A microchannel reactor for achieving droplet coalescence of different sizes and its application method

Abstract

This invention relates to a microchannel reactor for achieving droplet coalescence of different sizes and its usage method. The microchannel reactor for achieving droplet coalescence of different sizes consists of three parts: an upstream droplet generation module, a downstream microchannel expansion module, and a tail serpentine tube. The upstream droplet generation module is a double-T-shaped microchannel structure, which is symmetrically distributed along the axial direction. The double-T-shaped microchannel has three inlets: an axial main inlet (1-1) connected to the continuous phase fluid; two radial side inlets (1-2, 1-3) connected to two dispersed phase fluids respectively; and an axial outlet connected to the downstream microchannel expansion module. This microchannel reactor for achieving droplet coalescence of different sizes is reasonably designed and is conducive to ensuring stable coalescence of droplets of different sizes or droplets carrying different reactants within the microchannel.

Description

Technical Field

[0001] This invention belongs to the field of microfluidic manipulation, and specifically relates to a microchannel reactor for achieving droplet coalescence of different sizes and its usage method. Background Technology

[0002] Microfluidics is a science and technology for precisely manipulating and controlling microscale fluids. Its advantages include small size, high safety, ease of manipulation, and high mixing and mass transfer efficiency. Droplet microfluidics is an important branch of microfluidics, which mainly utilizes the mutual shearing of immiscible fluids flowing in microchannels to form tiny droplets. It has applications in industrial fields such as material synthesis, nanoparticle preparation, and enhanced extraction and separation processes. Microdroplets in microfluidic systems can serve as independent microreactors for chemical and biological reactions. To realize the use of microdroplets for biochemical reactions, the generation and aggregation of microdroplets carrying different reactants or different molar ratios are particularly important.

[0003] Polypropylene (PP) is a general-purpose thermoplastic with excellent properties such as high transparency, non-toxicity, and chemical resistance, and is widely used in many industrial fields such as chemical, construction, and packaging. In the polymerization of propylene to produce polypropylene, the solvent method is usually used. Propylene monomer is dissolved in an inert liquid solvent (such as hexane), and solvent polymerization is carried out under the action of a catalyst. The polymer is suspended in the solvent in a solid particle state. The solvent method uses a stirred tank reactor, which has a long and complex process, large investment in equipment, and high energy consumption. Due to the use of a stirred tank reactor, explosive polymerization may occur in the reactor due to a sharp rise in local reaction temperature. Microreactors can solve this problem well. Microdroplet reactors are small in size and have high safety.

[0004] Currently, microdroplet generation methods can be divided into active and passive methods. Active methods, due to the involvement of external energy, are more complex. Passive methods mainly include T-type generation, Y-type generation, flow-focusing generation, and coaxial generation. These methods share a common characteristic: they can form droplets of uniform size and good monodispersity. However, changing the operating conditions still cannot produce droplets of inconsistent sizes or droplets carrying different reactants. Similar to droplet generation, droplet coalescence technology can also be divided into active and passive droplet coalescence techniques based on whether external energy is involved. Active droplet coalescence refers to inducing coalescence by applying external electric fields, magnetic fields, temperature fields, lasers, sound waves, etc., to break up adjacent surfaces of the droplets to be coalesced. Passive droplet coalescence technology is generally divided into two types: one is "head-to-head" collision coalescence, and the other is to use the velocity difference between droplets to achieve a co-directional coalescence process, i.e., "chase" coalescence. A major difficulty in achieving the former is the difficulty in achieving synchronous arrival of droplets, thus the coalescence efficiency is not very high. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a microchannel reactor for realizing the coalescence of droplets of different sizes. The microchannel reactor for realizing the coalescence of droplets of different sizes is reasonably designed, which is conducive to ensuring the stable coalescence of droplets of different sizes or droplets carrying different reactants in the microchannel.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention relates to a microchannel reactor for achieving droplet coalescence of different sizes, characterized by comprising three parts: an upstream droplet generation module, a downstream microchannel expansion module, and a tail-end serpentine tubing.

[0008] The upstream droplet generation module is a double-T-shaped microchannel structure, which is symmetrically distributed along the axial direction;

[0009] The double-T microchannel has three inlets: an axial main inlet connected to the continuous phase fluid; two radial side inlets connected to two dispersed phase fluids respectively; and an axial outlet connected to the downstream microchannel expansion module.

[0010] The downstream microchannel expansion module includes two symmetrical horn-shaped connectors and an expansion channel with a rectangular cross-section connected between the two symmetrical horn-shaped connectors. The downstream microchannel expansion module is centrally symmetrical as a whole.

