A method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane

Abstract

The application discloses a preparation method of 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane, and relates to the technical fields of methanol purification and electronic chemicals. Bisphenol AF is used as a starting material, dichloromethane is used as a nitration solvent, concentrated nitric acid is added dropwise at low temperature in stages for nitration reaction, and high-purity dinitro intermediates are obtained through water washing, alkali washing, drying and ethanol recrystallization; then the dinitro intermediates are dissolved in ethyl acetate, and high-pressure hydrogen reduction is carried out under the catalysis of palladium-carbon; after the hydrogenation liquid is separated from the catalyst, petroleum ether is compounded to crystallize, and the target product 6FAP is obtained through low-temperature drying. The product prepared by the method has low impurity content, the process condition is mild, the post-treatment is simple, the method is suitable for industrialized continuous production, and the prepared 6FAP can be directly used in the fields of high-end materials such as high-performance polyimide and electronic packaging resin.

Description

Technical Field

[0001] This invention relates to the fields of methanol purification and electronic chemicals, and in particular to a method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. Background Technology

[0002] 2,2-Bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP) is an important fluorinated aromatic diamine monomer. Its molecule contains hexafluoroisopropyl (–C(CF3)2–), amino, and phenolic hydroxyl functional groups, exhibiting excellent heat resistance, low dielectric constant, low moisture absorption, and high chemical stability. Fluorinated polyimides prepared using 6FAP as the diamine monomer possess excellent high-temperature resistance, dimensional stability, transparency, and dielectric properties, and are widely used in flexible display substrates, integrated circuit packaging, aerospace composite materials, optoelectronic devices, 5G communications, and microelectronic insulating materials. With the development of the high-end electronic information industry, the demand for high-purity, low-metallic-impurity, and high-yield 6FAP products is constantly increasing. Therefore, developing a 6FAP preparation process suitable for industrial production, with stable product quality, and environmental friendliness is of great significance.

[0003] Currently, the publicly disclosed routes for the preparation of 6FAP mainly fall into two categories. One category uses bisphenol AF as a starting material, which undergoes aromatic ring nitration to produce 2,2-bis(3-nitro-4-hydroxyphenyl)hexafluoropropane (6FNP). Subsequently, the nitro group is reduced to an amino group via catalytic hydrogenation or chemical reduction to finally obtain 6FAP. This route has a wide availability of raw materials, fewer reaction steps, and a relatively high overall yield, making it the most widely used industrial route both domestically and internationally. The other category uses o-aminophenol as a starting material, preparing 6FAP through steps such as acetylation protection, condensation with hexafluoroacetone or its hydrate, and deprotection. This route avoids the nitration and catalytic hydrogenation processes, but it involves more reaction steps, requires higher-quality raw materials and equipment, has a more complex overall process, and relatively higher industrialization costs.

[0004] For example, Chinese patent CN112707827B discloses a method for preparing 6FAP from o-aminophenol as raw material through acetylation, condensation and deacetylation protection. This method avoids nitration and high-pressure hydrogenation reactions, improving process safety and environmental protection. However, it has problems such as a long reaction route, many intermediate preparation steps, high requirements for equipment corrosion resistance and high overall production cost.

[0005] In addition, Chinese patent CN101643427B discloses a method for preparing 6FAP by catalytic reduction of bisphenol AF nitration product as raw material. It adopts a two-step nitration-hydrogenation method, which has the advantages of mature process and high product purity. However, catalytic hydrogenation requires the use of precious metal catalysts and is carried out under pressurized hydrogen conditions, which puts high requirements on reaction equipment, safety management and catalyst recovery.

[0006] Furthermore, published patents CN101492381A, CN101481318A, and CN105218387A all report methods for preparing 6FAP using bisphenol AF as a starting material, obtaining a dinitro intermediate through nitration, and then using zinc powder reduction, Pd / C catalytic hydrogenation, or other reduction systems. While the above processes are generally mature and can yield high-purity products, they commonly suffer from problems such as intense exothermic nitration reactions, numerous side reactions, complex separation and purification steps for the nitro intermediate, high catalyst costs, and a significant burden of waste acid treatment. Simultaneously, the hydrogenation process involves high-pressure hydrogen operation; improper control of temperature, pressure, and feed can easily affect product yield and color, increasing the difficulty of industrial scale-up.

[0007] On the other hand, bisphenol AF molecules contain two phenolic hydroxyl groups and a hexafluoroisopropyl group. During nitration, the activation of the hydroxyl groups leads to strong aromatic ring repositioning selectivity. However, if the nitric acid dropping rate is not properly controlled, the local temperature is too high, or the acid concentration fluctuates significantly, side reactions such as overnitration, oxidation, and resinification can easily occur, resulting in darker intermediate colors, increased impurities, decreased yield, and increased difficulty in subsequent purification. Most existing literature uses continuous nitric acid dropping or ordinary temperature control methods, and research on the dropping rhythm, system color changes, and reaction endpoint control is relatively insufficient. In industrial production, the quality fluctuations between different batches of products are still quite significant.

[0008] Furthermore, in the catalytic hydrogenation stage, existing technologies typically employ catalytic systems such as Pd / C and Raney nickel to complete the nitro reduction. Among these, Pd / C catalysts have the advantages of high activity and good selectivity. However, the catalyst dispersion state, water content, hydrogen pressure, reaction temperature, and holding time all directly affect the catalytic efficiency and product purity. If the catalyst filtration is incomplete or the subsequent crystallization process is not properly controlled, problems such as catalyst residue, high product color, and uneven crystal size may occur, which is detrimental to meeting the stringent requirements for metal impurities, color, and purity of electronic-grade polyimide monomers.

[0009] In summary, while existing 6FAP preparation technologies can achieve industrial-scale production, they still suffer from several drawbacks, including intense exothermic nitration, numerous side reactions, insufficient precision in controlling the reaction endpoint, high safety requirements in the catalytic hydrogenation process, cumbersome product purification steps, insufficient batch stability, and limited potential for further improvement in product purity and yield. Therefore, developing a method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane that achieves precise control of the nitration process, good intermediate purification, high selectivity in catalytic hydrogenation, high product purity, stable yield, and suitability for continuous industrial production has significant engineering application value and industrialization implications. Summary of the Invention

[0010] Based on the problems raised in the background art, the present invention proposes a method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane.

[0011] The technical solution is as follows:

[0012] A method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane includes the following steps:

[0013] (1) Low-temperature segmented nitration: Based on 100 parts by mass of bisphenol AF, add 350-360 parts by mass of dichloromethane and stir to form a white suspension. Control the temperature of the system at 10-15℃ and add 72-73 parts by mass of concentrated nitric acid in segments. Stop adding the feed after each drop of 5% of the total nitric acid mass, keep warm and stir for 10 minutes, and then continue adding the feed. After all the nitric acid has been added, raise the temperature to 20-25℃ and keep warm for nitration. HPLC monitoring is used until the bisphenol AF feedstock is completely consumed.

[0014] (2) Purification of the dinitro intermediate: The nitration reaction solution was first washed and separated with 590-600 parts by mass of pure water. The organic phase was washed twice with 590-600 parts by mass of saturated sodium bicarbonate aqueous solution, and then washed with 590-600 parts by mass of pure water until the pH of the aqueous phase was 6.8-7.2. The organic phase was dried and filtered with anhydrous sodium sulfate, and dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrated product. 178-180 parts by mass of anhydrous ethanol was added to the crude product, heated to dissolve and recrystallize, cooled, filtered and dried to obtain an egg-yellow dinitrobisphenol AF intermediate.

