A method and system for resource-based treatment of nitropyrazole mixed acid waste liquid

Abstract

This invention discloses a method and system for the resource-based treatment of nitropyrazole-based mixed acid waste liquid, belonging to the field of wastewater resource-based treatment technology. The method includes: a method for treating pyrazole and N-nitropyrazole in N-nitration waste acid using advanced oxidation technology, and a method for recovering 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid. In the treatment of N-nitration waste acid solution, this invention employs advanced oxidation technology, eliminating the need for oxidants. It utilizes the acetic acid solution naturally present in the wastewater and added iron filings to achieve effective degradation of pyrazole and N-nitropyrazole. In the C-nitration process, this invention utilizes an extractant extraction method, effectively reducing costs, simplifying operation, and avoiding the risk of DNP explosion due to high-temperature heating. Simultaneously, the DNP extraction recovery rate reaches 99.8%, the recovered sulfuric acid concentration reaches 97%, and the COD content is below 100 mg / L.

Description

Technical Field

[0001] This invention relates to the field of wastewater resource utilization technology, specifically to a method and system for resource utilization of nitropyrazole mixed acid waste liquid. Background Technology

[0002] Nitropyrazole compounds are important chemical raw materials, and their synthesis and purification inevitably generate large amounts of wastewater. The synthesis of 3,4-dinitropyrazole (DNP) typically employs a three-step process: using pyrazole as a raw material, N-nitration (nitric acid nitration) yields N-nitropyrazole, followed by rearrangement and C-nitration to obtain 3,4-dinitropyrazole. Because the synthesis process requires a series of mixed acid reactions involving acetic acid, nitric acid, and sulfuric acid, the resulting wastewater is highly acidic. Furthermore, the wastewater contains nitro compounds such as pyrazole, N-nitropyrazole, 3-nitropyrazole, and 3,4-dinitropyrazole. This wastewater, containing large amounts of acidic nitro compounds, cannot be biodegraded once it enters the environment, and improper treatment can severely harm the ecological environment.

[0003] Traditional industrial wastewater treatment methods typically employ a combination of processes including stripping, thermal decomposition, and ammonia distillation to improve the biodegradability of wastewater. However, during this process, the wastewater contains large amounts of nitro compounds such as pyrazole, N-nitropyrazole, 3-nitropyrazole, and 3,4-dinitropyrazole, which pose certain safety hazards when heated at high temperatures. Furthermore, this method requires equipment that is resistant to high temperatures and corrosion, significantly increasing treatment costs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a treatment process for the resource-based recovery of DNP and sulfuric acid from mixed nitrate and sulfuric acid wastewater. This process addresses the safety hazards and high treatment costs associated with high-temperature heating in traditional processes involving stripping, thermal decomposition, and ammonia distillation. Furthermore, it utilizes advanced oxidation technology to effectively degrade nitro compounds in the water, achieving compliant discharge.

[0005] The present invention adopts the following technical solution.

[0006] The first aspect of the present invention discloses a method for resource-based treatment of nitropyrazole mixed acid waste liquid, comprising advanced oxidation treatment of pyrazole and N-nitropyrazole in N-nitration waste acid and recovery of 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid;

[0007] The method of using advanced oxidation to treat pyrazole and N-nitropyrazole in N-nitrated waste acid includes taking N-nitrated waste acid solution, mixing a set amount of iron filings, and shaking at a constant temperature under set conditions to obtain waste liquid after degradation of pyrazole and N-nitropyrazole.

[0008] The recovery of 3,4-dinitropyrazole and sulfuric acid from the C-nitration process waste liquid includes the recovery of 3,4-dinitropyrazole from the C-nitration process using an extractant and the recovery of sulfuric acid from the C-nitration process using a distillation method.

[0009] Preferably, the N-nitration waste acid solution is prepared by diluting the N-nitration waste water solution and then placing the diluted waste water solution into a reaction vessel.

[0010] Preferably, the set amount of iron filings is 0.01g to 0.1g of iron filings added to the reaction vessel.

[0011] Preferably, the set conditions are to place the reaction vessel in a water bath constant temperature shaker at room temperature and 0-300 rpm for 0-300 min.

[0012] Preferably, the method for recovering 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid includes:

[0013] The C-nitration process waste liquid and extractant were placed in a separatory funnel in a certain proportion and mixed thoroughly. After shaking, the mixture was allowed to stand to obtain a solution with a clear two-phase interface.

