperature ranges from about 0.1 to about 10°C above the crystallization temperature. 10. The method of claim 1 wherein the melt temperature ranges from about 1 to about 50°C the crystallization temperature. 1 1. The method of claim 1 further comprising the repetition of steps (a-g) utilizing the product as the feed. 12. T he method of claim 1 further comprising the repetition of steps (a-g) utilizing the mother liquor as the feed. 13. 1 he method of claim 1 further comprising the repetition of steps (a-g) utilizing the sweat as the feed. 14. The method of claim 1 further comprising combining the sweat with the mother liquor and utilizing the combination as the feed. 15. The method of claim 1 wherein a portion of the mother liquor that is removed in step (c) is contacted with a crystallization surface which is cooled to a crystallization temperature sufficient to cause the formation of crystals comprising dicarboxylic acids in a higher concentration than in the mother liquor and a second mother liquor comprising dicarboxylic acids in a lower concentration than in the mother liquor. 16. The method of claim 1 wherein the feed is concentrated to provide a dicarboxylic acid content of from about 70 to about 90 weight %. 17. The method of claim 1 wherein the concentration of dicarboxylic acids in the product is greater than about 96.0 weight % dicarboxylic acids based on the total weight of the product. 18. The method of claim 17 wherein the concentration of dicarboxylic acids in the product is greater than about 99.0 weight % dicarboxylic acids based on the total weight of the product. 19. The method of claim 18 wherein the concentration of dicarboxylic acids in the product is greater than 99.9 weight % dicarboxylic acids based on the total weight of the product 20. The product produced by the method of claim 1. 21. The product of claim 20 comprising greater than about 96.0 weight % dicarboxylic acids based on the total weight of the product. 22. The product of claim 21 comprising greater than about 99.0 weight % dicarboxylic acids based on the total weight of the product. 23. The product of claim 22 comprising greater than about 99.9 weight % dicarboxylic acids based on the total weight of the product. 24. The product of claim 20 wherein the dicarboxylic acids are selected from the group consisting of octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, heptadecanedioic acid, octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid, analogous olefinically mono-to poly-unsaturated α, ω long chain dicarboxylic acids and combinations thereof. 25. The product of claim 24 wherein the dicarboxylic acids are selected from the group consisting of nonanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid, octadecenedioic acid and combinations thereof. 26. A composition of two or more dicarboxylic acids selected from the group consisting of octanedioic acid, nonanedioic acid, decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, heptadecanedioic acid, octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid and analogous olefmically mono- and poly-unsaturated α, ω long chain dicarbox) lie acids wherein the dicarboxylic acids comprise 96.0 weight % or greater of the composition. 27. The composition of claim 26 wherein the dicarboxylic acids are selected from the group consisting of nonanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, eicosanedioic acid and octadecenedioic acid. 28. The composition of claim 26 wherein the dicarboxylic acids comprise at least about 99.0 w eight % or greater of the composition. 29. The composition of claim 28 wherein the dicarboxylic acids comprise at least about 99.9 eight % of the composition. 30. The composition of claim 26 wherein the dicarboxylic acids comprise greater than 60.0 weight % octadecenedioic acid. 31 . A method for producing and recovering dicarboxylic acids from a feed comprising the steps of: (a) providing a feed obtained by fermenting with a microorganism in a culture medium comprising a nitrogen source, an organic substrate and optionally a cosubstrate; (b) contacting the feed in a molten state with a crystallization surface; (c) cooling the crystallization surface to a crystallization temperature sufficient to cause the formation of crystals comprising dicarboxylic acids in a higher concentration than in the feed, and a mother liquor comprising dicarboxylic acids in a lower concentration than in the feed; (d) removing mother liquor from the crystals; (e) heating the crystals to a sweat temperature sufficient to cause melting of a portion of the crystals to form a sweat; (f) removing the sweat from the crystals; (g) heating the crystals to a melt temperature sufficient to cause the crystals to form a product; and (h) recovering the product. 32. The method of claim 31 wherein the product of dicarboxylic acids is selected from the group consisting of octanedioic acid, nonanedioic acid, decanedioic acid. undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, hexadecenedioic acid, heptadecanedioic acid, octadecanedioic acid, octadecenedioic acid, nonadecanedioic acid, eicosanedioic acid, heneicosanedioic acid, docosanedioic acid, trieicosanedioic acid, tetraeicosanedioic acid, analogous olefmically mono- and poly-unsaturated α, ω long chain dicarboxylic acids and combinations thereof. 33. The method of claim 32 wherein the product of dicarboxylic acids includes octadecenedioic acid. 34. The method of claim 31 wherein the microorganism is a veast cell. 35. The method of claim 34 wherein the yeast cell is a C. iropicalis cell. 36. The method of claim 35 wherein the C. iropicalis cell is a partially or completely beta-oxidation blocked C. iropicalis cell. 37. The method of claim 36 wherein the C. Iropicalis cell is a completely blocked C. iropicalis cell wherein both copies of the chromosomal POX5 gene and the chromosomal POX4A and POX4B genes are disrupted. 38. The method of claim 37 wherein the C. iropicalis cell is strain H5343.

Inventors: GOTTMAN ANNA M, KOZAK WILLIAM G, REBROVIC LOUIS, STALEY MICHAEL D, GOTTMAN, ANNA, M., KOZAK, WILLIAM, G., REBROVIC, LOUIS, STALEY, MICHAEL, D.
Applicants: COGNIS CORP, COGNIS CORPORATION
Application year: 2000
Main classification: C07C51
IPC codes: C07C51, C12P7