Micro-channel reactor and method for applying micro-channel reactor to nitration of benzene and benzene derivatives

Abstract

The invention discloses a microchannel reactor and a method for applying the microchannel reactor to nitration of benzene and benzene derivatives, and relates to the technical field of organic synthesis.The microchannel reactor comprises a first feeding channel, a second feeding channel, a first flow dividing section, a first mixing section, a second flow dividing section, a second mixing section, a third mixing section, a discharging channel and a delayed reaction assembly which are sequentially communicated, two reaction solutions enter the reactor through the first feeding channel and the second feeding channel respectively, and enter the delayed reaction assembly through the discharging channel after multiple times of shunting and mixing operation of the solutions is completed, so that the final nitration reaction is completed; the device further comprises heat exchange assemblies used for assisting solution cooling, and the second mixing section, the third mixing section and the delayed reaction assembly are all provided with the heat exchange assemblies. The sample adaptability of the reactor is effectively improved through mutual combination of a plurality of solution mixing modes, and meanwhile, the time required by the trifluorotoluene nitration process is shortened by adopting a gradient temperature control mode of the reactor.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a microchannel reactor and a method for applying the microchannel reactor to nitrate benzene and benzene derivatives. Background Art

[0002] The nitration process of benzene and benzene derivatives is a very important organic chemical reaction with important application value. It is widely needed in the fields of research and development of active ingredients in drugs, synthesis of important pesticides and fine chemical intermediates, and supply of basic chemical raw materials. Traditional production methods mostly adopt intermittent kettle production processes, with frequent safety accidents, relatively low reaction efficiency, poor product purity, and large amount of three wastes. It can no longer meet the requirements of high-quality development at this stage. It is urgent to realize the production of the above-mentioned important chemicals through a safe, green and efficient technology. Taking the nitration process of trifluorotoluene as an example, the intermittent process in patent CN111499517A needs to be kept warm for 6 to 10 hours, while the synthesis process of preparing m-nitrotrifluorotoluene by nitration of trifluorotoluene reported in current literature and patents mainly improves the process technology from aspects such as raw material ratio and reaction temperature, but lacks innovative improvements in production process equipment, and the production methods are all intermittent production processes. Similar problems also exist in the production processes of nitrobenzene and dinitronaphthalene.

[0003] In order to solve the above problems, the continuous nitration technology of benzene and benzene derivatives was developed, and the nitration reaction process of benzene and benzene derivatives was studied in depth. The study found that there are many problems in the application of general microchannel reactors: First, due to the low temperature and high viscosity of the raw materials in the early stage of the reaction, the system pressure will be high, making it difficult for the system to operate smoothly; second, if the reaction system maintains the same reaction temperature throughout the process, two situations will occur: First, when the reaction temperature is high, the system pressure will decrease, and the raw materials can be converted quickly, but the by-product content will increase; second, when the reaction temperature is low, the raw materials are converted slowly, the system pressure increases greatly, but the by-product content decreases, and it often requires a very long residence time; in addition, in order to reduce the system pressure and equipment cost, intermittent stirring for 5 to 30 minutes is required, resulting in the simple continuous nitration technology and reactor being unable to cope with the continuous nitration of benzene and benzene derivatives.

[0004] Therefore, how to develop a microchannel reactor and its application in the nitration of benzene and benzene derivatives to achieve uniform distribution and continuous and efficient mixing of the liquid, effectively improve the sample adaptability of the reactor, and at the same time, adopt a gradient temperature control method of the reactor to improve product selectivity while shortening the time required for the nitration process of benzene and benzene derivatives has become a technical problem that needs to be urgently solved by people in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a microchannel reactor and a method for applying the same to the nitration of benzene and benzene derivatives, so as to achieve uniform distribution and continuous and efficient mixing of liquid, effectively improve the sample adaptability of the reactor, and at the same time, adopt a gradient temperature control method of the reactor to improve product selectivity while shortening the time required for the nitration process of benzene and benzene derivatives.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a microchannel reactor, comprising a first feed channel, a second feed channel, a first flow splitting section, a first mixing section, a second flow splitting section, a second mixing section, a third mixing section, a discharge channel and a delayed reaction component which are sequentially connected and arranged, two reaction solutions respectively enter the interior of the reactor through the first feed channel and the second feed channel, and after completing multiple flow splitting and mixing operations of the solution, enter the delayed reaction component through the discharge channel to complete the final nitration reaction;

[0008] It also includes a heat exchange component for assisting in cooling the solution, and the second mixing section, the third mixing section and the delayed reaction component are all provided with the heat exchange component.

