Microchannel reactor and use thereof

Abstract

The application discloses a kind of microchannel reaction device and its application.The device includes mixing zone and reaction zone, the mixing zone includes sequentially communicated inlet channel, mixing channel and outlet channel, wherein, mixing channel includes several first mixing channels and several second mixing channels, and first mixing channel and second mixing channel are alternately arranged in circulation, each first mixing channel and each second mixing channel all have microscale eddy structure, and reaction zone is straight-through channel.This kind of structure configuration is suitable for a variety of high temperature, high pressure conditions under liquid phase reaction, in shorter residence time, can realize the uniform mixing of a variety of raw materials, and further raw materials are efficiently converted in subsequent delay reaction, for different reaction kinetics characteristics match reasonable mixing zone and the channel volume of reaction zone, can effectively optimize mass transfer, heat transfer efficiency in reaction process, guarantee efficient mixing efficiency and safety in chemical process flow.

Description

Technical Field

[0001] This invention relates to the fields of microchemical and fine chemical technology, specifically to a microchannel reaction device and its application. Background Technology

[0002] Microchemical technology originated in the early 1990s. This technology utilizes micron-sized channel reactors for reactions and is an emerging technology that can enhance processes such as mixing, separation, heat exchange, and control. A microchannel reactor is a reaction device with microstructures manufactured using microfabrication technology. Its internal sub-millimeter-level three-dimensional microscale structure can rapidly mix and disperse multiple fluids into a mixed fluid with a scale between 1 μm and 1 mm. Compared with traditional batch reactors, it has the following advantages: (1) continuous reaction process and improved synthesis efficiency; (2) controllable structure due to regular flow; (3) increased specific surface area due to microchannels, enabling rapid heat exchange; (4) enhanced mass transfer and mixing process, avoiding side reactions caused by reflux; (5) less raw material remaining in the reactor, making the reaction process safe and controllable; (6) scale-up can reduce scale-up effects.

[0003] Currently, major universities and companies both domestically and internationally have initiated research into microchemical technology. Examples include Ehrfeld's modular microreactors (a subsidiary of Bayer in Germany), IMM's SIMM microreactors (also in Germany), Siemens' Siprocess microreactor system, and Corning's G1-G4 microchannel technology. Furthermore, companies such as DuPont, BASF, Syrris, and Chinese companies like Shenshi, Microwell Technology, and Haomai have also developed their own microreactor systems and applied them to various reactions.

[0004] Patent application CN103894126A discloses a microchannel reactor and its application in preparing 1,2-hexanediol, significantly improving production efficiency and product purity. Patent application CN113620825A discloses a microchannel reactor and a method for preparing ethyl dimethylaminoacetate using this microchannel reactor, enabling continuous production and avoiding gas leakage problems. Patent application CN109293525A discloses a microchannel reactor and a method for preparing N-alkoxyoxaloyl alanine ester using this microchannel reactor. This method utilizes the microstructure and excellent mass and heat transfer capabilities of the microchannel reactor, offering advantages such as high yield and low energy consumption. However, these microchannel reactors have low mixing efficiency, which can lead to droplet breakage and backmixing in reversible reactions such as esterification, resulting in lower conversion rates and selectivity. Therefore, it is essential to develop microreactors under high-pressure conditions tailored to the physicochemical properties of the substrate. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing microchannel reactors, such as their unsuitability for high-pressure liquid-phase reactions and their low conversion rate and selectivity when used for esterification reactions, and to provide a microchannel reaction device and its application.

[0006] To achieve the above objectives, the present invention provides a microchannel reaction device, including a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel connected in sequence. The mixing channel includes a plurality of first mixing channels and a plurality of second mixing channels, and the first mixing channels and the second mixing channels are arranged alternately and cyclically. Each first mixing channel and each second mixing channel has a microscale flow structure. The reaction zone is a straight channel.

[0007] Preferably, the inlet channel of the mixing zone has at least two parallel channels, and the reactants enter the mixing channel vertically through the inlet channels.

[0008] Preferably, the inlet channel of the mixing zone has three parallel channels, and the hydraulic diameter of the inlet channel is 200-2000 μm and the length is 1-2 mm.

[0009] Preferably, the first mixing channel has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules. Module a1 is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. Taking the plane where the inlet channel is located as the reference plane, the slope of module a1 is 30-60°. The outlet of module a1 is connected to a... Module 2, a2, is a straight channel perpendicular to the reference plane, with a channel width of 0.5-1.5 mm, a height of 0.5-2 mm, a length of 1-5 mm, and a hydraulic diameter of 920-1380 μm. Modules a3, a4, and a5 are recirculation zones, where the fluid flow direction at the connection between modules a3 and a2 is perpendicular to the fluid flow direction within module a2. Module a4 is a mixing and recirculation zone, where the fluids from the upper and lower channels converge, mix, and then redistribute into two streams. A stream of fluid flows out, and the direction of the outflowing fluid is opposite to that of the fluid in module a2. The inlet cross-section is 0.5-2 mm wide and 1-4 mm high, and the outlet cross-section is 0.5-2 mm wide and 0.5-2 mm high. Module a5 is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1371-2056 μm, and the outlet hydraulic diameter is 946-1420 μm. The straight-line distance between the inlet and outlet is 0.5-2 mm, and the fluid flowing out of the outlet flows towards module a6. Module a6 and module a2 are symmetrical about each other along the central axis. The fluids in modules a6 and a7 are arranged and kept parallel to each other, with the fluid flow direction in module a6 being consistent with that in module a2. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module a7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight-line distance between the inlet and outlet sections is 1-3 mm. The fluid flowing out of the outlet enters the second mixing channel for further mixing.

