A simple method for the synthesis of aminoacetic acid

Abstract

The present application relates to the technical field of chemical production, in particular to a simple method for synthesizing aminoacetic acid. The method comprises the following steps: (1) preparing raw materials: placing chloroacetic acid in ethanol, dissolving the chloroacetic acid, and then introducing ammonia gas to react to obtain ammonium chloroacetate, with the reaction proceeding, ammonium chloroacetate is precipitated in the form of crystals, and the ammonium chloroacetate crystals are obtained by centrifugation; (2) ammoniation reaction: adding ammonium chloroacetate and a catalyst urotropine into a ternary mixed solvent to dissolve, after the dissolution is completed, introducing ammonia gas to carry out ammoniation reaction; (3) obtaining aminoacetic acid mixed crystals and mother liquor 2 containing the catalyst by centrifugal separation; (4) adding the catalyst and the ternary mixed solvent to the mother liquor 2, and then entering the next round of ammoniation reaction. The present application does not need to use high-energy consumption methods such as electrodialysis and low-temperature crystallization, has the advantages of easy recycling of the catalytic reaction system, low energy consumption, simple operation, high selectivity of aminoacetic acid, easy purification of the product and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical production, in particular to a simple method for synthesizing aminoacetic acid. BACKGROUND

[0002] Aminoacetic acid, also known as glycine, is the smallest and simplest amino acid in terms of molecular weight. According to the quality of aminoacetic acid products, it can be divided into four specifications: industrial grade, feed grade, pharmaceutical grade and food grade. In the fields of pesticides, food, medicine and feed, aminoacetic acid can be widely used as a pharmaceutical intermediate, food amino acid additive and poultry feed additive.

[0003] The methods for synthesizing aminoacetic acid include chloroacetic acid ammonolysis method, Strecker method, hydroxyacetonitrile method, direct hydantoin method and biological synthesis method. At present, the chloroacetic acid ammonolysis method is widely used in China to produce aminoacetic acid. The production process is as follows: under the catalysis of catalyst urotropine, chloroacetic acid and ammonia gas in an aqueous solvent react to form a mixture of aminoacetic acid and ammonium chloride, then a large amount of methanol is added to the reaction solution for alcoholysis to obtain crude aminoacetic acid, the crude aminoacetic acid is subjected to multi-step crystallization and drying to obtain aminoacetic acid product, and finally the filtrate is concentrated, crystallized and separated to obtain ammonium chloride. The main problems in the traditional process for producing aminoacetic acid are as follows:

[0004] (1) The catalyst cannot be recycled. After the reaction is completed, the aminoacetic acid is separated from the system by alcoholysis, while the ammonium chloride containing the catalyst still exists in the solution, which makes it impossible to recycle the catalyst;

[0005] (2) The consumption of catalyst urotropine is large. About 0.15 tons of urotropine is consumed to produce one ton of aminoacetic acid;

[0006] (3) A large amount of solvent such as methanol is used. A large amount of methanol is added to the ammonolysis reaction solution for alcoholysis to separate the crude aminoacetic acid;

[0007] (4) The crude aminoacetic acid synthesized has many impurities and is difficult to purify. Water is used as the solvent in the chloroacetic acid ammonolysis method, which can cause the aminoacetic acid to further undergo side reactions to generate imino diacetic acid, amino triacetic acid and other impurities. If the process parameters are not properly controlled, the catalyst urotropine can decompose to generate formaldehyde, which participates in the side reaction to generate methylene aminoacetic acid. Imino diacetic acid, amino triacetic acid and methylene aminoacetic acid are difficult to separate from aminoacetic acid.

[0008] Main reaction:

[0009] ;

[0010] Related side reactions:

[0011] .

