Preparation method of (R)-3-hydroxybutyric acid solid

Abstract

The invention belongs to the technical field of compound processing, and provides a preparation method of (R)-3-hydroxybutyric acid solid. The method comprises the following steps: mixing an (R)-3-hydroxybutyric acid solution with an adsorbent, filtering, taking a solid, drying, eluting, and carrying out reduced pressure distillation to obtain an (R)-3-hydroxybutyric acid solid, and adopting polar adsorption resin as the adsorbent. According to the method, the adsorbent after adsorption is subjected to vacuum drying to remove moisture, then elution and reduced pressure distillation are carried out, the solvent is removed, the (R)-3-hydroxybutyric acid solid is separated out, and the water content is low. Besides, the method adopts polar adsorption resin to perform specific adsorption on the (R)-3-hydroxybutyric acid solution, the polar adsorption resin has polar functional groups, can perform hydrogen bond adsorption on the (R)-3-hydroxybutyric acid with carboxyl groups, has high adsorption efficiency, and also avoids using strong-basicity anion exchange resin to adsorb the (R)-3-hydroxybutyric acid.

Description

Technical Field

[0001] The present invention relates to the technical field of compound processing, and more specifically, to a method for preparing (R)-3-hydroxybutyric acid solid. Background Art

[0002] 3-Hydroxybutyric acid (3-HB) is the monomer form of the natural polymer poly (R)-3-hydroxybutyric acid (hereinafter referred to as PHB), which exists in pure R configuration in the natural state. As an important ketone body in the body, 3-hydroxybutyric acid is produced by the degradation of long-chain fatty acids in the liver, transported to peripheral tissues through the blood and regulates the body's functions. 3-Hydroxybutyric acid has great application value and prospects in the health care products, food and pharmaceutical industries, including: accelerating weight loss; stimulating the expression of various health-promoting genes; reducing the occurrence of inflammatory complications; improving exercise performance and training efficiency; enhancing metabolic efficiency; providing the heart with optimal energy and reducing the incidence of cardiovascular diseases; improving insulin sensitivity; preventing cancer and related diseases caused by glucose metabolism disorders; increasing cognitive ability, preventing Alzheimer's disease, and prolonging life.

[0003] Solid beverages are popular beverages because they are not easily spoiled, have a long shelf life, are small in size, and are easy to carry and transport. To prepare solid beverages containing 3-hydroxybutyric acid, solid raw materials of 3-hydroxybutyric acid need to be used. Solid beverages generally require the water content of the product to be below 5wt%. Currently, commercial (R)-3-hydroxybutyric acid exists mainly in the form of its salt solid powder, mainly in the form of sodium salt, magnesium salt, and calcium salt. However, the cationic content of these salts is high and is not suitable for high-dose use. If the intake of (R)-3-hydroxybutyrate is too large, it will lead to excessive salt intake, which is not conducive to human health.

[0004] The commonly used method for preparing high-content (R)-3-hydroxybutyric acid crystals is mainly direct chemical synthesis (liquid phase oxidation method). The specific principle is as follows: 3-hydroxybutyraldehyde and oxygen are used as the main raw materials, cobalt acetate is used as a catalyst, and ethyl acetate is used as a solvent for reaction. After the reaction is completed, ethyl acetate and 3-hydroxybutyraldehyde with relatively low boiling points are removed by concentration. However, cobalt acetate as a catalyst and high-boiling point butenoic acid (3-butenoic acid and 2-butenoic acid) produced by side reactions are difficult to remove, especially the catalyst cobalt acetate is a carcinogen. If used as a food raw material, the residual by-products and cobalt acetate will bring safety hazards. Therefore, the (R)-3-hydroxybutyric acid prepared by this method is not suitable for use in food or health products. The main reactions and side reactions involved above are as follows:

[0005] Main reaction:

[0006] 2CH3CH(OH)CH2CHO+O2→2CH3CH(OH)CH2COOH

[0007] Side reaction:

