A one-pot method for preparing ethylene glycol dimethyl ether from ethylene glycol without catalyst

Abstract

The invention belongs to the technical field of ether organic compound synthesis, and is specifically related to a method for preparing ethylene glycol dimethyl ether by ethylene glycol without catalyst in a one-pot method, comprising the steps of: (1) adding ethylene glycol in a reactor, heating to 120-140 DEG C, passing through chloroform, controlling the amount of chloroform to be passed through to be 20%-50% of the total molar amount of ethylene glycol; (2) adding NaOH in batches in a reactor, stirring and reacting at a reaction temperature of 120-140 DEG C; (3) after the last batch of NaOH is added, sampling and detecting at intervals of 20-25 min, when measuring NaOH concentration <0.05mol / L in the reaction solution, the reaction ends, and filtering is performed, and the filtrate is subjected to post-processing distillation to obtain ethylene glycol dimethyl ether. The preparation raw material ethylene glycol of the present invention can be derived from biomass or coal, which reduces the dependence on petroleum resources, and the preparation method of the present invention also has the advantages of few side reactions and low production cost.

Description

Technical Field

[0001] The invention belongs to the technical field of ether organic compound synthesis, and particularly relates to a method for preparing ethylene glycol dimethyl ether from ethylene glycol in a one-pot process without a catalyst. Background Art

[0002] Ethylene glycol dimethyl ether (DME) is an organic compound with ether bonds and epoxy groups. It has excellent thermal stability and solubility. It can dissolve various resins and cellulose, and can be miscible with water and many organic solvents such as alcohols, ethers, ketones, esters, hydrocarbons and chlorinated hydrocarbons in any proportion. It is widely used in the synthesis of gas absorbents, extractants, paint strippers, chemical reaction solvents and pharmaceutical intermediates. In the field of lithium batteries, ethylene glycol dimethyl ether can be mixed with a variety of lithium salts to form a solution of lithium battery electrolyte, which can reduce the viscosity of the electrolyte and increase the energy density of the battery. In recent years, my country's terminal application fields such as energy storage, new energy vehicles, and consumer electronics have developed rapidly. As the basic raw material for the production of lithium battery electrolytes, the market demand for ethylene glycol dimethyl ether has grown accordingly. With the increasing global environmental awareness and the increase in demand for new materials, ethylene glycol dimethyl ether, as an environmentally friendly solvent and new material raw material, will have a broader market prospect.

[0003] The processes for synthesizing ethylene glycol dimethyl ether that have been developed so far include: methylation (as shown in the invention patent with publication number CN104892371A), ethylene oxide ring-opening method (as shown in the invention patent with publication number CN101263101A), oxidative coupling method of dimethyl ether (as shown in the invention patent with publication number CN1836775A), intermolecular dehydration method (as shown in the invention patent with publication number JP2004196783A), etc.

[0004] There are two main methods for industrial scale production: (1) Williamson synthesis method: starting from ethylene glycol monomethyl ether, firstly prepare the sodium alcoholate of ethylene glycol monomethyl ether, and then introduce methyl chloride gas to react to obtain ethylene glycol dimethyl ether; (2) Ethylene oxide ring opening method: under the catalysis of Lewis acid or heteropolyacid, ethylene oxide and dimethyl ether react to obtain ethylene glycol dimethyl ether. Among them, the Williamson synthesis method using ethylene glycol monomethyl ether as raw material has attracted widespread attention due to its high safety and low operating difficulty. The equation is as follows:

[0005] (1)CH3OCH2CH2OH+NaOH→CH3OCH2CH2ONa+H2O

[0006] (2)CH3OCH2CH2ONa+CH3Cl→CH3OCH2CH2OCH3+NaCl

[0007] This process uses a two-step method to prepare ethylene glycol dimethyl ether. In the first step, ethylene glycol monomethyl ether sodium is prone to side reactions under the action of water at a relatively high temperature, and the reaction system turns reddish brown, resulting in reduced product purity and dyeing of the byproduct sodium chloride in the second step, increasing the difficulty of post-processing and production costs. Therefore, in the Williamson synthesis method, if you want to improve product purity and avoid sodium chloride dyeing, how to remove water from the system is the key. Existing methods for removing water from the system include vacuum distillation or adding a water absorbent, but both have certain defects. The former inevitably causes raw material losses and increases equipment requirements; the latter increases raw material costs, and the subsequent recovery and reuse of the water absorbent must also be considered.

