A method for synthesizing N,N-dialkylhydroxylamine
By using the TS-1 titanium-silicon molecular sieve catalyst and quenching, separation, and vacuum concentration steps in a fixed-bed microchannel reactor, the problems of high exothermic reaction and numerous by-products in the synthesis of N,N-dialkylhydroxylamine were solved, achieving efficient and continuous low-temperature atmospheric pressure synthesis with high product yield and few by-products.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG SAINON CHEM
- Filing Date
- 2026-03-18
- Publication Date
- 2026-06-09
AI Technical Summary
The existing synthesis process of N,N-dialkylhydroxylamine has the problems of high exothermic reaction, high temperature leading to an increase in the by-product nitrone, long process, low yield, and complicated post-processing, making it difficult to achieve continuous operation and low temperature and atmospheric pressure operation.
Using a fixed-bed microchannel reactor and a titanium-silicon molecular sieve TS-1 catalyst, the continuous synthesis of N,N-dialkylhydroxylamine was achieved through the oxidation reaction of dialkylamine with hydrogen peroxide, combined with quenching, separation, and vacuum concentration steps.
It significantly improves the utilization rate of hydrogen peroxide, reduces the content of by-product nitrone, simplifies the process, facilitates industrial application, and achieves a product yield of up to 98% with less than 0.6% by-products.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for synthesizing N,N-dialkylhydroxylamine. Background Technology
[0002] N,N-Dialkylhydroxylamine (R1R2NOH) is a highly efficient polymerization inhibitor for monomers such as acrylates and styrene, and is also an intermediate in pharmaceuticals and pesticides. Some synthetic methods are as follows: In CN1314657C, N,N-dimethylethylamine, N,N-dimethylisopropylamine, or N,N-dimethylcyclohexylamine are used as raw materials, and H2O2 is used as an oxidant to synthesize the hydrate of N,N-dimethylhydroxylamine. However, this requires the decomposition of excess H2O2 with platinum black during the oxidation stage of the raw amine. In CN111909054A, diethylamine, hydrogen peroxide, and a titanium silicate catalyst are placed in a solvent for oxidation to obtain a crude product; the crude product is then subjected to negative pressure distillation and followed by filtration to obtain a filtrate; the filtrate is then subjected to fractional distillation to obtain N,N-diethylhydroxylamine. The reaction is a batch operation, and the catalyst needs to be recovered by filtration. In EP 0314147, Ti-Mg-Al ternary heterogeneous particles are used as catalysts to synthesize N,N-dialkylhydroxylamine by reacting the corresponding dialkylamine with H2O2. The reaction yield is 85%~92%, and 2%~4% of nitrone is produced as a byproduct. The nitrone needs to be removed by hydrogenation or reduction.
[0003] It can be seen that the traditional process for N,N-dialkylhydroxylamine in existing technologies involves a large amount of exothermic reaction, and high temperatures lead to an increase in byproducts such as nitrones and nitrosamines. Furthermore, post-treatment requires multiple extractions and vacuum distillations, resulting in a long process, low yield (75-85%), and a large amount of saline wastewater. Therefore, developing a new "continuous, low-temperature, atmospheric-pressure, and highly selective" process is of great significance for N,N-dialkylhydroxylamine production. Summary of the Invention
[0004] The purpose of this invention is to overcome the deficiencies in the prior art and provide a method for synthesizing N,N-dialkylhydroxylamine.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for synthesizing N,N-dialkylhydroxylamine, comprising the following steps: (1) Dialkylamine and hydrogen peroxide are introduced into a fixed-bed microchannel reactor for oxidation reaction to obtain a mixed solution; (2) The N,N-dialkylhydroxylamine is obtained by sequentially quenching, separating and concentrating the mixture under reduced pressure.
