Method for recovering D-calcium pantothenate mother liquor

Abstract

The invention discloses a method for recovering D-calcium pantothenate mother liquor. The recovery method comprises the following steps: S1, carrying out pretreatment, precipitation treatment and hydrolysis treatment on D-calcium pantothenate mother liquor to obtain a reaction solution 1; s2, carrying out lactonization reaction on a mixed solution of the reaction solution 1 and a solvent to obtain a reaction solution 2; and S3, carrying out solid-liquid separation on the reaction liquid 2 to obtain a solid, namely beta-alanine, and crystallizing the obtained liquid to obtain the D-pantoic acid lactone. According to the recovery method, high-purity beta-alanine and D-pantoic acid lactone can be obtained, and meanwhile, the recovery rate of the beta-alanine and the D-pantoic acid lactone is effectively increased; in the whole process, a large amount of acid is not needed for neutralization reaction, extraction operation is not needed, the input of organic solvents is reduced, and the production cost is effectively reduced.

Description

Technical Field

[0001] This invention relates to a method for recovering D-calcium pantothenate mother liquor. Background Technology

[0002] D-Calcium pantothenate, also known as vitamin B5, is a key precursor in the synthesis of coenzyme A and plays a crucial role in the breakdown and utilization of sugars, fats, and proteins. It is widely used in pharmaceuticals, feed additives, and the food industry. During the preparation of D-Calcium pantothenate, the mother liquor may contain several high-value chemical substances, including D-Calcium pantothenate, β-alanine calcium, calcium pantothenate, D-pantothenate lactone, and methanol. Recovering these components and using them as raw materials for D-Calcium pantothenate production not only avoids environmental pollution caused by waste but also reduces resource waste and effectively lowers production costs.

[0003] Currently, there are two main methods for recovering D-calcium pantothenate mother liquor: The first method involves hydrolyzing D-calcium pantothenate in an acidic solution to β-alanine and D-pantolytic acid lactone, followed by neutralization, extraction, concentration, and crystallization to obtain D-pantolytic acid lactone and β-alanine respectively (see CN110845307A). However, this method requires controlling the pH value between 1 and 3 during acidic hydrolysis, necessitating the use of large amounts of acid. Neutralization produces a large amount of salt, making desalination difficult and resulting in extremely low resource recovery rates. The second method involves hydrolyzing D-calcium pantothenate in an alkaline solution to generate β-alanine and pantolytic acid, then adjusting the pH value to 1 to 1.5 with acid to induce pantolytic acid lactone formation to D-pantolytic acid lactone. Subsequently, neutralization, extraction, concentration, and crystallization are performed to obtain the target products respectively (see CN113214046A). However, this method is essentially similar to the first one. Except for the different hydrolysis method, the other operations are basically the same. It also suffers from the problems of requiring a large amount of acid, generating a large amount of salt after neutralization and making desalination difficult, consuming a large amount of organic solvent for extraction, and having a low resource recovery rate. In addition, CN118290281A uses a solid acid catalyst to replace sulfuric acid and other substances for continuous hydrolysis and recovery. Although this avoids the salt generation problem, it still requires a large amount of organic solvent for extraction, resulting in high solvent recovery costs.

[0004] Therefore, there is an urgent need for an effective and low-cost method for recovering D-calcium pantothenate mother liquor. Summary of the Invention

[0005] The technical problem addressed by this invention is to overcome the problems of existing methods for recovering D-calcium pantothenate mother liquor, such as the need for large-scale organic solvent extraction, low resource recovery rate, large amounts of waste generated, difficult separation and purification, and high cost. This invention provides a method for recovering D-calcium pantothenate mother liquor. This method can obtain high-purity β-alanine and D-pantothenic acid lactone while effectively improving their recovery rates. Furthermore, the entire process does not require large amounts of acid for neutralization reactions, and D-pantothenic acid lactone can be obtained without extraction, simplifying the operation, reducing the input of organic solvents, and effectively lowering production costs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows.

