Method for recovering DL-pantoic acid lactone from DL-panthenol residual liquid

Abstract

The invention provides a method for recovering DL-pantoic acid lactone from DL-panthenol raffinate, which comprises the following steps: 1) mixing the DL-panthenol raffinate, water and an anionic surfactant to form a uniform stable phase; the anionic surfactant is selected from sodium dodecyl benzene sulfonate; 2) heating the uniform stable phase, preserving heat, and hydrolyzing to obtain a hydrolysate; 3) cooling the hydrolysate, and performing solvent extraction to obtain an extraction phase and a raffinate phase; and 4) carrying out evaporative crystallization on the extraction phase to obtain the DL-pantoic acid lactone. According to the method, the DL-pantoic acid lactone can be recycled from the DL-panthenol residual liquid, the recycling efficiency is high, the pH requirement range is mild, corrosion to equipment is small, reaction steps are reduced, the production cost is reduced, and the recycled DL-pantoic acid lactone can be used for synthesizing DL-calcium pantothenate and DL-panthenol. The hydrolysis rate is 64 to 99.5 percent, and the purity of the DL-pantoic acid lactone is more than 98.5 percent.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production waste liquid recovery, and in particular relates to a method for recovering DL-pantolactone from DL-pantoic acid residual liquid. Background Art

[0002] DL-pantoic acid lactone is a common chemical product. After being split into D-pantoic acid lactone, it is often used as a synthetic raw material for D-calcium pantothenate and D-panthenol, and is widely used in other pharmaceutical intermediates and raw materials for cosmetics. Currently, DL-pantoic acid lactone is mainly synthesized through the isobutyraldehyde-formaldehyde-sodium cyanide method or the glyoxylic acid-isobutyraldehyde method.

[0003] The synthesis of DL-panthenol is currently mainly carried out by the cooling crystallization method. During the crystallization process, some DL-panthenol will inevitably remain in the crystallization mother liquor. After the crystallization mother liquor is subjected to reduced pressure distillation to recover the solvent, some non-recoverable substances will still remain in the mother liquor. In the industry, this part of the non-recoverable residue is called DL-panthenol residual liquid.

[0004] CN111484463A discloses a method for recycling panthenol mother liquor, wherein the panthenol mother liquor is heated and the pH value is adjusted to 1-3 with an acid, and then the pantoic acid lactone is recovered after being kept warm and hydrolyzed; CN114394948A discloses a method for recycling panthenol mother liquor, wherein the panthenol mother liquor is heated and the pH value is adjusted to 10-13 with an alkali, and then the pantoic acid lactone is recovered after being kept warm and hydrolyzed. The above method has a low yield of pantoic acid lactone recovery, and the reaction conditions are extremely harsh. During the reaction, the pH needs to be monitored in real time and the pH needs to be kept within the required range, which increases the difficulty of personnel operation; in addition, the pH requirement range is strongly acidic or strongly alkaline, which greatly increases the corrosion of the equipment and causes an increase in production and maintenance costs. Therefore, a recovery process of DL-panthenol residual liquid with a higher yield and more environmental protection needs to be studied. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a method for recovering DL-pantoic acid lactone from DL-panthenol residual liquid. The method recovers DL-pantoic acid lactone from DL-panthenol residual liquid and can be used for the synthesis of DL-calcium pantothenate and DL-panthenol.

[0006] The present invention provides a method for recovering DL-pantolactone from DL-panthenol residual liquid, comprising the following steps:

[0007] 1) mixing DL-panthenol residual liquid, water and anionic surfactant to form a uniform stable phase; the anionic surfactant is sodium dodecylbenzene sulfonate;

[0008] 2) heating the homogeneous stable phase and keeping the temperature to hydrolyze the phase to obtain a hydrolyzate;

[0009] 3) cooling the hydrolyzate and then subjecting it to solvent extraction to obtain an extract phase and a raffinate phase;

[0010] 4) Evaporating and crystallizing the extract phase to obtain DL-pantolactone.

[0011] Preferably, in step 1), the anionic surfactant accounts for 1.7-1.8% of the mass of the mixed solution of DL-panthenol residual liquid and water.

[0012] Preferably, the hydrolysis temperature is 90-95° C., and the hydrolysis time is 1-4 hours.

