Method and device for synthesizing N-methyl morpholine oxide

Abstract

The invention discloses a method and a device for synthesizing N-methyl morpholine oxide, and relates to the technical field of chemical synthesis. The device comprises a synthesis kettle, a reaction kettle, a decomposition kettle and a filtering kettle. The synthesis method comprises the following steps: adding N-methylmorpholine and a synthetic catalyst carbonate into a synthesis kettle, and then dropwise adding a hydrogen peroxide solution; pressing into a reaction kettle, and carrying out constant-temperature reaction; pressing into a decomposition kettle, adding a decomposition catalyst, and carrying out decomposition reaction; and finally, pressing into a filtering kettle, vacuumizing and filtering to obtain the N-methyl morpholine oxide. Carbonate is used as a synthesis catalyst to accelerate the reaction speed, reduce the reaction temperature and reduce the content of residual hydrogen peroxide; and selectively decomposing the residual hydrogen peroxide by adopting a heteroatom-doped porous carbon catalyst. The device disclosed by the invention has semi-continuous operability and has a reference effect on expanded production of N-methyl morpholine oxide.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and particularly relates to a method and a device for synthesizing N-methylmorpholine N-oxide. Background Art

[0002] N-methylmorpholine N-oxide (abbreviated as NMMO) is an excellent solvent with extremely strong solubility for cellulose and is the only industrialized solvent for producing Lyocell fibers. Compared with the traditional viscose process, the Lyocell fiber production process has excellent properties such as simple process flow, green and environmentally friendly solvent NMMO that can be reused (recovery rate above 99.5%), wide and renewable raw material resources, excellent product performance and natural degradability. Therefore, Lyocell fiber is known as the "green fiber of the 21st century" and is a bio-based fiber that is key to the textile industries of various countries. Especially in the context of the increasingly prominent energy crisis problem, it indicates that synthetic fibers based on petroleum will gradually be replaced by new environmentally friendly fibers.

[0003] During the production process of Lyocell fibers, the product quality of the solvent NMMO is an important factor affecting its quality. However, in the existing synthesis process of NMMO, there are often problems such as long reaction time, low selectivity, high reaction temperature, and the entire process cannot achieve continuous operation, resulting in a long production cycle and cumbersome operation. Therefore, it is necessary to improve and optimize the existing process to improve its reaction efficiency, reduce its reaction temperature and reaction time. In addition, there is often a problem of excessive residual hydrogen peroxide after the synthesis reaction, resulting in the need for a cumbersome subsequent purification process to reduce the content of residual hydrogen peroxide. Therefore, it is necessary to adopt a suitable method to decompose the residual hydrogen peroxide to avoid complex purification processes. Summary of the Invention

[0004] In order to solve the above technical problems, the object of the present invention is to provide a method and a device for synthesizing N-methylmorpholine N-oxide to solve the problems of long cycle, complex operation, long reaction time, high reaction temperature and excessive residual H 2 O 2 in the existing NMMO synthesis technology.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: Provide a device for synthesizing N-methylmorpholine N-oxide, including a synthesis kettle, a reaction kettle, a decomposition kettle and a filtration kettle. The synthesis kettle, the reaction kettle, the decomposition kettle and the filtration kettle are sequentially connected through pipelines. Nitrogen inlets are provided on the synthesis kettle, the reaction kettle and the decomposition kettle; a raw material inlet is provided on the synthesis kettle, and a product outlet is provided on the filtration kettle.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows: Further, a first housing is provided outside the synthesis kettle, a cooling cavity is formed between the first housing and the synthesis kettle, and a cooling water inlet and a cooling water outlet are provided on the first housing.

[0007] Further, a second housing is provided outside the reaction kettle, a heating cavity is formed between the second housing and the reaction kettle, and a first hot water inlet and a first hot water outlet are provided on the second housing; a third housing is provided outside the decomposition kettle, a heating cavity is formed between the third housing and the decomposition kettle, and a second hot water inlet and a second hot water outlet are provided on the third housing.

