System and process for continuously preparing 3-(methylsulfonyl) propionic acid

Abstract

The invention relates to a system and a process for continuously preparing 3-(methylsulfonyl) propionic acid. The system comprises a feeding unit and a discharging unit, wherein the feeding unit comprises an acrylic acid continuous supply device, a sodium methyl mercaptide solution and sodium hydroxide solution mixed solution continuous supply device and an oxidizing agent continuous supply device; according to the system for continuously preparing the 3-(methylsulfonyl) propionic acid, provided by the invention, by using the continuous micro-channel reactor, rapid conversion and relatively high conversion rate of materials in addition reaction and oxidation reaction are realized; the safety of the oxidation reaction is effectively controlled, the liquid holdup is small, and the intrinsic safety of the oxidation reaction is reduced through the continuous reaction; by using the continuous extraction device, higher extraction efficiency is realized, the generation of three wastes is reduced, and higher yield is realized.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, in particular to a system and a process for continuously preparing 3-(methylsulfonyl)propionic acid. Background Art

[0002] 3-(Methylsulfonyl)propionic acid, molecular formula C4H8O4S, 3-(Methylsulfonyl)propionic acid is an organic intermediate, melting point 102-105°C, boiling point 409.0±28.0°C (Predicted), can be obtained by oxidation of 3-(methylthio)propionic acid, the oxidant can be selected from hydrogen peroxide or potassium persulfate.

[0003] For example, the document with publication number CN106631927A discloses a method for synthesizing 3-sulfonylpropionic acid compounds, which can obtain 3-sulfonylpropionic acid in one step, with green solvent and high yield. The propionic acid compounds directly synthesized in one step are important pharmaceutical intermediates, and provide a new method for synthesizing sulfonyl-substituted carboxylic acid compounds in the field of chemical synthesis.

[0004] However, in the actual production of 3-(methylsulfonyl)propionic acid, a kettle reaction is usually used for production operations, which has safety risks and the disadvantages of low extraction efficiency and low extraction purity.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The main purpose of the present application is to provide a system and process for the continuous preparation of 3-(methylsulfonyl)propionic acid, so as to solve the problems that the prior art uses a kettle reaction for production operation, has safety risks, and has the disadvantages of low extraction efficiency and low extraction purity.

[0007] In order to achieve the above object, according to one aspect of the present invention, a system for continuously preparing 3-(methylsulfonyl)propionic acid is provided, the system comprising: Feeding unit: The feeding unit includes an acrylic acid continuous feeding device, a sodium methyl mercaptan solution and sodium hydroxide solution mixed solution continuous feeding device and an oxidant continuous feeding device; Reaction unit: The reaction unit comprises a multi-stage microchannel continuous flow reactor, the inlet of the multi-stage microchannel continuous flow reactor is respectively connected to the outlet of the acrylic acid continuous drug supply device and the outlet of the sodium methyl mercaptan solution and sodium hydroxide solution mixed solution continuous supply device, and the multi-stage microchannel continuous flow reactor is connected to the outlet of the oxidant continuous supply device; Post-processing unit: the post-processing unit comprises a continuous countercurrent extraction device, and the continuous countercurrent extraction device is connected to the outlet of the multi-stage microchannel continuous flow reactor; A mixer is also provided on the pipeline between the acrylic acid continuous feeding device and the multi-stage microchannel continuous flow reactor, and the inlet of the mixer is connected to the outlet of the continuous feeding device for the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution.

[0008] Preferably, the continuous feeding device of the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution comprises a storage tank, which is used to store the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution, and the storage tank is connected to the inlet of the mixer.

[0009] Preferably, the acrylic acid continuous supply device is provided with an acrylic acid tank, the acrylic acid tank is used to store acrylic acid solution, and the acrylic acid tank is connected to the inlet of the mixer.

[0010] Preferably, the multi-stage microchannel continuous flow reactor comprises a primary reactor, a secondary reactor, and a tertiary reactor which are connected in sequence through pipelines, the outlet of the tertiary reactor is connected to the inlet of the continuous countercurrent extraction device, the inlet of the primary reactor is connected to the outlet of the mixer, and an oxidant continuous feeding device is connected to the pipeline between the primary reactor and the secondary reactor, the oxidant continuous feeding device comprises an oxidant storage tank, and the oxidant storage tank is used to store the oxidant.

