A method for preparing 3,3',4,4'-benzophenonetetracarboxylic acid

Abstract

The application discloses a preparation method of 3,3',4,4'-benzophenone tetraacid, which comprises the following steps: (1) performing a preliminary oxidation reaction on 3,3',4,4'-tetramethyl benzophenone with dilute nitric acid in a reaction kettle, oxidizing one methyl on the 3,3',4,4'-tetramethyl benzophenone into a carboxyl group to generate a monocarboxylic acid, or respectively oxidizing two methyl groups on the 3,3',4,4'-tetramethyl benzophenone into carboxyl groups to generate a dicarboxylic acid; and (2) performing a secondary oxidation reaction on the monocarboxylic acid or the dicarboxylic acid obtained in the step (1) with concentrated nitric acid in a micro-tube reactor to generate 3,3',4,4'-benzophenone tetraacid. The step-by-step oxidation method can realize micro-tube type reaction operation and enhances the safety of the reaction. Therefore, the micro-tube type reaction has the advantages of high efficiency, low cost, less waste and the like.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical synthesis, specifically, it relates to a method for preparing 3,3',4,4'-benzophenone tetracarboxylic acid. Background Technology

[0002] 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) is one of the important monomers for synthesizing polyimide (PI). PI resin synthesized from BTDA and other dianhydrides, and then with diamines, is used to manufacture thermoplastic polyimide (TPI) films, which can improve the adhesion strength between the film and copper foil. TPI films are mainly used in the production of flexible copper clad laminates (FCCLs), which are the substrates for flexible printed circuit boards (FPCs). BTDA is obtained by high-temperature or chemical dehydration of 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA).

[0003] The general method for synthesizing BTTA is to react oxalyl chloride with o-xylene via a Friedel-Crafts acylation reaction to generate 3,3',4,4'-tetramethylbenzophenone, and then oxidize the four methyl groups to generate four carboxylic acids, yielding 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA).

[0004] Oxidation is an important step, and there are two commonly used oxidation methods: (1) using acetic acid as a solvent, manganese and cobalt salts as catalysts, and oxygen as an oxidant, and reacting at high temperature and pressure in a reactor. Acetic acid is difficult to recover in this method, the reaction is difficult to complete, and the high temperature and pressure reaction of organic solvents in the presence of oxygen is prone to danger. (2) using dilute nitric acid as an oxidant, and reacting at high temperature and pressure in a reactor. This reaction is exothermic and releases nitric oxide gas, which is difficult to control in production.

[0005] Microtube reactors have many advantages, such as high reaction efficiency, low cost, and less waste generation, and are therefore widely used in organic chemical synthesis. However, microtube reactors can only be used for liquid feed, while 3,3',4,4'-tetramethylbenzophenone is a solid with a melting point of 140°C. It is difficult to feed the solid into a microtube reactor, and normal microtubes cannot achieve a solid-liquid-gas three-phase reaction. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a method for preparing 3,3',4,4'-benzophenone tetracarboxylic acid, which employs a stepwise oxidation method to achieve a microtubular reaction.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing 3,3',4,4'-benzophenone tetracarboxylic acid includes the following steps:

[0009] (1) A preliminary oxidation reaction is carried out in a reaction vessel with dilute nitric acid to oxidize one methyl group on 3,3',4,4'-tetramethylbenzophenone to a carboxyl group, generating a monocarboxylic acid; or...

[0010] The two methyl groups on 3,3',4,4'-tetramethylbenzophenone are oxidized to carboxyl groups to generate dicarboxylic acid;

[0011] (2) The monocarboxylic acid or dicarboxylic acid obtained in step (1) is subjected to a second oxidation reaction in a microtube reactor with concentrated nitric acid to generate 3,3',4,4'-benzophenone tetracarboxylic acid.

[0012] According to the present invention, the mass fraction of dilute nitric acid in step (1) is 20-25%.

[0013] According to the present invention, the molar ratio of nitric acid to 3,3',4,4'-tetramethylbenzophenone in step (1) is 2.2:1 to 2.3:1.

[0014] According to the present invention, in step (1), the temperature for the preliminary oxidation reaction of dilute nitric acid and 3,3',4,4'-tetramethylbenzophenone in the reactor is 120℃~127℃, the pressure is ≤0.15MPa, and the reaction time is 10min.

