Production process of nicotinamide used as cosmetic raw material
By alternately adding 3-cyanopyridine and sodium hydroxide in the nicotinamide production process, combined with microfiltration, ultrafiltration, decolorization and crystallization steps, the problems of high niacin content and high catalyst cost are solved, and nicotinamide products with high purity and high yield are achieved.
Patent Information
- Application Number
- CN202411906184.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-04-11
AI Technical Summary
In the existing nicotinamide production process, the niacin content is relatively high, which affects the purity and safety of the product. The catalyst costs are high, the catalytic activity is low, and the yield is low.
By alternately adding 3-cyanopyridine and sodium hydroxide during the hydrolysis and synthesis process, the reaction conditions and dropwise addition ratio are controlled, the production of niacin is reduced and the yield of niacinamide is improved. Further, through microfiltration, ultrafiltration, decolorization and crystallization, impurities and niacin are removed to improve product purity.
It effectively reduces the niacin content in niacinamide products, improves the purity and yield of niacinamide, and ensures the safety and quality of the product.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of pharmaceutical chemistry, and in particular relates to a production process of niacinamide used as a raw material for cosmetics. Background Art
[0002] Nicotinamide is a component of coenzyme I and coenzyme II, and is a coenzyme for many dehydrogenases. When it is deficient, it can affect the normal respiration and metabolism of cells and cause pellagra. Due to its antioxidant properties, it can slow down or block the formation of melanin, or act on cells that produce melanin, and can be used as an additive for whitening cosmetics.
[0003] The traditional synthesis methods of nicotinamide include chemical method and biological method. There are two main chemical methods. The first one is to use 3-methylpyridine as raw material, which is divided into two steps. The first step is to synthesize nicotinic acid from 3-methylpyridine, and β-methylpyridine is oxidized to nicotinic acid by air. The second step is to synthesize nicotinamide from nicotinic acid. Nicotinic acid reacts with ammonium hydroxide and then heats and dehydrates to obtain nicotinamide. This method is relatively complicated. The second one is to use 3-cyanopyridine as raw material. This method includes two methods. One is an oxidation method, using an insoluble catalyst (such as manganese dioxide) as a catalyst, and catalyzing a hydration reaction in a neutral medium, thereby avoiding the complex separation steps caused by the use of acid or alkaline catalysts, and excluding the generation of nicotinic acid. However, existing catalysts generally have the problems of low catalytic activity and low nicotinamide yield, and the use of catalysts is relatively expensive. The other is the hydrolysis method, in which 3-cyanopyridine is hydrolyzed under alkaline conditions to produce nicotinamide. Although this method does not require the use of expensive catalysts, it still has some problems, such as the generation of by-product nicotinic acid and difficulty in product separation, resulting in low yield. Nicotinic acid is often produced as a by-product during the production process of nicotinamide, which will affect the quality of nicotinamide and cause quality inspection indicators such as nicotinamide product content, pH value, and melting point to fail to meet the standards.
[0004] There are strict requirements on the niacin content in niacinamide for cosmetics. Niacin in cosmetics can cause certain irritation to the skin, causing flushing reactions on the skin, as well as comprehensive symptoms such as redness, swelling, and pain. Therefore, it is necessary to set limit requirements on the niacin content in the product. The niacin content in cosmetic-grade niacinamide should usually be less than 100ppm to ensure the safety of the product and reduce the risk of skin irritation. Summary of the invention
[0005] The purpose of the present invention is to provide a production process of niacinamide used as a raw material for cosmetics, reduce the niacin content in the niacinamide product, and improve the purity of the niacinamide product.
