Method and system for continuously preparing sodium sarcosine

Abstract

The invention relates to a method and system for continuously preparing sodium sarcosinate, and the method comprises the following steps: preparing an amine alkali solution; adding a chloroacetic acid aqueous solution and mixing with the prepared amine alkali solution; monitoring the adding proportion of the chloroacetic acid and the amine alkali, collecting a reaction solution of the chloroacetic acid aqueous solution and the amine alkali solution after a certain threshold value is reached, and taking at least part of the collected reaction solution as a circulating solution; wherein the amine-alkali solution is continuously added into the circulating liquid, the mixed circulating liquid is returned, the circulating liquid and the chloroacetic acid aqueous solution are mixed in a spraying mode and react, when discharging is needed, discharging liquid is collected, the alkali metal solution is added into the discharging liquid, methylamine in the discharging liquid is recycled, solid-liquid separation is conducted on the discharging liquid, and the methylamine-alkali mixed circulating liquid is obtained. Sodium chloride salt and a sodium sarcosinate solution are obtained; and in the production process, the circulating liquid is continuously recycled. According to the method, the content of byproducts such as MIDA in the product is effectively reduced, the yield of sodium sarcosinate is improved, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the preparation technology of sodium sarcosinate, and particularly to a method and system for the continuous preparation of sodium sarcosinate. Background Technology

[0002] Sodium sarcosinate, also known as sodium N-methylglycine, is a white, triangular solid crystalline solid. It is highly soluble in water and slightly soluble in ethanol. Sodium sarcosinate is mainly used in the production of creatine monohydrate, sarcosine, N-acylsarcosine, and their sodium salts. Creatine can effectively improve muscle strength, speed, and endurance, enhance physical fitness and training levels, and prevent fatigue. N-acylsarcosine can be used as an active agent in high-grade skin care creams, toothpastes, shampoos, as well as high-grade medicinal soaps and cosmetics. Sodium sarcosinate is also used as a dyeing auxiliary agent for fast dyes, a synthetic lubricant and rust inhibitor, a fiber dyeing agent, an antistatic agent, a softening agent, and a biochemical reagent. It is a bactericidal anionic surfactant widely used in the daily chemical industry.

[0003] Sodium sarcosinate is a non-irritating and easily biodegradable product, integral to daily life, resulting in high market demand. There are two methods for preparing sodium sarcosinate: one is the hydroxyacetonitrile method, also known as the hydrogen cyanide method; the other is the chloroacetic acid method, where chloroacetic acid reacts with methylamine in the presence of sodium hydroxide.

[0004] The existing process for producing sodium sarcosinate mainly involves a condensation reaction between hydroxyacetonitrile (or direct reaction between hydrogen cyanide and formaldehyde) and monomethylamine, followed by alkaline hydrolysis with liquid alkali to produce sodium sarcosinate. The technical (quality) indicators for preparing sodium sarcosinate aqueous solution using the hydroxyacetonitrile method are as follows:

[0005] In industrial production, hydroxyacetonitrile and monomethylamine must first be weighed separately in metering tanks before being introduced into a batch reactor for reaction. This results in a large equipment footprint, making it unsuitable for large-scale production. Furthermore, the batch production method involves long reaction times, leading to low production efficiency. Most importantly, the raw material hydroxyacetonitrile for the hydroxyacetonitrile process is expensive and highly toxic, posing significant operational risks.

[0006] The chloroacetic acid method uses chloroacetic acid as a raw material, which undergoes a condensation reaction with monomethylamine under alkaline conditions. In the presence of sodium hydroxide, an aqueous solution of sodium sarcosinate and sodium chloride is obtained. After removing the sodium chloride, the sodium sarcosinate product is obtained. The technical (quality) indicators for preparing sodium sarcosinate aqueous solution using the chloroacetic acid method are as follows:

[0007] The overall yield of the chloroacetic acid process is low, and the content of the byproduct MIDA is relatively high, which limits its downstream applications. Therefore, the industrial application of the chloroacetic acid process is greatly restricted. Summary of the Invention

[0008] The purpose of this invention is to provide a method and system for the continuous preparation of sodium sarcosinate, in order to solve the problems of the prior art.

