A continuous nitration reaction device in the form of a spiral inclined groove microchannel

Abstract

A continuous nitration reaction apparatus in the form of a spiral inclined groove microchannel is disclosed, relating to a continuous nitration reaction process device. This device features a grooved structure that induces the fluid to form a spiral flow component. The spiral fluid induced by the grooves has vortices on both sides of each groove forming a ring-shaped vortex structure. The feed unit's homogeneous solution of the nitrate and the mixed acid solution are connected to medium-pressure constant flow pumps A and B, respectively, via preheating capillaries. These preheating capillaries are connected to an inclined groove microchannel mixer. The inclined groove microchannel mixer, the inclined groove microreactor, and the preheating channel are all immersed in a constant temperature water bath. The reaction effluent pipe is connected to an ice bath collection device after passing through an online quenching unit, i.e., pump C, and is sequentially connected to a dichloromethane gradient extraction device, a water washing device, and an anhydrous sodium sulfate dehydration device, constituting the entire continuous nitration reaction process device. This reactor is a continuous flow microreactor; it enhances mixing, reaction, and heat exchange effects, and reduces pressure drop losses due to collisions.

Description

Technical Field

[0001] This utility model relates to a continuous nitration reaction device, and more particularly to a continuous nitration reaction device in the form of a spiral inclined groove microchannel. Background Technology

[0002] Micromixing reactors have significant applications in biomedical detection, chemical synthesis, nanomaterial preparation, and environmental monitoring. Their core objective is to achieve rapid and efficient mixing of fluids within micrometer-scale channels. Compared to active micromixers, passive micromixers, by optimizing the geometry of microchannels to induce fluid disturbances, offer advantages such as simple structure, low cost, and ease of integration, and have become a current research hotspot.

[0003] Chinese patent CN119565445A discloses a novel micro-mixer that greatly enhances mixing efficiency with a special configuration. However, its heat exchange area is not suitable for chemical production reactions that are highly exothermic, such as nitration, and its applicability is limited.

[0004] The grooved induced helical flow technology significantly enhances liquid-liquid mass transfer and induces helical vortices through its unique groove structure. The misaligned regions between spatially perpendicular grooves on two adjacent walls generate chaotic convection, greatly enhancing fluid mixing and reaction. The special groove structure increases microchannel complexity, strengthening mixing while reducing pressure drop losses due to collision friction. Furthermore, the unique groove configuration enhances the reactor's heat transfer performance, making it suitable for vigorous, highly exothermic reactions. The device is also easy to integrate and exhibits low pressure drop.

[0005] Chinese patent CN119462387A discloses a method for preparing nitrobenzene using a micromixer. This method utilizes multiple reaction modules and the enhanced heat exchange capabilities of the micromixer to design a novel approach for nitrobenzene preparation. This method offers stable equipment and reduces the formation rate of nitrophenols as a byproduct, but it involves a large number of reaction modules.

[0006] The nitration process is constrained by engineering defects in the nitration reactor: conventional batch reactors exhibit axial temperature deviation >15℃ (monitored by ASTM E2877) and heat transfer coefficient per unit volume <500W / (m³). 3 The system addresses technical shortcomings such as those related to K. The Taylor flow pattern and wall slip effect of microreactor systems can improve reactor volumetric efficiency to 5-8 times that of traditional equipment, meeting the exponential growth in market demand. Summary of the Invention

[0007] The purpose of this invention is to provide a continuous nitration reactor in the form of a spiral inclined groove microchannel. This device enhances the mixing process through its groove structure, generating a spiral vortex field using a special spiral groove structure. Furthermore, the misaligned regions between spatially perpendicular grooves on two adjacent walls produce chaotic convection, further increasing the phase contact area and enhancing mixing. This groove structure increases the complexity of the microchannel, enhancing the mixing effect while reducing pressure drop losses due to collision friction. In addition, since nitration is a violently exothermic reaction, the groove configuration enhances the reactor's heat transfer performance, preventing overheating.