[0011] The tail serpentine pipe consists of two sections of bent pipe (and several sections of straight pipe), and the tail serpentine pipe is centrally symmetrical.

[0012] Preferably, the upstream droplet generation module, the downstream microchannel expansion module, and the tail serpentine tube are first milled on a PMMA plate by a milling machine to form a base plate with each channel, and then a cover plate is used to cover and fix the base plate.

[0013] Preferably, the three inlets of the above-mentioned double-T microchannel all have square cross-sections and the same length.

[0014] Preferably, the total length of the downstream microchannel expansion module, including the horn-shaped connector, is 4.5 to 9 mm, and the distance from the upstream droplet generation module is 10 to 15 mm.

[0015] Preferably, the above-mentioned flared connector is a variable diameter channel with a length of 1.5~3 mm.

[0016] Preferably, the cross-section of the expansion channel is rectangular, the height of the expansion channel is the same as the channel height of the double-T microchannel, and the width of the expansion channel is twice the width of the double-T microchannel.

[0017] Preferably, the above-mentioned straight pipe includes a first straight pipe, a second straight pipe, a third straight pipe, a fourth straight pipe, and a fifth straight pipe. The first straight pipe is perpendicularly connected to the second straight pipe, the second straight pipe is connected to one end of a bend, the other end of the bend is connected to one end of the third straight pipe, the other end of the third straight pipe is connected to one end of the bend, the other end of the bend is connected to the fourth straight pipe, the fourth straight pipe is perpendicularly connected to the fifth straight pipe, and the tail end of the fifth straight pipe is a fluid outlet.

[0018] Preferably, the width and height of the above-mentioned double T-shaped microchannel are both 400~800μm, and the width of the expansion channel is 800~1600μm.

[0019] This invention relates to a method for using a microchannel reactor that enables the coalescence of droplets of different sizes.

[0020] Before use, first fill the entire channel with a continuous phase fluid: firstly, to ensure that there are no blockages or leaks in the channel; secondly, to eliminate swelling of the channel and ensure normal use thereafter.

[0021] In use, connect the PTFE tube to the fluid inlet and outlet on the plate surface and check for leaks at the connection. Connect the other end of the PTFE tube to the injection pump. The injection pump introduces two or more fluids into different inlet channels through pipelines. Under the shearing action of the continuous phase fluid, the dispersed phase fluid generates alternating droplets of different sizes in the double-T microchannel of the upstream droplet generation module. There is an initial interval between a set of alternating droplets, and then they continue to flow downstream along the flow direction. When they reach the downstream expansion structure, the large droplets at the front decrease in actual velocity due to the change in cross-sectional area, and merge with the smaller droplets that arrive later. The merged droplets continue to flow along the flow direction to the serpentine tube at the tail. After the merged droplets pass through the serpentine tube to balance the pressure, they flow out from the outlet. A collection device is connected after the PTFE tube at the outlet to collect waste liquid.

[0022] Preferably, after use, disconnect the PTFE tube from the fluid inlet and outlet, and clean the inside of the channel with deionized water. If the channel becomes blocked, disassemble the base plate and cover plate, rinse repeatedly with deionized water, and place in a ventilated and cool place to air dry naturally. When rinsing, do not use brushes, paper towels, etc. to rub the inside of the channel to avoid scratches that may affect the clarity of the channel.

[0023] Compared with the prior art, the present invention can achieve the following effects:

[0024] This invention combines an upstream double-T-shaped generation module with a downstream expansion module for aggregation. This allows for the generation of a pair of droplets of different sizes at the generation structure, with the corresponding dispersed phases on either side carrying different reactants. The downstream expansion module alters the actual droplet velocity due to changes in the channel cross-sectional area, enabling stable aggregation of two droplets of different sizes or droplets carrying different reactants within the expansion structure. Compared to existing technologies, this structure allows for the generation of droplets of different sizes by simply adjusting the flow rate of the injection pump, and the droplets can automatically pair. The paired droplets aggregate in a "chasing" manner within the expansion structure, eliminating the need for droplets of the same size and arriving synchronously in the "head-to-head" aggregation mode. Furthermore, using the channel structure described in this invention, the location of droplet aggregation is controllable, and the aggregation efficiency is 100%. This structure enables controllable polymerization of propylene. Attached Figure Description

[0025] Figure 1 This is a front view of a microchannel structure for achieving droplet aggregation of different sizes, as described in one embodiment.

