Method for continuously preparing glycine
By adopting continuous preparation method and microchannel reactor in glycine production, the problems of high catalyst consumption, difficulty in processing ammonium chloride mother liquor and safety hazards of large reactors are solved, and efficient and environmentally friendly glycine preparation is achieved.
Patent Information
- Application Number
- CN202411897582.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-23
- Publication Date
- 2025-03-28
AI Technical Summary
In the existing glycine production methods, the consumption of the catalyst Ulotropine is high and difficult to recover, resulting in environmental protection problems; the components of ammonium chloride mother liquor are complicated after multiple cycles, making it difficult to handle; large reactors have safety hazards.
Using a continuous preparation method, ammonia chloroacetic acid solution, ulotropine solution and ammonia gas are passed into the reactor through a microchannel reactor to prepare a glycine solution and circulate between the buffer tank and the reactor, followed by cooling, crystallization, centrifugation and drying to obtain the finished glycine.
It reduces the generation of by-products, improves product quality and environmental protection, reduces the consumption of catalysts, avoids the safety hazards of large reactors, and makes the mother liquor and clean liquid of glycine solution useful in other preparation processes.
Smart Images
Figure CN119707722A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of glycine preparation, and in particular to a method for continuously preparing glycine. Background Art
[0002] Glycine has important applications in food, medicine, agriculture and industry. At present, the industrial production of glycine mainly adopts the batch process. The reactor adopts an intermittent stirred tank. The catalyst urotropine is prepared into an aqueous solution and first added to the reactor. Then the chloroacetic acid solution and ammonia gas are simultaneously introduced into the reactor at a certain flow rate. The amination reaction occurs in the reactor. After that, a large amount of methanol is added to the feed liquid (synthetic liquid) for alcohol precipitation, and then centrifuged to obtain glycine crude product (containing glycine, a small amount of ammonium chloride and urotropine) and glycine mother liquor. The glycine crude product is washed, centrifuged and dried to obtain the glycine product; the glycine mother liquor is distilled to recover the methanol therein, and then concentrated, crystallized and centrifuged to obtain ammonium chloride crystals and ammonium chloride mother liquor.
[0003] However, the existing glycine production method has many disadvantages: high catalyst consumption and environmental problems. Among them, the catalyst urotropine is disposable and is not recycled after addition, and eventually enters the wastewater and products, which not only leads to excessive consumption, but also causes subsequent environmental problems. In addition, the ammonium chloride mother liquor is recycled in the mother liquor concentration process in the prior art. The ammonium chloride mother liquor contains by-products, glycine, urotropine, methanol, ammonium chloride and other substances produced by the amination reaction, and urotropine will decompose into formaldehyde and ammonia due to the high temperature during concentration. Formaldehyde easily reacts chemically with other components in the mother liquor. In this way, after the ammonium chloride mother liquor is recycled for many times, the components are very complex, and it looks like a reddish, viscous liquid, commonly known as "red water" in the industry, and it is quite difficult to handle.
[0004] "Yellow" ammonium chloride is difficult to handle because glycine, urotropine, reaction by-products and impurities are all in the ammonium chloride mother liquor, resulting in 60-70% of the ammonium chloride obtained by concentration meeting the product standards, and the remaining 30-40% of the ammonium chloride is yellow and sticky, and the quality does not meet the product standards and needs to be further processed. The problem of treating formaldehyde-containing wastewater. When concentrated, urotropine decomposes into formaldehyde and ammonia, and formaldehyde enters the concentrated fraction. Because formaldehyde is a bactericide, the concentrated fraction containing formaldehyde cannot directly enter the biochemical system. In addition, in the prior art, a large reactor is required in the process of preparing glycine, but there are safety hazards in the use of large reactors. Summary of the invention
[0005] In view of this, the present invention aims to provide a method for continuously preparing glycine to reduce the generation of by-products and improve product quality and environmental friendliness.
[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:
[0007] A method for continuously preparing glycine comprises the following steps:
[0008] S1, passing ammonium chloroacetate solution, urotropine solution and ammonia gas into a reactor with a microchannel to prepare a glycine solution;
[0009] S2, allowing the glycine solution obtained in step S1 to circulate between the reactor and the buffer tank;
[0010] S3, sequentially cooling, crystallizing, centrifuging and drying the glycine solution in step S2 to obtain finished glycine;
[0011] S4, concentrating the mother liquor of the glycine solution remaining in the step S3, and using the concentrated clear liquor to prepare the ammonium chloroacetate in the step S1, and using the remaining mother liquor to prepare the urotropine solution in the step S1 after removing ammonium chloride.