[0008] The invention patent with publication number CN118530097A discloses a one-step method for preparing ethylene glycol dimethyl ether without catalyst, wherein the method first adds ethylene glycol monomethyl ether to a reactor, heats to 50-70°C, introduces chloroform, then adds NaOH in batches to the reactor, stirs at a reaction temperature of 50-70°C for reaction, waits for the reaction to be completed, filters the obtained reaction solution, and obtains ethylene glycol dimethyl ether by post-treatment distillation of the filtrate. The method can greatly reduce the amount of decolorizing agent used, thereby reducing production costs, and obtains high-quality ultrafine sodium chloride byproducts, solving the problem of low product purity and high post-treatment difficulty caused by the side reaction of sodium ethylene glycol monomethyl ether and water in the Williamson synthesis method.

[0009] However, in both the Williamson synthesis method and the method disclosed in CN118530097A, ethylene glycol monomethyl ether is used as a raw material to prepare ethylene glycol dimethyl ether. There are two main methods for synthesizing ethylene glycol monomethyl ether: (1) by reacting methanol with ethylene oxide. The raw material source of this process is only from petrochemical industry, so the price of petroleum has a great impact on the production cost. In addition, ethylene oxide is explosive and its production and transportation are limited. (2) by reacting methanol with ethylene glycol under the action of solid acid, ethylene glycol monomethyl ether can also be synthesized. However, the catalyst used in this reaction process, such as perfluorosulfonic acid resin, is expensive. The catalyst is easily deformed due to the influence of temperature during use. It is also difficult to regenerate and is difficult to apply on a large scale. Therefore, in both the Williamson synthesis method and the method disclosed in CN118530097A, there is a problem of limited large-scale sources of raw material ethylene glycol monomethyl ether.

[0010] Therefore, developing a method for producing ethylene glycol dimethyl ether with less side reactions, high product purity, and cheap and readily available raw materials has become a technical problem that needs to be solved urgently. Summary of the invention

[0011] In order to solve the technical problems existing in the conventional production process of ethylene glycol dimethyl ether, the present invention provides a one-pot method for preparing ethylene glycol dimethyl ether from ethylene glycol without catalyst. The present invention can directly prepare ethylene glycol dimethyl ether from ethylene glycol, and the raw materials are cheap and readily available, the operation is simple, the yield is high, and the side reactions are few, and finally the clean production of ethylene glycol dimethyl ether can be achieved. The following technical means are specifically adopted:

[0012] A one-pot method for preparing ethylene glycol dimethyl ether from ethylene glycol without catalyst comprises the following steps:

[0013] (1) Add ethylene glycol to the reactor, heat to 120-140°C, and introduce methyl chloride, controlling the amount of methyl chloride introduced to be 20%-50% of the total molar amount of ethylene glycol;

[0014] (2) Adding NaOH in batches to the reaction kettle, stirring and reacting at a reaction temperature of 120-140°C; wherein the amount of NaOH added each time is 10-30% of the total molar amount of ethylene glycol, and the total amount of NaOH added is 140-180% of the total molar amount of ethylene glycol; after each addition of NaOH, sampling and testing are performed every 20-25 minutes, and when the NaOH concentration in the reaction solution is measured to be <0.05 mol / L, the next batch of NaOH is added;

[0015] (3) After the last batch of NaOH is added, samples are taken for testing every 20-25 min. When the NaOH concentration in the reaction solution is <0.05 mol / L, the reaction is completed and there are a large number of white sodium chloride crystals in the reaction system. After filtration, the filter cake is white by-product sodium chloride. The filtrate is post-treated and distilled to obtain ethylene glycol dimethyl ether.

