Magnetic microbubble catalyst and application thereof in alcohol amine coupling oxidation reaction

Abstract

The application discloses a magnetic microbubble catalyst, which is prepared by the following method, specifically, gas is dissolved in a solvent to obtain a gas-saturated solution, the gas-saturated solution is introduced into a microbubble generating device to obtain a microbubble solution, magnetic nanoparticles are added into the microbubble solution, and the magnetic nanoparticles are adsorbed on the surface of the microbubbles under the adsorption effect of the bubble interface to form magnetic microbubbles, and the magnetic microbubbles are uniformly dispersed in the solution to form a magnetic microbubble suspension. Through the construction of a gas-liquid-solid reaction intensification system based on the magnetic microbubbles, the catalytic reaction can be induced to occur on the surface of the magnetic nanoparticles adsorbed by the microbubbles, the material exchange rate of the catalytic reaction is effectively enhanced, the coupling efficiency of the alcohol amine oxidation reaction is greatly improved, and the yield of the product is improved.

Description

Technical Field

[0001] This invention relates to a magnetic microbubble catalyst, and also to the application of the above catalyst in the coupled oxidation reaction of alcoholamines. Background Technology

[0002] Imines are a large class of compounds containing carbon-nitrogen double bonds in their molecular structure, and they have wide applications in biomedicine, fine chemicals, and agricultural production. The traditional industrial method for synthesizing imines utilizes the condensation reaction between carbonyl compounds and amines. However, this process requires the addition of active aldehydes, Lewis acid catalysts, dehydrating agents, and high-temperature reaction conditions. Addressing the shortcomings of traditional methods, the synthesis of imines using an alcohol-amine coupling process is a novel and sustainable technological route.

[0003] Magnetic iron oxide nanoparticles are iron-based nanomaterials with advantages such as magnetic responsiveness, large specific surface area, low cost, good controllability, simple preparation process, and ease of functionalization. They exhibit excellent performance in multiphase catalysis fields such as catalytic oxidation, hydrogenation reduction, and water-gas conversion. Despite these advantages, the low catalytic efficiency of magnetic iron oxide nanoparticles at room temperature and pressure hinders their practical application in the coupled oxidation of alcoholamines. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a magnetic microbubble catalyst that exhibits good catalytic efficiency and can significantly improve the product yield when applied to the coupled oxidation reaction of alcoholamines.

[0005] Technical solution: The magnetic microbubble catalyst of the present invention is prepared by the following method: First, the gas is dissolved in a solvent to obtain a saturated gas solution, and the saturated gas solution is passed into a microbubble generating device to obtain a microbubble solution; magnetic nanoparticles are added to the microbubble solution, and the magnetic nanoparticles are adsorbed on the surface of the microbubble under the adsorption effect at the bubble interface to form magnetic microbubbles, and the magnetic microbubbles are uniformly dispersed in the solution to form a magnetic microbubble suspension.

[0006] Wherein, the gas is air or oxygen; the solvent is an organic solvent or water; the organic solvent is diethyl ether, acetone or toluene.

[0007] In the microbubble solution, the amount of bubbles generated was 4 × 10⁻⁶. 5 ~8×10 5 per mL.

[0008] The average particle size of the bubbles is 100–200 μm.

[0009] The amount of magnetic nanoparticles added is 0.1% to 0.5% of the weight of the microbubble solution (the weight of the microbubble solution before adding the nanoparticles).

[0010] The magnetic nanoparticles are iron oxide (γ-Fe2O3, Fe3O4) nanoparticles or MnFe2O4 nanoparticles.

[0011] The magnetic nanoparticles are either unmodified or modified with oleic acid, citric acid, polyethylene glycol, polyethyleneimine, or polylysine.

[0012] The magnetic nanoparticles have a particle size of 5–200 nm.

[0013] The microbubble generator can be a venturi tube type, a dissolved air pump type, a flow focusing type, or a T-type microchannel type.

[0014] The application of the above-mentioned magnetic microbubbles as catalysts in the coupled oxidation reaction of alcohols and amines is as follows: Equal molar amounts of alcohols and amines are mixed and added to the above-mentioned magnetic microbubble suspension. The reaction system is placed under an alternating magnetic field. The magnetic field is turned on, and the magnetocaloric effect of the magnetic nanoparticles is used to form hot spots in situ on the surface of the magnetic nanoparticles at the microbubble interface, so that the catalytic reaction can proceed rapidly. After the reaction, the corresponding imine product is obtained.

[0015] The alternating magnetic field has an oscillation frequency of 100kHz to 500kHz, a power of 100W to 3000W, and a magnetic field activation time of 30 to 60 minutes.

