A kind of synthetic method of 4-hexene-3-one

Abstract

The present invention relates to the technical field of acyclic or carbocyclic compounds, and in particular to a method for synthesizing 4-hexene-3-one. The present invention acylates propionic anhydride under the action of loaded aluminum chloride as a Lewis acid to form an acyl chloride, and then reacts with propylene and removes hydrogen chloride to obtain 4-hexene-3-one. Compared with the prior art, the loaded aluminum chloride prepared by the present invention not only has improved activity, but also has higher stability, so it can better catalyze the reaction, thereby improving the reaction yield.

Description

Technical Field

[0001] The invention relates to the technical field of acyclic or carbocyclic compounds, and in particular to a method for synthesizing 4-hexene-3-one. Background Art

[0002] 2,4-dihydroxy-3,6-dimethylbenzoic acid methyl ester is a fragrance monomer with a unique aroma and a good fixative. It is widely used in fine chemical products such as soaps, detergents, high-grade perfumes and tobacco. 4-Hexen-3-one is an important intermediate for the synthesis of 2,4-dihydroxy-3,6-dimethylbenzoic acid methyl ester. 4-Hexen-3-one, also known as rubberene, can be used as a raw material for important food additives and is also a food flavoring allowed by international standards. It is often used in soft drinks, cold drinks, candies, baked goods, jellies, puddings, gummies, seasonings, meat products, meat soups, milk, dairy products, and cereal products. Therefore, it has a wide range of uses in the chemical industry and fine chemical industry.

[0003] CN103058838A relates to a method for producing 4-hexen-3-one by dehydrating 4-hydroxy-3-hexanone, which mainly solves the problems of low catalyst activity, high reaction temperature and low air velocity in the prior art. The invention uses 4-hydroxy-3-hexanone as a raw material, and the reaction temperature is 200-400°C, and the air velocity relative to the mass of 4-hydroxy-3-hexanone liquid is 0.5-15 hours-1. The reaction raw material and the catalyst are contacted to generate 4-hexen-3-one; wherein the catalyst used includes the following components by weight: a) 40-95 parts of ZSM-11 molecular sieve with a silicon-aluminum molar ratio SiO2 / Al2O3 of 20-300 and a grain diameter of ≤5 microns; b) 5-60 parts of a binder; the technical solution of the ZSM-11 molecular sieve being acid-washed at least once solves the problem well, and can be used in the industrial production of 4-hydroxy-3-hexanone to produce 4-hexen-3-one.

[0004] CN114292174B relates to a method comprising reacting 2-butanone with acetaldehyde in the presence of a zinc complex catalyst in a reaction zone to produce a product mixture comprising 4-hexene-3-one and 3-methyl-3-pentene-2-one. The invention also relates to a method comprising: (a) reacting 2-butanone with acetaldehyde in the presence of a zinc complex catalyst to produce a product mixture comprising 4-hexene-3-one, 3-methyl-3-pentene-2-one and a zinc complex catalyst; (b) recovering the zinc complex catalyst from the product mixture; and (c) reusing the recovered zinc complex catalyst in the reaction step (a).

[0005] At present, the synthesis of 4-hexen-3-one is reported to be prepared by high-temperature dehydration of 4-hydroxy-3-hexanone. The high-temperature catalytic dehydration process has high energy consumption and high requirements for the selection of catalysts. The generated by-products and 4-hexen-3-one are difficult to separate, so the yield of 4-hexen-3-one is low. This synthesis method is not conducive to large-scale production. Summary of the invention

[0006] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a method for synthesizing 4-hexen-3-one.