[0011] Preferably, the continuous countercurrent extraction device comprises an extraction tank 1, an extraction tank 2, an extraction tank 3, and a butanone continuous drug supply device, wherein the inlet 1 of the extraction tank 1 is connected to the outlet of the tertiary reactor, the outlet 2 of the extraction tank 1 is connected to the inlet 1 of the extraction tank 2, the outlet 2 of the extraction tank 2 is connected to the inlet 1 of the extraction tank 3, the inlet 2 of the extraction tank 3 is connected to the butanone continuous drug supply device, the outlet 1 of the extraction tank 3 is connected to the inlet 2 of the extraction tank 2, and the outlet 1 of the extraction tank 2 is connected to the inlet 2 of the extraction tank 1; The material collecting device includes a decrystallization device and a centrifugal drying device which are connected in sequence. The decrystallization device is connected to the outlet 1 of the extraction tank 1, the outlet of the decrystallization device is connected to the inlet of the centrifugal drying device, and the product at the outlet 2 of the extraction tank 3 is discharged and collected through the water layer.

[0012] According to another aspect of the present invention, a process for continuously preparing 3-(methylsulfonyl)propionic acid is provided, which is carried out using the system for continuously preparing 3-(methylsulfonyl)propionic acid according to the first aspect, and the process comprises the following steps: step S1: mixing acrylic acid, a mixed solution of sodium methyl mercaptan solution and a sodium hydroxide solution to obtain a raw material mixed solution, wherein the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution is a mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution; step S2: passing the raw material mixed solution into a primary reactor in a multi-stage microchannel continuous flow reactor for reaction to obtain a reaction solution containing 3-(methylthio)propionic acid; step S3: passing the reaction solution containing 3-(methylthio)propionic acid and an oxidant solution into a secondary reactor and a tertiary reactor respectively for continuous reaction to obtain a reaction solution containing 3-(methylsulfonyl)propionic acid; step S4: purifying the reaction solution containing 3-(methylsulfonyl)propionic acid to obtain 3-(methylsulfonyl)propionic acid.

[0013] Preferably, in step S2 and step S3, the raw material mixture stays in the primary reactor, the secondary reactor and the tertiary reactor for 10-30 min, and the pressure in the primary reactor, the secondary reactor and the tertiary reactor is 0.3-1.5 MPa.

[0014] Preferably, in step S2 and step S3, the multi-stage microchannel continuous flow reactor includes a primary reactor, a secondary reactor, and a tertiary reactor connected in sequence by pipelines, the temperature of the primary reactor is 15-20°C, the temperature of the secondary reactor is 100-140°C; the temperature of the tertiary reactor is 20-25°C.

[0015] Preferably, in step S3, the oxidant includes at least one of hydrogen peroxide, hydrochloric acid solution and sodium tungstate solution, the total mass concentration of the acrylic acid solution is 30-60%, and the total mass concentration of the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution is 30-60%.

[0016] By applying the technical solution of the present application, the system for continuously preparing 3-(methylsulfonyl)propionic acid provided by the present application realizes rapid conversion of materials and good conversion rate of addition reaction and oxidation reaction by using a continuous microchannel reactor; effectively controls the safety of the oxidation reaction, reduces the liquid holding volume, and the continuous reaction reduces the intrinsic safety of the oxidation reaction; uses a continuous extraction device to achieve more efficient extraction efficiency, reduce the generation of three wastes, and achieve a higher yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of the system preparation of the present invention; Figure 2 It is the reaction flow chart of the system of the present invention; Figure 3It is a schematic diagram of the addition reaction synthesis route of the present invention; Figure 4 It is a schematic diagram of the oxidation reaction synthesis route of the present invention. DETAILED DESCRIPTION

[0018] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] As analyzed in the background technology of this application, the prior art uses a kettle reaction for production operation, which has the disadvantages of safety risks, large generation of three wastes, and high cost. In order to solve this problem, this application provides a system and process for continuously preparing 3-(methylsulfonyl)propionic acid.

