A method for the catalytic oxidation of olefins to produce epoxides

Abstract

The application provides a method for preparing an epoxide compound by catalytic oxidation of an olefin, which comprises using an olefin as a substrate, hydrogen peroxide as an oxygen source, and a polyacid metal oxoacid salt catalyst containing an ionic liquid to prepare the epoxide compound of the corresponding olefin in one step. The polyacid metal oxoacid salt catalyst containing the ionic liquid has the advantages of the ionic liquid and the polyacid metal oxoacid salt, and has the characteristics of adjustable acidity, good oxidation-reduction compatibility and good stability. Therefore, the method system has the advantages of green, environmental protection, high efficiency, low cost and wide substrate application range, and has the advantages of mild catalytic conditions, easy separation and recycling, low production cost and significant industrial application value.

Description

Technical Field

[0001] This invention relates to a method for the catalytic oxidation of olefins to prepare epoxides, and more particularly to a phase transfer catalyst applicable to a wide range of olefins, especially C2 and above olefins, for the catalytic oxidation of olefins to prepare epoxides and its epoxidation process, without the need for additional additives. Background Technology

[0002] Epoxides are a crucial class of chemical synthesis intermediates, widely used in petrochemicals, fine chemicals, and organic synthesis. Abroad, propylene oxide is produced via a co-oxidation method, where organic peroxides epoxidize olefins. However, this method produces not only propylene oxide but also co-products, making the production process complex and requiring significant infrastructure investment. This method is often used for high-value-added fine chemicals. In my country, epoxides such as propylene oxide, epichlorohydrin, and epiphenylene oxide are primarily produced using the chlorohydrin process, which is costly, polluting, and urgently needs improvement.

[0003] Industrially, apart from ethylene oxide, which is produced by the direct oxidation of ethylene by molecular oxygen, other epoxides with more than two carbon atoms cannot be directly oxidized to olefins. This is because 1) the epoxidation reactions of molecular oxygen reported in the literature often use relatively expensive oxidants such as PhIO3, ROOH, NaOCl, and KHSO3 to participate in the reaction, resulting in complex catalytic systems that are difficult to apply on a large scale in industry. 2) Some molecular oxygen, acting as an oxygen source, requires the presence of a co-reducing agent for the epoxidation of olefins. Examples include NaBH4 co-reducing agent [J.Mol.Cat.,29,153(1985)], ascorbic acid co-reducing agent [J.Chem.Soc.,Chem.Commun.,253(1983)], zinc powder co-reducing agent [J.Chem.Soc.,Chem.Commun., 791(1987)], and aldehyde or alcohol co-reducing agents [Chem.Lett.,1(1991); Bull.Chem.Soc.Jpn.,68,17(1995)]. However, these agents share common drawbacks: ① Co-reducing agents are expensive; ② Co-reducing agents have low utilization rates; ③ Co-reducing agents generate useless byproducts, resulting in significant waste and environmental pollution. Therefore, the industrial application value of co-reducing agent systems is not high.

[0004] To overcome the major drawbacks commonly found in the aforementioned epoxidation systems, patent CN1203231 proposes a method using a reversible oxidative and reductive monooxygen acceptor (H2A) as a co-reducing agent. This method, in conjunction with a transition metal catalyst, activates molecular oxygen to selectively catalytically epoxidize olefins to produce epoxides. The monooxygen acceptor is then catalytically hydrogenated back to its original state. However, the hydrogenation catalyst remains relatively expensive, resulting in a high cost for the molecular oxygen oxidation of olefins during epoxidation.

[0005] In contrast, hydrogen peroxide, as an oxygen source, is relatively inexpensive (600-700 yuan / ton) and only water is produced after the epoxidation reaction, making it environmentally friendly. However, when hydrogen peroxide is used as an oxygen source, the water in the reaction system, under the acidity of hydrogen peroxide, can cause further hydrolysis of the resulting epoxide compounds, generating diols, which reduces the selectivity and yield of the epoxide compounds. Therefore, additives such as phosphates, carbonates, and acetates are often added to the reaction to maintain the acidity of the reaction system and thus improve the selectivity of the epoxide compounds. However, in practice, when these additives are added to the reaction system, they can accumulate during the catalyst precipitation process after the epoxidation reaction, causing instability in the yield and selectivity of the epoxide compounds during recycling, making the process difficult to operate.

