A one-step continuous synthesis method for ethylene glycol diethyl ether

Abstract

This invention relates to the field of organic compound synthesis technology, specifically providing a one-step continuous synthesis method for ethylene glycol diethyl ether. The invention uses ethylene glycol, sodium hydroxide, and ethane chloride as raw materials, precisely controlling the reaction conditions. The resulting liquid mixture is filtered, and the collected solution is continuously collected and recycled back to the reactor until the selectivity for ethylene glycol diethyl ether in the collected solution reaches a preset target. The recycling process is then stopped, and the collected solution is output as ethylene glycol diethyl ether. This invention enables the two-step etherification reaction of ethylene glycol to proceed continuously in the same reaction system, eliminating the need to separate intermediate products, reducing production energy consumption and costs, and improving product yield and purity.

Description

Technical Field

[0001] This invention relates to the field of organic compound synthesis technology, and specifically to a one-step continuous synthesis method for ethylene glycol diethyl ether. Background Technology

[0002] Ethylene glycol diethyl ether (1,2-diethoxyethane, CAS 629-14-1) is an important polar aprotic solvent with a wide range of applications. Its core applications include: 1) as a highly efficient solvent for dissolving and diluting nitrocellulose, synthetic rubber, and various resins (such as epoxy resins and polyvinyl chloride resins), improving system compatibility and flowability; 2) as a reaction medium in organic synthesis, suitable for various organic synthesis processes such as the Grignard reaction and Wittig reaction, improving reaction selectivity and promoting smooth reaction progress; 3) as an extraction agent in the pharmaceutical industry for the extraction of active ingredients from natural products and the purification of drug intermediates; 4) as a lubricant additive, improving the low-temperature flowability and antioxidant properties of lubricants. It can also be used as a solvent in coatings and inks, and as an auxiliary solvent in battery electrolytes.

[0003] Currently, the industrial production of ethylene glycol diethyl ether mainly uses the Wiliamson synthesis method. This method uses ethylene glycol monoethyl ether (CH2CH2OCH2CH2OH), sodium hydroxide (NaOH), and ethane chloride (CH3CH2Cl) as raw materials, reacting them under the action of a phase transfer catalyst. Sodium chloride (NaCl) is a byproduct. Further distillation and purification yield the ethylene glycol diethyl ether product. This method is a two-step reaction. During the reaction, the reaction between monoethyl ether and sodium hydroxide produces an intermediate, sodium ether. If not converted in time, sodium ether may transform into other byproducts, affecting the conversion rate of ethylene glycol monoethyl ether. Furthermore, the sodium chloride byproduct produced in this method is reddish-brown in color and requires subsequent decolorization treatment, increasing costs.

[0004] CN1081176A describes a method for preparing ethylene glycol ethyl ether (or similar products) via the ethoxylation reaction of ethanol and ethylene oxide. This method employs a semi-continuous tank reactor, operates under high temperature and pressure conditions without a catalyst, and controls the product composition by adjusting the reaction flow rate. Strict control of the reaction ratios is required, and ethylene oxide is a flammable, explosive, and toxic substance, necessitating extremely high standards for equipment sealing and safety protection.

[0005] CN103641695A uses ethylene glycol as a raw material. By adding a catalyst to the reaction system, ethylene glycol ethyl ether and ethylene glycol diethyl ether are produced. The reaction requires high pressure, and the catalyst still needs to be recovered during the reaction process.

[0006] Therefore, developing a continuous one-step process for the preparation of ethylene glycol diethyl ether with mild reaction conditions, no catalyst required, easily manageable byproducts, and high conversion rate is of great practical significance and industrial application value for overcoming existing technological bottlenecks and reducing industrial production costs. Summary of the Invention

[0007] This invention provides a one-step method for preparing ethylene glycol diethyl ether. Using ethylene glycol, sodium hydroxide, and ethane chloride as raw materials, and under catalyst-free conditions, the two-step etherification reaction of ethylene glycol is carried out continuously in the same reaction system by precisely controlling the reaction conditions. There is no need to separate intermediate products, which reduces production energy consumption and cost, and improves product yield and purity.

[0008] To achieve the above-mentioned technical effects, the present invention adopts the following technical solution: A one-step continuous synthesis method for ethylene glycol diethyl ether includes the following steps: first, chloroethane is introduced into a reaction vessel, followed by the continuous addition of ethylene glycol and sodium hydroxide. The resulting mixture is filtered and then enters a buffer tank. The extract is continuously collected from the buffer tank and recycled back to the reaction vessel until the selectivity of ethylene glycol diethyl ether in the extract reaches a preset value. The recycling is then stopped, and the extract is output to obtain ethylene glycol diethyl ether.

