A method for continuously synthesizing ethylene glycol dimethyl ether

Abstract

The present invention belongs to the technical field of ether organic synthesis, and specifically relates to a method for continuously synthesizing ethylene glycol dimethyl ether. The method comprises the following steps: using ethylene glycol, sodium hydroxide, and methyl chloride as raw materials, performing a multi-stage continuous reaction in a liquid film reactor to synthesize ethylene glycol dimethyl ether, wherein ethylene glycol, sodium hydroxide, and methyl chloride are introduced into a first-stage liquid film reactor, and sodium hydroxide and methyl chloride are introduced into subsequent liquid film reactors. After the by-product sodium chloride is separated from the reaction product in the previous-stage liquid film reactor, it enters the next-stage liquid film reactor. After the by-product sodium chloride is separated from the reaction product in the last-stage liquid film reactor, a clarified liquid is obtained, and ethylene glycol dimethyl ether is obtained by distillation. The present invention develops a new process mode for continuously synthesizing ethylene glycol dimethyl ether products, providing a new approach for large-scale continuous production of ethylene glycol dimethyl ether.

Description

Technical Field

[0001] The invention belongs to the technical field of ether organic synthesis, and particularly relates to a method for continuously synthesizing ethylene glycol dimethyl ether. Background Art

[0002] Ethylene glycol dimethyl ether (DME), an organic compound containing C—C and C—O bonds, has become an indispensable chemical in numerous industrial sectors due to its excellent solubility, low toxicity, and environmentally friendly properties. As an organic solvent, it effectively dissolves a wide range of polar and non-polar chemicals, significantly improving solvent performance and exhibiting excellent results during preparation and use. Therefore, it is widely used in industrial products such as paints, coatings, and inks. Ethylene glycol dimethyl ether can also serve as an intermediate in chemical synthesis, used to synthesize other important chemicals and polymers, such as various types of polyurethane, and as a raw material for plastics manufacturing. Furthermore, Ethylene glycol dimethyl ether exhibits excellent low-temperature fluidity and oxidative stability in lubricants and hydraulic fluids, making it widely used in mechanical equipment requiring high-performance lubrication. As a cleaning agent, it effectively removes oil and other contaminants, particularly in the precision manufacturing and electronics industries, where it is used to clean equipment and components. In recent years, growing global environmental awareness has led to the introduction of relevant regulations in many countries, further driving the growing demand for low-volatility, low-toxicity solvents. As a green organic solvent, Ethylene glycol dimethyl ether is finding favor in a growing number of applications.

[0003] Existing methods for synthesizing ethylene glycol dimethyl ether primarily include the Williamson synthesis method and its improved process, the ethylene oxide ring-opening method, and the acid-catalyzed method. These methods suffer from numerous drawbacks. For example, the Williamson synthesis method typically employs a batch-type, two-step reaction. The production capacity of a single reaction depends on the size of the reaction equipment, severely limiting its industrial production capacity expansion. During the two-step production process, ethylene glycol monomethyl ether reacts with sodium hydroxide to form the intermediate sodium ethylene glycol monomethyl ether. This long residence time makes sodium ethylene glycol monomethyl ether prone to side reactions, reducing the atomic utilization rate of the reaction. The crude product produced by traditional synthesis methods is dark brown, resulting in high post-processing costs and significant environmental pollution. For example, the ethylene oxide and other raw materials used in the ethylene oxide ring-opening method are highly toxic and pose an explosion risk, requiring stringent storage and transportation requirements and increasing safety costs. For example, the catalyst in acid-catalyzed methods is easily deactivated and difficult to recover, requiring frequent replacement, increasing production costs. Furthermore, some early acid-catalyzed methods achieved ethylene glycol conversion rates of only 35%-50%, and ethylene glycol dimethyl ether selectivity of less than 20%, resulting in low raw material utilization.