[0009] Preferably, the first mixing section includes a first circular tube and first glass beads, the two ends of the first circular tube are respectively connected to the discharge port of the first diversion section and the feed port of the second diversion section, a plurality of the first glass beads are arranged on the inner cavity wall of the first circular tube, and the outer surface of the first glass beads is set to be smooth.

[0010] Preferably, the first shunt section comprises a first shunt channel and a solution shunt core, the solution shunt core is arranged inside the first shunt channel, and the outer peripheral wall of the solution shunt core is in contact with the inner wall of the first shunt channel, a central through hole is provided on the solution shunt core, and a plurality of inner grooves are radially arranged around the central through hole, the inner grooves are connected with the central through hole, and together constitute an inner shunt channel for the solution;

[0011] A plurality of outer grooves are arranged on the circumferential outer wall of the solution diversion core, and the outer grooves and the inner wall of the first diversion channel together constitute the outer diversion channel of the solution;

[0012] The first feed channel and the second feed channel are configured as sleeve structures and are respectively connected to the feed ports of the inner diversion channel and the outer diversion channel. The first circular tube is connected to the discharge ports of the inner diversion channel and the outer diversion channel.

[0013] Preferably, the second diversion section includes a second diversion channel and a diversion baffle, the diversion baffle is horizontally arranged inside the second diversion channel, and a plurality of L-shaped diversion holes for diverting the solution are provided on the diversion baffle, the axes of the discharge ends of the plurality of L-shaped diversion holes intersect at one point along the flow direction of the solution, and a hedging groove is provided on the side of the diversion baffle close to the second mixing section, the hedging groove is connected to the L-shaped diversion hole, and the second diversion channel is connected to the discharge port of the first circular tube.

[0014] Preferably, the second mixing section comprises a second circular tube, one end of which is connected to the second flow diversion channel;

[0015] The third mixing section includes a third circular tube and a threaded rod. The other end of the second circular tube is connected to the third circular tube. The threaded rod penetrates and is connected in the inner cavity of the second circular tube and the third circular tube. The pitch of the threaded rod gradually increases along the direction of solution flow. The discharge end of the third circular tube is set as a discharge channel.

[0016] Preferably, the delayed reaction assembly is composed of a plurality of interconnected tubular reactors, the feed end of the tubular reactor is connected to the discharge channel, and the discharge end of the tubular reactor is used to output the final product.

[0017] Preferably, the heat exchange assembly includes a heat exchange tube, and a plurality of the heat exchange tubes are respectively sleeved on the outside of the second circular tube, the third circular tube, and the tubular reactor to form a sleeve structure, each of the heat exchange tubes is sequentially provided with a heat exchange medium inlet and a heat exchange medium outlet along the flow direction of the heat exchange medium, and the outer side of the heat exchange tube is sleeved with a thermal insulation cotton layer.

[0018] Preferably, a method for nitrating benzene and benzene derivatives comprises the following steps:

[0019] Step 1: using benzene and its derivatives as raw materials, selecting a mixed acid prepared from fuming nitric acid and concentrated sulfuric acid as a nitrating agent, using two horizontal flow pumps with calibrated pump feed amounts to provide power, pumping the raw material solution and the nitrating agent solution to ensure that the molar ratio of nitric acid to the raw material is stable between 1.0 and 2.2;

[0020] Step 2: The benzene and its derivative raw material solution and the nitrating agent solution are respectively subjected to preliminary heat exchange through a heat exchange reactor, and then transported to the inside of a microchannel reactor through a first feed channel and a second feed channel, respectively. The solution is subjected to multiple diversion, mixing, heat exchange and nitration reaction operations in the microchannel reactor, and then the reaction residence time is extended by a delay reactor to complete the nitration reaction process. The residence time of the entire reaction process is 3 to 10 minutes, and the nitration reaction temperature is controlled at 0 to 85°C to finally obtain a nitration product.

