Main applications of o-fluoroaniline_Kain Industrial Additives

Background and overview^[1-2]

O-fluoroaniline is a light yellow liquid, oily; the color is not obvious when the amount is small. Slightly aromatic and poisonous. It is irritating to the skin, and its vapor or smoke is irritating to the eyes, mucous membranes and upper respiratory tract. When it enters the human body, it can form methemoglobin and cause cyanosis, which is harmful to the environment. This product is flammable and irritating. O-fluoroaniline is an important intermediate in the synthesis of fluorine-containing medicines and dyes. O-fluoroaniline can be used as a pharmaceutical synthesis intermediate. At present, o-fluoroaniline is mainly produced in China by reducing o-fluoronitrobenzene with iron powder. This process will produce a large amount of iron sludge (2.2t~2.4t of iron sludge will be produced for every 1t of o-fluoroaniline produced), and at the same time, A large amount of amine-containing wastewater is produced (8 to 10 tons of amine-containing wastewater is produced for every 1 ton of o-fluoroaniline produced), which causes great harm to the environment. Therefore, the application prospect of using catalytic hydrogenation reduction method to synthesize o-fluoroaniline is very good. A large number of literatures have reported on the batch catalytic hydrogenation reduction method using a kettle reactor and using Pt/C as the catalyst. This method has low initial investment and is easy to implement, but it requires a lot of manpower, has poor safety, and produces a large amount of waste liquid and waste residue. It has not yet been industrialized. At present, there are few literature reports on methods and catalysts for preparing o-fluoroaniline using fixed-bed continuous catalytic hydrogenation. This process is safe, environmentally friendly, has high production efficiency, requires few personnel, and is conducive to industrial production in the long run.

Apply^[1][3-5]

O-fluoroaniline is an important intermediate in the synthesis of fluorine-containing medicines and dyes. O-fluoroaniline can be used to synthesize the heat-sensitive dye FH-102, which is a black heat-sensitive dye with wide application and excellent performance. The dye can be used in the production of electronic computer terminal output printing paper, cardiac and electroencephalogram recording paper, telephone fax paper and transparent thermal film for oil fields. Examples of its application are as follows:

1) Preparation of 2-fluorobiphenyl, which belongs to the technical field of halogenated biphenyl. Using o-fluoroaniline and benzene as raw materials, o-fluoroaniline is diazotized and then coupled with benzene to obtain 2-fluorobiphenyl. Benzene, add trifluoroacetic acid, anhydrous magnesium sulfate, catalyst and benzene to the reaction kettle, stir and cool to 4-15°C, add isoamyl nitrite, control the temperature to 20-30°C, and add o-fluoroaniline dropwise , the reaction temperature is controlled at 30-45°C during the dropping process. After the addition is completed, the reaction is stirred for 1-3 hours at 25-32°C. After the reaction is completed, the reaction mixture is filtered, washed, dried, and distilled under reduced pressure to obtain 2-fluorine. biphenyl. The synthesis method of the invention is simple, and the synthesized 2-fluorobiphenyl has high yield and high purity.

2) Preparation of perbrominated quaternary ammonium salt and bromination of o-fluoroaniline to produce 4-bromo-2-fluoroaniline. The process steps are: add quaternary ammonium salt, o-fluoroaniline and solvent into the reaction bottle, stir and dissolve, slowly add bromine dropwise under the condition of controlling the temperature below 30°C, and finish the dripping in about 30 to 60 minutes, and then add the materials The temperature rises to about 40°C and the reaction takes about 2.5 hours; cool to room temperature, filter, wash the filter cake twice with solvent, then disperse the filter cake in the solvent, add 10% sodium hydroxide solution to neutralize to pH=7~ 8. Leave to separate the aqueous phase, wash the organic phase twice with deionized water and evaporate the solvent to obtain 4-bromo-2-fluoroaniline.

