A green process for the preparation of poly-2,3-dimethylaniline

Abstract

This invention relates to the field of polyaniline derivative preparation technology, and more particularly to a green preparation method for poly(2,3-dimethylaniline). The green preparation method provided by this invention includes mixing a reaction mother liquor for preparing poly(2,3-dimethylaniline), a nitric acid solution, and 2,3-dimethylaniline, and then adding Fe... 3+ The catalyst is subjected to a first heat treatment, hydrogen peroxide is added, and a second heat treatment is performed to obtain a first-use reaction mother liquor and a filter cake. The filter cake is post-treated to obtain the poly-2,3-dimethylaniline. The first-use reaction mother liquor is recycled according to the above process. During the above recycling process, when the COD content in the reaction mother liquor obtained after recycling is greater than 29000 mg / L, the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide is increased based on the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide during the first recycling process. The preparation method has high yield and is environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of polyaniline derivative preparation technology, and in particular to a green preparation method for poly2,3-dimethylaniline. Background Technology

[0002] Poly(2,3-dimethylaniline) is an important new type of functional polymer material for preparing polyaniline derivatives. Due to the substitution of two electron-donating groups (-CH3) on the aromatic ring, the rigidity of the polymer chain is effectively reduced, and the interchain forces are decreased. This results in better solubility and dispersibility in organic solvents than polyaniline, making it a potential replacement for polyaniline. Currently, the main methods used are ammonium persulfate oxidation and hydrogen peroxide / Fe... 2+ Oxidation method; In the above two methods, the reaction mother liquor is directly treated as waste, or the reuse rate is low when the reaction mother liquor is reused. Therefore, due to the large amount of excess reaction raw materials in the reaction mother liquor, the yield of poly-2,3-dimethylaniline cannot be effectively improved. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a green preparation method for poly(2,3-dimethylaniline), wherein the preparation method has high yield and is environmentally friendly.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a green preparation method for poly2,3-dimethylaniline, comprising the following steps: First application: After mixing the reaction mother liquor for preparing poly(2,3-dimethylaniline), nitric acid solution, and 2,3-dimethylaniline, Fe was added. 3+ The catalyst is subjected to a first heat treatment, hydrogen peroxide is added, and a second heat treatment is performed to obtain the first set of reaction mother liquor and filter cake. The filter cake is then post-processed to obtain the poly(2,3-dimethylaniline); The first set of reaction mother liquor is recycled according to the above process; In the above-mentioned cyclical process, when the COD content in the reaction mother liquor obtained after the cyclical process is greater than 29000 mg / L, the molar ratio of H2O2 to 2,3-dimethylaniline is increased based on the molar ratio of H2O2 to 2,3-dimethylaniline in the first cyclical process.

[0005] Preferably, when the COD content in the reaction mother liquor obtained after application is greater than 29000 mg / L, the molar ratio of H2O2 in the hydrogen peroxide to 2,3-dimethylaniline is (2.5~3.0):1; When the COD content in the reaction mother liquor obtained after application is less than 29000 mg / L, the molar ratio of H2O2 in the hydrogen peroxide to 2,3-dimethylaniline is (1.8~2.0):1.

[0006] Preferably, when the application is performed for the 5nth time, the COD content in the reaction mother liquor obtained after the application is greater than 29000 mg / L; When the number of times the reaction is applied is not the 5nth time, the COD content in the resulting mother liquor is less than 29000 mg / L.

[0007] Preferably, the mother liquor for preparing poly-2,3-dimethylaniline includes nitric acid and Fe. 3+ Catalyst, water, and 2,3-dimethylaniline with different degrees of polymerization; The mass percentage concentration of nitric acid in the reaction mother liquor for preparing poly(2,3-dimethylaniline) is 1.9-2.3%.

[0008] Preferably, the method for preparing the reaction mother liquor for preparing poly-2,3-dimethylaniline includes the following steps: Mix nitric acid solution and 2,3-dimethylaniline until completely dissolved, then add Fe. 3+ The catalyst was subjected to a first heat treatment, hydrogen peroxide was added, and a second heat treatment was performed. The mixture was then filtered while hot to obtain a filter cake and the reaction mother liquor for preparing poly(2,3-dimethylaniline). The nitric acid solution used in the preparation of the reaction mother liquor for the preparation of poly(2,3-dimethylaniline) has a mass percentage concentration of 3% to 4%.