[0006] The purpose of the present invention can be achieved through the following technical solutions:
[0007] The present invention provides a production process of niacinamide used as a cosmetic raw material, comprising the following steps:
[0008] Step 1, dissolving 3-cyanopyridine in water to prepare a 3-cyanopyridine aqueous solution, and dissolving sodium hydroxide in water to prepare a sodium hydroxide solution;
[0009] Step 2: Place 3-cyanopyridine aqueous solution in a reaction vessel, heat to 70-90° C., and add sodium hydroxide solution dropwise under constant temperature stirring, wherein the molar ratio of 3-cyanopyridine to sodium hydroxide is 5-6:1;
[0010] Step 3: After the sodium hydroxide solution is added dropwise, a 3-cyanopyridine aqueous solution is added dropwise to the reaction solution until the total molar ratio of 3-cyanopyridine and sodium hydroxide added in step 2 and step 3 is 9-10:1;
[0011] Step 4: After the addition of the 3-cyanopyridine aqueous solution is completed, a sodium hydroxide solution is added dropwise until the total molar ratio of 3-cyanopyridine and sodium hydroxide added in steps 2, 3 and 4 is 7-8:1. After the addition is completed, the reaction is continued under constant temperature stirring for 5-6 hours. After the reaction is completed, a crude nicotinamide solution is obtained;
[0012] Step 5, the crude nicotinamide solution is subjected to microfiltration and ultrafiltration to remove impurities, and activated carbon is added to the clear solution after ultrafiltration for decolorization. The decolorized solution is evaporated and concentrated to obtain a concentrated solution, the concentrated solution is placed in a crystallization kettle for cooling and crystallization, and centrifuged to obtain a nicotinamide wet product, and the wet product is placed in a vacuum drying oven for drying to obtain a nicotinamide product, wherein the nicotinic acid content in the nicotinamide product is <20ppm.
[0013] Furthermore, the concentration of the 3-cyanopyridine aqueous solution is 1.0-1.2 mol / L.
[0014] Furthermore, the concentration of the sodium hydroxide solution is 0.1-0.2 mol / L.
[0015] Furthermore, in step 2, the dropwise addition of the sodium hydroxide solution needs to be completed within 1.5-2.0 hours.
[0016] Furthermore, in step 3, the addition of the 3-cyanopyridine aqueous solution to the reaction solution needs to be completed within 0.5-1.0 h.
[0017] Furthermore, in step 4, the addition of the sodium hydroxide solution needs to be completed within 0.5-1.0 h.
[0018] Furthermore, the nicotinic acid content in the crude nicotinamide solution is less than 40 ppm.
[0019] Furthermore, the microfiltration uses a ceramic membrane with a pore size of 10 nm;
[0020] The ultrafiltration uses a ceramic membrane with a molecular weight cut-off of 1000D.
[0021] Furthermore, the amount of activated carbon added is 1-2% of the volume of the clear liquid after ultrafiltration.
[0022] Furthermore, the temperature of the evaporation concentration is 60-70°C.
[0023] Furthermore, the temperature of the cooling crystallization is 20-25°C, and the crystallization time is 4-5h.
[0024] Beneficial effects of the present invention:
[0025] (1) The present invention alternately adds 3-cyanopyridine and sodium hydroxide during the hydrolysis synthesis process. On the one hand, it can avoid the phenomenon that 3-cyanopyridine is gradually converted into nicotinamide as the reaction proceeds during the initial reaction, and nicotinamide is converted into nicotinic acid due to excessive sodium hydroxide in the reaction solution, thereby reducing the nicotinic acid content produced by the reaction. On the other hand, after 3-cyanopyridine is added dropwise during the reaction, the amount of 3-cyanopyridine in the reaction solution increases, which may result in the amount of 3-cyanopyridine remaining after the reaction is not completely reacted. Adding a small amount of sodium hydroxide again can promote the forward reaction of 3-cyanopyridine to generate nicotinamide, thereby avoiding the residual 3-cyanopyridine and improving the yield of nicotinamide.
