Preparation method of high-purity o-nitroaniline

Abstract

The invention discloses a preparation method of high-purity o-nitroaniline, and belongs to the technical field of fine chemical synthesis. Comprising the following steps: S1, uniformly mixing o-nitrochlorobenzene and stronger ammonia water, and heating for reaction to obtain a crude product mixture; s2, cooling the crude product mixture, adding an extracting agent for extraction, and standing for layering; concentrating and crystallizing a water phase to obtain a byproduct ammonium chloride, wherein an organic phase is an o-nitroaniline solution; s3, evaporating the o-nitroaniline solution through a falling film evaporator to remove 90%-95% of the solvent, and condensing and recycling the solvent to obtain an o-nitroaniline concentrated solution; and S4, distilling the o-nitroaniline concentrated solution by using a molecular distiller, and returning residues to the extraction process to obtain a distillate which is high-purity o-nitroaniline. According to the method, through extraction purification, low-temperature evaporation and molecular distillation, the problems of high chloride ion residue, high energy consumption and insufficient product purity in a traditional process are solved, and meanwhile resource utilization of by-products is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fine chemical synthesis, and particularly relates to a method for preparing high-purity o-nitroaniline. Background Art

[0002] O-nitroaniline, as a basic chemical raw material, is an intermediate for many dyes, pesticides, and pharmaceuticals, and is also used in fields such as auxiliaries. The current method for preparing o-nitroaniline is as follows: Using o-nitrochlorobenzene and ammonia water as raw materials, mixing them and feeding them into an ammoniation kettle, and carrying out an ammonolysis reaction under high temperature and high pressure conditions to obtain products such as o-nitroaniline, ammonium chloride, and water. After separating the aqueous phase in the ammoniation product, the remaining product is washed several times with process hot water to remove ammonium chloride, and then vacuum dried to obtain o-nitroaniline. Since o-nitroaniline is slightly soluble in water, part of the o-nitroaniline is dissolved and carried away by water during each water wash, and even after several water washes, the chloride ions dispersed in the o-nitroaniline cannot be completely removed, resulting in a low yield of o-nitroaniline, poor product purity, and high chloride ion content.

[0003] The patent application with the publication number CN1693301A discloses a method for preparing o-nitroaniline, including the following steps: Mixing o-nitrochlorobenzene and ammonia water to carry out an ammoniation reaction to obtain an ammoniation product composed of o-nitroaniline, ammonium chloride, and water; Mixing caustic alkali with the ammoniation product to form a reaction solution, and the dosage of the caustic alkali is required to make the pH value of the reaction solution reach 12 - 13, and stirring for 0.1 - 0.2 hours under this condition to further obtain a mixed product composed of o-nitroaniline, ammonium hydroxide, hydrochloride, and water; Carrying out vacuum distillation on the mixed product under the condition of a vacuum degree > 700 mmHg, distilling out ammonia water when the distillation temperature is from room temperature to 100 °C, and as the distillation continues, intercepting the fraction at a distillation temperature of 250 - 300 °C and cooling to obtain o-nitroaniline. This application has the characteristics of high yield, good product purity, no wastewater generation, long service life of equipment, and the waste remaining after preparing o-nitroaniline can be utilized, etc. However, the traditional ammonolysis method relies on water washing to remove ammonium chloride, but o-nitroaniline is slightly soluble in water, and repeated water washing causes product loss, and the chloride ions cannot be completely removed because they are entrapped inside the crystals, and the subsequent hydrogenation section requires the chloride ions < 10 ppm, and the existing processes do not meet the standards. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing high-purity o-nitroaniline to improve the purity of the prepared o-nitroaniline.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing high-purity o-nitroaniline, including the following steps:

[0007] S1. Mix o-nitrochlorobenzene and concentrated ammonia water evenly, heat up the reaction to obtain a crude product mixture;

[0008] S2. Cool down the crude product mixture, add an extractant for extraction, and let it stand for stratification; Concentrate and crystallize the aqueous phase to obtain the by-product ammonium chloride, and the organic phase is an o-nitroaniline solution;

[0009] S3. Evaporate and remove 90%-95% of the solvent from the o-nitroaniline solution through a falling film evaporator, condense and recycle the solvent for reuse, and obtain an o-nitroaniline concentrate;

[0010] S4. Distill the o-nitroaniline concentrate with a molecular distiller, return the residue to the extraction process, and the distillate is high-purity o-nitroaniline.

