Process for the preparation of 4,4'-difluorobenzophenone and method for the synthesis of polyether ether ketone in two steps with carbon tetrachloride

Abstract

The present application relates to the technical field of chemical synthesis, and particularly relates to a preparation method of 4,4'-difluorobenzophenone and a method for synthesizing polyether ether ketone by two steps of carbon tetrachloride. The preparation method of 4,4'-difluorobenzophenone comprises the following steps: under the condition that trifluoromethanesulfonic acid and N-methyl pyrrolidone exist, CCl4 and fluorobenzene are reacted, and the product is hydrolyzed to obtain 4,4'-difluorobenzophenone. The present application solves the problems of high cost, poor environmental protection and performance that cannot meet market requirements of PEEK by innovating raw material route, catalytic system and process parameters, realizes low-cost, green and high-performance synthesis of PEEK, the purity of the prepared DFBP monomer can reach >=99.99%, and the PEEK molecular weight distribution (PDI<=1.9) can be narrowed, and the method is suitable for industrialized production of PEEK materials used in high-end fields such as aerospace, medical devices and electronic and electrical appliances.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method for preparing 4,4'-difluorobenzophenone and a two-step method for synthesizing polyether ether ketone using carbon tetrachloride. Background Technology

[0002] Polyetheretherketone (PEEK) is a special engineering plastic whose main chain contains repeating units of "-O-C6H4-O-C6H4-CO-C6H4-". It has the characteristics of long-term service temperature of 250~260℃, resistance to strong acids and alkalis, mechanical strength close to that of metals, and excellent biocompatibility. It is known as "polymer gold" and is an indispensable key material in the field of high-end equipment manufacturing.

[0003] 4,4'-Difluorobenzophenone (DFBP) is a key intermediate in the preparation of PEEK. Currently, DFBP monomers are generally purchased externally, with a market price of about RMB 180,000 per ton, accounting for more than 60% of the total raw material cost. This results in a high selling price for PEEK products (about RMB 100-150 per kilogram), which limits the application expansion in the low-to-mid-end market.

[0004] On the other hand, the purity of current DFBP monomers is mostly 98~99% (containing 2,4'-isomer impurities >1%), and the temperature and pressure control in the polymerization process is rough, resulting in a wide molecular weight distribution of the product (PDI>2.0), and the tensile strength difference between batches can reach 8%~10%, which is difficult to meet the stringent requirements for performance consistency in high-end fields such as aerospace.

[0005] Furthermore, the traditional process for preparing PEEK currently uses a single diphenyl sulfone (DPS) solvent, and the post-treatment requires a large amount of organic solvents (such as acetone and ethanol) for washing, which generates sulfur-containing wastewater (COD>5000mg / L). Moreover, the recovery of by-products (such as NaCl and KCl) is difficult, and the environmental treatment cost accounts for 15% to 20% of the production cost, further increasing the cost. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing 4,4'-difluorobenzophenone and a two-step method for synthesizing polyether ether ketone using carbon tetrachloride, which produces 4,4'-difluorobenzophenone with high purity and reduces the production cost of polyether ether ketone.

[0007] To achieve the above objectives, the present invention provides a method for preparing 4,4'-difluorobenzophenone, comprising the following steps:

[0008] In the presence of trifluoromethanesulfonic acid (TfOH) and N-methylpyrrolidone (NMP), CCl4 reacts with fluorobenzene, and the product is hydrolyzed to give 4,4'-difluorobenzophenone.

[0009] Preferably, CCl4 is first pre-activated by mixing with trifluoromethanesulfonic acid and N-methylpyrrolidone, and then reacted with fluorobenzene.

[0010] This invention employs a trifluoromethanesulfonic acid and N-methylpyrrolidone composite catalytic system. During the pre-activation process, CCl4 generates an electrophilic attack reagent under the action of trifluoromethanesulfonic acid, and the addition of N-methylpyrrolidone improves the degree of activation.

[0011] The pre-activation temperature is preferably 60~80℃, more preferably 60, 70, or 80℃, or any of the above values ​​may be the upper or lower limit.

[0012] The pre-activation time is preferably 30 to 45 minutes, more preferably 30, 35, 40, or 45 minutes, or any of the above values ​​may be the upper or lower limit.