[0008] The beneficial effects of adopting the above further technical solutions are as follows: The synthesis kettle is an exothermic reaction and needs to be cooled with cooling water, the reaction kettle needs to be kept at a constant temperature with hot water, the jacket temperatures are different, and two kettles are used to avoid repeatedly switching cold and hot water.

[0009] Further, the first hot water outlet and the second hot water inlet are connected through a pipeline.

[0010] Further, stirring devices are provided in the synthesis kettle, the reaction kettle and the decomposition kettle.

[0011] Further, reserved ports are provided on the synthesis kettle, the reaction kettle and the decomposition kettle.

[0012] The present invention also provides a method for synthesizing N-methylmorpholine N-oxide using the above device for synthesizing N-methylmorpholine N-oxide, which successively includes the following steps: S1: Pass cooling water into the first housing, add N-methylmorpholine and a synthesis catalyst carbonate into the synthesis kettle, and then dropwise add a hydrogen peroxide solution to obtain a synthesis solution; S2: Pass nitrogen into the nitrogen inlet on the synthesis kettle, press the synthesis solution obtained in step S1 into the reaction kettle, pass hot water into the second housing, and carry out a constant temperature reaction at 50 - 80 °C for 2 - 6 h to obtain a reaction solution; S3: Pass nitrogen into the nitrogen inlet on the reaction kettle, press the reaction solution obtained in step S2 into the decomposition kettle, pass hot water into the third housing, then add a heteroatom-doped porous carbon catalyst, and carry out a decomposition reaction at 50 - 80 °C for 30 - 120 min to obtain a decomposition solution; S4: Pass nitrogen into the nitrogen inlet on the decomposition kettle, press the decomposition solution obtained in step S3 into the filtration kettle, and carry out vacuum filtration to obtain N-methylmorpholine N-oxide.

[0013] Further, in step S1, the volume mass ratio of N-methylmorpholine, the hydrogen peroxide solution and the synthesis catalyst carbonate is 50 mL: 50 - 60 mL: 0.08 - 0.12 g.

[0014] Further, in step S1, the volume-mass ratio of N-methylmorpholine, hydrogen peroxide solution, and the synthetic catalyst carbonate is 50 mL: 51-55 mL: 0.08-0.12 g.

[0015] Further, in step S1, the volume-mass ratio of N-methylmorpholine, hydrogen peroxide solution, and the synthetic catalyst carbonate is 50 mL: 51 mL: 0.1 g.

[0016] Further, in step S1, the synthetic catalyst carbonate is NH 4 HCO 3 、(NH 4 ) 2 CO 3 、Na 2 CO 3 、K 2 CO 3 or NaHCO 3 .

[0017] Further, in step S1, the concentration of the hydrogen peroxide solution is 25-35 wt%.

[0018] Further, in step S1, the concentration of the hydrogen peroxide solution is 30 wt%.

[0019] Further, in step S1, the time for dropping the hydrogen peroxide solution is 0.5-2 h.

[0020] Further, in step S1, the time for dropping the hydrogen peroxide solution is 1 h.

[0021] Further, in step S3, the proportion of the heteroatom-doped porous carbon catalyst added in the system is 0.02-0.08 wt%.

[0022] Further, in step S3, the proportion of the heteroatom-doped porous carbon catalyst added in the system is 0.08 wt%.

[0023] Further, in step S3, the heteroatom-doped porous carbon catalyst is prepared by the following method: Activated carbon and a heteroatom precursor are fully mixed by a planetary ball mill and calcined in an argon atmosphere at 600-1200 °C for 1-3 h to obtain the heteroatom-doped porous carbon catalyst. The heteroatom precursor is Na 2 S, Na 3 PO 4 , NaH 2 PO 4 , (NH 4 ) 2 CO 3 , melamine, urea, or thiourea.