[0006] To address the aforementioned issues with hydrogen peroxide as an oxygen source, we successfully designed a polyoxometalate catalyst containing an ionic liquid, leveraging the advantages of ionic liquids and polyoxometalates, such as adjustable acidity, good redox compatibility, and high stability. This catalyst combines the advantages of both ionic liquids and polyoxometalates, and its acidity is adjustable. When applied to the catalytic oxidation of olefins to epoxides, it requires no additives and offers advantages such as being green, environmentally friendly, highly efficient, low-cost, and having a wide range of applicable substrates. Furthermore, the catalytic conditions are mild, and it is easy to separate and recycle, reducing production costs and demonstrating significant industrial application value. Summary of the Invention

[0007] To address the aforementioned issues with hydrogen peroxide as an oxygen source, we successfully designed a polyoxometalate catalyst containing an ionic liquid, leveraging the advantages of ionic liquids and polyoxometalates, such as adjustable acidity, good redox compatibility, and high stability. This catalyst combines the advantages of both ionic liquids and polyoxometalates, and its acidity is adjustable. When applied to the catalytic oxidation of olefins to epoxides, it requires no additives and offers advantages such as being green, environmentally friendly, highly efficient, low-cost, and having a wide range of applicable substrates. Furthermore, the catalytic conditions are mild, and it is easy to separate and recycle, reducing production costs and demonstrating significant industrial application value.

[0008] The technical solution of this invention:

[0009] A method for preparing epoxides by catalytic oxidation of olefins, using olefins as substrates and hydrogen peroxide as oxygen source, and epoxidizing the corresponding olefins in one step under the action of a polyoxometalate catalyst containing ionic liquids.

[0010] The specific method is as follows: add a polyoxometalate catalyst containing ionic liquid and an organic solvent to a reaction vessel, introduce olefins, add hydrogen peroxide oxygen source under stirring, and react at a temperature of 10-100℃, an inert gas pressure of 0.1-4MPa, and stirring for 0.5-20 hours to prepare epoxides from olefins in one step.

[0011] The preparation method of the polyoxometalate catalyst containing ionic liquid:

[0012] (1) Synthesis of ionic liquid [BSIL]: Equal amounts of N-alkylimidazolium and 1,4-butanesulfonate lactone were mixed and magnetically stirred at 10-80℃ for 2-12h to obtain white precipitate [BSIL]; the obtained solid was washed 2-4 times with methyl tert-butyl ether and then dried at 25℃-60℃ for 1-8h for later use.

[0013] (2) Polyoxometalate catalysts containing ionic liquids [BSIL] 2-n M n H 1-n XN 12 O 48 Synthesis: Disperse a metal carbonate MCO3 (containing one or more of the divalent metals M = Mn, Cu, Co, and Ni) in water, and add H3XN dropwise to the resulting mixture. 12 O 48 An aqueous solution of (X = one or two of P and As; N = one or two of W and Mo); the resulting mixture is stirred at room temperature for 2-8 h and dried at 30-60 °C for 1-8 h to obtain M. n H 2-n H 1-n XN 12 O 48 (M = one or more of Mn, Cu, Co, and Ni);

[0014] M n H 2-n H 1-n XN 12 O 48 A series of polyoxometalate catalysts containing ionic liquids [BSIL] were obtained by adding 2-n molar amounts of BSIL dropwise to an aqueous solution, stirring at room temperature for 2-8 hours, and drying at 60-80℃ for 1-8 hours. 2-n M n H 1-n XN 12 O 48(Abbreviation: BSIL-POM, where X = one or two of P and As; N = one or two of W and Mo; M = one or more of Mn, Cu, Co, and Ni; 0.01 < n < 1.99, preferably 0.3 ≤ n ≤ 1.8).

[0015] The metal carbonate is one or more of copper carbonate, manganese carbonate, cobalt carbonate, and nickel carbonate.

