A double functional catalytic material with a coating structure and a preparation method and application thereof

Abstract

The application discloses a dual-functional catalytic material with a coating structure and a preparation method and application thereof. A silicon source is added into deionized water, mixed uniformly, then a structure directing agent is added, mixed uniformly, and then a cobalt acetylacetone ethanol solution is added to obtain a transparent solution; the transparent solution is crystallized to obtain a solid powder; palladium chloride and o-phenanthroline are dissolved in dimethyl sulfoxide, mixed uniformly to obtain a transparent solution; the solid powder is added into the transparent solution, mixed uniformly, and then heated to 80-120 DEG C, stirred for 6-12 hours, centrifuged, dried to obtain a powder, and the powder is calcined to obtain the dual-functional catalytic material with the coating structure. x The dual-functional catalytic material with the coating structure is constructed by a two-step ligand pyrolysis method, and the synergistic effect of the dual-functional catalytic material with the coating structure makes the dual-functional catalytic material have excellent ethyl acetate deep oxidation activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control technology, and specifically relates to a coated bifunctional catalytic material, its preparation method, and its application. Background Technology

[0002] Volatile organic compounds (VOCs) are organic compounds with a boiling point below 325°C at atmospheric pressure (250-101 kPa). VOCs are diverse, mainly including aliphatic hydrocarbons, oxygenated hydrocarbons, aromatic hydrocarbons and their derivatives, halogenated hydrocarbons, nitrogen-containing hydrocarbons, and sulfur-containing hydrocarbons. VOC emissions are associated with numerous anthropogenic sources, such as petroleum refining, petrochemical processing, solvent use, and many other industrial activities. Most emitted VOCs can lead to the formation of secondary pollutants, such as tropospheric ozone, peroxyacetyl nitrate, and secondary organic aerosols. These trigger increasingly serious problems of complex air pollution, such as photochemical smog and urban haze, and their toxicity and carcinogenicity to humans are well-documented. Oxygenated volatile organic compounds (OVOCs, such as formaldehyde, acetone, and ethyl acetate) are particularly concerning because they readily form ozone and are emitted in large quantities in the chemical industry. Ethyl acetate (EA) is a typical OVOC, commonly used as a solvent for cleaning circuit boards, stripping paint, and coatings, posing serious harm to human health and the environment. Therefore, developing an efficient strategy for removing EA is of great significance for controlling VOCs.

[0003] Catalytic oxidation technology, due to its advantages of high efficiency, energy saving, and environmental friendliness, is one of the most effective means of purifying low-concentration volatile hydrocarbons. The core of this strategy is the design and development of promising catalysts. Supported noble metal catalysts are widely used in the removal of oxygen-containing hydrocarbons due to their high activity and strong regenerability. However, the high price of noble metals and the tendency of active centers to aggregate, sinter, and deactivate limit their further industrial application prospects. Therefore, there is an urgent need to develop a highly active and stable catalyst based on the emission characteristics and molecular features of volatile oxygen-containing hydrocarbons to improve the pollutant conversion rate per unit palladium atom, while maintaining high activity and stability and reducing the cost of catalytic materials. Compared with traditional supported catalysts, core / yolk-shell noble metal NP@metal oxide nanostructures can optimize the activation energy gap of reactants and the binding force of intermediates during oxidation by adjusting the atomic and electronic structure of palladium, providing a good opportunity to control the interactions between different components.

[0004] While these nanostructures exhibit many fascinating catalytic properties, research on the catalytic performance of NP@metal oxide nanostructures is still in its early stages. Traditional core-shell catalyst preparation methods require multiple steps and demanding control of synthesis conditions, limiting catalyst design. This invention holds significant promise for applications in the low-temperature purification of volatile organic pollutants. Summary of the Invention

[0005] To overcome the problems of poor low-temperature activation and easy sintering at high temperatures in existing palladium-based catalytic materials, the purpose of this invention is to provide a coated bifunctional catalytic material, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a coated bifunctional catalytic material includes the following steps:

[0008] A silicon source was added to deionized water and mixed thoroughly. Then, a structure-directing agent was added and mixed thoroughly. Finally, a cobalt acetylacetone ethanol solution was added to obtain a transparent solution. The transparent solution was then crystallized to obtain a solid powder.

