Micro-scale reactor for realizing catalytic oxidation of low-concentration methane

Abstract

The micro-scale reactor comprises a gas flow equalizing unit, a gas flow guiding and preheating unit and a core micro-catalytic oxidation unit which are sequentially cascaded, the core micro-catalytic oxidation unit adopts a fractal flow channel design, raw material gas is uniformly distributed to a micro-flow channel catalytic layer, and the micro-flow channel catalytic layer is communicated with the gas flow equalizing unit. And fully contacting with the loaded high-efficiency catalyst to finish the catalytic oxidation reaction. The micro-scale structure obviously improves the activity and mass transfer efficiency of the catalyst, meanwhile, high-temperature gas generated by reaction rapidly preheats unreacted raw material gas in the flow guide pipe through a zigzag path, the heating time is shortened, and the energy consumption is reduced. According to the embodiment of the invention, safe and efficient emission reduction and resource utilization of low-concentration methane are realized by reinforcing micro-catalysis design and combining efficient heat energy utilization, and the method is suitable for methane treatment under coal mine gas and other complex working conditions, and has important industrial application value.

Description

Technical Field

[0001] The present application belongs to the technical field of micro-chemical equipment and methane emission reduction, and specifically relates to a micro-scale reactor for realizing catalytic oxidation of low-concentration methane. Background Art

[0002] Methane is an important greenhouse gas with a greenhouse effect potential 28 times that of carbon dioxide. Methane emission reduction and resource utilization have become key issues that need to be urgently addressed.

[0003] However, the utilization and treatment of low-concentration methane faces many challenges: methane concentration fluctuates greatly, the gas source is unstable, and it is often in the explosion range. It needs to be diluted to a safe concentration (below 25% lower explosion limit) through mixed air before it can enter the treatment device. In addition, the molecular structure of low-concentration methane is stable, and catalytic oxidation usually requires a high temperature environment above 600°C, which not only increases the time and energy consumption of heating, but also increases the complexity of the process. Therefore, the research and development of efficient treatment technology for low-concentration methane has become an urgent need at present.

[0004] Related technologies still have significant limitations in treating low-concentration methane. Traditional direct combustion technology has high requirements for methane concentration. It is difficult to achieve stable combustion of low-concentration methane, and it is accompanied by high energy consumption and greater safety risks. Although adsorption separation technology can regulate methane concentration, its high cost and low efficiency limit its application in coal mine gas emission scenarios. In contrast, catalytic oxidation technology is considered to be a key means to solve the problem of low-concentration methane utilization due to its high efficiency. However, current catalysts have high requirements for reaction conditions, and generally have problems such as poor low-temperature start-up performance, insufficient reaction stability, and limited anti-poisoning ability, which makes it difficult to meet the needs of complex working conditions of low-concentration methane. Therefore, technologies related to low-concentration methane treatment still have a lot of room for improvement in treatment efficiency, safety and applicability, and innovative solutions are urgently needed.

[0005] The preceding description is intended to provide general background information and does not necessarily constitute prior art. Summary of the invention

[0006] The present application aims to provide a microscale reactor suitable for catalytic oxidation reaction of low-concentration methane, which is used to solve the problems in processing efficiency, safety and applicability in the process of low-concentration gas treatment, and has broad industrial application value in particular in coal mine gas resource utilization and emission reduction.

[0007] To this end, one aspect of the present application provides a microscale reactor for realizing catalytic oxidation of low-concentration methane, wherein the microscale reactor comprises a gas flow equalization unit, a gas flow guiding and preheating unit and a core micro-catalytic oxidation unit which are cascaded in sequence;

[0008] The gas flow balancing unit comprises a plurality of honeycomb flow balancing mesh plates stacked in sequence, which are used to evenly distribute the mixed raw material gas entering the microscale reactor;

[0009] The gas guide and preheating unit comprises a plurality of guide baffles spaced apart along a first direction and a plurality of guide pipes passing through the guide baffles, for preheating the mixed raw material gas and uniformly introducing the mixed raw material gas into the core micro-catalytic oxidation unit;

[0010] The core micro-catalytic oxidation unit includes several groups of alternately stacked gas diversion layers and microchannel catalytic layers. The gas diversion layer includes a fractal channel for accurately distributing the mixed raw gas to the microchannel catalytic layer. The microchannel catalytic layer includes a plurality of microchannels with catalysts distributed therein. The microchannels are connected to the fractal channel for catalytically oxidizing the mixed raw gas.

[0011] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the honeycomb flow-averaging mesh plate is evenly distributed with hexagonal channels, and the side length of the cross-sectional shape of the hexagonal channels is 0.1 mm to 3 mm.

[0012] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the gas flow balancing unit includes four honeycomb flow balancing mesh plates stacked in sequence, and each of the honeycomb flow balancing mesh plates is rotated 45° relative to the previous honeycomb flow balancing mesh plate and stacked to achieve uniform distribution of the mixed raw material gas.

[0013] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the microscale reactor further includes a safety unit, the safety unit includes a shell, and the gas diversion and preheating unit and the core micro-catalytic oxidation unit are arranged in the shell.