[0016] The system is a phase transfer catalytic system. The catalyst itself is insoluble in the reaction medium, but after the catalyst combines with hydrogen peroxide, it dissolves in the reaction system. When the hydrogen peroxide is consumed, the catalyst returns to its original structure and precipitates from the reaction system. After simple separation, the catalyst can be recycled, and the recycling activity does not decrease significantly.

[0017] The organic solvents used include one or more of the following substances:

[0018] One or more of methanol, ethanol, n-propanol, isopropanol, tert-butanol, or tert-amyl alcohol in alcohol solvents;

[0019] Straight-chain alkanes, branched-chain alkanes, or cycloalkanes with C5-C12 in alkane solvents;

[0020] One or more of benzene, toluene, ethylbenzene, xylene, trimethylbenzene, or other mono-substituted or multi-substituted alkylbenzenes in aromatic solvents;

[0021] One or more of fatty acid esters, aromatic acid esters, or trialkyl phosphates such as trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, and trioctyl phosphate in ester solvents;

[0022] Ether solvents include one or more of alkyl ethers, aryl ethers, or aralkyl ethers;

[0023] Halogenated hydrocarbon solvents, including halogenated alkanes or chlorinated aromatics;

[0024] One or more of dialkyl ketones or aryl alkyl ketones in ketone solvents;

[0025] Nitrile solvents are one or more of acetonitrile, propionitrile, or benzonitrile;

[0026] The reaction organic solvent used can be a single solvent or a mixed solvent composed of two or more of the above solvents;

[0027] For 1 mmol of double bond in olefins, the solvent dosage is 0.05 mL - 5.0 mL, preferably 0.06 - 2.0 mL.

[0028] The hydrogen peroxide has a mass concentration of 15-70%, and the ratio of the amount of double bond in the olefin to the amount of H2O2 in the hydrogen peroxide is (1-10):1, preferably (1-5):1.

[0029] The olefins include one or more of the following: chain-terminal olefins, chain-internal olefins, cyclic olefins, and α,β-unsaturated ketones.

[0030] The chain-terminal olefins mentioned therein are one or more of the following C3-C20 chain-terminal olefins and their derivatives: styrene, cycloalkanyl ethylene, chloropropene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene.

[0031] The chain-like internal olefin is one or more of the C3-C20 chain olefins in which the carbon-carbon double bond is not at the end of the molecular chain.

[0032] The cyclic olefin is one or more of cyclopentene and its derivatives, cyclohexene and its derivatives, cycloheptene and its derivatives, and cyclooctene and its derivatives.

[0033] The α,β-unsaturated ketone is one or more of 2-cyclohexen-1-one, 4-hexen-3-one, chalcone and its derivatives, 3-methyl-2-cyclohexen-1-one, 4-methyl-3-penten-2-one, and 3-octen-2-one.

[0034] The epoxidation reaction of the olefin is carried out at a temperature of 10-100℃, an inert gas pressure of 0.1-4MPa, and a reaction time of 0.5-20 hours; preferably, the reaction temperature is 30-60℃, the inert gas pressure is 0.5-2MPa, and the reaction time is 2-8 hours.

[0035] The inert gas used is one or more of nitrogen, argon, and helium, with nitrogen being preferred.

[0036] Catalyst [BSIL] 2-n M n H 1-n XN 12 O 48 The molar ratio of the substance of BSIL-POM to the double bond in the olefin ranges from 0.1 to 5 mol%, with a preferred range of 0.5 to 2 mol%.

[0037] Catalyst [BSIL] 2-n M n H 1-n XN 12 O 48(Abbreviation: BSIL-POM) has both the functional groups of ionic liquid and polyoxometalate. The value range of n is 0.01 < n < 1.99, preferably 0.3 ≤ n ≤ 1.8. By adjusting the value of n, the acidity of the catalyst can be adjusted, and the corresponding epoxy compound can be obtained with high selectivity without the need to additionally add additives such as phosphates, carbonates, and acetates.

[0038] The N-alkylimidazole is one or more of N-methylimidazole, N-ethylimidazole, N-propylimidazole, and N-butylimidazole.

[0039] In summary, the catalytic system described in the present invention has significant industrial application value.

