A process for the preparation of cyclopropyl methyl ketone

Abstract

This invention belongs to the field of organic synthesis technology and discloses a method for preparing cyclopropyl methyl ketone, comprising at least the following steps: 1) A mixture of acetaldehyde and allyl halide or allyl ester, along with a catalyst, is formed in a reaction vessel, heated and stirred to induce a hydroacylation reaction. Unreacted raw materials are removed by vacuum distillation to obtain an intermediate product. 2) The intermediate product obtained in step 1) is mixed with an alkaline catalyst, heated and kept at a constant temperature to obtain crude cyclopropyl methyl ketone, which is then purified by distillation to obtain pure cyclopropyl methyl ketone. The preparation method of this invention uses inexpensive and readily available raw materials, exhibits high atom economy, and has significant economic benefits; the alkaline catalyst used in step 2) is regenerable and can be further scaled up industrially.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and specifically relates to a method for preparing cyclopropylmethyl ketone. Background Technology

[0002] Cyclopropyl methyl ketone (CPMK) is an important raw material for organic synthesis. Its molecular structure exhibits unique stability and reactivity, making it primarily used as an intermediate in pharmaceuticals and pesticides. For example, in the pharmaceutical field, it is used to prepare broad-spectrum antibacterial drugs such as ciprofloxacin and the anti-HIV drug efavirenz; in the pesticide field, CPMK is an indispensable intermediate for the plant growth regulator cyclophosphamide and the green pesticide pyraclostrobin. Therefore, CPMK has a wide range of applications.

[0003] Depending on the source of raw materials, there are two main methods for the industrial preparation of cyclopropyl methyl ketone. One method involves synthesizing 2-acetyl-γ-butyrolactone from petrochemical products ethylene oxide and ethyl acetoacetate. Cyclopropyl methyl ketone is then obtained by extruding one molecule of CO2 from 2-acetyl-γ-butyrolactone and sodium iodide at 170-200℃, with a yield of approximately 97%. However, this high-temperature reaction requires sophisticated equipment, and sodium iodide is easily oxidized, resulting in poor stability and increased production costs. Furthermore, the use of highly hazardous ethylene oxide introduces uncontrollable safety risks, hindering industrial application.

[0004] Another process for preparing cyclopropyl methyl ketone involves the hydrogenation of biomass-derived furfural to 2-methylfuran via copper-nickel catalysis. The 2-methylfuran is then converted to acetylacetonol under the catalysis of a palladium-on-carbon catalyst and dilute hydrochloric acid. Next, acetylacetonol is chlorinated with concentrated hydrochloric acid to obtain 5-chloro-2-pentanone. Finally, it is cyclized with an aqueous sodium hydroxide solution to obtain cyclopropyl methyl ketone. However, during the acidification process, at least one-third of the reactants are directly converted into tar waste rather than products, resulting in low selectivity and increased process costs. Furthermore, the hydrogenation catalyst requires frequent regeneration, extending the process cycle.

[0005] Existing methods for preparing cyclopropyl methyl ketones either suffer from low yield and low selectivity, or are cumbersome and time-consuming. Therefore, this invention is proposed. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing cyclopropyl methyl ketone with high yield, low raw material cost, and high atom economy.

[0007] To address the above problems, the present invention provides a method for preparing cyclopropyl methyl ketone, comprising at least the following steps:

[0008] 1) Acetaldehyde, an allyl compound, and a metal catalyst are mixed in a reactor and stirred to induce a hydroacylation reaction. Unreacted raw materials are removed by vacuum distillation to obtain an intermediate product. The allyl compound is an allyl halide or an allyl ester.

[0009] 2) The intermediate product obtained in 1) is mixed with an alkaline catalyst, heated and kept at a constant temperature to react and obtain crude cyclopropyl methyl ketone. Pure cyclopropyl methyl ketone is obtained by distillation.

[0010] Step 1) is a hydroacylation reaction.

[0011] Furthermore, in step 1), the molar ratio of the reactants acetaldehyde and allyl halide / allyl ester is (1-2):1, preferably 1.5:1.

[0012] In the above scheme, under the specified molar ratio, the allyl halide / allyl ester of the raw materials can react completely. Excess allyl halide / allyl ester will be oxidized to epoxy halide / propane ester. The formation of this byproduct reduces the selectivity of the product and increases the difficulty of separation.

