Microwave-assisted rapid reaction method of matremethrin

Abstract

The invention relates to the technical field of organic synthesis and microwave chemistry, and discloses a microwave-assisted rapid reaction method of matrichthrin, which comprises the following steps: S1, a condensation reaction stage: promoting a low-temperature condensation reaction of n-propionaldehyde and an alkaline solution through microwave radiation, controlling the reaction temperature at 0-5 DEG C, and accelerating the reaction process by using microwave radiation; and S2, a hydrogenation reaction stage: alternately replacing 2-methyl-2-pentenal in nitrogen and hydrogen by adopting a supported palladium catalyst and combining a microwave heating mode, then carrying out catalytic hydrogenation, and optimizing reaction conditions by adjusting microwave power and reaction pressure. The microwave-assisted technology is introduced, so that the reaction rate can be remarkably increased in the reaction stages of condensation, hydrogenation, oxidation, esterification and the like, the overall preparation time is effectively shortened, the problem that the operation time of a traditional method is long is solved, and the production efficiency of the matrichthrin is greatly improved.

Description

Technical Field

[0001] This invention relates to the fields of organic synthesis and microwave chemistry, specifically to a microwave-assisted rapid reaction method for chamomile esters. Background Technology

[0002] With the continuous development of chemical synthesis technology, chamomile esters, as important organic compounds, have wide applications in fragrances, pharmaceuticals, and pesticides. However, traditional methods for preparing chamomile esters typically involve multiple steps, including condensation, hydrogenation, oxidation, esterification, washing, and distillation, which involve complex reaction conditions and long operating times. In particular, the condensation reaction requires low-temperature control, the hydrogenation reaction demands high catalyst activity, and the oxidation reaction requires precise control of the aeration rate and temperature. Furthermore, the esterification process involves lengthy reflux heating, and subsequent washing and distillation steps also place high demands on operational precision. These factors, to some extent, limit production efficiency and increase energy consumption and costs. Summary of the Invention

[0003] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a microwave-assisted rapid reaction method for chamomile esters, which solves the problem of "increased energy consumption and cost" mentioned in the background technology.

[0004] To achieve the above objectives, the present invention provides a microwave-assisted rapid reaction method for chamomile esters, comprising the following steps: S1: Condensation reaction stage, microwave radiation promotes the low-temperature condensation reaction of propanal with alkaline solution, the reaction temperature is controlled at 0 to 5 degrees Celsius, and microwave radiation is used to accelerate the reaction process. S2: In the hydrogenation reaction stage, a supported palladium catalyst is used in combination with microwave heating to catalytically hydrogenate 2-methyl-2-pentenal after alternating nitrogen and hydrogen gas. The reaction conditions are optimized by adjusting the microwave power and reaction pressure. S3: In the oxidation reaction stage, anhydrous cobalt acetate is used as an oxidation catalyst. Combined with microwave radiation to control the air flow rate and reaction temperature, 2-methylpentanal is efficiently converted into 2-methylpentanoic acid. S4: In the esterification reaction stage, microwave heating is used instead of the traditional reflux heating method to carry out the esterification reaction of 2-methylvaleric acid and ethanol under the catalysis of toluenesulfonic acid, which reduces the reaction time and increases the yield. S5: The washing stage adopts a step-by-step washing process combined with microwave-assisted heating. By precisely controlling the temperature of the washing liquid and the stirring time, the separation efficiency is improved. S6: In the distillation stage, microwave-assisted heating is used to lower the boiling point of crude chamomile ester, shorten the distillation time, and improve the purity of the finished product.

[0005] Preferably, the specific operation of the condensation reaction stage of S1 includes: preparing 400ml of 10% sodium hydroxide solution in a 1000ml three-necked flask, cooling it to 0 to 5 degrees Celsius, turning on the microwave radiation device, setting the microwave power to 300W, and slowly adding 232g of n-propanal with stirring, controlling the dropping rate to maintain the reaction temperature not exceeding 5 degrees Celsius; after the dropping is completed, continue the reaction for 2 hours, separate the organic layer, wash it with 2×200ml of water, and distill to obtain 2-methyl-2-pentenal.