[0014] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the periphery of the guide baffle contacts the inner wall portion of the shell to define a baffle portion through which the gas cannot pass and a gap portion through which the gas passes, and the gap portions of adjacent guide baffles are staggered in a second direction perpendicular to the first direction, so that the high-temperature gas flowing out of the core micro-catalytic oxidation unit flows through the outside of the guide pipe along the tortuous path defined by the guide baffle to preheat the mixed raw gas in the guide pipe.

[0015] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the outer diameter of the guide tube is 1-30 mm, and the wall thickness is 0.5-5 mm; a plurality of the guide tubes evenly pass through the guide baffle, and the center distance between adjacent guide tubes is ≤50 mm.

[0016] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the fractal flow channel includes a multi-stage distribution flow channel, wherein the first-stage distribution flow channel is located at the center of the gas diversion layer, for introducing the fully preheated mixed raw gas; the two end outlets of the first-stage distribution flow channel are respectively connected to the middle inlet of the second-stage distribution flow channel; the two end outlets of the second-stage distribution flow channel are connected to the middle inlet of the third-stage distribution flow channel...the two end outlets of the N-1-stage distribution flow channel are connected to the middle inlet of the N-stage distribution flow channel; the two end outlets of the N-1-stage distribution flow channel are connected to the middle inlet of the N-stage distribution flow channel; the two end outlets of the N-stage distribution flow channel are connected to the microchannel catalytic layer through through holes to evenly distribute the mixed raw gas to the microchannel catalytic layer; wherein N is an integer greater than or equal to 2.

[0017] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the catalyst includes one or more of a transition metal oxide catalyst, a noble metal catalyst, a doped modified perovskite catalyst and a bimetallic oxide catalyst.

[0018] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the safety unit also includes a first sensor arranged at the air inlet of the shell, a second sensor arranged at the air outlet of the core micro-catalytic oxidation unit, a flame arrester arranged at the inlet of the gas equalizing unit, and an explosion-proof plate arranged at the air outlet of the core micro-catalytic oxidation unit.

[0019] Optionally, in combination with any of the above aspects, in another implementation of this aspect, the method for manufacturing the core micro-catalytic oxidation unit comprises the following steps:

[0020] (1) According to the selected material, the microchannels and through holes are processed on the substrate layer by micro-milling, dry / wet chemical etching, soft lithography, laser processing, LIGA process or electrical discharge machining process;

[0021] (2) uniformly attaching the catalyst to the surface and / or interior of the microfluidic channel to form the microfluidic channel catalytic layer;

[0022] (3) The gas diversion layer and the microchannel catalytic layer are stacked in sequence according to the design order, and the structure is packaged by clamping, plasma treatment or hot pressing bonding, and the smooth flow path of the gas is ensured.

[0023] Optionally, in combination with any of the above aspects, in another implementation of the present invention, the catalyst is uniformly attached to the surface and / or interior of the microchannel by one or more methods including slurry coating, sol-gel, electrophoretic deposition, impregnation, physical vapor deposition or chemical vapor deposition.

[0024] Optionally, in combination with any of the above aspects, in another implementation of the present aspect, the catalyst is uniformly distributed on the surface and / or inside of the microchannel by mixing and molding the catalyst nanoparticles with the preparation materials of the microchannel catalytic layer and then processing the microchannel structure.

[0025] As described above, the embodiments of the present application achieve precise distribution and efficient catalytic conversion of low-concentration methane through the innovative design of the core micro-catalytic oxidation unit. The microchannel catalytic layer is combined with the fractal flow channel distribution system to allow the raw gas to flow evenly through the microchannel structure loaded with high-efficiency catalysts, significantly improving the activity of the catalyst, the mass transfer efficiency of the gas, and the reaction rate. In addition, by rationally designing the gas flow path of the gas diversion and preheating unit, the generated high-temperature reaction gas can quickly preheat the unreacted mixed raw gas, greatly shortening the reaction heating time and reducing the system energy consumption.

[0026] On this basis, another embodiment of the present application also focuses on safety and adaptability in design, using multi-layer honeycomb flow-averaging mesh plates and double safety protection units to ensure stable operation of the equipment under complex working conditions. The reactor is compact and efficient in structure, has the characteristics of optimizing thermal energy utilization and efficient catalytic performance, and provides an efficient, economical and reliable solution for the reduction and resource utilization of low-concentration methane.

[0027] The above summary is provided to introduce some concepts in a simplified form, which will be further described in detail in the following detailed description. The above summary is neither intended to identify the key features or essential features of the claimed subject matter nor to be used to help determine the scope of the claimed subject matter. The claimed subject matter of the application is not limited to implementations that solve any or all of the disadvantages pointed out in the background technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the overall structure of a low-concentration methane catalytic oxidation micro-scale reactor proposed in one embodiment of the present application;

[0029] Figure 2 A schematic cross-sectional structure diagram of a low-concentration methane catalytic oxidation micro-scale reactor proposed in one embodiment of the present application;

[0030] Figure 3 A schematic diagram of the workflow path of a low-concentration methane catalytic oxidation micro-scale reactor proposed as an embodiment of the present application;

[0031] Figure 4 A schematic cross-sectional view of a honeycomb flow-sharing mesh plate in a gas flow-sharing unit of a low-concentration methane catalytic oxidation microreactor proposed in one embodiment of the present application;

