A method for efficiently preparing methyl alkyl ketones

Abstract

The application discloses a method for efficiently preparing methyl alkyl ketone. The reaction device comprises a storage tank, a static mixer, a dynamic tube reactor, a liquid separation device and a continuous hydrogenation device. The preparation process comprises the following steps: mixing acetone and aldehyde, preparing an alkali solution by using sodium hydroxide or potassium hydroxide as an alkali, making two materials enter the dynamic tube reactor at an equal flow rate, and reacting under certain conditions; and after the reaction mixture is collected and separated, the organic phase is subjected to hydrogenation through the continuous hydrogenation equipment to obtain the methyl alkyl ketone. The method has the advantages of low price of raw materials, high yield, less waste, short steps, simple process route and good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, and in particular to a method for the efficient preparation of methyl alkyl ketones. Background Technology

[0002] 2-Undecanone, also known as methyl nonyl ketone, is a colorless to slightly yellow liquid with a citrus oil and rue-like aroma. It is naturally found in houttuynia cordata, banana, strawberry, clove, ginger, and other plants in the Rutaceae family. Methyl nonyl ketone is the active ingredient in houttuynia cordata, emitting a citrus aroma, and is mainly used in the production of pharmaceuticals and fragrances. In my country, GB2760-2011 stipulates its use as an permitted edible flavoring agent for blending edible flavorings; it can also be used as an intermediate in flavoring production, and in the pharmaceutical industry for the production of houttuynin; furthermore, due to its strong odor, 2-undecanone can also be used as an insecticide or mosquito repellent. Similar compounds, such as 2-tetridecanone and 2-pentadecanone, have a fresh jasmine and celery-like aroma and are widely used as food additives, especially as food flavorings.

[0003]

[0004] The synthesis of methyl alkyl ketones generally involves regioselective oxidation of terminal double bonds via Wacker oxidation (J.Am. Chem. Soc. 2007, 129, 8, 2246–2247), but the catalysts used are very expensive. Methyl alkyl ketones can also be obtained through 1,4-addition of metal reagents to methyl vinyl ketones (Tetrahedron Letters, 1989, vol. 30, 3541-3544) or addition of Grignard reagents to acyl chlorides (Tetrahedron Letters, 1984, vol. 25, 4805-4808), but these methods have high raw material costs, pose certain safety risks with the use of Grignard reagents, and involve cumbersome post-treatment processes and high levels of waste. In 2008, Shiraishi reported a radical C-C bond coupling reaction between olefins and acetone under light irradiation to obtain methyl alkyl ketones, which shows promising industrial potential (Org. Lett. 2008, 10, 3117–3120). Patent CN121426653A reports a method for obtaining methyl alkyl ketones by alcohol-ketone condensation reaction using acetone and an alcohol catalyzed by a Ni-Cu / AC catalyst, but the reaction temperature is as high as 200–280°C, requiring significant energy and equipment.

[0005] Therefore, it is essential to develop a simple, efficient, universal method for synthesizing methyl alkyl ketones that is suitable for industrial production. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by mixing acetone and aldehydes, preparing an alkaline solution using sodium hydroxide or potassium hydroxide as the alkali, and then introducing both materials into a dynamic tube reactor at equal flow rates. The reaction mixture is then collected and separated, and the resulting organic phase is hydrogenated using a continuous hydrogenation device to obtain a methyl alkyl ketone. The advantages of this invention include low-cost raw materials, high yield, minimal waste, and simple operation, making it highly valuable for industrial applications.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] a. Mix acetone and aldehyde, and prepare an alkaline solution using sodium hydroxide or potassium hydroxide as the base. The two materials enter the dynamic tube reactor at the same flow rate and react under certain conditions to obtain a reaction intermediate.

[0009] b. The organic phase obtained after collecting and separating the reaction intermediates is hydrogenated through a continuous hydrogenation device to obtain methyl alkyl ketones.

[0010] Furthermore, the aldehyde mentioned in step a is any one of octanal, decanal, and dodecanoal.

[0011] Furthermore, in step a, acetone is both a reactant and a reaction solvent, and the molar ratio of acetone to aldehyde is 1:1 to 12:1, preferably 7:1.

[0012] Further, the alkaline solution mentioned in step a is one of sodium hydroxide solution, potassium hydroxide solution, and sodium methoxide solution, preferably sodium hydroxide solution.

[0013] Furthermore, the concentration of the alkaline solution is 1-20%, preferably 5%.

[0014] Furthermore, the hydrogenation catalyst in the hydrogenation equipment described in step b is palladium on carbon.

[0015] Furthermore, in step b, the hydrogen pressure during hydrogenation is 0.5~1.0 MPa, preferably 0.9 MPa.

[0016] Furthermore, the reaction temperature during hydrogenation in step b is 40~90℃, preferably 80℃.

[0017] The synthetic route for the methyl alkyl ketone is as follows:

[0018]

[0019] The advantages of this invention over the prior art are: the raw materials used in the synthesis are inexpensive, the yield is high, the process route is simple, and it has potential industrial application prospects. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products.