[0021] Preferably, the residence time of the benzene and its derivative raw material solution and the nitrating agent solution in the first feed channel, the second feed channel, the first diversion section, the first mixing section, the second diversion section, the second mixing section and the third mixing section is 1 to 3 minutes, and the residence time in the delayed reaction component is 1 to 5 minutes.

[0022] Preferably, the temperature in the second mixing section and the third mixing section is lower than the temperature in the subsequent delayed reactor. The temperature in the second mixing section and the third mixing section is set to 5-35°C, the temperature in the delayed reactor is set to 10-65°C, and the temperature in the reactor gradually increases with the increase of the residence time of the mixed solution.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are:

[0024] 1) The present invention changes the intermittent nitration process of benzene and benzene derivatives into a continuous nitration process, which effectively shortens the reaction time, improves efficiency, and achieves intrinsic safety;

[0025] 2) The present invention uses a microchannel reactor to achieve uniform distribution and continuous and efficient mixing of liquids, effectively improving the sample adaptability of the reactor. At the same time, the reactor gradient temperature control method is adopted to ensure both the rate of the nitration reaction and the selectivity of the product.

[0026] In general, the present invention provides a microchannel reactor and a method for nitrating benzene and benzene derivatives thereof, which can shorten the nitration reaction time, improve the product yield, and achieve intrinsic safety. At the same time, the reactor and the supporting system have good applicability and can be flexibly applied to different products as needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings.

[0028] Figure 1 A perspective view of the overall structure of a microchannel reactor of the present invention;

[0029] Figure 2 It is a schematic diagram of the overall structure of a microchannel reactor of the present invention;

[0030] Figure 3 It is a structural schematic diagram of the first diversion section of the present invention;

[0031] Figure 4 For the present invention Figure 3 The enlarged view of point A in the middle;

[0032] Figure 5 It is a schematic diagram of the connection structure of the first mixing section, the second flow dividing section, the second mixing section and the third mixing section of the present invention;

[0033] Figure 6It is a structural schematic diagram of the threaded rod of the present invention;

[0034] Figure 7 The figure is a flow chart of the trifluorotoluene nitration method in Example 1 of the present invention.

[0035] Explanation of the reference numerals: 1. first feed channel; 2. second feed channel; 3. first diversion section; 301. first diversion channel; 302. solution diversion core; 303. central through hole; 304. inner groove; 305. outer groove; 4. first mixing section; 401. first circular tube; 402. first glass beads; 5. second diversion section; 501. diversion baffle; 502. L-shaped diversion flow hole; 503. hedging groove; 6. second mixing section; 601. second circular tube; 7. third mixing section; 701. third circular tube; 702. threaded rod; 8. discharge channel; 9. delayed reaction component; 10. heat exchange component; 1001. heat exchange tube; 1002. heat exchange medium inlet; 1003. heat exchange medium outlet; 11. thermal insulation cotton layer; 12. temperature sensor probe. DETAILED DESCRIPTION

[0036] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] like Figure 1-6 As shown, a microchannel reactor comprises a first feed channel 1, a second feed channel 2, a first diverting section 3, a first mixing section 4, a second diverting section 5, a second mixing section 6, a third mixing section 7, a discharge channel 8 and a delayed reaction component 9 which are sequentially connected and arranged. Two reaction solutions enter the interior of the reactor through the first feed channel 1 and the second feed channel 2 respectively, and after completing multiple diverting and mixing operations of the solution, they enter the delayed reaction component 9 through the discharge channel 8 to complete the final nitration reaction;

[0038] It also includes a heat exchange component 10 for assisting in cooling the solution. The second mixing section 6 , the third mixing section 7 and the delayed reaction component 9 are all provided with the heat exchange component 10 .

