A method for continuously producing 3-chloro-4-fluoroaniline using a fixed-bed reactor

Abstract

The present invention belongs to the field of organic chemical technology, and in particular relates to a method for continuously producing 3-chloro-4-fluoroaniline using a fixed-bed reactor. The method comprises the following steps: (1) dissolving 3-chloro-4-fluoronitrobenzene in methanol to obtain a 3-chloro-4-fluoronitrobenzene solution; (2) reacting the 3-chloro-4-fluoronitrobenzene solution with hydrogen in a fixed-bed reactor filled with Ni-Cu / Al2O3 catalyst particles to obtain 3-chloro-4-fluoroaniline. The present invention uses a tubular fixed-bed reactor to achieve continuous 3-chloro-4-fluoronitrobenzene hydrogenation reaction process, reducing operating intensity; and the 3-chloro-4-fluoronitrobenzene conversion rate is greater than 99.5%, and the 3-chloro-4-fluoroaniline selectivity is greater than or equal to 99.2%.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical industry, and particularly relates to a method for continuously producing 3-chloro-4-fluoroaniline by adopting a fixed bed reactor. Background Art

[0002] Fluorochloroanilines are important intermediates in the synthesis of pharmaceuticals, pesticides, dyes, and other organic compounds. 3-Chloro-4-fluoroaniline is an intermediate in the synthesis of quinoline monoazo disperse dyes. Dyes synthesized with it exhibit excellent lightfastness and water-washability. 3-Chloro-4-fluoroaniline is also a key intermediate in the synthesis of the novel, highly effective, broad-spectrum anti-infective drug, norfloxacin, and serves as a foundational product for the third generation of quinolone acid drugs.

[0003] There are various methods for synthesizing 3-chloro-4-fluoroaniline, including one using 3-chloro-4-fluoronitrobenzene via a reduction reaction. In the presence of an electrolyte solution, NO₂ is reduced to NH₂ using metallic iron as a reducing agent. The reaction involves adding 3-chloro-4-fluoronitrobenzene, reduced iron powder, ethanol, and water to a reactor, heating to 60°C, stirring, and then adding hydrochloric acid, maintaining the temperature at 80-90°C. After the reaction is complete, the reaction solution is cooled, extracted with an organic solvent, dried, filtered, and the solvent removed. Finally, 3-chloro-4-fluoroaniline is distilled to yield white crystals. This reaction uses iron powder as a catalytic reduction. Although the process is relatively mature, it produces a large amount of acid mist and iron sludge containing aniline, causing significant pollution.

[0004] Based on factors such as the availability and low price of raw materials, simple operation, safety, yield, quality, requirements for waste treatment and equipment, domestic manufacturers often choose a synthetic route that uses o-dichlorobenzene as raw material, nitrates it to obtain 3,4-dichloronitrobenzene, replaces it with fluorine to obtain 3-chloro-4-fluoronitrobenzene, and finally reduces it to obtain 3-chloro-4-fluoroaniline. The specific route is shown below.

[0005]

[0006] Currently, the reaction mainly uses a reactor. For example, patent CN205295191U proposes a device for producing 3-chloro-4-fluoroaniline using a fluorination kettle, a water washing kettle, and a hydrogenation kettle. The device is simple to operate, has a high level of automatic control, and produces a high product yield. However, there are problems such as discontinuous operation, unstable reaction rate and conversion rate. Halogen salts contained in the raw materials can cause pitting corrosion on the inner surface of the reactor. Moreover, halogen-containing nitroaromatics are easily dehalogenated during the rehydrogenation process. After long-term operation, the reactor will suffer from extensive corrosion, which can damage the reactor and cause production shutdowns. Existing companies rely on frequent reactor replacement to ensure product production efficiency.

[0007] Chinese invention patent application CN104292113A discloses a method for preparing 3-chloro-4-fluoroaniline, belonging to the field of organic chemical technology. The method comprises the following steps: 3-chloro-4-fluoronitrobenzene and a 1% Pt / C catalyst are reacted at 50-100°C in a 0.1-5 MPa hydrogen atmosphere for 1-10 hours. The mass ratio of 3-chloro-4-fluoronitrobenzene to the 1% Pt / C catalyst is (200-400):1. This invention uses 3-chloro-4-fluoronitrobenzene as the raw material and employs a 1% Pt / C catalytic hydrogenation substitution reaction to prepare 3-chloro-4-fluoroaniline with a purity exceeding 99.5% and a yield exceeding 94%. However, the product purity and yield still need to be improved. Summary of the Invention