[0008] The objective of this utility model is achieved through the following technical solution:

[0009] A continuous nitration reaction device in the form of a spiral inclined groove microchannel is disclosed. The device is equipped with a groove structure to induce the fluid to form a spiral flow component. The spiral fluid induced by the groove has a ring-shaped vortex structure on both sides of each groove. The homogeneous solution of the nitrate and the mixed acid solution of the feed unit are respectively connected to medium-pressure constant flow pumps A and B to a preheating capillary. The preheating capillary is connected to an inclined groove microchannel mixer. The inclined groove microchannel mixer, the inclined groove microreactor, and the preheating channel are all immersed in a constant temperature water bath. The reaction effluent pipe is connected to an ice bath collection device after passing through an online quenching unit, i.e., pump C. It is then connected in sequence to a dichloromethane gradient extraction device, a water washing device, and an anhydrous sodium sulfate dehydration device to form the entire continuous nitration reaction process device.

[0010] The aforementioned continuous nitration reaction device in the form of a spiral inclined groove microchannel includes an inclined groove microchannel mixer, an inclined groove microchannel reactor, a medium-pressure constant flow pump, a high and low temperature circulation integrated machine, a digital temperature sensor, a constant temperature water bath micro-mixer, and an ice-water bath collection bottle.

[0011] The continuous nitration reaction device in the form of a spiral inclined groove microchannel includes dimensional parameters of the induced spiral flow groove static micromixer, including groove depth, groove width, distance between grooves, inclined groove angle, and micromixer inlet size.

[0012] The continuous nitration reaction device in the form of a spiral inclined groove microchannel is described above, wherein the grooves of the static micro-reaction device for inducing spiral flow are spiral-shaped.

[0013] The continuous nitration reaction device in the form of a spiral inclined groove microchannel includes micro-reaction conditions for the nitration reaction process, including groove depth, groove width, inclined groove angle, and micro-mixer inlet size.

[0014] The continuous nitration reaction device in the form of a spiral inclined groove microchannel includes a preheating capillary disc at the front end of the constant pressure pump micromixer in the nitration reaction process.

[0015] The continuous nitration reaction device in the form of a spiral inclined groove microchannel is provided, wherein the nitration reaction process is equipped with an ice-water bath collection device.

[0016] The advantages and effects of this utility model are:

[0017] This invention utilizes groove-induced spiral flow technology in its channel structure. Through the staggered structure between the grooves, it improves interphase mass transfer efficiency, ensuring high mass transfer efficiency while overcoming the drawback of large pressure drop in existing static mixers. The low pressure drop and high mass transfer efficiency make this device suitable for process scale-up in microchemical technology.

[0018] The device described in this utility model has no internal mechanical stirring structure, so the device has a simple structure, low cost, low energy consumption, and is easy to clean and disinfect, and can be widely used in the field of chemical engineering.

[0019] The device described in this utility model has the characteristics of low pressure drop and high mass transfer efficiency, and can be applied to the mixing and reaction processes of complex fluids in multiple systems.

[0020] The device described in this invention overcomes the problems of low production efficiency, thermal runaway, insufficient heat transfer area, poor mixing performance, and excessively long reaction time of traditional batch reactors. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the present utility model;

[0022] Figure 2 This is a cross-sectional comparative structural diagram of the spiral oblique groove microchannel of this utility model;

[0023] Figure 3 This is an isometric view of the spiral oblique groove microchannel of this utility model.

[0024] The figure shows: trench spacing - D; trench width - W; trench depth - H; trench inclination angle θ. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings.

[0026] Example 1

[0027] This invention relates to a continuous nitration reaction device in the form of a spiral inclined groove microchannel, the implementation of which is as follows.

