A preparation method of 4,4'-dinitrodiphenyl ether

Abstract

The present invention discloses a preparation method of 4,4'-dinitrodiphenyl ether. By using a one-pot method and a polar organic solvent as the reaction solvent, the raw material p-chloronitrobenzene and the catalyst are first pre-reacted to form an ester, then a carbonate auxiliary agent is added, and etherification occurs under an inert atmosphere to prepare 4,4'-dinitrodiphenyl ether. After filtration, the filtrate is decolorized, subjected to vacuum distillation, and alcohol precipitation to obtain the target product, and the mother liquor solvent is recovered and the kettle residue is recycled. The reaction of the present invention is simple and easy to control, has a short reaction time, few side reactions, and realizes the centralized treatment of organic waste, reducing the difficulty of post-treatment. All solvents involved in the whole process are recycled, the produced target product has a low cost and high purity, and the total yield reaches over 96.5%.

Description

Technical Field

[0001] The present invention relates to a preparation method of a fine chemical intermediate, and particularly to a preparation method of 4,4'-dinitrodiphenyl ether. Background Art

[0002] 4,4'-Dinitrodiphenyl ether (DNDPE, EINECS: 202-961-3, molecular formula: C12H8N2O5) is a fine chemical with high added value. In addition to being used as a raw material for synthesizing epoxy resin crosslinking agents, dye intermediates, and special spices, its reduction product 4,4'-diaminodiphenyl ether is an important intermediate in the fine chemical fields such as synthesis of medicine, dyes, pigments, pesticides, etc. At the same time, it is widely used as the main monomer for synthesizing heat-resistant plastics, such as polyimide resins, polymaleimide resins, polyurethanes, etc. Among them, polyimide, as a special engineering plastic with high temperature resistance, high insulation, and high mechanical strength, is widely used in the fields of aviation, aerospace, microelectronics liquid crystal, separation membranes, photoresists, etc. Whether as a structural material or as a functional material, the market demand is increasing day by day. Therefore, the research on the production process of 4,4'-dinitrodiphenyl ether with high yield and high quality is of great significance.

[0003] At present, there are mainly four methods for synthesizing DNDPE: (1) Dinitration of diphenyl ether; (2) p-Dinitrobenzene method; (3) Condensation of p-nitrochlorobenzene and p-nitrophenolate; (4) One-step condensation method of p-chloronitrobenzene. Among them, the condensation method of p-nitrochlorobenzene and p-nitrophenolate is the most industrially operable and is also the technology for large-scale production at home and abroad. However, the main disadvantages of this technology are that the price of p-nitrophenolate is relatively high, the dehydration before the reaction is required to be strict, and the reaction temperature is high, the time is long, and side reactions are likely to occur and explosions are likely to be triggered. The one-step condensation method of p-chloronitrobenzene can be divided into two types: (1) Using p-chloronitrobenzene as the raw material and strong base as the catalyst, the reaction is carried out in a polar solvent. US4558164 and many Japanese patents have detailed this method. However, the introduction of strong base will greatly limit the equipment and the dropping speed of the base needs to be strictly controlled. The production conditions are harsh and it is not conducive to industrial production; (2) p-chloronitrobenzene undergoes a target reaction with nitrite and alkali metal salt under a polar solvent, but NO and NO2 are formed during the reaction process, resulting in low product yield and environmental pollution. Later, the US patent US4558164 improved the second method, introduced benzoic acid or acetic acid as the catalyst, and obtained the target product by a one-pot method. This method does not produce polluting gases, but the temperature is relatively high, the product is easy to carbonize, and the post-treatment is difficult, and the yield is only 90%. In view of the above defects, Patent CN102603533A synthesized DNDPE by reacting p-chloronitrobenzene, NaOH, and CuI in an alcohol mixed solvent and recrystallized with ethyl acetate. This method introduced heavy metals and used a mixed solvent, which is easy to cause pollution in industrial production and the solvent ratio is difficult to control; Patent CN110776427A used halogenated benzene as the solvent and realized the one-step condensation preparation of DNDPE by carbonate and phase transfer catalyst. However, this technology has a high reaction temperature and a long time, and needs to be kept warm at 210-230 °C for 8-10 h, and a phase transfer catalyst is introduced, which is difficult to recover; Patent CN112724021A carried out an etherification reaction of p-nitrochlorobenzene and potassium acetate in a non-polar solvent such as toluene and o-dichlorobenzene under the catalysis of ionic liquid. This method has a more cumbersome pretreatment and regeneration of ionic liquid, and the addition speed needs to be strictly controlled, which is not conducive to industrial production. Summary of the Invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a method for preparing 4,4'-dinitrodiphenyl ether suitable for industrial production. The organic wastes in the whole process flow can finally be centrally treated, which not only reduces the difficulty and cost of organic waste treatment, but also ensures high efficiency and high yield.

