Extraction equipment and application thereof as well as system and method for synthesizing methyl thioglycolate

Abstract

The invention relates to the technical field of micro-chemical engineering and fine chemical engineering, and discloses extraction equipment, application of the extraction equipment and a system and method for synthesizing methyl mercaptoacetate. The extraction equipment comprises a mixing part and a separating part, and the mixing part is used for mixing extract liquor and an extracting agent; the separation part is provided with a separation cavity and a separation membrane arranged in the separation cavity, the separation cavity is divided into an organic phase channel and a water phase channel by the separation membrane, and the mixing part is communicated with the organic phase channel. The method can realize high-efficiency continuous production of methyl mercaptoacetate, and mainly solves the problems of difficult raw material storage, low raw material purity, tedious process, low yield, long reaction time and the like in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical fields of micro-chemical engineering and fine chemical engineering, and particularly relates to an extraction device and its application, as well as a system and method for synthesizing methyl mercaptoacetate. Background Art

[0002] Micro-chemical technology began in the early 1990s. This technology uses a micro-channel reactor at the micron level for reactions and is a new technology that can strengthen processes such as mixing, separation, heat exchange, and control. Micro-devices utilize the interaction between fluids and between fluids and the wall surface, as well as surface tension, in a confined space to disperse liquid-liquid / gas-liquid systems into liquid droplets in the range of 1 μm to 1 mm. By integrating and coupling micro-channel mixers, micro-channel reactors, and micro-separation devices, a new type of continuous production process is formed. Compared with traditional chemical processes, it has advantages such as a large specific surface area, a short mass transfer distance, a continuous reaction process, and an improved synthesis efficiency.

[0003] Methyl mercaptoacetate, also known as methyl thioglycolate, is an important intermediate for spices, pharmaceuticals, and pesticides, and can be used in the synthesis of stabilizers (such as PVC organotin heat stabilizers), herbicide thifensulfuron-methyl, low-temperature curing agents for epoxy resins, adhesives, and drugs such as articaine hydrochloride. There are mainly two synthesis processes for methyl mercaptoacetate: (1) The sodium thiosulfate method. Methanol is added to a reactor with reflux condensation, stirring is started, sodium thiosulfate is added, the temperature is controlled at 65 - 75°C, methyl chloroacetate is slowly added dropwise, the temperature is controlled at 70 - 80°C, the reaction time is 280 - 300 minutes, the final temperature is 80 - 85°C, after cooling, concentrated hydrochloric acid is added for acidification for 20 minutes, after hydrolysis, a certain amount of zinc powder is added in batches, and then the product is obtained after separation by extraction distillation, etc. This method has cumbersome operations and will generate a large amount of waste liquid and metal solid waste. (2) The mercaptoacetic acid esterification method, which is currently the mainstream method in industry. Using mercaptoacetic acid and methanol as starting materials, the crude product of methyl mercaptoacetate is obtained by refluxing in a stirred tank for 6 - 8 hours, and the yield of the synthesized methyl mercaptoacetate is 80 - 85%.

[0004] CN101580485A discloses a method for producing methyl mercaptoacetate. This method connects an intermittent kettle in series with a distillation device and successfully prepares high-purity methyl mercaptoacetate. However, this process has a long reaction time and a large consumption of methanol. CN115645991A discloses a micro-channel separation method and a micro-channel separation device for oil-water two-phase, which have a good separation effect on aqueous solutions and emulsions. CN110523279A discloses a membrane device and a separation method, which can significantly improve the separation efficiency of immiscible liquids. However, the molecular sieve membrane has poor tolerance to acidic substances.

[0005] There are many drawbacks in the current use of existing process methods and their devices: (1) The raw material mercaptoacetic acid must be stored refrigerated, otherwise it will decompose into mercapto compounds, resulting in a decrease in the purity of the raw material, and the quality of the raw material will also decline during a long transportation process; (2) The high price of mercaptoacetic acid limits the profit of this production process; (3) The raw material mercaptoacetic acid has a pungent and unpleasant odor and relatively high toxicity. During batch production, charging and discharging will cause the odor to escape, resulting in environmental pollution and personal injury; (4) The reaction time is long and the selectivity is low. Therefore, for this reaction process, it is very necessary to couple the reaction process and the separation process to develop a new continuous production process with high yield and high selectivity. Summary of the Invention

[0006] The object of the present invention is to overcome the problems existing in the prior art, such as difficult storage of raw materials, high price and low purity of raw materials, cumbersome process operation, pungent and unpleasant odor in the reaction process, low yield of the final product, long reaction time, etc., and to provide an extraction device and its application, as well as a system and method for synthesizing methyl mercaptoacetate, which have the advantages of high conversion rate and selectivity and continuity.