[0009] Palladium chloride and o-phenanthroline were dissolved in dimethyl sulfoxide and mixed thoroughly to obtain a transparent solution;

[0010] Solid powder is added to a transparent solution, mixed evenly, heated to 80-120℃, stirred for 6-12 hours, centrifuged, dried to obtain powder, and the powder is calcined to obtain a bifunctional catalytic material with a coated structure.

[0011] Furthermore, the mass ratio of silicon source, structure directing agent and cobalt acetylacetonate is 25-30:30-36:0.22-0.88.

[0012] Furthermore, the silicon source is tetraethyl orthosilicate.

[0013] Furthermore, the structure directing agent is tetrapropylammonium hydroxide.

[0014] Furthermore, the crystallization temperature is 170-190℃, and the time is 60-80h.

[0015] Furthermore, the molar ratio of palladium chloride to o-phenanthroline is 1:5 to 1:10.

[0016] Furthermore, the molar ratio of palladium chloride to cobalt acetylacetonate is 1:1 to 1:4.

[0017] Furthermore, the roasting temperature is 250-350℃, and the time is 2-3 hours.

[0018] A bifunctional catalytic material with a coated structure prepared according to the method, the specific surface area of ​​the bifunctional catalytic material being 205.22-278.95 cm². 2 / g, pore volume is 0.10-0.16cm³ 3 / g.

[0019] Application of a coated bifunctional catalytic material prepared according to the method in the purification of volatile oxygen-containing hydrocarbons.

[0020] Furthermore, at 120-220℃ and a space velocity of 75,000 h⁻¹ -1 Under conditions of oxygen volume concentration of 10-20%, the bifunctional catalytic material can achieve purification of ethyl acetate with a volume concentration of 0.04%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In this invention, a structure-directing agent is added to the silicon source to form regular molecular sieve channels and increase the specific surface area and pore volume of the support. Larger pore volumes facilitate the diffusion of macromolecular compounds into the catalyst particles, while higher specific surface areas promote the adsorption of pollutant molecules and the dispersion of active metals, thereby improving the catalyst's reactivity. A cobalt acetylacetone solution is added to the mixed solution, and a one-pot hydrothermal synthesis method is used to introduce the transition metal cobalt in situ during the molecular sieve crystallization process, aiming to allow cobalt to enter the molecular sieve channels. In this invention, the organic ligand o-phenanthroline is first combined with cobalt, and then a cobalt layer is formed near palladium through ligand pyrolysis, achieving Pd@Layered-CoO. x Construction of bimetallic active sites. Electron coupling of Pd-Co pairs facilitates the back-transfer of electrons from Pd nanoparticles to layered CoO. x On the shell, and promoted Pd 2+ Speciation greatly enhances the adsorption and activation of the electron-rich C=O bonds of the EA molecule. Furthermore, these core-shell Pd@Layered-CoO x The synergistic effect of the sites accelerates the activation and transformation of *O species, thereby inhibiting the formation of acetaldehyde and ethanol byproducts and ensuring the rapid and complete oxidation of ethyl acetate. Furthermore, the cobalt shell not only protects palladium from high-temperature stability but also enhances its water resistance by promoting the adsorption of water molecules on the cobalt species, significantly improving the stability of this palladium-based catalytic material. This invention successfully constructed a unique dual-active site for palladium coated with a cobalt layer on a molecular sieve support through a two-step ligand pyrolysis synthesis method. This addresses, to some extent, the high cost of supported noble metals, overcomes the shortcomings of existing palladium-based catalytic materials such as poor low-temperature activation and easy high-temperature sintering, and shows promise for universal application.

[0023] The bifunctional catalytic material with a coated structure prepared in this invention has a high specific surface area of ​​205.22-278.95 cm². 2 / g, pore volume is 0.10-0.16cm³ 3 / g.