[0039] Specifically, two reaction solutions are respectively transported to the inside of the microchannel reactor through the first feed channel 1 and the second feed channel 2. When the reaction solution flows through the first diversion section 3, the two solutions are divided into multiple strands. Subsequently, the multiple mixed solutions are quickly mixed in the first mixing section 4. The mixed solution is diverted again when passing through the second diversion section 5. The diverted solution enters the second mixing section 6 for another mixing operation. After the reaction solution undergoes multiple diversion and mixing operations in different ways, the mixing degree of the solution can be greatly improved.

[0040] Specifically, the first mixing section 4 includes a first circular tube 401 and a first glass bead 402, the two ends of the first circular tube 401 are respectively connected to the discharge port of the first diversion section 3 and the feed port of the second diversion section 5, a plurality of the first glass beads 402 are arranged on the inner cavity wall of the first circular tube 401, and the outer surface of the first glass bead 402 is set to a smooth state.

[0041] Specifically, the first diversion section 3 includes a first diversion channel 301 and a solution diversion core 302, wherein the solution diversion core 302 is arranged inside the first diversion channel 301, and the outer peripheral wall of the solution diversion core 302 is in contact with the inner wall of the first diversion channel 301, and the solution diversion core 302 is provided with a central through hole 303, and a plurality of inner grooves 304 are arranged radially around the central through hole 303, and the inner grooves 304 are connected with the central through hole 303, and together constitute an inner diversion channel for the solution;

[0042] A plurality of outer grooves 305 are arranged on the circumferential outer wall of the solution diversion core 302, and the outer grooves 305 and the inner wall of the first diversion channel 301 together constitute an outer diversion channel for the solution;

[0043] The first feed channel 1 and the second feed channel 2 are configured as sleeve structures and are respectively connected to the feed ports of the inner diversion channel and the outer diversion channel. The first circular tube 401 is connected to the discharge ports of the inner diversion channel and the outer diversion channel.

[0044] Specifically, the number of the inner grooves 304 and the number of the outer grooves 305 match each other, and the user can control the number of split streams of the reaction solution by controlling the number of the inner grooves 304 and the number of the outer grooves 305 .

[0045] Specifically, the effective cross-sectional area of ​​the inner groove 304 and the outer groove 305 is 0.03 to 0.1 square millimeters, and the number thereof is set to 10 to ensure that when the diverted solutions are mixed, the linear velocity of each solution can reach more than 1 m / s.

[0046] Specifically, the second flow dividing section 5 includes a second flow dividing channel and a flow dividing baffle 501, the flow dividing baffle 501 is horizontally arranged inside the second flow dividing channel, and the flow dividing baffle 501 is provided with a plurality of L-shaped flow dividing holes 502 for diverting the solution, the axes of the discharge ends of the plurality of L-shaped flow dividing holes 502 intersect at one point along the flow direction of the solution, and the flow dividing baffle 501 is provided with a hedging groove 503 on one side close to the second mixing section 6, the hedging groove 503 is connected to the L-shaped flow dividing holes 502, and the second flow dividing channel is connected to the discharge port of the first circular tube 401. This structural design can achieve uniform distribution and continuous and efficient mixing of the liquid.

[0047] Specifically, the number of L-shaped diversion holes 502 is set to 2 to 6, which can divide the mixed solution into 2 to 6 streams. The inner diameter of each hole is 1 to 2 mm, and the multiple streams of solution passing through the L-shaped diversion holes 502 present counter-angles, thereby further improving the mixing degree of the solution.

[0048] Specifically, the number of the L-shaped branching holes 502 in the present invention can be freely set by the user according to actual conditions.