[0008] To address these shortcomings, the present invention provides a method for the continuous production of 3-chloro-4-fluoroaniline using a fixed-bed reactor. This method enables the continuous hydrogenation of 3-chloro-4-fluoronitrobenzene, simplifies the process flow, and reduces operational intensity. Spraying PPS on the inner walls of the transversely grooved tubes reduces the corrosion of the fixed-bed reactor by corrosive substances in the 3-chloro-4-fluoronitrobenzene raw material used in the industrial process. This method also enhances heat transfer, reduces localized overheating of the catalyst within the tubes, and reduces the formation of byproducts.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed-bed reactor comprises the following steps:

[0011] (1) dissolving 3-chloro-4-fluoronitrobenzene in methanol to obtain a 3-chloro-4-fluoronitrobenzene solution;

[0012] (2) A 3-chloro-4-fluoronitrobenzene solution is mixed with hydrogen and reacted in a fixed bed reactor filled with Ni-Cu / Al2O3 catalyst particles to obtain 3-chloro-4-fluoroaniline.

[0013] Preferably, the mass concentration of the 3-chloro-4-fluoronitrobenzene solution in step (1) is 40%-50%, and triethylamine is further added to the 3-chloro-4-fluoronitrobenzene solution, and the molar ratio of triethylamine to 3-chloro-4-fluoronitrobenzene is 1.1-1.5:1.

[0014] Preferably, the particle size of the Ni-Cu / Al2O3 particles in step (2) is 2-3 mm, and the molar ratio of Ni to Cu is 2-2.5:1.

[0015] Preferably, the fixed bed reactor in step (2) is a shell-and-tube fixed bed reactor, and the shell-and-tubes are transverse grooved tubes sprayed with polyphenylene sulfide (PPS), and polyphenylene sulfide (PPS) is sprayed on the inner wall of the shell-and-tubes.

[0016] Further preferably, the spraying thickness is 0.2-0.5 mm, and the total length of a single tube is 1.9-2.1 m.

[0017] Furthermore, preferably, the spraying thickness is 0.2 mm, and the total length of a single tube is 2.0 m.

[0018] Further preferably, the minimum inner diameter of the transverse grooved tube is 25-32 mm, and the maximum inner diameter is 1.25-1.65 times the minimum inner diameter.

[0019] In another preferred embodiment, the minimum inner diameter of the transverse grooved tube is 25 mm, and the maximum inner diameter is 1.4 times the minimum inner diameter.

[0020] Preferably, the reaction temperature in step (2) is 60-100° C., the reaction pressure is 0.8-1.0 MPa, and the reaction time is 0.6-1 h.

[0021] Further preferably, the reaction temperature in step (2) is 70-80° C., and the reaction time is 0.7-0.9 h.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention uses a tubular fixed-bed reactor to achieve a continuous 3-chloro-4-fluoronitrobenzene hydrogenation reaction process, reducing operating intensity; and the 3-chloro-4-fluoronitrobenzene conversion rate is greater than 99.5%, and the 3-chloro-4-fluoroaniline selectivity is greater than 99.2%;

[0024] (2) The present invention uses PPS spray-coated tubular fixed bed to resist corrosion, thereby extending the service life of the reactor;

[0025] (3) The tubes of the present invention use transverse grooved tubes sprayed with PPS to enhance heat transfer performance without the need for a special PPS coating formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a fixed bed reactor for spraying PPS in the present invention;

[0027] Figure 2 The invention relates to a transverse grooved tube sprayed with PPS and loaded with catalyst particles. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are merely exemplary and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solutions of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, and such modifications and replacements fall within the scope of protection of the present invention.

[0029] Polyphenylene sulfide (PPS) powder raw material was provided by Zhejiang Xinhecheng Special Materials Co., Ltd., the powder model was DL201, and PPS spraying was completed by Zhejiang Deli Equipment Co., Ltd.

[0030] Example 1

[0031] The fixed bed reactor of spraying PPS used in the present invention is as follows Figure 1 shown.

[0032] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor comprises the following steps:

[0033] (1) mixing 3-chloro-4-fluoronitrobenzene and a methanol solution to obtain a 3-chloro-4-fluoronitrobenzene solution having a concentration of 50 wt %; further adding triethylamine to the solution, wherein the molar ratio of triethylamine to 3-chloro-4-fluoronitrobenzene is 1.2:1;

[0034] (2) 3-Chloro-4-fluoronitrobenzene solution and hydrogen enter the fixed bed reactor (e.g., a fixed bed reactor) sprayed with PPS and loaded with Ni-Cu / Al2O3 catalyst particles with a particle size of 2.5 mm (the molar ratio of Ni to Cu in the Ni-Cu / Al2O3 catalyst is 2.33:1) from the bottom of the fixed bed. Figure 2 As shown), the tubes are transverse grooved tubes sprayed with PPS, PPS is sprayed on the inner wall of the tubes, the spraying thickness is 0.2 mm, the total length of a single tube is 2.0 m, the minimum inner diameter is 25 mm, the maximum inner diameter is 1.4 times the minimum inner diameter, the reaction temperature is 80 ° C, the reaction pressure is 0.8 MPa, the residence time is 1 h, and the reaction products are collected at the outlet of the fixed bed reactor.