[0012] Furthermore, in the step S1, the circulation flow rate between the buffer tank and the reactor is 50-1000 L / min, and the ratio of the circulation flow rate between the buffer tank and the reactor to the feed flow rate is 1:1-1:100.
[0013] Furthermore, in the step S1, the preheating temperature of the buffer tank and the reactor is 55-75°C; and / or the operating temperature of the reactor is 55-75°C.
[0014] Further, in the step S1, the content of ammonium chloroacetate in the ammonium chloroacetate solution is 10-50%, and / or, in the step S1, the pH of the ammonium chloroacetate solution is 6-8.
[0015] Furthermore, in the step S1, the content of urotropine in the urotropine solution is 5-20%.
[0016] Furthermore, in step S1, the preparation time of the glycine solution is 0.5-10 min.
[0017] Furthermore, in the step S1, the mass ratio of the ammonium chloroacetate to the urotropine is 1:0.05-1:0.2; and / or, in the step S1, the equivalent ratio of the ammonium chloroacetate to the ammonia gas is 1:0.95-1:1.2.
[0018] Furthermore, in step S3, the terminal temperature of crystallization is 15-30°C, and the drying temperature is 80-100°C.
[0019] Furthermore, in step S4, the mother liquor of the glycine solution is concentrated by a crystallizer, and the operating temperature of the crystallizer is 40-60° C.; after concentration, the clear liquor of the glycine solution is 10%-30% of the mother liquor.
[0020] Furthermore, the reactor is a plate-type microchannel reactor or a rotary-cut tubular microchannel reactor.
[0021] Compared with the prior art, the present invention has the following advantages:
[0022] The method for continuously preparing glycine of the present invention can effectively improve the problem of excessively high local pH in the reactor through the circulation between the glycine solution buffer tank and the reactor, thereby reducing the hydrolysis of chloroacetic acid and the decomposition of urotropine in the ammonium chloroacetate solution, and can also enable the mother liquor and the clear liquid of the glycine solution to be used for the preparation of ammonium chloroacetate and urotropine, respectively, thereby facilitating the continuous preparation of glycine and being energy-saving and environmentally friendly; compared with the preparation method using a reactor, the reactor with a microchannel can utilize the efficient mass transfer and heat transfer capacity of the reactor, which is conducive to accelerating the complete conversion of ammonium chloroacetate, making the reaction efficient, thereby facilitating reducing the retention time of the reaction solution at a relatively high temperature, and also facilitating improving the energy-saving and environmentally friendly effect in the preparation process of glycine, and having better safety compared with the solution of using a large reactor in the prior art.
[0023] In addition, the range of the circulation velocity between the buffer tank and the reactor, and the range of the circulation velocity and feed flow rate ratio between the buffer tank and the reactor are conducive to improving the buffering effect of the glycine solution, thereby reducing the pH value of the glycine solution in the reactor, and further reducing the hydrolysis of chloroacetic acid and the decomposition of tropine. The setting of the preheating temperature range of the buffer tank and the reactor is conducive to ensuring the quality of the glycine solution and controlling the pH value of the glycine solution; the setting of the operating temperature of the reactor is conducive to improving the generation efficiency of the glycine solution. The setting of the content range of chloroacetic acid ammonium in the chloroacetic acid ammonium solution and the setting of the pH range of the chloroacetic acid ammonium solution are not only conducive to the generation efficiency of the glycine solution, but also conducive to reducing the hydrolysis of chloroacetic acid in the chloroacetic acid ammonium solution.
[0024] In addition, the content of urotropine in the urotropine solution is 5-20%, which is beneficial to the generation efficiency of the glycine solution. The setting of the residence time range of the glycine solution in the reactor is beneficial to ensuring the quality of the glycine solution. The mass ratio of ammonium chloroacetate to urotropine, and the equivalent ratio of ammonium chloroacetate to ammonia are beneficial to ensuring the preparation efficiency of glycine. The setting of the terminal temperature of crystallization and the drying temperature range is beneficial to improving the preparation efficiency of finished glycine. The product maturity of the crystallizer is beneficial to the preparation of finished glycine. Both the plate microchannel reactor and the rotary cut tube microchannel reactor are beneficial to improving the preparation efficiency of the glycine solution. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:
[0026] Figure 1 The present invention is a flowchart of the method for continuously preparing glycine according to an embodiment of the present invention. DETAILED DESCRIPTION
[0027] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.
