A supported copper-based catalyst with surface oxygen vacancies and a preparation method and application thereof

Abstract

The application provides a supported copper catalyst containing surface oxygen vacancies and a preparation method and application thereof. The method uses a metal oxide as a carrier, metal copper as a catalytic center, and forms a supported catalyst containing surface oxygen vacancies under a magnetic field. When the catalyst is used in the reaction of oxidizing an unsaturated alcohol into an unsaturated aldehyde, the reaction temperature is low, the catalytic efficiency is high, the service life is long, and the reaction yield is high.

Description

Technical Field

[0001] This invention belongs to the field of fine chemicals, specifically relating to a supported copper catalyst with oxygen vacancies on its surface, its preparation method, and its application. Background Technology

[0002] The oxidation of unsaturated alcohols to unsaturated aldehydes plays a crucial role in fine chemical production processes, such as the synthesis of 3-methyl-2-butenal, which is a key step in the synthesis of citral. Because both the raw material unsaturated alcohol and the product unsaturated aldehyde contain carbon-carbon double bonds, they are prone to polymerization side reactions under high-temperature reaction conditions.

[0003] US5149884 discloses a method for oxidizing 3-methyl-3-butenol to 3-methyl-2-butenal. This method uses silver as a catalyst and employs a tubular reactor, achieving a conversion rate of 52-55% and a selectivity of 90-92%. However, this method requires a large amount of precious silver, resulting in high costs and high reaction temperatures, making it difficult to reduce the amount of heavy component byproducts.

[0004] CN101977684A discloses the use of a supported noble metal catalyst in the preparation of unsaturated carbonyl compounds from unsaturated alcohols via oxidative dehydrogenation, obtained by applying a sparingly soluble noble metal compound from a suspension or solution onto a support and subsequently subjecting it to heat treatment, with a reaction selectivity of up to about 80% and a conversion of up to about 58%.

[0005] In summary, existing catalysts for the oxidation of unsaturated alcohols suffer from drawbacks such as high precious metal consumption, high reaction temperatures (300 to 450°C), and low reaction yields. Furthermore, the high reaction temperatures lead to polymerization and carbonization of the materials, resulting in short catalyst lifetimes and easy deactivation during the catalytic process. Therefore, it is necessary to develop a highly efficient catalyst that can reduce the reaction temperature and improve catalyst lifetime and reaction yield. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, one objective of this invention is to provide a supported copper catalyst with oxygen vacancies on its surface. When used for the oxidation of unsaturated alcohols to unsaturated aldehydes, this catalyst exhibits low reaction temperature, high catalytic efficiency, long lifespan, and high reaction yield.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A method for preparing a supported copper catalyst with oxygen vacancies on its surface, wherein the method uses a metal oxide as a support and metallic copper as a catalytic center, and processes the catalyst under magnetic field conditions to form a supported catalyst with oxygen vacancies on its surface.

[0009] In this invention, the copper oxide-supported catalyst is treated with a liquid reducing agent, causing oxygen to detach from the copper oxide and cerium oxide support lattice, forming oxygen vacancies. Surprisingly, we found that reduction-oxidation treatment under magnetic field conditions can improve the catalytic activity and stability of these oxygen vacancies. During the oxidation reaction, oxygen forms atomic adsorbed oxygen on the catalyst surface. This atomic adsorbed oxygen combines with unsaturated alcohols under the action of CuO, accelerating the transfer of atomic adsorbed oxygen between oxygen, CuO, and unsaturated alcohols. This allows the reaction to proceed normally at lower temperatures. The oxidation products rapidly detach from the catalytic center with the help of the promoter, preventing product growth and reducing polymerization or carbonization at high temperatures. This significantly improves the reaction yield, extends the catalyst lifespan, and avoids the use of large amounts of precious metals, thus reducing catalyst costs.

[0010] In one embodiment of the present invention, the method includes the following steps:

[0011] S1: Soluble copper salt dissolved in water, with added additives and carrier;

[0012] S2: Add a precipitant to precipitate;

[0013] S3: The catalyst intermediate obtained through post-processing;

[0014] S4: The intermediate is treated under magnetic field conditions to obtain a supported copper catalyst with oxygen vacancies on the surface.

