Method for removing nascent organic impurities in stripping solution recycling processes

Abstract

This invention relates to the field of stripping fluid purification technology, specifically disclosing a method for removing newly generated organic impurities during the recycling of stripping fluid. The method involves adding additives to the waste stripping fluid, preheating it to above 60°C for at least 0.5 hours, and then sequentially performing evaporation to remove slag and distillation purification to obtain regenerated stripping fluid. The newly generated organic impurity is 4-(diethylamino)-2-butanone, and the additives include hydrazine compounds and citric acid. This invention effectively removes the newly generated impurity 4-(diethylamino)-2-butanone from waste stripping fluid without introducing impurities and has the advantages of low cost.

Description

Technical Field

[0001] This invention relates to the field of stripping fluid purification technology, and more specifically to a method for removing newly generated organic impurities during the recycling of stripping fluid. Background Technology

[0002] The production process of display panels involves cleaning, coating, photolithography, etching / stripping, etc., and a large number of wet electronic chemicals are used throughout the process. Stripping solution is the most widely used wet electronic chemical, and its main component is a mixed organic solvent with good elution ability against photoresist. The waste liquid generated after the stripping process is called waste stripping solution. Because waste stripping solution is expensive, in order to save costs, users generally regenerate it for recycling.

[0003] However, during the reuse process, it was discovered that the content of an unknown substance in the stripping fluid waste liquid gradually increased, and the content accumulated with the number of reuses. When it exceeded 0.5%, it had a significant impact on product quality and reduced the proportion of reused liquid in the new liquid. However, the absolute content of the unknown substance was low, and it was difficult to separate, making it impossible to effectively separate and identify, which also increased the difficulty of targeted removal of the unknown substance. At the same time, low-cost, efficient removal without introducing impurities and reducing product quality is an even greater challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing newly generated organic impurities during the recycling of stripping fluid, which can effectively reduce or even remove newly generated impurities such as 4-(diethylamino)-2-butanone in waste stripping fluid.

[0005] This invention is achieved through the following technical solution:

[0006] A method for removing newly generated organic impurities during the recycling of stripping fluid involves adding additives to the waste stripping fluid, preheating it to above 60°C for at least 0.5 hours, and then sequentially performing evaporation to remove slag and distillation to purify it, thereby obtaining regenerated stripping fluid. The newly generated organic impurity is 4-(diethylamino)-2-butanone, and the additives include hydrazine compounds and citric acid.

[0007] This invention effectively reduces or even removes nascent organic impurities, namely 4-(diethylamino)-2-butanone, from waste stripping liquid by adding hydrazine compounds and citric acid to the waste stripping liquid, preheating it to above 60°C and holding it at that temperature for a period of time, and then performing conventional evaporation, slag removal, and distillation purification.

[0008] Furthermore, the waste stripping solution of this invention contains photoresist. If only hydrazine compounds are added to remove newly formed organic impurities, the photoresist will agglomerate and solidify during the waste stripping solution treatment process, affecting the operation of the entire treatment system and the removal efficiency of newly formed organic impurities. The agglomerated and solidified photoresist will form scale in the evaporation kettle, which not only affects the removal efficiency of newly formed organic impurities, but may also cause serious equipment blockage.

[0009] This invention improves the removal efficiency of 4-(diethylamino)-2-butanone by simultaneously adding hydrazine compounds and citric acid to the waste stripping solution. The hydrazine compounds remove the newly formed organic impurity 4-(diethylamino)-2-butanone, while the citric acid prevents the photoresist from agglomerating and curing.

[0010] In a preferred embodiment, the preheating temperature is 70-100°C.

[0011] In a preferred embodiment, the preheating temperature is 70-80°C.

[0012] The preheating temperature affects the removal efficiency of 4-(diethylamino)-2-butanone, a newly formed organic impurity, in the waste stripping liquid. When the temperature is below 50°C, the removal efficiency of 4-(diethylamino)-2-butanone is poor, and the removal efficiency is better as the temperature increases. When the temperature is raised to 80°C, after treatment by the method of the present invention, the regenerated stripping liquid contains almost no newly formed organic impurity 4-(diethylamino)-2-butanone.