[0024] The beneficial effects of adopting the above further technical solution are as follows: By using heteroatom-doped porous carbon catalysts, active functional groups (pyrrole N, pyridine N, graphitic N, thiophene S, and P-C) will be formed in the carbon materials, which is conducive to promoting the electron transfer of adjacent carbon atoms, increasing the charge density of adjacent carbon, and thus significantly improving the performance of catalytic decomposition of hydrogen peroxide. Compared with other metal-free catalysts, the carbon material-based catalyst has the following advantages: (1) The surface chemical properties are easy to regulate; (2) It has a rich pore structure; (3) It has excellent acid and alkali resistance; (4) It has high-temperature stability (it can still maintain a stable structure at 1023K in an inert atmosphere); (5) It is low-cost and environmentally friendly.

[0025] Further, the mass ratio of activated carbon to heteroatom precursor is 1:0.5 - 2.

[0026] Further, the ball milling time is 4h.

[0027] Further, the calcination heating rate is 5°C / min.

[0028] Further, in step S3, the decomposition reaction is carried out for 60 - 90min.

[0029] The present invention also provides N-methyl morpholine N-oxide prepared by the above method.

[0030] The present invention has the following beneficial effects: 1. The present invention selects to add solid carbonate as the provider of CO 2 , and the carbonate can decompose into CO 2 under heating conditions, which will not affect the product quality. Furthermore, using CO 2 as a catalyst has a good catalytic effect in the continuous synthesis of tertiary amine oxides, and the catalytic mechanism is as shown in formulas (1)-(4).

[0031] CO 2 + H 2 O ⇌ H 2 CO 3 ⇌ HCO 3 — + H + (1) H 2 O 2 + HCO 3 - ⇌ HCO 4 — + H 2 O(2) HCO 4 — +R 3 N+ H 2 O → HCO3 — + R 3 NO + H 2 O(3) HCO 4 — +R 3 N+ H 2 O 2 → HCO 3 — + R 3 NO + H 2 O 2 (4) 2. In the stage of synthesizing N-methyl morpholine N-oxide of the present invention, by adding carbonate, the reaction synthesis temperature can be reduced (from the original 70 °C to 50 °C) and the content of residual hydrogen peroxide can be reduced. There is no problem of excessive conductivity, and the catalyst for decomposing residual hydrogen peroxide is easy to recycle and reuse.

[0032] 3. The reaction device of the present invention has semi-continuous operability, which has a reference effect on the scale-up production of the reactor. The jacket circulating water uses demineralized water to reduce the waste of water resources.

[0033] 4. The present invention divides the synthesis of N-methyl morpholine N-oxide product into two stages, namely the synthesis of N-methyl morpholine N-oxide and the decomposition of residual hydrogen peroxide in N-methyl morpholine N-oxide. Aiming at the difficulty in recycling the heterogeneous catalyst in the synthesis, carbonate is used as the catalyst to accelerate the reaction rate, reduce the reaction temperature and reduce the content of residual hydrogen peroxide. At the same time, the reaction will not affect the product quality; for the decomposition of residual hydrogen peroxide in NMMO, a non-metal heteroatom-doped catalyst is used for selective decomposition. After filtration and regeneration, the catalyst can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the device diagram of the present invention.

[0035] Among them, 1. Synthesis kettle; 2. Reaction kettle; 3. Decomposition kettle; 4. Filtration kettle; 5. Nitrogen inlet; 6. Raw material inlet; 7. Product outlet; 8. Cooling water inlet; 9. Cooling water outlet; 10. First hot water inlet; 11. First hot water outlet; 12. Second hot water inlet; 13. Second hot water outlet; 14. Stirring device; 15. Reserved port. DETAILED DESCRIPTION OF THE INVENTION

[0036] The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. Those not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0037] The present invention provides a device for synthesizing N-methylmorpholine N-oxide (see Figure 1 ), which includes a synthesis kettle 1, a reaction kettle 2, a decomposition kettle 3 and a filtration kettle 4. The synthesis kettle 1, the reaction kettle 2, the decomposition kettle 3 and the filtration kettle 4 are connected in sequence through pipelines. Nitrogen inlets 5 are provided on the synthesis kettle 1, the reaction kettle 2 and the decomposition kettle 3; a raw material inlet 6 is provided on the synthesis kettle 1, and a product outlet 7 is provided on the filtration kettle 4.