[0004] Patent document CN119528700A discloses a one-pot method for preparing ethylene glycol dimethyl ether from ethylene glycol without a catalyst. This preparation method uses ethylene glycol as a raw material, does not require a catalyst, and produces a high-purity product. This method solves the problems of the above-mentioned prior art to a certain extent. However, this method still has the following disadvantages: ① At a reaction temperature of 120-140°C, some methanol is still generated; ② During the reaction, sodium hydroxide is added in batches to control the reaction rate, and repeated sampling and detection of the sodium hydroxide concentration in the reaction solution are required to determine the timing for adding the next batch of sodium hydroxide; and ③ The reaction time is long.

[0005] Therefore, developing a novel method for continuously synthesizing ethylene glycol dimethyl ether has become one of the issues of close concern in the field of organic synthesis technology. Summary of the Invention

[0006] To address the drawbacks of the above-mentioned prior art, the present invention discloses a method for continuously synthesizing ethylene glycol dimethyl ether. This method directly prepares ethylene glycol dimethyl ether from simple ethylene glycol. The raw materials are cheap and readily available, the equipment is simple to operate, the product yield is high, the reaction atom utilization rate is high, and the continuous clean production of ethylene glycol dimethyl ether can be achieved. The following technical means are specifically adopted:

[0007] A method for continuously synthesizing ethylene glycol dimethyl ether comprises the following steps: using ethylene glycol, sodium hydroxide and methyl chloride as raw materials, performing a multi-stage continuous reaction in a liquid film reactor to synthesize ethylene glycol dimethyl ether,

[0008] The first-stage liquid film reactor is fed with ethylene glycol, sodium hydroxide, and methyl chloride, and the subsequent stages of liquid film reactors are fed with sodium hydroxide and methyl chloride. The reaction product of the previous stage liquid film reactor is separated from the by-product sodium chloride and then fed into the next stage liquid film reactor. The reaction product of the last stage liquid film reactor is separated from the by-product sodium chloride to obtain a clarified liquid, which is subjected to rectification treatment to obtain ethylene glycol dimethyl ether. The ethylene glycol is a liquid, the sodium hydroxide is a solid, and the methyl chloride is a gas.

[0009] The chemical formula involved in the present invention is as follows:

[0010] (1)2HOCH2CH2OH+3NaOH→HOCH2CH2ONa+NaOCH2CH2ONa+3H2O

[0011] (2)HOCH2CH2ONa+CH3Cl→HOCH2CH2OCH3+NaCl

[0012] (3)NaOCH2CH2ONa+2CH3Cl→CH3OCH2CH2OCH3+2NaCl

[0013] (4)HOCH2CH2OCH3+NaOH→CH3OCH2CH2ONa+H2O

[0014] (5)CH3OCH2CH2ONa+CH3Cl→CH3OCH2CH2OCH3+NaCl

[0015] Furthermore, the reaction temperature in each level of liquid membrane reactor is 90-110°C. Preferably, the reaction temperature in each level of liquid membrane reactor is 100°C.

[0016] In the preparation method of ethylene glycol dimethyl ether disclosed in CN119528700A, the reaction temperature needs to be controlled at 120-140°C. When the temperature is lower than 120°C, the main reaction rate is significantly reduced, seriously affecting production efficiency. Therefore, in this method, it is impossible to control the formation of methanol by lowering the temperature.

[0017] The synthesis temperature of the present invention is controlled at 90-110°C. Compared with CN119528700A and other ethylene glycol dimethyl ether synthesis methods, the synthesis temperature is lower, the hydrolysis reaction of monochloromethane is less, and the by-product methanol generated is less. The present invention can achieve the synthesis temperature control at 90-110°C without affecting the reaction rate through the following improvements. ① The present invention adopts a liquid film reactor, which has better heat transfer efficiency than a reactor; ② The present invention synthesizes ethylene glycol dimethyl ether through a multi-stage continuous reaction, and the single-stage sodium hydroxide feed amount is about 1 / 2 of the total amount of ethylene glycol, thereby reducing the degree of reaction; ③ The present invention adopts a solid-liquid-gas three-phase feeding method, and the contact area between the materials is larger. Therefore, the present invention controls the temperature between 90-110°C, still maintaining a suitable reaction rate and maintaining a high production efficiency.

