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BR-112022013750-B1 - PROCESS FOR REMOVING LACTIC ACID FROM AN AQUEOUS SOLUTION OF MAGNESIUM CHLORIDE AND PROCESS FOR MANUFACTURING LACTIC ACID

BR112022013750B1BR 112022013750 B1BR112022013750 B1BR 112022013750B1BR-112022013750-B1

Abstract

METHOD FOR PURIFICATION OF MAGNESIUM CHLORIDE SOLUTIONS. The invention relates to a process for removing lactic acid from an aqueous solution of magnesium chloride containing lactic acid, the weight ratio of magnesium chloride to lactic acid in the aqueous solution of magnesium chloride containing lactic acid being at least 1:1, the process comprising the steps of subjecting the aqueous solution of magnesium chloride containing lactic acid to an evaporation step, resulting in the formation of a paste of MgCl2.MgL2.4H2O in an aqueous solution of magnesium chloride, subjecting the paste to a solid-liquid separation step, to separate the solid MgCl2.MgL2.4H2O from the aqueous solution of magnesium chloride, resulting in the removal of lactic acid from the aqueous solution of magnesium chloride containing lactic acid in the form of MgCl2.MgL2.4H2O. The process of the present invention makes it possible to efficiently remove lactic acid from aqueous magnesium chloride solutions containing lactic acid, resulting in magnesium chloride solutions with a low lactic acid content that can be further processed as desired. MgCl2.MgL2.4H2O (...).

Inventors

  • Jan Van Krieken
  • FESIA LESTARI LAKSMANA

Assignees

  • PURAC BIOCHEM B.V

Dates

Publication Date
20260310
Application Date
20210115
Priority Date
20200115

Claims (14)