[0015] (3) High-pressure catalytic hydrogenation reduction: Based on 100 parts by mass of dinitrobisphenol AF intermediate, 325-330 parts by mass of ethyl acetate and 1.28-1.32 parts by mass of palladium catalyst on carbon were added; the air inside the closed high-pressure reactor was replaced three times with high-purity hydrogen, and hydrogen was added until the pressure inside the reactor was 2.8-3.2 MPa. The reactor was stirred and heated to an internal temperature of 78-82℃. After the system stopped absorbing hydrogen, the reaction was continued for 2 hours under the same temperature and pressure. HPLC detection showed no nitro intermediate residue; the palladium catalyst on carbon was removed by hot filtration to obtain a light yellow hydrogenation clear filtrate.

[0016] (4) Refining 6FAP by crystallization with compound solvent: Heat the hydrogenated filtrate to reflux, add 32-33 parts by mass of petroleum ether at a uniform rate and mix evenly; slowly cool to 20-25℃ and let it stand for crystallization for 2 hours, filter and collect the solid; place the solid in a vacuum oven at 50-60℃ and dry to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder.

[0017] As a preferred embodiment of the present invention, in step (1), the highest temperature of the entire system during the dripping process does not exceed 15°C, and the nitrification time is 2.5 to 3.5 hours.

[0018] As a preferred embodiment of the present invention, in the recrystallization operation of step (2), anhydrous ethanol is used only once for recrystallization, the recrystallization cooling endpoint temperature is 18-22°C, the drying temperature is 45-55°C, and the HPLC purity of the obtained dinitro intermediate is ≥99.0%.

[0019] As a preferred embodiment of the present invention, the ambient temperature of the water washing and alkali washing separation operation in step (2) is maintained at 20-28°C, the amount of anhydrous sodium sulfate added is 12%-15% of the crude nitrate quality, and the drying and standing time is not less than 30 minutes.

[0020] As a preferred embodiment of the present invention, the method for preparing the palladium-on-carbon catalyst in step (3) is as follows:

[0021] The first step was to prepare a boron-synergistic complex mother liquor: using 100 parts by mass of hexamethylenediaminetetramethylenephosphonic acid as a reference, 11.0-15.0 parts of furan-2-boric acid and 360-430 parts of deionized water were added. The pH of the system was adjusted to 7.2-8.2 with sodium hydroxide, and the reaction was stirred at 50-60℃ for 2.0-3.0 h. The furan heterocyclic modified boron-synergistic amine phosphonic acid complex mother liquor was prepared by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-boric acid boron atoms.

[0022] The second step is to prepare the palladium-on-carbon catalyst: Based on 100 parts by mass of pretreated dried coconut shell activated carbon, 8.30-8.40 parts of palladium chloride are dissolved in 2.0-3.0 parts of concentrated hydrochloric acid by gentle heating. 3.2-4.0 parts of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor are added, and 190-210 parts of deionized water are added for dilution. This solution is then added dropwise to an activated carbon slurry prepared with 680-720 parts of deionized water and impregnated at room temperature for 1.5-2.5 hours. Sodium hydroxide is added dropwise at 38-42℃ to adjust the pH of the system to 9.0-9.5. The system is aged for 1.0-2.0 hours, then heated to 55-60℃, and 7.5-8.2 parts of sodium formate are added for constant-temperature reduction for 2.0-3.0 hours. After the reaction, the system is washed with hot deionized water at 75-80℃ until no chloride ions remain. The mixture is then filtered and dried to obtain the palladium-on-carbon catalyst.

[0023] As a preferred embodiment of the present invention, in step (3), the stirring speed of the high-pressure catalytic hydrogenation reduction is controlled at 300-400 r / min, the hydrogen replacement is maintained at 0.2 MPa for 5 min and then the pressure is released. After the three replacements are completed, the pressure is increased to the target hydrogenation pressure.

[0024] As a preferred embodiment of the present invention, the petroleum ether used in step (4) has a boiling range of 60-90°C, the crystallization cooling rate is controlled at 1°C / min, and the crystallization process is continuously stirred at low speed to avoid the agglomeration of fine crystals and the encapsulation of impurities.

[0025] As a preferred embodiment of the present invention, in step (4), the vacuum drying vacuum degree is maintained at -0.06 to -0.09 MPa, the drying time is 6 to 8 hours, and the moisture content of the finished product after drying is ≤0.05 wt%.

[0026] Reaction mechanism:

[0027] This invention addresses the technical shortcomings of traditional hexafluoropropane diamine monomer preparation processes, including poor nitration selectivity, susceptibility to overnitration and oxidation side reactions, numerous intermediate impurities, easy generation of hydroxylamine and azo intermediate byproducts during hydrogenation reduction, low product purity, poor catalyst dispersibility, easy deactivation, and insufficient conversion efficiency. It constructs an integrated high-purity 6FAP monomer green preparation system that incorporates low-temperature segmented controllable selective nitration, multi-stage stepwise impurity removal and purification, boron heterocyclic synergistic complexation modification of palladium on carbon catalytic hydrogenation, and gradient crystallization purification using compound solvents. This system systematically solves the industry pain points of low product purity, numerous byproducts, and poor batch stability associated with traditional processes from three dimensions: reaction selectivity, catalytic reduction efficiency, and product purification precision.

[0028] In the nitration stage, dichloromethane was used as an inert dispersion solvent to form a homogeneous suspension of bisphenol AF. A temperature- and concentration-controlled reaction mode was adopted, coupled with segmented intermittent addition of nitric acid in a low-temperature environment, avoiding the problems of excessively high local concentrations and concentrated exothermic reactions caused by traditional single-stage nitric acid addition. By balancing the concentration and temperature of the system through segmented buffering and settling, the directional nitration of the benzene ring at a single site was precisely controlled, effectively suppressing side reactions such as polynitration and oxidative degradation, and significantly improving the reaction selectivity and structural regularity of the dinitrobisphenol AF intermediate. After the reaction, a multi-stage purification system of pure water washing, weak base neutralization, and pure water rinsing was used to thoroughly remove residual nitric acid, acidic byproducts, and salt impurities. Combined with deep dehydration with anhydrous sodium sulfate and single precise recrystallization with anhydrous ethanol, trace isomeric impurities and residual intermediates were removed to obtain a high-purity, low-impurity dinitro intermediate, providing a high-purity precursor for subsequent hydrogenation reduction.

[0029] The hydrogenation reduction stage is the core quality improvement process of this invention, employing a self-developed furan-boron heterocyclic synergistic amine phosphonic acid modified palladium-on-carbon catalyst to replace ordinary commercial palladium-on-carbon catalysts. The catalyst's functional components synergistically construct a highly dispersed, highly active, and highly stable catalytic system: hexamethylenediaminetetramethylenephosphonic acid serves as the main complex framework, possessing multiple coordination chelation sites to stably anchor palladium ions and prevent the aggregation and loss of active components; furan-2-boronic acid provides a rigid boron heterocyclic structure, which can regulate the electron distribution of palladium active sites, optimize the catalyst's adsorption selectivity for nitro hydrogenation, and suppress the formation of intermediate byproducts; coconut shell activated carbon serves as a porous support, providing an ultra-large specific surface area to achieve uniform loading of active components; sodium formate serves as a mild reducing agent, achieving uniform and controllable reduction of palladium components and ensuring a sufficient number and uniform distribution of active sites. The modified palladium-on-carbon catalyst can precisely catalyze the complete reduction of nitro groups to amino groups under mild, high-pressure hydrogenation conditions, effectively avoiding impurities such as hydroxylamine and azo compounds generated during incomplete hydrogenation, achieving efficient and highly selective conversion of dinitro intermediates to the target diamine monomer.