[0010] Preferably, the second mixing channel has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules. Module b1 is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. Taking the plane of the inlet channel as the reference plane, the slope of module b1 is 120-150°. The outlet of module b1 is connected to module b2. Module b2 is a straight channel perpendicular to the reference plane, with a channel width of 0.5-1.5 mm, a height of 0.5-2 mm, a length of 1-5 mm, and a hydraulic diameter of 920-1380 μm. Modules b3, b4, and b5 form a recirculation zone, where the fluid flow direction at the connection between modules b3 and b2 is perpendicular to the fluid flow direction within module b2. Module b4 is a mixing and recirculation zone, where the fluids from the upper and lower channels converge and mix before being redistributed into two outflowing streams. The flow direction is opposite to that of the fluid in module b2. The inlet cross-section is 0.5-2 mm wide and 1-4 mm high, and the outlet cross-section is 0.5-2 mm wide and 0.5-2 mm high. Module b5 is a channel with a variable diameter at the front and back. The inlet hydraulic diameter is 1371-2056 μm, and the outlet hydraulic diameter is 946-1420 μm. The straight-line distance between the inlet and outlet is 0.5-2 mm, and the fluid flowing out of the outlet flows towards module b6. Module b6 and module b2 are arranged symmetrically and parallel to each other along the central axis, and module b6... The fluid flow direction inside is the same as that inside module b2. The channel width is 0.5-1.5mm, height is 0.5-2mm, length is 1-5mm, and hydraulic diameter is 920-1380μm. Module b7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380μm, and the hydraulic diameter at the outlet is 1200-1800μm. The straight-line distance between the inlet and outlet sections is 1-3mm. The fluid flowing out of the outlet enters the subsequent first mixing channel for further mixing or enters the reaction zone through the outlet channel for delayed reaction.

[0011] Preferably, the hydraulic diameter of the outlet channel of the mixing zone is 200-2000 μm and the length is 1-2 mm.

[0012] Preferably, the hydraulic diameter of the straight channel in the reaction zone is 200-2000 μm, more preferably 800-1500 μm; the length of the straight channel in the reaction zone is 20-100 cm, more preferably 50-100 cm; and the diameter of the straight channel in the reaction zone is the same as that of the outlet channel in the mixing zone.

[0013] Preferably, the material of each fluid channel of the microchannel reaction device is independently selected from stainless steel 316L, 904 stainless steel, Hastelloy, and silicon carbide ceramic.

[0014] A second aspect of the present invention provides a method for liquid-phase esterification reaction, which is carried out in the microchannel reaction device described above. The method includes: injecting the reactants and catalyst into the mixing zone through inlet channels for mixing, and then introducing them into the reaction zone for reaction.

[0015] Preferably, the method is used to synthesize methyl mercaptoacetate.

[0016] Preferably, the reaction conditions include: a temperature of 50-100℃, a pressure of 0-0.3MPa (gauge pressure), and a residence time of 30-90min.

[0017] The microchannel reaction device of this invention comprises two main regions: a mixing zone and a reaction zone. The mixing zone features a precision-machined, complex microscale flow structure for achieving uniform mixing of raw materials. The reaction zone is a straight-through channel for delayed reaction. This structural configuration is suitable for liquid-phase reactions under various high-temperature and high-pressure conditions. It can achieve uniform mixing of multiple raw materials within a short residence time and further efficiently convert the raw materials in the subsequent delayed reaction. By matching the channel volumes of the mixing and reaction zones appropriately to the reaction kinetics characteristics of different reactions, the mass and heat transfer efficiency during the reaction process can be effectively optimized, ensuring high mixing efficiency and safety in chemical processes. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the mixing zone in the microchannel reaction device described in this invention;

[0019] Figure 2 This is a schematic diagram of the structure of a portion of the fluid channels in the mixing zone of the microchannel reaction device described in this invention;

[0020] Figure 3 This is a top view of the structure of a single flow channel in the first mixing channel of the mixing zone in the microchannel reaction device of the present invention;

[0021] Figure 4 This is a top view of the structure of a flow channel in the second mixing channel of the mixing zone in the microchannel reaction device of the present invention.

[0022] Explanation of reference numerals in the attached figures

[0023] a) First mixing channel; b) Second mixing channel;

[0024] Module 1, A1; Module 2, A2; Module 3, A3; Module 4, A4; Module 5, A5; Module 6, A6; Module 7, A7;

[0025] 8. Module b1; 9. Module b2; 10. Module b3; 11. Module b4; 12. Module b5; 13. Module b6; 14. Module b7. Detailed Implementation

[0026] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or implying the number of indicated technical features. Therefore, unless otherwise stated, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "several" means two or more. The term "comprising" and any variations thereof mean non-exclusive inclusion, where one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0029] like Figure 1 and 2 As shown, the microchannel reaction device of the present invention includes a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel connected in sequence. The mixing channel includes several first mixing channels a and several second mixing channels b, which are arranged alternately and cyclically. Each first mixing channel a and each second mixing channel b has a microscale flow-around structure. The reaction zone is a straight-through channel. The mixing zone is used to achieve uniform mixing of multiple raw materials, and the reaction zone is used to perform a delayed reaction on the materials mixed in the mixing zone.