[0026] (2) In the reaction stage, the crude nicotinamide solution prepared by the present invention controls the nicotinic acid content to be below 40 ppm. After purification by membrane-decolorization-concentration-crystallization and other methods, nicotinic acid and other impurities in the nicotinamide product are removed. In the crystallization stage, the solubility of nicotinamide aqueous solution at different temperatures is different. Since the solubility of nicotinic acid in water is greater than 400 ppm, it will be separated with the filtrate. The remaining crystalline nicotinic acid content can be well controlled, thereby obtaining high-purity nicotinamide, whose nicotinic acid content is below 20 ppm. DETAILED DESCRIPTION
[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0028] Example 1
[0029] Step 1, dissolving 3-cyanopyridine in water to prepare a 1.0 mol / L 3-cyanopyridine aqueous solution, and dissolving sodium hydroxide in water to prepare a 0.1 mol / L sodium hydroxide solution;
[0030] Step 2: Place 3-cyanopyridine aqueous solution in a reaction vessel, heat to 85°C, and add sodium hydroxide solution dropwise under constant temperature stirring. The addition is completed over 1.5 hours, and the molar ratio of 3-cyanopyridine to sodium hydroxide is 5:1;
[0031] Step 3: After the sodium hydroxide solution is added dropwise, 3-cyanopyridine aqueous solution is added dropwise to the reaction solution. The addition takes 0.5 h. The total molar ratio of 3-cyanopyridine to sodium hydroxide added in step 2 and step 3 is 10:1.
[0032] Step 4: After the 3-cyanopyridine aqueous solution is added dropwise, a sodium hydroxide solution is added dropwise, and the addition is completed within 0.5 h. The total molar ratio of 3-cyanopyridine and sodium hydroxide added in steps 2, 3 and 4 is 8:1. After the addition is completed, the reaction is continued under constant temperature stirring for 6 h. After the reaction is completed, a crude nicotinamide solution is obtained.
[0033] Step 5: The crude nicotinamide solution is subjected to microfiltration (ceramic membrane with a pore size of 10 nm) and ultrafiltration (ceramic membrane with a molecular weight cutoff of 1000D) to remove impurities, and activated carbon is added to the ultrafiltration clear liquid for decolorization. The amount of activated carbon added is 1.5% of the volume of the ultrafiltration clear liquid. The decolorized liquid is evaporated and concentrated to obtain a concentrated solution. The evaporation and concentration temperature is set to 65°C. The concentrated solution is placed in a crystallization kettle for cooling and crystallization. The cooling and crystallization temperature is set to 25°C, and the crystallization time is 4h. After crystallization, centrifugation is performed to obtain a wet nicotinamide product, and the wet product is placed in a vacuum drying oven at 80°C for 4h and dried to obtain a nicotinamide product.
[0034] In this example, the crude nicotinamide solution was tested, and no 3-cyanopyridine was detected therein. The mass content of nicotinamide was 37.6%, the content of nicotinic acid was 20 ppm, and the yield of nicotinamide was 99.99%.
[0035] The specific test parameters of the crude nicotinamide solution after microfiltration are shown in Table 1.
[0036] Table 1
[0037]
[0038] The specific test parameters of the microfiltration clear fluid after microfiltration treatment are shown in Table 2.
[0039] Table 2
[0040]
[0041] The specific test parameters of the ultrafiltration clear liquid after activated carbon decolorization are shown in Table 3.
[0042] Table 3
[0043]
[0044] The specific detection parameters of the decolorized solution after evaporation and concentration are shown in Table 4.
[0045] Table 4
[0046]
[0047] The specific test parameters of the concentrated liquid after evaporation concentration treatment, cooling crystallization and centrifugal drying treatment are shown in Table 5.
[0048] Table 5
[0049]
[0050] The purity of niacinamide product reaches 99.7% and the niacin content is 11ppm.
[0051] Example 2
[0052] The only difference from Example 1 is that the molar ratio of 3-cyanopyridine and sodium hydroxide after dropwise addition in step 2, step 3 and step 4 is adjusted. The specific steps are as follows:
[0053] Step 1, dissolving 3-cyanopyridine in water to prepare a 1.0 mol / L 3-cyanopyridine aqueous solution, and dissolving sodium hydroxide in water to prepare a 0.1 mol / L sodium hydroxide solution;
[0054] Step 2: Place 3-cyanopyridine aqueous solution in a reaction vessel, heat to 85°C, and add sodium hydroxide solution dropwise under constant temperature stirring. The addition is completed over 1.5 hours, and the molar ratio of 3-cyanopyridine to sodium hydroxide is 5.5:1;
[0055] Step 3: After the sodium hydroxide solution is added dropwise, 3-cyanopyridine aqueous solution is added dropwise to the reaction solution. The addition is completed over 0.5 h. The molar ratio of the total added 3-cyanopyridine to sodium hydroxide in step 2 and step 3 is 9.5:1.