[0013] Preferably, the raffinate phase is distilled to obtain aminopropanol.

[0014] Preferably, the water accounts for 70% to 100% of the mass of the DL-panthenol residual liquid.

[0015] Preferably, the solvent used in the solvent extraction is ethyl acetate;

[0016] The temperature of solvent extraction is 20-40°C.

[0017] Preferably, the operating temperature of the evaporation crystallization is between 50 and 60° C., and the vacuum degree is controlled at above -0.085 MPa.

[0018] The present invention provides a method for recovering DL-pantoic acid lactone from DL-pantoic acid residual liquid, comprising the following steps: 1) mixing DL-pantoic acid residual liquid, water and anionic surfactant to form a uniform stable phase; the anionic surfactant is sodium dodecylbenzene sulfonate; 2) heating the uniform stable phase and keeping the temperature to hydrolyze to obtain a hydrolyzate; 3) cooling the hydrolyzate and then extracting with a solvent to obtain an extract phase and a raffinate phase; 4) evaporating and crystallizing the extract phase to obtain DL-pantoic acid lactone. The method can recover DL-pantoic acid lactone from DL-pantoic acid residual liquid, has high recovery efficiency, mild pH requirement range, low corrosion to equipment, reduces reaction steps, reduces production costs, and the recovered DL-pantoic acid lactone can be used for the synthesis of DL-calcium pantothenate and DL-pantoic acid. Experimental results show that the hydrolysis rate is 64-99.5%, and the purity of DL-pantoic acid lactone is above 98.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 FIG. 1 is a schematic diagram of a process for recovering DL-pantolactone from DL-panthenol residue in certain embodiments of the present invention. DETAILED DESCRIPTION

[0020] The present invention provides a method for recovering DL-pantolactone from DL-panthenol residual liquid, comprising the following steps:

[0021] 1) mixing DL-panthenol residual liquid, water and anionic surfactant to form a uniform stable phase; the anionic surfactant is sodium dodecylbenzene sulfonate;

[0022] 2) heating the homogeneous stable phase and keeping the temperature to hydrolyze the phase to obtain a hydrolyzate;

[0023] 3) cooling the hydrolyzate and then subjecting it to solvent extraction to obtain an extract phase and a raffinate phase;

[0024] 4) Evaporating and crystallizing the extract phase to obtain DL-pantolactone.

[0025] The main components of the DL-panthenol residual liquid in the present invention include DL-panthenol, DL-pantoic acid lactone, 3-aminopropanol and ethyl acetate. The anionic surfactant used in the present invention is sodium dodecylbenzene sulfonate (SDBC); the present invention avoids the strong acid or strong base environment that needs to be maintained throughout the traditional hydrolysis reaction by selecting the above-mentioned specific type of surfactant, thereby eliminating the acidification or alkalization and subsequent neutralization steps. The present invention is carried out under the pH environment presented by DL-panthenol itself, which significantly reduces the corrosion to the equipment, while reducing the danger brought by the strong acid or strong base environment, further reducing the production and maintenance costs, and is more environmentally friendly.

[0026] The above-mentioned surfactants also serve as catalysts to catalyze the hydrolysis of DL-panthenol in the DL-panthenol residual solution to generate DL-pantoic acid lactone, and then obtain the solid product DL-pantoic acid lactone after extraction and evaporation crystallization.

[0027] In the present invention, the water accounts for 70% to 100% of the mass of the DL-panthenol residual liquid; specifically 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, or 100%. The anionic surfactant accounts for 1.7 to 1.8% of the mass of the mixture of DL-panthenol residual liquid and water; in a specific embodiment, the anionic surfactant accounts for 1.75% of the mass of the mixture of DL-panthenol residual liquid and water.

[0028] After obtaining a homogeneous stable phase, the present invention heats the homogeneous stable phase and keeps it warm for hydrolysis to obtain a hydrolyzate. The hydrolysis temperature is 90-95°C, and the hydrolysis time is 1-4h; in a specific embodiment, the hydrolysis temperature is 90°C, 91°C, 92°C, 93°C, 94°C or 95°C; the hydrolysis time is 1h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h or 4h. Magnetic stirring is maintained during the heating and insulation process, and the stirring speed is 280-320rpm, preferably 290-310rpm; in a specific embodiment, the stirring speed is 300rpm. The present invention can almost completely hydrolyze DL-panthenol in the DL-panthenol residue to generate DL-pantoic acid lactone, and the hydrolysis efficiency is higher.