[0030] In the microchannel reaction device of the present invention, the inlet channel of the mixing zone has at least two parallel channels, and the reactants (including reactants, catalysts, and solvents) enter the mixing channel vertically through the inlet channels. In a preferred embodiment, the inlet channel of the mixing zone has three parallel channels, and the hydraulic diameter of the inlet channel is 200-2000 μm and the length is 1-2 mm.

[0031] In the microchannel reaction device described in this invention, preferably, as follows: Figure 3As shown, the first mixing channel a has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules, specifically modules a1, a2, a3, a4, a5, a6, and a7 connected sequentially. Specifically, module a1 is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. With the plane where the inlet channel is located as the reference plane, the slope of module a1 is 30-60°. The outlet of module a1 is connected to module a2, which is a straight channel perpendicular to the reference plane, with a channel width of 0. 5-1.5mm in diameter, 0.5-2mm in height, 1-5mm in length, and 920-1380μm in hydraulic diameter; Modules a3, a4, and a5 form a recirculation zone, where the fluid flow direction at the connection between module a3 and module a2 is perpendicular to the fluid flow direction within module a2; Module a4 is a mixing and recirculation zone, where the fluids from the upper and lower channels converge and mix before being redistributed into two outflowing streams, with the outflowing fluids flowing in the opposite direction to the flow direction of module a3. The fluid flow direction in module 2 is opposite. The inlet cross-section width is 0.5-2 mm and the height is 1-4 mm, while the outlet cross-section width and height are both 0.5-2 mm. Module a5 is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1371-2056 μm, and the outlet hydraulic diameter is 946-1420 μm. The straight-line distance between the inlet and outlet is 0.5-2 mm, and the fluid flowing out of the outlet flows towards module a6. Module a6 and module a2 are symmetrically arranged along the central axis and maintain mutual... The fluid flows in parallel channels, and the fluid flow direction in module a6 is the same as that in module a2. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module a7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight-line distance between the inlet and outlet sections is 1-3 mm. The fluid flowing out of the outlet enters the second mixing channel b for further mixing.

[0032] In the microchannel reaction device described in this invention, preferably, as follows: Figure 4As shown, the second mixing channel b has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules, specifically modules b1 (8), b2 (9), b3 (10), b4 (11), b5 (12), b6 (13), and b7 (14) connected sequentially. Specifically, module b1 (8) is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. Using the plane of the inlet channel as a reference plane, the slope of module b1 (8) is 120-150°. The outlet of module b1 (8) connects to module b2 (9), which is a straight channel perpendicular to the reference plane, with a channel width of 0.5-1.5 mm. The height is 0.5-2mm, the length is 1-5mm, and the hydraulic diameter is 920-1380μm; modules b3 (10), b4 (11), and b5 (12) are recirculation zones, and the fluid flow direction at the connection between module b3 (10) and module b2 (9) is perpendicular to the fluid flow direction within module b2 (9); module b4 (11) is a mixing and recirculation zone, where the fluids from the upper and lower channels converge and mix before being redistributed into two outflowing streams, with the outflowing fluids flowing in the same direction as the fluids within module b2 (9). Conversely, the inlet cross-section has a width of 0.5-2mm and a height of 1-4mm, while the outlet cross-section has a width of 0.5-2mm and a height of 0.5-2mm. Module b5 12 is a channel with a variable diameter at the front and rear, with an inlet hydraulic diameter of 1371-2056μm and an outlet hydraulic diameter of 946-1420μm. The straight-line distance between the inlet and outlet is 0.5-2mm, and the fluid flowing out of the outlet flows towards module b6. Module b6 13 and module b2 9 are arranged symmetrically and parallel to each other along the central axis, and the fluid flow direction within module b6 13 is... The fluid flow direction in module b2 9 is consistent. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module b7 14 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight-line distance between the inlet and outlet sections is 1-3 mm. The fluid flowing out of the outlet enters the subsequent first mixing channel (a) for further mixing or enters the reaction zone through the outlet channel for delayed reaction.

[0033] In the microchannel reaction device of the present invention, the hydraulic diameter of the outlet channel of the mixing zone can be 200-2000 μm and the length can be 1-2 mm.

[0034] In the microchannel reaction device of the present invention, the hydraulic diameter of the straight channel of the reaction zone is 200-2000 μm, preferably 800-1500 μm; the length of the straight channel of the reaction zone is 20-100 cm, preferably 50-100 cm; and the diameter of the straight channel of the reaction zone is the same as that of the outlet channel of the mixing zone.

[0035] In the microchannel reaction device of the present invention, the material of each fluid channel of the microchannel reaction device is independently selected from stainless steel 316L, 904 stainless steel, Hastelloy, and silicon carbide ceramic.

