A continuous microchannel reactor

Abstract

The utility model relates to a kind of continuous microchannel reaction device, including mixed reaction mechanism, raw material shunt mechanism, shunt control mechanism and temperature control module, mixed reaction mechanism includes microchannel mixer and multiple microchannel reactor units of series arrangement, raw material shunt mechanism includes first reactant input channel and second reactant input channel, first reactant input channel and one second reactant input channel are connected to microchannel mixer, at least another second reactant input channel shunt connection is connected to different microchannel reactor unit, and each branch of first reactant input channel and second reactant input channel is equipped with flow control unit, temperature control module includes the heat exchange mechanism of microchannel mixer and each microchannel reactor unit. The utility model can reduce the generation of by-product, can effectively improve production efficiency while reducing product separation cost.

Description

Technical Field

[0001] This utility model belongs to the field of chemical technology, specifically relating to a continuous microchannel reaction device and its application. Background Technology

[0002] A microchannel reactor is a fluid device with internal structural features on the sub-millimeter scale. Designed based on microfluidics principles, it utilizes microfluidic technology to cut the flowing reaction fluid through specially designed microstructural units, achieving mixing and heat exchange at micrometer-scale spatial and temporal dimensions, or even smaller. Microchannel reactors offer advantages for specific chemical reactions, including high reaction efficiency, good safety, small size, large specific surface area, and fast heat and mass transfer rates. However, for some rapidly exothermic reactions, which are intensely exothermic and prone to product degradation or byproduct formation due to transport constraints, strict control of the reactor's internal flow rate and temperature is crucial. Current microchannel reactor technologies are not yet ideal for precisely controlling the reaction process and byproducts.

[0003] Nitro compounds are widely used in various fields such as pharmaceuticals, pesticides, and dyes as important chemical intermediates. Currently, industrial nitration reactions generally use traditional batch reactors to produce nitro compounds. However, traditional batch reactors have many drawbacks, such as low mass and heat transfer efficiency. Therefore, during the exothermic nitration reaction process, temperature surges can easily occur, leading to explosions and safety accidents. Furthermore, excessively high local temperatures inside the reactor generate large amounts of byproducts such as dinitro compounds and isomers, reducing yield and increasing product separation costs.

[0004] In summary, there is an urgent need for a continuous microchannel reactor that can prevent excessively vigorous reactions within the reactor, reduce the generation of byproducts, and effectively improve production efficiency while reducing product separation costs. Utility Model Content

[0005] The purpose of this invention is to provide a continuous microchannel reaction device that can prevent excessively vigorous reactions in the reactor, reduce the generation of by-products, and effectively improve production efficiency while reducing product separation costs.

[0006] The above objective is achieved through the following technical solution: a continuous microchannel reaction device, comprising a mixing reaction mechanism, a raw material diversion mechanism, a diversion control mechanism, and a temperature control module. The mixing reaction mechanism includes a microchannel mixer and multiple microchannel reactor units arranged in series. The outlet of the microchannel mixer is connected to the inlet of the first microchannel reactor unit connected in series. The raw material diversion mechanism includes at least one first reactant input channel and at least two second reactant input channels. The first reactant input channel and one of the second reactant input channels are connected to the inlet of the microchannel mixer, and at least one other second reactant input channel is diverted to the inlet of different microchannel reactor units. Each branch of the first reactant input channel and the second reactant input channel is provided with an independent flow control unit. The temperature control module includes a heat exchange mechanism independently arranged in the microchannel mixer and each microchannel reactor unit, and a flow control element for independently controlling the flow rate of the heat exchange medium in each heat exchange mechanism.

[0007] In this novel reactor, particularly for liquid-liquid reactions, the first reactant is directly input into a microchannel mixer via its independent flow control unit. The second reactant is divided into multiple streams. One stream, connected to the microchannel mixer via an independent flow control unit and a second reactant input channel, is pre-mixed with the first reactant. After pre-mixing, it enters the first microchannel reactor unit and flows sequentially through subsequent microchannel reactor units for reaction. Simultaneously, the second reactant is input into different microchannel reactor units via another second reactant input channel to replenish the second reactant, increasing the concentration of the second reactant in each microchannel reactor unit. Each stream is controlled by an independent flow control unit.

