A microfluidic reaction chip for heterogeneous catalytic conversion of CO2

Abstract

A microfluidic reaction chip for the heterogeneous catalytic conversion of CO2 belongs to the fields of microfluidic technology and catalytic reaction. It includes a gas inlet channel, a liquid inlet channel, a gas-liquid mixing and dissolution unit, a catalyst loading zone, a catalyst filling channel, and a product collection channel. It enables efficient CO2 dissolution and efficient mixing, rapid mass transfer, and reaction with reactants in a microscale space. By enhancing the mass transfer characteristics of the microfluidic system, it significantly improves the reaction rate and product selectivity in the heterogeneous catalytic conversion of CO2, while simultaneously achieving continuous and miniaturized reaction processes. It can be used for the high-value resource conversion and utilization of CO2 and the study of heterogeneous catalytic reaction mechanisms, showing promising application prospects in environmental governance, new energy, and chemical synthesis.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, specifically to a microfluidic reaction chip for multiphase catalytic conversion of CO2 and its preparation method, belonging to the fields of microreactor technology and catalytic conversion technology. Background Technology

[0002] Converting CO2 into high-value-added chemicals through catalysis to achieve its resource utilization is considered an important approach that balances environmental protection and sustainable development. However, CO2 molecules are chemically stable, making activation and conversion difficult. Therefore, developing efficient and stable catalytic technologies is crucial for promoting its resource utilization. Among these technologies, heterogeneous catalysts have shown great promise for industrialization due to their low cost and ease of separation. In recent years, using inorganic solid catalysts to drive the reaction of CO2 with small organic molecules to generate high-value-added chemicals has become a research hotspot in related fields.

[0003] Traditional gas-liquid-solid multiphase catalytic processes for such reactions are typically carried out in autoclaves or fixed-bed reactors. However, these processes generally suffer from limited mass transfer efficiency, harsh reaction conditions, and difficulties in process control, thus restricting further improvements in conversion efficiency. In recent years, microfluidic chip technology has demonstrated enormous potential in the field of multiphase catalytic conversion due to its advantages such as flexible microchannel design, extremely high mass and heat transfer efficiency, and continuous flow operation. By immobilizing the catalyst within microchannels to form a microchannel fixed-bed reactor, precise control of the gas, liquid, and solid three-phase fluids and the reaction can be achieved, significantly increasing the interfacial area and thus greatly accelerating mass transfer and reaction rates. However, applying microfluidic technology to CO2 catalytic conversion still faces two major technical bottlenecks: firstly, the low dissolution efficiency of CO2 gas, resulting in large bubble sizes and limited gas-liquid contact area in traditional channels; and secondly, poor catalyst loading stability, prone to migration or leakage under high pressure, affecting reaction reproducibility.

[0004] Therefore, developing a microfluidic reaction chip that combines efficient micron-level bubble generation capability with a stable catalyst packing structure is of great scientific significance and application value for breaking through the current technical bottlenecks in CO2 catalytic conversion and promoting the practical application of its resource utilization technology. Summary of the Invention

[0005] Purpose of the invention: The present invention aims to overcome the shortcomings of the prior art and provide a microfluidic reaction chip for multiphase catalytic conversion of CO2. The chip has efficient gas-liquid dissolution and catalyst stable loading functions and is suitable for catalytic conversion reactions such as CO2 hydrogenation and reforming.

[0006] To achieve the above technical objectives, the present invention proposes a microfluidic reaction chip for multiphase catalytic conversion of CO2, including a glass substrate and multiple functional regions integrated within the substrate. The functional regions include: a gas injection channel (1), a liquid injection channel (2), a gas-liquid mixing and dissolution unit (3), a catalyst loading area (4), a catalyst filling channel (5), a product collection channel (6), and a plunger fixing unit (7).

