Preparation method and application of copper-vanadium tungsten oxygen cluster catalyst

Abstract

The invention relates to the technical field of catalyst material preparation, in particular to a preparation method and application of a copper-vanadium tungsten oxygen cluster catalyst.The preparation method comprises the steps that sodium tungstate, ammonium metavanadate, copper salt and isopropyl imidazole are dissolved in a certain volume of solvent according to a certain proportion, the mixture is put into a polytetrafluoroethylene reaction kettle, and the mixture is stirred to be uniform; and after reacting for a period of time at a certain temperature, gradually cooling to obtain [Cu (1-iPIM) 4] 3 [VW12O40]. The catalyst can realize a cascade reaction of olefin epoxidation and carbon dioxide cycloaddition, and the preparation method of the catalyst is simple in reaction process, has a clear molecular structure, and is beneficial to research on a catalytic reaction mechanism.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst material preparation, and relates to a preparation method of a copper-vanadium tungsten oxide cluster catalyst and application thereof. Background Art

[0002] In the context of sustainable green chemistry and the national dual carbon strategy, the use of carbon dioxide as a starting material to synthesize value-added functionalized chemicals has received widespread attention. The reaction of carbon dioxide and epoxides is 100% atomically efficient and is one of the few industrially feasible methods for producing cyclic carbonates. 2 Many excellent results of cycloaddition reactions have been widely reported. Traditionally, the synthesis of cyclic carbonates from low-cost olefin chemicals usually involves two steps: epoxidation of olefins and cycloaddition of carbon dioxide. However, two different catalysts are usually required in these two reactions (ACSCatal. 2024, 14, 19, 14639; Nat. Sci. Rev. 2024, 11, nwae305; Chem. Eng. J.2024, 490, 151704; ACS Sustainable Chem. Eng. 2024, 12, 16396; Dalton Trans.2024, 53, 17157; Inorg. Chem.2024, 63, 19299; Ind. Eng. Chem. Res. 2024, 63,16725). Therefore, the use of the same catalyst to synthesize cyclic carbonates from cheap and readily available olefins and carbon dioxide in series has attracted widespread attention. This process will avoid the tedious steps of separation and purification of intermediates. Recently, heterogeneous catalysts with multifunctional active sites have been studied to directly synthesize cyclic carbonates from olefins as raw materials. However, most of these catalysts require solvents or harsh conditions (high temperature, high pressure and long reaction time). Therefore, finding a catalyst that is economical, efficient, has mild reaction conditions, is environmentally friendly and easy to recycle remains a very important issue at present.

[0003] After researching existing literature (Nat. Commun. 2015, 6, 10007; J. CO 2 Util. 2020, 39,101173; Inorg. Chem. Front. 2023, 2088; Ind. Eng. Chem. Res. 2024, 63, 17148; J CO 2Utili. 2023, 72, 102497), it was found that there are few single-component dual-active-center polymetallic oxygen cluster catalysts that can effectively catalyze the tandem reaction of olefins to generate cyclic carbonates. Therefore, the one-step design and synthesis of a single-component catalyst with dual active centers is the key to solving the tandem reaction of olefin epoxidation and cycloaddition reaction. Based on this, the scheme of the present application is proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a copper-vanadium tungsten oxygen cluster catalyst in view of the fact that the catalyst component in the catalytic conversion olefin epoxidation and carbon dioxide cycloaddition reaction is not single, the production cost is high, the reaction efficiency is low, and the like, so as to play a synergistic catalytic role in the olefin epoxidation and carbon dioxide cycloaddition series reaction, so as to achieve the goal of being able to realize the olefin epoxidation and carbon dioxide cycloaddition series reaction under mild conditions under the action of a single-component catalyst.