[0020] In a typical embodiment of the present application, a system for continuously preparing 3-(methylsulfonyl)propionic acid, such as Figure 1-Figure 4 As shown, the system includes: a feeding unit: the feeding unit includes an acrylic acid continuous feeding device, a sodium methyl mercaptan solution and a sodium hydroxide solution mixed liquid continuous feeding device, and an oxidant continuous feeding device; a reaction unit: the reaction unit includes a multi-stage microchannel continuous flow reactor, and the inlet of the multi-stage microchannel continuous flow reactor is respectively connected to the acrylic acid continuous feeding device and the sodium methyl mercaptan solution and the sodium hydroxide solution mixed liquid continuous feeding device; a post-processing unit: the post-processing unit includes a continuous countercurrent extraction device and a collecting device connected in sequence, the continuous countercurrent extraction device is connected to the outlet of the multi-stage microchannel continuous flow reactor, and a mixer is also arranged on the pipeline between the acrylic acid continuous feeding device and the multi-stage microchannel continuous flow reactor, and the inlet of the mixer is also connected to the outlet of the sodium methyl mercaptan solution and the sodium hydroxide solution mixed liquid continuous feeding device.

[0021] By applying the technical solution of the present application, the system for continuously preparing 3-(methylsulfonyl)propionic acid provided by the present application can effectively reduce the generation of by-products, effectively shorten the reaction time, and improve the purity and yield of 3-(methylsulfonyl)propionic acid by sequentially connecting a feeding unit, a reaction unit, and a post-treatment unit, and passing them into a microchannel continuous flow reactor for reaction, which can not only reduce the production cost, but also facilitate large-scale production.

[0022] In some embodiments, the continuous feeding device for the mixture of sodium methyl mercaptan solution and sodium hydroxide solution includes a storage tank, which is used to store the mixture of sodium methyl mercaptan solution and sodium hydroxide solution, and the storage tank is connected to the inlet of the mixer. The acrylic acid continuous feeding device is provided with an acrylic acid tank, which is used to store acrylic acid solution, and the acrylic acid tank is connected to the inlet of the mixer. The oxidant continuous feeding device includes an oxidant storage tank, which is used to store the oxidant.

[0023] In some embodiments, the storage tank, acrylic acid tank and oxidant storage tank are not limited and are common storage tanks in the art. The present application uses a storage tank, an acrylic acid tank and an oxidant storage tank to store a mixture of sodium methyl mercaptan solution and sodium hydroxide solution, an acrylic acid solution and an oxidant solution, respectively. A feed pump 1 is connected to the pipeline between the storage tank and the mixer. The feed pump 1 can allow the mixture of sodium methyl mercaptan solution and sodium hydroxide solution to quickly enter the mixer under a certain pressure, thereby shortening the preparation time of 3-(methylsulfonyl)propionic acid; a feed pump 2 is connected to the pipeline between the acrylic acid tank and the mixer, which is used to quickly pass the acrylic acid solution into the mixer under a certain pressure to shorten the production time. The mixer is mainly used to fully mix the mixture of sodium methyl mercaptan solution and sodium hydroxide solution with the acrylic acid solution; a feed pump 3 is connected to the pipeline between the secondary reactor and the oxidant storage tank. The feed pump 3 can allow the oxidant solution to quickly enter the secondary reactor under a certain pressure.

[0024] In order to further improve the yield of 3-(methylthio)propionic acid, the mixed solution of sodium methylthiolate solution and sodium hydroxide solution and the acrylic acid solution are fully mixed in a mixer and then introduced into a primary reactor for reaction to avoid uneven mixing of the reaction solution resulting in unreacted raw materials continuing to participate in the reaction and generating a large amount of by-products, thereby avoiding a decrease in the yield of 3-(methylthio)propionic acid.

[0025] The above-mentioned mixer is connected to the inlet of the primary reactor, wherein the multi-stage microchannel continuous flow reactor adopts the high-efficiency mixer disclosed by patent CN218741627U. The above-mentioned multi-stage microchannel continuous flow reactor has the advantages of large specific surface area, excellent heat exchange effect, small liquid holdup and high controllability. It can not only ensure that the solution is fully mixed in the reactor, shorten the reaction time, and effectively improve the reaction efficiency, but also reduce safety hazards and ensure production safety. In addition, the multi-stage microchannel continuous flow reactor can realize hierarchical reaction by connecting the multi-stage reactors in series, thereby further improving the yield of 3-(methylsulfonyl)propionic acid.