[0013] In some specific embodiments, the preactivation includes the following steps:

[0014] In a high-pressure reactor equipped with stirring, temperature measurement, and pressure control functions, CCl4 and a composite catalyst are added, and high-purity N2 (purity ≥99.999%) is introduced to replace the catalyst three times (oxygen content <5ppm after each replacement). The temperature is raised to 60~80℃, and the reactor is stirred and activated for 30~45 minutes.

[0015] The mass ratio of trifluoromethanesulfonic acid to N-methylpyrrolidone is preferably 1:(0.2~0.4), more preferably 1:0.2, 1:0.3, 1:0.4, or any of the above values ​​as the upper or lower limit.

[0016] The total mass of the trifluoromethanesulfonic acid and N-methylpyrrolidone is preferably 0.5% to 1.0% of the mass of fluorobenzene, more preferably 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1.0% of the mass of fluorobenzene, or any of the above values ​​as the upper or lower limit.

[0017] The molar ratio of fluorobenzene to CCl4 is preferably 3 to 5:1, more preferably 3:1, 4:1, or 5:1, or any of the above values ​​may be the upper or lower limit.

[0018] The fluorobenzene is preferably mixed with the pre-activated CCl4 by dropwise addition. The dropwise addition rate is preferably 1~2 mL / min.

[0019] The preferred temperature for the above reaction is 120~140℃, more preferably 120, 130, 140℃, or any of the above values ​​as the upper or lower limit.

[0020] The pressure of the above reaction is preferably 0.3 to 0.5 MPa, more preferably 0.3, 0.4, or 0.5 MPa, or any of the above values ​​as the upper or lower limit.

[0021] The reaction time is preferably 4 to 6 hours, more preferably 4, 5, or 6 hours, or any of the above values ​​may be the upper or lower limit.

[0022] Preferably, after the reaction is completed, a purification process is also included.

[0023] The purification process preferably includes: water washing, alkali washing, distillation, and recrystallization.

[0024] The alkaline washing is preferably performed using a Na2CO3 solution.

[0025] After alkali washing, extraction is preferably performed, and the solvent for extraction is preferably dichloromethane.

[0026] The preferred method of distillation is to recover dichloromethane by atmospheric distillation, followed by vacuum distillation to collect the fraction.

[0027] The preferred solvent for recrystallization is ethanol.

[0028] In some specific implementations, the purification process includes:

[0029] Washing: After the reaction solution is cooled to room temperature, deionized water (liquid-solid ratio 5:1) is added and stirred for 30 minutes. The mixture is then allowed to stand and separate into layers to remove water-soluble impurities.

[0030] Alkali washing: Add 5wt% Na2CO3 solution (1:1 volume ratio with the reaction solution) to adjust the pH to 7-8 and remove residual TfOH;

[0031] Extraction: Extract three times with dichloromethane (volume ratio of 2:1 to the reaction liquid), and combine the organic phases;

[0032] Distillation: After recovering dichloromethane by atmospheric distillation, the organic phase is subjected to vacuum distillation (temperature 275~280℃, vacuum degree 10~15mmHg) and the fraction is collected.

[0033] Recrystallization: The fraction was recrystallized with 95% ethanol (solvent to crude product mass ratio 5~8:1) and dried under vacuum at 60~70℃ for 12~16 hours to obtain white DFBP crystals with a purity ≥99.99%.

[0034] The HCl gas generated in the reaction can be condensed (at a temperature of 5~10℃) and absorbed by water to produce industrial hydrochloric acid, which can be used in other chemical processes.

[0035] This invention also provides a two-step method for synthesizing polyetheretherketone using carbon tetrachloride, comprising the following steps:

[0036] S1) 4,4'-difluorobenzophenone was prepared using the above method;

[0037] S2) Polyether ether ketone is prepared by polymerization reaction using 4,4'-difluorobenzophenone and hydroquinone as raw materials.

[0038] The preferred molar ratio of 4,4'-difluorobenzophenone to hydroquinone is 1:(1.05~1.1).

[0039] Preferably, in step S2), an alkaline catalyst is added to the reaction system.

[0040] The alkaline catalyst preferably includes potassium carbonate and sodium carbonate.