[0032] Figure 5A schematic cross-sectional view of a guide baffle of a low-concentration methane catalytic oxidation micro-scale reactor proposed in one embodiment of the present application;

[0033] Figure 6 One of the three-dimensional structural schematic diagrams of the core micro-catalytic oxidation unit of the low-concentration methane catalytic oxidation micro-scale reactor proposed in one embodiment of the present application;

[0034] Figure 7 The second schematic diagram of the three-dimensional structure of the core micro-catalytic oxidation unit of the low-concentration methane catalytic oxidation micro-scale reactor proposed in one embodiment of the present application;

[0035] Figure 8 A schematic cross-sectional view of a gas splitter layer in a core micro-catalytic oxidation unit of a low-concentration methane catalytic oxidation micro-scale reactor proposed in one embodiment of the present application;

[0036] Fig. 9 A schematic cross-sectional view of a micro-catalytic oxidation unit in a core micro-catalytic oxidation unit of a micro-scale reactor for catalytic oxidation of low-concentration methane according to one embodiment of the present application;

[0037] Fig.10 is the methane conversion rate analyzed in Example 1 of the present application;

[0038] Fig.11 is the methane conversion rate analyzed in Example 2 of the present application;

[0039] Fig.12 is the methane conversion rate analyzed in Example 3 of the present application;

[0040] Fig.13 is the methane conversion rate analyzed in Example 4 of the present application;

[0041] Fig.14 is the methane conversion rate analyzed in Example 5 of the present application;

[0042] Fig.15 is the methane conversion rate analyzed in Example 6 of the present application.

[0043] Wherein: (1) core micro-catalytic oxidation unit; (101) gas diversion layer; (102) microchannel catalytic layer; (2) gas diversion and preheating unit; (201) diversion tube; (202) diversion baffle; (3) gas flow equalization unit; (301) honeycomb flow equalization mesh plate; (302) honeycomb plate; (401) shell; (402) first sensor; (403) second sensor; (404) flame arrester at the entrance; (405) explosion relief plate at the exit;

[0044] (406) Inspection door; (5) Raw gas inlet; (6) Reaction gas outlet. DETAILED DESCRIPTION

[0045] The embodiments of the present invention and the features in the embodiments may be combined with each other. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0046] Microscale catalytic reaction technology provides a new idea for the treatment and utilization of low-concentration methane. Compared with traditional reactors, microscale reactors have excellent mass transfer and heat transfer performance, which can significantly reduce the reaction starting temperature, shorten the heating time, and increase the reaction rate. In addition, its compact structural design and refined process control can effectively deal with the problem of low-concentration methane concentration fluctuations, and eliminate potential safety hazards by accurately controlling the mixing and dilution process. At the same time, the catalyst distribution in the microreactor is more uniform, and the catalytic efficiency and anti-deactivation performance are greatly improved, ensuring the long-term stable operation of the device under complex working conditions. The low-concentration gas catalytic reactor developed based on microscale catalytic reaction technology is expected to play an important role in the field of coal mine gas resource utilization, and provide effective technical support for achieving methane emission reduction and energy recovery.

[0047] To this end, the present application proposes a microscale reactor for realizing low-concentration methane catalytic oxidation, such as Figure 1-9 As shown, the microscale reactor includes a gas flow equalization unit 3, a gas flow guiding and preheating unit 2 and a core micro-catalytic oxidation unit 1 which are cascaded in sequence.

[0048] The gas flow balancing unit 3 includes a plurality of honeycomb flow balancing mesh plates 301 stacked in sequence, which are used to evenly distribute the mixed raw material gas entering the micro-scale reactor.

[0049] The gas diversion and preheating unit 2 includes a plurality of diversion baffles 202 spaced apart along a first direction and a plurality of diversion pipes 201 penetrating the diversion baffles 202, for preheating the mixed raw material gas and uniformly introducing the mixed raw material gas into the core micro-catalytic oxidation unit 1. The first direction is the transmission direction of the raw material reaction gas.

[0050] Optionally, the outer diameter of the flow guide tube 201 can be set to 1-30 mm and the wall thickness to 0.5-5 mm according to the different gas flux. Figure 5 As shown, the guide baffle 202 is evenly provided with openings, and a plurality of guide pipes 201 pass through the openings on the guide baffle 202 to achieve uniform distribution, and the center distance between adjacent guide pipes 201 is ≤50mm. The guide pipe 201 can be made of 316 stainless steel, which can withstand temperatures exceeding 600°C and has good heat transfer performance.

[0051] The core micro-catalytic oxidation unit 1 includes a plurality of groups of alternately stacked gas diversion layers 101 and microchannel catalytic layers 102. Among them, a fractal channel is provided on the gas diversion layer 101 for accurately distributing the mixed raw material gas to the microchannel catalytic layer 102. The microchannel catalytic layer 102 includes a plurality of microchannels with catalysts distributed therein, and the microchannels are connected to the fractal channels, so that the mixed raw material gas transported from the gas diversion and preheating unit 2 undergoes a catalytic oxidation reaction.

