阅读说明：本技术 层式熔融结晶制备高纯邻硝基苯胺的方法 (Method for preparing high-purity o-nitroaniline by layer-type melt crystallization ) 是由 王彦飞 曹腾飞 许史杰 杨静 杨立斌 朱亮 贾原媛 赵文立 韩梅 于 2021-08-05 设计创作，主要内容包括：本发明属于化工分离技术领域,公开了一种利用层式熔融结晶提纯制备高纯邻硝基苯胺的方法。该提纯方法包括以下步骤：1)预热化料：待结晶器内温度达到粗品的熔化温度后,将85～99％的邻硝基苯胺粗品加到层式熔融结晶器中使其熔化。2)：降温结晶：待原料全部熔化后,使结晶器内物料按照1～30K/h进行降温,结晶终温为30-45℃；3)升温发汗：待排出未结晶母液后,对晶体进行发汗,升温至71-74℃时,恒温0.5～1h。4)化料排料。本发明的优点是,提纯过程无需溶剂,避免了溶剂对产品的污染,又减少了溶剂回收过程,节省了设备投资,产品的纯度可达到99.9％以上。(The invention belongs to the technical field of chemical separation, and discloses a method for preparing high-purity o-nitroaniline by using layered melt crystallization purification. The purification method comprises the following steps: 1) preheating and material melting: and after the temperature in the crystallizer reaches the melting temperature of the crude product, adding 85-99% of the crude product of the o-nitroaniline into a layer-type melting crystallizer to melt the crude product. 2): cooling and crystallizing: after the raw materials are completely melted, cooling the materials in the crystallizer according to 1-30K/h, wherein the final crystallization temperature is 30-45 ℃; 3) warming and sweating: after discharging the non-crystallized mother liquor, sweating the crystals, and keeping the temperature constant for 0.5-1 h when the temperature is raised to 71-74 ℃. 4) Melting and discharging. The invention has the advantages that no solvent is needed in the purification process, the pollution of the solvent to the product is avoided, the solvent recovery process is reduced, the equipment investment is saved, and the purity of the product can reach more than 99.9 percent.)

1. A method for preparing o-nitroaniline by layered melt crystallization comprises the following steps:

1) preheating material, namely adding a certain amount of o-nitroaniline crude product into a preheated layer-type melt crystallizer to be heated and melted;

2) cooling and crystallizing: starting a temperature control program to cool the material in the crystallizer according to 1-30K/h, wherein the final crystallization temperature is 30-45 ℃;

3) warming and sweating: after discharging the non-crystallized mother liquor, sweating the crystals, wherein the heating rate is 1-60K/h, heating to 71-74 ℃, and keeping the temperature for 0.5-1 h;

4) material melting and discharging: the temperature is raised until the product is molten and then discharged from the crystallizer.

2. The layered melt crystallization method for preparing o-nitroaniline according to claim 1, wherein:

the o-nitroaniline crude product in the step 1) is an o-nitroaniline crude product obtained by an organic synthesis method, wherein the percentage content of the o-nitroaniline is 85-99%.

3. The layered melt crystallization method for preparing o-nitroaniline according to claim 1, wherein: the layer-type melt crystallization adopts a static or dynamic mode.

4. The layered melt crystallization method for preparing o-nitroaniline according to claim 1, wherein: and 2) when crystals are separated out, growing the crystals at constant temperature for 0.5-1 h, and then cooling according to a certain temperature program.

Technical Field

The invention belongs to the technical field of chemical separation, relates to a purification technology of o-nitroaniline, and particularly relates to a method for purifying the o-nitroaniline by utilizing melt crystallization.

Background

The o-nitroaniline is an important organic chemical raw material and is widely applied to the production and preparation of veterinary drugs, medicines and dyes. Meanwhile, the rubber antioxidant is also an intermediate for producing rubber antioxidant MB and o-phenylenediamine. According to the national standard GB/T4840-2016, the excellent o-nitroaniline product is orange-red flaky solid with the purity of more than or equal to 99.5 percent, however, the o-nitroaniline synthesized by the common industrial route contains light components such as benzofuran, o-chloroaniline, o-nitrophenol, o-nitrochlorobenzene and the like, the purity of the o-nitroaniline cannot meet the requirements of the excellent product, and no relevant report on the preparation of the ultra-pure o-nitroaniline is found.

Patent CN211170527U discloses an experimental apparatus that relates to and utilizes steam purification o-nitroaniline, its characterized in that primary filter screen, well effect filter screen and high-efficient filter screen distribute in proper order from big to little, very big reduction the foam of the o-nitroaniline after the purification. The preparation method of o-nitroaniline disclosed in patent CN1693301A relates to the purification of o-nitroaniline by distillation, and the purity reaches 99.8%. As for the o-nitroaniline products with high purity (more than or equal to 99.9 percent), the o-nitroaniline products cannot be prepared in the industry at present, and the purification method such as distillation and the like is possible to be realized only when the boiling point (250-300 ℃) of the o-nitroaniline is reached, so that the energy consumption is high, the equipment investment is large, and the operation cost is high.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for preparing high-purity o-nitroaniline by layered melt crystallization, wherein the purity of the obtained o-nitroaniline is more than 99.9%.

