A solid catalyst for preparing glycine and its use in the preparation of glycine

Abstract

The application discloses a solid catalyst for preparing glycine and application of the solid catalyst in preparation of glycine. At normal temperature and pressure, a reaction solvent and the solid catalyst for preparing glycine are added into a reaction container; the temperature is controlled; a chloroacetic acid solution and ammonia water are added dropwise into the reaction container; the pH value of the system is controlled through the dropping speed of the ammonia water; after the dropping is completed, the reaction is carried out at 45-60 DEG C for 1.5-2 hours; filtration is carried out; the filtrate is subjected to alcohol precipitation with methanol and temperature reduction crystallization; the crystal is dissolved with water; and glycine is obtained through separation and purification. The application solves the problem of'secondary pollution' caused by catalyst decomposition through the self-prepared solid catalyst for preparing glycine, reduces the catalyst usage amount in single reaction, realizes recycling of the catalyst, and reduces the cost. Through the water-phase reaction mode of bidirectional dropping of the chloroacetic acid solution and the ammonia water, the pH value of the reaction system can be controlled to be maintained in a range favorable to generation of glycine, and the occurrence of side reactions is effectively inhibited.

Description

Technical Field

[0001] This invention belongs to the field of glycine synthesis technology, specifically relating to a solid catalyst for preparing glycine and its application in the preparation of glycine. Background Technology

[0002] Glycine, also known as aminoacetic acid, is one of the simplest α-amino acids and an important fine chemical intermediate. It is primarily used in the synthesis of the herbicide glyphosate and is also widely used as a carbon dioxide solvent remover in the pharmaceutical, pesticide, food, feed, and fertilizer industries. With rising living standards, the food and pharmaceutical industries will become major consumers of glycine, indicating a huge market potential for this product.

[0003] Numerous methods for glycine preparation have been reported in existing domestic and international literature. Among them, the Strecker process using formaldehyde and sodium cyanide as main raw materials and the chloroacetic acid ammonolysis process using chloroacetic acid and ammonia as raw materials are two commonly used routes. The Strecker process suffers from the high toxicity of the cyanide raw material and stringent requirements for its transportation, storage, and use. The chloroacetic acid ammonolysis process, on the other hand, has advantages such as relative maturity, simple equipment, and less environmental pollution, making it the main method for glycine production in my country. The main and side reactions involved in the synthesis of glycine via chloroacetic acid ammonolysis are shown below:

[0004]

[0005] In existing publicly available technologies, the synthesis of glycine often uses hexamethylenetetramine as a catalyst. This catalyst is used in large quantities, is prone to decomposition during production, and is difficult to recover. To address this issue, professionals have invested considerable research and achieved some results. Chinese patent CN111116389A describes a composite catalytic system using 4-dimethylaminopyridine as the main catalyst, pyridine and pyridine base compounds, and hexamethylenetetramine and paraformaldehyde as co-catalysts. This system synthesizes a mixed solution of glycine and ammonium chloride in an aqueous phase and separates glycine using alcohol precipitation. Patent CN107216262B relates to a method using an ionic liquid as a catalyst, chloroacetic acid and ammonia as reactants, in a homogeneous system for ammonolysis, followed by recrystallization to obtain pure glycine.

[0006] Patent CN1111000021A discloses a method for synthesizing glycine by using an alcohol-water system and hexamethylenetetramine as the mother liquor, adding chloroacetic acid solution dropwise to a reaction vessel while simultaneously introducing ammonia gas, and controlling the pH value of the system at 75-85℃. In this method, the crystal size and adhesion phenomenon of the product are effectively controlled by introducing silicone oil and a crystallizing agent into the reaction system. However, because the liquid chloroacetic acid used in this method contains a certain amount of dichloroacetic acid and a small amount of trichloroacetic acid impurities, it will react with ammonia gas to produce ammonium dichloroacetate and ammonium trichloroacetate impurities.

[0007] Patent CN107868017A describes a method for producing glycine using organic solvents such as glycols. Glycine is synthesized by slowly introducing ammonia gas into an organic solvent system containing chloroacetic acid and the catalyst hexamethylenetetramine. This method allows for the recycling of the organic solvent. Patent CN1176062C discloses an alcohol-phase method for producing glycine. Although the catalyst can be recycled, the resulting glycine and ammonium chloride mixed crystals are separated using electrodialysis or alcohol precipitation, resulting in high energy consumption.