[0024] The coated bifunctional catalytic material prepared by this invention can be applied in the purification of volatile oxygen-containing hydrocarbons. It is effective at 120-220℃ and a space velocity of 75000 h⁻¹. -1 Under conditions of oxygen volume concentration of 10-20%, the purification of ethyl acetate with a volume concentration of 0.04% is achieved; the catalytic material prepared by the present invention has good thermal stability and water resistance. Attached Figure Description

[0025] Figure 1 These are field emission scanning electron microscope (FESEM) images of the bifunctional catalytic material with a coated structure in this invention; where (a) is at low magnification and (b) is at high magnification.

[0026] Figure 2 These are transmission electron microscope images of the bifunctional catalytic material with the coated structure in this invention; where: (a) is a HADDF image, and (b) and (c) are high-resolution images under bright field.

[0027] Figure 3 These are EDS-mapping images of the bifunctional catalytic material with the coating structure in this invention. (a) is an HADDF image, (b) is the EDS of Co, and (c) is the EDS of Pd.

[0028] Figure 4 The image shows the XRD pattern of the bifunctional catalytic material with a coated structure in this invention.

[0029] Figure 5 The purification efficiency curve of the coated bifunctional catalytic material for ethyl acetate in this invention.

[0030] Figure 6 This is a water resistance test of the bifunctional catalytic material with a coated structure in this invention.

[0031] Figure 7 This is a thermal stability test of the bifunctional catalytic material with a coated structure in this invention. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0033] This invention employs a one-pot synthesis method to in-situ introduce the transition metal cobalt to prepare a highly stable cobalt-doped molecular sieve support. Furthermore, it utilizes ligand pyrolysis to construct palladium-cobalt bimetallic active sites, thereby preparing a coated bifunctional catalytic material, Pd@Layered-CoO. x / MFI. In this invention, tetraethyl orthosilicate is used as the silicon source. Tetrapropylammonium hydroxide is added as a structure directing agent to form regular molecular sieve channels in the tetraethyl orthosilicate and to increase the specific surface area and pore volume of the support. A cobalt acetylacetone solution is added dropwise to the mixed solution, and transition metal cobalt is introduced in situ during the molecular sieve crystallization process via a hydrothermal reaction, with the aim of allowing cobalt to enter the channels of the molecular sieve. In this invention, the organic ligand o-phenanthroline is first combined with cobalt, and then a cobalt layer is formed near palladium through ligand pyrolysis, achieving Pd@Layered-CoO. x Construction of bimetallic active sites. Electron coupling of Pd-Co pairs facilitates the back-transfer of electrons from Pd nanoparticles to layered CoO. x On the shell, and promoted Pd 2+ Speciation greatly enhances the adsorption and activation of the electron-rich C=O bonds of the EA molecule. Furthermore, these core-shell Pd@Layered-CoO x The synergistic effect of the sites accelerates the activation and transformation of *O species, thereby inhibiting the formation of acetaldehyde and ethanol byproducts and ensuring the rapid and complete oxidation of ethyl acetate. Furthermore, the cobalt shell not only protects palladium from high-temperature stability but also enhances its water resistance by promoting the adsorption of water molecules on the cobalt species, significantly improving the stability of this palladium-based catalytic material. This invention successfully constructed a unique dual-active site for palladium coated with a cobalt layer on a molecular sieve support through a two-step ligand pyrolysis synthesis method. This addresses the high cost of supported noble metals to some extent, overcomes the shortcomings of existing palladium-based catalytic materials such as poor low-temperature activation and easy high-temperature sintering, and shows promise for universal application. The coated bifunctional catalytic material prepared in this invention exhibits a unique spatial structure effect and demonstrates excellent stability for the low-temperature purification of ethyl acetate.

[0034] The preparation method of the coated bifunctional catalytic material of the present invention includes the following steps:

[0035] (1) Add 25-30g of tetraethyl orthosilicate dropwise to 25-30g of deionized water and stir at 400-600rpm for 10min to disperse it evenly.

[0036] (2) Add 30-36g of the structure-directing agent tetrapropylammonium hydroxide to the transparent solution obtained in step (1) and stir at 400-600 rpm for 3 hours to disperse it evenly.

