A method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement

Abstract

The present invention discloses a method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement, which uses a palladium-based catalyst to catalyze the Carroll rearrangement reaction of 3-methyl-1-buten-3-ol and methyl acetoacetate to produce 6-methyl-5-hepten-2-one. The preparation method of the palladium-based catalyst includes: using palladium hexafluoroacetylacetonate and / or bis(acetonitrile)palladium chloride as the palladium source, depositing elemental palladium on Al2O3 by atomic layer deposition in the presence of a reducing agent to obtain a Pd / Al2O3 catalyst, and then uniformly dispersing the Pd / Al2O3 catalyst in a solution of an auxiliary metal chloride, impregnating to remove the solvent, and calcining the obtained solid at 250-350 °C to obtain the palladium-based catalyst; or uniformly dispersing Al2O3 in a mixed solution of palladium chloride and an auxiliary metal chloride, impregnating to remove the solvent, calcining the obtained solid at 250-350 °C, and then reducing it with hydrogen at 250-350 °C to obtain the palladium-based catalyst; the auxiliary metal is at least one of bismuth, zinc, cerium, and lanthanum.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and particularly relates to a method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement. Background Art

[0002] The Carroll rearrangement reaction, also known as the Carroll-Claisen rearrangement reaction, was first discovered in 1940, and refers to the reaction of allyl tertiary alcohol compounds with a certain structure and acetoacetic acid esters under the action of a known catalyst. Common catalysts are mainly organoaluminum salt systems, base-catalyzed systems, and palladium noble metal systems.

[0003] Oster et al. disclosed a method for preparing unsaturated ketones in a batch reactor in patent CN1271716A, which involves an organoaluminum catalyst, but the yield is not high and there are many reaction by-products. Norman et al. disclosed several possible organoaluminum catalysts in patent GB886353A: aluminum complexes with acetylacetone or acetoacetic acid esters, such as aluminum triacetylpyruvate, aluminum trimethylacetoacetate, and aluminum triethylacetoacetate. Etzrodt et al. optimized the design of organoaluminum salt catalysts. Patent CN1348434A disclosed a method for preparing γ,δ-unsaturated ketones by an improved Carroll reaction in the presence of an aluminum compound, wherein the aluminum compound contains at least one group formed by an alkyl acetoacetate and 1 or 2 alkoxy groups, or contains other unique groups formed by an alkyl acetoacetate. However, the above methods use batch reactor production, do not effectively improve the yield, and the CO2 discharged entrains some organic substances and cannot be effectively recovered, which does not belong to a green chemical process. In the preparation of methylheptenone by the Carroll rearrangement method, the traditional method uses strongly hygroscopic aluminum isopropoxide as a homogeneous catalyst and prepares it by dropwise addition of alkynol to methyl acetoacetate. Jiang Lele et al. used methylbutenol and methyl acetoacetate as raw materials and 1,8-diazabicyclo[5.4.0]undec-7-ene and aluminum isopropoxide as catalysts to react to obtain methylheptenone in patent CN107673959B. However, it is difficult to control the temperature by dropwise addition during the synthesis, and the yield is difficult to improve; and a large amount of organic and inorganic salt wastes are easily generated, and the "three wastes" discharge is large.

[0004] Liu Deming et al. disclosed a method for catalyzing the reaction of unsaturated alcohols with alkyl acetoacetates to produce γ,δ-unsaturated ketones using an alkali metal alkoxide-organic amine combined base catalyst in patent CN102115437A. The combined base catalyst used in the method of this invention is easy to recycle and is suitable for industrial production, but there are also problems of cumbersome process and difficult reaction condition control.

[0005] Tsuji improved the Carroll rearrangement reaction. Using Pd(OAc)2 as a catalyst, through the formation of an intermediate allyl cation / carboxylate anion organometallic complex, followed by decarboxylation and allylation, the Carroll rearrangement under mild conditions was achieved. However, the application of the relevant Pd catalyst in industrialization is still insufficient, and the organoaluminum catalytic system and the corresponding continuous tank reactor still dominate. In summary, in the existing Carroll rearrangement reaction system, the palladium-based catalyst system has the prospect of process scale-up, but there is still room for improvement in aspects such as large-scale industrial production and green and harmless treatment of tail gases in the existing technology. Summary of the Invention

[0006] The present invention provides a method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement, which can obtain 6-methyl-5-hepten-2-one in high yield.

