A continuous nitration reaction system

Abstract

The present application relates to a kind of continuous nitration reaction systems, wherein multiple microreactors are provided in the first reaction zone, and the microreactor includes multiple flow channel units, each flow channel unit includes multiple fully mixed flow microreactor units, the fully mixed flow microreactor unit realizes the forced mixing of nitration reaction in the form of high speed and buffer alternation, and the wide part between the second flow channel and the third flow channel in the fully mixed flow microreactor unit forms a certain volume of reaction cavity, so that the nitration substance and the nitration agent stay in the channel to maximize the nitration conversion of raw materials, the microreactor is also provided with heat exchange flow channel matched with mixing flow channel to realize the accurate control of reaction temperature, and under the premise of ensuring mixing effect, the second reaction zone uses the larger internal volume of mixing reactor to compensate for the defects of microreactor in residence time control.The present application can be applied to multiple varieties of continuous nitration, has high safety, high selectivity, high conversion rate and greater industrial application value.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering, specifically to a continuous nitration reaction system. Background Technology

[0002] Nitro compounds are important fine chemical intermediates, widely used in the synthesis of dyes, pesticides, pharmaceuticals, plastics, and energetic materials. Currently, industrial nitration reactions are generally produced using traditional batch reactor processes. However, these processes have many problems, such as high heat release and susceptibility to temperature runaway; low production efficiency due to sacrificing reaction time to control reactor temperature; and the generation of large amounts of waste acid and organic acidic wastewater, causing severe equipment corrosion and failing to meet the requirements of sustainable development. Furthermore, due to national environmental protection requirements, hazardous processes such as nitration should ideally be produced continuously. Therefore, there is an urgent need to develop a new, continuous, green, and efficient technology to solve or compensate for the problems of traditional reaction processes.

[0003] Nitration is a strongly exothermic reaction (the heat of reaction for benzene nitration is 145 kJ / mol). If the heat of reaction is not removed in time, the temperature rise of the reaction system will increase the reaction temperature and the rate of side reactions, especially the dinitrate content and the change in the isomer ratio. Patent CN107266321B discloses a method for the continuous nitration of trifluoromethoxybenzene, using pure trifluoromethoxybenzene as raw material and a mixture of fuming nitric acid and concentrated sulfuric acid as the nitrating agent. The two are strongly mixed in a microchannel reactor using a continuous conveying device to obtain the product trifluoromethoxynitrobenzene. Patent CN110003012A discloses a method for preparing benzene-based p-cresol nitrates, which mainly includes: passing nitrifying acid and molten organic matter to be nitrated into a microchannel reactor for reaction. The organic matter to be nitrated is solid at room temperature and does not solidify after being passed into the microchannel reactor, nor does it dissolve in the nitrifying acid for mixing and reaction, thus obtaining the corresponding nitration product. However, the above-mentioned patented methods are only applicable to a single product, and each product requires a different reaction device to achieve the ideal state. The devices have low applicability, can only be used for single-product development, and are cumbersome with high production costs. Summary of the Invention

[0004] The purpose of this invention is to provide a continuous nitration reaction system that is applicable to the continuous nitration of multiple varieties, and has high safety, high selectivity, high conversion rate and great industrial application value.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A continuous nitration reaction system includes a nitrifying agent storage tank, a nitrate storage tank, a first reaction zone, a second reaction zone, and a receiving tank. The first reaction zone includes a first integrated heating and cooling unit, a distributor valve, multiple microreactors, and multiple first delayed reactors. Each microreactor is equipped with a first material inlet, a second material inlet, a mixed liquid outlet, a heat exchange flow inlet, and a heat exchange flow outlet. The nitrifying agent storage tank is connected to the input end of the distributor valve via a first pipeline. The first material inlets of each microreactor are connected to the corresponding output ends of the distributor valve (10) via corresponding connecting branches, and each connecting branch is equipped with a control valve to control the on / off state of the pipeline. The nitrate storage tank is connected to the second material inlet of the first microreactor via a second pipeline. The mixed liquid outlet of any microreactor is connected to the second material inlet of the adjacent microreactor via a first intermediate pipeline, and a first delayed reactor is provided on the first intermediate pipeline. The last microreactor is connected via a connecting... The pipeline is connected to the second reaction zone, and a first delayed reactor is also provided on the connecting pipeline. One end of the first integrated heating and cooling unit is connected to the heat exchange inlet of the first microreactor, and the other end is connected to the heat exchange outlet of the last microreactor. The heat exchange outlet of any microreactor is connected to the heat exchange inlet of the adjacent microreactor through a pipeline. The second reaction zone includes a second integrated heating and cooling unit, multiple mixing reactors, and multiple second delayed reactors. The first mixing reactor is connected to the connecting pipeline, and adjacent mixing reactors are connected through a second intermediate pipeline, which is equipped with a second delayed reactor. The last mixing reactor is connected to the receiving tank through an output pipeline, which is also equipped with a second delayed reactor. Both the mixing reactor and the second delayed reactor are equipped with heat exchange inlets and outlets. The heat exchange inlets are all connected to the output end of the second integrated heating and cooling unit, and the heat exchange outlets are all connected to the input end of the second integrated heating and cooling unit.