[0012] In order to realize the recycling of the catalyst and reduce the production cost, the prior art often separates ammonium chloride from the reaction solution by low-temperature cooling, electrodialysis and other high-energy consumption and high-production-cost methods, so as to realize the recycling of the catalyst-containing filtrate:

[0013] Patent CN111196768A synthesizes aminoacetic acid by a two-step method. The technical scheme uses pyridine base compounds instead of urotropin catalyst, and produces aminoacetic acid by reacting chloroacetate with ammonia in alcohol-water mixed solvent with pyridine base as catalyst. The technical scheme realizes the recycling of the mixed solvent and the catalyst by adding solid chloroacetate to the reaction filtrate, cooling to 10 DEG C in the embodiment, and crystallizing ammonium chloride from the centrifugal liquid, but still has the following problems: the method needs low-temperature treatment to realize the recycling of the catalyst, and has large energy consumption; pyridine base compounds are expensive, which increases the production cost and is not conducive to industrial production.

[0014] Patent CN115124436A synthesizes aminoacetic acid by a one-step method. Chloroacetate is dissolved in water with urotropin, and then ammonia gas is introduced for ammoniation reaction to obtain a mixed solution of aminoacetic acid and ammonium chloride. The mixed solution is cooled and crystallized, and then centrifuged to obtain a stock solution and crystals. The stock solution is subjected to primary electrodialysis to obtain primary dialysate and organic liquid containing catalyst and aminoacetic acid, and the organic liquid is continuously recycled. The method can realize the recycling of the catalyst, but still has the following problems: the method needs to realize the recycling of the catalyst by electrodialysis, which has large energy consumption and complicated process, and increases the production cost. SUMMARY

[0015] In view of the technical problems of high energy consumption, large catalyst consumption, high alcohol consumption in alcohol crystallization, and difficulty in refining due to many impurities in the production of aminoacetic acid, the present application provides a simple method for synthesizing aminoacetic acid. The reaction crystallization method is used, the synergistic effect of the solvent and the anti-solvent is utilized, and the ternary solvent system is constructed by fine-tuning the ratio of the solvent and the anti-solvent. In the constructed ternary solvent system, the raw material chloroacetate and the catalyst urotropin are easily dissolved, while the reaction product aminoacetic acid and the by-product ammonium chloride are not dissolved. With the progress of the reaction, aminoacetic acid and ammonium chloride are crystallized in a molar ratio of 1:1, which avoids the continuous side reaction of aminoacetic acid. After the reaction is completed, the catalyst reaction system (reaction mother liquor) and the crystals can be separated by centrifugation. The present application does not need high-energy consumption methods such as electrodialysis and low-temperature crystallization, and has the advantages of easy recycling of the catalyst reaction system, low energy consumption, simple operation, high selectivity of aminoacetic acid, easy purification of the product, etc.

[0016] The technical scheme of the present application is as follows:

[0017] A simple method for synthesizing aminoacetic acid, comprising the following steps:

[0018] (1) Preparation of raw materials: chloroacetic acid is placed in ethanol, and after complete dissolution, ammonium chloroacetate is prepared by passing ammonia gas. As the reaction proceeds, ammonium chloroacetate is precipitated in the form of crystals, and after centrifugation, ammonium chloroacetate crystals and mother liquor 1 are obtained. Ammonium chloroacetate is used as a raw material for the amination reaction of aminoacetic acid, and mother liquor 1 is continuously recycled to prepare ammonium chloroacetate.

[0019] (2) Amination reaction: ammonium chloroacetate and the catalyst urotropine are added to a ternary mixed solvent and dissolved, and after complete dissolution, ammonia gas is passed to carry out the amination reaction.

[0020] The ternary mixed solvent system is composed of water, ethanol and a high-boiling aprotic polar organic solvent in a mass ratio of 2.9-3.0:1.5-1.6:4.6-4.8.

[0021] (3) Mixed crystal separation: the aminoacetic acid generated by the amination reaction has very low solubility in the ternary mixed solvent reaction system, and directly crystallizes out as the reaction proceeds, without the need for low-temperature treatment. Aminoacetic acid mixed crystals and mother liquor 2 containing the catalyst can be obtained by centrifugal separation.

[0022] (4) Catalytic recycling: after adding catalyst and ternary mixed solvent to mother liquor 2, it enters the next round of amination reaction.

[0023] Further, in step (1), the mass ratio of chloroacetic acid to ethanol is 0.32-0.42:1.

[0024] Further, in step (1), the reaction temperature is 25°C, and when the pH value of the reaction system reaches 7.3-7.5, the ammonia gas is stopped and the temperature is kept at 35°C for 40 minutes.