[0009] Preferably, in the process of preparing the reaction mother liquor for preparing poly-2,3-dimethylaniline: the Fe 3+ The molar ratio of catalyst to 2,3-dimethylaniline is (0.02~0.03):1; The hydrogen peroxide has a mass percentage concentration of 25% to 30%, and the molar ratio of H2O2 to 2,3-dimethylaniline in the hydrogen peroxide is (1.8 to 2.3):1.

[0010] Preferably, the mass percentage concentration of the nitric acid solution is 97-98%; The Fe 3+ The catalyst includes one or more of ferric chloride, ferric nitrate and ferric sulfate.

[0011] Preferably, the Fe used 3+ The mass of catalyst added is 2-5% of the initial catalyst mass; The Fe 3+ The molar ratio of the catalyst to the 2,3-dimethylaniline is (0.02~0.03):1.

[0012] Preferably, the mixing temperature is 40~50℃; The first insulation temperature is 40~50℃, and the time is 0.5~1h; The second insulation temperature is 40~50℃, and the time is 2~4h.

[0013] Preferably, after the second heat preservation is completed, the filter cake is further subjected to alkali washing, first water washing, second water washing and drying in sequence; The mass concentration of the alkaline solution is 2-5%; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution. The alkaline wash, the first water wash, and the second water wash are at room temperature, with independent rotation speeds of 200~300 rpm and independent time of 0.5~1 h; The drying process is vacuum drying, with a temperature of 60-65°C, a vacuum degree of 10-20 kPa, and a time of 6-10 hours.

[0014] This invention provides a green preparation method for poly(2,3-dimethylaniline), comprising the following steps: First application: After mixing the reaction mother liquor for preparing poly(2,3-dimethylaniline), nitric acid solution, and 2,3-dimethylaniline, Fe is added. 3+ The catalyst is subjected to a first heat treatment, hydrogen peroxide is added, and a second heat treatment is performed to obtain a first set of reaction mother liquor and filter cake. The filter cake is post-treated to obtain the poly(2,3-dimethylaniline). The first set of reaction mother liquor is recycled according to the above process. During the above recycling process, when the COD content in the reaction mother liquor obtained after recycling is greater than 29000 mg / L, the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide is increased based on the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide during the first recycling process. The green preparation method described in this invention provides a method for preparing poly(2,3-dimethylaniline) without waste acid emissions, and allows for the secondary utilization of low-polymerization-degree 2,3-dimethylaniline in the reaction mother liquor, thereby improving the yield of poly(2,3-dimethylaniline). This invention achieves sustainable reuse, greatly saves wastewater treatment costs, recovers low-polymerization-degree 2,3-dimethylaniline from the reaction mother liquor, and creates significant economic value. The preparation method is simple to operate; it uses hydrogen peroxide as an oxidant, which is green and environmentally friendly. Compared with the traditional ammonium persulfate process, it avoids the generation of large amounts of waste salt, reduces the difficulty of reusing the reaction mother liquor, and reduces the difficulty of post-treatment. Attached Figure Description

[0015] Figure 1 This is a schematic flowchart of the green preparation method of poly(2,3-dimethylaniline) according to the present invention. Detailed Implementation

[0016] like Figure 1 As shown, this invention provides a green preparation method for poly2,3-dimethylaniline, comprising the following steps: First application: After mixing the reaction mother liquor for preparing poly(2,3-dimethylaniline), nitric acid solution, and 2,3-dimethylaniline, Fe was added. 3+ The catalyst is subjected to a first heat treatment, hydrogen peroxide is added, and a second heat treatment is performed to obtain the first set of reaction mother liquor and filter cake. The filter cake is then post-processed to obtain the poly(2,3-dimethylaniline); The first set of reaction mother liquor is recycled according to the above process; In the above-mentioned cyclic reuse process, when the COD content in the reaction mother liquor obtained after reuse is greater than 29000 mg / L, the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide is increased based on the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide during the first reuse process.

[0017] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0018] The green preparation method of this invention includes the following first application: mixing the reaction mother liquor for preparing poly(2,3-dimethylaniline), nitric acid solution, and 2,3-dimethylaniline, and then adding Fe. 3+ The catalyst is subjected to a first heat treatment, hydrogen peroxide is added, and a second heat treatment is performed to obtain the first set of reaction mother liquor and filter cake.