[0007] To achieve the above object, on the one hand, the present invention discloses an extraction device, and the extraction device includes an extraction apparatus, and the extraction apparatus includes:

[0008] A mixing part for mixing an extraction liquid and an extractant;

[0009] A separation part having a separation chamber and a separation membrane disposed in the separation chamber, and the separation membrane divides the separation chamber into an organic phase channel and an aqueous phase channel, wherein the mixing part is communicated with the organic phase channel.

[0010] On the second aspect, the present invention discloses the application of the extraction device of the present invention in the preparation of synthetic mercaptoacetic acid, preferably in the separation of reaction materials for synthesizing mercaptoacetic acid.

[0011] On the third aspect, the present invention discloses a system for synthesizing methyl mercaptoacetate, and the system includes: a first-stage reaction unit, an extraction unit, a distillation unit, and a second-stage reaction unit that are connected in sequence, wherein,

[0012] The first-stage reaction unit is used for making a sodium hydrosulfide solution and a chloroacetic acid solution contact and react to obtain a material containing mercaptoacetic acid;

[0013] The extraction unit includes the extraction device of the present invention and is used for separating and extracting the material containing mercaptoacetic acid;

[0014] The distillation unit is used for distilling and separating the organic phase and obtaining mercaptoacetic acid;

[0015] The second-stage reaction unit is used to bring the methanol raw material into contact with thioglycolic acid from the distillation unit in the presence of a catalyst to produce methyl thioglycolate.

[0016] The fourth aspect of the present invention discloses a method for synthesizing methyl thioglycolate, which uses the system of the present invention and includes the following:

[0017] Bring a sodium hydrosulfide solution and a chloroacetic acid solution into contact in a first-stage reaction unit to obtain a material containing thioglycolic acid;

[0018] Along the material flow direction, the mixing part of the extraction device is successively provided with an inlet for the liquid to be extracted, an inlet for the pretreatment agent, and an inlet for the extractant. Among them, the pretreatment acidifying agent inlet feeds an acidifying agent, and after the material containing thioglycolic acid is acidified, it is mixed with the extractant in the mixing part and then enters the separation part for separation through a separation membrane to form an aqueous phase entering the aqueous phase channel and an organic phase containing thioglycolic acid entering the organic phase channel;

[0019] Bring the organic phase into a distillation unit for distillation to remove the extractant in the organic phase and obtain thioglycolic acid;

[0020] In the second-stage reaction unit, in the presence of a catalyst, bring thioglycolic acid into contact with the methanol raw material to produce methyl thioglycolate.

[0021] Through the above technical solutions, the present invention has the following advantages:

[0022] (1) The extraction equipment of the present invention realizes the separation of immiscible liquids online by utilizing the difference in solution wettability.

[0023] (2) For multi-stage extraction, the number of series stages can be adjusted according to the purity required in actual situations, which is beneficial to improving the purity of the liquid.

[0024] (3) The present invention replaces the traditional expensive thioglycolic acid raw material and avoids the problem of quality decline caused by raw material storage and transportation.

[0025] (4) The present invention couples the reaction and separation processes, avoids leakage during pouring and waste of human resources, and the reaction materials form a closed-loop circuit, avoiding environmental pollution and personal injury caused by the leakage of the smell of the raw material thioglycolic acid.

[0026] (5) The reaction unit of the present invention adopts two-stage microchannel mixers and microreactors, enabling the reaction materials to be fully and rapidly mixed, strengthening the heat transfer and mass transfer effects of the reaction in the microreactor, greatly shortening the reaction time, simultaneously suppressing the occurrence of side reactions, and improving the yield and selectivity of methyl thioglycolate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of the extraction equipment according to an embodiment of the present invention;

[0028] Figure 2 It is a schematic structural diagram of a system for synthesizing methyl mercaptoacetate according to an embodiment of the present invention.

[0029] Explanation of reference numerals

[0030] 1, 2, 7, 8, 9 metering pumps; 3 first mixing section; 4 first reaction section; 5 extraction device; 6 distillation column; 10 second mixing section; 11 second reaction section; 12 inlet for liquid to be extracted; 13 inlet for pretreatment agent; 14 inlet for extractant; 15 mixing section; 16 separation section; 17 aqueous phase channel; 18 organic phase channel; 31 first microchannel mixer; 41 first microreactor; 101 second microchannel mixer; 111 second microreactor. Specific embodiments

[0031] The following further elaborates on the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present invention, and are not intended to limit the present invention.

[0032] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0033] In the present invention, unless otherwise stated, the directional terms such as "upper, lower, left, right" generally refer to the upper, lower, left, and right as shown in the accompanying drawings; "inner, outer" refer to the inner and outer relative to the contour of each component itself.