[0015] In one embodiment of the present invention, the carrier in S1 is a fourth-period transition metal and / or lanthanide metal oxide, preferably one or more of cerium dioxide, titanium dioxide, and iron oxide.

[0016] In one embodiment of the present invention, the soluble copper salt in S1 is a soluble oxyacid salt and / or a copper halide, preferably one or more of copper chloride, copper nitrate, and copper sulfate, more preferably copper chloride and / or copper nitrate.

[0017] In one embodiment of the present invention, the auxiliary agent in S1 is zirconium oxide and / or zirconium salt, preferably zirconium oxide and / or zirconium chloride; preferably, the mass ratio of the soluble copper salt to water is 1:(500-20), more preferably 1:(200-30); preferably, the mass ratio of the soluble copper salt to the carrier is 1:(3-10), more preferably 1:(3-7); preferably, the mass ratio of the auxiliary agent to the carrier is 1:(30-100), more preferably 1:(50-70).

[0018] In one embodiment of the present invention, the precipitant in S2 is a hydroxide and / or halide of sodium and / or calcium, preferably sodium hydroxide and / or calcium chloride; preferably, the mass ratio of soluble copper salt to precipitant is 1:(1-3), more preferably 1:(1-2).

[0019] In one embodiment of the present invention, the post-processing in S3 includes filtration, washing, drying, and calcination; preferably, the drying temperature in S3 is 100-200°C, and the calcination temperature is 600-800°C.

[0020] In one embodiment of the present invention, the treatment in S4 involves treating the copper oxide-supported catalyst with a reducing agent under magnetic field conditions while maintaining these conditions. Preferably, the magnetic field strength is 1500–4500 Gauss, more preferably 1800–3000 Gauss. Preferably, the reducing agent is an organic reducing agent, preferably one or more of hydrazine, o-phenylenedioxoborane, and phenol, more preferably hydrazine and / or o-phenylenedioxoborane. Preferably, the mass ratio of reducing agent to carrier is (5-15):1. Preferably, the treatment temperature is 50-120°C, more preferably 70-100°C, the pressure is 0.5-3 MPaG, and the time is 1-6 h, more preferably 2-4 h. Preferably, the temperature is restored to normal under an oxygen-deficient environment, preferably with an oxygen volume fraction of 5%-20%, more preferably with an oxygen volume fraction of 10-18%.

[0021] Another object of the present invention is to provide a supported copper catalyst with oxygen vacancies on its surface.

[0022] A supported copper-based catalyst with oxygen vacancies on its surface, the catalyst being prepared by the method described above, wherein the oxygen vacancy content of the catalyst reaches 7-11%.

[0023] Another object of the present invention is to provide the use of a supported copper catalyst with oxygen vacancies on its surface.

[0024] Use of a supported copper catalyst with oxygen vacancies on its surface, wherein the catalyst is prepared by the method described above or is the catalyst described above, wherein the catalyst is used for the gas-solid phase catalytic oxidation reaction of unsaturated alcohols to unsaturated aldehydes, preferably for the gas-solid phase catalytic oxidation reaction of unsaturated alcohols to unsaturated aldehydes under low temperature conditions, more preferably for the catalytic oxidation of 3-methyl-3-butenol to 3-methyl-2-butenol under low temperature conditions of 210-270°C.

[0025] Compared with the prior art, the advantages of this invention are as follows:

[0026] (1) Avoid using precious metals in the catalyst synthesis process to reduce the production cost of the catalyst; the catalyst synthesis steps are short and easy to scale up production.

[0027] (2) When used for the oxidation of unsaturated alcohols to unsaturated aldehydes, it still maintains high catalytic efficiency at reaction temperatures below 300℃, with a reaction conversion rate of over 67% and a target product selectivity of over 98%. The lower reaction temperature greatly reduces the oxidation reaction byproduct tar, and the catalyst life exceeds 1800h. Detailed Implementation

[0028] The embodiments of the present invention are described in detail below. These embodiments are intended to explain the present invention and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in existing literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0029] The main raw material information is as follows:

[0030] Table 1 Chemical Information in Examples

[0031]

[0032]

[0033] The gas chromatography test conditions of this invention are as follows:

[0034] Instrument model: Agilent GC2030; Column: HP-5 (30m×0.25mm×0.25μm); Column temperature: initial temperature 40℃, increased to 120℃ at 5℃ / min, then increased to 250℃ at 15℃ / min, held for 6min; Injector temperature: 250℃; FID detector temperature: 250℃; Split injection, split ratio 60:1; Injection volume: 2.0μL; H2 flow rate: 40mL / min; Air flow rate: 360mL / min.