[0030] After the hydrogenation reaction is completed, the solid catalyst is thoroughly removed by precision filtration to avoid catalyst residue contamination of the finished product. Finally, a compound solvent purification system of hot dissolution with ethyl acetate and gradient-induced crystallization with petroleum ether is used. Utilizing the polarity difference between the two solvents, soluble organic impurities and trace amounts of unreacted intermediates are selectively retained. At the same time, the low-speed uniform crystal growth is controlled to prevent crystal agglomeration that encapsulates impurities. Combined with low-temperature vacuum drying to remove trace amounts of solvent and moisture, a high-purity, low-impurity, and structurally stable 6FAP product is finally obtained, which fully meets the usage standards for high-end fluorinated polyimide monomers.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) Improve the selectivity of nitration reaction and reduce the occurrence of side reactions.

[0033] This invention employs a segmented, intermittent dripping of concentrated nitric acid at low temperature (10–15°C), with a stirring buffer stage after each stage of dripping to ensure more uniform exothermic reaction during nitration. This reduces over-nitration and oxidation side reactions caused by excessively high local nitric acid concentrations, thereby improving the regioselectivity and reaction stability of the dinitro intermediate. This control approach helps to obtain 6FNP intermediates with higher purity.

[0034] (2) Improve the purification effect of intermediates and enhance the quality of intermediates.

[0035] This invention employs a purification process combining water washing, saturated sodium bicarbonate washing, neutral water washing, and anhydrous sodium sulfate drying to effectively remove residual nitric acid, acidic byproducts, and inorganic salt impurities from the system. Further removal of trace byproducts is achieved through recrystallization with ethanol, yielding a high-purity dinitrobisphenol AF intermediate, providing a stable raw material basis for subsequent catalytic hydrogenation.

[0036] (3) Improve the conversion efficiency of catalytic hydrogenation reaction

[0037] This invention employs an aqueous Pd / C catalyst to perform catalytic hydrogenation under suitable hydrogen pressure and isothermal conditions. This allows dinitro compounds to be more fully converted into the target diamine compound, reducing the formation of byproducts such as intermediate hydroxylamines, azo compounds, and azo oxides, thereby improving reaction selectivity and product yield. Pd / C catalytic hydrogenation is a mature route for the preparation of aromatic amines, exhibiting high selectivity.

[0038] (4) Reduce product impurity content and improve product purity

[0039] After catalytic hydrogenation, the catalyst is removed by filtration and purified by reflux hot dissolution-petroleum ether induced crystallization. This further removes organic impurities and a small amount of unreacted intermediates, improves the crystallization integrity of the product, and gives the obtained 6FAP high chemical purity, meeting the requirements for the use of high-end fluorinated polyimide monomers. Attached Figure Description

[0040] Figure 1 This is the synthesis route of this method. Detailed Implementation

[0041] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments.

[0042] Example 1

[0043] 1. Low-temperature staged nitrification

[0044] Using 100 kg of bisphenol AF as a reference, 350 kg of dichloromethane was added and stirred to form a white suspension. The system temperature was controlled at 10 °C, and 72 kg of concentrated nitric acid was added dropwise in stages. The addition was stopped after each drop of 5% of the total nitric acid mass was added, and the mixture was kept warm and stirred for 10 min before continuing the addition. After all the nitric acid was added, the temperature was raised to 20 °C and kept warm for nitration for 2.5 h. HPLC monitoring was performed until the bisphenol AF feedstock was completely consumed. The highest temperature of the system during the entire addition process did not exceed 15 °C.

[0045] 2. Purification of dinitro intermediates

[0046] The nitration reaction solution was first washed and separated with 590 kg of pure water. The temperature during the water washing and alkali washing separation was maintained at 20°C. The organic phase was washed twice with 590 kg of saturated sodium bicarbonate aqueous solution, and then washed with 590 kg of pure water until the pH of the aqueous phase was 6.8. The organic phase was dried and filtered with anhydrous sodium sulfate, with the amount of anhydrous sodium sulfate added being 12% of the crude nitrate product. The drying and standing time was not less than 30 min. Dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrate product. 178 kg of anhydrous ethanol was added to the crude product and heated to dissolve and recrystallize. Anhydrous ethanol was used only once for recrystallization. The recrystallization endpoint temperature was 18°C. After cooling and filtration, the product was dried at 45°C to obtain an egg-yellow dinitrobisphenol AF intermediate. The HPLC purity of the obtained dinitro intermediate was ≥99.0%.

[0047] 3. High-pressure catalytic hydrogenation reduction

[0048] Based on 100 kg of dinitrobisphenol AF intermediate, 325 kg of ethyl acetate and 1.28 kg of palladium on carbon catalyst were added. The air inside the sealed high-pressure reactor was replaced three times with high-purity hydrogen. Each hydrogen replacement was maintained at 0.2 MPa for 5 min before depressurization. After the three replacements, hydrogen was added to bring the internal pressure to 2.8 MPa. The mixture was stirred and heated to an internal temperature of 78 °C. The stirring speed of the hydrogenation reaction was controlled at 300 r / min. After the system stopped absorbing hydrogen, the temperature and pressure were maintained for 2 h. HPLC analysis showed no residual nitro intermediate. The palladium on carbon catalyst was removed by hot filtration, yielding a light yellow clear hydrogenated filtrate.

[0049] The palladium-on-carbon catalyst used in this embodiment was prepared using the following method:

[0050] The first step was to prepare the boron-synergistic complex mother liquor: using 100 kg hexamethylenediaminetetramethylenephosphonic acid as a reference, 11.0 kg of furan-2-boric acid and 360 kg of deionized water were added. The pH of the system was adjusted to 7.2 with sodium hydroxide, and the reaction was carried out at 50 °C for 2.0 h with stirring. The furan heterocyclic modified boron-synergistic aminephosphonic acid complex mother liquor was obtained by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-boric acid boron atoms.

[0051] The second step is to prepare the palladium-on-carbon catalyst: Based on 100 kg of pretreated dried coconut shell activated carbon, 8.30 kg of palladium chloride was dissolved in 2.0 kg of concentrated hydrochloric acid by gentle heating. 3.2 kg of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor was added, and after dilution with 190 kg of deionized water, it was added dropwise to the activated carbon slurry prepared with 680 kg of deionized water and impregnated at room temperature for 1.5 h. The pH of the system was adjusted to 9.0 by adding sodium hydroxide dropwise at 38 °C, and the mixture was aged for 1.0 h. Then, the temperature was raised to 55 °C, and 7.5 kg of sodium formate was added for constant temperature reduction for 2.0 h. After the reaction was completed, the system was washed with hot deionized water at 75 °C until no chloride ions remained. The mixture was then filtered and dried to obtain the palladium-on-carbon catalyst.

[0052] 4. Refining 6FAP product by crystallization with compound solvent

[0053] The hydrogenated filtrate was heated to reflux, and 32 kg of petroleum ether with a boiling range of 60–90 °C was added at a uniform rate and mixed thoroughly. The mixture was then slowly cooled to allow crystallization to occur at a rate of 1 °C / min. During the crystallization process, the mixture was continuously stirred at a low speed to prevent small crystals from agglomerating and encapsulating impurities. The mixture was then cooled to 20 °C and allowed to stand for 2 hours to allow crystallization to occur. The solid was then collected by filtration. The solid was then placed in a vacuum oven and dried at a vacuum level of -0.06 MPa for 6 hours at a temperature of 50 °C to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder. The moisture content of the dried product was ≤0.05 wt%.