[0007] A method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement, which uses a palladium-based catalyst to catalyze the Carroll rearrangement reaction of 3-methyl-1-buten-3-ol and methyl β-ketobutyrate to generate 6-methyl-5-hepten-2-one;

[0008] The preparation method of the palladium-based catalyst includes the steps:

[0009] (1) Hydrothermally react an aqueous solution of aluminum nitrate and urea with pH = 3 - 4 at 95 - 105 °C. After the reaction, take the solid and calcine it at 550 - 650 °C to obtain Al2O3; or,

[0010] Under stirring conditions, adjust the pH of the aluminum nitrate aqueous solution to 8.5 - 9.5 with ammonia, age, take the solid and calcine it at 550 - 650 °C to obtain Al2O3;

[0011] (2) Using palladium hexafluoroacetylacetonate and / or bis(acetonitrile)palladium chloride as the palladium source, in the presence of a reducing agent, deposit elemental palladium on the Al2O3 obtained in step (1) by atomic layer deposition to obtain a Pd / Al2O3 catalyst. Then, uniformly disperse the Pd / Al2O3 catalyst in a solution of an auxiliary metal chloride, impregnate to remove the solvent, and calcine the obtained solid at 250 - 350 °C to obtain the palladium-based catalyst; or,

[0012] Uniformly disperse the Al2O3 obtained in step (1) in a mixed solution of palladium chloride and an auxiliary metal chloride, impregnate to remove the solvent, calcine the obtained solid at 250 - 350 °C and then reduce it with hydrogen at 250 - 350 °C to obtain the palladium-based catalyst;

[0013] The auxiliary metal is at least one of bismuth, zinc, cerium, and lanthanum, preferably zinc.

[0014] In step (2), the reducing agent can be tert-butyl hydrazine.

[0015] The palladium content in the palladium-based catalyst can be 0.1 wt% to 5 wt%, preferably 1.5 wt% to 2.5 wt%, and more preferably 2 wt%.

[0016] The content of the promoter metal in the palladium-based catalyst can be 4 wt% to 10 wt%.

[0017] In a preferred example, the promoter metal is zinc, and the mass ratio of the promoter metal to palladium in the palladium-based catalyst is 3 to 5:1.

[0018] In a preferred example, in step (2), the deposition chamber temperature of the atomic layer deposition is 200 to 400 °C.

[0019] The temperature of the Carroll rearrangement reaction is preferably 250 to 280 °C, and the pressure is preferably 0.1 to 0.2 MPa.

[0020] The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to the present invention can use a fixed-bed reactor. The palladium-based catalyst is filled in the fixed-bed reactor. The Carroll rearrangement reaction is a gas-solid phase reaction. The 3-methyl-1-buten-3-ol and the methyl β-ketobutyrate enter the fixed-bed reactor in gaseous form.

[0021] Using a fixed-bed reactor can reduce the accumulation of reaction by-products (such as CO2 and methanol) and promote the reaction.

[0022] Furthermore, the total weight hourly space velocity of the 3-methyl-1-buten-3-ol and the methyl β-ketobutyrate in the Carroll rearrangement reaction is preferably 3 to 5 h -1 。

[0023] The volume ratio of the 3-methyl-1-buten-3-ol to the methyl β-ketobutyrate in the Carroll rearrangement reaction is preferably 5:3 to 5, and more preferably 5:4.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to the present invention can obtain 6-methyl-5-hepten-2-one in high yield by optimizing the catalyst system and reaction conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a graph of the yield of 6-methyl-5-hepten-2-one of the palladium-based catalyst for 200 h in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0028] Example 1

[0029] Dissolve 6.44 g of Al(NO3)3·9H2O and 9.28 g of urea in 200 mL of deionized water, and continuously stir at 400 rpm for 25 min. Adjust the pH value to 3.8. Use a stainless-steel autoclave lined with Teflon as the container and maintain it at 100 °C for 2 days. After hydrothermal treatment, wash the sample with deionized water and ethanol to neutralize. Then centrifuge and vacuum-dry the sample, and finally calcine it in air at a heating rate of 2 °C / min to 600 °C for 4 h to obtain Al2O3.