[0019] In this invention, the preparation of the reaction mother liquor for preparing poly-2,3-dimethylaniline preferably includes: Mix nitric acid solution and 2,3-dimethylaniline until completely dissolved, then add Fe. 3+ The catalyst is subjected to a first heat treatment, hydrogen peroxide is added, and a second heat treatment is performed. The mixture is then filtered while hot to obtain a filter cake and the reaction mother liquor for preparing poly(2,3-dimethylaniline).

[0020] In this invention, the mass percentage concentration of the nitric acid solution is preferably 3% to 4%, more preferably 3%, 3.2%, 3.4%, 3.6%, 3.8%, or 4%. In an embodiment of this invention, the mass percentage concentration of the nitric acid solution can be 4.02%.

[0021] In this invention, the molar ratio of nitric acid to 2,3-dimethylaniline in the nitric acid solution is (0.95~1.3):1, preferably 0.95:1, 1.0:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, or 1.3:1. In an embodiment of this invention, the molar ratio of nitric acid to 2,3-dimethylaniline in the nitric acid solution can be 1.07:1.

[0022] In this invention, the mixing temperature is preferably 40-50°C, more preferably 40°C, 42°C, 44°C, 46°C, 48°C, or 50°C. In an embodiment of this invention, the mixing temperature can be 40°C. In this invention, the mixing is preferably carried out under stirring conditions. This invention does not impose any special limitations on the stirring speed and time; speeds and times well known to those skilled in the art can be used to ensure uniform mixing. In an embodiment of this invention, the stirring speed can be 200 rpm.

[0023] In this invention, the mixing process is preferably carried out by adding the 2,3-dimethylaniline dropwise to the nitric acid solution under stirring conditions.

[0024] In this invention, the Fe 3+ The catalyst preferably includes one or more of ferric chloride, ferric nitrate, and ferric sulfate, when the Fe 3+ When the catalyst is two or more of the specific choices mentioned above, the present invention does not impose any special limitation on the ratio of the specific substances; they can be mixed in any ratio. In the embodiments of the present invention, the Fe... 3+ The catalyst can be ferric nitrate.

[0025] In this invention, the Fe 3+ The molar ratio of the catalyst to 2,3-dimethylaniline is preferably (0.02~0.03):1, more preferably 0.02:1, 0.022:1, 0.024:1, 0.026:1, 0.028:1 or 0.03:1. In embodiments of the present invention, the Fe... 3+ The molar ratio of the catalyst to 2,3-dimethylaniline can be 0.027:1.

[0026] The present invention relates to the Fe 3+ There are no special restrictions on the process of adding the catalyst; any process well known to those skilled in the art can be used.

[0027] In this invention, the preferred temperature for the first heat preservation is 40-50°C, more preferably 40°C, 42°C, 44°C, 46°C, 48°C, or 50°C; the preferred heat preservation time is 0.5-1 hour, more preferably 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, or 1 hour. In an embodiment of this invention, the temperature for the first heat preservation can be 42°C or 44°C, and the heat preservation time can be 0.5 hours.

[0028] In this invention, the mass percentage concentration of the hydrogen peroxide is preferably 25% to 30%, more preferably 25%, 26%, 27%, 28%, 29%, or 30%. In an embodiment of this invention, the mass percentage concentration of the hydrogen peroxide can be 27.5%.

[0029] In this invention, the molar ratio of H2O2 to 2,3-dimethylaniline in the hydrogen peroxide is preferably (1.8~2.3):1, more preferably 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1 or 2.3:1. In an embodiment of this invention, the molar ratio of H2O2 to 2,3-dimethylaniline in the hydrogen peroxide can be 1.96:1.

[0030] In this invention, the hydrogen peroxide is preferably added over a period of 1 to 3 hours, more preferably over 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. In an embodiment of this invention, the hydrogen peroxide is added over a period of 1.5 hours.

[0031] In this invention, the preferred temperature for the second heat preservation is 40-50°C, more preferably 40°C, 42°C, 44°C, 46°C, 48°C, or 50°C; the preferred time is 2-4 hours, more preferably 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours. In an embodiment of this invention, the temperature for the second heat preservation can be 45°C or 46°C, and the time can be 3 hours.

[0032] The present invention does not impose any special limitations on the hot filtration process; any process known to those skilled in the art can be used.