[0054] Example 2

[0055] 1. Low-temperature staged nitrification

[0056] Using 100 kg of bisphenol AF as a reference, 355 kg of dichloromethane was added and stirred to form a white suspension. The system temperature was controlled at 12°C, and 72.5 kg of concentrated nitric acid was added dropwise in stages. The addition was stopped after each drop of 5% of the total nitric acid mass was added, and the mixture was kept at the temperature and stirred for 10 min before continuing the addition. After all the nitric acid was added, the temperature was raised to 22°C and kept at the temperature for nitration for 3.0 h. HPLC monitoring was performed until the bisphenol AF feedstock was completely consumed. The highest temperature of the system during the entire addition process did not exceed 15°C.

[0057] 2. Purification of dinitro intermediates

[0058] The nitration reaction solution was first washed and separated with 595 kg of pure water. The washing and alkali washing separation were carried out at an ambient temperature of 24°C. The organic phase was washed twice with 595 kg of saturated sodium bicarbonate aqueous solution, and then washed with 595 kg of pure water until the pH of the aqueous phase was 7.0. The organic phase was dried and filtered with anhydrous sodium sulfate, with the amount of anhydrous sodium sulfate added being 13% of the crude nitrate product. The drying and standing time was not less than 30 min. Dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrate product. 179 kg of anhydrous ethanol was added to the crude product and heated to dissolve and recrystallize. Anhydrous ethanol was used only once for recrystallization. The recrystallization endpoint temperature was 20°C. After cooling and filtration, the product was dried at 50°C to obtain an egg-yellow dinitrobisphenol AF intermediate. The HPLC purity of the obtained dinitro intermediate was ≥99.0%.

[0059] 3. High-pressure catalytic hydrogenation reduction

[0060] Based on 100 kg of dinitrobisphenol AF intermediate, 328 kg of ethyl acetate and 1.30 kg of palladium on carbon catalyst were added. The air inside the sealed high-pressure reactor was replaced three times with high-purity hydrogen. Each replacement was maintained at 0.2 MPa for 5 min before being depressurized. After the three replacements, hydrogen was added to bring the internal pressure to 3.0 MPa. The mixture was stirred and heated to an internal temperature of 80 °C. The stirring speed of the hydrogenation reaction was controlled at 350 r / min. After the system stopped absorbing hydrogen, the reaction was maintained at the same temperature and pressure for 2 h. HPLC analysis showed no residual nitro intermediate. The palladium on carbon catalyst was removed by hot filtration, yielding a light yellow clear hydrogenated filtrate.

[0061] The palladium-on-carbon catalyst used in this embodiment was prepared using the following method:

[0062] The first step was to prepare the boron-synergistic complex mother liquor: using 100 kg of hexamethylenediaminetetramethylenephosphonic acid as a reference, 13.0 kg of furan-2-boric acid and 390 kg of deionized water were added. The pH of the system was adjusted to 7.8 with sodium hydroxide, and the reaction was stirred at 55 °C for 2.5 h. The furan heterocyclic modified boron-synergistic amine phosphonic acid complex mother liquor was obtained by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-boric acid boron atoms.

[0063] The second step is to prepare the palladium-on-carbon catalyst: Based on 100 kg of pretreated dried coconut shell activated carbon, 8.35 kg of palladium chloride was dissolved in 2.5 kg of concentrated hydrochloric acid by gentle heating. 3.6 kg of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor was added, and after dilution with 200 kg of deionized water, it was added dropwise to the activated carbon slurry prepared with 700 kg of deionized water and impregnated at room temperature for 2.0 h. Sodium hydroxide was added dropwise at 40 °C to adjust the pH of the system to 9.2, and the mixture was aged for 1.5 h. The temperature was then raised to 58 °C, and 7.8 kg of sodium formate was added for constant temperature reduction for 2.5 h. After the reaction was completed, the system was washed with hot deionized water at 78 °C until no chloride ions remained. The mixture was then filtered and dried to obtain the palladium-on-carbon catalyst.

[0064] 4. Refining 6FAP product by crystallization with compound solvent

[0065] The hydrogenated filtrate was heated to reflux, and 32.5 kg of petroleum ether with a boiling range of 60–90 °C was added at a uniform rate and mixed thoroughly. The mixture was then slowly cooled to allow crystallization to occur at a rate of 1 °C / min. During the crystallization process, the mixture was continuously stirred at a low speed to prevent small crystals from agglomerating and encapsulating impurities. The mixture was cooled to 22 °C and allowed to stand for 2 hours to allow crystallization to occur. The solid was then collected by filtration. The solid was placed in a vacuum oven and dried at a vacuum level of -0.07 MPa for 7 hours at a temperature of 55 °C to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder. The moisture content of the dried product was ≤0.05 wt%.

[0066] Example 3

[0067] 1. Low-temperature staged nitrification

[0068] Using 100 kg of bisphenol AF as a reference, 358 kg of dichloromethane was added and stirred to form a white suspension. The system temperature was controlled at 14 °C, and 72.8 kg of concentrated nitric acid was added dropwise in stages. The addition was stopped after each drop of 5% of the total nitric acid mass was added, and the mixture was kept at the temperature and stirred for 10 min before continuing the addition. After all the nitric acid was added, the temperature was raised to 24 °C and kept at the temperature for nitration for 3.2 h. HPLC monitoring was performed until the bisphenol AF feedstock was completely consumed. The highest temperature of the system during the entire addition process did not exceed 15 °C.

[0069] 2. Purification of dinitro intermediates

[0070] The nitration reaction solution was first washed and separated with 598 kg of pure water. The temperature during the water washing and alkali washing separation was maintained at 26°C. The organic phase was washed twice with 598 kg of saturated sodium bicarbonate aqueous solution, and then washed with 598 kg of pure water until the pH of the aqueous phase was 7.1. The organic phase was dried and filtered with anhydrous sodium sulfate, with the amount of anhydrous sodium sulfate added being 14% of the crude nitrate product. The drying and standing time was not less than 30 min. Dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrate product. 179.5 kg of anhydrous ethanol was added to the crude product and heated to dissolve and recrystallize. Anhydrous ethanol was used only once for recrystallization. The recrystallization endpoint temperature was 21°C. After cooling and filtration, the product was dried at 52°C to obtain an egg-yellow dinitrobisphenol AF intermediate. The HPLC purity of the obtained dinitro intermediate was ≥99.0%.

[0071] 3. High-pressure catalytic hydrogenation reduction

[0072] Based on 100 kg of dinitrobisphenol AF intermediate, 329 kg of ethyl acetate and 1.31 kg of palladium on carbon catalyst were added. The air inside the sealed high-pressure reactor was replaced three times with high-purity hydrogen. Each replacement was maintained at 0.2 MPa for 5 min before depressurization. After the three replacements, hydrogen was added to bring the internal pressure to 3.1 MPa. The mixture was stirred and heated to an internal temperature of 81 °C. The stirring speed of the hydrogenation reaction was controlled at 380 r / min. After the system stopped absorbing hydrogen, the reaction was maintained at the same temperature and pressure for 2 h. HPLC analysis showed no residual nitro intermediate. The palladium on carbon catalyst was removed by hot filtration, yielding a light yellow clear hydrogenated filtrate.

[0073] The palladium-on-carbon catalyst used in this embodiment was prepared using the following method:

[0074] The first step was to prepare the boron-synergistic complex mother liquor: using 100 kg hexamethylenediaminetetramethylenephosphonic acid as a reference, 14.0 kg of furan-2-boric acid and 410 kg of deionized water were added. The pH of the system was adjusted to 8.0 with sodium hydroxide, and the reaction was stirred at 58 °C for 2.8 h. The furan heterocyclic modified boron-synergistic amine phosphonic acid complex mother liquor was obtained by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-boric acid boron atoms.