[0013] In a preferred embodiment, the amount of hydrazine compound added is greater than or equal to 0.3% and the amount of citric acid added is 1.0-2.0% based on the volume of the waste stripping liquid.

[0014] In a preferred embodiment, the amount of hydrazine compound added is 0.3-1.0% based on the volume of the waste stripping liquid.

[0015] In a preferred embodiment, the amount of hydrazine compound added is 0.6-1.0% based on the volume of the waste stripping liquid.

[0016] In a preferred embodiment, the amount of hydrazine compound added is 0.6-0.8% and the amount of citric acid added is 1.0% based on the volume of the waste stripping liquid.

[0017] The amount of hydrazine added affects the removal efficiency of 4-(diethylamino)-2-butanone, a newly formed organic impurity, in the waste stripping liquid. Based on the volume of the waste stripping liquid, when the amount of hydrazine added is less than 0.3%, the removal effect on 4-(diethylamino)-2-butanone is very weak. When the amount of hydrazine added is 0.3%, the content of 4-(diethylamino)-2-butanone in the waste stripping liquid can be significantly reduced. When the amount of hydrazine added is 0.6%, after treatment by the method of this invention, the regenerated stripping liquid contains almost no 4-(diethylamino)-2-butanone. Further increasing the amount of hydrazine added at this point yields results in a similar effect to when the amount is 0.6%.

[0018] In a preferred embodiment, the preheating time is 1-4 hours, or 1-2 hours.

[0019] In a preferred embodiment, the following steps are included:

[0020] S1. Add the waste stripping liquid, hydrazine compounds and citric acid to the preheater and heat to above 60°C for at least 0.5 hours to obtain the pretreated waste stripping liquid.

[0021] S2. The pretreated waste stripping liquid is introduced into the evaporation kettle for evaporation and slag removal to obtain the evaporated liquid;

[0022] S3. The evaporated liquid is introduced into distillation column 1 for the first distillation purification to remove light components;

[0023] S4. The heavy components produced in distillation column 1 are introduced into distillation column 2 for a second distillation purification to remove the heavy components. The light components produced in distillation column 2 are the product regeneration stripping liquid.

[0024] In a preferred embodiment, the waste stripping fluid, hydrazine compounds, and citric acid are first added to a mixing tank for mixing, and then the mixed solution is added to a preheater for preheating treatment.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] 1. The method of the present invention, by adding hydrazine compounds and citric acid to the waste stripping liquid and preheating it to above 60°C for a period of time, followed by conventional evaporation, slag removal, and distillation purification, can effectively reduce or even remove the newly formed organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid. The content of the newly formed organic impurity 4-(diethylamino)-2-butanone in the regenerated stripping liquid can be reduced to as low as 0.01%, which greatly improves the quality of the regenerated stripping liquid.

[0027] 2. The method of the present invention does not introduce impurities (the added hydrazine compounds can react with the newly formed organic impurity 4-(diethylamino)-2-butanone via a mechanism to produce a high-boiling compound; excess hydrazine compounds and high-boiling compounds can be removed by distillation), nor does it introduce expensive reagents, thus having the advantage of low cost. In other words, the present invention not only improves the quality of the product regenerated stripping liquid, but also increases the reuse ratio of the recovered liquid in the new liquid, while not adding any new safety or environmental risks in production. It is a green and efficient treatment method. Attached Figure Description

[0028] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 A process flow diagram for treating waste stripping fluid using existing technologies;

[0030] Figure 2 The present invention provides a process flow for treating waste stripping fluid. Figure 1 ;

[0031] Figure 3 The present invention provides a process flow for treating waste stripping fluid. Figure 2 . Detailed Implementation

[0032] 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. The illustrative embodiments and descriptions of this invention are for illustrative purposes only and are not intended to limit the invention. The embodiments described below are some, but not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0033] In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, materials, or methods are not specifically described to avoid obscuring the invention. Unless otherwise specified, the materials, instruments, and reagents used in the following embodiments are commercially available. Unless otherwise specified, the techniques used in the embodiments are conventional methods well known to those skilled in the art.

