WO2001038284A1 - Traitement ameliore de l'acide lactique, procedes, agencements et produits - Google Patents

Traitement ameliore de l'acide lactique, procedes, agencements et produits Download PDF

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WO2001038284A1
WO2001038284A1 PCT/US2000/031979 US0031979W WO0138284A1 WO 2001038284 A1 WO2001038284 A1 WO 2001038284A1 US 0031979 W US0031979 W US 0031979W WO 0138284 A1 WO0138284 A1 WO 0138284A1
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lactic acid
vapor
vapor phase
range
solution
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PCT/US2000/031979
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English (en)
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George Quarderer, Jr.
Lanny A. Robbins
Christopher M. Ryan
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Cargill Dow Llc
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Priority to AU16619/01A priority Critical patent/AU1661901A/en
Publication of WO2001038284A1 publication Critical patent/WO2001038284A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/42—Separation; Purification; Stabilisation; Use of additives
    • C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
    • C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation

Definitions

  • the present disclosure relates to lactic acid processing. It particularly concerns methods for purifying lactic acid/water mixtures under conditions selected to facilitate downstream processing and to control racemization.
  • lactic acid as a commodity chemical, for example for use in the production of various industrial polymers, is known.
  • Such use of lactic acid has become of particular interest, because polymers formed from lactic acid, i.e. polylactic acid and many of its products, are hydrolyzable, biodegradable and/or compostable. Additionally, lactic acid can be readily produced by fermentation; thus providing the possibility of commodity plastics formed using renewable carbon sources.
  • Lactic acid has a chiral center and is found in both the D- and L- forms. Management and control of the chiral purity of the lactic acid used to form the polymer can be important for industrial applications of the polymer, see for example U.S. patents: 5,142,023; 5,338,822; 5,484,881; and, 5,536,807, these four patents being incorporated herein by reference.
  • lactic acid during the fermentation process can be managed under conditions which allow for production with a relatively high degree (for example at least 90%, typically at least 98%) of chiral purity, downstream processing with many conventional techniques can lead to undesirable amounts of racemization.
  • a preferred method of processing lactic acid generally comprises conducting a vapor based transfer of an aqueous solution of lactic acid, typically under a system pressure within the range of 30-200 mm Hg, more preferably 40-120 mm Hg, most preferably 40-60 mm Hg.
  • the vapor phase transfer is conducted at the temperature of not more than 200 °C, more preferably not more than 180°C.
  • the vapor phase transfer is conducted on an aqueous solution of lactic acid comprising at least 25 wt. % lactic acid (i.e., lactic acid monomer and oligomer), and not more than 88 wt. % lactic acid. More preferably, it is conducted on an aqueous solution comprising 40-80 wt. % lactic acid, at a pressure of about 40-60 mm Hg.
  • the preferred process is integrated with a downstream prepolymerization or oligomerization process, such that the transferred vapor phase is fed directly into the oligomerization process, as a vapor, for condensation within the oligomerization process.
  • the integration is such that both the vapor phase transfer and the downstream oligomerization process are conducted at the same pressure (e.g., 30-200 mm Hg,) and under an inert atmosphere (e.g. nitrogen).
  • preferred techniques for conducting the processes are provided, as well as preferred definition of equipment.
  • a preferred purified vapor phase composition of lactic acid is defined.
  • Fig. 1 is a schematic presentation of a lactic acid isolation and purification process
  • Fig. 2 is a schematic presentation of a step of, and equipment for, vapor phase transfer of a lactic acid solution
  • Fig. 3 is a schematic presentation of a vapor/liquid separator.
  • the present disclosure generally concerns lactic acid processing, and it particularly concerns a preferred processing step conducted in an overall processing scheme involving: (a) generation of lactic acid for example by fermentation, and, (b) eventual generation of a purified lactic acid product from that lactic acid.
  • the lactic acid from the process would typically either: (1) be isolated for later use or, (2) for certain preferred applications, be introduced directly into a process for preferred generation of lactide.
  • Techniques related to overall processing schemes which relate to the generation and isolation of lactic acid are characterized in U.S.S.N. 08/950,289, U.S.S.N. 09/132,720, and U.S.S.N. 09/412,085. These three applications each having previously been incorporated herein by reference.
  • A. A typical lactic acid process.
  • Fig. 1 represents a typical approach to obtaining a lactic acid solution which can be processed, using techniques according to the present disclosure.
  • reference letter (F) indicates the lactic acid solution being removed from the processing operation, to be directed into a lactic acid purification and, if desired, a processing system, according to the present disclosure. 1. Terminology.
  • the source of lactate material includes a fermentation broth.
  • fermentation refers to any metabolic process that produces a useful product by a mass culture of microorganisms.
  • microorganisms are suitable for use in the fermentation process, for example, bacteria, yeast and fungi.
  • lactate material herein refers to 2-hydroxypropionate in either its free acid or salt form and also to lactic acid oligomers, such as lactoyl lactate, in their free acid and/or salt form.
  • lactic acid and “free lactic acid”, abbreviated HLa are employed interchangeably herein to refer to the acid form, e.g., 2- hydroxypropionic acid, also called the “undissociated” form and lactic acid oligomers in the acid form, such as lactoyl lactate.