[0007] This invention provides a method for recovering D-calcium pantothenate mother liquor, which includes the following steps:

[0008] S1 and D-calcium pantothenate mother liquor were pretreated, precipitated and hydrolyzed to obtain reaction solution 1;

[0009] The pretreatment includes a distillation step;

[0010] The precipitation treatment includes precipitation under the action of ammonium salt, followed by solid-liquid separation to obtain liquid.

[0011] The hydrolysis treatment includes a step of hydrolysis under the action of ammonia gas or ammonia water; the mass ratio of the "ammonia gas or ammonia water" to the D-calcium pantothenate mother liquor is not less than 1.25% based on the mass of ammonia; and the hydrolysis temperature is not less than 60°C.

[0012] The order of precipitation treatment and hydrolysis treatment is not limited.

[0013] S2. The mixture of reaction solution 1 and solvent undergoes a lactone reaction to obtain reaction solution 2;

[0014] The solvent is a non-water-soluble organic solvent; the temperature of the lactone reaction is not lower than 80°C.

[0015] S3. The reaction solution 2 is separated into solid and liquid components. The solid obtained is β-alanine, and the liquid obtained is crystallized to obtain D-indohydrin lactone.

[0016] In this invention, the D-calcium pantothenate mother liquor can be the mother liquor remaining after crystallization of D-calcium pantothenate in an actual industrial production process using D-indophosphoprol as a raw material, or the mother liquor remaining after crystallization of D-calcium pantothenate in a process using DL-calcium pantothenate as a raw material. Specifically, the D-calcium pantothenate mother liquor typically includes D-calcium pantothenate, calcium β-alanine, D-indophosphoprol, calcium pantothenate, methanol, water, and a small amount of unavoidable impurities (e.g., methyl pantothenate). Those skilled in the art will understand its specific meaning.

[0017] In some specific embodiments, the D-calcium pantothenate mother liquor comprises 5% D-calcium pantothenate, 2.4% β-alanine calcium, 1% D-pantothenic acid lactone, 2.3% pantothenic acid calcium, 84% methanol, 5% water, and the balance methyl pantothenate; the percentages are the mass percentages of each component in the D-calcium pantothenate mother liquor.

[0018] In this invention, the meaning of "measured by the mass of ammonia" can be: when the hydrolysis is carried out under the condition of ammonia gas being introduced, the mass of ammonia represents the mass of ammonia gas, and the mass of ammonia gas can be obtained by weighing the gas cylinder; when the hydrolysis is carried out under the condition of adding ammonia water, the mass of ammonia represents the mass of ammonia in the ammonia water, which can be calculated, for example, by the mass and concentration of ammonia water.

[0019] In this invention, the distillation in step S1 is intended to recover methanol from the D-calcium pantothenate mother liquor, and can be carried out under the conditions for methanol recovery by distillation as is conventional in the art.

[0020] In some embodiments, step S1 further includes a step of dissolving and diluting with water after distillation, wherein the mass of the water and the D-calcium pantothenate mother liquor is preferably 1%-5%, for example 3%.

[0021] In some embodiments, in step S1, the ammonium salt includes one or more of ammonium carbonate, ammonium sulfate, ammonium phosphate, ammonium oxalate, and ammonium stearate. The ammonium salt can form a poorly water-soluble salt with calcium ions in the D-calcium pantothenate mother liquor, such as calcium pantothenate, calcium indomethacin, and calcium β-alanine, facilitating direct filtration removal. Furthermore, using an ammonium salt avoids introducing cations other than ammonium ions, thus ensuring the smooth progress of the subsequent lactone reaction and preventing the generation of inorganic salt impurities.