[0022] Example 1

[0023] Preparation of 2-Undecone:

[0024] 686.07 g of acetone and 216.37 g of octaldehyde were mixed in storage tank 1, and 245 g of 5% alkaline solution (sodium hydroxide) was prepared in storage tank 2. The liquids from storage tanks 1 and 2 were then fed into a static mixer at flow rates of 20 mL / min and 4 mL / min, respectively. The mixture flowing out of the mixer entered a dynamic tubular reactor, which was subjected to a reaction at 80°C, a pressure of 0.15 MPa, a flow rate of 23 mL / min, and a reaction time of 10 min. The reaction mixture from the tubular reactor was separated in a separator, and the upper organic phase entered storage tank 3. Then, it was fed into a continuous flow hydrogenation unit at a rate of 20 mL / min, with Pd / C column packing, a reaction pressure of 0.7 MPa, a reaction temperature of 80°C, and a reaction time of 5 min.

[0025] Sampling and GC analysis showed that the 2-undecanone content was 93.9%. The 2-undecanone acetone solution was transferred to a three-necked flask for solvent removal and acetone recovery. Subsequent vacuum distillation yielded 254.66 g of the 2-undecanone product, with a yield of 88% and a purity of 99.3%.

[0026] Example 2

[0027] Preparation of 2-tridecone:

[0028] 686.07 g of acetone and 263.7 g of decanal were mixed in storage tank 1, and 245 g of 5% alkaline solution (sodium hydroxide) was prepared in storage tank 2. The liquids from storage tanks 1 and 2 were then fed into a static mixer at flow rates of 21 mL / min and 4 mL / min, respectively. The mixture flowing out of the mixer entered a dynamic tubular reactor, which was subjected to a reaction at a temperature of 90°C, a pressure of 0.15 MPa, a flow rate of 24 mL / min, and a reaction time of 10 min. The reaction mixture from the tubular reactor was separated in a separator, and the upper organic phase entered storage tank 3. Then, it was fed into a continuous flow hydrogenation unit at a rate of 20 mL / min, with a Pd / C column packing material, a reaction pressure of 0.7 MPa, a reaction temperature of 80°C, and a reaction time of 5 min.

[0029] Sampling and GC analysis showed that the 2-tetridetone content was 94%. The above 2-tetridetone acetone solution was transferred to a three-necked flask for solvent removal and acetone recovery. After vacuum distillation, 305.51 g of 2-tetridetone product was obtained, with a yield of 91% and a purity of 99.7%.

[0030] Example 3

[0031] Preparation of 2-pentadecanone:

[0032] 686.07 g of acetone and 311.04 g of dodecylaldehyde were mixed in storage tank 1, and 245 g of 5% alkaline solution (sodium hydroxide) was prepared in storage tank 2. The liquids from storage tanks 1 and 2 were then fed into a static mixer at flow rates of 22 mL / min and 4 mL / min, respectively. The mixture flowing out of the mixer entered a dynamic tubular reactor, which was subjected to a reaction at 80°C, 0.15 MPa, and a flow rate of 25 mL / min for 10 min. The reaction mixture from the tubular reactor was separated in a separator, and the upper organic phase entered storage tank 3. Then, it was fed into a continuous flow hydrogenation unit at a rate of 20 mL / min, with Pd / C column packing, a reaction pressure of 0.7 MPa, a reaction temperature of 80°C, and a reaction time of 5 min.

[0033] Sampling and GC analysis showed that the 2-pentadecanone content was 95%. The 2-pentadecanone acetone solution was transferred to a three-necked flask for solvent removal and acetone recovery. After vacuum distillation, 347.21 g of 2-pentadecanone product was obtained, with a yield of 90% and a purity of 99.9%.

[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for efficiently preparing methyl alkyl ketones, characterized in that, The method includes the following steps: Acetone and aldehyde are mixed to form material A, and an alkaline solution is prepared to form material B. The two materials are fed into a dynamic tubular reactor at the same flow rate and reacted under certain conditions to obtain a reaction intermediate. The organic phase obtained after collecting and separating the reaction intermediates is hydrogenated through a continuous hydrogenation device to obtain methyl alkyl ketones.

2. The method for efficiently preparing methyl alkyl ketones according to claim 1, characterized in that: The aldehyde is any one of octanal, decanal, and dodecaldehyde.

3. The method for efficiently preparing methyl alkyl ketones according to claim 1, characterized in that: The acetone is both a reactant and a reaction solvent, and the molar ratio of acetone to aldehyde is 1:1 to 12:

1.

4. The method for efficiently preparing methyl alkyl ketones according to claim 1, characterized in that: The alkaline solution is one of sodium hydroxide solution, potassium hydroxide solution, and sodium methoxide solution.

5. The method for efficiently preparing methyl alkyl ketones according to claim 1, characterized in that: The concentration of the alkaline solution is 1-20%.

6. The method for efficiently preparing methyl alkyl ketones according to claim 2, characterized in that: The hydrogenation catalyst in the hydrogenation equipment is palladium on carbon.

7. The method for efficiently preparing methyl alkyl ketones according to claim 2, characterized in that: The hydrogen pressure during hydrogenation is 0.5~1.0 MPa.

8. The method for efficiently preparing methyl alkyl ketones according to claim 2, characterized in that: The reaction temperature during hydrogenation is 40~90℃.

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