[0038] A first shell is arranged outside the synthesis kettle 1. A cooling cavity is formed between the first shell and the synthesis kettle 1. A cooling water inlet 8 and a cooling water outlet 9 are provided on the first shell.

[0039] A second shell is arranged outside the reaction kettle 2. A heating cavity is formed between the second shell and the reaction kettle 2. A first hot water inlet 10 and a first hot water outlet 11 are provided on the second shell; a third shell is arranged outside the decomposition kettle 3. A heating cavity is formed between the third shell and the decomposition kettle. A second hot water inlet 12 and a second hot water outlet 13 are provided on the third shell.

[0040] The first hot water outlet 11 and the second hot water inlet 12 are connected through a pipeline.

[0041] Stirring devices 14 are provided in the synthesis kettle 1, the reaction kettle 2 and the decomposition kettle 3.

[0042] Reserved ports 15 are provided on the synthesis kettle 1, the reaction kettle 2 and the decomposition kettle 3.

[0043] The raw material inlet 6 on the synthesis kettle 1 is used to dropwise add hydrogen peroxide solution, and the reserved port 15 is used to add N-methylmorpholine and a synthesis catalyst carbonate. The cooling water inlet 8 and the cooling water outlet 9 are used to introduce and discharge cooling water; The first hot water inlet 10 and the first hot water outlet 11 are used to introduce and discharge hot water for heating the reaction kettle 2; The second hot water inlet 12 and the second hot water outlet 13 are used to introduce and discharge hot water for heating the decomposition kettle; The stirring device 14 is used to stir during the reaction process; The reserved port 15 can also be used for sampling and temperature measurement.

[0044] Example 1: A method for synthesizing N-methylmorpholine N-oxide includes the following steps: S1: Coolant water is introduced into the first shell, and N-methylmorpholine and catalyst NH 4 HCO 3 are added into the synthesis kettle 1, and then a hydrogen peroxide solution (30 wt%) is dropwise added for 1 h to obtain a synthesis solution; wherein, the volume mass ratio of N-methylmorpholine, the hydrogen peroxide solution and the catalyst is 50 mL: 55 mL: 0.1 g; S2: nitrogen is introduced into the nitrogen inlet 5 on the synthesis reactor 1, the synthetic solution obtained in step S1 is pressed into the reaction reactor 2, hot water is introduced into the second shell, and a constant temperature reaction is carried out at 50° C. for 2 hours to obtain a reaction solution; S3: nitrogen is introduced into the nitrogen inlet 5 on the reactor 2, the reaction solution obtained in step S2 is pressed into the decomposition reactor 3, hot water is introduced into the third shell, and then a heteroatom-doped porous carbon catalyst (accounting for 0.08 wt% in the system) is added from the reserved port 15 on the decomposition reactor 3, and a decomposition reaction is carried out at 50° C. for 60 minutes to obtain a decomposition solution; Among them, the nitrogen-doped porous carbon catalyst was prepared by the following method: activated carbon and urea (mass ratio of 1:1.8) were fully mixed by a planetary ball mill, and calcined at 1000°C in an argon atmosphere for 2 h to obtain a nitrogen-doped porous carbon catalyst.

[0045] S4: nitrogen is introduced into the nitrogen inlet 5 on the decomposition kettle 3, and the decomposition solution obtained in step S3 is pressed into the filtering kettle 4, and vacuum filtered to obtain nitrogen methyl morpholine oxide from the product outlet 7. The catalyst obtained by filtration can be regenerated and used.