[0026] In the present application, the multi-stage microchannel continuous flow reactor includes a primary reactor, a secondary reactor, and a tertiary reactor. The outlet of the tertiary reactor is connected to the inlet of the continuous countercurrent extraction device, the inlet of the primary reactor is connected to the outlet of the mixer, and the pipeline between the primary reactor and the secondary reactor is connected to an oxidant continuous feeding device. By connecting the three-stage reactor in series to form a multi-stage microchannel continuous flow reactor, on the one hand, graded temperature control can be achieved to avoid violent reaction to generate a large amount of by-products, further control the reaction rate, and improve the conversion rate of 3-(methylsulfonyl)propionic acid. On the other hand, the reaction raw material liquid can be fully mixed in the multi-stage microchannel continuous flow reactor, thereby shortening the reaction time, improving the reaction efficiency, and facilitating large-scale production.

[0027] The above-mentioned continuous countercurrent extraction device includes extraction tank 1, extraction tank 2, extraction tank 3, and a butanone continuous drug supply device. The inlet 1 of the extraction tank 1 is connected to the outlet of the three-stage reactor, the outlet 2 of the extraction tank 1 is connected to the inlet 1 of the extraction tank 2, the outlet 2 of the extraction tank 2 is connected to the inlet 1 of the extraction tank 3, the inlet 2 of the extraction tank 3 is connected to the butanone continuous drug supply device, the outlet 1 of the extraction tank 3 is connected to the inlet 2 of the extraction tank 2, and the outlet 1 of the extraction tank 2 is connected to the inlet 2 of the extraction tank 1.

[0028] In some embodiments, the liquid inlet on the extraction tank 1, the extraction tank 2, and the extraction tank 3 and the connection between the extraction pipeline and the solvent pipeline are all provided with control valves, and the control system controls the opening and closing of each control valve to execute the mutual series connection between each extraction tank. The present invention adopts a positive pressure closed extraction tank, and each extraction tank takes in liquid from the bottom of the tank and discharges liquid from the top of the tank, ensuring that there is no air residue in the tank to avoid the risk of oxidation of the extraction liquid; according to the different raw materials and different batches of the same raw materials, according to the mass concentration of the extraction liquid of each extraction tank, the user can set the flow path of the extraction liquid, and achieve the highest extraction yield by controlling the mass concentration gradient of the extraction liquid at the outlet of each extraction tank. At the same time, the extraction tank 3 is connected to the butanone continuous drug supply device, which is convenient for conveying the butanone solution, and the butanone solution and 3-(methylsulfonyl) propionic acid form a countercurrent, so that the butanone solution and 3-(methylsulfonyl) propionic acid can be fully in contact, improving the extraction efficiency of the extractant, and then increasing the yield of 3-(methylsulfonyl) propionic acid.

[0029] In the present application, the material collecting device includes a decrystallization device and a centrifugal drying device which are connected in sequence. The decrystallization device is connected to an outlet of an extraction tank, which not only improves the efficiency of liquid separation but also avoids the discharge of waste liquid and reduces environmental pollution.

[0030] In another typical embodiment of the present application, a process for continuously preparing 3-(methylsulfonyl)propionic acid is provided, which is carried out using the system for continuously preparing 3-(methylsulfonyl)propionic acid according to the first aspect, and the process comprises the following steps: Step S1: mixing acrylic acid, a mixed solution of sodium methyl mercaptan solution and a sodium hydroxide solution to obtain a raw material mixed solution, wherein the mixed solution of sodium methyl mercaptan solution and the sodium hydroxide solution is a mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution; Step S2: passing the raw material mixed solution into a primary reactor for reaction to obtain a reaction solution containing 3-(methylthio)propionic acid; Step S3: passing the 3-(methylthio)propionic acid reaction solution and an oxidant solution into a secondary reactor and a tertiary reactor for continuous reaction to obtain a 3-(methylsulfonyl)propionic acid aqueous solution; Step S4: purifying the 3-(methylsulfonyl)propionic acid aqueous solution reaction solution to obtain 3-(methylsulfonyl)propionic acid.