[0005] The technical solution adopted by the present invention is:

[0006] The present invention provides a method for preparing 4,4'-dinitrodiphenyl ether, which comprises the following steps: S1 Etherification: In a reaction kettle, p-chloronitrobenzene is dispersed in an organic solvent, a catalyst is added under stirring, the temperature is raised to the esterification temperature, and the reaction is kept warm for 0.5 h. Then, a certain amount of auxiliary agent is added. After the air in the kettle is fully replaced with nitrogen, the temperature is raised to the etherification temperature, and the reaction is kept warm while ensuring that the inside of the kettle is under a certain pressure. The content of p-chloronitrobenzene in the reaction kettle is controlled to be 10-15% as the end point. After reaching the end point, the temperature is lowered to 65 °C.

[0007] S2 Filtration: The system obtained in step S1 is filtered, and the filter cake after filtration is washed with a certain volume of washing solvent.

[0008] S3 Decolorization: The filtrate after filtration in step S2 enters a decolorization kettle for decolorization, and is filtered after decolorization.

[0009] S4 Vacuum distillation: The filtrate obtained in step S3 enters a distillation kettle for vacuum distillation.

[0010] S5 Alcohol precipitation: The liquid in the distillation kettle in step S4 is pumped into an alcohol precipitation kettle and an alcohol solvent is added. After the material precipitates, it is suction-filtered, and the filter cake is washed and then dried to obtain the finished product.

[0011] Furthermore, in step S1, the catalyst is sodium benzoate, potassium benzoate, sodium acetate or potassium acetate; the auxiliary agent is sodium carbonate or potassium carbonate; in step S1, the organic solvent is dimethyl sulfoxide, dimethyl sulfone, sulfolane, N,N-diethylformamide, N,N-diethylformamide or N-methylpyrrolidone; in step S1, the mass ratio of p-chloronitrobenzene to the volume of the organic solvent is 1:2-5; the molar ratio of p-chloronitrobenzene, the auxiliary agent to the catalyst is 1:0.5-1.5:0.05-0.25.

[0012] Furthermore, in step S1, the esterification temperature is 90-120 °C; the etherification temperature is 160-220 °C; the pressure inside the kettle during the etherification process is maintained at 0.2-0.7 MPa.

[0013] Furthermore, in step S2, after the reaction kettle is cooled, the pressure is released, the material is discharged and filtered, and the filter cake after filtration is washed with a certain volume of washing solvent. The washing solvent is the organic solvent in step S1, and the dosage is 10-15% of the dosage of the organic solvent in step S1; the washing solvent after washing enters the decolorization kettle.

[0014] Furthermore, in step S3, a certain amount of activated carbon is added to the decolorization kettle, the temperature is raised to 80-90 °C for decolorization, the decolorization time is 0.5-1 h, and it is filtered while it is hot. The filtrate enters the distillation kettle; the added mass of the activated carbon is 5-10% of the theoretical production amount of the target product.

[0015] The theoretical production amount of the target product is calculated according to the following formula:

[0016]

[0017]

[0018] Wherein:

[0019] The mass of m - p - chloronitrobenzene;

[0020] 157.55 - The molecular weight of p - chloronitrobenzene;

[0021] 260.21 - The molecular weight of dinitrodiphenyl ether..

[0022] Further, in step S4, after starting the vacuum pump group and waiting for the vacuum degree in the distillation kettle to reach - 0.1 MPa, vacuum distillation is carried out. After the volume of the distilled solvent reaches the specified amount, the vacuum distillation is stopped, and the temperature is lowered to the boiling point temperature of the alcohol solvent used in alcohol precipitation in step S5. The liquid in the distillation kettle is pumped into the alcohol precipitation kettle, and the distillate is recycled as an organic solvent;

[0023] The calculation of the volume of the distilled solvent reaching the specified amount is as follows: The amount of distillate = The mass of the washing solvent in step S2+The mass of the organic solvent in step S1×(40 - 60)%.

[0024] Further, in step S5, the liquid in the distillation kettle in step S4 is pumped into the alcohol precipitation kettle and an alcohol solvent is added under stirring. The material precipitates, and it is heated to reflux and pulped for 0.5 h, then cooled to room temperature, filtered by suction. The filter cake is washed with the corresponding alcohol solvent as the washing liquid and then dried to obtain the finished product. The filtrate after suction filtration and the washing liquid after washing are pumped into the residue kettle together;

[0025] The alcohol solvent is methanol, ethanol or propanol. The dosage of the alcohol solvent is 10 - 12 times the volume of the remaining organic solvent in the liquid pumped into the alcohol precipitation kettle after vacuum distillation in step S4; In step S5, when washing the filter cake, the dosage of the washing liquid is 5% of the dosage of the alcohol solvent used in alcohol precipitation.

[0026] Further, it also includes step S6 distilling the kettle residue. After starting the vacuum pump group and waiting for the vacuum degree in the residue kettle to reach - 0.1 MPa, vacuum distillation is carried out. After the remaining alcohol solvent in the kettle residue test is less than the specified value, the distillation is stopped, and at the same time, the specific mass of p - chloronitrobenzene in the kettle residue is measured. The distilled alcohol solvent is recycled as the alcohol solvent used in alcohol precipitation in step S5.