[0006] Preferably, the dialkylamine described in step (1) has the structural formula shown in formula (1): Equation (1); Wherein, R1 is a straight-chain alkyl group with 1 to 12 carbon atoms or a branched alkyl group with 1 to 12 carbon atoms; R2 is a straight-chain alkyl group with 1 to 12 carbon atoms or a branched alkyl group with 1 to 12 carbon atoms; Alternatively, an aliphatic ring consisting of R1, R2, and nitrogen atoms with 5 to 7 carbon atoms.
[0007] Preferably, the concentration of hydrogen peroxide in step (1) is 30~50 wt%; In step (1), the molar ratio of dialkylamine to hydrogen peroxide in hydrogen peroxide is 1:1~1.5.
[0008] As a preferred embodiment, in step (1), the fixed-bed microchannel reactor is filled with titanium-silicon molecular sieve TS-1, and the molar ratio of silicon to titanium in titanium-silicon molecular sieve TS-1 is 30~60:1.
[0009] Preferably, the oxidation reaction in step (1) is carried out at a temperature of 20~100℃, a pressure of 0.3~1MPa, and a residence time of 5~600s.
[0010] Preferably, the concentration of the quenching solution in step (2) is 0.1~15 wt%; The solute in the quenching solution is one or more of sodium sulfite, sodium bisulfite, sodium metabisulfite, and sodium thiosulfate.
[0011] Preferably, the quenching temperature in step (2) is ≤30℃; The volumetric flow rate ratio of the quenching solution and the mixture is 1:20~50.
[0012] Preferably, the membrane pore size separated in step (2) is ≤0.25μm and the pressure is ≥0.1MPa.
[0013] Preferably, the temperature for vacuum concentration in step (2) is 40~60℃ and the vacuum degree is -0.085~-0.095MPa.
[0014] This invention provides a method for synthesizing N,N-dialkylhydroxylamine, comprising the following steps: (1) passing dialkylamine and hydrogen peroxide into a fixed-bed microchannel reactor for oxidation reaction to obtain a mixture; (2) sequentially quenching, separating, and concentrating the mixture under reduced pressure to obtain the N,N-dialkylhydroxylamine. This invention provides a method for the continuous synthesis of N,N-dialkylhydroxylamine in a fixed-bed microchannel reactor, which significantly improves the utilization rate of hydrogen peroxide, reduces the content of by-product nitrone, and features a simple, easy-to-operate, and continuous process, thus facilitating industrial application. Detailed Implementation
[0015] This invention provides a method for synthesizing N,N-dialkylhydroxylamine, comprising the following steps: (1) Dialkylamine and hydrogen peroxide are introduced into a fixed-bed microchannel reactor for oxidation reaction to obtain a mixed solution; (2) The N,N-dialkylhydroxylamine is obtained by sequentially quenching, separating and concentrating the mixture under reduced pressure.
[0016] In this invention, the structural formula of the dialkylamine described in step (1) is shown in formula (1): Equation (1); Wherein, R1 is a straight-chain alkyl group with 1 to 12 carbon atoms or a branched alkyl group with 1 to 12 carbon atoms; R2 is a straight-chain alkyl group with 1 to 12 carbon atoms or a branched alkyl group with 1 to 12 carbon atoms; Alternatively, an aliphatic ring consisting of R1, R2, and nitrogen atoms with 5 to 7 carbon atoms.
[0017] In this invention, the dialkylamine is preferably dimethylamine, diethylamine, diisopropylamine, di-n-butylamine, N-methylbutylamine, pyrrolidine, piperidine, or N-methylcyclohexylamine.
[0018] In this invention, the concentration of hydrogen peroxide in step (1) is preferably 30-50 wt%, more preferably 35-45 wt%, and even more preferably 38-42 wt%.
[0019] In this invention, the molar ratio of dialkylamine to hydrogen peroxide in step (1) is preferably 1:1 to 1.5, more preferably 1:1.1 to 1.4, and even more preferably 1:1.2 to 1.3.
[0020] In this invention, the fixed-bed microchannel reactor in step (1) is filled with titanium-silicon molecular sieve TS-1. The molar ratio of silicon to titanium in the titanium-silicon molecular sieve TS-1 is preferably 30~60:1, more preferably 35~55:1, and even more preferably 40~50:1.