  • lactic acid monomer refers to 2-hydroxypropionic acid in the acid form.
  • lactate salt for example, as the sodium (or calcium) salt of lactic acid or sodium lactate (or calcium lactate) and the salt or "dissociated” form of lactic acid oligomers.
  • Nutrient medium refers to media in the form originally provided to the microorganism for fermentation and typically includes a carbon source, a nitrogen source and other nutrients.
  • the term “fermentation broth” refers to a mixture that includes lactate material (e.g., free lactic acid and lactate salt) produced after some or all of the originally provided nutrients have been consumed and fermentation products including lactate material have been excreted into the media by the microorganism.
  • the fermentation broth can include recycle streams from other processes, including the processes described herein.
  • the fermentation broth is also referred to as a "source of lactate material.”
  • “Clarified solution” refers to the source of lactate material or fermentation broth after at least some impurities have been removed.
  • polylactic acid or “polylactate” are intended to refer to any polymer comprising at least 50% by wt. polymer units of lactic acid residue or lactide residue. Thus, the two terms include within their scope polylactides.
  • polylactic acid and polylactate without more, are not meant to specifically identify the polymerized monomer, for example whether the material polymerized was lactide (lactic acid dimer) or lactic acid itself.
  • the amount of lactate material in a solution can be represented by the weight percent of lactate material present calculated as if it was all in the undissociated or acid form; or the weight percent of lactate material present in the solution calculated as if it was all in the dissociated or salt form.
  • the amount of lactate material in a solution (by wt. %) is provided herein, it generally represents the weight percent of lactate material present calculated as if it was all in the undissociated or acid form, and as if it were all in the monomer (non-oligomer) form, unless otherwise noted.
  • non- oligomerized lactic acid and 13% by wt., lactic acid in the oligomer form when a concentration of an aqueous lactic acid solution is reported, on a wt. % basis for lactic acid, the calculation is meant to be a theoretical lactic acid concentration by wt., without regard to the amount which is non-oligomerized lactic acid vs. the amount which has been incorporated into oligomers, due to the referenced equilibria, unless otherwise specified.
  • chiral purity is sometimes used to characterize the lactic acid solution.
  • 95% chiral purity means 95% of the lactic acid/lactate content is in one of the two possible enantiomers: i.e.; either D- or L-. Such a composition could alternatively be characterized as 10% racemic or 90% optically pure.
  • the pressure of the prepolymer formation system refers to the pressure of the vapor stream exiting the condenser of the prepolymer formation system, unless otherwise noted. Since differences in pressure are generally needed to obtain gas flow, the pressure in the liquid/vapor separator or at the feed inlet to the evaporator may be higher than the pressure indicated. Engineering techniques for minimizing the pressure differences are known. 2. Sources of Lactate Material; Fig. 1(A).
  • the process described herein provides a method for obtaining a purified lactic acid solution from a source of lactate material.
  • suitable sources of lactate material include, but are not limited to, a fermentation broth, a recycle stream from polylactic acid production which contains lactate material, or recycled polylactic acid (e.g., post-consumer waste or production scraps) that has been hydrolyzed to form a solution containing lactate material.
  • the source of lactate material is a fermentation broth.
  • fermentation broth includes a fermentation broth which includes recycle streams from the process described herein or other processes.
  • the techniques described herein are not limited in application to only those lactic acid compositions obtained from fermentation.
  • the source of lactate material includes compounds other than lactic acid as impurities.
  • fermentation broths may include both lactic acid and lactate salt, collectively referred to as lactate material, along with cellular debris, residual carbohydrates, amino acids, nutrients (or nutrient media) and other impurities.
  • lactate material a compound that includes lactic acid (monomer and/or oligomer) in an aqueous carrier with less than about 5.0 g/L impurities, more preferably less than about 1.0 g/L impurities, most preferably less than about 0.1 g/L impurities.
  • the acceptable concentration of impurities can vary depending on the intended commercial use of the solution and the concentration of lactic acid within the solution.
  • the phrase "purified lactic acid solution", without further definition, refers to a solution which contains: (1) between about 5 wt% to about 90 wt% lactic acid; (2) an aqueous carrier; and, (3) no more than about 5.0 g/L impurities.
  • preferred such solutions will be those which contain no more than about 1.0 g/L, more typically no more than about 0.1 g/L impurities, and most typically no more than 0.05 g/L of impurities, such as proteins, carbohydrates, cellular debris, salts, etc.
  • preferred such solutions will be those which contain between about 10 wt % to about 90 wt% lactic acid, more typically between about 25 wt. % to about 88 wt. % lactic acid, most typically about 60 wt% to about 75 wt% lactic acid.
  • a "clarification" process may optionally be performed to reduce the presence of suspended cell mass and other high molecular weight compounds (e.g., impurities having a molecular weight (MW) of about 5,000 Da and greater, typically and especially those having a MW of about 40,000 Da and greater) in the source of lactate material.
  • the step of clarification includes cross-flow filtration. More preferably, a two-stage cross-flow filtration technique is employed. A discussion relating to clarification and approach is provided in U.S.S.N. 09/412,085 previously incorporated herein by reference.
