Method for recovering tartaric acid from tartrate
By using azeotropic distillation method of acetonitrile and water in the tartaric acid recovery process, the problems of high energy consumption, high cost and low recovery rate in the prior art are solved, and efficient and stable recycling of tartaric acid is achieved.
Patent Information
- Application Number
- CN202411880890.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-19
- Publication Date
- 2025-05-30
AI Technical Summary
The method for recycling tartaric acid in the prior art has problems such as high energy consumption, high cost and low recovery rate. Especially during the concentration process, alcohol solvents are prone to esterification with tartaric acid, which reduces the recovery rate.
Acetonitrile is used as an organic solvent and azeotrope with water to distillate to avoid the esterification reaction of alcoholic solvents and tartaric acid, and the recovery of tartaric acid is carried out through steps such as acidification, neutralization, distillation and crystallization.
It improves the recovery rate of tartaric acid, reduces process energy consumption, and has stable product quality, which meets the policy requirements of energy conservation and environmental protection.
Abstract
Description
Technical Field
[0001] The present invention relates to the field of chemical technology, and in particular to a method for recovering tartaric acid from tartrate salts. Background Art
[0002] Tartaric acid is commonly used in the preparation of drugs, mordants, tanning agents, etc. It is a relatively expensive and widely used chiral resolving agent. It is also an acidulant in food additives, with a better sour taste than malic acid, lactic acid, etc. The largest use of tartaric acid is as a beverage additive and it is also a raw material for the pharmaceutical industry. In the mirror-making industry, tartaric acid is an important auxiliary agent and reducing agent, which can control the formation rate of silver mirrors and obtain a very uniform coating.
[0003] Currently, the general method for recovering tartaric acid is to add calcium chloride to wastewater for reaction to form calcium tartrate precipitate, so as to separate tartaric acid from the wastewater. Then, using water as a solvent, calcium tartrate is added, and then sulfuric acid is added for stirring reaction. The generated calcium sulfate can be filtered out from the water. Then, the obtained aqueous tartaric acid solution is subjected to decolorization adsorption refining by a secondary or multi-stage anion and cation exchange column, and evaporated and concentrated to crystallize to obtain the recovered tartaric acid. In this method, due to the evaporation and concentration of the aqueous tartaric acid solution, the evaporation of water consumes a large amount of steam, with high energy consumption and cost, which does not conform to the energy-saving and environmental protection policies, and the quality of the recovered product fluctuates greatly.
[0004] CN1414939A discloses a method for recovering and recycling D-tartaric acid. In this method, in the presence of a solvent ethanol or methanol, the waste liquid containing sodium tartrate is acid-neutralized to obtain sodium hydrogen tartrate, and then after neutralization, it is filtered, concentrated, and washed to obtain tartaric acid. Although this method avoids the process of evaporation and concentration of water and reduces the energy consumption, the recovery rate of tartaric acid in this method is not high. The recovery rate of tartaric acid from sodium hydrogen tartrate is only 83%, and the recovery rate from potassium hydrogen tartrate is only 25%. Summary of the Invention
[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for recovering tartaric acid from tartrate salts with stable process, high recovery rate, and low process energy consumption.
[0006] The inventors found that in the process of recovering tartaric acid in the prior art, the main reason for the reduction of the recovery rate may be that during the concentration process, the alcohol solvent is prone to esterification reaction with tartaric acid, thereby reducing the recovery rate of tartaric acid.
[0007] To solve the above technical problems, the technical solution of the present invention is as follows:
[0008] A method for recovering tartaric acid from tartrate salts, comprising the following steps:
[0009] 1) Acidification: After acidifying tartrate with an acid in the presence of an organic solvent and water, filter to obtain an acidified filter cake and a filtrate.
[0010] 2) Neutralization: Add a base to the filtrate to neutralize the excessive acid in the acidification process, and then filter to obtain a neutralized filter cake and a neutralized mother liquor;
[0011] 3) Rectification: Rectify the neutralized mother liquor to azeotropically distill a distillate containing the solvent and water;
[0012] 4) Crystallization: Control the stirring of the rectification kettle liquid, cool it for crystallization, and then dry it to obtain tartaric acid.
[0013] In step 1), the organic solvent is a solvent miscible with water and is not an alcohol solvent.
[0014] Preferably, in step 1), the solvent in the acidification process is acetonitrile, the acid used for acidification is sulfuric acid, the amount of sulfuric acid is controlled to be 0.5 - 1 times the molar amount of tartrate, and the use of acetonitrile can effectively improve the recovery rate.