[0034] The present invention discloses an extraction device on the one hand, as Figure 1 shown. The extraction device includes an extraction device, and the extraction device includes a mixing section 15 and a separation section 16. Among them, the mixing section 15 is used to mix the extraction liquid and the extractant; the separation section 16 has a separation chamber and a separation membrane disposed in the separation chamber. The separation membrane divides the separation chamber into an organic phase channel 18 and an aqueous phase channel 17. Among them, the mixing section 15 is communicated with the organic phase channel 18. Thus, the materials in the mixing section are separated by the separation membrane to form an aqueous phase and an organic phase.

[0035] The extraction device of the present invention realizes the separation of immiscible liquids online by utilizing the difference in solution wettability.

[0036] To improve the extraction effect, in some embodiments of the present invention, there are multiple extraction devices 5 in the extraction equipment of the present invention. The multiple extraction devices are connected in series and / or in parallel to achieve multi-stage extraction of the material. Preferably, the number of multi-stage extractions is 1-10 stages. Specifically, for example, N extraction devices are connected in series to form an N-stage extraction equipment, where N is a natural number from 1 to 10. The mixing part of the (N + 1)-th extraction device is connected to the aqueous phase channel 17 of the N-th extraction device to achieve multi-stage extraction of the aqueous phase. It can be understood that the present invention is not limited to the above series form. According to the working conditions, it can also be set, for example, in the form of multiple extraction devices in parallel in each stage of the N-stage extraction equipment. The present invention has no special requirements for the setting form of the multiple extraction devices, as long as the purpose of multi-stage extraction of the aqueous phase in the present invention can be achieved. The present invention will not elaborate on this anymore.

[0037] It should be noted that, in some embodiments of the present invention, the liquid to be extracted needs to be pretreated (such as acidification) before extraction. For this purpose, the mixing part 15 is provided with a mixing channel. Along the flow direction of the material in the mixing channel, the mixing channel is successively and spacedly provided with a liquid-to-be-extracted inlet 12, a pretreatment agent inlet 13, and an extractant inlet 14.

[0038] In some embodiments of the present invention, preferably, the mixing channel is connected to the liquid-to-be-extracted inlet 12, the pretreatment agent inlet 13, and the extractant inlet 14 at an angle of 60-90°. More preferably, the mixing channel is perpendicularly connected to the liquid-to-be-extracted inlet 12, the pretreatment agent inlet 13, and the extractant inlet 14 respectively. In the embodiments of the present invention, only the vertically connected form shown in the figure is used as an example to illustrate the advantages of the present invention, but the present invention is not limited thereto.

[0039] In some embodiments of the present invention, the extraction device of the present invention is set as a micro-scale extraction device. Preferably, the mixing channel is set as a micro-mixing channel. More preferably, the hydraulic diameter of the micro-mixing channel is 200-5000 μm, and the length is 1-100 mm. Thus, it has the advantages of short mass transfer distance and good heat transfer performance.

[0040] In some embodiments of the present invention, the extraction device of the present invention is set as a micro-scale extraction device, and the hydraulic diameters of the organic phase channel 18 and the aqueous phase channel 17 are the same, preferably 200-2000 μm. Thus, it has the advantages of short mass transfer distance and good heat transfer performance. The second aspect of the present invention discloses the application of the extraction equipment described in the present invention in the preparation of thioglycolic acid, preferably in the separation of reaction materials for synthesizing thioglycolic acid.

[0041] It should be noted that there are many drawbacks in the synthesis of methyl thioglycolate in the prior art. For example, 1) Thioglycolic acid must be stored refrigerated, otherwise it will decompose into sulfhydryl compounds, resulting in a decrease in the purity of the raw material, and the long transportation process will also lead to a decline in the quality of the raw material; 2) The raw material thioglycolic acid has a pungent and unpleasant odor and high toxicity. Transferring and pouring materials during batch production will cause the odor to escape, resulting in environmental pollution and personal injuries; 3) The high price of thioglycolic acid limits the profit of this production process; 4) The reaction time is long and the selectivity is low.