[0025] Further, in step (2), the high-boiling aprotic polar organic solvent is N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAC), preferably DMAC. DMF and DMAC have very low solubility for aminoacetic acid and ammonium chloride.

[0026] Further, in step (2), the mass ratio of ammonium chloroacetate, ternary mixed solvent and urotropine is 7.5-8.0:23-25:0.9-1.1.

[0027] Further, in step (2), the amination reaction temperature is controlled at 55°C±1°C.

[0028] Further, in step (2), the pH value of the reaction system and the ammonia flux establish a PLC interlock, and by adjusting the ammonia flux, the pH value of the reaction system is controlled between 7.1 and 7.3.

[0029] Further, in step (2), the ammoniation reaction is stopped when the HPLC monitoring system shows that the concentration of ammonium chloroacetate is zero.

[0030] Further, in step (3), the ammoniation reaction product is allowed to stand for 30 min before being centrifuged and filtered.

[0031] Further, in step (4), the amount of the ternary mixed solvent added each time is 2.5wt.%-3wt.% of the amount of the ternary mixed solvent added in the ammoniation reaction, and the amount of the catalyst added each time is 2wt.%-2.5wt.% of the amount of the catalyst added in the ammoniation reaction.

[0032] The present application synthesizes aminoacetic acid by a reaction crystallization method which is simple to operate and has a catalytic reaction system that can be recycled. By establishing a ternary solvent system in which the catalyst and the reaction raw materials are easily dissolved, but the reaction product is difficult to dissolve, the recycling of the catalytic reaction system is achieved. By using the synergistic effect of the solvent and the anti-solvent, the solubility of aminoacetic acid and ammonium chloride in the reaction system is precisely adjusted, so that the aminoacetic acid and ammonium chloride produced by the ammoniation reaction are all crystallized out in a molar ratio close to 1:1. This allows the mixed crystals and the catalytic reaction system to be completely separated, thereby realizing the recycling of the catalyst and the solvent. Moreover, the reaction product, aminoacetic acid, and ammonium chloride are crystallized out in a timely manner during the reaction, avoiding side reactions and reducing impurity content. The catalytic reaction system can be recycled for up to 48 times before the color turns yellow. The organic solvent is recovered by distillation and then reused.

[0033] The main mechanism is as follows: After the hydrophilic organic solvent (ethanol and DMAC or DMF) is added to the aqueous solution, the dielectric constant of the medium water is reduced, increasing the electrostatic attraction between the aminoacetic acid molecules and the ammonium chloride molecules, which aggregate to form crystalline precipitates. The hydration of the water-soluble organic solvent (ethanol and DMAC or DMF) itself reduces the concentration of free water, compressing the thickness of the original hydration layer on the surface of the hydrophilic solute aminoacetic acid and ammonium chloride molecules, reducing their hydrophilicity, leading to dehydration and aggregation, and crystalline precipitates are precipitated.

[0034] The present application has the following advantages:

[0035] 1. The process for recycling the catalytic reaction system of the present application is simple and has low energy consumption. Without the aid of high-energy and high-cost methods such as electrodialysis and low temperature, the aminoacetic acid and ammonium chloride in the reaction solution are completely separated, and the filtrate containing the catalyst is reused to realize recycling. By using the reaction crystallization method and the synergistic effect of the solvent and the anti-solvent in the ternary mixed solvent, the aminoacetic acid and ammonium chloride in the reaction process are all crystallized out in a molar ratio close to 1:1. After simple centrifugal separation, the catalytic reaction system mother liquor and the aminoacetic acid mixed crystals can be efficiently separated and recycled, and the catalytic reaction system can be recycled for up to 48 times.

[0036] 2. The method of the present application does not use toxic methanol, and the amount of organic solvent used is small, which is more environmentally friendly. The reaction crystallization method is used to avoid using methanol for alcohol precipitation, and the solvent recycling effect is good. Only 2.5wt.%-3wt.% of the amount of ternary mixed solvent is needed to be added each time, which greatly reduces the amount of solvent used.

[0037] 3. The catalyst consumption of the method of the present application is low. Through the recycling of the catalytic reaction system, the consumption of the catalyst and the production cost are greatly reduced. Only 2wt.%-2.5wt.% of the amount of catalyst is needed to be added each time.