The purpose of the invention is realized by the following technical scheme:

a method for purifying o-nitroaniline by layered melt crystallization, which comprises the following steps:

1) material melting: weighing a certain amount of o-nitroaniline crude product, adding into a layer type crystallizer, and preheating the material to melt.

2) Cooling and crystallizing: cooling the material in the crystallizer according to 1-30K/h, wherein the final crystallization temperature is 30-45 ℃;

3) warming and sweating: after discharging the non-crystallized mother liquor, sweating the crystals, wherein the heating rate is 1-60K/h, heating to 71-74 ℃, and keeping the temperature for 0.5 h.

4) Material melting and discharging: heating to melt the product, and discharging from the crystallizer to obtain high-quality o-nitroaniline with the product purity of more than 99.9 percent and the light component content of less than 0.12 percent.

Further, the o-nitroaniline crude product used in the step 1) is an o-nitroaniline crude product obtained by an organic synthesis method, wherein the molar percentage content of the o-nitroaniline is 85-99%.

Further, in the step 2), when crystals are separated out, growing the crystals at constant temperature for 0.5 to 1 hour, and then cooling according to a certain temperature program.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a method for separating pure o-nitroaniline from an o-nitroaniline-containing crude product, which adopts a layered melt crystallization process, is suitable for an o-nitroaniline crude product (the molar percentage of the o-nitroaniline is 85-99 percent), does not add any solvent, reduces the operation cost, simplifies the operation, is environment-friendly, does not generate three wastes, and obtains the o-nitroaniline with the purity of more than 99.9 percent.

Detailed description of the invention

In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be described in detail with reference to the best embodiments

Example 1

257.42g of crude o-nitroaniline with the content of 88 percent is put into a 300mL layered melt crystallizer, the temperature is increased to 72 ℃ until the material is completely melted into liquid, and the temperature is reduced at the rate of 15K/h until the final crystallization temperature is 36 ℃; after which the mother liquor is discharged. Then the temperature is increased to the final sweating temperature of 74 ℃ at the temperature increase rate of 30K/h. Then, the sweating liquid is discharged, and the temperature is raised to melt and discharge the materials.

The product purity obtained by the operations is 99.91%, the light component content is 0.02%, and the one-way yield is 40.04%.

Example 2

259.44g of o-nitroaniline crude product with the content of 90 percent is put into a 300mL layered melt crystallizer, the temperature is raised to 72 ℃ until the material is completely melted into liquid, and the temperature is lowered to the final crystallization temperature of 37 ℃ at the cooling rate of 12K/h; after which the mother liquor is discharged. Then rapidly increasing the temperature to the sweating final temperature of 73 ℃ at the temperature increasing rate of 12K/h. Then, the sweating liquid is discharged, and the temperature is raised to melt and discharge the materials.

The product purity obtained by the operations is 99.95%, the light component content is 0.03%, and the one-way yield is 43.90%.

Example 3

250.51g of o-nitroaniline crude product with the content of 95 percent is put into a 300mL layered melt crystallizer, the temperature is raised to 72 ℃ until the material is completely melted into liquid, and the temperature is lowered to 36 ℃ at the crystallization final temperature at the cooling rate of 18K/h; after which the mother liquor is discharged. Then the temperature is rapidly increased to the final sweating temperature of 74 ℃ at the temperature increase rate of 15K/h. Then, the sweating liquid is discharged, and the temperature is raised to melt and discharge the materials.

The product purity obtained by the operations is 99.84%, the light component content is 0.04%, and the one-way yield is 46.78%.

Example 4

244.57g of an o-nitroaniline crude product with the content of 97 percent is put into a 300mL layered melt crystallizer, the temperature is raised to 72 ℃ until the material is completely melted into liquid, and the temperature is lowered to 36 ℃ at the final crystallization temperature at the cooling rate of 10K/h; after which the mother liquor is discharged. Then rapidly increasing the temperature to 72 ℃ of the final sweating temperature at the temperature increasing rate of 10K/h. Then, the sweating liquid is discharged, and the temperature is raised to melt and discharge the materials.

The product purity obtained by the operations is 99.95%, the light component content is 0.03%, and the one-way yield is 50.49%.

Example 5

236.37g of o-nitroaniline crude product with the content of 97.5 percent is put into a 300mL layered melt crystallizer, the temperature is raised to 72 ℃ until the material is completely melted into liquid, and the temperature is lowered to the final crystallization temperature of 41 ℃ at the cooling rate of 16K/h; after which the mother liquor is discharged. Then the temperature is rapidly increased to the final sweating temperature of 71 ℃ at the temperature increase rate of 16K/h. Then, the sweating liquid is discharged, and the temperature is raised to melt and discharge the materials.

The purity of the product obtained by the operations is 99.94%, the content of light components is 0.03%, and the one-way yield is 53.53%.

The above description is only a preferred embodiment of the present invention, and for those skilled in the art, the present invention should not be limited by the description of the present invention, which should be interpreted as a limitation.