[0075] The second step is to prepare the palladium-on-carbon catalyst: Based on 100 kg of pretreated dried coconut shell activated carbon, 8.38 kg of palladium chloride was dissolved in 2.8 kg of concentrated hydrochloric acid by gentle heating. 3.8 kg of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor was added, and after dilution with 205 kg of deionized water, it was added dropwise to the activated carbon slurry prepared with 710 kg of deionized water and impregnated at room temperature for 2.2 h. Sodium hydroxide was added dropwise at 41 °C to adjust the pH of the system to 9.3, and the system was aged for 1.8 h. Then the temperature was raised to 59 °C, and 8.0 kg of sodium formate was added for constant temperature reduction for 2.8 h. After the reaction, the system was washed with hot deionized water at 79 °C until no chloride ions remained. The system was then filtered and dried to obtain the palladium-on-carbon catalyst.

[0076] 4. Refining 6FAP product by crystallization with compound solvent

[0077] The hydrogenated filtrate was heated to reflux, and 32.8 kg of petroleum ether with a boiling range of 60–90 °C was added at a uniform rate and mixed thoroughly. The mixture was then slowly cooled to allow crystallization to occur at a rate of 1 °C / min. Low-speed stirring was maintained throughout the crystallization process to prevent the agglomeration of fine crystals that could trap impurities. The mixture was cooled to 24 °C and allowed to stand for 2 hours to allow crystallization. The solid was then collected by filtration. The solid was dried in a vacuum oven at -0.08 MPa for 7.5 hours at 58 °C to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder. The moisture content of the dried product was ≤0.05 wt%.

[0078] Example 4

[0079] 1. Low-temperature staged nitrification

[0080] Using 100 kg of bisphenol AF as a reference, 360 kg of dichloromethane was added and stirred to form a white suspension. The system temperature was controlled at 15°C, and 73 kg of concentrated nitric acid was added dropwise in stages. The addition was stopped after each drop of 5% of the total nitric acid mass was added, and the mixture was kept at the temperature and stirred for 10 min before continuing the addition. After all the nitric acid was added, the temperature was raised to 25°C and kept at the temperature for nitration for 3.5 h. HPLC monitoring was performed until the bisphenol AF feedstock was completely consumed. The highest temperature of the system during the entire addition process did not exceed 15°C.

[0081] 2. Purification of dinitro intermediates

[0082] The nitration reaction solution was first washed and separated with 600 kg of pure water. The temperature during the water washing and alkali washing separation was maintained at 28°C. The organic phase was washed twice with 600 kg of saturated sodium bicarbonate aqueous solution, and then washed with 600 kg of pure water until the pH of the aqueous phase was 7.2. The organic phase was dried and filtered with anhydrous sodium sulfate, with the amount of anhydrous sodium sulfate added being 15% of the crude nitrate product. The drying and standing time was not less than 30 min. Dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrate product. 180 kg of anhydrous ethanol was added to the crude product and heated to dissolve and recrystallize. Anhydrous ethanol was used only once for recrystallization. The recrystallization endpoint temperature was 22°C. After cooling and filtration, the product was dried at 55°C to obtain an egg-yellow dinitrobisphenol AF intermediate. The HPLC purity of the obtained dinitro intermediate was ≥99.0%.

[0083] 3. High-pressure catalytic hydrogenation reduction

[0084] Based on 100 kg of dinitrobisphenol AF intermediate, 330 kg of ethyl acetate and 1.32 kg of palladium on carbon catalyst were added. The air inside the sealed high-pressure reactor was replaced three times with high-purity hydrogen. Each hydrogen replacement was maintained at 0.2 MPa for 5 min before depressurization. After the three replacements were completed, hydrogen was added to bring the internal pressure to 3.2 MPa. The mixture was stirred and heated to an internal temperature of 82 °C. The stirring speed of the hydrogenation reaction was controlled at 400 r / min. After the system stopped absorbing hydrogen, the temperature and pressure were maintained for 2 h. HPLC analysis showed no residual nitro intermediate. The palladium on carbon catalyst was removed by hot filtration, yielding a light yellow clear hydrogenated filtrate.

[0085] The palladium-on-carbon catalyst used in this embodiment was prepared using the following method:

[0086] The first step was to prepare a boron-synergistic complex mother liquor: using 100 kg of hexamethylenediaminetetramethylenephosphonic acid as a reference, 15.0 kg of furan-2-boric acid and 430 kg of deionized water were added. The pH of the system was adjusted to 8.2 with sodium hydroxide, and the reaction was carried out at 60 °C for 3.0 h with stirring. The furan heterocyclic modified boron-synergistic amine phosphonic acid complex mother liquor was prepared by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-boric acid boron atoms.

[0087] The second step is to prepare the palladium-on-carbon catalyst: Based on 100 kg of pretreated dried coconut shell activated carbon, 8.40 kg of palladium chloride was dissolved in 3.0 kg of concentrated hydrochloric acid by gentle heating. 4.0 kg of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor was added, and after dilution with 210 kg of deionized water, it was added dropwise to the activated carbon slurry prepared with 720 kg of deionized water and impregnated at room temperature for 2.5 h. Sodium hydroxide was added dropwise at 42℃ to adjust the pH of the system to 9.5, and the system was aged for 2.0 h. Then the temperature was raised to 60℃, and 8.2 kg of sodium formate was added for constant temperature reduction for 3.0 h. After the reaction was completed, the system was washed with hot deionized water at 80℃ until no chloride ions remained. The system was then filtered and dried to obtain the palladium-on-carbon catalyst.

[0088] 4. Refining 6FAP product by crystallization with compound solvent

[0089] The hydrogenated filtrate was heated to reflux, and 33 kg of petroleum ether with a boiling range of 60–90 °C was added at a uniform rate and mixed thoroughly. The mixture was then slowly cooled to allow crystallization to occur, with a cooling rate controlled at 1 °C / min. During the crystallization process, the mixture was continuously stirred at a low speed to prevent small crystals from agglomerating and encapsulating impurities. The mixture was cooled to 25 °C and allowed to stand for 2 hours to allow crystallization to occur. The solid was then collected by filtration. The solid was placed in a vacuum oven and dried at 60 °C for 8 hours, maintaining a vacuum level of -0.09 MPa. This yielded high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder with a moisture content of ≤0.05 wt% after drying.

[0090] Comparative Example 1

[0091] 1. Low-temperature staged nitrification

[0092] Using 100 kg of bisphenol AF as a reference, 350 kg of dichloromethane was added and stirred to form a white suspension. The system temperature was controlled at 10 °C, and 72 kg of concentrated nitric acid was added dropwise in stages. The addition was stopped after each drop of 5% of the total nitric acid mass was added, and the mixture was kept warm and stirred for 10 min before continuing the addition. After all the nitric acid was added, the temperature was raised to 20 °C and kept warm for nitration for 2.5 h. HPLC monitoring was performed until the bisphenol AF feedstock was completely consumed. The highest temperature of the system during the entire addition process did not exceed 15 °C.

[0093] 2. Purification of dinitro intermediates

[0094] The nitration reaction solution was first washed and separated with 590 kg of pure water. The temperature during the water washing and alkali washing separation was maintained at 20°C. The organic phase was washed twice with 590 kg of saturated sodium bicarbonate aqueous solution, and then washed with 590 kg of pure water until the pH of the aqueous phase was 6.8. The organic phase was dried and filtered with anhydrous sodium sulfate, with the amount of anhydrous sodium sulfate added being 12% of the crude nitrate product. The drying and standing time was not less than 30 min. Dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrate product. 178 kg of anhydrous ethanol was added to the crude product and heated to dissolve and recrystallize. Anhydrous ethanol was used only once for recrystallization. The recrystallization endpoint temperature was 18°C. After cooling and filtration, the product was dried at 45°C to obtain an egg-yellow dinitrobisphenol AF intermediate. The HPLC purity of the obtained dinitro intermediate was ≥99.0%.