[0021] In this invention, the temperature of the oxidation reaction in step (1) is preferably 20~100℃, more preferably 30~70℃, and even more preferably 40~60℃; the pressure is preferably 0.3~1MPa, more preferably 0.4~0.9MPa, and even more preferably 0.5~0.8MPa; the residence time is preferably 5~600s, more preferably 100~500s, and even more preferably 200~400s.
[0022] In this invention, after the oxidation reaction is completed, a quenching solution is continuously injected at the reactor outlet to quench the residual hydrogen peroxide; the concentration of the quenching solution in step (2) is preferably 0.1~15wt%, more preferably 5~10wt%, and more preferably 7~8wt%.
[0023] In this invention, the solute in the quenching solution is one or more of sodium sulfite, sodium bisulfite, sodium metabisulfite, and sodium thiosulfate.
[0024] In this invention, the quenching temperature in step (2) is preferably ≤30℃, more preferably ≤25℃, and even more preferably ≤20℃.
[0025] In this invention, the volumetric flow rate ratio of the quenching solution and the mixture is preferably 1:20~50, more preferably 1:25~45, and even more preferably 1:30~40.
[0026] In this invention, the membrane pore size separated in step (2) is preferably ≤0.25μm, more preferably ≤0.2μm, and even more preferably ≤0.15μm; the pressure is preferably ≥0.1MPa, more preferably ≥0.15MPa, and even more preferably ≥0.2MPa; a hydrophilic-hydrophobic composite membrane is used for separation to obtain an organic phase, and the organic phase is subsequently concentrated under reduced pressure.
[0027] In this invention, the temperature of vacuum concentration in step (2) is preferably 40~60℃, more preferably 45~55℃, and even more preferably 48~52℃; the vacuum degree is preferably -0.085~-0.095MPa, more preferably -0.086~-0.094MPa, and even more preferably -0.088~-0.092MPa.
[0028] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0029] Example 1
[0030] The raw material di-n-butylamine and 35 wt% hydrogen peroxide were pumped into a fixed-bed microchannel reactor packed with TS-1 granular catalyst at a di-n-butylamine to hydrogen peroxide molar ratio of 1:1.15. The reaction temperature was controlled at 55℃, the reaction pressure at 0.6 MPa, and the reaction residence time at 30 s. The reactor outlet was quenched with 5 wt% Na2SO3 aqueous solution as H2O2, with a quenching solution to mixed liquid volume flow rate ratio of 1:30 and an outlet temperature of 25℃. After treatment, the reaction liquid was subjected to membrane separation to obtain the organic phase, which was then subjected to vacuum distillation to obtain the target product N,N-dibutylhydroxylamine.
[0031] Microchannel reactor: silicon carbide module, channel hydraulic diameter 1 mm, length 1.2 m, liquid holdup 12 mL; Catalyst: TS-1 particles (Si / Ti=45, particle size 0.4µm) with a packing height of 0.8 m and a porosity of 0.42; Membrane separation: PVDF / PTFE composite membrane, pore size 0.22µm, operating pressure 0.1 MPa; Concentration under reduced pressure: vacuum degree -0.091 MPa, temperature 50℃, yielding 98.7% N,N-dibutylhydroxylamine. The yield of N,N-dibutylhydroxylamine was 96.4%, with 0.18% nitrone as a byproduct and 3 ppm of residual H2O2.
[0032] Example 2
[0033] The difference from Example 1 is that the raw material is dimethylamine.
[0034] Example 3
[0035] The difference from Example 1 is that the raw material is diisopropylamine.
[0036] Example 4
[0037] The difference from Example 1 is that the raw material is N-methylbutanamine.
[0038] Example 5
[0039] The difference from Example 1 is that the raw material is pyrrolidine.
[0040] Example 6
[0041] The difference from Example 1 is that the raw material is piperidine.
[0042] Example 7
[0043] The difference from Example 1 is that the raw material is N-methylcyclohexylamine.
