Preparation method of chromium picolinate and mother liquor treatment of chromium picolinate

Abstract

The invention discloses a chromium picolinate preparation method, which comprises: placing 2-picolinic acid, a chromium source and a solvent in a container, and carrying out a complexation reaction at a temperature of 30-100 DEG C to prepare a first solution; keeping the temperature at 30-100 DEG C, adding a reducing agent into the first solution, adding an alkaline regulator, regulating the pH value to 5-7, and stirring and dispersing to obtain a second solution; and pulping the second solution to obtain a solid product and a mother solution, and drying the solid product to obtain chromium picolinate crystal particles. The synthesis is simple, and the product purity, yield and yield are high; the reducing agent is added to treat hexavalent chromium generated in the reaction, so that the content of hexavalent chromium in the product is greatly reduced, and the product is safer and more reliable; the mother liquor can be recycled, no wastewater and sewage treatment station needs to be built, the energy consumption is low, and the method has remarkable cost advantage and economic benefit and is suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a preparation method of chromium picolinate and mother liquor treatment thereof. Background Art

[0002] Chromium picolinate is an important organic chromium compound that has attracted attention for its potential benefits in nutritional supplementation and health, and is therefore widely used as a nutritional supplement and animal feed additive.

[0003] The existing methods for preparing chromium picolinate are quite diverse. From the perspective of raw materials, the main methods are to synthesize chromium picolinate from 2-methylpyridine, 2-vinylpyridine and 2-pyridinecarboxaldehyde. The principle is to first prepare 2-pyridinecarboxylic acid and then react with Cr 3+ The salt complexation reaction obtains chromium picolinate. In this type of reaction, the extension of the reaction chain will inevitably lead to an increase in by-products, resulting in a decrease in yield and greater difficulties in environmental protection treatment. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing chromium picolinate and mother liquor treatment thereof, and the specific technical scheme is as follows:

[0005] A method for preparing chromium picolinate comprises the following steps:

[0006] Step 1: placing 2-picolinic acid, a chromium source and a solvent in a container, and performing a complexation reaction at 30-100° C. to obtain a first solution;

[0007] Step 2: maintaining the temperature at 30-100° C., adding a reducing agent to the first solution, and adding an alkaline regulator, adjusting the pH to 5-7, and stirring and dispersing to obtain a second solution;

[0008] Step 3: The second solution is slurried to obtain a solid product and a mother liquor, and the solid product is dried to obtain chromium picolinate crystal particles.

[0009] Preferably, the chromium source in step 1 is at least one of chromium chloride, chromium sulfate, chromium nitrate, chromium chloride crystalline hydrate, chromium sulfate crystalline hydrate or chromium nitrate crystalline hydrate.

[0010] Preferably:

[0011] The reducing agent in step 2 is at least one of ferrous sulfate, sodium sulfite, sodium bisulfite, and sodium thiosulfate;

[0012] The alkaline regulator in step 2 is at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

[0013] Preferably, the molar ratio of 2-picolinic acid to the chromium source in step 1 is (2.5-3.5):1.

[0014] Preferably, the solvent in step 1 is water, and the ratio of the mass of the solvent to the total mass of the 2-methylpyridine and the chromium source is (1-3):1.

[0015] Preferably:

[0016] The time of the complexation reaction in step 1 is 1 to 4 hours;

[0017] The stirring time in step 2 is 0.5 to 1 h.

[0018] Preferably, the slurrying in step 3 specifically includes: placing the second solution in a crystallization kettle, and obtaining the solid product and mother liquor after cooling, crystallization and centrifugation.

[0019] Preferably, the 2-pyridinecarboxylic acid in step 1 is prepared by hydrolyzing 2-cyanopyridine under alkaline conditions and neutralizing it with an acid, wherein the alkaline conditions are achieved by adding the same alkaline regulator as in step 2, and the acid radical of the acid is the same as the acid radical of the chromium source in step 1.