[0049] Specifically, the second mixing section 6 includes a second circular tube 601, and one end of the second circular tube 601 is connected to the second flow distribution channel;

[0050] The third mixing section 7 includes a third circular tube 701 and a threaded rod 702. The other end of the second circular tube 601 is connected to the third circular tube 701. The threaded rod 702 penetrates and is connected in the inner cavity of the second circular tube 601 and the third circular tube 701. The pitch of the threaded rod 702 gradually increases along the direction of solution flow. The discharge end of the third circular tube 701 is set as a discharge channel 8.

[0051] Specifically, the second circular tube 601 and the third circular tube 701 are both provided with a temperature sensor probe 12 for detecting the temperature of the solution.

[0052] Specifically, the threaded rod 702 matches the size of the second round tube 601 and the third round tube 701 .

[0053] Specifically, the delayed reaction assembly 9 is composed of a plurality of interconnected tubular reactors, the feed end of the tubular reactor is connected to the discharge channel 8, and the discharge end of the tubular reactor is used to output the final product.

[0054] Specifically, the number of tubular reactors in the present invention can be freely set by the user according to actual conditions.

[0055] Specifically, the heat exchange component 10 includes a heat exchange tube 1001, and a plurality of the heat exchange tubes 1001 are respectively sleeved on the outside of the second circular tube 601, the third circular tube 701, and the tubular reactor to form a sleeve structure, and each of the heat exchange tubes 1001 is sequentially provided with a heat exchange medium inlet 1002 and a heat exchange medium outlet 1003 along the flow direction of the heat exchange medium.

[0056] Specifically, each heat exchange tube 1001 is equipped with a heat exchange device so as to achieve individual adjustment of the heat exchange temperature of different heat exchange tubes 1001 .

[0057] Specifically, each tubular reactor is set with a different heat exchange temperature, and the temperature range is set to 0-50°C.

[0058] Specifically, the outer side of the heat exchange tube 1001 is covered with a heat-insulating cotton layer 11 .

[0059] Specifically, Figure 7 As shown, a method for nitrating benzene and benzene derivatives comprises the following steps:

[0060] Step 1: using benzene and its derivatives as raw materials, selecting a mixed acid prepared from fuming nitric acid and concentrated sulfuric acid as a nitrating agent, using two horizontal flow pumps with calibrated pump feed amounts to provide power, pumping the raw material solution and the nitrating agent solution to ensure that the molar ratio of nitric acid to the raw material is stable between 1.0 and 2.2;

[0061] Step 2: The benzene and its derivative raw material solution and the nitrating agent solution are respectively subjected to preliminary heat exchange through a heat exchange reactor, and then transported to the inside of a microchannel reactor through a first feed channel 1 and a second feed channel 2, respectively. The solution is subjected to multiple diversion, mixing, heat exchange and nitration reaction operations in the microchannel reactor, and then the reaction residence time is extended by a delay reactor to complete the nitration reaction process. The residence time of the entire reaction process is 3 to 10 minutes, and the nitration reaction temperature is controlled at 0 to 85°C to finally obtain a nitration product.

[0062] Specifically, the following are the test results of nitration of different benzene ring derivative raw materials:

[0063] Example 1

[0064] Pure trifluorotoluene is used as a raw material, a mixed acid of fuming nitric acid and concentrated sulfuric acid is used as a nitrating agent, the molar ratio of nitric acid to the raw material is 1.10, and two horizontal flow pumps are used to feed at a total flow rate of 40 ml / min. The two solutions are respectively subjected to preliminary heat exchange through a heat exchange reactor, the temperature of the heat exchange reactor is set to 8° C., and then are respectively transported to the inside of the microchannel reactor through a first feed channel 1 and a second feed channel 2. Then, the two solutions are respectively diverted through 10 groups of inner diversion channels and outer diversion channels. The multiple diverted solutions enter the first circular tube 401 in the first mixing section 4 and collide and mix with the first glass microbead 402. The mixed solution is passed through the second diversion channel. The four L-shaped branch flow holes 502 with an inner diameter of 1 to 2 mm in the flow section 5 are counter-mixed, and then pass through the second mixing section 6 and the third mixing section 7 in sequence, and leave the third mixing section 7 through the discharge channel 8, wherein the inner diameter of the third circular tube 701 in the third mixing section 7 is set to 4 mm, the temperature in the second mixing section 6 and the third mixing section 7 is set to 15°C, the discharge channel 8 connects two delayed reaction components 9, the temperature in the first section tubular reactor is set to 15°C, the temperature in the second section tubular reactor is set to 45°C, and the discharge port of the second section tubular reactor outputs the nitration product m-nitrotrifluorotoluene, the total liquid holding capacity of the system is 260 ml, and the residence time is 390s.