[0030] Load palladium by atomic layer deposition, preheat the cavity to 300 °C. Add 0.2 g of the above-prepared Al2O3 to the sample dish, slowly evacuate the vacuum, use palladium hexafluoroacetylacetonate as the palladium source, and simultaneously introduce tert-butylhydrazine as the reducing agent for palladium to obtain elemental palladium. Perform 24 cycles to obtain the Pd / Al2O3 catalyst. Respectively take 1 g of the Pd / Al2O3 catalyst and 0.16 g of ZnCl2 and put them into 50 mL of deionized water. Mix the two solutions and stir-dry at 80 °C, and dry at 100 °C for 12 h. Finally, heat it to 300 °C at a rate of 5 °C / min and calcine for 6 h to obtain the Pd-Zn / Al2O3 palladium-based catalyst.

[0031] Example 2

[0032] Add 1 g of Al(NO3)3·9H2O to 200 mL of deionized water, continuously stir at 400 rpm for 25 min, then slowly drop the ammonia solution into the suspension and stir vigorously, carefully adjust the pH value of the mixture to 9.0. Continuously stir at 400 rpm for another 30 min, age at room temperature for 20 h, filter and wash with distilled water. Then centrifuge the sample and vacuum-dry it, and finally calcine it in air at a heating rate of 2 °C / min at 600 °C for 4 h to obtain Al2O3.

[0033] Subsequent steps are the same as in Example 1.

[0034] Example 3

[0035] Stir aluminum triisopropoxide (purity 98%) at 80 - 85 °C for 1 h for deionized hydrolysis, add HNO3, the molar ratio of HNO3 to Al is 1:1, reflux at 98 °C for 12 h to form a sol, store it at 98 °C in air for 2 h, dry at 80 °C, and finally calcine it in air at a heating rate of 2 °C / min at 600 °C for 4 h to obtain Al2O3.

[0036] The following is the same as Example 1.

[0037] Example 4

[0038] The difference from Example 1 is only that Al2O3 is replaced with commercially available calcium carbonate of equal mass.

[0039] Example 5

[0040] The difference from Example 1 is only that Al2O3 is replaced with commercially available silicon dioxide of equal mass.

[0041] Example 6

[0042] The difference from Example 1 is only that Al2O3 is replaced with ZSM-5 of equal mass.

[0043] Experiment 1

[0044] Weigh 0.5 g of the catalysts of Examples 1 to 6 respectively, each add 1.5 g of quartz sand for dilution, and use a fixed-bed reactor. The reaction pressure is 0.1 MPa, the reaction temperature is 250 °C. 3-methyl-1-buten-3-ol and methyl acetoacetate are pumped into the preheating vaporizer through a liquid-phase pump respectively, and the total feed flow rate is controlled to be 0.05 mL / min by the pumping speed of the liquid-phase stream. The total weight hourly space velocity of 3-methyl-1-buten-3-ol and methyl acetoacetate is 5 h -1 , the volume ratio of alcohol to ester in the feed is 5:4, and the yield of 6-methyl-5-hepten-2-one is obtained. The results are shown in Table 1. The yield test of the palladium-based catalyst of Example 1 for 6-methyl-5-hepten-2-one was carried out under the above conditions for 200 h, and the results are shown in the appendix Figure 1 .

[0045] Table 1

[0046] Example Support Pd Loading Volume Ratio of Alcohol to Ester Pressure Temperature Weight Hourly Space Velocity Yield 1 Aluminum Oxide - Hydrothermal Method 2wt% 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 2 Aluminum Oxide - Precipitation Method 2wt% 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 89％ 3 Aluminum Oxide - Sol - Gel Method 2wt% 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 77％ 4 Calcium Carbonate 2wt% 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 81％ 5 Silicon Oxide 2wt% 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 78％ 6 ZSM - 5 2wt% 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 83％

[0047] Result analysis: Comparing Examples 1 to 6, from the results, different carrier preparation methods and types will affect the performance of the palladium-based catalyst in the Carroll rearrangement reaction to prepare 6-methyl-5-hepten-2-one. Alumina prepared by the hydrothermal method and the precipitation method is the preferred carrier. In the appendix Figure 1 , during the 200 h test time, the yield of 6-methyl-5-hepten-2-one remained at about 95%, indicating that the Pd-Zn / Al2O3 catalyst has high stability in the Carroll rearrangement reaction to prepare 6-methyl-5-hepten-2-one and has the prospect of industrialization.