[0033] In this invention, the filter cake is preferably subjected to alkali washing, a first water washing, a second water washing, and drying sequentially. The alkali washing preferably uses an alkali solution with a mass concentration of 2-5%, preferably a sodium hydroxide solution or a potassium hydroxide solution. In an embodiment of this invention, the alkali solution is specifically a 3% sodium hydroxide solution. The alkali washing, the first water washing, and the second water washing are preferably carried out under stirring conditions. The temperature of the alkali washing, the first water washing, and the second water washing is preferably room temperature. The rotation speed is preferably 200-300 rpm, and the time is preferably 0.5-1 h. In an embodiment of this invention, the rotation speed of the alkali washing, the first water washing, and the second water washing is 250 rpm, and the time is 0.5 h. In this invention, the purpose of the first and second water washings is mainly to remove sodium or potassium salts from the product, avoiding the problem of reduced material corrosion resistance caused by the presence of sodium or potassium. In this invention, the washing liquid obtained after the first water washing is preferably used as a solvent to prepare an alkali solution for the above-mentioned alkali washing process; the washing liquid obtained after the second water washing is preferably reused in the first water washing process to reduce the amount of washing water used and the amount of wastewater discharged.

[0034] In this invention, the drying is preferably vacuum drying, and the vacuum drying temperature is preferably 60-65℃, more preferably 60℃, 61℃, 62℃, 63℃, 64℃, or 65℃; the vacuum degree is preferably 10-20 kPa, more preferably 10 kPa, 12 kPa, 14 kPa, 16 kPa, 18 kPa, or 20 kPa; the time is preferably 6-10 h, more preferably 6 h, 7 h, 8 h, 9 h, or 10 h. In an embodiment of this invention, the vacuum drying temperature can be 60℃, the vacuum degree can be 15 kPa, and the time can be 8 h.

[0035] In this invention, a portion of the reaction mother liquor used to prepare poly-2,3-dimethylaniline is reused in subsequent processes. The remaining portion of the reaction mother liquor used to prepare poly-2,3-dimethylaniline is mixed with the alkaline washing water obtained from the above-mentioned alkaline washing and treated to obtain nitrogen fertilizer. This invention does not impose any special limitations on the process for obtaining nitrogen fertilizer; any process well-known to those skilled in the art can be used. In this invention, the above process can effectively recover nitrogen from nitric acid, reducing wastewater treatment. In an embodiment of this invention, the process for obtaining nitrogen fertilizer specifically involves sequentially performing ammonia neutralization, concentration, crystallization, and filtration to obtain the nitrogen fertilizer.

[0036] In this invention, the preferred mass ratio of the mother liquor for partially preparing poly(2,3-dimethylaniline) to the remaining mother liquor for preparing poly(2,3-dimethylaniline) is (7.0~8.0):1, more preferably 7.0:1, 7.1:1, 7.2:1, 7.3:1, 7.4:1, 7.5:1, 7.6:1, 7.7:1, 7.8:1, 7.9:1, or 8.0:1. In an embodiment of this invention, the mass ratio of the mother liquor for partially preparing poly(2,3-dimethylaniline) to the remaining mother liquor for preparing poly(2,3-dimethylaniline) can be 7.6:1.

[0037] In this invention, the reaction mother liquor for preparing poly(2,3-dimethylaniline) preferably comprises nitric acid, a catalyst, water, and 2,3-dimethylaniline with different degrees of polymerization. In this invention, the mass percentage concentration of nitric acid in the reaction mother liquor for preparing poly(2,3-dimethylaniline) is preferably 1.9-2.3%, more preferably 1.9%, 2.0%, 2.1%, 2.2%, or 2.3%.

[0038] In this invention, during the first application process, the mass percentage concentration of the nitric acid solution is preferably 97-98%; the nitric acid solution is preferably commercially available industrial nitric acid.

[0039] In this invention, the Fe 3+ The preferred type of catalyst is Fe as described in the above technical solution. 3+ The types of catalysts will not be discussed further here.

[0040] In this invention, the molar ratio of the total amount of nitric acid (the total amount of nitric acid in the reaction mother liquor and the added nitric acid) to the 2,3-dimethylaniline is preferably (0.95~1.15):1, more preferably 0.95:1, 1.0:1, 1.05:1, 1.1:1 or 1.15:1.

[0041] In this invention, the Fe used is 3+ The mass of the catalyst added is preferably 2 to 5% of the initial catalyst mass, more preferably 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0042] In this invention, the Fe 3+ The molar ratio of the catalyst to the 2,3-dimethylaniline is preferably (0.02~0.03):1, more preferably 0.02:1, 0.022:1, 0.024:1, 0.026:1, 0.028:1 or 0.03:1.