[0009] This invention discloses a method for the continuous preparation of sodium sarcosinate, comprising: preparing an amine-base solution; mixing the prepared amine-base solution with an aqueous chloroacetic acid solution; monitoring the addition ratio of chloroacetic acid to amine-base, and when a certain threshold is reached, collecting the reaction solution of the aqueous chloroacetic acid solution and amine-base solution, and using at least a portion of the collected reaction solution as a circulating liquid; wherein, an amine-base solution is continuously added to the circulating liquid, the mixed circulating liquid is returned, and mixed with the aqueous chloroacetic acid solution by spraying and reacting; when discharge is required, the discharge liquid is collected, an alkali metal solution is added to the discharge liquid, methylamine in the discharge liquid is recovered, and the discharge liquid is subjected to solid-liquid separation to obtain sodium chloride salt and sodium sarcosinate solution; and the circulating liquid is continuously recycled during the production process.

[0010] According to one embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, the threshold is that the molar amount of chloroacetic acid added is 5% of the molar amount of amine in the amine-based solution.

[0011] According to an embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, the reaction temperature of the amine base solution and the chloroacetic acid solution is controlled at 5-50°C, preferably 15-40°C.

[0012] According to one embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, the reaction time of the amine base solution and the chloroacetic acid solution is controlled to be 10-120 min, preferably 30-90 min.

[0013] According to one embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, methylamine is obtained by evaporation or distillation of the feed liquid, the feed liquid is then concentrated, cooled to 20°C, and then separated into solid and liquid components to obtain sodium chloride salt and sodium sarcosinate solution.

[0014] According to an embodiment of a method for continuously preparing sodium sarcosinate according to the present invention, the preparation of the amine-base solution includes: preparing anhydrous methylamine into an aqueous methylamine solution with a mass percentage concentration greater than 30%, and then adding a certain proportion of sodium hydroxide to form the amine-base solution.

[0015] According to one embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, the aqueous chloroacetic acid solution is an 80% aqueous chloroacetic acid solution.

[0016] According to one embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, after preparing the amine-base solution, the amine-base solution is first circulated as a circulating liquid, and then an aqueous solution of chloroacetic acid is added to mix with the circulating amine-base solution.

[0017] According to one embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, the concentration of the aqueous methylamine solution is 40wt%-80wt%.

[0018] According to an embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, the molar ratio of the aqueous methylamine solution to sodium hydroxide in the preparation of the amine base solution is 0.5-2.5, preferably 1.0-2.0.

[0019] According to an embodiment of a method for the continuous preparation of sodium sarcosinate according to the present invention, in the mixing process of aqueous chloroacetic acid solution and amine base solution, the molar ratio of amine base solution to chloroacetic acid is controlled to be greater than 3:1, preferably 5:1-15:1.

[0020] This invention discloses a system for the continuous preparation of sodium sarcosinate, comprising: a jet mixing reactor, a reaction vessel, a discharge pump, a heat exchanger, and a circulation pump; the jet mixing reactor has a main material circulation channel and a chloroacetic acid jetting channel, and is capable of controlling the flow rate of chloroacetic acid; the reaction vessel into which the amine-base solution and chloroacetic acid solution mixed in the jet mixing reactor flow; the circulation pump is used to pump the circulating liquid from the reaction vessel back into the reaction vessel; the heat exchanger is used to control the temperature of the material before the circulating liquid enters the jet mixing reactor; the first outlet of the reaction vessel is connected to the circulation pump, the circulation pump is connected to the heat exchanger, the outlet of the heat exchanger is connected to the jet mixing reactor, one inlet of the jet mixing reactor is connected to chloroacetic acid, and the other outlet is connected to the reaction vessel to realize continuous circulation reaction; the second outlet of the reaction vessel is connected to the discharge pump.

[0021] Compared to existing intermittent dropwise reactions, this invention uses a cyclic continuous reaction, which allows for simple and precise control of the reaction ratio, temperature, and uniformity of the mixing of the two materials. The entire reaction system can be maintained in a stable state, effectively reducing the content of byproducts such as MIDA in the product, increasing the yield of sodium sarcosinate, and reducing production costs. Attached Figure Description

[0022] Figure 1 The diagram shown is a schematic diagram of the system for the continuous reaction production of sodium sarcosinate according to the present invention. Detailed Implementation

[0023] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0024] To illustrate the technical effects of the preparation method of the present invention, examples are provided below. Unless otherwise specified, all raw materials used in the following examples are existing products, and all methods used are conventional methods. Unless otherwise specified, all material contents refer to mass percentages.

[0025] This invention provides a method for the continuous preparation of sodium sarcosinate, comprising the following steps:

[0026] Prepare an amine-base solution;

[0027] The aqueous chloroacetic acid solution and the amine base solution are thoroughly mixed by dripping or spraying, with spraying being the preferred method.