[0005] The design ideas of the present invention are as follows: 1. Sodium tungstate, ammonium metavanadate, copper salt and isopropyl imidazole were hydrothermally synthesized to construct copper-vanadium tungsten oxygen cluster catalyst, which synergistically catalyzed olefin epoxidation and carbon dioxide cycloaddition at multiple active sites during the reaction process; 2. Apply copper-vanadium tungsten oxide cluster catalysts with a clear structure to the cycloaddition reaction of olefin epoxidation and carbon dioxide to achieve the goal of obtaining cyclic carbonates with high carbon dioxide conversion rate and high selectivity.

[0006] The crystal structure information of the above catalyst is obtained by the following method: the crystal of the copper-vanadium tungsten oxygen cluster catalyst is synthesized by a conventional hydrothermal method. The specific technical scheme is as follows: Sodium tungstate, ammonium metavanadate, copper salt and isopropyl imidazole were dissolved in deionized water and stirred at room temperature. -1 HCl was used to adjust the pH value of the mixture to about 6.6. After that, the mixture was placed in a stainless steel reactor and reacted at a certain temperature for a certain time. o C h -1 The autoclave was cooled to room temperature at a rate of 4 ] 3 [VW 12 O 40 ].

[0007] The preferred solution is: dissolve sodium tungstate (0.9-1.5 mmol), ammonium metavanadate (1.7-2.5 mmol), copper chloride (0.6-1.2 mmol) and isopropyl imidazole (3.5-5.0 mmol) in 10-15 mL of deionized water and stir at room temperature. -1HCl was added to adjust the pH value of the mixture to about 6.6-8.2. Afterwards, the mixture was placed in a polytetrafluoroethylene-lined reactor and heated at 120-160 o C for 48h~120h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of 4 ] 3 [VW 12 O 40 ]. The yield is about 30-50%.

[0008] The product was characterized by single crystal X-ray diffraction and powder X-ray diffraction to obtain accurate information about the crystal structure. The specific results are as follows: The molecular formula of the crystal is [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 ], the catalyst crystallized in rhombohedral space group R-3. The catalyst consists of three [Cu(1-iPIM) 4 ] unit and a [VW 12 O 40 ] unit. In [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 ], [Cu(1-iPIM) 4 The Cu1 in the unit is hexacoordinated by the four N atoms of the two isopropylimidazoles and the two O atoms of the polyanion in a distorted octahedral geometry. 12 O 40 ] unit shows a classic Keggin-type structure. Each W atom has a twisted WO 6 Octahedral environment, every three WO 6 The octahedral bodies are connected by shared edges in a triangular arrangement, forming a W 3 O 13 group. It is worth noting that each [VW 12 O 40 ] units as inorganic ligands, through O t (terminal oxygen) with three [Cu(1-iPIM) 4 ] units are covalently bonded to stabilize the 3D structure. Structural analysis revealed that this type of catalyst contains two active centers, one of which is [VW 12 O 40 ] unit active site, one is [Cu(1-iPIM) 4 ] unit active sites, and the two contribute to olefin epoxidation and carbon dioxide cycloaddition reactions respectively, playing a synergistic catalytic role.

[0009] The present invention mainly synthesizes a copper-vanadium tungsten oxygen cluster catalyst for olefin epoxidation and carbon dioxide cycloaddition, and has applied it to the olefin epoxidation and carbon dioxide cycloaddition reaction. This type of catalyst can realize the tandem reaction of olefin epoxidation and carbon dioxide cycloaddition, and the preparation method of this type of catalyst has a simple reaction process.

[0010] The present invention has the following beneficial effects:

[0011] 1. The preparation method is simple, and the catalysts have a clear molecular structure, which is conducive to studying the mechanism of catalytic reactions.

[0012] 2. The catalyst has polymetallic oxygen cluster anion active sites and metal cation active sites, both of which contribute to olefin epoxidation and carbon dioxide cycloaddition reactions respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 ] schematic diagram of the crystal structure; Figure 2 The compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 ]’s RXRD characterization diagram. DETAILED DESCRIPTION

[0014] In order to demonstrate the essential features and significant improvements of the present invention, the following examples are used to further illustrate the implementation methods and effects.

