A method for low-temperature hydrolysis treatment of nitroglycerin ester in waste acid

Abstract

This application discloses a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid, relating to the field of wastewater treatment technology. Addressing the problems of high energy consumption, secondary pollution, stringent reaction conditions, and significant safety risks in existing waste acid treatment processes containing nitroglycerin esters, this application adopts the following scheme: 5-20% (by weight) of purified water is added to the waste acid solution at a low temperature of 0-20℃ for dilution. A quaternary ammonium salt phase transfer catalyst is added and mixed thoroughly. Ultrasonic treatment is then applied, and the temperature is raised to 60-120℃ and maintained for reaction. After the reaction, the solution is cooled by ultrasonication to obtain the hydrolysate. This method combines the synergistic effects of acid catalysis, phase transfer catalysis, and ultrasound, enabling efficient degradation of nitroglycerin esters in waste acid under mild conditions. It achieves de-energized and harmless treatment, eliminates safety hazards, reduces energy consumption, is simple to operate, and is easily scalable for large-scale production.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, specifically to a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid. Background Technology

[0002] Nitrate ester plasticizers have long been used as energetic plasticizers in solid propellant and propellant formulations due to their excellent plasticizing effect and high energy. Nitrate ester plasticized polyether propellants represent the current development direction of solid propellants. Nitroglycerin esters (NG), as a new generation of energetic plasticizers for high-energy propellants, have advantages such as low cost, low glass transition temperature, good low-temperature mechanical properties, and low burning rate of the basic components, and are therefore widely used.

[0003] Waste acid treatment is a crucial component of the nitroglycerin production process. It involves the safe handling and recovery of nitroglycerin esters and their derivatives contained in the waste acid left over from the separation process. Nitroglycerin ester production generates a large amount of waste acid, which contains sulfuric acid, nitric acid, nitric acid, and lower nitrate esters such as nitric acid dinitrate. These lower nitrate esters can further react to generate nitric acid. This nitric acid floats freely on the surface of the waste acid liquid; once it accumulates, it can undergo an autocatalytic reaction, posing a significant hazard and easily leading to decomposition and explosion.

[0004] Currently, the main methods for treating waste acid generated during nitrate ester synthesis include dilution and discharge, direct thermal decomposition, and post-dilution thermal decomposition. Dilution and discharge methods cause secondary pollution and do not completely eliminate safety hazards. Direct thermal decomposition typically involves controlling the treatment temperature between 200-350℃, resulting in low yield rates, requiring multiple treatments, high costs, and demanding sophisticated equipment. Direct dilution of the treated waste acid containing nitroglycerin followed by thermal decomposition can eliminate safety hazards and has strong applicability, but it is energy-intensive and costly. Existing research uses a dilution-vacuum thermal decomposition method to treat waste acid generated during the synthesis of nitroglycerin / triethylene glycol dinitrate (NG / TEGDN) mixed nitrate esters. At a treatment temperature of 150-180℃, the waste acid treatment effect is good, with the ester content in the treated waste acid being <0.5%. Therefore, developing new methods for treating waste acid containing nitroglycerin esters is of significant research importance.

[0005] To address the aforementioned issues, this application employs low-temperature hydrolysis technology to directly and harmlessly treat nitroglycerin esters in waste acid in the presence of a small amount of water. This achieves the de-energization of nitroglycerin esters, eliminates the hazards of subsequent waste acid treatment, and solves the problems of high energy consumption and environmental pollution in existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the primary objective of this application is to provide a low-temperature hydrolysis method for treating nitroglycerin esters in waste acid. This application achieves the hydrolysis of nitroglycerin esters in the waste acid solution under low-temperature conditions by diluting the waste acid with a small amount of water and through the catalytic action of a quaternary ammonium salt phase transfer catalyst and the waste acid itself. Ultrasonic stimulation further enhances the reaction efficiency. This method enables the efficient removal of the hazardous compound nitroglycerin esters and features simple operation, mild reaction conditions, and ease of large-scale production.

[0007] To achieve the above objectives, this application provides the following technical solution:

[0008] This application provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid, comprising the following steps:

[0009] Diluted waste acid is obtained by adding pure water to the waste acid solution at a low temperature of 0-20℃.

[0010] Add a quaternary ammonium salt phase transfer catalyst to the diluted waste acid and stir until homogeneous;

[0011] The diluted waste acid containing the catalyst is transferred to a reaction vessel, ultrasonication is turned on, and the temperature is raised to 60-120℃. The reaction is maintained at this temperature until it ends. Heating is stopped, ultrasonication is continued, and the mixture is allowed to cool naturally to room temperature to obtain the hydrolysate.

[0012] Preferably, the temperature of the low-temperature condition is 0-8℃.