[0014] Open the lid of the separatory funnel and turn the knob to separate the two phases;

[0015] Take the above separated extract and place it in a vacuum distillation apparatus. Under set conditions, rotary evaporate to recover 3,4-dinitropyrazole.

[0016] Take the separated mother liquor and place it in a distillation column. Adjust the distillation temperature and recover sulfuric acid.

[0017] Preferably, the 3,4-dinitropyrazole content in the C-nitration process waste liquid is not less than 3.95%, and the extractant is ethyl acetate.

[0018] Preferably, the set conditions for rotary evaporation are rotary evaporation at a vacuum of -0.1 MPa and a temperature of 80°C.

[0019] Preferably, during the distillation process, the reboiler and distillation column are heated at atmospheric pressure, and the temperature of the reboiler and the upper and lower sections of the distillation column is kept the same. The temperature of each heating point is gradually increased from 80°C, with each increase being 10°C, and each temperature is maintained for more than half an hour.

[0020] Preferably, during the distillation process, when a fraction is generated, the fraction is collected after maintaining full reflux for 10 minutes at a reflux ratio of 1:1.

[0021] The second aspect of the present invention discloses a system for resource-based treatment of nitropyrazole mixed acid waste liquid, which performs the method for resource-based treatment of nitropyrazole mixed acid waste liquid, including: a mixing module, an extraction module, a rotary evaporation module and a distillation module;

[0022] The mixing module includes a conical flask and a water bath constant temperature shaker, used to degrade pyrazole and N-nitropyrazole in N-nitrated waste acid;

[0023] The extraction module includes a separatory funnel for separating 3,4-dinitropyrazole and sulfuric acid;

[0024] The rotary evaporation module includes a vacuum distillation unit for rotary evaporation to recover 3,4-dinitropyrazole;

[0025] The distillation module includes a reboiler and a distillation column, used for distilling and recovering sulfuric acid.

[0026] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0027] This invention employs advanced oxidation technology in the treatment of N-nitration waste acid solution, eliminating the need for an oxidant. It utilizes the acetic acid solution naturally present in the wastewater and added iron filings to effectively degrade pyrazole and N-nitropyrazole. In the C-nitration process, compared to traditional high-temperature heating processes, the extraction method using an extractant effectively reduces costs, simplifies operation, and avoids the risk of 3,4-dinitropyrazole explosion caused by high-temperature heating. Simultaneously, the 3,4-dinitropyrazole extraction recovery rate reaches 99.8%. The method described in this invention achieves the separation of nitric acid and sulfuric acid in the mother liquor after extraction and the resource recovery of sulfuric acid, with a recovered sulfuric acid concentration of 97% and a COD content below 100 mg / L. Attached Figure Description

[0028] Figure 1 The degradation performance of nitro compounds by different amounts of iron filings;

[0029] Figure 2 It refers to the extraction performance of different extractants;

[0030] Figure 3 The effect is due to the ethyl acetate extraction ratio;

[0031] Figure 4 The effect is due to the number of ethyl acetate extractions;

[0032] Figure 5 It is (a) the extract and mother liquor; (b) the recovered 3,4-dinitropyrazole;

[0033] Figure 6 This refers to the changes in sulfuric acid content and COD in the high-temperature oxidative degradation solution;

[0034] Figure 7 It represents the change in nitric acid content in the high-temperature oxidative degradation solution. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0036] In recent years, my country has actively promoted the clean substitution of fuel raw materials, emphasized the clean and low-carbon transformation of key industries, and promoted clean production processes. Among these efforts, wastewater reuse is an important means of water conservation and emission reduction. The recovery and utilization of nitropyrazole compounds in wastewater can also create value for enterprises. The recovery of 3,4-dinitropyrazole and sulfuric acid from wastewater has significant economic and environmental benefits. At the same time, advanced oxidation technology can effectively treat the remaining tailwater containing other nitro compounds, achieving compliance with discharge standards.

[0037] The embodiments of the present invention provide a method for resource-based treatment of nitropyrazole mixed acid waste liquid, including using advanced oxidation technology to treat pyrazole and N-nitropyrazole in N-nitration waste acid and recovering 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid.