[0007] The gas-liquid mixing and dissolving unit (3) has a U-shaped frame channel in the plane. The U-shaped frame channel has multiple parallel connecting channels (3-2) connected to the two sides (3-1). The center of the U-shaped frame channel has a central connecting channel (3-3) that runs through and connects all the connecting channels (3-2). The central connecting channel (3-3) is parallel to the two sides (3-1), and the connecting channels (3-2) are perpendicular to the two sides (3-1). The diameter of the connecting channels (3-2) is smaller than the diameter of the U-shaped frame channel and the diameter of the central connecting channel (3-3).

[0008] The catalyst loading area (4) includes multiple catalyst channels (4-1) and a common channel (4-2);

[0009] The plunger fixing unit (7) is composed of two channels with different diameters connected together. The end of the large diameter channel (7-1) is rounded and connected to the small diameter channel (7-2), which is used to retain and fix the plunger. The diameter of the large diameter channel (7-1) is larger than the plunger size, and the diameter of the small diameter channel (7-2) is smaller than or equal to the plunger size.

[0010] The gas injection channel (1) is connected to the end of the central connecting channel (3-3); the liquid injection channel (2) is connected to the end of the first side of the U-shaped frame channel, and the second side channel (3-1) of the U-shaped frame channel is connected to the large-diameter channel (7-1) of the plunger fixing unit (7). The corresponding small-diameter channel (7-2) is connected to the front end of each straight catalyst channel (4-1). At the same time, the catalyst filling channel (5) is connected to the rear end of the small-diameter channel (7-2) and the front end of each straight catalyst channel (4-1). The rear end of each straight catalyst channel (4-1) is connected by a common channel (4-2). The common channel (4-2) is connected to the large-diameter channel (7-1) of another plunger fixing unit (7), and the corresponding small-diameter channel (7-2) is connected to the product collection channel (6). The common channel (4-2) is perpendicular to the plunger fixing unit (7), and the plunger fixing unit (7) is connected in the middle of the common channel (4-2).

[0011] Each straight catalyst channel (4-1) is filled with catalyst (8), and a mesoporous silica plunger (9) is filled in the large-diameter channel (7-1) of the plunger fixing unit (7). The mesoporous silica plunger (9) is used to seal the catalyst (8) in the catalyst filling area (4).

[0012] Preferably, the gas injection channel (1) has a circular cross-section with a diameter between 100 and 440 μm.

[0013] Preferably, the liquid injection channel (2) has a circular cross-section with a diameter between 100 and 440 μm.

[0014] Preferably, the gas-liquid mixing and dissolving unit (3) has a circular cross-section, and the diameter of the two sides (3-1) and the bottom connecting channel, i.e. the entire U-shaped channel, is 100~440 μm. The diameter of the central connecting channel (3-3) is 100~440 μm, and the diameter of the U-shaped channel is equal to the diameter of the central connecting channel (3-3). The diameter of the connecting fine channel (3-2) is 5~50 μm. The entire U-shaped channel, the central connecting channel (3-3), and the connecting fine channel (3-2) form a stepped composite channel.

[0015] Preferably, the catalyst channel (4-1) has a circular cross-section with a diameter between 100 and 440 μm and a length between 10 and 300 mm; the multiple catalyst channels (4-1) are one or more combinations of parallel array channels, straight channels, and curved channels.

[0016] Preferably, the catalyst-filled channel (5) has a circular cross-section with a diameter between 100 and 440 μm.

[0017] Preferably, the product collection channel (6) has a circular cross-section with a diameter between 100 and 440 μm.

[0018] Preferably, the channel cross-section of the plunger fixing unit (7) is circular, with the diameter of the large-diameter channel (7-1) between 100 and 440 μm; the diameter of the small-diameter channel (7-2) between 80 and 100 µm, and the length between 0.5 and 2 mm.

[0019] The mesoporous silica plunger (9) is a single-particle plunger with a particle size of 80~120 μm or an in-situ generated porous SiO2 plunger with a pore size of 1~10 μm. It is used to trap catalyst particles, but allows gas and liquid to pass through.