[0013] It should be noted that the waste acid contains sulfuric acid (60-70%), nitric acid (5-10%), water (15-25%), and nitroglycerin esters (1-9%). The large amounts of concentrated sulfuric acid and nitric acid will release a lot of heat during the dilution process with water. Therefore, the dilution process needs to be controlled at low temperatures to avoid the decomposition of nitroglycerin esters due to excessively high temperatures.

[0014] Preferably, the amount of purified water added is 5-20% of the mass of the waste acid solution, and more preferably 16.5%.

[0015] It should be noted that diluting the waste acid with water serves two purposes: firstly, it increases the water content, allowing the hydrolysis reaction to proceed; secondly, it limits the amount of water added to avoid over-diluting and causing H+ to be released. + Lowering the concentration weakens the acid-catalyzed hydrolysis effect. Furthermore, experiments showed that the hydrolysis efficiency of nitroglycerin was highest when the amount of water added was 16.5% of the mass of the waste acid solution.

[0016] Preferably, the quaternary ammonium salt phase transfer catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, and benzyltriethylammonium chloride.

[0017] It should be noted that in diluted waste acid, nitroglycerin esters are the organic phase, while the waste acid is the aqueous phase. The hydrolysis reaction can only occur at the interface between the two phases, resulting in high mass transfer resistance and low efficiency. However, using quaternary ammonium salts as phase transfer catalysts can improve the hydrolysis efficiency. The quaternary ammonium cations combine with acid radicals in the aqueous phase to form lipophilic ion pairs, which then transfer H+-containing... + The acid radical anions are carried from the aqueous phase to the organic phase, allowing the hydrolysis reaction to occur inside the organic phase, thereby increasing the hydrolysis rate.

[0018] Preferably, the amount of the quaternary ammonium salt phase transfer catalyst is 0.1-0.5% of the mass of the diluted waste acid.

[0019] Preferably, the stirring rate is 50-100 rpm and the stirring time is 5-10 min.

[0020] Preferably, the power density of the ultrasound is 0.5-1 W / cm². 2 The frequency is 20-40kHz.

[0021] It should be noted that during the hydrolysis reaction, ultrasound is used to refine the nitroglycerin droplets, increasing the contact area between the two phases. This, in conjunction with the phase transfer catalyst, enhances the hydrolysis reaction rate.

[0022] Preferably, the heating rate is 1-3°C / min.

[0023] Preferably, the temperature of the heat preservation reaction is 60-100℃.

[0024] Preferably, the heat preservation reaction time is 0.1-2 hours, and more preferably 0.15-0.7 hours.

[0025] The beneficial effects of this application are:

[0026] This solution employs low-temperature hydrolysis to treat waste acid containing nitroglycerin esters. The safe degradation of nitroglycerin esters can be achieved at 60-120℃ with no harmful emissions, saving energy and reducing pollutant emissions. Simultaneously, by adding a quaternary ammonium salt catalyst, utilizing its amphiphilic cation properties, it can carry H+. + Entering nitroglycerin esters enables phase transfer of reactants, improving hydrolysis efficiency. On the other hand, its surfactant properties can significantly reduce interfacial tension between the two phases and increase the effective contact area, thereby accelerating the hydrolysis rate of nitroglycerin esters. When combined with an ultrasonic device during the reaction, the ultrasonic cavitation effect is used to pulverize the nitroglycerin ester oil droplets into micron or even nano-sized droplets, forming a metastable emulsion. This increases the contact area between the two phases, reduces the mass transfer resistance at the macroscopic phase interface, and further accelerates the hydrolysis rate of nitroglycerin esters. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A flowchart of a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid provided in this application.

[0029] Figure 2 The content of esters in the hydrolysate at different reaction times in Example 2.

[0030] Figure 3 The following are liquid phase spectra of ester content in waste acid after 0 min and 40 min of hydrolysis reaction in Example 2: (a) Liquid phase spectra of ester content at 0 min of reaction, (b) Liquid phase spectra of ester content after 40 min of reaction.

[0031] Figure 4 The exothermic DSC spectrum of the hydrolysis reaction process in Example 7 is shown. Detailed Implementation

[0032] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0034] The following specific embodiments further illustrate this point:

[0035] Example 1

[0036] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0037] 1. At a temperature of 5℃, add 5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0038] 2. Take 100g of diluted waste acid, add 0.2g of tetrabutylammonium bromide, and stir at 80rpm for 8min.

[0039] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 0.7 W / cm³. 2The temperature was increased to 60°C at a frequency of 30 kHz and a rate of 2°C / min. The temperature was maintained for 1 hour. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 1.

[0040] Example 2

[0041] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0042] 1. At 5℃, add 16.5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0043] 2. Take 100g of diluted waste acid, add 0.2g of tetrabutylammonium bromide, and stir at 80rpm for 8min.