[0040] The polyoxometalate catalyst containing ionic liquid in the present invention has both the advantages of ionic liquid and polyoxometalate, and has the characteristics of adjustable acidity, good redox compatibility, and good stability. Therefore, this method system has the advantages of being green, environmentally friendly, efficient, low-cost, and having a wide substrate application range, and the catalytic conditions are mild, easy to separate and recycle, reduce production costs, and have significant industrial application value. Detailed implementation mode

[0041] The present invention will be described in detail below in conjunction with the embodiments, but the scope of the present invention is not limited to the following embodiments.

[0042] Example 1

[0043] Preparation of catalyst

[0044] (1) Synthesis of ionic liquid [BSIL]-A: Mix equimolar amounts of N-methylimidazole and 1,4-butanesultone, and stir magnetically at 30 °C for 6 h to obtain a white precipitate [BSIL]. The obtained solid is washed three times with methyl tert-butyl ether, and then vacuum dried at 50 °C for 4 h for standby.

[0045] (2) Synthesis of polyoxometalate catalyst [BSIL] containing ionic liquid 2-n M n H 1-n XN 12 O 48 : Disperse 5 mmol of metal carbonate MCO3 (M is Mn, Cu, Co or Ni respectively) into 30 mL of deionized water, and add 20 mL of an aqueous solution of H3PW 12 O 48 (10 mmol) dropwise to the obtained mixture; stir the obtained mixture at room temperature for 6 h, and vacuum dry at 50 °C for 4 h to obtain M 0.5 H2PW 12 O 48 (M is Mn, Cu, Co or Ni respectively).

[0046] M 0.5 H2PW 12 O 48 A series of polyoxometalate catalysts containing ionic liquids [BSIL] were obtained by adding 15 mmol of BSIL dropwise to an aqueous solution, stirring at room temperature for 6 h, and then drying under vacuum at 50 °C for 4 h. 1.5 M 0.5 H 0.5 PW 12 O 48 (Abbreviated as M-BSIL-POM-1, where X = P; N = W; M is Mn, Cu, Co, or Ni respectively; n = 0.5)

[0047] Example 2

[0048] Catalyst preparation

[0049] (1) Synthesis of ionic liquid [BSIL]-B: Equal amounts of N-ethylimidazole and 1,4-butanesulfonate lactone were mixed and magnetically stirred at 30°C for 6 h to obtain a white precipitate [BSIL]. The obtained solid was washed three times with methyl tert-butyl ether and then vacuum dried at 50°C for 4 h for later use.

[0050] (2) Polyoxometalate catalysts containing ionic liquids [BSIL] 2-n M n XN 12 O 48 Synthesis: 10 mmol of metal carbonate MCO3 (M being Mn, Cu, Co, or Ni) was dispersed in 30 mL of deionized water, and 20 mL of H3PW was added dropwise to the resulting mixture. 12 O 48 A 10 mmol aqueous solution was used; the resulting mixture was stirred at room temperature for 6 h and then vacuum dried at 50 °C for 4 h to obtain MHPW. 12 O 48 (M represents Mn, Cu, Co, or Ni). MHPW 12 O 48 A series of polyoxometalate catalysts containing ionic liquids [BSIL]MPW were obtained by adding 10 mmol of BSIL dropwise to an aqueous solution, stirring at room temperature for 6 h, and then drying under vacuum at 50 °C for 4 h. 12 O 48 (Abbreviated as M-BSIL-POM-2, where X = P; N = W; M is Mn, Cu, Co, or Ni respectively; n = 1)

[0051] Example 3

[0052] Preparation of cyclohexane oxide

[0053] In a 100 mL three-necked flask, the atmosphere was purged three times with nitrogen, and the catalyst [BSIL] was added sequentially under a nitrogen flow. 1.5 Cu 0.5 H 0.5 PW 12 O 48 0.10 mmol (Cu-BSIL-POM-1), 15 mL anisole, 30 mmol cyclohexene, and a 35% (w / w) hydrogen peroxide solution containing 15 mmol H₂O₂ were used. The reaction was carried out under an inert nitrogen atmosphere of 0.1 MPa in a sealed flask at 60 °C for 4 h. During this time, the catalyst precipitated from the reaction system. The conversion rate of cyclohexene relative to hydrogen peroxide was 98.4%, and the selectivity for cyclohexane oxide was 98.5%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated in a cyclic reaction. The reaction results are shown in the table below.