[0008] CH3CH(OH)CH2CHO→CH3CH-CHCHO+H2O

[0009] 2CH3CH-CHCHO+O2→2CH3CH-CHCOOH

[0010] CH3CH(OH)CH2COOH→CH3CH-CHCOOH+H2O

[0011] CH3CH(OH)CH2COOH→CH2=CHCH2COOH+H2O

[0012] In addition, PHB degradation can also be used to prepare (R)-3-hydroxybutyric acid, mainly in the following three ways: (1) Alkaline degradation method: first use a strong base to hydrolyze PHB to prepare 3-hydroxybutyrate, and then use acid to neutralize to obtain (R)-3-hydroxybutyric acid. (2) Acid-catalyzed hydrolysis method: use acid-catalyzed hydrolysis of PHB to prepare (R)-3-hydroxybutyric acid. (3) PHB is first alcoholyzed to produce 3-hydroxybutyrate, and 3-hydroxybutyrate is then hydrolyzed to prepare 3-hydroxybutyric acid. Although the above three methods avoid the impurities brought by the high-content 3-hydroxybutyric acid crystals obtained by direct chemical synthesis, the prepared 3-hydroxybutyric acid products are all 3-hydroxybutyric acid aqueous solutions, in which the 3-hydroxybutyric acid content is low (generally less than 50%), and liquid (R)-3-hydroxybutyric acid has a high water content and poor stability, and cannot be used as a raw material for solid beverages. If the above prepared 3-hydroxybutyric acid aqueous solution is directly concentrated, not only the solid content of the 3-hydroxybutyric acid aqueous solution is difficult to reach more than 80%, but a liquid substance is still obtained, and in the concentration process, 3-hydroxybutyric acid undergoes condensation and dehydration to form part of the by-product 3-hydroxybutyrate oligomers (hydroxyl and carboxyl groups undergo esterification reaction). If an adsorbent is used to adsorb the active ingredient, an eluent is generally used directly for direct elution, but other impurities will be brought into the system during the elution process, resulting in insufficient purity of the finished product. In addition, for the adsorption and separation of organic acid active ingredients, strongly alkaline ion exchange resins are currently commonly used for adsorption and separation, using the principle of positive and negative charge adsorption to increase the adsorption amount, but at the same time, strong polar molecules such as water are also adsorbed, so in the subsequent elution process, it is still necessary to concentrate and remove, and become a viscous substance, which causes the viscosity of the system to increase, and it is still impossible to achieve the purpose of completely removing water directly by concentration. In addition, there are two forms of strong alkaline ion exchange resins, one is the hydroxide form (OH-form) and the other is the chloride form (Cl-form). If the hydroxide form of strong alkaline ion exchange resin is used to adsorb (R)-3-hydroxybutyric acid, a neutralization reaction will occur to produce a large amount of water. After the adsorption is completed, a lot of water will remain. In addition, even if this form of strong alkaline ion exchange resin is food grade, it also has a heavy odor of odorous amines, which will also affect the quality of the final (R)-3-hydroxybutyric acid. If the chloride form of strong alkaline ion exchange resin is used for adsorption, a large amount of chloride ions will be brought to the final (R)-3-hydroxybutyric acid solid, which is not conducive to its subsequent application.

[0013] Therefore, there is an urgent need to develop a method for preparing a (R)-3-hydroxybutyric acid solid with low water content and high purity (free of oligomers, other impurities in the system, harmful substances, etc.) to meet the requirements for preparing solid beverages. Summary of the invention

[0014] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for preparing a (R)-3-hydroxybutyric acid solid. The present invention improves the preparation process of the (R)-3-hydroxybutyric acid solid so that the obtained (R)-3-hydroxybutyric acid solid has a low water content (the water content of the (R)-3-hydroxybutyric acid solid is ≤1wt%), and avoids the generation of oligomers during the dehydration process, does not contain toxic impurities (no heavy metals are detected), and has high purity, thereby solving the problem that the current (R)-3-hydroxybutyric acid solid is difficult to be used in solid preparations (such as solid beverages).