[0008] Patent US5155264A1 uses chloroacetic acid and ammonia as raw materials to separate the product glycine in the presence of a catalyst and organic amine. However, the amount of catalyst and organic amine used is large, resulting in high cost, which is not conducive to industrial production.

[0009] From the perspective of existing technologies, there is still much room for research in areas such as the technology for synthesizing glycine using chloroacetic acid ammonolysis, catalyst recycling, and the high efficiency and selectivity of catalysts. Summary of the Invention

[0010] To address the problems of poor selectivity, low yield, low purity, and high cost in the preparation of glycine in existing technologies, this invention provides a solid catalyst for the preparation of glycine and its application in the preparation of glycine. The catalyst uses a two-way dropwise addition of chloroacetic acid solution and ammonia water, employs a solid catalyst, and improves the synthesis efficiency, selectivity, and yield of glycine by controlling the system temperature and pH value.

[0011] This invention is achieved through the following technical solution:

[0012] A solid catalyst for preparing glycine is prepared by the following method: a soluble metal salt solution is loaded onto a support as a precursor, calcined at 300-600°C, cooled, impregnated in a liquid alkyl tertiary amine, dried, and ground to obtain the solid catalyst for preparing glycine.

[0013] Further, the soluble metal salt is one or more of magnesium nitrate, barium nitrate, and copper nitrate, and the mass percentage concentration of the soluble metal salt solution is 5-20%; the support is γ-Al₂O₃ or SiO₂; the molecular formula of the liquid alkyl tertiary amine is [missing information]. In this context, R1, R2, and R3 are alkyl groups with 2 ≤ n ≤ 16 carbon atoms.

[0014] Furthermore, the alkyl group R1=R2=R3 and has 2≤n≤4 carbon atoms; or R1=R2≠R3, R1 and R2 are -CH3, and R3 is an alkyl group with 8≤n≤16 carbon atoms.

[0015] Furthermore, the soluble metal salt solution is expressed as a mass ratio of M, calculated as metal oxide, to the carrier.金属氧化物 M 载体 The ratio is 10~30:100; the high-temperature calcination time is 1~3h; and the impregnation time is 15~30h.

[0016] In this invention, the solid catalyst for preparing glycine is described in its application in the preparation of glycine.

[0017] Furthermore, the method for preparing glycine using a solid catalyst includes the following steps:

[0018] (1) At room temperature and pressure, the reaction solvent and the solid catalyst used to prepare glycine are added to the reaction vessel;

[0019] (2) Control the temperature in the reaction vessel, add chloroacetic acid solution and ammonia water dropwise to the reaction vessel, and control the pH value of the system by the dropwise flow rate of ammonia water;

[0020] (3) After the addition is complete, keep the reaction at 45~60℃ for 1.5~2h. After the reaction is complete, filter the solution, precipitate the filtrate with methanol and cool it down to crystallize.

[0021] (4) Dissolve the crystals obtained from step (3) in water and separate and purify them to obtain glycine.

[0022] Further, the reaction solvent in step (1) is reverse osmosis water; the amount of the reaction solvent added is 15-30% of the total amount of materials added; the amount of the solid catalyst used to prepare glycine added is 0.5-5% of the mass of chloroacetic acid.

[0023] Further, in step (2), the temperature in the reaction vessel is 40~70℃; the mass percentage concentration of ammonia is 20~25%; the chloroacetic acid solution is methanol or aqueous solution of chloroacetic acid, and the mass percentage concentration of the chloroacetic acid solution is 10~80%; the pH value of the system is controlled by the drop rate of ammonia; the chloroacetic acid solution and ammonia are added to the reaction vessel simultaneously in a bidirectional dropping manner.

[0024] Furthermore, in step (2), the temperature in the reaction vessel is 45~60℃, the mass percentage concentration of the chloroacetic acid solution is 50~75%, and the pH value of the system is controlled by the droplet flow rate of ammonia water to be 7.5~9.

[0025] Furthermore, in step (3), the amount of methanol used is 1 to 5 times the mass of the filtrate; the separation and purification method described in step (4) is one of the following: cryogenic method at 10℃ to -5℃, membrane separation method, or electrodialysis method.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) This invention replaces traditional catalysts such as hexamethylenetetramine and other liquid catalysts with a self-made solid catalyst for the preparation of glycine, which effectively solves the problem of "secondary pollution" of the system caused by catalyst decomposition or dissolution in the reaction system in the prior art, greatly reduces the amount of catalyst used in a single reaction, and also facilitates the separation of catalyst and product and the recycling of catalyst, thereby reducing costs.