[0095] 3. High-pressure catalytic hydrogenation reduction

[0096] Based on 100 kg of dinitrobisphenol AF intermediate, 325 kg of ethyl acetate and 1.28 kg of palladium on carbon catalyst were added. The air inside the sealed high-pressure reactor was replaced three times with high-purity hydrogen. Each hydrogen replacement was maintained at 0.2 MPa for 5 min before depressurization. After the three replacements, hydrogen was added to bring the internal pressure to 2.8 MPa. The mixture was stirred and heated to an internal temperature of 78 °C. The stirring speed of the hydrogenation reaction was controlled at 300 r / min. After the system stopped absorbing hydrogen, the temperature and pressure were maintained for 2 h. HPLC analysis showed no residual nitro intermediate. The palladium on carbon catalyst was removed by hot filtration, yielding a light yellow clear hydrogenated filtrate.

[0097] The palladium-on-carbon catalyst used in this embodiment was prepared using the following method:

[0098] Based on 100 kg of pretreated dried coconut shell activated carbon, 8.30 kg of palladium chloride was dissolved in 2.0 kg of concentrated hydrochloric acid by gentle heating. 3.2 kg of furan-2-boric acid was added, and after dilution with 190 kg of deionized water, the solution was added dropwise to an activated carbon slurry prepared with 680 kg of deionized water and impregnated at room temperature for 1.5 h. Sodium hydroxide was added dropwise at 38 °C to adjust the pH of the system to 9.0, and the system was aged for 1.0 h. The temperature was then raised to 55 °C, and 7.5 kg of sodium formate was added for constant-temperature reduction for 2.0 h. After the reaction was completed, the system was washed with hot deionized water at 75 °C until no chloride ions remained. The solution was filtered and dried to obtain the palladium-on-carbon catalyst.

[0099] 4. Refining 6FAP product by crystallization with compound solvent

[0100] The hydrogenated filtrate was heated to reflux, and 32 kg of petroleum ether with a boiling range of 60–90 °C was added at a uniform rate and mixed thoroughly. The mixture was then slowly cooled to allow crystallization to occur at a rate of 1 °C / min. During the crystallization process, the mixture was continuously stirred at a low speed to prevent small crystals from agglomerating and encapsulating impurities. The mixture was then cooled to 20 °C and allowed to stand for 2 hours to allow crystallization to occur. The solid was then collected by filtration. The solid was then placed in a vacuum oven and dried at a vacuum level of -0.06 MPa for 6 hours at a temperature of 50 °C to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder. The moisture content of the dried product was ≤0.05 wt%.

[0101] Comparative Example 2

[0102] 1. Low-temperature staged nitrification

[0103] Using 100 kg of bisphenol AF as a reference, 350 kg of dichloromethane was added and stirred to form a white suspension. The system temperature was controlled at 10 °C, and 72 kg of concentrated nitric acid was added dropwise in stages. The addition was stopped after each drop of 5% of the total nitric acid mass was added, and the mixture was kept warm and stirred for 10 min before continuing the addition. After all the nitric acid was added, the temperature was raised to 20 °C and kept warm for nitration for 2.5 h. HPLC monitoring was performed until the bisphenol AF feedstock was completely consumed. The highest temperature of the system during the entire addition process did not exceed 15 °C.

[0104] 2. Purification of dinitro intermediates

[0105] The nitration reaction solution was first washed and separated with 590 kg of pure water. The temperature during the water washing and alkali washing separation was maintained at 20°C. The organic phase was washed twice with 590 kg of saturated sodium bicarbonate aqueous solution, and then washed with 590 kg of pure water until the pH of the aqueous phase was 6.8. The organic phase was dried and filtered with anhydrous sodium sulfate, with the amount of anhydrous sodium sulfate added being 12% of the crude nitrate product. The drying and standing time was not less than 30 min. Dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrate product. 178 kg of anhydrous ethanol was added to the crude product and heated to dissolve and recrystallize. Anhydrous ethanol was used only once for recrystallization. The recrystallization endpoint temperature was 18°C. After cooling and filtration, the product was dried at 45°C to obtain an egg-yellow dinitrobisphenol AF intermediate. The HPLC purity of the obtained dinitro intermediate was ≥99.0%.

[0106] 3. High-pressure catalytic hydrogenation reduction

[0107] Based on 100 kg of dinitrobisphenol AF intermediate, 325 kg of ethyl acetate and 1.28 kg of palladium on carbon catalyst were added. The air inside the sealed high-pressure reactor was replaced three times with high-purity hydrogen. Each hydrogen replacement was maintained at 0.2 MPa for 5 min before depressurization. After the three replacements, hydrogen was added to bring the internal pressure to 2.8 MPa. The mixture was stirred and heated to an internal temperature of 78 °C. The stirring speed of the hydrogenation reaction was controlled at 300 r / min. After the system stopped absorbing hydrogen, the temperature and pressure were maintained for 2 h. HPLC analysis showed no residual nitro intermediate. The palladium on carbon catalyst was removed by hot filtration, yielding a light yellow clear hydrogenated filtrate.

[0108] The palladium-on-carbon catalyst used in this embodiment was prepared using the following method:

[0109] The first step was to prepare the boron-synergistic complex mother liquor: 100 kg of hexamethylenediaminetetramethylenephosphonic acid was used as the standard, and 360 kg of deionized water was added. The pH of the system was adjusted to 7.2 with sodium hydroxide, and the reaction was carried out at 50 °C for 2.0 h. The furan heterocyclic modified boron-synergistic aminephosphonic acid complex mother liquor was obtained by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-borate boron atoms.

[0110] The second step is to prepare the palladium-on-carbon catalyst: Based on 100 kg of pretreated dried coconut shell activated carbon, 8.30 kg of palladium chloride was dissolved in 2.0 kg of concentrated hydrochloric acid by gentle heating. 3.2 kg of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor was added, and after dilution with 190 kg of deionized water, it was added dropwise to the activated carbon slurry prepared with 680 kg of deionized water and impregnated at room temperature for 1.5 h. The pH of the system was adjusted to 9.0 by adding sodium hydroxide dropwise at 38 °C, and the mixture was aged for 1.0 h. Then, the temperature was raised to 55 °C, and 7.5 kg of sodium formate was added for constant temperature reduction for 2.0 h. After the reaction was completed, the system was washed with hot deionized water at 75 °C until no chloride ions remained. The mixture was then filtered and dried to obtain the palladium-on-carbon catalyst.

[0111] 4. Refining 6FAP product by crystallization with compound solvent

[0112] The hydrogenated filtrate was heated to reflux, and 32 kg of petroleum ether with a boiling range of 60–90 °C was added at a uniform rate and mixed thoroughly. The mixture was then slowly cooled to allow crystallization to occur at a rate of 1 °C / min. During the crystallization process, the mixture was continuously stirred at a low speed to prevent small crystals from agglomerating and encapsulating impurities. The mixture was then cooled to 20 °C and allowed to stand for 2 hours to allow crystallization to occur. The solid was then collected by filtration. The solid was then placed in a vacuum oven and dried at a vacuum level of -0.06 MPa for 6 hours at a temperature of 50 °C to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder. The moisture content of the dried product was ≤0.05 wt%.

[0113] Comparative Example 3

[0114] 1. Low-temperature staged nitrification

[0115] Using 100 kg of bisphenol AF as a reference, 350 kg of dichloromethane was added and stirred to form a white suspension. The system temperature was controlled at 10 °C, and 72 kg of concentrated nitric acid was added dropwise in stages. The addition was stopped after each drop of 5% of the total nitric acid mass was added, and the mixture was kept warm and stirred for 10 min before continuing the addition. After all the nitric acid was added, the temperature was raised to 20 °C and kept warm for nitration for 2.5 h. HPLC monitoring was performed until the bisphenol AF feedstock was completely consumed. The highest temperature of the system during the entire addition process did not exceed 15 °C.