[0016] The mechanism of synthesizing ethylene glycol dimethyl ether of the present invention is as follows:

[0017] Ethylene glycol and sodium hydroxide can generate two kinds of ethylene glycol sodium salts, which can then react with chloromethane to generate ethylene glycol dimethyl ether and ethylene glycol monomethyl ether, respectively. Ethylene glycol monomethyl ether can then react with sodium hydroxide and chloromethane to generate ethylene glycol dimethyl ether. The unreacted ethylene glycol and ethylene glycol monomethyl ether can then be separated by distillation. The chemical reaction equations involved in the synthesis process are as follows:

[0018] (1)HOCH2CH2OH+3NaOH→HOCH2CH2ONa+NaOCH2CH2ONa+3H2O

[0019] (2) NaOCH2CH2ONa+2CH3Cl→CH3OCH2CH2OCH3+2NaCl

[0020] (3)HOCH2CH2ONa+CH3Cl→HOCH2CH2OCH3+NaCl

[0021] (4) HOCH2CH2OCH3+NaOH+CH3Cl→CH3OCH2CH2OCH3+NaCl+H2O.

[0022] The preparation method of the present invention adopts ethylene glycol as a reaction raw material, and has the advantages of low price and wide source compared with ethylene glycol monomethyl ether commonly used in the prior art. The present invention simplifies the traditional two-step method into a one-step method, and adds sodium hydroxide in batches, and introduces monochloromethane before adding sodium hydroxide, so that the unstable ether sodium produced by the reaction is consumed in time, which can not only promote the forward reaction, but also eliminate the raw materials for the occurrence of side reactions from the source. Therefore, compared with the existing preparation method, the present invention has the advantages of cheap and easy-to-obtain raw materials, few side reactions, and high product purity.

[0023] The inventors have found that when preparing ethylene glycol dimethyl ether from ethylene glycol, chloromethane and NaOH, at a lower reaction temperature, the main reaction rate is slow or even basically non-reactive, and at a higher reaction temperature, the reaction is intense, the temperature is difficult to control, and the by-products (such as methanol generated by chloromethane and sodium hydroxide aqueous solution at a higher temperature) increase significantly. Therefore, on this basis, considering factors such as comprehensive reaction efficiency, the present invention controls the reaction temperature at 120-140°C.

[0024] Furthermore, the reaction temperature in step (2) is 130-135°C.

[0025] Furthermore, in step (1), the amount of methyl chloride introduced is controlled to be 40%-50% of the total molar amount of ethylene glycol.

[0026] Furthermore, in step (1), the amount of methyl chloride introduced is controlled to be 40% of the total molar amount of ethylene glycol.

[0027] Furthermore, the amount of NaOH added each time in step (2) is 15%-25% of the total molar amount of ethylene glycol.

[0028] Furthermore, the amount of NaOH added each time in step (2) is 20% of the total molar amount of ethylene glycol.

[0029] Furthermore, the NaOH added in step (2) is in the form of flakes or particles.

[0030] Furthermore, the reaction solution obtained in step (3) is colorless or light yellow.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention develops a new process for preparing ethylene glycol dimethyl ether using ethylene glycol as a raw material. Ethylene glycol can be derived from biomass or coal, thereby reducing dependence on petroleum resources. The one-pot method can be used to quickly consume the intermediate sodium ether produced by the reaction, thereby effectively avoiding the occurrence of side reactions. The by-product is white sodium chloride, which can effectively reduce the amount of decolorizing agent used, thereby reducing production costs.

[0033] (2) The present invention adds sodium hydroxide to the reaction system in batches, thereby ensuring that the alkali added each time is reacted in time, and solid sedimentation and agglomeration will not occur. At the same time, the thermal runaway phenomenon caused by the violent exothermic reaction is effectively avoided, and monochloromethane can also be ensured to react with sodium ether to generate ethylene glycol dimethyl ether in a very short time, thereby reducing the occurrence of side reactions.

[0034] (3) The present invention controls the reaction temperature at 120-140° C., which can ensure that the reaction proceeds quickly and smoothly while minimizing the amount of by-product methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the gas chromatogram of the reaction solution obtained in Example 1.