[0031] In the step S2 and step S3, the raw material mixture stays in the primary reactor, the secondary reactor and the tertiary reactor for 10-30 min (e.g., 10 min, 15 min, 20 min, 25 min, 30 min). If the residence time is too long, not only the by-products generated by the reaction increase, but also the yield of 3-(methylsulfonyl)propionic acid decreases, the production cost increases, and energy is wasted. If the residence time is too short, the sodium methyl mercaptan solution and the sodium hydroxide solution mixture, the acrylic acid solution and the oxidant solution do not react completely, resulting in a waste of raw materials and a decrease in the yield of 3-(methylsulfonyl)propionic acid. The pressure in the primary reactor, the secondary reactor and the tertiary reactor is 0.3-1. 5Mpa (such as 0.3MPa, 0.5MPa, 0.8MPa, 1.0MPa, 1.2MPa, 1.5MPa), step S2, the multistage microchannel continuous flow reactor includes a primary reactor, a secondary reactor, and a tertiary reactor connected in sequence by pipelines, the temperature of the primary reactor is 15-20°C (such as 15°C, 16°C, 17°C, 18°C, 19°C, 20°C), the temperature of the secondary reactor is 100-140°C (such as 100°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C); the temperature of the tertiary reactor is 20-25°C (such as 20°C, 21°C, 22°C, 22°C, 24°C, 25°C).

[0032] In some embodiments, in step S3, the oxidant includes at least one of hydrogen peroxide, hydrochloric acid solution, and sodium tungstate solution, preferably hydrogen peroxide, the total mass concentration of acrylic acid solution is 30-60% (such as 30%, 35%, 40%, 45%, 50%, 60%), the total mass concentration of sodium methyl mercaptan solution and sodium hydroxide solution is 30-60% (such as 30%, 35%, 40%, 45%, 50%, 60%), the total mass concentration of oxidant is 20-30%, and more preferably 25%. If the mass concentration of the oxidant is too low, it will not provide enough oxidizing ions, and a large amount of oxidant needs to be added, which requires a higher capacity of the multi-stage microchannel continuous flow reactor and increases the production cost. If the mass concentration of the oxidant is too high, the reaction rate will be accelerated, and the reaction process will be more volatile, which will bring safety hazards.

[0033] In the following, in combination with the examples and comparative examples, 3-(methylsulfonyl)propionic acid was prepared by using a multi-stage microchannel continuous flow reactor and a batch reactor, respectively, to further illustrate the beneficial effects of the present application.

[0034] Example 1 This embodiment provides a process for continuously preparing 3-(methylsulfonyl)propionic acid, which is carried out in the system provided above, and the method specifically comprises the following steps: 1. Acrylic acid, sodium methyl mercaptan solution and sodium hydroxide solution are stored in an acrylic acid tank and a storage tank respectively and the liquid levels are monitored. An acrylic acid solution (10 g) with a mass concentration of 30%, a sodium methyl mercaptan solution with a mass concentration of 30% and a sodium hydroxide solution (12 g) with a mass concentration of 30% are introduced into a mixer for mixing, and then the mixed solution is introduced into a primary reactor for reaction. The temperature of the primary reactor is controlled at 15° C., the residence time of the primary reactor is 10 min, and the pressure of the reactor is 1 MPa to obtain a reaction solution containing 3-(methylthio)propionic acid; (2) mixing the reaction solution containing 3-(methylthio)propionic acid with a 20% mass concentration of hydrogen peroxide solution (12.4 g) and passing it into a secondary reactor and a tertiary reactor for continuous reaction, wherein the residence time in the secondary reactor and the tertiary reactor is 10 min, and the pressure of the primary reactor, the secondary reactor, and the tertiary reactor is controlled to be 1 MPa, and the temperature of the secondary reactor and the tertiary reactor is 120° C. and 25° C., respectively, to obtain a reaction solution containing 3-(methylsulfonyl)propionic acid; (3) The reaction solution containing 3-(methylsulfonyl)propionic acid is passed into a continuous countercurrent extraction device, and liquid-liquid extraction is performed using butanone. Finally, the aqueous layer is collected and dried to obtain 3-(methylsulfonyl)propionic acid. The butanone layer produced during the extraction process is treated and collected by a decrystallization device and a centrifugal device.

[0035] Example 2 The difference between this embodiment and embodiment 1 is that in steps (1) and (2), the temperature of the first reactor of the multi-stage microchannel continuous flow reactor is controlled at 15°C, the temperature of the second reactor is 100°C, and the temperature of the third reactor is 25°C.

[0036] Example 3 The difference between this embodiment and embodiment 1 is that in steps (1) and (2), the temperature of the first reactor of the multi-stage microchannel continuous flow reactor is controlled at 10°C, the temperature of the second reactor is 120°C, and the temperature of the third reactor is 25°C.

