Process for the production of pyromellitic acid

Abstract

The application discloses a production method of pyromellitic acid. The method comprises the following steps: contacting tetramethylbenzene with a catalyst to generate an oxidation reaction in the presence of an oxygen-containing gas to obtain pyromellitic acid; and the catalyst comprises carbon nanomaterial and alkali metal peroxysulfuric acid hydrogen salt. The pyromellitic acid prepared by the method of the application has no transition metal salt residue, the reaction has no corrosion, and the method of the application has the advantages of high pyromellitic acid yield.

Description

Technical Field

[0001] This invention belongs to the field of pyromellitic acid, and specifically relates to a method for producing pyromellitic acid. Background Technology

[0002] Pyromellitic acid (1,2,4,5-phenylenetetracarboxylic acid, PMA) is an important organic intermediate widely used in the preparation of various high-end fine materials. The dehydration product of pyromellitic acid is pyromellitic dianhydride (1,2,4,5-phenylenetetracarboxylic dianhydride, PMDA), which is one of the important precursors for the synthesis of polyimide (PI). Polyimide is a special polymer material with advantages such as wide operating temperature, chemical resistance, and high strength. DuPont first launched commercial polyimide in 1961. Since then, polyimide, as a special engineering material, has been widely used in aerospace, microelectronics, nanotechnology, liquid crystals, separation membranes, lasers, and other fields. Therefore, the green production of pyromellitic acid is of great significance for the efficient synthesis of polyimide.

[0003] The synthesis of PMMA generally involves the oxidation of mesitylene (1,2,4,5-tetramethylbenzene), which is further divided into gas-phase and liquid-phase methods. Although the gas-phase method can directly generate PMDA, the high reaction temperature results in numerous byproducts and lower product purity, requiring further hydrolysis of PMDA to PMA for purification. Liquid-phase oxidation typically uses transition metal / bromine catalysts, which are highly corrosive and hazardous, easily causing equipment corrosion and significant wastewater pollution.

[0004] US5041633 discloses a method for preparing pyromellitic acid (PMA) using a Co-Mn-Br homogeneous catalyst to catalytically oxidize mesitylene. However, the problem of residual transition metal ions causing corrosion in the product and equipment remains unresolved, and the yield of PMA prepared by this method needs further improvement.

[0005] Existing methods for preparing pyromellitic acid suffer from various problems, including the potential for residual transition metal ions, corrosion of the reaction apparatus, and low yields. Therefore, further research and development of methods for producing pyromellitic acid is of great significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for producing pyromellitic acid. The pyromellitic acid prepared by this method has no transition metal salt residues, the reaction is non-corrosive, and the method of this invention has the advantages of high pyromellitic acid yield.

[0007] This invention provides a method for producing pyromellitic tetracarboxylic acid, wherein the method includes the following steps:

[0008] In the presence of oxygen-containing gas, mesitylene reacts with a catalyst to undergo an oxidation reaction to yield pyromellitic acid; preferably, the catalyst comprises carbon nanomaterials and alkali metal persulfate.

[0009] According to the present invention, the oxygen-containing gas is preferably air.

[0010] According to the present invention, the alkali metal peroxymonosulfate includes potassium monoperoxymonosulfate. Potassium monoperoxymonosulfate is a triple salt formed by the combination of potassium peroxymonosulfate, potassium bisulfate, and potassium sulfate, with the molecular formula 2KHSO5·KHSO4·K2SO4, abbreviated as PMS.

[0011] According to the present invention, the carbon nanomaterial includes at least one of carbon nanotubes and carbon nanofibers.

[0012] According to the present invention, the mass ratio of alkali metal persulfate to carbon nanomaterial in the catalyst is 0.5 to 10, preferably 4 to 7.

[0013] According to the present invention, in the catalyst, the mass ratio of alkali metal persulfate to mesitylene is 0.05 to 0.5, preferably 0.1 to 0.2.

[0014] According to the present invention, the temperature of the oxidation reaction is 120–270°C, preferably 180–220°C.

[0015] According to the present invention, the pressure of the oxidation reaction is 10 to 30 bar. Preferably, nitrogen gas is introduced to adjust the pressure of the oxidation reaction.

