Preparation method of high-purity eugenol glycidyl ether

Abstract

The invention discloses a preparation method of high-purity eugenol glycidyl ether, which comprises the following steps: step 1, uniformly mixing eugenol, epoxy chloropropane and a phase transfer catalyst, carrying out etherification reaction, and recovering excessive epoxy chloropropane through reduced pressure distillation after the reaction; step 2, adding a sodium hydroxide aqueous solution into the reactor, carrying out ring-closure reaction to obtain a crude product, and washing with water to obtain high-purity eugenol glycidyl ether; the concentration of the sodium hydroxide aqueous solution is 45-60wt%. The method disclosed by the invention is simple, the yield of the eugenol glycidyl ether can be remarkably improved only by simply optimizing the original two-step process without a complicated post-treatment process, the purity is improved from 90% to 97% or above, and the emission of three wastes is remarkably reduced.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for preparing high-purity eugenol glycidyl ether. Background Art

[0002] Eugenol glycidyl ether is an epoxide synthesized from bio-based raw materials. It is mainly produced by the reaction of eugenol and epichlorohydrin. Eugenol is a natural phenolic compound that is widely found in essential oils of plants such as cloves and cinnamon. Its molecules contain functionalized allyl bonds, which is conducive to its further processing and utilization.

[0003] Eugenol glycidyl ether has a variety of uses, mainly as an intermediate in chemical reactions and a modifier for epoxy resins. It can introduce specific properties to epoxy resins, such as improving the flexibility of the resin, reducing its hardness and increasing its thermal stability. In addition, due to its natural origin and low toxicity, eugenol glycidyl ether also has potential applications in some biomedical and food packaging materials.

[0004] At present, the method for synthesizing eugenol glycidyl ether by epichlorohydrin reported in the literature is mainly divided into a one-step method and a two-step method. The one-step method is to mix eugenol and epichlorohydrin at one time, directly add sodium hydroxide, and perform ring-opening reaction and ring-closing reaction at the same time. The two-step method is to first allow eugenol and epichlorohydrin to undergo a ring-opening reaction, and then add sodium hydroxide for a ring-closing reaction. Among them, although the reaction system of the one-step method is simple, the reaction conditions are not easy to control, and more by-products may be produced, resulting in a lower purity of eugenol glycidyl ether. The product obtained by the two-step method has a higher purity, but due to process problems, some impurities are still difficult to purify, which will affect subsequent processing and utilization.

[0005] For example, a Chinese patent document with application publication number CN107445921A discloses a preparation method, product and application of high-purity eugenol glycidyl ether. The preparation method comprises the following steps: mixing epichlorohydrin, eugenol and benzyltriethylammonium chloride, performing a ring-opening reaction, adding an aqueous sodium hydroxide solution, and performing a ring-closing reaction to obtain a crude product; the crude product is subjected to reduced pressure distillation and then subjected to low-temperature recrystallization to obtain eugenol epoxy; the low-temperature recrystallization treatment comprises the following steps: mixing the liquid obtained by reduced pressure distillation with an organic solvent, reducing the temperature to -20 to -0°C, and filtering to obtain purified eugenol epoxy.

[0006] The preparation method is to perform a series of vacuum distillation and low temperature recrystallization after treatment after the two-step reaction is completed to obtain a crude product. The post-treatment process is relatively complicated and cumbersome, and the post-treatment process required is relatively long, which is not conducive to meeting the subsequent rapid production needs and industrial device production. At the same time, since the recovery of excess epichlorohydrin is carried out after the reaction is completed, water can attack the chlorine atoms of epichlorohydrin as a nucleophilic agent under alkaline conditions in the second step, and a nucleophilic substitution reaction occurs to generate glycidol, which affects the purity of the recovered epichlorohydrin, and is also not conducive to repeated use in industrial production. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention discloses a method for preparing high-purity eugenol glycidyl ether. The method is simple and only requires simple optimization on the original two-step process. Without the need for complex post-treatment processes, the yield of eugenol glycidyl ether can be significantly improved, and the purity can be increased from 90% to 97% or above, and the discharge of three wastes can be significantly reduced.