[0041] The mass ratio of potassium carbonate to sodium carbonate is preferably 1 to 5:1, more preferably 1:1, 2:1, 3:1, 4:1, or 5:1, or any of the above values ​​may be the upper or lower limit.

[0042] The molar ratio of the alkaline catalyst to hydroquinone is preferably 2.2 to 2.4:1, more preferably 2.2:1, 2.3:1, or 2.4:1, or any of the above values ​​as the upper or lower limit.

[0043] The alkaline catalyst can more effectively deprotonate phenol to form a strongly nucleophilic sodium phenolate, which is key to the SNAr substitution reaction. Simultaneously, the alkaline environment helps suppress the side reaction of hydroxyl group substitution by fluorine (forming diphenol), improving the yield and purity of the target product, thus playing a dual role as an "activator" and a "fluoride ion scavenger."

[0044] The solvents used in the polymerization reaction preferably include diphenyl sulfone (DPS) and sulfolane. The introduction of a mixed solvent system of diphenyl sulfone and sulfolane is a key "upgrade" to the traditional PEEK synthesis process.

[0045] Diphenyl sulfone (DP) is responsible for providing a high-boiling-point, highly polar environment to dissolve polymer chains and maintain high-temperature reaction conditions.

[0046] Sulfolane acts like a "lubricant," reducing the "viscosity" of the system and allowing the polymer chains to remain fluid at high temperatures, thus avoiding the "PEEK slurry blockage" problem.

[0047] The volume ratio of the diphenyl sulfone to the sulfolane is 1 to 5:1, more preferably 1:1, 2:1, 3:1, 4:1, or 5:1, or any of the above values ​​may be the upper or lower limit.

[0048] The total mass of the solvent is preferably 2.5 to 3 times the total mass of 4,4'-difluorobenzophenone, more preferably 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0 times, or any of the above values ​​may be the upper or lower limit.

[0049] Preferably, the polymerization reaction includes a prepolymerization stage and a polymerization stage.

[0050] The temperature of the prepolymerization stage is preferably 180~200℃, more preferably 180, 190, 200℃, or any of the above values ​​as the upper or lower limit.

[0051] During the prepolymerization stage, prepolymers with a number average molecular weight of 10,000 to 15,000 are formed.

[0052] The polymerization stage is preferably a gradient heating-pressurization process.

[0053] In some specific implementations, step S2) specifically includes:

[0054] The mixed solvent of diphenyl sulfone and sulfolane was heated to 195°C and kept constant. Under nitrogen protection, the mixture was stirred rapidly. Hydroquinone was added to the molten mixed solvent. After the hydroquinone was completely dissolved, potassium carbonate / sodium carbonate composite salt was added. Under nitrogen protection and rapid stirring, the temperature was rapidly increased to the first temperature and reacted for 5-30 minutes. Then, 4,4'-difluorobenzophenone was added to the system, and the temperature was rapidly increased to the second temperature and reacted for 1-3 hours. Then, a gradient temperature-pressure mode was adopted. The viscosity of the reaction system was monitored throughout the process using a torque sensor. When the torque reached 1.8-2.0 times the initial value, the polymerization endpoint was determined.

[0055] The first temperature is preferably 230~260℃, more preferably 230, 240, 250℃, or any of the above values ​​as the upper or lower limit.

[0056] The second temperature is preferably 280~300℃, more preferably 280, 285, 290, 295, 300℃, or any of the above values ​​as the upper or lower limit.

[0057] The preferred method of gradient heating-pressurization includes:

[0058] Phase 1: Temperature rises from 190℃ to 220℃, and pressure rises from 0.5MPa to 1.0MPa;

[0059] Second stage: The temperature rises from 220℃ to 280℃, and the pressure rises from 1.0MPa to 1.5MPa;

[0060] The third stage: the temperature rises from 280℃ to 310℃, and the pressure rises from 1.5MPa to 2.0MPa.

[0061] In some specific embodiments, the gradient temperature-pressure increase preferably includes:

[0062] Phase 1: Temperature rises from 190℃ to 205℃, and pressure rises from 0.5MPa to 1.0MPa;

[0063] Second stage: The temperature rises from 220℃ to 280℃, and the pressure rises from 1.0MPa to 1.5MPa;

[0064] The third stage: the temperature rises from 280℃ to 310℃, and the pressure rises from 1.5MPa to 2.0MPa.