[0015] According to the present invention, the mass fraction of concentrated nitric acid in step (2) is 65% to 70%.

[0016] According to the present invention, in step (2), the concentrated nitric acid and the product obtained in step (1) undergo a second oxidation reaction in a reactor at a temperature of 170°C to 175°C, a pressure of 1.0 MPa to 1.5 MPa, and a reaction time of 3 min.

[0017] According to the present invention, in step (1), when the two methyl groups on 3,3',4,4'-tetramethylbenzophenone are oxidized to carboxyl groups to generate dicarboxylic acid, one methyl group on each of the two benzene rings is oxidized to a carboxyl group.

[0018] The beneficial effects of this invention are:

[0019] This invention pretreats the reaction mixture and employs a stepwise oxidation method to oxidize one or two methyl groups of 3,3',4,4'-tetramethylbenzophenone into monocarboxylic acids or dicarboxylic acids. The monocarboxylic and dicarboxylic acids are soluble in dilute nitric acid at 120°C, allowing them to be smoothly pumped into a microtube reactor, thus achieving microtube-based reaction operation and enhancing reaction safety. This results in the advantages of high efficiency, low cost, and minimal waste associated with microtube-based reactions. Attached Figure Description

[0020] Figure 1A schematic diagram of the process flow for the reaction system used to prepare 3,3',4,4'-benzophenone tetracarboxylic acid.

[0021] Figure 2 The hydrogen spectrum is obtained by verifying the product prepared by the method described in this invention.

[0022] In the diagram: 1. Mixer; 2. Reactor; 3. Microtube reactor; 4. Tail gas absorption device; 11. Mixer inlet; 12. Mixer outlet; 13. First agitator; 14. First thermometer; 21. Coil; 22. Coil inlet; 23. Second agitator; 24. Second thermometer; 25. Coil outlet; 31. First inlet of microtube reactor; 32. Second inlet of microtube reactor; 33. Outlet of microtube reactor; 41. First pressure relief valve; 42. Second pressure relief valve; 43. Third pressure relief valve; 51. Solid-liquid feed pump; 52. Liquid feed pump. Detailed Implementation

[0023] The present invention will be further explained and illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions.

[0024] like Figure 1 The diagram shown is a schematic of the process flow of the reaction system used to prepare 3,3',4,4'-benzophenone tetracarboxylic acid in this embodiment. The reaction system includes a mixer 1, which has a mixer inlet 11 and a mixer outlet 12. A first stirrer 13 and a first thermometer 14 extend into the mixer 1. The mixer outlet 12 is connected to a tail gas absorption device 4 through a first pipe. A first pressure relief valve 41 is provided on the first pipe to pump the gas generated in the mixer 1 into the tail gas absorption device 4.

[0025] The reactor 2 is provided with a 30cm long (Φ5mm) coil 21 along its inner wall. The coil 21 is provided with a coil inlet 22 and a coil outlet 25. The second stirrer 23 and the second thermometer 24 extend into the reactor 2. The mixer 1 is connected to the reactor 2 through a second pipe. The second pipe is provided with a solid-liquid feed pump 51. The coil outlet 25 in the reactor 2 is connected to the first feed inlet 31 of the microtube reactor on the microtube reactor 3 through a third pipe. The third pipe is provided with a liquid feed pump 52. The reactor 2 is connected to the tail gas absorption device 4 through a fourth pipe. The fourth pipe is provided with a second pressure relief valve 42.

[0026] The microtube reactor 3 is provided with a first inlet 31, a second inlet 32, and an outlet 33. The outlet 33 is connected to the tail gas absorption device 4 through a fifth pipe, and a third pressure relief valve 43 is provided on the fifth pipe.

[0027] The working process of the reaction system used in this embodiment to prepare 3,3',4,4'-benzophenone tetracarboxylic acid is as follows:

[0028] In mixer 1, the reaction mixture, namely 3,3',4,4'-tetramethylbenzophenone and dilute nitric acid, is mixed evenly. This mixture is then pumped into reaction vessel 2 via solid-liquid feed pump 51 for pretreatment, whereby 3,3',4,4'-tetramethylbenzophenone is first oxidized to one or two methyl groups to form a monocarboxylic acid or dicarboxylic acid. The monocarboxylic acid or dicarboxylic acid dissolves in dilute nitric acid at 120°C. The solution is then pumped into microtube reactor 3 via liquid feed pump 52 for further oxidation, oxidizing the monocarboxylic acid or dicarboxylic acid to 3,3',4,4'-benzophenone tetracarboxylic acid. The chemical reaction formula is as follows:

[0029]

[0030] Example 1

[0031] (1) 13 kg of 20% dilute nitric acid (41.3 mol) and 4.5 kg (18.9 mol) of 3,3',4,4'-tetramethylbenzophenone are injected into mixer 1 through mixer inlet 11. The first stirrer 13 is turned on to stir and the two substances are mixed evenly to obtain a solid-liquid mixture. The pressure of the first pressure relief valve 41 is set to 0.1 MPa or 0.15 MPa.

[0032] (2) The internal capacity of the reactor 2 is 1L. 200g of the solid-liquid mixture obtained in the above steps is pumped into the reactor 2 through the solid-liquid feed pump 51. The second stirrer 23 is turned on to stir, so that the solid-liquid mixture undergoes a preliminary oxidation reaction in the reactor 2. The pressure of the second pressure relief valve 42 is set to 0.15MPa. The temperature is raised to 120℃ and reacted for 10min.

[0033] Within this 10 minutes, 300g of the solid-liquid mixture obtained in step (1) is pumped in, so that the coil 21 is immersed below the liquid surface, and the temperature inside the reactor 2 is maintained at 120-122°C, so that one or two methyl groups in 3,3',4,4'-tetramethylbenzophenone are oxidized by dilute nitric acid to become monocarboxylic acid or dicarboxylic acid, and the monocarboxylic acid or dicarboxylic acid dissolves in dilute nitric acid at 120°C.

[0034] (3) Turn on the microtube reactor 3, set the reaction temperature to 170℃, open the third pressure relief valve 43 and set the pressure to 1.5MPa, and pump the solution obtained after step (2) into the microtube reactor 3 from the first feed port 31 of the microtube reactor at a rate of 30mL / min through the liquid feed pump 52. Add concentrated nitric acid with a mass fraction of 65% into the microtube reactor 3 from the second feed port 32 of the microtube reactor at a rate of 30mL / min. The reaction solution stays in the microtube reactor 3 for 3min.

[0035] Meanwhile, the reaction vessel is observed through the sight glass. The speed at which the solid-liquid mixture obtained in step (1) is pumped into the reaction vessel 2 by the solid-liquid feed pump 51 is adjusted so that the liquid level in the reaction vessel 2 is kept balanced. The feeding is completed in about 8 hours.

[0036] (4) Cool the obtained reaction solution to room temperature, precipitate a white solid, filter it, wash it once with 2L of pure water, and dry it to obtain a white powder product.

[0037] 5.50 kg (15.4 mol) of 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA) was obtained, with a yield of 81.5%. The purity of the product was determined to be 97.5% by high performance liquid chromatography (HPLC).

[0038] Example 2

[0039] (1) 11 kg of 25% dilute nitric acid (43.7 mol) and 4.5 kg (18.9 mol) of 3,3',4,4'-tetramethylbenzophenone are injected into mixer 1 through mixer inlet 11. The first stirrer 13 is turned on to stir and the two substances are mixed evenly to obtain a solid-liquid mixture. The pressure of the first pressure relief valve 41 is set to 0.1 MPa or 0.15 MPa.

[0040] (2) The internal capacity of the reactor 2 is 1L. 200g of the solid-liquid mixture obtained in the above steps is pumped into the reactor 2 through the solid-liquid feed pump 51. The second stirrer 23 is turned on, the pressure of the second pressure relief valve 42 is set to 0.15MPa, and the temperature is raised to 125℃ and reacted for 10min.

[0041] Within this 10 minutes, 300g of the solid-liquid mixture obtained in step (1) is pumped in, so that the coil 21 is immersed below the liquid surface, and the temperature inside the reactor 2 is maintained at 125-127°C, so that one or two methyl groups in 3,3',4,4'-tetramethylbenzophenone are oxidized by dilute nitric acid to become monocarboxylic acid or dicarboxylic acid, which dissolve in dilute nitric acid at 120°C.