[0026] Figure 2 This is a partially enlarged view of an expansion module of an embodiment of a microchannel structure for achieving droplet aggregation of different sizes (the dimensions in the figure are in mm).

[0027] Figure 3 This is another type of microchannel structure involved in Example 2;

[0028] In the diagram, 1, 2, and 3 are fluid inlet channels; 5 and 6 are flared connectors; 7 is an expansion channel; 8, 9, 10, 11, and 12 are square cross-section pipes; A and B are bends; 13 is the fluid outlet; and K is the base plate. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] refer to Figure 1 The microchannel reactor for achieving droplet aggregation of different sizes according to the present invention comprises three parts: an upstream droplet generation module, a downstream microchannel expansion module, and a tail serpentine tube.

[0032] The upstream droplet generation module is a double-T-shaped microchannel structure, which is symmetrically distributed along the axial direction;

[0033] The double-T microchannel has three inlets: an axial main inlet 1-1, which connects to the continuous phase fluid; two radial side inlets 1-2 and 1-3, which connect to two dispersed phase fluids respectively; and an axial outlet connected to the downstream microchannel expansion module. The three inlets are the inlet ends of three fluid inlet channels 1, 2, and 3.

[0034] The downstream expansion module includes two symmetrical horn-shaped connectors 5 and 6 and an expansion channel 7 with a rectangular cross-section connecting the two symmetrical horn-shaped connectors. The downstream microchannel expansion module is centrally symmetrical.

[0035] The tail-end serpentine pipe consists of two bends A and B and several straight pipes. The tail-end serpentine pipe is centrally symmetrical. The straight pipes include a first straight pipe 8, a second straight pipe 9, a third straight pipe 10, a fourth straight pipe 11, and a fifth straight pipe 12. The first straight pipe 8 is perpendicularly connected to the second straight pipe 9. The second straight pipe 9 is connected to one end of bend A. The other end of bend A is connected to one end of the third straight pipe 10. The other end of the third straight pipe 10 is connected to one end of bend B. The other end of bend B is connected to the fourth straight pipe 11. The fourth straight pipe 11 is perpendicularly connected to the fifth straight pipe 12. The tail end of the fifth straight pipe 12 is the fluid outlet 13.

[0036] During manufacturing, the upstream droplet generation module, the downstream microchannel expansion module, and the tail serpentine tube are first milled on a PMMA plate by a milling machine to form a base plate with each channel, and then a cover plate is used to cover and fix the base plate.

[0037] The three inlets of the double-T microchannel all have square cross-sections and the same length. The downstream microchannel expansion module, including the horn-shaped connector, has a total length of 4.5~9 mm and is 10~15 mm away from the upstream droplet generation module. The horn-shaped connector is a variable-diameter channel with a length of 1.5~3 mm. The expansion channel 7 has a rectangular cross-section and the height of the expansion channel 7 is the same as the channel height of the double-T microchannel. The width of the expansion channel 7 is twice the width of the double-T microchannel. Specifically, the width and height of the double-T microchannel are both 400~800 μm, and the width of the expansion channel 7 is 800~1600 μm.

[0038] The specific steps of this invention to realize the microchannel structure for droplet aggregation of different sizes and the method of using the microchannel reactor are as follows:

[0039] Before use, first fill the entire channel with a continuous phase fluid: firstly, to ensure that there are no blockages or leaks in the channel; secondly, to eliminate swelling of the channel and ensure normal use thereafter.

[0040] In use, connect the PTFE tube to the fluid inlet and outlet, and check for leaks at the connection. Connect the other end of the PTFE tube to the injection pump. The injection pump introduces two or more fluids into different inlet channels through pipelines. Under the shearing action of the continuous phase fluid, the dispersed phase fluid generates alternating droplets of different sizes in the double-T microchannel of the upstream droplet generation module. There is an initial interval between a set of alternating droplets, and then they continue to flow downstream along the flow direction. When they reach the downstream expansion structure, the large droplets at the front decrease in actual velocity due to the change in cross-sectional area, and merge with the smaller droplets that arrive later. The merged droplets continue to flow along the flow direction to the serpentine tube at the tail. After the merged droplets pass through the serpentine tube to balance the pressure, they flow out from the outlet. A collection device is connected after the PTFE tube at the outlet to collect waste liquid.

[0041] After use, disconnect the PTFE tube from the fluid inlet and outlet, and clean the inside of the channel with deionized water. If the channel becomes blocked, remove the base plate and cover plate and rinse repeatedly with deionized water. After rinsing, place it in a ventilated and cool place to air dry naturally. When rinsing, do not use brushes, paper towels, etc. to rub the inside of the channel to avoid scratches that may affect the clarity of the channel.