[0035] Instrument model: Agilent GC2030; Column: CHIRALDEX G-TA 180℃: 30m x 250μm x 0.12μm; Column temperature: initial 80℃, then 2℃ / min to 130℃ for 1 minute, then 10℃ / min to 170℃ for 10 minutes, run time 40 minutes. Injector temperature: 80℃; FID detector temperature: 200℃; Split injection, split ratio 100:1; Injection volume: 2.0μL; H2 flow rate: 40mL / min; Air flow rate: 400mL / min.

[0036] Experimental magnetic field equipment: Jinzhengmao EM series

[0037] Drying equipment: Shanghai Jinghong DHG-9203A

[0038] Calcination equipment: Jinan Lure MF-15-12TP

[0039] Characterization of oxygen vacancies: Electron paramagnetic resonance (EPR) spectroscopy.

[0040] Catalyst test conditions in the examples:

[0041] 3-Methyl-3-buten-1-ol was vaporized into 180°C steam and then mixed with air before passing through a catalyst bed. The molar ratio of oxygen to 3-methyl-3-buten-1-ol in the feed was 1:2. The reactor temperature was controlled at 270°C, and the volume hourly space velocity (VHSV) of the 3-methyl-3-buten-1-ol feed was 35 h⁻¹. -1 The product was condensed and analyzed by gas chromatography to determine the conversion rate and the total selectivity of the target products 3-methyl-3-buten-1-aldehyde and 3-methyl-2-buten-1-aldehyde.

[0042] Example 1

[0043] 5.2 g of copper chloride was dissolved in 250 g of pure water. 0.5 g of zirconium oxide and 32 g of cerium dioxide were added to the aqueous solution and stirred until homogeneous. 8.4 g of sodium hydroxide was added to the mixture. The precipitate was filtered out, dried at 150 °C, and then transferred to a muffle furnace for calcination at 650 °C for 4 h. The mixture was then allowed to return to room temperature to obtain a copper-supported catalyst. The copper-supported catalyst was soaked in 200 g of hydrazine at 90 °C and 1 MPa(G) for 2.5 h, maintaining a magnetic field strength of 2200 Gauss during the soaking process. The solid was filtered out, and the magnetic field strength was kept constant. The mixture was then allowed to return to room temperature in an atmosphere with an oxygen concentration of 12 v% to obtain a copper-supported catalyst with oxygen vacancies on its surface, containing 10.6% oxygen vacancies.

[0044] Under the catalyst test conditions, the oxidation reaction of 3-methyl-3-buten-1-ol was catalyzed with a conversion rate of 67.6%, a target product selectivity of 98.4%, and a catalyst lifetime of over 1800 h.

[0045] Example 2

[0046] 5.3 g of copper nitrate was dissolved in 250 g of pure water. 0.6 g of zirconium chloride and 32 g of cerium dioxide were added to the aqueous solution and stirred until homogeneous. 8.4 g of calcium chloride was added to the mixture. The precipitate was filtered out, dried at 100 °C, and then transferred to a muffle furnace for calcination at 680 °C for 4 h. The mixture was then allowed to return to room temperature to obtain a copper-supported catalyst. The copper-supported catalyst was soaked in 300 g of o-phenylenedioxoborane at 80 °C and 1.5 MPa(G) for 3 h, maintaining a magnetic field strength of 2500 Gauss during the soaking process. The solid was filtered out, and the magnetic field strength was kept constant. The mixture was then allowed to return to room temperature under an oxygen concentration of 15 v% to obtain a copper-supported catalyst with oxygen vacancies on its surface, containing 11% oxygen vacancies.

[0047] Under the catalyst test conditions, the oxidation reaction of 3-methyl-3-buten-1-ol was catalyzed with a conversion rate of 66.1%, a target product selectivity of 98.7%, and a catalyst lifetime of over 1800 h.