[0006] Preferably, the specific operation of the hydrogenation reaction stage of S2 includes: adding 300 ml of 2-methyl-2-pentenal and 3 g of supported palladium catalyst into a microwave reactor, first purging with nitrogen three times, then purging with hydrogen three times; setting the microwave power to 500 W, the reaction pressure to 2 MPa, and controlling the reaction temperature to 80 degrees Celsius until the reaction is complete; filtering to recover the catalyst, and distilling the filtrate to obtain 2-methylpentenal.

[0007] Preferably, the specific operation of the oxidation reaction stage of S3 includes: adding 400g of 2-methylpentanal to a microwave reactor, adding 4g of anhydrous cobalt acetate as an oxidation catalyst, setting the microwave power to 400W, controlling the reaction temperature to 20 to 30 degrees Celsius, slowly introducing air until the reaction is complete; and filtering to obtain 2-methylpentanic acid.

[0008] Preferably, the specific operation of the esterification reaction stage of S4 includes: adding 3.0g toluenesulfonic acid, 132g ethanol and 300g 2-methylvaleric acid to a microwave reactor, turning on the stirrer and starting microwave heating, setting the microwave power to 600W, raising the temperature to 110 to 130 degrees Celsius, and refluxing the reaction to the endpoint; recovering excess ethanol, cooling the reaction solution to 40 degrees Celsius, and transferring the crude product to a washing vessel.

[0009] Preferably, the specific operation of the washing stage of S5 includes: adding 5% sodium carbonate solution at a ratio of approximately 12:1 based on the mass of the crude product, turning on microwave-assisted heating to 50 degrees Celsius, stirring for 1.5 hours, letting stand for 2 hours to separate the water layer; then adding water at a ratio of 10:1, stirring for 1.5 hours, using pH test paper to check that the pH value is close to 7, letting stand for 2 hours to separate the water layer, and transferring the crude chamomile ester to a distillation column.

[0010] Preferably, the specific operation of the distillation stage of S6 includes: placing crude chamomile ester in a microwave-assisted distillation device, setting the microwave power to 700W, gradually heating to the target boiling point, and collecting the distillate to obtain the finished chamomile ester.

[0011] Preferably, the method further includes online monitoring of reaction parameters at each stage, including real-time recording and adjustment of temperature, pressure, microwave power, and reaction time, to ensure precise control of reaction conditions at each stage.

[0012] Preferably, the microwave reactor includes a multi-layer heat insulation structure and an adjustable microwave transmitter. The multi-layer heat insulation structure consists of a high-temperature resistant ceramic layer, a metal shielding layer, and a heat insulation layer from the inside out. The adjustable microwave transmitter can adapt to the needs of different reaction stages by changing the microwave frequency and power density.

[0013] Preferably, the microwave radiation accelerates the collision frequency between reactants through the polar molecular dipole rotation mechanism, significantly shortening the reaction time during the condensation reaction stage.

[0014] This invention provides a microwave-assisted rapid reaction method for chamomile esters. It has the following beneficial effects: (1) By introducing microwave-assisted technology, the present invention can significantly accelerate the reaction rate in each reaction stage such as condensation, hydrogenation, oxidation and esterification, effectively shorten the overall preparation time, solve the problem of long operation time of traditional methods, and greatly improve the production efficiency of chamomile ester. In addition, the microwave radiation of the present invention can improve the reaction efficiency by promoting the dipole rotation of polar molecules, selectively activating reaction molecules and catalyst active sites, etc. At the same time, the microwave reactor with multi-layer heat insulation structure reduces energy loss and reduces the energy consumption per unit product, which is conducive to controlling production costs.