[0028] The homogeneous solution of 2,4-difluoronitrobenzene and the mixed acid solution from the feed unit are pumped by medium-pressure constant flow pumps A and B, respectively, into a preheated capillary tube and then mixed in a slanted groove microchannel reactor. The resulting mixture then undergoes nitration in the capillary channel. To ensure environmental stability, the slanted groove microchannel reactor, the capillary channel, and the preheating channel are all immersed in a constant temperature water bath. Finally, the reaction effluent is quenched online (using pump C to inject a pre-cooling quenching agent at a molar ratio of 1:1.2) and then collected in an ice bath. It then undergoes sequential dichloromethane gradient extraction (1:3 ratio), alkali washing (5% NaOH solution), water washing (conductivity ≤5 μS / cm), and dehydration with anhydrous sodium sulfate to obtain a high-purity nitration product.

[0029] The reaction system used is:

[0030]

[0031] Based on a gas chromatography system (GC-2010SE, Rtx-5MS column), the internal standard method was used to quantify the reaction selectivity. A gradient temperature control program was set: initial isothermal phase (70℃, 2 min) → primary gradient (15℃ / min to 150℃, 2 min) → secondary gradient (20℃ / min to 300℃, 3 min). The injector and FID detector were maintained at isothermal conditions of 280℃ and 300℃, respectively, with a carrier gas (high-purity nitrogen) linear rate of 1 mL / min and a split ratio of 30:1. A component quantitative model was constructed using peak area normalization, and the structure of the organic phase components was confirmed by coupling GC-MS (Rtx-5MS capillary column).

[0032] Product characterization: 1,5-Difluoro-2,4-dinitrobenzene

[0033]

[0034] Final results: 100% conversion rate, 45 s reaction time, 333 K reaction temperature.

[0035] Example 2

[0036] The reaction system used is:

[0037]

[0038] The implementation method is as follows:

[0039] The heterogeneous solution of o-xylene and the nitric acid solution from the feed unit are pumped by medium-pressure constant flow pumps A and B, respectively, into a preheated capillary tube and then mixed in a slanted groove microchannel reactor. The resulting mixture then undergoes a nitration reaction in the capillary channel. To ensure environmental stability, the slanted groove microchannel reactor, the capillary channel, and the preheating channel are all immersed in a constant temperature water bath. The residence time can be adjusted by changing the volumetric flow rate. After the reaction, the effluent is quenched online (using a pre-cooling quenching agent injected by pump C at a molar ratio of 1:1.2) and then collected in an ice bath. Finally, the quenched mixture is separated in a separation device. The organic phase containing nitro compounds and o-xylene is located in the upper layer, while the lower layer is the waste acid from the reaction. The organic layer is washed with 5% NaOH aqueous solution and deionized water, respectively, and then dried with Na2SO4 to obtain the product. The waste acid is concentrated and recycled, resulting in a concentrated nitric acid concentration of 82-84%. High-purity nitration products are ultimately obtained.

[0040] Based on a gas chromatography system (GC-2010SE, Rtx-5MS column), the internal standard method was used to quantify the reaction selectivity. A gradient temperature control program was set: initial isothermal phase (70℃, 2 min) → primary gradient (15℃ / min to 150℃, 2 min) → secondary gradient (20℃ / min to 300℃, 3 min). The injector and FID detector were maintained at isothermal conditions of 280℃ and 300℃, respectively, with a carrier gas (high-purity nitrogen) linear rate of 1 mL / min and a split ratio of 30:1. A component quantitative model was constructed using peak area normalization, and the structure of the organic phase components was confirmed by coupling GC-MS (Rtx-5MS capillary column).

[0041] Product characterization: 3-nitro-o-xylene and 4-nitro-o-xylene

[0042]

[0043] In a microchannel continuous flow system, the reactant system was set as an equimolar ratio of fuming nitric acid (98% concentration) and o-xylene, with a total material throughput of 30 mL·min. -1 The residence time was 1 min. Thermodynamic monitoring showed that the activation threshold temperature of mononitration occurred at 283 K, and the critical point of polynitration phase transition reached 313 K. The cumulative effect of reaction heat was quantified by an adiabatic model. Among them, the enthalpy of formation of mononitration ΔH was estimated empirically by equation (1), and the adiabatic temperature rise ΔT was calculated by heat transfer-reaction coupling by equation (2).