[0015] Preferably, in step 1), the tartrate is sodium tartrate or potassium tartrate.
[0016] Preferably, in step 1), the mass of the organic solvent is 5 - 15 times the mass of the tartrate.
[0017] Preferably, in step 2), the base used in the neutralization process is one of sodium carbonate and sodium bicarbonate, and the pH of the neutralized mother liquor is controlled to be 1.5 - 2.5.
[0018] Preferably, in step 3), the top temperature during rectification is controlled at 70.0 - 75.0 °C until the amount of the solution in the kettle is 25% - 30% of the total input mass.
[0019] Preferably, in step 3), after the distillate is dehydrated by fractions, the solvent is recycled. As a further preference, the fraction dehydration is to add flake alkali or anhydrous sodium sulfate.
[0020] Preferably, in step 4), during the cooling crystallization, the cooling rate is controlled at 5 - 10 °C / h and gradually cooled to -5 - 10 °C (preferably 2 - 6 °C), then the crystallization time is 1 - 3 hours (preferably 1 - 2 hours), and then filter to obtain tartaric acid.
[0021] Furthermore, the specific solution of the present invention is as follows:
[0022] 1) Prepare an aqueous solution of sodium tartrate in acetonitrile:
[0023] Add sodium tartrate to a three-necked flask, successively add acetonitrile and water, turn on the stirring paddle, and start stirring and pulping to mix sodium tartrate, acetonitrile, and water evenly.
[0024] 2) Acidification:
[0025] Place the three-necked flask containing the mixed solution in step 1) in a cold trap, set the temperature to 0 °C and continue stirring. When the temperature of the mixed solution stabilizes at 0 °C, use a constant-pressure dropping funnel to add concentrated sulfuric acid dropwise to the three-necked flask. After the addition is complete, transfer it to a water bath at 30 °C, keep it warm for 3 h, and then perform suction filtration to obtain sodium sulfate and the suction filtration mother liquor.
[0026] 3) Neutralization: Add sodium bicarbonate to the suction filtration mother liquor to neutralize the excess concentrated sulfuric acid. Stir at 30 °C for 0.5 h, then perform suction filtration and rinsing.
[0027] 4) Azeotropic distillation:
[0028] Add the neutralized mother liquor to the distillation column. After acetonitrile and water are distilled out as an azeotrope fraction, add flake soda to remove water. After layering and filtration, the acetonitrile is recycled to the next batch, and the alkaline water is sold externally.
[0029] 5) Cooling crystallization, separation and drying
[0030] Place the three-necked flask containing the bottom product of the column in a cold trap, start stirring, stir slowly, gradually cool down to 4 °C, keep it stable for 1 h for crystal growth, perform suction filtration to obtain wet tartaric acid, and dry it at 65 - 75 °C for 5 h to obtain the tartaric acid product. The mother liquor is recycled to the next batch for use.
[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0032] (1) In the present invention, acetonitrile is used to replace the alcohol solvent, which can effectively avoid the esterification reaction between the alcohol solvent and carboxylic acid or inorganic oxyacid, and improve the recovery rate of tartaric acid.
[0033] (2) In the present invention, the method of azeotropic distillation of organic solvent acetonitrile and water is adopted. The azeotropic temperature of acetonitrile and water is 76 °C. The method of azeotropic distillation of organic solvent and water is used to replace the aqueous phase method, which reduces the energy consumption during the distillation operation. Specific embodiments
[0034] The technical solutions of the present invention will be further described below through specific examples. It should be understood that the following examples are only for illustrative and explanatory purposes of the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.
[0035] Example 1
[0036] Add 82.40 g of 25% sodium tartrate aqueous solution to a 500 mL three-necked flask, add 248.04 g of solvent acetonitrile, stir, then weigh 15.94 g of concentrated sulfuric acid and place it in a constant-pressure separatory funnel. Slowly add it dropwise at 0 °C. After the addition is complete, transfer the three-necked flask to a water bath at 30 °C, keep it warm for 3 h, and then filter by suction.
[0037] Add 2.02 g of sodium bicarbonate to the mother liquor to neutralize the excessive concentrated sulfuric acid. Stir at 30 °C for 0.5 h, then filter by suction and wash. After neutralization, pH = 1.50.
[0038] Rectify the mother liquor in a column (number of plates 10, reflux ratio 3:1). Control the vacuum degree at -0.075 to -0.095 Mpa, the top temperature at 70 - 75 °C, and when the bottom temperature is 84 °C, all the water is taken out. Continue to take out the distillate until 87.50 g of bottom liquid remains in the three-necked flask, and then stop rectification.