[0020] The chip substrate is made of glass, and the two chip substrates are interlocked and bonded together to place multiple functional areas in the middle.

[0021] The catalyst filling channel (5) is finally sealed.

[0022] In this invention, the gas enters through channel (1), and the reaction solution enters through channel (2). The gas and liquid phases mix and dissolve at structural unit (3). The microbubbles generated under the action of fluid shear force further increase the contact area between the gas and liquid phases, thereby improving the mixing efficiency. Complete dissolution occurs within 5 seconds.

[0023] If heating is required during the reaction, the substrate can be heated.

[0024] The technical solutions provided by this invention have the following advantages and beneficial effects:

[0025] 1) High-efficiency gas-liquid dissolution: By using channel structures of different diameters, the fluid shear force is used to break up bubbles in the narrow diameter channel region to generate micron-sized bubbles, which significantly increases the gas-liquid contact surface area and solves the problems of slow gas dissolution rate and insufficient dissolution in traditional and existing microfluidic chips;

[0026] 2) Stable catalyst loading: The use of channel structures with different diameters to fix the mesoporous silica plungers effectively solves the problems of catalyst movement and leakage under high pressure, and improves reaction reproducibility;

[0027] 3) High structural integration: It integrates gas dissolution and catalytic reaction functions into a single chip, making it suitable for high-throughput screening and reaction mechanism research. Attached Figure Description

[0028] Figure 1 A schematic diagram of the chip structure involved in this invention;

[0029] Figure 2 Micrograph of the stepped depth gas-liquid mixing channel structure involved in this invention;

[0030] Figure 3 A diagram illustrating the dissolution of the bubble channels involved in this invention;

[0031] Figure 4 Schematic diagram of plunger-retained catalyst

[0032] Figure 5 Schematic diagram and micrograph of mesoporous SiO2 single-particle plunger fixation and catalyst filling.

[0033] Figure 6 Micrograph of in-situ polymerized porous SiO2 plunger.

[0034] Gas injection channel (1), liquid injection channel (2), gas-liquid mixing and dissolution unit (3), side (3-1), connecting fine channel (3-2), central connecting channel (3-3), catalyst loading area (4), catalyst channel (4-1), common channel (4-2), catalyst filling channel (5), product collection channel (6), plunger fixing unit (7), large diameter channel (7-1), small diameter channel (7-2), catalyst (8), plunger (9). Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments. Detailed implementation methods and specific operating procedures are given. The embodiments will help to understand the present invention, but the scope of protection of the present invention is not limited to the following embodiments.

[0036] Example 1

[0037] Design and construct a gas dissolution microfluidic chip; chip structure details are attached. Figure 1 First, a first photomask was used to etch all channel areas of the chip except for the lateral channels within the gas dissolution unit, forming a baseline depth of 215 μm. After etching and complete removal of the photoresist, the photoresist was recoated, and then a second photomask was used to expose all channels of the chip. The second etching depth was 5 μm, resulting in a stepped structure with depths of 220 μm (215+5) and 5 μm. Therefore, after the upper and lower chips were bonded, the diameter of the gas injection channel (1) was 440 μm; the diameter of the liquid injection channel (2) was 440 μm; and the diameters of the gas-liquid mixing and dissolution channel (3) were 440 μm and 10 μm, respectively. This design achieved ideal results in the experiment. When CO2 gas was introduced into the chip and met the liquid in the dissolution channel, bubbles with a size in the micrometer range were successfully generated. Thanks to the extremely small bubble size and optimized channel geometry, these bubbles were completely dissolved within seconds. This process demonstrates the excellent performance of this chip structure in terms of efficient mass transfer.

[0038] This invention, through the design of a gas dissolution microfluidic chip with a precise structure, enables the rapid generation and dissolution of micron-sized bubbles under the premise of high efficiency and stability. It effectively solves the problems of traditional gas dissolution methods, such as bulky equipment, low efficiency, uneven bubble generation, insufficient dissolution, easy clogging, and poor stability of existing microfluidic chips.