[0015] (2) The present invention realizes online monitoring and automatic adjustment of reaction parameters at each stage through sensor network and data acquisition system, which can accurately control key factors such as low temperature conditions of condensation reaction, catalytic environment of hydrogenation reaction, and gas flow rate and temperature of oxidation reaction, thereby improving the stability and controllability of reaction process and helping to ensure product quality. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall process flow of the present invention; Figure 2 This is a schematic diagram of the condensation reaction stage of the present invention; Figure 3 This is a schematic diagram of the hydrogenation reaction stage of the present invention; Figure 4 This is a schematic diagram of the oxidation reaction stage of the present invention; Figure 5 This is a schematic diagram of the esterification reaction stage of the present invention; Figure 6 This is a schematic diagram of the washing stage process of the present invention; Figure 7 This is a schematic diagram of the distillation stage process of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0018] Please see Figure 1 - Figure 7 This invention provides a microwave-assisted rapid reaction method for chamomile esters, comprising the following steps: S1: Condensation Reaction Stage. Specifically, a 1000ml three-necked flask is prepared as the main reaction vessel. This vessel needs to be equipped with a stirrer, condenser, and temperature sensor to achieve real-time monitoring of the reaction process and ensure that the reaction system is maintained at a low temperature. 400ml of a 10% sodium hydroxide solution is added to the three-necked flask as an alkaline medium, and the solution is cooled to between 0 and 5°C. The microwave radiation device is turned on with a power of 300W, and the stirrer is started simultaneously to evenly disperse the reactants. During stirring, 232g of n-propanal is slowly added dropwise, controlling the dropping rate to keep the reaction temperature below 5°C. After the addition is complete, the reaction continues under microwave radiation for 2 hours to ensure complete reaction. After the reaction, the organic layer is separated and washed with 2×200ml of distilled water to remove unreacted alkali and other impurities. The organic layer is then transferred to a distillation apparatus for vacuum distillation to obtain the intermediate product 2-methyl-2-pentenal. In this process, microwave radiation increases the collision frequency between reactants by promoting the dipole rotation mechanism of polar molecules, thereby accelerating the condensation reaction.

[0019] S2: The hydrogenation reaction stage. Specifically, a pressure-resistant microwave reactor is used as the main equipment. This reactor needs to have a multi-layered heat-insulating structure, including an inner high-temperature resistant ceramic layer, a middle metal shielding layer, and an outer insulation layer to prevent microwave leakage and improve energy utilization. 300 ml of 2-methyl-2-pentenal and 3 g of supported palladium catalyst are added to the reactor. The choice of catalyst is crucial to the reaction efficiency; therefore, the specific surface area and active site distribution of the supported palladium catalyst must be rigorously screened to ensure its effective catalysis of the hydrogenation process. After adding the reactants, the reactor is first purged with nitrogen three times and then with hydrogen three times to remove oxygen from the air and prevent side reactions.

[0020] Furthermore, the microwave power was set to 500W, the reaction pressure to 2MPa, and the reaction temperature was controlled at 80℃ using an external heating device. Under microwave radiation, hydrogen molecules were selectively activated and underwent a hydrogenation reaction with 2-methyl-2-pentenal until the reaction was complete. After the reaction, the catalyst was recovered by filtration and stored for subsequent recycling, while the filtrate was transferred to a distillation unit for further processing to finally obtain 2-methylpentanal. In this process, microwave radiation significantly improved the catalyst utilization rate by selectively heating the active sites on the catalyst surface while avoiding local overheating.