[0028] When the molar amount of chloroacetic acid added reaches a certain proportion of the molar amount of amine in the amine-alkali solution, it indicates that the solution can be discharged. For example, when the molar amount of chloroacetic acid added reaches more than 5% of the molar amount of amine in the amine-alkali solution, the reaction solution of chloroacetic acid aqueous solution and amine-alkali solution is collected. A portion of the collected reaction solution can be used as the discharge solution, and another portion can be used as the circulating solution, or all of it can be used as the circulating solution.

[0029] Start by continuously adding amine-base solution to the circulating liquid, return the mixed circulating liquid, and mix it with chloroacetic acid aqueous solution by spraying, while maintaining the recycling of the circulating liquid in the reaction solution;

[0030] For the collected effluent, an alkali metal solution is added to the effluent, and then the methylamine in the effluent is recovered. Then, the effluent is subjected to solid-liquid separation to obtain sodium chloride salt and sodium sarcosinate solution.

[0031] The reaction involves continuously reacting the amine-alkali solution and the chloroacetic acid solution in a certain ratio, with continuous discharge. The reaction temperature is controlled at 5-50 degrees Celsius, and the reaction time is controlled at 10-120 minutes.

[0032] In one embodiment, sodium hydroxide or other alkali metal hydroxide catalyst is added to the effluent, and methylamine is recovered by evaporation or distillation; the effluent after evaporation or distillation of methylamine is further concentrated, then cooled to 20°C, and then separated into solid and liquid components to obtain sodium chloride salt and sodium sarcosinate solution.

[0033] The preparation of the amine-base solution specifically includes: preparing anhydrous methylamine into an aqueous solution with a mass percentage concentration greater than 30%, and adding a certain proportion of sodium hydroxide to form the amine-base solution. In one embodiment, the molar ratio of the methylamine aqueous solution to sodium hydroxide is 0.5-2.5, preferably 1.0-2.0.

[0034] The initial reaction, which involves thoroughly mixing the chloroacetic acid aqueous solution and the amine-alkali solution via spraying, specifically includes: adding a certain amount of the prepared amine-alkali solution to the reaction vessel, starting the circulation pump, and then opening the chloroacetic acid solution feed valve of the spray reactor to ensure that 80% chloroacetic acid aqueous solution is thoroughly mixed with the amine-alkali solution through the spray reactor. The temperature is controlled by a heat exchanger in the circulation pipeline, and the rate of chloroacetic acid addition is adjusted to maintain the temperature in the reaction vessel between 5-50 degrees Celsius. This step is required for the initial reaction; after circulation begins, this step can be omitted, and the circulating liquid can continue to be used for spraying and mixing the amine-alkali solution with the chloroacetic acid aqueous solution. In the initial reaction, where the chloroacetic acid aqueous solution and the amine-alkali solution are thoroughly mixed by dripping or spraying, only the reaction temperature needs to be controlled. When the molar amount of chloroacetic acid added reaches more than 5% of the molar amount of amine in the amine-alkali solution, the continuous flow of the amine-alkali solution is started and maintained.

[0035] The mixing of amine base solution and chloroacetic acid aqueous solution by spraying can be either spraying the amine base solution and mixing it with the chloroacetic acid aqueous solution, or spraying the amine base solution and the chloroacetic acid aqueous solution together.

[0036] In one embodiment, the concentration of the aqueous methylamine solution is greater than 30 wt%, preferably 40 wt%-80 wt%.

[0037] In one embodiment, the mixed circulating liquid is returned and mixed with the aqueous chloroacetic acid solution by spraying at a reaction temperature of 5-50°C, preferably 15-40°C.

[0038] In one embodiment, the mixed circulating liquid is returned and mixed with the chloroacetic acid aqueous solution by spraying, and the reaction residence time is 10-120 min, preferably 30-90 min. Specifically, the reaction residence time is achieved by controlling the discharge rate of the reaction liquid.

[0039] In one embodiment, the mixed circulating liquid is returned, and the molar ratio of the amine base solution to chloroacetic acid, which is mixed with the chloroacetic acid aqueous solution by spraying, is greater than 3:1, preferably 5:1-15:1.

[0040] In one embodiment, the circulating liquid is returned after mixing and mixed with the aqueous chloroacetic acid solution by spraying. The spraying method includes: using a high-pressure pump or other power device, the circulating liquid is sprayed at high speed into the aqueous chloroacetic acid solution to form a highly turbulent mixing zone with the aqueous chloroacetic acid solution, so as to increase the contact area and achieve uniform mixing of the two solutions at the microscale.