[0008] In this way, the microchannel mixer improves the initial mixing efficiency, disperses the injection of the second reactant, achieves batch feeding, disperses the heat release, and achieves heat equalization. Simultaneously, since the heat release varies within each microchannel reactor unit during the reaction, each microchannel mixer and each microchannel reactor unit is equipped with an independent heat exchange mechanism for temperature control. Individual temperature control of different microchannel reactor units allows for more stable control of the reaction temperature and avoids localized overheating. Overall, the internal flow rate and temperature of the reactor can be strictly controlled, effectively preventing explosions and safety accidents caused by strong exothermic temperature surges. Furthermore, it allows for control of by-product parameters, improving yield while reducing product separation costs.

[0009] A further technical solution is that the liquid holding capacity of the microchannel reactor units arranged in series increases in a predetermined gradient from the first microchannel reactor unit to the last microchannel reactor unit.

[0010] In other words, the first unit has the smallest liquid holding capacity, and the last unit has the largest. The specific microchannel reactor unit with different liquid holding capacities is selected based on different reaction conditions. Generally, due to the decreasing reactant concentration and rate-decreasing characteristic as the reaction proceeds, the high exothermic phase in the early stages requires small volumes for rapid heat transfer, while the later stages require large volumes to ensure complete reaction. However, it should be noted that the liquid holding capacity of the intermediate microchannel reactor units from the first to the last does not always increase continuously. For example, the liquid holding capacity may increase from the first to the second, and from the second to the third, but may not increase further afterward. This indicates that the overall liquid holding capacity increases in a predetermined gradient from the first to the last microchannel reactor unit.

[0011] A further technical solution is that the internal flow channel of the microchannel reactor unit includes multiple heart-shaped structures. The heart-shaped structure includes a branching section and a confluence section. The branching section and the confluence section are alternately connected and connected in series to form a micro-reaction tube. The branching section is used to divide the fluid into two branches that enter the confluence section. The confluence section can turn the fluid and merge it into a single flow path to enter the branching section of the next heart-shaped structure.

[0012] The internal flow channel structure of this microchannel reactor unit enhances the mixing effect through the collision of splitting and merging flows. Furthermore, during the reaction process, the high-temperature fluid is evenly distributed to the two branches multiple times, which facilitates rapid heat transfer to the heat exchange mechanism of the microchannel reactor unit for timely heat exchange and reduces the risk of side reactions caused by local overheating.

[0013] A further technical solution is that the heat exchange mechanism includes at least two opposing heat exchange modules, with the microchannel reactor sandwiched between the heat exchange modules. Each heat exchange module is equipped with a heat exchange medium channel and a heat exchange medium connector, the latter connecting to the heat exchange medium channel. The microchannel reactor unit adopts a two-sided, independently covered heat exchange design, with simultaneous temperature control on the upper and lower surfaces of the reactor. This facilitates precise temperature control of the material, thereby enabling better control of the reaction.

[0014] A further technical solution is that the heat exchange module includes a main heat exchange plate, an auxiliary heat exchange plate, and a sealing gasket arranged opposite to each other, wherein the sealing gasket is disposed between the main heat exchange plate and the auxiliary heat exchange plate to form the heat exchange medium flow channel.

[0015] A further technical solution is that the microchannel reactor unit is provided with a ferrule connector. The connecting end of the ferrule connector passes through the heat exchange module and is connected to the liquid inlet or liquid outlet of the microchannel reactor unit. The connecting section of the ferrule connector is conical and has a limiting step extending radially outward. The inner walls of the liquid inlet and the liquid outlet are provided with a stepped structure that is adapted to the connecting section of the ferrule connector and is smaller on the outside and larger on the inside. The limiting step abuts against the stepped structure to form a stepped sealing.

[0016] The ferrule connector is preferably made of polytetrafluoroethylene (PTFE). The tapered connecting section of the ferrule connector fits snugly against the outer small and inner large stepped structure of the inlet / outlet. Combined with the contact between the limiting step and the stepped structure, a double sealing effect is achieved by sealing the tapered surface and the stepped surface, resulting in a tighter fit. This effectively prevents material leakage from gaps under high pressure, making it particularly suitable for pressure fluctuation scenarios that may occur in strongly exothermic reactions. On the other hand, the limiting step can bear part of the axial pressure, distributing the force between the ferrule connector and the reactor interface to the stepped surface, preventing axial displacement or deformation of the connecting section due to high pressure. Combined with the high pressure resistance of PTFE, the overall pressure resistance limit of the structure is further improved. Tests have verified that the pressure resistance can reach 10MPa, far exceeding that of traditional silicon carbide microchannel reactors (2-3MPa), making it safer and more stable.