[0037] (3) Add dropwise a 0.22-0.88g cobalt acetylacetone solution that has been dissolved in 40mL ethanol to the transparent solution obtained in step (2), and then stir at 400-800rpm for 3h to form a blue-green transparent solution.

[0038] (4) Place the greenish-blue transparent solution obtained in step (3) into a hydrothermal reactor for crystallization at a temperature of 170-190℃ for 60-80h.

[0039] (5) Filter the milky white suspension obtained in step (4), wash it with ethanol and deionized water, and dry it at 100-120℃ to obtain a light pink solid powder.

[0040] (6) Dissolve 0.5-2 mL of 0.25 mol / L palladium chloride solution and o-phenanthroline in dimethyl sulfoxide, and stir at 600-800 rpm for 5 min to mix them evenly; the molar ratio of palladium to o-phenanthroline is 1:5-10.

[0041] (7) Add the powder obtained in step (5) to the transparent solution obtained in step (6) and stir at 600-800 rpm for 30 min to disperse it evenly: the molar ratio of palladium to cobalt is 1:1-1:4.

[0042] (8) After heating the solution in step (7) to 80-120℃, continue stirring at 600-800 rpm for 6-12 hours.

[0043] (9) After the solution obtained in step (8) has cooled to room temperature, centrifuge at 6000-9000 rpm, wash with deionized water and ethanol, and dry at 100-120℃ to obtain a light yellow solid powder.

[0044] (10) The powder obtained in step (9) is calcined in air at a temperature of 250-350℃ for 2-3 hours.

[0045] The bifunctional catalytic material with a coated structure prepared in this invention has a high specific surface area (205.22-278.95 cm²). 2 / g) and pore volume (0.10-0.16cm) 3 / g); the coated bifunctional catalytic material can be applied in the purification of volatile oxygen-containing hydrocarbons. Specifically, at 120-220℃ and a space velocity of 75000h... -1 Under conditions of oxygen volume concentration of 10-20%, the purification of ethyl acetate with a volume concentration of 0.04% is achieved; the catalytic material prepared by the present invention has good thermal stability and water resistance.

[0046] The following are specific examples.

[0047] Example 1 describes the preparation of a highly stable molecular sieve support (Co-MFI) using a one-step synthesis method.

[0048] (1) Add 25g of tetraethyl orthosilicate dropwise to 25g of deionized water and stir at 500rpm for 10min to disperse it evenly.

[0049] (2) Add 30g of tetrapropylammonium hydroxide to the transparent solution obtained in step (1) and stir at 500rpm for 3h to disperse it evenly.

[0050] (3) Dissolve 0.22g of cobalt acetylacetonate in 40mL of ethanol, add the cobalt acetylacetonate solution dropwise to the transparent solution obtained in step (2), and then stir at 500rpm for 3h to form a blue-green transparent solution.

[0051] (4) Place the greenish-blue transparent solution obtained in step (3) in a hydrothermal reactor and crystallize it at a temperature of 180°C for 60 hours.

[0052] (5) The milky white suspension obtained in step (4) is filtered, washed five times with ethanol and deionized water, and dried at 120°C to obtain a light pink solid, which is the cobalt-doped molecular sieve support (Co-MFI).

[0053] Example 2 uses ligand pyrolysis to construct a special coating structure.

[0054] (1) Dissolve 0.5 mL of palladium chloride solution (0.25 mol / L, dissolved in dimethyl sulfoxide) and 0.34 g of o-phenanthroline in 50 mL of dimethyl sulfoxide, and stir at 800 rpm for 5 min to make them evenly mixed;

[0055] (2) Accurately weigh 0.5g of the Co-MFI solid powder prepared in Example 1 into the transparent solution obtained in step (1), and stir at 600rpm for 30min to disperse it evenly.

[0056] (3) After heating the mixed solution obtained in step (2) to 120°C, continue stirring at 600 rpm for 6 hours;

[0057] (4) After cooling the bright yellow suspension obtained in step (3) to room temperature, centrifuge at 8000 rpm, wash with deionized water and ethanol, and dry at 120°C to obtain a light yellow solid powder.

