Preparation method for synthesizing N-methylmorpholine through two-step method

Abstract

The invention relates to the technical field of organic chemical synthesis, in particular to a preparation method for synthesizing N-methylmorpholine by a two-step method, which comprises a chlorination reaction and a ring closing reaction, in the chlorination reaction, diethylene glycol and concentrated hydrochloric acid are subjected to the chlorination reaction under the catalysis of zinc chloride and concentrated sulfuric acid, and a hydrochloric acid aqueous solution of dichloroethyl ether is generated; the ring closing reaction comprises the following steps: mixing a hydrochloric acid aqueous solution of dichloroethyl ether with methylamine and calcium hydroxide to carry out ring closing reaction, and distilling the reaction liquid to obtain N-methylmorpholine. According to the preparation method, diethylene glycol and methylamine are taken as raw materials, and the problems of high investment, high energy consumption and difficulty in obtaining high-purity products in the existing industrial synthesis route are solved through a two-step efficient synthesis preparation method.

Description

Technical Field

[0001] The invention relates to the technical field of organic chemical synthesis, in particular to a two-step preparation method for synthesizing nitrogen methylmorpholine. Background Art

[0002] As a key precursor for the synthesis of oxo-nitromethylmorpholine (NMMO), nitrogen-methylmorpholine (NMM) has been widely used in many fields, including lyocell fiber, medicine, and pesticides. Currently, there are several main synthetic routes for NMM: the first is the morpholine methylation method, which uses formaldehyde as the methylation reagent. However, formaldehyde itself is highly toxic, and after the reaction is completed, the product separation process faces many difficulties; the second is the diethylene glycol-methylamine one-pot method, which requires the use of harsh conditions such as high temperature and high pressure. This method not only consumes a lot of energy, but also has huge equipment investment costs; the third is the dichloroethyl ether-methylamine ring closure method, which uses sodium hydroxide as a dehalogenation reagent. The byproduct sodium chloride produced by the reaction is difficult to handle, and the raw material dichloroethyl ether is not easy to obtain. In addition, highly toxic chlorine or sulfonyl chloride is often used as a chlorination reagent in its production process, which puts great pressure on environmental protection work.

[0003] Existing NMM synthesis methods suffer from a host of issues, including high raw material toxicity, demanding reaction conditions, high byproduct disposal costs, and low product purity. These issues contribute to the high production cost of NMM and are significantly inconsistent with current trends in green chemistry. Therefore, developing a low-cost, environmentally friendly NMM synthesis process is crucial for industrial production. Summary of the Invention

[0004] The present invention aims to provide a two-step method for synthesizing nitrogen methylmorpholine. The method uses diethylene glycol and methylamine as raw materials and is synthesized through two-step high-efficiency reactions, thereby solving the problems of high investment, high energy consumption and difficulty in obtaining high-purity products in the existing industrial synthesis route.

[0005] To achieve the above object, the present invention provides a two-step method for synthesizing nitrogen methylmorpholine, comprising a chlorination reaction and a ring-closure reaction;

[0006] The chlorination reaction is to react diethylene glycol with concentrated hydrochloric acid under the catalysis of zinc chloride and concentrated sulfuric acid to produce a hydrochloric acid aqueous solution of dichloroethyl ether;

[0007] The ring-closure reaction is to mix a hydrochloric acid aqueous solution of dichloroethyl ether with methylamine and calcium hydroxide to carry out a ring-closure reaction, and the reaction solution is distilled to obtain nitrogen methylmorpholine.

[0008] Preferably, in the chlorination reaction, the mass ratio of concentrated hydrochloric acid to concentrated sulfuric acid is 20:1 to 40:1.

[0009] More preferably, the mass ratio of concentrated hydrochloric acid to concentrated sulfuric acid is 30:1.

[0010] Preferably, in the chlorination reaction, the mass ratio of diethylene glycol to zinc chloride is 2:1 to 3:1, and the reaction temperature is 130 to 170°C.

[0011] More preferably, the reaction temperature is 150°C.

[0012] Preferably, in the ring-closure reaction, the molar ratio of dichloroethyl ether, methylamine and calcium hydroxide is 1:2.5-3.5:1-1.5.

[0013] More preferably, the molar ratio of dichloroethyl ether, methylamine and calcium hydroxide is 1:3:1.2.

[0014] Preferably, in the ring-closure reaction, the reaction temperature is 80-100° C. and the reaction time is 1-3 hours.

[0015] Preferably, in the ring-closure reaction, the reaction solution is distilled to obtain an aqueous solution of nitrogen-methylmorpholine, 40% sodium hydroxide solution is added to the aqueous solution of nitrogen-methylmorpholine, the mixture is allowed to stand for separation, and the mixture is dried after separation to obtain nitrogen-methylmorpholine.