[0007] The present invention acylates propionic anhydride under the action of loaded aluminum chloride as Lewis acid to form acyl chloride, and then reacts with propylene and removes hydrogen chloride to obtain 4-hexene-3-one. In the acylation reaction of propionic anhydride, aluminum chloride, as a Lewis acid catalyst, mainly plays the following roles: forming acyl carbon cations: aluminum chloride accepts electron pairs provided by oxygen atoms of propionic anhydride to form acyl carbon cations, which are highly electrophilic intermediates; promoting electrophilic substitution: acyl carbon cations react with aromatic compounds or other compounds containing nucleophilic sites to perform electrophilic substitution to form aromatic ketones or other acylated products; improving reaction rate: aluminum chloride significantly improves the rate of acylation reaction through catalysis, making the reaction faster and more efficient; stabilizing reaction intermediates: aluminum chloride can also stabilize some reaction intermediates, reduce the activation energy of the reaction, and thus promote the reaction. Although aluminum chloride is a strong, non-toxic Lewis acid catalyst, it forms an extended network in the solid state and is not easily soluble in many organic solvents. In addition, aluminum chloride is also hygroscopic, so it needs to be processed under an inert atmosphere for more complex applications. In view of these defects of aluminum chloride, the present invention provides a kind of aluminum chloride after loading, which destroys the dense crystal structure and significantly enhances the reactivity of the solid by mechanical ball milling, and uses potato starch and urea as biomass carriers. Since starch is porous and rich in carbon and oxygen-containing functional groups, it can be used as an excellent carrier for enhancing metal dispersion and reducing metal leaching, and nitrogen provides nitrogen-containing functional groups. After grinding, the metal components are well embedded in the carrier and form strong interactions. The loaded aluminum chloride not only has improved activity, but also has higher stability, so it can better catalyze the reaction, thereby improving the reaction yield.

[0008] To achieve the above object, the present invention provides a method for synthesizing 4-hexen-3-one, comprising the following steps:

[0009] Under nitrogen atmosphere and low temperature, the loaded aluminum chloride is added to dichloromethane, propionic anhydride is added dropwise under temperature control after mixing evenly, propylene is introduced after continuing to mix evenly, and the mixed solution is added to water to cool down for hydrolysis after the reaction, and the temperature is maintained at 10-20° C. and stirred before separation, and the aqueous phase is distilled under reduced pressure to recover the by-products, and the organic phase is washed with a saturated sodium carbonate solution, separated, and the organic phase is distilled to obtain 4-hexen-3-one.

[0010] Furthermore, the low temperature ranges from 0 to 5°C.

[0011] Furthermore, the temperature range of the temperature control is 5 to 10°C.

[0012] Furthermore, the reaction time is 1 to 3 hours.

[0013] Furthermore, the cooling temperature range is 0 to 5°C.

[0014] Furthermore, the stirring time is 1 to 2 hours.

[0015] Preferably, the synthesis method of 4-hexen-3-one comprises the following steps:

[0016] In a nitrogen atmosphere, at 0-5°C, the loaded aluminum chloride is added to dichloromethane, mixed evenly, and propionic anhydride is added dropwise at a temperature of 5-10°C. After continued mixing, propylene is introduced. After reacting for 1-3 hours, the mixed solution is added to water and cooled to 0-5°C for hydrolysis. The temperature is maintained at 10-20°C and stirred for 1-2 hours, and then the liquids are separated. The aqueous phase is distilled under reduced pressure to recover the by-products. The organic phase is washed with a saturated sodium carbonate solution, separated, and the organic phase is distilled to obtain 4-hexen-3-one.

[0017] The preparation method of the loaded aluminum chloride comprises the following steps:

[0018] X1. Mix potato starch and urea, dry them, calcine them, grind them and sieve them to obtain a carrier;

[0019] X2. Mix the carrier with aluminum chloride, add zirconium oxide balls for ball milling, and vacuum dry to obtain the loaded aluminum chloride.

[0020] Furthermore, the mass ratio of the potato starch to the urea to the aluminum chloride is 20-60:2-6:6-15.

[0021] Furthermore, the calcination is performed at 700° C. for 2 h.

[0022] Furthermore, the ball milling time is 2 to 4 hours.

[0023] Preferably, the method for preparing the loaded aluminum chloride comprises the following steps:

[0024] X1. Mix potato starch and urea, dry them, calcine them at 700°C for 2h, grind and sieve them to obtain a carrier;

[0025] X2. Mix the carrier with aluminum trichloride, with the mass ratio of potato starch to urea to aluminum trichloride being 20-60:2-6:6-15, add 10 times the mass of zirconium oxide balls for ball milling, ball milling for 2-4 hours, and vacuum drying to obtain the loaded aluminum trichloride.

[0026] Beneficial effects of the present invention:

[0027] 1. Compared with the prior art, the present invention provides a loaded aluminum chloride, which destroys the dense crystal structure and significantly enhances the reactivity of the solid by mechanical ball milling. Potato starch and urea are used as biomass carriers. Since starch is porous and rich in carbon and oxygen-containing functional groups, it can be used as an excellent carrier for enhancing metal dispersion and reducing metal leaching. Nitrogen provides nitrogen-containing functional groups. After grinding, the metal components are well embedded in the carrier and form strong interactions.