[0022] In this invention, in step S1, the amount of ammonium salt used can be selected according to the molar ratio of ammonium ions in the ammonium salt to calcium ions in the D-calcium pantothenate mother liquor. Specifically, the molar ratio of ammonium ions in the ammonium salt to calcium ions in the D-calcium pantothenate mother liquor can be (2.0-2.1):1, for example, 2.02:1, 2.04:1, 2.06:1, or 2.08:1. This molar ratio range ensures that calcium ions in the system are fully precipitated and removed. If the molar ratio is below this range, it is difficult to remove calcium ions completely; if the molar ratio is above this range, it not only causes waste, but also, in addition to ammonium carbonate which can decompose, excessive amounts of other ammonium salts may lead to the formation of impurities in the system, reducing the recovery quality of β-alanine.

[0023] In some implementations, in step S1, the precipitation is carried out under stirring conditions.

[0024] In some implementations, the precipitation time in step S1 is 0.5-2 hours, for example, 1 hour.

[0025] In this invention, in step S1, the solid-liquid separation can be performed according to conventional operations in the art, such as by filtration.

[0026] In this invention, in step S1, the endpoint of the hydrolysis is that the content of D-calcium pantothenate in the reaction solution is ≤0.2% (w / w). After the hydrolysis step, both D-calcium pantothenate and D-indolactone in the D-calcium pantothenate mother liquor will be hydrolyzed into D-ammonium indolactone.

[0027] In some implementations, the hydrolysis temperature in step S1 is 60-100°C, for example, 70°C, 80°C, or 90°C. Excessively high temperatures result in high system pressure, posing a certain safety risk.

[0028] In some implementations, in step S1, the mass ratio of the "ammonia gas or ammonia water" to the D-calcium pantothenate mother liquor is 1.25%-4.0%, for example 1.5%, 2.0% or 3.0%, based on the mass of ammonia.

[0029] In some implementations, step S1 may further include a distillation step to recover ammonia water after hydrolysis. When the hydrolysis is carried out under conditions where ammonia gas is introduced, the ammonia gas will also exist in the form of ammonia water after entering the system; those skilled in the art will understand its specific meaning.

[0030] In this invention, in step S2, the solvent can be a high-boiling-point (boiling point higher than the lactonization reaction temperature) non-water-soluble organic solvent that is difficult to react with ammonia. The solvent azeotropically removes water produced in the lactonization reaction, promotes the discharge of ammonia from the decomposition of D-pantolactone, and separates the product from ammonia and water, thereby accelerating the lactonization reaction to generate D-pantolactone. Simultaneously, it avoids the situation where L-pantolactone cannot crystallize after racemization under alkaline conditions, leading to a decrease in yield.

[0031] In some embodiments, in step S2, the solvent includes one or more of isobutyl acetate, sec-butyl acetate, tert-butyl acetate, and toluene.

[0032] In some embodiments, in step S2, the mass percentage of the solvent and the D-calcium pantothenate mother liquor in step S1 is 1.5%-2.5%, for example 1.8%, 1.9%, 2.0%, 2.3% or 2.4%.

[0033] In this invention, in step S2, the endpoint of the lactone reaction is that the D-indohydric acid content in the reaction solution is ≤0.1% (w / w).

[0034] In some embodiments, the temperature of the lactone reaction in step S2 is 80-120°C.

[0035] In some embodiments, in step S2, the lactone formation reaction is carried out under atmospheric pressure concentration or vacuum concentration, preferably under vacuum concentration. The vacuum degree for atmospheric pressure concentration can be 0.1 MPa, which is conventional in the art; the vacuum degree for vacuum concentration is preferably 0.01-0.04 MPa, for example, 0.02 MPa, 0.025 MPa, or 0.035 MPa. The vacuum degree in this step can be selected according to the boiling point of the water-insoluble organic solvent and the lactone formation reaction temperature.

[0036] In this invention, in step S3, the solid-liquid separation can be performed according to conventional operations in the art, such as by filtration.