[0038] 4. The pH value of the reaction key process index of the method of the present application is easy to control, which greatly reduces the generation of impurities. During the ammoniation reaction process, the pH value of the reaction system and the ammonia flux establish a PLC interlock, and by adjusting the size of the ammonia flux, the pH value of the reaction system is accurately controlled between 7.1-7.3, avoiding the decomposition of the catalyst caused by large fluctuations in the pH value.

[0039] 5. The method of the present application has high yield of aminoacetic acid and less mixed crystal impurities. The self-made high-purity ammonium chloroacetate is used as raw material, and the reaction crystallization method is used. The reaction product aminoacetic acid and ammonium chloride can crystallize and separate from the reaction system in time, avoiding the occurrence of side reactions. The content of aminoacetic acid in the mixed crystal is 58.2wt.%-58.6wt.%, and the content of ammonium chloride is 41.2wt.%-41.6wt.%, which is close to the theoretical molar ratio of 1:1 of the two products. The total yield of aminoacetic acid and ammonium chloride is more than 95%, and the yield of aminoacetic acid can reach more than 92%. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0041] Figure 1 is the process flow chart of the specific embodiment of the present application. DETAILED DESCRIPTION

[0042] In order to make the person skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0043] Example 1 Preparation of ammonium chloroacetate

[0044] In a reaction vessel equipped with a thermometer, stirring, heating, and circulating water cooling, chloroacetic acid was placed in ethanol at a mass ratio of 0.40:1. After complete dissolution, ammonia gas was introduced, and the reaction was carried out at 25°C. When the pH value of the reaction system reached 7.3-7.5, the ammonia gas was stopped, and the temperature was maintained at 35°C for 50 min. During the reaction, ammonium chloroacetate was precipitated in the form of crystals. After centrifugation, ammonium chloroacetate crystals and mother liquor 1 were obtained. Ammonium chloroacetate was used as the raw material for the ammoniation reaction in step (2), and mother liquor 1 was continuously used to prepare ammonium chloroacetate. The content of the prepared ammonium chloroacetate was 99.7wt.%, and the yield of ammonium chloroacetate was 99.2%.

[0045] Example 2 Preparation of aminoacetic acid and recycling of mother liquor 2

[0046] At 35°C, a reaction vessel equipped with a thermometer, stirring, heating, and circulating water cooling was added with 3450g of a ternary mixed solvent (composition of the ternary mixed solvent: water 1100g, ethanol 600g, DMF 1750g), 1120g of ammonium chloroacetate, and 140g of urotropine catalyst were added and dissolved. After complete dissolution, ammonia gas was introduced, and the ammoniation reaction was carried out, with the reaction temperature controlled between 54-56°C. The pH value of the reaction system was interlocked with the ammonia flux by PLC, and the ammonia flux was adjusted to control the pH value between 7.1-7.3. When the concentration of ammonium chloroacetate in the system was zero, as monitored by HPLC, the ammonia gas was stopped, and the reaction was stopped. After the reaction solution of step (2) was allowed to stand for 30 min, centrifugal separation was carried out to obtain aminoacetic acid mixed crystals and mother liquor 2. To the mother liquor 2, 91g of a ternary mixed solvent (2.64wt.% of the initial amount of the ternary mixed solvent) and 3.0g of catalyst (2.14wt.% of the initial amount of the catalyst) were added, and the mixture was used in the next cycle of ammoniation reaction.

[0047] After 10 cycles of catalysis, the reaction mother liquor was colorless and transparent. For the production of one ton of aminoacetic acid, the average consumption of urotropine catalyst was 22.24kg, and the average amount of ternary mixed solvent used was 561kg. The average content of aminoacetic acid in the obtained aminoacetic acid mixed crystals was 58.3wt.%, and the content of ammonium chloride was 41.2wt.%, with a molar ratio of 1.0:0.992. The yield of aminoacetic acid was 92.7%.

