A method for treating waste gas from production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride
By treating the organic solvents in the waste gas through condensation and deep oxidation, and using organic absorbent and alkaline solution to generate high-purity nitrates, the problem of organic solvent impurities in the waste gas during the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride was solved, and the by-products were utilized for resource utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEBEI DONGLI NEW MATERIAL CO LTD
- Filing Date
- 2022-12-15
- Publication Date
- 2026-05-12
AI Technical Summary
The waste gas produced during the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride contains a high concentration of organic solvents, resulting in low purity and poor quality of the byproduct nitrate, which cannot be utilized as a resource.
The organic solvents in the waste gas are removed by condensation treatment, and nitrogen oxides are deeply oxidized by organic absorbent and air. Then, high-purity nitrates are generated by absorption with an alkaline solution.
This method achieves effective separation of organic solvents and complete oxidation of nitrogen oxides in waste gas, producing nitrates that meet standards, realizing the resource utilization of resources, and reducing production costs.
Abstract
Description
Technical Field
[0001] This invention relates to the field of waste gas resource utilization technology, and provides a method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride. Background Technology
[0002] 3,3',4,4'-Diphenyl ether tetracarboxylic dianhydride (ODPA) is an important monomer for synthesizing polyimides. Monoether anhydride-type polyimides (PEI) synthesized using ODPA as a monomer exhibit superior properties. It has become an invaluable material in electrical insulation materials, electrode miniaturization, high capacity, and improved heat resistance, and also has significant applications in the manufacture of high-temperature oil-free bearings. In recent years, the rapid development of industries such as aerospace, missiles, electronics, electrical machinery, and transportation has created an urgent need for new polymer materials that can maintain structural strength under conditions of drastic temperature fluctuations, high-dose penetrating radiation, and corrosive media. PEI is one of the ideal materials that meets these requirements. However, with the large-scale and industrialized development of ODPA, some problems encountered in small-batch production are becoming increasingly apparent in mass production, particularly related environmental issues.
[0003] Currently, the main method for synthesizing 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride involves using N,N-dimethylformamide (DMF) or dimethylacetamide (DMAC) as solvents and N-methyl-4-nitrophthalimide as a raw material. The mixture undergoes coupling condensation to obtain oxobis-(N-methylphthalimide), followed by hydrolysis, acidification, recrystallization purification, and dehydration. However, the above synthesis process generates waste gas containing high concentrations of N,N-dimethylformamide or dimethylacetamide. These organic solvents accompany the waste gas into the waste gas treatment system, reacting with the alkaline absorbent to generate impurities such as dimethylamine. Furthermore, the waste gas is difficult to fully convert into nitric acid, resulting in low purity and poor quality of the nitrate byproduct generated after absorption by the alkaline absorbent. The obtained nitrate does not meet standard requirements and cannot be sold as a byproduct, hindering its recycling and causing resource waste. Summary of the Invention
[0004] To address the problem in existing technologies where the waste gas generated during the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride is contaminated with organic solvents and other impurities, resulting in low purity and poor quality of the byproduct nitrate, this invention provides a method for preparing nitrate using the waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride. This method effectively removes impurities from the waste gas during the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, thereby achieving clean production of the byproduct nitrate and realizing the resource utilization of the byproduct.
[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:
[0006] In a first aspect, the present invention provides a method for preparing nitrates from waste gas produced by the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, comprising the following steps:
[0007] The waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride is condensed to obtain a recovered solvent and treated waste gas. The treated waste gas and air are simultaneously passed into an organic absorbent liquid for deep treatment for 1-3 minutes. Then, the treated mixed gas is passed into a strong alkaline solution for absorption. The resulting alkaline absorbent liquid is distilled, filtered, and dried to obtain the byproduct nitrate.
[0008] The organic absorbent is at least one of liquid paraffin or glycerin.
[0009] The exhaust gas is a mixed gas generated during the coupling condensation reaction in the production process of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride.
[0010] The waste gas generated by the coupling condensation reaction of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride contains a high concentration of organic solvents. These organic solvents enter the waste gas treatment system along with the waste gas, affecting the oxidation of nitrogen oxides in the waste gas and causing incomplete oxidation. This results in the production of some nitrous acid. After subsequent absorption by a strongly alkaline absorbent, the organic solvents easily react with the strong alkaline solution to generate the impurity dimethylamine, while the nitrous acid reacts with the strong alkaline solution to generate nitrite. This results in the generated byproduct nitrate being mixed with nitrite and other impurities, with low purity and poor quality.