[0020] The present invention also provides a method for treating a mother liquor for preparing chromium picolinate, comprising the following steps: subjecting the mother liquor obtained by any one of the preparation methods described above to electrodialysis treatment to obtain a crystalline salt and a third solution, and adding the third solution to the container of step 1.

[0021] Preferably, the electrodialysis treatment specifically comprises:

[0022] A cation exchange membrane is arranged in the container so that the container is divided into a first compartment and a second compartment;

[0023] The mother solution is placed in a container, and after a DC electric field is applied on both sides of the container, the crystal particles precipitated in the first compartment or the second compartment are the crystalline salt, and the remaining solution in the container is the third solution.

[0024] The preparation method of chromium picolinate and the mother liquor treatment thereof provided by the present invention have the following beneficial effects:

[0025] (1) The synthesis is simple, and the product purity, output and yield are high.

[0026] (ii) Adding a reducing agent to treat the hexavalent chromium generated in the reaction greatly reduces the hexavalent chromium content in the product, making the product safer and more reliable.

[0027] (III) The mother liquor can be recycled, and there is no need to build wastewater or sewage treatment plants. It has low energy consumption, significant cost advantages and economic benefits, and is suitable for large-scale production. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below. The description in this part is only exemplary and explanatory and should not have any limiting effect on the protection scope of the present invention.

[0029] This embodiment provides a method for preparing chromium picolinate, comprising the following steps:

[0030] Step 1: 2-picolinic acid, a chromium source and a solvent are placed in a container, and a complex reaction occurs at 30-100° C. to prepare a first solution.

[0031] Step 2: maintaining the temperature at 30-100° C., adding a reducing agent into the first solution, and adding an alkaline regulator, adjusting the pH to 5-7, and preparing a second solution after stirring and dispersing.

[0032] Step 3: The second solution is slurried to obtain a solid product and a mother liquor, and the solid product is dried to obtain chromium picolinate crystal particles.

[0033] In the above steps, the reaction chain length for preparing chromium picolinate is reduced, thereby reducing the types of reaction products and further increasing the yield of chromium picolinate.

[0034] Furthermore, in step 1, the chromium source is at least one of chromium chloride, chromium sulfate, chromium nitrate, chromium chloride crystalline hydrate, chromium sulfate crystalline hydrate or chromium nitrate crystalline hydrate.

[0035] Further:

[0036] In step 2, the reducing agent is at least one of ferrous sulfate, sodium sulfite, sodium bisulfite, and sodium thiosulfate.

[0037] In step 2, the alkaline regulator is at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

[0038] Furthermore, in step 1, the molar ratio of 2-pyridinecarboxylic acid to the chromium source is (2.5-3.5):1, so that the chromium source can be completely consumed during the complex reaction between the two to avoid residual chromium ions.

[0039] Furthermore, in step 1, the solvent is water, and the ratio of the mass of the solvent to the total mass of 2-methylpyridine and the chromium source is (1-3):1.

[0040] Further:

[0041] The complexation reaction time in step 1 is 1 to 4 hours.

[0042] The stirring time in step 2 is 0.5 to 1 h.

[0043] Furthermore, the slurrying in step 3 specifically includes: placing the second solution in a crystallization kettle, and obtaining a solid product and a mother liquor after cooling, crystallization and centrifugation.

[0044] Among them, at room temperature or low temperature, the solubility of chromium picolinate in water is extremely low, while the reducing agent and alkaline additives added in the preparation process have a high solubility in water. Therefore, by placing the second solution in a crystallization kettle and cooling it, chromium picolinate can be crystallized and precipitated, and the solid and liquid are separated by centrifugation to obtain a solid product of chromium picolinate.

[0045] Furthermore, in step 1, 2-pyridinecarboxylic acid is prepared by hydrolyzing 2-cyanopyridine under alkaline conditions and neutralizing it with an acid, wherein the alkaline condition is achieved by adding the same alkaline regulator as in step 2, and the acid radical is the same as the acid radical of the chromium source in step 1, thereby avoiding the occurrence of other types of by-products when preparing 2-pyridinecarboxylic acid.