[0015] A first aspect of the present invention provides a method for preparing a (R)-3-hydroxybutyric acid solid.

[0016] Specifically, a method for preparing a (R)-3-hydroxybutyric acid solid comprises the following steps:

[0017] The (R)-3-hydroxybutyric acid solution and the adsorbent are mixed, filtered, and the solid is taken and dried, eluted, and distilled under reduced pressure to obtain the (R)-3-hydroxybutyric acid solid;

[0018] The adsorbent is a polar adsorption resin.

[0019] The present invention first utilizes the hydrogen bond adsorption principle, uses an adsorbent to adsorb (R)-3-hydroxybutyric acid in a (R)-3-hydroxybutyric acid solution, and then filters, then dries the filtered solid, removes residual water, and then elutes to obtain a solution containing (R)-3-hydroxybutyric acid, and removes the solvent by reduced pressure distillation, thereby precipitating a high-purity (R)-3-hydroxybutyric acid solid with low water content. The existing conventional adsorption separation method usually directly elutes the adsorbent after adsorption, but inevitably causes impurities and brings in water again. The present invention first vacuum dries the adsorbent after adsorption to remove moisture, then elutes, and removes the solvent by reduced pressure distillation to precipitate (R)-3-hydroxybutyric acid solid, so that the water content can be better reduced. In addition, the present invention uses a polar adsorption resin to specifically adsorb the (R)-3-hydroxybutyric acid solution, wherein the polar adsorption resin has polar functional groups (for example, ester bonds and cyano groups, amide groups and other functional groups, which contain polar functional groups such as nitrogen and sulfur), and can hydrogen bond adsorb the (R)-3-hydroxybutyric acid with a carboxyl group, with high adsorption efficiency, and avoids the use of a strong alkaline anion exchange resin to adsorb the (R)-3-hydroxybutyric acid.

[0020] Preferably, the polar adsorption resin is a food-grade polar adsorption resin, and / or the polar adsorption resin is a polar adsorption resin containing a carboxyl group.

[0021] More preferably, the polar adsorption resin is at least one of a polar adsorption resin containing a methacrylic acid-2-methacrylic acid copolymer, a polar adsorption resin containing a polyacrylic acid resin, and a polar adsorption resin containing a methacrylic acid-amide resin.

[0022] More preferably, the polar adsorption resin is at least one of the polar adsorption resins of model HP2MGL, model AB-8, and model LSI-960.

[0023] Preferably, the drying is vacuum drying, and / or the drying temperature is 50-70° C., and / or the drying time is 5-10 h.

[0024] Preferably, the elution is solvent boiling circulation reflux elution. Using solvent boiling circulation reflux elution can firstly reduce the amount of solvent used, secondly increase the subsequent vacuum distillation amount, and thirdly reduce energy consumption.

[0025] Preferably, the eluent used for the elution is at least one of anhydrous methanol, anhydrous ethanol, acetone, methyl formate, ethyl formate and ethyl acetate.

[0026] More preferably, the eluent used for the elution is anhydrous ethanol.

[0027] Preferably, the eluent used for the elution is a food grade solvent.

[0028] Preferably, the relative vacuum pressure of the reduced pressure distillation is below -0.09 MPa, and / or the temperature of the reduced pressure distillation is 50-70°C, and / or the time of the reduced pressure distillation is 0.5-2h.

[0029] Preferably, the water content of the (R)-3-hydroxybutyric acid solid is ≤1 wt%.

[0030] A second aspect of the present invention provides a solid beverage.

[0031] A solid beverage, the components of which include (R)-3-hydroxybutyric acid solid, and the (R)-3-hydroxybutyric acid solid is prepared by the above-mentioned preparation method.