[0044] Example 8
[0045] The difference from Example 1 is that the hydrogen peroxide concentration is 30 wt%.
[0046] Example 9
[0047] The difference from Example 1 is that the hydrogen peroxide concentration is 40 wt%.
[0048] Example 10
[0049] The difference from Example 1 is that the dwell time is 60 seconds.
[0050] Example 11
[0051] The difference from Example 1 is the dwell time of 90 seconds.
[0052] Example 12
[0053] The difference from Example 1 is that the reaction temperature is 80°C.
[0054] Example 13
[0055] The difference from Example 1 is that the reaction temperature is 100°C.
[0056] Comparative Example 1 (CN111909054)
[0057] 1 mol of di-n-butylamine, 2 mol of acetone solvent, and 12.09 g of titanium silicate catalyst were placed in a reaction vessel, stirred under closed pressure, and heated to 55°C. 1.5 mol of 35% hydrogen peroxide solution was added dropwise over 4 hours. After the addition was complete, the mixture was kept at the same temperature for 1 hour to carry out a closed-loop oxidation reaction under normal pressure. After the reaction was completed, 93.7% N,N-dibutylhydroxylamine was obtained by extraction and vacuum distillation, with a yield of 82% and 2.1% nitrone as a byproduct.
[0058] The products of the examples and comparative examples were tested, and the results are recorded in Table 1.
[0059] Table 1 Product Test Results
[0060] As can be seen from Table 1, the method provided by the present invention has an effective utilization rate of hydrogen peroxide ≥95%, an N,N-dialkylhydroxylamine content ≥98%, and a by-product nitrone impurity of <0.6%.
[0061] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for synthesizing N,N-dialkylhydroxylamine, characterized in that, Includes the following steps: (1) Dialkylamine and hydrogen peroxide are introduced into a fixed-bed microchannel reactor for oxidation reaction to obtain a mixed solution; (2) The N,N-dialkylhydroxylamine is obtained by sequentially quenching, separating and concentrating the mixture under reduced pressure.
2. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 1, characterized in that, The structural formula of the dialkylamine mentioned in step (1) is shown in formula (1): Equation (1); Wherein, R1 is a straight-chain alkyl group with 1 to 12 carbon atoms or a branched alkyl group with 1 to 12 carbon atoms; R2 is a straight-chain alkyl group with 1 to 12 carbon atoms or a branched alkyl group with 1 to 12 carbon atoms; Alternatively, an aliphatic ring consisting of R1, R2, and nitrogen atoms with 5 to 7 carbon atoms.
3. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 2, characterized in that, The concentration of hydrogen peroxide in step (1) is 30~50 wt%; In step (1), the molar ratio of dialkylamine to hydrogen peroxide in hydrogen peroxide is 1:1~1.
5.
4. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 3, characterized in that, In step (1), the fixed-bed microchannel reactor is filled with titanium-silicon molecular sieve TS-1, and the molar ratio of silicon to titanium in titanium-silicon molecular sieve TS-1 is 30~60:
1.
5. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 4, characterized in that, The oxidation reaction in step (1) is carried out at a temperature of 20~100℃, a pressure of 0.3~1MPa, and a residence time of 5~600s.
6. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 5, characterized in that, The concentration of the quenching solution used in step (2) is 0.1~15wt%; The solute in the quenching solution is one or more of sodium sulfite, sodium bisulfite, sodium metabisulfite, and sodium thiosulfate.
7. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 6, characterized in that, The quenching temperature in step (2) is ≤30℃; The volumetric flow rate ratio of the quenching solution and the mixture is 1:20~50.
8. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 7, characterized in that, The membrane pore size separated in step (2) is ≤0.25μm and the pressure is ≥0.1MPa.
9. The method for synthesizing N,N-dialkylhydroxylamine as described in claim 8, characterized in that, In step (2), the temperature for vacuum concentration is 40~60℃ and the vacuum degree is -0.085~-0.095MPa.