[0042] To solve the above problems, on the basis of the foregoing disclosure, the present invention discloses a system for synthesizing methyl thioglycolate, as Figure 2 shown. The system includes: a first-stage reaction unit, an extraction unit, a distillation unit, and a second-stage reaction unit that are connected in sequence. Among them,

[0043] The first-stage reaction unit is used to bring a sodium hydrosulfide solution and a chloroacetic acid solution into contact to obtain a material containing thioglycolic acid;

[0044] The extraction unit includes the extraction device 5 of the present invention. Among them, the mixing part 15 of the extraction device 5 is connected to the first-stage reaction unit. The material containing thioglycolic acid is separated by extraction and through a separation membrane to form an aqueous phase (water, chloroacetic acid) and an organic phase containing thioglycolic acid. Among them, the organic phase enters the organic phase channel 18, and the aqueous phase enters the aqueous phase channel 17;

[0045] The distillation unit includes a distillation column 6 connected to the organic phase channel 17, which is used to remove the extractant in the organic phase and obtain thioglycolic acid; in the present invention, there are no special requirements for the distillation column, and the commonly used distillation columns in the prior art can be used in the present invention. And before distillation, generally a reboiler is used to preheat the organic phase;

[0046] The second-stage reaction unit is connected to the bottom of the distillation column 6 and is used to bring the bottom material thioglycolic acid of the distillation column 6 into contact with methanol raw material in the presence of a catalyst to generate methyl thioglycolate.

[0047] In this way, using the system of the present invention to replace the traditional expensive thioglycolic acid raw material with sodium hydrosulfide raw material and chloroacetic acid raw material can avoid the problem of quality decline caused by raw material storage and transportation. At the same time, the coupling reaction and the separation process are avoided, leakage during pouring and waste of human resources are avoided, and the reaction materials form a closed-loop circuit, avoiding environmental pollution and personal injuries caused by the leakage of the odor of the raw material thioglycolic acid.

[0048] To improve the yield and selectivity of methyl thioglycolate, in some embodiments of the present invention, the first-stage reaction unit includes: a first mixing part 3 and a first reaction part 4 that are connected. Among them, the first mixing part 3 is used to mix the sodium hydrosulfide solution and the chloroacetic acid solution and then enter the first reaction part 4 for reaction.

[0049] The yield and selectivity of methyl thioglycolate are improved. In some embodiments of the present invention, the second-stage reaction unit includes a second mixing section 10 and a second reaction section 11 that are connected and communicate with each other. Among them, the second mixing section 10 is connected to the bottom of the distillation column 6. The second mixing section 10 is used to mix the methanol raw material, the catalyst, and the bottom discharge (thioglycolic acid) of the distillation column 6, and then enter the second reaction section 11 for reaction.

[0050] In some embodiments of the present invention, on the basis of the foregoing disclosure, the first mixing section 3 and the second mixing section 10 are each set to be capable of realizing at least one mixing method among extended convection, separation and recombination, and cross-flow countercurrent. Preferably, the first mixing section 3 and the second mixing section 10 each include a microchannel mixer; the first reaction section 4 and the second reaction section 11 each include a microreactor. Preferably, the microreactor is selected from a microchannel reactor and / or a microtube reactor. In this way, the reaction unit uses two-stage microchannel mixers and microreactors, enabling the reaction materials to be fully and rapidly mixed, strengthening the heat and mass transfer effects of the reaction in the microreactor, greatly shortening the reaction time, while suppressing the occurrence of side reactions and improving the yield and selectivity of methyl thioglycolate.

[0051] In some embodiments of the present invention, the material of the microchannel mixer is selected from at least one of 316L stainless steel, 904 stainless steel, Hastelloy, and silicon carbide ceramic.

[0052] In some embodiments of the present invention, the equivalent diameter of the microchannels of the microchannel mixer and the microreactor is the same. Preferably, the equivalent diameter is 200 - 2000 μm. In this way, it has the advantages of short mass transfer distance and good heat transfer performance.

[0053] In order to overcome the problems existing in the existing process technologies, such as difficult raw material storage, high raw material price and low purity, cumbersome process operation, pungent and unpleasant odor in the reaction process, low final product yield, and long reaction time, the fourth aspect of the present invention provides a method for synthesizing methyl thioglycolate. This method uses the system for synthesizing methyl thioglycolate disclosed in the present invention, and this method includes the following:

[0054] Contact a sodium hydrosulfide solution and a chloroacetic acid solution in the first-stage reaction unit to obtain a material containing thioglycolic acid;

[0055] Along the material flow direction, the mixing section of the extraction device is successively provided with a liquid to be extracted inlet 12, a pretreatment agent inlet 13, and an extractant inlet 14. Among them, the pretreatment acidifying agent inlet 13 feeds an acidifying agent. In this way, after the material containing thioglycolic acid is acidified and mixed with the extractant in the mixing section 15, it enters the separation section 16 and is separated by a separation membrane to form an aqueous phase entering the aqueous phase channel 17 and an organic phase containing thioglycolic acid entering the organic phase channel 18.

[0056] The organic phase is fed into the distillation column 6 for distillation to remove the extractant in the organic phase, and thioglycolic acid is obtained.

[0057] In the second-stage reaction unit, in the presence of a catalyst, thioglycolic acid is contacted with a methanol raw material to produce methyl thioglycolate.