[0027] Furthermore, it also includes step S7 of recycling the still residue. Pump the still residue in the still residue kettle into the reaction kettle. After adding chloronitrobenzene to the reaction kettle, disperse it in an organic solvent, add a catalyst, heat up to the esterification temperature, and keep the reaction for 0.5 h. Then add a certain amount of auxiliary agent. After fully replacing the air in the kettle with nitrogen, heat up to the etherification temperature and keep the reaction while ensuring a certain pressure in the kettle. Control the content of p-chloronitrobenzene in the reaction kettle to be 10 - 15% as the end point. After reaching the end point, cool down to 65°C; repeat steps S2 - S7;

[0028] In step S7, the added mass of the chloronitrobenzene = the mass of chloronitrobenzene to be added per batch - the amount of chloronitrobenzene contained in the still residue, and the volume of the organic solvent = the amount of organic solvent to be added per batch - the volume of the organic solvent contained in the still residue.

[0029] In step S7, the added mass of the chloronitrobenzene = the mass of chloronitrobenzene to be added per batch - the amount of chloronitrobenzene contained in the still residue, and the volume of the organic solvent = the amount of organic solvent to be added per batch - the volume of the organic solvent contained in the still residue.

[0030] Furthermore, in step S6, the specified value of the alcohol solvent in the still residue is that the mass fraction of the alcohol solvent contained in the still residue is 1%; in step S7, the organic solvent, washing solvent, alcohol solvent, and washing solution are all recycled solvents. When the amount is insufficient, supplement the corresponding fresh solvent, and the recycling times are more than 10 times. Description of the Drawings

[0031] Figure 1 It is the chromatogram of the product obtained in step S6 of the present invention;

[0032] Figure 2 It is the chromatogram of the product obtained in step S7 of the present invention.

[0033] The beneficial effects of the present invention are:

[0034] The present invention adopts a one-pot method, selects a polar organic solvent as the reaction solvent, pre-reacts the raw material p-chloronitrobenzene with a catalyst to form an ester first, then adds a carbonate assistant, and carries out etherification under an inert atmosphere to prepare 4,4'-dinitrodiphenyl ether. The pre-reaction treatment is adopted to quickly initiate the target reaction, which is beneficial to shortening the reaction time. Subsequently, decolorization, vacuum distillation, alcohol precipitation, distillation residue, and recycling of the still residue are carried out. The reaction of the present invention is simple, has low requirements for equipment, short reaction time, high yield and high purity of the obtained product. All solvents involved in the whole process are recycled, the demand for fresh solvents is small, and the still residue can be recycled more than 10 times. Compared with the traditional discharging method, i.e., water precipitation discharging, alcohol precipitation discharging can not only remove a large amount of impurities, but also the subsequent solvent recovery is fast, energy-saving and easy to achieve. The recycling process enables the final centralized treatment of organic wastes in the whole process flow, which not only reduces the difficulty and cost of organic waste treatment, but also ensures high efficiency and high yield. By implementing the technical solution of the present invention, 4,4'-dinitrodiphenyl ether with high yield and high purity can be obtained, and the process operation is suitable for industrial production. Detailed implementation manners

[0035] The following combines the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, other embodiments obtained by other persons in the art without making creative efforts fall within the protection scope of the present invention.

[0036] It should be noted that the terms used here are only for describing specific implementation manners and are not intended to limit the exemplary implementation manners according to the present application. As used here, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.

[0037] Example 1

[0038] S1 Etherification: Disperse 157.55 kg of p-chloronitrobenzene (PCNB) in 315 L of dimethyl sulfoxide, add 8.01 kg of potassium benzoate under stirring, heat up to 90 °C, keep warm for 0.5 h, then add 69.10 kg of K2CO3. Under stirring, displace the air in the kettle with N2 three times, heat up to 160 °C, ensure the pressure in the kettle is 0.2 MPa, keep warm for reaction. When the remaining p-chloronitrobenzene in the system is 10.0%, the reaction time is 5.5 h, and then cool down to 65 °C.

[0039] Chromatographic method for determining the end point of the etherification reaction and the product content:

[0040] Liquid chromatograph model: Shimadzu LC-15C

[0041] Chromatographic column: C18 column, 4.6×250mm

[0042] Mobile phase: Acetonitrile: water (V:V) = 7:3

[0043] Flow rate: 1 mL / min

[0044] Column temperature: 35 °C

[0045] Wavelength: 254 nm

[0046] Sample preparation method:

[0047] Etherification end point: 0.1 mL of the system is dissolved in 10 mL of acetonitrile, and the injection volume is 3 μL;

[0048] Product content: 10 micrograms of the sample is dissolved in 10 mL of acetonitrile, and the injection volume is 2 μL.

[0049] S2 Filtration: The system obtained in step S1 is filtered. Specifically, after the reaction kettle in S1 is cooled, the pressure is first relieved, then filtered, and the filter cake is washed with 31.5 L of dimethyl sulfoxide as the washing solvent. The filtrate and the washed washing solvent are pumped into the decolorization kettle.

[0050] S3 Decolorization: 6.50 kg of activated carbon is added to the decolorization kettle under stirring, heated to 80 - 90 °C, decolorized for 0.5 h, and filtered while it is hot.