[0044]

[0045] Final results: When the temperature of the mononitration reaction was 283K, the temperature rise under adiabatic conditions reached a maximum of 567K, which was significantly higher than the temperature of 313K during the continuous nitration reaction. At the same time, the adiabatic temperature rise also reached the decomposition temperature of fuming nitric acid, 320K.

[0046] Example 3

[0047] The reaction system used is:

[0048] HNO3 + H2SO4 → NO2 + +H2O+HSO4 -

[0049]

[0050] The implementation method is as follows:

[0051] The trifluoromethylbenzene dispersion and nitric acid solution are separately pumped by medium-pressure constant flow pumps A and B to the preheating capillary, and then introduced into the inclined groove microchannel reactor for mixing. The mixed system completes the nitration conversion process in the subsequently connected capillary reaction section. To ensure thermodynamic stability, the entire reaction system (including the microchannel reactor, capillary, and preheating components) is completely immersed in a constant temperature circulating water bath. The residence time of the system can be precisely controlled by adjusting the flow parameters of the delivery pumps. When the reaction is terminated, the reaction solution is instantly cooled by an online quenching unit (pre-cooling quencher is injected by pump C at a 1:1.2 molar ratio), and then collected in a low-temperature receiving device. Separation and purification stage: After standing and phase separation, an upper organic phase (containing the target nitro compound and o-xylene) and a lower acidic waste liquid are obtained. The organic phase is washed sequentially with a 5% sodium hydroxide solution and deionized water gradient, and then dried with anhydrous sodium sulfate to obtain the crude product. The waste acid is concentrated and regenerated under reduced pressure, and the nitric acid concentration is increased to 82-84%, which can be recycled for subsequent batch reactions. This process can ultimately yield the target nitration product with a purity >99%.

[0052] Based on a gas chromatography system (GC-2010SE, Rtx-5MS column), the internal standard method was used to quantify the reaction selectivity. A gradient temperature control program was set: initial isothermal phase (70℃, 2 min) → primary gradient (15℃ / min to 150℃, 2 min) → secondary gradient (20℃ / min to 300℃, 3 min). The injector and FID detector were maintained at isothermal conditions of 280℃ and 300℃, respectively, with a carrier gas (high-purity nitrogen) linear rate of 1 mL / min and a split ratio of 30:1. A component quantitative model was constructed using peak area normalization, and the structure of the organic phase components was confirmed by coupling GC-MS (Rtx-5MS capillary column).

[0053] Product characterization: m-nitrotrifluorotoluene and o-nitrotrifluorotoluene

[0054]

[0055] Final results: 100% conversion rate, 45 s reaction time, 333 K reaction temperature.

[0056] Comparative Example 1:

[0057] The preparation method of Example 1 was adopted, except that the microreactor system was replaced with a 500mL autoclave. The specific method was as follows: the heterogeneous o-xylene solution was added to the autoclave, stirring was started, and mixed acid was slowly added through the dripping system (rate control: added in 1-2 hours) to maintain the temperature at 50-60℃ (the temperature was precisely controlled by the jacket circulating water ±2℃, and the pressure was kept slightly positive (0.05-0.1MPa) to prevent leakage of volatile substances. Finally, heating was stopped, and rapid cooling was started to below 20℃. A quenching agent was added to decompose the residual nitric acid. The mixture was allowed to stand and separate into layers, separating the organic phase and the waste acid phase, and then washed with water until neutral.

[0058] Final results: 100% conversion rate, 7200 s reaction time, 353 K reaction temperature.