[0013] Furthermore, in step 1), the allyl compound is any one of allyl chloride, allyl iodine, allyl bromide, allyl acetate, allyl p-toluenesulfonate, allyl p-nitrobenzenesulfonate, allyl methanesulfonate, and allyl trifluoromethanesulfonate.

[0014] Furthermore, in step 1), the molar ratio of the metal catalyst to the reactant allyl compound is (0.001-0.06):1, preferably 0.01:1.

[0015] In the above scheme, when the mass of the metal catalyst and the mass of acetaldehyde are within the aforementioned limits, the metal catalyst exhibits good catalytic effect on the reaction in step 1), effectively catalyzing the hydroacylation reaction between acetaldehyde and allyl halide / allyl ester. The reaction rate increases with the increase of catalyst dosage. When the amount of metal catalyst is low, the reaction time is prolonged, and the production efficiency decreases; however, when the amount of metal catalyst is too high, the reaction rate does not increase significantly, increasing production costs and hindering industrial application.

[0016] Furthermore, the reaction temperature in step 1) is -10 to 80°C, preferably 25 to 40°C.

[0017] In the above schemes, when the reaction temperature is within the above-defined range, acetaldehyde and allyl halides / allyl esters can undergo hydroacylation under the catalysis of a metal catalyst. If the reaction temperature is too low, the reaction rate will be reduced and the production cycle will be increased. If the reaction temperature is too high, some allyl halides / allyl esters will generate epoxy halides / propane esters, resulting in a low reaction yield and difficulty in separating and purifying intermediate products.

[0018] Furthermore, the metal catalyst used in step 1) may be one or a combination of several of the following: cobalt acetate (II), cobalt chloride hexahydrate (II), anhydrous cobalt chloride (II), cobalt naphthenate (II), cobalt acetylacetonate (III), cobalt octacarbonyl (II), dichloro(pentamethylcyclopentadienyl)rhodium(III) dimer, tri(triphenylphosphine)rhodium chloride (I), dimeric rhodium acetate (II), hydrated rhodium trichloride (III), potassium hexachlororhodium(III) acid, rhodium(II) octoate dimer, (4,4'-di-tert-butyl-2,2'-bipyridine)bis[(2-pyridyl)phenyl]iridium(III) hexafluorophosphate, iridium chloride trihydrate (III), and tri(2-phenylpyridine)iridium(III).

[0019] Further, step 1) can be performed by adding the raw material and catalyst to the reactor, heating to the reaction temperature and stirring, and then cooling to room temperature to obtain the intermediate product. Alternatively, the mixture can be stirred at room temperature, and then directly post-processed after the reaction is complete.

[0020] Furthermore, the intermediate obtained in step 1) is purified by distillation.

[0021] Furthermore, the alkaline catalyst used in step 2) is a rare earth metal supported catalyst, which includes a support and a rare earth metal active component supported on the support.

[0022] Furthermore, the rare earth metal active component is selected from one or more of Sc, Y, La, Ce, Pr, and Nd; preferably, the rare earth metal active component is La.

[0023] Among them, the active component of the alkaline catalyst should have reasonable alkalinity and stability, that is, to ensure both good catalytic activity and regenerability. Although alkali metal and alkaline earth metal active components have good catalytic activity, they are prone to irreversible deactivation due to the absorption of CO2 from the air. Therefore, rare earth metals are selected as the catalytic active component.

[0024] In the above scheme, the active component exists in the form of oxide on the support, making the catalyst more basic. According to Baldwin's favorable ring formation rule, the stronger the basicity of the catalyst, the more it can promote the formation of three-membered rings, thereby improving the reaction yield, shortening the production cycle, and reducing energy consumption.

[0025] Furthermore, the support is one or more of Al2O3, SiO2, and MgO; preferably, the support is Al2O3 (γ-crystal form, with a specific surface area of ​​approximately 185 m²). 2 / g, can be used directly with products such as Bailingwei Technology, product number: 902601)

[0026] Among the above methods, the use of spherical Al2O3 supports offers advantages such as large specific surface area, high activity, good formability, and easy recyclability. Therefore, it can support a large amount of active components, increasing catalytic sites and improving catalytic performance. Furthermore, the moderate acidity and basicity of Al2O3 increase product yield and selectivity, and the prepared catalyst is less prone to agglomeration and has a long service life, making it suitable for industrial applications.