[0017] A further technical solution is that the first reactant input channel includes a first reactant storage tank and a first delivery pipeline connecting the first reactant storage tank and the microchannel mixer; the second reactant input channel includes multiple second reactant storage tanks, and the multiple second reactant storage tanks are respectively connected to the corresponding microchannel reactor unit through the second delivery pipeline; or the second reactant input channel includes one second reactant storage tank, and the second reactant storage tank is connected to the corresponding microchannel reactor unit through multiple second delivery pipelines.

[0018] A further technical solution is to install preheating heat exchangers on the first and second conveying pipelines. In this way, the materials from each pipeline are preheated to a predetermined temperature by the heat exchangers before entering the microchannel mixer or microchannel reactor unit.

[0019] A further technical solution is that the temperature control module also includes a main circulation pipeline and a heat exchange medium supply unit. The main circulation pipeline includes multiple branch pipelines that are respectively connected to the heat exchange mechanisms of the microchannel mixer and the microchannel reactor unit. The flow control component is set on the branch pipelines. The heat exchange medium supply unit is used to regulate the temperature of the heat exchange medium to a preset range and can provide power for the circulation flow of the heat exchange medium in the main circulation pipeline and the branch pipelines.

[0020] A further technical solution is that the heat exchange medium supply unit is an integrated cold and hot circulation unit, and the flow control component is a flow control valve.

[0021] Compared with the prior art, the implementation of the present invention has the following technical effects: (1) By adopting a batch precise feeding strategy, the feeding rhythm can be adjusted according to the reaction requirements, making the reaction process more peaceful and avoiding excessively violent reactions in the front reactor, thereby reducing the generation of by-products, which not only improves production efficiency but also reduces product separation costs. At the same time, it enables continuous production, which greatly improves production efficiency.

[0022] (2) The use of one-piece molded silicon carbide as the reaction plate of the microchannel reactor not only has strong corrosion resistance and oxidation resistance, but also is suitable for high-temperature oxidation environment; its high thermal conductivity ensures efficient and uniform mass and heat transfer, avoiding local temperature differences; its high mechanical strength can withstand high pressure conditions and has a long service life; its high chemical inertness reduces material contamination and is suitable for the production of high-purity products; its excellent high-temperature stability and low coefficient of thermal expansion can reduce thermal stress; its large specific surface area and short diffusion distance enhance the material mixing effect and further support the efficient operation of continuous production.

[0023] (3) By accurately metering, preheating and premixing the reactants, the foundation is laid for the efficient reaction in the subsequent microchannel reactor, and the stability and matching degree of the initial reaction conditions are improved. Attached Figure Description

[0024] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of this utility model. The illustrative embodiments of this utility model and their descriptions are used to explain this utility model and do not constitute an improper limitation of this utility model.

[0025] Figure 1 This is a schematic diagram of the arrangement structure of a continuous microchannel reaction device according to one embodiment of the present invention. Figure 2 This is a cross-sectional schematic diagram of a microchannel reactor unit according to one embodiment of the present invention; Figure 3 This is an exploded view of the connection structure between the microchannel reactor unit and the heat exchange mechanism according to one embodiment of the present invention.

[0026] In the picture: 1. Microchannel mixer 2. Microchannel reactor unit 3. Preheating heat exchanger 4. Flow control unit 5 First reactant storage tank; 6 Second reactant storage tank; 7 Flow control components; 8 Main circulation pipeline. 9 Heat exchange medium supply unit 10 Heart-shaped structure 11 Branch section 12 Merging section 13 Microreactor 14 Main Heat Exchanger Plate 15 Auxiliary Heat Exchanger Plate 16 Sealing Gasket 17 Compression Fitting 18 Heat Exchange Medium Fitting Detailed Implementation The present invention will now be described in detail with reference to the accompanying drawings. This description is merely illustrative and explanatory, and should not be construed as limiting the scope of protection of the present invention. Furthermore, those skilled in the art can combine the features in the embodiments described herein and in different embodiments according to the description in this document.