[0018] At the same time, the inventors found in experimental studies that too low a reaction temperature would slow the reaction rate of the sodium alkoxide and sodium ether intermediates, prolong the residence time of the intermediates, intensify side reactions, significantly deepen the color of the system, and increase side reactions. Therefore, the present invention further controls the reaction temperature to 90-110°C, which can ensure the normal conversion of the sodium alkoxide and sodium ether intermediates while reducing methanol generation and reducing side reactions.

[0019] Furthermore, the reaction time in each level of liquid membrane reactor is 20 to 30 minutes. Preferably, the reaction time in each level of liquid membrane reactor is 25 minutes.

[0020] Compared with the method disclosed in CN119528700A, the reaction time of the present invention is greatly shortened. This is because: 1) the heat exchange efficiency is improved. The liquid film reactor uses a high speed to make the system in a thin liquid film state inside the reactor, thereby increasing the heat exchange effect of the reaction; 2) the three-phase feeding method and the liquid film reaction method can effectively increase the contact area between solid, liquid and gas; 3) the degree of reaction is reduced; 4) this method can filter out the generated sodium chloride in time, the reaction is faster, and sodium chloride is prevented from wrapping around sodium hydroxide, thereby affecting the progress of the reaction.

[0021] Furthermore, the feed rate of ethylene glycol is 300-500 g / min, preferably, the feed rate of ethylene glycol is 400 g / min.

[0022] Furthermore, the feed rate of sodium hydroxide in the liquid membrane reactors at each stage is 96.6-161.0 g / min, and the feed amount is 0.49-0.51 times the total feed amount of ethylene glycol in the first-stage horizontal reactor. The feed amount is calculated based on the amount of substance. Preferably, the feed rate of sodium hydroxide is 128.8 g / min, and the feed amount of sodium hydroxide in the liquid membrane reactors at each stage is 1 / 2 of the total feed amount of ethylene glycol in the first-stage horizontal reactor.

[0023] Furthermore, the reaction pressure in each level of liquid membrane reactor is 0.2-0.4 MPa, preferably, the reaction pressure is 0.3 MPa.

[0024] Furthermore, a four-stage continuous reaction is performed in a liquid membrane reactor to synthesize ethylene glycol dimethyl ether. Taking into account the conversion of each component, reaction degree, reaction time, and production cost, the four-stage continuous synthesis reaction is optimal.

[0025] Furthermore, the mass fraction of ethylene glycol in the clarified liquid is less than 5%.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention develops a new process mode for the continuous synthesis of ethylene glycol dimethyl ether products. Using cheap and readily available ethylene glycol as the reaction raw material, the continuous production of ethylene glycol dimethyl ether is achieved through a multi-stage feeding and discharging method, providing a new idea for large-scale continuous production of ethylene glycol dimethyl ether.

[0028] (2) The present invention uses cheap and readily available ethylene glycol as the reaction raw material and does not require the participation of a catalyst. In the continuous production process of the present invention, the processing volume of the reaction materials is relatively small, and the reaction is carried out under relatively stable conditions, reducing the safety risks caused by large-scale centralized material processing. Due to the stable reaction conditions and high ethylene glycol conversion rate, the waste and pollutants generated are relatively small, achieving full utilization of resources and energy conservation and emission reduction. Therefore, the present invention effectively solves the disadvantages of the Williamson synthesis method, the ethylene oxide ring-opening method, and the acid catalysis method.