[0008] The specific technical solutions are as follows:

[0009] A method for preparing high-purity eugenol glycidyl ether comprises the following steps:

[0010] Step 1, mixing eugenol, epichlorohydrin and a phase transfer catalyst uniformly and performing an etherification reaction, and recovering excess epichlorohydrin by vacuum distillation after the reaction;

[0011] Step 2, adding a sodium hydroxide aqueous solution into a reactor, obtaining a crude product through a ring-closing reaction, and washing with water to obtain high-purity eugenol glycidyl ether;

[0012] The concentration of the sodium hydroxide aqueous solution is 45-60 wt %.

[0013] The preparation method disclosed in the present invention is a simple optimization of the original two-step process. After the etherification reaction in step 1, the excess epichlorohydrin is first recovered by vacuum distillation, and a high-concentration sodium hydroxide aqueous solution (concentration of 45-60wt%) is added in the closed-loop reaction in step 2. High-purity and high-yield eugenol glycidyl ether can be prepared by simple water washing. Through further characterization, it is found that when the process of first recovering excess epichlorohydrin by vacuum distillation is adopted, a new substance 1,3-dichloropropanol is unexpectedly generated. The appearance of this substance also contributes to the conversion of eugenol in the second step reaction. Combined with the high-concentration sodium hydroxide aqueous solution, the technical effect of significantly improving the purity and yield of eugenol glycidyl ether is finally achieved.

[0014] Comparative tests have shown that if the high-concentration sodium hydroxide aqueous solution in step 2 is replaced with a low-concentration (20-40 wt%) sodium hydroxide aqueous solution, the yield and purity of the target product will be significantly reduced.

[0015] Comparative tests also found that if the excess epichlorohydrin is not recovered in step 1, the target product with high yield and high purity cannot be obtained regardless of whether a high concentration or a low concentration of sodium hydroxide aqueous solution is used in step 2; the purity and yield of the recovered epichlorohydrin are also low.

[0016] The structural formula of the eugenol glycidyl ether is shown in the following formula (I):

[0017]

[0018] In step 1:

[0019] Preferably, the phase transfer catalyst is selected from quaternary ammonium salt phase transfer catalysts; specifically, one or more selected from benzyltriethylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium chloride.

[0020] Preferably, based on the mass of eugenol, the phase transfer catalyst accounts for 0.3-2.0wt%; specifically, it can be selected from 0.3wt%, 0.4wt%, 0.5wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.5wt%, 1.8wt%, 2.0wt% or any value within the above range;

[0021] More preferably, the proportion of the phase transfer catalyst is 0.5 to 1.0%.

[0022] Preferably, the molar ratio of eugenol to epichlorohydrin is 1:(4-8), which can be specifically selected from 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8 or any ratio within the above range;

[0023] More preferably, the molar ratio of eugenol to epichlorohydrin is 1:(4.5-6.0).

[0024] In step 1:

[0025] Preferably, the etherification reaction temperature is 60-110°C, specifically can be selected from 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C or any value within the above range;

[0026] A further preferred etherification reaction temperature is 70 to 80°C.

[0027] Preferably, the etherification reaction time is 1 to 5 hours; specifically, it can be selected from 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or any value within the above range; the specific time can be adaptively adjusted according to the temperature of the etherification reaction.

[0028] In the vacuum distillation, the fraction with a temperature of 70 to 90° C. is collected, and the recovered epichlorohydrin can be recycled and used for etherification reaction.

[0029] In step 2:

[0030] Preferably, the molar ratio of eugenol to NaOH is 1:(1.0-1.1); specifically, it can be selected from 1:1.0, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.1 or any ratio within the above range.

[0031] Preferably, the ring-closing reaction is carried out at a temperature of 50-70°C, specifically 50°C, 55°C, 60°C, 65°C, 70°C or any value within the above range.

[0032] Preferably, the ring-closing reaction time is 3 to 6 hours; specifically, it can be selected from 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours or any value within the above range; the specific time can be adaptively adjusted according to the temperature of the ring-closing reaction.