[0042] (3) Turn on the microtube reactor 3, set the reaction temperature to 170℃, open the third pressure relief valve 43 and set the pressure to 1.5MPa, and pump the solution obtained after step (2) into the microtube reactor 3 from the first feed port 31 of the microtube reactor at a rate of 30mL / min through the liquid feed pump 52. Add concentrated nitric acid with a mass fraction of 65% into the microtube reactor 3 from the second feed port 32 of the microtube reactor at a rate of 30mL / min. The reaction solution stays in the microtube reactor 3 for 3min.

[0043] Meanwhile, the reaction vessel is observed through the sight glass. The speed at which the solid-liquid mixture obtained in step (1) is pumped into the reaction vessel 2 by the solid-liquid feed pump 51 is adjusted so that the liquid level in the reaction vessel 2 is kept balanced. The feeding is completed in about 8 hours.

[0044] (4) Cool the obtained reaction solution to room temperature, precipitate a white solid, filter it, wash it once with 2L of pure water, and dry it to obtain a white powder product.

[0045] 5.48 kg (15.3 mol) of 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA) was obtained, with a yield of 81.0%. The purity of the product was determined to be 97.3% by high performance liquid chromatography (HPLC).

[0046] Example 3

[0047] (1) Inject 13 kg of 20% dilute nitric acid (41.3 mol) and 4.5 kg (18.9 mol) of 3,3',4,4'-tetramethylbenzophenone into mixer 1 through mixer inlet 11. Turn on the first stirrer 13 to stir and mix the two substances evenly to obtain a solid-liquid mixture. Set the pressure of the first pressure relief valve to 0.1 MPa or 0.15 MPa.

[0048] (2) The internal capacity of the reactor 2 is 1L. 200g of the solid-liquid mixture obtained in the above steps is pumped into the reactor 2 through the solid-liquid feed pump 51. The second stirrer 23 is turned on, the pressure of the second pressure relief valve 42 is set to 0.15MPa, and the temperature is raised to 120℃ and reacted for 10min.

[0049] Within this 10 minutes, 300g of the solid-liquid mixture obtained in step (1) is pumped in, so that the coil 21 is immersed below the liquid surface, and the temperature inside the reactor 2 is maintained at 120-122°C, so that one or two methyl groups in 3,3',4,4'-tetramethylbenzophenone are oxidized by dilute nitric acid to become monocarboxylic acid or dicarboxylic acid, and the monocarboxylic acid or dicarboxylic acid dissolves in dilute nitric acid at 120°C.

[0050] (3) Turn on the microtube reactor 3, set the reaction temperature to 175℃, open the third pressure relief valve 43 and set the pressure to 1.5MPa, and pump the solution obtained after step (2) into the microtube reactor 3 from the first feed port 31 of the microtube reactor at a rate of 30mL / min through the liquid feed pump 52. Add concentrated nitric acid with a mass fraction of 65% into the microtube reactor 3 from the second feed port 32 of the microtube reactor at a rate of 30mL / min. The reaction solution stays in the microtube reactor 3 for 3min.

[0051] Meanwhile, the reaction vessel is observed through the sight glass. The speed at which the solid-liquid mixture obtained in step (1) is pumped into the reaction vessel 2 by the solid-liquid feed pump 51 is adjusted so that the liquid level in the reaction vessel 2 is kept balanced. The feeding is completed in about 8 hours.

[0052] (4) Cool the obtained reaction solution to room temperature, precipitate a white solid, filter it, wash it once with 2L of pure water, and dry it to obtain a white powder product.

[0053] 5.57 kg (15.6 mol) of 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA) was obtained, with a yield of 82.5%. The purity of the product was determined to be 97.6% by high performance liquid chromatography (HPLC).

[0054] Example 4

[0055] (1) Inject 13 kg of 20% dilute nitric acid (41.3 mol) and 4.5 kg (18.9 mol) of 3,3',4,4'-tetramethylbenzophenone into mixer 1 through mixer inlet 11. Turn on the first stirrer 13 to stir and mix the two substances evenly to obtain a solid-liquid mixture. Set the pressure of the first pressure relief valve to 0.1 MPa or 0.15 MPa.

[0056] (2) The internal capacity of the reactor 2 is 1L. 200g of the solid-liquid mixture obtained in the above steps is pumped into the reactor 2 through the solid-liquid feed pump 51. The second stirrer 23 is turned on, the pressure of the second pressure relief valve 42 is set to 0.15MPa, and the temperature is raised to 120℃ and reacted for 10min.