[0038] The method for treating pyrazole and N-nitropyrazole in N-nitrated waste acid using advanced oxidation technology includes the following steps:

[0039] Step 1: After diluting the N-nitration wastewater solution by 100 times, take 50 mL of the solution into a 250 mL Erlenmeyer flask, and quickly add 0.01 g to 0.1 g of iron filings to each Erlenmeyer flask.

[0040] Step 2: Place the conical flask in a water bath constant temperature shaker at room temperature and 0-300 rpm for 0-300 min to obtain the waste liquid after degradation of pyrazole and N-nitropyrazole.

[0041] Preferably, the conical flask is placed in a water bath at 25°C and 200 rpm and shaken for 300 minutes. Figure 1 As shown, (a) shows the degradation effect of 1-nitropyrazole under different iron filings dosage; (b) shows the fitting results of the degradation kinetics of 1-nitropyrazole under different iron filings dosage.

[0042] The method for recovering 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid includes the following steps:

[0043] Step A: Place the C-nitration process waste liquid and extractant in a separatory funnel according to the set ratio, mix thoroughly, shake well and let stand to obtain a solution with a clear two-phase interface;

[0044] The 3,4-dinitropyrazole content in the C-nitration process waste liquid is not less than 3.95%.

[0045] The extractant is ethyl acetate.

[0046] The volume ratio of the waste liquid to the extractant liquid is 1:1. It is worth noting that when ethyl acetate is used as the extractant, the extraction effect increases with the increase of the volume of ethyl acetate.

[0047] Step B: Open the lid of the separatory funnel and turn the knob to separate the two phases;

[0048] Step C: Take the above-separated extract, place it in a vacuum distillation apparatus, and rotary evaporate it under set conditions to obtain 3,4-dinitropyrazole.

[0049] In step C, the conditions are set as follows: vacuum degree is adjusted to -0.1MPa, and rotary evaporation is performed at 80℃.

[0050] Step D: Take the separated mother liquor, place it in a distillation column, adjust the distillation temperature, and recover sulfuric acid.

[0051] In step D, the reboiler and distillation column are heated under atmospheric pressure. During the distillation process, the temperature of the reboiler and the upper and lower sections of the distillation column is maintained at the same level. The temperature of each heating point is gradually increased from 80°C, and to maintain a stable state, the temperature is increased by 10°C each time, and each temperature is maintained for more than half an hour. When a fraction is produced, it is kept under total reflux for 10 minutes, and then the fraction is collected at a reflux ratio of 1:1.

[0052] Example 1:

[0053] The wastewater obtained from the C-nitration reaction during the production of 3,4-dinitropyrazole has the following physicochemical properties: pH = 1, 3,4-dinitropyrazole content approximately 3.95%, H₂SO₄ content approximately 29.1%, and HNO₃ content approximately 3.3%. The wastewater was thoroughly mixed with ethyl acetate / toluene / chloroform / carbon tetrachloride as extractants at a volume ratio of 1:1 and shaken well. After standing until the interface between the two phases was clear, the separatory funnel was opened and the knob was turned to separate the two phases. The 3,4-dinitropyrazole content in each phase was calculated. Figure 2 As shown, using ethyl acetate / chloroform / carbon tetrachloride / toluene as extractants, the extraction rates, i.e., extraction efficiency, of 3,4-dinitropyrazole reached 87.1%, 1.4%, 23.9%, and 4.9%, respectively.

[0054] When ethyl acetate was used as the extractant, the separated extract was placed in a vacuum distillation apparatus, the vacuum degree in the reactor was adjusted to -0.1 MPa, and rotary evaporation was carried out at 80°C. After all the liquid was distilled off, 3,4-dinitropyrazole solid was obtained, with a recovery rate of 95.5%.

[0055] When ethyl acetate is used as the extractant, the separated mother liquor is placed in a distillation column. The reboiler and the distillation column are heated under normal pressure, maintaining the same temperature throughout the distillation process. The temperature at each heating point is gradually increased from 80°C, with each increase in 10°C increments maintained for at least half an hour to ensure stability. When a fraction is produced, it is kept under total reflux for 10 minutes, then the fraction is collected at a 1:1 reflux ratio. The temperature is continued to rise to 240°C to obtain recovered sulfuric acid, with a final concentration exceeding 97%.