[0046] Embodiment 2: A method for synthesizing nitrogen methyl morpholine oxide comprises the following steps: S1: Cooling water is introduced into the first shell, and nitrogen methyl morpholine and catalyst Na are added into the synthesis reactor 1. 2 CO 3 , then add a hydrogen peroxide solution (25wt%) dropwise for 0.5h to obtain a synthetic solution; wherein the volume mass ratio of nitrogen methylmorpholine, hydrogen peroxide solution and catalyst is 50mL:52mL:0.08g; S2: nitrogen is introduced into the nitrogen inlet 5 on the synthesis reactor 1, the synthetic solution obtained in step S1 is pressed into the reaction reactor 2, hot water is introduced into the second shell, and a constant temperature reaction is carried out at 55° C. for 4 hours to obtain a reaction solution; S3: nitrogen is introduced into the nitrogen inlet 5 on the reactor 2, the reaction solution obtained in step S2 is pressed into the decomposition reactor 3, hot water is introduced into the third shell, and then sulfur-doped porous carbon catalyst (accounting for 0.02 wt% in the system) is added from the reserved port 15 on the decomposition reactor 3, and a decomposition reaction is carried out at 60° C. for 70 minutes to obtain a decomposition solution; Among them, the sulfur-doped porous carbon catalyst was prepared by the following method: activated carbon and thiourea (mass ratio of 1:1.4) were fully mixed by a planetary ball mill, and calcined at 600°C in an argon atmosphere for 1 hour to obtain a sulfur-doped porous carbon catalyst.

[0047] S4: nitrogen is introduced into the nitrogen inlet 5 on the decomposition kettle 3, and the decomposition solution obtained in step S3 is pressed into the filtering kettle 4, and vacuum filtered to obtain nitrogen methyl morpholine oxide from the product outlet 7. The catalyst obtained by filtration can be regenerated and used.

[0048] Embodiment 3: A method for synthesizing nitrogen methyl morpholine oxide comprises the following steps: S1: Cooling water is introduced into the first shell, and nitrogen methyl morpholine and catalyst (NH 4 ) 2 CO 3 , then add a hydrogen peroxide solution (35wt%) dropwise for 2h to obtain a synthetic solution; wherein the volume mass ratio of nitrogen methylmorpholine, hydrogen peroxide solution and catalyst is 50mL:51mL:0.12g; S2: nitrogen is introduced into the nitrogen inlet 5 on the synthesis reactor 1, the synthetic solution obtained in step S1 is pressed into the reaction reactor 2, hot water is introduced into the second shell, and a constant temperature reaction is carried out at 80° C. for 6 hours to obtain a reaction solution; S3: nitrogen is introduced into the nitrogen inlet 5 on the reaction kettle 2, the reaction solution obtained in step S2 is pressed into the decomposition kettle 3, hot water is introduced into the third shell, and then a phosphorus-doped porous carbon catalyst (accounting for 0.07 wt% in the system) is added from the reserved port 15 on the decomposition kettle 3, and a decomposition reaction is carried out at 80° C. for 90 minutes to obtain a decomposition solution; The phosphorus-doped porous carbon catalyst was prepared by the following method: activated carbon and Na 3 PO 4 The raw materials were fully mixed in a planetary ball mill and calcined at 1200 °C in an argon atmosphere for 3 h to obtain a phosphorus-doped porous carbon catalyst.

[0049] S4: nitrogen is introduced into the nitrogen inlet 5 on the decomposition kettle 3, and the decomposition solution obtained in step S3 is pressed into the filtering kettle 4, and vacuum filtered to obtain nitrogen methyl morpholine oxide from the product outlet 7. The catalyst obtained by filtration can be regenerated and used.

[0050] Embodiment 4: A method for synthesizing nitrogen methyl morpholine oxide comprises the following steps: In step S1, the volume of the hydrogen peroxide solution is 51 mL, and the rest is the same as in Example 1.

[0051] Embodiment 5: A method for synthesizing nitrogen methyl morpholine oxide comprises the following steps: In step S1, the volume of the hydrogen peroxide solution is 53 mL, and the rest is the same as in Example 1.

[0052] Embodiment 6: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S2, the constant-temperature reaction temperature is 60 °C, and the rest is the same as in Example 4.