[0029] (3) The present invention adopts a liquid film reactor as a reaction device, a three-phase feeding method, and a multi-stage continuous reaction synthesis method. At the same time, the by-product sodium chloride is removed in a timely manner during the synthesis process, thereby achieving a reduction in synthesis temperature and a shortening of reaction time. In essence, the present invention is a dynamic and stable mode for the one-pot synthesis of ethylene glycol dimethyl ether, which not only reduces the economic losses caused by frequent start and stop reactions, but also effectively improves the production capacity of ethylene glycol dimethyl ether. The relatively stable reaction state can reduce the occurrence of side reactions and improve the atomic utilization rate of the reaction. Therefore, the present invention also effectively solves the disadvantages of the one-pot catalyst-free method for preparing ethylene glycol dimethyl ether from ethylene glycol disclosed in CN119528700A. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A synthesis device for ethylene glycol dimethyl ether used in the embodiments and comparative examples of the present invention;

[0031] Figure 2 This is a gas chromatogram of the reaction liquid before distillation in Example 1;

[0032] Figure 3 This is the gas chromatogram of the ethylene glycol dimethyl ether product prepared in Example 1.

[0033] In the figure, 1-ethylene glycol storage tank, 2-sodium hydroxide feeder A, 3-sodium hydroxide feeder B, 4-sodium hydroxide feeder C, 5-sodium hydroxide feeder D, 6-monochloromethane storage tank A, 7-monochloromethane storage tank B, 8-monochloromethane storage tank C, 9-monochloromethane storage tank D, 10-liquid film reactor A, 11-liquid film reactor B, 12-liquid film reactor C, 13-liquid film reactor D, 14-filter A, 15-filter B, 16-filter C, 17-filter D, 18-liquid metering pump A, 19-liquid metering pump B, 20-liquid metering pump C, 21-liquid metering pump D, 22-liquid metering pump E, 23-hot and cold integrated machine A, 24-hot and cold integrated machine B, 25-hot and cold integrated machine C, 26-hot and cold integrated machine D, 27-distillation system. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings.

[0035] The raw materials used in the examples and comparative examples of the present invention are all common commercially available products.

[0036] The liquid film reactor used in the examples and comparative examples of the present invention is a dynamic liquid film continuous flow reactor, model: HCR100.

[0037] First combine Figure 1 The specific process of continuous synthesis of ethylene glycol dimethyl ether in the embodiment is described. It should be emphasized that: Figure 1 This is only an example of a synthesis device of the present invention. The synthesis method of the present invention does not necessarily need to be based on Figure 1 The synthesis device is realized.

[0038] Start the hot and cold integrated machine A23, the hot and cold integrated machine B24, the hot and cold integrated machine C25, and the hot and cold integrated machine D26, and adjust the oil temperature of the hot and cold integrated machine so that the temperature of the liquid film reactor A10, the liquid film reactor B11, the liquid film reactor C12, and the liquid film reactor D13 all reach 90-110°C.

