A method for preparing high purity 5-chloro-2-methylaniline

Abstract

The present application relates to a kind of methods for preparing high-purity 5-chloro-2-methylaniline, 1) chlorination: 2-nitrotoluene, ferric chloride, organic sulfide are added to reaction bottle, after reaction is completed, the system is heated to 105~110 ℃ and is degassed 2~5h, and 4-chloro-2-nitrotoluene crude product is obtained.2) Preliminary purification: the 4-chloro-2-nitrotoluene crude product obtained in 1) is heated to 50~60 ℃, slowly cooled to 30~40 ℃, there is a small amount of crystallization in the system, keep 1h, filter, filter cake is recycled and reused, and the filtrate is higher-purity 4-chloro-2-nitrotoluene.3) Reduction: 4-chloro-2-nitrotoluene, ethanol, Pt / C are added to autoclave, after gas replacement, heating to 40~50 ℃, and reaction 2~3h. After reaction is completed, the reaction liquid is dehydrated under reduced pressure, and the concentrated liquid is washed with water.4) Rectification purification.The advantages are high product yield, high purity, low cost, and small environmental pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of preparation and purification of chlorinated aromatic amine compounds, and particularly relates to a method for preparing high-purity 5-chloro-2-methylaniline. BACKGROUND

[0002] 5-chloro-2-methylaniline is an important chemical, pharmaceutical, pesticide and dye intermediate. It can be used for dyeing clothes made of various materials and for manufacturing fast pigments. In the dye industry, it can be directly used for synthesizing dye phenol.

[0003] In the prior art, a patent with the publication number CN102234235 A discloses a method for synthesizing 5-chloro-2-methylaniline. The method uses 4-chloro-2-nitrotoluene as a raw material, and then uses sulfide and ammonium salt for reduction and rectification. The method uses 4-chloro-2-nitrotoluene as a raw material, and uses aluminum-nickel alloy as a catalyst for catalytic hydrogenation, and then is purified by rectification. The method has high requirements for equipment.

[0004] The above methods all use 4-chloro-2-nitrotoluene as a raw material, which has a high price. Only one reduction step is performed, and the product has a small profit space. SUMMARY

[0005] To solve the above technical problems, the present application provides a method for preparing high-purity 5-chloro-2-methylaniline, which solves the problems of low product purity, large pollution and high cost in the prior art.

[0006] The technical scheme of the present application is as follows:

[0007] A method for preparing high-purity 5-chloro-2-methylaniline is performed according to the following steps:

[0008] 1) chlorination: 2-nitrotoluene, ferric chloride and organic sulfide are added to a reaction bottle, and the temperature is increased to 60-80 DEG C. The reaction is performed for 15-20 hours. After the reaction is completed, the system is heated to 105-110 DEG C for 2-5 hours for degassing, and 4-chloro-2-nitrotoluene is obtained. The specific reaction equation is as follows:

[0009] wherein n, m and x = 2-22;

[0010] 2) preliminary purification: the 4-chloro-2-nitrotoluene obtained in step 1) is heated to 50-60 DEG C, and then is slowly cooled to 30-40 DEG C. A small amount of crystals is generated in the system, and is maintained for 1 hour. Filtration is performed, and the filter cake is recovered and reused. The filtrate is high-purity 4-chloro-2-nitrotoluene.

[0011] 3) Reduction: 4-chloro-2-nitrotoluene, ethanol, Pt / C were added into an autoclave, after gas replacement, the temperature was raised to 40-50℃, and the reaction was carried out for 2-3h. After the reaction was completed, the ethanol was removed under reduced pressure, and the concentrated solution was washed with water.

[0012] 4) Purification by rectification: the concentrated solution obtained in 3) was added into a rectification reactor, and 5-chloro-2-methylaniline with high purity was obtained by rectification.

[0013] Further, the molar equivalent ratio of 2-nitrotoluene to chlorine in step 1) is 1:1.05-1:1.5; the catalyst used is FeCl3+C n H m S x The selectivity of the intermediate product obtained by chlorination is 80-86%

[0014] Further, the purity of the intermediate product after preliminary purification in step 2) is 95%.

[0015] Further, the reducing agent in step 3) is sodium hydrosulfite.

[0016] Further, the purity of 5-chloro-2-methylaniline obtained by rectification in step 4) is greater than 99.5%.

[0017] The advantages of the present application are that the process is perfect, 2-nitrotoluene is reacted with chlorine, FeCl3+C n H m S x is used as the catalyst, the intermediate crude product is obtained by reaction, and then reduced by sodium hydrosulfite after preliminary purification to obtain 5-chloro-2-methylaniline crude product, which is then purified by rectification to obtain 5-chloro-2-methylaniline with high purity. The product has high yield, high purity, low cost and small environmental pollution. DETAILED DESCRIPTION Example 1

[0018] Into a 500ml four-necked flask were added 411g of 2-nitrotoluene, 1.5g of FeCl3, and 1.5g of (C2H5)2S, and the temperature was raised to 60℃. Chlorine was introduced through a lower extension pipe, and the amount of chlorine used was 225g. Sampling was controlled, and if it was unqualified, chlorine was continuously introduced until 2-nitrotoluene was less than 0.5%. The temperature was raised to 105-110℃ and maintained for 2h, and the selectivity of 4-chloro-2-nitrotoluene was 80.5%.