[0028] In the description of the present invention, it should be noted that if there are terms indicating orientation or positional relationship such as "upper", "lower", "inner", "back", etc., they are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, if there are terms such as "first", "second", etc., they are also used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0029] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.
[0030] This embodiment relates to a method for continuously preparing glycine, such as Figure 1 As shown in , the following steps are included:
[0031] S1. Passing ammonium chloroacetate solution, urotropine solution and ammonia into a reactor with a microchannel to obtain a glycine solution. S2. Allowing the glycine solution obtained in step S1 to circulate between the reactor and the buffer tank. S3. Cooling, crystallizing, centrifuging and drying the glycine solution in step S2 in sequence to obtain finished glycine. S4. Concentrating the mother liquor of the glycine solution remaining in step S3, and using the concentrated clear liquor to prepare the ammonium chloroacetate in step S1. The remaining mother liquor is used to prepare the urotropine solution in step S1 after removing ammonium chloride.
[0032] The method for preparing glycine continuously described in this embodiment can effectively improve the problem of excessively high local pH in the reactor through the circulation between the glycine solution buffer tank and the reactor, thereby reducing the hydrolysis of chloroacetic acid and the decomposition of urotropine in the chloroacetic acid ammonium solution, and can also make the mother liquor and clear liquid of the glycine solution respectively available for the preparation of ammonium chloroacetate and urotropine, thereby facilitating the continuous preparation of glycine and benefiting energy conservation and environmental protection. Compared with the preparation method of the reactor, by using a reactor with a microchannel, the efficient mass transfer and heat transfer capacity of the reactor can be utilized, which is beneficial to accelerate the complete conversion of chloroacetic acid ammonium, making the reaction efficient, thereby helping to reduce the retention time of the reaction solution at a higher temperature, and also helping to improve the energy conservation and environmental protection effect in the glycine preparation process.
[0033] Based on the above overall introduction, the flow chart of the method for continuously preparing glycine described in this embodiment is referred to Figure 1 As a preferred embodiment, the chloroacetic acid ammonium solution in this embodiment is obtained by using a reactor. Specifically, water and methanol are added to the reactor and stirred, and chloroacetic acid is added to the reactor, stirred to dissolve, and then ammonia gas is introduced into the reactor to obtain the chloroacetic acid ammonium solution.
[0034] Wherein, in step S1, the pH of the ammonium chloroacetate solution is 6-8, and the pH of the ammonium chloroacetate solution is preferably 7.0-7.5. This is conducive to reducing the hydrolysis of chloroacetic acid in the ammonium chloroacetate solution. During specific implementation, the pH of the ammonium chloroacetate solution can be, for example, 7.0, 7.1, 7.2, 7.3, 7.4 or 7.5. As a preferred embodiment, the content of ammonium chloroacetate in the ammonium chloroacetate solution is 10-50%, for example, the content of ammonium chloroacetate in the ammonium chloroacetate solution can be, for example, 10%, 12%, 14% or 15%. The setting of the content range of ammonium chloroacetate in the ammonium chloroacetate solution here is conducive to improving the generation efficiency of glycine.
[0035] To prepare the urotropine solution, water and methanol are added to a storage tank, and after stirring, urotropine is added to the storage tank, and dissolved to obtain the urotropine solution. The content of urotropine in the urotropine solution is 5-20%. In specific implementation, the content of urotropine in the urotropine solution can be, for example, 5%, 10%, 12%, 15%, 18% or 20%. The setting of the urotropine content range in the urotropine solution is also conducive to improving the production efficiency of glycine.
[0036] In this embodiment, the reactor is a plate microchannel reactor or a rotary cut tube microchannel reactor, both of which have microreaction channels, which are conducive to improving the preparation of glycine. As a preferred embodiment, the mass ratio of ammonium chloroacetate to urotropine is 1:0.05-1:0.2, and the mass ratio here is specifically a molar mass ratio. For example, the mass ratio of ammonium chloroacetate to urotropine is 1:0.05, 1:0.1; 1:0.15 or 1:0.2, etc. The equivalent ratio of ammonium chloroacetate to ammonia is 1:0.95-1:1.2. For example, the equivalent ratio of ammonium chloroacetate to ammonia can be 1:0.95, 1:1, or 1:1.2, etc. The setting of the mass ratio range of ammonium chloroacetate to urotropine and the setting of the equivalent ratio range of ammonium chloroacetate to ammonia are both conducive to improving the production quality of glycine.