[0056] Step 4: After the 3-cyanopyridine aqueous solution is added dropwise, a sodium hydroxide solution is added dropwise, and the addition is completed within 0.5 h. The total molar ratio of 3-cyanopyridine and sodium hydroxide added in steps 2, 3 and 4 is 7.5:1. After the addition is completed, the reaction is continued under constant temperature stirring for 6 h. After the reaction is completed, a crude nicotinamide solution is obtained.
[0057] Step 5: The crude nicotinamide solution is subjected to microfiltration (ceramic membrane with a pore size of 10 nm) and ultrafiltration (ceramic membrane with a molecular weight cutoff of 1000D) to remove impurities, and activated carbon is added to the ultrafiltration clear liquid for decolorization. The amount of activated carbon added is 2% of the volume of the ultrafiltration clear liquid. The decolorized liquid is evaporated and concentrated to obtain a concentrated solution. The evaporation and concentration temperature is set to 65°C. The concentrated solution is placed in a crystallization kettle for cooling and crystallization. The cooling and crystallization temperature is set to 25°C, and the crystallization time is 4h. After crystallization, centrifugation is performed to obtain a wet nicotinamide product, and the wet product is placed in a vacuum drying oven at 80°C for 4h and dried to obtain a nicotinamide product.
[0058] In this example, the crude nicotinamide solution was tested, and no 3-cyanopyridine was detected therein. The mass content of nicotinamide was 36.9%, the content of nicotinic acid was 15 ppm, and the yield of nicotinamide was 99.95%.
[0059] The specific test parameters of the crude nicotinamide solution after microfiltration are shown in Table 6.
[0060] Table 6
[0061]
[0062] The specific test parameters of the microfiltration clear fluid after microfiltration treatment are shown in Table 7.
[0063] Table 7
[0064]
[0065] The specific test parameters of the ultrafiltration clear liquid after activated carbon decolorization are shown in Table 8.
[0066] Table 8
[0067]
[0068] The specific detection parameters of the decolorized liquid after evaporation and concentration are shown in Table 9.
[0069] Table 9
[0070]
[0071] The specific test parameters of the concentrated liquid after evaporation concentration treatment, cooling crystallization and centrifugal drying are shown in Table 10.
[0072] Table 10
[0073]
[0074] The purity of niacinamide product reaches 99.6% and the niacin content is 9ppm.
[0075] Example 3
[0076] The only difference from Example 1 is that the molar ratio of 3-cyanopyridine and sodium hydroxide after dropwise addition in step 2, step 3 and step 4 is adjusted. The specific steps are as follows:
[0077] Step 1, dissolving 3-cyanopyridine in water to prepare a 1.0 mol / L 3-cyanopyridine aqueous solution, and dissolving sodium hydroxide in water to prepare a 0.1 mol / L sodium hydroxide solution;
[0078] Step 2: Place 3-cyanopyridine aqueous solution in a reaction vessel, heat to 85°C, and add sodium hydroxide solution dropwise under constant temperature stirring. The addition is completed over 1.5 hours, and the molar ratio of 3-cyanopyridine to sodium hydroxide is 6:1;
[0079] Step 3: After the sodium hydroxide solution is added dropwise, 3-cyanopyridine aqueous solution is added dropwise to the reaction solution. The addition is completed over 0.5 h. The total molar ratio of 3-cyanopyridine and sodium hydroxide added in step 2 and step 3 is 9:1.
[0080] Step 4: After the 3-cyanopyridine aqueous solution is added dropwise, a sodium hydroxide solution is added dropwise, and the addition is completed within 0.5 h. The total molar ratio of 3-cyanopyridine and sodium hydroxide added in steps 2, 3 and 4 is 7:1. After the addition is completed, the reaction is continued under constant temperature stirring for 6 h. After the reaction is completed, a crude nicotinamide solution is obtained.