[0036] Figure 2 This is the gas chromatogram of ethylene glycol dimethyl ether obtained in Example 1. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is clearly and completely described below in conjunction with specific embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect.

[0038] The raw materials used in the examples and comparative examples of the present invention are all common commercially available products.

[0039] Example 1

[0040] This embodiment discloses a one-pot method for preparing ethylene glycol dimethyl ether from ethylene glycol without catalyst, and the specific steps are as follows:

[0041] (1) Add 400 g of ethylene glycol to a reaction kettle and heat to 130° C.; introduce methyl chloride, and control the amount of methyl chloride introduced to be 40% of the total molar amount of ethylene glycol added.

[0042] (2) NaOH was added to the reaction kettle in 9 batches, and the reaction was stirred at a reaction temperature of 130°C. The amount of NaOH added each time was 20% of the total molar amount of ethylene glycol added, and the total amount of NaOH added was 180% of the total molar amount of ethylene glycol. After each addition of NaOH, samples were taken every 20 minutes for testing. When the NaOH concentration in the reaction solution was <0.05 mol / L, the next batch of NaOH was added.

[0043] (3) After the last batch of NaOH was added, samples were taken every 20 minutes for testing. When the NaOH concentration in the reaction solution was <0.05 mol / L, the reaction was completed. The total reaction time was 13.5 h.

[0044] There are a lot of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-treated and distilled to obtain 495.87g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white by-product sodium chloride, and the mass of sodium chloride after drying is 644.01g.

[0045] The specific operation of the above sampling test is: stop stirring when sampling, take 3 mL from the sampling port after 5 minutes, filter and titrate the NaOH concentration.

[0046] After the last batch of NaOH reaction was completed, a gas chromatograph (model: Shimadzu 2010PRO) equipped with a TCD detector was used to detect the components of the reaction solution and the purified ethylene glycol dimethyl ether.

[0047] The gas chromatogram of the reaction solution is shown in Figure 1 As shown, the retention time is 6.173min for ethylene glycol dimethyl ether peak, the retention time is 3.817min for water peak, the retention time is 4.006min for methanol peak, the retention time is 6.329min for ethylene glycol monomethyl ether peak, and the retention time is 8.263min for ethylene glycol peak. It can be seen from the figure that ethylene glycol dimethyl ether is the main component of the reaction liquid, and there are a small amount of unreacted ethylene glycol, intermediate ethylene glycol monomethyl ether and product water as well as trace by-product methanol in the system.

[0048] The gas chromatogram of ethylene glycol dimethyl ether is as follows Figure 2 As shown, combined Figure 1 , Figure 2 It can be seen that the purity of ethylene glycol dimethyl ether prepared in this embodiment is relatively high, reaching more than 99%.

[0049] Example 2

[0050] The difference from Example 1 is that the reaction temperature in this example is 120° C., and other parameter conditions are the same as in Example 1.

[0051] The total reaction time of the method described in this embodiment is 20.7h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is light yellow. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 487.51g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 632.74g.

[0052] Example 3

[0053] The difference from Example 1 is that the reaction temperature in this example is 140° C., and other parameter conditions are the same as in Example 1.

[0054] The total reaction time of the method described in this embodiment is 11.7h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 493.26g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 640.89g.

[0055] Example 4

[0056] The difference from Example 1 is that the reaction temperature in this example is 135° C., and other parameter conditions are the same as in Example 1.

[0057] The total reaction time of the method described in this embodiment is 12.6h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 491.69g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 638.65g.

[0058] Example 5

[0059] The difference from Example 1 is that in step (2) described in this example, the amount of NaOH added each time is 10% of the total molar amount of ethylene glycol added, and other parameter conditions are the same as in Example 1.

[0060] The total reaction time of the method described in this embodiment is 27h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 492.74g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 640.00g.

[0061] Example 6

[0062] The difference from Example 1 is that in step (2) described in this example, the amount of NaOH added each time is 30% of the total molar amount of ethylene glycol added, and other parameter conditions are the same as in Example 1.