[0037] In some implementations, step S3 further includes a step of cooling the reaction liquid 2 before solid-liquid separation, preferably cooling it to 50-80°C, for example 55°C, 60°C or 70°C.

[0038] According to conventional understanding in the art, step S3, after the solid-liquid separation to obtain a solid, may further include a step of drying the solid.

[0039] In some embodiments, in step S3, the crystallization is carried out below 0°C. The crystallization mother liquor can be used for the preparation of D-calcium pantothenate.

[0040] According to conventional understanding in the art, step S3, after crystallization, may further include the steps of solid-liquid separation to obtain solid and drying.

[0041] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0042] The reagents and raw materials used in this invention are all commercially available.

[0043] The positive and progressive effects of this invention are as follows:

[0044] The recovery method of this invention mainly involves precipitation with ammonium salts, followed by hydrolysis under the action of ammonia gas or ammonia water. With the use of non-water-soluble organic solvents and key process parameters (such as the temperature of hydrolysis and lactone reaction, and the amount of ammonia used), methanol, high-purity β-alanine, and high-purity D-pantolactone are effectively recovered from D-calcium pantothenate mother liquor. The recovery rate of β-alanine can reach over 95%, and the recovery rate of D-pantolactone can reach over 92%.

[0045] The entire process does not require the use of large amounts of acid for neutralization reactions, and D-pantolactone can be obtained without extraction. This simplifies the operation, reduces the input of organic solvents, avoids salt residue, effectively reduces production costs, and also enables the recovery and reuse of ammonia, ensuring ammonia balance. Detailed Implementation

[0046] The present invention is further illustrated below by way of examples, but these examples do not limit the invention to the scope of the embodiments described. Unless otherwise specified, experimental methods in the following examples were performed according to conventional methods and conditions, or selected according to the product instructions. Unless otherwise specified, all reagents and materials used are commercially available.

[0047] The main components of the D-calcium pantothenate mother liquor used in the following examples and comparative examples are as follows (by mass percentage):

[0048] 5% D-calcium pantothenate, 2.4% β-alanine calcium, 1% D-pantolyl lactone, 2.3% calcium pantothenate, 84% methanol, 5% water and trace impurities (0.3% methyl pantothenate), pH value above 9.

[0049] In the following examples and comparative examples, the relevant data on the recovered β-alanine and D-pantolactone were obtained in the following manner:

[0050] (1) Purity:

[0051] All results were obtained using high-performance liquid chromatography.

[0052] (2) Recovery rate:

[0053] β-Alanine yield = (molar amount of β-alanine recovered) ÷ (molar amount of β-alanine + molar amount of calcium pantothenate × 2) × 100%;

[0054] D-Pantothenic acid lactone yield = molar amount of D-pantothenic acid lactone recovered ÷ (molar amount of D-pantothenic acid lactone + molar amount of calcium pantothenate × 2) × 100%.

[0055] Example 1

[0056] S1. Take 1000g of D-calcium pantothenate mother liquor (containing 0.285mol of calcium ions), distill to recover methanol, dilute with water to 300g, add 28.8g of ammonium carbonate (0.30mol) and stir for 1h to precipitate, then filter. Add 80g of 25% (w / w) ammonia water to the filtrate, heat to 90℃, and hydrolyze until the end (D-calcium pantothenate content ≤0.2%). Distill to recover ammonia and water, and the remaining solution is reaction solution 1.

[0057] S2. Add 20g of isobutyl acetate to reaction solution 1, adjust the vacuum to 0.02MPa, and carry out the lactone reaction at 100℃ until the end (D-pantolytic acid content ≤0.1%). The resulting solution is reaction solution 2.

[0058] S3. Cool reaction solution 2 to 60℃ and filter. Dry the solid to obtain 36.7g of β-alanine with a purity of 98.4wt% and a yield of 95.0%. Continue to cool the filtrate to below 0℃ to crystallize, filter, and dry the solid to obtain 51.0g of D-pantolactone with a purity of 99.2wt% and a yield of 93.0%.