[0039] Transfer the three-necked flask to a cold trap, slowly cool down, control the cooling rate at 5 - 10 °C / h and gradually cool down to 4 °C, cool and crystallize, keep warm for crystal growth for 1.1 h, filter by suction, and dry the solid tartaric acid at 65 °C for 5 h to obtain tartaric acid product. The mother liquor is applied to the next batch.
[0040] After analysis of the recovered tartaric acid, the yield is 89.52%, the HPLC content is ≥99.2%, and the melting point is 169 - 171 °C.
[0041] Example 2
[0042] Add 91.09 g of 23% sodium tartrate aqueous solution to a 500 mL three-necked flask, add 201.15 g of solvent acetonitrile, stir, then weigh 18.65 g of concentrated sulfuric acid and place it in a constant-pressure separatory funnel. Slowly add it dropwise at 0 °C. After the addition is complete, transfer the three-necked flask to a water bath at 30 °C, keep it warm for 3 h, and then filter by suction.
[0043] Add 2.58 g of sodium bicarbonate to the mother liquor to neutralize the excessive concentrated sulfuric acid. Stir at 30 °C for 0.5 h, then filter by suction and wash. After neutralization, pH = 1.62.
[0044] Rectify the mother liquor, control the vacuum degree at -0.075 to -0.095 Mpa, the top temperature at 70 - 75 °C, and when the bottom temperature is 84 °C, all the water is taken out. Continue to take out the distillate until 92.50 g of bottom liquid remains in the three-necked flask, and then stop rectification.
[0045] Transfer the three-necked flask to a cold trap, slowly cool down, control the cooling rate at 5 - 10 °C / h and gradually cool down to 2 °C, cool and crystallize, keep warm for crystal growth for 1.1 h, filter by suction, and dry the solid tartaric acid at 70 °C for 5 h to obtain tartaric acid product. The mother liquor is applied to the next batch.
[0046] The recovered tartaric acid was analyzed, with a yield of 89.93%, an HPLC content of ≥99.2%, and a melting point of 169 - 171°C.
[0047] Example 3
[0048] Add 76.93 g of 27% sodium tartrate aqueous solution to a 500 mL three-necked flask, add 201.53 g of solvent acetonitrile, stir, then weigh 20.36 g of concentrated sulfuric acid and place it in a constant-pressure dropping funnel. Start slowly dropping it at 0°C. After the dropping is completed, transfer the three-necked flask to a 30°C water bath and keep it warm for 3 h, then filter by suction.
[0049] Add 3.27 g of sodium bicarbonate to the mother liquor to neutralize the excessive concentrated sulfuric acid. Stir at 30°C for 0.5 h, then filter by suction and wash. The pH after neutralization is 1.70.
[0050] Rectify the mother liquor in a column. Control the vacuum degree at -0.075 to -0.095 Mpa, the top temperature at 70 - 75°C, and when the bottom temperature is 84°C, all the water is taken out. Continue to take out the distillate until 82.30 g of residue remains in the three-necked flask, then stop rectification.
[0051] Transfer the three-necked flask to a cold trap, slowly cool down, control the cooling rate at 5 - 10°C / h and gradually cool down to 6°C, cool and crystallize, keep it warm for crystal growth for 1.2 h, filter by suction, and dry the solid tartaric acid at 75°C for 5 h to obtain the tartaric acid product. The mother liquor is applied to the next batch.
[0052] The recovered tartaric acid was analyzed, with a yield of 90.02%, an HPLC content of ≥99.2%, and a melting point of 169 - 171°C.
[0053] Example 4
[0054] Add 94.6 g of 25% potassium tartrate aqueous solution to a 500 mL three-necked flask, add 200.15 g of solvent acetonitrile, stir, then weigh 20.16 g of concentrated sulfuric acid and place it in a constant-pressure dropping funnel. Start slowly dropping it at 0°C. After the dropping is completed, transfer the three-necked flask to a 30°C water bath and keep it warm for 3 h, then filter by suction.
[0055] Add 3.09 g of sodium bicarbonate to the mother liquor to neutralize the excessive concentrated sulfuric acid. Stir at 30°C for 0.5 h, then filter by suction and wash. The pH after neutralization is 2.5.
[0056] Rectify the mother liquor in a column. Control the vacuum degree at -0.075 to -0.095 Mpa, the top temperature at 70 - 75°C, and when the bottom temperature is 84°C, all the water is taken out. Continue to take out the distillate until 80.5 g of residue remains in the three-necked flask, then stop rectification.