[0054]

[0055] Comparative Example 1

[0056] Preparation of cyclohexane oxide: According to patent CN1401425A, the catalyst [(C2H5)3NCH2Ph]2HAsMo2O was prepared. 10

[0057] In a 100 mL three-necked flask, nitrogen gas was purged three times, and the catalyst [(C2H5)3NCH2Ph]2HAsMo2O was added sequentially under a nitrogen gas flow. 10 0.10 mmol, 25 mL anisole, 30 mmol cyclohexene, and a 35% (w / w) hydrogen peroxide solution containing 15 mmol H₂O₂ were added to a sealed reaction flask under an inert nitrogen atmosphere of 0.1 MPa. The reaction was carried out at 60 °C for 4 h. During this time, the catalyst precipitated from the reaction system. The conversion rate of cyclohexene relative to hydrogen peroxide was 98.0%, and the selectivity for cyclohexane oxide was 94.5%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated in a cyclic reaction. The reaction results are shown in the table below. During the catalyst cycling process, the activity and epoxy selectivity gradually decreased.

[0058]

[0059] Example 4

[0060] Preparation of 2-methyl-2,3-epoxypentane

[0061] In a 100 mL three-necked flask, the atmosphere was purged three times with nitrogen, and the catalyst [BSIL] was added sequentially under a nitrogen flow. 1.5 Co 0.5 H 0.5 PW12 O 48 0.10 mmol of (Co-BSIL-POM-1), 30 mL of butyl acetate, 30 mmol of 2-methyl-2-pentene, and a 35% (w / w) hydrogen peroxide solution containing 15 mmol of H₂O₂ were added. The reaction was carried out under an inert nitrogen atmosphere of 0.1 MPa in a sealed reaction flask at 50 °C for 4 h. During this time, the catalyst precipitated from the reaction system. The conversion rate of 2-methyl-2-pentene relative to hydrogen peroxide was 96.4%, and the selectivity for 2-methyl-2,3-epoxypentane was 98.5%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated for reuse.

[0062] Example 5

[0063] Preparation of 1,2-epoxyhexane

[0064] In a 100 mL three-necked flask, the atmosphere was purged three times with nitrogen, and the catalyst [BSIL] was added sequentially under a nitrogen flow. 1.5 Ni 0.5 H 0.5 PW 12 O 48 0.10 mmol of (Ni-BSIL-POM-1), 15 mL of mesitylene, 30 mmol of 1-hexene, and a 50% hydrogen peroxide solution containing 15 mmol of H₂O₂ were used. The reaction was carried out under an inert nitrogen atmosphere of 0.1 MPa in a sealed flask at 60 °C for 4 h. During this time, the catalyst precipitated from the reaction system. The conversion rate of 1-hexene relative to hydrogen peroxide was 97.0%, and the selectivity for 1,2-epoxyhexane was 97.6%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated for recycling.

[0065] Example 6

[0066] Preparation of epoxyphenylene oxide

[0067] In a 100 mL three-necked flask, the atmosphere was purged three times with nitrogen, and the catalyst [BSIL] was added sequentially under a nitrogen flow. 1.5 Co 0.5 H 0.5 PW 12 O 48 (

[0068] 0.20 mmol of Co-BSIL-POM-1, 15 mL of mesitylene, 30 mmol of styrene, and a 50% hydrogen peroxide solution containing 10 mmol of H2O2 were used. The reaction was carried out under an inert nitrogen atmosphere of 0.1 MPa in a sealed reaction flask at 60 °C for 3 h. During this time, the catalyst precipitated from the reaction system. The conversion rate of styrene relative to hydrogen peroxide was 95.5%, and the selectivity for epoxide was 97.7%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated for recycling.

[0069] Example 7

[0070] Preparation of 1,2-epoxydodecane

[0071] In a 150 mL stainless steel reactor, [BSIL] 1.5 Cu 0.5 H 0.5 PW 12 O 48 (Cu-BSIL-POM-1) 0.20 mmol, 15 mL tert-butanol, 30 mmol 1-dodecene, and a 50% hydrogen peroxide solution containing 15 mmol H₂O₂ were used in a sealed reactor. The reactor was purged with nitrogen three times to maintain an inert atmosphere of 1.5 MPa nitrogen and reacted at 60 °C for 4 h. At this point, the catalyst precipitated from the reaction system. The conversion rate of 1-dodecene relative to hydrogen peroxide was 97.6%, and the selectivity for 1,2-epoxydodecane was 97.2%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated for recycling.