[0034] The waste stripping liquid mainly contains organic matter 1 and organic matter 2. Organic matter 1 is diethylene glycol butyl ether; organic matter 2 is nitromethylethanolamine or nitromethylformamide. Depending on the manufacturer that produces the waste liquid, organic matter 2 is different, namely nitromethylethanolamine or nitromethylformamide.

[0035] like Figure 1 As shown, the existing waste stripping liquid (waste liquid) treatment process is as follows: the waste stripping liquid is directly introduced into an evaporation kettle for evaporation and slag removal to obtain evaporated liquid (solvent); the evaporated liquid is introduced into distillation column 1 for the first distillation purification to remove the light components (wastewater) generated in distillation column 1; the heavy components generated in distillation column 1 are introduced into distillation column 2 for the second distillation purification to remove the heavy components (diethanolamine / triethanolamine, etc.) generated in distillation column 2; the light components obtained in distillation column 2 are the product (regenerated stripping liquid). In addition to organic matter 1 and organic matter 2, the regenerated stripping liquid also contains a newly generated impurity, 4-(diethylamino)-2-butanone.

[0036] Existing processes cannot remove 4-(diethylamino)-2-butanone from waste stripping fluid. As the number of times the stripping fluid is recycled increases, new impurities gradually accumulate. Furthermore, because the boiling point of this organic impurity lies between the boiling points of the two active components in the stripping fluid, it is collected along with the active components during the distillation process of the waste stripping fluid and remains in the recycled fluid, making it impossible to remove. Moreover, the customer generates this impurity again during the use of the recycled stripping fluid, resulting in a gradual accumulation of organic impurities.

[0037] Therefore, existing waste stripping fluid treatment methods cannot remove newly generated impurities after customer process changes. This invention uses gas chromatography to detect 4-(diethylamino)-2-butanone as a newly generated impurity in the waste stripping fluid. 4-(diethylamino)-2-butanone is an existing substance, and its structure is shown below:

[0038]

[0039] To remove newly formed impurities such as 4-(diethylamino)-2-butanone from the waste stripping solution, Figure 2 As shown, this embodiment provides a method for removing newly generated organic impurities during the recycling of stripping fluid. Additives are added to the waste stripping fluid, which is preheated to above 60°C for at least 0.5 hours, and then subjected to evaporation and slag removal, and distillation purification in sequence to obtain regenerated stripping fluid. The newly generated organic impurity is 4-(diethylamino)-2-butanone, and the additives include hydrazine compounds and citric acid.

[0040] The method in this embodiment involves adding hydrazine compounds to the waste stripping liquid, preheating it to above 60°C and holding it at that temperature for a period of time, and then performing conventional evaporation, slag removal, and distillation purification. This method can effectively reduce or even remove the newly formed organic impurity 4-(diethylamino)-2-butanone in the waste stripping liquid. The content of the newly formed organic impurity 4-(diethylamino)-2-butanone in the regenerated stripping liquid can be reduced to as low as 0.01%, which greatly improves the quality of the regenerated stripping liquid.

[0041] The hydrazine compounds of this invention can react with the newly formed organic impurity 4-(diethylamino)-2-butanone. Theoretically, as long as the structure contains hydrazine, it can react with the newly formed organic impurity 4-(diethylamino)-2-butanone. Therefore, the hydrazine compounds can be organic or inorganic hydrazine compounds. Among them, organic hydrazine compounds include methylhydrazine, dimethylhydrazine, ethylhydrazine, or phenylhydrazine; inorganic hydrazine compounds include hydrazine and hydrazine salts (hydrazine sulfate or hydrazine nitrate, etc.).