[0016] Preferably, the unreacted methylamine in the distillation process is condensed and recovered and recycled for the ring-closure reaction.

[0017] Preferably, the by-products after distillation include calcium chloride and calcium hydroxide, and concentrated sulfuric acid is added to the by-products to convert the calcium chloride and calcium hydroxide into calcium sulfate precipitate and hydrogen chloride gas, which is absorbed by water to produce concentrated hydrochloric acid for recycling in the chlorination reaction.

[0018] More preferably, the calcium sulfate precipitate is separated, washed, dried and then recycled as an industrial gypsum product.

[0019] Preferably, the chlorination reaction and the ring-closure reaction are both carried out using a modular continuous reaction device, the material of the reaction device is glass or polytetrafluoroethylene, and multiple reaction devices form an independent mobile reaction unit device.

[0020] More preferably, the production capacity of a single mobile reaction unit device is 0.5 to 2 tons / day, and the total production capacity can be adjusted by combining multiple mobile reaction unit devices.

[0021] Beneficial effects of the present invention:

[0022] (1) The two-step reaction of the present invention has a high conversion rate, and the reaction to generate nitrogen methylmorpholine can be carried out in a quantitative manner, which reduces the work of separation and purification, reduces the total cost, reduces the pressure of handling by-products, and makes the production process efficient and simple. In addition, the product prepared by the two-step method has a high purity, which increases the added value of the product and overcomes the problems of the prior art that require a distillation tower for refining, increases fixed investment and energy consumption, and has low product purity.

[0023] (2) The two-step reaction of the present invention is coupled, that is, the by-products of the ring-closing reaction are recycled as the reaction raw materials of the chlorination reaction, without generating additional pollutants, forming an internal cycle of elements, improving the atomic utilization rate, reducing the emission of chemical pollutants, and being green and environmentally friendly.

[0024] (3) The present invention uses basic chemical raw materials such as concentrated hydrochloric acid and calcium hydroxide, which are inexpensive and in stable supply, thereby reducing costs. At the same time, the by-products produced can be acidified to prepare calcium sulfate precipitate and concentrated hydrochloric acid. The calcium sulfate precipitate can be used as a raw material in the fields of building materials and soil conditioners, thereby achieving waste recycling. The concentrated hydrochloric acid is returned to the chlorination reaction for recycling, achieving a closed-loop circulation of halogen atoms (Cl), avoiding the discharge of chlorine-containing wastewater, and effectively circumventing the risk of pollution to the water environment.

[0025] (4) The present invention abandons the large-scale distillation equipment required by traditional processes, which not only saves equipment purchase and maintenance costs, but also reduces energy consumption expenditures; it adopts modular continuous reaction devices for production, that is, multiple modular reaction devices form independent mobile reaction unit devices, and the total production capacity can be adjusted by combining multiple mobile reaction unit devices, which is convenient for disassembly and transportation, and supports a flexible production mode of "install and use, start and stop at any time". Compared with traditional large-scale chemical plants, it significantly reduces operating costs and safety management difficulties, effectively avoids common safety risks in chemical production, and also avoids problems such as the amplification effect caused by scale expansion, thereby enhancing the adaptability and reliability of the process.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the mobile reaction unit device of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described below with reference to the accompanying drawings and examples. Unless otherwise defined, technical or scientific terms used herein shall have the same meanings as those commonly understood by persons of ordinary skill in the art to which the present invention pertains. The above-mentioned features or features described in the specific examples of the present invention may be combined in any manner. These specific examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention.

[0029] Example 1

[0030] The present invention provides a two-step method for synthesizing nitrogen methylmorpholine, comprising the following steps:

[0031] S1. Chlorination reaction

[0032] S1.1. Add 26.5 g of diethylene glycol and 10.2 g of zinc chloride to a three-necked flask equipped with a thermometer. Connect one end of the flask to a distillation apparatus. Heat to 150°C with stirring until the mixture becomes clear.

[0033] S1.2. Pump 120 mL of a mixed acid of concentrated hydrochloric acid and concentrated sulfuric acid in a mass ratio of 30:1 into a three-necked flask at a rate of 5 mL / min, and collect the condensate by distillation. After the reaction, 110 mL of a slightly yellowish transparent condensate is obtained, i.e., a hydrochloric acid aqueous solution of dichloroethyl ether. The purity of the dichloroethyl ether in the aqueous solution is >97.0% (NMR purity).

[0034] S2, ring closure reaction

[0035] S2.1. Add the hydrochloric acid solution of dichloroethyl ether and methylamine obtained in S1 to a 500 mL three-necked flask equipped with a distillation apparatus to obtain a mixed solution. Add more water to dilute the mixture to 300 mL. Add calcium hydroxide while stirring, and heat to 80°C for 1-2 h.