[0036] In some embodiments, the microchannel reaction device includes a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel connected in sequence. The inlet channel of the mixing zone has at least two parallel channels, and the reactants enter the mixing channel vertically through the inlet channel. The mixing channel includes a plurality of first mixing channels a and a plurality of second mixing channels b, which are arranged alternately and cyclically. Each first mixing channel a and each second mixing channel b has a microscale flow-around structure. The hydraulic diameter of the outlet channel of the mixing zone can be 200-2000 μm, and the length can be 1-2 mm. The reaction zone is a straight channel with a hydraulic diameter of 200-2000 μm and a length of 20-100 cm. The diameter of the straight channel is the same as that of the outlet channel of the mixing zone.

[0037] In other embodiments, the microchannel reaction device includes a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel connected in sequence. The inlet channel of the mixing zone has three parallel channels with a hydraulic diameter of 200-2000 μm and a length of 1-2 mm. The mixing channel includes several first mixing channels a and several second mixing channels b, which are arranged alternately and cyclically. Each first mixing channel a and each second mixing channel b has a microscale flow-around structure. The outlet channel of the mixing zone has a hydraulic diameter of 200-2000 μm and a length of 1-2 mm. The reaction zone is a straight channel with a hydraulic diameter of 800-1500 μm and a length of 50-100 cm. The diameter of the straight channel is the same as that of the outlet channel of the mixing zone.

[0038] In other embodiments, the microchannel reaction device includes a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel that are connected sequentially. The inlet channel of the mixing zone has at least two parallel channels, and the reactants enter the mixing channel vertically through the inlet channel. The mixing channel includes a plurality of first mixing channels a and a plurality of second mixing channels b, and the first mixing channels a and second mixing channels b are arranged alternately and cyclically. Each first mixing channel a and each second mixing channel b has a microscale flow-around structure.

[0039] The first mixing channel a has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules. Module a1 is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. With the plane where the inlet channel is located as the reference plane, the slope of module a1 is 30-60°. The outlet of module a1 is connected to module a2. Module 2 (a2) is a straight channel perpendicular to the reference plane, with a width of 0.5-1.5 mm, a height of 0.5-2 mm, a length of 1-5 mm, and a hydraulic diameter of 920-1380 μm. Modules 3 (a3), 4 (a4), and 5 (a5) form a recirculation zone. The fluid flow direction at the connection between module 3 (a3) ​​and module 2 (a2) is perpendicular to the fluid flow direction within module 2 (a2). Module 4 (a4) is a mixing and recirculation zone where the fluids from the upper and lower channels converge, mix, and then redistribute into two streams. A stream of fluid flows out, and the direction of the outflowing fluid is opposite to that of the fluid in module a2 2. The inlet cross-section is 0.5-2mm wide and 1-4mm high, and the outlet cross-section is 0.5-2mm wide and 0.5-2mm high. Module a5 5 is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1371-2056μm, and the outlet hydraulic diameter is 946-1420μm. The straight-line distance between the inlet and outlet is 0.5-2mm, and the fluid flowing out of the outlet flows towards module a6 6. Module a6 6 and module a2 2 are aligned with each other along the central axis. The fluids in modules a6 and a7 are arranged in parallel and the fluid flow direction in modules a2 and a8 is the same as that in modules a2. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module a7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight-line distance between the inlet and outlet sections is 1-3 mm. The fluid flowing out of the outlet enters the second mixing channel b for further mixing.

[0040] The second mixing channel b has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules. Module b1 is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. Taking the plane where the inlet channel is located as the reference plane, the slope of module b1 is 120-150°. The outlet of module b1 is connected to module b2. Module 2 is a straight channel perpendicular to the reference plane, with a channel width of 0.5-1.5 mm, a height of 0.5-2 mm, a length of 1-5 mm, and a hydraulic diameter of 920-1380 μm. Modules b3, b4, and b5 are recirculation zones. The fluid flow direction at the connection between module b3 and module b2 is perpendicular to the fluid flow direction within module b2. Module b4 is a mixing and recirculation zone. The fluids from the upper and lower channels converge and mix within module b4, then redistribute into two outflowing streams, with the outflowing fluids flowing in the opposite direction to the direction of the flow within module b2. The fluid flow direction within module b2 is opposite. The inlet cross-section has a width of 0.5-2 mm and a height of 1-4 mm, while the outlet cross-section has a width of 0.5-2 mm and a height of 0.5-2 mm. Module b5 is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1371-2056 μm, and the outlet hydraulic diameter is 946-1420 μm. The straight-line distance between the inlet and outlet is 0.5-2 mm, and the fluid exiting the outlet flows towards module b6. Module b6 and module b2 are arranged symmetrically and parallel to each other along the central axis, and the fluid flow within module b6... The flow direction of the fluid is consistent with that of the fluid in module b2. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module b7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight-line distance between the inlet and outlet sections is 1-3 mm. The fluid flowing out of the outlet enters the subsequent first mixing channel (a) for further mixing or enters the reaction zone through the outlet channel for delayed reaction.

[0041] The hydraulic diameter of the outlet channel of the mixing zone can be 200-2000 μm and the length can be 1-2 mm; the reaction zone is a straight channel with a hydraulic diameter of 200-2000 μm and a length of 20-100 cm, and the diameter of the straight channel is the same as that of the outlet channel of the mixing zone.