[0011] Furthermore, the molar ratio of o-nitrochlorobenzene to concentrated ammonia water is 1:5-8.

[0012] Furthermore, the heating reaction is carried out at 180-190 °C and 4-5 MPa for 3-4 h.

[0013] Furthermore, the cooling is to cool down to 60-80 °C.

[0014] Furthermore, the extractant comprises a combination of at least one aromatic hydrocarbon solvent and at least one oxygen-containing organic solvent.

[0015] Furthermore, the aromatic hydrocarbon solvent is one or a combination of benzene, toluene, xylene, and mesitylene.

[0016] Furthermore, the oxygen-containing organic solvent is one or a combination of acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, THF, and 2-methyltetrahydrofuran.

[0017] Furthermore, the volume ratio of the aromatic hydrocarbon solvent to the oxygen-containing organic solvent is 1-5:1.

[0018] Furthermore, the extraction is carried out with stirring at 45-55 °C for 30-40 min.

[0019] Furthermore, the conditions for evaporation and removal are to remove the solvent at -0.09~-0.098 MPa and 95-105 °C.

[0020] Furthermore, the evaporation temperature of the distillation is 140-150 °C, and the system pressure is 0.1-0.5 Pa.

[0021] Furthermore, the scraping film rotation speed of the distillation is 200-300 rpm, and the feeding rate is 5-8 kg / h·m2.

[0022] The beneficial effects of the present invention:

[0023] (1) The preparation method of high-purity o-nitroaniline provided by the present invention adopts a three-step collaborative purification technology. First, non-aqueous solvent extraction is used for separation to replace the traditional water washing scheme, eliminating the dissolution loss of o-nitroaniline. Secondly, film evaporation is used to remove the solvent, and the solvent is rapidly removed at low temperature. Finally, molecular distillation is used for refining, which can deeply remove chloride ions and heavy components.

[0024] (2) In the extractant used in the present invention, the aromatic hydrocarbon in the extractant dissolves the benzene ring of o-nitroaniline through π-π interaction, and the carbonyl group of the oxygen-containing solvent forms an n-π* bond with the nitro group of o-nitroaniline, while Cl- remains in the aqueous phase due to strong hydration. The molecular distillation adopted: under a high vacuum of 0.1–0.5 Pa, the difference in the mean free path between o-nitroaniline (molecular weight 138) and the chlorine-containing heavy components (such as unreacted raw material o-nitrochlorobenzene, molecular weight 157.5) is > 30%, realizing molecular-level separation. The two work together to greatly reduce the Cl- content, improve the product purity, and reduce the dissolution loss.

[0025] (3) The preparation method of high-purity o-nitroaniline provided by the present invention meets the requirements of green chemistry and sustainable development. The aqueous phase is concentrated and crystallized to recover the high-purity NH4Cl by-product, the solvent is recovered and reused, and the chlorine-containing heavy components are recycled in a closed loop, realizing nearly zero discharge of "three wastes". Specific Embodiments

[0026] The specific embodiments of the present invention will be described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0027] Example 1

[0028] This example provides a preparation method of high-purity o-nitroaniline, including the following steps:

[0029] S1. 1 mol of o-nitrochlorobenzene and 6 mol of 25% ammonia water are placed in an autoclave and reacted at 190 °C and 4 MPa for 4 h to obtain a crude product mixture;

[0030] S2. The crude product mixture is cooled to 70 °C, and an extractant (120 mL of toluene + 40 mL of cyclohexanone) is added for extraction, stirred at 50 °C for 30 min, and left to stand for phase separation; the aqueous phase is concentrated and crystallized to obtain the by-product ammonium chloride, and the organic phase is the o-nitroaniline solution;

[0031] S3. The o-nitroaniline solution is evaporated in a falling-film evaporator to remove 95% of the solvent, and the solvent is condensed and recycled to obtain an o-nitroaniline concentrate;

[0032] S4. Distill the o-nitroaniline concentrate using a short-path molecular still at an evaporating surface temperature of 145°C, a condensing surface temperature of 65°C, a system pressure of 0.3 Pa, a scraping speed of 300 rpm, and a feed rate of 6 kg / h·m². The residue is returned to the extraction step, and the distillate is high-purity o-nitroaniline.