[0059] Example 2

[0060] S1. Take 1000g of D-calcium pantothenate mother liquor (containing 0.285mol of calcium ions), distill to recover methanol, dilute with water to 300g, add 28.2g of ammonium carbonate (0.293mol), stir for 1h to precipitate, then filter, add 100g of 25% (w / w) ammonia water to the filtrate, heat to 80℃, and hydrolyze until the end (D-calcium pantothenate content ≤0.2%), distill to recover ammonia and water, and the remaining solution is reaction solution 1.

[0061] S2. Add 20g of tert-butyl acetate to reaction solution 1, adjust the vacuum to 0.01MPa, and carry out the lactone reaction at 90℃ until the end (D-pantolytic acid content ≤0.1%). The resulting solution is reaction solution 2.

[0062] S3. Cool reaction solution 2 to 70℃ and filter. Dry the solid to obtain 37.0g of β-alanine with a purity of 98.5wt% and a yield of 95.8%. Continue to cool the filtrate to below 0℃ to crystallize, filter, and dry the solid to obtain 51.8g of D-pantolactone with a purity of 99.0wt% and a yield of 94.6%.

[0063] Example 3

[0064] S1. Take 1000g of D-calcium pantothenate mother liquor (containing 0.285mol of calcium ions), distill to recover methanol, dilute with water to 300g, add 37.6g of ammonium sulfate (0.285mol), stir for 1h to precipitate, then filter, pass 30g of ammonia gas through the filtrate, heat to 100℃, and hydrolyze until the end (D-calcium pantothenate content ≤0.2%), distill to recover ammonia and water, and the remaining solution is reaction solution 1.

[0065] S2. Add 23g of toluene to reaction solution 1, adjust the vacuum to 0.025MPa, and carry out the lactone reaction at 100℃ until the end (D-pantolytic acid content ≤0.1%). The resulting solution is reaction solution 2.

[0066] S3. Cool reaction solution 2 to 50℃ and filter. Dry the solid to obtain 37.1g of β-alanine with a purity of 98.9wt% and a yield of 96.2%. Continue to cool the filtrate to below 0℃ to crystallize, filter, and dry the solid to obtain 51.2g of D-pantolactone with a purity of 99.1wt% and a yield of 93.5%.

[0067] Example 4

[0068] S1. Take 1000g of D-calcium pantothenate mother liquor (containing 0.285mol of calcium ions), distill to recover methanol, dilute with water to 300g, add 28.6g of ammonium phosphate (0.192mol), stir for 1h to precipitate, then filter, pass 12.5g of ammonia gas through the filtrate, heat to 100℃, and hydrolyze until the end (D-calcium pantothenate content ≤0.2%). Distill to recover ammonia and water, and the remaining solution is reaction solution 1.

[0069] S2. Add 25g of toluene to reaction solution 1, adjust the vacuum to 0.035MPa, and carry out the lactone reaction at 95℃ until the end (D-pantolytic acid content ≤0.1%). The resulting solution is reaction solution 2.

[0070] S3. Cool reaction solution 2 to 55℃ and filter. Dry the solid to obtain 36.9g of β-alanine with a purity of 99.0wt% and a yield of 95.7%. Continue to cool the filtrate to below 0℃ to crystallize, filter, and dry the solid to obtain 51.2g of D-pantolactone with a purity of 99.1wt% and a yield of 93.2%.

[0071] Example 5

[0072] S1. Take 1000g of D-calcium pantothenate mother liquor (containing 0.285mol of calcium ions), distill to recover methanol, dilute with water to 300g, add 36.8g of ammonium oxalate (0.296mol), stir for 1h to precipitate, then filter, pass 30g of ammonia gas through the filtrate, heat to 60℃, and hydrolyze until the end (D-calcium pantothenate content ≤0.2%), distill to recover ammonia and water, and the remaining solution is reaction solution 1.

