Synthesis method of tris (hydroxymethyl) aminomethane

Abstract

The invention relates to a synthesis method of tris (hydroxymethyl) aminomethane. The method comprises the following steps: after nitromethane and paraformaldehyde are subjected to condensation reaction to generate trihydroxymethyl nitromethane, firstly, the reaction is stopped by adopting acid, then, the pH value of reaction liquid after the condensation reaction is adjusted by using alkali liquor, hydrogenation reduction reaction is performed after vacuum degassing, the reaction liquid is dehydrated to remove moisture in the reaction liquid, and the trihydroxymethyl nitromethane is obtained. And concentrating, desolventizing, crystallizing, filtering and drying to obtain a trihydroxymethyl aminomethane product. The method disclosed by the invention is beneficial to reduction of side reactions, is easy to purify the trihydroxymethyl aminomethane, reduces three wastes, and can improve the product quality of the trihydroxymethyl aminomethane and increase the yield of the trihydroxymethyl aminomethane.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to an optimization method for synthesizing trishydroxymethylaminomethane. Background Art

[0002] Tris(hydroxymethyl)aminomethane is an important organic compound. It is an amino acid buffer that can absorb hydrogen ions to correct acidosis. It is often used for acute metabolic and respiratory acidosis. It is an ideal drug and an important pharmaceutical intermediate. It can be used to synthesize multi-purpose oxazolines, oxazolidines, etc., such as pesticides, pharmaceuticals, surfactants, gasoline and lubricant fillers, defoamers, water-based coatings, plasticizers, etc.

[0003] In the prior art, the preparation of tris(hydroxymethyl)aminomethane mainly uses nitromethane and paraformaldehyde as raw materials, and is obtained through condensation, hydrogenation reduction, cooling crystallization and other steps. For example, CN 1800142A discloses a method for synthesizing tris(hydroxymethyl)aminomethane, which uses nitromethane and excess paraformaldehyde as main raw materials, and condenses to form tris(hydroxymethyl)nitromethane at a certain temperature; then, under a certain temperature, pressure, solvent and catalyst, hydrogenation reduction reaction, crystallization, and recrystallization are performed to form tris(hydroxymethyl)aminomethane. In the process of prior art synthesis, there are raw materials or impurities that have not reacted completely, especially paraformaldehyde, which has high reactivity and is easily depolymerized into monomeric formaldehyde, causing a large amount of by-products, resulting in sticky silk in the system during the subsequent desolventization process, difficulty in product crystallization, and insufficient purity. In addition, the product tris(hydroxymethyl)amino is purified by traditional methanol refining. After the methanol is removed, the viscosity of the system will increase sharply, and the boiling point will also increase, resulting in the difficulty of separating and purifying the viscous by-products and products, and ultimately leading to an increase in high boiling points. High boiling materials have complex components, high boiling points, high viscosity, strong corrosiveness, and are flammable and explosive. High boiling materials are difficult to use or treat directly, and are often handed over to hazardous waste companies for treatment at 300-400 yuan per ton. In addition to increasing the production costs of enterprises, it also brings challenges to environmental protection and resource recycling. This is a technical problem that urgently needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide an improved method for synthesizing tris(hydroxymethyl)aminomethane, so as to increase the yield of tris(hydroxymethyl)aminomethane and reduce the production cost.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A method for synthesizing tris(hydroxymethyl)aminomethane, wherein tris(hydroxymethyl)nitromethane is prepared by condensation reaction of nitromethane and paraformaldehyde, and then tris(hydroxymethyl)nitromethane is prepared by hydrogenation reduction, and the method is characterized in that:

[0007] (1) After nitromethane and paraformaldehyde undergo condensation reaction to generate tris(hydroxymethyl)nitromethane, an acid is first used to terminate the reaction, and then an alkali solution is used to adjust the pH value of the reaction solution after the condensation reaction;

[0008] (2) after vacuum degassing, hydrogenation reduction reaction is performed;

[0009] (3) dehydrating the reaction solution after the hydrogenation reduction reaction in step (2) to remove water in the reaction solution, and then filtering and drying to obtain the tris(hydroxymethyl)aminomethane product.