[0058] (5) The solid obtained in step (4) is calcined in air at 300℃ for 2 hours. This yields the coated bifunctional catalytic material Pd@L-CoO. x / MFI.

[0059] See Figure 1 All materials prepared by this invention exhibit the symbiotic hexagonal single-crystal morphology of MFI-type zeolite, with a uniform particle size distribution between 200-300 nanometers.

[0060] See Figure 2 The bifunctional catalytic material with a coating structure prepared by the present invention exhibits a distinct layered coating structure.

[0061] See Figure 3 ,from Figure 3 Analysis of the results shows that the bifunctional catalytic material with a coating structure prepared in this invention exhibits a unique structure of distinct layered cobalt-coated palladium particles.

[0062] See Figure 4 The bifunctional catalytic material with a coated structure prepared by the present invention has good crystallinity and clear crystal phase.

[0063] Example 3

[0064] Dissolve 0.5 mL of palladium chloride solution (0.25 mol / L, dissolved in dimethyl sulfoxide) and 0.34 g of o-phenanthroline in 50 mL of dimethyl sulfoxide, and stir at 800 rpm for 5 min to mix them evenly.

[0065] The carrier obtained in Example 1 was accurately weighed at 0.5 g and dispersed in the solution. The mixture was stirred at 800 rpm for 30 min to ensure uniform dispersion. The mixed solution was heated to 60°C and stirred at 800 rpm for 6 h. After cooling to room temperature, the solution was centrifuged at 8000 rpm for 5 min, washed five times with deionized water and ethanol, and dried at 100°C to obtain a pale yellow solid powder. This powder was then calcined in air at 300°C for 2 h at a heating rate of 2°C / min. The resulting pale yellow solid powder is the coated bifunctional catalytic material.

[0066] Example 4

[0067] First, take 0.5 mL of palladium chloride solution (0.25 mol / L, dissolved in dimethyl sulfoxide) and 0.34 g of o-phenanthroline and dissolve them in 50 mL of dimethyl sulfoxide. Stir rapidly at 900 rpm for 5 min to ensure uniform mixing.

[0068] 0.5 g of the solid powder from Example 1 was added while continuously stirring, and the mixture was stirred at 800 rpm for 30 min at room temperature to ensure uniform dispersion. The mixture was then heated to 120 °C and stirred for 12 h. After cooling to room temperature, the mixture was centrifuged five times with a 1:1 mixture of ethanol and deionized water, 5 min each time at 8000 rpm. The centrifuged product was dried overnight at 60 °C. Finally, it was calcined in air at 300 °C for 2 h at a heating rate of 2 °C / min. The resulting solid powder is the coated bifunctional catalytic material.

[0069] Example 5

[0070] (1) Add 25g of tetraethyl orthosilicate dropwise to 25g of deionized water and stir at 600rpm for 10min to disperse it evenly.

[0071] (2) Add 30g of tetrapropylammonium hydroxide to the transparent solution obtained in step (1) and stir at 600rpm for 3h to disperse it evenly.

[0072] (3) Dissolve 0.88g of cobalt acetylacetonate in 40mL of ethanol, add the cobalt acetylacetonate solution dropwise to the transparent solution obtained in step (2), and then stir at 800rpm for 3h to form a blue-green transparent solution.

[0073] (4) Place the greenish-blue transparent solution obtained in step (3) in a hydrothermal reactor and crystallize it at a temperature of 180°C for 60 hours.

[0074] (5) The milky white suspension obtained in step (4) was filtered, washed with ethanol and deionized water, and dried at 120°C to obtain a solid.

[0075] (6) Dissolve 2 mL of palladium chloride solution (0.25 mol / L, dissolved in dimethyl sulfoxide) and 1.36 g of o-phenanthroline in 50 mL of dimethyl sulfoxide, and stir at 800 rpm for 5 min to make them evenly mixed;

[0076] (7) Accurately weigh 0.5g of the solid obtained in step (5) into the transparent solution obtained in step (6), and stir at 700rpm for 30min to disperse it evenly.