  1. 1. A process for removing lactic acid from an aqueous solution of magnesium chloride containing lactic acid, the weight ratio of magnesium chloride to lactic acid in the aqueous solution of magnesium chloride containing lactic acid being at least 1:1, characterized in that the process comprises the steps of: - subjecting the aqueous solution of magnesium chloride containing lactic acid to an evaporation step, resulting in the formation of a paste of MgCl2.MgL2.4H2O in an aqueous solution of magnesium chloride, - subjecting the paste to a solid-liquid separation step, to separate the solid MgCl2.MgL2.4H2O from the aqueous solution of magnesium chloride, resulting in the removal of lactic acid from the aqueous solution of magnesium chloride containing lactic acid in the form of MgCl2.MgL2.4H2O.
  2. 2. Process according to claim 1, characterized in that the weight ratio of magnesium chloride to lactic acid is at least 1.5:1, in particular at least 2:1, more particularly at least 4:1 and at most 70:1, in particular at most 50:1, more particularly at most 40:1, in some embodiments at most 20:1.
  3. 3. Process according to claim 1 or 2, characterized in that the magnesium chloride solution containing lactic acid has a magnesium chloride concentration in the range of 5 to 35% by weight, in particular in the range of 10-35% by weight, more particularly in the range of 15-35% by weight.
  4. 4. Process according to any one of claims 1 to 3, characterized in that the evaporation step is carried out in one or more stages, at a temperature in the range of 50 to 200 °C, in particular in the range of 80 to 150 °C and/or at reduced pressure, in particular at a pressure in the range of 0.01 to 0.9 bar (1000 Pa to 90000 Pa), more particularly in the range of 0.01 to 0.35 bar (1000 Pa to 35000 Pa).
  5. 5. Process according to any one of claims 1 to 4, characterized in that the evaporation is continued until the solution has a magnesium chloride concentration in the range of 30 to 47% by weight, in particular in the range of 38 to 45% by weight.
  6. 6. Process according to any one of claims 1 to 5, characterized in that the paste of MgCl2.MgL2.4H2O in a magnesium chloride solution comprises at least 2% by weight of MgCl2.MgL2.4H2O, in particular at least 4% by weight and at most 50% by weight of MgCl2.MgL2.4H2O, in particular at most 40% by weight, more particularly at most 30% by weight, in some embodiments at most 20% by weight.
  7. 7. Process according to any one of claims 1 to 6, characterized in that the magnesium chloride solution obtained from the separation step has a magnesium chloride concentration in the range of 35 to 47% by weight, in particular at least 37% by weight, in particular at least 39% by weight and/or at most 47% by weight, in particular at most 45% by weight.
  8. 8. Process according to any one of claims 1 to 7, characterized in that the concentration of lactic acid in the magnesium chloride solution obtained from the separation step is at most 1% by weight, in particular at most 0.5% by weight, more particularly at most 0.2% by weight.
  9. 9. A process according to any one of claims 1 to 8, characterized in that a magnesium chloride solution containing lactic acid with a lactic acid concentration of 0.5 to 7% by weight and a magnesium chloride concentration of 15 to 25% by weight is subjected to one or more evaporation steps, resulting in a paste of 4 to 40% by weight of MgCl2.MgL2.4H2O in a magnesium chloride solution with a magnesium chloride concentration of 35 to 47% by weight, and the paste is subjected to a solid-liquid separation step resulting in solid MgCl2.MgL2.4H2O and a magnesium chloride solution with a lactic acid concentration of less than 0.5% by weight.
  10. 10. Process for the manufacture of lactic acid, characterized in that it comprises the steps of: - subjecting a carbon source to a fermentation step to form lactic acid, which fermentation step comprises the steps of fermenting a carbon source by means of a microorganism in a fermentation medium to form lactic acid; - neutralizing at least part of the lactic acid by adding a magnesium base selected from magnesium oxide and magnesium hydroxide to the fermentation medium, thus obtaining magnesium lactate; - subjecting the magnesium lactate to an acidification step in which the magnesium lactate is contacted with HCl in an aqueous environment to form an aqueous mixture comprising lactic acid and magnesium chloride; - subjecting the aqueous mixture comprising lactic acid and magnesium chloride to a separation step, to form an effluent comprising lactic acid and an aqueous solution of magnesium chloride containing lactic acid and recovering the effluent comprising lactic acid from the process; - subjecting the aqueous solution of magnesium chloride containing lactic acid, the weight ratio of magnesium chloride to lactic acid In an aqueous solution of magnesium chloride containing lactic acid with a ratio of at least 1:1, a single evaporation step results in the formation of a paste of MgCl2.MgL2.4H2O in an aqueous solution of magnesium chloride. Then, the paste is subjected to a solid-liquid separation step to separate the solid MgCl2.MgL2.4H2O from the aqueous solution of magnesium chloride.
  11. 11. Process according to claim 10, characterized in that the solid MgCl2.MgL2.4H2O is recycled at least in part to the acidification step.
  12. 12. Process according to claim 10 or 11, characterized in that the magnesium chloride solution derived from the solid-liquid separation step is provided at least in part to a thermal decomposition step, wherein the magnesium chloride is reacted with water to form solid magnesium oxide and gaseous HCl, wherein the solid MgO can be recycled at least in part to the fermentation step, as such or after having been converted into magnesium hydroxide, and the gaseous HCl can, if desired, be recycled at least in part to the acidification step as such, or after having been dissolved in water to form an aqueous solution of HCl.
  13. 13. A process according to any one of claims 10 to 12, characterized in that the lactic acid separated from the magnesium chloride solution containing lactic acid is subjected to one or more steps selected from separation by an extractor and purification, for example, one or more purification steps selected from the washing group, activated carbon treatment, recrystallization, distillation and filtration.
  14. 14. Process according to any one of claims 10 to 13, characterized in that lactic acid is converted into lactide or polylactic acid.

