Preparation method of high-purity nicotinamide

Abstract

The invention provides a preparation method of high-purity nicotinamide. The method comprises the following steps: mixing feed liquid containing nicotinamide and nicotinic acid with alkali to obtain mixed liquid; wherein the alkali comprises one or more of alkali metal hydroxide, alkali metal carbonate and alkali metal bicarbonate; and concentrating and crystallizing the mixed solution to obtain the high-purity nicotinamide. The method provided by the invention can reduce the content of nicotinic acid in nicotinamide and improve the purity of nicotinamide.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for preparing high-purity nicotinamide. Background Art

[0002] Nicotinamide and niacin are collectively referred to as vitamin PP. Nicotinic acid is converted into niacinamide in the human body, which is the precursor of coenzyme I (nicotinamide adenine dinucleotide, NAD) and coenzyme II (nicotinamide adenine dinucleotide phosphate, NADP). Nicotinamide can penetrate into human skin. After topical application of niacinamide, the level of coenzyme I in skin cells increases, which is evidence of percutaneous absorption. As a precursor of the coenzyme NADP family, niacinamide plays a significant role in improving skin, which is manifested in the following 6 aspects (Bissett DL, Oblong JE, Saud A, et al. Topical niacinamide provides skin aging appearance benefits while enhancing barrier function[J]. J Clin Dermatol 2003,32S:9–18): (1) Antioxidant capacity; (2) Epidermal barrier function. After topical application of niacinamide, the epidermal barrier function is improved along with the improvement of keratin differentiation. At the same time, the improvement of barrier function is also reflected in reducing epidermal water loss and increasing the water content of the stratum corneum, that is, improving the moisturizing ability; (3) Improving erythema and pigmentation; (4) Inhibiting skin yellowing. The role of topical niacinamide is to inhibit oxidation processes, such as protein oxidation, glycosylation and Maillard reaction (the increase in collagen oxidation products in human skin increases 5 times from 20 to 80 years old), thereby inhibiting skin yellowing; (5) Fine lines and wrinkles. Niacinamide increases the levels of epidermal proteins keratin, filaggrin and involucrin, and increases the production of dermal matrix collagen; (6) Pigmentation: Topical niacinamide can effectively reduce epidermal pigmentation and reduce pigmentation spots.

[0003] Nicotinic acid interacts with receptors in the skin and has a better drug conditioning effect on the skin than nicotinamide. However, nicotinic acid receptors are G-protein coupled receptors, and stimulation leads to peripheral vasodilation, resulting in a flushing reaction of the skin. Most users strongly reject this. In order to reduce the irritation of nicotinic acid as much as possible, the content of nicotinic acid in nicotinamide used in cosmetics must be low enough. However, the concentration of nicotinic acid in commercially available nicotinamide is usually relatively high, for example, the nicotinic acid content is around 6000-8000ppm. Therefore, how to reduce the nicotinic acid in nicotinamide becomes particularly important. In U.S. Patent No. 3,678,060, nicotinic acid is removed by a resin method, but the process is complicated and uneconomical.

[0004] Therefore, there is still a need for a method for effectively removing nicotinic acid from nicotinamide to improve the purity of nicotinamide. Summary of the invention

[0005] In order to solve one of the above technical problems existing in the prior art, the present invention provides a method for preparing high-purity nicotinamide. The present application has found through research that at 25°C, the solubility of nicotinamide in water and methanol is more than 30%, but the solubility in anhydrous ethanol and ethyl acetate is only 2%, and the solubility of nicotinic acid in water is about 1%. The present application has also found that the salt formed by nicotinic acid and ammonia water is not stable, and will decompose into nicotinic acid and ammonia when the temperature exceeds 35°C, but the salt formed with alkali metals (such as sodium nicotinate) is very stable. The solubility of sodium nicotinate in water is more than 30%, so when crystallizing, 15-20% of the water is retained in the concentrate to form sodium nicotinate and finally remain in the mother liquor, so that nicotinamide with low nicotinic acid content can be obtained, thereby improving the purity of nicotinamide. In addition, the present invention has also found that the use of a lower concentration of sodium hydroxide can further prevent the hydrolysis of nicotinamide.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a method for preparing high-purity nicotinamide, which comprises the following steps:

[0008] Mixing a feed liquid containing nicotinamide and nicotinic acid with a base to obtain a mixed liquid; wherein the base comprises one or more of an alkali metal hydroxide, an alkali metal carbonate, and an alkali metal bicarbonate;

[0009] The mixed solution is concentrated and crystallized to obtain high-purity nicotinamide.