[0048] Example 7

[0049] Replace palladium hexafluoroacetylacetonate in Example 1 with palladium trimethylacetate, and the rest is the same as Example 1.

[0050] Example 8

[0051] Replace palladium hexafluoroacetylacetonate in Example 1 with bis(acetonitrile)palladium dichloride, and the rest is the same as Example 1.

[0052] Experiment 2

[0053] Under the same reaction conditions as in Experiment 1, the yields of 6-methyl-5-hepten-2-one exhibited by the catalysts of Example 7 and Example 8 in the Carroll rearrangement for the preparation of 6-methyl-5-hepten-2-one were obtained. The results are shown in Table 2.

[0054] Table 2

[0055] Example Precursor Volume Ratio of Alcohol to Ester Pressure Temperature Weight Hourly Space Velocity Yield 1 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 7 Palladium Trimethylacetate 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 78％ 8 Bis(acetonitrile)palladium(II) Chloride 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 92％

[0056] Result analysis: Comparing Example 1, Examples 7 - 8, it can be seen from the results that different Pd precursors have a great influence on the performance of the palladium-based alumina catalyst in the Carroll rearrangement for the preparation of 6-methyl-5-hepten-2-one. This may be because the boiling point of the precursor affects the effective deposition amount during atomic layer deposition. Palladium hexafluoroacetylacetonate and bis(acetonitrile)palladium dichloride precursors are preferred.

[0057] Example 9

[0058] Prepare Al2O3 in the same way as in Example 1.

[0059] Take 2 g of the above-prepared Al2O3 and add it to 100 mL of deionized water. Take 0.073 g of PdCl2 and 0.325 g of ZnCl2 and dissolve them in 100 mL of deionized water. Mix the two solutions and stir-dry at 80 °C, then dry at 100 °C for 12 h. Finally, heat to 300 °C at a rate of 5 °C / min and calcine for 6 h to obtain the Pd-Zn / Al2O3 catalyst.

[0060] Example 10

[0061] Prepare Al2O3 in the same way as in Example 1.

[0062] Take 2 g of the above-prepared Al2O3 and add it to 100 mL of deionized water. Take 0.073 g of PdCl2 and 0.325 g of ZnCl2 and dissolve them in 100 mL of deionized water. Mix the two solutions and stir at 80 °C for 4 h, wash with deionized water, filter and recover, dry at 110 °C for 8 h, and then repeat the above operations on the dried sample twice. Finally, heat to 300 °C at a rate of 5 °C / min and calcine for 6 h to obtain the Pd-Zn / Al2O3 catalyst.

[0063] Experiment 3

[0064] The catalysts obtained in Example 9 and Example 10 were reduced at 300 °C in an H2 atmosphere for 1 h, and the remaining reaction conditions were the same as those in Experiment 1, and the yields of 6-methyl-5-hepten-2-one exhibited by the catalysts in Example 9 and 10 in the Carroll rearrangement to prepare 6-methyl-5-hepten-2-one were obtained. The results are shown in Table 3.

[0065] Table 3

[0066] Example Preparation Method Precursor Pd Loading Pressure Temperature Weight Hourly Space Velocity Yield 1 Atomic Layer Deposition Method Palladium Hexafluoroacetylacetonate 2wt% 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 9 Impregnation Method <![CDATA[PdCl2]]> 2wt% 0.1MPa 250℃ <![CDATA[5h -1 > 90％ 10 Ion Exchange Method <![CDATA[PdCl2]]> 1.7wt% 0.1MPa 250℃ <![CDATA[5h -1 > 85％

[0067] Result analysis: Comparing Example 1 with Example 9 and 10, from the results, the Pd-Zn / Al2O3 catalyst prepared by atomic layer deposition exhibited the best yield in the Carroll rearrangement to prepare 6-methyl-5-hepten-2-one. The yield of the catalyst prepared by the impregnation method was relatively low but higher than that prepared by the ion exchange method. Considering industrial applications, the impregnation method is a preparation method of Carroll rearrangement catalyst with greater application prospects.