[0037] The operating temperature of the reactor in this embodiment is 55-75°C, which is conducive to improving the production efficiency of glycine. If the operating temperature is lower than 55°C, the reaction speed will be too slow, affecting the production efficiency. When the working temperature is stable above 75°C, too many impurities will be produced in the reaction, thereby affecting the purity of the product and further affecting the yield of the product. For example, the operating temperature of the reactor may be 55°C, 60°C, 65°C or 75°C, etc. In step S1, the preparation time of the glycine solution is 0.5-10min, for example, the residence time may be 0.5min, 1min, 2min, 4min, 6min, 8min or 10min. The setting of the residence time range here is conducive to ensuring the production efficiency of the glycine solution and preventing the yield of the glycine solution product from decreasing due to too short a residence time.
[0038] In addition, in step S1 of the present embodiment, the circulation flow rate between the buffer tank and the reactor is 50-1000 L / min, and the circulation flow rate and feed flow rate ratio between the buffer tank and the reactor is 1:1-1:100. The feed flow rate refers to the flow rate of the chloroacetic acid ammonia solution, the urotropine solution and the ammonia gas into the reactor. Here, the range of the circulation flow rate between the buffer tank and the reactor, and the setting of the circulation flow rate and feed flow rate ratio range between the buffer tank and the reactor are conducive to improving the buffering effect of the glycine solution, thereby helping to reduce the pH value of the glycine solution in the reactor, and then helping to reduce the hydrolysis of chloroacetic acid and the decomposition of tropine.
[0039] In specific operation, the circulation flow rate between the buffer tank and the reactor is 50 L / min, 100 L / min, 200 L / min, 300 L / min, 400 L / min, 500 L / min, 600 L / min, 700 L / min, 800 L / min or 1000 L / min. The ratio of the circulation flow rate to the feed flow rate can be, for example, 1:1, 1:10, 1:20, 1:40, 1:50, 1:60, 1:80, 1:90 or 1:100. Of course, the values in the above ranges can also be selected according to the use requirements.
[0040] In order to further improve the effect of reducing the pH value of the glycine solution in the reactor, in step S1, the preheating temperature of the buffer tank and the reactor is 55-75°C. The setting of the preheating temperature range is conducive to improving the preparation efficiency and quality of glycine. During the specific operation, a heat exchanger can be used to adjust the preheating temperature. In this embodiment, the glycine solution after buffering flows into the material receiving tank, and then enters the crystallizer through the material receiving tank for crystallization. The crystallizer can realize continuous cooling and crystallization of the glycine solution. The crystallized glycine is centrifuged by a centrifugal device and dried by drying to obtain finished glycine.
[0041] Wherein, in step S3, the terminal temperature of crystallization of the glycine solution in the crystallizer is 15-30°C, which is conducive to improving the crystallization efficiency of glycine, and then to improving the preparation efficiency of glycine. In addition, the drying temperature when drying the centrifuged glycine is 80-100°C, and the setting of the drying temperature range here is conducive to ensuring the quality and drying efficiency of the finished glycine. During the specific operation, the terminal temperature of crystallization can be 15°C, 20°C, 25°C or 30°C. The drying temperature can be, for example, 80°C, 82°C, 85°C, 88°C, 90°C, 95°C or 100°C, etc.
[0042] In step S4, the mother liquor of the glycine solution is concentrated by a crystallizer, wherein the temperature of the crystallizer is 40-60°C, and the clear liquor of the concentrated glycine solution is 10%-30% of the mother liquor. Specifically, the crystallizer can be a continuous evaporation concentration crystallizer, and the setting of the crystallizer temperature range is conducive to improving the concentration efficiency. Among them, the temperature of the crystallizer can be, for example, 40°C, 45°C, 50°C, 55°C or 60°C. The clear liquor of the concentrated glycine solution is 10%, 20%, 25% or 30% of the mother liquor.
[0043] In this embodiment, the remaining mother liquor is centrifuged to remove ammonium chloride, and the mother liquor after removing ammonium chloride is used to prepare the urotropine solution.
[0044] The method for continuously preparing glycine in the examples is described below in conjunction with multiple preparation examples in Table 1.