[0028] (2) The present invention adopts a bidirectional dropwise aqueous phase reaction method of chloroacetic acid solution and ammonia water, which is conducive to controlling the pH value of the reaction system to maintain within the range that is conducive to the formation of glycine and effectively suppressing the occurrence of side reactions;

[0029] (3) The method for preparing a solid catalyst for preparing glycine according to the present invention, and the method for preparing glycine using the catalyst are safe, simple to operate and easy to scale up for industrial production. Detailed Implementation

[0030] To further illustrate the positive significance of this invention, the invention is described in detail below through examples. These examples are merely illustrative and do not limit the scope of application of this invention. Based on the disclosure herein, those skilled in the art can make changes to the reagents, catalysts, and reaction process conditions within the scope of this invention. All equivalent changes or modifications made according to the spirit and essence of this invention should be covered within the protection scope of this invention.

[0031] The parts mentioned in the following examples are parts by weight.

[0032] Example 1

[0033] (1) Preparation of solid catalyst for glycine preparation: A 25% magnesium nitrate solution (converted to magnesium oxide) was mixed with γ-Al2O3 at a mass ratio of 1:5. After calcination at 400℃ for 1.5h and cooling, the mixture was impregnated in tripropylamine at room temperature (20℃) for 24h. After drying and grinding, a solid catalyst for glycine preparation (composite nano-supported organic amine-K2O / γ-Al2O3 solid catalyst) was obtained.

[0034] (2) Under normal temperature and pressure conditions, 50 parts of reverse osmosis water and 2.84 parts of the solid catalyst prepared in Example 1 for the preparation of glycine were added to the reaction vessel;

[0035] (3) Under stirring, the temperature of the reaction system in the reactor is controlled at 55±2℃. 157.5 parts of chloroacetic acid aqueous solution (the mass percentage concentration of chloroacetic acid aqueous solution is 65%) and 102 parts of ammonia water (the mass percentage concentration of ammonia water is 25%) are added to the reactor simultaneously in a two-way dropping manner. The pH value of the system is controlled to be 8.0±0.2 by the drop rate of ammonia water.

[0036] (4) After the addition is complete, keep the reaction at 50±2℃ for 2 hours, then filter and separate. The solid catalyst separated for the preparation of glycine is reused. The filtrate is transferred to an aging kettle, and methanol twice the mass of the filtrate is added to crystallize and cooled to room temperature. The crystals are filtered out, and the methanol and water obtained by distillation of the filtrate are recycled. The crystals obtained in step (4) are dissolved in water and separated by cryogenic treatment at -10~-8℃ to obtain 65.76 parts of glycine.

[0037] (5) The separated glycine was tested: the purity of glycine was 99.15%; the selectivity of the main reaction in this reaction was 94.35%; and the selectivities of the by-product iminodiacetic acid and aminotriacetic acid were 1.38% and 4.27%, respectively.

[0038] Example 2

[0039] (1) Preparation of solid catalyst for glycine preparation: A 20% copper nitrate solution (converted to copper oxide) was mixed with SiO2 at a mass ratio of 1:4. After calcination at 300℃ for 2 hours and cooling, the mixture was impregnated in dodecyl dimethyl tertiary amine at room temperature (20℃) for 24 hours. After drying and grinding, a solid catalyst for glycine preparation (composite nano-supported organic amine-CuO-MgO / SiO2 solid catalyst) was obtained.

[0040] (2) Under normal temperature and pressure conditions, 100 parts of reverse osmosis water and 2.84 parts of the solid catalyst prepared in Example 1 for the preparation of glycine were added to the reaction vessel;

[0041] (3) Under stirring, the temperature of the reaction system in the reactor is controlled at 50±2℃. 236.25 parts of chloroacetic acid aqueous solution (the mass percentage concentration of chloroacetic acid aqueous solution is 65%) and 153 parts of ammonia water (the mass percentage concentration of ammonia water is 25%) are added to the reactor simultaneously in a two-way dropping manner. The pH value of the system is controlled to be 7.5±0.1 by the drop rate of ammonia water.