[0009] The preset target is that the selectivity of ethylene glycol diethyl ether reaches 80%.

[0010] The reaction equation involved in this invention is as follows: (1)HOCH2CH2OH+NaOH→HOCH2CH2ONa+H2O; (2)HOCH2CH2ONa+CH3CH2Cl→HOCH2CH2OCH2CH3+NaCl; (3)HOCH2CH2OCH2CH3+NaOH→CH3CH2OCH2CH2ONa+H2O; (4)CH3CH2OCH2CH2ONa+CH3CH2Cl→CH3CH2OCH2CH2OCH2CH3+NaCl.

[0011] The one-step continuous synthesis method for ethylene glycol diethyl ether specifically includes the following steps: a. Introduce nitrogen gas into the reactor to perform gas replacement, so that the reactor is in a nitrogen protective atmosphere; b. Start the reactor heating system to heat up the reactor. After reaching the reaction temperature, continuously introduce chloroethane through the chloroethane inlet device and adjust the inlet flow rate. c. Start the ethylene glycol feed pump and continuously feed ethylene glycol into the reactor through the buffer tank; at the same time, turn on the sodium hydroxide solid feeder and control the amount of sodium hydroxide fed by adjusting the solid feed frequency to ensure that the molar ratio of ethylene glycol to sodium hydroxide is fixed. d. After the reaction system has reached the cycle residence time, the mixed liquid after the reaction is continuously discharged from the reactor and enters the filter to remove the by-product sodium chloride solid; the filtered filtrate enters the buffer tank and is pumped back into the reactor through the outlet pump of the buffer tank for circulation reaction. e. Once the selectivity of ethylene glycol diethyl ether in the produced fluid reaches the preset target, the circulation is stopped, and the produced fluid is continuously extracted from the outlet of the buffer tank to obtain the product ethylene glycol diethyl ether.

[0012] Preferably, the temperature, pressure, feed flow rate, and circulation flow rate inside the reactor are continuously monitored and kept stable during the reaction process.

[0013] Specifically, step a is to first start the vacuum pump to evacuate the entire reaction system to a vacuum level ≥0.08MPa, then turn off the vacuum pump and introduce nitrogen gas for replacement. Repeat the replacement 2 to 3 times to ensure that there is no air residue in the reaction system.

[0014] Preferably, in step b, the reaction temperature is 150~170℃, and more preferably, the reaction temperature is 160℃.

[0015] Preferably, in step b, chloroethane is introduced to maintain the pressure inside the reactor at 2-4 bar to ensure that chloroethane can participate in the reaction in gaseous form. More preferably, the reaction pressure is 3 bar.

[0016] Preferably, in step c, the flow rate of the ethylene glycol feed pump is 90~120mL / min, and more preferably, the flow rate of the feed pump is 100mL / min.

[0017] Preferably, in step c, the molar ratio of ethylene glycol to sodium hydroxide is maintained at 1:(0.2~0.5), and more preferably, the molar ratio of ethylene glycol to sodium hydroxide is 1:0.4.

[0018] Preferably, in step d, the circulation residence time refers to the average residence time of the reactants in a single cycle in the reactor, which is obtained by dividing the effective volume of the reactor by the circulation flow rate; the circulation residence time is 10~20min, and more preferably, the circulation residence time is 15min. If the time is too short, sodium hydroxide will not participate in the reaction in time and will be filtered out in the filter, increasing the cost of raw materials.

[0019] Preferably, in step d, the filter temperature is set to 10~30℃, and more preferably, the filter temperature is set to 20℃ to ensure that sodium chloride and unreacted sodium hydroxide can precipitate in the filter; Preferably, in step d, the temperature of the buffer tank is set to 30~50℃, and more preferably, the temperature of the buffer tank is set to 40℃.

[0020] Preferably, in step d, the circulation flow rate is 90~110mL / min.

[0021] More preferably, the cyclic reaction time is 7-9 hours, preferably 8 hours.

[0022] Compared with existing methods, the advantages of this invention are as follows: 1. This invention employs a continuous production method for ethylene glycol diethyl ether, using ethylene glycol, sodium hydroxide, and ethane chloride as raw materials. Compared to preparing ethylene glycol diethyl ether from ethylene glycol monoethyl ether, this method offers significant cost advantages. The continuous production of ethylene glycol diethyl ether is achieved through liquid circulation within the system.