[0027] The embodiments of this utility model are as follows, please refer to... Figures 1-3A continuous microchannel reactor device includes a mixing reaction mechanism, a raw material diversion mechanism, a diversion control mechanism, and a temperature control module. The mixing reaction mechanism includes a microchannel mixer 1 and multiple microchannel reactor units 2 arranged in series. The outlet of the microchannel mixer 1 is connected to the inlet of the first microchannel reactor unit 2 connected in series. The raw material diversion mechanism includes at least one first reactant input channel and at least two second reactant input channels. The first reactant input channel and one of the second reactant input channels are connected to the inlet of the microchannel mixer 1, and at least one other second reactant input channel is diverted to the inlet of different microchannel reactor units 2. Each branch of the first reactant input channel and the second reactant input channel is provided with an independent flow control unit 4. The temperature control module includes a heat exchange mechanism independently arranged in the microchannel mixer 1 and each microchannel reactor unit 2, and a flow control element 7 for independently controlling the flow rate of the heat exchange medium in each heat exchange mechanism.

[0028] In this reactor, particularly for liquid-liquid reactions, the first reactant is directly input into the microchannel mixer 1 via its independent flow control unit 4. The second reactant is divided into multiple streams. One stream is connected to the microchannel mixer 1 via an independent flow control unit 4 and a second reactant input channel for premixing with the first reactant. After premixing, it enters the first microchannel reactor unit 2 and flows sequentially through subsequent microchannel reactor units 2 for reaction. Simultaneously, the second reactant is input into different microchannel reactor units 2 via another second reactant input channel to replenish the second reactant, increasing the concentration of the second reactant in each microchannel reactor unit 2. The flow rate of each stream is controlled by an independent flow control unit 4.

[0029] In this way, the microchannel mixer 1 improves the initial mixing efficiency, the second reactant is injected in a dispersed manner, achieving batch feeding, dispersing the heat release, and achieving heat equalization. Simultaneously, since the heat release varies within each microchannel reactor unit 2 during the reaction, both the microchannel mixer 1 and each microchannel reactor unit 2 are equipped with independent heat exchange mechanisms for temperature control. Individual temperature control of different microchannel reactor units 2 allows for more stable control of the reaction temperature, avoiding localized overheating. Overall, the internal flow rate and temperature of the reactor can be strictly controlled, effectively preventing explosions and safety accidents caused by strong exothermic temperature surges. Simultaneously, it allows for control of by-product parameters, improving yield while reducing product separation costs.

[0030] It should be noted that the liquid holdup of microchannel mixer 1 (ME) is very small, serving a premixing function, and its liquid holdup is not included in the total liquid holdup of the system. The two raw materials will undergo a partial but not vigorous reaction in the ME, as the ME primarily functions as a premixer, and the residence time of the raw materials is very short, allowing insufficient time for complete reaction. Premixing facilitates thorough mixing and reaction of the two materials in microchannel reactor unit 2 (MR). Depending on the situation, a second reactant is added to different amounts of MR, ensuring that the total amount of the second reactant added to the ME and MR, in molar ratio to the first reactant added to the ME, meets the reaction requirements.

[0031] In addition, when the second reactant is fed into different microchannel reactor units 2 through another second reactant input channel, the microchannel reactor unit 2 to be injected can be selected according to the actual situation, and the input amount of the second reactant is controlled by the flow control unit 4.

[0032] In one specific embodiment, the ME material is one of Inconel 625, Inconel 750, Hastelloy C276, or silicon carbide ceramic, selected as an SV-type unit. The SV-type unit is a cylinder assembled from corrugated plates of a specific specification. Its technical characteristics are: maximum dispersion of 1-2 μm, and liquid-liquid and gas-gas phase non-uniformity coefficients of sX≤1~5%. It is suitable for liquid-liquid, liquid-gas, and gas-gas mixing emulsions, reactions, absorption, extraction, and enhanced heat transfer processes with a viscosity ≤102 centipoise. dh≤3.5 is suitable for clean media with a viscosity ≤102 centipoise, and dn≥5. The applied media may contain a small amount of non-adhesive impurities.

[0033] The flow control unit 4 is preferably a metering pump.

[0034] All pipe fittings in the reactor unit that come into contact with the material are made of corrosion-resistant Inconel 625, Inconel 750, and Hastelloy C276 alloy.

[0035] The pump body and pipelines in contact with the corrosive materials are made of polytetrafluoroethylene (PTFE) and Hastelloy C276; the material pipelines are also made of PTFE and Hastelloy C276; and the material pipelines are connected by compression fittings.

[0036] Based on the above embodiments, in another embodiment of the present invention, the liquid holding capacity of the microchannel reactor units 2 arranged in series increases in a predetermined gradient from the first microchannel reactor unit 2 to the last microchannel reactor unit 2.

