阅读说明：本技术 层式熔融结晶制备高纯2,4-二硝基氯苯的方法 (Method for preparing high-purity 2, 4-dinitrochlorobenzene by layer-type melt crystallization ) 是由 王彦飞 许史杰 刘云龙 乔鹏伟 吴劲 王海任 杨静 杨立斌 朱亮 贾原媛 赵文立 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制备高纯2,4-二硝基氯苯的方法。该提纯方法包括以下步骤：1)进料：将含量85％左右的2,4-二硝基氯苯液相粗品加到层式熔融结晶器中。2)：降温结晶：待进料完成后,使结晶器内物料按照1～30K/h进行降温,结晶终温为27-48℃；3)升温发汗：待排出未结晶母液后,对晶体进行发汗,升温至48-51℃时,恒温0.5～1h。4)化料排料。本发明的方法可以利用低品位的循环冷却水作为分离能量媒介,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,同时没有产生其他副产品,避免了繁琐的提纯分离工艺,节省了设备投资,简化了操作步骤并降低操作成本,得到产品纯度≥99.8％的2,4-二硝基氯苯,无三废排放,回收率高。(The invention belongs to the technical field of chemical separation, and discloses a method for preparing high-purity 2, 4-dinitrochlorobenzene by utilizing layer-type melt crystallization. The purification method comprises the following steps: 1) feeding: adding the crude 2, 4-dinitrochlorobenzene liquid phase with the content of about 85 percent into a layer-type melt crystallizer. 2): cooling and crystallizing: after the feeding is finished, cooling the materials in the crystallizer according to 1-30K/h, wherein the final crystallization temperature is 27-48 ℃; 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 48-51 ℃. 4) Melting and discharging. The method can utilize low-grade circulating cooling water as a separation energy medium, does not need a solvent, avoids the pollution of the solvent to products, reduces the solvent recovery process, does not produce other byproducts, avoids a complicated purification and separation process, saves equipment investment, simplifies operation steps, reduces operation cost, obtains the 2, 4-dinitrochlorobenzene with the product purity of more than or equal to 99.8 percent, does not discharge three wastes, and has high recovery rate.)

1. A method for preparing 2, 4-dinitrochlorobenzene by layered melt crystallization comprises the following steps:

step 1) adding a certain amount of 2, 4-dinitrochlorobenzene liquid-phase crude product into a preheated layer-type melt crystallizer, cooling according to 1-30K/h after the materials are completely melted into liquid, and controlling the final crystallization temperature to be 27-48 ℃;

step 2) sweating the crystals after discharging the non-crystallized mother liquor, wherein the heating rate is 1-60K/h, the temperature is raised to 48-51 ℃, the temperature is kept for 0.5-1 h, and the sweating liquid is discharged;

and 3) heating until the product is molten, and discharging the product into a product tank to obtain the purified 2, 4-dinitrochlorobenzene.

2. The method for preparing 2, 4-dinitrochlorobenzene by layer-type melt crystallization according to claim 1, characterized in that: the 2, 4-dinitrochlorobenzene liquid-phase crude product obtained in the step 1) is obtained by a nitration reaction method, wherein the percentage content of the 2, 4-dinitrochlorobenzene is more than or equal to 85 percent.

3. The method for preparing 2, 4-dinitrochlorobenzene by layer-type melt crystallization according to claim 1, characterized in that: and 3) opening a bottom valve of the device while heating, and discharging the sweating liquid into a sweating liquid tank to be used as a next batch of raw materials for application.

4. The method for preparing 2, 4-dinitrochlorobenzene by layer-type melt crystallization according to claim 1, characterized in that: step 1) adding a certain amount of 2, 4-dinitrochlorobenzene liquid-phase crude product into a preheated layer-type melt crystallizer, and heating to 50-60 ℃ to completely melt the material.

Technical Field

The invention belongs to the technical field of chemical separation, relates to a purification technology of 2, 4-dinitrochlorobenzene, and particularly relates to a method for purifying 2, 4-dinitrochlorobenzene by utilizing melt crystallization.