[0039] Example 2

[0040] This embodiment proposes a catalyst loading method based on a mesoporous silica single-particle plunger. First, a mesoporous silica single particle with a diameter of approximately 100 µm is introduced from the catalyst filling inlet (5). Using a syringe connected to an external capillary tube at the inlet (5), the single particle is pushed through the catalyst filling zone (4) to the plunger fixing unit (7) at a flow rate of 100 µL / min. Since the particle size of the single particle is larger than the diameter of the narrow channel (7-2) of 80~100 µm, when the fluid pushes the single particle forward, the particle is stuck at the inlet of the narrow channel and cannot pass through, while the liquid flows through the gap between the particle and the channel wall. Therefore, the single-particle plunger is finally fixed between the channel (7-1) and the channel (7-2). After the plunger is fixed, a suspension containing the catalyst is pumped in from the inlet (5) with driving pressure provided by a nitrogen cylinder. The catalyst particles are effectively trapped in the channel because they cannot pass through the gap. To prevent catalyst leakage from the front end of the catalyst filling zone (4) during the reaction, after the catalyst is loaded, a single-particle plunger is added to the plunger fixing unit (7) in front of the catalyst filling zone (4) using the same method as described above, thereby fixing the catalyst at both ends. This method not only simplifies the catalyst loading process, but also allows for precise control of the plunger position and catalyst loading amount by controlling the flow rate and the sequential introduction of particles, significantly improving the controllability, accuracy, and reproducibility of the experiment.

[0041] Example 3

[0042] This embodiment proposes another high-temperature in-situ polymerization plunger technology, which can directly form a stable porous SiO2 plunger in the channel. This method does not require a plunger fixing unit (7). The technology uses Frit Kit for microbore capillary columns reagent (commercially available reagent, NEXT ADVANCE) to react in the channel to generate a silica plunger with a porous structure. First, the prepared Frit Kit for microbore capillary columns reagent is injected into the product collection channel (6) using a syringe, and then placed in an oven and heated at 100°C for more than 4 hours to generate a porous SiO2 plunger in situ. The gas injection channel (1), liquid injection channel (2), and gas-liquid mixing and dissolution unit (3) are filled with water to ensure that the catalyst can enter the filling area (4). Then, the catalyst is filled from the catalyst filling channel (5). The driving pressure is provided by a nitrogen cylinder, and the suspension containing the catalyst is pumped in. The catalyst particles are effectively trapped in the channel because they cannot pass through the gaps of the porous SiO2 plunger. After the catalyst is loaded, a plunger reagent is injected into the catalyst filling channel (5) using a syringe and heated in an oven to generate a plunger through in-situ polymerization, thereby encapsulating both ends of the catalyst and sealing the channel 5. This method can achieve high-stability catalyst loading.