[0016] This invention utilizes the strong adsorption capacity of microbubbles for suspended solid particles in a liquid phase to produce magnetic microbubbles. By adsorbing a solid catalyst onto the bubble surface, the gas inside the bubble and the liquid outside the bubble rapidly exchange substances on the solid catalyst surface, thereby significantly enhancing the reaction efficiency of the gas-liquid-solid three-phase reaction system. Simultaneously, heating the magnetic nanoparticles with an alternating magnetic field to create localized hot spots not only enhances the catalytic effect of magnetic iron oxide nanoparticles on the alcoholamine coupling reaction, improving production efficiency and reducing reaction energy consumption, but also allows for rapid recovery of the catalyst under static magnetic field conditions after the reaction, achieving recycling.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: By constructing a gas-liquid-solid reaction enhancement system based on magnetic microbubbles, the present invention can induce catalytic reactions to take place on the surface of magnetic nanoparticles adsorbed by microbubbles, effectively enhancing the mass exchange rate of the catalytic reaction, thereby significantly improving the coupling efficiency of the alcohol amine oxidation reaction and thus increasing the yield of the product. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the principle of the magnetic microbubble-catalyzed oxidation reaction of alcoholamines according to the present invention. Detailed Implementation

[0019] Example 1

[0020] The method for preparing magnetic microbubbles according to the present invention specifically involves: firstly, dissolving air in diethyl ether to obtain a gas-saturated diethyl ether solution; then passing the gas-saturated diethyl ether solution into a Venturi bubble generator to obtain an air microbubble diethyl ether solution (the gas inside the microbubbles is air); the amount of bubbles generated in the microbubble diethyl ether solution is 4.6 × 10⁻⁶. 5 The average particle size of the bubbles is 100 μm. Take 20 mL of microbubble ether solution into a flask, add citric acid-modified Fe3O4 nanoparticles with an average particle size of 100 nm, the amount of Fe3O4 nanoparticles added is 0.1% of the weight of the microbubble solution, and incubate at room temperature (25℃) for 24 h. The magnetic nanoparticles are adsorbed on the surface of the microbubble under the adsorption effect of the bubble interface to form magnetic microbubbles. The magnetic microbubbles are uniformly dispersed in the ether to form a magnetic microbubble suspension.

[0021] 1 mmol of 4-chlorobenzyl alcohol and 1 mmol of n-butylamine (as reactants) were added to the magnetic microbubble suspension of Example 1. The mass of the added catalyst (magnetic microbubbles) was 0.1 g (calculated as Fe). The reaction was carried out at 100 kHz and 100 W for 30 min. After the reaction, the Fe3O4 nanoparticles in the solution were recovered using an external static magnetic field. The magnetic nanoparticles were recycled. The solution after the reaction was analyzed by gas chromatography. The yield of the product N-butyl-1-(4-chlorophenyl)methylimine was 68.2%.

[0022] Comparative Example 1

[0023] 1 mmol of 4-chlorobenzyl alcohol and 1 mmol of n-butylamine (as reactants) were mixed, and 0.1 g of Fe3O4 nanoparticles (calculated as Fe) were added as a catalyst. The mixture was reacted at 100 kHz and 100 W for 30 min. The solution was analyzed by gas chromatography after the reaction. The yield of the product N-butyl-1-(4-chlorophenyl)methylimine was 22.1%.

[0024] Example 2

[0025] The method for preparing magnetic microbubbles according to the present invention specifically involves: firstly, dissolving air in acetone to obtain a gas-saturated acetone solution; then passing the gas-saturated acetone solution into a Venturi bubble generator to obtain an air microbubble acetone solution (the gas inside the microbubbles is air); the amount of bubbles generated in the microbubble acetone solution is 5.0 × 10⁻⁶. 5The number of microbubbles per mL was 100 μm. 20 mL of microbubble acetone solution was placed in a flask, and oleic acid-modified MnFe2O4 nanoparticles with an average particle size of 100 nm were added to it. The amount of MnFe2O4 nanoparticles added was 0.3% of the weight of the microbubble solution. The mixture was incubated at room temperature (25 °C) for 24 h. The magnetic nanoparticles were adsorbed onto the surface of the microbubbles under the adsorption effect at the bubble interface to form magnetic microbubbles. The magnetic microbubbles were uniformly dispersed in acetone to form a magnetic microbubble suspension.

[0026] 2 mmol of benzyl alcohol and 2 mmol of cyclohexylamine (as reactants) were added to the magnetic microbubble suspension of Example 2. The mass of the added catalyst (magnetic microbubbles) was 0.1 g (Mn and Fe are both calculated as Fe). The reaction was carried out at 300 kHz and 1000 W for 30 min. After the reaction, the MnFe2O4 nanoparticles in the solution were recovered using an external static magnetic field. The magnetic nanoparticles were recycled. The solution after the reaction was analyzed by gas chromatography. The yield of the product N-cyclohexyl-1-phenylmethylimine was 79.2%.