[0052] After low-concentration methane is mixed with air, it enters the reactor as raw gas, and first passes through the honeycomb flow-equalizing mesh plate 301 in the gas flow-equalizing unit 3 to achieve uniform distribution of the mixed gas. The gas then enters the flow-guiding pipe 201 of the gas diversion and preheating unit 2, where it is further evenly mixed during the diversion process, and the heat exchange efficiency is improved by extending the gas residence time. The gas then enters the core micro-catalytic oxidation unit 1. In the gas diversion layer 101, the raw gas is evenly distributed to several microchannels of the microchannel catalytic layer 102 through the fractal flow channel, and is fully contacted with the loaded high-efficiency methane catalytic oxidation catalyst in the microchannel catalytic layer to complete the catalytic oxidation reaction.

[0053] Optionally, each honeycomb flow-averaging mesh plate 301 is composed of a honeycomb plate 302 , and the honeycomb plate 302 has hexagonal channels evenly distributed thereon, and the side length of the cross-section of the hexagonal channels is 0.1 mm to 3 mm.

[0054] As an optional embodiment, the gas flow equalization unit 1 includes four honeycomb flow equalization mesh plates 301 stacked in sequence, and each honeycomb flow equalization mesh plate 301 is rotated 45° relative to the previous honeycomb flow equalization mesh plate 301 and stacked. Therefore, the mixed raw gas entering from the air inlet can fully ensure uniform mixing and distribution of the gas when passing through the staggered and stacked honeycomb flow equalization mesh plates 301, thereby avoiding local differences in subsequent catalytic reactions.

[0055] Optionally, the microscale reactor also includes a safety unit, specifically, the safety unit includes a shell 401, a sensor, an inlet flame arrester 404 and an outlet explosion relief piece 405. The shell 401 is a metal cylinder and can be made of materials such as stainless steel and aluminum alloy. The gas diversion and preheating unit 2 and the core micro-catalytic oxidation unit 1 are both arranged in the shell 401. The air inlet is equipped with a first sensor 402 for real-time monitoring of the parameters of the raw gas flow entering the reactor, such as flow, pressure and temperature, so as to achieve dynamic regulation of the raw gas flow by linkage with the control system. The air outlet is equipped with a second sensor 403 to detect the temperature, pressure and concentration of the main components of the reaction generated gas in real time; the alarm system can be linked to trigger a safety protection mechanism, such as adjusting the reaction parameters or emergency shutdown, when the temperature or pressure of the generated gas exceeds the set value. An inlet flame arrester 404 is also provided after the inlet 5 of the mixed raw gas, and an outlet explosion relief piece 405 is provided at the outlet to provide double safety protection to prevent the risk of explosion caused by uneven mixing of the raw gas.

[0056] Optionally, the periphery of the guide baffle 202 contacts the inner wall portion of the housing 401 to define a flow-blocking portion through which gas cannot pass and a gap portion through which gas can pass. Figure 5 As shown, the periphery of the guide baffle 202 is in the shape of a circular segment, the arc portion contacts the inner wall of the shell 401 to form a sealing section, and the gas cannot pass through; while the straight segment portion does not contact the inner wall of the shell 401 to form a gap portion, and the gas can pass through. Figure 3 , the gaps between adjacent guide baffles 202 are staggered in the second direction, so that the high-temperature gas flowing out of the core micro-catalytic oxidation unit 1 flows through the outside of the guide pipe 201 along the tortuous path defined by the guide baffles 202, and then is guided to the gas outlet. In other words, the high-temperature gas generated by the reaction is guided by the guide baffles in the gas guide and preheating unit, and flows through the outside of the guide pipe in an S-shaped path 601, so as to achieve rapid preheating of the unreacted methane gas in the guide pipe, thereby improving the thermal efficiency of the system and significantly reducing energy consumption.

[0057] Further, see Figure 6-9 , which shows a more detailed structure of the core micro-catalytic oxidation unit 1. Figure 8As shown, the fractal flow channel on the gas flow dividing layer 101 includes a multi-stage distribution flow channel, wherein the first-stage distribution flow channel 1002 is located at the center 1001 of the gas flow dividing layer 101, and is used to introduce the fully preheated mixed raw material gas; the two end outlets of the first-stage distribution flow channel 1002 are respectively connected to the middle inlet of the second-stage distribution flow channel 1003; the two end outlets of the second-stage distribution flow channel 1003 are connected to the middle inlet of the third-stage distribution flow channel 1004... The two end outlets of the N-1-stage distribution flow channel are connected to the middle inlet of the N-stage distribution flow channel; the two end outlets of the N-stage distribution flow channel are connected to the microchannel catalytic layer through the through hole 1005, so as to evenly distribute the mixed raw material gas to the microchannel catalytic layer 102. Wherein, N is an integer greater than or equal to 2.

[0058] like Fig. 9 As shown, further, the through hole 1006 of the microchannel catalytic layer 102 in the core micro-catalytic oxidation unit 1 receives several streams of raw gas diverted by the gas diversion layer 101, and these raw gas flows evenly along the corresponding multiple microchannels 1007 in the microchannel catalytic layer. Each microchannel 1007 is loaded with a high-efficiency methane catalytic oxidation catalyst, so that the raw gas is fully in contact with the catalyst during the flow and completes the catalytic oxidation reaction. The gas generated by the reaction is collected to the central collection area of ​​the microchannel catalytic layer 102 through the microchannel gas flow collection port 1008, ensuring the uniform collection of the reaction gas and guiding it to the subsequent processing unit.