[0007] The microreactor includes a first intermediate plate and a second intermediate plate stacked together, with a mixing channel formed between the first intermediate plate and the second intermediate plate. The mixing channel includes multiple channel units connected in sequence, and each channel unit includes an input channel, a fully mixed flow microreactor unit, a connecting channel, and a buffer channel. The input channel is connected to the first fully mixed flow microreactor unit, the buffer channel is connected to the last fully mixed flow microreactor unit, and adjacent fully mixed flow microreactor units are connected by corresponding connecting channels. The first material inlet and the second material inlet are both connected to the input channel of the first channel unit, and the mixed liquid outlet is connected to the buffer channel of the last channel unit. The buffer channel of any intermediate channel unit is connected to the input channel of the adjacent channel unit.

[0008] The fully mixed-flow microreactor unit has a first baffle plate, a second baffle plate, and a flow-dividing module inside its unit cavity. The first baffle plate and the second baffle plate are symmetrically arranged on both sides of the flow-dividing module. A first flow channel is formed between the first baffle plate and the unit cavity. A second flow channel is formed between the first baffle plate and the flow-dividing module. The second flow channel is narrow at both ends and wide in the middle, and the inlet end of the second flow channel is narrower than the outlet end. A third flow channel is formed between the flow-dividing module and the second baffle plate. The third flow channel is narrow at both ends and wide in the middle, and the outlet end of the third flow channel is narrower than the inlet end. A fourth flow channel is formed between the second baffle plate and the unit cavity. The middle parts of the second flow channel and the middle parts of the third flow channel form a reaction cavity for material retention.

[0009] The diameters of both the input channel and the connecting channel are smaller than the diameter of the buffer channel.

[0010] The microreactor also includes fixed side plates on both sides, and heat exchange channels are formed between the first intermediate plate and the corresponding fixed side plate, as well as between the second intermediate plate and the corresponding fixed side plate. The input end of the heat exchange channel is connected to the heat exchange inlet, and the output end of the heat exchange channel is connected to the heat exchange outlet.

[0011] The shape of the heat exchange channel matches that of the mixing channel.

[0012] The first intermediate plate, the second intermediate plate, and the fixed side plate form a microreactor plate group, and the microreactor includes one or more microreactor plate groups.

[0013] The first pipeline is sequentially equipped with a first metering pump, a first check valve, a first heat exchanger, a first temperature sensor, and a first pressure sensor.

[0014] The second pipeline is sequentially equipped with a second metering pump, a second check valve, a second heat exchanger, a second temperature sensor, and a second pressure sensor.

[0015] Temperature sensors and sampling valves are installed on the first intermediate pipeline between adjacent microreactors, the connecting pipeline between the first reaction zone and the second reaction zone, the second intermediate pipeline between adjacent mixing reactors, and the output pipeline.

[0016] The advantages and positive effects of this invention are as follows:

[0017] 1. The first reaction zone of this invention is equipped with multiple microreactors, and each microreactor includes multiple flow channel units. Each flow channel unit includes multiple fully mixed flow microreactor units. The fully mixed flow microreactor units achieve forced mixing of the nitration reaction through high-speed and buffering. In addition, the wide part in the middle of the second and third flow channels of the fully mixed flow microreactor units forms a reaction chamber of a certain volume, so that the nitrated material and the nitrifying agent stay in the channel for 0.01-10 seconds to maximize the nitration conversion of the raw materials. Furthermore, the diameter of the input flow channel and the connecting flow channel of the flow channel unit is smaller than that of the buffer flow channel, and the mixed liquid in the input flow channel and the connecting flow channel flows out in a high-speed jet. The flow rate of the mixed liquid in the buffer flow channel is slowed down, thereby further forming a high-speed and buffering form to achieve the purpose of rapid, multiple, and uniform mixing of the fluid.