Background

2, 4-dinitrochlorobenzene is an important organic chemical raw material and is widely applied to the production and preparation of explosives, medical intermediates, dyes, pesticides and chemical auxiliaries. According to the specifications of the China chemical industry standard (HG/T2553-2018), the products are classified into superior products, first-class products and qualified products according to the difference of the crystallization points and the purities of the products. The purity of the superior product is more than or equal to 99.8 percent. The 2, 4-dinitrochlorobenzene synthesized by the current industrial route generally adopts nitration reaction, the number of byproducts is large in the reaction process, the purification process is complicated and complex, the equipment investment is large, the emission of three wastes is large, more importantly, the high-purity preparation of the 2, 4-dinitrochlorobenzene is difficult to realize, and the purity is generally only 53-99%.

Patent CN 112707823A discloses a system and a method for green, safe, high-efficiency and continuous production of 2, 4-dinitrochlorobenzene, wherein the product purity can reach 99-99.8%, but the product purity still cannot reach the superior product standard of 2018 China chemical industry standard (HG/T2553-. The patent CN 112250579A discloses a continuous production method of 2, 4-dinitrochlorobenzene, which can eliminate local back mixing in the reaction process and provide high-efficiency mass transfer advantage to improve the yield of 2, 4-dinitrochlorobenzene, but the product purity is only about 97 percent at most. Patent CN102093223A proposes an improved method for producing 2, 4-dinitrochlorobenzene, which is characterized in that the nitration product is continuously stirred by adding clean water, so that the transition layer between dilute acid and the material is thoroughly eliminated, and the yield and the purity are improved, but the purity is not reported. Patent CN104045563A reports a process route to produce high purity 2, 4-dinitrochlorobenzene by reaction, extraction, concentration, neutralization, but no relevant purity is reported in the examples. Patent CN112707822A discloses a method for preparing 2, 4-dinitrochlorobenzene by one-step adiabatic continuous nitration of chlorobenzene, wherein the purity of the product can reach 99-99.8%, but the purity of the product is difficult to reach more than 99.8%. Patent CN112679362A discloses an extraction system and process for producing an acid phase from 2, 4-dinitrochlorobenzene, which can effectively remove nitric acid and organic matters in the acid phase. The purification process of the 2, 4-dinitrochlorobenzene has the problems of high operation temperature, large potential safety hazard, more three-waste discharge, complex process, difficulty in reaching the standard of superior products in the chemical industry and the like, so that the development of a green crystallization and separation process of high-purity 2, 4-dinitrochlorobenzene products is urgent.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for preparing high-purity 2, 4-dinitrochlorobenzene by layered melt crystallization, wherein the purity of the obtained 2, 4-dinitrochlorobenzene is more than 99.8 percent.

The technical scheme for realizing the purpose of the invention is as follows:

a method for purifying 2, 4-dinitrochlorobenzene by melt crystallization, comprising the steps of:

1) feeding: adding a certain amount of 2, 4-dinitrochlorobenzene liquid-phase crude product into a crystallizer, and heating to 50-60 ℃ to completely melt the material.

2) Cooling and crystallizing: starting a temperature control program to cool the materials in the crystallizer according to 1-30K/h, wherein the final crystallization temperature is 27-48 ℃;

3) warming and sweating: and (3) sweating the crystals after discharging the mother liquor which is not crystallized, wherein the heating rate is 1-60K/h, the temperature is increased to 48-51 ℃, and the constant temperature is kept for 0.5-1 h.

4) Material melting and discharging: heating to melt the product, transferring the product into a product tank to obtain the superior 2, 4-dinitrochlorobenzene product with the purity of more than 99.8 percent and the content of other impurities of less than 0.2 percent.

Further, the crude 2, 4-dinitrochlorobenzene product used in the step 1) is a crude 2, 4-dinitrochlorobenzene product obtained by a continuous nitration method, wherein the molar percentage content of the 2, 4-dinitrochlorobenzene is more than or equal to 85%.

Further, the temperature rise final temperature in the step 3) is not higher than 51 ℃.