[0023] 2. The reaction of this invention does not require the addition of a catalyst, and the entire system is a closed system. By controlling the solid feed rate, sodium hydroxide can react in a timely manner, which greatly reduces the loss of raw materials. The by-product sodium chloride is removed by filtering. There is no need to separate intermediate products during the reaction process. The reaction conditions are mild and the conversion rate of ethylene glycol is high. Attached Figure Description

[0024] Figure 1 This is the verification spectrum of ethylene glycol diethyl ether synthesized in Example 1; Figure 2 The continuous process production apparatus in Example 1. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] The raw materials used in each embodiment and comparative example are all commercially available raw materials commonly used in the art. The specific sources will not be described here. Those skilled in the art can select them according to their implementation needs.

[0027] In all embodiments and comparative examples, the entire system must be purged before the reaction to ensure that no air remains in the reaction system. First, start the vacuum device to evacuate the entire reaction system to a vacuum degree ≥0.08MPa, then turn off the vacuum device and introduce nitrogen gas for purging. Repeat the purging 2-3 times.

[0028] Example 1 First, the reactor heating system is started to raise the reactor temperature to 160°C. Then, chloroethane is continuously introduced through the chloroethane inlet device, and the inlet flow rate is adjusted to maintain a stable pressure of 3 bar inside the reactor. The ethylene glycol feed pump is started, continuously feeding ethylene glycol into the reactor through the buffer tank at a feed rate of 100 mL / min. Simultaneously, the sodium hydroxide solid feeder is turned on, controlling the feed rate to 40% of the molar amount of ethylene glycol (28.72 g / min). The feed frequency is calibrated by weighing. After the reaction system has reached a circulation residence time of 15 minutes, the mixed liquid after the reaction is continuously discharged from the reactor into a filter (circulation flow rate of 100 mL / min). The filter jacket temperature is controlled at 20°C to filter out the byproduct sodium chloride solid and unreacted sodium hydroxide. The filtered filtrate enters the buffer tank, which is maintained at 40°C by a constant temperature water bath device, and then pumped back to the reactor for recirculation. After 8 hours of recirculation, the collected liquid is continuously collected from the buffer tank outlet to obtain the product ethylene glycol diethyl ether.

[0029] During the continuous reaction for 9 hours, samples were taken from the outlet of the buffer tank every hour, for a total of 9 times. The mass fraction of each component was analyzed by gas chromatography (e.g., Figure 1 The following table shows the gas chromatogram of the sample taken at 8 hours.

[0030] Table 1. Mass fraction of each component in Example 1

[0031] In the initial stage of the reaction (1-4 hours), ethylene glycol is rapidly consumed, and the concentration of ethylene glycol monoethyl ether, as an intermediate, rises to a peak (40%). After 4 hours, ethylene glycol monoethyl ether continues to be converted into the target product, ethylene glycol diethyl ether. By 8 hours, the raw material ethylene glycol is almost completely consumed, with a very low residual amount, and the content of the target product tends to stabilize. If the reaction time is shortened, the intermediate conversion is incomplete, resulting in insufficient yield of the target product; if the reaction time is extended, the product content does not increase, but instead increases production energy consumption and reduces production efficiency. Considering factors such as raw material conversion rate, product yield, product purity, and industrial production cost, 8 hours was ultimately determined to be the optimal reaction time for the system in this embodiment. At 8 hours, the content of ethylene glycol diethyl ether stabilizes at 65%, the residual ethylene glycol is only 0.417%, the ethylene glycol conversion rate is 99.58%, and the selectivity of ethylene glycol diethyl ether is 82.89%.

[0032] Example 2 The reaction temperature was controlled at 170℃, and the pressure inside the reactor was maintained at 4 bar. The ethylene glycol feed rate was 120 mL / min, and the sodium hydroxide feed amount was 50% of the molar amount of ethylene glycol (43.08 g / min). The filter temperature was 20℃, and the buffer tank temperature was 30℃. The remaining steps were the same as in Example 1. The reaction was carried out continuously for 8 hours, and samples were taken from the outlet of the buffer tank every 1 hour for a total of 8 times. The mass fraction of each component was analyzed by gas chromatography, and the results are shown in the table below.