[0056] Example 2:

[0057] The wastewater obtained from the C-nitration reaction during the production of 3,4-dinitropyrazole has the following physicochemical properties: pH = 1, 3,4-dinitropyrazole content approximately 3.95%, H₂SO₄ content approximately 29.1%, and HNO₃ content approximately 3.3%. The wastewater was mixed thoroughly with ethyl acetate as an extractant at volume ratios of 5:1, 3:1, 1:1, 1:3, and 1:5, and shaken well. After standing, once the interface between the two phases was clear, the separatory funnel was opened and the knob was turned to separate the two phases. The 3,4-dinitropyrazole content in each phase was calculated. Figure 3 As shown, when ethyl acetate is used as the extractant, the extraction efficiency increases with the increase of ethyl acetate volume, in the following order: 25.9%, 68.6%, 80.4%, 86.8%, and 94.7%.

[0058] The separated extract was placed in a vacuum distillation apparatus, the vacuum degree in the reactor was adjusted to -0.1 MPa, and rotary evaporation was carried out at 80°C. After all the liquid was distilled off, 3,4-dinitropyrazole solid was obtained, and the recovery rate was 96%.

[0059] The separated mother liquor was placed in a distillation column, and the reboiler and column were heated under atmospheric pressure. Throughout the distillation process, the temperature of the reboiler and the upper and lower sections of the column was maintained at the same level. The temperature at each heating point was gradually increased from 80°C, with each increase in 10°C increments maintained for at least half an hour to ensure stability. When a fraction was produced, total reflux was maintained for 10 minutes, and then the fraction was collected at a 1:1 reflux ratio. The temperature was continued to rise to 240°C to obtain recovered sulfuric acid, with a final concentration exceeding 97%.

[0060] Example 3:

[0061] The wastewater obtained from the C-nitration reaction during the production of 3,4-dinitropyrazole has the following physicochemical properties: pH = 1, 3,4-dinitropyrazole content approximately 3.95%, H₂SO₄ content approximately 29.1%, and HNO₃ content approximately 3.3%. The wastewater was mixed thoroughly with ethyl acetate as an extractant at a volume ratio of 1:1 and shaken well. Extraction was performed 1, 2, 3, 4, and 5 times respectively. After standing, once the interface between the two phases was clear, the lid of the separatory funnel was opened and the knob was turned to separate the two phases. The 3,4-dinitropyrazole content in each phase was calculated. Figure 4 As shown, when ethyl acetate is used as the extractant, the overall extraction efficiency increases with the number of extractions, at 84.9%, 99.5%, 99.6%, 99.8%, and 99.8% respectively. The extraction efficiency for each extraction initially increases, then decreases, and tends to stabilize, at 84.9%, 97.2%, 39.4%, 34.0%, and 35.7% respectively.

[0062] The separated extract was placed in a vacuum distillation apparatus, and the vacuum degree in the reactor was adjusted to -0.1 MPa. Rotary distillation was carried out at 80°C until all the liquid was distilled off, yielding 3,4-dinitropyrazole solid. Figure 5 The recovery rate of all of them can reach 96%.

[0063] The separated mother liquor was placed in a distillation column, and the reboiler and column were heated under atmospheric pressure. Throughout the distillation process, the temperature of the reboiler and the upper and lower sections of the column was maintained at the same level. The temperature at each heating point was gradually increased from 80°C, with each increase in 10°C increments maintained for at least half an hour to ensure stability. When distillate was produced, it was kept under total reflux for 10 minutes, and then the distillate was collected at a 1:1 reflux ratio, continuing heating until the temperature reached 240°C. Figure 6 As shown, the sulfuric acid content increases with time, especially at 130℃, where it increases dramatically. At 240℃, the recovered sulfuric acid has a final concentration of over 97%, and the COD content is below 100 mg / L. Figure 7 As shown, the nitric acid content drops sharply from 80℃. When the temperature reaches 110℃, all the nitric acid vaporizes and is expelled as nitrogen oxides. When the temperature reaches 240℃, the nitric acid content is less than 0.01%.

[0064] The present invention also provides a system for resource-based treatment of nitropyrazole mixed acid waste liquid, which implements the method for resource-based treatment of nitropyrazole mixed acid waste liquid, including: a mixing module, an extraction module, a rotary evaporation module and a distillation module;

[0065] The mixing module includes a conical flask and a water bath constant temperature shaker, used to degrade pyrazole and N-nitropyrazole in N-nitrated waste acid;

[0066] It is worth noting that the conical flask is merely one choice of reaction vessel for experimental environments. In engineering practice, any reaction vessel with mixing function used by those skilled in the art to implement this invention falls within the scope of this invention.