[0015] Embodiment 1: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (0.9 mmol), ammonium metavanadate (1.7 mmol), copper chloride (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 10 mL of deionized water and stirred at room temperature for 2 h. -1 The pH of the mixture was adjusted to about 6.6 with HCl. The mixture was then placed in a stainless steel reactor and heated at 160 o C for 72 h. Then, o C h -1The autoclave was cooled to room temperature at a rate of 1.5 %. Yellow crystals were separated, washed with water, and air-dried. Yield: 33%.

[0016] Embodiment 2: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (1.0 mmol), ammonium metavanadate (1.7 mmol), copper chloride (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 9 mL of deionized water and stirred at room temperature for 2 h. -1 HCl was added to adjust the pH value of the mixture to about 6.6. Afterwards, the mixture was placed in a stainless steel reactor and heated at 130 o C for 96 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of 1.5 %. Yellow crystals were separated, washed with water, and air-dried. Yield: 31%.

[0017] Embodiment 3: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (1.3 mmol), ammonium metavanadate (1.7 mmol), copper chloride (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 10 mL of deionized water and stirred at room temperature for 2 h. -1 The pH value of the mixture was adjusted to about 7.5 with HCl. The mixture was then placed in a stainless steel reactor and heated at 140 o C for 120 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of 1.5 %. Yellow crystals were separated, washed with water, and air-dried. Yield: 36%.

[0018] Embodiment 4: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (1.5 mmol), ammonium metavanadate (1.7 mmol), copper chloride (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 11 mL of deionized water and stirred at room temperature for 2 h. -1 HCl was added to adjust the pH value of the mixture to about 8.0. Afterwards, the mixture was placed in a stainless steel reactor and heated at 160 o C for 96 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of 1.5 %. Yellow crystals were separated, washed with water, and air-dried. Yield: 37%.

[0019] Embodiment 5: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (0.9 mmol), ammonium metavanadate (2.3 mmol), copper chloride (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 10 mL of deionized water and stirred at room temperature for 2 h. -1 The pH value of the mixture was adjusted to about 6.6 with HCl. The mixture was then placed in a stainless steel reactor and heated at 150 o C for 120 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of . Yellow crystals were separated, washed with water, and air-dried. Yield: 41%.

[0020] Embodiment 6: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (0.9 mmol), ammonium metavanadate (2.5 mmol), copper chloride (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 10 mL of deionized water and stirred at room temperature for 2 h. -1 The pH value of the mixture was adjusted to about 7.0 with HCl. The mixture was then placed in a stainless steel reactor and heated at 150 o C for 96 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of 1.5 %. Yellow crystals were separated, washed with water, and air-dried. Yield: 43%.

[0021] Embodiment 7: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (0.9 mmol), ammonium metavanadate (1.7 mmol), copper chloride (1.2 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 10 mL of deionized water and stirred at room temperature for 2 h. -1 The pH of the mixture was adjusted to about 6.6 with HCl. The mixture was then placed in a stainless steel reactor and heated at 160 o C for 120 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of 1.5 %. Yellow crystals were separated, washed with water, and air-dried. Yield: 47%.

[0022] Embodiment 8: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (0.9 mmol), ammonium metavanadate (1.7 mmol), copper acetate (0.6 mmol), and isopropylimidazole (5.0 mmol) was dissolved in 12 mL of deionized water and stirred at room temperature for 2 h. -1 The pH of the mixture was adjusted to about 6.6 with HCl. The mixture was then placed in a stainless steel reactor and heated at 160 o C for 120 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of 1.5 %. Yellow crystals were separated, washed with water, and air-dried. Yield: 31%.

[0023] Embodiment 9: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (0.9 mmol), ammonium metavanadate (1.7 mmol), copper chloride (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 10 mL of deionized water and stirred at room temperature for 2 h. -1The pH value of the mixture was adjusted to about 7.6 with HCl. The mixture was then placed in a stainless steel reactor and heated at 160 o C for 5 days. Then, o C h -1 The autoclave was cooled to room temperature at a rate of . Yellow crystals were separated, washed with water, and air-dried. Yield: 50%.