[0057] Within this 10 minutes, 300g of the solid-liquid mixture obtained in step (1) is pumped in, so that the coil 21 is immersed below the liquid surface, and the temperature inside the reactor 2 is maintained at 120-122°C, so that one or two methyl groups in 3,3',4,4'-tetramethylbenzophenone are oxidized by dilute nitric acid to become monocarboxylic acid or dicarboxylic acid, and the monocarboxylic acid or dicarboxylic acid dissolves in dilute nitric acid at 120°C.

[0058] (3) Turn on the microtube reactor 3, set the reaction temperature to 175℃, open the third pressure relief valve 43 and set the pressure to 1.5MPa, and pump the solution obtained after step (2) into the microtube reactor 3 from the first feed port 31 of the microtube reactor at a rate of 30mL / min through the liquid feed pump 52. Add concentrated nitric acid with a mass fraction of 70% from the second feed port 32 of the microtube reactor at a rate of 28mL / min. The reaction solution stays in the microtube reactor 3 for 3min.

[0059] Meanwhile, the reaction vessel is observed through the sight glass. The speed at which the solid-liquid mixture obtained in step (1) is pumped into the reaction vessel 2 by the solid-liquid feed pump 51 is adjusted so that the liquid level in the reaction vessel 2 is kept balanced. The feeding is completed in about 8 hours.

[0060] (4) Cool the obtained reaction solution to room temperature, precipitate a white solid, filter it, wash it once with 2L of pure water, and dry it to obtain a white powder product.

[0061] 5.52 kg (15.4 mol) of 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA) was obtained, with a yield of 81.5%. The purity of the product was determined to be 97.2% by high performance liquid chromatography (HPLC).

[0062] In the above embodiments, the nitrogen oxide gas generated by the oxidation process and the decomposition of dilute nitric acid is drawn into the tail gas absorption device 4 through the first pressure relief valve 41, the second pressure relief valve 42 and the third pressure relief valve 43 respectively.

[0063] like Figure 2 As shown, the product obtained was confirmed by proton NMR spectroscopy to be 3,3',4,4'-benzophenone tetracarboxylic acid (BTTA).

[0064] The above description is merely an example of the embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing 3,3',4,4'-benzophenonetetracarboxylic acid, characterized by, The method comprises the following steps: (1) performing a preliminary oxidation reaction on 3,3',4,4'-tetramethylbenzophenone with dilute nitric acid in a reaction kettle to oxidize one methyl group on the 3,3',4,4'-tetramethylbenzophenone into a carboxyl group, thereby generating a monocarboxylic acid; or, performing a preliminary oxidation reaction on 3,3',4,4'-tetramethylbenzophenone with dilute nitric acid in a reaction kettle to oxidize two methyl groups on the 3,3',4,4'-tetramethylbenzophenone into carboxyl groups, thereby generating a dicarboxylic acid; (2) performing a secondary oxidation reaction on the monocarboxylic acid or the dicarboxylic acid obtained in step (1) with concentrated nitric acid in a micro-tube reactor, thereby generating 3,3',4,4'-benzophenonetetracarboxylic acid.

2. The production method according to claim 1, wherein The mass fraction of the dilute nitric acid in step (1) is 20-25%.

3. The production method according to claim 1, wherein The molar ratio of the nitric acid to the 3,3',4,4'-tetramethylbenzophenone in step (1) is 2.2:1-2.3:

1.

4. The production method according to claim 1, wherein The preliminary oxidation reaction of the dilute nitric acid and the 3,3',4,4'-tetramethylbenzophenone in step (1) is performed in a reaction kettle at a temperature of 120-127°C, a pressure of ≤0.15 MPa, and a reaction time of 10 min.

5. The production method according to claim 1, wherein The mass fraction of the concentrated nitric acid in step (2) is 65-70%.

6. The production method according to claim 1, wherein The secondary oxidation reaction of the concentrated nitric acid and the product obtained in step (1) in step (2) is performed in a reaction kettle at a temperature of 170-175°C, a pressure of ≤1.5 MPa, and a reaction time of 3 min.

7. The production method according to claim 1, wherein In step (1), when the two methyl groups on the 3,3',4,4'-tetramethylbenzophenone are oxidized into carboxyl groups to generate a dicarboxylic acid, one methyl group on each benzene ring is oxidized into a carboxyl group.

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