Method for synthesizing N-methyl morpholine oxide without catalysis

Abstract

The invention belongs to the field of synthesis of organic compounds, and particularly discloses a method for synthesizing N-methylmorpholine oxide without catalysis, N-methylmorpholine oxide and hydrogen peroxide are used as raw materials, N-methylmorpholine oxide is generated through azeotropic dehydration reaction under the catalyst-free condition, operation is convenient, and the reaction process is shortened; no catalyst is used, so that the problems that the catalyst is difficult to recycle, more side reactions exist and the like are solved, and the yield and the purity of the N-methylmorpholine oxide are improved; in addition, the organic solvent used in the method can be reused, so that the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the field of synthesis of organic compounds, in particular to a method for synthesizing N-methylmorpholine oxide without catalysis. Background Art

[0002] N-methylmorpholine oxide (NMMO) is a high-grade tertiary amine oxide and an excellent solvent, especially in the spinning of artificial fibers. Artificial fibers produced with N-methylmorpholine (NMM) as a solvent have better wet properties and strength than ordinary viscose fibers and are similar to cotton fibers. The product quality is high and the synthesis process is green and pollution-free. It is called "green artificial fiber" (Lyocell fiber). Therefore, the development of an efficient synthesis process for NMMO has obvious economic benefits and is of great practical significance to the development of the textile industry.

[0003] Chinese patent publication number CN110467587A discloses a method for synthesizing NMMO. Under the conditions of 0.4-1MPa and 60-90°C, ruthenium / nitrogen-doped porous carbon is used as a catalyst to catalyze the reaction of NMM and O2 to synthesize NMMO for 4-8h. The NMM conversion rate can reach up to 89.6%, and the NMMO selectivity can reach up to 91.5%.

[0004] Chinese patent publication number CN113604823A discloses a method for synthesizing N-methyl morpholine oxide. The process is carried out at a current density of 0.5 to 1.5 A / cm 2 Under the conditions of 0-100℃, NMM and water are used as raw materials, and NMMO is generated by electrolysis reaction under the action of catalyst. The reaction time is 1-10h, and the NMM conversion rate can reach up to 99.5%, and the NMMO selectivity can reach up to 98.6%.

[0005] Chinese patent publication number CN111939966A discloses a method for synthesizing N-methylmorpholine oxide, wherein a basic molecular sieve catalyst is mixed with NMM at 30-90°C, and ozone is introduced into the mixture to synthesize NMMO. The reaction time is 3-9h, the NMM conversion rate can reach up to 92.6%, and the NMM O selectivity can reach up to 98.7%.

[0006] The above three methods have problems such as complicated catalyst preparation methods and low conversion rates. The first method requires the preparation of catalysts under pressure and high temperature conditions, which has certain requirements for equipment. The catalysts used in the second method, such as sulfuric acid and ammonium sulfate, are highly corrosive to metal equipment. Long-term use will shorten the life of the equipment and increase maintenance costs. The third method uses ozone, a hazardous substance, and does not achieve process safety. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method for synthesizing N-methylmorpholine oxide without catalysis.

[0008] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0009] A method for synthesizing N-methylmorpholine oxide without catalysis comprises the following steps:

[0010] S1, mixing N-methylmorpholine with an organic solvent in a molar ratio of 1:0.8-2.0 to obtain a mixed solution;

[0011] S2, slowly adding hydrogen peroxide to the mixed solution according to the molar ratio of N-methylmorpholine to hydrogen peroxide of 1:0.5-2.0, and controlling the temperature of the mixed solution to be 0-40° C. during the feeding process;

[0012] S3, then controlling the reaction temperature of the mixed solution to 40-90° C., while N-methylmorpholine reacts with hydrogen peroxide, the dehydrating agent and water azeotropy, when no water is removed, stopping heating and stirring, cooling and crystallizing the obtained product, separating the product from the organic solvent, and vacuum drying to obtain N-methylmorpholine oxide.