[0036] The molar ratio of dichloroethyl ether, methylamine and calcium hydroxide is n((C2H4Cl)2O):n(CH3NH2):n(Ca(OH)2)=1:3:1.2.

[0037] S2.2. After the reaction is completed, the reaction solution is distilled to obtain an aqueous solution of nitrogen-methylmorpholine. A 40% sodium hydroxide solution is added to the aqueous solution of nitrogen-methylmorpholine, and the mixture is allowed to stand for separation. The upper layer of the separated solution is the nitrogen-methylmorpholine solution, which is dried to obtain nitrogen-methylmorpholine with a purity of >99% (NMR purity).

[0038] Unreacted methylamine during the distillation process is condensed, recovered, and recycled for the ring-closure reaction. The residual liquid at the bottom of the still after distillation is a byproduct, including calcium chloride and calcium hydroxide. Concentrated sulfuric acid is added to the byproduct to convert the calcium chloride and calcium hydroxide into calcium sulfate precipitate and hydrogen chloride gas. The hydrogen chloride gas is absorbed by water to produce concentrated hydrochloric acid, which is recycled for the chlorination reaction.

[0039] The precipitated calcium sulfate is filtered, washed with distilled water, and dried to obtain the calcium sulfate product. The washed liquid can be used as the absorption liquid for the next hydrogen chloride gas.

[0040] Example 2

[0041] The present invention provides a two-step method for synthesizing nitrogen methylmorpholine, comprising the following steps:

[0042] S1. Chlorination reaction

[0043] S1.1. Add 16.5 g of diethylene glycol and 8.0 g of zinc chloride to a three-necked flask equipped with a thermometer. Connect one end of the flask to a distillation apparatus. Heat to 150°C with stirring until the mixture becomes clear.

[0044] S1.2. Pump 120 mL of a mixed acid of concentrated hydrochloric acid and concentrated sulfuric acid in a mass ratio of 20:1 into a three-necked flask at a rate of 5 mL / min, and collect the condensate by distillation. After the reaction, 108 mL of a slightly yellowish transparent condensate is obtained, i.e., a hydrochloric acid aqueous solution of dichloroethyl ether. The purity of the dichloroethyl ether in the aqueous solution is >97.6% (NMR purity).

[0045] S2, ring closure reaction

[0046] S2.1. Add the hydrochloric acid solution of dichloroethyl ether and methylamine obtained in S1 to a 500 mL three-necked flask equipped with a distillation apparatus to obtain a mixed solution. Add more water to dilute the mixture to 300 mL. Add calcium hydroxide while stirring, and heat to 80°C for 1-2 h.

[0047] The molar ratio of dichloroethyl ether, methylamine and calcium hydroxide is n((C2H4Cl)2O):n(CH3NH2):n(Ca(OH)2)=1:2.5:1.

[0048] S2.2. After the reaction is completed, the reaction solution is distilled to obtain an aqueous solution of nitrogen-methylmorpholine. A 40% sodium hydroxide solution is added to the aqueous solution of nitrogen-methylmorpholine, and the mixture is allowed to stand for separation. The upper layer of the separated solution is the nitrogen-methylmorpholine solution, which is dried to obtain nitrogen-methylmorpholine with a purity of >99% (NMR purity).

[0049] Unreacted methylamine during the distillation process is condensed, recovered, and recycled for the ring-closure reaction. The residual liquid at the bottom of the still after distillation is a byproduct, including calcium chloride and calcium hydroxide. Concentrated sulfuric acid is added to the byproduct to convert the calcium chloride and calcium hydroxide into calcium sulfate precipitate and hydrogen chloride gas. The hydrogen chloride gas is absorbed by water to produce concentrated hydrochloric acid, which is recycled for the chlorination reaction.

[0050] The precipitated calcium sulfate is filtered, washed with distilled water, and dried to obtain the calcium sulfate product. The washed liquid can be used as the absorption liquid for the next hydrogen chloride gas.

[0051] Example 3

[0052] The present invention provides a two-step method for synthesizing nitrogen methylmorpholine, comprising the following steps:

[0053] S1. Chlorination reaction

[0054] S1.1. Add 36.2 g of diethylene glycol and 12.5 g of zinc chloride to a three-necked flask equipped with a thermometer. Connect one end of the flask to a distillation apparatus. Heat to 150°C with stirring until the mixture becomes clear.

[0055] S1.2. Pump 120 mL of a mixed acid of concentrated hydrochloric acid and concentrated sulfuric acid in a mass ratio of 40:1 into a three-necked flask at a rate of 5 mL / min, and collect the condensate by distillation. After the reaction, 112 mL of a slightly yellowish transparent condensate is obtained, i.e., a hydrochloric acid aqueous solution of dichloroethyl ether. The purity of the dichloroethyl ether in the aqueous solution is >97.2% (NMR purity).