[0032] Preferably, the water content in the solid beverage is ≤5wt%.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The present invention first mixes a (R)-3-hydroxybutyric acid solution and an adsorbent, filters, takes a solid and dries it, elutes it, and distills it under reduced pressure to obtain a (R)-3-hydroxybutyric acid solid, wherein a polar adsorption resin is used as an adsorbent. The present invention first uses the principle of electrostatic adsorption to adsorb the (R)-3-hydroxybutyric acid in the (R)-3-hydroxybutyric acid solution using an adsorbent, then filters it, then dries the filtered solid, removes residual water, and then elutes it to obtain a solution containing (R)-3-hydroxybutyric acid, distills it under reduced pressure to remove the solvent, and precipitates a (R)-3-hydroxybutyric acid solid, which has low water content and high purity, and the content can reach 98.43-99.04wt%, and the optical purity of the (R)-3-hydroxybutyric acid is 95.18-96.18%, and no heavy metals such as arsenic, lead, mercury, and cadmium are detected. The present invention first vacuum-dries the adsorbent after adsorption to remove moisture, then performs elution and reduced pressure distillation, removes the solvent, and precipitates (R)-3-hydroxybutyric acid solid with low water content. In addition, the present invention uses polar adsorption resin to specifically adsorb (R)-3-hydroxybutyric acid solution, wherein the polar adsorption resin has polar functional groups, and can hydrogen bond adsorption of (R)-3-hydroxybutyric acid with carboxyl, with high adsorption efficiency, and also avoids the use of strong basic anion exchange resin to adsorb (R)-3-hydroxybutyric acid. And the polar adsorption resin after solvent elution of the present invention can also be reused, which is more environmentally friendly and cost-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the solvent boiling circulation reflux device used in the present invention. DETAILED DESCRIPTION

[0036] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0037] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0038] Raw materials and detection methods involved in the embodiments and comparative examples of the present invention:

[0039] (R)-3-Hydroxybutyric acid solution: The mass concentration of (R)-3-hydroxybutyric acid is 42.80wt%, model D3HB50, food grade, manufacturer, Zhuhai Maidefa Biotechnology Co., Ltd.

[0040] Polar adsorption resin: Model HP2MGL, food grade; Manufacturer: Mitsubishi Chemical Resins.

[0041] Polar adsorption resin: model AB-8, food grade; manufacturer, Xi'an Lanxiao Technology New Materials Co., Ltd.

[0042] Polar adsorption resin: Model LSI-960, food grade; Manufacturer: Xi'an Lanxiao Technology New Materials Co., Ltd.

[0043] Hydroxide-type strong alkaline anion exchange resin: Model 201ⅹ7, food grade; Manufacturer: Hebi Haige Chemical Technology Co., Ltd.

[0044] Chloride-type strong alkaline anion exchange resin: Model 201ⅹ7, food grade; manufacturer, Hebi Haige Chemical Technology Co., Ltd.

[0045] Non-polar adsorption resin: Model D-101, food grade; Manufacturer: Xi'an Lanxiao Technology New Materials Co., Ltd.

[0046] Optical purity testing method: refer to GB / T 613-2007.

[0047] Detection method for heavy metal content: refer to GB 5009.268-2016 Method 1.

[0048] Example 1

[0049] A method for preparing a (R)-3-hydroxybutyric acid solid comprises the following steps:

[0050] (1) Adsorption and filtration: Take 300 g of (R)-3-hydroxybutyric acid solution (D3HB50, content 42.80 wt%), add it to a 1000 mL beaker, stir, add 200 mL of polar adsorption resin HP2MGL while stirring, and stir for 1 hour; filter, and use liquid chromatography to detect the obtained filtrate, and no (R)-3-hydroxybutyric acid should be detected; if there is residual (R)-3-hydroxybutyric acid in the filtrate, use polar adsorption resin to adsorb the (R)-3-hydroxybutyric acid until it is completely adsorbed;