[0046] This embodiment also provides a method for treating a mother liquor for preparing chromium picolinate, comprising the following steps: subjecting the mother liquor obtained by any of the preparation methods described above to electrodialysis treatment to obtain a crystalline salt and a third solution, and adding the third solution to the container of step 1.

[0047] Among them, since the molar amount of 2-pyridinecarboxylic acid is greater than the molar amount of the chromium source during the complex reaction, 2-pyridinecarboxylic acid will remain in the mother liquor after the two are fully reacted. After the mother liquor is electrodialyzed, some impurities in the mother liquor become crystalline salts and precipitate, and 2-pyridinecarboxylic acid can remain in the third solution and circulate to participate in the complex reaction of step 1, thereby avoiding the problem of wastewater discharge in the preparation process.

[0048] Furthermore, the electrodialysis treatment specifically includes:

[0049] A cation exchange membrane is arranged in the container to divide the container into a first compartment and a second compartment.

[0050] The mother solution is placed in a container, and after a DC electric field is applied on both sides of the container, the crystal particles precipitated in the first compartment or the second compartment are crystalline salt, and the remaining solution in the container is the third solution.

[0051] Specific examples are provided below. The provided examples may enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way.

[0052] Example 1

[0053] First, 2-picolinic acid (99.0%, 30g) is dissolved in 103.6g of water, and then chromium chloride hexahydrate (97.5%, 21.8g) is added, and the complex reaction is carried out at 80°C for 3 hours to obtain a dark red first solution; sodium thiosulfate (98%, 2g) is added to the first solution, and sodium hydroxide (96%, 9.5g) is added to adjust the pH to 6.4, and the mixture is kept warm and stirred for 1h to obtain a second solution; the second solution is slurried into a crystallization kettle, cooled, crystallized, and centrifuged. After drying, the filter cake is dried to obtain 32.7g of dark red product chromium picolinate crystal particles with a yield of 98%. The mother liquor is treated with electrodialysis to obtain crystalline salt sodium chloride and a third solution, and the third solution is circulated for the above-mentioned complex reaction.

[0054] Example 2

[0055] First, 2-picolinic acid (99.0%, 30g) is dissolved in 103.6g of the third solution (if the third solution is insufficient, clean water is added to make up), then chromium chloride hexahydrate (97.5%, 21.8g) is added, and the complex reaction is carried out at 50°C for 3.5 hours to obtain a dark red first solution; sodium thiosulfate (98%, 1g) is added to the first solution, and sodium hydroxide flakes (96%, 9.5g) is added to adjust the pH to 6.4, and the mixture is kept warm and stirred for 0.5h to obtain a second solution; the second solution is slurried into a crystallization kettle, cooled, crystallized, and centrifuged. After drying, the filter cake is dried to obtain 32.0g of dark red product chromium picolinate crystal particles with a yield of 96%. The mother liquor is treated with electrodialysis to obtain crystalline salt sodium chloride and the third solution, and the third solution is circulated for the above-mentioned complex reaction.

[0056] Example 3

[0057] First, 2-picolinic acid (99.0%, 30g) is dissolved in 103.6g of the third solution (if the third solution is insufficient, clean water is added to make up), then chromium sulfate hexahydrate (97.5%, 20.5g) is added, and the complex reaction is carried out at 70°C for 3 hours to obtain a dark red first solution; sodium thiosulfate (98%, 1g) is added to the first solution, and sodium hydroxide flakes (96%, 9.5g) is added to adjust the pH to 6.4, and the mixture is kept warm and stirred for 0.5h to obtain a second solution; the second solution is slurried into a crystallization kettle, cooled, crystallized, and centrifuged. After drying, the filter cake is dried to obtain 32.5g of dark red product chromium picolinate crystal particles with a yield of 97.4%. The mother liquor is treated with electrodialysis to obtain crystalline salt sodium sulfate and the third solution, and the third solution is circulated for the above-mentioned complex reaction.