[0018] 2. The microreactor of the present invention is also provided with a heat exchange channel that matches the mixing channel. The heat exchange channel, together with the high-speed buffer alternating channel unit, carries away the heat, which can achieve precise control of the reaction temperature. The heat exchange channel is located between the two intermediate plates and the corresponding fixed side plates. This design allows the heat in the reaction channel to be directly transferred to the heat exchange channel through the intermediate plates themselves, which improves the heat exchange efficiency by more than 30% and is not easy to block.

[0019] 3. The present invention also includes a second reaction zone. Under the premise of ensuring the mixing effect, the second reaction zone makes up for the defects of microreactor in residence time control by utilizing the larger internal volume of the mixing reactor. The present invention can use the first reaction zone alone or combine the first reaction zone with the second reaction zone according to actual needs. The configuration of the first reaction zone and the second reaction zone provides a guarantee for the mixing of raw materials and the selectivity of products in the nitration process, and can be applied to the continuous nitration of multiple varieties.

[0020] 4. This invention can convert nearly 100% of the nitrate in a reaction time that is two orders of magnitude shorter than that of traditional processes. Furthermore, by using a method of uniformly distributing the nitrifying agent, the generation of by-products can be greatly reduced, resulting in high product selectivity. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention.

[0022] Figure 2 for Figure 1 Front view of the microreactor in the middle.

[0023] Figure 3 for Figure 2 A schematic diagram of the internal structure of the microreactor in the image.

[0024] Figure 4 for Figure 3 Schematic diagram of the mixing channel in the middle.

[0025] Figure 5for Figure 4 A schematic diagram of the fully mixed-flow microreactor unit structure in the diagram.

[0026] Figure 6 for Figure 3 A schematic diagram of the heat exchange channel.

[0027] Wherein, 1 is the nitrifying agent storage tank, 2 is the nitrate storage tank, 3 is the first pipeline, 301 is the first metering pump, 302 is the first check valve, 303 is the first heat exchanger, 4 is the second pipeline, 401 is the second metering pump, 402 is the second check valve, 403 is the second heat exchanger, 5 is the sampling valve, 6 is the mixing reactor, 7 is the second extended-time reactor, 8 is the microreactor, 801 is the mixed liquid outlet, 802 is the second material inlet, 803 is the first material inlet, 804 is the heat exchange flow inlet, 805 is the heat exchange flow outlet, 806 is the input channel, and 807 is the total... The mixed-flow micro-reaction unit comprises: 8071 as the first baffle plate, 8072 as the second baffle plate, 8073 as the flow splitting module, 8074 as the first flow channel, 8075 as the second flow channel, 8076 as the third flow channel, 8077 as the fourth flow channel, 808 as the connecting flow channel, 809 as the buffer flow channel, 810 as the first intermediate plate, 811 as the second intermediate plate, 812 as the fixed side plate, 9 as the first delayed reactor, 10 as the splitting valve, 11 as the first reaction zone, 12 as the first integrated heating and cooling unit, 13 as the second reaction zone, 14 as the second integrated heating and cooling unit, and 15 as the receiving tank. Detailed Implementation

[0028] The invention will now be described in further detail with reference to the accompanying drawings.