[0053] Example 7: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S3, the decomposition reaction time is 90 min, and the rest is the same as in Example 4.

[0054] Comparative Examples 1-4: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S1, the addition amounts of the catalyst NH 4 HCO 3 are 0, 0.025 g, 0.05 g, and 0.075 g respectively, and the rest is the same as in Example 1.

[0055] Comparative Example 5: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S1, the volume of the hydrogen peroxide solution is 49 mL, and the rest is the same as in Example 1.

[0056] Comparative Examples 6-7: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S2, the constant-temperature reaction temperatures are 40 °C and 90 °C respectively, and the rest is the same as in Example 4.

[0057] Comparative Examples 8-10: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S2, the constant-temperature reaction times are 0.5 h, 1 h, and 1.5 h respectively, and the rest is the same as in Example 4.

[0058] Comparative Examples 11-13: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S3, the heteroatom-doped porous carbon catalysts are 0.005 wt%, 0.01 wt%, and 0.015 wt% respectively, and the rest is the same as in Example 4.

[0059] Comparative Examples 14-16: A method for synthesizing N-methylmorpholine N-oxide, comprising the following steps: In step S3, the decomposition reaction times are 10 min, 20 min, and 40 min respectively, and the rest is the same as in Example 4.

[0060] Test Example I. Catalyst NH 4 HCO3 Increased dosage The reaction solutions prepared in step S2 of Example 1 and Comparative Examples 1-4 were subjected to content detection. Sampling was carried out from the reserved port 15 using a syringe sampler. The specific detection method was as follows: Determination of hydrogen peroxide concentration: The titanium salt spectrophotometry was used to determine the concentration of H 2 O 2 . The principle was that H 2 O 2 could form an orange complex peroxy titanic acid (TiO 4+ •H 2 O 2 or H 2 TiO 2 ) with Ti 4 in an acidic solution. The color depth of the complex was proportional to the concentration of H 2 O 2 . This method was basically not affected by the remaining oxidants in the sample. First, an acidic Ti(SO 4 ) 2 developer solution was prepared. Then, the reacted solution was added to a volumetric flask, and Ti(SO 4 ) 2 developer was added. The concentration of H 2 O 2 was determined by ultraviolet-visible spectrophotometry (characteristic wavelength: 400 nm).

[0061] Determination of NMMO: Weigh about 1.5 g of the sample, accurate to 0.0002 g, place it in a 250 mL Erlenmeyer flask, dissolve it with 30 mL of a mixed solution of ethylene glycol + isopropyl alcohol (1+1), add 6 drops of a mixed indicator solution, and titrate it with a hydrochloric acid standard titration alcohol solution until it turns reddish-brown as the end point.

[0062] Result calculation: The mass fraction ω 1 of N-methylmorpholine N-oxide, expressed as a percentage, was calculated according to the following formula:

[0063] Determination of NMM: Weigh 0.5 g of the sample, accurate to 0.0002 g, dissolve it in water, make up the volume to 100 mL in a volumetric flask, filter it, and take the filtrate for determination. Record the chromatographic peak area. Liquid chromatography conditions: Chromatographic column C 18 column 250 mm × 4.6 mm × 5 μm; Mobile phase: methanol and 0.05% ammonia water (30+70); Detection wavelength, flow rate and injection volume were 220 nm, 0.8 mL / min and 20 μL respectively.

[0064] Result calculation:

[0065] The results are shown in Table 1 (contents of each component in the system).

[0066] Table 1 NH 4 HCO 3 Dosage on the product

[0067] It can be seen from Figure 1 that with the addition of NH 4 HCO 3 , the content of residual H 2 O 2 can be effectively reduced. When the dosage of NH 4 HCO 3 is 0.05 g, the concentration of residual H 2 O 2 drops to 16726 mg / L. When the dosage of NH 4 HCO 3 increases to 0.1 g, the concentration of H 2 O 2 increases to 26223 mg / L again. Considering the requirement of the concentration of NMM, with the increase of the concentration of NH 4 HCO 3 , the residual amount of NMM can be effectively reduced. Considering comprehensively, the optimal dosage of NH 4 HCO 3 is 0.1 g.