[0043] In this invention, the first heat preservation process preferably refers to the first heat preservation process of the above technical solution, and will not be described again here.

[0044] In this invention, the mass percentage concentration of the hydrogen peroxide is preferably the mass percentage concentration described in the above technical solution, and will not be repeated here.

[0045] In this invention, the molar ratio of H2O2 to 2,3-dimethylaniline in the hydrogen peroxide is preferably (1.8~2.0):1, more preferably 1.8:1, 1.9:1 or 2.0:1.

[0046] In this invention, the process of adding hydrogen peroxide is preferably the same as that described in the above technical solution, and will not be repeated here.

[0047] In this invention, the second heat preservation process preferably refers to the second heat preservation process of the above-described technical solution, and will not be described in detail here.

[0048] After the second heat preservation, the present invention preferably includes hot filtration. The present invention does not have any special limitations on the hot filtration process, and any process known to those skilled in the art can be used.

[0049] In this invention, the hot filtration method can effectively maintain the temperature of the reaction mother liquor and reduce energy consumption.

[0050] After obtaining the first set of reaction mother liquor and filter cake, the present invention preferably refers to the above-described technical solution to perform post-processing on the filter cake by sequentially performing alkaline washing, first water washing, second water washing, and drying, which will not be elaborated here. The present invention preferably refers to the first set of processes described in the above-described technical solution to use the first set of reaction mother liquor, which will not be elaborated here.

[0051] In this invention, by alkali washing the filter cake, the process of synthesizing poly2,3-dimethylaniline, which involves washing with a large amount of water and then drying, is reduced, which significantly reduces the difficulty of the post-processing and also reduces the amount of wastewater discharged.

[0052] In this invention, when the COD content in the reaction mother liquor obtained after the application is greater than 29000 mg / L, the molar ratio of H2O2 in the hydrogen peroxide to 2,3-dimethylaniline is preferably (2.5~3.0):1, more preferably 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0:1, where n is a positive integer. Other processes refer to the above technical solution and will not be repeated here. In this invention, when the application is performed for the 5nth time, the COD content in the reaction mother liquor obtained after the application is greater than 29000 mg / L.

[0053] In this invention, when the number of times the reaction is applied is 5n, the yield of poly(2,3-dimethylaniline) is 102-105%, and the COD content in the reaction mother liquor after application is reduced to 6000-8000 mg / L.

[0054] In this invention, when the COD content in the reaction mother liquor obtained after the overlay is less than 29000 mg / L, the molar ratio of H2O2 in the hydrogen peroxide to 2,3-dimethylaniline is preferably (1.8~2.0):1, more preferably 1.8:1, 1.9:1, or 2.0:1. In this invention, when the overlay is not the 5nth time, the COD content in the reaction mother liquor obtained after the overlay is less than 29000 mg / L.

[0055] In this invention, when the number of times the compound is applied is not the 5nth time, the yield of poly2,3-dimethylaniline is 97-99%.

[0056] In this invention, after four cycles of using the mother liquor, the COD content in the mother liquor rises to 29,000-32,000 mg / L, which is relatively high. Without further control measures, the resulting product is brown. With more cycles, the product exhibits discoloration and fragmentation during electrochemical testing, indicating that it contains low-polymerization-degree or unreacted 2,3-dimethylaniline salts. Even after washing and drying the product with a large amount of water, discoloration and fragmentation still occur during electrochemical testing, indicating that the salts are essentially impossible to remove. Therefore, this invention, while ensuring product quality, limits the number of cycles of untreated mother liquor use to four, followed by one more treatment, then four more cycles, and then one more treatment. In the 5nth cycle, increasing the amount of hydrogen peroxide prolongs the oxidative polymerization time of 2,3-dimethylaniline, allowing for effective utilization of the low-polymerization-degree 2,3-dimethylaniline in the mother liquor.

[0057] In this invention, by controlling the COD content in the reaction mother liquor, the sustainable reuse of the reaction mother liquor is ensured, greatly saving the wastewater treatment cost, and recovering the low-polymerization degree 2,3-dimethylaniline in the reaction mother liquor, creating significant economic value.

[0058] In this invention, the green preparation method can be applied an unlimited number of times.