[0058] Thus, by using the method of the present invention to replace the traditional expensive thioglycolic acid raw material with sodium hydrosulfide raw material and chloroacetic acid raw material, problems such as quality degradation caused by raw material storage and transportation can be avoided. At the same time, the coupling reaction and separation process can avoid leakage during pouring and waste of human resources. The reaction materials form a closed-loop circuit, avoiding environmental pollution and personal injury caused by the leakage of the odor of the raw material thioglycolic acid.

[0059] To improve the yield and selectivity of methyl thioglycolate, in some embodiments of the present invention, in the first-stage reaction unit: the sodium hydrosulfide solution and the chloroacetic acid solution are mixed by a microchannel mixer and then fed into a microreactor for reaction.

[0060] In some embodiments of the present invention, in the first-stage reaction unit, the molar ratio of the chloroacetic acid solution based on chloroacetic acid to the sodium hydrosulfide solution based on sodium hydrosulfide is 1:0.8 - 2.5.

[0061] In some embodiments of the present invention, in the first-stage reaction unit, the sodium hydrosulfide solution is a 20 - 40 wt% aqueous solution of sodium hydrosulfide, and the chloroacetic acid solution is a 30 - 45 wt% aqueous solution of chloroacetic acid.

[0062] In some embodiments of the present invention, in the first-stage reaction unit, the reaction conditions of the first-stage reaction unit include: the reaction temperature is 20 - 60 °C, and the residence time is 5 - 30 min.

[0063] In some embodiments of the present invention, the flow rate in the mixing channel of the extraction device is controlled to be 0 - 12 mL / min.

[0064] In some embodiments of the present invention, the aqueous phase is subjected to multi-stage extraction through a multi-stage extraction device formed by connecting multiple extraction devices of the present invention in series and / or in parallel. That is, the aqueous phase of each stage enters the next stage for repeated extraction. Preferably, the aqueous phase in the present invention undergoes 0 - 9 stages of extraction.

[0065] In some embodiments of the present invention, acidification is carried out by adding through the pretreatment inlet 13 to adjust the pH of the material containing thioglycolic acid to 1 - 2. Preferably, the acidifying agent includes one or more of hydrochloric acid, sulfuric acid, phosphoric acid, and boric acid.

[0066] In some embodiments of the present invention, the dosage ratio of the extractant to the volume of the extraction liquid is 0.8 - 1.5:1.

[0067] In some embodiments of the present invention, the extraction conditions are normal temperature and normal pressure.

[0068] In some embodiments of the present invention, the extractant enters the mixing section through the extractant inlet 14. The extractant includes an organic solvent, preferably at least one of diethyl ether, isopropyl ether, isobutyl ether, petroleum ether, or methyl isobutyl ketone. In the embodiments of the present invention, diethyl ether is used as an example to illustrate the advantages of the present invention, but the present invention is not limited thereto.

[0069] The present invention realizes the separation of immiscible liquids online by utilizing the difference in solution wettability. It can be understood that common acid-resistant separation membranes can be used in the present invention. The following is a demonstration, but it does not limit the scope of the present invention. In some embodiments of the present invention, the material of the separation membrane is selected from one or more of Hastelloy, 316L stainless steel, and perfluoropolymer.

[0070] In the present invention, there are no special requirements for the distillation conditions, and common distillation steps can be used in the present invention. The following is a demonstration, but it does not limit the scope of the present invention. In some embodiments of the present invention, the distillation conditions of the distillation column 6 include: pressure 0 - 1 Mpa, and the top outlet temperature is 50 - 100 °C.

[0071] To improve the yield and selectivity of methyl thioglycolate, in some embodiments of the present invention, in the second-stage reaction unit, the methanol raw material, the catalyst, and thioglycolic acid are mixed through a microchannel mixer and then introduced into a microreactor for reaction. In some embodiments of the present invention, the volume flow ratio of the methanol raw material to the thioglycolic acid is 2:1 - 4:1.

[0072] In some embodiments of the present invention, the methanol content in the methanol raw material is ≥99.8 wt%, and the water content is less than 50 ppm.

[0073] In some embodiments of the present invention, the mass ratio of the catalyst to thioglycolic acid is 0.5 - 10:100.

[0074] In some embodiments of the present invention, the catalyst includes one or more of concentrated sulfuric acid, heteropolyacid, chloride, p-toluenesulfonic acid, methanesulfonic acid, and superacid, preferably p-toluenesulfonic acid. Among them, concentrated sulfuric acid refers to a commercially available reagent with a concentration of 98%, and superacid refers to a solid superacid with a Hammett acidity function H exceeding that of concentrated sulfuric acid, such as acidic resin, sulfate metal oxide, such as TiO 2 / SO 4 2- 、SO 4 - / Fe 3 0 4 -Al 2 0 3etc., the chloride can be titanium trichloride, thionyl chloride, ferric chloride, etc. In the embodiments of the present invention, p-toluenesulfonic acid and sulfuric acid are used as examples to illustrate the advantages of the present invention, but the present invention is not limited thereto.