[0068] Examples 11 to 13

[0069] The number of cycles in Example 1 was changed to 12, 18, and 30 times in sequence, and the rest was the same as Example 1.

[0070] Experiment Four

[0071] Under the same reaction conditions as in Experiment 1, the yields of 6-methyl-5-hepten-2-one exhibited by the catalysts in Examples 11 to 13 in the Carroll rearrangement to prepare 6-methyl-5-hepten-2-one were obtained. The results are shown in Table 4.

[0072] Table 4

[0073] Example Precursor Number of Cycles Pd Loading Pressure Temperature Weight Hourly Space Velocity Yield 1 Palladium Hexafluoroacetylacetonate 24 2wt% 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 11 Palladium Hexafluoroacetylacetonate 12 1wt% 0.1MPa 250℃ <![CDATA[5h -1 > 86％ 12 Palladium Hexafluoroacetylacetonate 18 1.5wt% 0.1MPa 250℃ <![CDATA[5h -1 > 91％ 13 Palladium Hexafluoroacetylacetonate 30 2.5wt% 0.1MPa 250℃ <![CDATA[5h -1 > 93％

[0074] Result analysis: Comparing Example 1 with Examples 11 to 13, from the results, the loading amount of palladium on the alumina surface affected the yield of 6-methyl-5-hepten-2-one. The preferred Pd loading amount was 1.5 wt% to 2.5 wt%, and more preferably 2 wt%.

[0075] Examples 14 to 15

[0076] 0.16 g of zinc chloride in Example 1 was changed to 0.11 g and 0.23 g in sequence, and the rest was the same as Example 1.

[0077] Experiment Five

[0078] Under the same reaction conditions as in Experiment 1, the yields of 6-methyl-5-hepten-2-one exhibited by the catalysts in Examples 14 to 15 in the Carroll rearrangement for the preparation of 6-methyl-5-hepten-2-one were obtained. The results are shown in Table 5.

[0079] Table 5

[0080] Example Promoter Zn Loading Pressure Temperature Weight Hourly Space Velocity Yield 1 Zinc Chloride 7wt% 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 14 Zinc Chloride 5wt% 0.1MPa 250℃ <![CDATA[5h -1 > 77％ 15 Zinc Chloride 10wt% 0.1MPa 250℃ <![CDATA[5h -1 > 89％

[0081] Result analysis: Comparing Example 1 with Examples 14 to 15, from the results, when the loading ratio of the metal promoter to Pd is 7:2, 6-methyl-5-hepten-2-one has the maximum yield.

[0082] Examples 16 - 18

[0083] The zinc chloride in Example 1 was successively changed to bismuth chloride, cerium chloride heptahydrate, and lanthanum chloride heptahydrate, and the rest were the same as in Example 1.

[0084] Experiment Six

[0085] Under the same reaction conditions as in Experiment 1, the yields of 6-methyl-5-hepten-2-one exhibited by the catalysts in Examples 16 to 18 in the Carroll rearrangement for the preparation of 6-methyl-5-hepten-2-one were obtained. The results are shown in Table 6.

[0086] Table 6

[0087] Example Promoter Promoter Metal Loading Pressure Temperature Weight Hourly Space Velocity Yield 1 Zinc Chloride 7wt% 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 16 Bismuth Chloride 7wt% 0.1MPa 250℃ <![CDATA[5h -1 > 79％ 17 Cerium Chloride Heptahydrate 7wt% 0.1MPa 250℃ <![CDATA[5h -1 > 89％ 18 Lanthanum Chloride Heptahydrate 7wt% 0.1MPa 250℃ <![CDATA[5h -1 > 87％

[0088] Result analysis: Comparing Example 1 with Examples 16 to 18, from the results, the type of metal promoter has a greater influence on the yield of 6-methyl-5-hepten-2-one, and zinc chloride is preferred. This is because compared with bismuth, cerium, and lanthanum, zinc oxide in the palladium-based alumina catalyst provides appropriate basicity, which can assist in accelerating the Claisen reaction rate and is more prone to decarboxylation reaction.