[0042] In other embodiments, the microchannel reaction device includes a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel that are sequentially connected. The inlet channel of the mixing zone has three parallel channels with a hydraulic diameter of 200-2000 μm and a length of 1-2 mm. The mixing channel includes several first mixing channels a and several second mixing channels b, which are arranged alternately and cyclically. Each first mixing channel a and each second mixing channel b has a microscale flow-around structure.

[0043] The first mixing channel a has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules. Module a1 is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. With the plane where the inlet channel is located as the reference plane, the slope of module a1 is 30-60°. The outlet of module a1 is connected to module a2. Module 2 (a2) is a straight channel perpendicular to the reference plane, with a width of 0.5-1.5 mm, a height of 0.5-2 mm, a length of 1-5 mm, and a hydraulic diameter of 920-1380 μm. Modules 3 (a3), 4 (a4), and 5 (a5) form a recirculation zone. The fluid flow direction at the connection between module 3 (a3) ​​and module 2 (a2) is perpendicular to the fluid flow direction within module 2 (a2). Module 4 (a4) is a mixing and recirculation zone where the fluids from the upper and lower channels converge, mix, and then redistribute into two streams. A stream of fluid flows out, and the direction of the outflowing fluid is opposite to that of the fluid in module a2 2. The inlet cross-section is 0.5-2mm wide and 1-4mm high, and the outlet cross-section is 0.5-2mm wide and 0.5-2mm high. Module a5 5 is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1371-2056μm, and the outlet hydraulic diameter is 946-1420μm. The straight-line distance between the inlet and outlet is 0.5-2mm, and the fluid flowing out of the outlet flows towards module a6 6. Module a6 6 and module a2 2 are aligned with each other along the central axis. The fluids in modules a6 and a7 are arranged in parallel and the fluid flow direction in modules a2 and a8 is the same as that in modules a2. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module a7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight-line distance between the inlet and outlet sections is 1-3 mm. The fluid flowing out of the outlet enters the second mixing channel b for further mixing.

[0044] The second mixing channel b has two symmetrically arranged upper and lower flow channels along the central axis. Each flow channel is divided into seven modules. Module b1 is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm, and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm, and the channel height is 0.5-2 mm. The straight-line distance between the inlet and outlet sections is 1-3 mm. Taking the plane where the inlet channel is located as the reference plane, the slope of module b1 is 120-150°. The outlet of module b1 is connected to module b2. Module 2 is a straight channel perpendicular to the reference plane, with a channel width of 0.5-1.5 mm, a height of 0.5-2 mm, a length of 1-5 mm, and a hydraulic diameter of 920-1380 μm. Modules b3, b4, and b5 are recirculation zones. The fluid flow direction at the connection between module b3 and module b2 is perpendicular to the fluid flow direction within module b2. Module b4 is a mixing and recirculation zone. The fluids from the upper and lower channels converge and mix within module b4, then redistribute into two outflowing streams, with the outflowing fluids flowing in the opposite direction to the direction of the flow within module b2. The fluid flow direction within module b2 is opposite. The inlet cross-section has a width of 0.5-2 mm and a height of 1-4 mm, while the outlet cross-section has a width of 0.5-2 mm and a height of 0.5-2 mm. Module b5 is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1371-2056 μm, and the outlet hydraulic diameter is 946-1420 μm. The straight-line distance between the inlet and outlet is 0.5-2 mm, and the fluid exiting the outlet flows towards module b6. Module b6 and module b2 are arranged symmetrically and parallel to each other along the central axis, and the fluid flow within module b6... The flow direction of the fluid is consistent with that of the fluid in module b2. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module b7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight-line distance between the inlet and outlet sections is 1-3 mm. The fluid flowing out of the outlet enters the subsequent first mixing channel (a) for further mixing or enters the reaction zone through the outlet channel for delayed reaction.

[0045] The hydraulic diameter of the outlet channel of the mixing zone can be 200-2000 μm and the length can be 1-2 mm; the reaction zone is a straight channel with a hydraulic diameter of 800-1500 μm and a length of 50-100 cm, and the diameter of the straight channel is the same as that of the outlet channel of the mixing zone.

[0046] The present invention also provides a method for liquid-phase esterification reaction, which is carried out in the microchannel reaction device described above. The method includes: injecting the reactants and catalyst into the mixing zone through inlet channels for mixing, and then entering the reaction zone for reaction.

[0047] In some embodiments, the liquid-phase esterification reaction method of the present invention is used to synthesize methyl mercaptoacetate, wherein the inlet channel of the mixing zone in the microchannel reactor has three parallel channels (upper, middle, and lower). A first reactant (e.g., methanol) enters the mixing zone through the upper and lower channels, and a second reactant (e.g., mercaptoacetic acid) enters the mixing zone through the middle channel after dissolving the catalyst. The catalyst concentration can be 0.5-10% by weight. The catalyst can be, for example, selected from p-toluenesulfonic acid, concentrated sulfuric acid, methanesulfonic acid, titanium trichloride, and SO4. 2- / TiO2 is a super acid.

[0048] In a preferred embodiment, when synthesizing methyl mercaptoacetate using the microchannel reaction apparatus described in this invention, the reaction conditions include: a temperature of 50-100°C, a pressure of 0-0.3 MPa (gauge pressure), and a residence time of 30-90 min.