[0073] S2. Add 19g of sec-butyl acetate to reaction solution 1, adjust the vacuum to 0.04MPa, and carry out the lactone reaction at 85℃ until the end (D-pantolytic acid content ≤0.1%). The resulting solution is reaction solution 2.

[0074] S3. Cool reaction solution 2 to 80℃ and filter. Dry the solid to obtain 36.8g of β-alanine with a purity of 99.1wt% and a yield of 95.4%. Continue to cool the filtrate to below 0℃ to crystallize, filter, and dry the solid to obtain 51.6g of D-pantolactone with a purity of 99.1wt% and a yield of 94.1%.

[0075] Example 6

[0076] S1. Take 1000g of D-calcium pantothenate mother liquor (containing 0.285mol of calcium ions), distill to recover methanol, dilute with water to 300g, add 36.1g of ammonium oxalate (0.291mol) and stir for 1h to precipitate, then filter. Add 60g of 25% (w / w) ammonia water to the filtrate, heat to 70℃, and hydrolyze until the end (D-calcium pantothenate content ≤0.2%). Distill to recover ammonia and water, and the remaining solution is reaction solution 1.

[0077] S2. Add 18g of isobutyl acetate to reaction solution 1, adjust the vacuum to 0.01MPa, and carry out the lactone reaction at 110℃ until the end (D-pantolytic acid content ≤0.1%). The resulting solution is reaction solution 2.

[0078] S3. Cool reaction solution 2 to 60℃ and filter. Dry the solid to obtain 37.2g of β-alanine with a purity of 99.1wt% and a yield of 96.5%. Continue to cool the filtrate to below 0℃ to crystallize, filter, and dry the solid to obtain 51.7g of D-pantolytic acid lactone with a purity of 99.1wt% and a yield of 94.4%.

[0079] Example 7

[0080] The D-calcium pantothenate mother liquor was recovered according to the method in Example 1, except that in step S1, 26.0 g of ammonium carbonate (0.271 mol, with a molar ratio of 0.95:1 to the calcium content in the D-calcium pantothenate mother liquor) was added. This yielded 36.7 g of β-alanine with a purity of 96.2 wt% and a yield of 95.0%. It also yielded 51.0 g of D-pantolytic lactone with a purity of 99.2 wt% and a yield of 93.0%.

[0081] Example 8

[0082] The D-calcium pantothenate mother liquor was recovered according to the method in Example 1, except that in step S1, after distilling to recover methanol from the D-calcium pantothenate mother liquor, it was diluted with water, and 80g of 25% (w / w) ammonia water was added first. The temperature was raised to 90°C, and hydrolysis was carried out until completion (D-calcium pantothenate content ≤0.2%). Then, 28.8g of ammonium carbonate (0.30mol) was added and stirred for 1h to precipitate. After filtration, the filtrate was distilled to recover ammonia and water. 36.7g of β-alanine was obtained with a purity of 98.5wt% and a yield of 95.0%. 51.0g of D-pantolytic lactone was obtained with a purity of 99.2wt% and a yield of 93.0%.

[0083] Example 9

[0084] The mother liquor of D-calcium pantothenate was recovered according to the method of Example 1, except that in step S3, the temperature was lowered to 50°C and filtered to obtain 36.7 g of β-alanine with a purity of 95.4 wt% and a yield of 95.0%. 44.9 g of D-pantolytic lactone with a purity of 99.2 wt% and a yield of 82.0% was also obtained.

[0085] Comparative Example 1

[0086] The mother liquor of D-calcium pantothenate was recovered according to the method of Example 1. The difference was that in step S1, 35g of 25% (w / w) ammonia water was added to the filtrate and the temperature was raised to 90°C for hydrolysis. However, the residual D-calcium pantothenate was 8%, and the hydrolysis was incomplete.