[0051] (2) Drying: Place the filtered polar adsorption resin on a watch glass, spread it out, wrap it with a layer of 200-mesh food-grade nylon filter cloth, and then place it in a vacuum drying oven at 60°C and a relative vacuum pressure of -0.1 MPa for 8 hours;

[0052] (3) Elution: Assemble the solvent boiling circulation reflux device ( Figure 1, connect a spherical condenser, a constant pressure funnel, a three-necked round-bottom flask, and a heater in sequence from top to bottom), then add 600 mL of anhydrous ethanol to the three-necked round-bottom flask, place a piece of medical cotton at the bottom of the constant pressure funnel to prevent the adsorbent from flowing into the round-bottom flask, then put the dried adsorbent into the constant pressure funnel, then boil and reflux, and rinse for 3 hours; if there is (R)-3-hydroxybutyric acid residue in the adsorbent, continue boiling and reflux until the (R)-3-hydroxybutyric acid in the adsorbent is washed clean (take 10 mL of adsorbent and soak it in 20 mL of anhydrous ethanol for 30 minutes, then use a liquid high performance chromatograph to detect whether the soaking liquid contains (R)-3-hydroxybutyric acid, which is used to determine whether there is (R)-3-hydroxybutyric acid residue in the adsorbent. The following examples and comparative examples all use this method to determine whether there is (R)-3-hydroxybutyric acid residue in the adsorbent);

[0053] (4) Vacuum distillation to remove the solvent: The ethanol solution containing (R)-3-hydroxybutyric acid after elution was subjected to vacuum distillation using a rotary evaporator at a temperature of 60°C and a relative vacuum pressure of -0.09 MPa. The vacuum distillation was continued until there was no fraction. The time was about 1 hour, and a crystal clear (R)-3-hydroxybutyric acid solid was obtained, weighing 122.20 g, with a content of 98.65 wt% (residual water and (R)-3-hydroxybutyric acid oligomers may be present), a yield of about 93.89%, a chloride ion content of 0.085 wt%, and a water content of 0.55 wt%. The optical purity was detected using a specific polarimeter, and the optical purity of (R)-3-hydroxybutyric acid was 96.18%, and no heavy metals such as arsenic, lead, mercury, and cadmium were detected.

[0054] Example 2

[0055] A method for preparing a (R)-3-hydroxybutyric acid solid, which differs from Example 1 in that in step (1), the polar adsorption resin is replaced by a polar adsorption resin AB-8. Finally, a crystal-clear (R)-3-hydroxybutyric acid solid is obtained, with a weight of 121.89g, a content of 99.04wt%, a yield of about 94.02%, a chloride ion content of 0.081%, and a water content of 0.45wt%. The optical purity is detected by a specific polarimeter, and the optical purity of (R)-3-hydroxybutyric acid is 95.45%, and no heavy metals such as arsenic, lead, mercury, and cadmium are detected.

[0056] Example 3

[0057] A method for preparing a (R)-3-hydroxybutyric acid solid, which differs from Example 1 in that in step (1), the polar adsorption resin is replaced by the polar adsorption resin LSI-960. Finally, a crystal-clear (R)-3-hydroxybutyric acid solid is obtained, with a weight of 121.13g, a content of 98.43wt%, a yield of about 92.86%, a chloride ion content of 0.083%, and a water content of 0.64wt%. The optical purity is detected by a specific polarimeter, and the optical purity of (R)-3-hydroxybutyric acid is 95.23%, and no heavy metals such as arsenic, lead, mercury, and cadmium are detected.

[0058] Example 4

[0059] A method for preparing a (R)-3-hydroxybutyric acid solid, which is different from that in Example 1, in step (1), the polar adsorption resin is replaced by the polar adsorption resin recovered in Example 1. Finally, a crystal-clear (R)-3-hydroxybutyric acid solid is obtained, with a weight of 121.04g, a content of 98.76wt%, a yield of about 93.10%, a chloride ion content of 0.081%, and a water content of 0.67wt%. The optical purity is detected by a specific polarimeter, and the optical purity of the (R)-3-hydroxybutyric acid is 95.18%, and no heavy metals such as arsenic, lead, mercury, and cadmium are detected.

