A method for continuously and efficiently synthesizing 1-naphylamine based on a micro-packed bed reactor

Abstract

The present application relates to the technical fields of fine chemical intermediates synthesis, in particular to a method for continuous flow high-efficiency synthesis of 1-naphthylamine based on micro-packed bed reactor, which adopts Pd / C as catalyst, mixes 1-nitronaphthalene raw material liquid with hydrogen, and then passes into the micro-packed bed reactor to carry out continuous flow catalytic hydrogenation reaction. Through optimization of process conditions such as reaction temperature, reaction pressure, mass fraction of 1-nitronaphthalene in raw material liquid, and molar ratio of hydrogen to 1-nitronaphthalene, the conversion rate of 1-nitronaphthalene reaches 92.68%, and the selectivity of 1-naphthylamine reaches 99.9%. The reaction pressure is optimized and predicted by using Aspen Plus process simulation software, and the conversion rate of 1-nitronaphthalene can reach 98% under the condition of 4 MPa. The present application has the advantages of high mass transfer and heat transfer efficiency, good intrinsic safety, and high degree of process continuity, solves the problems of long reaction period, poor safety, and unstable batch of traditional batch kettle process, is suitable for green continuous production of 1-naphthylamine, and has wide industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of fine chemical intermediate synthesis technology, and in particular to a method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor. Background Technology

[0002] 1-Naphthylamine is an important aromatic amine fine chemical intermediate, widely used in pharmaceuticals, pesticides, dyes, rubber additives, and other fields. In recent years, with the continuous development of downstream application markets, the demand for 1-naphthylamine products has been increasing year by year. Developing efficient, safe, and green 1-naphthylamine synthesis processes has significant industrial application value.

[0003] The mainstream industrial methods for preparing 1-naphthylamine include chemical reduction and catalytic hydrogenation. Early industrial production often employed the iron powder reduction method, which uses 1-nitronaphthalene as a raw material. This method reduces the nitro group to an amino group in the presence of iron powder and hydrochloric acid or ferric chloride. However, this method suffers from severe pollution, poor product quality, high energy consumption, and severe equipment corrosion. In recent years, catalytic hydrogenation has gradually become a research hotspot in the synthesis of 1-naphthylamine due to its significant advantages, including environmental friendliness, high atom economy, and good product quality, and it has broad prospects for industrial application.

[0004] Existing technologies for the catalytic hydrogenation of 1-nitronaphthalene to 1-naphthylamine mostly employ batch reactors. These reactors require the addition of catalyst and raw materials to a reaction vessel, where a gas-liquid-solid three-phase reaction occurs under high temperature and pressure. The catalyst is then recovered through filtration after the reaction. Patent CN101434550A discloses a batch hydrogenation process using a supported nickel catalyst, employing ethanol as a solvent, and conducting a batch reaction for 3–8 hours at 60–90 °C and 1.5–3.0 MPa, achieving a 1-nitronaphthalene conversion rate of 95%–99%. While this process achieves a high conversion rate technically, it still suffers from low mass and heat transfer efficiency, high liquid holdup, poor safety, and weak process controllability. Catalytic hydrogenation is a strongly exothermic reaction, and in batch reactors, localized heat accumulation can easily lead to temperature runaway or decreased selectivity. 1-nitronaphthalene and its hydrogenation products pose certain risks under high temperature and pressure conditions, and the batch reactor process presents significant safety risks, hindering its further industrial scale-up application.

[0005] To address the aforementioned drawbacks of batch reactor processes, continuous flow hydrogenation processes have attracted widespread attention due to their advantages such as high automation, safe operation, and high space-time yield. Trickling bed reactors are currently a common reactor type used in the continuous catalytic hydrogenation production of 1-nitronaphthalene. Patent CN107540553B discloses a method for the catalytic hydrogenation of 1-nitronaphthalene to prepare 1-naphthylamine using a supported Ni₂P catalyst in a trickling bed reactor. This technical solution uses a mixture of 1-nitronaphthalene and piperidine as raw material, operating at 413–453 K, 3.0–5.0 MPa, and a mass hourly space velocity (WHSV) of 0.25–0.5 h⁻¹. -1 Under conditions where the hydrogen-naphthalene molar ratio is 6–12:1, the conversion rate of 1-nitronaphthalene reaches 100%, and the selectivity of 1-naphthylamine reaches 100%. This trickle bed process avoids the separation problem between catalyst and product in batch reactor reactions, and the supported Ni2P catalyst has good resistance to sulfur poisoning. However, traditional trickle beds still have problems such as large bed pressure drop, insufficient mass transfer enhancement, wide residence time distribution, and the tendency of high-concentration substrates to cause local hot spots, making it difficult to achieve stable and continuous production with lower energy consumption and higher efficiency, thus limiting its further industrialization. Summary of the Invention