[0065] The heating rate in the first stage is preferably ≤0.5℃ / min, and the residence time in the first stage is preferably 0.5~3h, more preferably 0.5, 1.0, 1.5, 2.0, 2.5, 3.0h, or any of the above values ​​as the upper or lower limit.

[0066] The heating rate in the second stage is preferably ≤1.0℃ / min, and the residence time in the first stage is preferably 0.5~3h, more preferably 0.5, 1.0, 1.5, 2.0, 2.5, 3.0h, or any of the above values ​​as the upper or lower limit.

[0067] The heating rate of the third stage is preferably ≤0.8℃ / min, and the residence time of the first stage is preferably 0.5~3h, more preferably 0.5, 1.0, 1.5, 2.0, 2.5, 3.0h, or any of the above values ​​as the upper or lower limit.

[0068] The present invention employs the aforementioned gradient heating-pressurization mode during the polymerization reaction process. Its introduction helps to overcome the quality fluctuations (such as yellowing and molecular weight instability) that are prone to occur during high-temperature polymerization, ensuring the stability and consistency of product quality.

[0069] Preferably, in this invention, 3% DFBP (by mass of the total monomer) is added 30 minutes before the reaction endpoint for end-capping treatment to inhibit chain growth and stabilize molecular weight.

[0070] After the polymerization reaction is completed, post-processing is preferably also included.

[0071] The post-processing preferably includes precipitation, extraction, and drying.

[0072] The precipitation is preferably carried out by cooling the reaction product to 100~120℃, then pouring it into deionized water and stirring until complete precipitation; the temperature of the deionized water is preferably 80~90℃.

[0073] The extraction is preferably supercritical CO2 extraction, the extraction temperature is preferably 50~60℃, the extraction pressure is preferably 10~15 MPa, and the CO2 flow rate during the extraction process is preferably 50~60 kg / (h・kg PEEK). The extraction operation can remove residual solvent and catalyst.

[0074] The drying process is preferably vacuum drying, the vacuum drying temperature is preferably 120~140℃, and the vacuum drying time is preferably 24~30h.

[0075] Experimental results show that the performance of PEEK products prepared using the above method is significantly improved, specifically:

[0076] 1. Molecular weight: Weight-average molecular weight (Mw) 85,000~95,000 g / mol, which is 30% higher than that of traditional processes (60,000~80,000 g / mol);

[0077] 2. Molecular weight distribution: PDI 1.7~1.9, narrower than traditional process (PDI>2.0), with small performance differences between batches;

[0078] 3. Thermal properties: Melting point 343~345℃ (334~338℃ for traditional process), initial decomposition temperature >550℃ (530℃ for traditional process);

[0079] 4. Mechanical properties: Tensile strength ≥105MPa (90~100MPa for traditional process), flexural modulus ≥4.0GPa (3.8GPa for traditional process).

[0080] This invention provides a method for preparing 4,4'-difluorobenzophenone, comprising the following steps: reacting CCl4 with fluorobenzene in the presence of trifluoromethanesulfonic acid and N-methylpyrrolidone, and hydrolyzing the product to obtain 4,4'-difluorobenzophenone.

[0081] Compared with existing technologies, this invention uses carbon tetrachloride (CCl4, market price approximately 3000 RMB / ton) as the starting material, replacing purchased DFBP. On the one hand, the raw material cost is reduced by more than 30%, and combined with the recovery of the by-product HCl (which can generate additional revenue), the total cost is reduced by 35%~40% compared with traditional processes. High-performance PEEK can then be synthesized through a two-step closed-loop process of "CCl4-DFBP-PEEK," which can promote the application of PEEK in low-to-mid-end fields such as automotive lightweighting and consumer electronics. On the other hand, this invention uses supercritical CO2 extraction (no solvent residue, solvent recovery rate >95%) to replace traditional solvent washing, reducing wastewater discharge by more than 90%, and solid waste (mainly salts) can be recycled as industrial raw materials.