[0013] Preferably, the molar ratio of N-methylmorpholine to the organic solvent is 1:1.2.

[0014] Preferably, the organic solvent is one of benzene, methylcyclopentane, n-hexane and cyclohexane.

[0015] Preferably, the molar ratio of N-methylmorpholine to hydrogen peroxide is 1:1.2.

[0016] Compared with the prior art, the invention uses N-methylmorpholine and hydrogen peroxide as raw materials, and generates N-methylmorpholine oxide by azeotropic dehydration reaction under the condition of no catalyst, which is convenient to operate and shortens the reaction process; no catalyst is used, thus avoiding the problems of difficulty in catalyst recovery and more side reactions, and improving the yield and purity of N-methylmorpholine oxide; in addition, the organic solvent used in the invention can be reused, thus reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a preparation route for N-methylmorpholine oxide. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0019] Unless otherwise specified, the raw materials and equipment used in the following examples were commercially available.

[0020] Example 1

[0021] Reference Figure 1 This example exemplifies a method for synthesizing N-methylmorpholine oxide without catalysis, using N-methylmorpholine and hydrogen peroxide as raw materials and n-hexane as an organic solvent, and the specific steps are as follows:

[0022] (1) Add 50 mL of N-methylmorpholine (NMM) and 100 mL of n-hexane into the reaction axe, and slowly add 61 mL of H2O2 (the molar ratio of NMM to H2O2 is 1:0.8) into the axe. During the feeding process, the temperature in the axe is controlled at 0-40°C.

[0023] (2) After H2O2 is completely added, the reaction temperature in the axe is controlled to be 70℃.

[0024] (3) When no water is removed, stop heating and stirring, allow the product to cool and crystallize, separate the product from n-hexane, dry it in vacuum, and weigh it. Analyze it by HPLC to obtain the NMM conversion rate and NMMO yield.

[0025] NMM conversion rate = (NMM addition amount - NMM residual amount) / NMM addition amount;

[0026] NMMO yield = target product production / reaction product feed amount.

[0027] Example 2

[0028] The difference from Example 1 is that the molar ratio of NMM to H2O2 is 1:0.9.

[0029] Example 3

[0030] The difference from Example 1 is that the molar ratio of NMM to H2O2 is 1:1.

[0031] Example 4

[0032] The difference from Example 1 is that the molar ratio of NMM to H2O2 is 1:1.1.

[0033] Example 5

[0034] The difference from Example 1 is that the molar ratio of NMM to H2O2 is 1:1.2.

[0035] Example 6

[0036] The difference from Example 1 is that the molar ratio of NMM to H2O2 is 1:1.3.

[0037] Example 7

[0038] The difference from Example 1 is that the molar ratio of NMM to H2O2 is 1:1.4.

[0039] The NMM conversion rate and NMMO yield data of Examples 1 to 7 are shown in Table 1.

[0040] Table 1

[0041] Example 1 2 3 4 5 6 7 Reaction temperature (℃) 70 70 70 70 70 70 70 Amount of n-hexane (ml) 100 100 100 100 100 100 100 NMM conversion rate (%) 89.1 90.4 91.3 94.6 97.6 97.9 98.4 NMMO yield (%) 76.7 83.5 91.2 92.2 93.1 91.3 89.7

[0042] As can be seen from Table 1, with the increase of the proportion of H2O2, the conversion rate of NMM and the yield of NMMO are significantly improved. When the molar ratio of NMM to H2O2 is 1:1.2, the conversion rate of NMM and the yield of NMMO are both above 93%. However, when the molar ratio of NMM to H2O2 is further increased, the increase in the conversion rate of NMM decreases, and the yield decreases significantly. Therefore, the optimal molar ratio of NMM to H2O2 is 1:1.2.

[0043] Example 8

[0044] The difference from Example 5 is that the reaction temperature is 75°C.