[0059] Thus, efficient distribution and uniform delivery of gas are achieved, ensuring sufficient contact between the gas and the catalyst in the microchannel catalytic layer 102, thereby improving the catalytic reaction efficiency and system stability.

[0060] Furthermore, the manufacturing method of the core micro-catalytic oxidation unit 1 comprises the following steps:

[0061] (1) According to the selected material, the microchannels and through holes are processed on the substrate layer by micro-milling, dry / wet chemical etching, soft lithography, laser processing, LIGA process or electrical discharge machining process;

[0062] (2) uniformly attaching the catalyst to the surface and / or interior of the microfluidic channel to form the microfluidic channel catalytic layer;

[0063] (3) The gas diversion layer and the microchannel catalytic layer are stacked in sequence according to the design order, and the structure is packaged by clamping, plasma treatment or hot pressing bonding, and the smooth flow path of the gas is ensured.

[0064] Furthermore, the types of methane catalytic oxidation catalysts used in the microchannel catalytic layer 102 of the core micro-catalytic oxidation unit 1 include but are not limited to transition metal oxides (such as Cr2O3, Mn2O3, Fe2O3, Co3O4, NiO and CuO), precious metal catalysts (such as Pd, Pt and Rh) and supported catalysts thereof, as well as doped and modified perovskite catalysts (such as LaMnO3 doped with Ni and Co) and bimetallic oxides (such as Co-Mn-based composite oxides).

[0065] The catalyst loading methods include surface loading method and mixed loading method, and the corresponding catalyst loading method can be selected according to the material of the microchannel catalyst layer 102. The surface loading method uses one or more methods of slurry coating, sol-gel, electrophoretic deposition, impregnation, physical vapor deposition or chemical vapor deposition to uniformly attach the catalyst to the microchannel wall. The mixed loading method processes the microchannel structure by mixing catalyst nanoparticles with chip preparation materials to achieve uniform distribution and efficient attachment of the catalyst in the microchannel, thereby ensuring the stability and efficiency of the catalytic reaction.

[0066] Furthermore, after the core micro-catalytic oxidation unit 1 is manufactured, the packaged component units are precisely docked and cascaded to form a complete microscale reactor.

[0067] The beneficial effects of the present application are reflected in the following aspects: Through the innovatively designed microscale reactor, the methane catalytic oxidation reactor shows excellent performance in the catalytic conversion of low-concentration methane, and has the significant advantages of high safety, low energy consumption and high catalytic efficiency. The reaction device adopts a unique gas diversion and preheating unit design, and uses the high-temperature gas generated by the reaction to quickly preheat the raw gas in an S-shaped path, effectively shortening the reaction preparation time and reducing overall energy consumption. The core micro-catalytic oxidation unit combines precise dendritic fractal flow channels and microchannel catalytic layer structures to greatly improve the mass transfer and heat transfer efficiency of the gas, while optimizing the catalyst activity and utilization rate to achieve efficient oxidation conversion of methane. In addition, the modular structural design of the device is not only suitable for coal mine gas resource utilization and emission reduction, but also easy to manufacture and large-scale promotion, and has important industrial application value in the fields of efficient energy utilization and environmental protection.

[0068] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application.

[0069] Embodiment 1:

[0070] This embodiment provides a micro-scale reactor for catalytic oxidation of low-concentration methane, wherein the core micro-catalytic oxidation unit 1 in the micro-catalytic oxidation chamber is made of aluminum oxide, the catalyst is transition metal oxide NiO, and the catalyst is loaded by a slurry coating method in a surface loading method.

[0071] The following combination Figures 1 to 9 To illustrate the reaction process of this embodiment. In the low-concentration methane catalytic oxidation micro-scale reactor provided in this embodiment, low-concentration methane is mixed with air and enters the reactor as raw gas from the raw gas inlet 5, and first passes through the honeycomb flow-equalizing mesh plate 301 in the gas flow-equalizing unit 3. The honeycomb flow-equalizing mesh plate is composed of four layers of hexagonal honeycomb plates 302 stacked together, and a multi-layer rotating stacking structure is adopted to make the mixed gas evenly distributed when flowing through the honeycomb plate, thereby ensuring the uniformity of the gas. Subsequently, the evenly distributed gas enters the guide tube 201, and in the guide tube, the gas is further evenly mixed and heat exchange is achieved through the preheating effect of the external guide baffle 202 during the guide process. The length and structural design of the guide tube 201 together with the external guide baffle constitute the gas guide and preheating unit 2, which quickly approaches the start-up temperature required for the catalytic oxidation reaction by extending the residence time of the raw gas, thereby laying a thermodynamic foundation for the subsequent catalytic oxidation reaction.

[0072] Reference Figure 6-9 The preheated raw gas enters the core micro-catalytic oxidation unit 1, which is composed of 10 groups of alternately stacked gas diversion layers 101 and microchannel catalytic layers 102. Figure 8 The gas distribution layer 101 adopts a branch-like fractal flow channel design to evenly distribute the raw gas entering from the central core inlet 1001 to 100 branch flow channels. For example, in the first-level distribution flow channel 1002, the raw gas is divided into three streams and flows to their respective sub-flow channels; in the second-level distribution flow channel 1003, the gas flow is again divided into three streams and enters the next-level sub-flow channel; in the third-level distribution flow channel 1004, the gas flow is again divided into two streams and finally transported to the inside of the microchannel catalytic layer 102 through the through hole 1005 connected to the microchannel catalytic layer.