[0082] This invention solves the problems of high cost, poor environmental performance, and inability to meet market requirements of PEEK by innovating raw material routes, catalytic systems, and process parameters. It realizes low-cost, green, and high-performance synthesis of PEEK, and the purity of the prepared DFBP monomer can reach ≥99.99%. It can also narrow the molecular weight distribution of PEEK (PDI≤1.9), which is suitable for the industrial production of PEEK materials in high-end fields such as aerospace, medical devices, and electronics. Attached Figure Description

[0083] Figure 1 A process flow diagram for the two-step synthesis of PEEK using carbon tetrachloride provided by this invention;

[0084] Among them, 1-fluorobenzene storage tank; 2-CCl4 storage tank; 3-composite catalyst storage tank; 4-alkylation reactor; 5-HCl recovery system; 6-purification system (including water washing tank, alkali washing tank, distillation column, crystallizer); 7-DFBP storage tank; 8-hydroquinone storage tank; 9-alkali catalyst storage tank; 10-composite solvent storage tank; 11-polymerization reactor; 12-supercritical CO2 extraction device; 13-drying device; 14-PEEK finished product tank. Detailed Implementation

[0085] To further illustrate the present invention, a detailed description is provided below with reference to embodiments. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0086] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0087] Example 1: Small-scale test (preparation of 500g PEEK)

[0088] Step 1: DFBP Synthesis

[0089] 1.1 Raw material usage:

[0090] 300g (3.2mol) of fluorobenzene, 85g (0.54mol) of CCl4, 2.4g of TfOH, and 0.72g of NMP;

[0091] 1.2 Reaction conditions:

[0092] In a high-pressure reactor equipped with stirring, temperature measurement, and pressure control functions, CCl4 and a composite catalyst were added, and high-purity N2 (purity ≥99.999%) was introduced to replace the catalyst three times (oxygen content <5ppm after each replacement). The temperature was raised to 70℃ and stirred for 30 minutes to activate the reactor.

[0093] Fluorobenzene was added dropwise at a rate of 1.5 mL / min, with the temperature simultaneously increased to 130 °C and the reaction pressure controlled at 0.4 MPa during the addition process. The reaction was maintained at this temperature for 5 hours.

[0094] Hydrolysis is carried out after the reaction: the pH of the system is controlled at 7.5-8.5, and the hydrolysis reaction is carried out for 4-6 hours by steam azeotropism or heating to boiling. Unreacted CCl4 and fluorobenzene are recovered by condenser.

[0095] 1.3 Multi-stage purification:

[0096] Washing: After the reaction solution is cooled to room temperature, deionized water (liquid-solid ratio 5:1) is added and stirred for 30 minutes. The mixture is then allowed to stand and separate into layers to remove water-soluble impurities.

[0097] Alkali washing: Add 5wt% Na2CO3 solution (1:1 volume ratio with the reaction solution) to adjust the pH to 7-8 and remove residual TfOH;

[0098] Extraction: Extract three times with dichloromethane (volume ratio of 2:1 to the reaction liquid), and combine the organic phases;

[0099] Distillation: After recovering dichloromethane by atmospheric distillation, the organic phase is subjected to vacuum distillation (temperature 275~280℃, vacuum degree 10~15mmHg) and the fraction is collected.

[0100] Recrystallization: The fraction was recrystallized with 95% ethanol (solvent to crude product mass ratio 5~8:1), and dried under vacuum at 60~70℃ for 12~16 hours to obtain white DFBP crystals with a purity ≥99.99%;

[0101] 1.4 Purification Results:

[0102] DFBP yield was 279g, purity was 99.99% (HPLC detection), 2,4'-isomer content was 0.3%, and yield was 82%.

[0103] Step 2: PEEK aggregation

[0104] 2.1 Raw material dosage: DFBP 100g (0.48mol), hydroquinone 45g (0.41mol), potassium carbonate 68g (0.49mol), sodium carbonate 12g (0.11mol), DPS 220g, sulfolane 73g;

[0105] 2.2 Polymerization conditions: Prepolymerization temperature 190℃, time 1h; main polymerization is carried out according to the parameters in Table 1, and 3g of DFBP is added for end capping when the torque reaches 1.9 times the initial value (reaction 6.5h);

[0106] 2.3 Specific Process:

[0107] Nitrogen purging: Solvent and catalyst are added to the polymerization reactor, and high-purity N2 is introduced to replace oxygen. The oxygen content is detected by an online oxygen content detector (oxygen content ≤ 0.5%).