[0006] The purpose of this invention is to provide a method for the efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor, in order to solve the problems of low mass and heat transfer efficiency, product selectivity, large equipment size, and high safety risks in the existing catalytic hydrogenation of 1-nitronaphthalene to prepare 1-naphthylamine as mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor, comprising the following steps:

[0008] (1) Dissolve 1-nitronaphthalene in an organic solvent to prepare a raw material solution, wherein the concentration of 1-nitronaphthalene in the raw material solution is 2 wt% to 50 wt%;

[0009] (2) The raw material liquid obtained in step (1) is mixed with hydrogen and then introduced into a micro-packed bed reactor, wherein the reaction tube of the micro-packed bed reactor is filled with particulate catalyst;

[0010] (3) Catalytic hydrogenation reaction was carried out at a reaction temperature of 40-75 °C, a reaction pressure of 0.5-4 MPa, and a molar ratio of hydrogen to 1-nitronaphthalene of 3.44:1-15:1.

[0011] (4) Collect the reaction products and obtain 1-naphthylamine after gas-liquid separation.

[0012] Further, the organic solvent mentioned in step (1) is acetonitrile.

[0013] Furthermore, the concentration of 1-nitronaphthalene in the raw material solution in step (1) is preferably 2 wt% to 15 wt%.

[0014] Furthermore, the particulate catalyst mentioned in step (2) is a Pd / C catalyst.

[0015] Furthermore, the particle size of the Pd / C catalyst is 0.6–0.8 mm.

[0016] Furthermore, in step (2), the liquid phase flow rate of the raw material liquid is 0.4 to 1.5 mL / min, and the flow rate of hydrogen is 8 to 40 SCCM.

[0017] Furthermore, the residence time of the gas-liquid mixture formed by mixing the raw material liquid with hydrogen in step (2) in the micro-packed bed reactor is 39 to 148 s.

[0018] Furthermore, the reaction temperature in step (3) is 55-65 °C, the reaction pressure is 1.5-4 MPa, and the molar ratio of hydrogen to 1-nitronaphthalene is 3.44:1-10:1.

[0019] Furthermore, the liquid phase flow rate of the feed liquid is 0.4–0.8 mL / min, and the flow rate of hydrogen is 20–40 SCCM.

[0020] Further, in step (2), the raw material liquid and hydrogen are first introduced into a micro mixer for mixing to form a gas-liquid mixture before entering the micro packed bed reactor; the micro packed bed reactor is equipped with a jacket, and the reaction temperature is controlled by introducing a constant temperature heat exchange medium into the jacket.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. Excellent mass and heat transfer performance and high reaction efficiency: The microscale channels of the micro-packed bed reactor greatly enhance the gas-liquid-solid three-phase contact, significantly improving mass transfer efficiency. Simultaneously, the microchannels have a large specific surface area and strong heat exchange capacity, effectively removing the large amount of reaction heat released during the hydrogenation reaction and avoiding local overheating and runaway phenomena. Through systematic optimization of reaction temperature, pressure, feed concentration, and hydrogen-naphthalene molar ratio, the conversion rate of 1-nitronaphthalene can reach 98%, and the selectivity of 1-naphthylamine reaches 99.9%.

[0023] 2. High inherent safety: The micro-packed bed reactor has a small liquid holdup and a small amount of hazardous materials in the reactor, making the reaction process easy to control. This achieves inherent safety in the nitro reduction reaction and significantly reduces safety risks.