[0048] Example 3 Preparation of aminoacetic acid and recycling of mother liquor 2

[0049] Into a reaction vessel equipped with a thermometer, a stirrer, a heater, and a circulating water cooling system, 3450 g of a ternary mixed solvent (consisting of 1100 g of water, 600 g of ethanol, and 1750 g of DMF) was charged at 35°C, and 1120 g of ammonium chloroacetate and 140 g of urotropine catalyst were added and dissolved. After completion of the dissolution, ammonia gas was introduced to perform an ammoniation reaction, and the reaction temperature was controlled at 54-56°C. The pH value of the reaction system was interlocked with the ammonia gas flux to control the pH value at 7.1-7.3 by adjusting the ammonia gas flux. When the HPLC monitoring of the system showed that the concentration of ammonium chloroacetate was zero, the introduction of ammonia gas was stopped, and the reaction was terminated. After the reaction solution was allowed to stand for 30 min, centrifugal separation was performed to obtain a mixed crystal of aminoacetic acid and a mother liquor 2. To the mother liquor 2, 96.6 g of the ternary mixed solvent (2.80 wt.% of the initial amount of the ternary mixed solvent) and 3.36 g of the catalyst (2.40 wt.% of the initial amount of the catalyst) were added, and the mixture was subjected to the next cycle of the ammoniation reaction.

[0050] After 20 cycles of the catalysis, the mother liquor became light yellow, but had no effect on the color of the product. In terms of one ton of aminoacetic acid produced, the average consumption of the catalyst urotropine was 13.57 kg, and the average amount of the ternary mixed solvent used was 344 kg. The average content of aminoacetic acid in the obtained mixed crystal of aminoacetic acid was 58.2 wt.%, and the content of ammonium chloride was 41.4 wt.%, with a molar ratio of 1.0:0.998. The yield of aminoacetic acid was 92.1%.

[0051] Example 4 Preparation of aminoacetic acid and recycling of the mother liquor 2

[0052] Into a reaction vessel equipped with a thermometer, a stirrer, a heater, and a circulating water cooling system, 3450 g of a ternary mixed solvent (consisting of 1100 g of water, 600 g of ethanol, and 1750 g of DMF) was charged at 35°C, and 1120 g of ammonium chloroacetate and 140 g of urotropine catalyst were added and dissolved. After completion of the dissolution, ammonia gas was introduced to perform an ammoniation reaction, and the reaction temperature was controlled at 54-56°C. The pH value of the reaction system was interlocked with the ammonia gas flux to control the pH value at 7.1-7.3 by adjusting the ammonia gas flux. When the HPLC monitoring of the system showed that the concentration of ammonium chloroacetate was zero, the introduction of ammonia gas was stopped, and the reaction was terminated. After the reaction solution was allowed to stand for 30 min, centrifugal separation was performed to obtain a mixed crystal of aminoacetic acid and a mother liquor 2. To the mother liquor 2, 96.6 g of the ternary mixed solvent (2.80 wt.% of the initial amount of the ternary mixed solvent) and 3.36 g of the catalyst (2.40 wt.% of the initial amount of the catalyst) were added, and the mixture was subjected to the next cycle of the ammoniation reaction.

[0053] After 20 cycles of catalysis, the reaction mother liquor remained colorless and transparent. The average consumption of catalyst urotropine was 13.57 kg and the average consumption of ternary mixed solvent was 352 kg per ton of aminoacetic acid produced. The average content of aminoacetic acid in the obtained aminoacetic acid mixed crystal was 58.5 wt.%, the content of ammonium chloride was 41.3 wt.%, the molar ratio thereof was 1.0:0.991, and the yield of aminoacetic acid was 93.9%.

[0054] Example 5 Preparation of aminoacetic acid and recycling of mother liquor 2

[0055] At 35°C, 3450 g of ternary mixed solvent (ternary mixed solvent composition: water 1100 g, ethanol 600 g, DMAC 1750 g) was added to a reaction vessel equipped with a thermometer, stirring, heating, and circulating water cooling, 1120 g of ammonium chloroacetate and 140 g of urotropine catalyst were added and dissolved, after dissolution, ammonia gas was introduced, and the reaction was carried out at a temperature of 54-56°C. The pH value of the reaction system was interlocked with the ammonia flux by PLC, and the ammonia flux was adjusted to control the pH value between 7.1-7.3. When the HPLC monitoring system showed that the concentration of ammonium chloroacetate was zero, the introduction of ammonia gas was stopped, and the reaction was stopped. After the reaction solution was allowed to stand for 30 min, centrifugal separation was carried out to obtain aminoacetic acid mixed crystal and mother liquor 2. 100 g of ternary mixed solvent (i.e. 2.90 wt.% of the initial amount of ternary mixed solvent) and 3.43 g of catalyst (i.e. 2.45 wt.% of the initial amount of catalyst) were added to the mother liquor 2, and the next round of amination reaction was carried out for recycling.