[0081] Step 5: The crude nicotinamide solution is subjected to microfiltration (ceramic membrane with a pore size of 10 nm) and ultrafiltration (ceramic membrane with a molecular weight cutoff of 1000D) to remove impurities, and activated carbon is added to the ultrafiltration clear liquid for decolorization. The amount of activated carbon added is 1% of the volume of the ultrafiltration clear liquid. The decolorized liquid is evaporated and concentrated to obtain a concentrated solution. The evaporation and concentration temperature is set to 65°C. The concentrated solution is placed in a crystallization kettle for cooling and crystallization. The cooling and crystallization temperature is set to 25°C, and the crystallization time is 4h. After crystallization, centrifugation is performed to obtain a wet nicotinamide product, and the wet product is placed in a vacuum drying oven at 80°C for 4h, and dried to obtain a nicotinamide product.
[0082] In this example, the crude nicotinamide solution was tested, and no 3-cyanopyridine was detected therein. The mass content of nicotinamide was 34.5, the content of nicotinic acid was 34 ppm, and the yield of nicotinamide was 99.90%.
[0083] The specific test parameters of the crude nicotinamide solution after microfiltration are shown in Table 11.
[0084] Table 11
[0085]
[0086] The specific test parameters of the microfiltration clear fluid after microfiltration treatment are shown in Table 12.
[0087] Table 12
[0088]
[0089] The specific test parameters of the ultrafiltration clear liquid after activated carbon decolorization are shown in Table 13.
[0090] Table 13
[0091]
[0092] The specific detection parameters of the decolorized liquid after evaporation and concentration treatment are shown in Table 14.
[0093] Table 14
[0094]
[0095] The specific test parameters of the concentrated liquid after evaporation concentration treatment, cooling crystallization and centrifugal drying treatment are shown in Table 15.
[0096] Table 15
[0097]
[0098] The purity of niacinamide product reaches 99.7% and the niacin content is 11ppm.
[0099] Comparative Example 1
[0100] Compared with Example 1, the nicotinamide production process of this comparative example does not alternately add 3-cyanopyridine and sodium hydroxide. The specific steps are as follows:
[0101] Step 1, dissolving 3-cyanopyridine in water to prepare a 1.0 mol / L 3-cyanopyridine aqueous solution, and dissolving sodium hydroxide in water to prepare a 0.1 mol / L sodium hydroxide solution;
[0102] Step 2: Place 3-cyanopyridine aqueous solution in a reaction vessel, heat to 85°C, and add sodium hydroxide solution dropwise under constant temperature stirring. The addition is completed over 1.5 hours, and the molar ratio of 3-cyanopyridine to sodium hydroxide is 8:1;
[0103] Step 3: After the addition is completed, continue to stir and react at a constant temperature for 7 hours, and after the reaction is completed, a crude nicotinamide solution is obtained;
[0104] Step 4: The crude nicotinamide solution is subjected to microfiltration (ceramic membrane with a pore size of 10 nm) and ultrafiltration (ceramic membrane with a molecular weight cutoff of 1000D) to remove impurities, and activated carbon is added to the ultrafiltration clear liquid for decolorization. The amount of activated carbon added is 1.5% of the volume of the ultrafiltration clear liquid. The decolorized liquid is evaporated and concentrated to obtain a concentrated solution. The evaporation and concentration temperature is set to 65°C. The concentrated solution is placed in a crystallization kettle for cooling and crystallization. The cooling and crystallization temperature is set to 25°C, and the crystallization time is 4h. After crystallization, centrifugation is performed to obtain a wet nicotinamide product, and the wet product is placed in a vacuum drying oven at 80°C for 4h, and dried to obtain a nicotinamide product.
[0105] In this example, the crude nicotinamide solution was tested, and the mass content of 3-cyanopyridine was 1.07%, the mass content of nicotinamide was 33.4%, the content of nicotinic acid was 52 ppm, and the yield of nicotinamide was 96.75%.
[0106] The specific test parameters of the crude nicotinamide solution after microfiltration treatment are shown in Table 16.
[0107] Table 16
[0108]
[0109] The specific test parameters of the microfiltration clear fluid after microfiltration treatment are shown in Table 17.
[0110] Table 17
[0111]
[0112] The specific test parameters of the ultrafiltration clear liquid after activated carbon decolorization are shown in Table 18.