[0027] Furthermore, the rare earth metal active component accounts for 5% to 50% of the mass percentage of the carrier, preferably 30%.

[0028] In the above schemes, when the loading of the active component is within the aforementioned limits, the reaction yield increases with the increase of the loading. However, when the loading reaches 30%, further increasing the loading of the active component does not significantly improve the reaction yield and increases the preparation cost; if the loading is too low, the reaction yield will decrease due to insufficient catalytic sites. Therefore, under the premise of ensuring high product yield and low production cost, the loading of the active component is determined to be 30%.

[0029] Furthermore, the alkaline catalyst is prepared using an equal-volume impregnation method. The catalyst preparation process includes: after activating the support, weighing the metal nitrate corresponding to the required loading amount to prepare an aqueous solution, impregnating the support in the prepared aqueous solution under vigorous stirring, and ultrasonically ensuring uniform impregnation. The resulting mixture is dried in an oven and then calcined in a muffle furnace at 600°C for 3 hours. After cooling, the supported catalyst is obtained. Repeating the above synthesis method yields catalysts with different loading amounts. The catalyst preparation method is simple and reusable, possessing industrial application value.

[0030] Furthermore, in step 2), the mass ratio of the alkaline catalyst to the intermediate product is (0.001-0.10):1, preferably 0.06:1.

[0031] In the above scheme, when the mass of the alkaline catalyst and the mass of the intermediate product are within the above-mentioned limits, the catalyst can efficiently promote the formation of cyclopropyl methyl ketone. When the amount of catalyst used is small, the production cycle is prolonged and the production efficiency is reduced; however, when the amount of catalyst used is too large, too much raw material is adsorbed, which is not conducive to the separation of products, and the reaction rate is not significantly improved, but rather the production cost is increased.

[0032] Furthermore, the reaction temperature in step 2) is 175-190℃, preferably 185℃.

[0033] In the above scheme, when the reaction temperature is within the specified range, the intermediate product undergoes cyclization in the presence of a basic catalyst to generate the target product, cyclopropylmethyl ketone. However, if the reaction temperature is too high, coke formation is likely to occur, resulting in the loss of raw materials; if the reaction temperature is too low, the reaction rate will be too slow.

[0034] Further, the specific operation of the post-reaction distillation in step 2) can be as follows: add crude cyclopropyl methyl ketone to a 250 mL three-necked flask, attach a 15 cm long spiky distillation column, heat and fractionate, and collect the fraction at 114℃±1℃, which is the pure cyclopropyl methyl ketone.

[0035] Specifically, the preparation method of cyclopropyl methyl ketone in this invention is as follows:

[0036]

[0037] Wherein, R is Cl, Br, I, OTs, OMs, ONs, Otf, or OAc. Cat.1 indicates the metal catalyst used in step 1), and Cat.2 indicates the rare earth metal supported catalyst used in step 2).

[0038] The beneficial effects of this invention are as follows:

[0039] 1. This invention uses acetaldehyde and allyl halide / allyl ester as raw materials to prepare cyclopropyl methyl ketone. The raw materials are inexpensive and readily available, have high atom economy, and can be reacted at a lower temperature, which reduces production energy consumption and has significant economic benefits.

[0040] 2. The supported catalyst used in step 2) has high activity and can be regenerated by alkaline washing. It is not prone to carbon buildup and has good reusability, which reduces production costs.

[0041] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0042] The accompanying drawings, which form part of this invention, are provided to further illustrate the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention, but do not constitute an undue limitation of the invention.

[0043] Figure 1 This is the 1H NMR spectrum of 5-chloro-2-pentanone, the intermediate product prepared in Example 1 of this invention.

[0044] Figure 2 This is the 1H NMR spectrum of the cyclopropylmethyl ketone prepared in Example 1 of this invention.

[0045] Figure 3 This is the N2 adsorption-desorption isotherm of the alkaline catalyst La@Al2O3 in Example 1 of this invention.

[0046] Figure 4 This is the XRD pattern of the alkaline catalyst La@Al2O3 in Example 1 of this invention.

[0047] Figure 5This is the SEM spectrum of the alkaline catalyst La@Al2O3 in Example 1 of this invention.