[0057] Transfer the three-necked flask to a cold trap, slowly cool down, control the cooling rate at 5-10 °C / h and gradually cool down to 3 °C, cool and crystallize, keep the temperature for crystal growth for 1.1 h, dry the solid tartaric acid at 70 °C for 5 h after filtration, obtain the tartaric acid product, and recycle the mother liquor to the next batch.
[0058] After analysis, the recovery rate of the recycled tartaric acid is 89.90%, the HPLC content is ≥99.1%, and the melting point is 169-171 °C.
[0059] Example 5
[0060] Add 80.40 g of 25% sodium tartrate aqueous solution to a 500 mL three-necked flask, add 200.52 g of solvent toluene, stir, then weigh 20.23 g of concentrated sulfuric acid and place it in a constant pressure separatory funnel. Slowly add the acid dropwise at 0 °C. After the addition is completed, transfer the three-necked flask to a water bath at 30 °C, keep the temperature for 3 h, and then filter.
[0061] Add 3.05 g of sodium bicarbonate to the mother liquor to neutralize the excess concentrated sulfuric acid. Stir at 30 °C for 0.5 h, then filter and wash. The filtration speed is slow, and the pH after neutralization is 1.71.
[0062] Rectify the mother liquor in a tower, control the vacuum degree at -0.075 to -0.095 Mpa, when the top temperature of the tower is 82-85 °C and the bottom temperature of the tower is 94 °C, all the water is taken out. Continue to take out the distillate until 73.01 g of bottom liquid remains in the three-necked flask, and then stop rectification.
[0063] Transfer the three-necked flask to a cold trap, slowly cool down, control the cooling rate at 5-10 °C / h and gradually cool down to 5 °C, cool and crystallize, keep the temperature for crystal growth for 1.2 h, dry the solid tartaric acid at 75 °C for 5 h after filtration, obtain the tartaric acid product, which is viscous in state and has a poor crystal form, and recycle the mother liquor to the next batch.
[0064] After analysis, the recovery rate of the recycled tartaric acid is 71.23%, the HPLC content is ≥76.2%, and the melting point is 169-171 °C.
Claims
1. A method for recovering tartaric acid from a tartrate, characterized in that The following steps are involved: 1) Acidification: adding an inorganic acid in the presence of an organic solvent and water to acidify the tartrate, and filtering to obtain an acidified filter cake and a filtrate; 2) Neutralization: adding alkali to the filtrate to neutralize the excess acid in the acidification process, and then filtering to obtain a neutralized filter cake and a neutralized mother liquor; 3) Distillation: distill the neutralized mother liquor to obtain a distillate containing an organic solvent and water by azeotropic distillation; 4) Crystallization: Control the stirring and cooling of the distillation kettle liquid to obtain tartaric acid; In step 1), the organic solvent is a solvent miscible with water and is not an alcohol solvent.
2. The method for recovering tartaric acid from tartrate according to claim 1, characterized in that In step 1), the organic solvent used in the acidification process is acetonitrile; the inorganic acid is sulfuric acid, and the amount of sulfuric acid is controlled to be 0.5 to 1 times the molar amount of tartaric acid salt.
3. The method for recovering tartaric acid from tartrate according to claim 1, characterized in that In step 1), the tartrate is sodium tartrate or potassium tartrate.
4. The method for recovering tartaric acid from tartrate according to claim 1, characterized in that In step 1), the mass of the organic solvent is 8 to 12 times the mass of the tartrate.
5. The method for recovering tartaric acid from tartrate according to claim 1, characterized in that In step 2), the alkali used in the neutralization process is one of sodium carbonate and sodium bicarbonate, and the pH of the mother liquor after neutralization is controlled to be 1.5-2.
5.
6. The method for recovering tartaric acid from tartrate according to claim 1, characterized in that: In step 3), the top temperature of the tower is controlled at 70.0-75.0° C. during the distillation process, and the amount of solution in the bottom of the tower is 25%-30% of the total mass of the input.
7. The method for recovering tartaric acid from tartrate according to claim 1, characterized in that: In step 3), the distillate is fractionated to remove water and then the solvent is reused.
8. The method for recovering tartaric acid from tartrate according to claim 7, characterized in that The fraction is dehydrated by adding caustic soda flakes or anhydrous sodium sulfate.
9. The method for recovering tartaric acid from tartrate according to claim 1, characterized in that: In step 4), during the cooling crystallization, the cooling rate is controlled to be 5-10°C / h, and the temperature is gradually lowered to 2-6°C, and the crystal growth time is kept for 1-2 hours, and then tartaric acid is obtained by filtration.