[0075] In some embodiments of the present invention, the reaction conditions in the second-stage reaction unit include: the reaction temperature is 50-100 °C, the reaction pressure is 0-1 MPa, and the residence time is 5-20 min.

[0076] The advantages of the present invention are illustrated below through examples, but the present invention is not limited thereto.

[0077] The following Examples 1-16 adopt a system as Figures 1-2 shown. The system includes a first microchannel mixer 31, a first microreactor 41, an extraction device 5, a distillation column 6, a second microchannel mixer 101, and a second microreactor 111 that are connected in sequence. The first microchannel mixer 31 is connected to a sodium hydrosulfide solution feed pipeline and a chloroacetic acid solution feed pipeline. A metering pump 1 is installed on the sodium hydrosulfide solution feed pipeline, and a metering pump 2 is installed on the chloroacetic acid solution feed pipeline. The second microchannel mixer 101 is connected to the bottom of the distillation column 6 through a pipeline (a metering pump 8 and a reboiler are installed on this pipeline) and is provided with a methanol raw material feed pipeline (a metering pump 7 is installed) and a catalyst feed pipeline (a metering pump 9 is installed). A separation membrane is arranged in the separation chamber of the extraction device 5 to divide the separation chamber into an organic phase channel 18 and an aqueous phase channel 17. The micro-mixing channel of the extraction device is vertically connected to the organic phase channel 18. Along the flow direction of the material in the mixing channel, the micro-mixing channel is successively vertically provided with a liquid to be extracted inlet 12, a pretreatment agent inlet 13, and an extractant inlet 14. The extraction device is set to at least one stage. If it is set to a multi-stage extraction device, it is formed by connecting multiple extraction devices as Figure 1 shown in series (each stage includes an extraction device such as the (N + 1)-th stage extraction device Figure 1 shown), wherein the micro-mixing channels of the (N + 1)-th stage extraction devices are connected.

[0078] Example 1

[0079] The hydraulic diameter of the micro-mixing channel is 1000 μm, and the length is 10 mm; the hydraulic diameters of the organic phase channel 18 and the aqueous phase channel 17 are the same, which is 2000 μm; the materials of the first microchannel mixer 31 and the second microchannel mixer 101 are both stainless steel 316L, and the equivalent diameters of the microchannels in the first microchannel mixer 31, the first microreactor 41, the second microchannel mixer 101, and the second microreactor 111 are the same, all of which are 1000 μm.

[0080] Sodium hydrosulfide and solid chloroacetic acid are each prepared into aqueous solutions. The concentration of the sodium hydrosulfide solution is 25 wt%, and the concentration of the chloroacetic acid solution is 30 wt%. The two streams of materials are mixed evenly by the first microchannel mixer 31 and then enter the first microreactor 41 for reaction. The reaction temperature is 30 °C, and the residence time is controlled at 7 min to obtain the first-stage reaction solution.

[0081] The first-stage reaction solution, the acidifying agent hydrochloric acid, and the organic solvent ether enter the multi-stage extraction device in sequence, with a volume ratio of 1:1:1. The pH is adjusted to 1.5, and the flow rate in the mixing channel of the extraction device is controlled at 1.5 mL / min. The porous microfilm material in each extraction device is perfluoropolymer polytetrafluoroethylene, and the number of extraction stages is 3. The extraction conditions include: normal temperature, normal pressure;

[0082] The organic phase discharged from the organic phase channel 18 is heated to 70 °C by a reboiler and enters the distillation column 6. The distillation conditions include: a pressure of 0.1 Mpa and a top outlet temperature of 60 °C.

[0083] The bottom collected liquid of the distillation column 6 is used as the raw material for the second-stage reactor as raw material 1. The catalyst p-toluenesulfonic acid is dissolved in methanol as raw material 2. After mixing through a micromixer, it enters the second-stage microreactor for reaction. The catalyst is 5 wt% of the amount of the bottom liquid. The temperature is 90 °C. The volume ratio of methanol (the purity of commercially available anhydrous methanol is 99.8 wt%, and the water content is less than 50 ppm) to the flow rate of the bottom liquid is 1.7:1. The residence time is controlled at 10 min, and the reaction pressure is 1.0 MPa. After the final product is discharged, it is analyzed and tested by gas chromatography. The yield of methyl mercaptoacetate is 94.5%, and the selectivity is 99%.