  • an optional concentration step is indicated at (H).
  • the source of lactate material for example a clarified broth
  • the source of lactate material is concentrated to provide for preferred handling in downstream processes. This is described in U.S.S.N. 09/412,085, previously incorporated herein by reference.
  • a typical concentration of a clarified broth from a fermentation process would be about 8 to 18 wt. % lactate material. Evaporation of water adequate to provide for a concentration of about 15 to 30 wt% lactate material, prior to an acidulation step, would typically be preferred.
  • a variety of useable evaporation or concentration techniques can be used. In general, falling film evaporators or rising film evaporators can be used with a multi-effect evaporator or heating could be provided by mechanical vapor recompression, or thermal recompression.
  • a strong acid such as sulfuric acid
  • the source of lactate material includes calcium lactate so that the acidulation process results in the formation of lactic acid and calcium sulfate (gypsum).
  • the calcium sulfate or gypsum generated in the previous step of the acidulation is only slightly soluble in water. Thus, it can be readily separated from the aqueous lactic acid solution. For example, techniques such as rotary drum filtration, belt filtration, press filtration, centrifugal separation or decantation, or a combination of these techniques, can be used.
  • aqueous back extraction the step of extracting lactic acid from the extractant back into an aqueous phase is sometimes referred to as the "aqueous back extraction".
  • the operating temperature of an aqueous back extraction process is typically at least about 70°C.
  • Sulfuric acid may be included in the amine extractant as an enhancer.
  • the amine extractant may include a hydrocarbon fraction (for example kerosene) and an organic enhancer (for example octanol).
  • the sulfuric acid can be present in the amine extractant as residual sulfuric acid from the acidulation step; added during the amine extraction step; or added to the amine extractant prior to or during the extraction step.
  • the '023 patent describes a process that involves: (a) feeding concentrated lactic acid to a prepolymer reactor; (b) polymerizing the concentrated lactic acid to polylactic acid in the prepolymer reactor, by removal of water; (c) feeding the resulting polylactic acid prepolymer to a lactide reactor; (d) removing crude lactide as a vapor from the lactide reactor; (e) conducting purification of the lactide; and, (f) eventually, conducting polymerization of the lactide to polylactide.
  • prepolymer reactor and variants thereof is used to refer to equipment to which the purified lactic acid is provided, to be processed with removal of water to a prepolymer (oligomer) solution of lactic acid prior to lactide formation.
  • the disclosure of the '023 patent particularly concerns steps involving prepolymerization of lactic acid and processing through to generation of a purified lactide stream. Polylactide formation, from the resulting purified lactide, is described for example in U.S. patent Nos. 5,338,822; 5,525,706; 5,475,080;
  • lactic acid racemization i.e. loss of chiral purity
  • Presence of material which can catalyze racemization and
  • the rate of lactic acid racemization is generally found to increase, with the presence of certain ionic salts in the lactic acid solution, even in relatively low amounts, i.e. on the order of 5 to 500 ppm. Included within such racemization salts or catalysts are the salts of the Group I and the Group II metal cations, for example sodium, potassium, calcium and magnesium salts.
  • an otherwise preferred approach to processing of lactic acid includes a step which involves formation of calcium salts.
  • the presence of calcium ions within the lactic acid solution would result in a step which involves formation of calcium salts.
  • a step of isolating the lactic acid from residual amounts of the calcium ions is desirable, provided the step does not involve undesirable amounts of exposure of the lactic acid to heat, which, as explained in the next section, generally exacerbates racemization of the lactic acid.
  • Prolonged exposure of aqueous lactic acid solutions to heat generates racemization.
  • prolonged exposures i.e. exposures of 5 hours
  • the amount of racemization depends on the combination of time and temperature, meaning that the same amount of racemization can occur by holding the lactic acid at a high temperature for a short time or holding the lactic acid at a lower temperature for a longer time.
  • oligomers i.e. polylactic acid
  • a prepolymer reactor a prepolymer reactor
  • oligomers i.e. polylactic acid
  • Such a process is generally conducted at a pressure of about 30-200 mm Hg, to facilitate removal and eventual condensation of the water vapor.
  • the temperature of the bottoms (oligomers) in the prepolymer reactor will be maintained at about 100 °C to 150°C, during this stage of processing, for periods of at least 5 minutes to 300 minutes.
  • the polylactic acid is formed in the prepolymer reactor, it is treated, in a lactide formation step, with further exposure to heat to generate crude lactide which is removed from the solution as a vapor. Again, this is a step of further exposure to heat, with racemization exacerbated by the presence of any racemization catalysts in the reactor bottoms.
  • lactic acid is not sufficiently pure, prolonged heating of the lactic acid solution may cause the lactic acid solution to change from a virtually colorless solution to a slightly yellow, yellow, brown or black solution, depending on the temperature, the length of time the solution is exposed to that temperature and the impurity level.
  • Such color formation may be undesirable if the color is not easily separated from the lactic acid monomers, oligomers and/or lactide because it could result in a colored polylactic acid product.