[0039] The ethylene glycol in the ethylene glycol storage tank 1 enters the liquid film reactor A10 at a feed rate of 300-500 g / min through the liquid metering pump A18. At the same time, the sodium hydroxide feeder A2 and the monochloromethane storage tank A6 are opened with a feed rate of 96.6-161.0 g / min. In terms of the amount of substance, the feed amount of the sodium hydroxide is 1 / 2 of the total feed amount of ethylene glycol. The reaction pressure is controlled to be 0.2-0.4 MPa. After reacting in the liquid film reactor A10 for 20-30 min, the ethylene glycol enters the filter A14 to remove the sodium chloride generated by the reaction. The clarified liquid enters the liquid film reactor B11 through the liquid metering pump B19. The sodium hydroxide feeder B3 and the monochloromethane storage tank B7 are adjusted so that the amount of the sodium hydroxide feed still accounts for 1 / 2 of the total feed amount of ethylene glycol. The reaction pressure remains unchanged. After reacting in the liquid film reactor B11 for 20-30 min, the ethylene glycol enters the filter A14 to remove the sodium chloride generated by the reaction. The clarified liquid enters the liquid film reactor B11 through the liquid metering pump B19. min later, it enters filter B15 to remove sodium chloride generated by the reaction. The clarified liquid enters liquid film reactor C12 via liquid metering pump C20. The sodium hydroxide feeder C4 and the chloromethane storage tank C8 are adjusted so that the amount of sodium hydroxide feed material accounts for 1 / 2 of the total ethylene glycol feed amount, and the reaction pressure remains unchanged. After reacting in liquid film reactor C12 for 20-30 min, it enters filter C16 to remove sodium chloride generated by the reaction. The clarified liquid enters liquid film reactor D13 via liquid metering pump D21. The sodium hydroxide feeder D5 and the chloromethane storage tank D9 are adjusted so that the amount of sodium hydroxide feed material accounts for 1 / 2 of the total ethylene glycol feed amount, and the reaction pressure remains unchanged. After reacting in liquid film reactor D13 for 20-30 min, it enters filter D17 to remove sodium chloride generated by the reaction. The reaction effect is sampled and tested. The clarified liquid (the clarified liquid here is the reaction liquid in the embodiment and the comparative example) enters distillation system 27 via liquid metering pump E22 to obtain ethylene glycol dimethyl ether product after separation.

[0040] Example 1

[0041] The temperature of each level of liquid membrane reactor was 90°C, the feed rate of ethylene glycol was 300 g / min, the feed rate of sodium hydroxide was 96.6 g / min, the reaction pressure was 0.2 MPa, the reaction residence time was 20 min, the by-product sodium chloride was a yellow solid, the reaction liquid was a yellow liquid, and the yield of ethylene glycol dimethyl ether was 83.3%.

[0042] Figure 2 The gas chromatogram of the reaction solution of this embodiment is shown in FIG. Figure 2 It can be seen from the figure that the main component in the reaction solution is ethylene glycol dimethyl ether. Figure 3 The gas chromatogram of the glycol dimethyl ether product obtained after the rectification of this embodiment is shown in FIG. Figure 3 It can be seen that the purity of the product is high.

[0043] Example 2

[0044] The temperature of each level of liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 300 g / min, the feed rate of sodium hydroxide was 96.6 g / min, the reaction pressure was 0.2 MPa, the reaction residence time was 20 min, the by-product sodium chloride was a light yellow solid, the reaction liquid was a light yellow liquid, and the yield of ethylene glycol dimethyl ether was 87.6%.

[0045] Example 3

[0046] The temperature of each level of liquid membrane reactor was 110°C, the feed rate of ethylene glycol was 300 g / min, the feed rate of sodium hydroxide was 96.6 g / min, the reaction pressure was 0.2 MPa, the reaction residence time was 20 min, the by-product sodium chloride was a light yellow solid, the reaction liquid was a yellow liquid, and the yield of ethylene glycol dimethyl ether was 85.4%.

[0047] Example 4

[0048] The temperature of each level of liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.2 MPa, the reaction residence time was 20 min, the by-product sodium chloride was a light yellow solid, the reaction liquid was a light yellow liquid, and the yield of ethylene glycol dimethyl ether was 89.5%.

[0049] Example 5

[0050] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 500 g / min, the feed rate of sodium hydroxide was 161.0 g / min, the reaction pressure was 0.2 MPa, the reaction residence time was 20 min, the by-product sodium chloride was a light yellow solid, the reaction liquid was a yellow liquid, and the yield of ethylene glycol dimethyl ether was 87.6%.

[0051] Example 6

[0052] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 20 min, the by-product sodium chloride was a gray solid, the reaction liquid was a light yellow liquid, and the yield of ethylene glycol dimethyl ether was 90.5%.