[0037] Example 4 The difference between this embodiment and embodiment 1 is that in steps (1) and (2), the temperature of the first reactor of the multi-stage microchannel continuous flow reactor is controlled at 15°C, the temperature of the second reactor is 120°C, and the temperature of the third reactor is 20°C.

[0038] Example 5 The difference between this embodiment and embodiment 1 is that in steps (1) and (2), the reaction time of the first-stage reactor, the second-stage reactor and the third-stage reactor is 30 minutes.

[0039] Example 6 The difference between this embodiment and embodiment 1 is that in steps (1) and (2), the reaction module pressures of the first-stage reactor, the second-stage reactor, and the third-stage reactor are all 1.5 MPa.

[0040] Example 7 The difference between this embodiment and embodiment 1 is that in steps (1) and (2), the reaction module pressures of the first-stage reactor, the second-stage reactor, and the third-stage reactor are all 0.3 MPa.

[0041] Comparative Example 1 This comparative example provides a method for preparing 3-(methylsulfonyl)propionic acid, which is carried out according to the following steps: A 30% acrylic acid solution (10 g), a 30% sodium methyl mercaptan solution, a 30% sodium hydroxide solution (12 g) and a 20% hydrogen peroxide solution (12.4 g) were sequentially added into a batch reactor for reaction at a temperature of 40° C. for 6 h. After the reaction was completed, the temperature was cooled to room temperature, butanone solution was added for liquid-liquid extraction, the organic phase was collected for concentration, solid-liquid separation was performed, and 3-(methylsulfonyl)propionic acid was obtained after drying.

[0042] Comparative Example 2 This comparative example provides a method for preparing 3-(methylsulfonyl)propionic acid, which is carried out according to the following steps: A 30% acrylic acid solution (10 g), a 30% sodium methyl mercaptan solution and a 30% sodium hydroxide solution (12 g) are mixed in a first pipeline to obtain a mixed solution (controlled at 40° C.), a 20% hydrogen peroxide solution (12.4 g) is introduced into a second pipeline, the mixed solution and the 20% hydrogen peroxide solution (12.4 g) are introduced into a tubular reactor for reaction (the temperature of the tubular reactor is controlled at 65° C.), the raw material mixed solution stays in the tubular reactor for 15 minutes, the pressure of the tubular reactor is controlled at 0.2 MPa, and a reaction solution of 3-(methylsulfonyl) propionic acid is obtained. A butanone solution is added to the reaction solution of 3-(methylsulfonyl) propionic acid for liquid-liquid extraction, and the organic phase is collected for concentration, solid-liquid separation, and drying to obtain 3-(methylsulfonyl) propionic acid.

[0043] Test Example 1 The yield and purity of 3-(methylsulfonyl)propionic acid provided in the above examples and comparative examples were calculated respectively, and the results are shown in Table 1 below: From the data obtained from Example 1 and Comparative Examples 1 and 2, it can be seen that after adding a microchannel continuous flow reactor and reacting in multiple channels, it can be seen that the yield and purity of 3-(methylsulfonyl)propionic acid are significantly improved compared to direct reaction. After adding a microchannel continuous flow reactor, the yield and purity of 3-(methylsulfonyl)propionic acid are significantly improved. The above embodiments of the present invention achieve the following technical effects: the system for continuously preparing 3-(methylsulfonyl)propionic acid provided by the present application, by sequentially connecting a feeding unit, a reaction unit and a post-treatment unit, and passing them into a microchannel continuous flow reactor for reaction, can effectively reduce the generation of by-products, effectively shorten the reaction time, and improve the purity and yield of 3-(methylsulfonyl)propionic acid, which can not only reduce production costs, but also facilitate large-scale production.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A system for continuously preparing 3-(methylsulfonyl)propionic acid, characterized in that: The system comprises: Feeding unit: The feeding unit includes an acrylic acid continuous feeding device, a sodium methyl mercaptan solution and sodium hydroxide solution mixed solution continuous feeding device and an oxidant continuous feeding device; Reaction unit: the reaction unit comprises a multi-stage microchannel continuous flow reactor, a mixer is arranged on the pipeline between the acrylic acid continuous drug supply device and the multi-stage microchannel continuous flow reactor, the multi-stage microchannel continuous flow reactor comprises a primary reactor, a secondary reactor, and a tertiary reactor connected in sequence through pipelines, the outlet of the tertiary reactor is connected to the inlet of the continuous countercurrent extraction device, the inlet of the primary reactor is connected to the outlet of the mixer, an oxidant continuous feeding device is connected on the pipeline between the primary reactor and the secondary reactor, the oxidant continuous feeding device comprises an oxidant storage tank, and the oxidant storage tank is used to store the oxidant; Post-processing unit: The post-processing unit comprises a continuous countercurrent extraction device, the inlet of which is connected to the outlet of the multi-stage microchannel continuous flow reactor.