[0033] Example 2

[0034] Compared with Example 1, this embodiment differs in that the distillation conditions of the molecular distiller are adjusted, and the specific implementation steps are as follows:

[0035] S1. React 1 mol of o-nitrochlorobenzene with 6 mol of 25% aqueous ammonia in an autoclave at 190°C and 4 MPa for 4 h to obtain a crude mixture;

[0036] S2. Cool the crude mixture to 70°C, add an extractant (120 mL of toluene + 40 mL of cyclohexanone) for extraction, stir at 50°C for 30 min, and allow to stand for stratification; concentrate the aqueous phase and crystallize to obtain by-product ammonium chloride, and the organic phase is an o-nitroaniline solution;

[0037] S3, evaporating the o-nitroaniline solution through a falling film evaporator to remove 95% of the solvent, and condensing the solvent for recycling to obtain an o-nitroaniline concentrate;

[0038] S4. Distill the o-nitroaniline concentrate using a short-path molecular distiller with an evaporation surface temperature of 150°C, a condensation surface temperature of 65°C, a system pressure of 0.4 Pa, a scraping speed of 200 rpm, and a feed rate of 7 kg / h·m 2 The residue is returned to the extraction process, and the distillate is high-purity o-nitroaniline.

[0039] The remaining raw materials and preparation process remain the same as in Example 1.

[0040] Example 3

[0041] Compared with Example 1, this embodiment differs in that the proportion of aromatic hydrocarbon solvent in the extractant is increased. The specific implementation steps are as follows:

[0042] S1. React 1 mol of o-nitrochlorobenzene with 6 mol of 25% aqueous ammonia in an autoclave at 190°C and 4 MPa for 4 h to obtain a crude mixture;

[0043] S2. Cool the crude mixture to 70°C, add an extractant (130 mL of toluene + 30 mL of cyclohexanone) for extraction, stir at 50°C for 30 min, and allow to stand for stratification; concentrate the aqueous phase and crystallize to obtain by-product ammonium chloride, and the organic phase is an o-nitroaniline solution;

[0044] S3. Evaporate and remove 95% of the solvent from the o-nitroaniline solution through a falling film evaporator. The solvent is condensed and recycled for reuse to obtain a concentrated o-nitroaniline solution.

[0045] S4. Distill the concentrated o-nitroaniline solution using a short-path molecular distiller. The evaporation surface temperature is 145°C, the condensation surface temperature is 65°C, the system pressure is 0.3 Pa, the scraping film rotation speed is 300 rpm, and the feeding rate is 6 kg / h·m2. The residue is returned to the extraction process, and the distillate is high-purity o-nitroaniline.

[0046] The remaining raw materials and the preparation process are the same as those in Example 1.

[0047] Example 4

[0048] Compared with Example 1, the difference in this example is that the proportion of aromatic solvents in the extractant is reduced. The specific implementation steps are as follows:

[0049] S1. React 1 mol of o-nitrochlorobenzene with 6 mol of 25% ammonia water in an autoclave at 190°C and 4 MPa for 4 h to obtain a crude product mixture.

[0050] S2. Cool the crude product mixture to 70°C, add an extractant (80 mL of toluene + 80 mL of cyclohexanone) for extraction, stir at 50°C for 30 min, and let it stand for phase separation. The aqueous phase is concentrated and crystallized to obtain the by-product ammonium chloride, and the organic phase is the o-nitroaniline solution.

[0051] S3. Evaporate and remove 95% of the solvent from the o-nitroaniline solution through a falling film evaporator. The solvent is condensed and recycled for reuse to obtain a concentrated o-nitroaniline solution.

[0052] S4. Distill the concentrated o-nitroaniline solution using a short-path molecular distiller. The evaporation surface temperature is 145°C, the condensation surface temperature is 65°C, the system pressure is 0.3 Pa, the scraping film rotation speed is 300 rpm, and the feeding rate is 6 kg / h·m2. The residue is returned to the extraction process, and the distillate is high-purity o-nitroaniline.

[0053] The remaining raw materials and the preparation process are the same as those in Example 1.

[0054] Example 5

[0055] Compared with Example 1, the difference in this example is that the extractant is replaced with xylene and butyl acetate. The specific implementation steps are as follows:

[0056] S1. React 1 mol of o-nitrochlorobenzene with 6 mol of 25% ammonia water in an autoclave at 190°C and 4 MPa for 4 h to obtain a crude product mixture.