[0029] like Figures 1-6 As shown, the present invention includes a nitrifying agent storage tank 1, a nitrated substance storage tank 2, a first reaction zone 11, a second reaction zone 13, and a receiving tank 15. The first reaction zone 11 includes a first integrated heating and cooling unit 12, a distribution valve 10, multiple microreactors 8, and multiple first delayed-action reactors 9, as shown. Figure 2As shown, the microreactor 8 is equipped with a first material inlet 803, a second material inlet 802, a mixed liquid outlet 801, a heat exchange flow inlet 804, and a heat exchange flow outlet 805. The nitrifying agent storage tank 1 is connected to the input end of the branch valve 10 via a first pipeline 3. The first pipeline 3 is sequentially equipped with a first metering pump 301, a first check valve 302, a first heat exchanger 303, a first temperature sensor, and a first pressure sensor. The first material inlets 803 on each microreactor 8 are connected to the corresponding output ends of the branch valve 10 via corresponding connecting branches. Each connecting branch is equipped with a control valve to control the on / off state of the pipeline. The nitrated substance storage tank 2 is connected to the second material inlet 802 on the first microreactor 8 via a second pipeline 4. The pipeline 4 is sequentially equipped with a second metering pump 401, a second one-way valve 402, a second heat exchanger 403, a second temperature sensor, and a second pressure sensor. The mixed liquid outlet 801 of any microreactor 8 is connected to the second material inlet 802 of the adjacent microreactor 8 through a first intermediate pipeline, and a first delayed reactor 9 is provided on the first intermediate pipeline. The last microreactor 8 is connected to the second reaction zone 13 through a connecting pipeline, and a first delayed reactor 9 is also provided on the connecting pipeline. One end of the first integrated heating and cooling unit 12 is connected to the heat exchange inlet 804 of the first microreactor 8, and the other end is connected to the heat exchange outlet 805 of the last microreactor 8. The heat exchange outlet 805 of any microreactor 8 is connected to the heat exchange inlet 804 of the adjacent microreactor 8 through a pipeline. The second reaction zone 13 includes a second integrated heating and cooling unit 14, multiple mixing reactors 6, and multiple second delayed-release reactors 7. The first mixing reactor 6 is connected to the connecting pipeline, adjacent mixing reactors 6 are connected via a second intermediate pipeline, and a second delayed-release reactor 7 is installed on the second intermediate pipeline. The last mixing reactor 6 is connected to the receiving tank 15 via an output pipeline, and the output pipeline also contains a second delayed-release reactor 7. Each mixing reactor 6 and each delayed-release reactor 7 has a heat exchange inlet and a heat exchange outlet. The heat exchange inlets are all connected to the output end of the second integrated heating and cooling unit 14, and the heat exchange outlets are all connected to the input end of the second integrated heating and cooling unit 14. The integrated heating and cooling unit and the distributor valve 10 are both technologies known in the art and are commercially available products.

[0030] like Figures 2-6 As shown, in this embodiment, the microreactor 8 includes a first intermediate plate 810 and a second intermediate plate 811 stacked together, and a mixing channel is formed between the first intermediate plate 810 and the second intermediate plate 811, as shown. Figure 4As shown, the mixing channel includes multiple channel units connected in sequence, and each channel unit includes an input channel 806, a fully mixed micro-reaction unit 807, a connecting channel 808, and a buffer channel 809. The input channel 806 is connected to the first fully mixed micro-reaction unit 807, the buffer channel 809 is connected to the last fully mixed micro-reaction unit 807, and adjacent fully mixed micro-reaction units 807 are connected by corresponding connecting channels 808. The first material inlet 803 and the second material inlet 802 are both connected to the input channel 806 of the first channel unit. The mixed liquid outlet 801 is connected to the buffer channel 809 of the last channel unit, and the buffer channel 809 of any intermediate channel unit is connected to the input channel 806 of the adjacent channel unit.

[0031] like Figure 5 As shown, the fully mixed-flow micro-reaction unit 807 has a first baffle plate 8071, a second baffle plate 8072, and a flow-dividing module 8073 inside its unit cavity. The first baffle plate 8071 and the second baffle plate 8072 are symmetrically arranged on both sides of the flow-dividing module 8073. A first flow channel 8074 is formed between the first baffle plate 8071 and the unit cavity. A second flow channel 8075 is formed between the first baffle plate 8071 and the flow-dividing module 8073. The second flow channel 8075 is narrow at both ends and wide in the middle, and the inlet end of the second flow channel 8075 is narrower than the outlet end. A third flow channel 8076 is formed between the flow-dividing module 8073 and the second baffle plate 8072. The third flow channel 8076 is narrow at both ends and wide in the middle, and the outlet end of the third flow channel 8076 is narrower than the inlet end. A fourth flow channel 8077 is formed between the second baffle plate 8072 and the unit cavity. After the mixture is output from the first channel 8074, due to the narrow inlet end of the second channel 8075, a portion of the mixture first flows into the second channel 8075 at high speed, and then the flow rate slows down. The other portion of the mixture first enters the third channel 8076, and then flows out at high speed from the outlet end of the third channel 8076 and mixes again with the mixture in the second channel 8075 before being input into the fourth channel 8077. Thus, the forced mixing of the nitration reaction is achieved through high speed and buffering. Moreover, the wide part between the second channel 8075 and the third channel 8076 forms a reaction chamber of a certain volume, allowing the nitrated material and the nitrifying agent to stay in the channel for 0.01-10 seconds to maximize the nitration conversion of the raw materials.