[0028] 2. The present invention acylates propionic anhydride under the action of loaded aluminum chloride as Lewis acid to form an acyl chloride, which is then reacted with propylene and hydrogen chloride is removed to obtain 4-hexen-3-one. Compared with the prior art, the loaded aluminum chloride prepared by the present invention not only has improved activity, but also has higher stability, so it can better catalyze the reaction, thereby improving the reaction yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0030] Aluminum trichloride, specific surface area: 151.23m 2 / g.

[0031] Example 1

[0032] A method for synthesizing 4-hexen-3-one comprises the following steps, measured in parts by weight:

[0033] Under nitrogen atmosphere and 5°C, add 50 parts of loaded aluminum chloride to 300 parts of dichloromethane, mix well and control the temperature at 5°C before adding 50 parts of propionic anhydride dropwise. Continue to mix well and then introduce 25 parts of propylene. After reacting for 2 hours, add the mixed solution into water and cool to 5°C for hydrolysis. Keep the temperature at 15°C and stir for 1.5 hours before separating the liquids. Wash the organic phase with saturated sodium carbonate solution, separate the layers and distill the organic phase to obtain 4-hexen-3-one.

[0034] The preparation method of the loaded aluminum chloride comprises the following steps:

[0035] X1. Mix 60 parts of potato starch and 6 parts of urea, dry them, calcine them at 700° C. for 2 h, grind and sieve to obtain a carrier;

[0036] X2. Mix 30 parts of the carrier with 12 parts of aluminum trichloride, add 10 times the mass of zirconium oxide balls for ball milling, ball milling for 4 hours, and vacuum dry to obtain the loaded aluminum trichloride.

[0037] Comparative Example 1

[0038] A method for synthesizing 4-hexen-3-one comprises the following steps:

[0039] Under nitrogen atmosphere and 5°C, add 20 parts of aluminum chloride to 300 parts of dichloromethane, mix well, control the temperature at 5°C, add 50 parts of propionic anhydride dropwise, continue to mix well, then pass 25 parts of propylene, react for 2 hours, add the mixed solution into water, cool to 5°C for hydrolysis, maintain the temperature at 15°C, stir for 1.5 hours, separate the liquids, wash the organic phase with saturated sodium carbonate solution, separate the layers, and distill the organic phase to obtain 4-hexen-3-one.

[0040] Comparative Example 2

[0041] A method for synthesizing 4-hexen-3-one comprises the following steps:

[0042] Under nitrogen atmosphere and 5°C, add 50 parts of loaded aluminum chloride to 300 parts of dichloromethane, mix well and control the temperature at 5°C before adding 50 parts of propionic anhydride dropwise. Continue to mix well and then introduce 25 parts of propylene. After reacting for 2 hours, add the mixed solution into water and cool to 5°C for hydrolysis. Keep the temperature at 15°C and stir for 1.5 hours before separating the liquids. Wash the organic phase with saturated sodium carbonate solution, separate the layers and distill the organic phase to obtain 4-hexen-3-one.

[0043] The preparation method of the loaded aluminum chloride comprises the following steps:

[0044] X1. Mix 60 parts of potato starch and 6 parts of urea, dry them, grind them and sieve them to obtain a carrier;

[0045] X2. Mix 30 parts of the carrier with 12 parts of aluminum trichloride, add 10 times the mass of zirconium oxide balls for ball milling, ball milling for 4 hours, and vacuum dry to obtain the loaded aluminum trichloride.

[0046] Comparative Example 3

[0047] A method for synthesizing 4-hexen-3-one comprises the following steps:

[0048] Under nitrogen atmosphere and 5°C, 47.6 parts of loaded aluminum chloride were added to 300 parts of dichloromethane. After mixing evenly, 50 parts of propionic anhydride were added dropwise at 5°C. After continuing to mix evenly, 25 parts of propylene were introduced. After reacting for 2 hours, the mixed solution was added into water and cooled to 5°C for hydrolysis. The temperature was maintained at 15°C and stirred for 1.5 hours, and then the liquids were separated. The organic phase was washed with saturated sodium carbonate solution, separated, and the organic phase was distilled to obtain 4-hexen-3-one.