[0068] II. Dosage of hydrogen peroxide solution The reaction solutions prepared in step S2 of Examples 1, 4 - 5 and Comparative Example 5 were subjected to content detection, and the results are shown in Table 2.

[0069] Table 2 Influence of hydrogen peroxide solution dosage on the product

[0070] It can be seen from Table 2 that with the increase of the dosage of H 2 O 2 , the concentration of NMM decreases, but the content of residual hydrogen peroxide is relatively high, reaching 26223 mg / L. When the dosage of H 2 O 2 decreases, the content of residual hydrogen peroxide decreases, but the content of NMM will increase again. Therefore, the dosage of H 2 O 2 is selected as 51 ml. The reason for the analysis is that when the dosage of H 2 O 2 is large, the molecules in the NMMO synthesis reaction have more opportunities to contact, and the reaction can be better completed.

[0071] III. Isothermal reaction temperature The reaction solutions obtained in step S2 of Examples 4 and 6 and Comparative Examples 6-7 were subjected to content detection, and the results are shown in Table 3.

[0072] Table 3 Influence of constant-temperature reaction temperature on the product

[0073] As can be seen from Table 3, increasing the synthesis temperature is beneficial to improving the conversion rate of NMM and reducing the concentration of H 2 O 2 to 12536 mg / L. The mass fraction of NMM does not differ much between 50-90°C. Selecting 50°C can also meet the reaction requirements. The higher the temperature, the more beneficial it is for the reaction to proceed, but it will also increase energy consumption. Considering comprehensively, 50°C is selected as the optimal reaction condition.

[0074] IV. Constant-temperature reaction time The reaction solutions obtained in step S2 of Example 4 and Comparative Examples 8-10 were subjected to content detection, and the results are shown in Table 4.

[0075] Table 4 Influence of synthesis reaction time on product indexes

[0076] As can be seen from Table 4, increasing the reaction time is beneficial to improving the conversion rate of NMM, and the concentration of H 2 O 2 decreases from 43829 mg / L to 16643 mg / L. With the extension of the reaction time, it helps the synthesis reaction to proceed fully. Selecting 2 h can also meet the reaction requirements. The longer the time, the more beneficial it is for the reaction to proceed, but it will also increase energy consumption. Considering comprehensively, 2 h is selected as the optimal reaction condition.

[0077] V. Dosage of heteroatom-doped porous carbon catalyst The N-methylmorpholine N-oxide obtained in step S4 of Example 4 and Comparative Examples 11-13 was subjected to content detection, and the results are shown in Table 5.

[0078] Table 5 Influence of dosage of heteroatom-doped porous carbon catalyst on the final product

[0079] As can be seen from Table 5, with the increase in the dosage of the heteroatom-doped porous carbon catalyst, the content of residual H 2 O 2 decreases significantly, while the concentrations of NMMO and NMM do not change significantly, indicating that the heteroatom-doped porous carbon catalyst has an obvious decomposition effect on H 2 O 2 and does not affect other indexes.

[0080] VI. Decomposition reaction time The content of N-methylmorpholine N-oxide prepared in step S4 of Examples 4 and 7 and Comparative Examples 14-16 was detected, and the results are shown in Table 6.

[0081] Table 6 Influence of decomposition reaction time on the final product

[0082] As can be seen from Table 6, the present invention can reduce the H 2 O 2 concentration from 16560 mg / L to 87 mg / L within 60 min.

[0083] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A device for synthesizing nitrogen methyl morpholine oxide, characterized in that, The invention comprises a synthesis kettle (1), a reaction kettle (2), a decomposition kettle (3) and a filtering kettle (4), wherein the synthesis kettle (1), the reaction kettle (2), the decomposition kettle (3) and the filtering kettle (4) are connected in sequence through pipelines, and the synthesis kettle (1), the reaction kettle (2) and the decomposition kettle (3) are all provided with a nitrogen inlet (5); the synthesis kettle (1) is provided with a raw material inlet (6), and the filtering kettle (4) is provided with a product outlet (7).