[0011] The method provided by this invention first treats the waste gas from the production process of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride using a condenser. Physical condensation removes the organic solvents (DMF / DMAC) doped into the waste gas, and some impurities dissolved in the organic solvents are also removed, thus achieving effective separation of the gas and organic solvents. The separated gas is then transported to an organic absorbent liquid, which simultaneously introduces air to induce deep oxidation. The organic absorbent liquid further absorbs any uncondensed organic solvents and their decomposition products. The main nitrogen oxides in the waste gas are oxidized by sufficient air to generate nitric acid, which is then absorbed by an alkaline absorbent liquid to obtain high-quality nitrate as a byproduct, enabling the resource utilization of nitrate. This method solves the problem in existing technologies where the waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride contains impurities such as organic solvents, resulting in poor-quality nitrate that cannot be sold as a byproduct, leading to resource waste.
[0012] Preferably, the organic absorbent is a mixture of liquid paraffin and glycerin in a mass ratio of 1:1-2.5.
[0013] Preferably, the condensation process is carried out using a condenser, and the condensation gas flow rate is 300L / h-450L / h.
[0014] Preferably, the temperature of the refrigerant in the condenser is 5-10°C.
[0015] More preferably, the refrigerant temperature is 7°C.
[0016] By condensing the waste gas produced in the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, the entrained organic solvents can be removed through physical condensation. This avoids the subsequent reaction of the alkaline absorbent with a large amount of organic solvent to form dimethylamine, which would cause quality problems for the byproduct nitrate.
[0017] Preferably, the volume ratio of the treated waste gas to air is 1:2.5-3.0.
[0018] Preferably, the flow rate of the treated waste gas into the organic absorbent liquid is 280L / h-290L / h, and the flow rate of the air into the organic absorbent liquid is 600L / h-800L / h.
[0019] Preferably, the temperature of the organic absorbent is 20-35°C.
[0020] Preferably, the strong alkaline solution is one or more of sodium hydroxide solution, potassium hydroxide solution, or calcium hydroxide solution.
[0021] Preferably, the pH of the strong alkaline solution is 10.0-14.0.
[0022] Preferably, the vacuum degree of the distillation is 0.07MPa~0.085MPa, and the distillation temperature is 75℃-90℃.
[0023] Preferably, the filtration is a post-centrifugation filtration.
[0024] More preferably, the centrifugation speed is 400-450 r / min and the centrifugation time is 10-20 min.
[0025] Preferably, the vacuum degree of the drying process is 0.08~0.095MPa, and the temperature is 50-65℃.
[0026] Preferably, the pH at the end of the absorption of the alkaline absorbent solution is 8.0-9.5.
[0027] This invention utilizes the principle of acid-base neutralization to absorb oxidized nitrogen oxides. When the pH is 8-9.5, the alkaline absorption solution has reached saturation, and absorption can be stopped and replaced with a new alkaline solution.
[0028] This invention removes organic solvents from the waste gas produced during the coupling condensation reaction of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride by condensing the waste gas, and then obtains nitrates as a byproduct that meets the standards through deep treatment and absorption of the waste gas. This achieves the resource utilization of industrial hazardous waste, reduces production costs, and makes the resource utilization of the 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride production process more efficient and green. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0030] Example 1
[0031] This embodiment provides a method for preparing nitrates from waste gas produced by 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride production. The specific steps are as follows:
[0032] 30 kg of N-methyl-4-nitrophthalimide was added to the system as a raw material, 85 kg of DMF as a solvent, and 2.5 kg of sodium nitrite as a catalyst. After condensation for 12 h, oxobis-(N-methylphthalimide) was obtained. The gas generated during the reaction was fed into a condenser at a flow rate of approximately 380 L / h. After water condensation at 7 °C, 0.82 kg of DMF was recovered. Then, liquid paraffin was simultaneously introduced at a flow rate of approximately 280 L / h and an air flow rate of 600 L / h for treatment. The treated gas was then absorbed using 24 kg of 25% sodium hydroxide solution (pH 12.8). After absorption, the pH was 8.95.
[0033] The absorbent was subjected to vacuum distillation at 0.08 MPa and 80°C to remove water. After cooling to room temperature, it was centrifuged at 400 r / min for 20 min to obtain sodium nitrate mother liquor and 10.5 kg of sodium nitrate. After vacuum drying at 0.085 MPa and 55°C, 10.08 kg of sodium nitrate was obtained. The TOC content was 1.3 mg / L, the sodium nitrate content was 99.65%, and the moisture content was 0.32%, which meets the requirements of Grade I general industrial grade in GB / T 4553-2016.