[0048] Example 3

[0049] 5.2 g of copper sulfate was dissolved in 250 g of pure water. 0.5 g of zirconium oxide and 32 g of cerium dioxide were added to the aqueous solution and stirred until homogeneous. 8.4 g of sodium hydroxide was added to the mixture. The precipitate was filtered out, dried at 200 °C, and then transferred to a muffle furnace for calcination at 600 °C for 4 h. The mixture was then allowed to return to room temperature to obtain a copper-supported catalyst. The copper-supported catalyst was soaked in 250 g of hydrazine at 80 °C and 1.5 MPa(G) for 2 h, maintaining a magnetic field strength of 2200 Gauss during the soaking process. The solid was filtered out, and the magnetic field strength was kept constant. The mixture was then allowed to return to room temperature in an atmosphere with an oxygen concentration of 12 v% to obtain a copper-supported catalyst with oxygen vacancies on its surface, containing 8.7% oxygen vacancies.

[0050] Under the catalyst test conditions, the oxidation reaction of 3-methyl-3-buten-1-ol was catalyzed with a conversion rate of 57.1%, a target product selectivity of 94.2%, and a catalyst lifetime of over 1800 h.

[0051] Example 4

[0052] 5,2-Copper chloride was dissolved in 250g of pure water. 0.5g of zirconium oxide and 32g of iron oxide were added to the aqueous solution and stirred until homogeneous. 11.4g of sodium hydroxide was added to the mixture. The precipitate was filtered out, dried at 180℃, and then transferred to a muffle furnace for calcination at 800℃ for 4 hours. The mixture was then allowed to return to room temperature to obtain a copper-supported catalyst. The copper-supported catalyst was soaked in 250g of phenol at 85℃ and 0.5MPa(G) for 2 hours, maintaining a magnetic field strength of 1500 Gauss during the soaking process. The solid was filtered out, and the magnetic field strength was kept constant. The mixture was then allowed to return to room temperature in an atmosphere with an oxygen concentration of 14v%, yielding a copper-supported catalyst with oxygen vacancies on its surface, containing 8.9% oxygen vacancies.

[0053] Under the catalyst testing conditions, the oxidation reaction of 3-methyl-3-buten-1-ol was catalyzed with a conversion rate of 58.2%, a target product selectivity of 95.6%, and a catalyst lifetime of over 1800 hours.

[0054] Example 5

[0055] 12.5 g of copper nitrate was dissolved in 250 g of pure water. 0.4 g of zirconium oxide and 40 g of cerium dioxide were added to the aqueous solution and stirred until homogeneous. 12.5 g of calcium hydroxide was added to the mixture. The precipitate was filtered out, dried at 150 °C, and then transferred to a muffle furnace for calcination at 650 °C for 4 h. The mixture was then allowed to return to room temperature to obtain a copper-supported catalyst. The copper-supported catalyst was soaked in 200 g of hydrazine at 70 °C and 2.5 MPa(G) for 4 h, maintaining a magnetic field strength of 4500 Gauss during the soaking process. The solid was filtered out, and the magnetic field strength was kept constant. The mixture was then allowed to return to room temperature in an atmosphere with an oxygen concentration of 5 v% to obtain a copper-supported catalyst with oxygen vacancies on its surface, containing 9.8% oxygen vacancies.

[0056] Under the catalyst test conditions, the oxidation reaction of 3-methyl-3-buten-1-ol was catalyzed with a conversion rate of 64.8%, a target product selectivity of 96.7%, and a catalyst lifetime of over 1800 h.

[0057] Example 6

[0058] 0.5 g of copper chloride was dissolved in 250 g of pure water. 0.1 g of zirconium oxide and 5 g of cerium dioxide were added to the aqueous solution and stirred until homogeneous. 1.5 g of calcium chloride was added to the mixture. The precipitate was filtered out, dried at 160 °C, and then transferred to a muffle furnace for calcination at 700 °C for 4 h. The mixture was then allowed to return to room temperature to obtain a copper-supported catalyst. The copper-supported catalyst was soaked in 150 g of hydrazine at 80 °C and 3 MPa(G) for 1 h, maintaining a magnetic field strength of 2000 Gauss during the soaking process. The solid was filtered out, and the magnetic field strength was kept constant. The mixture was then allowed to return to room temperature in an atmosphere with an oxygen concentration of 18 v% to obtain a copper-supported catalyst with oxygen vacancies on its surface, containing 7.3% oxygen vacancies.

