Decoloration method of hydrogenated liquid in preparation of 2, 2, 6, 6-tetramethyl-4-aminopiperidine

Abstract

The invention relates to the field of fine chemical engineering, in particular to a decoloring method of a hydrogenated solution in preparation of 2, 2, 6, 6-tetramethyl-4-aminopiperidine. The method specifically comprises the following steps: 1) adding a hydrogenated filtrate in the preparation of 2, 2, 6, 6-tetramethyl-4-aminopiperidine into a reaction kettle, and then adding a decolorizing agent; (2) heating the reaction kettle, stirring, and keeping the pressure at 0-0.5 MPa, the reaction temperature at 20-100 DEG C and the reaction time at 0.5-10 hours to finish the decolorization reaction; and 3) filtering the reaction liquid, and then carrying out post-treatment to obtain a finished product of 2, 2, 6, 6-tetramethyl-4-aminopiperidine. In the preparation process of the 2, 2, 6, 6-tetramethyl-4-aminopiperidine, the intermediate (hydride) of the 2, 2, 6, 6-tetramethyl-4-aminopiperidine is decolored, and a relatively simple decoloring agent and related operation procedures are adopted for decoloring, so that the overall chromaticity of the obtained 2, 2, 6, 6-tetramethyl-4-aminopiperidine is lower than 5Hazen, and the product quality of the 2, 2, 6, 6-tetramethyl-4-aminopiperidine is effectively ensured.

Description

Technical Field

[0001] The invention relates to the field of fine chemicals, and in particular to a method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine. Background Art

[0002] Tetramethylpiperidinamine (i.e. 2,2,6,6-tetramethyl-4-piperidinamine) is an important hindered amine light stabilizer intermediate and pharmaceutical intermediate. Especially in the field of hindered amine light stabilizers, it is an important raw material for bonded and polymerized high molecular weight hindered amine light stabilizers.

[0003] At present, there are many industrial synthesis methods for 2,2,6,6-tetramethyl-4-aminopiperidine. The main synthesis principle is to obtain it by hydrogenation and post-treatment in the presence of a certain concentration of ammonia water, Raney nickel or Raney cobalt; and the authorization publication number CN111689893B discloses a preparation method of 2,2,6,6-tetramethyl-4-aminopiperidine, which mainly uses supported nickel as a catalyst to react 2,2,6,6-tetramethylpiperidone with ammonia water to obtain 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenated liquid, which is then decolorized and post-treated. The decolorization and post-treatment process mainly includes cooling and settling, filtering and atmospheric distillation, and negative pressure distillation to obtain a 2,2,6,6-tetramethyl-4-aminopiperidine product.

[0004] However, it is found in practice that the chromaticity of the 2,2,6,6-tetramethyl-4-aminopiperidine product obtained by the decolorization post-treatment in the above method is generally high (>20 Hazen), and the longer the storage time, the higher the chromaticity, which greatly affects the product quality; therefore, there is an urgent need for a decolorization method for the hydrogenation liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine that can be used for industrial production to reduce the product chromaticity and ensure product quality. Summary of the invention

[0005] In order to solve the problems existing in the prior art that the chromaticity of 2,2,6,6-tetramethyl-4-aminopiperidine is generally high (>20 Hazen) and the chromaticity increases with the storage time, the present invention provides a method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine.

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

[0007] The present invention provides a method for decolorizing a hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine, which specifically comprises the following steps:

[0008] 1) Add the hydrogenation filtrate in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine into the reaction kettle, and then add the decolorizing agent;

[0009] 2) The reactor is heated and stirred, the pressure is maintained at 0-0.5 MPa, the reaction temperature is 20-100°C, the reaction time is 0.5-10h, and the decolorization reaction is completed;

[0010] 3) Filter the reaction solution and perform post-treatment to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine.

[0011] Furthermore, in step 1), the hydrogenated filtrate in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine is prepared by adding 2,2,6,6-tetramethylpiperidone, ammonia water and a supported nickel catalyst into a reaction container, heating the temperature to 110-125° C. and then introducing hydrogen, and the specific steps are as follows: step 1, adding ammonia water and a supported nickel catalyst into a kettle; step 2, adding 2,2,6,6-tetramethylpiperidone, mixing under stirring conditions, replacing the air in the kettle with an inert gas and then heating the temperature to 110-120° C.; step 3, introducing hydrogen, maintaining the reaction temperature at 110-125° C. until the reaction is completed to obtain a hydrogenated liquid, and then filtering out the hydrogenated filtrate of the catalyst.

[0012] Furthermore, the decolorizing agent in step 1) is any one of activated carbon, molecular sieve, cation exchange resin, sodium borohydride, sodium sulfite, sodium bisulfite, and sodium thiosulfate.

[0013] Furthermore, the decolorizing agent in step 1) is a mixture of any of activated carbon, molecular sieve, cation exchange resin, sodium borohydride, sodium sulfite, sodium bisulfite, and sodium thiosulfate.