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

the invention provides a method for separating pure 2, 4-dinitrochlorobenzene from a crude product containing 2, 4-dinitrochlorobenzene, which adopts a layered melt crystallization process, is suitable for the crude product of 2, 4-dinitrochlorobenzene (the mole percentage content of the 2, 4-dinitrochlorobenzene is more than or equal to 85 percent), does not add a solvent, reduces the operation cost, simplifies the operation, is environment-friendly, does not generate three wastes, and obtains a superior product of which the purity of the 2, 4-dinitrochlorobenzene is more than 99.8 percent and the content of other impurities is less than 0.2 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

501.03g of 2, 4-dinitrochlorobenzene crude product with the content of 98.70 percent is put into a 500mL layered melt crystallizer, the temperature is raised to 55 ℃ until the material is completely melted into liquid, and the temperature is reduced to 31 ℃ according to the cooling rate of 6K/h; after which the mother liquor is discharged. Then the temperature is rapidly increased to 50 ℃ at a temperature increase rate of 30K/h. Then, the sweat is discharged, and the temperature is raised to melt the materials to obtain the product.

The product obtained by the above operations has a mass of 327.19g, a purity of 99.92% and a single-pass yield of 66.11%. The overall yield was 90.05%.

Example 2

501.64g of crude 2, 4-dinitrochlorobenzene with the content of 95.20 percent is put into a 500mL layered melt crystallizer, the temperature is raised to 55 ℃ until the materials are completely melted into liquid, and the temperature is lowered to 29 ℃ according to the cooling rate of 20K/h; after which the mother liquor is discharged. Then the temperature is raised to 50 ℃ at a heating rate of 10K/h. Then, the sweat is discharged, and the temperature is raised to melt the materials to obtain the product.

The product obtained by the above operations has a mass of 330.63g, a purity of 99.91% and a single-pass yield of 69.17%. The total yield is 93.55%.

Example 3

505.54g of crude 2, 4-dinitrochlorobenzene with the content of 97.45 percent is put into a 500mL layered melt crystallizer, the temperature is raised to 55 ℃ until the materials are completely melted into liquid, the temperature is lowered at the speed of 6K/h, and mother liquor is discharged after the temperature is lowered to 29 ℃.

Then the temperature is rapidly raised to 49.5 ℃ at a temperature rising rate of 10K/h. Then, the sweating liquid is discharged, and the temperature is raised to melt and discharge the materials.

The product obtained by the above operations has a mass of 330.82g, a purity of 99.89% and a single-pass yield of 67.08%. The total yield is 94.22%.

Example 4

501.20g of crude 2, 4-dinitrochlorobenzene with the content of 96.70 percent is put into a 500mL layer-type melt crystallizer, the temperature is raised to 55 ℃ until the materials are completely melted into liquid, then the temperature is lowered according to the cooling rate of 12K/h, and mother liquor is discharged after the temperature is lowered to 33 ℃.

Then the temperature is raised to 48 ℃ at a temperature rise rate of 15K/h. Then, the sweating liquid is discharged, and the temperature is raised to melt and discharge the materials.

The product obtained by the above operations has a mass of 263.15g, a purity of 99.87% and a single-pass yield of 54.22%. The total yield is 89.05%.

Example 5

500.48g of 2, 4-dinitrochlorobenzene crude product with the content of 98.50 percent is put into a 500mL layered melt crystallizer, the temperature is raised to 55 ℃ until the material is completely melted into liquid, the temperature is reduced at the temperature of 42 ℃ according to the cooling rate of 25K/h, and when the temperature is reduced to 40 ℃, the temperature is reduced to 36 ℃ at the cooling rate of 15K/h; then the temperature is reduced to 32 ℃ at the cooling rate of 8K/h; after which the mother liquor is discharged.

And then heating to 50 ℃ at the heating rate of 8K/h, then discharging sweat, and heating to melt and discharge the materials.

The product obtained by the above operations has a mass of 291.94g, a purity of 99.94% and a single-pass yield of 59.18%. The total yield is 90.01%.

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.