[0089] Examples 19 - 20

[0090] The difference from Example 1 is only that the cavity temperature was successively changed from 300 °C to 200 °C and 400 °C, and the rest were the same.

[0091] Experiment Seven

[0092] Under the same reaction conditions as in Experiment 1, the yields of 6-methyl-5-hepten-2-one exhibited by the catalysts in Examples 19 to 20 in the Carroll rearrangement for the preparation of 6-methyl-5-hepten-2-one were obtained. The results are shown in Table 7.

[0093] Table 7

[0094] Example Precursor Chamber Temperature Pressure Temperature Weight Hourly Space Velocity Yield 1 Palladium Hexafluoroacetylacetonate 300℃ 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 19 Palladium Hexafluoroacetylacetonate 200℃ 0.1MPa 250℃ <![CDATA[5h -1 > 92％ 20 Palladium Hexafluoroacetylacetonate 400℃ 0.1MPa 250℃ <![CDATA[5h -1 > 90％

[0095] Result analysis: Comparing Example 1 with Examples 19 - 20, from the results, with the change of the Pd atom deposition chamber temperature, the yield difference of 6-methyl-5-hepten-2-one is small. The preferred chamber deposition temperature of the Pd-based alumina catalyst is 300 °C. At chamber temperatures above the boiling point of the precursor, the metal can be effectively loaded on the surface.

[0096] Examples 21 - 24

[0097] Using the catalyst prepared in Example 1, the feed ratio of the reactant alcohol ester in Experiment 1 was changed to 5:1, 5:2, 5:3, 1:1 in sequence, and the others were the same.

[0098] Examples 25 - 28

[0099] Using the catalyst prepared in Example 1, the weight hourly space velocity of the reactants in Experiment 1 was changed to 2 h -1 、3 h -1 、4 h -1 、6 h -1 in sequence, and the others were the same.

[0100] Examples 29 - 30

[0101] Using the catalyst prepared in Example 1, the reaction pressure in Experiment 1 was changed to 0.2 MPa and 0.3 MPa in sequence, and the others were the same.

[0102] Examples 31 - 33

[0103] Using the catalyst prepared in Example 1, the reaction temperature in Experiment 1 was changed to 200 °C, 280 °C, 300 °C in sequence, and the others were the same.

[0104] Experiment VIII

[0105] Table 8 shows the yields of 6-methyl-5-hepten-2-one in Examples 21 - 33.

[0106] Table 8

[0107] Example Precursor Volume Ratio of Alcohol to Ester Pressure Temperature Weight Hourly Space Velocity Yield 1 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 250℃ <![CDATA[5h -1 > 95％ 21 Palladium Hexafluoroacetylacetonate 5:1 0.1MPa 250℃ <![CDATA[5h -1 > 72％ 22 Palladium Hexafluoroacetylacetonate 5:2 0.1MPa 250℃ <![CDATA[5h -1 > 79％ 23 Palladium Hexafluoroacetylacetonate 5:3 0.1MPa 250℃ <![CDATA[5h -1 > 86％ 24 Palladium Hexafluoroacetylacetonate 1:1 0.1MPa 250℃ <![CDATA[5h -1 > 88％ 25 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 250℃ <![CDATA[2h -1 > 82％ 26 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 250℃ <![CDATA[3h -1 > 90％ 27 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 250℃ <![CDATA[4h -1 > 93％ 28 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 250℃ <![CDATA[6h -1 > 77％ 29 Palladium Hexafluoroacetylacetonate 5:4 0.2MPa 250℃ <![CDATA[5h -1 > 91％ 30 Palladium Hexafluoroacetylacetonate 5:4 0.3MPa 250℃ <![CDATA[5h -1 > 85％ 31 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 200℃ <![CDATA[5h -1 > 64％ 32 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 280℃ <![CDATA[5h -1 > 91％ 33 Palladium Hexafluoroacetylacetonate 5:4 0.1MPa 300℃ <![CDATA[5h -1 > 75％