[0072] Example 8

[0073] Preparation of epoxide octane

[0074] In a 150 mL stainless steel reactor, [BSIL]CuPW 12 O 48 0.20 mmol (Cu-BSIL-POM-2), 15 mL of 1,2-dichloroethane, 30 mmol cyclooctene, and a 50% (w / w) hydrogen peroxide solution containing 15 mmol H₂O₂ were used in a sealed reactor. The reactor was purged with nitrogen three times to maintain an inert atmosphere of 2 MPa nitrogen and reacted at 80 °C for 4 h. At this point, the catalyst precipitated from the reaction system. The conversion rate of cyclooctene relative to hydrogen peroxide was 97.6%, and the selectivity for cyclooctene oxide was 96.2%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated for recycling.

[0075] Example 9

[0076] Preparation of epichlorohydrin

[0077] In a 150 mL stainless steel reactor, [BSIL]CuPW 12 O 48 1.73 mmol of (Cu-BSIL-POM-2), 346 mmol of allyl chloride (which is both the substrate and solvent), and a 50% hydrogen peroxide solution containing 87 mmol of H2O2 were used in a sealed reactor. The reactor was purged with nitrogen three times to maintain an inert atmosphere of 0.5 MPa nitrogen. The reaction was carried out at 60°C for 2 hours. During this time, the catalyst precipitated from the reaction system. The conversion rate of allyl chloride to hydrogen peroxide was 99.0%, and the selectivity for epichlorohydrin was 98.2%. The catalyst was recovered by filtration and dried under vacuum at 50°C for 4 hours. The above operation was then repeated for recycling. The reaction results are shown in the table below.

[0078]

[0079]

[0080] Example 10

[0081] Preparation of propylene oxide

[0082] In a 500 mL stainless steel reactor, [BSIL]CuPW 12 O 48 (Cu-BSIL-POM-2) 3.46 mmol, propylene 346 mmol, and a 50% hydrogen peroxide solution containing 87 mmol H2O2, along with 200 mL of 1,2-dichloroethane, were reacted in a sealed reactor. The reactor was purged with nitrogen three times to maintain an inert atmosphere of 1.5 MPa nitrogen at 40 °C for 3 h. During this time, the catalyst precipitated from the reaction system. The conversion rate of propylene to hydrogen peroxide was 99.03%, and the selectivity for propylene oxide was 98.5%. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h. The above operation was then repeated for recycling. The reaction results are shown in the table below.

[0083]

[0084] Example 11

[0085] Substrate expansion for the catalytic epoxidation of olefins to prepare epoxides

[0086] The reaction conditions are as follows:

[0087] In a 150 mL stainless steel reactor, [BSIL]CuPW 12 O 48(Cu-BSIL-POM-2) 0.20 mmol, 50 mL 1,2-dichloroethane, olefins containing 30 mmol of double bonds and 50% hydrogen peroxide solution containing 30 mmol of H2O2, were used in a sealed reactor. The reactor was purged with nitrogen three times to maintain an inert atmosphere of 0.5 MPa nitrogen and reacted at 60 °C for 4 h. At this time, the catalyst precipitated from the reaction system. The relative hydrogen peroxide conversion of the olefins and the selectivity of the corresponding epoxides are shown in the table below. The catalyst was recovered by filtration and dried under vacuum at 50 °C for 4 h.

[0088]

[0089]

[0090] Comparative Example 2

[0091] 2.4 g of cyclohexene was dissolved in 40 mL of 1,2-dichloroethane, and 2 g of 50% hydrogen peroxide aqueous solution was added, along with 0.29 mmol of [(CH3)3C]2. 16 H 33 [N]3(PO4)(WO3)4, 0.04 g Na2HPO3, reacted at 55℃ for 4 h. The conversion rate of cyclohexene relative to hydrogen peroxide was 98%, and the selectivity of cyclohexane oxide was 99%. The catalyst was recovered by filtration and dried under vacuum at 50℃ for 4 h. The above operation was then repeated for recycling. The reaction results are shown in the table below.