[0049] The preparation method of the loaded aluminum chloride comprises the following steps:

[0050] X1. Dry 60 parts of potato starch, calcine at 700°C for 2h, grind and sieve to obtain a carrier;

[0051] X2. Mix 28 parts of the carrier with 12 parts of aluminum trichloride, add 10 times the mass of zirconium oxide balls for ball milling, ball milling for 4 hours, and vacuum dry to obtain the loaded aluminum trichloride.

[0052] Comparative Example 4

[0053] A method for synthesizing 4-hexen-3-one comprises the following steps, measured in parts by weight:

[0054] Under nitrogen atmosphere and 5°C, 31 parts of loaded aluminum chloride were added to 300 parts of dichloromethane. After mixing evenly, 50 parts of propionic anhydride were added dropwise at 5°C. After continuing to mix evenly, 25 parts of propylene were introduced. After reacting for 2 hours, the mixed solution was added into water and cooled to 5°C for hydrolysis. The temperature was maintained at 15°C and stirred for 1.5 hours, and then the liquids were separated. The organic phase was washed with saturated sodium carbonate solution, separated, and the organic phase was distilled to obtain 4-hexen-3-one.

[0055] The preparation method of the loaded aluminum chloride comprises the following steps:

[0056] X1. Dry 60 parts of urea, calcine at 700°C for 2h, grind and sieve to obtain a carrier;

[0057] X2. Mix 14 parts of the carrier with 12 parts of aluminum trichloride, add 10 times the mass of zirconium oxide balls for ball milling, ball milling for 4 hours, and vacuum dry to obtain the loaded aluminum trichloride.

[0058] Test Example 1

[0059] The 4-hexen-3-one prepared in the control example and the example was recorded and the yield was calculated. The specific data are shown in Table 1.

[0060] Table 1 Yield of 4-hexene-3-one in the comparative examples and embodiments

[0061] Experimental protocol 4-Hexen-3-one yield / % Example 1 97.5 Comparative Example 1 90.1 Comparative Example 2 92.2 Comparative Example 3 93.4 Comparative Example 4 93.6

[0062] In the acylation reaction of propionic anhydride, aluminum chloride, as a Lewis acid catalyst, mainly plays the following roles, forming acyl carbon ions: aluminum chloride accepts the electron pairs provided by the oxygen atoms of propionic anhydride to form acyl carbon ions, which are highly electrophilic intermediates; promote electrophilic substitution: acyl carbon ions react with aromatic compounds or other compounds containing nucleophilic sites to undergo electrophilic substitution to form aromatic ketones or other acylated products; increase reaction rate: aluminum chloride significantly increases the rate of acylation reaction through catalysis, making the reaction faster and more efficient; stabilize reaction intermediates: aluminum chloride can also stabilize some reaction intermediates, reduce the activation energy of the reaction, and thus promote the reaction. Although aluminum chloride is a potent, non-toxic Lewis acid catalyst, it forms an extended network in the solid state and is not easily soluble in many organic solvents. In addition, aluminum chloride is also hygroscopic and is prone to deliquescence and hydrolysis under normal conditions. In the present invention, aluminum chloride can be stably dispersed in a carrier by loading it, thereby protecting it from the possibility of being hydrolyzed. The aluminum chloride loaded on the carrier formed by calcining potato starch and urea in Example 1 may be more evenly dispersed in the carrier due to the porous structure formed after calcining starch and urea, so as to obtain a uniform and dense pore structure, so that the aluminum chloride is more evenly dispersed in the carrier, so the catalytic activity is enhanced compared with the uncalcined control example 2. In Example 1, aluminum chloride is embedded in the carrier after mechanical grinding, which significantly enhances the interaction between them and is conducive to the formation of a solid support structure, while the increase of oxygen-containing functional groups and nitrogen-containing functional groups caused by potato starch and urea contributes to the lattice distortion and the formation of a compact metal carrier structure, thereby improving the catalytic activity and stability. Compared with the uncalcined carrier, the porous and dense structure formed by calcination in Example 1 may be more beneficial to the improvement of activity, which may also be the reason why the yield of Example 1 is higher than that of Control Example 2. Compared with Example 1, Control Examples 3 to 4 have fewer types of carriers, which may affect the number of oxygen-containing functional groups and nitrogen-containing functional groups in the carrier, thereby affecting the catalytic activity.

[0063] Test Example 2

[0064] The specific surface area of ​​the catalysts used in the control examples and the examples was tested and recorded. The specific data is shown in Table 2.