[0051] S4 Vacuum distillation: The filtrate from the decolorization kettle is pumped into the vacuum distillation kettle. Under stirring, the vacuum pump group is started. After the vacuum degree in the kettle reaches -0.1 MPa, vacuum distillation is carried out. The distillate volume of dimethyl sulfoxide is 189 L (31.5 L + 315 L × 50%) and then the distillation is stopped.

[0052] S5 Alcohol precipitation: After the distillation is stopped, it is pumped into the alcohol precipitation kettle. After the temperature of the alcohol precipitation kettle drops to 65 °C, 1575 L (315 L × 50% × 10 times) of methanol is slowly added, refluxed and slurried at 68 °C for 0.5 h, cooled to 25 °C, filtered by suction, and the filter cake is washed with 78.8 L (1575 L × 5%) of methanol as the washing liquid. The filter cake is dried to obtain the finished product; Quality of the finished product in S5: 104.56 kg, Chromatographic purity: 99.93%, Chromatogram is shown in Figure 1 , Yield: 88.79%.

[0053] S6 Residue in the distillation kettle: The filtrate and washing liquid in S5 enter the residue kettle.

[0054] Under stirring, the vacuum pump group is started. When the vacuum degree in the kettle reaches 0.1 MPa, vacuum distillation is carried out. When the methanol content in the residue is monitored to be 0.5%, the distillation is stopped. The volume of the distilled alcohol liquid is 1400 L, and the distilled methanol is recycled as the alcohol solvent for alcohol precipitation in step S5.

[0055] The PCNB content in the still residue is 15.06 kg, and the volume is 155 L.

[0056] Step S7: Recycling of the still residue

[0057] Pump 155 L of the still residue into the reaction kettle, and pump in 196 L (351 L - 155 L) of fresh dimethyl sulfoxide. Disperse 142.49 kg (157.55 kg - 15.06 kg) of p-chloronitrobenzene in the reaction kettle. Add 8.01 kg of potassium benzoate with stirring, slowly heat up to 90 °C, keep warm for 0.5 h, then add 69.10 kg of K2CO3. With stirring, displace the air in the kettle with N2 three times, heat up to 160 °C, ensure the pressure in the kettle is 0.2 MPa, keep warm for the reaction. When the remaining p-chloronitrobenzene in the system is about 10.5%, the reaction time is 5.5 h. Cool down to 65 °C, relieve the pressure, filter, wash the filter cake with 31.5 L of dimethyl sulfoxide as the washing solvent, and pump the filtrate and the washed washing solvent into the decolorization kettle.

[0058] Add 6.50 kg of activated carbon to the decolorization kettle with stirring, heat up to 80 - 90 °C, decolorize for 0.5 h, filter while it is hot, and pump the filtrate into the vacuum distillation kettle. Under the stirring state, turn on the vacuum pump set. After the vacuum degree in the kettle reaches -0.1 MPa, carry out vacuum distillation. Stop distillation when the volume of the distillate is 189 L (31.5 L + 315 L × 50%), and pump it into the alcohol precipitation kettle. After the temperature in the alcohol precipitation kettle drops to 65 °C, slowly add 1400 L of the distilled alcohol solution and 175 L (1575 L - 1400 L) of fresh methanol, reflux and beat at 68 °C for 0.5 h, cool down to room temperature, filter by suction, and wash the filter cake with 78.8 L (1575 L × 5%) of methanol as the washing liquid. Dry the filter cake to obtain the finished product. The quality of the finished product in S7: 114.51 kg, chromatographic purity: 99.92%, see Figure 2 , yield: 97.58%. The filtrate and the washing liquid enter the still residue distillation kettle.

[0059] With stirring, turn on the vacuum pump set. When the vacuum degree in the kettle reaches 0.1 MPa, carry out distillation. Stop distillation when the methanol content in the still residue is monitored to be 0.8%, and the volume of the distilled alcohol solution is 1500 L.

[0060] The PCNB content in the still residue is 15.56 kg, and the volume is 165 L.

[0061] For subsequent recycling as above, recycle 10 times, and the yield is about 96.5% or more.

[0062] During recycling, in step S7, the added mass of p-chloronitrobenzene = the mass of p-chloronitrobenzene to be added in each batch - the amount of p-chloronitrobenzene contained in the still residue, and the volume of the organic solvent = the amount of organic solvent to be added in each batch - the volume of the organic solvent contained in the still residue.

[0063] In step S6, the specified value of the residual alcohol solvent in the still residue is that the mass fraction of the alcohol solvent contained in the still residue is 1%; in step S7, the organic solvent, washing solvent, alcohol solvent, and washing solution are all recycled solvents, and when the amount is insufficient, the corresponding fresh solvent is supplemented.

[0064] Example 2

[0065] S1 Etherification: 157.55 kg of p-chloronitrobenzene is dispersed in 475 L of DMF. Under stirring, 8.20 kg of sodium acetate is added, and the temperature is slowly raised to 100 °C. After maintaining the temperature for 0.5 h, 105.99 kg of Na2CO3 is added. Under stirring, the air in the kettle is replaced with N2 three times, and the temperature is raised to 190 °C. Ensure that the pressure in the kettle is 0.4 MPa, maintain the reaction temperature, and monitor the reaction. When the remaining p-chloronitrobenzene in the system is about 13.0%, the reaction time is 4.5 h, and the temperature is lowered to 65 °C.