[0053] Example 7

[0054] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.4 MPa, the reaction residence time was 20 min, the by-product sodium chloride was a gray solid, the reaction liquid was a light yellow liquid, and the yield of ethylene glycol dimethyl ether was 88.3%.

[0055] Example 8

[0056] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 25 min, the byproduct sodium chloride was a white solid, the reaction liquid was a colorless liquid, and the yield of ethylene glycol dimethyl ether was 95.4%.

[0057] Example 9

[0058] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 30 min, the by-product sodium chloride was a gray solid, the reaction liquid was a colorless liquid, and the yield of ethylene glycol dimethyl ether was 88.7%.

[0059] Comparative Example 1

[0060] The temperature of each level of liquid membrane reactor was 80°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 30 min, the by-product sodium chloride was a brown solid, the reaction liquid was a brown liquid, and the yield of ethylene glycol dimethyl ether was 68.4%.

[0061] Comparative Example 2

[0062] The temperature of each level of liquid membrane reactor was 120°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 30 min, the byproduct sodium chloride was an orange solid, the reaction liquid was a brown liquid, and the yield of ethylene glycol dimethyl ether was 65.3%.

[0063] Comparative Example 3

[0064] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 200 g / min, the feed rate of sodium hydroxide was 64.4 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 25 min, the by-product sodium chloride was a yellow solid, the reaction liquid was an orange liquid, and the yield of ethylene glycol dimethyl ether was 78.7%.

[0065] Comparative Example 4

[0066] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 600 g / min, the feed rate of sodium hydroxide was 193.2 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 25 min, the by-product sodium chloride was a gray solid, the reaction liquid was a yellow liquid, and the yield of ethylene glycol dimethyl ether was 67.8%.

[0067] Comparative Example 5

[0068] The temperature of each level of liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.1 MPa, the reaction residence time was 25 min, the by-product sodium chloride was a brown solid, the reaction liquid was a brown liquid, and the yield of ethylene glycol dimethyl ether was 63.6%.

[0069] Comparative Example 6

[0070] The temperature of each level of liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.5 MPa, the reaction residence time was 25 min, the by-product sodium chloride was a gray solid, the reaction liquid was a light green liquid, and the yield of ethylene glycol dimethyl ether was 70.4%.

[0071] Comparative Example 7

[0072] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 15 min, the by-product sodium chloride was a gray solid, the reaction liquid was a yellow liquid, and the yield of ethylene glycol dimethyl ether was 65.1%.

[0073] Comparative Example 8

[0074] The temperature of each liquid membrane reactor was 100°C, the feed rate of ethylene glycol was 400 g / min, the feed rate of sodium hydroxide was 128.8 g / min, the reaction pressure was 0.3 MPa, the reaction residence time was 35 min, the by-product sodium chloride was a yellow solid, the reaction liquid was an orange liquid, and the yield of ethylene glycol dimethyl ether was 71.5%.

[0075] The experimental results of Examples 1 to 9 show that the yield of ethylene glycol dimethyl ether prepared by the preparation method of the present invention is high, the color of the byproduct sodium chloride is lighter, and the color of the reaction solution is also lighter, indicating that the synthesis method of the present invention achieves better results.

[0076] By comparing the experimental results of Comparative Example 1, Comparative Example 2 with Example 9, it can be seen that when the reaction temperature is too high or too low, the color of sodium chloride and the reaction solution is darker, and the yield of ethylene glycol dimethyl ether is lower. This is mainly because when the reaction temperature is too high or too low, the occurrence of side reactions is promoted and the residence time of sodium ether is affected. If the sodium ether stays in the system for too long and is not converted in time, the color of the reaction system will deepen.

[0077] By comparing the experimental results of Comparative Example 3, Comparative Example 4 with Example 8, it can be seen that the feed rate of ethylene glycol will also affect the color and yield of the reaction system. This is mainly because the feed rate of ethylene glycol is too fast or too slow, which will promote the occurrence of side reactions and also affect the residence time of sodium ether.

