Method for continuously producing N-methylmorpholine oxide

Abstract

The invention discloses a method for continuously producing N-methylmorpholine oxide, and relates to the technical field of chemical synthesis, and the method comprises the following steps: placing N-methylmorpholine in an NMM raw material tank, placing hydrogen peroxide in an H2O2 raw material tank, and placing an additive in an additive tank; n-methylmorpholine, hydrogen peroxide and an additive are pumped into the dynamic tubular reactor at the same time through a metering pump to be subjected to an oxidation reaction; an outlet of the dynamic tubular reactor is connected with a buffer tank, a reaction product entering the buffer tank is subjected to impurity removal through a core filter and then enters a product collecting tank, and N-methyl morpholine oxide is obtained. The method has the advantages of mild reaction conditions, short reaction time, high yield, low content of the by-product nitrosomorpholine and the like, and the continuous production process is matched with highly automatic control, so that the production cost is remarkably reduced, the production efficiency and the safety performance are greatly improved, various requirements of industrial production are completely met, and the method is suitable for industrial production. Wide application prospects are shown.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, specifically to a method for the continuous production of N-methylmorpholine oxide. Background Technology

[0002] N-Methylmorpholine N-oxide (NMMO) is an important organic solvent and catalyst widely used in cellulose production, polyester plastic foaming catalysis, and the synthesis of organic reagents and pharmaceutical intermediates. Regarding the synthesis of NMMO, two main methods are relatively mature both domestically and internationally: hydrogen peroxide oxidation and molecular oxygen-aldehyde catalytic oxidation. Among these, hydrogen peroxide oxidation, due to its mild reaction conditions and excellent product quality, has been widely used in industrial production, and this is currently the most commonly used NMMO preparation method in my country.

[0003] Currently, the industrial production of NMMO in China generally adopts a batch reactor process, which involves precisely controlling the dropping rate of hydrogen peroxide in a reactor containing a catalyst to achieve the oxidation reaction. Commonly used catalytic systems include basic ion exchange resins, transition metal compounds (such as copper hydroxide and manganese dioxide), quaternary ammonium salts, and molybdenum-silicon hollow microspheres and titanium dioxide. However, this process has significant shortcomings: on the one hand, existing catalytic systems typically require temperatures above 70°C to ensure a reaction conversion rate of over 85%, making the process conditions quite stringent; on the other hand, due to the limited heat transfer performance of the reactor, the entire reaction process often requires continuous heating for 4-6 hours or even longer, resulting in low production efficiency and complex subsequent separation and purification steps for the product.

[0004] The patent application CN114940666B, entitled "A High-Yield Synthesis Method of N-Methylmorpholine Oxide Aqueous Solution," utilizes a microchannel reactor. Under conditions of a hydrogen peroxide to N-methylmorpholine molar ratio of 1.2:1, a reaction temperature of 70°C, and a pressure of 0.2 MPa, a product yield of 98.5% can be obtained with only a 2-minute residence time. Experimental data shows that the product obtained by this process is superior to traditional methods in terms of pH value and color index. However, based on the formation mechanism of nitrosomorpholine (a known carcinogen), a high-temperature environment may be detrimental to inhibiting the formation of this byproduct. Therefore, developing a production method with short reaction time, high yield, low byproduct impurity content, high production efficiency, and high safety performance is an urgent problem to be solved in the development of process technology in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for continuous production of N-methylmorpholine oxide, so as to solve the technical problems existing in the prior art, such as long reaction time, low yield, high content of impurities in by-products, and low production efficiency.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for continuous production of N-methylmorpholine oxide specifically includes the following steps:

[0008] S1. Place N-methylmorpholine (NMM) in the NMM raw material tank, hydrogen peroxide in the H2O2 raw material tank, and additives in the additive tank;

[0009] Furthermore, the additive is either an aqueous solution of bicarbonate or a carbonic acid solution;

[0010] Furthermore, the molar concentration of the bicarbonate aqueous solution is 0.2-0.5 mol / L;

[0011] Furthermore, the mass concentration of the carbonic acid solution is 1.0-2.0 g / L;

[0012] S2. N-methylmorpholine, hydrogen peroxide and additives are simultaneously pumped into a dynamic tubular reactor using a metering pump to undergo an oxidation reaction.

[0013] Furthermore, the molar ratio of N-methylmorpholine, hydrogen peroxide, and additives is 1:0.9-1.2:0.002-0.05;

[0014] Furthermore, the hydrogen peroxide can be fed in either a single-stage feeding method or a continuous segmented feeding method.