[0045] Example 9

[0046] The difference from Example 5 is that the reaction temperature is 80°C.

[0047] Example 10

[0048] The difference from Example 5 is that the reaction temperature is 85°C.

[0049] Embodiment 11

[0050] The difference from Example 5 is that the reaction temperature is 90°C.

[0051] The NMM conversion rate and NMMO yield data of Examples 8 to 11 are shown in Table 2.

[0052] Table 2

[0053] Example 8 9 10 11 <![CDATA[Molar ratio of NMM to H2O2]]> 1:1.2 1:1.2 1:1.2 1:1.2 Reaction temperature (℃) 75 80 85 90 Hexane consumption (hours) 100 100 100 100 NMM conversion rate (%) 98.8 98.6 91.9 89.3 NMMO yield (%) 94.2 94.1 87.7 85.2

[0054] As shown in Table 2, as the reaction temperature increases, the conversion rate of NMM and the yield of NMMO increase accordingly. When the reaction temperature is 75°C, the conversion rate of NMM and the yield of NMMO both reach more than 94%. When the reaction temperature is further increased, the conversion rate of NMM and the yield of NMMO decrease significantly, which shows that the reaction temperature has a significant effect on the reaction results. Therefore, the optimal reaction temperature is 75°C.

[0055] Example 12

[0056] The difference from Example 9 is that the amount of n-hexane used is 90 mL.

[0057] Example 13

[0058] The difference from Example 9 is that the amount of n-hexane used is 80 mL.

[0059] Embodiment 14

[0060] The difference from Example 9 is that the amount of n-hexane used is 70 mL.

[0061] Embodiment 15

[0062] The difference from Example 9 is that the amount of n-hexane used is 60 mL.

[0063] The NMM conversion rate and NMMO yield data of Examples 12 to 15 are shown in Table 3.

[0064] Table 3

[0065]

[0066]

[0067] It can be seen from Table 3 that with the decrease in the amount of n-hexane, the conversion rate of NMM and the yield of NMMO have no obvious changes. Therefore, the optimal amount of n-hexane is 70 mL.

[0068] In summary, the present invention uses N-methylmorpholine and hydrogen peroxide as raw materials, and utilizes azeotropic dehydration reaction to generate N-methylmorpholine oxide under the condition of no catalyst, which is convenient to operate and shortens the reaction process; no catalyst is used, which avoids the problems of difficulty in catalyst recovery and more side reactions, and improves the yield and purity of N-methylmorpholine oxide.

[0069] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for synthesizing N-methylmorpholine oxide without catalysis, characterized in that: The following steps are involved: S1, mixing N-methylmorpholine and an organic solvent in a molar ratio of 1:0.8-2.0 to obtain a mixed solution; S2, slowly adding hydrogen peroxide to the mixed solution according to the molar ratio of N-methylmorpholine to hydrogen peroxide of 1:0.5-2.0, and controlling the temperature of the mixed solution to be 0-40° C. during the feeding process; S3, then controlling the reaction temperature of the mixed solution to 40-90° C., while N-methylmorpholine reacts with hydrogen peroxide, the dehydrating agent and water azeotropy, when no water is removed, stopping heating and stirring, cooling and crystallizing the obtained product, separating the product from the organic solvent, and vacuum drying to obtain N-methylmorpholine oxide.

2. The method for synthesizing N-methylmorpholine oxide without catalysis according to claim 1, characterized in that: The molar ratio of the N-methylmorpholine to the organic solvent is 1:1.

2.

3. The method for synthesizing N-methylmorpholine oxide without catalysis according to claim 1 or 2, characterized in that: The organic solvent is one of benzene, methylcyclopentane, n-hexane and cyclohexane.

4. The method for synthesizing N-methylmorpholine oxide without catalysis according to claim 1, characterized in that: The molar ratio of N-methylmorpholine to hydrogen peroxide is 1:1.2.

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