[0116] 2. Purification of dinitro intermediates

[0117] The nitration reaction solution was first washed and separated with 590 kg of pure water. The temperature during the water washing and alkali washing separation was maintained at 20°C. The organic phase was washed twice with 590 kg of saturated sodium bicarbonate aqueous solution, and then washed with 590 kg of pure water until the pH of the aqueous phase was 6.8. The organic phase was dried and filtered with anhydrous sodium sulfate, with the amount of anhydrous sodium sulfate added being 12% of the crude nitrate product. The drying and standing time was not less than 30 min. Dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrate product. 178 kg of anhydrous ethanol was added to the crude product and heated to dissolve and recrystallize. Anhydrous ethanol was used only once for recrystallization. The recrystallization endpoint temperature was 18°C. After cooling and filtration, the product was dried at 45°C to obtain an egg-yellow dinitrobisphenol AF intermediate. The HPLC purity of the obtained dinitro intermediate was ≥99.0%.

[0118] 3. High-pressure catalytic hydrogenation reduction

[0119] Based on 100 kg of dinitrobisphenol AF intermediate, 325 kg of ethyl acetate and 1.28 kg of palladium on carbon catalyst were added. The air inside the sealed high-pressure reactor was replaced three times with high-purity hydrogen. Each hydrogen replacement was maintained at 0.2 MPa for 5 min before depressurization. After the three replacements, hydrogen was added to bring the internal pressure to 2.8 MPa. The mixture was stirred and heated to an internal temperature of 78 °C. The stirring speed of the hydrogenation reaction was controlled at 300 r / min. After the system stopped absorbing hydrogen, the temperature and pressure were maintained for 2 h. HPLC analysis showed no residual nitro intermediate. The palladium on carbon catalyst was removed by hot filtration, yielding a light yellow clear hydrogenated filtrate.

[0120] The palladium-on-carbon catalyst used in this embodiment was prepared using the following method:

[0121] The first step was to prepare the boron-synergistic complex mother liquor: using 100 kg hexamethylenediaminetetramethylenephosphonic acid as a reference, 11.0 kg of furan-2-boric acid and 360 kg of deionized water were added. The pH of the system was adjusted to 7.2 with sodium hydroxide, and the reaction was carried out at 50 °C for 2.0 h with stirring. The furan heterocyclic modified boron-synergistic aminephosphonic acid complex mother liquor was obtained by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-boric acid boron atoms.

[0122] The second step is to prepare the palladium-on-carbon catalyst: Based on 100 kg of pretreated dried coconut shell activated carbon, 8.30 kg of palladium chloride was dissolved in 2.0 kg of concentrated hydrochloric acid by gentle heating. 3.2 kg of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor was added, and after dilution with 190 kg of deionized water, it was added dropwise to the activated carbon slurry prepared with 680 kg of deionized water and impregnated at room temperature for 1.5 h. The pH of the system was adjusted to 9.0 by adding sodium hydroxide dropwise at 38 °C, and the system was aged for 1.0 h. Then the temperature was raised to 55 °C and reduced at a constant temperature for 2.0 h. After the reaction was completed, the system was washed with hot deionized water at 75 °C until no chloride ions remained. The system was then filtered and dried to obtain the palladium-on-carbon catalyst.

[0123] 4. Refining 6FAP product by crystallization with compound solvent

[0124] The hydrogenated filtrate was heated to reflux, and 32 kg of petroleum ether with a boiling range of 60–90 °C was added at a uniform rate and mixed thoroughly. The mixture was then slowly cooled to allow crystallization to occur at a rate of 1 °C / min. During the crystallization process, the mixture was continuously stirred at a low speed to prevent small crystals from agglomerating and encapsulating impurities. The mixture was then cooled to 20 °C and allowed to stand for 2 hours to allow crystallization to occur. The solid was then collected by filtration. The solid was then placed in a vacuum oven and dried at a vacuum level of -0.06 MPa for 6 hours at a temperature of 50 °C to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder. The moisture content of the dried product was ≤0.05 wt%.

[0125] Test methods

[0126] (1) Determination of product purity (HPLC)

[0127] Testing instrument: Agilent 1260 or equivalent high performance liquid chromatograph.

[0128] Chromatographic conditions

[0129] Column: C18 (250 mm × 4.6 mm, 5 μm)

[0130] Mobile phase: Methanol / water = 70 / 30 (volume ratio)

[0131] Flow rate: 1.0 mL / min

[0132] Column temperature: 30 ℃

[0133] Detection wavelength: 280 nm

[0134] Injection volume: 10 μL

[0135] Product purity was calculated using the area normalization method.

[0136] (2) Determination of intermediate purity

[0137] Using the above HPLC conditions, only the mobile phase ratio was changed to

[0138] Methanol / water = 65 / 35

[0139] Determine the purity of dinitrobisphenol AF.

[0140] (3) Yield calculation

[0141] Calculated based on theoretical output.

[0142] Nitration yield (%) = Actual mass of dinitro intermediate obtained ÷ Theoretical mass × 100%

[0143] Hydrogenation yield (%) = Actual mass of 6FAP obtained ÷ Theoretical mass × 100%

[0144] Total yield = product of two-step yields.

[0145] Table 1 Test Results

[0146] Product purity (HPLC, %) Purity of dinitro intermediate (HPLC, %) Nitrification yield (%) Hydrogenation yield (%) Overall yield (%) Example 1 99.77 99.3 75.2 75.4 56.70 Example 2 99.84 99.5 75.3 75.6 56.93 Example 3 99.89 99.6 75.5 75.8 57.23 Example 4 99.93 99.8 75.8 76.1 57.68 Comparative Example 1 97.88 97.4 65.4 71.6 45.69 Comparative Example 2 98.45 98.2 68.3 72.5 49.69 Comparative Example 3 98.76 98.5 71.8 71.6 50.12

[0147] Based on the comprehensive test results of intermediate purity, finished product purity, by-product residue, and product stability, it can be seen that compared with the traditional preparation process of ordinary palladium on carbon catalysis, conventional one-time nitration, and single solvent crystallization, the low-temperature segmented selective nitration coupled with boron heterocyclic modified palladium on carbon catalytic hydrogenation and compound solvent gradient purification process of this invention can significantly improve the purity of the target product, greatly reduce the residue of various organic by-products and impurities, and the overall product quality and batch stability are superior to the traditional process. The self-made modified palladium on carbon catalyst has a clear division of labor among its functional components and outstanding synergistic catalytic quality improvement effect.

[0148] Hexamethylenediaminetetramethylenephosphonic acid is the core complex stabilizing component of the catalyst. With its abundant phosphonic acid coordination sites, it can form a stable chelate structure with palladium ions, effectively preventing the aggregation, migration and loss of palladium active components during impregnation, reduction and hydrogenation reactions. This significantly improves the catalyst loading uniformity and cycle stability, which is the key to ensuring the long-term and efficient operation of the catalytic system.

[0149] Furan-2-boronic acid serves as the core for catalytic selective modification. Its unique rigid structure of the furan-boron heterocyclic ring can precisely regulate the electron cloud distribution of the palladium active site, optimize the catalyst's specific adsorption and hydrogenation activation ability for nitro functional groups, weaken the side catalytic effect on benzene rings and hydroxyl groups, effectively inhibit side reactions, improve the reaction selectivity of nitro reduction, and reduce the generation of intermediate impurities.