[0059] In this invention, the green preparation method described herein uses Fe 3+ Hydrogen peroxide and nitric acid form an oxidizing system; under acidic conditions, Fe... 3+ It has an oxidizing effect and can oxidize and polymerize 2,3-dimethylaniline, while producing Fe. 2+ The generated Fe 2+ The catalytic oxidation of hydrogen peroxide to polymerize 2,3-dimethylaniline continues, converting hydrogen peroxide into water. Water is a clean energy source. After oxidation, Fe... 2+ Converted to Fe 3+ Part of Fe 3+Direct oxidative polymerization of 2,3-dimethylaniline, with some Fe 3+ By participating in the hydrogen peroxide-Fenton oxidation system, the oxidative degradation effect of hydrogen peroxide is avoided, thus improving the yield of poly(2,3-dimethylaniline). Furthermore, the above-mentioned recycling process results in no waste acid discharge. This invention develops a green production process with no waste acid discharge by recycling the reaction mother liquor, which also avoids the phenomenon of continuous increase in COD during the recycling process, leading to a decline in product quality. In addition, the recycling of the reaction mother liquor also recovers low-polymerization-degree 2,3-dimethylaniline, thereby improving the yield of poly(2,3-dimethylaniline).

[0060] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0061] Example 1 After adding 469 g of 4.02% nitric acid solution (0.29 mol of HNO3) to the reaction flask, the mixture was heated to 40 °C and stabilized under stirring at 200 rpm. Then, 33 g of 0.27 mol of 2,3-dimethylaniline (HNO3 to 2,3-dimethylaniline molar ratio 1.07:1) was added dropwise until completely dissolved. Finally, 1.78 g of 0.0074 mol of ferric nitrate was added, and the mixture was kept at 42 °C. The mixture was heated for 30 minutes, and then 66 g of 27.5% hydrogen peroxide (0.53 mol of H2O2, with a molar ratio of H2O2 to 2,3-dimethylaniline of 1.96:1) was slowly added dropwise over 1.5 hours. After the addition was completed, the mixture was kept at 45°C for 3 hours. After the reaction was completed, the reaction solution was filtered while hot to obtain 63.3 g of the first filter cake and 506.48 g of the first reaction mother liquor (acidity of 1.98%, calculated as nitric acid). 35.7g of the first reaction mother liquor was neutralized to obtain the first-1 alkaline wash water; The first filter cake was mixed with 69.3g of a 3% sodium hydroxide solution and stirred for 0.5h at room temperature and 250rpm. After filtration, 61.4g of the first filter cake and 71.2g of the first alkaline wash water were obtained. The first-1 alkaline wash water and the first-2 alkaline wash water are mixed, neutralized with ammonia, concentrated, crystallized and filtered to obtain nitrogen fertilizer; The first and second filter cakes were added to 66g of water for a first wash (at room temperature, stirred at 250rpm for 0.5h), filtered, and 60.8g of the first and third filter cakes and 66.6g of the first wash water were obtained. The first to third filter cakes were added to 66g of water for a second wash (at room temperature, stirred at 250rpm for 0.5h), and filtered to obtain 60.5g of the first to fourth filter cakes and 66.3g of the first to second wash water; The filter cakes from the first to fourth stages were vacuum dried (60°C, 15 kPa, 8 h) to obtain 29.8 g of poly(2,3-dimethylaniline) (yield 90.3%). First time using: 470.78g of the first reaction mother liquor was added to a clean 1L reactor, followed by 9.5g of 97.6% nitric acid. The mixture was heated to 40℃ at 200rpm, and 33g of 2,3-dimethylaniline (0.27mol) was added dropwise until the solid was completely dissolved. Then, 0.08g of ferric nitrate (0.00033mol) was added, and the mixture was stirred at 44℃ for 0.5h. 66g of 27.5% hydrogen peroxide (0.53mol of H2O2) was slowly added dropwise over 1.5h, and the mixture was stirred at 46℃ for 3h. The reaction mixture was filtered while hot to obtain 67.8g of the second-first filter cake and 511.56g of the second reaction mother liquor (acidity 1.93%, based on nitric acid). 