[0073] Reference Fig. 9, the raw gas is transported to the microchannel catalytic layer 102 through the through hole 1005, and further enters the microchannel 1007 loaded with a high-efficiency methane catalytic oxidation catalyst through the through hole 1006. The microchannel catalytic layer 102 includes 100 microchannels of the same design. When the gas flows in the channel, it fully contacts the catalyst on the wall surface, and a catalytic oxidation reaction occurs, and methane is efficiently converted into a high-temperature purified gas. After the purified gas is collected through the reaction gas flow collection port 1008, it enters the next group of micro-catalytic oxidation units as a new round of raw gas, and the catalytic oxidation reaction is cyclically carried out. The high-temperature gas generated by the reaction flows through the guide baffle in an S-shaped path, and the unreacted methane gas in the guide tube 201 is quickly preheated by external heating, realizing an efficient preheating cycle of the reaction gas to the raw gas, thereby significantly reducing the overall system energy consumption.

[0074] Finally, the purified gas that has completed the reaction is discharged from the reaction gas outlet 6. To ensure the safe operation of the system, the reactor is equipped with a safety protection unit 4 consisting of a shell 401, an air inlet sensor 402, an air outlet sensor 403, an inlet flame arrester 404, an outlet explosion relief plate 405 and an inspection door 406 to provide comprehensive safety protection. Through the above design, the microscale reactor of the present application can efficiently and safely achieve catalytic oxidation of low-concentration methane under complex working conditions such as coal mines, while having significant energy efficiency and reliability, and is suitable for industrial application scenarios of resource utilization and environmental protection.

[0075] Preparation method: A micro-milling process is used to carve a pre-set channel pattern on the surface of each layer of a micro-catalytic reaction unit made of aluminum oxide, and the holes are drilled. About 0.1g of NiO nanoparticles are weighed as a catalyst, mixed with an appropriate amount of deionized water, a dispersant and a viscosity regulator in a certain proportion, and placed in a high-speed homogenizer for stirring until the mixture is uniformly mixed to form a uniform slurry. The side of the micro-catalytic reaction unit with a microchannel structure is immersed in the prepared slurry for 10-20 minutes so that the catalyst can fully adhere to the surface and inside of the microchannel. The reaction unit is then taken out and the excess slurry on the surface and in the pores is blown off with an air gun to ensure the uniformity of the catalyst distribution and the patency of the microchannel. Finally, the treated reaction unit is placed in a muffle furnace or a tubular furnace and calcined at a temperature of 400-800°C for 2-6 hours to fix the catalyst and enhance its adhesion, providing a stable and efficient catalytic active surface for the catalytic oxidation reaction.

[0076] Reference Figure 6 and Figure 7 The gas diversion layer coated with catalyst nanoparticles and the microchannel catalytic layer are used as a group of micro-catalytic oxidation units. Multiple groups of micro-catalytic oxidation units are aligned with each other, and the gaps between the layers are filled with adhesives. The layers are fixed and packaged with clamps and installed in the micro-catalytic oxidation chamber of the reactor.

[0077] The detection analysis includes the following steps:

[0078] 1. According to the experimental device design, multiple groups of micro-catalytic oxidation units are connected in series through pipelines to form a catalytic reaction module, and the module is placed in a heat preservation device. The module is connected to the methane gas source, air gas source, preheater, pressure regulator, flow meter, gas chromatograph and multiple control valves in sequence to ensure that the gas flow path of the device is closed and controllable.

[0079] 2. The raw gas is a mixture of 1% methane (CH4) and 99% air, and the flow rate is set to 100 mL / min. The inlet and outlet gases of the reactor are monitored and analyzed online by gas chromatographs. The conversion rate of methane is calculated by the formula: CH4 (%) = 100*(CH 4in -CH 4out ) / CH 4in Among them, the reaction equation of methane catalytic oxidation is: Main reaction:

[0080] 3. The temperature is controlled from room temperature to 600°C, and maintained for 10-30 minutes to ensure that the system is stable before starting the measurement. The measurement process is carried out in a cooling manner, and the temperature is controlled at 700°C, 600°C, 500°C, and 400°C in turn, and remains stable at each temperature point. Samples are taken and analyzed every 10 minutes, and six sets of data are collected at each temperature point. By analyzing the exhaust gas components at different temperatures, the low-temperature activity of the catalyst and the stability of its catalytic performance are evaluated.

[0081] Reference Fig.10 , using gas chromatography for online analysis, the main component detected was CH4 (CO and H2 were not detected). NiO catalyst showed excellent catalytic performance at different temperatures: the methane conversion rate reached more than 99.8% at 700℃, 99.5% at 600℃, 98.3% at 500℃, and 18.7% at 400℃.

[0082] Embodiment 2:

[0083] This embodiment provides a microscale reactor for catalytic oxidation of low-concentration methane, wherein the microcatalytic oxidation unit material in the microcatalytic oxidation chamber is polydimethylsiloxane (PDMS), the catalyst is transition metal oxide Fe2O3, and the catalyst is loaded by a mixed loading method.

[0084] Reaction process: The reaction process is consistent with that in Example 1.