[0033] Table 2. Mass fraction of each component in Example 2

[0034] The reaction rate is accelerated under high temperature and high pressure, reaching the peak value of ethylene glycol monoethyl ether (42.5%) in 3 hours. After 8 hours, the residual ethylene glycol is 0.38%, the content of ethylene glycol diethyl ether is 68%, and the conversion rate of ethylene glycol is 99.62%, with a selectivity of 83.56% for ethylene glycol diethyl ether. However, under high temperature and high pressure, the color of the reaction solution is darker than that in Example 1, changing from light yellow to reddish brown, and the color of the by-product sodium chloride is also darker, increasing the post-processing cost.

[0035] Comparative Example 1 Ethylene glycol diethyl ether was prepared by a two-step method, using ethylene glycol monoethyl ether, sodium hydroxide, and ethane chloride as raw materials under catalyst-free conditions.

[0036] The traditional intermittent two-step process is adopted: Step 1: Add 600g of ethylene glycol monoethyl ether to the reactor, and add sodium hydroxide in two batches, with each batch being 50% of the total molar amount of ethylene glycol monoethyl ether. The reaction temperature is 160℃ and the reaction time is 3h. The product color gradually turns reddish-brown. Step 2: After the reaction is complete, chloroethane is introduced into the system to maintain the reaction pressure at 3 bar. Samples are taken and tested every 1 hour. The reaction time is 6 hours.

[0037] After the reaction, the reaction solution was a reddish-brown liquid, and the byproduct sodium chloride was reddish in color. Gas chromatography analysis of the reaction solution showed a 65% conversion rate of ethylene glycol monoethyl ether and a 79% selectivity for ethylene glycol diethyl ether. The reaction cycle was longer under catalyst-free conditions, and the raw material cost increased compared to Example 1.

[0038] Comparative Example 2 Ethylene glycol diethyl ether was prepared in one step using ethylene glycol, sodium hydroxide, and ethane chloride as raw materials under catalyst-free conditions.

[0039] A batch one-step method was used to prepare ethylene glycol diethyl ether. 600g of ethylene glycol was added to a reactor, followed by the introduction of ethane chloride. The reaction pressure was maintained at 3 bar. The first batch of sodium hydroxide (40% of the total molar amount of ethylene glycol) was added. After 1 hour of reaction, the reactor was cooled, and sodium chloride was filtered out. The filtrate was collected. The filtrate was returned to the reactor, and the temperature was raised again, with ethane chloride introduced to maintain the pressure at 3 bar. The second batch of sodium hydroxide (40% of the total molar amount of ethylene glycol) was added, and this process was repeated three times (i.e., sodium hydroxide was added in five batches). During the reaction, it was observed that the reaction time gradually increased with each batch, from only 1 hour for the first batch to 3 hours, with a total reaction time of 10 hours. Gas chromatography analysis of the final reaction solution showed an ethylene glycol conversion rate of 91.2% and a diethyl ether selectivity of 57.08%, indicating that a significant amount of ethylene glycol monoethyl ether remained unconverted. Because a large amount of sodium hydroxide is produced as a byproduct during the reaction, the reaction requires multiple cooling, filtration, and refeeding processes, which is cumbersome and results in significant material loss during material transfer.

[0040] Comparative Example 3 This comparative example uses the synthesis apparatus of patent CN120423938A. The specific preparation steps are as follows: start the heating system of each stage of liquid film reactor, set the temperature of the integrated heating and cooling unit to 160℃, pump ethylene glycol into liquid film reactor A at a feed rate of 100mL / min, and simultaneously turn on sodium hydroxide feeder A and chloroethane storage tank A (that is, use the monochloromethane storage tank A in patent CN120423938A to store chloroethane, and the same applies to the chloroethane storage tank below), continuously introduce chloroethane, and then maintain the reaction pressure at 3 bar by adjusting the gas flow rate. The sodium hydroxide feed rate was controlled at 50% of the total ethylene glycol feed rate (by molar amount). After reacting for 20 minutes in liquid membrane reactor A, the reaction liquid entered filter A. The clarified liquid was pumped into liquid membrane reactor B via a metering pump. The sodium hydroxide feeder B and ethane storage tank B were adjusted so that the sodium hydroxide feed rate was 50% of the total ethylene glycol feed rate (by molar amount). The reaction pressure remained constant. After reacting for 20 minutes, the solution entered filter B. After filtering out sodium chloride, the solution entered liquid membrane reactor C for further reaction. The liquid after reacting in liquid membrane reactor C was filtered and then entered liquid membrane reactor D for further reaction (the reaction conditions and feed rates in liquid membrane reactors B, C, and D were the same as in liquid membrane reactor A). The final filtered reaction solution was analyzed, and the ethylene glycol conversion rate was 76.19%, and the selectivity for ethylene glycol diethyl ether was 36.65%. In this comparative example, the conversion rate of ethylene glycol obtained using a non-recycled continuous process was only 76.19%, far lower than that of Example 1 (99.58%). This is because chloroethane has a longer carbon chain and greater steric hindrance, making it highly susceptible to E2 elimination reactions in strongly alkaline and high-temperature reaction systems. This results in the removal of a large amount of hydrogen chloride to generate gaseous ethylene as a byproduct, rather than the target nucleophilic substitution reaction, directly causing a large loss of raw materials. At the same time, diethyl substitution is much more difficult than dimethyl substitution. Under a non-recycled continuous process, the intermediate cannot continue to react deeply and remains largely in the reaction system, ultimately leading to an extremely low single-pass conversion rate of the target product, making efficient synthesis impossible.