3) Preparing 3-fluoro-4 morpholinoaniline, including the following steps: (1) reducing o-fluoronitrobenzene to obtain o-fluoroaniline; (2) adding o-fluoroaniline and a deacidifying agent to an organic solvent , then slowly add disubstituted ether to the reaction system at 100~150°C. After the addition is completed, stir the reaction at 100~200°C to prepare o-fluoro-morpholinobenzene; (3) Use 65% to 98% mass fraction of nitric acid As a nitrating agent, using acetic acid as a solvent, nitrate the o-fluoro-morpholinobenzene obtained in step (2) to obtain 3-fluoro-4-morpholinonitrobenzene; (4) reduce the 3- morpholinobenzene obtained in step (3) Fluoro-4-morpholinonitrobenzene gives 3-fluoro-4-morpholinoaniline. Since the present invention uses o-fluoronitrobenzene as the starting reactant, the raw material is cheap and therefore the production cost can be reduced. At the same time, no fluorine-containing wastewater is produced during the preparation process of the invention, which causes little environmental pollution and is environmentally friendly.

Preparation^[1-2]

Method 1: A method for preparing o-fluoroaniline by hydrogenating o-fluoronitrobenzene. The method includes the following steps:

Step 1. Load the catalyst into the fixed bed reactor. Pour nitrogen into the fixed bed reactor filled with the catalyst at room temperature until the air in the fixed bed reactor is exhausted, and then add nitrogen into the fixed bed reactor. The reducing gas diluted with nitrogen is introduced, and the temperature of the fixed bed reactor is raised to 120°C to 280°C at a heating rate of 1°C/min to 10°C/min; the catalyst includes Al₂ O₃ carrier, Pt, metal M₁ and metal M_{supported on Al₂O₃ carrier sub>2}, the mass percentage of Pt in the catalyst is 0.05% to 1%, the mass percentage of metal M₁ is 0.05% to 3%, and the metal M_{The mass percentage of 2} is 0.01% to 3%; the metal M₁ is Pd, Sn or Zn; the metal M₂ is K , Co, Ga, In, Mn, Ag or Ce; the volume percentage of reducing gas in the reducing gas diluted with nitrogen is 3% to 10%; the ratio of the flow rate of the reducing gas diluted with nitrogen to the mass of the catalyst is (3～20): 1, where the unit of flow rate is mL/min and the unit of mass is g.

Step 2: Mix o-fluoronitrobenzene steam and hydrogen preheated to 150°C to 260°C to obtain a mixed gas. Pour the mixed gas into the fixed bed reactor, and at the same time stop feeding the diluted nitrogen gas. Reducing gas, the reaction temperature is 120℃~Under the condition of 280℃, catalytic hydrogenation reaction is carried out on the catalyst;

Step 3: Send the material after the catalytic hydrogenation reaction in step 2 to the condenser for condensation, so that the o-fluoroaniline vapor in the material is converted into a liquid state, and then the liquid o-fluoroaniline is passed through the oil-water separator Separate to obtain oily o-fluoroaniline.

Method 2: A method for producing o-fluoroaniline, including the following steps: filling a continuous reactor with water, replacing it with nitrogen once, raising the temperature to 65°C, and mixing o-fluoronitrobenzene and a catalyst to obtain Mixture A, mix the dehalogenation inhibitor and water at the same time to obtain mixture B. The mass ratio of o-fluoronitrobenzene, catalyst, dehalogenation inhibitor and water is 100:2:0.1:400. Mix mixture A and mixture B evenly. Finally, it is added to the continuous reactor. At the same time, 8kg of hydrogen is introduced into the continuous reactor to ensure a pressure of 3MPa and maintain continuous feeding. After 10 hours, the reaction ends. The product is stratified through the stratified tank, and the upper layer is a water layer. Reuse, the lower layer is the product; the catalyst includes the following components by weight: 5 parts by weight of TEMPO, 1 part by lanthanum oxide, 1 part by nanosilver, and 1 part by activated carbon; the inhibitory dehalogenation agent includes the following components by weight : 3 parts sodium phosphite, 2 parts triethanolamine, 1 part hypophosphorous acid.