[0016] According to the present invention, the oxidation reaction takes 60 to 150 minutes.

[0017] According to the present invention, preferably, carbon nanomaterials are first added to mesitylene, and then alkali metal persulfate is added.

[0018] According to the present invention, preferably, after the reaction is completed, cooling crystallization is carried out at a temperature of 10 to 60°C.

[0019] According to the present invention, the oxidation reaction is a liquid-phase reaction. Preferably, mesitylene is dispersed in a solvent. More preferably, the solvent includes at least one of acetic acid and water. Even more preferably, the mass ratio of the solvent added to mesitylene is 2 to 10.

[0020] Compared with the prior art, the main beneficial effects of the present invention are as follows:

[0021] In the production method of pyromellitic acid of the present invention, no transition metals or bromine catalysts are involved in the reaction. The pyromellitic acid prepared by the method has no transition metal residues, the reaction is non-corrosive, and there is very little waste in the whole reaction process. It also has the advantages of high yield and low impurities of pyromellitic acid. Detailed Implementation

[0022] The technical solution of the present invention will be described in detail below with reference to the embodiments.

[0023] In this invention, the inner diameter of the carbon nanotubes in each example is 5–10 nm.

[0024] Example 1

[0025] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 2.5 g of carbon nanotubes were added. The mixture was gradually heated to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The mixture was then heated again to 200 °C and the pressure increased to 30 bar, and the reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize, and the filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 92.3 mol.%, and the PMA selectivity was 91.5 mol.%.

[0026] For ease of comparison, the experimental results are listed in Table 1.

[0027] Example 2

[0028] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 10.0 g of carbon nanotubes were added. The mixture was gradually heated to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The mixture was then heated again to 200 °C and the pressure increased to 30 bar, and the reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize, and the filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 92.2 mol.%, and the PMA selectivity was 82.1 mol.%.

[0029] For ease of comparison, the experimental results are listed in Table 1.

[0030] Example 3

[0031] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 1.5 g of carbon nanotubes were added. The mixture was gradually heated to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The mixture was then heated again to 200 °C and the pressure increased to 30 bar, and the reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize, and the filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 85.2 mol.%, and the PMA selectivity was 90.6 mol.%.

[0032] For ease of comparison, the experimental results are listed in Table 1.

[0033] Example 4

[0034] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 1.25 g of carbon nanotubes were added. The temperature in the stirred tank was gradually increased to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The temperature in the stirred tank was raised again to 200 °C, and the pressure was increased to 30 bar. The reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize. The filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion rate was 83.1 mol.%, and the PMA selectivity was 91.0 mol.%.

[0035] For ease of comparison, the experimental results are listed in Table 1.

[0036] Example 5

[0037] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 2.5 g of carbon nanofibers were added. The mixture was gradually heated to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The mixture was then heated again to 200 °C and the pressure increased to 30 bar, and the reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanofibers. The filtrate was cooled at 15 °C to crystallize, and the filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 90.5 mol.%, and the PMA selectivity was 89.7 mol.%.

[0038] For ease of comparison, the experimental results are listed in Table 1.

[0039] Example 6

[0040] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 5 g of carbon nanotubes were added. The temperature in the stirred tank was gradually increased to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 20 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The temperature in the stirred tank was raised again to 200 °C, and the pressure was increased to 30 bar. The reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize. The filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion rate was 95.2 mol.%, and the PMA selectivity was 85.8 mol.%.

[0041] For ease of comparison, the experimental results are listed in Table 1.

[0042] Example 7

[0043] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 5 g of carbon nanotubes were added. The temperature in the stirred tank was gradually increased to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 5 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The temperature in the stirred tank was raised again to 200 °C, and the pressure was increased to 30 bar. The reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize. The filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion rate was 80.2 mol.%, and the PMA selectivity was 90.1 mol.%.

[0044] For ease of comparison, the experimental results are listed in Table 1.