[0056] After 30 cycles of catalysis, the reaction mother liquor remained colorless and transparent. The average consumption of catalyst urotropine was 10.63 kg and the average consumption of ternary mixed solvent was 282 kg per ton of aminoacetic acid produced. The average content of aminoacetic acid in the obtained aminoacetic acid mixed crystal was 58.4 wt.%, the content of ammonium chloride was 41.2 wt.%, the molar ratio thereof was 1.0:0.990, and the yield of aminoacetic acid was 93.4%.

[0057] Example 6 Preparation of aminoacetic acid and recycling of mother liquor 2

[0058] Into a reaction vessel equipped with a thermometer, a stirrer, a heater, and a circulating water cooling system, 3450 g of a ternary mixed solvent (composition of the ternary mixed solvent: water 1100 g, ethanol 600 g, DMAC 1750 g) was added, followed by the addition of 1120 g of ammonium chloroacetate and 140 g of urotropine as a catalyst, and then the mixture was dissolved. After the completion of the dissolution, ammonia gas was introduced, and an amination reaction was performed at a temperature of 54-56°C. The pH value of the reaction system was interlocked with the ammonia gas flux by means of a PLC, and the ammonia gas flux was adjusted to control the pH value to be 7.1-7.3. When the concentration of ammonium chloroacetate in the system was zero, as monitored by HPLC, the introduction of ammonia gas was stopped, and the reaction was terminated. After the reaction solution was allowed to stand for 30 min, centrifugal separation was performed to obtain a mixture of aminoacetic acid and a mother liquor 2. To the mother liquor 2, 90 g of the ternary mixed solvent (2.60 wt.% of the initial amount of the ternary mixed solvent) and 2.94 g of the catalyst (2.10 wt.% of the initial amount of the catalyst) were added, and the mixture was subjected to the next amination reaction cycle.

[0059] After 48 cycles of the catalysis, the reaction mother liquor became yellow. In terms of one ton of aminoacetic acid produced, the average consumption of the catalyst urotropine was 7.72 kg, and the average amount of the total solvent used was 214 kg. The average content of aminoacetic acid in the total mixture of aminoacetic acid obtained was 58.3 wt.%, and the content of ammonium chloride was 41.3 wt.%, the molar ratio of which was 1.0:0.994. The yield of aminoacetic acid was 92.8%.

[0060] Comparative Example 1

[0061] Into a reaction vessel equipped with a thermometer, a stirrer, a heater, and a circulating water cooling system, 6000 mL of an organic solvent (methanol 1000 mL, ethanol 2500 mL, DMAC 2500 mL) was added, followed by the addition of 1120 g of ammonium chloroacetate and 140 g of urotropine as a catalyst. After the mixture was stirred and dissolved, ammonia gas was introduced to perform an amination reaction at a temperature of 50-65°C until the pH value reached 7.3. The reaction was terminated. The crude aminoacetic acid crystals were filtered out at a temperature of 40°C to obtain 726.8 g of aminoacetic acid having a content of 82.6%.

[0062] The filtered organic solvent was added with 1120 g of ammonium chloroacetate in batches, and the mixture was cooled to a temperature of 20°C. Crude ammonium chloride and a reaction organic solvent containing ammonium chloroacetate were filtered out. The crude ammonium chloride was washed with methanol, filtered, and dried to obtain 421.5 g of ammonium chloride.