[0029] Hydrolysis rate = (mass content of DL-panthenol in DL-panthenol residue - residual content of DL-panthenol after hydrolysis) ÷ mass content of DL-panthenol in DL-panthenol residue.

[0030] After the hydrolysis is completed, the present invention cools the hydrolyzate and then performs solvent extraction to obtain an extract phase and a raffinate phase. The extractant used in the solvent extraction is ethyl acetate. The temperature of the solvent extraction is 20 to 40°C.

[0031] The present invention evaporates and crystallizes the extract phase to obtain DL-pantoic acid lactone. The temperature of the evaporation and crystallization is 50-60°C, preferably 55-60°C, more preferably 58-60°C; the vacuum degree of the evaporation and crystallization is above -0.085MPa.

[0032] The present invention preferably distills the raffinate phase to obtain aminopropanol.

[0033] Figure 1 The present invention is a schematic diagram of a process for recovering DL-pantoic acid lactone from DL-pantoic acid residual liquid in certain embodiments of the present invention; DL-pantoic acid residual liquid, water and sodium dodecylbenzene sulfonate are mixed and dissolved, and hydrolyzed at 90-95° C. for more than 1 hour, and the hydrolyzate is extracted to obtain an extract phase and a raffinate phase; aminopropanol is recovered from the raffinate phase, and the extract phase is evaporated and crystallized to obtain DL-pantoic acid lactone (purity above 98.5%).

[0034] To further illustrate the present invention, a method for recovering DL-pantoic acid lactone from DL-panthenol residual liquid provided by the present invention is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1

[0036] (1) 40 g of DL-panthenol residual liquid was taken, 40 g of water was added, and after dissolution and clarification, the pH value of the material was measured to be 8.95, then 1.4 g of SDBC was added, and stirred until it was completely dissolved, and the mass content of DL-panthenol in the material was sampled and tested to be 19.2%, and the mass content of DL-pantolactone was 3.69%;

[0037] (2) Use a constant temperature heating magnetic stirrer to heat the material to 95°C, keep the temperature for 1 hour, and keep the magnetic stirring speed at 300r / min during the heating and insulation process;

[0038] (3) After the reaction, the material was cooled to 25°C to obtain 81.2g of hydrolysis reaction liquid. The residual content of DL-panthenol in the material was 6.76%, the content of DL-pantoic acid lactone was 11.58%, and the hydrolysis rate was 64.81% (hydrolysis rate calculation formula = (19.2%-6.76%) ÷ 19.2%). 160g of ethyl acetate was added and fully extracted at 25°C. After standing and stratification, 170.3g of the extract phase containing the product DL-pantoic acid lactone and 65.9g of the raffinate phase were obtained;

[0039] (4) taking the extract obtained in step (3), evaporating and crystallizing (temperature 58-60° C., vacuum degree above -0.085 MPa) to obtain 9.08 g of the product DL-pantolactone, the purity of which was 98.5% after testing;

[0040] (5) distilling the raffinate phase obtained in step (3) to obtain aminopropanol.

[0041] Example 2

[0042] (1) 50 g of DL-panthenol residual liquid was taken, 50 g of water was added, and after dissolution and clarification, the pH value of the material was measured to be 8.77. At this time, 1.82 g of SDBC was added, and stirred until it was completely dissolved. The mass content of DL-panthenol in the material was sampled and tested, and the mass content of DL-pantolactone was 18.87%, and the mass content of DL-pantolactone was 3.79%;

[0043] (2) Use a constant temperature heating magnetic stirrer to heat the material to 95°C, keep the temperature for 2 hours, and keep the magnetic stirring speed at 300r / min during the heating and insulation process;

[0044] (3) After the reaction, the material was cooled to 25°C to obtain 101.7g of hydrolysis reaction liquid. The residual content of DL-panthenol in the material was 2.07%, the content of DL-pantoic acid lactone was 14.44%, and the hydrolysis rate was 89.01%. 200g of ethyl acetate was added and fully extracted at 25°C. After standing and stratification, 213.9g of the extract phase containing the product DL-pantoic acid lactone and 81.9g of the raffinate phase were obtained;

[0045] (4) taking the extract obtained in step (3), evaporating and crystallizing (temperature 58-60° C., vacuum degree above -0.085 MPa) to obtain 14.32 g of the product DL-pantolactone, the purity of which was 98.5% after testing;

[0046] (5) distilling the raffinate phase obtained in step (3) to obtain aminopropanol.