[0041] Figure 1This is a schematic diagram of the continuous reaction system for producing sodium sarcosinate used in this embodiment of the invention, including: a reaction vessel 1, a circulating pump 2, a heat exchanger 3, a jet mixing reactor 4, and a discharge pump 5. The reactor 1 has its inlet connected to the outlet of the chloroacetic acid and amine-alkali solution mixed in the jet mixing reactor 4. The first outlet of the reactor 1 is connected to the circulating pump 2, and the second outlet is connected to the discharge pump 5. The circulating pump 2 has its inlet connected to the reaction vessel 1 and its outlet connected to the heat exchanger 3. It also has an amine-alkali solution inlet to mix the amine-alkali solution raw material with the circulating liquid after the reaction. The heat exchanger 3 has its inlet connected to the circulating pump 2 and its outlet connected to the jet mixing reactor 4, cooling the raw materials and materials before sending them to the jet mixing reactor 4, effectively ensuring the reaction conditions. The jet mixing reactor 4 has one inlet connected to the heat exchanger 3 and another inlet for chloroacetic acid feedstock. The outlet is connected to the reactor 1. This high-speed jet mixing of the two materials ensures strong mixing and reaction intensity. The reactor utilizes the recycled material after the reaction, fully leveraging the excess methylamine in the reaction system. Furthermore, the system's reaction equilibrium principle suppresses further side reactions, thus increasing yield and reducing side reactions. The discharge pump 5 has its inlet connected to the second outlet of the reactor 1 and its outlet connected to the next process step, allowing the qualified reaction material to be transferred to subsequent processing.

[0042] The following comparative analysis demonstrates the differences in technical effects between the present invention and existing technologies.

[0043] Comparative Example 1 (Prior Art): Chloroacetic acid was added dropwise to an aqueous solution of methylamine for reaction.

[0044] Step 1: Add a methylamine aqueous solution to the reaction vessel, and then slowly add 32% liquid alkali;

[0045] Step 2: Slowly add 80% chloroacetic acid aqueous solution to the reaction vessel, controlling the temperature of the reaction vessel within 5-50℃, and keep it at this temperature for 30-60 minutes after the addition is complete;

[0046] Step 3: Slowly add a certain amount of sodium hydroxide to the solution obtained in Step 2, which is mainly sodium sarcosinate, and then distill the solution to recover the unreacted methylamine.

[0047] Step 4: Concentrate the material after amine removal in Step 3, cool the concentrated solution to 20°C, and then perform solid-liquid separation to remove sodium chloride solid. The resulting mother liquor is the sodium sarcosinate solution. Specific experimental data are as follows:

[0048]

[0049] Comparative Example 2 (Invention): Continuous Reaction

[0050] Step 1: Add methylamine aqueous solution to the reaction vessel, then slowly add 32% liquid alkali;

[0051] Step 2: Start the circulation pump, then open the chloroacetic acid solution feed valve of the jet reactor to allow the 80% chloroacetic acid aqueous solution to be fully mixed with the amine-alkali solution through the jet reactor. Control the temperature through the heat exchanger in the circulation pipeline, and adjust the rate of chloroacetic acid addition to keep the temperature in the reactor between 5-50 degrees Celsius.

[0052] Step 3: When the molar amount of chloroacetic acid added in step 2 reaches the experimental ratio, the valve of the amine-alkali solution can be opened to continuously introduce the amine-alkali solution, so that the amine-alkali solution and chloroacetic acid solution are continuously added to react in a certain ratio. Similarly, the temperature in the reactor is controlled at 5-50 degrees Celsius, and the residence time of the material in the reactor is controlled at 10-120 minutes, and the material can be continuously discharged.

[0053] Step 4: Slowly add a certain amount of sodium hydroxide to the solution obtained in the previous step, and then distill the solution to recover the unreacted methylamine.

[0054] Step 5: Concentrate the material after amine removal, cool it to 20℃, and then perform solid-liquid separation to remove sodium chloride solid. The resulting mother liquor is the sodium sarcosinate solution. Specific experimental data are as follows:

[0055]

[0056] The comparative examples above clearly demonstrate that this invention can improve yield, reduce byproducts, and achieve a more complete reaction. The patented method of this invention is a simple and efficient chemical process.