[0024] 3. Small equipment size and easy to scale up: The micro packed bed reactor has a compact structure and small size, which facilitates multi-channel parallel scale-up and makes it easy to directly scale up from laboratory scale to industrial scale. The scale-up effect is small, which can effectively shorten the industrialization process.

[0025] 4. Continuous production and low cost: It realizes the continuous production of 1-naphthylamine by hydrogenation of 1-nitronaphthalene. The process is simple and highly automated. The catalyst is fixed in the reactor and does not require frequent loading, unloading and filtration separation, which avoids mechanical loss of catalyst, reduces production costs, improves production efficiency and has broad market application prospects. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the continuous flow synthesis of 1-naphthylamine using a micro-packed bed reactor according to the present invention.

[0027] In the diagram: 1. Storage bottle containing 1-nitronaphthalene solution; 2. Metering pump for conveying 1-nitronaphthalene; 3. Hydrogen cylinder; 4. Mass flow meter; 5. Gas phase preheating tube; 6. Liquid phase preheating tube; 7. Micro mixer; 8. Micro packed bed reactor filled with solid particulate catalyst; 9. Thermostat; 10. Back pressure valve; 11. Gas-liquid separator. Detailed Implementation

[0028] The core of this invention lies in achieving efficient gas-liquid-solid three-phase contact through microscale channels in a micro-filled bed reactor. Therefore, as long as the catalyst can be effectively and stably fixed within these microscale channels, ensuring sufficient contact with the reactants, the objective of this invention can be achieved. Those skilled in the art will know that, in addition to the most commonly used particle packing method, other fixing methods are also applicable, such as wall-mounted and honeycomb types. The invention will be further described in detail below with reference to specific embodiments, but the scope of protection of this invention is not limited to the following embodiments. Without departing from the concept of this invention, those skilled in the art can make various modifications and improvements to the technical solution of this invention, and all such modifications and improvements should fall within the scope of protection of this invention.

[0029] Example 1

[0030] Experiments were conducted according to the method of the present invention. An acetonitrile solution of 1-nitronaphthalene with a concentration of 5 wt% was prepared. The hydrogen flow rate was controlled at 20 SCCM, the feed liquid flow rate at 0.4 mL / min, and the molar ratio of hydrogen to 1-nitronaphthalene at 9.8:1. The solution and hydrogen were mixed in a T-type micro-mixer. The resulting gas-liquid mixture was then passed through a micro-packed bed packed with Pd / C catalyst. The reaction temperature was set at 50 °C, the reaction pressure at 1.7 MPa, and the residence time at 148 s. The reaction product was collected at the outlet of the micro-packed bed reactor. The obtained product was analyzed, and the conversion rate of 1-nitronaphthalene reached 42.6%, and the selectivity of 1-naphthylamine reached 99.9%.

[0031] Example 2

[0032] Experiments were conducted according to the method of the present invention. An acetonitrile solution of 1-nitronaphthalene with a concentration of 5 wt% was prepared. The hydrogen flow rate was controlled at 20 SCCM, the feed liquid flow rate at 0.4 mL / min, and the molar ratio of hydrogen to 1-nitronaphthalene at 9.8:1. The solution and hydrogen were mixed in a T-type micro-mixer. The resulting gas-liquid mixture was then passed through a micro-packed bed packed with Pd / C catalyst. The reaction temperature was set at 55 °C, the reaction pressure at 1.7 MPa, and the residence time at 148 s. The reaction product was collected at the outlet of the micro-packed bed reactor. The obtained product was analyzed, and the conversion rate of 1-nitronaphthalene reached 86.01%, and the selectivity of 1-naphthylamine reached 99.9%.

[0033] Example 3

[0034] Experiments were conducted according to the method of the present invention. An acetonitrile solution of 1-nitronaphthalene with a concentration of 5 wt% was prepared. The hydrogen flow rate was controlled at 20 SCCM, the feed liquid flow rate at 0.4 mL / min, and the molar ratio of hydrogen to 1-nitronaphthalene at 9.8:1. The solution and hydrogen were mixed in a T-type micro-mixer. The resulting gas-liquid mixture was then passed through a micro-packed bed packed with Pd / C catalyst. The reaction temperature was set at 60 °C, the reaction pressure at 1.7 MPa, and the residence time at 148 s. The reaction product was collected at the outlet of the micro-packed bed reactor. The obtained product was analyzed, and the conversion rate of 1-nitronaphthalene reached 82.95%, and the selectivity of 1-naphthylamine reached 99.9%.

