Safe and green synthesis method of high-purity diethylhydroxylamine

Abstract

The invention discloses a safe and green synthesis method of high-purity diethylhydroxylamine, and belongs to the technical field of chemical synthesis processes. According to the method, triethylamine is taken as a raw material, in an organic solvent, sodium percarbonate (or potassium monohydrogen persulfate composite salt and potassium persulfate) is taken as an oxidizing agent, a composite system formed by sodium tungstate and sodium pyrophosphate is taken as a catalyst, and triethylamine nitrogen oxide is generated through reaction at 20-70 DEG C for 6-20 hours. And after the reaction is finished, filtering to remove solid impurities, concentrating the filtrate to recover the organic solvent, and carrying out reduced pressure thermal cracking on the obtained triethylamine nitrogen oxide at 90-140 DEG C under the absolute pressure of 0.01-0.1 Mpa for 2-5 hours to obtain the diethylhydroxylamine product. The solid oxidizing agent is adopted to replace traditional hydrogen peroxide, water is prevented from being introduced from the source, the problem that the product purity is low due to residual water in a traditional process is solved, the product purity can reach 92.6% at most, the mole yield can reach 89.2% at most, and the organic solvent can be efficiently recycled.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, specifically relating to a safe and green synthesis method for high-purity diethylhydroxylamine. Background Technology

[0002] Diethylhydroxylamine (CAS No.: 3710-84-7) is a colorless or pale yellow liquid at room temperature, soluble in organic solvents such as ethanol, ether, chloroform, and benzene, and readily soluble in water. This product belongs to the disubstituted hydroxylamine derivatives and is industrially used as a polymerization inhibitor, chain transfer agent, developing aid in color photography, vulcanizing agent and modifier for silicone rubber, corrosion inhibitor and passivator for metals, and also as a deoxidizer, mild reducing agent, and antioxidant for photosensitive resins in steam boiler water systems. Its structural formula is: Currently, the main industrial methods for synthesizing diethylhydroxylamine are the diethylamine oxidation method and the triethylamine oxidative cracking method. The diethylamine oxidation method uses titanium silicate molecular sieves (such as HTS) as catalysts, directly oxidizing diethylamine with hydrogen peroxide to obtain the product diethylhydroxylamine. However, its core problem lies in the strong reducing properties of diethylhydroxylamine itself, which is easily further oxidized in the reaction system to byproducts (nitroketone compounds). This leads to a decrease in yield, and impurities or polymers generated by the side reactions clog the catalyst pores. The triethylamine oxidative cracking method uses hydrogen peroxide to oxidize triethylamine to produce triethylamine nitrogen oxides. After concentrating the water in the reaction system, it is then cracked to obtain the diethylhydroxylamine product. However, after the concentration stage, the residual water in the reaction solution is difficult to completely remove. This residual water directly affects the subsequent cracking reaction, resulting in a significant decrease in the yield and purity of the target product, diethylhydroxylamine, and the use of hydrogen peroxide generates a large amount of wastewater. The purity of the product from the traditional triethylamine oxidative cracking method is typically below 80%, and the molar yield is below 70%. The triethylamine oxidative cracking method disclosed in Chinese patent CN 109096144 A uses hydrogen peroxide as an oxidant, which poses a risk to storage and transportation safety.

[0003] In summary, the traditional method for preparing diethylhydroxylamine from triethylamine has the following problems: 1) high cost of catalysts; 2) increased safety hazards due to the storage, transportation and use of hydrogen peroxide; 3) large amount of waste liquid generated during the oxidation process; and 4) low purity and yield of the product. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the traditional diethylhydroxylamine preparation process and provide a safe and green synthesis method for high-purity diethylhydroxylamine. Specifically, this invention addresses the issues of poor safety, severe environmental pollution, and low product purity associated with traditional diethylhydroxylamine preparation processes by providing a green, safe, and efficient new method for preparing high-purity diethylhydroxylamine. This method utilizes sodium percarbonate as a solid oxidant, combined with the highly efficient catalytic effect of a sodium tungstate-sodium pyrophosphate composite catalyst, to efficiently and selectively oxidize triethylamine in an anhydrous reaction system, fundamentally solving the safety, environmental protection, and product quality problems of traditional processes.