[0048] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0049] Exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. Those skilled in the art will understand that the following embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0050] The alkaline catalyst used in the following examples can be obtained by the following preparation method:

[0051] Weigh 1.0 kg of spherical Al2O3 support and calcine it in a muffle furnace at 400℃ for 1 h to activate the support. Weigh 934.2 g of La(NO3)3·6H2O, dissolve it in 400 mL of deionized water, add the above support with vigorous stirring, and sonicate for 30 min to ensure uniform distribution of the impregnation solution.

[0052] The resulting mixture was dried in an oven at 110°C for 2 hours, and then placed in a muffle furnace. In an air atmosphere, the temperature was increased to 600°C at a rate of 10°C / min, and calcined for 3 hours. After cooling to room temperature, the spherical catalyst containing 30% La@Al2O3 was obtained.

[0053] The "30%" refers to the fact that the mass of La in the supported catalyst is 30% of the mass of the support; by changing the amount of nitrate, catalysts with different loading amounts can be obtained; by using other metal nitrates, catalysts with different metal supports can be obtained; by using other supports, catalysts with different supports can be obtained.

[0054] This type of catalyst can also be regenerated. Specific regeneration methods are as follows:

[0055] If the catalyst becomes deactivated after repeated use, the catalyst bed should be rinsed with a 5% NaOH solution until the pH of the washing solution no longer decreases. Then, it should be washed with deionized water until the washing solution is neutral. Catalyst regeneration is completed by vacuum drying at 110℃ for 2 hours.

[0056] Example 1

[0057] 76.5 g (1 mol) of allyl chloride, 66.1 g (1.5 mol) of acetaldehyde, and 9.3 g (0.01 mol) of rhodium tris(triphenylphosphine) chloride were added to a 250 mL three-necked flask. The mixture was kept at 25 °C with stirring under air for 5 hours. Unreacted raw materials were removed by vacuum distillation for recycling. The byproduct acetic acid was then removed by distillation, finally yielding 90.4 g of the intermediate product 5-chloro-2-pentanone, with a yield of 75%. The resulting liquid product was used directly in the next step without purification.

[0058] 80 g of the intermediate product 5-chloro-2-pentanone was injected into the feed tank of a fixed-bed reactor. 6 g of spherical catalyst (30% La@Al2O3) was loaded into the fixed-bed reactor tube. The feed was preheated and the bed temperature was adjusted to 70°C. A peristaltic pump was used to continuously feed the catalyst bed at a rate of 1 g / min, yielding crude cyclopropyl methyl ketone. The crude product was then distilled using a 150 mm spiked column. The fraction collected at 114°C ± 1°C under atmospheric pressure yielded 53.0 g of pure cyclopropyl methyl ketone, with a yield of 95%.

[0059] In this embodiment, the total yield of pure cyclopropyl methyl ketone was 71% based on the initial raw material allyl chloride.

[0060] Example 2

[0061] 120.9 g (1 mol) of allyl bromide, 66.1 g (1.5 mol) of acetaldehyde, and 6.5 g (0.01 mol) of tris(2-phenylpyridine)iridium were added to a 250 mL three-necked flask. The mixture was kept at 25 °C under air and stirred. Unreacted raw materials were removed by vacuum distillation for recycling. The byproduct acetic acid was then removed by distillation, finally yielding 115.5 g of the intermediate product 5-bromo-2-pentanone, with a yield of 70%. The resulting liquid product was used directly in the next step without purification.

[0062] 80 g of the intermediate product 5-bromo-2-pentanone was injected into the feed tank of a fixed-bed reactor. 6 g of spherical catalyst (25% La@SiO2) was loaded into the fixed-bed reactor tube. The feed preheating and bed temperature were adjusted to 70°C. A peristaltic pump was used to continuously feed the catalyst bed at a rate of 1 g / min, yielding crude cyclopropyl methyl ketone. The crude product was then distilled using a 150 mm spiked column. The fraction collected at 114°C ± 1°C under atmospheric pressure yielded 36.7 g of pure cyclopropyl methyl ketone, with a yield of 90%.

[0063] In this embodiment, the total yield of pure cyclopropyl methyl ketone is 63% based on the initial raw material allyl bromide.