[0058] Example 4

[0059] First, 2-picolinic acid (99.0%, 30g) is dissolved in 103.6g of the third solution (if the third solution is insufficient, clean water is added to make up), then chromium nitrate nonahydrate (99%, 32.2g) is added, and the complex reaction is carried out at 70°C for 3 hours to obtain a dark red first solution; sodium thiosulfate (98%, 1g) is added to the first solution, and sodium hydroxide flakes (96%, 9.5g) is added to adjust the pH to 6.4, and the mixture is kept warm and stirred for 0.5h to obtain a second solution; the second solution is slurried into a crystallization kettle, cooled, crystallized, and centrifuged. After drying, the filter cake is dried to obtain 32.35g of dark red product chromium picolinate crystal particles with a yield of 97%. The mother liquor is treated by electrodialysis to obtain crystalline salt sodium nitrate and the third solution, and the third solution is circulated for the above-mentioned complex reaction.

[0060] Example 5

[0061] First, 2-picolinic acid (99.0%, 30g) is dissolved in 103.6g of the third solution (if the third solution is insufficient, clean water is added to make up), then chromium chloride hexahydrate (97.5%, 21.8g) is added, and the complex reaction is carried out at 95°C for 1 hour to obtain a dark red first solution; sodium thiosulfate (98%, 2g) is added to the first solution, and sodium hydroxide flakes (96%, 9.5g) is added to adjust the pH to 6.4, and the mixture is kept warm and stirred for 0.5h to obtain a second solution; the second solution is slurried to a crystallization kettle, cooled, crystallized, and centrifuged. After drying, the filter cake is dried to obtain 32.65g of dark red product chromium picolinate crystal particles with a yield of 97.9%. The mother liquor is treated with electrodialysis to obtain crystalline salt sodium chloride and the third solution, and the third solution is circulated for the above-mentioned complex reaction.

[0062] Comparative Example (without reducing agent)

[0063] First, 2-picolinic acid (99.0%, 30g) is dissolved in 103.6g of the third solution (if the third solution is insufficient, clean water is added to make up), then chromium chloride hexahydrate (97.5%, 21.8g) is added, and the complex reaction is carried out at 80°C for 3 hours to obtain a dark red first solution; sodium hydroxide flakes (96%, 9.5g) is added to the first solution to adjust the pH to 6.4, and the solution is kept warm and stirred for 1h to obtain a second solution; the second solution is slurried into a crystallization kettle, cooled, crystallized, and centrifuged. After drying, the filter cake is dried to obtain 32.88g of dark red product chromium picolinate crystal particles with a yield of 98.6%. The mother liquor is treated with electrodialysis to obtain crystalline salt sodium chloride and the third solution, and the third solution is circulated for the above-mentioned complex reaction.

[0064] The test data of Examples 1 to 5 and the comparative example are shown in Table 1 below. Wherein, yield = actual yield / theoretical yield*100%.

[0065] Table 1 Test data of embodiments and comparative examples

[0066]

[0067]

[0068] Note: The content of chromium picolinate and chromium (III) shall be determined according to NY / T 916-2004.

[0069] As can be seen from Table 1, the yields of Examples 1 to 5 all reached more than 95%, the content of chromium picolinate reached more than 98.5%, and the hexavalent chromium was less than 5ppm; and the hexavalent chromium content of the comparative example was 23.8ppm because no reducing agent was added, which was significantly higher than that of the example. It is once again illustrated that the technical solution provided by the present invention is used to synthesize chromium picolinate, which has the characteristics of high product purity, output, and yield, low hexavalent chromium content, safer and more reliable products, and good process stability. From the mother liquor circulation of Examples 2 to 5 and the comparative example, the test results of the synthetic product all performed well, indicating that the effect of treating the mother liquor by electrodialysis is significant, and there is no need to build a wastewater or sewage treatment station for special treatment, which is both economical and environmentally friendly.