[0087] Comparative Example 2

[0088] The mother liquor of D-calcium pantothenate was recovered according to the method of Example 1. The difference was that in step S1, 80g of 25% (w / w) ammonia water was added to the filtrate and the temperature was raised to 50°C for hydrolysis. However, the residual D-calcium pantothenate was 15%, and the hydrolysis was incomplete.

[0089] Comparative Example 3

[0090] The mother liquor of D-calcium pantothenate was recovered according to the method of Example 1. The difference was that in step S2, the lactone reaction temperature was controlled at 50°C, but the residual D-pantothenic acid reached 21%, and the lactone reaction was incomplete.

[0091] As can be seen from the results of Examples 1-9 and Comparative Examples 1-3, when using the method provided by the present invention to recover β-alanine and D-pantolactone, the recovery rate of β-alanine can be as high as 95% or more, and the purity can be as high as 95 wt% or more, while the recovery rate of D-pantolactone can be as high as 82% or more, and the purity can be as high as 99 wt% or more.

[0092] Under preferred conditions, the purity of D-pantolactone obtained in Examples 1-6 is ≥99wt%, and the yield is ≥93%, while the purity of β-alanine is ≥98wt%, and the yield is ≥95%.

[0093] Compared to Example 1, Example 7 interchanged the precipitation and hydrolysis steps, but the yield and purity of β-alanine and D-indohydrin did not change significantly, indicating that the order of the two steps can be changed.

[0094] Compared to Example 1, Example 8 reduced the amount of ammonium salt used in the precipitation step; Example 9 reduced the temperature for recovering β-alanine; and the yield and purity of the obtained β-alanine and D-indohydrin were both reduced.

[0095] Compared to Example 1, Comparative Example 1 reduced the amount of ammonia used in the hydrolysis step; Comparative Example 2 lowered the hydrolysis reaction temperature; and Comparative Example 3 lowered the lactone reaction temperature. In all cases, the hydrolysis or lactone reaction was incomplete.

[0096] This demonstrates that by selecting appropriate ammonium salt type and dosage, ammonia dosage, hydrolysis temperature, solvent type, solvent dosage, lactonization temperature, and β-alanine recovery temperature, precipitation desalting, D-pantolytic acid hydrolysis, and D-pantolytic acid ammonium lactonization reactions can be made more complete. This results in better separation of β-alanine and D-pantolytic acid lactone in the solvent, leading to higher yields of D-pantolytic acid lactone and β-alanine, while avoiding the generation of impurities and improving purity.

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering D-calcium pantothenate mother liquor, characterized in that, The method for recovering the D-calcium pantothenate mother liquor includes the following steps: S1 and D-calcium pantothenate mother liquor were pretreated, precipitated and hydrolyzed to obtain reaction solution 1; The pretreatment includes a distillation step; The precipitation treatment includes precipitation under the action of ammonium salt, followed by solid-liquid separation to obtain liquid. The hydrolysis treatment includes a step of hydrolysis under the action of ammonia gas or ammonia water; the mass ratio of the "ammonia gas or ammonia water" to the D-calcium pantothenate mother liquor is not less than 1.25% based on the mass of ammonia; and the hydrolysis temperature is not less than 60°C. The order of precipitation treatment and hydrolysis treatment is not limited. S2. The mixture of reaction solution 1 and solvent undergoes a lactone reaction to obtain reaction solution 2; The solvent is a non-water-soluble organic solvent; the temperature of the lactone reaction is not lower than 80°C. S3. The reaction solution 2 is separated into solid and liquid components. The solid obtained is β-alanine, and the liquid obtained is crystallized to obtain D-indohydrin lactone.

2. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, The method for recovering D-calcium pantothenate mother liquor meets one or two of the following conditions: (1) In step S1, the ammonium salt includes one or more of ammonium carbonate, ammonium sulfate, ammonium phosphate, ammonium oxalate and ammonium stearate; (2) In step S1, the molar ratio of ammonium ions in the ammonium salt to calcium ions in the D-calcium pantothenate mother liquor is (2.0-2.1):1, for example 2.02:1, 2.04:1, 2.06:1 or 2.08:

1.

3. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, The method for recovering the D-calcium pantothenate mother liquor meets one or two of the following conditions: (1) In step S1, the hydrolysis temperature is 60-100℃, for example 70℃, 80℃ or 90℃; (2) In step S1, the mass ratio of the "ammonia gas or ammonia water" to the D-calcium pantothenate mother liquor is 1.25%-4.0%, for example 1.5%, 2.0% or 3.0%, based on the mass of ammonia.

4. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, The method for recovering D-calcium pantothenate mother liquor meets one or two of the following conditions: (1) In step S2, the solvent includes one or more of isobutyl acetate, sec-butyl acetate, tert-butyl acetate and toluene; (2) In step S2, the mass percentage of the solvent and the D-calcium pantothenate mother liquor in step S1 is 1.5%-2.5%, for example 1.8%, 1.9%, 2.0%, 2.3% or 2.4%.

5. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, The method for recovering D-calcium pantothenate mother liquor meets one or two of the following conditions: (1) In step S2, the temperature of the lactone reaction is 80-120℃; (2) In step S2, the lactone reaction is carried out under atmospheric pressure concentration or vacuum concentration, preferably under vacuum concentration; the vacuum degree of atmospheric pressure concentration is, for example, 0.1 MPa; the vacuum degree of vacuum concentration is preferably 0.01-0.04 MPa, for example, 0.02 MPa, 0.025 MPa or 0.035 MPa.

6. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, In step S3, before the solid-liquid separation, the reaction liquid 2 is further cooled, preferably to 50-80°C, for example 55°C, 60°C or 70°C.

7. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, In step S1, the D-calcium pantothenate mother liquor includes D-calcium pantothenate, β-calcium alanine, D-indolactone, calcium indolactone, methanol, water, and unavoidable impurities; the impurities include, for example, methyl pantothenate. Preferably, in step S1, the D-calcium pantothenate mother liquor comprises 5% D-calcium pantothenate, 2.4% β-alanine calcium, 1% D-indolactone, 2.3% indolactone calcium, 84% methanol, 5% water, and the balance being methyl pantothenate; the percentages are the mass percentages of each component in the D-calcium pantothenate mother liquor.

8. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, The method for recovering D-calcium pantothenate mother liquor satisfies one or more of the following conditions: (1) In step S1, the distillation process further includes the step of dissolving and diluting with water, wherein the mass of the water and the D-calcium pantothenate mother liquor is preferably 1%-5%, for example 3%; (2) In step S1, the precipitation is carried out under stirring conditions; (3) In step S1, the precipitation time is 0.5-2 hours, for example, 1 hour; (4) In step S1, the solid-liquid separation is carried out by filtration; (5) In step S1, after hydrolysis, the step of distilling to recover ammonia water may also be included.

9. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, The method for recovering D-calcium pantothenate mother liquor meets one or two of the following conditions: (1) In step S1, the endpoint of the hydrolysis is that the content of D-calcium pantothenate in the reaction solution is ≤0.2% (w / w). (2) In step S2, the endpoint of the lactone reaction is that the content of D-indohydrol acid in the reaction solution is ≤0.1% (w / w).

10. The method for recovering D-calcium pantothenate mother liquor as described in claim 1, characterized in that, The method for recovering D-calcium pantothenate mother liquor satisfies one or more of the following conditions: (1) In step S3, the solid-liquid separation is performed by filtration; (2) In step S3, after the solid-liquid separation is completed, the solid is further dried. (3) In step S3, the crystallization is carried out below 0°C; (4) In step S3, after crystallization, the solid is further separated from the liquid and dried.