[0077] (8) After heating the mixed solution obtained in step (7) to 120°C, continue stirring at 800 rpm for 6 hours;

[0078] (9) After cooling the bright yellow suspension obtained in step (8) to room temperature, centrifuge at 8000 rpm, wash with deionized water and ethanol, and dry at 120°C to obtain a light yellow solid powder.

[0079] (10) The solid obtained in step (9) is calcined in air at a temperature of 300°C for 2 hours. This results in a bifunctional catalytic material with a coated structure.

[0080] Example 6

[0081] (1) Add 30g of tetraethyl orthosilicate dropwise to 30g of deionized water and stir at 400rpm for 10min to disperse it evenly.

[0082] (2) Add 36g of tetrapropylammonium hydroxide to the transparent solution obtained in step (1) and stir at 600rpm for 3h to disperse it evenly.

[0083] (3) Dissolve 0.11g of cobalt acetylacetonate in 40mL of ethanol, add the cobalt acetylacetonate solution dropwise to the transparent solution obtained in step (2), and then stir at 800rpm for 3h to form a blue-green transparent solution.

[0084] (4) Place the greenish-blue transparent solution obtained in step (3) in a hydrothermal reactor and crystallize it at a temperature of 190°C for 60 hours.

[0085] (5) The milky white suspension obtained in step (4) was filtered, washed with ethanol and deionized water, and dried at 120°C to obtain a solid.

[0086] (6) Dissolve 0.5 mL of palladium chloride solution (0.25 mol / L, dissolved in dimethyl sulfoxide) and o-phenanthroline in 50 mL of dimethyl sulfoxide, and stir at 800 rpm for 5 min to mix them evenly; the molar ratio of palladium to o-phenanthroline is 1:5.

[0087] (7) Accurately weigh the solid obtained in step (5) into the transparent solution obtained in step (6), and stir at 700 rpm for 30 min to disperse it evenly. The molar ratio of palladium to cobalt is 1:1.

[0088] (8) After heating the mixed solution obtained in step (7) to 120°C, continue stirring at 600 rpm for 12 h;

[0089] (9) After cooling the bright yellow suspension obtained in step (8) to room temperature, centrifuge at 8000 rpm, wash with deionized water and ethanol, and dry at 120°C to obtain a light yellow solid powder.

[0090] (10) The solid obtained in step (9) is calcined in air at a temperature of 300°C for 2 hours. This results in a bifunctional catalytic material with a coated structure.

[0091] Example 7

[0092] (1) Add 25g of tetraethyl orthosilicate dropwise to 25g of deionized water and stir at 600rpm for 10min to disperse it evenly.

[0093] (2) Add 30g of tetrapropylammonium hydroxide to the transparent solution obtained in step (1) and stir at 400rpm for 3h to disperse it evenly.

[0094] (3) Dissolve 0.88g of cobalt acetylacetonate in 40mL of ethanol, add the cobalt acetylacetonate solution dropwise to the transparent solution obtained in step (2), and then stir at 400rpm for 3h to form a blue-green transparent solution.

[0095] (4) Place the greenish-blue transparent solution obtained in step (3) in a hydrothermal reactor and crystallize it at a temperature of 170°C for 80 hours.

[0096] (5) The milky white suspension obtained in step (4) was filtered, washed with ethanol and deionized water, and dried at 110°C to obtain a solid.

[0097] (6) Dissolve 1 mL of palladium chloride solution (0.25 mol / L, dissolved in dimethyl sulfoxide) and o-phenanthroline in 50 mL of dimethyl sulfoxide, and stir at 700 rpm for 5 min to mix them evenly; the molar ratio of palladium to o-phenanthroline is 1:10.

[0098] (7) Accurately weigh the solid obtained in step (5) into the transparent solution obtained in step (6), and stir at 800 rpm for 30 min to disperse it evenly. The molar ratio of palladium to cobalt is 1:4.

[0099] (8) After heating the mixed solution obtained in step (7) to 100°C, continue stirring at 800 rpm for 6 hours;

[0100] (9) After cooling the bright yellow suspension obtained in step (8) to room temperature, centrifuge at 9000 rpm, wash with deionized water and ethanol, and dry at 110°C to obtain a light yellow solid powder.