[0033] Preferably, during the closed-loop reaction, a pressure reducing device is opened to drain water to ensure that the concentration of the sodium hydroxide aqueous solution is stable during the reaction.

[0034] Preferably, the water washing is performed using a saturated NaCl aqueous solution, and after washing, water is removed to obtain high-purity eugenol glycidyl ether.

[0035] Preferably, after washing, the product is dehydrated under reduced pressure at 100°C.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The invention discloses a method for preparing high-purity eugenol glycidyl ether. The method is simple and only requires simple optimization on the original two-step process. After the etherification reaction in step 1, excess epichlorohydrin is firstly recovered by reduced pressure distillation, and a high-concentration sodium hydroxide aqueous solution is added in the closed-loop reaction in step 2, and finally the method is simply washed with water; no complicated and lengthy post-treatment process is required, and the discharge of three wastes is significantly reduced.

[0038] The eugenol glycidyl ether prepared by the present invention has high purity and high yield, the purity can reach 97% or above, and can reach 99% at the highest; the yield is not less than 92%, and can reach 95% at the highest; and the recovered epichlorohydrin also has a yield of up to 98% and a purity of 99%, and the above data are far higher than the existing technical level. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention discloses a process flow chart of the method for preparing high-purity eugenol glycidyl ether;

[0040] Figure 2 This is a gas chromatography-mass spectrometry diagram of the two-step product of eugenol glycidyl ether prepared in Example 1;

[0041] Figure 3 This is a gas chromatography-mass spectrometry diagram of the two-step product of eugenol glycidyl ether prepared in Comparative Example 1. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0043] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0044] Example 1

[0045] 20 kg of eugenol (121.9 mol), 60 kg of epichlorohydrin (648.6 mol) and 0.1 kg of tetrabutylammonium bromide were put into a reaction kettle. After replacing the atmosphere in the kettle with nitrogen, the temperature was raised to 70 ° C for reaction for 2 hours. Then, the pressure reducing device was opened to recover the excess epichlorohydrin, and the fraction at 70 ° C was collected. The first step of the reaction was completed after there was no distillate.

[0046] The temperature was lowered to 55°C, and 10.4 kg of 50 wt% NaOH aqueous solution was continuously added to the kettle. The vacuum distillation apparatus was opened to allow water to flow out slowly. The reaction was stopped after 4 hours of reaction to complete the second step of reaction.

[0047] The aqueous phase was discharged through the discharge port, and a saturated NaCl solution was added to wash the organic phase twice. The organic phase was retained in the kettle, heated to 100°C, and the decompression device was turned on to remove water for 1 hour to obtain a light yellow clear liquid eugenol glycidyl ether.

[0048] Comparative Example 1

[0049] 20 kg of eugenol, 60 kg of epichlorohydrin and 0.1 kg of tetrabutylammonium bromide were added into the reaction kettle. After replacing the atmosphere in the kettle with nitrogen, the temperature was raised to 70° C. and reacted for 2 hours to complete the first step of the reaction.

[0050] The temperature was lowered to 55° C., and 10.4 kg of 50 wt % NaOH aqueous solution was added to the kettle. The reaction was stopped after 4 hours of reaction to complete the second step of reaction.

[0051] The aqueous phase was discharged through the discharge port, and a saturated NaCl solution was added to wash the organic phase twice. The organic phase was retained in the kettle, heated to 80°C, and the decompression device was turned on to recover epichlorohydrin to obtain a crude product of eugenol glycidyl ether. The crude product was dissolved in methanol and recrystallized at -5°C for 24 hours, the white crystals were collected and the methanol was removed by vacuum distillation to obtain a light yellow clear liquid eugenol glycidyl ether.

[0052] The two-step reaction products in Example 1 and Comparative Example 1 were detected and analyzed by gas chromatography-mass spectrometry, see Figure 2 (Example 1) and Figure 3 (Comparative Example 1), the gas chromatography data of the two-step products are listed in the following Table 1.