[0049] The microchannel reaction device and its applications described in this invention are further illustrated below through embodiments. These embodiments are implemented based on the technical solution of this invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of this invention is not limited to the following embodiments.

[0050] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0051] Example 1

[0052] The microchannel reaction device used in this embodiment includes a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel that are connected sequentially. The mixing channel includes a plurality of first mixing channels a and a plurality of second mixing channels b, and the first mixing channels a and the second mixing channels b are arranged alternately and cyclically.

[0053] The first mixing channel a is divided into 7 modules. Module a1 is a channel with varying diameters at both ends. The hydraulic diameter at the inlet is 1714 μm, and the channel height is 1.5 mm. The hydraulic diameter at the outlet is 1150 μm, and the channel height is 1.45 mm. The straight-line distance between the inlet and outlet sections is 2 mm. With the plane containing the inlet channel as the reference plane, the slope of module a1 is 45°. The outlet of module a1 connects to module a2, which is a straight channel perpendicular to the reference plane. The channel is 0.95mm wide, 1.45mm high, and 3mm long, with a hydraulic diameter of 1150μm. Modules A3, A4, and A5 form a reflux zone. The fluid flow direction at the connection between module A3 and module A2 is perpendicular to the fluid flow direction within module A2. Module A4 is a mixing and reflux zone, where the fluids from the upper and lower channels converge, mix, and then redistribute into two streams that flow outwards. The fluid flow direction is opposite to that in module a2. The inlet cross-section is 1 mm wide and 3 mm high, and the outlet cross-section is 2 mm wide and 1.5 mm high. Module a5 is a channel with a variable diameter at the front and back. The inlet hydraulic diameter is 1714 μm, the outlet hydraulic diameter is 1183 μm, and the height is 1.45 mm. The straight-line distance between the inlet and outlet cross-sections is 1 mm. The fluid flowing out of the outlet flows towards module a6. Module a6 and module a2 are symmetrical about each other along the central axis. The fluids in modules a6 and a2 are arranged parallel to each other, and the fluid flow direction in module a6 is the same as that in module a2. The channel is 0.95 mm wide, 1.45 mm high, and 3 mm long, with a hydraulic diameter of 1150 μm. Module a7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 1150 μm, and the hydraulic diameter at the outlet is 1500 μm. The straight-line distance between the inlet and outlet sections is 2 mm. The fluid flowing out of the outlet enters the second mixing channel b for further mixing.

[0054] The second mixing channel b is divided into 7 modules. Module b1 is a channel with varying diameters at both ends. The hydraulic diameter at the inlet is 1714 μm, and the channel height is 1.5 mm. The hydraulic diameter at the outlet is 1150 μm, and the channel height is 1.45 mm. The straight-line distance between the inlet and outlet sections is 2 mm. Using the plane containing the inlet channel as the reference plane, the slope of module b1 is 135°. The outlet of module b1 connects to module b2. Module b2 is a straight channel perpendicular to the reference plane, with a width of 0. 0.95mm high, 1.45mm long, 3mm long, with a hydraulic diameter of 1150μm; modules b3, b4, and b5 are recirculation zones, with the fluid flow direction at the connection between modules b3 and b2 perpendicular to the fluid flow direction within module b2; module b4 is a mixing and recirculation zone, where the fluids from the upper and lower channels converge and mix before being redistributed into two outflowing streams, with the outflowing fluids flowing in the opposite direction to the flow direction within module b2. The fluid flows in opposite directions. The inlet cross-section is 1mm wide and 3mm high, while the outlet cross-section is 2mm wide and 1.5mm high. Module b5 is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1714μm, the outlet hydraulic diameter is 1183μm, and the height is 1.45mm. The straight-line distance between the inlet and outlet cross-sections is 1mm. The fluid flowing out of the outlet flows towards module b6. Module b6 and module b2 are arranged symmetrically and parallel to each other along the central axis, and the flow within module b6... The flow direction of the fluid is consistent with that in module b2. The channel is 0.95 mm wide, 1.45 mm high, and 3 mm long, with a hydraulic diameter of 1150 μm. Module b7 is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 1150 μm, and the hydraulic diameter at the outlet is 1500 μm. The straight-line distance between the inlet and outlet sections is 2 mm. The fluid flowing out of the outlet enters the subsequent first mixing channel a for further mixing or enters the reaction zone via the outlet channel for delayed reaction.

[0055] The inlet channel has three parallel channels arranged at the top, middle and bottom. The hydraulic diameter of the inlet channel is 1000 μm, and the hydraulic diameter of the outlet channel is 1000 μm and the length is 1 mm. After the material is fully mixed, it flows out of the outlet channel into the reaction zone.

[0056] The reaction zone is a straight channel with a total length of 50cm and a hydraulic diameter of 1000μm;

[0057] All of the above fluid channels are made of Hastelloy alloy.

[0058] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 81.8%, and the selectivity of methyl mercaptoacetate was 85.7%.

[0059] Example 2

[0060] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0061] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 70°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 85.0%, and the selectivity of methyl mercaptoacetate was 86.3%.

[0062] Example 3

[0063] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0064] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was 0.2 MPa, and the reaction temperature was 80 °C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 88.1%, and the selectivity of methyl mercaptoacetate was 86.5%.