[0108] Result analysis: Comparing Example 1 with Examples 21 - 24, after changing the volume ratio of the two reactant molecules, it is found that the preferred volume ratio of 3-methyl-1-buten-3-ol: methyl β-ketobutyrate is 5:4, and the yield of 6-methyl-5-hepten-2-one is the highest at this time. Comparing Example 1 with Examples 25 - 27, with the increase of the reaction weight hourly space velocity, the yield of 6-methyl-5-hepten-2-one first increases and then decreases, and the preferred value is 5 h -1。Comparing Example 1 with Examples 29 to 30, as the reaction pressure increases, the yield of 6-methyl-5-hepten-2-one decreases, and preferably it is 0.1 MPa. Comparing Example 1 with Examples 31 to 33, as the reaction temperature increases, the yield of 6-methyl-5-hepten-2-one first increases and then decreases, and the preferred reaction temperature range is 250 to 280 °C.

[0109] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement, characterized in that, The Carroll rearrangement reaction of 3-methyl-1-buten-3-ol and methyl acetoacetate is catalyzed by a palladium-based catalyst to produce 6-methyl-5-hepten-2-one; The preparation method of the palladium-based catalyst includes the steps: (1) An aqueous solution of aluminum nitrate and urea with a pH of 3-4 is subjected to hydrothermal reaction at 95-105 °C. After the reaction ends, the solid is calcined at 550-650 °C to obtain Al2O3; alternatively, Under stirring conditions, the pH of the aluminum nitrate aqueous solution is adjusted to 8.5-9.5 with ammonia, aged, and the solid is calcined at 550-650 °C to obtain Al2O3; (2) Using palladium hexafluoroacetylacetonate and / or bis(acetonitrile)palladium chloride as the palladium source, in the presence of a reducing agent, elemental palladium is deposited on the Al2O3 obtained in step (1) by atomic layer deposition to obtain a Pd / Al2O3 catalyst. Then, the Pd / Al2O3 catalyst is uniformly dispersed in a solution of an auxiliary metal chloride, the solvent is removed by impregnation, and the obtained solid is calcined at 250-350 °C to obtain the palladium-based catalyst; alternatively, The Al2O3 obtained in step (1) is uniformly dispersed in a mixed solution of palladium chloride and an auxiliary metal chloride, the solvent is removed by impregnation, and the obtained solid is calcined at 250-350 °C and then reduced with hydrogen at 250-350 °C to obtain the palladium-based catalyst; The auxiliary metal is at least one of zinc, cerium, and lanthanum.

2. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, characterized in that, In step (2), the reducing agent is tert-butyl hydrazine.

3. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, wherein, The palladium content in the palladium-based catalyst is 0.1 wt% - 5 wt%.

4. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, characterized in that, The palladium content in the palladium-based catalyst is 1.5 wt% - 2.5 wt%.

5. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, characterized in that, The palladium content in the palladium-based catalyst is 2 wt%.

6. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, wherein The content of the auxiliary metal in the palladium-based catalyst is 4 wt% - 10 wt%.

7. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, characterized in that, The auxiliary metal is zinc, and the mass ratio of the auxiliary metal to palladium in the palladium-based catalyst is 3-5:

1.

8. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, wherein, In step (2), the deposition chamber temperature of the atomic layer deposition is 200-400 °C.

9. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, wherein The temperature of the Carroll rearrangement reaction is 250-280 °C, and the pressure is 0.1-0.2 MPa.

10. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, wherein, A fixed-bed reactor is used. The palladium-based catalyst is filled in the fixed-bed reactor. The Carroll rearrangement reaction is a gas-solid phase reaction. The 3-methyl-1-buten-3-ol and the methyl acetoacetate enter the fixed-bed reactor in gaseous form.

11. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 10, wherein, The total weight hourly space velocity of the 3-methyl-1-buten-3-ol and the methyl acetoacetate in the Carroll rearrangement reaction is 3 to 5 h -1 .

12. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 1, characterized in that, In the Carroll rearrangement reaction, the volume ratio of the 3-methyl-1-buten-3-ol to the methyl acetoacetate is 5:3-5.

13. The method for preparing 6-methyl-5-hepten-2-one by Carroll rearrangement according to claim 12, wherein, In the Carroll rearrangement reaction, the volume ratio of the 3-methyl-1-buten-3-ol to the methyl acetoacetate is 5:4.

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