[0059] Under the catalyst test conditions, the oxidation reaction of 3-methyl-3-buten-1-ol was catalyzed with a conversion rate of 50.1%, a target product selectivity of 94.4%, and a catalyst lifetime of over 1800 h.

[0060] Comparative Example 1

[0061] Compared with Example 1, the only difference is that the magnetic field strength was adjusted to 0, resulting in an oxygen vacancy content of 1.6% in the supported copper catalyst.

[0062] Under the catalyst test conditions, the oxidation of 3-methyl-3-buten-1-ol was catalyzed with a conversion of 13.8% and a target product selectivity of 49.6%.

[0063] Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a supported copper-based catalyst with surface oxygen vacancies, characterized in that, The method uses metal oxide as a support and copper as a catalytic center, and processes it under magnetic field conditions to form a supported catalyst with oxygen vacancies on its surface.

2. The method of claim 1, wherein, The method includes the following steps S1: Soluble copper salt dissolved in water, with added additives and carrier; S2: Add a precipitant to precipitate; S3: The catalyst intermediate obtained through post-processing; S4: The intermediate is treated under magnetic field conditions to obtain a supported copper catalyst with oxygen vacancies on the surface.

3. The method according to claim 1 or 2, characterized in that, The carrier described in S1 is a fourth-period transition metal and / or lanthanide metal oxide, preferably one or more of cerium dioxide, titanium dioxide, and iron oxide; And / or, the soluble copper salt described in S1 is a soluble oxyacid salt and / or a copper halide, preferably one or more of copper chloride, copper nitrate, and copper sulfate, more preferably copper chloride and / or copper nitrate; And / or, the additives in S1 are zirconium oxides and / or zirconium salts, preferably zirconium oxide and / or zirconium chloride; Preferably, the mass ratio of the soluble copper salt to water is 1:(500-20), more preferably 1:(200-30); Preferably, the mass ratio of the soluble copper salt to the carrier is 1:(3-10), more preferably 1:(3-7); Preferably, the mass ratio of the additive to the carrier is 1:(30-100), more preferably 1:(50-70).

4. The method according to claim 1 or 2, characterized in that, The precipitant in S2 is a hydroxide and / or halide of sodium and / or calcium, preferably sodium hydroxide and / or calcium chloride; Preferably, the mass ratio of soluble copper salt to precipitant is 1:(1-3), more preferably 1:(1-2).

5. The method according to claim 1 or 2, characterized in that, The post-processing in S3 includes filtration, washing, drying, and calcination; Preferably, the drying temperature in S3 is 100-200℃, and the calcination temperature is 600-800℃.

6. The method of claim 1 or 2, wherein, The treatment method in S4 is to treat the copper oxide supported catalyst with a reducing agent under magnetic field conditions while maintaining the magnetic field conditions. Preferably, the magnetic field strength of the magnetic field condition is 1500–4500 Gauss, more preferably 1800–3000 Gauss; Preferably, the reducing agent is an organic reducing agent, preferably one or more of hydrazine, o-phenylenedioxoborane, and phenol, more preferably hydrazine and / or o-phenylenedioxoborane; Preferably, the mass ratio of reducing agent to carrier is (5-15):1; Preferably, the treatment temperature is 50-120℃, more preferably 70-100℃, the pressure is 0.5-3MPaG, and the time is 1-6h, more preferably 2-4h; Preferably, the temperature is restored to normal in an oxygen-deficient environment, preferably with an oxygen volume fraction of 5%-20%, and more preferably with an oxygen volume fraction of 10-18%.

7. A supported copper-based catalyst with surface oxygen vacancies, prepared by the method according to any one of claims 1 to 6, characterized in that, The catalyst has an oxygen vacancy content of 7-11%.

8. Use of a supported copper catalyst with oxygen vacancies on its surface, wherein the catalyst is prepared by any one of claims 1-6, or is the catalyst of claim 7, wherein the catalyst is used for catalyzing the gas-solid phase catalytic oxidation reaction of unsaturated alcohols to unsaturated aldehydes, preferably for catalyzing the gas-solid phase catalytic oxidation reaction of unsaturated alcohols to unsaturated aldehydes under low temperature conditions, more preferably for catalyzing the oxidation of 3-methyl-3-butenol to 3-methyl-2-butenol under low temperature conditions of 210-270°C.

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