[0065] Example 4

[0066] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0067] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was 0.2 MPa, and the reaction temperature was 90 °C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 92.1%, and the selectivity of methyl mercaptoacetate was 94.4%.

[0068] Example 5

[0069] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0070] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to ensure a residence time of 60 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 87.5%, and the selectivity of methyl mercaptoacetate was 90.1%.

[0071] Example 6

[0072] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0073] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 1% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 80.5%, and the selectivity of methyl mercaptoacetate was 78.5%.

[0074] Example 7

[0075] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0076] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 3% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 92.3%, and the selectivity of methyl mercaptoacetate was 87.8%.

[0077] Example 8

[0078] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0079] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 8% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 92.3%, and the selectivity of methyl mercaptoacetate was 77.8%.

[0080] Example 9

[0081] Based on the microchannel reaction device of Example 1, the hydraulic diameter of the outlet channel is 1500 μm and the length is 1 mm; the total length of the straight channel in the reaction zone is 50 cm and the hydraulic diameter is 1500 μm.

[0082] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The methanol:mercaptoacetic acid molar ratio was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 76.3%, and the selectivity of methyl mercaptoacetate was 76.8%.

[0083] Example 10

[0084] Based on the microchannel reaction device of Example 1, the hydraulic diameter of the outlet channel is 2000 μm and the length is 1 mm; the total length of the straight channel in the reaction zone is 50 cm and the hydraulic diameter is 2000 μm.

[0085] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 3:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 71.8%, and the selectivity of methyl mercaptoacetate was 68.7%.

[0086] Example 11

[0087] The microchannel reaction device used in this embodiment is the same as that in the previous embodiment.

[0088] The above-described microchannel reaction apparatus was used to synthesize methyl mercaptoacetate. The raw materials were thoroughly mixed in the mixing zone before entering the reaction zone for reaction. The product was then discharged and analyzed by liquid chromatography. The raw materials were mercaptoacetic acid, methanol, and p-toluenesulfonic acid, which were separately delivered by metering pumps. Methanol entered through the upper and lower channels of the inlet channel, while mercaptoacetic acid, after dissolving p-toluenesulfonic acid, entered through the middle channel of the inlet channel. The catalyst concentration was 5% by weight, the reaction pressure was atmospheric pressure, and the reaction temperature was 60°C. The flow rate and reaction channel length were controlled by the metering pump to maintain a residence time of 30 min. The molar ratio of methanol to mercaptoacetic acid was set to 4:1 using the metering pump. Finally, the product was discharged through the outlet. Product analysis results showed that the conversion rate of mercaptoacetic acid was 85.8%, and the selectivity of methyl mercaptoacetate was 90.7%.

[0089] Example 12

[0090] Based on the microchannel reaction device of Example 1, only a number of first mixing channels a are configured in the mixing channel of the mixing zone, but no second mixing channel b is configured.

[0091] The process for synthesizing methyl mercaptoacetate was the same as in the examples. The product analysis results showed that the conversion rate of mercaptoacetic acid was 45.5%, and the selectivity of the product methyl mercaptoacetate was 69.2%.

[0092] Example 13

[0093] Based on the microchannel reaction device of Example 1, only a number of second mixing channels b are configured in the mixing channel of the mixing zone, and no first mixing channel a is configured.

[0094] The process for synthesizing methyl mercaptoacetate was the same as in the examples. The product analysis results showed that the conversion rate of mercaptoacetic acid was 42.3%, and the selectivity of the product methyl mercaptoacetate was 70.5%.

[0095] As can be seen from the results of the above embodiments, in the microchannel reaction device of the present invention, by introducing a microscale flow structure with a specific structure, the mixing efficiency can be effectively improved, the backmixing problem in the esterification reaction can be reduced, and the product conversion rate and selectivity can be improved.