[0037] That is, the first unit has the smallest liquid holding capacity, and the last unit has the largest liquid holding capacity. Specifically, different liquid holding capacities of microchannel reactor units 2 are selected based on different reaction conditions. Generally, due to the decreasing reactant concentration and rate-decreasing characteristic as the reaction proceeds, the high exothermic phase in the early stage requires small volumes for rapid heat transfer, while the later stage requires large volumes to ensure complete reaction. However, it should be noted that the intermediate microchannel reactor units 2 from the first to the last do not always increase in volume continuously. For example, the volume may increase from the first to the second, and from the second to the third, but may not increase further thereafter. This indicates that overall, the volume of microchannel reactor units 2 increases in a predetermined gradient from the first to the last.

[0038] Based on the above embodiments, in another embodiment of the present invention, such as Figure 2 The internal flow channel of the microchannel reactor unit 2 includes multiple heart-shaped structures 10. Each heart-shaped structure 10 includes a branch section 11 and a confluence section 12. The branch section 11 and the confluence section 12 are alternately connected and connected in series to form a micro-reaction tube 13. The branch section 11 is used to divide the fluid into two branches that enter the confluence section 12. The confluence section 12 can turn the fluid and merge it into a single flow path to enter the branch section 11 of the next heart-shaped structure 10.

[0039] The internal flow channel structure of this microchannel reactor unit 2 enhances the mixing effect through the collision of splitting and merging flows. Furthermore, during the reaction process, the high-temperature fluid is evenly distributed to the two branches multiple times, which facilitates rapid heat transfer to the heat exchange mechanism of the microchannel reactor unit 2 for timely heat exchange and reduces the risk of side reactions caused by local overheating.

[0040] Based on the above embodiments, in another embodiment of the present invention, such as Figure 3 The heat exchange mechanism includes at least two opposing heat exchange modules, with the microchannel reactor sandwiched between them. Each heat exchange module has a heat exchange medium channel and a heat exchange medium connector 18, which connects to the heat exchange medium channel. The microchannel reactor unit 2 adopts a two-sided independent heat exchange design, with synchronous temperature control on both the upper and lower surfaces of the reactor. This facilitates precise temperature control of the material, thereby enabling better control of the reaction.

[0041] Based on the above embodiments, in another embodiment of the present invention, such as Figure 3 The heat exchange module includes a main heat exchange plate 14, an auxiliary heat exchange plate 15 and a sealing gasket 16 arranged opposite to each other. The sealing gasket 16 is disposed between the main heat exchange plate 14 and the auxiliary heat exchange plate 15 to form the heat exchange medium flow channel.

[0042] Based on the above embodiments, in another embodiment of the present invention, such as Figure 3The microchannel reactor unit 2 is provided with a ferrule connector 17. The connecting end of the ferrule connector 17 passes through the heat exchange module and is connected to the liquid inlet or liquid outlet of the microchannel reactor unit 2. The connecting section of the ferrule connector 17 is conical and has a limiting step extending radially outward. The inner walls of the liquid inlet and the liquid outlet are provided with a stepped structure that is adapted to the connecting section of the ferrule connector 17 and is smaller on the outside and larger on the inside. The limiting step abuts against the stepped structure to form a stepped sealing.

[0043] The ferrule connector 17 is preferably made of polytetrafluoroethylene (PTFE). The tapered connecting section of the ferrule connector 17 fits snugly against the outer small and inner large stepped structure of the inlet / outlet. Combined with the contact between the limiting step and the stepped structure, a double sealing effect is achieved by sealing the tapered surface and the stepped surface, resulting in a tighter fit. This effectively prevents material leakage from gaps under high pressure, making it particularly suitable for pressure fluctuation scenarios that may occur in strongly exothermic reactions. On the other hand, the limiting step can bear part of the axial pressure, distributing the force between the ferrule connector 17 and the reactor interface to the stepped surface, preventing axial displacement or deformation of the connecting section due to high pressure. Combined with the high pressure resistance of PTFE, the overall pressure resistance limit of the structure is further improved. Tests have verified that the pressure resistance can reach 10 MPa, which is far higher than that of traditional silicon carbide microchannel reactors (2-3 MPa), making it safer and more stable.