[0078] From the comparison of the experimental results of Comparative Examples 5 and 6 with those of Example 8, it can be seen that the reaction pressure also affects the color and yield of the reaction system. This is mainly because when the pressure is low, the conversion rate of sodium ether is slowed down, resulting in a longer residence time. When the pressure is high, it is speculated that the pressure of monochloromethane is too high, the degree of hydrolysis increases, and the generated HCl has a certain corrosive effect on the reactor, resulting in the liquid being light green (containing Fe 2+ ).

[0079] By comparing the experimental results of Comparative Example 7, Comparative Example 8 with Example 8, it can be seen that the reaction time also affects the color and yield of the reaction system. This is mainly because when the reaction time is short, the sodium ether conversion is not timely and the color of the system becomes darker. When the reaction time is long, the side reactions will increase.

[0080] In summary, the present invention provides a method for the continuous synthesis of ethylene glycol dimethyl ether, enabling the direct preparation of ethylene glycol dimethyl ether from simple ethylene glycol, thus achieving continuous production of ethylene glycol dimethyl ether. The reaction utilizes a continuous solid-liquid-gas three-phase feeding method, significantly reducing the occurrence of side reactions. The raw materials are inexpensive and readily available, the equipment is simple to operate, the product selectivity is good, and the reaction atom utilization rate is high, providing a new approach for the continuous and clean production of ethylene glycol dimethyl ether.

Claims

1. A method for continuously synthesizing ethylene glycol dimethyl ether, characterized in that: The method comprises the following steps: using ethylene glycol, sodium hydroxide and methyl chloride as raw materials, adopting a solid-liquid-gas three-phase feeding method, and performing a four-stage continuous reaction in a liquid film reactor to synthesize ethylene glycol dimethyl ether. The first-stage liquid membrane reactor is fed with ethylene glycol, sodium hydroxide and monochloromethane, and the subsequent stages of liquid membrane reactors are fed with sodium hydroxide and monochloromethane. The reaction product in the previous stage liquid membrane reactor is separated from the by-product sodium chloride and then enters the next stage liquid membrane reactor. The reaction product in the last stage liquid membrane reactor is separated from the by-product sodium chloride to obtain a clarified liquid, which is subjected to rectification treatment to obtain ethylene glycol dimethyl ether. The reaction temperature in each level of liquid membrane reactor is 90~110℃; The feed rate of sodium hydroxide in each stage of liquid membrane reactor is 96.6-161.0 g / min, and the feed amount is 0.49-0.51 times the total feed amount of ethylene glycol in the first stage horizontal reactor, and the feed amount is calculated on a substance basis.

2. The method for continuously synthesizing ethylene glycol dimethyl ether according to claim 1, wherein The reaction time in each level of liquid membrane reactor is 20~30min.

3. The method for continuous synthesis of ethylene glycol dimethyl ether according to claim 1, wherein The feed rate of the ethylene glycol is 300-500 g / min.

4. The method for continuously synthesizing ethylene glycol dimethyl ether according to claim 1, wherein The sodium hydroxide feed amount in each stage of the liquid membrane reactor is 1 / 2 of the total ethylene glycol feed amount in the first stage horizontal reactor, and the feed amount is calculated based on the amount of substance.

5. The method for continuous synthesis of ethylene glycol dimethyl ether according to claim 1, wherein The reaction pressure in each level of liquid membrane reactor is 0.2~0.4Mpa.

6. The method for continuously synthesizing ethylene glycol dimethyl ether according to claim 1, wherein The reaction temperature of the liquid membrane reactors at each level is 100° C., the reaction time is 25 min, and the reaction pressure is 0.3 MPa.

7. The method for continuous synthesis of ethylene glycol dimethyl ether according to claim 1, wherein The mass fraction of ethylene glycol in the clarified liquid is less than 5%.

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