[0010] In the present invention, the alkali metal includes but is not limited to: lithium, sodium, potassium, etc. In some embodiments, the alkali includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. In some embodiments, the alkali includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. In some embodiments, the alkali includes sodium hydroxide.

[0011] The alkali in the present invention can be an aqueous solution of alkali, and the mass concentration of the alkali solution is preferably 1-10%, such as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value therebetween, more preferably 3-8%.

[0012] According to some embodiments of the present invention, the amount of the base is such that the pH value of the mixed solution is 6.8-7.5.

[0013] According to some embodiments of the present invention, in the liquid containing niacinamide and niacin, the mass content of niacinamide is 50-60%, and the mass content of niacin is 5000-8000 ppm.

[0014] According to some embodiments of the present invention, the concentration comprises: concentrating the mixed solution to a nicotinamide content of 75%-90%, for example, 75%, 78%, 80%, 82%, 85%, 88%, 90% or any value therebetween, preferably 80%-88%, more preferably 82%-88%.

[0015] According to some embodiments of the present invention, the crystallization comprises mixing the concentrated solution obtained after concentration with a low-carbon alcohol, and then cooling and crystallizing. In the present invention, the low-carbon alcohol includes but is not limited to: methanol. In some embodiments, the amount of the low-carbon alcohol is 3-5 times the mass of nicotinamide in the concentrated solution. In some embodiments, the crystallization is carried out by cooling to 10-30°C.

[0016] According to some embodiments of the present invention, the feed solution containing nicotinamide and nicotinic acid includes a reaction solution obtained by reacting 3-cyanopyridine under the catalysis of cyanohydratase.

[0017] According to some embodiments of the present invention, when the feed liquid containing nicotinamide and nicotinic acid is a reaction liquid obtained by reacting 3-cyanopyridine under the catalysis of cyanohydratase, the method further comprises: before concentrating the mixed liquid, heating the mixed liquid and filtering and decolorizing it. In some embodiments, the heating temperature is 80-90°C. In some embodiments, the filtration comprises membrane filtration, preferably using a ceramic membrane with a pore size of 100nm-200nm for filtration. In some embodiments, the decolorization treatment comprises decolorization treatment using activated carbon. In some embodiments, the temperature of the decolorization treatment is 60-70°C.

[0018] According to some embodiments of the present invention, the method further comprises: drying the crystals after crystallization to obtain a nicotinamide product; preferably, the drying is performed under vacuum conditions.

[0019] According to some embodiments of the present invention, the method comprises the following steps:

[0020] (S1) adjusting the pH of the liquid containing nicotinamide and nicotinic acid to 6.8-7.5 using a sodium hydroxide solution having a mass concentration of 1-10%, preferably 3-8%, to obtain a mixed solution;

[0021] (S2) heating the mixed solution to 80-90° C. and filtering the mixed solution using a ceramic membrane having a pore size of 100 nm-200 nm to obtain a filtrate;

[0022] (S3) The filtrate is decolorized with activated carbon and then concentrated in vacuum to a nicotinamide content of 75%-90%, preferably 80%-88%, and methanol is added and then cooled to crystallize to obtain a wet nicotinamide product. The wet nicotinamide product is vacuum dried to obtain high-purity nicotinamide.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The method of the present invention adds alkaline substances such as alkali metal hydroxides or weak acid salts into a feed liquid containing nicotinamide and nicotinic acid, so that the nicotinic acid in the nicotinamide is in the form of nicotinic acid alkali metal salt, which has high solubility in water and is stable and not easy to decompose at high temperature, thereby reducing the nicotinic acid content in the nicotinamide and preparing nicotinamide with high purity. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to constitute any limitation to the present invention.

[0026] The reagents used in the following experiments of the present invention, unless otherwise specified, are all conventional commercial products or reagents prepared by conventional methods, and the methods used in the experiments, unless otherwise specified, are all conventional experimental methods. The instruments used in the experiments, unless otherwise specified, can all be obtained through commercial channels.