  • Many applications for polylactic acid desire a colorless resin. Based on Malliard chemistry, carbohydrates and amino acids are compounds that are likely to degrade and cause color formation. Therefore, it may be desirable to separate the carbohydrates and amino acids from the feed stream entering the prepolymer formation reactor.
  • Wilson Equation See e.g. Molecular Thermodyanmics of Fluid-Phase Equilibria (2 nd Edition), by J.M Prauznitz, R.N. Lichtenthaler, and E. Gomes de Azevedo, Prentice-Hall Inc., Englewood Cliffs, NJ 1986 pgs. 234 to 237) and this thermodyanmic model was used to predict the temperature of the water/lactic acid vapor, at 50 mm Hg, as a function of the concentration of the lactic acid solution. These results are reported below, in Table 1.
  • Group I and Group II salts and other impurities with low volatility, such as carbohydrates, amino acids, and color bodies, to some extent there are factors favoring that the vapor transfer occur with a solution of lactic acid and water which is relatively dilute, i.e. less than 88% lactic acid, with the advantage favoring, in general, the more dilute solutions (especially ⁇ 80%) due to lower temperatures being involved.
  • a lower concentration of lactic acid in the aqueous lactic acid solution requires a greater amount of time for evaporation or vapor transfer and to obtain complete transfer of materials (other than residual catalysts, etc.).
  • lactic acid In general, for aqueous solutions having a concentration above about 88%) wt. lactic acid on a theoretical basis, significant losses of lactic acid may occur due to two mechanisms. First, when concentrating lactic acid above 88 wt%, lactic acid can be lost in the overhead stream. Second, a higher level of lactic acid in the oligomer form would be produced during the concentration, and as is discussed later, the oligomers have a lower vapor pressure than lactic acid and require a higher temperature in orrder to be distilled overhead during the lactic acid vaporization step. Aqueous solutions having a concentration of lactic acid of below about 25 wt.
  • an efficiently conducted vapor transfer of a lactic acid solution can be conducted using the techniques described herein, with a solution having a lactic acid concentration of ⁇ 88%, typically about 25-80 wt. %, preferably 40-80% and more preferably around 60-75 wt. % lactic acid.
  • concentrations of lactic acid in aqueous solution can be readily obtained from the aqueous phase of the aqueous back extraction using conventional techniques for concentrating aqueous solutions. This can be conducted using conventional mechanical vapor recompression evaporators, multi-effect evaporators, or thermal recompression evaporators such as those available from Dedert Corporation, Olympia Fields, IL.
  • % will typically have involve some losses of lactic acid due to evaporation of lactic acid itself during the concentration step.
  • a transfer can be conducted such that the chiral purity of the lactic acid after vapor transfer is maintained within about 1.0%, more preferably within 0.5%, and most preferably within about 0.2% of the value measured after the back extraction. That is, preferably the concentration of the aqueous solution from the aqueous back extraction to a preferred level for vapor transfer, and the conduct of the vapor transfer for purification described below, are steps conducted with conditions selected such that the chiral purity of the lactic acid in the aqueous back extraction is not reduced significantly.
  • the material is concentrated and transferred in the vapor transfer step, into the prepolymer reactor, without a modification in the chiral purity such that the chiral purity is any less than about 97% more preferably not less than about 97.5%, and most preferably not any less than about 97.8% when the vapor phase is introduced into the prepolymer reactor.
  • an aqueous back extraction containing lactic acid with a chiral purity of about 98 % can readily be introduced into processes according to the present invention, and can be concentrated to a solution having about 65-75 wt.
  • % lactic acid using a low residence time evaporator wherein the concentrated solution has a chiral purity of at least 97.5%. It is foreseen that, using the techniques described herein, such a concentrated solution (i.e. 65-75 wt. % lactic acid), can be converted into a vapor phase wherein: at least 80% of the lactic acid in the concentrated solution is vaporized; and, the chiral purity of the lactic acid in the vapor phase (measurable by condensing the vapor phase) is at least 97.0%.
  • a concentrated solution i.e. 65-75 wt. % lactic acid
  • the chiral purity of a lactic acid feed for some commercial polylactic acid products can be as low as 85 % chiral purity. However, the chiral purity of the lactic acid feed is more typically greater than 95 %, more preferably greater than 97%), most preferably greater than 98%.
  • a desirable integrated process for recovering lactic acid from an aqueous back extraction of a lactic acid purification step, and providing lactic acid into a prepolymer reactor for a step of polylactic acid formation.
  • the conditions are provided such that undesirable levels of racemization due to prolonged exposure to heat and/or racemization catalysts, are avoided.
  • the conditions also tend to reduce the reaction of carbohydrates and amino acids, thus reducing color formation.
  • the conditions are preferably such that undesirable levels of racemization catalysts are not directed into the polylactic acid reactor.
  • the conditions tend to reduce the amount of carbohydrates, amino acids, and/or other impurities that cause color formation directed into the polylactic acid reactor. Instead, these impurities are separated from the lactic acid vapor stream.
  • an aqueous lactic acid solution is vaporized, in a vaporization process, to separate lactic acid, as a vapor, from bottoms which typically include oligomers and concentrated amounts of residual racemization catalysts.