[0101] (10) The solid obtained in step (9) is calcined in air at a temperature of 250°C for 3 hours. This is the bifunctional catalytic material with a coated structure.

[0102] Example 8

[0103] (1) Add 28g of tetraethyl orthosilicate dropwise to 28g of deionized water and stir at 500rpm for 10min to disperse it evenly.

[0104] (2) Add 33.6 g of tetrapropylammonium hydroxide to the transparent solution obtained in step (1) and stir at 500 rpm for 3 h to disperse it evenly.

[0105] (3) Dissolve 0.22g of cobalt acetylacetonate in 40mL of ethanol, add the cobalt acetylacetonate solution dropwise to the transparent solution obtained in step (2), and then stir at 600rpm for 3h to form a blue-green transparent solution.

[0106] (4) Place the greenish-blue transparent solution obtained in step (3) in a hydrothermal reactor and crystallize it at a temperature of 180°C for 70 hours.

[0107] (5) The milky white suspension obtained in step (4) was filtered, washed with ethanol and deionized water, and dried at 100°C to obtain a solid.

[0108] (6) Dissolve 2 mL of palladium chloride solution (0.25 mol / L, dissolved in dimethyl sulfoxide) and o-phenanthroline in 50 mL of dimethyl sulfoxide, and stir at 600 rpm for 5 min to mix them evenly; the molar ratio of palladium to o-phenanthroline is 1:8.

[0109] (7) Accurately weigh the solid obtained in step (5) into the transparent solution obtained in step (6), and stir at 600 rpm for 30 min to disperse it evenly. The molar ratio of palladium to cobalt is 1:2.

[0110] (8) After heating the mixed solution obtained in step (7) to 80°C, continue stirring at 700 rpm for 9 hours;

[0111] (9) After cooling the bright yellow suspension obtained in step (8) to room temperature, centrifuge at 6000 rpm, wash with deionized water and ethanol, and dry at 100°C to obtain a light yellow solid powder.

[0112] (10) The solid obtained in step (9) is calcined in air at a temperature of 350°C for 2 hours. This results in a bifunctional catalytic material with a coated structure.

[0113] Example 9: Activity of the coated bifunctional catalytic material in catalytic degradation of ethyl acetate

[0114] The catalytic reaction was carried out in a fixed bed. The catalyst obtained in Example 2 was pressed into tablets and sieved (40-60 mesh). 0.2 g of the sieved catalytic material was accurately weighed. Ethyl acetate was used as the probe gas, and the concentration of the reactants was controlled at 600-800 ppm. The reaction space velocity was 75,000 h⁻¹. -1With an oxygen volume concentration of 20%, the catalytic activity of the catalyst was tested at temperatures of 120℃, 140℃, 160℃, 180℃, 200℃, and 220℃. The reaction products were monitored and analyzed by gas chromatography-mass spectrometry.

[0115] See Figure 5 ,from Figure 5 Analysis shows that the Pd@L-CoO coating structure bifunctional catalytic material prepared in this invention... x / MFI and Co-MFI catalysts are used for the catalytic oxidation of ethyl acetate. Co-MFI has almost no purification ability for ethyl acetate. The bifunctional catalyst Pd@L-CoO with a coated structure is used. x / MFI exhibits excellent low-temperature degradation efficiency for ethyl acetate, capable of degradation at 120-220℃ and a space velocity of 75,000 h⁻¹. -1 Under conditions of 10-20% oxygen volume concentration, complete mineralization of ethyl acetate with a volume concentration of 0.04% can be achieved, and 90% of ethyl acetate can be deeply purified at 179℃.

[0116] Example 10: Water resistance test of the coated bifunctional catalytic material

[0117] The catalyst obtained in Example 2 was pressed into tablets and sieved (40-60 mesh). 0.2 g of the sieved catalyst material was accurately weighed and placed in the fixed bed of the evaluation device. Activation was performed at 200°C for 1 h, using ethyl acetate as the probe gas. The concentration of the reactants was controlled at 800 ppm, and the reaction space velocity was 75,000 h⁻¹. -1 With an oxygen concentration of 20%, after the catalytic reaction stabilized at 170℃, 2 vol.% H2O water vapor was introduced, and the catalytic activity of the catalyst under mixed component atmosphere conditions was continuously tested. After 3 hours, the H2O water vapor was cut off, and the catalytic activity of the catalyst material was tested again until it stabilized.