[0015] Furthermore, the feed flow rate ratio of N-methylmorpholine to hydrogen peroxide is 1:0.8-1.4;

[0016] Furthermore, the residence time of the raw material in the dynamic tubular reactor is 10-30 min;

[0017] Furthermore, the reaction temperature is 35-65℃;

[0018] Furthermore, the rotational speed of the dynamic tubular reactor is 200-400 rpm;

[0019] Furthermore, the pressure of the dynamic tubular reactor is 0.3-0.6 MPa;

[0020] Furthermore, the material of the dynamic tubular reactor is any one of stainless steel, silicon carbide, or Hastelloy.

[0021] S3. Connect the outlet of the dynamic tubular reactor to the buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine.

[0022] The reaction equation is as follows:

[0023]

[0024] The beneficial effects of this invention are:

[0025] 1. This invention proposes a method for continuous production of N-methylmorpholine oxide, using bicarbonate or carbonic acid as a catalyst, which saves the process of recovering solid catalysts, simplifies the process flow, and significantly shortens the reaction time.

[0026] 2. This invention introduces a new process for a dynamic tubular reactor. The new process has a high degree of automation and requires no manual intervention, which improves production safety and significantly reduces production costs.

[0027] 2. This invention uses bicarbonate and carbonic acid aqueous solution as auxiliary oxidizing agents, which has lower production costs and better meets the needs of industrial production compared with traditional catalyst systems.

[0028] 4. The production method provided by this invention has mild reaction conditions, a stable and controllable reaction process, can effectively suppress the occurrence of side reactions, significantly reduce the amount of byproduct nitrosomorpholine generated, and greatly improve the reaction conversion rate. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the system process for the continuous production of N-methylmorpholine in Examples 1-5. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For example, the types and sources of raw materials involved in the examples and comparative examples are shown in Table 1, which is as follows:

[0032] Table 1

[0033] raw material source N-Methylmorpholine Anhui Haoyuan Chemical Group Co., Ltd. hydrogen peroxide Anhui Haoyuan Chemical Group Co., Ltd. ammonium bicarbonate Sinopharm Chemical Reagent Co., Ltd. Sodium bicarbonate Sinopharm Chemical Reagent Co., Ltd. Calcium bicarbonate Anhui Haoyuan Chemical Group Co., Ltd. Manganese dioxide Sinopharm Chemical Reagent Co., Ltd.

[0034] Example 1

[0035] S1. Place 2L of 99.9% N-methylmorpholine in an NMM raw material tank, 2L of 27.5% hydrogen peroxide in an H2O2 raw material tank, and 200mL of 0.3mol / L ammonium bicarbonate aqueous solution in an additive tank.

[0036] S2. An oxidation reaction is carried out simultaneously by pumping N-methylmorpholine, hydrogen peroxide, and ammonium bicarbonate aqueous solution into a dynamic tubular reactor via an NMM metering pump, an H2O2 metering pump, and an additive metering pump. The molar ratio of N-methylmorpholine, hydrogen peroxide, and ammonium bicarbonate is 1:1.05:0.02. The feed rates of N-methylmorpholine and hydrogen peroxide are 52.9 g / min and 67.5 g / min, respectively. The reaction residence time is 25 min, the reaction temperature is 50℃, the rotation speed of the dynamic tubular reactor is 200 rpm, the reaction pressure is 0.55 MPa, and the material of the dynamic tubular reactor is stainless steel.

[0037] S3. Connect the outlet of the dynamic tubular reactor to the intermediate buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine oxide.

[0038] Example 2

[0039] S1. Place 2L of 99.9% N-methylmorpholine in an NMM raw material tank, 2L of 27.5% hydrogen peroxide in an H2O2 raw material tank, and 200mL of 0.2mol / L sodium bicarbonate aqueous solution in an additive tank.

[0040] S2. N-methylmorpholine, hydrogen peroxide, and sodium bicarbonate aqueous solution are simultaneously pumped into a dynamic tubular reactor via an NMM metering pump, an H2O2 metering pump, and an additive metering pump to undergo an oxidation reaction. The molar ratio of N-methylmorpholine, hydrogen peroxide, and sodium bicarbonate is 1:0.95:0.01. The feed rates of N-methylmorpholine and hydrogen peroxide are 46.3 g / min and 54.1 g / min, respectively. The reaction residence time is 30 min, the reaction temperature is 40℃, the rotation speed of the dynamic tubular reactor is 250 rpm, the reaction pressure is 0.45 MPa, and the material of the dynamic tubular reactor is stainless steel.