[0024] Embodiment 10: Compound [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 Preparation of A mixture of sodium tungstate (0.9 mmol), ammonium metavanadate (1.7 mmol), copper nitrate (0.6 mmol), and isopropylimidazole (3.5 mmol) was dissolved in 10 mL of deionized water and stirred at room temperature for 2 h. -1 HCl was added to adjust the pH value of the mixture to about 8.2. Afterwards, the mixture was placed in a stainless steel reactor and heated at 160 o C for 120 h. Then, o C h -1 The autoclave was cooled to room temperature at a rate of . Yellow crystals were separated, washed with water, and air-dried. Yield: 41%.

[0025] Embodiment 11: Application of copper-vanadium tungsten oxide cluster catalysts to olefin epoxidation and carbon dioxide cycloaddition reactions: 1 mmol olefin, 2 mmol anhydrous TBHP and 0.13 mmol% catalyst were added sequentially into a Shrek tube equipped with a magnetic stirrer. The reaction mixture was heated to 60 o C for 24 hours, cooled to room temperature, and then quantitatively analyzed by GC and GC-MS.

[0026] 1 mmol of epoxide, 5 mmol of TBAB and 0.13 mmol% of catalyst were added sequentially into a flask containing CO. 2 The reaction mixture was heated to 80 o C for 24 hours, cooled to room temperature, and then quantitatively analyzed by GC and GC-MS.

[0027] As shown below, the catalyst [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 ] The results of olefin epoxidation and carbon dioxide cycloaddition are as follows:

[0028] The above results show that [Cu(1-iPIM) 4 ] 3 [VW 12 O 40 ] It shows efficient catalytic activity in the epoxidation reaction of synthetic olefins. Under the condition of tert-butyl hydroperoxide as oxidant, it can effectively catalyze the conversion of styrene to generate epoxystyrene compounds, and the yield can reach 88% within 24 hours. The catalyst is filtered, and then in the second step of the catalytic reaction, this catalyst can synthesize cyclic carbonate products under solvent-free conditions, and the yield can reach 99%. The results show that this copper-vanadium tungsten oxide cluster catalyst can realize the reaction of synthesizing the final product cyclic carbonate from olefins under mild conditions, highlighting the ability of green catalytic carbon dioxide conversion, and solving the scientific problem that the previous literature reported that it was impossible to catalyze the olefin epoxidation and carbon dioxide cycloaddition tandem reactions at the same time.

[0029] Of course, the above embodiments of the present invention are only examples for illustrating the present invention, and are not intended to limit the specific implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above examples. It is impossible to give detailed examples of all implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing copper-vanadium tungsten oxide clusters, characterized in that: The steps are as follows: sodium tungstate, ammonium metavanadate, copper salt and isopropyl imidazole are sequentially added to a container and mixed in a certain volume of solvent, reacted at a certain temperature for a certain time, cooled to room temperature, and [Cu(1-iPIM)4]3[VW 12 O 40 ], wherein the molar ratio of sodium tungstate: ammonium metavanadate: copper salt: isopropyl imidazole is 0.9 ~ 1.5: 1.7 ~ 2.5: 0.6 ~ 1.2: 3.5 ~ 5.

0.

2. The method for preparing a copper-vanadium tungsten oxide cluster catalyst according to claim 1, characterized in that: The solvent used is water, the molar volume ratio (mmol / mL) of sodium tungstate to solvent is 0.9~1.5:8~12, the pH is adjusted to 6.6~8.2, the copper salt is copper chloride, the reaction temperature is 100~160℃, and the reaction time is 48h~120h.

3. Use of the copper-vanadium tungsten oxide cluster catalyst obtained by the preparation method according to any one of claims 1 to 2 in catalyzing the epoxidation of olefins and the cycloaddition reaction of carbon dioxide.

Images