2. The system for continuously preparing 3-(methylsulfonyl)propionic acid according to claim 1, characterized in that: The continuous feeding device for the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution comprises a storage tank, which is used to store the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution, and the storage tank is connected to an inlet of the mixer.

3. The system for continuously preparing 3-(methylsulfonyl)propionic acid according to claim 1, characterized in that: The acrylic acid continuous supply device comprises an acrylic acid tank, which is used to store acrylic acid solution and is connected to the second inlet of the mixer.

4. The system for continuously preparing 3-(methylsulfonyl)propionic acid according to claim 1, characterized in that: The continuous countercurrent extraction device comprises an extraction tank 1, an extraction tank 2, an extraction tank 3, and a butanone continuous drug supply device, wherein the inlet 1 of the extraction tank 1 is connected to the outlet of the three-stage reactor, the outlet 2 of the extraction tank 1 is connected to the inlet 1 of the extraction tank 2, the outlet 2 of the extraction tank 2 is connected to the inlet 1 of the extraction tank 3, the inlet 2 of the extraction tank 3 is connected to the butanone continuous drug supply device, the outlet 1 of the extraction tank 3 is connected to the inlet 2 of the extraction tank 2, and the outlet 1 of the extraction tank 2 is connected to the inlet 2 of the extraction tank 1; The material collecting device includes a decrystallization device and a centrifugal drying device which are connected in sequence. The decrystallization device is connected to the outlet 1 of the extraction tank 1, the outlet of the decrystallization device is connected to the inlet of the centrifugal drying device, and the product at the outlet 2 of the extraction tank 3 is discharged and collected through the water layer.

5. A process for continuously preparing 3-(methylsulfonyl)propionic acid, characterized in that: The process is carried out using the system according to any one of claims 1 to 4, wherein the process comprises the following steps: Step S1: mixing acrylic acid, sodium methyl mercaptan solution and sodium hydroxide solution in a mixer to obtain a raw material mixed solution; Step S2: passing the raw material mixed solution into a primary reactor in a multi-stage microchannel continuous flow reactor for reaction to obtain a reaction solution containing 3-(methylthio)propionic acid; Step S3: introducing the reaction solution containing 3-(methylthio)propionic acid and the oxidant solution into the secondary reactor and the tertiary reactor respectively for continuous reaction to obtain a reaction solution containing 3-(methylsulfonyl)propionic acid; Step S4: purifying the reaction solution containing 3-(methylsulfonyl)propionic acid to obtain 3-(methylsulfonyl)propionic acid.

6. The process for continuously preparing 3-(methylsulfonyl)propionic acid according to claim 5, characterized in that: In the step S2 and step S3, the reaction time of the primary reactor, the secondary reactor and the tertiary reactor is 10-30 min, and the pressure in the primary reactor, the secondary reactor and the tertiary reactor is 0.3-1.5 Mpa.

7. The process for continuously preparing 3-(methylsulfonyl)propionic acid according to claim 5, characterized in that: In step S2 and step S3, the multi-stage microchannel continuous flow reactor includes a primary reactor, a secondary reactor, and a tertiary reactor connected in sequence by pipelines, the temperature of the primary reactor is 15-20°C, the temperature of the secondary reactor is 100-140°C; the temperature of the tertiary reactor is 20-25°C.

8. The process for continuously preparing 3-(methylsulfonyl)propionic acid according to claim 6, characterized in that: In step S3, the oxidant includes at least one of hydrogen peroxide, hydrochloric acid solution, and sodium tungstate solution, the mass concentration of the acrylic acid solution is 30-50%, and the total mass concentration of the mixed solution of sodium methyl mercaptan solution and sodium hydroxide solution is 30-60%.

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