[0064] Example 3

[0065] 100.1 g (1 mol) of allyl acetate, 66.1 g (1.5 mol) of acetaldehyde, and 3.6 g (0.01 mol) of cobalt(III) acetylacetonate were added to a 250 mL three-necked flask. The mixture was kept at 25 °C under air and stirred. Unreacted raw materials were removed by vacuum distillation for recycling. The byproduct acetic acid was then removed by distillation, finally yielding 98.0 g of the intermediate product, 4-oxopentyl acetate, with a yield of 68%. The resulting liquid product was used directly in the next step without purification.

[0066] 80 g of the intermediate product, 4-oxoamyl acetate, was injected into the feed tank of a fixed-bed reactor. 6 g of spherical catalyst (20% La@Al₂O₃) was loaded into the fixed-bed reactor tube. The feed was preheated and the bed temperature was adjusted to 70 °C. A peristaltic pump was used to continuously feed the catalyst bed at a rate of 1 g / min, yielding crude cyclopropyl methyl ketone. The crude product was then distilled using a 150 mm spiked column. The fraction collected at 114 °C ± 1 °C under atmospheric pressure yielded 38.7 g of pure cyclopropyl methyl ketone, with a yield of 83%.

[0067] In this embodiment, the total yield of pure cyclopropyl methyl ketone is 56% based on the initial raw material allyl acetate.

[0068] Example 4

[0069] 212.3 g (1 mol) of allyl p-toluenesulfonate, 66.1 g (1.5 mol) of acetaldehyde, and 4.4 g (0.01 mol) of rhodium dimer acetate were added to a 250 mL three-necked flask. The mixture was kept at 25 °C with stirring under air for 5 hours. Unreacted raw materials were removed by vacuum distillation for recycling. The byproduct acetic acid was then removed by distillation, finally yielding 181.8 g of the intermediate product, 4-oxopentyl p-toluenesulfonate, with a yield of 71%. The resulting liquid product was used directly in the next step without purification.

[0070] 80 g of the intermediate product p-toluenesulfonic acid-4-oxopentyl ester was injected into the feed tank of a fixed-bed reactor. 6 g of spherical catalyst (15% La@Al2O3) was loaded into the fixed-bed reaction tube. The feed preheating and bed temperature were adjusted to 70 °C. A peristaltic pump was used to continuously feed the catalyst bed at a rate of 1 g / min, yielding crude cyclopropyl methyl ketone. The crude product was then distilled using a 150 mm spiked column. The fraction collected at 114 °C ± 1 °C under atmospheric pressure yielded 20.5 g of pure cyclopropyl methyl ketone, with a yield of 78%.

[0071] In this embodiment, the total yield of pure cyclopropyl methyl ketone is 55% based on the initial raw material allyl p-toluenesulfonate.

[0072] Comparative Example 1

[0073] This embodiment uses the following steps to synthesize cyclopropylmethyl ketone:

[0074] 100g of 2-methylfuran, 8g of 5% palladium on carbon (palladium loading was 5% of the activated carbon mass, and the product was moistened with 55% water by mass), and 10g of 10% hydrochloric acid were added to a stainless steel reactor. The mixture was heated to 30°C and stirred, with hydrogen gas continuously introduced at 0.3 MPa, and the reaction was maintained at this temperature for 32 hours. After the hydrogenation reaction was completed, the mixture was transferred to a neutralization reactor, where the added hydrochloric acid was neutralized with an 8% sodium carbonate solution. After neutralization, the mixture was allowed to stand and separated. The organic phase was transferred to a distillation vessel, and unreacted raw materials were removed by vacuum distillation to obtain 118g of the intermediate product penta-1-ol-4-one, with a yield of 95%.

[0075] 280g of 20% hydrochloric acid and 100g of pent-1-ol-4-one were added to a reaction vessel, heated to about 60°C and stirred, and the reaction was maintained at this temperature for 1 hour. The temperature was then increased to 90°C, and 72g of the product 5-chloro-2-pentanone was distilled off under reduced pressure, with a yield of 61%. The hydrochloric acid was recovered and reused.

[0076] 77 g of a 32% sodium hydroxide solution and 55 g of 5-chloro-2-pentanone were added to a reaction vessel, heated to approximately 70°C and stirred, and the reaction was maintained at this temperature for 2 hours. After cooling to room temperature, the organic phase was extracted, and the product cyclopropyl methyl ketone was obtained by vacuum distillation, yielding 37 g of cyclopropyl methyl ketone, with a yield of 97%.