Description

[001] The present invention relates to a process for purifying magnesium chloride solutions, in particular magnesium chloride solutions containing limited amounts of lactic acid. The invention also relates to a method of manufacturing lactic acid through a fermentation process. [002] Lactic acid can be manufactured through the fermentation of a carbon source, such as carbohydrates or glycerol, by microorganisms. In this fermentation process, a carbohydrate source is typically fermented by a microorganism to form lactic acid. The liquid in which the carbohydrate source is fermented is called the fermentation broth or fermentation medium. The formation of lactic acid during fermentation will result in a decrease in the pH of the fermentation broth. Since such a decrease in pH can impair the metabolic process of the microorganism, a common practice is to add a neutralizing agent, i.e., a base, to the fermentation medium in order to neutralize the pH. As a result, the lactic acid produced in the fermentation medium is typically present in the form of a lactate salt. [003] To recover lactic acid from the fermentation medium after fermentation, downstream processing is necessary. One of the steps in downstream processing is an acidification step, in which the lactate salt is brought into contact with an inorganic acid in an aqueous medium, resulting in the formation of lactic acid and an inorganic salt. For example, if the lactate salt in the fermentation medium is a magnesium salt, acidification with HCl will result in the formation of a solution containing dissolved lactic acid and dissolved magnesium chloride. [004] The next step is then to separate the lactic acid from the magnesium chloride solution. Since both lactic acid and magnesium chloride have high solubility in water, this separation is not straightforward. [005] Document WO00/17378 describes the manufacture of lactic acid through fermentation, pH adjustment with Ca(OH)2 or Mg(OH)2, addition of HCl and extraction of lactic acid from magnesium chloride solution with a solvent selected from amines, alcohols, and ethers, preferably isoamyl alcohol, diisopropyl ether and Alamine 336. The solvent containing the lactic acid is then brought into contact with water to generate a lactic acid solution, which is further processed. [006] Document WO2013/093028 describes the extraction of lactic acid from a magnesium chloride solution using an extractant selected from the C5+ ketone group, diethyl ether and methyl tert-butyl ether, thus obtaining an organic lactic acid solution and a residual magnesium chloride solution. [007] One problem that occurs in this extraction process is that the extraction of lactic acid from the magnesium chloride solution will not be complete. Limited amounts of lactic acid will remain in the magnesium chloride solution. This is disadvantageous for two reasons. Firstly, the presence of lactic acid in the magnesium chloride solution will reduce the yield of lactic acid for the entire process. Secondly, it has been found that the lactic acid present in the magnesium chloride solution interferes with the further processing of the magnesium chloride solution, which requires the solution to be highly concentrated. The removal of lactic acid was considered difficult, on the one hand because the amount of lactic acid in the magnesium chloride solution will be relatively small compared to the amount of magnesium chloride in the solution and, on the other hand, because both magnesium chloride and lactic acid have high solubility in water. [008] Therefore, there is a need in the art for a process for removing limited quantities of lactic acid from a magnesium chloride solution. The present invention provides such a process. [009] The present invention relates to a process for removing lactic acid from an aqueous solution of magnesium chloride containing lactic acid, the weight ratio of magnesium chloride to lactic acid in the aqueous solution of magnesium chloride containing lactic acid being at least 1:1, the process comprising the steps of: - subjecting the aqueous solution of magnesium chloride containing lactic acid to an evaporation step, resulting in the formation of a paste of MgCl2.MgL2.4H2O in an aqueous solution of magnesium chloride, - subjecting the paste to a solid-liquid separation step, to separate the solid MgCl2.MgL2.4H2O from the aqueous solution of magnesium chloride. The separation of the solid MgCl2.MgL2.4H2O from the aqueous solution of magnesium chloride results in the removal of lactic acid from the aqueous solution of magnesium chloride containing lactic acid in the form of MgCl2.MgL2.4H2O. [010] It has been found that the process of the present invention makes it possible to efficiently remove lactic acid from aqueous magnesium chloride solutions containing lactic acid, resulting in magnesium chloride solutions with a low lactic acid content that can be further processed as desired. The solid MgCl2.MgL2.4H2O can also b