[0053] Table 1

[0054]

[0055]

[0056] Figure 2 This is a gas chromatography-mass spectrometry diagram of the two-step product of preparing eugenol glycidyl ether in Example 1. It is observed that by detecting the product of the first step reaction, no epichlorohydrin component is detected, indicating that the excess epichlorohydrin has been completely recovered. Most of the raw material eugenol is converted into eugenol glycidyl ether EUEP and eugenol epichlorohydrin ether EUO, indicating that in the first step of etherification, a part of eugenol has been directly converted into eugenol glycidyl ether, and a new product 1,3 dichloropropanol is generated at the same time. Since the etherification reaction is a reversible reaction, a small part of EUO will be converted into eugenol when epichlorohydrin is recovered in the first step, and this part of the raw material will continue to be converted in the second step. In the second step reaction process, 1,3 dichloropropanol is closed to epichlorohydrin under the action of high concentration NaOH and continues to react with eugenol. At the same time, EUO is also closed to generate eugenol glycidyl ether. After the second step reaction, the product is detected. The purity of eugenol glycidyl ether is as high as 99%, and it can be crystallized into white crystals in a 4°C environment.

[0057] Figure 3 This is a gas chromatography-mass spectrometry diagram of the two-step products of preparing eugenol glycidyl ether in Comparative Example 1. It is observed that in the first step, epichlorohydrin is ring-opened and undergoes etherification reaction with eugenol to generate eugenol epichlorohydrin ether EUO, and a small part is directly converted into eugenol glycidyl ether; in the second step, eugenol epichlorohydrin ether is ring-closed under the action of NaOH to generate eugenol glycidyl ether. After the epichlorohydrin is recovered by reduced pressure distillation, the purity is only 95.2% when no recrystallization is performed.

[0058] By comparison, it can be seen that the preparation method disclosed in the present invention generates a new substance 1,3-dichloropropanol in the first step product, which helps the conversion of eugenol in the second step reaction and ultimately increases the purity of eugenol glycidyl ether to as high as 99%.

[0059] Example 2

[0060] 20 kg of eugenol, 57 kg (616 mol) of epichlorohydrin and 0.2 kg of benzyltriethylammonium chloride were put into a reaction kettle. After replacing the atmosphere in the kettle with nitrogen, the temperature was raised to 85 ° C for reaction for 2 hours. Then the pressure reducing device was opened to recover the excess epichlorohydrin. The first step of the reaction was completed after there was no distillate.

[0061] The temperature was lowered to 60°C, and 10.4 kg of 50 wt% NaOH aqueous solution was added to the kettle. The vacuum distillation device was opened to allow water to flow out slowly. The reaction was stopped after 4 hours of reaction to complete the second step of the reaction.

[0062] The aqueous phase was discharged through the discharge port, and a saturated NaCl solution was added to wash the organic phase twice. The organic phase was retained in the kettle, heated to 100°C, and the decompression device was turned on to remove water for 1 hour to obtain a light yellow clear liquid eugenol glycidyl ether.

[0063] Example 3

[0064] The preparation process is basically the same as that of Example 1, except that the concentration of the NaOH aqueous solution is replaced with 45 wt % and the mass is replaced with 11.55 kg.

[0065] Example 4

[0066] The preparation process is substantially the same as that of Example 1, except that the concentration of the NaOH aqueous solution is replaced with 55 wt % and the mass is replaced with 9.45 kg.

[0067] Example 5

[0068] The preparation process is substantially the same as that of Example 1, except that the concentration of the NaOH aqueous solution is replaced with 60 wt % and the mass is replaced with 8.67 kg.

[0069] Comparative Example 2

[0070] The preparation process is substantially the same as that of Comparative Example 1, except that the concentration of the NaOH aqueous solution is replaced with 20 wt % and the mass is replaced with 26 kg.

[0071] Comparative Example 3

[0072] The preparation process is basically the same as that of Example 1, except that the concentration of the NaOH aqueous solution is replaced with 40 wt % and the mass is replaced with 13 kg.