[0057] S2. Cool the crude product mixture to 70°C, add the extractant (120 mL of xylene + 30 mL of butyl acetate) for extraction, stir at 50°C for 30 min, and let it stand for phase separation; concentrate and crystallize the aqueous phase to obtain the by-product ammonium chloride, and the organic phase is the o-nitroaniline solution;

[0058] S3. Evaporate and remove 95% of the solvent from the o-nitroaniline solution through a falling film evaporator, condense and recycle the solvent, and obtain the o-nitroaniline concentrate;

[0059] S4. Distill the o-nitroaniline concentrate using a short-path molecular distiller, with the evaporation surface temperature at 145°C, the condensation surface temperature at 65°C, the system pressure at 0.3 Pa, the scraping film speed at 300 rpm, and the feeding rate at 6 kg / h·m². The residue is returned to the extraction process, and the distillate is high-purity o-nitroaniline.

[0060] The remaining raw materials and the preparation process are the same as those in Example 1.

[0061] Example 6

[0062] Compared with Example 1, the difference in this example is that the extractant is replaced with n-heptane and methyl isobutyl ketone. The specific implementation steps are as follows:

[0063] S1. React 1 mol of o-nitrochlorobenzene with 6 mol of 25% ammonia water in an autoclave at 190°C and 4 MPa for 4 h to obtain a crude product mixture;

[0064] S2. Cool the crude product mixture to 70°C, add the extractant (120 mL of n-heptane + 30 mL of methyl isobutyl ketone) for extraction, stir at 50°C for 30 min, and let it stand for phase separation; concentrate and crystallize the aqueous phase to obtain the by-product ammonium chloride, and the organic phase is the o-nitroaniline solution;

[0065] S3. Evaporate and remove 95% of the solvent from the o-nitroaniline solution through a falling film evaporator, condense and recycle the solvent, and obtain the o-nitroaniline concentrate;

[0066] S4. Distill the o-nitroaniline concentrate using a short-path molecular distiller, with the evaporation surface temperature at 145°C, the condensation surface temperature at 65°C, the system pressure at 0.3 Pa, and the scraping film speed at 300 rpm, and the feeding rate at 6 kg / h·m 2 . The residue is returned to the extraction process, and the distillate is high-purity o-nitroaniline.

[0067] The remaining raw materials and the preparation process are the same as those in Example 1.

[0068] Example 7

[0069] Compared with Example 1, the difference in this example is that the amount of ammonia water is increased. The specific implementation steps are as follows:

[0070] S1. React 1 mol of o-nitrochlorobenzene with 8 mol of 25% ammonia water in an autoclave at 190 °C and 4 MPa for 4 h to obtain a crude product mixture;

[0071] S2. Cool the crude product mixture to 70 °C, add an extractant (120 mL of toluene + 40 mL of cyclohexanone) for extraction, stir at 50 °C for 30 min, and let it stand for liquid separation; Concentrate and crystallize the aqueous phase to obtain the by-product ammonium chloride, and the organic phase is an o-nitroaniline solution;

[0072] S3. Evaporate and remove 95% of the solvent from the o-nitroaniline solution through a falling-film evaporator, and condense and recycle the solvent for reuse to obtain an o-nitroaniline concentrate;

[0073] S4. Distill the o-nitroaniline concentrate using a short-path molecular distiller, with the evaporation surface temperature at 145 °C, the condensation surface temperature at 65 °C, the system pressure at 0.3 Pa, the scraping film speed at 300 rpm, and the feeding rate at 6 kg / h·m2. The residue is returned to the extraction process, and the distillate is high-purity o-nitroaniline.

[0074] The remaining raw materials and the preparation process are the same as those in Example 1.