[0066] Chromatographic method for determining the end point of the etherification reaction and the product content:

[0067] Liquid chromatograph model: Shimadzu LC-15C

[0068] Chromatographic column: C18 column, 4.6×250 mm

[0069] Mobile phase: Acetonitrile:Water (V:V) = 7:3

[0070] Flow rate: 1 mL / min

[0071] Column temperature: 35 °C

[0072] Wavelength: 254 nm

[0073] Sample preparation method:

[0074] Etherification end point: 0.1 mL of the system is dissolved in 10 mL of acetonitrile, and the injection volume is 3 μL;

[0075] Product content: 10 micrograms of the sample is dissolved in 10 mL of acetonitrile, and the injection volume is 2 μL.

[0076] S2 Filtration: The system obtained in step S1 is filtered. Specifically, after the reaction kettle of the reaction system obtained in S1 is cooled, the pressure is first released, and then filtered. The filter cake is washed with 47.5 L of DMF as the washing solvent, and the filtrate and the washing solvent after washing are pumped into the decolorization kettle.

[0077] S3 Decolorization: 9.10 kg of activated carbon is added to the decolorization kettle under stirring, and the temperature is raised to 80 - 90 °C for decolorization for 0.7 h, and then filtered while it is hot.

[0078] S4 Vacuum distillation: The filtrate from the decolorization kettle is pumped into the vacuum distillation kettle. Under stirring, start the vacuum pump group. After the vacuum degree in the kettle reaches 0.1 MPa, carry out vacuum distillation. Stop distillation when the volume of the DMF distillate is 332.5 L (47.5 L + 475 L × 60%).

[0079] S5 Alcohol precipitation: After stopping distillation, pump it into the alcohol precipitation kettle. After the temperature of the alcohol precipitation kettle drops to 78 °C, add 2090 L (475 L × 40% × 11 times) of ethanol, reflux and beat the pulp at 80 °C for 0.5 h, cool down to room temperature, filter by suction, and wash the filter cake with 104.5 L (2090 L × 5%) of ethanol as the washing solution. Dry the filter cake to obtain the finished product. Quality of the S5 finished product: 100.66 kg, Chromatographic purity: 99.95%, Yield: 88.35%.

[0080] S6 Residue in the distillation kettle: The filtrate and washing solution from S5 enter the residue distillation kettle.

[0081] Under stirring, start the vacuum pump group. When the vacuum degree in the kettle reaches 0.1 MPa, carry out distillation. Stop distillation when the ethanol content in the residue is monitored to be 0.8%. The volume of the distilled alcohol solution is 1800 L. The distilled ethanol is recycled as the alcohol solvent for alcohol precipitation in step S5.

[0082] The content of PCNB in the residue is 19.66 kg and the volume is 230 L.

[0083] Step S7 Recycling of the residue in the kettle:

[0084] Pump 230 L of the residue into the reaction kettle, and pump in 245 L (475 - 230) of new DMF. Disperse 137.89 kg (157.55 kg - 19.66 kg) of p-chloronitrobenzene in the reaction kettle, add 105.99 kg of Na2CO3. Under stirring, displace the air in the kettle with N2 three times, heat up to 190 °C, ensure the pressure in the kettle is 0.3 MPa, keep the temperature for reaction. When the remaining p-chloronitrobenzene in the system is monitored to be about 13.2%, the reaction time is 4.5 h. Cool down to 65 °C, relieve the pressure, filter, wash the filter cake with 47.5 L of DMF as the washing solvent. Pump the filtrate and the washed washing solvent into the decolorization kettle.

[0085] Under stirring, 9.10 kg of activated carbon was added to the decolorization kettle, and the temperature was raised to 80 - 90 °C for 0.7 h of decolorization. Then, it was filtered while hot, and the filtrate was pumped into the vacuum distillation kettle. Under the stirring state, the vacuum pump group was started. After the vacuum degree in the kettle reached 0.1 MPa, vacuum distillation was carried out. When the volume of the DMF distillate reached 332.5 L (47.5 L + 475 L × 60%), the distillation was stopped and pumped into the alcohol precipitation kettle. After the temperature of the alcohol precipitation kettle dropped to 78 °C, 1800 L of ethanol distillate and 290 L of fresh ethanol (2090 L - 1800 L) were added. It was refluxed and slurried at 80 °C for 0.5 h, cooled to room temperature, filtered, and the filter cake was washed with 104.5 L (2090 L × 5%) of ethanol washing solution. The filter cake was dried to obtain the finished product; S5 Quality of the finished product: 114.61 kg Chromatographic purity: 99.92% Yield: 97.67%.

[0086] The filtrate and the washing solution entered the residue distillation kettle.

[0087] Under stirring, the vacuum pump group was started. When the vacuum degree in the kettle reached 0.1 MPa, the temperature was raised for distillation. When the ethanol content in the residue was monitored to be 0.7%, the distillation was stopped, and the volume of the distilled alcohol solution was 1900 L.