[0044] Based on the above embodiments, in another embodiment of the present invention, such as Figure 1 The first reactant input channel includes a first reactant storage tank 5 and a first delivery pipeline connecting the first reactant storage tank 5 and the microchannel mixer 1. The second reactant input channel includes a plurality of second reactant storage tanks 6, and the plurality of second reactant storage tanks 6 are respectively connected to the corresponding microchannel reactor unit 2 through the second delivery pipeline; or the second reactant input channel includes one second reactant storage tank 6, and the second reactant storage tank 6 is connected to the corresponding microchannel reactor unit 2 through the plurality of second delivery pipelines.

[0045] Based on the above embodiments, in another embodiment of the present invention, such as Figure 1 The first and second conveying pipelines are equipped with preheating heat exchangers 3. Thus, after the materials in each pipeline are heated to a predetermined temperature by the preheating heat exchangers 3, they enter the microchannel mixer 1 or the microchannel reactor unit 2.

[0046] Based on the above embodiments, in another embodiment of the present invention, such as Figure 1The temperature control module further includes a main circulation pipeline 8 and a heat exchange medium supply unit 9. The main circulation pipeline 8 includes multiple branch pipelines that are respectively connected to the heat exchange mechanisms of the microchannel mixer 1 and the microchannel reactor unit 2. The flow control element 7 is disposed on the branch pipelines. The heat exchange medium supply unit 9 is used to regulate the temperature of the heat exchange medium to a preset range and can provide power for the circulation flow of the heat exchange medium in the main circulation pipeline 8 and the branch pipelines. The heat exchange medium supply unit 9 is preferably an integrated hot and cold circulation unit, and the flow control element 7 is a flow control valve.

[0047] To achieve the above objectives, this utility model also provides an application of any of the above-mentioned continuous microchannel reaction devices for nitration reactions, wherein the first reactant is an organic compound and the second reactant is a mixed acid including nitric acid.

[0048] Experiments have verified that, for highly exothermic liquid-liquid nitration reactions using digestion, benzene, or halogenated benzene (such as m-dichlorobenzene) as substrates, and mixed acids in a specific ratio as nitrating agents, the continuous feeding, independent and precise temperature control, corrosion-resistant sealing, and efficient mass and heat transfer characteristics of this utility model device can achieve safe and stable operation of such reactions, significantly improve the conversion rate of raw materials and the yield of target nitro compounds, and reduce the formation of byproducts such as isomers.

[0049] To better understand the technical solution of this utility model, specific application embodiments are provided below: Example 1 2,5-Dichloronitrobenzene is prepared by nitration of m-dichlorobenzene. The reaction equation is: C6H4Cl2 + HNO3 → C6H3Cl2NO2 + H2O A mixed acid, prepared by mixing 90% concentrated nitric acid and 98% concentrated sulfuric acid at a mass ratio of 1:2.8, is added to three storage tanks, V2, V3, and V4. m-Dichlorobenzene is added to storage tank V1. Feed pump P1, made of 316L stainless steel, controls the flow rate of m-Dichlorobenzene. Feed pumps P2, P3, and P4, made of Hastelloy C276 stainless steel, control the flow rate of the mixed acid exiting from storage tanks V2, V3, and V4, respectively. Microchannel mixer 1HE1 is made of Hastelloy C276 stainless steel, and the microchannel reactor is made of silicon carbide with a flow channel cross-sectional area of ​​3 mm². The liquid holding capacities of MR1, 2, 3, 4, and 5 are 3 ml, 4.5 ml, 4.5 ml, 10 ml, and 10 ml, respectively. The feed rate of m-dichlorobenzene was 24.5 ml / min for pump P1, and the feed rates of mixed acid pumps P2, P3, and P4 were 5 ml / min, 5 ml / min, and 4.5 ml / min, respectively. The heat exchange medium temperature in heat exchangers HE1, HE2, HE3, and HE4 was 26℃. The outlet temperature of the material in microchannel mixer 1 was 35℃, and the outlet temperature of the material in the microchannel reactor was 60-65℃. The total residence time of the material in the microchannel reactor was 50 s (the residence time is determined by the volumetric flow rate of the feed and the total liquid holdup in the reactor). After the reaction in the reactor was completed, the material entered a three-necked flask with a stirrer and was quenched with water. After quenching, the nitrobenzene product in the bottom organic phase was washed three times with deionized water for phase separation. The separated organic phase product was dried with anhydrous sodium sulfate and filtered to obtain pure nitrobenzene. Sampling and testing showed that the conversion rate of the organic phase raw material was 99.3%, the yield of 2,5-dichloronitrobenzene was 98.2%, the dinitrate was 0.6%, and the isomer was 0.5%. Control Experiment A: The nitration of m-dichlorobenzene was carried out using a microchannel reactor with existing technology. The reactor channel size was 3 mm², and the liquid holding capacity was 32 ml. A mixed acid and benzene prepared at a mass ratio of 1:2.8 were fed separately via a plunger pump at the same feed rate as above. The total residence time of the materials in the microchannel reactor was 50 s. After the reaction was completed in the reactor, the materials were transferred to a three-necked flask with a stirrer and quenched with water. After quenching, the nitrobenzene product was in the bottom organic phase. It was washed three times with deionized water for phase separation. The separated organic phase product was dried with anhydrous sodium sulfate and filtered to obtain pure nitrobenzene. Sampling analysis showed an organic phase raw material conversion rate of 91.2%, a 2,5-dichloronitrobenzene yield of 88.3%, a dinitrate yield of 1.3%, and an isomer yield of 1.2%.