[0085] Preparation method: The processing method of the micro-catalytic oxidation unit adopts soft lithography, specifically, first use drawing software to draw the required geometric channel structure, and use photolithography to prepare an anode template with a microchannel pattern on the surface of a silicon wafer.

[0086] The PDMS prepolymer and its matching curing agent are mixed in a ratio of 10:1, stirred and mixed evenly, and then poured onto the prepared anode mold. In the process of preparing the reaction unit layer 200, about 0.2g of Fe2O3 catalyst nanopowder is added to the PDMS mixed prepolymer and stirred evenly. The mold is vacuumed to remove bubbles in the mixed prepolymer, and placed in an oven at 70-90°C and heated for 2-6 hours until it is completely cured.

[0087] The demoulding cutting is carried out and holes are punched using a puncher. The layers of the micro-catalytic oxidation unit are aligned and processed using an oxygen plasma cleaning machine. The bonded and completed chip layers are firmly adhered to each other and installed in the micro-catalytic oxidation chamber of the reactor.

[0088] The detection and analysis steps are consistent with those in Example 1.

[0089] Reference Fig.11 , using gas chromatography for online analysis, the main component detected was CH4 (CO and H2 were not detected). The Fe2O3 catalyst showed excellent catalytic performance at different temperatures: the methane conversion rate reached 99.3% at 700℃, 99.8% at 600℃, 86.8% at 500℃, and 14.8% at 400℃.

[0090] Embodiment 3:

[0091] This embodiment provides a microscale reactor for catalytic oxidation of low-concentration methane, wherein the microcatalytic oxidation unit material in the microcatalytic oxidation chamber is polydimethylsiloxane (PDMS), the catalyst is transition metal oxide CO3O4, and the catalyst is loaded by a mixed loading method.

[0092] Reaction process: The reaction process is consistent with that in Example 1.

[0093] Preparation method: The preparation method is consistent with Example 2.

[0094] The detection and analysis steps are consistent with those in Example 1.

[0095] Reference Fig.12 , using gas chromatography for online analysis, the main component detected was CH4 (CO and H2 were not detected). The CO3O4 catalyst showed excellent catalytic performance at different temperatures: the methane conversion rate reached 99.7% at 700℃, 99.2% at 600℃, 78.2% at 500℃, and 7.2% at 400℃.

[0096] Embodiment 4:

[0097] This embodiment provides a micro-scale reactor for catalytic oxidation of low-concentration methane, wherein the micro-catalytic oxidation unit in the micro-catalytic oxidation chamber is made of aluminum oxide, the catalyst is transition metal oxide Mn2O3, and the catalyst is loaded by a slurry coating method in a surface loading method.

[0098] Reaction process: The reaction process is consistent with that in Example 1.

[0099] Preparation method: The preparation method is consistent with Example 1.

[0100] The detection and analysis steps are consistent with those in Example 1.

[0101] Reference Fig.13 , using gas chromatography for online analysis, the main component detected was CH4 (CO and H2 were not detected). Mn2O3 catalyst showed excellent catalytic performance at different temperatures: the methane conversion rate reached 98.8% at 700℃, 98.8% at 600℃, 66.8% at 500℃, and 7.2% at 400℃.

[0102] Embodiment 5:

[0103] This embodiment provides a micro-scale reactor for catalytic oxidation of low-concentration methane, wherein the micro-catalytic oxidation unit in the micro-catalytic oxidation chamber is made of aluminum oxide, the catalyst is transition metal oxide CuO, and the catalyst is loaded by a slurry coating method in a surface loading method.

[0104] Reaction process: The reaction process is consistent with that in Example 1.

[0105] Preparation method: The preparation method is consistent with that in Example 1.

[0106] The detection and analysis steps are consistent with those in Example 1.

[0107] Reference Fig.14 , using gas chromatography for online analysis, the main component detected was CH4 (CO and H2 were not detected). CuO catalyst showed excellent catalytic performance at different temperatures: the methane conversion rate reached 99.8% at 700℃, 99.5% at 600℃, 34% at 500℃, and 4.8% at 400℃.

[0108] Embodiment 6:

[0109] This embodiment provides a micro-scale reactor for catalytic oxidation of low-concentration methane, wherein the micro-catalytic oxidation unit in the micro-catalytic oxidation chamber is made of aluminum oxide, the catalyst is transition metal oxide Cr2O3, and the catalyst is loaded by a slurry coating method in a surface loading method.

[0110] Reaction process: The reaction process is consistent with that in Example 1.

[0111] Preparation method: The preparation method is consistent with Example 1.

[0112] The detection and analysis steps are consistent with those in the embodiment.

[0113] Reference Fig.15 , using gas chromatography for online analysis, the main component detected was CH4 (CO and H2 were not detected). Cr2O3 catalyst showed excellent catalytic performance at different temperatures: the methane conversion rate reached 98% at 700℃, 76% at 600℃, 15% at 500℃, and 2.1% at 400℃.

[0114] The above shows and describes the basic principles, main features and excellent characteristics of the present application. Those skilled in the art should understand that the above embodiments do not limit the protection scope of the present application in any form, and all technical solutions obtained by equivalent replacement and the like fall within the protection scope of the present application.