[0027] The present invention provides a method for preparing high-purity nicotinamide, comprising the following steps:

[0028] Mixing a feed solution containing nicotinamide and nicotinic acid with a base to obtain a mixed solution; wherein the base comprises one or more of an alkali metal hydroxide, an alkali metal carbonate, and an alkali metal bicarbonate;

[0029] The mixed solution is concentrated and crystallized to obtain high-purity nicotinamide.

[0030] As a specific implementation, the feed liquid containing nicotinamide and nicotinic acid is a reaction liquid obtained by reacting 3-cyanopyridine under the catalysis of cyanohydratase.

[0031] As a specific embodiment, the preparation method comprises:

[0032] (1) adjusting the pH of a liquid containing nicotinamide and nicotinic acid to 7.2-7.5 using a sodium hydroxide solution, and then heating to 80-90° C. to obtain a mixed solution;

[0033] (2) membrane filtration: using a ceramic membrane with a pore size of 100 nm to filter and intercept the catalytic enzyme preparation protein in the mixed solution while it is hot to obtain a filtrate;

[0034] (3) Activated carbon adsorption: adding activated carbon to the filtrate to adsorb impurities and then decarbonize and filter to obtain a clear filtrate;

[0035] (4) The filtered clear liquid is vacuum concentrated to a nicotinamide content of 82%-88%, methanol is added, stirred evenly, and then cooled to crystallize.

[0036] Furthermore, in step (1), the nicotinamide concentration in the slurry containing nicotinamide and nicotinic acid is 550-600 g / L, and the nicotinic acid content is 5000-8000 ppm.

[0037] Furthermore, in step (3), the mass ratio of the filtrate to the activated carbon is (0.5-1):100, and the decolorization temperature is 60-70°C.

[0038] Furthermore, in step (4), the mass ratio of the amount of methanol used to the mass of nicotinamide in the concentrated solution is (3-5):1.

[0039] Furthermore, in step (4), after stirring evenly, the temperature is lowered to 10-30° C. for crystallization.

[0040] Furthermore, in step (4), the nicotinamide wet product is obtained by filtering after cooling and crystallization, and the nicotinamide finished product is obtained after vacuum drying, and the mother liquor can be concentrated and used for crystallization.

[0041] The "nicotinamide enzyme catalytic solution" used in the following examples and comparative examples of the present invention is a reaction solution obtained by catalyzing the reaction of 3-cyanopyridine with cyanohydratase (also known as "nitrile hydratase").

[0042] Example 1

[0043] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a sodium hydroxide solution with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonization and filtration are performed to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 85%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization are started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 99.8%, and the residual nicotinic acid is 13 ppm.

[0044] Example 2

[0045] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a sodium hydroxide solution with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonized and filtered to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 90%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization is started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, a nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 98.3%, and the residual nicotinic acid is 1650 ppm.

[0046] Example 3

[0047] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a sodium hydroxide solution with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonization and filtration are performed to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 80%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization is started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 97.1%, and the residual nicotinic acid is 11 ppm.

[0048] Example 4

[0049] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a sodium hydroxide solution with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonization and filtration are performed to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 75%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization are started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 96.5%, and the residual nicotinic acid is 12 ppm.

[0050] Example 5

[0051] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a sodium hydroxide solution with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and stirred evenly while hot, and then continued to stir for 0.5 hours, and then decarbonized and filtered to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 95%, 1000 kg of methanol is added, stirred evenly, and then cooling and crystallization are started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 96.5%, and the residual nicotinic acid is 5600 ppm.

[0052] Example 6

[0053] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a sodium carbonate solution with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonization and filtration are performed to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 85%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization are started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 99.7%, and the residual nicotinic acid is 13 ppm.

[0054] Example 7

[0055] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a potassium hydroxide solution with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonization and filtration are performed to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 85%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization are started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 99.8%, and the residual nicotinic acid is 13 ppm.

[0056] Example 8

[0057] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a sodium hydroxide solution with a mass concentration of 20% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonization and filtration are performed to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 85%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization are started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 96.6%, and the residual nicotinic acid is 5361 ppm.

[0058] Comparative Example 1

[0059] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and ammonia water with a mass concentration of 5% is used to adjust the pH value to 6.8-7.2; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and stirred evenly while hot, and then continued to stir for 0.5 hours, and then decarbonized and filtered to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 85%, 1000 kg of methanol is added, stirred evenly, and then cooling and crystallization are started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 96.3%, and the residual nicotinic acid is 13652 ppm.