[0063] Comparative Example 2

[0064] Into a reaction vessel equipped with a thermometer, stirring, heating, and water circulation cooling, 3450 g of an organic solvent (1725 g of ethanol and 1725 g of DMAC) was added, and 1120 g of ammonium chloroacetate and 140 g of urotropine catalyst were added and dissolved by stirring, and then the ammonia reaction was started by passing in ammonia gas, and the temperature was controlled at 50-65°C, and the reaction was stopped when the pH reached 7.3. The aminoacetic acid crystal crude product was filtered out at a temperature of 40°C, and 728.5 g of aminoacetic acid with a content of 75.1% was obtained.

[0065] The filtered organic solvent was added with 1120 g of ammonium chloroacetate in batches, and the temperature was lowered to 20°C, and ammonium chloride crude product and the recycled reaction organic solvent containing ammonium chloroacetate were filtered out. The crude ammonium chloride was washed with methanol, filtered, and dried, and 425.8 g of ammonium chloride was obtained.

[0066] As can be seen from the comparative examples and the comparative example, when the mixed solvent used in the ammonia reaction lacks water, it is difficult to form a reaction crystallization environment, resulting in low yield of the reaction products aminoacetic acid and ammonium chloride; and because of the large amount of residual aminoacetic acid and ammonium chloride in the filtered organic solvent, the ammonia reaction is affected, and the catalytic recycling effect is very poor. In addition, methanol with high toxicity is used in Comparative Example 1, and the solvent consumption is large, and the environmental protection is poor.

[0067] Although the present application has been described in detail with reference to the preferred embodiments, the present application is not limited to the preferred embodiments. Any modifications or replacements made by those skilled in the art without departing from the spirit and essence of the present application shall be included in the scope of the present application. Any modifications or replacements made by those skilled in the art within the scope of the present application disclosed herein shall be included in the scope of the present application.

Claims

1. A method for the facile synthesis of aminoacetic acid, characterized in that, The method comprises the following steps: (1) preparing raw materials: placing chloroacetic acid in ethanol, dissolving, and then introducing ammonia to obtain ammonium chloroacetate, centrifuging to obtain ammonium chloroacetate crystals and mother liquor 1, and continuously recycling mother liquor 1 to prepare ammonium chloroacetate; (2) ammoniation reaction: adding ammonium chloroacetate and catalyst urotropine into a ternary mixed solvent to dissolve, dissolving, and then introducing ammonia to perform ammoniation reaction, and controlling the ammoniation reaction temperature at 55℃±1℃; The ternary mixed solvent system is composed of water, ethanol and high-boiling aprotic polar organic solvent in a mass ratio of 2.9-3.0:1.5-1.6:4.6-4.8, and the high-boiling aprotic polar organic solvent is N,N-dimethylacetamide; The mass ratio of ammonium chloroacetate, ternary mixed solvent and urotropine is 7.5-8.0:23-25:0.9-1.1; (3) mixed crystal separation: ammonium chloride and aminoacetic acid generated in the ammoniation reaction are directly crystallized without low-temperature treatment, and mixed crystal of aminoacetic acid and mother liquor 2 containing catalyst are obtained by centrifugal separation; (4) catalytic circulation: adding catalyst and ternary mixed solvent to mother liquor 2, and then entering the next round of ammoniation reaction.

2. The method of claim 1, wherein, In step (1), the mass ratio of chloroacetic acid to ethanol is 0.32-0.42:

1.

3. The method of claim 1, wherein, In step (1), the reaction temperature is 25℃, when the pH value of the reaction system reaches 7.3-7.5, stop introducing ammonia and perform heat preservation, the heat preservation temperature is 35℃, and the heat preservation time is 40min.

4. The method of claim 1, wherein, In step (2), the pH value of the reaction system and the ammonia flux establish PLC interlocking, the pH value of the reaction system is controlled between 7.1-7.3 by adjusting the ammonia flux, and the ammoniation reaction is stopped when the concentration of ammonium chloroacetate in the system is zero.

5. The method of claim 1, wherein, In step (3), the ammoniation reaction product is centrifuged after standing for 30min.

6. The method of claim 1, wherein, The amount of ternary mixed solvent added each time is 2.5wt.%-3wt.% of the amount of ternary mixed solvent added in the ammoniation reaction, and the amount of catalyst added each time is 2wt.%-2.5wt.% of the amount of catalyst added in the ammoniation reaction.

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