[0042] This invention improves the removal efficiency of 4-(diethylamino)-2-butanone by simultaneously adding hydrazine compounds and citric acid to the waste stripping solution. The hydrazine compounds remove the newly formed organic impurity 4-(diethylamino)-2-butanone, while the citric acid prevents the photoresist from agglomerating and curing.

[0043] Preferably, the preheating temperature is 70-100℃.

[0044] More preferably, the preheating temperature is 70-80℃.

[0045] Preferably, the amount of hydrazine compound added is greater than or equal to 0.3% based on the volume of waste stripping liquid; the amount of citric acid added is 1.0-2.0%.

[0046] More preferably, the amount of hydrazine compound added is 0.3-1.0% based on the volume of the waste stripping liquid.

[0047] More preferably, the amount of hydrazine compound added is 0.6-1.0% based on the volume of the waste stripping liquid.

[0048] More preferably, the amount of hydrazine compound added is 0.6-0.8% and the amount of citric acid added is 1.0% based on the volume of the waste stripping liquid.

[0049] Preferably, the preheating time is 1-4 hours, and more preferably, the preheating time is 1-2 hours.

[0050] In a specific case, such as Figure 2 , Figure 3 As shown, a method for removing newly generated organic impurities during the recycling of stripping fluid includes the following steps:

[0051] S1. Add the waste stripping liquid, hydrazine compound and citric acid to the preheater and heat to above 60°C for at least 0.5 hours to obtain the pretreated waste stripping liquid; preferably, first add the waste stripping liquid, hydrazine compound and citric acid to the mixing tank for mixing, and then add the mixed solution to the preheater for preheating treatment.

[0052] S2. The pretreated waste stripping liquid is introduced into the evaporation kettle for evaporation and slag removal to obtain the evaporated liquid;

[0053] S3. The evaporated liquid is introduced into distillation column 1 for the first distillation purification to remove light components;

[0054] S4. The heavy components produced in distillation column 1 are introduced into distillation column 2 for a second distillation purification to remove the heavy components. The light components produced in distillation column 2 are the product regeneration stripping liquid.

[0055] To better illustrate the effectiveness of the method described in this embodiment, the following specific examples are used for explanation:

[0056] Example 1:

[0057] A method for removing newly generated organic impurities during the recycling of stripping fluid includes the following steps:

[0058] First, 50 mL of waste stripping liquid, 0.15 mL of hydrazine compound and 0.5 g of citric acid are added to a mixing tank and mixed. Then, the mixed solution is added to a preheater for preheating treatment at 80 °C for 1 hour to obtain pretreated waste stripping liquid. The pretreated waste stripping liquid is then subjected to evaporation and slag removal, and secondary distillation for purification to obtain regenerated stripping liquid.

[0059] In this embodiment, based on the volume of the waste stripping liquid, the amount of hydrazine compound added is 0.3%, and the amount of citric acid added (m / v) is 1.0%; the hydrazine compound is methylhydrazine, and the original waste stripping liquid contains organic matter 1, organic matter 2, and impurities, among which the content of the newly formed impurity 4-(diethylamino)-2-butanone is 0.55; organic matter 1 is diethylene glycol butyl ether; organic matter 2 is N-methylethanolamine.

[0060] Example 2:

[0061] This embodiment is based on Embodiment 1, but differs from Embodiment 1 in that the amount of hydrazine compound added is different. In this embodiment, the amount of hydrazine compound added is 0.4% based on the volume of the waste stripping liquid. Specifically:

[0062] First, add 50 mL of waste stripping liquid, 0.2 mL of hydrazine compound, and 0.5 g of citric acid to a mixing tank and mix them. Then, add the mixed solution to a preheater for preheating treatment at 80 °C for 1 hour.