  • the conditions in the vapor transfer are conducted such that the pressure of the system is maintained at between about 30- 200 mm Hg, more typically 40-120 mm Hg, most typically less than 60 mm Hg, for example about 40-60 mm Hg.
  • a reason for the preferred pressure is that this pressure will be the typical preferred pressure for the formation of polylactic acid in a prepolymer reactor.
  • the vaporized water/lactic acid solution from the vaporization step is fed directly into a downstream polylactic acid prepolymer reactor; i.e. the vapor transfer step is preferably integrated with the prepolymer formation step.
  • One reason it is preferred to conduct the prepolymer reactor under conditions of about 50 mm Hg relates to the fact that water vaporizes at about 38°C, at 50 mm Hg.
  • a ready supply of cooling water to the water condenser is available at about 25°- 28°C, it will typically be preferred that the vapor be taken off the polylactic acid prepolymer formation reaction at about 38°C.
  • This operating pressure allows the use of relatively inexpensive cooling tower water for condensing the overhead stream from the prepolymer reactor.
  • aqueous lactic acid composition comprising at least about 25%) by wt. lactic acid, typically at least 30% by wt. lactic acid.
  • the bottom figure on lactic acid concentration is defined by: (1) concentrations readily achievable in cost effectively designed aqueous back extraction or stripping processes, from a typical amine extraction process; and (2) a preferred minimum level to reduce residence time in vapor transfer equipment.
  • the upper level of preferred concentration for the aqueous lactic acid material fed into the vapor transfer process will be about 88 wt. % lactic acid.
  • the transfer will be conducted with a material having a concentration of no greater than about 75 wt. % lactic acid.
  • concentration step may have led to losses in lactic acid due to evaporation.
  • concentration of lactic acid introduced into the vapor transfer process will be about 45-75%, preferably as concentrated as reasonably obtainable within that range, and thus most preferably it is about 65-75 wt. % lactic acid.
  • This concentration can be readily achieved by water evaporation from a less concentrated solution, for example by using mechanical vapor recompression evaporator as previously described. In general, it is observed that such concentration processes can be conducted in such a manner that they do not lead to undesirable levels of racemization.
  • a preferred aqueous lactic acid vaporization and vapor transfer process is conducted by introducing into the vaporization system an aqueous lactic acid composition comprising about 65-75%, by wt. lactic acid; and, conducting the vapor transfer at about 30-200 mm Hg, typically about 40-120 mm Hg, more typically about 40-60 mm Hg. In general, this will involve heating the composition adequately to provide a vapor temperature of about 100 °C to 200 °C, more preferably 120 °C to 200 °C.
  • the temperature of the vapor stream depends greatly upon the operating pressure, the amount of lactic acid oligomers present in the lactic acid feed, and the fraction of the feed being vaporized.
  • the increase in boiling point temperature with increasing pressure is known. It has been found the presence of lactic acid oligomers increases the vapor temperature.
  • lactic acid both monomer and oligomer
  • the amount of oligomer increases the vapor temperature required to reach that amount of vaporization increases. This is due to the lower volatility of the oligomers when compared to lactic acid which need to be vaporized to reach a fixed vaporization rate. In other words, a higher temperature is required to evaporate more of a lower volatility compound.
  • a relatively dilute lactic acid stream e.g., ⁇ 40 wt% is fed into the evaporation step.
  • a more concentrated lactic acid stream e.g., > 40 wt%) that has not reached equilibrium with respect to oligomer formation is fed into the evaporation step.
  • a non-equilibrium, concentrated lactic acid solution can be produced by quickly evaporating water from a dilute solution to form a concentrated solution.
  • the time required for the evaporation must be small compared to the time required for oligomer formation.
  • the time required for evaporation can be reduced by using equipment having a high surface area to volumetric hold up ratio, such as a mechanically wiped film evaporator, a falling film evaporator, or rising film evaporator.
  • the time required for oligomer formation can be increased by operating the evaporation process at a low temperature and avoiding the presence of esterification catalysts.
  • evaporating at low temperatures results in operating at pressures below atmospheric pressure (e.g., 50 to 500 mm Hg).
  • the hold time between the water evaporation step (lactic acid concentration) and lactic acid vaporization can be reduced to provide a lactic acid feed stream with less oligomer.
  • the oligomer content of the lactic acid solution fed to the evaporation step contains 70 wt%, more preferably 50 wt%, most preferably 20 wt% of the oligomers that would be present if the solution had reached equilibrium with respect to oligomer formation.
  • an aqueous solution of lactic acid will be considered vaporized by a vaporization process if at least 70%), by wt., of the solution is vaporized, i.e. if the vaporization process generates a two phase mixture
  • vapor/liquid comprising at least 70% by wt. vapor phase.
  • Typical vaporization processes as described herein will involve at least 80% vaporization, by wt., typically 90-98% vaporization, by wt.
  • the separated vapor stream is transferred directly into a prepolymer reactor for polylactic acid, and is condensed within the reactor. Within that reactor, then, polylactic acid oligomer and polymer is formed, with removal of water.
  • the reactor conditions will typically be about 50 mm Hg (i.e. 40 to 60), with a vapor temperature (H 2 O being removed) of about 38°C (i.e. 34 to 42).