[0065] Table 2 Specific surface area test results of catalysts in control examples and embodiments

[0066] Experimental protocol <![CDATA[Specific surface area / m 2 / g]]> Example 1 252.34 Comparative Example 1 151.23 Comparative Example 2 200.57 Comparative Example 3 244.82 Comparative Example 4 241.36

[0067] As a catalyst, the effect of the specific surface area of ​​aluminum chloride on the reaction is mainly reflected in the following aspects: the availability of active sites. A larger specific surface area of ​​the catalyst means that there are more active sites for the reactant molecules to contact and adsorb, thereby increasing the interaction between the reactants and the catalyst, which helps to improve the catalytic efficiency; reaction rate. A larger specific surface area can provide more reaction sites, allowing more reactant molecules to participate in the reaction at the same time, which usually leads to an increase in the reaction rate; selectivity. An increase in the specific surface area of ​​the catalyst may affect the selectivity of the reaction. In some cases, a larger surface area may increase the chance of side reactions, while in other cases, it may help to improve the catalytic selectivity for a specific reaction path; the dispersion of the catalyst. Catalysts with larger specific surface areas usually have better dispersion, which means that the catalyst particles are more evenly distributed in the reaction system, which helps to improve the catalytic efficiency; thermal stability. In some cases, catalysts with larger specific surface areas may have better thermal stability because they are usually more firmly bound to the carrier, which helps to maintain the structure and activity of the catalyst under high temperature reaction conditions. It can be seen from the test results that mechanical grinding can significantly increase the specific surface area. This is because grinding will break larger particles into smaller sizes, thereby increasing the total surface area. The grinding process may introduce microscopic defects and cracks on the surface of the particles, which will also increase the surface area. Grinding helps to improve the dispersibility of the components in the mixture, reduce agglomeration, and make the particles more evenly distributed, thereby increasing the specific surface area. Grinding can also change the morphology of the particles, such as from a block or agglomerate to a finer powder, which will also increase the specific surface area. Grinding, as a means of mechanical activation, can increase the reactivity of the material, promote the interaction between materials, and help form a more stable composite material. Grinding may increase the porosity of the material, especially when there is a pore structure in the mixture, which will further increase the specific surface area. Therefore, the specific surface areas of Example 1 and Comparative Examples 2 to 3 are greater than those of Comparative Example 1. Compared with Example 1, the specific surface area of ​​Control Examples 2 to 4 is obviously lower in Control Example 2. This may be because the starch can form a porous and dense structure after calcination, so the specific surface area increases more significantly. In Control Example 2, no calcination was performed, while in Control Example 4, urea was calcined to form carbides or carbon elements.

[0068] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for synthesizing 4-hexen-3-one, characterized in that: The steps include: Under nitrogen atmosphere and low temperature, add the loaded aluminum chloride to dichloromethane, mix well and then control the temperature to add propionic anhydride dropwise, continue to mix well and then add propylene, add the mixed solution to water to cool and hydrolyze, keep the temperature at 10-20°C and stir, separate the liquids, distill the aqueous phase under reduced pressure to recover the by-products, wash the organic phase with saturated sodium carbonate solution, separate the layers, and obtain 4-hexen-3-one after distillation of the organic phase; The preparation method of the loaded aluminum chloride comprises the following steps: X1. Mix potato starch and urea, dry them, calcine them at 700°C for 2h, grind and sieve them to obtain a carrier; X2. Mix the carrier with aluminum trichloride. The mass ratio of potato starch to urea to aluminum trichloride is 20-60:2-6:6-15. Add 10 times the mass of zirconium oxide balls for ball milling. Ball mill for 2-4 hours. After vacuum drying, the loaded aluminum trichloride is obtained.

2. The method for synthesizing 4-hexen-3-one according to claim 1, characterized in that: The low temperature ranges from 0 to 5°C.

3. The method for synthesizing 4-hexen-3-one according to claim 1, characterized in that: The temperature range of the temperature control is 5-10°C.

4. The method for synthesizing 4-hexen-3-one according to claim 1, characterized in that: The reaction time is 1 to 3 hours.

5. The method for synthesizing 4-hexen-3-one according to claim 1, characterized in that: The temperature range of the cooling is 0~5℃.

6. The method for synthesizing 4-hexen-3-one according to claim 1, characterized in that: The stirring time is 1 to 2 hours.

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