[0044] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 0.7 W / cm³. 2 The temperature was increased to 60°C at a frequency of 30 kHz and a rate of 2°C / min. The reaction was maintained at this temperature for 1 hour. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 2.

[0045] Example 3

[0046] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0047] 1. At 5℃, add 20g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0048] 2. Take 100g of diluted waste acid, add 0.2g of tetrabutylammonium bromide, and stir at 80rpm for 8min.

[0049] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 0.7 W / cm³. 2 The temperature was increased to 60°C at a frequency of 30 kHz and a rate of 2°C / min. The reaction was maintained at this temperature for 1 hour. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 3.

[0050] Example 4

[0051] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0052] 1. At 5℃, add 16.5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0053] 2. Take 100g of diluted waste acid, add 0.2g of tetrabutylammonium bromide, and stir at 80rpm for 8min.

[0054] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 0.7 W / cm³. 2 The temperature was increased to 70°C at a frequency of 30 kHz and a rate of 2°C / min. The reaction was maintained at this temperature for 1 hour. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 4.

[0055] Example 5

[0056] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0057] 1. At 5℃, add 16.5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0058] 2. Take 100g of diluted waste acid, add 0.2g of tetrabutylammonium bromide, and stir at 80rpm for 8min.

[0059] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 0.7 W / cm³. 2 The temperature was increased to 90°C at a frequency of 30 kHz and a rate of 2°C / min. The reaction was maintained at this temperature for 1 hour. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 5.

[0060] Example 6

[0061] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0062] 1. At 5℃, add 16.5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0063] 2. Take 100g of diluted waste acid, add 0.2g of tetrabutylammonium bromide, and stir at 80rpm for 8min.

[0064] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 0.7 W / cm³. 2 The temperature was increased to 100°C at a frequency of 30 kHz and a rate of 2°C / min. The reaction was maintained at this temperature for 0.7 h. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 6.

[0065] Example 7

[0066] like Figure 1As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0067] 1. At 5℃, add 16.5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0068] 2. Take 100g of diluted waste acid, add 0.2g of tetrabutylammonium bromide, and stir at 80rpm for 8min.

[0069] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 0.7 W / cm³. 2 The temperature was increased to 120°C at a frequency of 30 kHz and a rate of 2°C / min. The reaction was maintained at this temperature for 0.15 h. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 7.

[0070] Example 8

[0071] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0072] 1. At 0℃, add 18g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0073] 2. Take 100g of diluted waste acid, add 0.1g of tetrabutylammonium chloride, and stir at 100rpm for 10min.

[0074] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic generator at a power density of 0.5 W / cm³. 2 The temperature was increased to 60°C at a frequency of 20 kHz and a rate of 1°C / min. The reaction was maintained at this temperature for 2 hours. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 8.

[0075] Example 9

[0076] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0077] 1. At 20℃, add 5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0078] 2. Take 100g of diluted waste acid, add 0.5g of tetrabutylammonium hydrogen sulfate, and stir at 50rpm for 5min.

[0079] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 1 W / cm³. 2The temperature was increased to 90°C at a frequency of 40 kHz and a rate of 3°C / min. The reaction was maintained at this temperature for 0.1 h. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 9.

[0080] Example 10

[0081] like Figure 1 As shown, this embodiment provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid:

[0082] 1. At 8℃, add 5g of purified water to 100g of waste acid solution to obtain diluted waste acid.

[0083] 2. Take 100g of diluted waste acid, add 0.5g of benzyltriethylammonium chloride, and stir at 50rpm for 5min.

[0084] 3. Transfer the diluted waste acid with added catalyst to the reaction vessel, and turn on the ultrasonic treatment at a power density of 1 W / cm³. 2 The temperature was increased to 100°C at a frequency of 40 kHz and a rate of 3°C / min. The reaction was maintained at this temperature for 0.5 h. After the reaction was completed, the heating was stopped, and the mixture was sonicated and allowed to cool naturally to room temperature to obtain the hydrolysate of Example 10.

[0085] Comparative Example 1

[0086] This comparative example provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid. Compared with Example 2, the difference is that no quaternary ammonium salt phase transfer catalyst is added during the treatment process. The remaining steps are the same as in Example 2 and will not be repeated here.

[0087] Comparative Example 2

[0088] This comparative example provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid. Compared with Example 2, the difference is that the ultrasonic device is not turned on during the treatment process. The remaining steps are the same as those in Example 2, and will not be repeated here.

[0089] Comparative Example 3

[0090] This comparative example provides a low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid. Compared with Example 2, the difference is that the reaction temperature is 130°C, while the other steps are the same as in Example 2, and will not be repeated here.