[0088] The content of PCNB in the residue was 15.56 kg, and the volume was 232 L.

[0089] For subsequent reuse as above, after 10 times of reuse, the yield was about 96.5% or more.

[0090] During reuse, in step S7, the added mass of the chloronitrobenzene = the mass of the chloronitrobenzene to be added per batch - the amount of chloronitrobenzene contained in the residue, and the volume of the organic solvent = the amount of the organic solvent to be added per batch - the volume of the organic solvent contained in the residue.

[0091] In step S6, the specified value of the alcohol solvent in the residue was that the mass fraction of the alcohol solvent contained in the residue was 1%; in step S7, the organic solvent, the washing solvent, the alcohol solvent, and the washing solution were all recycled solvents, and when the amount was insufficient, the corresponding fresh solvent was supplemented.

[0092] Example 3

[0093] S1 Etherification: 157.55 kg of p-chloronitrobenzene was dispersed in 630 L of NMP. Under stirring, 24.54 kg of potassium acetate was added, and the temperature was slowly raised to 120 °C. After holding for 0.5 h, 207.30 kg of K2CO3 was added. Under stirring, the air in the kettle was replaced with N2 three times, and the temperature was raised to 220 °C, ensuring the pressure in the kettle was 0.7 MPa. After holding for the reaction, when the remaining p-chloronitrobenzene in the system was about 14.9%, the reaction duration was 3.5 h, and the temperature was cooled to 65 °C.

[0094] Chromatographic method for determining the end point of the etherification reaction and the product content:

[0095] Liquid Chromatography Model: Shimadzu LC-15C

[0096] Chromatographic Column: C18 Column, 4.6×250mm

[0097] Mobile Phase: Acetonitrile:Water (V:V) = 7:3

[0098] Flow Rate: 1mL / min

[0099] Column Temperature: 35°C

[0100] Wavelength: 254nm

[0101] Sample Preparation Method:

[0102] Etherification Endpoint: 0.1mL of the system is dissolved in 10mL of acetonitrile, injection volume 3μL;

[0103] Product Content: 10 micrograms of the sample is dissolved in 10mL of acetonitrile, injection volume 2μL.

[0104] In step S2, the system obtained in step S1 is filtered. Specifically, after the reaction kettle in the reaction system obtained in S1 is cooled, first filter: relieve pressure, filter, wash the filter cake with 63.0L of NMP as the washing solvent, and pump the filtrate and the washed washing solvent into the decolorization kettle.

[0105] S3 Decolorization: Add 13.0kg of activated carbon to the decolorization kettle under stirring, heat up to 80 - 90°C, decolorize for 1h, and filter while it is hot.

[0106] S4 Vacuum Distillation: The filtrate from the decolorization kettle is pumped into the vacuum distillation kettle. Under stirring, start the vacuum pump group. After the vacuum degree in the kettle reaches 0.1MPa, slowly heat up for vacuum distillation. Stop distillation when the volume of the NMP distillate is 315L (63.0L + 630L×40%).

[0107] S5 Alcohol Precipitation: After stopping distillation, pump it into the alcohol precipitation kettle. After the temperature of the alcohol precipitation kettle drops to 97°C, slowly add 4536L (630L×60%×12 times) of propanol, reflux and stir at 99°C for 0.5h, cool down to room temperature, filter by suction, and wash the filter cake with 226.8L (4536L×5%) of propanol as the washing liquid. Dry the filter cake to obtain the finished product. S5 Finished Product Quality: 99.66kg Chromatographic Purity: 99.92% Yield: 88.16%.

[0108] Step S6 Residue in the Distillation Kettle: The filtrate and the washing liquid enter the residue distillation kettle.

[0109] Under stirring, start the vacuum pump group. When the vacuum degree in the kettle reaches 0.1MPa, heat up for distillation. Stop distillation when the propanol content in the residue is monitored to be 0.8%. The volume of the distilled alcohol liquid is 4400L. The distilled propanol is recycled as the alcohol solvent for alcohol precipitation in step S5.

[0110] The PCNB content in the kettle residue is 20.76 kg, and the volume is 290 L.

[0111] Step S7: Recycling of kettle residue

[0112] Pump 290 L of kettle residue into the reaction kettle, and pump in 340 L (630 - 290) of fresh NMP. Disperse 136.79 kg (157.55 kg - 20.76 kg) of p-chloronitrobenzene in the reaction kettle. Add 24.54 kg of potassium acetate under stirring, slowly heat up to 120 °C, after holding for 0.5 h, add 207.30 kg of K2CO3. Under stirring, displace the air in the kettle with N2 three times, heat up to 220 °C, ensure the pressure in the kettle is 0.7 MPa, hold for reaction. When the remaining p-chloronitrobenzene in the system is about 14.9%, the reaction time is 3.5 h. Cool down to 65 °C, relieve the pressure, filter, wash the filter cake with 63.0 L of NMP as the washing solvent, and pump the filtrate and the washed washing solvent into the decolorization kettle.