[0045] Example 8

[0046] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 2.5 g of carbon nanotubes were added. The mixture was gradually heated to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The mixture was then heated again to 150 °C and the pressure increased to 30 bar, and the reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize, and the filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 82.1 mol.%, and the PMA selectivity was 80.3 mol.%.

[0047] For ease of comparison, the experimental results are listed in Table 1.

[0048] Example 9

[0049] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 2.5 g of carbon nanotubes were added. The mixture was gradually heated to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The mixture was then heated again to 260 °C and the pressure increased to 30 bar, and the reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize, and the filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 91.3 mol.%, and the PMA selectivity was 78.2 mol.%.

[0050] For ease of comparison, the experimental results are listed in Table 1.

[0051] Comparative Example 1

[0052] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 2.5 g of activated carbon was added. The temperature in the stirred tank was gradually increased to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium persulfate (PMS) was added, and air was introduced at a rate of 10 L / min. The temperature in the stirred tank was raised again to 200 °C, and the pressure increased to 30 bar. The reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and activated carbon. The filtrate was cooled at 15 °C to crystallize. The filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 65.2 mol.%, and the PMA selectivity was 51.3 mol.%.

[0053] For ease of comparison, the experimental results are listed in Table 1.

[0054] Comparative Example 2

[0055] 100 g of mesitylene (98 wt.%) was added to 400 g of acetic acid solvent and stirred until homogeneous. Then, 2.5 g of carbon nanotubes were added. The mixture was gradually heated to 140 °C over 50 min while nitrogen gas was introduced, maintaining a pressure of 20 bar. Subsequently, 10 g of potassium sulfate was added, and air was introduced at a rate of 10 L / min. The mixture was then heated again to 200 °C and the pressure increased to 30 bar, and the reaction was carried out for 2 h. The reaction solution was filtered while hot to remove solid impurities and carbon nanotubes. The filtrate was cooled at 15 °C to crystallize, and the filtered solid was then dried in an oven at 100 °C for 6 h to obtain pyromellitic acid (PMA) product. The mesitylene conversion was 35.5 mol.%, and the PMA selectivity was 14.2 mol.%.

[0056] For ease of comparison, the experimental results are listed in Table 1.

[0057] Table 1

[0058]

[0059]

[0060] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for producing pyromellitic acid, characterized by, The method comprises the following steps: contacting durene with a catalyst to generate an oxidation reaction in the presence of an oxygen-containing gas to obtain pyromellitic acid; the catalyst is a carbon nanomaterial and an alkali metal hydrogen persulfate; The alkali metal hydrogen persulfate is potassium monopersulfate; The carbon nanomaterial is at least one of carbon nanotubes and carbon nanofibers; The mass ratio of the alkali metal hydrogen persulfate to the carbon nanomaterial is 0.5-10; The temperature of the oxidation reaction is 120-270 DEG C.

2. The production method according to claim 1, characterized by, The mass ratio of the alkali metal hydrogen persulfate to the carbon nanomaterial is 4-7.

3. The production method according to claim 1, characterized by, The mass ratio of the alkali metal hydrogen persulfate to durene is 0.05-0.

5.

4. The production method according to claim 1, characterized by, The mass ratio of the alkali metal hydrogen persulfate to durene is 0.1-0.

2.

5. The production method according to claim 1, characterized by, The temperature of the oxidation reaction is 180-220 DEG C.

6. The production method according to claim 1, characterized by, The pressure of the oxidation reaction is 10-30 bar.

7. The production method according to claim 1, characterized by, The time of the oxidation reaction is 60-150 min.

8. The production method according to claim 1, characterized by, The oxidation reaction is a liquid phase reaction.

9. The production method according to claim 8, characterized by, Durene is dispersed in a solvent to perform the liquid phase reaction.

10. The production method according to claim 9, characterized by, The solvent is at least one of acetic acid and water.

11. The production method according to claim 9, characterized by, The mass ratio of the solvent to durene is 2-10.

12. The production method according to claim 1, characterized by, The carbon nanomaterial is added to durene first, and then the alkali metal hydrogen persulfate is added.

13. The production method according to claim 1, characterized by, After the reaction is completed, cooling crystallization is performed, and the temperature of the cooling crystallization is 10-60 DEG C.

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