[0067] The extraction module includes a separatory funnel for separating 3,4-dinitropyrazole and sulfuric acid;

[0068] The rotary evaporation module includes a vacuum distillation unit for rotary evaporation to recover 3,4-dinitropyrazole;

[0069] The distillation module includes a reboiler and a distillation column, used for distilling and recovering sulfuric acid.

[0070] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0071] This invention employs advanced oxidation technology in the treatment of N-nitration waste acid solution, eliminating the need for an oxidant. It utilizes the acetic acid solution naturally present in the wastewater and added iron filings to effectively degrade pyrazole and N-nitropyrazole. In the C-nitration process, compared to traditional high-temperature heating processes, the extraction method using an extractant effectively reduces costs, simplifies operation, and avoids the risk of DNP explosion caused by high-temperature heating. Simultaneously, the DNP extraction recovery rate reaches 99.8%. The method described in this invention achieves the separation of nitric acid and sulfuric acid in the mother liquor after extraction and the resource recovery of sulfuric acid, with a recovered sulfuric acid concentration of 97% and a COD content below 100 mg / L.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for resource-based treatment of nitropyrazole mixed acid waste liquid, characterized in that: include: Advanced oxidation treatment of pyrazole and N-nitropyrazole in N-nitration waste acid and recovery of 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid; The advanced oxidation treatment of pyrazole and N-nitropyrazole in N-nitrated waste acid includes: taking an N-nitrated waste acid solution containing an acetic acid solution, mixing a set amount of iron filings, and shaking it at a constant temperature under set conditions to obtain waste liquid after degradation of pyrazole and N-nitropyrazole; The recovery of 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid includes: recovering 3,4-dinitropyrazole from the C-nitration process using an extractant and recovering sulfuric acid from the C-nitration process using a distillation method; the method for recovering 3,4-dinitropyrazole and sulfuric acid from C-nitration process waste liquid specifically includes: The C-nitration process waste liquid and extractant were placed in a separatory funnel in a certain proportion and mixed thoroughly. After shaking, the mixture was allowed to stand to obtain a solution with a clear two-phase interface. The extractant was ethyl acetate. Open the lid of the separatory funnel and turn the knob to separate the two phases; Take the above separated extract and place it in a vacuum distillation apparatus. Under set conditions, rotary evaporate to recover 3,4-dinitropyrazole. Take the separated mother liquor and place it in a distillation column. Adjust the distillation temperature and recover sulfuric acid.

2. The method for resource-based treatment of nitropyrazole mixed acid waste liquid according to claim 1, characterized in that: The N-nitration waste acid solution is prepared by diluting the N-nitration waste water solution and then placing the diluted solution into a reaction vessel.

3. The method for resource-based treatment of nitropyrazole mixed acid waste liquid according to claim 1, characterized in that: The specified amount of iron filings is 0.01 g to 0.1 g of iron filings added to the reaction vessel.

4. The method for resource-based treatment of nitropyrazole mixed acid waste liquid according to claim 1, characterized in that: The constant temperature oscillation under the set conditions is to place the reaction vessel in a water bath constant temperature oscillator at room temperature and 0-300 rpm for a reaction time of 0-300 min.

5. The method for resource-based treatment of nitropyrazole mixed acid waste liquid according to claim 1, characterized in that: The 3,4-dinitropyrazole content in the C-nitration process waste liquid is not less than 3.95%.

6. The method for resource-based treatment of nitropyrazole mixed acid waste liquid according to claim 1, characterized in that: The rotary evaporation under the specified conditions is performed by adjusting the vacuum degree to -0.1 MPa and evaporating at 80°C.

7. The method for resource-based treatment of nitropyrazole mixed acid waste liquid according to claim 1, characterized in that: During the distillation process, the reboiler and distillation column are heated under normal pressure. The temperature of the reboiler and the upper and lower sections of the distillation column is kept the same. The temperature of each heating point is gradually increased from 80°C, with each increase being 10°C, and each temperature is maintained for more than half an hour.

8. The method for resource-based treatment of nitropyrazole mixed acid waste liquid according to claim 7, characterized in that: During the distillation process, when a fraction is produced, it is kept under full reflux for 10 minutes and then the fraction is collected at a reflux ratio of 1:1.

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