[0063] Example 3:

[0064] This embodiment is based on Example 1, but differs from Example 1 in that the amount of hydrazine compound added is different. In this embodiment, the amount of hydrazine compound added is 0.6% based on the volume of the waste stripping liquid. Specifically:

[0065] First, add 50 mL of waste stripping liquid, 0.3 mL of hydrazine compound, and 0.5 g of citric acid to a mixing tank and mix them. Then, add the mixed solution to a preheater for preheating treatment at 80 °C for 1 hour.

[0066] Example 4:

[0067] This embodiment is based on Embodiment 1, but differs from Embodiment 1 in that the amount of hydrazine compound added is different. In this embodiment, the amount of hydrazine compound added is 0.8% based on the volume of the waste stripping liquid. Specifically:

[0068] First, add 50 mL of waste stripping liquid, 0.4 mL of hydrazine compound, and 0.5 g of citric acid to a mixing tank and mix them. Then, add the mixed solution to a preheater for preheating treatment at 80 °C for 1 hour.

[0069] Example 5:

[0070] This embodiment is based on Embodiment 1, but differs from Embodiment 1 in that the amount of hydrazine compound added is different. In this embodiment, the amount of hydrazine compound added is 1.0% based on the volume of the waste stripping liquid. Specifically:

[0071] First, add 50 mL of waste stripping liquid, 0.5 mL of hydrazine compound, and 0.5 g of citric acid to a mixing tank and mix them. Then, add the mixed solution to a preheater for preheating treatment at 80°C for 1 hour.

[0072] Comparative Example 1:

[0073] This comparative example is based on Example 1, but differs from Example 1 in that no hydrazine compounds are added.

[0074] Comparative Example 2:

[0075] This comparative example is based on Example 1, but differs from Example 1 in that the amount of organic alkali added is different. In this comparative example, the amount of hydrazine compound added is 0.2% based on the volume of waste stripping liquid. Specifically:

[0076] First, add 50 mL of waste stripping liquid, 0.1 mL of hydrazine compound, and 0.5 g of citric acid to a mixing tank and mix them. Then, add the mixed solution to a preheater for preheating treatment at 80 °C for 1 hour.

[0077] Comparative Example 3:

[0078] This embodiment is based on Embodiment 4, but differs from Embodiment 4 in that citric acid is not added.

[0079] Comparative Example 4:

[0080] This embodiment is based on Embodiment 4, but differs from Embodiment 4 in that the amount of citric acid added is different; the amount of citric acid added is 0.2g.

[0081] The contents of newly formed impurities 4-(diethylamino)-2-butanone and the contents of the two active ingredients in the regenerated stripping solutions prepared in Examples 1-5 and Comparative Examples 1-2 were detected by gas chromatography. The results are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] Organic compound 1 is diethylene glycol butyl ether; organic compound 2 is N-methylethanolamine.

[0086] The chromatographic conditions for gas chromatography are as follows:

[0087] Chromatographic column: DB-1 column or other chromatographic column capable of achieving equivalent separation;

[0088] Column temperature: Start at 60℃ and increase to 270℃ at a rate of 20℃ / min;

[0089] Inlet temperature: 250℃;

[0090] Detector temperature: 300℃;

[0091] Carrier gas (nitrogen) flow rate: 1.0 mL / min;

[0092] Hydrogen flow rate: 35 mL / min;

[0093] Airflow rate: 350 mL / min;

[0094] Flow split ratio: 80:1;

[0095] Injection volume: 0.2uL.

[0096] The data in Table 1 shows that:

[0097] The content of newly formed organic impurities, specifically 4-(diethylamino)-2-butanone, in the regenerated stripping solution decreases with increasing dosage of hydrazine compounds. When the dosage of hydrazine compounds is less than 0.3%, the removal effect on 4-(diethylamino)-2-butanone in the waste stripping solution is very weak. When the dosage of hydrazine compounds is 0.3%, the content of 4-(diethylamino)-2-butanone in the waste stripping solution can be significantly reduced. When the dosage of hydrazine compounds is 0.6%, after treatment by the method of this invention, the regenerated stripping solution contains almost no newly formed organic impurities of 4-(diethylamino)-2-butanone. Further increasing the dosage of hydrazine compounds at this point yields results in a similar effect to the dosage of 0.6%.