[0010] In the condensation reaction process of nitromethane and paraformaldehyde, there is an excess of paraformaldehyde, and excess formaldehyde will be produced after the condensation reaction, producing corresponding by-products. The subsequent system is also prone to viscosity, resulting in the tris(hydroxymethyl)aminomethane product being difficult to purify. The inventor of this patent found that the reaction liquid after the condensation reaction is vacuum degassed to remove low-boiling substances, mainly formaldehyde and a small amount of nitromethane, which is conducive to the subsequent hydrogenation reaction toward the main reaction. Although a small amount of methanol will be taken away during the degassing process, methanol can be recovered by condensation. In addition, the hydrogenation process of synthesizing tris(hydroxymethyl)aminomethane is a process of producing water. After the reaction is completed, the water content will increase accordingly, and tris(hydroxymethyl)aminomethane has a great solubility in water and a low solubility in solvents such as methanol. On the contrary, impurities have a good solubility in the solvent methanol. In the existing conventional desolventizing process, the solvent methanol will be separated first. After a large amount of solvent is separated, the viscosity of the system will increase sharply, and the boiling point will also increase, making it more difficult to remove water, while the tris(hydroxymethyl)aminomethane product is still dissolved in water and difficult to separate, causing the tris(hydroxymethyl)aminomethane product to turn yellow and the tris(hydroxymethyl)aminomethane yield to decrease. In addition, as the temperature rises, the viscous byproducts and products are more difficult to separate and purify. The inventor of this patent has improved the purification process of the tris(hydroxymethyl)aminomethane product, removing water in advance, and then making it an anhydrous system, which does not affect the total amount of the product in the solvent system. Then, the desolventizing process is carried out, and the product can be more easily and more crystallized, thereby increasing the yield of the tris(hydroxymethyl)aminomethane product.

[0011] According to the technical solution of the present invention, the vacuum degree of the vacuum degassing is: 40-70kpa, specifically 40kpa, 50kpa, 60kpa, 70kpa and the like.

[0012] According to the technical solution of the present invention, the temperature of the vacuum degassing is 5-35°C, specifically 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C.

[0013] According to the technical solution of the present invention, the vacuum degassing time is 5-20 minutes, specifically 5 minutes, 10 minutes, 15 minutes, and 20 minutes.

[0014] According to the technical solution of the present invention, the dehydration is carried out by using any one of calcium oxide, magnesium oxide, silica gel and molecular sieve.

[0015] According to the technical solution of the present invention, the dehydration temperature is controlled at 30-50°C, specifically 30°C, 35°C, 40°C, 45°C, 50°C.

[0016] According to the technical solution of the present invention, the pH value is adjusted to 6.5-7.5. The present invention uses acid to terminate the reaction first and adjust the pH value to 5-6, and then adjust the pH value to 6.5-7.5 with alkali, which can quickly reduce the activity of the reaction system, prevent overreaction or produce unnecessary products, and then adjust the pH with alkali solution, then the reaction solution can be subsequently treated under milder conditions to ensure the stability and purity of the product. Trimethylolnitromethane is synthesized using nitromethane and paraformaldehyde. Although the synthesis is completed to form three methylol groups, the methylol groups are unstable due to steric hindrance, and are easily dropped off, and the product is placed for a long time to change color and turn yellow. Therefore, the present invention uses acid to terminate the reaction to stabilize the three methylol groups, but the reaction system is easily corroded in acidic reaction equipment, and the catalyst of catalytic hydrogenation is corroded, so the pH value is adjusted, in addition to extending the use time of production equipment, the normal use of subsequent reaction catalysts can also be guaranteed.

[0017] According to the technical solution of the present invention, the acid is selected from any one of hydrochloric acid, sulfuric acid and phosphoric acid.

[0018] According to the technical solution of the present invention, the alkali is selected from any one of sodium hydroxide and potassium hydroxide.

[0019] Beneficial Effects

[0020] From the above reaction steps and process, it can be seen that the beneficial effects of the present invention are:

[0021] 1. The synthesis method of tris(hydroxymethyl)aminomethane provided by the present invention is conducive to reducing the occurrence of side reactions, facilitating the purification of tris(hydroxymethyl)aminomethane, reducing three wastes, and having good product quality;

[0022] 2. The synthesis method of tris(hydroxymethyl)aminomethane provided by the present invention has stable production, is easy to carry out industrial optimization production under existing production conditions, and is easy to promote industrialization. It can improve the product quality of tris(hydroxymethyl)aminomethane and increase the output of tris(hydroxymethyl)aminomethane.