[0075] Example 8

[0076] Compared with Example 1, the difference in this example is that the amount of ammonia water used is reduced. The specific implementation steps are as follows:

[0077] S1. React 1 mol of o-nitrochlorobenzene with 5 mol of 25% ammonia water in an autoclave at 190 °C and 4 MPa for 4 h to obtain a crude product mixture;

[0078] S2. Cool the crude product mixture to 70 °C, add an extractant (120 mL of toluene + 40 mL of cyclohexanone) for extraction, stir at 50 °C for 30 min, and let it stand for liquid separation; Concentrate and crystallize the aqueous phase to obtain the by-product ammonium chloride, and the organic phase is an o-nitroaniline solution;

[0079] S3. Evaporate and remove 95% of the solvent from the o-nitroaniline solution through a falling-film evaporator, and condense and recycle the solvent for reuse to obtain an o-nitroaniline concentrate;

[0080] S4. Distill the o-nitroaniline concentrate using a short-path molecular distiller, with the evaporation surface temperature at 145 °C, the condensation surface temperature at 65 °C, the system pressure at 0.3 Pa, the scraping film speed at 300 rpm, and the feeding rate at 6 kg / h·m2. The residue is returned to the extraction process, and the distillate is high-purity o-nitroaniline.

[0081] The remaining raw materials and the preparation process are the same as those in Example 1.

[0082] Comparative Example 1

[0083] This comparative example is different from Example 1 in that molecular distillation is not used. The specific implementation steps are as follows:

[0084] S1. React 1 mol of o-nitrochlorobenzene with 6 mol of 25% ammonia water in an autoclave at 190°C and 4 MPa for 4 h to obtain a crude product mixture;

[0085] S2. Cool the crude product mixture to 70°C, add an extractant (120 mL of toluene + 40 mL of cyclohexanone) for extraction, stir at 50°C for 30 min, and let it stand for phase separation; Concentrate and crystallize the aqueous phase to obtain the by-product ammonium chloride, and the organic phase is an o-nitroaniline solution;

[0086] S3. Evaporate and remove the solvent from the o-nitroaniline solution through a falling film evaporator, condense and recycle the solvent, and obtain o-nitroaniline.

[0087] The remaining raw materials and the preparation process are the same as those in Example 1.

[0088] Comparative Example 2

[0089] This comparative example is different from Example 1 in that the extractant extraction is replaced by conventional water washing. The specific implementation steps are as follows:

[0090] S1. React 1 mol of o-nitrochlorobenzene with 6 mol of 25% ammonia water in an autoclave at 190°C and 4 MPa for 4 h to obtain a crude product mixture;

[0091] S2. Cool the crude product mixture to 70°C, transfer the organic phase (containing o-nitroaniline and residual NH4Cl) after separating the aqueous phase to a washing kettle, keep the system temperature at 60 - 80°C to avoid the precipitation of o-nitroaniline due to low temperature crystallization, use 80°C process hot water, and wash it 3 times by continuous countercurrent washing; The amount of water for each washing is 1 times the volume of the organic phase, the stirring rate is 300 rpm, and the time is 10 min / time. High-purity o-nitroaniline is obtained by layer detection.

[0092] The remaining raw materials and the preparation process are the same as those in Example 1.

[0093] Performance Test

[0094] Test the yield, purity and chloride ion content of o-nitroaniline obtained by the preparation methods provided in Examples 1 - 8 and Comparative Examples 1 - 2 of the present invention;

[0095] The results are shown in Table 1:

[0096] Table 1

[0097] Project Yield (%) Purity (%) Cl-Content (ppm) Example 1 95.4 99.5 8 Example 2 94.5 99.4 10 Example 3 94.7 99.1 12 Example 4 93.8 98.8 13 Example 5 95.3 99.3 20 Example 6 95.1 99.2 24 Example 7 95.3 99.4 9 Example 8 94.6 99.3 9 Comparative Example 1 88.7 98.1 64 Comparative Example 2 86.8 98.5 180

[0098] As can be seen from Table 1, in Example 1, short-path molecular distillation was adopted, and the yield (95.4%) and purity (99.5%) were significantly higher than those in Comparative Example 1 (without molecular distillation, the yield was 88.7% and the purity was 98.1%); the Cl- residue decreased from 64 ppm to 8 ppm. Molecular distillation separates through high vacuum (0.1 - 0.5 Pa) and low temperature (134 °C lower than the boiling point), avoiding the decomposition of heat-sensitive substances and efficiently removing chlorine-containing heavy components at the same time. In Example 2, the distillation conditions were adjusted: after the distillation parameters were optimized, the yield (94.5%) and Cl- (10 ppm) fluctuated slightly, indicating that the evaporation temperature and pressure need to be precisely matched to balance the separation efficiency and the risk of thermal degradation.