[0035] Example 4

[0036] Experiments were conducted according to the method of the present invention. An acetonitrile solution of 1-nitronaphthalene with a concentration of 5 wt% was prepared. The hydrogen flow rate was controlled at 20 SCCM, the feed liquid flow rate at 0.4 mL / min, and the molar ratio of hydrogen to 1-nitronaphthalene at 9.8:1. The solution and hydrogen were mixed in a T-type micro-mixer. The resulting gas-liquid mixture was then passed through a micro-packed bed packed with Pd / C catalyst. The reaction temperature was set at 55 °C, the reaction pressure at 1.4 MPa, and the residence time at 148 s. The reaction product was collected at the outlet of the micro-packed bed reactor. The obtained product was analyzed, and the conversion rate of 1-nitronaphthalene reached 83.66%, and the selectivity of 1-naphthylamine reached 99.9%.

[0037] Example 5

[0038] Experiments were conducted according to the method of the present invention. An acetonitrile solution of 1-nitronaphthalene with a concentration of 5 wt% was prepared. The hydrogen flow rate was controlled at 7 SCCM, the feed liquid flow rate at 0.4 mL / min, and the molar ratio of hydrogen to 1-nitronaphthalene was 3.44:1. The solution and hydrogen were mixed in a T-type micro-mixer, and the resulting gas-liquid mixture was passed through a micro-packed bed packed with Pd / C catalyst. The reaction temperature was set at 55 °C, the reaction pressure at 1.7 MPa, and the residence time at 148 s. The reaction product was collected at the outlet of the micro-packed bed reactor. The obtained product was analyzed, and the conversion rate of 1-nitronaphthalene reached 79.7%, and the selectivity of 1-naphthylamine reached 95%.

[0039] Example 6

[0040] Experiments were conducted according to the method of the present invention. An acetonitrile solution of 1-nitronaphthalene with a concentration of 2 wt% was prepared. The hydrogen flow rate was controlled at 20 SCCM, the feed liquid flow rate at 0.4 mL / min, and the molar ratio of hydrogen to 1-nitronaphthalene was 9.8:1. The solution and hydrogen were mixed in a T-type micro-mixer. The resulting gas-liquid mixture was then passed through a micro-packed bed packed with Pd / C catalyst. The reaction temperature was set at 55 °C, the reaction pressure at 1.7 MPa, and the residence time at 148 s. The reaction product was collected at the outlet of the micro-packed bed reactor. The obtained product was analyzed, and the conversion rate of 1-nitronaphthalene reached 92.68%, and the selectivity of 1-naphthylamine reached 99.9%.

[0041] Experimental Example 7

[0042] Due to limited experimental conditions, the existing experimental setup has a back pressure limit of 1.7 MPa. To broaden the process operating window and determine the optimal process parameters for micro-packed bed catalytic hydrogenation, a plug flow (RPlug) kinetic reaction model for micro-packed bed hydrogenation was constructed using Aspen Plus V11, based on the intrinsic kinetic model of 1-nitronaphthalene hydrogenation measured in a small-scale test according to this invention. The system property method used was NRTL-RK to accurately describe the non-ideal gas-liquid system of acetonitrile-aromatics under high pressure. The reaction module input was a power-law intrinsic kinetic model, with the kinetic reference based on the mass of the Pd / C catalyst. The reactor geometry, catalyst loading, and bed porosity all adopted the measured physical dimensions of the micro-packed bed of this invention. At a reaction temperature of 55 °C, a 1-nitronaphthalene solution mass fraction of 2%, a hydrogen flow rate of 20 SCCM, and a feed liquid flow rate of 0.4 mL / min, the simulation results of the increased system pressure are shown in Table 1.

[0043] Table 1. Aspen simulation predictions of 1-nitronaphthalene conversion rates under different hydrogen pressures.