[0056] S2, ring closure reaction

[0057] S2.1. Add the hydrochloric acid solution of dichloroethyl ether and methylamine obtained in S1 to a 500 mL three-necked flask equipped with a distillation apparatus to obtain a mixed solution. Add more water to dilute the mixture to 300 mL. Add calcium hydroxide while stirring, and heat to 80°C for 1-2 h.

[0058] The molar ratio of dichloroethyl ether, methylamine and calcium hydroxide is n((C2H4Cl)2O):n(CH3NH2):n(Ca(OH)2)=1:3.5:1.5.

[0059] S2.2. After the reaction is completed, the reaction solution is distilled to obtain an aqueous solution of nitrogen-methylmorpholine. A 40% sodium hydroxide solution is added to the aqueous solution of nitrogen-methylmorpholine, and the mixture is allowed to stand for separation. The upper layer of the separated solution is the nitrogen-methylmorpholine solution, which is dried to obtain nitrogen-methylmorpholine with a purity of >99% (NMR purity).

[0060] Unreacted methylamine during the distillation process is condensed, recovered, and recycled for the ring-closure reaction. The residual liquid at the bottom of the still after distillation is a byproduct, including calcium chloride and calcium hydroxide. Concentrated sulfuric acid is added to the byproduct to convert the calcium chloride and calcium hydroxide into calcium sulfate precipitate and hydrogen chloride gas. The hydrogen chloride gas is absorbed by water to produce concentrated hydrochloric acid, which is recycled for the chlorination reaction.

[0061] The precipitated calcium sulfate is filtered, washed with distilled water, and dried to obtain the calcium sulfate product. The washed liquid can be used as the absorption liquid for the next hydrogen chloride gas.

[0062] like Figure 1 As shown, the reactions of Examples 1 to 3 of the present invention can all be carried out using a modular continuous reaction apparatus. The reaction apparatus is made of glass or polytetrafluoroethylene, and multiple reaction apparatuses form independent mobile reaction units. The production capacity of a single mobile reaction unit is 1 ton / day, and the total production capacity can be adjusted by combining multiple mobile reaction units.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A two-step method for synthesizing nitrogen-methylmorpholine, characterized in that: Including chlorination reaction and ring closure reaction; The chlorination reaction is to react diethylene glycol with concentrated hydrochloric acid under the catalysis of zinc chloride and concentrated sulfuric acid to produce a hydrochloric acid aqueous solution of dichloroethyl ether; The ring-closure reaction is to mix a hydrochloric acid aqueous solution of dichloroethyl ether with methylamine and calcium hydroxide to carry out a ring-closure reaction, and the reaction solution is distilled to obtain nitrogen methylmorpholine.

2. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 1, wherein: In the chlorination reaction, the mass ratio of concentrated hydrochloric acid to concentrated sulfuric acid is 20:1 to 40:

1.

3. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 1, wherein: In the chlorination reaction, the mass ratio of diethylene glycol to zinc chloride is 2:1 to 3:1, and the reaction temperature is 130 to 170°C.

4. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 1, wherein: In the ring-closure reaction, the molar ratio of dichloroethyl ether, methylamine and calcium hydroxide is 1:2.5-3.5:1-1.

5.

5. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 1, wherein: In the ring-closure reaction, the reaction temperature is 80-100° C. and the reaction time is 1-3 hours.

6. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 1, wherein: In the ring-closure reaction, the reaction solution is distilled to obtain an aqueous solution of nitrogen-methylmorpholine, 40% sodium hydroxide solution is added to the aqueous solution of nitrogen-methylmorpholine, the solution is allowed to stand to separate the layers, and the layers are separated and then dried to obtain nitrogen-methylmorpholine.

7. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 6, wherein: The unreacted methylamine in the distillation process is condensed and recovered and recycled for the ring-closure reaction.

8. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 6, wherein: The by-products after distillation include calcium chloride and calcium hydroxide. Concentrated sulfuric acid is added to the by-products to convert the calcium chloride and calcium hydroxide into calcium sulfate precipitate and hydrogen chloride gas. The hydrogen chloride gas is absorbed by water to produce concentrated hydrochloric acid for recycling in the chlorination reaction.

9. The method for preparing nitrogen-methylmorpholine by a two-step method according to claim 1, wherein: Both the chlorination reaction and the ring-closure reaction are carried out using a modular continuous reaction device. The material of the reaction device is glass or polytetrafluoroethylene, and multiple reaction devices form an independent mobile reaction unit device.

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