[0005] The technical solution adopted in this invention is: Using triethylamine as a raw material, in the presence of an organic solvent, an oxidant and a composite catalyst consisting of sodium tungstate and sodium pyrophosphate are added. After reacting at a reaction temperature of 20-70°C for 6-20 hours, the mixture is filtered, and the organic solvent in the filtrate is evaporated to obtain triethylamine oxides. The obtained triethylamine oxides are then pyrolyzed at 90-140°C and an absolute pressure of 0.01-0.1 MPa for 2-5 hours to obtain diethylhydroxylamine.

[0006] The organic solvent is methanol, ethanol, a methanol-ethanol mixture, acetonitrile, isopropanol, or tert-butanol.

[0007] The oxidizing agent is sodium percarbonate, potassium perhydrogen persulfate complex salt, or potassium persulfate.

[0008] The molar ratio of triethylamine to oxidant (such as sodium percarbonate) is 1:0.3 to 1.2, which ensures that the oxidant is sufficient, and the preferred molar ratio is 1:0.5 to 1.2.

[0009] In the composite catalyst system, the mass ratio of sodium tungstate to sodium pyrophosphate is 1:2~5, and the total amount of catalyst is 0.5%~2% of the mass of triethylamine.

[0010] After the reaction is complete, the organic solvent removed by concentration of the filtrate can be recycled for the next cycle.

[0011] This invention uses a solid oxidant to replace traditional hydrogen peroxide, avoiding the introduction of moisture at the source and solving the problem of low product purity caused by residual moisture in traditional processes. The product purity can reach up to 92.6%, and the molar yield can reach up to 89.2%. At the same time, it eliminates the safety risks in the storage, transportation and use of hydrogen peroxide, and no process wastewater is generated. Organic solvents can be efficiently recovered, combining the advantages of safety, environmental protection and high product quality.

[0012] Further optimization involves using triethylamine as a raw material, reacting it in an anhydrous organic solvent with sodium percarbonate as an oxidant and a composite system of sodium tungstate and sodium pyrophosphate as a catalyst at 20-70°C for 6-20 hours to generate triethylamine nitrogen oxides. After the reaction, solid impurities are removed by filtration, and the filtrate is concentrated to recover the organic solvent. The obtained triethylamine nitrogen oxides are then subjected to reduced pressure thermal decomposition at 90-140°C and an absolute pressure of 0.01-0.1 MPa for 2-5 hours to obtain diethylhydroxylamine.

[0013] The synthetic route of this invention is as follows: The specific solution of the present invention is as follows: Assemble a mechanical stirrer in a 500 mL three-necked flask. Add triethylamine, anhydrous methanol, sodium percarbonate, sodium tungstate, and sodium pyrophosphate sequentially, with a sodium tungstate to sodium pyrophosphate mass ratio of 1:2–5, and the total catalyst amount being 0.5%–2% of the triethylamine mass. React at 20–70 °C for 6–20 hours under mechanical stirring. After the reaction, filter the resulting solid-liquid mixture while hot to recover solid sodium carbonate. Remove the methanol solvent from the filtrate by rotary evaporation to obtain crude triethylamine oxide. Perform vacuum thermal pyrolysis on this crude product at 90–140 °C under a pressure of 0.01–0.1 MPa for 2–5 hours, finally collecting a colorless and transparent diethylhydroxylamine product.

[0014] Preferably, the mass ratio of sodium tungstate to sodium pyrophosphate in the solution is 1:3~4.