[0084] Example 2

[0085] Sodium hydrosulfide and solid chloroacetic acid are each prepared into aqueous solutions. The concentration of the sodium hydrosulfide solution is 25 wt%, and the concentration of the chloroacetic acid solution is 30 wt%. The two streams of materials are mixed evenly by the first microchannel mixer and then enter the first microreactor for reaction. The reaction temperature is 20 °C, and the residence time is controlled at 7 min to obtain the first-stage reaction solution.

[0086] The first-stage reaction solution, the acidifying agent, and the organic solvent enter the multi-stage extraction device. The porous microfilm material in each extraction device is perfluoropolymer, and the number of extraction stages is 3. The organic phase discharged from the organic phase channel 18 is heated to 70 °C by a reboiler and enters the distillation column.

[0087] The collected liquid at the bottom of the distillation column is used as the raw material for the second-stage reactor and is fully mixed with methanol, and then enters the second-stage micro-reactor for reaction. The catalyst p-toluenesulfonic acid is dissolved in methanol, and the catalyst concentration is 5% of the mass fraction of the bottom liquid. The temperature is 90 °C, and the volume ratio of the flow rates of methanol and the bottom liquid is 1.7:1. The residence time is controlled to be 10 min. After the final product is discharged, it is analyzed and tested by gas chromatography. The yield of methyl mercaptoacetate is 85.5%, and the selectivity is 97%.

[0088] The parameter settings in Examples 2-16 are as shown in Table 1 below, and other parameter settings are the same as in Example 1:

[0089] Table 1:

[0090]

[0091] Comparative Example 1

[0092] In a batch stirred tank, the same feed amount as in Example 1 was added, and the reaction conditions were also the same as in Example 1. After reacting for 8 h, the yield of methyl mercaptoacetate was 48.7%, and the selectivity was 80.8%.

[0093] Comparative Example 2

[0094] Different from Example 1, instead of using the oil-water separation extraction device of the present invention, an extraction device in the form of traditional static liquid-liquid extraction in the prior art is used.

[0095] Result: The yield of methyl mercaptoacetate was 80.5%, and the selectivity was 90.5%

[0096] It can be seen from the results of the above examples that the present invention can effectively improve the efficiency of the reaction process, reduce the generation of by-products, and thus improve the conversion rate and selectivity of the product.

[0097] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any suitable combination of individual specific technical features. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. But these simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An extraction device, characterized in that: The extraction equipment comprises an extraction device, and the extraction device (5) comprises: A mixing section (15) for mixing the extracting liquid and the extracting agent; The separation section (16) comprises a separation chamber and a separation membrane arranged in the separation chamber, wherein the separation membrane divides the separation chamber into an organic phase channel (18) and an aqueous phase channel (17), wherein the mixing section (15) is connected to the organic phase channel (18).

2. The extraction device according to claim 1, characterized in that The extraction device (5) is provided with a plurality of extraction devices, and the plurality of extraction devices are connected in series and / or in parallel to achieve multi-stage extraction of the material, and preferably the number of the multi-stage extraction is 1-10 stages; and / or The hydrodynamic diameters of the organic phase channel (18) and the aqueous phase channel (17) are the same, preferably 200-2000 μm.

3. The extraction device according to claim 1 or 2, characterized in that: The mixing section (15) is provided with a mixing channel; Preferably, along the flow direction of the logistics in the mixing channel, the mixing channel is provided with an inlet for the liquid to be extracted (12), an inlet for the pretreatment agent (13) and an inlet for the extraction agent (14) in sequence; and / or Preferably, the mixing channel is configured as a micro-mixing channel, and more preferably, the micro-mixing channel has a hydraulic diameter of 200-5000 μm and a length of 1-100 mm; and / or Preferably, the mixing channel is connected to the extracting liquid inlet (12), the pretreatment agent inlet (13) and the extracting agent inlet (14) at an angle of 60-90°, more preferably vertically; and / or Preferably, the material of the separation membrane is selected from one or more of Hastelloy, 316L stainless steel and perfluoropolymer.

4. The use of any one of the extraction devices described in claims 1 to 3 in the synthesis of thioglycolic acid, preferably in the separation of the reaction mass of the synthesis of thioglycolic acid.

5. A system for synthesizing methyl thioglycolate, characterized in that: The system comprises: a first-stage reaction unit, an extraction unit, a distillation unit and a second-stage reaction unit which are connected in sequence, wherein: The first stage reaction unit is used to contact and react the sodium hydrosulfide solution with the chloroacetic acid solution to obtain a material containing thioglycolic acid; The extraction unit comprises the extraction device according to any one of claims 1 to 3, which is used for separating and extracting the material containing thioglycolic acid; The distillation unit is used to separate the organic phase by distillation and obtain thioglycolic acid; The second-stage reaction unit is used to contact the methanol raw material and the thioglycolic acid from the distillation unit in the presence of a catalyst to produce methyl thioglycolate.