[0113] Add 13.0 kg of activated carbon to the decolorization kettle under stirring, heat up to 80 - 90 °C, decolorize for 1 h, filter while it is hot, and pump the filtrate into the vacuum distillation kettle. Under the stirring state, turn on the vacuum pump set. After the vacuum degree in the kettle reaches 0.1 MPa, carry out vacuum distillation. Stop distillation when the volume of the NMP distillate is 315 L (63.0 L + 630 L × 40%), and pump it into the alcohol precipitation kettle. After the temperature in the alcohol precipitation kettle drops to 97 °C, slowly add 4400 L of propanol distillate and 136 L (4536 L - 4400 L) of propanol, reflux and slurry at 99 °C for 0.5 h, cool down to room temperature of 25 °C, filter by suction, and wash the filter cake with 226.8 L (4536 L × 5%) of propanol. Dry the filter cake to obtain the finished product; Quality of S7 product: 110.51 kg, Chromatographic purity: 99.95%, Yield: 97.87%.

[0114] The filtrate and the washing liquid enter the kettle residue distillation kettle.

[0115] Under stirring, turn on the vacuum pump set. When the vacuum degree in the kettle reaches 0.1 MPa, carry out distillation. Stop distillation when the propanol content in the kettle residue is monitored to be 0.6%, and the volume of the distillate alcohol liquid is 4450 L.

[0116] The PCNB content in the kettle residue is 20.89 kg, and the volume is 298 L.

[0117] For subsequent recycling as above, recycle 10 times, and the yield is about 96.5% or more.

[0118] During recycling, in step S7, the added mass of the chloronitrobenzene = the mass of chloronitrobenzene to be added per batch - the amount of chloronitrobenzene contained in the kettle residue, and the volume of the organic solvent = the amount of organic solvent to be added per batch - the volume of the organic solvent contained in the kettle residue.

[0119] In step S6, the specified value of the residual alcohol solvent in the kettle residue is that the mass fraction of the alcohol solvent contained in the kettle residue is 1%; in step S7, the organic solvent, washing solvent, alcohol solvent and washing solution are all recycled solvents, and the corresponding fresh solvents are supplemented when the amount is insufficient.

[0120] The present invention adopts a one-pot method, using a polar organic solvent as the reaction solvent. First, the raw material p-chloronitrobenzene and the catalyst are pre-reacted to form an ester, then a carbonate auxiliary agent is added, and etherification occurs under an inert atmosphere to prepare 4,4'-dinitrodiphenyl ether. After filtration, the filtrate is decolorized, vacuum distilled, and alcohol-precipitated to obtain the target product, and the mother liquor solvent is recycled and the kettle residue is reused. The reaction of the present invention is simple and easy to control, with a short reaction time and few side reactions, and realizes the centralized treatment of organic waste, reducing the difficulty of post-treatment. All the solvents involved in the whole process are reused, and the target product produced has a low cost, high purity, and the total yield reaches more than 96.5%.

[0121] The biggest unexpected discovery of the present invention is that in the reaction system, as long as the concentration of p-chloronitrobenzene is within a certain range, there are very few side reactions such as so-called carbonization, polymerization, and ether bond cleavage in the system. Coupled with the assistance of the alcohol precipitation process and the reuse process, a target product with a high yield and high purity can be obtained. It may be that within the concentration range of 10-15% of p-chloronitrobenzene, the target reaction is the main reaction, and as the concentration of the raw material decreases, the side reactions will intensify.

[0122] At present, the technical solution of the present invention has been pilot-tested, that is, small-scale experiments before large-scale production of the product; after the pilot test, user usage research has been carried out on a small scale, and the research results show that the user satisfaction is relatively high; now it has started to prepare for the formal production and industrialization of the product (including research on intellectual property risk early warning).