[0108] Material melting: The mixed solvent of diphenyl sulfone and sulfolane was heated to 190°C and kept constant. Under nitrogen protection, the mixture was stirred rapidly. Hydroquinone was added to the molten mixed solvent. After the hydroquinone was completely dissolved, potassium carbonate / sodium carbonate composite salt was added. The reaction was carried out for 15 minutes under nitrogen protection and rapid stirring. Then, 4,4'-difluorobenzophenone was added to the system, and the temperature was rapidly raised to 205°C. After reacting for 2 hours, a gradient temperature-pressure mode was adopted (see Table 1). The viscosity of the reaction system was monitored throughout the process using a torque sensor. When the torque reached 1.9 times the initial value, the polymerization endpoint was determined.

[0109] End-capping treatment: 30 minutes before the endpoint, add DFBP to end cap, which accounts for 3% of the total mass of the monomer;

[0110] Post-treatment: Supercritical CO2 extraction temperature 55℃, pressure 15MPa, time 2h; drying temperature 130℃, time 28h;

[0111] 2.4 Product Performance: PEEK yield 125g, 89%; Mw = 91000 g / mol, PDI = 1.85; melting point 344℃, tensile strength 108MPa, flexural modulus 4.1GPa, batch-to-batch performance variation 2.5%.

[0112] Table 1 Gradient temperature-pressure parameters in the main polymerization stage

[0113]

[0114] Example 2: Pilot-scale production (preparation of 500 kg PEEK)

[0115] Step 1: DFBP synthesis (scaled up according to Example 1)

[0116] Raw material usage:

[0117] 300 kg of fluorobenzene, 85 kg of CCl4, 2.4 kg of TfOH, and 0.72 kg of NMP;

[0118] Process adjustments: A continuous distillation column (30 theoretical plates) was used instead of batch distillation, and a continuous crystallizer (cooling rate 5℃ / h) was used for recrystallization.

[0119] Purification results: DFBP yield was 277.1 kg, purity was 99.99%, and yield was 81.5%.

[0120] Step 2: PEEK polymerization (scaled up to the same scale as Example 1)

[0121] Raw material usage: DFBP 277.1kg, other raw materials scaled up proportionally.

[0122] Process adjustments: The stirring rate was reduced from 500 rpm in the pilot test to 300 rpm (to ensure uniform mass transfer), and the residence time in each stage of the main polymerization was extended by 10%; supercritical CO2 extraction was carried out using continuous equipment (processing capacity 10 kg / h).

[0123] Product performance: PEEK yield 326 kg, 86.9%; Mw = 92000 g / mol, PDI = 1.88; melting point 345℃, tensile strength 106 MPa, flexural modulus 4.0 GPa; batch-to-batch performance variation 2.8%.

[0124] Comparative Example 1

[0125] The only difference from step 1 of Example 1 is that NMP is not added; the rest of the steps are the same as step 1 of Example 1.

[0126] Purification results:

[0127] Purification results: DFBP yield 265.7g, purity 99.99%, yield 78.15%. Product performance: Raw material usage: DFBP 265.7g, other raw materials scaled up proportionally.

[0128] PEEK yield: 270.7 g, yield: 81.5%, Mw: 89000 g / mol, PDI: 1.95; melting point: 339℃, tensile strength: 100 MPa, flexural modulus: 3.9 GPa; batch-to-batch performance variation: 4.7%.

[0129] Comparative Example 2

[0130] The only difference from step 1 of Example 1 is that AlCl3 is used as the catalyst, with an addition amount of 450g, and NMP is not added. The remaining steps are the same as step 1 of Example 1.

[0131] Purification results:

[0132] Purification results: DFBP yield 262.5g, purity 99.99%, yield 77.2%. Product performance: Raw material usage: DFBP 262.5g, other raw materials scaled up proportionally.

[0133] PEEK yield: 264.1 g, yield: 80.5%, Mw: 85000 g / mol, PDI: 2.04; melting point: 337℃, tensile strength: 98 MPa, flexural modulus: 3.8 GPa; batch-to-batch performance variation: 5.5%.

[0134] Comparative Example 3

[0135] Raw materials: 100g of purchased DFBP (99% purity), 45g of hydroquinone, 70g of potassium carbonate, and 300g of DPS;

[0136] Process: single temperature 280℃, pressure 1.0MPa, reaction for 8h, followed by washing with acetone and drying;

[0137] Product performance: PEEK yield 98.1g, with a yield of 78.23%.