[0091] To demonstrate the beneficial effects of this application, the ester content of the hydrolysates obtained in Examples 1-10 and Comparative Examples 1-3 was tested using the following methods:

[0092] The test was performed using high performance liquid chromatography (HPLC). A reversed-phase C18 column was used with methanol-water as the mobile phase (methanol:water volume ratio 55:45), a flow rate of 1 mL / min, a column temperature of 25 °C, a detection wavelength of 205 nm, and an injection volume of 10 μL. The test results are shown in Table 1.

[0093] Table 1. Test data of hydrolysates from Examples 1-10 and Comparative Examples 1-3

[0094] Hydrolysate sample Ester content (%) Heat release from water (J) Example 1 0.63 No obvious heat release Example 2 0.41 No obvious heat release Example 3 0.56 No obvious heat release Example 4 0.38 No obvious heat release Example 5 0.26 No obvious heat release Example 6 0.14 4.08 Example 7 0.03 9.09 Example 8 0.43 No obvious heat release Example 9 0.42 1.24 Example 10 0.31 3.16 Comparative Example 1 1.24 No obvious heat release Comparative Example 2 1.09 No obvious heat release Comparative Example 3 0.02 16.3

[0095] As can be seen from the test results in Table 1 above, the ester content in the hydrolysates obtained from Examples 1-10 is lower than that in Comparative Examples 1-2. Figure 2 and Figure 3 As can be seen, in Example 2, the ester content in the waste acid solution decreased significantly as the hydrolysis reaction proceeded. Because no phase transfer catalyst was added in Comparative Example 1, the hydrolysis efficiency of nitroglycerin esters was reduced, and the nitroglycerin esters in the waste acid solution could not be completely hydrolyzed and decomposed. Similarly, in Comparative Example 2, the lack of ultrasonic cavitation effect resulted in low hydrolysis reaction efficiency, leading to a higher ester content in the hydrolysate. Furthermore, a comparison of the ester content in Examples 1, 2, and 3 shows that the lowest ester content in the hydrolysate was achieved when 16.5% of the waste acid solution mass of purified water was added during dilution; this ratio represents the optimal dilution ratio. A comparison of the ester content in Examples 2, 4, 5, 6, and 7 shows that the ester content in the hydrolysate decreased with increasing reaction temperature, due to the more vigorous hydrolysis reaction of nitroglycerin esters at high temperatures. (See Table 1 and...) Figure 4 As shown, exothermic reactions occur during the dilution of waste acid as the temperature increases. As can be seen from Examples 6, 7, 9, 10 and Comparative Example 3, significant exothermic reactions occur when the temperature reaches above 90°C, and the exothermic reaction increases significantly when the temperature reaches 130°C. Therefore, in order to reduce the reaction risk, the temperature should be set below 120°C, which also reduces energy consumption and reaction risk.

[0096] In summary, the low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid adopted in this application has significant advantages. Its reaction conditions are mild, and it is not easy to cause dangerous situations such as explosions. The lower reaction temperature can save energy consumption and reduce treatment costs. At the same time, the small molecule organic matter and sulfuric acid and nitric acid remaining after the hydrolysis reaction can be recovered through subsequent processes, saving resources and reducing pollutant emissions. It is suitable for fields such as the treatment of nitrated waste acid.

[0097] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.

Claims

1. A method for low-temperature hydrolysis treatment of nitroglycerin esters in waste acid, characterized in that, Includes the following steps: Diluted waste acid is obtained by adding pure water to the waste acid solution at a low temperature of 0-20℃. Add a quaternary ammonium salt phase transfer catalyst to the diluted waste acid and stir until homogeneous; The diluted waste acid containing the catalyst was transferred to a reaction vessel, and the ultrasonic treatment was turned on. The temperature was raised to 60-120℃ and then maintained for reaction. After the reaction was completed, the heating was stopped, the ultrasonic treatment was continued, and the mixture was allowed to cool naturally to room temperature to obtain the hydrolysate. The amount of purified water added is 5-20% of the mass of the waste acid solution; The quaternary ammonium salt phase transfer catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, and benzyltriethylammonium chloride.

2. The low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid according to claim 1, characterized in that, The amount of the quaternary ammonium salt phase transfer catalyst used is 0.1-0.5% of the mass of the diluted waste acid.

3. The low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid according to claim 1, characterized in that, The stirring rate is 50-100 rpm, and the stirring time is 5-10 min.

4. The low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid according to claim 1, characterized in that, The power density of the ultrasound is 0.5-1 W / cm². 2 The frequency is 20-40kHz.

5. The low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid according to claim 1, characterized in that, The heating rate is 1-3℃ / min.

6. The low-temperature hydrolysis treatment method for nitroglycerin esters in waste acid according to claim 1, characterized in that, The heat preservation reaction time is 0.1-2 hours.

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