[0060] Comparative Example 1 (direct concentration method)

[0061] A method for preparing a (R)-3-hydroxybutyric acid solid comprises the following steps:

[0062] (1) Take 300 g of (R)-3-hydroxybutyric acid solution (D3HB50, content 42.80 wt%);

[0063] (2) Use a rotary evaporator to perform vacuum distillation at a temperature of 60°C and a relative vacuum pressure of less than -0.09 MPa. Vacuum distillation is performed until there is no fraction, which takes about 4 hours to obtain a viscous liquid. The temperature is raised to 95°C, and vacuum distillation is continued until there is no fraction, which takes about 2 hours. It is still a viscous liquid, and solid (R)-3-hydroxybutyric acid cannot be obtained. The content of (R)-3-hydroxybutyric acid is 78.25wt%, the chloride ion content is 0.072%, and the water content is 21.50wt%.

[0064] In Comparative Example 1, the (R)-3-hydroxybutyric acid solution was directly concentrated by vacuum distillation, but only a viscous liquid was obtained, and solid (R)-3-hydroxybutyric acid could not be obtained.

[0065] Comparative Example 2 (using hydroxide-type strong basic anion exchange resin)

[0066] A method for preparing a (R)-3-hydroxybutyric acid solid, which differs from Example 1 in that, in step (1), the polar adsorption resin is replaced with a hydroxide-type strong basic anion exchange resin (model 201ⅹ7). Finally, the reduced pressure distillation is carried out until there is no fraction, which takes about 3 hours and is a viscous substance. The temperature is raised to 95°C, and the reduced pressure distillation is continued until there is no fraction, which takes about 2 hours to obtain a highly viscous substance without fluidity, which is difficult to pour out from a rotary evaporation bottle and has a more obvious odor of stinky amines. The content of (R)-3-hydroxybutyric acid is 89.25wt%, the chloride ion content is 0.85%, and the water content is 10.56wt%.

[0067] Compared with Example 1, Comparative Example 2 uses a hydroxide-type strong basic anion exchange resin, resulting in a high water content in the final (R)-3-hydroxybutyric acid product, making it difficult to prepare a solid beverage and having a smelly amine odor.

[0068] Comparative Example 3 (using chlorine-type strong basic anion exchange resin)

[0069] A method for preparing a (R)-3-hydroxybutyric acid solid, which is different from that of Example 1, is that in step (1), the polar adsorption resin is replaced with a chlorine-type strong basic anion exchange resin (model 201ⅹ7). Finally, the reduced pressure distillation is carried out until there is no fraction, which takes about 3 hours and is a viscous substance. The temperature is raised to 95°C, and the reduced pressure distillation is continued until there is no fraction, which takes about 2 hours to obtain a highly viscous substance without fluidity, which is difficult to pour out from a rotary evaporator. The content of (R)-3-hydroxybutyric acid is 89.55wt%, the chloride ion content is 2.1%, and the water content is 10.20wt%.

[0070] Compared with Example 1, Comparative Example 3 uses a chloride-type strong alkaline anion exchange resin, resulting in a high water content and high chloride ion content in the final (R)-3-hydroxybutyric acid product, making it difficult to prepare a solid beverage.