[0035] The product was processed and analyzed, and the conversion rate of 3-chloro-4-fluoronitrobenzene was 99.8%, and the selectivity of 3-chloro-4-fluoroaniline was 99.2%.

[0036] Example 2

[0037] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor comprises the following steps:

[0038] (1) mixing 3-chloro-4-fluoronitrobenzene and a methanol solution to obtain a 3-chloro-4-fluoronitrobenzene solution having a concentration of 50 wt %; further adding triethylamine to the solution, wherein the molar ratio of triethylamine to 3-chloro-4-fluoronitrobenzene is 1.1:1;

[0039] (2) 3-Chloro-4-fluoronitrobenzene solution and hydrogen enter the PPS-sprayed shell-and-tube fixed-bed reactor filled with Ni-Cu / Al2O3 catalyst particles with a particle size of 2.0 mm (the molar ratio of Ni to Cu in the Ni-Cu / Al2O3 catalyst is 2:1) from the bottom of the fixed bed. The shell-and-tube reactor adopts transverse grooved tubes sprayed with PPS. PPS is sprayed on the inner wall of the shell-and-tube reactor with a spraying thickness of 0.2 mm. The total length of a single shell-and-tube reactor is 2.0 m, the minimum inner diameter is 25 mm, and the maximum inner diameter is 1.4 times the minimum inner diameter. The reaction temperature is 70 ° C, the reaction pressure is 1 MPa, and the residence time is 0.6 h. The reaction products are collected at the outlet of the fixed-bed reactor.

[0040] The product was processed and analyzed, and the conversion rate of 3-chloro-4-fluoronitrobenzene was 99.6%, and the selectivity of 3-chloro-4-fluoroaniline was 99.5%.

[0041] Example 3

[0042] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor comprises the following steps:

[0043] (1) mixing 3-chloro-4-fluoronitrobenzene and a methanol solution to obtain a 3-chloro-4-fluoronitrobenzene solution having a concentration of 50 wt %; further adding triethylamine to the solution, wherein the molar ratio of triethylamine to 3-chloro-4-fluoronitrobenzene is 1.5:1;

[0044] (2) 3-Chloro-4-fluoronitrobenzene solution and hydrogen enter the PPS-sprayed shell-and-tube fixed-bed reactor filled with Ni-Cu / Al2O3 catalyst particles with a particle size of 3.0 mm (the molar ratio of Ni to Cu in the Ni-Cu / Al2O3 catalyst is 2.5:1) from the bottom of the fixed bed. The shell-and-tube reactor adopts transverse grooved tubes sprayed with PPS. PPS is sprayed on the inner wall of the shell-and-tube reactor with a spraying thickness of 0.2 mm. The total length of a single shell-and-tube reactor is 2.0 m, the minimum inner diameter is 25 mm, and the maximum inner diameter is 1.4 times the minimum inner diameter. The reaction temperature is 100 ° C, the reaction pressure is 0.8 MPa, and the residence time is 1 h. The reaction products are collected at the outlet of the fixed-bed reactor.

[0045] The product was processed and analyzed, and the conversion rate of 3-chloro-4-fluoronitrobenzene was 99.8%, and the selectivity of 3-chloro-4-fluoroaniline was 99.2%.

[0046] Example 4

[0047] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor comprises the following steps:

[0048] (1) 3-chloro-4-fluoronitrobenzene and a methanol solution are mixed to obtain a 3-chloro-4-fluoronitrobenzene solution having a concentration of 40 wt %; triethylamine is further added to the solution, wherein the molar ratio of triethylamine to 3-chloro-4-fluoronitrobenzene is 1.2:1;

[0049] (2) 3-Chloro-4-fluoronitrobenzene solution and hydrogen enter the PPS-sprayed shell-and-tube fixed-bed reactor filled with Ni-Cu / Al2O3 catalyst particles with a particle size of 2.5 mm (the molar ratio of Ni to Cu in the Ni-Cu / Al2O3 catalyst is 2.33:1) from the bottom of the fixed bed. The shell-and-tube reactor adopts transverse grooved tubes sprayed with PPS. PPS is sprayed on the inner wall of the shell-and-tube reactor with a spraying thickness of 0.2 mm. The total length of a single shell-and-tube reactor is 2.0 m, the minimum inner diameter is 25 mm, and the maximum inner diameter is 1.4 times the minimum inner diameter. The reaction temperature is 80 ° C, the reaction pressure is 0.8 MPa, and the residence time is 1 h. The reaction products are collected at the outlet of the fixed-bed reactor.