[0042] Example 1

[0043] The microreactor used in this embodiment is as follows: Figure 1 As shown, fluid inlets 1-1, 1-2, and 1-3 are all 1.3 mm circular holes, connected to external PTFE tubing; inlet channels 1, 2, and 3 have square cross-sections, with a width and height of 600 μm and a length of 10 mm, and the channels on both sides are symmetrically distributed; the downstream expansion module has a total length of 4.5 mm (including the flared connection), located 15 mm from the side channel inlets, with the expansion module height remaining constant, and the expansion channel width being twice the width of the upstream main channel; in the serpentine pipe arrangement, straight pipes 8 and 12 have a length of 5 mm, bends A and B have a radius of curvature of 3.4 mm, and straight pipe 10 has a length of 28 mm. Deionized water is introduced as the dispersed phase into the two side channel inlets 1-2 and 1-3, and n-octanol is introduced as the continuous phase into the main channel inlet 1-1. Adjusting the flow rates of the two phases causes the generating module to produce alternating droplets of different sizes. Experiments show that the droplet coalescence efficiency in the downstream expansion channel is 100%.

[0044] This indicates that the microchannel structure in this experiment can achieve efficient and controllable aggregation of droplets of different sizes, and fix the position of droplet aggregation.

[0045] Example 2

[0046] The microreactor used in this embodiment is as follows: Figure 1As shown, fluid inlets 1-1, 1-2, and 1-3 are all 1.3 mm circular holes, connected to external PTFE tubing; inlet channels 1, 2, and 3 have square cross-sections, with a width and height of 600 μm and a length of 10 mm, symmetrically distributed on both sides; the downstream expansion module has a total length of 4.5 mm (including the flared connection), located 15 mm from the side channel inlets, with a constant height, and the expansion channel width is twice the width of the upstream main channel; in the serpentine pipe arrangement, straight pipes 8 and 12 are 5 mm long, bends A and B have a radius of curvature of 3.4 mm, and straight pipe 10 is 28 mm long. Deionized water is introduced as the dispersed phase through the two side channel inlets 1-2 and 1-3, and n-octanol is introduced as the continuous phase through the main channel inlet 1-1. Adjusting the flow rates of the two phases causes the generating module to produce alternating droplets of different sizes. Another microreactor is shown... Figure 3 As shown, the inlet and outlet conditions are consistent with the microchannel designed in this invention, and the channel cross-sectional area is also consistent with the microchannel designed in this invention. Through experimental comparison, the microchannel designed in this invention can achieve controllable droplet coalescence position, greatly shortening the time taken for the entire coalescence process, shortening the channel length, and reducing the amount of PMMA sheet material used.

[0047] Example 3

[0048] The microreactor used in this embodiment is as follows: Figure 1 As shown, the dimensions of each part remain unchanged. Propylene and its liquid solvent hexane are introduced into the microchannel through inlet 1-2 as the dispersed phase, while a mixture of triethylaluminum and titanium trichloride is introduced into the microchannel through inlet 1-3 as another dispersed phase. Experiments show that the two dispersed phase droplets coalesce within the expanded structure, and the propylene monomer polymerizes into polypropylene. The resulting product has high quality, a fast polymerization rate, and a controllable polymerization process.

[0049] This invention combines an upstream double-T-shaped generation module with a downstream expansion module for aggregation. This allows for the generation of a pair of droplets of different sizes at the generation structure, with the corresponding dispersed phases on either side carrying different reactants. The downstream expansion module alters the actual droplet velocity due to changes in the channel cross-sectional area, enabling stable aggregation of two droplets of different sizes or droplets carrying different reactants within the expansion structure. Compared to existing technologies, this structure allows for the generation of droplets of different sizes by simply adjusting the flow rate of the injection pump, and the droplets can automatically pair. The paired droplets aggregate in a "chasing" manner within the expansion structure, eliminating the need for droplets of the same size and arriving synchronously in the "head-to-head" aggregation mode. Furthermore, using the channel structure described in this invention, the location of droplet aggregation is controllable, and the aggregation efficiency is 100%. This structure enables controllable polymerization of propylene.