[0098] Without the use of hydrazine compounds, the removal of newly generated impurities during the waste stripping fluid treatment process is completely ineffective.

[0099] Table 2 shows a comparison of the removal efficiency of 4-(diethylamino)-2-butanone, a newly generated organic impurity, with and without the addition of citric acid.

[0100] Table 2

[0101]

[0102]

[0103] The data in Table 2 shows that:

[0104] Compared to adding hydrazine alone, adding both hydrazine compounds and citric acid together resulted in a higher removal efficiency for the newly formed organic impurity 4-(diethylamino)-2-butanone. Furthermore, when the amount of citric acid added was low, the removal efficiency for the newly formed organic impurity 4-(diethylamino)-2-butanone decreased accordingly.

[0105] The added citric acid will be removed during subsequent distillation (citric acid is non-volatile and will be removed during the evaporation and slag removal process).

[0106] Example 6:

[0107] This embodiment is based on Embodiment 5, but differs from Embodiment 5 in that the preheating temperature is different. Specifically:

[0108] First, add 50 mL of waste stripping liquid, 0.5 mL of hydrazine compound and 0.5 g of citric acid to the mixing tank and mix them. Then, add the mixed solution to the preheater for preheating treatment at 60 °C for 1 hour.

[0109] Example 7:

[0110] This embodiment is based on Embodiment 5, but differs from Embodiment 5 in that the preheating temperature is different. Specifically:

[0111] First, add 50 mL of waste stripping fluid, 0.5 mL of hydrazine compound and 0.5 g of citric acid to a mixing tank and mix them. Then, add the mixed solution to a preheater for preheating treatment at 70 °C for 1 hour.

[0112] Comparative Example 5:

[0113] This comparative example is based on Example 5, but differs from Example 5 in that the preheating temperature is different. Specifically:

[0114] First, add 50 mL of waste stripping liquid, 0.5 mL of hydrazine compound and 0.5 g of citric acid to the mixing tank and mix them. Then, add the mixed solution to the preheater for preheating treatment at 50 °C for 1 hour.

[0115] The contents of newly formed impurities 4-(diethylamino)-2-butanone and the contents of the two active ingredients in the regenerated stripping solutions prepared in Examples 6-7 and Comparative Example 5 were detected by gas chromatography. The results are shown in Table 3.

[0116] Table 3

[0117] Preheating temperature Organic matter 1 Organic matter 2 New impurities Comparative Example 5 50℃ 9.21 90.08 0.36 Example 6 60℃ 9.44 89.89 0.22 Example 7 70℃ 9.46 89.89 0.07 Example 5 80℃ 9.50 90.03 0.01

[0118] The data in Table 3 shows that:

[0119] The preheating temperature affects the removal efficiency of 4-(diethylamino)-2-butanone, a newly formed organic impurity, in the waste stripping liquid. When the temperature is below 50°C, the removal efficiency of 4-(diethylamino)-2-butanone is poor, and the removal efficiency is better as the temperature increases. When the temperature rises to 80°C, after treatment by the method of the present invention, the regenerated stripping liquid contains almost no newly formed organic impurity 4-(diethylamino)-2-butanone.

[0120] Example 8:

[0121] This embodiment is based on Example 5, but differs from Example 5 in that the hydrazine compound used is different; this embodiment uses phenylhydrazine.

[0122] Example 9:

[0123] This embodiment is based on Example 5, but differs from Example 5 in that the hydrazine compound used is different; this embodiment uses hydrazine.

[0124] Example 10:

[0125] This embodiment is based on Example 5, but differs from Example 5 in that the hydrazine compound used is different; this embodiment uses hydrazine sulfate.

[0126] Comparative Example 6:

[0127] This comparative example is based on Example 5, but differs from Example 5 in that hydrazine compounds are not used.