[0073] Comparative Example 4

[0074] The preparation process is basically the same as that of Example 1, except that the concentration of the NaOH aqueous solution is replaced with 30 wt % and the mass is replaced with 17.3 kg.

[0075] The yield and purity of epichlorohydrin recovered in each embodiment and comparative example and the yield and purity of the final product are listed in Table 2 below.

[0076] Table 2

[0077]

[0078] In Examples 1 to 5, high recovery rate and high purity of epichlorohydrin, as well as high yield and high purity of the target product eugenol glycidyl ether were achieved.

[0079] By comparing Example 1 with Comparative Examples 1 and 2, it can be found that the yield and purity of epichlorohydrin recovered by the prior art are significantly lower than those of the present invention, and the yield and purity of the target product eugenol glycidyl ether before recrystallization are much lower than those of the present invention, and the purity after a lengthy recrystallization process is comparable to that of the present invention.

[0080] By comparing Example 1 with Comparative Examples 3 and 4, it can be found that the concentration of the sodium hydroxide aqueous solution in the preparation method is critical. When the concentration is lower than 45wt%, such as 30wt% or 40wt%, the yield and purity of the target product eugenol glycidyl ether will be significantly reduced.

[0081] The above-mentioned embodiments are preferred embodiments, but the protection scope of the present invention is not limited thereto. A person skilled in the art can easily understand the spirit of the present invention based on the above-mentioned embodiments and make different extensions and changes. However, as long as they do not deviate from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for preparing high-purity eugenol glycidyl ether, characterized in that: The steps include: Step 1, mixing eugenol, epichlorohydrin and a phase transfer catalyst uniformly and performing an etherification reaction, and recovering excess epichlorohydrin by vacuum distillation after the reaction; Step 2, adding a sodium hydroxide aqueous solution into a reactor, obtaining a crude product through a ring-closing reaction, and washing with water to obtain high-purity eugenol glycidyl ether; The concentration of the sodium hydroxide aqueous solution is 45-60 wt %.

2. The method for preparing high-purity eugenol glycidyl ether according to claim 1, characterized in that: In step 1: The phase transfer catalyst is selected from quaternary ammonium salt phase transfer catalysts; Based on the mass of eugenol, the phase transfer catalyst accounts for 0.3-2.0wt%; The feeding molar ratio of eugenol to epichlorohydrin is 1:(4-8).

3. The method for preparing high-purity eugenol glycidyl ether according to claim 2, characterized in that: The phase transfer catalyst is selected from one or more of benzyltriethylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium chloride.

4. The method for preparing high-purity eugenol glycidyl ether according to claim 1, characterized in that: In step 1: The etherification reaction is carried out at a temperature of 60 to 110° C. and a time of 1 to 5 hours; In the vacuum distillation, the fraction with a temperature of 70 to 90° C. is collected, and the recovered epichlorohydrin can be recycled and used for etherification reaction.

5. The method for preparing high-purity eugenol glycidyl ether according to claim 1, characterized in that: In step 2, the molar ratio of eugenol to NaOH is 1:(1.0-1.1).

6. The method for preparing high-purity eugenol glycidyl ether according to claim 1, characterized in that: In step 2, the ring-closing reaction is carried out at a temperature of 50 to 70° C. for 3 to 6 hours.

7. The method for preparing high-purity eugenol glycidyl ether according to claim 1, characterized in that: In step 2, during the closed-loop reaction, the pressure reducing device is opened to drain water to ensure that the concentration of the sodium hydroxide aqueous solution is stable during the reaction.

8. The method for preparing high-purity eugenol glycidyl ether according to claim 1, characterized in that: In step 2, the water washing is performed using a saturated NaCl aqueous solution, and after washing, water is removed to obtain high-purity eugenol glycidyl ether.

9. The method for preparing high-purity eugenol glycidyl ether according to any one of claims 1 to 8, characterized in that: In step 2, the concentration of the sodium hydroxide aqueous solution is 50-60wt%.

10. The method for preparing high-purity eugenol glycidyl ether according to claim 9, characterized in that: In step 1, the molar ratio of eugenol to epichlorohydrin is 1:(4.5-6.0).

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