  • the vapor transfer step is conducted with equipment that provides for effective vaporization (at a high rate) so as to provide a short length of time of exposure of the liquid composition to heat.
  • Equipment useable includes conventional falling film evaporators and rising film evaporators, appropriately constructed and configured for operation under conditions of about 30-200 mm Hg, and vapor temperatures on the order of about 100 to 200°C.
  • Such equipment is commercially available from Dedert Corporation (Olympia Fields, IL).
  • a preferred system will be a rising film evaporator, configured and controlled to provide a two phase outflow comprising about 2-10% liquid, the remainder being vapor. This outward flow would be directed to a conventional vapor/liquid separator, for example, an impingment separator (discussed in Chemical Engineer's Handbook, referenced earlier). The separated vapor phase is then directed (directly, i.e. without modification) into a downstream polylactic acid prepolymer reactor.
  • a liquid feed 1 containing lactic acid is fed into an evaporator 2.
  • Heat input 3 into the evaporator produces a two phase liquid- vapor stream 4.
  • the liquid-vapor stream 4 is fed into a liquid-vapor separator 5 to obtain a liquid stream 6 and a separated vapor stream 7.
  • the vapor stream 7 is then fed into a prepolymer reactor 8.
  • water is removed 9 to form lactide oligomers 10 (bottoms).
  • the liquid feed 1 includes about 25 wt % to about 88 wt %, more preferably about 40-80 wt%, most preferably about 60-75 wt.
  • the evaporator 2 is a rising film or a falling film evaporator, more preferably a rising film evaporator.
  • heat applied to the liquid feed causes bubbles of vapor to form in the liquid feed.
  • heat is applied at a temperature about 10°C to about 25°C higher than the desired vapor temperature.
  • the temperature of the vapor coming off the evaporator is between about 100°C and 200 °C.
  • enough heat is applied to the liquid feed to produce a liquid-vapor stream which contains about 2 to 10 wt. % liquid and 98 to 90 wt. % vapor.
  • a liquid-vapor separator 5 is shown schematically in Figure 3.
  • the liquid- vapor stream 4 is fed into a liquid- vapor separator 5 such that the liquid-vapor stream 4 is directed at a wall 20 of the separator 5.
  • the liquid phase 21 drains along the wall, for example, by the force of gravity, and exits from the base 22 of the separator 5.
  • the vapor phase 7 of the liquid-vapor stream rises and exits the separator 5 from the top 25.
  • the vapor stream 7 is then fed into a prepolymer reactor 8, Fig. 2 is an example of a prepolymer reactor is a distillation column. In the prepolymer reactor 8, water is removed from the vapor stream 7 which causes the lactic acid monomers to polymerize to form lactic acid oligomers.
  • lactic acid vapor be fed into a prepolymer reactor
  • PCT 92/00292 describes a method for making lactide using fixed bed catalysts from a lactic acid vapor stream.
  • U.S. Patent 5,023,349 also describes the formation of lactide from lactic acid vapor stream.
  • the lactic acid vapor could be condensed to a liquid state and used in any application of lactic acid.
  • lactic acid solutions containing 88 wt% (Experiment la) and 60 wt% (Experiment lb) total lactic acid The lactic acid solutions may include lactic acid, lactoyllactic acid, and other intermolecular lactic acid esters.
  • a lactic acid solution containing 88 wt% lactic acid and 12 wt% water is commercially available from Purac America (Lincolnshire, IL) and Archer Daniels Midland (Decater, IL)
  • the 60 wt% lactic acid solution was prepared by combining water and lactic acid to obtain the correct lactic acid to water ratio. No hydrolysis of the lactic acid was performed. For each experiment, approximately 40 to 50 lb. of lactic acid solution was used.
  • the following equipment was used: a feed pump, a preheater, a boiling tube heat exchanger, a liquid/vapor separator, a condenser/receiver, a bottoms pump, a hot oil circulation system, and a vacuum pump.
  • the feed pump was a positive displacement pump capable of pumping 6.1 gal/hr at a discharge pressure of 1000 psig.
  • the preheater was a double-pipe heat exchanger constructed out of
  • the inner jacket heat transfer area was 0.393 sq. ft.
  • the lactic acid feed flowed inside the inner tube.
  • the boiling tube evaporator was a double pipe heat exchanger which included a 1" O.D. 316 stainless steel tube jacketed by a 1.5" Schedule 40 316 stainless steel pipe.
  • the heat exchanger was 5 feet long and provided 1.57 sq. ft. of heat transfer area.
  • the inner pipe had Kenics static mixing elements to aid in the heat transfer and keep the vapor and liquid mixed.
  • the outlet stream from the preheater passed through the 1 " inner tube and was vaporized. Hot oil flowed in the outer jacket at a significantly higher temperature than the inner jacket.
  • This boiling tube evaporator was mounted vertically with feed fluid rising up through the heat exchanger. In the liquid/vapor separator, vapor was withdrawn from the separator via a 1" opening in the upper section of the vessel.
  • Liquid was removed at the bottom of the separator.