[0065] Normalized analysis by gas chromatography showed: raw material conversion rate was 100%, and selectivity was 90.53%.

[0066] Example 2

[0067] Pure benzene is used as a raw material, a mixed acid of fuming nitric acid and concentrated sulfuric acid is used as a nitrating agent, the molar ratio of nitric acid to the raw material is 2.07, and two horizontal flow pumps are used to feed at a total flow rate of 173 ml / min. The two solutions are respectively subjected to preliminary heat exchange through a heat exchange reactor, the temperature of the heat exchange reactor is set to 50°C, and then are respectively transported to the inside of the microchannel reactor through a first feed channel 1 and a second feed channel 2. Then, the two solutions are respectively diverted through 10 groups of inner diversion channels and outer diversion channels. The multiple solutions after diversion enter the first circular tube 401 in the first mixing section 4 and collide and mix with the first glass microbead 402. The mixed solution passes through the second diversion section 5 The liquid is counter-mixed after passing through six L-shaped branch flow holes 502 with an inner diameter of 1 to 2 mm, and then passes through the second mixing section 6 and the third mixing section 7 in sequence, and leaves the third mixing section 7 through the discharge channel 8, wherein the inner diameter of the third circular tube 701 in the third mixing section 7 is set to 4 mm, the temperature in the second mixing section 6 and the third mixing section 7 is set to 60-65°C, the discharge channel 8 connects two delayed reaction components 9, the temperature in the first tubular reactor is set to 65-70°C, the temperature in the second tubular reactor is set to 80-85°C, and the discharge port of the second tubular reactor outputs the nitration product dinitrobenzene, the total liquid holding capacity of the system is 260 ml, and the residence time is 90.1s.

[0068] Normalized analysis by gas chromatography showed that the benzene conversion rate was 99.8%, the m-dinitrobenzene selectivity was 91.3%, and the trinitrophenol content was less than 100 ppm.

[0069] Example 3

[0070] A mixed solution of naphthalene and dichloroethane is used as a raw material, a mixed acid of fuming nitric acid and concentrated sulfuric acid is used as a nitrating agent, the molar ratio of nitric acid to the raw material is 2.1, and two horizontal flow pumps are used to feed at a total flow rate of 65 ml / min. The two solutions are respectively subjected to preliminary heat exchange through a heat exchange reactor, the temperature of the heat exchange reactor is set to 0-2° C., and then are respectively transported to the inside of the microchannel reactor through a first feed channel 1 and a second feed channel 2. Then, the two solutions are respectively shunted through 10 groups of inner shunt channels and outer shunt channels. The multiple solutions after shunting enter the first circular tube 401 in the first mixing section 4 and collide and mix with the first glass microbead 402. The mixed solution passes through the second The four L-shaped diversion holes 502 with an inner diameter of 1 to 2 mm in the diversion section 5 are counter-mixed, and then pass through the second mixing section 6 and the third mixing section 7 in sequence, and leave the third mixing section 7 through the discharge channel 8, wherein the inner diameter of the third circular tube 701 in the third mixing section 7 is set to 4 mm, the temperature in the second mixing section 6 and the third mixing section 7 is set to 0-5°C, the discharge channel 8 connects two delayed reaction components 9, the temperature in the first section tubular reactor is set to 25-35°C, the temperature in the second section tubular reactor is set to 65-75°C, and the discharge port of the second section tubular reactor outputs the nitration product dinitronaphthalene, the total liquid holding capacity of the system is 260 ml, and the residence time is 240s.