[0050] The product was processed and analyzed, and the conversion rate of 3-chloro-4-fluoronitrobenzene was 99.3%, and the selectivity of 3-chloro-4-fluoroaniline was 99.3%.

[0051] Comparative Example 1

[0052] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor is disclosed, which differs from Example 1 only in that the transverse grooved tubes sprayed with PPS are replaced with circular tube arrays sprayed with PPS.

[0053] The product was processed and analyzed. The conversion rate of 3-chloro-4-fluoronitrobenzene in this comparative example was 99.0%, and the selectivity of 3-chloro-4-fluoroaniline was 97.4%.

[0054] Comparative Example 2

[0055] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor, which differs from Example 1 only in that the minimum inner diameter is 25 mm and the maximum inner diameter is twice the minimum inner diameter.

[0056] The conversion rate of 3-chloro-4-fluoronitrobenzene in this comparative example was 98.9%, and the selectivity of 3-chloro-4-fluoroaniline was 97.6%.

[0057] Comparative Example 3

[0058] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor, which differs from Example 1 only in that the minimum inner diameter is 25 mm and the maximum inner diameter is 1.12 times the minimum inner diameter.

[0059] The conversion rate of 3-chloro-4-fluoronitrobenzene in this comparative example was 99%, and the selectivity of 3-chloro-4-fluoroaniline was 96.8%.

[0060] Comparative Example 4

[0061] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor, which differs from Example 1 only in that the molar ratio of Ni to Cu in the Ni-Cu / Al2O3 catalyst is 0.5:1.

[0062] The conversion rate of 3-chloro-4-fluoronitrobenzene in this comparative example was 98.8%, and the selectivity of 3-chloro-4-fluoroaniline was 88.0%.

[0063] Comparative Example 5

[0064] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor, which differs from Example 1 only in that the molar ratio of Ni to Cu in the Ni-Cu / Al2O3 catalyst is 4:1.

[0065] The conversion rate of 3-chloro-4-fluoronitrobenzene in this comparative example was 89.8%, and the selectivity of 3-chloro-4-fluoroaniline was 80.2%.

[0066] Comparative Example 6

[0067] A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor is provided, the difference from Example 1 being that the reaction temperature is 110°C.

[0068] The conversion rate of 3-chloro-4-fluoronitrobenzene in this comparative example was 98.8%, and the selectivity of 3-chloro-4-fluoroaniline was 96.1%.

[0069] The above detailed description is a specific description of one feasible embodiment of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not depart from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A method for continuously producing 3-chloro-4-fluoroaniline using a fixed bed reactor, characterized in that: The following steps are involved: (1) dissolving 3-chloro-4-fluoronitrobenzene in methanol to obtain a 3-chloro-4-fluoronitrobenzene solution; (2) Mixing 3-chloro-4-fluoronitrobenzene solution with hydrogen and reacting in a fixed bed reactor filled with Ni-Cu / Al2O3 catalyst particles to obtain 3-chloro-4-fluoroaniline. In step (2), the molar ratio of Ni to Cu in the Ni-Cu / Al2O3 particles is 2-2.5:1; the fixed bed reactor is a shell-and-tube fixed bed reactor, and the shell-and-tube adopts a transverse grooved tube sprayed with polyphenylene sulfide, and the polyphenylene sulfide is sprayed on the inner wall of the shell-and-tube; the minimum inner diameter of the transverse grooved tube is 25-32 mm, and the maximum inner diameter is 1.25-1.65 times the minimum inner diameter.

2. The method according to claim 1, characterized in that The mass concentration of the 3-chloro-4-fluoronitrobenzene solution in step (1) is 40%-50%, and triethylamine is further added to the 3-chloro-4-fluoronitrobenzene solution, and the molar ratio of the triethylamine to the 3-chloro-4-fluoronitrobenzene is 1.1-1.5:

1.

3. The method according to claim 1, characterized in that The particle size of the Ni-Cu / Al2O3 particles in step (2) is 2-3 mm.

4. The method according to claim 1, wherein The spraying thickness is 0.2-0.5 mm, and the total length of a single tube is 1.9-2.1 m.

5. The method according to claim 4, characterized in that The spraying thickness is 0.2 mm, and the total length of a single tube is 2.0 m.

6. The method according to claim 1, characterized in that The minimum inner diameter of the transverse grooved tube is 25 mm, and the maximum inner diameter is 1.4 times the minimum inner diameter.

7. The method according to claim 1, characterized in that The reaction temperature in step (2) is 60-100° C., the reaction pressure is 0.8-1.0 MPa, and the reaction time is 0.6-1 h.

8. The method according to claim 7, characterized in that The reaction temperature in step (2) is 70-80° C., and the reaction time is 0.7-0.9 h.

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