[0044] Serial Number Reaction pressure P / MPa Conversion rate / % 1 0.5 77.52 2 1.0 85.48 3 1.5 90.27 4 2.0 93.22 5 2.5 95.16 6 3.0 96.45 7 3.5 97.33 8 4.0 98.00

[0045] Comparative Example 1

[0046] In patent CN116396173A, a supported nickel-based catalyst is used to continuously hydrogenate nitronaphthalene to prepare 1-naphthylamine in a fixed-bed reactor. The catalyst reduction conditions are: reduction with a H2 / N2 mixture at 260–320 °C and 2–3 MPa for 2–8 h. The reaction conditions are: temperature 60–180 °C, pressure 0.2–2.0 MPa, hydrogen to nitronaphthalene molar ratio 10–100, nitronaphthalene solution hourly space velocity 0.1–1.2 g / (g·h), solvent can be methanol, ethanol, N,N-dimethylformamide, etc., and nitronaphthalene concentration 200–700 kg / m³. 3 Under optimal process conditions, this patented technology can achieve complete conversion of 1-nitronaphthalene and 100% selectivity for 1-naphthylamine.

[0047] Comparative Example 2

[0048] In patent CN107540553B, a supported Ni₂P catalyst is used to prepare 1-naphthylamine by hydrogenation of 1-nitronaphthalene in a trickle bed reactor. A mixture of 1-nitronaphthalene and piperidine is used as the raw material, with 1-nitronaphthalene comprising 5–15 wt% and piperidine 85–95 wt%. The reaction temperature is 413–453 K, the pressure is 3.0–5.0 MPa, and the mass hourly space velocity (WHSV) is 0.25–0.5 h⁻¹. -1 The molar ratio of hydrogen to 1-nitronaphthalene is 6–12:1. Under the optimal process conditions of this patent, complete conversion of 1-nitronaphthalene can be achieved, with 100% selectivity for 1-naphthylamine.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor, characterized in that, Includes the following steps: (1) Dissolve 1-nitronaphthalene in an organic solvent to prepare a raw material solution, wherein the concentration of 1-nitronaphthalene in the raw material solution is 2 wt% to 50 wt%; (2) The raw material liquid obtained in step (1) is mixed with hydrogen and then introduced into a micro-packed bed reactor, wherein the reaction tube of the micro-packed bed reactor is filled with particulate catalyst; (3) Catalytic hydrogenation reaction was carried out at a reaction temperature of 40-75 °C, a reaction pressure of 0.5-4 MPa, and a molar ratio of hydrogen to 1-nitronaphthalene of 3.44:1-15:

1. (4) Collect the reaction products and obtain 1-naphthylamine after gas-liquid separation.

2. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 1, characterized in that, The organic solvent mentioned in step (1) is acetonitrile.

3. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 1, characterized in that, The concentration of 1-nitronaphthalene in the raw material solution in step (1) is 2 wt% to 15 wt%.

4. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 1, characterized in that, The particulate catalyst mentioned in step (2) is a Pd / C catalyst.

5. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 4, characterized in that, The particle size of the Pd / C catalyst is 0.6–0.8 mm.

6. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 1, characterized in that, The liquid phase flow rate of the raw material liquid in step (2) is 0.4 to 1.5 mL / min, and the flow rate of hydrogen is 8 to 40 SCCM.

7. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 1, characterized in that, The residence time of the gas-liquid mixture formed by mixing the raw material liquid with hydrogen in step (2) in the micro-packed bed reactor is 39 to 148 s.

8. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 1, characterized in that, The reaction temperature in step (3) is 55-65 °C, the reaction pressure is 1.5-4 MPa, and the molar ratio of hydrogen to 1-nitronaphthalene is 3.44:1-10:

1.

9. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 6, characterized in that, The liquid phase flow rate of the feed liquid is 0.4–0.8 mL / min, and the flow rate of hydrogen is 20–40 SCCM.

10. The method for efficient continuous flow synthesis of 1-naphthylamine based on a micro-packed bed reactor according to claim 1, characterized in that, In step (2), the raw material liquid and hydrogen are first introduced into a micro mixer for mixing to form a gas-liquid mixture before entering a micro packed bed reactor. The micro packed bed reactor is equipped with a jacket, and the reaction temperature is controlled by introducing a constant temperature heat exchange medium into the jacket.

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