[0071] Normalized analysis by gas chromatography showed that the conversion rate of naphthalene was 100%, and the selectivity of the target product 1,5-dinitronaphthalene+1,8-dinitronaphthalene was >93%.

[0072] Example 4

[0073] With p-cresol as raw material and fuming nitric acid as nitrating agent, the molar ratio of nitric acid to raw material is 1.05, and two horizontal flow pumps are used to feed at a total flow rate of 74 ml / min. The two solutions are respectively subjected to preliminary heat exchange through a heat exchange reactor, and the temperature of the heat exchange reactor is set to 15°C. Then, the two solutions are respectively transported to the inside of the microchannel reactor through a first feed channel 1 and a second feed channel 2. Then, the two solutions are respectively diverted through 10 groups of inner diversion channels and outer diversion channels. The diverted multiple solutions enter the first circular tube 401 in the first mixing section 4 and collide and mix with the first glass microbead 402. The mixed solution passes through the five groups in the second diversion section 5. The mixture is counter-mixed after passing through an L-shaped branch flow hole 502 with an inner diameter of 1 to 2 mm, and then passes through the second mixing section 6 and the third mixing section 7 in sequence, and leaves the third mixing section 7 through the discharge channel 8, wherein the inner diameter of the third circular tube 701 in the third mixing section 7 is set to 4 mm, the temperature in the second mixing section 6 and the third mixing section 7 is set to 15-20°C, the discharge channel 8 connects two delayed reaction components 9, the temperature in the first tubular reactor is set to 20-25°C, the temperature in the second tubular reactor is set to 25-35°C, and the discharge port of the second tubular reactor outputs the nitration product, the total liquid holding capacity of the system is 260 ml, and the residence time is 210s.

[0074] Normalized analysis by gas chromatography showed that the conversion rate of p-cresol was 99.5%, and the selectivity was >99%.

[0075] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0076] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A microchannel reactor, characterized in that: The invention comprises a first feed channel (1), a second feed channel (2), a first flow dividing section (3), a first mixing section (4), a second flow dividing section (5), a second mixing section (6), a third mixing section (7), a discharge channel (8) and a delayed reaction component (9) which are sequentially connected and arranged. Two reaction solutions enter the interior of the reactor through the first feed channel (1) and the second feed channel (2) respectively. After completing multiple flow dividing and mixing operations of the solution, the two reaction solutions enter the delayed reaction component (9) through the discharge channel (8) to complete the final nitration reaction. It also includes a heat exchange component (10) for assisting in cooling the solution, and the second mixing section (6), the third mixing section (7) and the delayed reaction component (9) are all provided with the heat exchange component (10).

2. A microchannel reactor according to claim 1, characterized in that: The first mixing section (4) comprises a first circular tube (401) and first glass beads (402); the two ends of the first circular tube (401) are respectively connected to the discharge port of the first diversion section (3) and the feed port of the second diversion section (5); a plurality of the first glass beads (402) are arranged on the inner cavity wall of the first circular tube (401), and the outer surface of the first glass beads (402) is arranged to be smooth.

3. A microchannel reactor according to claim 2, characterized in that: The first flow diversion section (3) comprises a first flow diversion channel (301) and a solution flow diversion core (302), wherein the solution flow diversion core (302) is arranged inside the first flow diversion channel (301), and the outer peripheral wall of the solution flow diversion core (302) is in contact with the inner wall of the first flow diversion channel (301), and the solution flow diversion core (302) is provided with a central through hole (303), and a plurality of inner grooves (304) are arranged radially around the central through hole (303), and the inner grooves (304) are connected to the central through hole (303), and together constitute an inner flow diversion channel for the solution; A plurality of outer grooves (305) are arranged on the circumferential outer wall of the solution diversion core (302), and the outer grooves (305) and the inner wall of the first diversion channel (301) together constitute an outer diversion channel for the solution; The first feed channel (1) and the second feed channel (2) are arranged as sleeve structures and are respectively connected to the feed ports of the inner diversion channel and the outer diversion channel; the first circular tube (401) is connected to the discharge ports of the inner diversion channel and the outer diversion channel.