[0063] The total reaction time of the method described in this embodiment is 9 hours. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is light yellow. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 482.81g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 628.47g.

[0064] Example 7

[0065] The difference from Example 1 is that in step (1) of this example, the amount of chloroform introduced is controlled to be 20% of the total molar amount of ethylene glycol added, and the other parameter conditions are the same as those in Example 1.

[0066] The total reaction time of the method described in this embodiment is 15 hours. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is light yellow. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 479.15g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 622.88g.

[0067] Example 8

[0068] The difference from Example 1 is that in step (1) of this example, the amount of chloroform introduced is controlled to be 30% of the total molar amount of ethylene glycol added, and other parameter conditions are the same as in Example 1.

[0069] The total reaction time of the method described in this embodiment is 14.1h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is light yellow. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 488.56g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 635.12g.

[0070] Example 9

[0071] The difference from Example 1 is that in step (1) of this example, the amount of methyl chloride introduced is controlled to be 50% of the total molar amount of ethylene glycol added, and the other parameter conditions are the same as those in Example 1.

[0072] The total reaction time of the method described in this embodiment is 13.5h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 496.92g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 644.80g.

[0073] Example 10

[0074] The difference from Example 1 is that in step (2) of this embodiment, NaOH is added to the reactor in 7 batches, and the total amount of NaOH added is 140% of the total molar amount of ethylene glycol monomethyl ether added. Other parameter conditions are the same as in Example 1.

[0075] The total reaction time of the method described in this embodiment is 10.5h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 384.86g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 499.54g.

[0076] Comparative Example 1

[0077] The difference from Example 1 is that the reaction temperature in this comparative example is 110° C., and other parameter conditions are the same as in Example 1.

[0078] The total reaction time of the method described in this comparative example is 29.3h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 485.42g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 630.3g.

[0079] Comparative Example 2

[0080] The difference from Example 1 is that the reaction temperature in this comparative example is 150° C., and other parameter conditions are the same as in Example 1.

[0081] The total reaction time of the method described in this comparative example is 10 hours. There are a large number of yellow sodium chloride crystals in the reaction system, and the reaction solution is bright yellow. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 476.54g of ethylene glycol dimethyl ether; the residual solid and the filter cake are yellow byproduct sodium chloride, and the mass of sodium chloride after drying is 621.99g.

[0082] Comparative Example 3

[0083] The difference from Example 1 is that in step (1) of this comparative example, the amount of methyl chloride introduced is controlled to be 18% of the total molar amount of ethylene glycol, and other parameter conditions are the same as those in Example 1.

[0084] The total reaction time of the method described in this comparative example is 15h. After the first batch of NaOH is added, light yellow sodium chloride crystals are precipitated after stirring for 20min. As the reaction proceeds, the color of the system gradually changes to dark yellow. A large amount of solids are precipitated in the reaction system. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 601.79g of ethylene glycol dimethyl ether; the residual solid and the filter cake are yellow-brown byproduct sodium chloride, and the mass of sodium chloride after drying is 600.42g.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that in step (2) described in this example, the amount of NaOH added each time is 8% of the total molar amount of ethylene glycol added, and other parameter conditions are the same as in Example 1.

[0087] The total reaction time of the method described in this comparative example is 28h. There are a large number of white sodium chloride crystals in the reaction system, and the reaction solution is colorless. The obtained reaction solution is filtered, and the filtrate is post-treated and distilled to obtain 500.57 g of ethylene glycol dimethyl ether; the residual solid and the filter cake are white byproduct sodium chloride, and the mass of sodium chloride after drying is 649.87g.

[0088] Comparative Example 5

[0089] The difference from Example 1 is that in step (2) described in this example, the amount of NaOH added each time is 50% of the total molar amount of ethylene glycol added, and other parameter conditions are the same as in Example 1.

[0090] The total reaction time of the method described in this comparative example is 9h. After the first batch of NaOH is added, the system quickly changes from colorless to reddish brown, and a temperature rise phenomenon occurs in the violent reaction. After the reaction is completed, there are a large number of sodium chloride crystals in the system, and the reaction solution is reddish brown. The obtained reaction solution is filtered, and the filtrate is post-processed and distilled to obtain 434.21g of ethylene glycol dimethyl ether; the residual solid and the filter cake are reddish brown byproduct sodium chloride, and the mass of sodium chloride after drying is 566.18g.