[0034] Example 2
[0035] This embodiment provides a method for preparing nitrates from waste gas produced by 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride production. The specific steps are as follows:
[0036] 30 kg of N-methyl-4-nitrophthalimide was added to the system as a raw material, 85 kg of DMF as a solvent, and 2.5 kg of sodium nitrite as a catalyst. After condensation for 12 h, oxobis-(N-methylphthalimide) was obtained. The gas generated during the reaction was fed into a condenser at a flow rate of approximately 370 L / h. After water condensation at 7 °C, 0.75 kg of DMF was recovered. Then, liquid paraffin was simultaneously introduced at a flow rate of approximately 290 L / h and an air flow rate of 800 L / h for treatment. The treated gas was then absorbed using 23.8 kg of 25% sodium hydroxide solution (pH 12.2). After absorption, the pH was 9.0.
[0037] The absorbent was subjected to vacuum distillation at 0.085 MPa and 85°C to remove water. After cooling to room temperature, it was centrifuged at 450 r / min for 20 min to obtain sodium nitrate mother liquor and 9.88 kg of sodium nitrate. This was then dried under vacuum at 0.085 MPa and 55°C.
[0038] 9.49 kg of sodium nitrate was obtained. The TOC content was 0.9 mg / L, the sodium nitrate content was 99.68%, and the moisture content was 0.30%, which meets the requirements of Grade I general industrial product in GB / T 4553-2016.
[0039] Example 3
[0040] This embodiment provides a method for preparing nitrates from waste gas produced by 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride production. The specific steps are as follows:
[0041] 30 kg of N-methyl-4-nitrophthalimide, 85 kg of DMAC, and 2.5 kg of sodium nitrite were added to the system. After a condensation reaction for 12 h, oxobis-(N-methylphthalimide) was obtained. The gas generated during the reaction was fed into a condenser at a flow rate of approximately 350 L / h. After water condensation at 7 °C, 0.79 kg of DMF was recovered. Then, liquid paraffin was simultaneously introduced at a flow rate of approximately 280 L / h and an air flow rate of 750 L / h for treatment. The treated gas was then absorbed using 23.8 kg of 25% sodium hydroxide solution (pH 12.5). After absorption, the pH was 9.15.
[0042] The absorbent was subjected to vacuum distillation at 0.080 MPa and 85°C to remove water. After cooling to room temperature, it was centrifuged at 500 r / min for 18 min to obtain sodium nitrate mother liquor and 10.43 kg of sodium nitrate. After vacuum drying at 0.085 MPa and 55°C, 9.49 kg of sodium nitrate was obtained. The TOC content was 0.9 mg / L, the sodium nitrate content was 99.67%, and the moisture content was 0.31%, which meets the requirements of Grade I general industrial grade in GB / T 4553-2016.
[0043] Example 4
[0044] This embodiment provides a method for preparing nitrates from waste gas produced by 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride production. The specific steps are as follows:
[0045] 30 kg of N-methyl-4-nitrophthalimide, 85 kg of DMAC, and 2.5 kg of sodium nitrite were added to the system. After a condensation reaction for 12 h, oxobis-(N-methylphthalimide) was obtained. The gas generated during the reaction was fed into a condenser at a flow rate of approximately 380 L / h. After water condensation at 7 °C, 0.82 kg of DMF was recovered. Then, a mixture of liquid paraffin and glycerol with a mass ratio of 1:1.5 was simultaneously introduced at a flow rate of approximately 280 L / h and an air flow rate of 750 L / h for further treatment. The treated gas was then absorbed using 23.8 kg of 25% sodium hydroxide solution (pH 12.7). After absorption, the pH was 9.05.
[0046] The absorbent was subjected to vacuum distillation at 0.085 MPa and 85°C to remove water. After cooling to room temperature, it was centrifuged at 500 r / min for 18 min to obtain sodium nitrate mother liquor and 10.97 kg of sodium nitrate. After vacuum drying at 0.085 MPa and 55°C, 10.49 kg of sodium nitrate was obtained. The TOC content was tested to be 0.5 mg / L and the sodium nitrate content was 99.89%, which meets the requirements of Grade I general industrial product in GB / T 4553-2016.