4. A microchannel reactor according to claim 2, characterized in that: The second diversion section (5) comprises a second diversion channel and a diversion baffle (501), wherein the diversion baffle (501) is horizontally arranged inside the second diversion channel, and a plurality of L-shaped diversion holes (502) for diverting the solution are provided on the diversion baffle (501), the axes of the discharge ends of the plurality of L-shaped diversion holes (502) intersect at one point along the flow direction of the solution, and a hedging groove (503) is provided on the side of the diversion baffle (501) close to the second mixing section (6), and the hedging groove (503) is connected to the L-shaped diversion holes (502), and the second diversion channel is connected to the discharge port of the first circular tube (401).

5. A microchannel reactor according to claim 4, characterized in that: The second mixing section (6) comprises a second circular tube (601), one end of the second circular tube (601) being connected to the second flow dividing channel; The third mixing section (7) comprises a third circular tube (701) and a threaded rod (702); the other end of the second circular tube (601) is connected to the third circular tube (701); the threaded rod (702) penetrates and is connected in the inner cavities of the second circular tube (601) and the third circular tube (701); and the pitch of the threaded rod (702) gradually increases along the direction of solution flow; and the discharge end of the third circular tube (701) is arranged as a discharge channel (8).

6. A microchannel reactor according to claim 5, characterized in that: The delayed reaction component (9) is composed of a plurality of interconnected tubular reactors, the feed end of the tubular reactor is connected to the discharge channel (8), and the discharge end of the tubular reactor is used to output the final product.

7. A microchannel reactor according to claim 6, characterized in that: The heat exchange component (10) comprises a heat exchange tube (1001), wherein a plurality of the heat exchange tubes (1001) are respectively sleeved on the outside of the second circular tube (601), the third circular tube (701), and the tubular reactor to form a sleeve structure, and each of the heat exchange tubes (1001) is provided with a heat exchange medium inlet (1002) and a heat exchange medium outlet (1003) in sequence along the flow direction of the heat exchange medium, and a heat insulation cotton layer (11) is sleeved on the outside of the heat exchange tube (1001).

8. A method for nitrating benzene and benzene derivatives, characterized in that: A microchannel reactor according to any one of claims 1 to 7, comprising the following steps: Step 1: using benzene and its derivatives as raw materials, selecting a mixed acid prepared from fuming nitric acid and concentrated sulfuric acid as a nitrating agent, using two horizontal flow pumps with calibrated pump feed amounts to provide power, pumping the raw material solution and the nitrating agent solution to ensure that the molar ratio of nitric acid to the raw material is stable between 1.0 and 2.2; Step 2: The benzene and its derivative raw material solution and the nitrating agent solution are respectively subjected to preliminary heat exchange through a heat exchange reactor, and then transported to the inside of a microchannel reactor through a first feed channel (1) and a second feed channel (2), respectively. The solution is subjected to multiple diversion, mixing, heat exchange and nitration reaction operations in the microchannel reactor, and then the reaction residence time is extended by a time delay reactor to complete the nitration reaction process. The residence time of the entire reaction process is 3 to 10 minutes, and the nitration reaction temperature is controlled at 0 to 85° C., and finally a nitration product is obtained.

9. The method for nitrating benzene and benzene derivatives according to claim 8, characterized in that: The residence time of the benzene and its derivative raw material solution and the nitrating agent solution in the first feed channel (1), the second feed channel (2), the first diversion section (3), the first mixing section (4), the second diversion section (5), the second mixing section (6) and the third mixing section (7) is 1 to 3 minutes, and the residence time in the delayed reaction component (9) is 1 to 5 minutes.

10. The method for nitrating benzene and benzene derivatives according to claim 8, characterized in that: The temperature in the second mixing section (6) and the third mixing section (7) is lower than the temperature in the subsequent delayed reactor. The temperature in the second mixing section (6) and the third mixing section (7) is set to 5-35°C, and the temperature in the delayed reactor is set to 10-65°C.

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