40.78g of the first reaction mother liquor was neutralized to obtain the second-first alkaline wash water; The second-first filter cake was mixed with 68.7g of a 3.06% sodium hydroxide solution and stirred for 0.5h at room temperature and 250rpm. After filtration, 65.5g of the second-second filter cake and 71.0g of the second-second alkaline wash water were obtained. The 2-1 alkaline wash water and the 2-2 alkaline wash water are mixed, neutralized with ammonia, concentrated, crystallized and filtered to obtain nitrogen fertilizer; The second-2 filter cake was added to 66g of water for a first wash (room temperature, stirring at 250rpm for 0.5h), and filtered to obtain 64.8g of the second-3 filter cake and 66.7g of the second-1 wash water; The second and third filter cakes were added to 66g of water for a second wash (at room temperature, stirred at 250rpm for 0.5h), and filtered to obtain 63.9g of the second and fourth filter cakes and 66.9g of the second and second wash water; The second to fourth filter cakes were vacuum dried (60°C, 15 kPa, 8 h) to obtain 32.4 g of poly(2,3-dimethylaniline) (yield 98.2%). Second application ~ Fourth application: The processes for the second to fourth applications are the same as those for the first application. The mass, yield, and COD of the obtained poly2,3-dimethylaniline in the reaction mother liquor are shown in Table 1. Fifth application: Add 470.78g of the fifth reaction mother liquor (acidity 1.91%) obtained from the fourth reuse to a clean 1L reactor, then add 9.88g of 97.6% nitric acid. Heat to 40℃ at 200rpm, add 33g of 2,3-dimethylaniline (0.27mol) dropwise until the solid is completely dissolved, then add 0.08g of ferric nitrate (0.00033mol). Keep the mixture at 42℃ and stir for 0.5h, then slowly add 90.9g of 27.5% hydrogen peroxide (0.74mol of H2O2) dropwise over 1.5h. Keep the mixture at 46℃ and stir for 3h. Filter the reaction solution while hot to obtain 72.4g of the 6-1 filter cake and 532.96g of the sixth reaction mother liquor (acidity 1.84%, based on nitric acid). Neutralize 62.18g of the mother liquor from the sixth reaction to obtain the 6-1 alkaline washing water; The 6-1 filter cake was mixed with 69.5g of a 3.88% sodium hydroxide solution and stirred for 0.5h at room temperature and 250rpm. After filtration, 70.4g of the 6-2 filter cake and 71.5g of the 6-2 alkaline wash water were obtained. The 6-1 alkaline wash water and the 6-2 alkaline wash water are mixed, neutralized with ammonia, concentrated, crystallized and filtered to obtain nitrogen fertilizer; The 6-2 filter cake was added to 66g of water for a first wash (room temperature, stirring at 250rpm for 0.5h), and filtered to obtain 70.2g of the 6-3 filter cake and 66.2g of the 6-1 wash water; The 6-3 filter cake was added to 66g of water for a second wash (at room temperature, stirred at 250rpm for 0.5h), and filtered to obtain 69.5g of the 6-4 filter cake and 66.7g of the 6-2 wash water; The filter cakes from the 6th to 4th batches were vacuum dried (60°C, 15 kPa, 8 h) to obtain 32.4 g of poly(2,3-dimethylaniline) (yield 102.7%). Sixth to ninth time using this technique: The process of the sixth to ninth application is the same as the process of the first application. The mass, yield and COD of the obtained poly(2,3-dimethylaniline) and the reaction mother liquor are shown in Table 1. Tenth time using: Following the process of the fifth application, the mass, yield and COD of the obtained poly(2,3-dimethylaniline) in the reaction mother liquor are shown in Table 1. Eleventh application to fourteenth application: The processes of the eleventh to fourteenth applications refer to the process of the first application. The mass, yield and COD of the obtained poly(2,3-dimethylaniline) in the reaction mother liquor are shown in Table 1. The fifteenth application: Following the process of the fifth application, the mass, yield, and COD of the obtained poly(2,3-dimethylaniline) in the reaction mother liquor are shown in Table 1.

[0062] Comparative Example 1 Referring to Example 1, the difference is that the process of the first application is still followed for the fifth application, and the application is repeated 7 times. The mass, yield and COD of poly(2,3-dimethylaniline) obtained after the 7th application are shown in Table 1.

[0063] Comparative Example 2 Referring to Example 1, the difference is that the process of first to fifteenth application is not performed, and the amount of hydrogen peroxide used is 90.9g. The mass, yield and COD of the obtained poly(2,3-dimethylaniline) in the reaction mother liquor are shown in Table 1.

[0064] Table 1. Mass, yield, and COD of poly(2,3-dimethylaniline) obtained from different number of applications in Example 1, Comparative Examples 1 and 2, respectively.