[0032] like Figures 4-5 As shown, the diameters of the input channel 806 and the connecting channel 808 are both smaller than the diameter of the buffer channel 809. The mixed liquids in the input channel 806 and the connecting channel 808 flow out in a high-speed jet manner, while the mixed liquids in the buffer channel 809 flow at a slower speed, in order to further form a high-speed and buffered form, so as to achieve the purpose of rapid, multiple, and uniform mixing of fluids.

[0033] like Figure 2 As shown, the microreactor 8 also includes fixed side plates 812 on both sides, and heat exchange channels are formed between the first intermediate plate 810 and the corresponding fixed side plate 812, and between the second intermediate plate 811 and the corresponding fixed side plate 812, as shown. Figure 6 As shown, the shape of the heat exchange channel matches the shape of the mixing channel. In this embodiment, the mixing channel has a reciprocating bend shape, and the heat exchange channel also has a reciprocating bend shape to correspondingly cover each channel unit of the mixing channel. The input end of the heat exchange channel is connected to the heat exchange inlet 804, and the output end of the heat exchange channel is connected to the heat exchange outlet 805. Since there is a large heat of solution and part of the heat of reaction during two-phase mixing, this invention utilizes the heat exchange channel in conjunction with a high-speed buffer-type channel unit to remove heat, achieving precise control of the reaction temperature. The microreactor 8 of this invention is suitable for liquid-liquid heterogeneous nitration reactions. It is made of HC276 or SiC material, suitable for multiple flow ratios and various nitration reactions, and has a large specific surface area and high mass and heat transfer coefficients.

[0034] like Figure 2 As shown, the first intermediate plate 810, the second intermediate plate 811 and the fixed side plate 812 form a microreactor plate group. The microreactor 8 can be equipped with one or more microreactor plate groups as needed. Adjacent microreactor plate groups are separated by the fixed side plate 812, which has a heat conduction effect.

[0035] The microreactor 8 can be manufactured using traditional processing methods (chemical etching, subtractive manufacturing) or 3D printing (additive manufacturing is formed by sintering metal powder with extremely high precision). The number of flow channel units and the number of fully mixed flow microreactor units 807 in each flow channel unit are designed according to actual needs.

[0036] like Figure 1 As shown, the mixing reactor 6 employs an SK-type static mixer or a microchannel reactor with a large liquid holdup. Its heat exchange channels can control the nitration reaction temperature within the mixing or reaction channels at the experimentally required temperature with very high heat transfer efficiency, eliminating hot spots. The mixing reactor 6 is a technology known in the art.

[0037] like Figure 1 As shown, in this embodiment, the first time-delay reactor 9 and the second time-delay reactor 7 can be cylindrical reactors with coiled tubular structures and heat exchange jackets, which are well-known technologies in the art and are commercially available products.

[0038] The second reaction zone 13, while ensuring the mixing effect, uses the larger internal volume of the mixing reactor 6 to compensate for the defects of the microreactor 8 in residence time control. The configuration of the first reaction zone 11 and the second reaction zone 13 provides a guarantee for the mixing of raw materials and the selectivity of products in the nitration process.

[0039] like Figure 1 As shown, temperature sensors and sampling valves 5 are provided on the first intermediate pipeline between adjacent microreactors 8, the connecting pipeline between the first reaction zone 11 and the second reaction zone 13, the second intermediate pipeline between adjacent mixing reactors 6, and the output pipeline.

[0040] The working principle of this invention is as follows:

[0041] like Figure 1 As shown, during operation, the nitrifying agent enters the branch valve 10 through the first pipeline 3, and then flows through the branch valve 10 to each microreactor 8 via corresponding connecting branches. The substance to be nitrated is input into the first microreactor 8 through the second pipeline 4. The mixture in any microreactor 8 passes through the adjacent first delayed reactor 9 before entering the next microreactor 8. This invention allows control over the number of connecting branches opened according to the needs of the substance to be nitrated. And as... Figures 2-6 As shown, the mixing channel of the microreactor 8 includes multiple channel units, each channel unit including multiple fully mixed-flow microreactor units 807. The fully mixed-flow microreactor units 807 achieve forced mixing of the nitration reaction through high-speed and buffering. Moreover, the wide section between the second channel 8075 and the third channel 8076 in the fully mixed-flow microreactor unit 807 forms a reaction chamber of a certain volume, allowing the nitrated material and nitrifying agent to remain in the channel for 0.01-10 seconds to maximize the nitration conversion of the raw materials. In addition, the input flow of the channel unit... The diameters of channel 806 and connecting channel 808 are both smaller than those of buffer channel 809. The mixed liquids in both channels 806 and 808 flow out in high-speed jets, while the flow rate of the mixed liquid in buffer channel 809 slows down, further creating a high-speed and buffered flow pattern. This achieves rapid, multiple, and uniform mixing of the fluids. Furthermore, the microreactor 8 is equipped with a heat exchange channel matching the mixing channel. This heat exchange channel, in conjunction with the high-speed buffered flow channel unit, removes heat, enabling precise control of the reaction temperature. The second reaction zone 13, while ensuring mixing effectiveness, utilizes the larger internal volume of the mixing reactor 6 to compensate for the shortcomings of the microreactor 8 in residence time control. The configuration of the first reaction zone 11 and the second reaction zone 13 ensures the mixing of raw materials and the selectivity of products in the nitration process.

[0042] The following are some application examples for further explanation.

[0043] Application Example 1

[0044] This application example uses pure trifluoromethoxybenzene as raw material and a mixture of fuming nitric acid and concentrated sulfuric acid as nitrating agent. The nitrating agent is divided into two streams and mixed with the raw material. The nitric acid mass concentration in the nitrating agent is 24.1%, and the water mass concentration is 2%. The raw material and nitrifying acid are fed at flow rates of 10 mL / min and 11 mL / min, respectively, through a first metering pump 301 and a second metering pump 401. That is, the feed ratio of nitric acid to trifluoromethoxybenzene is 1.0 in molar terms. In this application example, the microreactor has 8 channels with an equivalent diameter of 0.25 mm and a liquid holding volume of 40 ml. The materials are vigorously mixed and undergo an initial reaction in the first reaction zone 11 (the reactant conversion was tested to be 70%–80%). The mixed materials are then further mixed and reacted in the second reaction zone 13. In this application example, the equivalent diameter of channel 6 in the mixing reactor is 2-6 mm, with a liquid holdup of 10 ml. The second delay reactor 7 uses a circular coil made of Hastelloy alloy with a diameter of 3 mm and a liquid holdup of 50 ml, allowing the reactants to remain in the second reaction zone 13 for 180 seconds. Simultaneously, the reaction temperatures in the first reaction zone 11 and the second reaction zone 13 are controlled at 5-10 °C. The system outlet yields the product nitrotrifluoromethoxybenzene and waste acid. The two phases are separated, the upper layer products are combined, and the products are washed alternately with water and alkaline water until neutral. The product concentrations of the meso, para, and ortho mononitrates are quantified using an Agilent 7890 gas chromatograph with a DB-1701 column, based on peak area.

[0045] Analysis showed that the raw material conversion rate was 99.8%, and the meta-, para-, and ortho-monotides were 0.02%, 92.7%, and 7.08%, respectively, while the dinitrate was 0.00%.

[0046] Application Example 2

[0047] This application example uses pure trifluoromethoxybenzene as raw material and a mixture of fuming nitric acid and concentrated sulfuric acid as nitrifying agent. The nitrifying agent is divided into three streams and mixed with the raw material. The mass concentration of nitric acid in the nitrifying agent is 20.1%, and the mass concentration of water is 2%. The raw material and nitrifying acid are fed at flow rates of 7 mL / min and 11 mL / min, respectively, through the first metering pump 301 and the second metering pump 401. That is, the feed ratio of nitric acid to trifluoromethoxybenzene is 1.05 in molar terms. In this application example, the microreactor 8 has an equivalent channel diameter of 0.6 mm and a liquid holding capacity of 30 ml. The materials are vigorously mixed and undergo an initial reaction in the first reaction zone 11 (with a tested reactant conversion rate of 60%–70%). The mixed materials are then further mixed and reacted in the second reaction zone 13. In this application example, the mixing reactor 6 has an equivalent channel diameter of 2–6 mm and a liquid holding capacity of 10 ml. The second tubular time-delay reactor 7 uses a circular coil made of Hastelloy alloy with a diameter of 3 mm and a liquid holding capacity of 80 ml, allowing the reactants to remain in the second reaction zone 13 for 300 seconds. Simultaneously, the reaction temperatures in both the first and second reaction zones 11 are controlled at 5–10 °C. The system outlet yields the product nitrotrifluoromethoxybenzene and waste acid. The two phases are separated, the upper layer products are combined, and the products are washed alternately with water and alkaline water until neutral. The product concentrations (intermediate, para, and ortho-nitrates) are quantified using an Agilent 7890 gas chromatograph with a DB-1701 column, based on peak area.