[0043] This invention provides a microfluidic reaction chip for multiphase catalytic conversion of CO2 and its preparation method. It includes a precision-structured microfluidic chip for efficient gas dissolution, as well as the concept and method for immobilizing and filling multiphase catalysts. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2, characterized in that, It includes a glass substrate and multiple functional areas integrated within the substrate, the functional areas including: a gas injection channel (1), a liquid injection channel (2), a gas-liquid mixing and dissolution unit (3), a catalyst loading area (4), a catalyst filling channel (5), a product collection channel (6), and a plunger fixing unit (7). The gas-liquid mixing and dissolving unit (3) has a U-shaped frame channel in the plane. The U-shaped frame channel has multiple parallel connecting channels (3-2) connected to the two sides (3-1). The center of the U-shaped frame channel has a central connecting channel (3-3) that runs through and connects all the connecting channels (3-2). The central connecting channel (3-3) is parallel to the two sides (3-1), and the connecting channels (3-2) are perpendicular to the two sides (3-1). The diameter of the connecting channels (3-2) is smaller than the diameter of the U-shaped frame channel and the diameter of the central connecting channel (3-3). The catalyst loading area (4) includes multiple catalyst channels (4-1) and a common channel (4-2); The plunger fixing unit (7) is composed of two channels with different diameters connected together. The end of the large diameter channel (7-1) is rounded and connected to the small diameter channel (7-2), which is used to retain and fix the plunger. The diameter of the large diameter channel (7-1) is larger than the plunger size, and the diameter of the small diameter channel (7-2) is smaller than or equal to the plunger size. The gas injection channel (1) is connected to the end of the central connecting channel (3-3); the liquid injection channel (2) is connected to the end of the first side of the U-shaped frame channel; the second side channel (3-1) of the U-shaped frame channel is connected to the large diameter channel (7-1) of the plunger fixing unit (7); the corresponding small diameter channel (7-2) is connected to the front end of each straight catalyst channel (4-1); at the same time, the catalyst filling channel (5) is connected to the rear end of the small diameter channel (7-2) and the front end of each straight catalyst channel (4-1); the rear end of each straight catalyst channel (4-1) is connected by a common channel (4-2); the common channel (4-2) is connected to the large diameter channel (7-1) of another plunger fixing unit (7); the corresponding small diameter channel (7-2) is connected to the product collection channel (6). Each straight catalyst channel (4-1) is filled with catalyst (8), and a mesoporous silica plunger (9) is filled in the large-diameter channel (7-1) of the plunger fixing unit (7). The mesoporous silica plunger (9) is used to seal the catalyst (8) in the catalyst filling area (4).

2. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, The gas injection channel (1) has a circular cross-section with a diameter between 100 and 440 μm.

3. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, The liquid injection channel (2) has a circular cross-section with a diameter between 100 and 440 μm.

4. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, The gas-liquid mixing and dissolving unit (3) has a circular cross-section. The diameter of the two sides (3-1) and the bottom connecting channel, i.e. the entire U-shaped channel, is 100~440 μm. The diameter of the central connecting channel (3-3) is 100~440 μm. The diameter of the U-shaped channel and the diameter of the central connecting channel (3-3) are equal. The diameter of the connecting fine channel (3-2) is 5~50 μm. The entire U-shaped channel, the central connecting channel (3-3), and the connecting fine channel (3-2) form a stepped composite channel.

5. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, The catalyst channel (4-1) has a circular cross-section with a diameter between 100 and 440 μm; the multiple catalyst channels (4-1) are one or more combinations of parallel array channels, straight channels, and curved channels, and the length of the catalyst channel (4-1) is 10 to 300 mm.

6. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, The catalyst-filled channel (5) has a circular cross-section with a diameter between 100 and 440 μm; The product collection channel (6) has a circular cross-section with a diameter between 100 and 440 μm.

7. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, The channel cross-section of the plunger fixing unit (7) is circular. The diameter of the large-diameter channel (7-1) is between 100 and 440 μm; the diameter of the small-diameter channel (7-2) is between 80 and 100 µm, and the length is between 0.5 and 2 mm. The mesoporous silica plunger (9) is a single-particle plunger with a particle size of 80~120 μm or an in-situ generated porous SiO2 plunger with a pore size of 1~10 μm. It is used to trap catalyst particles, but allows gas and liquid to pass through.

8. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, The chip substrate is made of glass, and two chip substrates are interlocked and bonded together to place multiple functional areas in the middle. After the catalyst is filled, the catalyst filling channel (5) is finally sealed.

9. A microfluidic reaction chip for heterogeneous catalytic conversion of CO2 according to claim 1, characterized in that, Gas enters through channel (1), and reaction solution enters through channel (2). The gas and liquid phases mix and dissolve at structural unit (3). The microbubbles generated by the fluid under shear force further increase the contact area between the gas and liquid phases and improve the mixing efficiency.

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