[0015] Preferably, the total amount of catalyst used in the scheme is 0.8% to 2% of the mass of triethylamine. Preferably, the molar ratio of triethylamine to sodium percarbonate in the scheme is 1:0.5~0.8.

[0016] Preferably, the reaction temperature in the scheme is 40~70℃.

[0017] Preferably, the reaction time in the scheme is 10~15h.

[0018] The beneficial effects of this invention lie in the use of sodium percarbonate as a solid oxygen source, which synergistically works with a sodium tungstate-sodium pyrophosphate composite catalyst to oxidize triethylamine. Sodium tungstate, as the catalytic active center, effectively activates the active oxygen released from sodium percarbonate, significantly improving its oxidation efficiency and reaction rate for triethylamine, thus avoiding the runaway risk caused by the rapid decomposition of hydrogen peroxide. Sodium pyrophosphate, as a key ligand and stabilizer, forms a stable, soluble complex with sodium tungstate, preventing sodium tungstate from precipitating or deactivating in the reaction system, ensuring the persistence and high efficiency of the catalytic active center, thereby jointly constituting a highly selective and highly active catalytic system.

[0019] Fundamentally improving product quality: The aforementioned synergistic effect ensures the efficient and stable conversion of triethylamine to triethylamine oxides, inhibiting side reactions such as excessive oxidation. Simultaneously, the introduction of solid sodium percarbonate prevents moisture introduction at the source, making the subsequent thermal decomposition reaction more thorough, ultimately increasing the purity of diethylhydroxylamine to a maximum of 92.6% and the yield to a maximum of 89.2%.

[0020] Comprehensive upgrade in safety and environmental protection: It completely eliminates the risks of storing, transporting and using liquid hydrogen peroxide, generates no process wastewater during the reaction process, the solvent can be recycled, and the by-product sodium carbonate can be recovered, thus achieving inherent safety and green environmental protection of the process.

[0021] Comparison table of traditional processes and this invention: Attached Figure Description

[0022] Table 1 shows the average peak area of ​​diethylhydroxylamine standard solution at different concentrations.

[0023] Figure 1 This is the external standard curve for diethylhydroxylamine.

[0024] Figure 2 The NMR spectrum of the target product, diethylhydroxylamine.

[0025] Figure 3 The product is a diethylhydroxy compound obtained through cleavage. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto: Example 1 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (63.3 g, 200 mmol), sodium tungstate (0.1 g, 0.34 mmol), sodium pyrophosphate (0.36 g, 1.36 mmol), and methanol (50 mL) were added. The reaction was carried out at 70 °C for 20 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to vacuum pyrolysis at 125 °C and 0.01 MPa for 3 h to obtain a transparent liquid diethylhydroxylamine, weighing 21.5 g. Gas chromatography analysis showed a purity of 92.6% and a molar yield of 89.3%.

[0027] Example 2 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (63.3 g, 200 mmol), sodium tungstate (0.05 g, 0.17 mmol), sodium pyrophosphate (0.18 g, 0.68 mmol), and methanol (50 mL) were added. The reaction was carried out at 70 °C for 15 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to vacuum pyrolysis at 125 °C and 0.01 MPa for 3 h to obtain a transparent liquid diethylhydroxylamine, weighing 21.0 g. Gas chromatography analysis showed a purity of 91.4% and a molar yield of 86.1%.

[0028] Example 3 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (63.3 g, 200 mmol), sodium tungstate (0.025 g, 0.09 mmol), sodium pyrophosphate (0.09 g, 0.34 mmol), and methanol (50 mL) were added. The reaction was carried out at 70 °C for 6 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to reduced pressure pyrolysis at 125 °C and 0.01 MPa for 3 h to obtain a transparent liquid diethylhydroxylamine, weighing 18.2 g. Gas chromatography analysis showed a purity of 84.9% and a molar yield of 69.3%.