[0023] 3. The present invention provides a method for synthesizing tris(hydroxymethyl)aminomethane, which reduces the corresponding high-boiling substances while increasing the yield of tris(hydroxymethyl)aminomethane, thereby effectively reducing the cost of three waste treatment. DETAILED DESCRIPTION

[0024] The following is an explanation of the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are for describing specific embodiments rather than for limiting the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, any methods, equipment, and materials of the prior art that are similar or equivalent to the methods, equipment, and materials in the embodiments of the present invention may be used to implement the present invention, based on the prior art mastery of those skilled in the art and the description of the present invention.

[0027] Embodiment 1:

[0028] Add 51g of paraformaldehyde, 45g of methanol and 0.2g of potassium hydroxide to a four-necked flask, stir to dissolve, add 30g of nitromethane dropwise, keep warm at 50℃ for 3 hours, adjust pH to 5 with hydrochloric acid after the reaction, and adjust pH to 7.0 with sodium hydroxide. 70kpa, 5℃, vacuum degassing for 5min; then put the reaction product into an autoclave, add 180g of methanol and 12g of nickel, maintain the pressure at 3Mpa, control the temperature at 40℃, maintain the pressure for 2 hours when the pressure no longer drops, and after the hydrogenation is completed, add 60g of calcium oxide to the reaction solution to dehydrate the reaction solution, control the temperature at 30℃, stir for 0.5 hour, filter out the calcium oxide, concentrate and desolventize the filtrate in a rotary evaporator, cool to 0℃ for crystallization, filter and dry to obtain 46.3g of trishydroxymethylaminomethane product with a purity of 99.57% and 6.8g of high boiling products.

[0029] Embodiment 2:

[0030] Add 51g of paraformaldehyde, 45g of methanol and 0.2g of potassium hydroxide to a four-necked flask, stir to dissolve, add 30g of nitromethane dropwise, keep warm at 50℃ for 3 hours, adjust pH to 5 with hydrochloric acid after the reaction, and adjust pH to 6.5 with sodium hydroxide. 40kpa, 35℃, vacuum degassing for 10min; then put the reaction product into an autoclave, add 180g of methanol and 12g of nickel, keep the pressure at 3Mpa, control the temperature at 40℃, when the pressure no longer drops, keep the pressure for 1.5 hours, after the hydrogenation is completed, add 60g of magnesium oxide to the reaction solution to dehydrate the reaction solution, control the temperature at 30℃, stir for 0.5 hours, filter out the oxidation, concentrate and desolventize the filtrate in a rotary evaporator, cool to 0℃ for crystallization, filter and dry to obtain 45.7g of trishydroxymethylaminomethane product with a purity of 99.61% and 7.0g of high boiling products.

[0031] Embodiment 3:

[0032] Add 51g of paraformaldehyde, 45g of methanol and 0.2g of potassium hydroxide to a four-necked flask, stir to dissolve, add 30g of nitromethane dropwise, keep warm at 50℃ for 3 hours, adjust pH to 6 with sulfuric acid after the reaction, and then adjust pH to 7.5 with sodium hydroxide. 60kpa, 15℃, vacuum degassing for 15min; then put the reaction product into an autoclave, add 180g of methanol and 12g of nickel, keep the pressure at 3Mpa, and control the temperature at 40℃. When the pressure no longer drops, keep the pressure for 2 hours. After the hydrogenation is completed, add 55g of silica gel to the reaction solution to dehydrate the reaction solution, control the temperature at 35℃, stir for 0.5 hour, filter out the silica gel, concentrate and desolventize the filtrate in a rotary evaporator, cool to 0℃ for crystallization, filter and dry to obtain 45.2g of trishydroxymethylaminomethane product with a purity of 99.65% and 7.1g of high boiling products.