[0048] Analysis showed that the raw material conversion rate was 99.9%, and the percentages of meta-, para-, and ortho-nitrates were 0.01%, 92.8%, and 7.09%, respectively, while the dinitrate was 0.00%.

[0049] Application Example 3

[0050] This application example uses p-cresol and dichloroethane solution as raw materials and dilute nitric acid as nitrating agent. The p-cresol solution is divided into three streams and mixed with dilute nitric acid. The mass concentration of dilute nitric acid is 15%, and the mass concentration of p-cresol is 25%. The p-cresol solution and dilute nitric acid are fed through the first metering pump 301 and the second metering pump 401 at flow rates of 12 mL / min and 25 mL / min, respectively. That is, the feed ratio of nitric acid to p-cresol is 1.8 in molar terms. In this application example, the microreactor 8 has an equivalent channel diameter of 0.2 mm and a liquid holding capacity of 40 ml. The materials are vigorously mixed and undergo an initial reaction in the first reaction zone 11 (with a tested reactant conversion rate of 50%–60%). The mixed materials are then further mixed and reacted in the second reaction zone 13. In this application example, the mixing reactor 6 has an equivalent channel diameter of 2–6 mm and a liquid holding capacity of 20 ml. The second delay reactor 7 uses a circular coil made of Hastelloy material with a diameter of 3 mm and a liquid holding capacity of 90 ml, allowing the reactants to remain in the second reaction zone 13 for 180 seconds. Simultaneously, the reaction temperatures in both the first reaction zone 11 and the second reaction zone 13 are controlled at 20–25 °C. The reaction liquid is collected at the system outlet and subjected to separation and post-processing to obtain the product. The concentration of the product o-nitro-p-cresol is quantified by peak area using an Agilent 7890 gas chromatograph.

[0051] Analysis showed that the conversion rate of the phenol solution raw material was 100%, the content of o-nitro-p-cresol was 99.5%, and the content of dinitrates and impurities (tar) was 0.5%.