[0050] Comparing the results of Case A and Control Experiment A, it can be seen that Case A has fewer by-products, while the microchannel reactor used in the production of dichlorobenzene nitration using existing technology has more by-products and a lower product yield.

[0051] Using the microchannel reactor of this invention for nitration allows for more precise temperature control, preventing excessively vigorous local reactions that could lead to numerous byproducts and affect purity and yield.

[0052] Example 2 The preparation of nitrobenzene by benzene nitration is shown in the following reaction equation: C6H6 + HNO3 → C6H5NO2 + H2O A mixed acid solution prepared by mixing 90% concentrated nitric acid and 98% concentrated sulfuric acid in a mass ratio of 1:3.0 is added to storage tanks V2, V3, and V4, while benzene is added to storage tank V1.

[0053] Feed pump P1, made of 316L stainless steel, controls the flow rate of nitrobenzene. Feed pumps P2, P3, and P4, made of Hastelloy C276 stainless steel, control the flow rates of mixed acid exiting from storage tanks V2, V3, and V4, respectively. Micromixer HE1 is made of Hastelloy C276 stainless steel, and the microreactor is made of silicon carbide with a flow channel cross-sectional area of ​​3 mm². The liquid holding capacities of MR1, 2, 3, 4, and 5 are 6 ml, 12 ml, 12 ml, 15 ml, and 15 ml, respectively. The feed rate of m-dichlorobenzene was 15 ml / min using pump P1, and the feed rates of mixed acid pumps P2, P3, and P4 were 17.5 ml / min, 12.5 ml / min, and 15 ml / min, respectively. The heat exchange medium temperatures of heat exchangers HE1, HE2, HE3, and HE4 were 15℃, -20℃, -15℃, and -10℃, respectively. The outlet temperature of the micro-mixer was 30℃, and the outlet temperature of the microreactor was 50-55℃. The total residence time of the material in the microreactor was 60 s. After the reaction was completed in the reactor, the material entered a three-necked flask with a stirrer and was quenched with water. After quenching, the nitrobenzene product in the bottom organic phase was washed three times with deionized water for phase separation. The separated organic phase product was dried with anhydrous sodium sulfate and filtered to obtain pure nitrobenzene. Sampling and testing showed that the conversion rate of the organic phase raw material was 99.9%, the yield of 2,5-dichloronitrobenzene was 99.5%, and the dinitrate was 0.4%.

[0054] Control experiment B used a microreactor with existing technology to prepare nitrobenzene by benzene nitration. The reactor channel size was 3 mm², and the liquid holding capacity was 32 ml. The mixed acid and benzene, prepared at a mass ratio of 1:3.0, were fed separately in one batch using a plunger pump at the same feed rate as above. The total residence time of the materials in the microreactor was 60 s. After the reaction was completed in the reactor, the materials were transferred to a three-necked flask with a stirrer and quenched with water. After quenching, the nitrobenzene product was in the bottom organic phase. It was washed three times with deionized water to separate the phases. The separated organic phase product was dried with anhydrous sodium sulfate and filtered to obtain pure nitrobenzene. Sampling and testing showed that the organic phase raw material conversion rate was 92.4%, the yield of 2,5-dichloronitrobenzene was 91.7%, and the dinitrate was 1.2%.