[0050] The specific embodiments described above further illustrate the inventive purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microchannel reactor for achieving droplet coalescence of different sizes, characterized in that: It consists of three parts: an upstream droplet generation module, a downstream microchannel expansion module, and a tail-end serpentine tubing. The upstream droplet generation module is a double-T-shaped microchannel structure, which is symmetrically distributed along the axial direction; The double-T microchannel has three inlets: an axial main inlet (1-1) that connects to the continuous phase fluid; two radial side inlets (1-2, 1-3) that connect to two dispersed phase fluids respectively; and an axial outlet that connects to the downstream microchannel expansion module. The downstream microchannel expansion module includes two symmetrical horn-shaped connectors (5, 6) and an expansion channel (7) with a rectangular cross-section connected between the two symmetrical horn-shaped connectors. The downstream microchannel expansion module is centrally symmetrical. The tail serpentine pipe consists of two bent pipe sections (A, B) and several straight pipe sections, and the tail serpentine pipe is centrally symmetrical.

2. The microchannel reactor for achieving droplet coalescence of different sizes according to claim 1, characterized in that: The upstream droplet generation module, the downstream microchannel expansion module, and the tail serpentine tube are first milled on a PMMA plate by a milling machine to form a base plate with each channel, and then a cover plate is used to cover and fix the base plate.

3. The microchannel reactor for achieving droplet coalescence of different sizes according to claim 1 or 2, characterized in that: The three inlets of the double-T microchannel all have square cross-sections and the same length.

4. The microchannel reactor for achieving droplet coalescence of different sizes according to claim 3, characterized in that: The downstream microchannel expansion module includes a horn-shaped connector with a total length of 4.5~9 mm and is located 10~15 mm from the upstream droplet generation module.

5. The microchannel reactor for achieving droplet coalescence of different sizes according to claim 4, characterized in that: The flared connector is a variable diameter channel with a length of 1.5~3 mm.

6. The microchannel reactor for achieving droplet coalescence of different sizes according to claim 5, characterized in that: The expansion channel (7) has a rectangular cross-section, and its height is the same as that of the double-T microchannel. The width of the expansion channel (7) is twice the width of the double-T microchannel.

7. The microchannel reactor for achieving droplet coalescence of different sizes according to claim 6, characterized in that: The straight pipes include a first straight pipe (8), a second straight pipe (9), a third straight pipe (10), a fourth straight pipe (11), and a fifth straight pipe (12). The first straight pipe (8) is perpendicularly connected to the second straight pipe (9). The second straight pipe (9) is connected to one end of a bend (A). The other end of the bend (A) is connected to one end of the third straight pipe (10). The other end of the third straight pipe (10) is connected to one end of a bend (B). The other end of the bend (B) is connected to the fourth straight pipe (11). The fourth straight pipe (11) is perpendicularly connected to the fifth straight pipe (12). The tail of the fifth straight pipe (12) is a fluid outlet (13).

8. The microchannel reactor for achieving droplet coalescence of different sizes according to claim 7, characterized in that: The width and height of the double T-shaped microchannel are both 400~800μm, and the width of the expansion channel (7) is 800~1600μm.

9. A method of using a microchannel reactor for achieving droplet coalescence of different sizes as described in any one of claims 1-8, characterized in that: Before use, first fill the entire channel with a continuous phase fluid: firstly, to ensure that there is no blockage or leakage in the channel; secondly, to eliminate swelling of the channel and ensure normal use thereafter. In use, connect the PTFE tube to the fluid inlet and outlet on the plate surface and check for leaks at the connection. Connect the other end of the PTFE tube to the injection pump. The injection pump introduces two or more fluids into different inlet channels through pipelines. Under the shearing action of the continuous phase fluid, the dispersed phase fluid generates alternating droplets of different sizes in the double-T microchannel of the upstream droplet generation module. There is an initial interval between a set of alternating droplets, and then they continue to flow downstream along the flow direction. When they reach the downstream expansion structure, the large droplets at the front decrease in actual velocity due to the change in cross-sectional area, and merge with the smaller droplets that arrive later. The merged droplets continue to flow along the flow direction to the serpentine tube at the tail. After the merged droplets pass through the serpentine tube to balance the pressure, they flow out from the outlet. A collection device is connected after the PTFE tube at the outlet to collect waste liquid.

10. The method of using the microchannel reactor for achieving droplet coalescence of different sizes according to claim 9, characterized in that: After use, disconnect the PTFE tube from the fluid inlet and outlet. Clean the inside of the channel with deionized water. After rinsing, place it in a ventilated and cool place to air dry naturally. When rinsing, do not use a brush or paper towel to rub the inside of the channel, so as not to cause scratches that affect the clarity of the channel.

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