[0041] S3. Connect the outlet of the dynamic tubular reactor to the intermediate buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine oxide.

[0042] Example 3

[0043] S1. Place 2L of 99.9% N-methylmorpholine in an NMM raw material tank, 2L of 27.5% hydrogen peroxide in an H2O2 raw material tank, and 200mL of 0.3mol / L potassium bicarbonate aqueous solution in an additive tank.

[0044] S2. N-methylmorpholine, hydrogen peroxide, and potassium bicarbonate aqueous solution are simultaneously pumped into a dynamic tubular reactor via an NMM metering pump, an H2O2 metering pump, and an additive metering pump to undergo an oxidation reaction. The molar ratio of N-methylmorpholine, hydrogen peroxide, and potassium bicarbonate is 1:1.10:0.015. The feed rates of N-methylmorpholine and hydrogen peroxide are 42.7 g / min and 57.2 g / min, respectively. The reaction residence time is 30 min, the reaction temperature is 45℃, the rotation speed of the dynamic tubular reactor is 350 rpm, the reaction pressure is 0.30 MPa, and the material of the dynamic tubular reactor is stainless steel.

[0045] S3. Connect the outlet of the dynamic tubular reactor to the intermediate buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine oxide.

[0046] Example 4

[0047] S1. Place 2L of 99.9% N-methylmorpholine in an NMM raw material tank, 2L of 27.5% hydrogen peroxide in an H2O2 raw material tank, and 200mL of 1.6g / L carbonic acid solution in an additive tank.

[0048] S2. N-methylmorpholine, hydrogen peroxide, and carbonic acid solution are simultaneously pumped into a dynamic tubular reactor via an NMM metering pump, an H2O2 metering pump, and an additive metering pump to undergo an oxidation reaction. The molar ratio of N-methylmorpholine, hydrogen peroxide, and carbonic acid solution is 1:1.15:0.02. The feed rates of N-methylmorpholine and hydrogen peroxide are 63.5 g / min and 89.1 g / min, respectively. The reaction residence time is 20 min, the reaction temperature is 55℃, the rotation speed of the dynamic tubular reactor is 200 rpm, the reaction pressure is 0.50 MPa, and the material of the dynamic tubular reactor is stainless steel.

[0049] S3. Connect the outlet of the dynamic tubular reactor to the intermediate buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine oxide.

[0050] Example 5

[0051] S1. Place 2L of 99.9% N-methylmorpholine in an NMM raw material tank, 2L of 27.5% hydrogen peroxide in an H2O2 raw material tank, and 200mL of 0.2mol / L ammonium bicarbonate aqueous solution in an additive tank.

[0052] S2. N-methylmorpholine, hydrogen peroxide, and ammonium bicarbonate aqueous solution are simultaneously pumped into a dynamic tubular reactor via an NMM metering pump, an H2O2 metering pump, and an additive metering pump to undergo an oxidation reaction. The molar ratio of N-methylmorpholine, hydrogen peroxide, and ammonium bicarbonate is 1:1.08:0.02. Hydrogen peroxide is fed continuously in two stages. The feed rates of N-methylmorpholine and hydrogen peroxide are 41.7 g / min, 29.5 g / min, and 25.5 g / min, respectively. The reaction residence time is 30 min, the reaction temperature is 45℃, the rotation speed of the dynamic tubular reactor is 250 rpm, the reaction pressure is 0.60 MPa, and the material of the dynamic tubular reactor is stainless steel.

[0053] S3. Connect the outlet of the dynamic tubular reactor to the intermediate buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine oxide.

[0054] Example 6

[0055] S1. Place 2L of 99.9% N-methylmorpholine in an NMM raw material tank, 2L of 27.5% hydrogen peroxide in an H2O2 raw material tank, and 200mL of 0.5mol / L calcium bicarbonate aqueous solution in an additive tank.

[0056] S2. N-methylmorpholine, hydrogen peroxide, and calcium bicarbonate aqueous solution are simultaneously pumped into a dynamic tubular reactor via an NMM metering pump, an H2O2 metering pump, and an additive metering pump to undergo an oxidation reaction. The molar ratio of N-methylmorpholine, hydrogen peroxide, and calcium bicarbonate is 1:1.02:0.012. The feed rates of N-methylmorpholine and hydrogen peroxide are 88.5 g / min and 110.1 g / min, respectively. The reaction residence time is 15 min, the reaction temperature is 55℃, the rotation speed of the dynamic tubular reactor is 200 rpm, the reaction pressure is 0.50 MPa, and the material of the dynamic tubular reactor is stainless steel.