[0047] Comparative Example 1
[0048] This comparative example provides a method for preparing nitrates from waste gas produced by 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride production. The specific steps are as follows:
[0049] 30 kg of N-methyl-4-nitrophthalimide, 85 kg of DMAC, and 2.5 kg of sodium nitrite were added to the system. After a condensation reaction for 12 h, oxobis-(N-methylphthalimide) was obtained. The gas generated during the reaction was fed into a condenser at a flow rate of approximately 350 L / h. After water condensation at 7 °C, 0.79 kg of DMF was recovered. Then, polyethylene glycol 400 was simultaneously introduced at a flow rate of approximately 280 L / h and an air flow rate of 750 L / h for treatment. The treated gas was then absorbed using 23.8 kg of 25% sodium hydroxide solution. After absorption, the pH was 9.15.
[0050] The absorbent was subjected to vacuum distillation at 0.085 MPa and 85°C to remove water. After cooling to room temperature, it was centrifuged at 500 r / min for 18 min to obtain sodium nitrate mother liquor and 10.5 kg of sodium nitrate. This was then dried under vacuum at 0.085 MPa and 55°C.
[0051] 10.08 kg of sodium nitrate was obtained. The TOC content was 2310 mg / L, the sodium nitrate content was 97.33%, and the moisture content was 0.32%, which does not meet the standard of Grade I general industrial products in GB / T 4553-2016.
[0052] Comparative Example 2
[0053] This comparative example provides a method for preparing nitrates from waste gas produced by 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride production. The specific steps are as follows:
[0054] 30 kg of N-methyl-4-nitrophthalimide, 85 kg of DMAC, and 2.5 kg of sodium nitrite were added to the system. After a condensation reaction for 12 h, oxobis-(N-methylphthalimide) was obtained. The gas generated during the reaction was fed into a condenser at a flow rate of approximately 380 L / h. After water condensation at 7 °C, 0.79 kg of DMF was recovered. Then, liquid paraffin was simultaneously introduced at a flow rate of approximately 290 L / h and an air flow rate of 780 L / h for treatment. The treated gas was then absorbed using 23.8 kg of a 25% ammonia solution (pH 9.0). After absorption, the pH was 9.17.
[0055] The absorbent was subjected to vacuum distillation at 0.085 MPa and 85°C to remove water. After cooling to room temperature, it was centrifuged at 500 r / min for 18 min to obtain sodium nitrate mother liquor and 10.5 kg of sodium nitrate. This was then dried under vacuum at 0.080 MPa and 55°C.
[0056] 10.08 kg of sodium nitrate was obtained. The TOC content was 1115 mg / L, the sodium nitrate content was 97.78%, and the moisture content was 0.38%, which does not meet the standard of Grade I general industrial products in GB / T 4553-2016.
[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, characterized in that, Includes the following steps: The waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride is condensed to obtain a recovered solvent and treated waste gas; the treated waste gas and air are simultaneously passed into an organic absorbent liquid, and then the treated mixed gas is passed into a strong alkaline solution for absorption; the resulting alkaline absorbent liquid is distilled, filtered, and dried to obtain the byproduct nitrate. The organic absorbent is a liquid paraffin, glycerin, or a mixture of liquid paraffin and glycerin.
2. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1, characterized in that, The organic absorbent is a mixed solution of liquid paraffin and glycerin in a mass ratio of 1:1-2.
5.
3. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1, characterized in that, The condensation treatment is carried out using a condenser, and the flow rate of the waste gas from the production of 3',4,4'-diphenyl ether tetracarboxylic dianhydride is 300L / h-450L / h; the temperature of the refrigerant in the condenser is 5-10℃.
4. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1, characterized in that, The volume ratio of the treated waste gas to air is 1:2.5-3.
0.
5. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1, characterized in that, The flow rate of the treated waste gas into the organic absorbent liquid is 280L / h-290L / h, and the flow rate of the air into the organic absorbent liquid is 600L / h-800L / h.
6. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1 or 5, characterized in that, The temperature of the organic absorbent is 20℃-35℃.
7. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1, characterized in that, The strong alkaline solution is one or more of sodium hydroxide solution, potassium hydroxide solution, or calcium hydroxide solution.
8. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1 or 7, characterized in that, The pH of the strong alkaline solution is 10.0-14.
0.
9. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1, characterized in that, The vacuum degree of the distillation is 0.07MPa~0.085MPa, and the distillation temperature is 75℃-90℃.
10. The method for treating waste gas from the production of 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride as described in claim 1, characterized in that, The pH at the endpoint of absorption with alkaline absorbent solution is 8.0-9.5.