[0029] Example 4 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (63.3 g, 200 mmol), sodium tungstate (0.05 g, 0.17 mmol), sodium pyrophosphate (0.18 g, 0.68 mmol), and methanol (50 mL) were added. The reaction was carried out at 20 °C for 20 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered. The main solid component was sodium carbonate, which could be recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to reduced pressure pyrolysis at 130 °C and 0.01 MPa for 2 h to obtain a transparent liquid diethylhydroxylamine, weighing 16.5 g. Gas chromatography analysis showed a purity of 86.4% and a molar yield of 64.0%.

[0030] Example 5 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (63.3 g, 200 mmol), sodium tungstate (0.08 g, 0.27 mmol), sodium pyrophosphate (0.16 g, 0.60 mmol), and methanol (50 mL) were added. The reaction was carried out at 50 °C for 20 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to vacuum pyrolysis at 125 °C and 0.01 MPa for 3 h to obtain a transparent liquid diethylhydroxylamine, weighing 19.7 g. Gas chromatography analysis showed a purity of 87.8% and a molar yield of 77.6%.

[0031] Example 6 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (26.4 g, 84 mmol), sodium tungstate (0.05 g, 0.17 mmol), sodium pyrophosphate (0.18 g, 0.68 mmol), and methanol (50 mL) were added. The reaction was carried out at 70 °C for 17 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to reduced pressure pyrolysis at 125 °C and 0.1 MPa for 5 h to obtain a transparent liquid diethylhydroxylamine, weighing 14.9 g. Gas chromatography analysis showed a purity of 86.2% and a molar yield of 57.6%.

[0032] Example 7 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (52.4 g, 167 mmol), sodium tungstate (0.05 g, 0.17 mmol), sodium pyrophosphate (0.2 g, 0.7 mmol), and methanol (50 mL) were added. The reaction was carried out at 70 °C for 17 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to vacuum pyrolysis at 90 °C and 0.01 MPa for 5 h to obtain a transparent liquid diethylhydroxylamine, weighing 21.6 g. Gas chromatography analysis showed a purity of 89.4% and a molar yield of 86.7%.

[0033] Example 8 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (95.0 g, 0.3 mmol), sodium tungstate (0.05 g, 0.17 mmol), sodium pyrophosphate (0.18 g, 0.68 mmol), and methanol (50 mL) were added. The reaction was carried out at 70 °C for 17 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The methanol in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to reduced pressure pyrolysis at 140 °C and 0.01 MPa for 2 h to obtain a transparent liquid diethylhydroxylamine, weighing 22.6 g. Gas chromatography analysis showed a purity of 84.7% and a molar yield of 85.9%.

[0034] Example 9 A mechanically stirred apparatus was set up in a 500 mL three-necked flask. Triethylamine (25.3 g, 250 mmol), sodium percarbonate (63.3 g, 200 mmol), sodium tungstate (0.05 g, 0.17 mmol), sodium pyrophosphate (0.18 g, 0.68 mmol), and a 50 mL mixture of ethanol and methanol were added. The reaction was carried out at 70 °C for 17 h to obtain an oxidation reaction solution. The solid in the obtained reaction solution was filtered, and the main solid component, sodium carbonate, was recovered. The solvent in the filtrate was removed by rotary evaporation. The concentrated solution was subjected to vacuum pyrolysis at 125 °C and 0.01 MPa for 5 h to obtain a transparent liquid diethylhydroxylamine, weighing 21.5 g. Gas chromatography analysis showed a purity of 90.7% and a molar yield of 87.5%.

[0035] Example 10 The diethylhydroxylamine product was analyzed using a gas chromatograph, specifically an Agilent 8860 gas chromatograph with an Agilent HP-5 column (30m × 0.32mm × 0.25μm), an injection volume of 1μL, and an FID detector.