[0138] Mw=75000 g / mol, PDI=2.1; melting point 336℃, tensile strength 95MPa, batch-to-batch performance difference 8.5%; raw material cost is 32% higher than Example 1, and wastewater discharge is 12 times that of Example 1.

[0139] The performance of PEEK prepared in Examples 1-2 and Comparative Example 3 was tested, and the results are shown in Table 2.

[0140] Table 2 Performance Test Comparison of Examples 1-2 and Comparative Example 3

[0141]

[0142]

[0143] The experimental results of the above examples and comparative examples demonstrate that the TfOH-NMP composite catalytic system used in this invention to prepare DFBP achieves higher yield and purity. Further application to the preparation of PEEK can reduce costs and wastewater discharge, and the prepared PEEK exhibits higher molecular weight, narrower molecular weight distribution, and superior mechanical properties.

[0144] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing 4,4'-difluorobenzophenone, comprising the following steps: In the presence of trifluoromethanesulfonic acid and N-methylpyrrolidone, CCl4 reacts with fluorobenzene, and the product is hydrolyzed to give 4,4'-difluorobenzophenone.

2. The method for preparing 4,4'-difluorobenzophenone according to claim 1, characterized in that, The molar ratio of fluorobenzene to CCl4 is 3~5:

1.

3. The method for preparing 4,4'-difluorobenzophenone according to claim 1, characterized in that, The mass ratio of trifluoromethanesulfonic acid to N-methylpyrrolidone is 1:(0.2~0.4). The total mass of the trifluoromethanesulfonic acid and N-methylpyrrolidone is 0.5% to 1.0% of the mass of fluorobenzene.

4. The method for preparing 4,4'-difluorobenzophenone according to claim 1, characterized in that, The reaction temperature is 120~140℃; The reaction pressure is 0.3~0.5 MPa; The reaction time is 4-6 hours.

5. The method for preparing 4,4'-difluorobenzophenone according to claim 1, characterized in that, After the reaction is completed, a purification process is also included; The purification process includes: water washing, alkali washing, distillation, and recrystallization.

6. The method for preparing 4,4'-difluorobenzophenone according to claim 1, characterized in that, Includes the following steps: CCl4 is first pre-activated by mixing with trifluoromethanesulfonic acid and N-methylpyrrolidone, and then reacted with fluorobenzene.

7. The method for preparing 4,4'-difluorobenzophenone according to claim 6, characterized in that, The pre-activation temperature is 60~80℃; The pre-activation time is 30-45 minutes.

8. A two-step method for synthesizing polyetheretherketone using carbon tetrachloride, comprising the following steps: S1) 4,4'-difluorobenzophenone is prepared by the method according to any one of claims 1 to 7; S2) Polyether ether ketone is prepared by polymerization reaction using 4,4'-difluorobenzophenone and hydroquinone as raw materials.

9. The method for synthesizing polyetheretherketone via a two-step carbon tetrachloride process according to claim 8, characterized in that, In step S2), an alkaline catalyst is added to the reaction system; The alkaline catalyst includes potassium carbonate and sodium carbonate; The mass ratio of potassium carbonate to sodium carbonate is 1~5:1; The molar ratio of the alkaline catalyst to hydroquinone is 2.2~2.4:1; The solvents for the polymerization reaction include diphenyl sulfone and sulfolane; The volume ratio of the diphenyl sulfone to the sulfolane is 1~5:

1.

10. The method for synthesizing polyetheretherketone via a two-step carbon tetrachloride process according to claim 8, characterized in that, The polymerization reaction includes a prepolymerization stage and a polymerization stage; The temperature of the prepolymerization stage is 180~200℃; The polymerization stage is a gradient temperature-pressure increase; The gradient temperature-pressure boosting includes: Phase 1: Temperature rises from 190℃ to 220℃, and pressure rises from 0.5MPa to 1.0MPa; Second stage: The temperature rises from 220℃ to 280℃, and the pressure rises from 1.0MPa to 1.5MPa; The third stage: the temperature rises from 280℃ to 310℃, and the pressure rises from 1.5MPa to 2.0MPa.

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