[0096] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A microchannel reaction device, characterized in that, It includes a mixing zone and a reaction zone. The mixing zone includes an inlet channel, a mixing channel, and an outlet channel that are connected in sequence. The mixing channel includes a plurality of first mixing channels (a) and a plurality of second mixing channels (b), and the first mixing channels (a) and the second mixing channels (b) are arranged alternately and cyclically. Each first mixing channel (a) and each second mixing channel (b) has a microscale flow structure. The reaction zone is a straight channel. The first mixing channel (a) has two layers of flow channels arranged symmetrically along the central axis. Each layer of flow channels is divided into seven modules. Module a1 (1) is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm and the channel height is 0.5-2 mm. The straight-line distance between the inlet section and the outlet section is 1-3 mm. Taking the plane where the inlet channel is located as the reference plane, the slope of module a1 (1) is 30-60°. The outlet of module a1 (1) is connected to module a2 (2). Module a2 (2) is a straight channel perpendicular to the reference plane and has a channel width of 0.5-1.5 mm. The height is 0.5-2mm, the length is 1-5mm, and the hydraulic diameter is 920-1380μm; modules a3 (3), a4 (4), and a5 (5) are recirculation zones. The fluid flow direction at the connection between module a3 (3) and module a2 (2) is perpendicular to the fluid flow direction in module a2 (2); module a4 (4) is a mixing recirculation zone. The fluids from the upper and lower channels converge and mix in module a4 (4) and then redistribute into two streams of fluid flowing out. The direction of the outflowing fluid is opposite to the direction of the fluid flowing in module a2 (2). The inlet cross-section width is 0.5-2mm, the height is 1-4mm, and the outlet cross-section width is 0.5-2mm. mm, height is 0.5-2mm; module a5 (5) is a channel with a variable diameter at the front and rear, with an inlet hydraulic diameter of 1371-2056μm and an outlet hydraulic diameter of 946-1420μm, a straight distance between the inlet and outlet of 0.5-2mm, and the fluid flowing out of the outlet flows towards module a6 (6); module a6 (6) and module a2 (2) are arranged symmetrically along the central axis and remain parallel to each other, and the fluid flow direction in module a6 (6) is the same as that in module a2 (2). The fluid flow direction in module a2 (2) is consistent. The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module a7 (7) is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight distance between the inlet section and the outlet section is 1-3 mm. The fluid flowing out of the outlet enters the second mixing channel (b) to continue mixing. The second mixing channel (b) has two layers of flow channels arranged symmetrically along the central axis. Each layer of flow channels is divided into seven modules. Module b1 (8) is a channel with a variable diameter at the front and rear. The hydraulic diameter at the inlet is 1371-2056 μm and the channel height is 0.5-2 mm. The hydraulic diameter at the outlet is 920-1380 μm and the channel height is 0.5-2 mm. The straight-line distance between the inlet section and the outlet section is 1-3 mm. Taking the plane where the inlet channel is located as the reference plane, the slope of module b1 (8) is 120-150°. The outlet of module b1 (8) is connected to module b2 (9). 9) is a straight channel perpendicular to the reference plane, with a channel width of 0.5-1.5mm, a height of 0.5-2mm, a length of 1-5mm, and a hydraulic diameter of 920-1380μm; modules b3 (10), b4 (11), and b5 (12) are recirculation zones, and the fluid flow direction at the connection between module b3 (10) and module b2 (9) is perpendicular to the fluid flow direction within module b2 (9); module b4 (11) is a mixing and recirculation zone, where the fluids from the upper and lower channels converge and mix within module b4 (11) before being redistributed into two streams flowing out. The outflowing fluid flows in the opposite direction to the fluid flow in module b2 (9). The inlet cross-section is 0.5-2mm wide and 1-4mm high, and the outlet cross-section is 0.5-2mm wide and 0.5-2mm high. Module b5 (12) is a channel with a variable diameter at the front and rear. The inlet hydraulic diameter is 1371-2056μm, and the outlet hydraulic diameter is 946-1420μm. The straight-line distance between the inlet and outlet is 0.5-2mm, and the fluid flowing out of the outlet flows towards module b6 (13). Module b6 (13) and module b2 (9) are arranged symmetrically and parallel to each other along the central axis. The fluid flow direction in module b6 (13) is the same as that in module b2 (9). The channel width is 0.5-1.5 mm, the height is 0.5-2 mm, the length is 1-5 mm, and the hydraulic diameter is 920-1380 μm. Module b7 (14) is a channel with a variable diameter at the front and back. The hydraulic diameter at the inlet is 920-1380 μm, and the hydraulic diameter at the outlet is 1200-1800 μm. The straight distance between the inlet section and the outlet section is 1-3 mm. The fluid flowing out of the outlet enters the subsequent first mixing channel (a) for further mixing or enters the reaction zone through the outlet channel for delayed reaction.

2. The microchannel reaction device according to claim 1, characterized in that, The inlet channel of the mixing zone has at least two parallel channels, and the reactants enter the mixing channel vertically through the inlet channels.

3. The microchannel reaction device according to claim 2, characterized in that, The inlet channel of the mixing zone has three parallel channels, and the hydraulic diameter of the inlet channel is 200-2000μm and the length is 1-2mm.

4. The microchannel reaction device according to any one of claims 1-3, characterized in that, The hydraulic diameter of the outlet channel of the mixing zone is 200-2000 μm, and the length is 1-2 mm.

5. The microchannel reaction device according to any one of claims 1-3, characterized in that, The hydraulic diameter of the straight channel in the reaction zone is 200-2000 μm; the length of the straight channel in the reaction zone is 20-100 cm; and the diameter of the straight channel in the reaction zone is the same as that of the outlet channel in the mixing zone.

6. The microchannel reaction device according to claim 5, characterized in that, The hydraulic diameter of the straight channel in the reaction zone is 800-1500 μm.

7. The microchannel reaction device according to claim 5, characterized in that, The length of the straight passage in the reaction zone is 50-100cm.

8. The microchannel reaction device according to any one of claims 1-3, characterized in that, The materials of each fluid channel in the microchannel reaction device are independently selected from stainless steel 316L, 904 stainless steel, Hastelloy, and silicon carbide ceramic.

9. A method for liquid-phase esterification reaction, characterized in that, The method is implemented in the microchannel reaction apparatus according to any one of claims 1-8, the method comprising: injecting the reaction raw materials and the catalyst into the mixing zone through the inlet channel for mixing, and then entering the reaction zone for reaction.

10. The method according to claim 9, characterized in that, The method is used to synthesize methyl mercaptoacetate.

11. The method according to claim 10, characterized in that, The reaction conditions include: a temperature of 50-100℃, a pressure of 0-0.3MPa, and a residence time of 30-90min.

Images