[0092] Comparative Example 3

[0093] 2.4 g of cyclohexene was dissolved in 40 mL of 1,2-dichloroethane, and 2 g of 50% hydrogen peroxide aqueous solution was added, along with 0.29 mmol of [(CH3)3C]2. 16 H 33 [N]3(PO4)(WO3)4 was reacted at 55℃ for 4 hours. The conversion rate of cyclohexene to hydrogen peroxide was 88%, and the selectivity of cyclohexane oxide was 95%. The catalyst was recovered by filtration and dried under vacuum at 50℃ for 4 hours. The above operation was then repeated for recycling. The reaction results are shown in the table below.

[0094] Comparative Example 4

[0095] 2.4 g of cyclohexene was dissolved in 40 mL of 1,2-dichloroethane, and 2 g of 50% hydrogen peroxide aqueous solution, 0.29 mmol of [BSIL]-B, 0.29 mmol of CuCO3, and 0.29 mmol of H3PW were added. 12 O 48The mixture was directly mixed and reacted at 55°C for 4 hours. The conversion rate of cyclohexene to hydrogen peroxide was 80.2%, and the selectivity for cyclohexane oxide was 75.1%. The catalyst was recovered by filtration and dried under vacuum at 50°C for 4 hours. The above operation was then repeated for recycling. The reaction results are shown in the table below.

[0096] Example 26

[0097] 2.4 g of cyclohexene was dissolved in 40 mL of 1,2-dichloroethane, and 2 g of 50% hydrogen peroxide aqueous solution was added, along with 0.29 mmol of [BSIL]CuPW. 12 O 48 (Cu-BSIL-POM-2) was reacted at 55℃ for 4 hours. The conversion rate of cyclohexene to hydrogen peroxide was 98%, and the selectivity for cyclohexane oxide was 99%. The catalyst was recovered by filtration and dried under vacuum at 50℃ for 4 hours. The above operation was then repeated using the recovered catalyst for recycling. The reaction yield % is shown in the table below.

[0098]

[0099] In summary, by comparing the experimental results of Comparative Example 2, Comparative Example 3, and Example 26 (the molar ratio of cyclohexene to H2O2 in hydrogen peroxide was 1:1), it is proven that the catalyst in this system [BSIL] is effective. 2-n M n 1-nXN 12 O 48 (Abbreviated BSIL-POM, where X = P, As; N = W, Mo; M = Mn, Cu, Co, Ni; 0.01)

Claims

1. A method for preparing epoxides by catalytic oxidation of olefins, characterized in that: Using olefins as substrates and hydrogen peroxide as oxygen source, epoxides of the corresponding olefins were prepared by one-step epoxidation under the action of polyoxometalate catalysts containing ionic liquids. The specific method is as follows: add a polyoxometalate catalyst containing ionic liquid and an organic solvent to a reaction vessel, introduce olefins, add hydrogen peroxide oxygen source under stirring, and react in one step to prepare epoxides by oxidizing olefins at a temperature of 10-100 °C, an inert gas pressure of 0.1-4 MPa, and stirring for 0.5-20 hours. The preparation method of the polyoxometalate catalyst containing ionic liquid: (1) Synthesis of ionic liquid [BSIL]: Equal amounts of N-alkylimidazolium and 1,4-butanesulfonate lactone were mixed and magnetically stirred at 10-80℃ for 2-12 h to obtain white precipitate [BSIL]; the obtained solid was washed 2-4 times with methyl tert-butyl ether and then dried at 25℃-60℃ for 1-8 h for later use. (2) Polyoxometalate catalysts containing ionic liquids [BSIL] 2-n M n H 1-n XN 12 O 48 Synthesis: Disperse the metal carbonate MCO3 in water, with +2 valence metals M = one or more of Mn, Cu, Co, and Ni, and add H3XN dropwise to the resulting mixture. 12 O 48 An aqueous solution was prepared; the resulting mixture was stirred at room temperature for 2-8 h, dried at 30-60 °C for 1-8 h, and X = one or both of P and As; N = one or both of W and Mo to obtain M. n H 2-n H 1-n XN 12 O 48， M = one or more of Mn, Cu, Co, and Ni; Add M n H 2-n H 1-n XN 12 O 48 Dropwise add an aqueous solution of 2 - n moles of H to BSIL and stir at room temperature for 2 - 8 h, then dry at 60 - 80 °C for 1 - 8 h to obtain a series of polyoxometalate catalysts containing ionic liquids [BSIL] 2-n M n H 1-n XN 12 O 48 , abbreviated as BSIL - POM, where X is one or two of P and As; N is one or two of W and Mo; M is one or more of Mn, Cu, Co, and Ni; 0.01 < n < 1.99; the metal carbonate is one or more of copper carbonate, manganese carbonate, cobalt carbonate, and nickel carbonate.