[0042] (4) After the addition is complete, keep the reaction at 50±2℃ for 2 hours, then filter and separate. The solid catalyst separated for the preparation of glycine is reused. The filtered liquid is transferred to an aging kettle, and methanol three times the mass of the liquid is added to crystallize and cooled to room temperature. The crystals are filtered out, and the methanol and water obtained by distillation of the liquid are recycled.

[0043] (5) The crystals obtained in step (4) were dissolved in water and separated by cryogenic treatment at -10~-8℃ to obtain 102.69 parts of glycine;

[0044] The separated glycine was tested and found to have a purity of 99.12%; the main reaction selectivity was 93.06%; and the selectivities of the byproducts iminodiacetic acid and aminotriacetic acid were 2.04% and 4.90%, respectively.

[0045] Example 3

[0046] (1) Preparation of solid catalyst for glycine preparation: An equimolar mixture of barium nitrate (8% by mass) and magnesium nitrate (25% by mass) (converted to the total amount of barium oxide and magnesium oxide) was mixed with γ-Al2O3 at a mass ratio of 1:3. After calcination at 400℃ for 2 hours and cooling, the mixture was impregnated in tripropylamine at room temperature (20℃) for 24 hours. After drying and grinding, a solid catalyst for glycine preparation (composite nano-supported organic amine-BaO-MgO / SiO2 solid catalyst) was obtained.

[0047] (2) Under normal temperature and pressure conditions, 100 parts of reverse osmosis water and 4.25 parts of the solid catalyst prepared in Example 1 for the preparation of glycine were added to the reaction vessel;

[0048] (3) Under stirring, the temperature of the reaction system in the reactor is controlled at 50±2℃. 236.25 parts of chloroacetic acid aqueous solution (the mass percentage concentration of chloroacetic acid aqueous solution is 65%) and 153 parts of ammonia water (the mass percentage concentration of ammonia water is 25%) are added to the reactor simultaneously in a two-way dropping manner. The pH value of the system is controlled to be 9.0±0.1 by the drop rate of ammonia water.

[0049] (4) After the addition is complete, keep the reaction at 50±2℃ for 2 hours, then filter and separate. The solid catalyst separated for the preparation of glycine is reused. The filtered liquid is transferred to an aging kettle, and methanol twice the mass of the liquid is added to crystallize and cooled to room temperature. The crystals are filtered out, and the methanol and water obtained by distillation of the liquid are recycled.

[0050] (5) The crystals obtained in step (4) were dissolved in water and separated by cryogenic treatment at -10~-8℃ to obtain 98.74 parts of glycine;

[0051] The separated glycine was tested: the purity of glycine was 99.03%; the selectivity of the main reaction was 93.21%; and the selectivities of the byproducts iminodiacetic acid and aminotriacetic acid were 2.75% and 5.04%, respectively.

[0052] Example 4

[0053] The catalyst used in this application to prepare glycine is the solid catalyst recovered in step (4) of Example 1 for preparing glycine. Other process conditions and operation steps are the same as in Example 1. After the catalyst is recycled twice, the selectivity for preparing glycine is 90.23%, and the purity of glycine after separation and purification is 99.02%.

[0054] Comparative Example 1

[0055] (1) Under normal temperature and pressure conditions, 50 parts of reverse osmosis water and 15.7 parts of hexamethylenetetramine were added to the reactor;

[0056] (2) Under stirring, the temperature of the reaction system in the reactor is controlled at 55±2℃. 157.5 parts of chloroacetic acid aqueous solution (the mass percentage concentration of chloroacetic acid aqueous solution is 65%) and 102 parts of ammonia water (the mass percentage concentration of ammonia water is 25%) are added to the reactor simultaneously by bidirectional dripping. The pH value of the system is controlled to be 8.0±0.2 by the ammonia water dripping flow rate.

[0057] (3) After the addition is complete, keep the reaction at 50±2℃ for 2 hours. Transfer the reaction solution to an aging kettle, add twice the mass of the reaction solution of methanol to crystallize and cool to room temperature. Filter out the crystals, and separate the filtrate by distillation to obtain methanol and water for recycling.

[0058] (4) The crystals obtained in step (4) were dissolved in water and separated by cryogenic treatment at -10~-8℃ to obtain 70.35 parts of glycine;

[0059] The separated glycine was tested and found to have a purity of 98.79%; the main reaction selectivity was 85.23%; and the selectivities of the byproducts iminodiacetic acid and aminotriacetic acid were 10.13% and 4.64%, respectively.