6. The system according to claim 5, characterized in that The one-stage reaction unit comprises: A first mixing section (3) and a first reaction section (4) are connected to each other, wherein the first mixing section (3) is used to mix the sodium hydrosulfide solution and the chloroacetic acid solution and then enter the first reaction section (4) for reaction; and / or The second stage reaction unit includes: A second mixing section (10) and a second reaction section (11) are connected, wherein the second mixing section (10) is connected to the discharge section of the distillation unit, and the second mixing section (10) is used to mix the methanol raw material, the catalyst and the thioglycolic acid before entering the second reaction section (11) for reaction.

7. The system according to claim 6, characterized in that The first mixing section (3) and the second mixing section (10) are each configured to achieve at least one mixing mode of extended convection, separation recombination and cross-flow counterflow, and preferably the first mixing section (3) and the second mixing section (10) each include a microchannel mixer; and / or The first reaction part (4) and the second reaction part (11) each include a microreactor, and preferably the microreactor is selected from a microchannel reactor and / or a microtube reactor.

8. The system according to claim 7, characterized in that The material of the microchannel mixer is selected from at least one of stainless steel 316L, 904 stainless steel, Hastelloy and silicon carbide ceramics; and / or The microchannel mixer has the same equivalent diameter as the microchannel of the microreactor, preferably an equivalent diameter of 200-2000 μm.

9. A method for synthesizing methyl thioglycolate, characterized in that: The method adopts the system described in any one of claims 5 to 8, including the following: Contacting a sodium hydrosulfide solution with a chloroacetic acid solution in a first-stage reaction unit to obtain a material containing thioglycolic acid; Along the material flow direction, the mixing part of the extraction device is provided with an inlet for a liquid to be extracted (12), a pretreatment agent inlet (13) and an extractant inlet (14) in sequence, wherein the pretreatment acidifying agent inlet (13) is fed with an acidifying agent to acidify the material containing thioglycolic acid and then mix it with the extractant to separate into an aqueous phase and an organic phase containing thioglycolic acid; The organic phase is passed into a distillation unit for distillation to obtain thioglycolic acid; In the second-stage reaction unit, the obtained thioglycolic acid is brought into contact with a methanol raw material in the presence of a catalyst to produce methyl thioglycolate.

10. The method according to claim 9, wherein: In a reaction unit: The sodium hydrosulfide solution and the chloroacetic acid solution are mixed in a microchannel mixer and then introduced into a microreactor for reaction; and / or The sodium hydrosulfide solution is a 20-40 wt% sodium hydrosulfide aqueous solution, and the chloroacetic acid solution is a 30-45 wt% chloroacetic acid aqueous solution; and / or The reaction conditions of the first stage reaction unit include: reaction temperature of 20-60° C. and residence time of 5-30 min.

11. The method according to claim 9 or 10, wherein: Controlling the flow rate in the mixing channel of the extraction device to 0-12 mL / min; and / or The aqueous phase is subjected to extraction steps 0-9; and / or Adding an acidulant to adjust the pH of the material containing thioglycolic acid to 1-2, preferably the acidulant comprises one or more of hydrochloric acid, sulfuric acid, phosphoric acid and boric acid; and / or The volume ratio of the extractant to the extracting liquid is 0.8-1.5:1; and / or The extraction conditions include: normal temperature and pressure; and / or The extractant comprises an organic solvent, preferably at least one of ethyl ether, isopropyl ether, isobutyl ether, petroleum ether or methyl isobutyl methyl ether.

12. The method according to any one of claims 9 to 11, wherein: The distillation conditions include: pressure 0-1Mpa, tower top outlet temperature 50-100°C; and / or In the second-stage reaction unit, the methanol raw material, the catalyst and the thioglycolic acid are mixed through a microchannel mixer and then introduced into a microreactor for reaction; and / or The volume flow ratio of methanol feedstock to thioglycolic acid is 2:1-4:1; and / or The methanol content in the methanol raw material is ≥99.8wt%, and the water content is less than 50ppm.

13. The method according to any one of claims 9 to 12, wherein: The mass ratio of the catalyst to the thioglycolic acid is 0.5-10:100; and / or The catalyst comprises one or more of concentrated sulfuric acid, heteropolyacid, chloride, p-toluenesulfonic acid, methanesulfonic acid and superacid; and / or The reaction conditions in the second-stage reaction unit include: reaction temperature of 50-100° C., reaction pressure of 0-1 MPa, and residence time of 5-20 min.

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