2. The device for synthesizing nitrogen methyl morpholine oxide according to claim 1, characterized in that: A first shell is arranged outside the synthesis kettle (1), a cooling cavity is formed between the first shell and the synthesis kettle (1), and a cooling water inlet (8) and a cooling water outlet (9) are arranged on the first shell.

3. The device for synthesizing nitrogen methyl morpholine oxide according to claim 1, characterized in that: A second shell is arranged outside the reaction kettle (2), a heating cavity is formed between the second shell and the reaction kettle (2), and a first hot water inlet (10) and a first hot water outlet (11) are arranged on the second shell; a third shell is arranged outside the decomposition kettle (3), a heating cavity is formed between the third shell and the decomposition kettle (3), and a second hot water inlet (12) and a second hot water outlet (13) are arranged on the third shell.

4. The device for synthesizing nitrogen methyl morpholine oxide according to claim 3, characterized in that: The first hot water outlet (11) and the second hot water inlet (12) are connected via a pipeline.

5. The device for synthesizing nitrogen methyl morpholine oxide according to claim 1, characterized in that: The synthesis kettle (1), the reaction kettle (2) and the decomposition kettle (3) are all provided with a stirring device (14).

6. A method for synthesizing nitrogen methyl morpholine oxide using the device for synthesizing nitrogen methyl morpholine oxide according to any one of claims 1 to 5, characterized in that: The following steps are included in sequence: S1: Cooling water is introduced into the first shell, nitrogen methyl morpholine and a synthesis catalyst carbonate are added into the synthesis reactor (1), and then a hydrogen peroxide solution is added dropwise to obtain a synthesis solution; S2: nitrogen is introduced into the nitrogen inlet (5) on the synthesis reactor (1), the synthesis solution obtained in step S1 is pressed into the reaction reactor (2), hot water is introduced into the second shell, and a constant temperature reaction is carried out at 50-80° C. for 2-6 hours to obtain a reaction solution; S3: nitrogen is introduced into the nitrogen inlet (5) on the reaction kettle (2), the reaction solution obtained in step S2 is pressed into the decomposition kettle (3), hot water is introduced into the third shell, and then a heteroatom-doped porous carbon catalyst is added, and a decomposition reaction is carried out at 50-80° C. for 30-120 minutes to obtain a decomposition solution; S4: nitrogen is introduced into the nitrogen inlet (5) on the decomposition kettle (3), and the decomposition solution obtained in step S3 is pressed into the filtration kettle (4), and vacuum filtered to obtain nitrogen methyl morpholine oxide.

7. The method for synthesizing nitrogen methyl morpholine oxide according to claim 6, characterized in that: In step S1, the volume mass ratio of nitrogen methylmorpholine, hydrogen peroxide solution and synthetic catalyst carbonate is 50 mL: 50-60 mL: 0.08-0.12 g.

8. The method for synthesizing nitrogen methyl morpholine oxide according to claim 6, characterized in that: In step S1, the synthetic catalyst carbonate is NH4HCO3, (NH4)2CO3, Na2CO3, K2CO3 or NaHCO3.

9. The method for synthesizing nitrogen methyl morpholine oxide according to claim 6, characterized in that: In step S3, the heteroatom-doped porous carbon catalyst is prepared by the following method: activated carbon and a heteroatom precursor are mixed by a planetary ball mill, and calcined at 600-1200°C in an argon atmosphere for 1-3 hours to obtain a heteroatom-doped porous carbon catalyst, wherein the heteroatom precursor is Na2S, Na3PO4, NaH2PO4, (NH4)2CO3, melamine, urea or thiourea.

10. Nitrogen methyl morpholine oxide obtained by the method for synthesizing nitrogen methyl morpholine oxide according to any one of claims 6 to 9.

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