[0060] Comparative Example 2

[0061] (1) The preparation of the solid catalyst used to prepare glycine is the same as in Example 1;

[0062] (2) Under normal temperature and pressure conditions, 113 parts of reverse osmosis water, 2.84 parts of the solid catalyst prepared in Example 1 for the preparation of glycine and 94.5 parts of solid chloroacetic acid were added to the reaction vessel;

[0063] (3) Under stirring, control the temperature of the reaction system in the reactor at 55±2℃. Under stirring, control the temperature of the reaction system at 55±2℃ and add 102 parts of ammonia water dropwise at a uniform rate.

[0064] (4) After the addition is complete, keep the reaction at 50±2℃ for 2 hours, then filter and separate. The solid catalyst used to prepare glycine is separated and reused. The filtered liquid is transferred to an aging kettle, and methanol twice the mass of the liquid is added to crystallize and cooled to room temperature. The crystals are filtered out, and the methanol and water obtained by distillation of the liquid are recycled.

[0065] Analysis revealed that glycine accounted for 75.16% of the product, while iminodiacetic acid accounted for 17.95% and aminotriacetic acid had a selectivity of 6.89%.

Claims

1. A solid catalyst for the preparation of glycine, characterized in that, The following method was used to prepare a solid catalyst for the preparation of glycine by loading a soluble metal salt solution onto a support as a precursor, calcining it at a high temperature of 300-600℃, cooling it, impregnating it in a liquid alkyl tertiary amine, drying it, and grinding it. The soluble metal salt is one or more of magnesium nitrate, barium nitrate, and copper nitrate, and the mass percentage concentration of the soluble metal salt solution is 5-20%; the support is γ-Al₂O₃ or SiO₂; the molecular formula of the liquid alkyl tertiary amine is [missing information]. ; The alkyl group is defined as R1=R2=R3, and has 2≤n≤4 carbon atoms; or R1=R2≠R3, R1 and R2 are -CH3, and R3 is an alkyl group with 8≤n≤16 carbon atoms.

2. The solid catalyst for preparing glycine according to claim 1, characterized in that, The soluble metal salt solution is converted to a mass ratio of M metal oxide to M carrier of 10-30:100 (based on metal oxide); the high-temperature calcination time is 1-3 hours; and the impregnation time is 15-30 hours.

3. The use of the solid catalyst for preparing glycine according to any one of claims 1 to 2 in the preparation of glycine.

4. The application according to claim 3, characterized in that, The method for preparing glycine using a solid catalyst includes the following steps: (1) At room temperature and pressure, the reaction solvent and the solid catalyst used to prepare glycine are added to the reaction vessel; (2) Control the temperature in the reaction vessel, add chloroacetic acid solution and ammonia water dropwise to the reaction vessel, and control the pH value of the system by the dropwise flow rate of ammonia water; (3) After the addition is complete, keep the reaction at 45 ~ 60℃ for 1.5 ~ 2 h. After the reaction is complete, filter the solution, precipitate the filtrate with methanol and cool it down to crystallize. (4) Dissolve the crystals obtained from step (3) in water and separate and purify them to obtain glycine.

5. The application according to claim 4, characterized in that, The reaction solvent in step (1) is reverse osmosis water; the amount of the reaction solvent added is 15 to 30% of the total amount of materials added; the amount of the solid catalyst used to prepare glycine added is 0.5 to 5% of the mass of chloroacetic acid.

6. The application according to claim 4, characterized in that, In step (2), the temperature in the reaction vessel is 40-70℃; the mass percentage concentration of ammonia is 20-25%; the chloroacetic acid solution is methanol or aqueous solution of chloroacetic acid, and the mass percentage concentration of the chloroacetic acid solution is 10-80%; the pH value of the system is controlled by the drop rate of ammonia; the chloroacetic acid solution and ammonia are added to the reaction vessel simultaneously in a bidirectional dropping manner.

7. The application according to claim 4, characterized in that, In step (2), the temperature in the reaction vessel is 45 ~ 60℃, the mass percentage concentration of the chloroacetic acid solution is 50 ~ 75%, and the pH value of the system is controlled by the droplet flow rate of ammonia water to 7.5 ~ 9.

8. The application according to claim 4, characterized in that, In step (3), the amount of methanol used is 1 to 5 times the mass of the filtrate; the separation and purification method described in step (4) is one of the following: cryogenic method at 10℃ to -5℃, membrane separation method, or electrodialysis method.

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