[0070] Implementation principle:

[0071] Since the molar amount of 2-pyridinecarboxylic acid is greater than the molar amount of the chromium source during the complex reaction, 2-pyridinecarboxylic acid will remain in the mother liquor after the two are fully reacted. After the mother liquor is electrodialyzed, some impurities in the mother liquor become crystalline salts and precipitate, and 2-pyridinecarboxylic acid can remain in the third solution and circulate to participate in the complex reaction of step 1, thereby avoiding the problem of wastewater discharge in the preparation process.

[0072] The principles and implementation methods of the present invention are described herein using specific examples, and the description of the above embodiments is only used to help understand the method and core ideas of the present invention. The above are only preferred implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention, which should be within the protection scope of the present invention.

Claims

1. A method for preparing chromium picolinate, characterized in that: The steps include: S1: placing 2-picolinic acid, a chromium source and a solvent in a container, and performing a complex reaction at 30-100° C. to obtain a first solution; S2: maintaining the temperature at 30-100° C., adding a reducing agent to the first solution, and adding an alkaline regulator, adjusting the pH to 5-7, and stirring and dispersing to obtain a second solution; S3: The second solution is slurried to obtain a solid product and a mother liquor, and the solid product is dried to obtain chromium picolinate crystal particles.

2. The preparation method according to claim 1, characterized in that: The chromium source in step S1 is at least one of chromium chloride, chromium sulfate, chromium nitrate, chromium chloride crystalline hydrate, chromium sulfate crystalline hydrate or chromium nitrate crystalline hydrate.

3. The preparation method according to claim 1, characterized in that: The reducing agent in step S2 is at least one of ferrous sulfate, sodium sulfite, sodium bisulfite, and sodium thiosulfate; The alkaline regulator in step S2 is at least one of sodium hydroxide, potassium hydroxide, sodium bicarbonate and potassium bicarbonate.

4. The preparation method according to claim 1, characterized in that: The molar ratio of 2-picolinic acid to the chromium source in step S1 is (2.5-3.5):

1.

5. The preparation method according to claim 1, characterized in that: In step S1, the solvent is water, and the ratio of the mass of the solvent to the total mass of the 2-methylpyridine and the chromium source is (1-3):

1.

6. The preparation method according to claim 1, characterized in that: The time of the complexation reaction in step S1 is 1 to 4 hours; The stirring time in step S2 is 0.5 to 1 h.

7. The preparation method according to claim 5, characterized in that: The slurrying in step S3 specifically includes: placing the second solution in a crystallization kettle, and obtaining the solid product and mother liquor after cooling, crystallization and centrifugation.

8. The preparation method according to claim 1, characterized in that: The 2-pyridinecarboxylic acid in step S1 is prepared by hydrolyzing 2-cyanopyridine under alkaline conditions and neutralizing it with an acid, wherein the alkaline conditions are achieved by adding the same alkaline regulator as in step S2, and the acid radical of the acid is the same as the acid radical of the chromium source in step S1.

9. A method for treating a mother liquor for preparing chromium picolinate, characterized in that: The method comprises the following steps: subjecting the mother solution obtained by the preparation method according to any one of claims 1 to 8 to electrodialysis treatment to obtain crystalline salt and a third solution, and adding the third solution into the container of step S1.

10. The method for preparing mother liquor of chromium picolinate according to claim 9, characterized in that: The electrodialysis treatment specifically comprises: A cation exchange membrane is arranged in the container so that the container is divided into a first compartment and a second compartment; The mother solution is placed in a container, and after a DC electric field is applied on both sides of the container, the crystal particles precipitated in the first compartment or the second compartment are the crystalline salt, and the remaining solution in the container is the third solution.

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