[0047] Example 3

[0048] (1) 40 g of DL-panthenol residual liquid was taken, 40 g of water was added, and after dissolution and clarification, the pH value of the material was measured to be 9.03. At this time, 1.41 g of SDBC was added, and stirred until it was completely dissolved. The DL-panthenol content in the material was sampled and tested, and the content of DL-pantolactone was 19.52% and 3.53% respectively;

[0049] (2) Use a constant temperature heating magnetic stirrer to heat the material to 95°C, keep the temperature for 3 hours, and keep the magnetic stirring speed at 300r / min during the heating and insulation process;

[0050] (3) After the reaction, the material was cooled to 25°C to obtain 80.9g of hydrolysis reaction liquid. The residual content of DL-panthenol in the material was 1.07%, the content of DL-pantoic acid lactone was 15.23%, and the hydrolysis rate was 94.53%. 160g of ethyl acetate was added and fully extracted at 25°C. After standing and stratification, 176.1g of the extract phase containing the product DL-pantoic acid lactone and 62.5g of the raffinate phase were obtained;

[0051] (4) taking the extract obtained in step (3), evaporating and crystallizing (temperature 58-60° C., vacuum degree above -0.085 MPa) to obtain 12.01 g of the product DL-pantolactone, the purity of which was 98.7% after testing;

[0052] (5) distilling the raffinate phase obtained in step (3) to obtain aminopropanol.

[0053] Example 4

[0054] (1) 40 g of DL-panthenol residual liquid was taken, 40 g of water was added, and after dissolution and clarification, the pH value of the material was measured to be 8.89, then 1.43 g of SDBC was added, and stirred until it was completely dissolved, and the mass content of DL-panthenol in the material was sampled and tested to be 19.39%, and the mass content of DL-pantolactone was 3.62%;

[0055] (2) Use a constant temperature heating magnetic stirrer to heat the material to 95°C, keep the temperature for 4 hours, and keep the magnetic stirring speed at 300r / min during the heating and insulation process;

[0056] (3) After the reaction, the material was cooled to 25°C to obtain 80.6g of hydrolysis reaction liquid. The residual content of DL-panthenol in the material was 0.13%, the content of DL-pantoic acid lactone was 15.83%, and the hydrolysis rate was 99.31%. 160g of ethyl acetate was added and fully extracted at 25°C. After standing and stratification, 176.3g of the extract phase containing the product DL-pantoic acid lactone and 61.7g of the raffinate phase were obtained;

[0057] (4) taking the extract obtained in step (3), evaporating and crystallizing (temperature 58-60° C., vacuum degree above -0.085 MPa) to obtain 12.53 g of the product DL-pantolactone, the purity of which was 98.6% after testing;

[0058] (5) distilling the raffinate phase obtained in step (3) to obtain aminopropanol.

[0059] Comparative Example 1

[0060] (1) 40 g of DL-panthenol residual liquid was taken, 40 g of water was added, and the pH value of the material was measured to be 8.82 after dissolution and clarification, and the material was stirred until it was completely dissolved, and the DL-panthenol content in the material was sampled and tested to be 19.17%, and the content of DL-pantolactone was 3.14%;

[0061] (2) Use a constant temperature heating magnetic stirrer to heat the material to 95°C, keep the temperature for 4 hours, and keep the magnetic stirring speed at 300r / min during the heating and insulation process;

[0062] (3) After the reaction, the material was cooled to 25° C. to obtain 78.7 g of a hydrolysis reaction solution. The residual content of DL-panthenol in the material was 12.36%, the content of DL-pantolactone was 7.46%, and the hydrolysis rate was 35.54%.