  • the liquid/vapor feed entered via a 1" O.D. tube that extended to the middle of the separator from the top flange of the separator .
  • the bottom of the separator had a conical shape to facilitate removal of the liquid.
  • a simple coil-in-shell condenser was used to condense the vapor from the liquid/vapor separator. Additional cooling was provided by a cooling jacketing.
  • the condenser was constructed using 4" Schedule 40 316 stainless steel pipe.
  • the distillate was collected in a 4.5 gallon receiver.
  • the cooling media entered the cooling coil at 10°F.
  • a bottoms pump was used to discharge higher viscosity liquid that collected at the bottom of the liquid/vapor separator.
  • the hot oil heating system included a Julabo HT6-C2 heater capable of producing 6.1 kW with Julabo H350 fluid circulating through the system.
  • the system was designed to handle temperatures up to 350°C.
  • Julabo fluid was only used to heat the boiling tube evaporator.
  • the vacuum pump was capable of pumping 500 L/min of free air and capable of reaching 0.0001 mm Hg. Nitrogen was added to the inlet of the vacuum pump to maintain the pressure of the liquid/vapor separator. A control valve was used to adjust gas flow into the vacuum pump.
  • Feed Composition (wt %)
  • the process disclosed herein is capable of providing a lactic acid vapor in which the chiral purity is not reduced as compared to the lactic acid feed and when the fraction of feed evaporated is about 80%.
  • the process can provide a vapor from which impurities, such as carbohydrates, amino acids, color bodies and salts are removed, without racimization of the lactic acid.

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  • Organic Chemistry (AREA)
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  • Oil, Petroleum & Natural Gas (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

L'invention concerne des procédés de traitement de l'acide lactique. Les procédés consistent, d'une manière générale, à vaporiser une solution d'acide lactique aqueuse, à des fins de purification. Les conditions préférées de la vaporisation comprennent des pressions dans la gamme de 30-200 mmHg ainsi qu'une atmosphère inerte (azote). De préférence, le procédé est exécuté sur une solution aqueuse contenant 60-75 % en poids d'acide lactique. Le matériel et les systèmes préférés d'exécution du procédé sont également décrits. Le procédé est de préférence intégré à une prépolymérisation ou une oligomérisation d'acide polylactique aval. Un courant de vapeur préféré destiné à être orienté dans ce processus aval est défini.
PCT/US2000/031979 1999-11-24 2000-11-21 Traitement ameliore de l'acide lactique, procedes, agencements et produits WO2001038284A1 (fr)

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AU16619/01A AU1661901A (en) 1999-11-24 2000-11-21 Improved lactic acid processing; methods; arrangements; and, products

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US44872799A 1999-11-24 1999-11-24
US09/448,727 1999-11-24

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WO2013192450A1 (fr) * 2012-06-20 2013-12-27 Opx Biotechnologies, Inc. Purification d'acide 3-hydroxypropionique à partir d'un bouillon de culture cellulaire brut et production d'acrylamide
US8652816B2 (en) 2007-12-04 2014-02-18 Opx Biotechnologies, Inc. Compositions and methods for 3-hydroxypropionate bio-production from biomass
US8809027B1 (en) 2009-09-27 2014-08-19 Opx Biotechnologies, Inc. Genetically modified organisms for increased microbial production of 3-hydroxypropionic acid involving an oxaloacetate alpha-decarboxylase
US8883464B2 (en) 2009-09-27 2014-11-11 Opx Biotechnologies, Inc. Methods for producing 3-hydroxypropionic acid and other products
JP2016104763A (ja) * 2009-07-16 2016-06-09 ピュラック バイオケム ビー． ブイ． 液状乳酸組成物及びその調製方法
US9512057B2 (en) 2013-03-15 2016-12-06 Cargill, Incorporated 3-hydroxypropionic acid compositions
US9566232B2 (en) 2012-06-13 2017-02-14 Evofem, Inc. Compositions and methods for enhancing the efficacy of contraceptive microbicides
US10047383B2 (en) 2013-03-15 2018-08-14 Cargill, Incorporated Bioproduction of chemicals
US10337038B2 (en) 2013-07-19 2019-07-02 Cargill, Incorporated Microorganisms and methods for the production of fatty acids and fatty acid derived products
US10465213B2 (en) 2012-08-10 2019-11-05 Cargill, Incorporated Microorganisms and methods for the production of fatty acids and fatty acid derived products
US10494654B2 (en) 2014-09-02 2019-12-03 Cargill, Incorporated Production of fatty acids esters
WO2022080905A1 (fr) * 2020-10-16 2022-04-21 주식회사 엘지화학 Procédé de vaporisation d'acide lactique, appareil de vaporisation d'acide lactique et procédé de préparation d'acide acrylique
US11337989B2 (en) 2013-12-19 2022-05-24 Evofem, Inc. Compositions and methods for inhibiting inflammation and diseases using an alginic acid-based antimicrobial compound
US11345938B2 (en) 2017-02-02 2022-05-31 Cargill, Incorporated Genetically modified cells that produce C6-C10 fatty acid derivatives
US11408013B2 (en) 2013-07-19 2022-08-09 Cargill, Incorporated Microorganisms and methods for the production of fatty acids and fatty acid derived products
US11419835B2 (en) 2016-10-04 2022-08-23 Evofem, Inc. Method of treatment and prevention of bacterial vaginosis

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BE1008099A3 (fr) * 1994-03-04 1996-01-16 Brussels Biotech Sa Production semi-continue de polylactides par ouverture de cycle lactides obtenus a partir de derives d'acide lactique.