[0057] This invention utilizes a circulating spray mixing process between an amine-base aqueous solution and chloroacetic acid. By controlling the addition rate of the amine-base solution and chloroacetic acid, as well as the reaction temperature, the reaction becomes more uniform than the traditional dropwise reaction, eliminating the problem of localized chloroacetic acid excess and reducing side reactions. Simultaneously, during the cyclic reaction, the unreacted material containing monomethylamine from the reactor is recycled into the spray mixer, along with the newly added amine-base solution, ensuring that the molar ratio of monomethylamine to chloroacetic acid reaches its maximum value, fully utilizing the excess methylamine in the reaction. Furthermore, the continuous cyclic reaction returns some material, indirectly suppressing side reactions and maintaining a stable material ratio under the same reaction conditions. This further reduces the generation of the byproduct MIDA, controlling it to less than 2%, resulting in a molar yield of sodium sarcosinate of at least 92%, which can be further increased to over 95% under optimized conditions.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for the continuous preparation of sodium sarcosinate, characterized in that, include: Preparation of amine-based solutions; Add the aqueous solution of chloroacetic acid and mix with the prepared amine base solution; Monitor the addition ratio of chloroacetic acid and amine base. When a certain threshold is reached, collect the reaction solution of chloroacetic acid aqueous solution and amine base solution, and use at least a portion of the collected reaction solution as a circulating liquid. The process involves continuously adding an amine-alkali solution to the circulating liquid, returning the mixed circulating liquid, mixing it with an aqueous chloroacetic acid solution via spraying, and reacting it. When discharge is required, the discharge liquid is collected, an alkali metal solution is added to the discharge liquid, methylamine in the discharge liquid is recovered, and the discharge liquid undergoes solid-liquid separation to obtain sodium chloride salt and sodium sarcosinate solution. The circulating liquid is continuously recycled throughout the production process.

2. The method as described in claim 1, characterized in that, The threshold is that the molar amount of chloroacetic acid added is 5% of the molar amount of amine in the amine-based solution.

3. The method as described in claim 1, characterized in that, The reaction temperature of the amine-alkali solution and the chloroacetic acid solution is controlled at 5-50℃, preferably 15-40℃.

4. The method as described in claim 1, characterized in that, The reaction time between the amine base solution and the chloroacetic acid solution is controlled to be 10-120 min, preferably 30-90 min.

5. The method as described in claim 1, characterized in that, Methylamine is obtained by evaporation or distillation of the feed liquid, which is then concentrated, cooled to 20°C, and then separated into solid and liquid components to obtain sodium chloride salt and sodium sarcosinate solution.

6. The method as described in claim 1, characterized in that, The preparation of the amine-base solution involves: preparing anhydrous methylamine into an aqueous solution with a mass percentage concentration greater than 30%, and then adding a certain proportion of sodium hydroxide to form the amine-base solution.

7. The method as described in claim 1, characterized in that, The aqueous solution of chloroacetic acid is an 80% aqueous solution of chloroacetic acid.

8. The method as described in claim 1, characterized in that, After preparing the amine-alkali solution, the amine-alkali solution is first circulated as a circulating liquid, and then chloroacetic acid aqueous solution is added and mixed with the circulating amine-alkali solution.

9. The method as described in claim 6, characterized in that, The concentration of the aqueous solution of methylamine is 40wt%-80wt%.

10. The method as described in claim 6, characterized in that, The molar ratio of methylamine aqueous solution to sodium hydroxide in preparing the amine-base solution is 0.5-2.5, preferably 1.0-2.

0.

11. The method as described in claim 1, characterized in that, For the mixing process of aqueous chloroacetic acid solution and amine base solution, the molar ratio of amine base solution to chloroacetic acid should be controlled to be greater than 3:1, preferably 5:1-15:

1.

12. A system for the continuous preparation of sodium sarcosinate by any of the methods of claims 1-11, characterized in that, include: Jet mixing reactor, reaction vessel, discharge pump, heat exchanger and circulation pump; The jet mixing reactor has a main material circulation channel and a chloroacetic acid injection channel, and can control the addition flow rate of chloroacetic acid; The amine-alkali solution and chloroacetic acid solution mixed in the jet mixing reactor flow into the reaction vessel; A circulation pump is used to pump the circulating liquid from the reactor back into the reactor. A heat exchanger is used to control the temperature of the material before the circulating liquid enters the jet mixing reactor; The first outlet of the reactor is connected to a circulating pump, which is connected to a heat exchanger. The outlet of the heat exchanger is connected to a jet reactor. One inlet of the jet mixing reactor is connected to chloroacetic acid, and the other outlet is connected to the reactor to achieve continuous circulation reaction. The second outlet of the reactor is connected to a discharge pump.

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