2. The method according to claim 1, characterized in that: The organic solvents used include one or more of the following substances: One or more of the following alcohol solvents: methanol, ethanol, n-propanol, isopropanol, tert-butanol, or tert-amyl alcohol; Alkane solvents containing C5-C12 straight-chain alkanes, branched alkanes, or cycloalkanes; One or more of the following aromatic solvents: benzene, toluene, ethylbenzene, xylene, trimethylbenzene, or other mono- or poly-substituted alkylbenzenes; The ester solvent contains fatty acid esters, aromatic esters, or one or more of the following: trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, and trioctyl phosphate. Ether solvents include one or more of alkyl ethers, aromatic ethers, or aromatic alkyl ethers; Halogenated hydrocarbon solvents, including halogenated alkanes or chlorinated aromatics; One or more of dialkyl ketones or arylalkyl ketones in ketone solvents; Nitrile solvents are one or more of acetonitrile, propionitrile, or benzyl nitrile; The organic solvent used in the reaction can be a single solvent or a mixture of two or more of the above solvents; The solvent volume required for 1 mmol of double bond in an olefin is 0.05 mL to 5.0 mL.

3. The method according to claim 1, characterized in that: The mass concentration of the hydrogen peroxide is 15-70%, and the ratio of the amount of double bond in the olefin to the amount of H2O2 in the hydrogen peroxide is (1-10):

1.

4. The method according to claim 1, characterized in that: The olefins include one or more of the following: chain-terminal olefins, chain-internal olefins, cyclic olefins, and α,β-unsaturated ketones. The chain-like terminal olefins are one or more of styrene, cycloalkanyl ethylene, chloropropene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene and their derivatives. The chain-like internal olefin is one or more of the C3-C20 chain olefins in which the carbon-carbon double bond is not at the end of the molecular chain. The cyclic olefin is one or more of cyclopentene and its derivatives, cyclohexene and its derivatives, cycloheptene and its derivatives, and cyclooctene and its derivatives. The α,β-unsaturated ketone is one or more of 2-cyclohexen-1-one, 4-hexen-3-one, chalcone and its derivatives, 3-methyl-2-cyclohexen-1-one, 4-methyl-3-penten-2-one, and 3-octen-2-one.

5. The method according to claim 1, characterized in that: The epoxidation reaction of the olefin is carried out at a temperature of 10-100°C, an inert gas pressure of 0.1-4 MPa, and a reaction time of 0.5-20 hours. The inert gas used is one or more of nitrogen, argon, and helium.

6. The method according to claim 1, characterized in that: Catalyst [BSIL] 2-n M n H 1-n XN 12 O 48 The molar ratio of the abbreviation BSIL-POM to the double bond in the olefin ranges from 0.1 to 5 mol.

7. The method according to claim 1 or 6, characterized in that: Catalyst [BSIL] 2-n M n H 1-n XN 12 O 48 It has both the functional groups of ionic liquid and polyoxometalate. The value range of n is 0.01 < n < 1.

99. By adjusting the value of n, the acidity of the catalyst can be adjusted, and the corresponding epoxide can be obtained with high selectivity without the need to additionally add phosphate, carbonate, acetate additives.

8. The method according to claim 1, characterized in that: N-alkylimidazole is one or more of N-methylimidazole, N-ethylimidazole, N-propylimidazole, and N-butylimidazole.

Images