[0113] Table 18
[0114]
[0115] The specific detection parameters of the decolorized liquid after evaporation and concentration treatment are shown in Table 19.
[0116] Table 19
[0117]
[0118] The specific test parameters of the concentrated liquid after evaporation concentration treatment, cooling crystallization and centrifugal drying treatment are shown in Table 20.
[0119] Table 20
[0120]
[0121]
[0122] The purity of niacinamide product reaches 96.4%, and the niacin content is 23ppm.
[0123] It can be seen from the test results of Examples 1 to 3 and Comparative Example 1 that in Examples 1 to 3, the molar ratio of 3-cyanopyridine to sodium hydroxide in the process of alternately dropping 3-cyanopyridine and sodium hydroxide is adjusted to control the generation of nicotinic acid and the conversion of 3-cyanopyridine during the reaction. Under the conditions of Example 2, the nicotinic acid content in the crude nicotinamide solution is the lowest. Based on Comparative Example 1, it can be seen that when the alternate dropwise addition of raw materials is not performed, the nicotinic acid content in the product is high, resulting in a lower purity in the final nicotinamide product. The purity of the nicotinamide product in the examples can reach more than 99%, while the purity in the comparative example is much lower than 99%.
[0124] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.
[0125] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A process for producing niacinamide as a cosmetic raw material, characterized in that: The following steps are involved: Step 1, dissolving 3-cyanopyridine in water to prepare a 3-cyanopyridine aqueous solution, and dissolving sodium hydroxide in water to prepare a sodium hydroxide solution; Step 2: Place 3-cyanopyridine aqueous solution in a reaction vessel, heat to 70-90° C., and add sodium hydroxide solution dropwise under constant temperature stirring, wherein the molar ratio of 3-cyanopyridine to sodium hydroxide is 5-6:1; Step 3: After the sodium hydroxide solution is added dropwise, a 3-cyanopyridine aqueous solution is added dropwise to the reaction solution until the total molar ratio of 3-cyanopyridine and sodium hydroxide added in step 2 and step 3 is 9-10:1; Step 4: After the addition of the 3-cyanopyridine aqueous solution is completed, a sodium hydroxide solution is added dropwise until the total molar ratio of 3-cyanopyridine and sodium hydroxide added in steps 2, 3 and 4 is 7-8:
1. After the addition is completed, the reaction is continued under constant temperature stirring for 5-6 hours. After the reaction is completed, a crude nicotinamide solution is obtained; Step 5, the crude nicotinamide solution is subjected to microfiltration and ultrafiltration to remove impurities, and activated carbon is added to the clear solution after ultrafiltration for decolorization. The decolorized solution is evaporated and concentrated to obtain a concentrated solution, the concentrated solution is placed in a crystallization kettle for cooling and crystallization, and centrifuged to obtain a nicotinamide wet product, and the wet product is placed in a vacuum drying oven for drying to obtain a nicotinamide product, wherein the nicotinic acid content in the nicotinamide product is <20ppm.
2. A process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: The concentration of the 3-cyanopyridine aqueous solution is 1.0-1.2 mol / L; The concentration of the sodium hydroxide solution is 0.1-0.2 mol / L.
3. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: In step 2, the sodium hydroxide solution is added dropwise and the addition should be completed within 1.5-2.0 hours.
4. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: In step 3, the 3-cyanopyridine aqueous solution is added dropwise to the reaction solution and the addition is completed within 0.5-1.0 h.
5. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: In step 4, the addition of sodium hydroxide solution needs to be completed within 0.5-1.0 h.
6. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: The nicotinic acid content in the crude nicotinamide solution is ≤40ppm.
7. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: The microfiltration uses a ceramic membrane with a pore size of 10 nm; The ultrafiltration uses a ceramic membrane with a molecular weight cut-off of 1000D.
8. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: The amount of activated carbon added is 1-2% of the volume of the ultrafiltration clear liquid.
9. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: The temperature of the evaporation concentration is 60-70°C.
10. The process for producing niacinamide as a cosmetic raw material according to claim 1, characterized in that: The temperature of the cooling crystallization is 20-25°C, and the crystallization time is 4-5h.