[0150] Coconut shell activated carbon supports provide a porous, high specific surface area framework structure for catalytic reactions, which can uniformly disperse active palladium components, increase the contact area of ​​catalytic reactions, reduce mass transfer resistance, and improve the hydrogenation reaction rate and reaction uniformity. At the same time, it has excellent adsorption and impurity removal capabilities, which can help adsorb trace impurities in the system and further optimize the purity of the reaction system.

[0151] Sodium formate reducing agent achieves mild and controllable reduction. Compared with strong reducing agents, it can avoid the rapid agglomeration and growth of palladium crystals, ensuring that the active palladium crystals are small in size and uniformly distributed, maximizing the exposure of catalytic active sites, improving catalytic activity and hydrogenation conversion efficiency, and ensuring complete reduction of intermediates without residue.

[0152] The modified palladium-carbon catalytic system, constructed synergistically from various components, combines the advantages of high activity, high selectivity, and high stability. Combined with a complete process of precise front-end nitration control, multi-stage purification, and back-end gradient crystallization refining, it ensures ultra-high purity of the product from the source of impurity control, process quality improvement, and end-of-line refining. The resulting 6FAP monomer has extremely low impurity content, regular structure, and stable performance, which can fully meet the needs of large-scale preparation of high-end fluorinated polyimides and special polymer materials.

[0153] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, characterized in that, Includes the following steps: (1) Low-temperature segmented nitration: Based on 100 parts by mass of bisphenol AF, add 350-360 parts by mass of dichloromethane and stir to form a white suspension. Control the temperature of the system at 10-15℃ and add 72-73 parts by mass of concentrated nitric acid in segments. Stop adding the feed after each drop of 5% of the total nitric acid mass, keep warm and stir for 10 minutes, and then continue adding the feed. After all the nitric acid has been added, raise the temperature to 20-25℃ and keep warm for nitration. HPLC monitoring is performed until the bisphenol AF feedstock is completely consumed. (2) Purification of the dinitro intermediate: The nitration reaction solution was first washed and separated with 590-600 parts by weight of pure water. The organic phase was washed twice with 590-600 parts by weight of saturated sodium bicarbonate aqueous solution, and then washed with 590-600 parts by weight of pure water until the pH of the aqueous phase was 6.8-7.

2. The organic phase was dried and filtered with anhydrous sodium sulfate, and dichloromethane was removed by rotary evaporation under reduced pressure to obtain a yellow crude nitrated product. 178-180 parts by weight of anhydrous ethanol was added to the crude product, heated to dissolve and recrystallize, cooled, filtered and dried to obtain an egg-yellow dinitrobisphenol AF intermediate. (3) High-pressure catalytic hydrogenation reduction: Based on 100 parts by weight of dinitrobisphenol AF intermediate, 325-330 parts by weight of ethyl acetate and 1.28-1.32 parts by weight of palladium catalyst on carbon were added; the air inside the closed high-pressure reactor was replaced three times with high-purity hydrogen, and hydrogen was added until the pressure inside the reactor was 2.8-3.2 MPa. The reactor was stirred and heated to an internal temperature of 78-82℃. After the system stopped absorbing hydrogen, the reaction was continued for 2 hours under the same temperature and pressure. HPLC detection showed no nitro intermediate residue; the palladium catalyst on carbon was removed by hot filtration to obtain a light yellow hydrogenation clear filtrate. (4) Refining 6FAP product by crystallization with compound solvent: Heat the hydrogenated filtrate to reflux, add 32-33 parts by weight of petroleum ether at a uniform rate and mix well; slowly cool to 20-25℃ and let it stand for crystallization for 2 hours, filter and collect the solid; place the solid in a vacuum oven at 50-60℃ and dry to obtain high-purity white 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane powder; In step (3), the palladium-on-carbon catalyst is prepared by using hexamethylenediaminetetramethylenephosphonic acid, furan-2-boric acid, and deionized water as raw materials. After adjusting the pH, the catalyst is stirred at a constant temperature to obtain a boron-synergistic complex mother liquor. Then, the palladium chloride hydrochloric acid solution is diluted with the complex mother liquor and impregnated with pretreated coconut shell activated carbon. After alkaline aging, the catalyst is reduced by sodium formate at a constant temperature, washed with hot water to remove chlorine, filtered and dried to obtain a furan heterocyclic modified boron-synergistic aminephosphonic acid coordinated palladium-on-carbon catalyst.

2. The method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane according to claim 1, characterized in that: In step (1), the highest temperature of the entire system during the dripping process does not exceed 15°C, and the nitrification time is 2.5 to 3.5 hours.

3. The method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane according to claim 1, characterized in that: In step (2) recrystallization, anhydrous ethanol is used only once for recrystallization. The recrystallization cooling endpoint temperature is 18-22℃, the drying temperature is 45-55℃, and the HPLC purity of the obtained dinitro intermediate is ≥99.0%.

4. The method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane according to claim 1, characterized in that: The operating temperature for the water washing and alkali washing separation in step (2) is maintained at 20-28°C. The amount of anhydrous sodium sulfate added is 12%-15% of the crude nitrate quality, and the drying and standing time is not less than 30 minutes.

5. The method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane according to claim 1, characterized in that: The preparation method of the palladium-on-carbon catalyst in step (3) is as follows: The first step was to prepare a boron-synergistic complex mother liquor: using 100 parts by mass of hexamethylenediaminetetramethylenephosphonic acid as a reference, 11.0-15.0 parts of furan-2-boric acid and 360-430 parts of deionized water were added. The pH of the system was adjusted to 7.2-8.2 with sodium hydroxide, and the reaction was stirred at 50-60℃ for 2.0-3.0 h. The furan heterocyclic modified boron-synergistic amine phosphonic acid complex mother liquor was prepared by utilizing the multi-point dynamic coordination assembly of phosphonic acid oxygen atoms and furan-2-boric acid boron atoms. The second step is to prepare the palladium-on-carbon catalyst: Based on 100 parts by mass of pretreated dried coconut shell activated carbon, 8.30-8.40 parts of palladium chloride are dissolved in 2.0-3.0 parts of concentrated hydrochloric acid by gentle heating. 3.2-4.0 parts of furan heterocyclic modified boron synergistic amine phosphonic acid complex mother liquor are added, and 190-210 parts of deionized water are added for dilution. This solution is then added dropwise to an activated carbon slurry prepared with 680-720 parts of deionized water and impregnated at room temperature for 1.5-2.5 hours. Sodium hydroxide is added dropwise at 38-42℃ to adjust the pH of the system to 9.0-9.

5. The system is aged for 1.0-2.0 hours, then heated to 55-60℃, and 7.5-8.2 parts of sodium formate are added for constant-temperature reduction for 2.0-3.0 hours. After the reaction, the system is washed with hot deionized water at 75-80℃ until no chloride ions remain. The mixture is then filtered and dried to obtain the palladium-on-carbon catalyst.

6. The method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane according to claim 1, characterized in that: In step (3), the stirring speed of the high-pressure catalytic hydrogenation reduction is controlled at 300-400 r / min. After each hydrogen replacement, the pressure is maintained at 0.2 MPa for 5 minutes and then released. After three replacements, the pressure is increased to the target hydrogenation pressure.

7. The method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane according to claim 1, characterized in that: The petroleum ether used in step (4) has a boiling range of 60-90℃, and the crystallization cooling rate is controlled at 1℃ / min. The crystallization process is continuously stirred at low speed to avoid the agglomeration of fine crystals that encapsulate impurities.

8. The method for preparing 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane according to claim 1, characterized in that: In step (4), the vacuum degree is maintained at -0.06 to -0.09 MPa, the drying time is 6 to 8 hours, and the moisture content of the finished product after drying is ≤0.05 wt%.

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