[0115] The parts not involved in this application are the same as the existing technology or can be realized by processing with the existing technology.

Claims

1. A microscale reactor for realizing low-concentration methane catalytic oxidation, characterized in that: The microscale reactor comprises a gas flow equalization unit, a gas flow guiding and preheating unit and a core micro-catalytic oxidation unit which are cascaded in sequence; The gas flow balancing unit comprises a plurality of honeycomb flow balancing mesh plates stacked in sequence, which are used to evenly distribute the mixed raw material gas entering the microscale reactor; The gas flow guiding and preheating unit comprises a plurality of flow guiding baffles spaced apart along a first direction and a plurality of flow guiding pipes passing through the flow guiding baffles, and is used to preheat the mixed raw material gas and uniformly guide it into the core micro-catalytic oxidation unit; The core micro-catalytic oxidation unit includes several groups of alternately stacked gas diversion layers and microchannel catalytic layers. The gas diversion layer includes a fractal channel for accurately distributing the mixed raw gas to the microchannel catalytic layer. The microchannel catalytic layer includes a plurality of microchannels with catalysts distributed therein. The microchannels are connected to the fractal channel for catalytically oxidizing the mixed raw gas.

2. The microscale reactor according to claim 1, characterized in that The honeycomb flow-averaging mesh plate is evenly distributed with hexagonal channels, and the side length of the cross-section of the hexagonal channels is 0.1 mm to 3 mm.

3. The microscale reactor according to claim 1 or 2, characterized in that: The gas flow balancing unit includes four honeycomb flow balancing mesh plates stacked in sequence, and each of the honeycomb flow balancing mesh plates is rotated 45° relative to the previous honeycomb flow balancing mesh plate and stacked to achieve uniform distribution of the mixed raw material gas.

4. The microscale reactor according to claim 1, characterized in that The microscale reactor further comprises a safety unit, which comprises a shell, and the gas guiding and preheating unit and the core micro-catalytic oxidation unit are arranged in the shell.

5. The microscale reactor according to claim 4, characterized in that The periphery of the guide baffle is in contact with the inner wall portion of the shell to define a baffle portion through which the gas cannot pass and a gap portion through which the gas can pass. The gap portions of adjacent guide baffles are staggered in a second direction perpendicular to the first direction, so that the high-temperature gas flowing out of the core micro-catalytic oxidation unit flows through the outside of the guide pipe along the tortuous path defined by the guide baffle to preheat the mixed raw gas in the guide pipe.

6. The microscale reactor according to claim 1, 4 or 5, characterized in that: The outer diameter of the guide pipe is 1-30 mm, and the wall thickness is 0.5-5 mm; a plurality of the guide pipes evenly pass through the guide baffle, and the center distance between adjacent guide pipes is ≤50 mm.

7. The microscale reactor according to claim 1, characterized in that The fractal flow channel includes a multi-stage distribution flow channel, wherein the first-stage distribution flow channel is located at the center of the gas diversion layer, and is used to introduce the mixed raw material gas that has been fully preheated; the two end outlets of the first-stage distribution flow channel are respectively connected to the middle inlet of the second-stage distribution flow channel; the two end outlets of the second-stage distribution flow channel are connected to the middle inlet of the third-stage distribution flow channel... The two end outlets of the N-1-stage distribution flow channel are connected to the middle inlet of the N-stage distribution flow channel; the two end outlets of the N-stage distribution flow channel are connected to the microchannel catalytic layer through through holes to evenly distribute the mixed raw material gas to the microchannel catalytic layer; wherein N is an integer greater than or equal to 2.

8. The microscale reactor according to claim 1 or 7, characterized in that: The catalyst includes one or more of a transition metal oxide catalyst, a noble metal catalyst, a doped and modified perovskite catalyst and a bimetallic oxide catalyst.

9. The microscale reactor according to claim 4, characterized in that: The safety unit also includes a first sensor arranged at the air inlet of the shell, a second sensor arranged at the air outlet of the core micro-catalytic oxidation unit, a flame arrester arranged at the inlet of the gas equalizing unit, and an explosion relief plate arranged at the air outlet of the core micro-catalytic oxidation unit.

10. The microscale reactor according to claim 1 or 7, characterized in that: The manufacturing method of the core micro-catalytic oxidation unit comprises the following steps: (1) machining the microchannels and through holes on the substrate layer by micro-milling, dry / wet chemical etching, soft lithography, laser machining, LIGA process or electrospark machining process according to the selected material; (2) uniformly attaching the catalyst to the surface and / or interior of the microfluidic channel to form the microfluidic channel catalytic layer; (3) stacking the gas diversion layer and the microchannel catalytic layer in sequence according to the design order, packaging the structure by clamping, plasma treatment or hot pressing bonding, and ensuring the smooth flow of the gas flow path.

11. The microscale reactor according to claim 10, characterized in that: The catalyst is uniformly attached to the surface and / or inside of the microchannel by one or more methods selected from slurry coating, sol-gel, electrophoretic deposition, impregnation, physical vapor deposition or chemical vapor deposition.

12. The microscale reactor according to claim 10, characterized in that: The catalyst nanoparticles are mixed with the materials for preparing the microchannel catalytic layer and then processed into the microchannel structure, thereby achieving uniform distribution of the catalyst on the surface and / or inside of the microchannel.

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