[0041] As can be seen from the comparison of the above examples and comparative examples, the present invention adopts a continuous recycling process to prepare ethylene glycol diethyl ether from ethylene glycol, sodium hydroxide, and ethane chloride, which has significant advantages over the prior art: the ethylene glycol conversion rate can reach 99.58% (Example 1), which is much higher than that of the batch process (Comparative Example 2, 91.2%) and the non-recycling continuous process (Comparative Example 3, 76.19%); compared with the route using ethylene glycol monoethyl ether as the starting material, it effectively reduces the raw material cost, and no external catalyst is required throughout the process, eliminating the intermediate product distillation and separation process. At the same time, the product of this method has excellent selectivity, low impurity content, and the by-products are easy to recover and reuse, making it highly feasible for industrial implementation and possessing good economic and application value.

Claims

1. A one-step continuous synthesis method for ethylene glycol diethyl ether, characterized in that, The process includes the following steps: First, chloroethane is introduced into the reactor, followed by the continuous addition of ethylene glycol and sodium hydroxide. The resulting mixture is filtered and then enters a buffer tank. The extract is continuously collected from the buffer tank and circulated back to the reactor until the selectivity of ethylene glycol diethyl ether in the extract reaches the preset target. The circulation is then stopped, and the extract is output to obtain ethylene glycol diethyl ether.

2. The method according to claim 1, characterized in that, Specifically, the steps include the following: a. Introduce nitrogen gas into the reactor to perform gas replacement, so that the reactor is in a nitrogen protective atmosphere; b. Start the reactor heating system to heat the reactor until it reaches the reaction temperature, then continuously introduce chloroethane. c. Start the ethylene glycol feed pump and continuously feed ethylene glycol into the reactor through the buffer pipe; at the same time, turn on the sodium hydroxide solid feeder and control the amount of sodium hydroxide fed to ensure that the molar ratio of ethylene glycol to sodium hydroxide is fixed. d. After the reaction system has reached the cycle residence time, the mixed liquid after the reaction is continuously discharged from the reactor and enters the filter to remove the by-product sodium chloride solid; the filtered filtrate enters the buffer tank and is pumped back into the reactor through the outlet pump of the buffer tank for circulation reaction. e. Once the selectivity of ethylene glycol diethyl ether in the produced fluid reaches the preset target, the circulation is stopped, and the produced fluid is continuously extracted from the outlet of the buffer tank. After distillation, the product ethylene glycol diethyl ether is obtained.

3. The method according to claim 1, characterized in that, The preset target is that the selectivity of ethylene glycol diethyl ether reaches 80%.

4. The method according to claim 2, characterized in that, Step a is to first start the vacuum pump to evacuate the entire reaction system to a vacuum level ≥0.08MPa, then turn off the vacuum pump and introduce nitrogen gas for replacement. Repeat the replacement 2 to 3 times.

5. The method according to claim 2, characterized in that, In step b, the reaction temperature is 150~170℃; In step b, chloroethane is introduced to maintain a pressure of 2-4 bar inside the reactor.

6. The method according to claim 2, characterized in that, In step c, the flow rate of the ethylene glycol feed pump is 90~120mL / min; In step c, the molar ratio of ethylene glycol to sodium hydroxide is maintained at 1:(0.2~0.5).

7. The method according to claim 2, characterized in that, In step d, the cycle dwell time is 10~20 minutes.

8. The method according to claim 2, characterized in that, In step d, the filter temperature is set to 10~30℃; In step d, the temperature of the buffer tank is set to 30~50℃.

9. The method according to claim 2, characterized in that, In step d, the circulation flow rate is 90~110 mL / min.

10. The method according to claim 3, characterized in that, The cyclic reaction time is 7-9 hours.

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