[0123] The above-described embodiments are the preferred embodiments of the present invention, rather than an exhaustive list of the feasible embodiments of the present invention. For those skilled in the art, various improvements made without departing from the spirit and essence of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A preparation method of 4,4′-dinitrodiphenyl ether, characterized in that, It includes the following steps: S1 Etherification: Disperse p-chloronitrobenzene in an organic solvent in a reaction kettle, add a catalyst under stirring, heat up to the esterification temperature, keep the temperature for reaction for 0.5 h, then add a certain amount of auxiliary agent. After fully replacing the air in the kettle with nitrogen, heat up to the etherification temperature, keep the temperature for reaction, and ensure that the kettle is under a certain pressure. Control the content of p-chloronitrobenzene in the reaction kettle at 10 - 15% as the end point. After reaching the end point, cool down to 65 °C. S2 Filtration: Filter the system obtained in step S1, and wash the filtered cake with a certain volume of washing solvent. S3 Decolorization: The filtrate after filtration in step S2 enters a decolorization kettle for decolorization, and then is filtered after decolorization. S4 Vacuum distillation: The filtrate obtained in step S3 enters a distillation kettle for vacuum distillation. S5 Alcohol precipitation: Pump the liquid in the distillation kettle in step S4 into an alcohol precipitation kettle and add an alcohol solvent. After the material precipitates, carry out suction filtration. The filtered cake is washed and then dried to obtain the finished product. S6 Residue in the distillation kettle: Start the vacuum pump group. After the vacuum degree in the residue kettle reaches -0.1 MPa, carry out vacuum distillation. After testing that the remaining alcohol solvent in the residue is less than the specified value, stop the distillation. At the same time, measure the specific mass of p-chloronitrobenzene in the residue kettle. The distilled alcohol solvent is recycled as the alcohol solvent for alcohol precipitation in step S5. S7 Recycling of the residue in the kettle: Pump the residue in the residue kettle into the reaction kettle. After adding p-chloronitrobenzene to the reaction kettle, disperse it in an organic solvent, add a catalyst, heat up to the esterification temperature, and keep the temperature for reaction for 0.5 h. Then add a certain amount of auxiliary agent. After fully replacing the air in the kettle with nitrogen, heat up to the etherification temperature, keep the temperature for reaction, and ensure that the kettle is under a certain pressure. Control the content of p-chloronitrobenzene in the reaction kettle at 10 - 15% as the end point. After reaching the end point, cool down to 65 °C; repeat steps S2 - S7; in step S7, the added mass of p-chloronitrobenzene = the mass of p-chloronitrobenzene to be added in each batch - the amount of p-chloronitrobenzene contained in the residue in the kettle, and the volume of the organic solvent = the amount of organic solvent to be added in each batch - the volume of the organic solvent contained in the residue in the kettle.

2. The preparation method of 4,4'-dinitrodiphenyl ether according to claim 1, characterized in that, In step S1, the catalyst is sodium benzoate, potassium benzoate, sodium acetate or potassium acetate; the auxiliary agent is sodium carbonate or potassium carbonate; in step S1, the organic solvent is dimethyl sulfoxide, dimethyl sulfone, sulfolane, N,N-diethylformamide, N,N-diethylformamide or N-methylpyrrolidone; in step S1, the mass ratio of p-chloronitrobenzene to the volume of the organic solvent is 1:2 - 5; the molar ratio of p-chloronitrobenzene, the auxiliary agent to the catalyst is 1:0.5 - 1.5:0.05 - 0.

25.

3. The preparation method of 4,4'-dinitrodiphenyl ether according to claim 1, characterized in that, In step S1, the esterification temperature is 90 - 120 °C; the etherification temperature is 160 - 220 °C; the pressure in the kettle during the etherification process is maintained at 0.2 - 0.7 MPa.

4. The preparation method of 4,4'-dinitrodiphenyl ether according to claim 1, characterized in that, In step S2, after the reaction kettle cools down, relieve the pressure, discharge the material for filtration, and wash the filtered cake with a certain volume of washing solvent. The washing solvent is the organic solvent in step S1, and the dosage is 10 - 15% of the dosage of the organic solvent in step S1; the washing solvent after washing enters the decolorization kettle.

5. The preparation method of 4,4'-dinitrodiphenyl ether according to claim 1, characterized in that, In step S3, a certain amount of activated carbon is added to the decolorization kettle, and the temperature is raised to 80-90 °C for decolorization. The decolorization time is 0.5-1 h. Then, it is filtered while it is hot, and the filtrate enters the distillation kettle; the added mass of the activated carbon is 5-10% of the theoretical production amount of the target product.

6. The preparation method of 4,4'-dinitrodiphenyl ether according to claim 1, characterized in that, In step S4, the vacuum pump group is started. After the vacuum degree in the distillation kettle reaches -0.1 MPa, vacuum distillation is carried out. After the volume of the distilled solvent reaches the specified amount, the vacuum distillation is stopped, and the temperature is lowered to the boiling point temperature of the alcohol solvent used in alcohol precipitation in step S5. The liquid in the distillation kettle is pumped into the alcohol precipitation kettle, and the distillate is recycled as an organic solvent; the calculation of the volume of the distilled solvent reaching the specified amount is as follows: the amount of distillate = the mass of the washing solvent in step S2 + the mass of the organic solvent in step S1 × (40-60)%.

7. A method for preparing 4,4'-dinitrodiphenyl ether according to claim 1, characterized in that, In step S5, the liquid in the distillation kettle in step S4 is pumped into the alcohol precipitation kettle, and an alcohol solvent is added under stirring. The material precipitates, and it is heated to reflux and pulped for 0.5 h. Then, it is cooled to room temperature and filtered by suction. The filter cake is washed with the corresponding alcohol solvent as the washing liquid and then dried to obtain the finished product. The filtrate after suction filtration and the washing liquid after washing are pumped into the residue kettle together; the alcohol solvent is methanol, ethanol or propanol, and the dosage of the alcohol solvent is 10-12 times the volume of the remaining organic solvent in the liquid pumped into the alcohol precipitation kettle after vacuum distillation in step S4; in step S5, when washing the filter cake, the dosage of the washing liquid is 5% of the dosage of the alcohol solvent in alcohol precipitation.

8. A method for preparing 4,4'-dinitrodiphenyl ether according to claim 7, characterized in that, In step S6, the specified value of the alcohol solvent in the residue is that the mass fraction of the alcohol solvent in the residue is 1%.

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