[0060] Comparative Example 2

[0061] 600 kg of nicotinamide enzyme catalytic liquid (nicotinic acid content of 6800 ppm, nicotinamide content of 56%) is taken, and a potassium hydroxide solution with a mass concentration of 5% is used to adjust the pH value to 8.0; then the temperature is raised to 80-90° C., and a ceramic membrane with a pore size of 100 nm is used to filter and intercept the catalytic enzyme preparation protein while hot; 5 kg of activated carbon is added to the obtained clear liquid, and the mixture is stirred evenly while hot, and the stirring is continued for 0.5 h, and then decarbonized and filtered to obtain a filtered clear liquid, and the decolorization temperature is 60-70° C. The filtered clear liquid is vacuum concentrated, and after concentrating to a nicotinamide content of 85%, 1000 kg of methanol is added, and the mixture is stirred evenly, and then cooling and crystallization is started, and the temperature of cooling and crystallization is 10-30° C. After cooling and crystallization, a nicotinamide wet product is obtained by filtering, and the wet product is vacuum dried to obtain a nicotinamide finished product, and the mother liquor can be concentrated and applied for crystallization, and the purity of the obtained nicotinamide is 93.6%, and the residual nicotinic acid is 36352 ppm.

[0062] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing high-purity nicotinamide, comprising the following steps: The feed liquid containing nicotinamide and nicotinic acid is mixed with a base to obtain a mixed liquid; wherein, The base includes one or more of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates; The mixed solution is concentrated and crystallized to obtain high-purity nicotinamide.

2. The preparation method according to claim 1, characterized in that: The alkali includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate; Preferably, the base comprises one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate; More preferably, the base comprises sodium hydroxide.

3. The preparation method according to claim 1 or 2, characterized in that: The amount of the alkali is such that the pH value of the mixed solution is 6.8-7.5; and / or the alkali comprises an alkali solution with a mass concentration of 1-10%, preferably 3-8%.

4. The preparation method according to any one of claims 1 to 3, characterized in that In the liquid containing nicotinamide and nicotinic acid, the mass content of nicotinamide is 50-60%, and the mass content of nicotinic acid is 5000-8000 ppm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The concentration comprises: concentrating the mixed solution to a nicotinamide mass content of 75-90%, preferably 80%-88%, more preferably 82%-88%.

6. The preparation method according to any one of claims 1 to 4, characterized in that: The crystallization comprises: mixing the concentrated solution obtained after concentration with a low-carbon alcohol, and then cooling and crystallizing; Preferably, the low-carbon alcohol comprises methanol; Preferably, the amount of the low-carbon alcohol is 3-5 times the mass of nicotinamide in the concentrated solution; Preferably, the crystallization is carried out by cooling to 10-30°C.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The feed liquid containing nicotinamide and nicotinic acid includes a reaction liquid obtained by reacting 3-cyanopyridine under the catalysis of cyanohydratase.

8. The preparation method according to claim 7, characterized in that: The method further comprises: before concentrating the mixed solution, heating the mixed solution and filtering and decolorizing the mixed solution; Preferably, the heating temperature is 80-90°C; Preferably, the filtration comprises membrane filtration, preferably, the filtration is performed using a ceramic membrane with a pore size of 100 nm to 200 nm; Preferably, the decolorization treatment comprises decolorization treatment using activated carbon; Preferably, the temperature of the decolorization treatment is 60-70°C.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The method further comprises: drying the crystals after crystallization to obtain a nicotinamide product; preferably, the drying is performed under vacuum conditions.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: (S1) adjusting the pH of the liquid containing nicotinamide and nicotinic acid to 6.8-7.5 using a sodium hydroxide solution having a mass concentration of 1-10%, preferably 3-8%, to obtain a mixed solution; (S2) heating the mixed solution to 80-90° C. and filtering the mixed solution using a ceramic membrane having a pore size of 100 nm-200 nm to obtain a filtrate; (S3) The filtrate is decolorized with activated carbon and then concentrated in vacuum to a nicotinamide content of 82%-88%, methanol is added and then cooled and crystallized to obtain a wet nicotinamide product, and the wet nicotinamide product is vacuum dried to obtain high-purity nicotinamide.