[0118] See Figure 6 ,from Figure 6 Analysis of the results shows that the coated bifunctional catalytic material prepared in this invention exhibits good water resistance during the low-temperature purification of ethyl acetate. The introduction of 2 vol.% low-concentration water vapor only produces a temporary competitive adsorption effect and does not damage the structure of the palladium active sites.

[0119] Example 11 Thermal stability test of the coated bifunctional catalytic material

[0120] The catalyst obtained in Example 2 was first calcined in a muffle furnace at different high temperatures for different times: 300°C for 24 hours, 800°C for 12 hours, and 900°C for 12 hours. Then, it was tableted, and 0.2 g of 40-60 mesh catalytic material was accurately weighed and placed in the fixed bed of the evaluation device. Activation was performed at 200°C for 1 hour, using ethyl acetate as the probe gas. The concentration of the reactants was controlled at 800 ppm, and the reaction space velocity was 75,000 h⁻¹. -1 With an oxygen concentration of 20%, the catalytic activity of the catalyst was tested at temperatures of 120℃, 140℃, 160℃, 180℃, 200℃, and 220℃. The reaction products were monitored and analyzed by gas chromatography-mass spectrometry.

[0121] See Figure 7 The bifunctional catalytic material with a coated structure prepared by this invention still exhibits extremely excellent activity after high-temperature calcination, proving its excellent thermal stability.

[0122] This invention is not limited to the above embodiments, and variations in its specific structure are permitted. All modifications made within the scope of the independent claims of this invention are also within the scope of protection of this invention.

[0123] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing a coated bifunctional catalytic material, characterized in that, Includes the following steps: A silicon source was added to deionized water and mixed thoroughly. Then, a structure-directing agent was added and mixed thoroughly. Finally, a cobalt acetylacetone ethanol solution was added to obtain a transparent solution A. The transparent solution A was then crystallized to obtain a solid powder. Palladium chloride and o-phenanthroline were dissolved in dimethyl sulfoxide and mixed thoroughly to obtain a clear solution B; Add solid powder to transparent solution B, mix evenly, heat to 80-120°C, stir for 6-12 h, centrifuge, dry to obtain powder, calcine the powder to obtain a bifunctional catalytic material with a coated structure; The structure directing agent is tetrapropylammonium hydroxide.

2. The method for preparing the coated bifunctional catalytic material according to claim 1, characterized in that, The mass ratio of silicon source, structure directing agent and cobalt acetylacetonate is 25-30:30-36:0.22-0.

88.

3. The method for preparing the coated bifunctional catalytic material according to claim 1, characterized in that, The silicon source is tetraethyl orthosilicate.

4. The method for preparing the coated bifunctional catalytic material according to claim 1, characterized in that, The crystallization temperature is 170-190°C, and the time is 60-80 h.

5. The method for preparing the coated bifunctional catalytic material according to claim 1, characterized in that, The molar ratio of palladium chloride to o-phenanthroline is 1:5-1:

10.

6. The method for preparing the coated bifunctional catalytic material according to claim 1, characterized in that, The molar ratio of palladium chloride to cobalt acetylacetone is 1:1 to 1:

4.

7. The method for preparing the coated bifunctional catalytic material according to claim 1, characterized in that, The roasting temperature is 250-350 °C, and the time is 2-3 h.

8. A coated bifunctional catalytic material prepared by the method according to any one of claims 1-7, characterized in that, The specific surface area of ​​the bifunctional catalytic material is 205.22-278.95 cm². 2 / g, pore volume 0.10-0.16 cm³ 3 / g.

9. The application of a coated bifunctional catalytic material prepared by the method according to any one of claims 1-7 in the purification of volatile oxygen-containing hydrocarbons.

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