[0059] Comparative Example 2:

[0060] The preparation method of Example 3 was adopted, except that the microreactor system was replaced with a T-type microreactor. Specifically, the trifluoromethylbenzene dispersion and nitric acid solution were separately delivered to the preheating section capillary via medium-pressure constant flow pumps A / B, and then introduced into the T-type microreactor for mixing. The mixed system completed the nitration conversion process in the subsequently connected capillary reaction section. To ensure thermodynamic stability, the entire reaction system (including the microchannel reactor, capillary, and preheating components) was completely immersed in a constant temperature circulating water bath. The residence time of the system could be precisely controlled by adjusting the flow parameters of the delivery pump. When the reaction was terminated, the reaction solution was instantly cooled by an online quenching unit (pre-cooling quencher injected by pump C at a molar ratio of 1:1.2), and then collected in a low-temperature receiving device. Separation and purification stage: After standing and phase separation, an upper organic phase (containing the target nitro compound and o-xylene) and a lower acidic waste liquid were obtained. The organic phase was washed sequentially with 5% sodium hydroxide solution and deionized water gradient, and then dried with anhydrous sodium sulfate to obtain the crude product. After being concentrated and regenerated under reduced pressure, the nitric acid concentration of the waste acid is increased to 82-84%, which can be recycled for subsequent batch reactions. This process can ultimately obtain the target nitration product with a purity >99%.

[0061] Final results: conversion rate 22%s, reaction time 45s, reaction temperature 333K.

[0062] For those skilled in the art, various modifications and improvements can be made without departing from the concept of this utility model, and these modifications and improvements are all within the protection scope of this utility model. The protection scope of this utility model is defined by the appended claims.

[0063] The technical features of the above embodiments can be technically adjusted and combined according to process requirements. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A continuous nitration reactor in the form of a helical slotted microchannel characterized in that, The device is equipped with a grooved structure to induce fluid to form a spiral flow component; the spiral fluid induced by the groove has a ring-shaped vortex structure on both sides of each groove; the homogeneous solution of the nitrate to be nitrated and the mixed acid solution pipeline of the feeding unit are respectively connected to the medium-pressure constant flow pumps A and B to preheat the capillary tube, and the preheating capillary tube is connected to the inclined groove microchannel mixer. The inclined groove microchannel mixer, the inclined groove microreactor, and the preheating channel are all immersed in a constant temperature water bath. The reaction effluent pipe is connected to an ice bath collection device after passing through an online quenching unit, namely pump C, and is then connected in sequence to a dichloromethane gradient extraction device, a water washing device, and an anhydrous sodium sulfate dehydration device to form the entire continuous nitration reaction process device.

2. A continuous nitration reaction apparatus in the form of a helical slant-groove microchannel according to claim 1, characterized in that, The process apparatus for the nitration reaction of the spiral groove microchannel includes a groove microchannel mixer, a groove microchannel reactor, a medium-pressure constant flow pump, a high and low temperature circulation integrated machine, a digital temperature sensor, a constant temperature water bath micro-mixer, and an ice water bath collection bottle.

3. The continuous nitration reaction device in the form of a spiral inclined groove microchannel according to claim 1, characterized in that, The dimensional parameters of the groove static micro-mixing device for the spiral fluid induced by the groove include groove depth, groove width, distance between grooves, angle of the inclined groove, and inlet size of the micro-mixer.

4. The continuous nitration reaction device in the form of a spiral inclined groove microchannel according to claim 1, characterized in that, The grooves of the groove static microreactor device for the spiral fluid induced by the groove are spiral-shaped.

5. The continuous nitration reaction device in the form of a spiral inclined groove microchannel according to claim 1, characterized in that, The micro-reaction conditions of the nitration process include trench depth, trench width, inclined trench angle, and micro-mixer inlet size.

6. The continuous nitration reaction apparatus in the form of a spiral inclined groove microchannel according to claim 1, characterized in that, The nitration process includes a preheating capillary disc at the front end of the constant flow pump micromixer.

7. The continuous nitration reaction apparatus in the form of a spiral inclined groove microchannel according to claim 1, characterized in that, The nitration process is equipped with an ice-water bath collection device.

Images