[0014] Furthermore, the amount of the decolorizing agent used in step 1) is 0.01%-10% of the mass of the 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation filtrate.

[0015] Furthermore, the amount of the decolorizing agent used is 0.1%-1% of the mass of the 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation filtrate.

[0016] Furthermore, the reaction time of the decolorization reaction in step 2) is 3 to 6 hours.

[0017] Furthermore, the post-treatment includes the following operations: 1) the temperature is reduced to below 90°C; 2) the reaction system is divided into upper and lower layers after sedimentation, and the catalyst is recovered from the lower layer for application; 3) the upper clear liquid is filtered, and then subjected to atmospheric distillation and negative pressure distillation.

[0018] The beneficial effects achieved by the present invention are:

[0019] In the preparation process of 2,2,6,6-tetramethyl-4-aminopiperidine, the intermediate (hydride) is decolorized by using a relatively simple decolorizing agent and related operation procedures, so that the overall chromaticity of the obtained 2,2,6,6-tetramethyl-4-aminopiperidine is lower than 5 Hazen, and the product quality of the 2,2,6,6-tetramethyl-4-aminopiperidine is effectively ensured; meanwhile, the product of the invention has obvious decolorization effect, simple treatment steps, low treatment cost, and the low-chromaticity 2,2,6,6-tetramethyl-4-aminopiperidine product is conducive to storage and does not affect the product quality, thereby ensuring the industrialized production of 2,2,6,6-tetramethyl-4-aminopiperidine. DETAILED DESCRIPTION

[0020] In order to facilitate those skilled in the art to understand the present invention, specific embodiments of the present invention are described.

[0021] 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.

[0022] The raw material of the invention is prepared based on the existing 2,2,6,6-tetramethyl-4-aminopiperidine preparation method, and specifically comprises the following steps: adding 2,2,6,6-tetramethylpiperidone, ammonia water and a supported nickel catalyst into a reaction container, heating the temperature to 110-125°C and then introducing hydrogen, and the specific steps are as follows: step 1, adding ammonia water and a supported nickel catalyst into a kettle; step 2, adding 2,2,6,6-tetramethylpiperidone, mixing under stirring conditions, replacing the air in the kettle with an inert gas and then heating the temperature to 110-120°C; step 3, introducing hydrogen, maintaining the reaction temperature at 110-125°C until the reaction is completed to obtain a hydrogenated liquid, and filtering the hydrogenated filtrate from which the catalyst is removed, thereby obtaining the raw material 2,2,6,6-tetramethyl-4-aminopiperidone hydrogenated filtrate used in the invention.

[0023] Example 1

[0024] Group 1: Add 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid and 1g of activated carbon into a stirred kettle. Maintain 0.5MPa, stir and keep the temperature in the kettle at 20℃, stir and keep warm for 10h, and the decolorization reaction is completed.

[0025] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 2 Hazen after testing.

[0026] Group 2:

[0027] 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid and 0.5g of activated carbon were added to the stirring kettle. Maintaining normal pressure, stirring and heating, when the temperature in the kettle was kept at 50°C, stirring and keeping warm for 5h, the decolorization reaction was completed.

[0028] The reaction solution was filtered and then distilled to obtain a finished 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished 2,2,6,6-tetramethyl-4-aminopiperidine was 0 Hazen after testing.

[0029] Group 3:

[0030] 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid and 0.2g of activated carbon were added to the stirring kettle. Maintaining 0MPa, stirring and heating, when the temperature in the kettle was maintained at 100°C, stirring and heating for 1h, the decolorization reaction was completed.

[0031] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 3 Hazen after testing.

[0032] Example 2

[0033] Group 1: Add a mixture of 100 g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid, 0.5 g of activated carbon and 0.5 g of sodium bisulfite into a stirring kettle; maintain 0.5 MPa, stir and keep the temperature in the kettle at 20°C, stir and keep warm for 10 hours, and the decolorization reaction is completed.

[0034] The reaction solution was filtered and then distilled to obtain a finished 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished 2,2,6,6-tetramethyl-4-aminopiperidine was 4 Hazen after testing.

[0035] Group 2: Add a mixture of 100 g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid, 0.25 g of activated carbon and 0.25 g of sodium bisulfite into a stirring kettle; maintain normal pressure, stir and heat up, and when the temperature in the kettle is maintained at 50°C, stir and keep warm for 5 hours, and the decolorization reaction is completed.

[0036] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 2 Hazen after testing.

[0037] The third group: add a mixture of 100g 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid, 0.1g activated carbon and 0.1g sodium bisulfite into a stirring kettle; maintain 0MPa, stir and heat up, maintain the temperature in the kettle at 100℃, stir and keep warm for 1h, and the decolorization reaction is completed.

[0038] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 1 Hazen after testing.