[0063] Comparative Example 2

[0064] (1) 40 g of DL-panthenol residual liquid was taken, 40 g of water was added, and after dissolution and clarification, the pH value of the material was measured to be 8.80. At this time, 1.43 g of polysorbate (anionic surfactant) was added, and stirred until it was completely dissolved. The DL-panthenol content in the material was sampled and tested to be 19.01%, and the content of DL-pantolactone was 3.64%;

[0065] (2) Use a constant temperature heating magnetic stirrer to heat the material to 95°C, keep the temperature for 4 hours, and keep the magnetic stirring speed at 300r / min during the heating and insulation process;

[0066] (3) After the reaction, the material was cooled to 25° C. to obtain 80.7 g of a hydrolysis reaction solution. The residual content of DL-panthenol in the material was 10.32%, the content of DL-pantolactone was 9.07%, and the hydrolysis rate was 45.71%.

[0067] Comparative Example 3

[0068] (1) 40 g of DL-panthenol residual liquid was taken, 40 g of water was added, and the pH value of the material was measured after dissolution and clarification, and 1.43 g of polyquaternium-6 (cationic surfactant) was added, and stirred until it was completely dissolved. The mass content of DL-panthenol in the material was sampled and tested, and the mass content of DL-pantolactone was 19.23%, and the mass content of DL-pantolactone was 3.55%;

[0069] (2) Use a constant temperature heating magnetic stirrer to heat the material to 95°C, keep the temperature for 4 hours, and keep the magnetic stirring speed at 300r / min during the heating and insulation process;

[0070] (3) After the reaction, the material was cooled to 25° C. to obtain 80.2 g of a hydrolysis reaction solution. The residual content of DL-panthenol in the material was sampled and tested to be 13.38%, the content of DL-pantolactone was 7.19%, and the hydrolysis rate was 30.42%.

[0071] The results of the relevant quality indicators of the products obtained by hydrolyzing the above-mentioned embodiments and comparative examples of the present invention are shown in Table 1.

[0072] Table 1. Results of SDBC-catalyzed DL-raffinate hydrolysis at different times

[0073]

[0074] As can be seen from the above embodiments, the present invention provides a method for recovering DL-pantoic acid lactone from DL-pantoic acid residue, comprising the following steps: 1) mixing DL-pantoic acid residue, water and anionic surfactant to form a uniform stable phase; the anionic surfactant is sodium dodecylbenzene sulfonate; 2) heating the uniform stable phase and keeping it warm to hydrolyze to obtain a hydrolyzate; 3) cooling the hydrolyzate and then extracting it with a solvent to obtain an extract phase and a raffinate phase; 4) evaporating and crystallizing the extract phase to obtain DL-pantoic acid lactone. The method can recover DL-pantoic acid lactone from DL-pantoic acid residue, has high recovery efficiency, mild pH requirement range, low corrosion to equipment, reduces reaction steps, reduces production costs, and the recovered DL-pantoic acid lactone can be used for the synthesis of DL-calcium pantothenate and DL-pantoic acid. Experimental results show that the hydrolysis rate is 64-99.5%, and the purity of DL-pantoic acid lactone is above 98.5%.

[0075] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for recovering DL-pantolactone from DL-panthenol residue, comprising the following steps: 1) mixing DL-panthenol residual liquid, water and anionic surfactant to form a uniform stable phase; the anionic surfactant is sodium dodecylbenzene sulfonate; 2) heating the homogeneous stable phase and keeping the temperature to hydrolyze the phase to obtain a hydrolyzate; 3) cooling the hydrolyzate and then subjecting it to solvent extraction to obtain an extract phase and a raffinate phase; 4) Evaporating and crystallizing the extract phase to obtain DL-pantolactone.

2. The method according to claim 1, characterized in that: In the step 1), the anionic surfactant accounts for 1.7-1.8% of the mass of the mixed solution of DL-panthenol residual liquid and water.

3. The method according to claim 1, characterized in that The hydrolysis temperature is 90-95° C., and the hydrolysis time is 1-4 hours.

4. The method according to claim 1, characterized in that: The raffinate phase is distilled to obtain aminopropanol.

5. The method according to claim 1, characterized in that The water accounts for 70% to 100% of the mass of the DL-panthenol residual liquid.

6. The method according to claim 1, characterized in that The solvent used in the solvent extraction is ethyl acetate; The temperature of solvent extraction is 20-40°C.

7. The method according to claim 1, characterized in that The operating temperature of the evaporation crystallization is between 40 and 50° C., and the vacuum degree is controlled above -0.085 MPa.

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