[0077] In this comparative example, the total yield of cyclopropyl methyl ketone was 54% based on the initial feedstock 2-methylfuran.

[0078] Comparative Example 2

[0079] This embodiment uses the following steps to synthesize cyclopropylmethyl ketone:

[0080] 40 g of pre-cooled sodium hydroxide, 250 mL of methanol, 130 g of ethyl acetoacetate, and 60 mL of ethylene oxide were stirred at 0-2 °C for 12 h, and then the mixture was heated to 30 °C and reacted for another 3 h. After the reaction was complete, hydrochloric acid was added to adjust the pH to 3-3.5. The residue was removed by filtration, and the filtrate was extracted with diethyl ether. The organic phase was then distilled under reduced pressure to obtain 78.5 g of crude 2-acetyl-γ-butyrolactone, with a yield of 61%.

[0081] 500g of pre-cooled 20% hydrochloric acid and 279g of crude 2-acetyl-γ-butyrolactone were mixed evenly and heated to boiling. When the reaction solution turned dark green, distillation was immediately carried out. The distillate was extracted with diethyl ether, and the organic phase was distilled under reduced pressure to obtain 164g of crude 5-chloro-2-pentanone, with a yield of 78%.

[0082] 18 g of sodium hydroxide, 1.54 g of benzyltriethylammonium chloride, and 18 mL of water were stirred and heated to boiling. 36 g of crude 5-chloro-2-pentanone was added dropwise, and the mixture was refluxed for 1 h. After cooling to room temperature, the mixture was extracted with diethyl ether and distilled under normal pressure to obtain 21.2 g of cyclopropylmethyl ketone, with a yield of 84%.

[0083] In this comparative example, the total yield of cyclopropyl methyl ketone was 40% based on the initial raw material ethyl acetoacetate.

[0084] As can be seen from Examples 1-4 and Comparative Examples 1 and 2 above, the preparation method of cyclopropyl methyl ketone used in this invention has simple steps, inexpensive raw materials, high atom utilization rate and overall yield, and obvious advantages, and has higher industrial application value.

Claims

1. A method for preparing cyclopropyl methyl ketone, characterized in that, Includes the following steps: 1) The raw material acetaldehyde, allyl compound, and metal catalyst are mixed in a reactor to form a mixed system. The mixture is stirred to carry out a hydroacylation reaction. After the reaction, the unreacted raw material is removed by vacuum distillation to obtain an intermediate product. The allyl compound is an allyl halide. The metal catalyst is one or a combination of tris(triphenylphosphine)rhodium(I) and tris(2-phenylpyridine)iridium(III). 2) The intermediate product obtained in step 1) is mixed with an alkaline catalyst, heated and kept at a constant temperature to react and obtain crude cyclopropylmethyl ketone. The crude cyclopropylmethyl ketone is then obtained by distillation. The alkaline catalyst is a rare earth metal supported catalyst, wherein the rare earth metal active component is selected from one or more of Sc, Y, La, Ce, Pr, and Nd, and the support is one or more of Al2O3, SiO2, and MgO. The active component exists in the form of oxides on the support.

2. The method for preparing cyclopropyl methyl ketone according to claim 1, characterized in that, In step 1), the molar ratio of the reactants acetaldehyde and allyl compound is (1-2):

1.

3. The method for preparing cyclopropyl methyl ketone according to claim 1, characterized in that, In step 1), the allyl compound is any one of allyl chloride, allyl iodine, and allyl bromide.

4. The method for preparing cyclopropyl methyl ketone according to claim 1, characterized in that, In step 1), the molar ratio of the metal catalyst to the allyl compound is (0.001-0.06):

1.

5. The method for preparing cyclopropyl methyl ketone according to claim 1, characterized in that, In step 1), the reaction temperature is -10~80℃.

6. The method for preparing cyclopropyl methyl ketone according to claim 1, characterized in that, In step 2), the mass ratio of the alkaline catalyst to the intermediate product is (0.001-0.10):

1.

7. The method for preparing cyclopropyl methyl ketone according to claim 1, characterized in that, The rare earth metal active component accounts for 5% to 50% of the mass percentage of the carrier.

8. The method for preparing cyclopropyl methyl ketone according to claim 1, characterized in that, In step 2), the reaction temperature is 175-190℃.

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