[0033] Embodiment 4:

[0034] Add 51g of paraformaldehyde, 45g of methanol and 0.2g of potassium hydroxide to a four-necked flask, stir to dissolve, add 30g of nitromethane dropwise, and react at 50°C for 3 hours. After the reaction, adjust the pH to 5 with phosphoric acid, and then adjust the pH to 7.0 with sodium hydroxide. 70kpa, 5°C, vacuum degassing for 20min; then put the reaction product into an autoclave, add 180g of methanol and 12g of nickel, maintain the pressure at 3Mpa, and control the temperature at 40°C. When the pressure no longer drops, maintain the pressure for 2 hours. After the hydrogenation is completed, add 65g of molecular sieves to the reaction solution to dehydrate the reaction solution, control the temperature at 30°C, stir for 0.5 hour, filter out calcium oxide, concentrate and desolventize the filtrate in a rotary evaporator, cool to 0°C for crystallization, filter and dry to obtain 46.2g of trishydroxymethylaminomethane product with a purity of 99.62% and 6.9g of high boiling products.

[0035] Comparative Example 1

[0036] Add 51g of paraformaldehyde, 45g of methanol and 0.2g of potassium hydroxide to a four-necked flask, stir and dissolve, add 30g of nitromethane dropwise, keep the temperature at 50℃ for 3 hours, adjust pH to 5 with hydrochloric acid after the reaction, put the reaction product into an autoclave, add 180g of methanol and 12g of nickel, keep the pressure at 3Mpa, control the temperature at 40℃, keep the pressure for 2 hours when the pressure stops dropping, cool to 0℃ for crystallization after hydrogenation, filter and dry to obtain 37.6g of tris(hydroxymethyl)aminomethane product with a purity of 99.05%. 7.8g of high boiling substances.

[0037] Comparative Example 1 is a scheme for synthesizing tris(hydroxymethyl)aminomethane products in the prior art. For comparison with Example 1, see Table 1. Compared with Example 1, the tris(hydroxymethyl)aminomethane product in Comparative Example 1 is reduced by 8.7 g, accounting for 18.8% of the product of Example 1. The high-boiling substances are increased by 1 g, accounting for 14.7% of the high-boiling substances in Example 1. The preparation of tris(hydroxymethyl)aminomethane using the technical scheme of the present invention can effectively increase the product yield of tris(hydroxymethyl)aminomethane, reduce the occurrence of side reactions, reduce the output of high-boiling substances, and save the cost of three waste treatment.

[0038] Table 1 Comparison between Example 1 and Comparative Example 1

[0039] Example 1 Comparative Example 1 Tris(hydroxymethyl)aminomethane yield 46.3g 37.6g purity 99.57％ 99.05％ High boiling weight 6.8g 7.8g

[0040] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art. Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents. The aforementioned embodiments and methods described in the present invention may vary based on the abilities, experiences and preferences of those skilled in the art.

[0041] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

[0042] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for synthesizing tris(hydroxymethyl)aminomethane, comprising preparing tris(hydroxymethyl)nitromethane by condensation reaction of nitromethane and paraformaldehyde, and then preparing tris(hydroxymethyl)nitromethane by hydrogenation reduction of tris(hydroxymethyl)nitromethane, characterized in that: (1) After nitromethane and paraformaldehyde undergo condensation reaction to generate trimethylolnitromethane, an acid is first used to terminate the reaction, and then an alkali solution is used to adjust the pH value of the reaction solution after the condensation reaction; (2) after vacuum degassing, hydrogenation reduction reaction is performed; (3) Dehydrating the reaction solution after the hydrogenation reduction reaction in step (2) to remove water from the reaction solution, then concentrating and desolventizing, crystallizing, filtering, and drying to obtain the tris(hydroxymethyl)aminomethane product.

2. The method according to claim 1, characterized in that The vacuum degree of the vacuum degassing is: 40-70kpa.

3. The method according to claim 1, characterized in that The temperature of the vacuum degassing is 5-35°C.

4. The method according to claim 1, characterized in that The vacuum degassing time is 5-20min.

5. The method according to claim 1, characterized in that The dehydration is carried out by using any one of calcium oxide, magnesium oxide, silica gel and molecular sieve.

6. The method according to claim 1, characterized in that The dehydration temperature is controlled at 30-50°C.

7. The method according to claim 1, characterized in that The pH value was adjusted to 6.5-7.

5.

8. The method according to claim 1, characterized in that The acid is selected from any one of hydrochloric acid, sulfuric acid and phosphoric acid.

9. The method according to claim 1, characterized in that The alkali is selected from any one of sodium hydroxide and potassium hydroxide.