[0091] The yield of ethylene glycol dimethyl ether obtained by the methods described in the examples and comparative examples, the color of the reaction solution, the color of the byproduct sodium chloride, and the total reaction time are shown in Table 1.

[0092] Table 1

[0093]

[0094] It can be seen from Examples 1 to 10 in Table 1 that the preparation method of the present invention is used to prepare ethylene glycol dimethyl ether, which has the advantages of easy availability of raw materials, few side reactions, and high product yield, and the by-products are all high-quality sodium chloride.

[0095] From the comparison of Comparative Examples 1-2 with Example 1 in Table 1, it can be seen that when the reaction temperature is low, the main reaction rate is slow, the total reaction time is long, and the production efficiency is low. When the reaction temperature is high, the reaction is too intense, and a large amount of by-products other than sodium chloride, such as methanol, are produced, resulting in coloring of the reaction solution and sodium chloride.

[0096] From the comparison between Comparative Example 3 and Example 1 in Table 1, it can be seen that when the amount of methyl chloride introduced is too small, the reaction time is slightly increased, and the insufficient gas volume leads to an increase in by-products, which in turn leads to more obvious coloration of the reaction solution and sodium chloride.

[0097] From the comparison of Comparative Examples 4 to 5 with Example 1 in Table 1, it can be seen that when too little sodium hydroxide is added each time, the production efficiency is low; when too much sodium hydroxide is added each time, the reaction will be violently exothermic, thermal runaway will occur, and a large amount of by-products other than sodium chloride, such as methanol, will be produced, resulting in coloration of the reaction solution and sodium chloride, and the yield of the product will also be greatly affected.

Claims

1. A one-pot method for preparing ethylene glycol dimethyl ether from ethylene glycol without catalyst, characterized in that: The steps include: (1) Add ethylene glycol to a reaction kettle, heat to 120-140° C., and introduce methyl chloride, wherein the amount of methyl chloride introduced is controlled to be 20%-50% of the total molar amount of ethylene glycol; (2) adding NaOH in batches to the reaction kettle, stirring and reacting at a reaction temperature of 120-140° C.; The amount of NaOH added each time is 10-30% of the total molar amount of ethylene glycol, and the total amount of NaOH added is 140-180% of the total molar amount of ethylene glycol; After each addition of NaOH, take samples for testing every 20-25 minutes. When the NaOH concentration in the reaction solution is <0.05 mol / L, add the next batch of NaOH. (3) After the last batch of NaOH is added, sampling is performed every 20-25 minutes. When the concentration of NaOH in the reaction solution is less than 0.05 mol / L, the reaction is completed, and the filtrate is filtered. The filtrate is post-treated and distilled to obtain ethylene glycol dimethyl ether; The NaOH added in step (2) is in the form of flakes or particles.

2. The method for preparing ethylene glycol dimethyl ether according to claim 1, characterized in that: The reaction temperature in step (2) is 130-135°C.

3. The method for preparing ethylene glycol dimethyl ether according to claim 1, characterized in that: In the step (1), the amount of methyl chloride introduced is controlled to be 40-50% of the total molar amount of ethylene glycol.

4. The method for preparing ethylene glycol dimethyl ether according to claim 3, characterized in that: In the step (1), the amount of methyl chloride introduced is controlled to be 40% of the total molar amount of ethylene glycol.

5. The method for preparing ethylene glycol dimethyl ether according to claim 1, characterized in that: In the step (2), the amount of NaOH added each time is 15%-25% of the total molar amount of ethylene glycol.

6. The method for preparing ethylene glycol dimethyl ether according to claim 5, characterized in that: The amount of NaOH added each time in step (2) is 20% of the total molar amount of ethylene glycol.

7. The method for preparing ethylene glycol dimethyl ether according to claim 1, characterized in that: The reaction solution obtained in step (3) is colorless or light yellow.

Images