[0039] Example 3

[0040] Group 1: Add 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid and 1g of sodium borohydride into a stirring kettle; maintain 0.5MPa, stir and keep the temperature in the kettle at 20°C, stir and keep warm for 10 hours, and the decolorization reaction is completed.

[0041] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 3 Hazen after testing.

[0042] The second group: 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid and 0.5g of sodium borohydride were added to a stirring kettle; the temperature was raised by stirring while maintaining normal pressure, and when the temperature in the kettle was maintained at 50°C, the temperature was stirred and kept warm for 5h, and the decolorization reaction was completed.

[0043] The reaction solution was filtered and then distilled to obtain a finished 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished 2,2,6,6-tetramethyl-4-aminopiperidine was 0 Hazen after testing.

[0044] The third group: 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation liquid and 0.2g of sodium borohydride were added to the stirring kettle; the temperature was stirred and increased while maintaining 0MPa, and when the temperature in the kettle was maintained at 100°C, the temperature was stirred and kept for 1h, and the decolorization reaction was completed.

[0045] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 2 Hazen after testing.

[0046] Example 4

[0047] Group 1: Add 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenated liquid and 1g of cation exchange resin into a stirring kettle; maintain 0.5MPa, stir and keep the temperature in the kettle at 20°C, stir and keep warm for 10h, and the decolorization reaction is completed.

[0048] The reaction solution was filtered and then distilled to obtain a finished 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished 2,2,6,6-tetramethyl-4-aminopiperidine was 4 Hazen after testing.

[0049] The second group: 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenated liquid and 0.5g1g of cation exchange resin were added to a stirring kettle; the temperature was raised by stirring while maintaining normal pressure, and when the temperature in the kettle was maintained at 50°C, the temperature was stirred and kept warm for 5h, and the decolorization reaction was completed.

[0050] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 3 Hazen after testing.

[0051] The third group: 100g of 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenated liquid and 0.2g1g of cation exchange resin were added to the stirring kettle; the pressure was maintained at 0MPa, the temperature was stirred and increased, and when the temperature in the kettle was maintained at 100°C, the temperature was stirred and kept warm for 1h, and the decolorization reaction was completed.

[0052] The reaction solution was filtered and then distilled to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine; and the chromaticity of the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine was 3 Hazen after testing.

[0053] The above-described embodiments of the present invention do not constitute a limitation on the protection scope of the present invention. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine, characterized in that: The specific steps include: 1) Add the hydrogenation filtrate in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine into the reaction kettle, and then add the decolorizing agent; 2) The reactor is heated and stirred, the pressure is maintained at 0-0.5 MPa, the reaction temperature is 20-100°C, the reaction time is 0.5-10h, and the decolorization reaction is completed; 3) Filter the reaction solution and perform post-treatment to obtain the finished product of 2,2,6,6-tetramethyl-4-aminopiperidine.

2. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine according to claim 1, characterized in that: The hydrogenation filtrate in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine in step 1) is prepared by adding 2,2,6,6-tetramethylpiperidone, ammonia water and a supported nickel catalyst into a reaction container, heating the temperature to 110-125° C. and then introducing hydrogen. The specific steps are as follows: step 1, adding ammonia water and a supported nickel catalyst into a kettle; step 2, adding 2,2,6,6-tetramethylpiperidone, mixing under stirring conditions, replacing the air in the kettle with an inert gas and then heating the kettle to 110-120° C.; step 3, introducing hydrogen, maintaining the reaction temperature at 110-125° C. until the reaction is completed to obtain a hydrogenation liquid, and then filtering the hydrogenation filtrate to remove the catalyst.

3. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine according to claim 2, characterized in that: The decolorizing agent in step 1) is any one of activated carbon, molecular sieve, cation exchange resin, sodium borohydride, sodium sulfite, sodium bisulfite, and sodium thiosulfate.

4. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine according to claim 2, characterized in that: The decolorizing agent in step 1) is a mixture of any of activated carbon, molecular sieve, cation exchange resin, sodium borohydride, sodium sulfite, sodium bisulfite, and sodium thiosulfate.

5. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine according to any one of claims 2 to 4, characterized in that: The amount of the decolorizing agent used in the step 1) is 0.01%-10% of the mass of the 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation filtrate.

6. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine according to claim 4, characterized in that: The dosage of the decolorizing agent is 0.1%-1% of the mass of the 2,2,6,6-tetramethyl-4-aminopiperidine hydrogenation filtrate.

7. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine according to any one of claims 2 to 4, characterized in that: The reaction time of the decolorization reaction in step 2) is 3 to 6 hours.

8. A method for decolorizing hydrogenated liquid in the preparation of 2,2,6,6-tetramethyl-4-aminopiperidine according to claim 2, characterized in that: The post-processing includes the following operations: 1) The temperature drops below 90°C; 2) After sedimentation, the reaction system is divided into two layers, and the catalyst is recovered from the lower layer for reuse; 3) Filter the supernatant and then perform atmospheric distillation and negative pressure distillation.