[0099] Example 3 (high proportion of aromatics): Cl- residue 12 ppm, purity 99.1%; Example 4 (low proportion of aromatics): Cl- residue 13 ppm, purity 98.8%. This is because aromatic solvents (such as toluene) have a high affinity for ONA, and oxygen-containing solvents (such as cyclohexanone) strengthen the removal of Cl- through complexation; too high a proportion of aromatics may reduce the Cl- complexation ability of the solvent, resulting in an increase in residues.

[0100] Example 5 (xylene + butyl acetate): Cl- residue 20 ppm, purity 99.3%; Example 6 (n-heptane + MIBK): Cl- residue 24 ppm, purity 99.2%. The toluene-cyclohexanone combination (Example 1) has the best comprehensive performance, which may be related to the permeation barrier effect of toluene on Cl- and the polarity synergy of cyclohexanone; the replacement solvents result in a decrease in the Cl- removal efficiency due to polarity differences.

[0101] Compared with Example 1, Examples 7 - 8 only differ in the adjustment of the o-nitrochlorobenzene and concentrated ammonia components. From the results, the prepared o-nitroaniline has a high yield, high purity, and low Cl- content.

[0102] Comparative Example 2 (conventional water washing): The Cl- residue was as high as 180 ppm, and the yield (86.8%) was significantly lower than that in Example 1 (95.4%). This is because single water washing cannot effectively remove Cl- in the organic phase, and the solvent was not recovered, resulting in material loss.

[0103] Advantages of Example 1: Composite extraction + solvent recycling (recovery rate ≥ 95%) reduces raw material costs, and the by-product NH4Cl (purity ≥ 99%) can be recycled, meeting the requirements of green chemistry.

[0104] The above only discloses several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for preparing high-purity o-nitroaniline, characterized in that, It includes the following steps: S1. Mix o-nitrochlorobenzene and concentrated ammonia water evenly, raise the temperature for reaction to obtain a crude product mixture; S2. Cool down the crude product mixture, add an extractant for extraction, and let it stand for layering; the aqueous phase is concentrated and crystallized to obtain the by-product ammonium chloride, and the organic phase is the o-nitroaniline solution; S3. Evaporate and remove 90%-95% of the solvent from the o-nitroaniline solution through a falling film evaporator, condense and recycle the solvent for reuse to obtain a concentrated o-nitroaniline solution; S4. Distill the concentrated o-nitroaniline solution with a molecular distiller, return the residue to the extraction process, and the distillate is high-purity o-nitroaniline.

2. The preparation method of a high-purity o-nitroaniline according to claim 1, characterized in that, The molar ratio of the o-nitrochlorobenzene to the concentrated ammonia water is 1:5-8.

3. The preparation method of a high-purity o-nitroaniline according to claim 1, characterized in that, The temperature-raising reaction is carried out at 180-190°C and 4-5 MPa for 3-4 h; the temperature reduction is to reduce the temperature to 60-80°C.

4. The preparation method of a high-purity o-nitroaniline according to claim 1, wherein The extractant comprises a combination of at least one aromatic hydrocarbon solvent and at least one oxygen-containing organic solvent.

5. The preparation method of a high-purity o-nitroaniline according to claim 4, characterized in that, The aromatic hydrocarbon solvent is one or a combination of benzene, toluene, xylene, and mesitylene.

6. The preparation method of a high-purity o-nitroaniline according to claim 4, characterized in that, The oxygen-containing organic solvent is one or a combination of acetone, cyclohexanone, methyl isobutyl ketone, ethyl acetate, butyl acetate, THF, and 2-methyltetrahydrofuran.

7. The preparation method of a high-purity o-nitroaniline according to claim 4, characterized in that, The volume ratio of the aromatic hydrocarbon solvent to the oxygen-containing organic solvent is 1-5:

1.

8. The preparation method of a high-purity o-nitroaniline according to claim 1, characterized in that, The extraction is carried out with stirring at 45-55°C for 30-40 min; the conditions for evaporation and removal are to remove the solvent at -0.09 to -0.098 MPa and 95-105°C.

9. The preparation method of a high-purity o-nitroaniline according to claim 1, characterized in that, The evaporation temperature for the distillation is 140-150°C, and the system pressure is 0.1-0.5 Pa.

10. The preparation method of a high-purity o-nitroaniline according to claim 1, characterized in that, The scraping film rotation speed of the distillation is 200 - 300 rpm, and the feeding rate is 5 - 8 kg / h·m 2 .