[0065] As can be seen from the settings of Comparative Example 2, due to the low COD content (5000~10000 mg / L) in the initial reaction mother liquor, the excessive hydrogen peroxide caused the reaction product to be over-oxidized and degraded, resulting in a significant decrease in the yield of poly(2,3-dimethylaniline) and a coked and hardened product.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A green preparation method for poly2,3-dimethylaniline, characterized in that, Includes the following steps: First application: After mixing the reaction mother liquor for preparing poly(2,3-dimethylaniline), nitric acid solution, and 2,3-dimethylaniline, Fe was added. 3+ The catalyst is subjected to a first heat treatment, hydrogen peroxide is added, and a second heat treatment is performed to obtain the first set of reaction mother liquor and filter cake. The filter cake is then post-processed to obtain the poly(2,3-dimethylaniline); The first set of reaction mother liquor is recycled according to the above process; In the above-mentioned cyclic reuse process, when the COD content in the reaction mother liquor obtained after reuse is greater than 29000 mg / L, the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide is increased based on the molar ratio of H2O2 to 2,3-dimethylaniline in hydrogen peroxide during the first reuse process.

2. The green preparation method as described in claim 1, characterized in that, When the COD content in the reaction mother liquor obtained after application is greater than 29000 mg / L, the molar ratio of H2O2 in the hydrogen peroxide to 2,3-dimethylaniline is (2.5~3.0):1; When the COD content in the reaction mother liquor obtained after application is less than 29000 mg / L, the molar ratio of H2O2 in the hydrogen peroxide to 2,3-dimethylaniline is (1.8~2.0):

1.

3. The green preparation method as described in claim 2, characterized in that, When the application is performed for the 5nth time, the COD content in the reaction mother liquor obtained after the application is greater than 29000 mg / L; When the number of times the reaction is applied is not the 5nth time, the COD content in the resulting mother liquor is less than 29000 mg / L.

4. The green preparation method as described in claim 1, characterized in that, The mother liquor for preparing poly2,3-dimethylaniline includes nitric acid and Fe. 3+ Catalyst, water, and 2,3-dimethylaniline with different degrees of polymerization; The mass percentage concentration of nitric acid in the reaction mother liquor for preparing poly(2,3-dimethylaniline) is 1.9-2.3%.

5. The green preparation method as described in claim 1 or 4, characterized in that, The method for preparing the reaction mother liquor for preparing poly-2,3-dimethylaniline includes the following steps: Mix nitric acid solution and 2,3-dimethylaniline until completely dissolved, then add Fe. 3+ The catalyst was subjected to a first heat treatment, hydrogen peroxide was added, and a second heat treatment was performed. The mixture was then filtered while hot to obtain a filter cake and the reaction mother liquor for preparing poly(2,3-dimethylaniline). The nitric acid solution used in the preparation of the reaction mother liquor for the preparation of poly(2,3-dimethylaniline) has a mass percentage concentration of 3% to 4%.

6. The green preparation method as described in claim 5, characterized in that, In the process of preparing the reaction mother liquor for the preparation of poly-2,3-dimethylaniline: the Fe 3+ The molar ratio of catalyst to 2,3-dimethylaniline is (0.02~0.03):1; The hydrogen peroxide has a mass percentage concentration of 25% to 30%, and the molar ratio of H2O2 to 2,3-dimethylaniline in the hydrogen peroxide is (1.8 to 2.3):

1.

7. The green preparation method as described in claim 1 or 4, characterized in that, The mass percentage concentration of the nitric acid solution is 97-98%; The Fe 3+ The catalyst includes one or more of ferric chloride, ferric nitrate and ferric sulfate.

8. The green preparation method as described in claim 1, characterized in that, The Fe used 3+ The mass of catalyst added is 2-5% of the initial catalyst mass; The Fe 3+ The molar ratio of the catalyst to the 2,3-dimethylaniline is (0.02~0.03):

1.

9. The green preparation method according to claim 1, characterized in that, The mixing temperature is 40~50℃; The first insulation temperature is 40~50℃, and the time is 0.5~1h; The second insulation temperature is 40~50℃, and the time is 2~4h.

10. The green preparation method according to claim 1, characterized in that, After the second heat preservation is completed, the filter cake is further subjected to alkali washing, first water washing, second water washing and drying in sequence; The mass concentration of the alkaline solution is 2-5%; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution. The alkaline wash, the first water wash, and the second water wash are at room temperature, with independent rotation speeds of 200~300 rpm and independent time of 0.5~1 h; The drying process is vacuum drying, with a temperature of 60-65°C, a vacuum degree of 10-20 kPa, and a time of 6-10 hours.

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