[0027] Comparative Example 2

[0028] 2 mmol of benzyl alcohol and 2 mmol of cyclohexylamine (as reactants) were mixed, and 0.1 g of MnFe2O4 nanoparticles (Mn and Fe are both calculated as Fe) were added as a catalyst. The mixture was reacted at 300 kHz and 1000 W for 30 min. The solution was analyzed by gas chromatography after the reaction, and the yield of the product N-cyclohexyl-1-phenylmethylimine was 35.5%.

[0029] Example 3

[0030] The method for preparing magnetic microbubbles according to the present invention specifically involves: firstly, dissolving oxygen in toluene to obtain a gas-saturated toluene solution; then passing the gas-saturated toluene solution into a dissolved gas pump to obtain an oxygen microbubble toluene solution (the gas inside the microbubbles is oxygen); the amount of bubbles generated in the microbubble toluene solution is 7.9 × 10⁻⁶. 5 The number of microbubbles per mL was 200 μm. 20 mL of microbubble toluene solution was placed in a flask, and unmodified γ-Fe2O3 nanoparticles with an average particle size of 20 nm were added to it. The amount of γ-Fe2O3 nanoparticles added was 0.5% of the weight of the microbubble solution. The mixture was incubated at room temperature (25 °C) for 24 h. The magnetic nanoparticles were adsorbed onto the surface of the microbubbles under the adsorption effect at the bubble interface to form magnetic microbubbles. The magnetic microbubbles were uniformly dispersed in toluene to form a magnetic microbubble suspension.

[0031] 2 mmol of benzyl alcohol and 2 mmol of aniline (as reactants) were added to the magnetic microbubble suspension of Example 3. The mass of the added catalyst (magnetic microbubble) was 0.1 g (calculated as Fe). The reaction was carried out at 500 kHz and 3000 W for 30 min. After the reaction, the iron oxide nanoparticles in the solution were recovered by an external static magnetic field to realize the recycling of magnetic nanoparticles. The solution after the reaction was analyzed by gas chromatography, and the yield of the product N-benzylidene aniline was 93.5%.

[0032] Comparative Example 3

[0033] 2 mmol of benzyl alcohol and 2 mmol of aniline (as reactants) were mixed, and 0.1 g (calculated as Fe) of γ-Fe2O3 nanoparticles were added as a catalyst. The mixture was reacted at 500 kHz and 3000 W for 30 min. The solution was analyzed by gas chromatography after the reaction, and the yield of N-benzyl aniline was 42.3%.

Claims

1. A magnetic microbubble catalyst, characterized in that: The solution is prepared by the following method: First, the gas is dissolved in a solvent to obtain a saturated gas solution. The saturated gas solution is then passed into a microbubble generator to obtain a microbubble solution. Magnetic nanoparticles are added to the microbubble solution. The magnetic nanoparticles are adsorbed onto the surface of the microbubbles under the adsorption effect at the bubble interface to form magnetic microbubbles. The magnetic microbubbles are uniformly dispersed in the solution to form a magnetic microbubble suspension. The solvent is diethyl ether, acetone, or toluene. The amount of magnetic nanoparticles added is 0.1-0.5% of the weight of the microbubble solution.

2. The magnetic microbubble catalyst according to claim 1, characterized in that: The gas is air or oxygen.

3. The magnetic microbubble catalyst according to claim 1, characterized in that: In the microbubble solution, the amount of bubbles generated is 4 × 10⁻⁶. 5 ~8×10 5 per mL.

4. The magnetic microbubble catalyst according to claim 1, characterized in that: The average particle size of the bubbles is 100~200μm.

5. The magnetic microbubble catalyst according to claim 1, characterized in that: The magnetic nanoparticles are iron oxide nanoparticles or MnFe2O4 nanoparticles.

6. The magnetic microbubble catalyst according to claim 1, characterized in that: The magnetic nanoparticles are either unmodified or modified with oleic acid, citric acid, polyethylene glycol, polyethyleneimine, or polylysine.

7. The application of the magnetic microbubbles as a catalyst in the coupled oxidation reaction of alcoholamines according to claim 1, characterized in that, Specifically, equimolar amounts of alcohols and amines are mixed and added to the above-mentioned magnetic microbubble suspension. The reaction system is placed under an alternating magnetic field, the magnetic field is turned on, and the corresponding imine product is obtained after the reaction.

8. The application of magnetic microbubbles as a catalyst in the coupled oxidation reaction of alcoholamines according to claim 7, characterized in that: The oscillation frequency of the alternating magnetic field is 100kHz~500kHz, the power is 100W~3000W, and the magnetic field is turned on for 30~60 minutes.

9. The application of the magnetic microbubbles as a catalyst in the coupled oxidation reaction of alcoholamines according to claim 7, characterized in that: In the alcohol-amine coupled oxidation reaction system, when the molar amount of alcohol and amine compounds added is 1~5 mmol, the mass of the added magnetic microbubbles is 0.1~0.2 g based on Fe.

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