[0055] Comparing the results of Case B and Control Experiment B, it can be seen that Case B has fewer by-products. When using the existing microreactor technology to produce m-nitrobenzene, the raw material conversion rate of Case B is lower than that of this scheme, with more by-products and a lower product yield.

[0056] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A continuous microchannel reaction device, characterized in that, The device includes a mixing and reaction mechanism, a raw material diversion mechanism, a diversion control mechanism, and a temperature control module. The mixing and reaction mechanism includes a microchannel mixer and multiple microchannel reactor units arranged in series. The outlet of the microchannel mixer is connected to the inlet of the first microchannel reactor unit connected in series. The raw material diversion mechanism includes at least one first reactant input channel and at least two second reactant input channels. The first reactant input channel and one of the second reactant input channels are connected to the inlet of the microchannel mixer, and at least one other second reactant input channel is diverted to the inlet of a different microchannel reactor unit. Each branch of the first reactant input channel and the second reactant input channel is equipped with an independent flow control unit. The temperature control module includes a heat exchange mechanism independently installed in the microchannel mixer and each microchannel reactor unit, and a flow control element for independently controlling the flow rate of the heat exchange medium in each heat exchange mechanism.

2. The continuous microchannel reaction device according to claim 1, characterized in that, The liquid holding capacity of the microchannel reactor units arranged in series increases in a predetermined gradient from the first microchannel reactor unit to the last microchannel reactor unit.

3. The continuous microchannel reaction device according to claim 1, characterized in that, The internal flow channels of the microchannel reactor unit include multiple heart-shaped structures. Each heart-shaped structure includes a branching section and a confluence section. The branching section and the confluence section are alternately connected and connected in series to form a micro-reaction tube. The branching section is used to split the fluid into two branches that enter the confluence section. The confluence section can turn the fluid and merge it into a single flow path to enter the branching section of the next heart-shaped structure.

4. The continuous microchannel reaction device according to claim 1, characterized in that, The heat exchange mechanism includes at least two heat exchange modules arranged opposite each other, the microchannel reactor is sandwiched between the heat exchange modules, the heat exchange modules are provided with heat exchange medium channels and heat exchange medium connectors, and the heat exchange medium connectors are connected to the heat exchange medium channels.

5. The continuous microchannel reaction device according to claim 4, characterized in that, The heat exchange module includes a main heat exchange plate, an auxiliary heat exchange plate, and a sealing gasket arranged opposite to each other. The sealing gasket is disposed between the main heat exchange plate and the auxiliary heat exchange plate to form the heat exchange medium flow channel.

6. The continuous microchannel reaction device according to claim 4, characterized in that, The microchannel reactor unit is equipped with a ferrule connector. The connecting end of the ferrule connector passes through the heat exchange module and is connected to the inlet or outlet of the microchannel reactor unit. The connecting section of the ferrule connector is conical and has a limiting step extending radially outward. The inner walls of the inlet and outlet are equipped with a stepped structure that is adapted to the connecting section of the ferrule connector and is smaller on the outside and larger on the inside. The limiting step abuts against the stepped structure to form a stepped sealing seal.

7. The continuous microchannel reaction device according to any one of claims 1 to 6, characterized in that, The first reactant input channel includes a first reactant storage tank and a first delivery pipeline connecting the first reactant storage tank and the microchannel mixer. The second reactant input channel includes multiple second reactant storage tanks, each of which is connected to a corresponding microchannel reactor unit via a second delivery pipeline. Alternatively, the second reactant input channel includes one second reactant storage tank, which is connected to a corresponding microchannel reactor unit via multiple second delivery pipelines.

8. The continuous microchannel reaction device according to claim 7, characterized in that, Preheating heat exchangers are installed on the first and second delivery pipelines.

9. The continuous microchannel reaction device according to claim 7, characterized in that, The temperature control module also includes a main circulation pipeline and a heat exchange medium supply unit. The main circulation pipeline includes multiple branch pipelines that are respectively connected to the heat exchange mechanisms of the microchannel mixer and the microchannel reactor unit. The flow control component is installed on the branch pipelines. The heat exchange medium supply unit is used to regulate the temperature of the heat exchange medium to a preset range and can provide power for the circulation flow of the heat exchange medium in the main circulation pipeline and the branch pipelines.

10. The continuous microchannel reaction device according to claim 9, characterized in that, The heat exchange medium supply unit is an integrated cold and hot circulation unit, and the flow control component is a flow control valve.

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