[0019] First, the temperature was lowered to 60℃, and then slowly lowered to 32-35℃. When a small amount of solid was precipitated in the reaction bottle, the temperature was maintained at this temperature for 2h, and then filtered. The filtrate was used.

[0020] The filtrate was added to a 5L autoclave, 3L ethanol was added, 25g of 3% Pt / C catalyst was added, hydrogen was replaced for 3-5 times, the temperature was increased to 40-50°C, the pressure was controlled at 0.6MPa, and when the pressure in the autoclave no longer decreased, the reaction was completed. The temperature was decreased to room temperature, the reaction kettle was opened, the reaction liquid was filtered, and the filtrate was concentrated to obtain 5-chloro-2-methyl aniline crude product.

[0021] The crude product obtained in the above step was added to a rectifying flask, the vacuum pump was started, heating was started, and after the reflux of the rectifying column was stabilized, the top temperature was 112°C, the reflux ratio was set to 15:1, and the front fraction was accepted. When the top temperature increased to 115°C, the sample was taken for detection, and when the purity of the sample was greater than 98.5%, the reflux ratio was set to 3:1, and the product was collected. 297g of 5-chloro-2-methyl aniline was obtained, with a GC purity of 99.6% and a yield of 70.2% Example 2

[0022] A 1L four-necked flask was added with 548g of 2-nitrotoluene, 2.0g of FeCl3, and 2.0g of (C6H5)2S, and the temperature was increased to 60°C. Chlorine gas was introduced through a lower extension pipe, and the amount of chlorine gas used was 300g. If the sample did not meet the control requirements, chlorine gas was continuously introduced until the content of 2-nitrotoluene was less than 0.5%. The temperature was increased to 105-110°C and maintained for 2h, and the content of 4-chloro-2-nitrotoluene was 84.3%.

[0023] The temperature was first decreased to 60°C, and then slowly decreased to 32-35°C. When a small amount of solid precipitated in the reaction flask, the temperature was maintained at this temperature for 2h, and then filtered. The filtrate was used.

[0024] The filtrate was added to a 5L autoclave, 3.6L ethanol was added, 30g of 3% Pt / C catalyst was added, hydrogen was replaced for 3-5 times, the temperature was increased to 40-50°C, the pressure was controlled at 0.6MPa, and when the pressure in the autoclave no longer decreased, the reaction was completed. The temperature was decreased to room temperature, the reaction kettle was opened, the reaction liquid was filtered, and the filtrate was concentrated to obtain 5-chloro-2-methyl aniline crude product.

[0025] The crude product obtained in the above step was added to a rectifying flask, the vacuum pump was started, heating was started, and after the reflux of the rectifying column was stabilized, the top temperature was 112°C, the reflux ratio was set to 15:1, and the front fraction was accepted. When the top temperature increased to 115°C, the sample was taken for detection, and when the purity of the sample was greater than 98.5%, the reflux ratio was set to 3:1, and the product was collected. 413.5g of 5-chloro-2-methyl aniline was obtained, with a GC purity of 99.8% and a yield of 73.2%.

Claims

1. A process for the preparation of 5-chloro-2-methylaniline, characterized in that, The following steps are taken: 1) chlorination: 2-nitrotoluene, ferric chloride, organic sulfide are added to a reaction bottle, the temperature is raised to 60-80 DEG C, chlorine is introduced, and the reaction is carried out for 15-20 h. After the reaction is completed, the system is heated to 105-110 DEG C and degassed for 2-5 h to obtain 4-chloro-2-nitrotoluene crude product. The specific reaction equation is as follows: ， 2) preliminary purification: the 4-chloro-2-nitrotoluene crude product obtained in 1) is heated to 50-60 DEG C, slowly cooled to 30-40 DEG C, a small amount of crystals is formed in the system, and the system is maintained for 1 h. The filtrate is high-purity 4-chloro-2-nitrotoluene. 3) reduction: 4-chloro-2-nitrotoluene, ethanol, and Pt / C are added to an autoclave, hydrogen is replaced after the reaction, the temperature is raised to 40-50 DEG C, and the reaction is carried out for 2-3 h. After the reaction is completed, the ethanol is removed under reduced pressure, and the concentrated solution is washed with water. 4) rectification and purification: the concentrated solution obtained in 3) is added to a rectification reaction kettle, and rectification and purification are carried out to obtain high-purity 5-chloro-2-methyl aniline. In step 1), the molar ratio of 2-nitrotoluene to chlorine is 1:1.05-1:1.

5. The organic sulfide is (C2H5)2S or (C6H5)2S. The selectivity of the intermediate product obtained by chlorination is 80-86%. The purity of the intermediate product after preliminary purification in step 2) is 95%. The purity of the 5-chloro-2-methyl aniline product obtained by rectification in step 4) is greater than 99.5%.

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