[0045] Table 1:
[0046]
[0047]
[0048]
[0049]
[0050] As shown in Table 1, when each parameter is within a reasonable range, the reaction solution is prepared by multiple cycles, and when the cycle reaches 50 times, the color of the reaction solution in each preparation example is light yellow, and the overall yield is greater than 97%. It can be seen from this that the method for continuously preparing glycine in this embodiment, based on the advantages of continuous flow technology, uses a new fluid process to replace the traditional batch glycine process to produce glycine, which has great potential, is expected to complete the conversion of glycine in a relatively short time, reduce the generation of by-products, improve the yield, and can improve product quality, reduce production costs, improve economy and environmental protection, and ultimately obtain higher economic and social benefits.
[0051] In addition, in the method for continuous preparation of glycine in this embodiment, the use of a reactor with a microchannel not only facilitates more precise pH control and shortens the reaction time, but also makes the color of the reaction solution lighter during the application process.
[0052] Specifically, through impurity analysis, it can be known that the reaction needs to accurately control the pH of the reaction process to reduce the hydrolysis of chloroacetic acid and the decomposition of tropine. The use of a continuous method can accurately control the pH of the reaction process throughout the process. Through the circulation between the buffer tank and the microreactor, the problem of excessively high local pH in the reactor can be further effectively shortened, thereby reducing the hydrolysis of chloroacetic acid and the decomposition of tropine. In addition, in the kettle reaction, the time for dripping and aging adds up to about 1.5-2h to meet the central control requirements. In the reactor, due to its efficient mass transfer and heat transfer capabilities, the complete conversion of chloroacetic acid ammonia can be achieved in a short time.
[0053] Furthermore, the glycine solution generated in the autoclave process cannot be transferred in time, and the reaction can be terminated by cooling down until all the materials react completely, because the long-term high temperature will deepen the color of the reaction solution. In the present embodiment, by optimizing the steps, the reaction time is shorter, and the time of the reaction solution at high temperature is reduced, so the color of the reaction solution is lighter than the autoclave during the application. In addition, the method for preparing glycine continuously in the present embodiment does not need to use a large-scale reactor, and has better safety compared to the method of using a large-scale reactor in the traditional preparation scheme.
[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for continuously preparing glycine, characterized in that: The following steps are involved: S1, passing ammonium chloroacetate solution, urotropine solution and ammonia gas into a reactor with a microchannel to prepare a glycine solution; S2, allowing the glycine solution obtained in step S1 to circulate between the reactor and the buffer tank; S3, sequentially cooling, crystallizing, centrifuging and drying the glycine solution in step S2 to obtain finished glycine; S4, concentrating the mother liquor of the glycine solution remaining in the step S3, and using the concentrated clear liquor to prepare the ammonium chloroacetate in the step S1, and using the remaining mother liquor to prepare the urotropine solution in the step S1 after removing ammonium chloride.
2. The method for continuously preparing glycine according to claim 1, characterized in that: In the step S1, the circulation flow rate between the buffer tank and the reactor is 50-1000 L / min, and the ratio of the circulation flow rate between the buffer tank and the reactor to the feed flow rate is 1:1-1:
100.
3. The method for continuously preparing glycine according to claim 1, characterized in that: In the step S1, the preheating temperature of the buffer tank and the reactor is 55-75° C.; and / or, The operating temperature of the reactor is 55-75°C.
4. The method for continuously preparing glycine according to claim 1, characterized in that: In the step S1, the content of ammonium chloroacetate in the ammonium chloroacetate solution is 10-50%, and / or, In the step S1, the pH of the ammonium chloroacetate solution is 6-8.
5. The method for continuously preparing glycine according to claim 1, characterized in that: In the step S1, the content of urotropine in the urotropine solution is 5-20%.
6. The method for continuously preparing glycine according to claim 1, characterized in that: In step S1, the preparation time of the glycine solution is 0.5-10 min.
7. The method for continuously preparing glycine according to claim 1, characterized in that: In the step S1, the mass ratio of the ammonium chloroacetate to the hexamine is 1:0.05-1:0.2; and / or, In the step S1, the equivalent ratio of the ammonium chloroacetate to the ammonia gas is 1:0.95-1:1.
2.
8. The method for continuously preparing glycine according to claim 1, characterized in that: In step S3, the terminal temperature of crystallization is 15-30°C, and the drying temperature is 80-100°C.
9. The method for continuously preparing glycine according to claim 1, characterized in that: In the step S4, the mother liquor of the glycine solution is concentrated by a crystallizer, and the operating temperature of the crystallizer is 40-60° C.; After concentration, the clear liquid of the glycine solution is 10%-30% of the mother liquid.
10. The method for continuously preparing glycine according to any one of claims 1 to 9, characterized in that: The reactor is a plate-type microchannel reactor or a rotary-cut tubular microchannel reactor.