[0021] S3: Oxidation reaction stage. Specifically, a pressure-resistant microwave reactor is used as the main equipment. 400g of 2-methylpentanal is added to the reactor along with 4g of anhydrous cobalt acetate as an oxidation catalyst. Anhydrous cobalt acetate acts as an oxygen activator in this process; the amount used needs to be adjusted according to the reaction scale to ensure the smooth progress of the oxidation reaction. The microwave power is set to 400W, and the reaction temperature is controlled within the range of 20~30℃. Air is slowly introduced through a gas flow meter to provide sufficient oxygen molecules to participate in the oxidation reaction. During this process, microwave radiation promotes the oxidation reaction by enhancing the activation energy of oxygen molecules, while real-time monitoring of reaction temperature and pressure ensures reaction safety. After the reaction is complete, the catalyst and unreacted solid impurities are filtered out to obtain the target product, 2-methylpentanic acid. To ensure the high efficiency of the oxidation reaction, the temperature and pressure changes inside the reactor need to be checked regularly, and the microwave power and air introduction rate adjusted according to the actual situation. S4: Esterification stage. Specifically, another pressure-resistant microwave reactor is used as the main equipment. 3.0g of toluenesulfonic acid is added as a catalyst, 132g of ethanol as the esterification reagent, and 300g of 2-methylvaleric acid as the reaction substrate. Toluenesulfonic acid, as a proton donor, effectively promotes the esterification reaction; its dosage needs to be adjusted according to the reaction scale to ensure smooth reaction. The stirring device is turned on, and microwave heating is started. The microwave power is set to 600W, raising the reaction temperature to the range of 110~130℃. Under microwave radiation, the reaction system quickly reaches reflux and is maintained under reflux until the endpoint. After the reaction, excess ethanol is recovered through distillation, and the reaction solution is cooled to 40℃ to avoid damage to the target product from high temperatures. The crude product is transferred to a washing vessel for further processing. During this process, microwave heating reduces the risk of local overheating through a uniformly distributed energy field and significantly shortens the reaction time.

[0022] S5: Washing stage. Specifically, a step-by-step washing process combined with microwave-assisted heating is used to improve separation efficiency. A 5% sodium carbonate solution is added at a ratio of approximately 12:1 (crude product mass). Microwave-assisted heating is then initiated to 50°C and stirred for 1.5 hours to fully dissolve acidic impurities in the crude product. After standing for 2 hours, the aqueous layer is separated, and distilled water is added at a ratio of 10:1. The mixture is stirred for 1.5 hours, and the pH of the aqueous layer is checked using pH paper to ensure it is close to 7, guaranteeing complete removal of acidic impurities. After standing for 2 hours, the aqueous layer is separated again, and the crude chamomile ester is transferred to a distillation column for further processing. During this process, microwave-assisted heating accelerates the dissolution process by increasing the temperature of the washing solution while preventing the target product from decomposing due to excessive heat.

[0023] S6: In the distillation stage, crude basilyl ester is placed in a distillation column using a microwave-assisted distillation apparatus. The microwave power is set to 700W, and the temperature is gradually increased to the target boiling point. Microwave radiation reduces the thermal conductivity resistance inside the liquid, thereby reducing energy loss during distillation and shortening the distillation time. The distillate is collected to obtain the finished basilyl ester, and its purity is determined by gas chromatography. In this process, microwave-assisted heating reduces energy loss during distillation and shortens the distillation time by lowering the thermal conductivity resistance inside the liquid.

[0024] Furthermore, reaction parameters at each stage are monitored online throughout the entire preparation process, including real-time recording and adjustment of temperature, pressure, microwave power, and reaction time. Automated management of the reaction process is achieved by introducing a sensor network and data acquisition system. The sensor network includes temperature sensors, pressure sensors, and microwave power sensors. These sensors transmit real-time data to the central control system via the data acquisition system, allowing operators to monitor the reaction progress and make necessary adjustments. Additionally, the microwave reactor includes a multi-layered insulation structure and an adjustable microwave transmitter. The multi-layered insulation structure consists of a high-temperature resistant ceramic layer, a metal shielding layer, and a thermal insulation layer, from the inside out. The adjustable microwave transmitter adapts to the needs of different reaction stages by changing the microwave frequency and power density.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A microwave-assisted rapid reaction method for chamomile esters, characterized in that, Includes the following steps: S1: Condensation reaction stage, microwave radiation promotes the low-temperature condensation reaction of propanal with alkaline solution, the reaction temperature is controlled at 0 to 5 degrees Celsius, and microwave radiation is used to accelerate the reaction process. S2: In the hydrogenation reaction stage, a supported palladium catalyst is used in combination with microwave heating to catalytically hydrogenate 2-methyl-2-pentenal after alternating nitrogen and hydrogen gas. The reaction conditions are optimized by adjusting the microwave power and reaction pressure. S3: In the oxidation reaction stage, anhydrous cobalt acetate is used as an oxidation catalyst. Combined with microwave radiation to control the air flow rate and reaction temperature, 2-methylpentanal is efficiently converted into 2-methylpentanoic acid. S4: In the esterification reaction stage, microwave heating is used instead of the traditional reflux heating method to carry out the esterification reaction of 2-methylvaleric acid and ethanol under the catalysis of toluenesulfonic acid, which reduces the reaction time and increases the yield. S5: The washing stage adopts a step-by-step washing process combined with microwave-assisted heating. By precisely controlling the temperature of the washing liquid and the stirring time, the separation efficiency is improved. S6: In the distillation stage, microwave-assisted heating is used to lower the boiling point of crude chamomile ester, shorten the distillation time, and improve the purity of the finished product.

2. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The specific operation of the condensation reaction stage of S1 includes: preparing 400 ml of 10% sodium hydroxide solution in a 1000 ml three-necked flask, cooling it to 0 to 5 degrees Celsius, turning on the microwave radiation device, setting the microwave power to 300 W, and slowly adding 232 g of n-propanal with stirring, controlling the dropping rate to maintain the reaction temperature not exceeding 5 degrees Celsius; after the addition is completed, continue the reaction for 2 hours, separate the organic layer, wash it with 2 × 200 ml of water, and distill to obtain 2-methyl-2-pentenal.

3. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The specific operation of the hydrogenation reaction stage of S2 includes: adding 300 ml of 2-methyl-2-pentenal and 3 g of supported palladium catalyst into a microwave reactor, purging with nitrogen three times, and then purging with hydrogen three times; setting the microwave power to 500 W, the reaction pressure to 2 MPa, and controlling the reaction temperature to 80 degrees Celsius until the reaction is complete; filtering to recover the catalyst, and distilling the filtrate to obtain 2-methylpentenal.

4. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The specific operation of the oxidation reaction stage of S3 includes: adding 400g of 2-methylpentanal to a microwave reactor, adding 4g of anhydrous cobalt acetate as an oxidation catalyst, setting the microwave power to 400W, controlling the reaction temperature to 20 to 30 degrees Celsius, slowly introducing air until the reaction is complete; and filtering to obtain 2-methylpentanic acid.

5. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The specific operation of the esterification reaction stage of S4 includes: adding 3.0g toluenesulfonic acid, 132g ethanol and 300g 2-methylvaleric acid to a microwave reactor, turning on the stirrer and starting the microwave heating, setting the microwave power to 600W, raising the temperature to 110 to 130 degrees Celsius, and refluxing the reaction to the endpoint; recovering excess ethanol, cooling the reaction solution to 40 degrees Celsius, and transferring the crude product to a washing vessel.

6. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The specific operation of the washing stage of S5 includes: adding 5% sodium carbonate solution at a ratio of approximately 12:1 based on the mass of the crude product, turning on microwave-assisted heating to 50 degrees Celsius, stirring for 1.5 hours, letting stand for 2 hours to separate the water layer; then adding water at a ratio of 10:1, stirring for 1.5 hours, using pH test paper to check that the pH value is close to 7, letting stand for 2 hours to separate the water layer, and transferring the crude chamomile ester to a distillation column.

7. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The specific operation of the distillation stage of S6 includes: placing crude chamomile ester in a microwave-assisted distillation device, setting the microwave power to 700W, gradually heating to the target boiling point, and collecting the distillate to obtain the finished chamomile ester.

8. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The method also includes online monitoring of reaction parameters at each stage, including real-time recording and adjustment of temperature, pressure, microwave power, and reaction time, to ensure precise control of reaction conditions at each stage.

9. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The microwave reactor includes a multi-layer heat insulation structure and an adjustable microwave transmitter. The multi-layer heat insulation structure consists of a high-temperature resistant ceramic layer, a metal shielding layer, and a heat insulation layer from the inside out. The adjustable microwave transmitter can adapt to the needs of different reaction stages by changing the microwave frequency and power density.

10. The microwave-assisted rapid reaction method for chamomile esters according to claim 1, characterized in that: The microwave radiation accelerates the collision frequency between reactants through the polar molecular dipole rotation mechanism, significantly shortening the reaction time during the condensation reaction stage.

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