[0071] Comparative Example 4

[0072] A method for preparing a (R)-3-hydroxybutyric acid solid comprises the following steps:

[0073] (1) 300 g of (R)-3-hydroxybutyric acid solution (D3HB50, content 42.80 wt%) was added to a 1000 mL beaker, and then stirred. 200 mL of adsorption resin (model HP2MGL) was added while stirring, and stirred for 1 h; filtration was performed, and (R)-3-hydroxybutyric acid in the obtained filtrate was detected by liquid chromatography. If there was any residue in the filtrate, an adsorbent was used to adsorb the (R)-3-hydroxybutyric acid;

[0074] (2) Assemble a solvent boiling circulation reflux device, add 600 mL of anhydrous ethanol to a three-necked round-bottom flask, place a piece of medical cotton at the bottom of a constant pressure funnel to prevent the adsorbent from flowing into the round-bottom flask, then place the dried adsorbent into the constant pressure funnel, boil and reflux, and elute for 3 hours. If there is any (R)-3-hydroxybutyric acid remaining in the adsorbent, continue boiling and reflux to completely elute the (R)-3-hydroxybutyric acid in the adsorbent;

[0075] (3) The ethanol solution containing (R)-3-hydroxybutyric acid after elution was subjected to vacuum distillation using a rotary evaporator at a temperature of 60°C and a relative vacuum pressure of less than -0.09 MPa. The vacuum distillation was performed until there was no fraction, which took about 3 hours and was a viscous substance. The temperature was raised to 95°C and the vacuum distillation was continued until there was no fraction, which took about 2 hours to obtain a highly viscous substance without fluidity, which was difficult to pour out from the rotary evaporator. The content of (R)-3-hydroxybutyric acid was 91.15wt%, the chloride ion content was 0.05%, and the water content was 8.44wt%.

[0076] Comparative Example 4 uses model HP2MGL adsorption resin, and the adsorption resin after filtration is not dried, but directly subjected to solvent boiling circulation reflux elution. Since the HP2MGL adsorption resin contains a methacrylate polar group skeleton structure, it also adsorbs a lot of water during the process of adsorbing (R)-3-hydroxybutyric acid. As a result, if the adsorption is not dried to remove the water and eluted, the water in the adsorbent will also be eluted and mixed into the product, ultimately making it impossible to prepare solid (R)-3-hydroxybutyric acid later.

Claims

1. A method for preparing a (R)-3-hydroxybutyric acid solid, characterized in that: The steps include: The (R)-3-hydroxybutyric acid solution and the adsorbent are mixed, filtered, and the solid is taken and dried, eluted, and distilled under reduced pressure to obtain the (R)-3-hydroxybutyric acid solid; The adsorbent is a polar adsorption resin.

2. The preparation method according to claim 1, characterized in that: The polar adsorption resin is a food-grade polar adsorption resin, and / or the polar adsorption resin is a polar adsorption resin containing a carboxyl group.

3. The preparation method according to claim 2, characterized in that: The polar adsorption resin is at least one of a polar adsorption resin containing a methacrylic acid-2-methacrylic acid copolymer, a polar adsorption resin containing a polyacrylic acid resin, and a polar adsorption resin containing a methacrylic acid-amide resin.

4. The preparation method according to claim 1, characterized in that: The drying is vacuum drying, and / or the drying temperature is 50-70° C., and / or the drying time is 5-10 h.

5. The preparation method according to claim 1, characterized in that: The elution is solvent boiling circulation reflux elution.

6. The preparation method according to claim 1, characterized in that: The eluent used for the elution is at least one of anhydrous methanol, anhydrous ethanol, acetone, methyl formate, ethyl formate and ethyl acetate.

7. The preparation method according to claim 1, characterized in that: The eluent used in the elution is a food grade solvent.

8. The preparation method according to claim 1, characterized in that: The relative vacuum pressure of the reduced pressure distillation is below -0.09 MPa, and / or the temperature of the reduced pressure distillation is 50-70° C., and / or the time of the reduced pressure distillation is 0.5-2 h.

9. The preparation method according to claim 1, characterized in that: The water content of the (R)-3-hydroxybutyric acid solid is ≤1wt%.

10. A solid beverage, characterized in that: The components of the solid beverage include (R)-3-hydroxybutyric acid solid, and the (R)-3-hydroxybutyric acid solid is prepared by the preparation method according to any one of claims 1 to 9.

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