[0057] S3. Connect the outlet of the dynamic tubular reactor to the intermediate buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine oxide.

[0058] Comparative Example

[0059] S1. Place 180g of N-methylmorpholine with a mass fraction of 99.9% in a three-necked flask, and add 2.5g of manganese dioxide as a catalyst to the three-necked flask;

[0060] S2. Place 300g of 27.5% hydrogen peroxide in a constant pressure funnel and add it dropwise to the three-necked flask of S1. Heat the flask in a water bath to 60°C and react for 7 hours.

[0061] S3. After the reaction is complete, the product is filtered to remove the catalyst and then purified to obtain N-methylmorpholine oxide.

[0062] The N-methylmorpholine synthesized in the examples and comparative examples were subjected to performance tests. The specific testing instruments or methods are as follows:

[0063] Yield: Calculated as the ratio of actual product output to theoretically calculated product output;

[0064] Nitrosmorpholine content: determined according to national standard GB / T 38405-2019;

[0065] pH value: pH meter;

[0066] Colorimetry: Colorimetry is measured using a colorimeter in accordance with the national standard GB / T 3143.

[0067] The test results are listed in Table 2, as follows:

[0068] Table 2

[0069]

[0070]

[0071] As shown in Table 2, the method for preparing NMMO using this invention achieves a yield of over 92.6%, a color intensity as low as 25 Hazen units, and a byproduct nitrosomorpholine content as low as 70 ppb. In particular, the specific implementation method in Example 3 achieves a yield of 98.6%, a color intensity as low as 12 Hazen units, and a byproduct nitrosomorpholine content that is only 29% of that in the comparative example (conventional method). Compared to the comparative example, the method provided by this invention has advantages such as mild reaction conditions, short reaction time, high yield, and low byproduct nitrosomorpholine content, fully meeting the requirements of industrial production and possessing broad application prospects.

[0072] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for continuous production of N-methylmorpholine oxide, characterized in that, Includes the following steps: S1. Place N-methylmorpholine in the NMM raw material tank, hydrogen peroxide in the H2O2 raw material tank, and additives in the additive tank; S2. N-methylmorpholine, hydrogen peroxide and additives are simultaneously pumped into a dynamic tubular reactor using a metering pump to undergo an oxidation reaction. S3. Connect the outlet of the dynamic tubular reactor to the buffer tank. The reaction product entering the buffer tank is filtered by a core filter and then enters the product collection tank to obtain N-methylmorpholine oxide.

2. The method for continuous production of N-methylmorpholine oxide according to claim 1, characterized in that, In step S1, the additive is either an aqueous solution of bicarbonate or a carbonic acid solution.

3. The method for continuous production of N-methylmorpholine oxide according to claim 2, characterized in that, In step S1, the molar concentration of the bicarbonate aqueous solution is 0.2-0.5 mol / L.

4. The method for continuous production of N-methylmorpholine oxide according to claim 2, characterized in that, In step S1, the mass concentration of the carbonic acid solution is 1.0-2.0 g / L.

5. The method for continuous production of N-methylmorpholine oxide according to claim 1, characterized in that, In step S2, the molar ratio of N-methylmorpholine, hydrogen peroxide, and additives is 1:0.9-1.2:0.002-0.

05.

6. The method for continuous production of N-methylmorpholine oxide according to claim 1, characterized in that, In step S2, the hydrogen peroxide feeding method is either a single-stage feeding or a continuous segmented feeding.

7. The method for continuous production of N-methylmorpholine oxide according to claim 1, characterized in that, In step S2, the feed flow rate ratio of N-methylmorpholine and hydrogen peroxide is 1:0.8-1.

4.

8. The method for continuous production of N-methylmorpholine oxide according to claim 1, characterized in that, In step S2, the residence time of the raw material in the dynamic tubular reactor is 10-30 min, and the reaction temperature is 35-65℃.

9. The method for continuous production of N-methylmorpholine oxide according to claim 1, characterized in that, In step S2, the rotational speed of the dynamic tubular reactor is 200-400 rpm, and the pressure is 0.3-0.6 MPa.

10. The method for continuous production of N-methylmorpholine oxide according to claims 1-9, characterized in that, The dynamic tubular reactor is made of any one of stainless steel, silicon carbide, or Hastelloy.

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