WO1998055442A1 (fr) * 1997-06-06 1998-12-10 'BRUSSELS BIOTECH' en abrégé '2B' Procede de purification d'acide lactique
WO2000056693A1 (fr) * 1999-03-22 2000-09-28 Purac Biochem B.V. Procede de purification d'acide lactique a l'echelle industrielle

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BE1008099A3 (fr) * 1994-03-04 1996-01-16 Brussels Biotech Sa Production semi-continue de polylactides par ouverture de cycle lactides obtenus a partir de derives d'acide lactique.
WO1998055442A1 (fr) * 1997-06-06 1998-12-10 'BRUSSELS BIOTECH' en abrégé '2B' Procede de purification d'acide lactique
WO2000056693A1 (fr) * 1999-03-22 2000-09-28 Purac Biochem B.V. Procede de purification d'acide lactique a l'echelle industrielle

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8652816B2 (en) 2007-12-04 2014-02-18 Opx Biotechnologies, Inc. Compositions and methods for 3-hydroxypropionate bio-production from biomass
JP2016104763A (ja) * 2009-07-16 2016-06-09 ピュラック バイオケム ビー． ブイ． 液状乳酸組成物及びその調製方法
US10100342B2 (en) 2009-09-27 2018-10-16 Cargill, Incorporated Method for producing 3-hydroxypropionic acid and other products
US8809027B1 (en) 2009-09-27 2014-08-19 Opx Biotechnologies, Inc. Genetically modified organisms for increased microbial production of 3-hydroxypropionic acid involving an oxaloacetate alpha-decarboxylase
US8883464B2 (en) 2009-09-27 2014-11-11 Opx Biotechnologies, Inc. Methods for producing 3-hydroxypropionic acid and other products
US9388419B2 (en) 2009-09-27 2016-07-12 Cargill, Incorporated Methods for producing 3-hydroxypropionic acid and other products
US9428778B2 (en) 2009-09-27 2016-08-30 Cargill, Incorporated Method for producing 3-hydroxypropionic acid and other products
US9566232B2 (en) 2012-06-13 2017-02-14 Evofem, Inc. Compositions and methods for enhancing the efficacy of contraceptive microbicides
US11439610B2 (en) 2012-06-13 2022-09-13 Evofem, Inc. Compositions and methods for enhancing the efficacy of contraceptive microbicides
US10568855B2 (en) 2012-06-13 2020-02-25 Evofem, Inc. Compositions and methods for enhancing the efficacy of contraceptive microbicides
WO2013192450A1 (fr) * 2012-06-20 2013-12-27 Opx Biotechnologies, Inc. Purification d'acide 3-hydroxypropionique à partir d'un bouillon de culture cellulaire brut et production d'acrylamide
US10465213B2 (en) 2012-08-10 2019-11-05 Cargill, Incorporated Microorganisms and methods for the production of fatty acids and fatty acid derived products
US10815473B2 (en) 2013-03-15 2020-10-27 Cargill, Incorporated Acetyl-CoA carboxylases
US10047383B2 (en) 2013-03-15 2018-08-14 Cargill, Incorporated Bioproduction of chemicals
US9512057B2 (en) 2013-03-15 2016-12-06 Cargill, Incorporated 3-hydroxypropionic acid compositions
US10155937B2 (en) 2013-03-15 2018-12-18 Cargill, Incorporated Acetyl-CoA carboxylases
US10337038B2 (en) 2013-07-19 2019-07-02 Cargill, Incorporated Microorganisms and methods for the production of fatty acids and fatty acid derived products
US11408013B2 (en) 2013-07-19 2022-08-09 Cargill, Incorporated Microorganisms and methods for the production of fatty acids and fatty acid derived products
US11337989B2 (en) 2013-12-19 2022-05-24 Evofem, Inc. Compositions and methods for inhibiting inflammation and diseases using an alginic acid-based antimicrobial compound
US10494654B2 (en) 2014-09-02 2019-12-03 Cargill, Incorporated Production of fatty acids esters
US11419835B2 (en) 2016-10-04 2022-08-23 Evofem, Inc. Method of treatment and prevention of bacterial vaginosis
US11345938B2 (en) 2017-02-02 2022-05-31 Cargill, Incorporated Genetically modified cells that produce C6-C10 fatty acid derivatives
WO2022080905A1 (fr) * 2020-10-16 2022-04-21 주식회사 엘지화학 Procédé de vaporisation d'acide lactique, appareil de vaporisation d'acide lactique et procédé de préparation d'acide acrylique
EP4206177A4 (fr) * 2020-10-16 2024-03-27 Lg Chem, Ltd. Procédé de vaporisation d'acide lactique, appareil de vaporisation d'acide lactique et procédé de préparation d'acide acrylique

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