Claims

1. A continuous nitration reaction system, characterized in that: The system includes a nitrifying agent storage tank (1), a nitrate storage tank (2), a first reaction zone (11), a second reaction zone (13), and a receiving tank (15). The first reaction zone (11) includes a first integrated heating and cooling unit (12), a distributor valve (10), multiple microreactors (8), and multiple first delayed reactors (9). The microreactors (8) are equipped with a first material inlet (803), a second material inlet (802), a mixed liquid outlet (801), a heat exchange flow inlet (804), and a heat exchange flow outlet (805). The nitrifying agent storage tank (1) is connected to the distributor valve (10) via a first pipeline (3). The first material inlet (803) of each microreactor (8) is connected to the corresponding output end of the branch valve (10) through the corresponding connecting branch. Each connecting branch is equipped with a control valve to control the opening and closing of the pipeline. The nitrate storage tank (2) is connected to the second material inlet (802) of the first microreactor (8) through the second pipeline (4). The mixed liquid outlet (801) of any microreactor (8) is connected to the second material inlet (802) of the adjacent microreactor (8) through the first intermediate pipeline. The first intermediate pipeline is equipped with a first delay reactor (9). The last microreactor... The reactor (8) is connected to the second reaction zone (13) via a connecting pipe, and the connecting pipe is also equipped with a first delayed reactor (9). One end of the first integrated heating and cooling unit (12) is connected to the heat exchange inlet (804) of the first microreactor (8), and the other end is connected to the heat exchange outlet (805) of the last microreactor (8). The heat exchange outlet (805) of any microreactor (8) is connected to the heat exchange inlet (804) of the adjacent microreactor (8) via a pipe. The second reaction zone (13) includes a second integrated heating and cooling unit (14), multiple mixing reactors (6), and multiple second delayed reactors (7). The first mixing reactor (6) is connected to the connecting pipeline. Adjacent mixing reactors (6) are connected through a second intermediate pipeline, and a second delay reactor (7) is provided on the second intermediate pipeline. The last mixing reactor (6) is connected to the receiving tank (15) through an output pipeline, and a second delay reactor (7) is also provided on the output pipeline. Both the mixing reactor (6) and the second delay reactor (7) are provided with heat exchange inlets and heat exchange outlets. The heat exchange inlets are connected to the output end of the second integrated cooling and heating unit (14), and the heat exchange outlets are connected to the input end of the second integrated cooling and heating unit (14). The microreactor (8) includes a first intermediate plate (810) and a second intermediate plate (811) stacked together, and a mixing channel is formed between the first intermediate plate (810) and the second intermediate plate (811). The mixing channel includes a plurality of channel units connected in sequence, and each channel unit includes an input channel (806), a fully mixed-flow microreactor unit (807), a connecting channel (808), and a buffer channel (809). The input channel (806) is connected to the fully mixed-flow microreactor unit (807) at the beginning, and the buffer channel (809) is connected to the connecting channel (808). The flushing channel (809) is connected to the end fully mixed micro-reaction unit (807), and adjacent fully mixed micro-reaction units (807) are connected through corresponding connecting channels (808). The first material inlet (803) and the second material inlet (802) are both connected to the input channel (806) of the first channel unit. The mixed liquid outlet (801) is connected to the buffer channel (809) of the end channel unit. The buffer channel (809) of any intermediate channel unit is connected to the input channel (806) of the adjacent channel unit. The fully mixed-flow micro-reaction unit (807) has a first baffle plate (8071), a second baffle plate (8072), and a flow-dividing module (8073) inside its unit cavity. The first baffle plate (8071) and the second baffle plate (8072) are symmetrically arranged on both sides of the flow-dividing module (8073). A first flow channel (8074) is formed between the first baffle plate (8071) and the unit cavity, and a second flow channel (8075) is formed between the first baffle plate (8071) and the flow-dividing module (8073). The second flow channel (8075) consists of two... The second flow channel (8075) has a narrow head and a wide middle shape, and the inlet end of the second flow channel (8075) is narrower than the outlet end. A third flow channel (8076) is formed between the flow divider module (8073) and the second baffle plate (8072). The third flow channel (8076) has a narrow head and a wide middle shape, and the outlet end of the third flow channel (8076) is narrower than the inlet end. A fourth flow channel (8077) is formed between the second baffle plate (8072) and the unit cavity. A reaction cavity for material retention is formed in the middle of the second flow channel (8075) and the middle of the third flow channel (8076).

2. The continuous nitration reaction system according to claim 1, characterized in that: The diameters of the input channel (806) and the connecting channel (808) are both smaller than the diameter of the buffer channel (809).

3. The continuous nitration reaction system according to claim 1, characterized in that: The microreactor (8) also includes fixed side plates (812) on both sides, and heat exchange channels are formed between the first intermediate plate (810) and the corresponding fixed side plate (812) and between the second intermediate plate (811) and the corresponding fixed side plate (812). The input end of the heat exchange channel is connected to the heat exchange inlet (804), and the output end of the heat exchange channel is connected to the heat exchange outlet (805).

4. The continuous nitration reaction system according to claim 3, characterized in that: The shape of the heat exchange channel matches that of the mixing channel.

5. The continuous nitration reaction system according to claim 3, characterized in that: The first intermediate plate (810), the second intermediate plate (811) and the fixed side plate (812) form a microreactor plate group, and the microreactor (8) includes one or more microreactor plate groups.

6. The continuous nitration reaction system according to claim 1, characterized in that: The first pipeline (3) is provided with a first metering pump (301), a first check valve (302), a first heat exchanger (303), a first temperature sensor and a first pressure sensor in sequence.

7. The continuous nitration reaction system according to claim 1, characterized in that: The second pipeline (4) is sequentially equipped with a second metering pump (401), a second check valve (402), a second heat exchanger (403), a second temperature sensor, and a second pressure sensor.

8. The continuous nitration reaction system according to claim 1, characterized in that: Temperature sensors and sampling valves (5) are provided on the first intermediate pipeline between adjacent microreactors (8), the connecting pipeline between the first reaction zone (11) and the second reaction zone (13), the second intermediate pipeline between adjacent mixing reactors (6), and the output pipeline.

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