[0036] The gas chromatography detection method is as follows: Example 11 (1) Preparation of diethylhydroxylamine standard solution Accurately weigh 250 mg of diethylhydroxylamine standard using an analytical balance and add it to a 25 mL volumetric flask. Dissolve the standard in a small amount of chromatographic methanol by sonication, then add chromatographic methanol to the mark and mix well. Take five 10 mL volumetric flasks and accurately pipette five different volumes (100 μL, 200 μL, 400 μL, 800 μL, and 1000 μL) of diethylhydroxylamine standard solution into the corresponding volumetric flasks. Add chromatographic methanol to the mark to prepare a series of concentration samples (0.1 mg / mL, 0.2 mg / mL, 0.4 mg / mL, 0.8 mg / mL, and 1 mg / mL). Shake well and set aside. (2) Plotting the standard curve of diethylhydroxylamine Five different concentrations of diethylhydroxylamine (0.1 mg / mL, 0.2 mg / mL, 0.4 mg / mL, 0.8 mg / mL, and 1 mg / mL) were prepared. Each concentration was injected three times with an equal volume, and the average value was recorded (Table 1). A standard curve was then fitted based on the average value for each concentration. Figure 1 ). Figure 1 The x-axis represents the concentration of diethylhydroxylamine (mg / mL), and the y-axis represents the average peak area. The linear regression equation is y = 365.83x - 4.93, R0. 2 =0.999, indicating a good linear relationship.

[0037] Table 1 Example 12 Diethylhydroxylamine 1 ¹H NMR (400MHz, DMSO-d6) spectra indicate that, due to the influence of methylene coupling, in 1 At the high field of HNMR, a strong methyl proton peak appeared, with chemical shifts of 0.89 ppm, 0.91 ppm, and 0.92 ppm, indicating that -CH2- is adjacent to -CH3, and the two -CH3 atoms share the same environment. The methylene proton peak should have been a quartet, but only a broad peak appeared at 2.41 ppm, indicating that the nitrogen atom is adjacent to -CH2- and has a significant impact on the coupling of the -CH2- splitting peak. The peak at 3.33 ppm represents water in the solvent and does not affect product identification. The proton peak of the active hydrogen in the hydroxyl group (-OH) appeared at the low field, with a chemical shift of 7.48 ppm.

Claims

1. A safe and green method for synthesizing high-purity diethylhydroxylamine, characterized in that: Using triethylamine as a raw material, a composite catalyst and oxidant consisting of sodium tungstate and sodium pyrophosphate were added in the presence of an organic solvent. After the reaction, the mixture was filtered, and the organic solvent in the filtrate was evaporated to obtain triethylamine nitrides. The obtained triethylamine nitrides were then cracked to obtain diethylhydroxylamine.

2. The synthesis method according to claim 1, characterized in that: The organic solvent is methanol, ethanol, a methanol-ethanol mixture, acetonitrile, isopropanol, or tert-butanol.

3. The synthesis method according to claim 1, characterized in that: The oxidant is sodium percarbonate, potassium perhydrogen persulfate complex salt, or potassium persulfate.

4. The synthesis method according to claim 1, characterized in that: The molar ratio of triethylamine to sodium percarbonate is 1:0.3~1.

2.

5. The synthesis method according to claim 1, characterized in that: The reaction time is 6 to 20 hours.

6. The synthesis method according to claim 1, characterized in that: The reaction temperature is 20~70℃.

7. The synthesis method according to claim 1, characterized in that: The pyrolysis conditions are: temperature of 90~140℃, pressure of 0.01Mpa~0.1Mpa, and pyrolysis time of 2~5h.

8. The synthesis method according to claim 1, characterized in that: In the composite catalyst system, the mass ratio of sodium tungstate to sodium pyrophosphate is 1:2~5, and the total amount of catalyst is 0.5%~2% of the mass of triethylamine.

9. The synthesis method according to claim 1, characterized in that: After the reaction is complete, the organic solvent removed by concentration of the filtrate can be recycled for the next cycle.

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