[0128] Comparative Example 7:

[0129] This comparative example is based on Example 5, except that an equal amount of sodium hydroxide is used instead of hydrazine compounds.

[0130] Comparative Example 8:

[0131] This comparative example is based on Example 5, except that an equal amount of calcium oxide is used to replace the hydrazine compound.

[0132] Comparative Example 9:

[0133] This comparative example is based on Example 5, except that triethanolamine is used instead of hydrazine compounds.

[0134] The contents of newly formed impurities 4-(diethylamino)-2-butanone and the contents of the two active ingredients in the regenerated stripping solutions prepared in Examples 5, 8-10, and Comparative Examples 6-9 were detected by gas chromatography. The results are shown in Table 4.

[0135] Table 4

[0136] additive Organic matter 1 Organic matter 2 New impurities Comparative Example 6 Citric acid 8.90 89.89 0.55 Comparative Example 7 Sodium hydroxide and citric acid 8.91 89.89 0.54 Comparative Example 8 Calcium oxide and citric acid 8.91 89.89 0.55 Comparative Example 9 Triethanolamine and citric acid 8.84 89.89 0.54 Example 5 Methylhydrazine and citric acid 9.50 90.03 0.01 Example 8 phenylhydrazine and citric acid 9.52 90.06 0.01 Example 9 Hydrazine and citric acid 9.50 90.02 0.01 Example 10 hydrazine sulfate and citric acid 9.53 90.04 0.01

[0137] As shown in Table 4, hydrazine compounds are effective in removing the newly formed impurity 4-(diethylamino)-2-butanone from the regeneration stripping solution. Other bases are ineffective against the newly formed impurity 4-(diethylamino)-2-butanone. Furthermore, organic and inorganic hydrazine compounds have comparable effects.

[0138] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for removing newly generated organic impurities during the recycling of stripping fluid, characterized in that, Additives are added to the waste stripping liquid, and the mixture is preheated for at least 0.5 hours at a temperature of 70-80°C. Then, the mixture is subjected to evaporation and slag removal followed by distillation purification to obtain a regenerated stripping liquid. The newly generated organic impurity is 4-(diethylamino)-2-butanone. The additives include hydrazine compounds and citric acid. Based on the volume of the waste stripping liquid, the amount of hydrazine compounds added is 0.6-1.0%, and the amount of citric acid added is 1.0-2.0%. The specific steps include: S1. Add the waste stripping liquid, the hydrazine compound and the citric acid to a preheater and heat to 70-80°C for at least 0.5 hours to obtain pretreated waste stripping liquid; S2. The pretreated waste stripping liquid is introduced into the evaporation kettle for evaporation and slag removal to obtain the evaporated liquid; S3. The evaporated liquid is introduced into distillation column 1 for the first distillation purification to remove light components; S4. The heavy components produced in distillation column 1 are introduced into distillation column 2 for a second distillation purification to remove the heavy components. The light components produced in distillation column 2 are the product regeneration stripping liquid. The waste stripping liquid contains organic matter 1 and organic matter 2, wherein organic matter 1 is diethylene glycol butyl ether and organic matter 2 is N-methylethanolamine or N-methylformamide.

2. The method for removing newly generated organic impurities during the recycling of stripping fluid according to claim 1, characterized in that, Based on the volume of the waste stripping liquid, the amount of hydrazine compound added is 0.6-0.8%, and the amount of citric acid added is 1.0%.

3. The method for removing newly generated organic impurities during the recycling of stripping fluid according to claim 1, characterized in that, The preheating time is 1-4 hours.

4. The method for removing newly generated organic impurities during the recycling of stripping fluid according to claim 3, characterized in that, The preheating time is 1-2 hours.

5. The method for removing newly generated organic impurities during the recycling of stripping fluid according to claim 1, characterized in that, First, the waste stripping liquid, the hydrazine compound, and the citric acid are added to a mixing tank for mixing, and then the mixed solution is added to the preheater for preheating treatment.

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