Composite catalyst for degrading VOCs (Volatile Organic Compounds) and preparation method thereof

Abstract

The invention relates to a composite catalyst for degrading VOCs and a preparation method thereof, and belongs to the technical field of catalyst preparation, and the composite catalyst comprises the following raw materials: sepiolite, potassium permanganate, copper trifluoroacetate hydrate, zinc acetate dihydrate, a chloroplatinic acid solution and octadecanoic acid. The sepiolite with a layered porous structure and relatively high adsorption performance is selected as a carrier, so that the VOCs adsorption speed is increased; and potassium permanganate and copper trifluoroacetate hydrate are assisted to increase the specific surface area of sepiolite, so that a foundation is laid for loading zinc acetate dihydrate and platinum metal nanoparticles, more sites are effectively provided as channels for rapid flowing of VOCs molecules in the catalyst, and mass transfer and degradation of the VOCs molecules in the catalyst are facilitated. In other words, in the VOCs treatment process, adsorption, mass transfer and degradation occur at the same time, and all the raw materials supplement one another, so that the prepared catalyst has outstanding photocatalysis and durability.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and specifically relates to a composite catalyst for degrading VOCs and a preparation method thereof. Background Art

[0002] Pollutant emissions such as volatile organic solvents (VOCs) generated in industry and daily life not only directly threaten human health, but also generate smog under the action of sunlight, seriously polluting the atmospheric environment and causing secondary pollution. Traditional VOCs treatment methods include high-altitude exhaust by induced draft, combustion treatment, condensation collection, and biological treatment, etc. However, these methods currently have various limitations, such as high energy consumption, high requirements for the performance of catalysts, etc. Moreover, there are very few catalysts on the market that can meet the high demands of each enterprise and have excellent VOCs degradation effects. Therefore, researching and developing a composite catalyst with outstanding VOCs degradation ability has become an important technical research direction. Summary of the Invention

[0003] The purpose of the present invention is to provide a composite catalyst for degrading VOCs and a preparation method thereof. The present invention selects sepiolite with a layered porous structure and strong adsorption performance as the carrier, which increases the speed of adsorbing VOCs; supplemented with potassium permanganate and copper trifluoroacetate hydrate to increase the specific surface area of sepiolite, laying a foundation for loading zinc acetate dihydrate and platinum metal nanoparticles, effectively providing more sites as channels for VOCs molecules to flow rapidly in the catalyst, facilitating the mass transfer and degradation of VOCs molecules inside the catalyst. That is, during the treatment of VOCs, adsorption, mass transfer, and degradation occur simultaneously, and each raw material complements each other, making the prepared catalyst have outstanding photocatalytic effect and durability, and solving the problem of weak VOCs degradation and removal effects in the existing composite catalyst technology.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A composite catalyst for degrading VOCs, the composite catalyst comprises the following raw materials in parts by weight:

[0006]

[0007]

[0008] As a preferred embodiment of the present invention, the chloroplatinic acid solution is a chloroplatinic acid solution of a H2PtCl6-ethylene glycol mixed solution (20mg Pt / 100mL) prepared with ethylene glycol.

[0009] As a preferred embodiment of the present invention, the composite catalyst further comprises deionized water, sodium hydroxide solution, absolute ethanol, and sodium borohydride solution.

[0010] As a preferred embodiment of the present invention, the concentration of the sodium hydroxide solution is 5 moL / L, and the sodium borohydride solution is an ethanol solution of 6 wt% sodium borohydride.

[0011] As a preferred embodiment of the present invention, the preparation method of the composite catalyst comprises the following steps:

[0012] S10. Respectively pretreat sepiolite and potassium permanganate to obtain pretreated sepiolite and mixture A, and set aside;

[0013] S20. Add the pretreated sepiolite to mixture A, adjust the pH of the solution and stir. After stirring is completed, let it stand, filter by suction, wash, and dry under controlled temperature to obtain intermediate material A. Mix intermediate material A and copper trifluoroacetate hydrate evenly, grind, and sieve to obtain intermediate material B;

[0014] S30. Mix intermediate material B and absolute ethanol evenly, successively add zinc acetate dihydrate and chloroplatinic acid solution and disperse them by ultrasonic wave, adjust the pH of the solution, add stearic acid, and stir at a controlled speed to obtain mixture B;

[0015] S40. Add the sodium borohydride solution to mixture B, stir evenly, then carry out oil bath under controlled temperature, then centrifuge, wash, and dry under controlled temperature to obtain the composite catalyst.

[0016] As a preferred embodiment of the present invention, S10 specifically comprises the following steps:

[0017] S11. Mix sepiolite and deionized water and stir. Separate the scum, filter, and dry under controlled temperature. Grind the dried sepiolite, dry under controlled temperature, and sieve to obtain pretreated sepiolite, and set aside;

[0018] S12. Mix potassium permanganate and deionized water evenly to obtain mixture A, and set aside.

[0019] As a preferred embodiment of the present invention, in S11, the dosage ratio of sepiolite to deionized water is 1 g: 10 - 11 mL; the stirring time is 0.5 - 1 h; the temperature for drying under controlled temperature is 60 - 70 °C; the temperature for drying under controlled temperature is 75 - 80 °C; the sieving is through a 300 - mesh sieve.

[0020] As a preferred embodiment of the present invention, in S12, the dosage ratio of potassium permanganate to deionized water is 1 g: 69 - 72 mL.

[0021] As a preferred embodiment of the present invention, the method of adding the pretreated sepiolite in S20 is to add it while stirring; the specific operation of adjusting the pH of the solution and stirring is: adjusting the pH of the solution to 7.0 - 7.5 with sodium hydroxide solution and stirring for 1 - 2 h; the standing is standing at room temperature for 10 - 12 h; the washing is washing with ultrapure water for 3 - 5 times; the temperature of the temperature-controlled drying is 100 - 105 °C; the sieving is sieving through a 300-mesh sieve.

[0022] As a preferred embodiment of the present invention, the dosage ratio of the intermediate material B and absolute ethanol in S30 is 1 g: 65 - 70 mL; the time of ultrasonic dispersion is 20 - 30 min; the operation of adjusting the pH of the solution is adjusting the pH of the solution to 7.0 with sodium hydroxide solution; the speed of the controlled-speed stirring is 300 - 320 r / min, and the time is 1.5 - 2 h.

[0023] As a preferred embodiment of the present invention, the dosage ratio of the mixed solution B and sodium borohydride solution in S40 is 1 g: 20 - 25 mL; the temperature of the temperature-controlled oil bath is 90 - 100 °C, and the time is 3 - 4 h; the washing is washing with deionized water for 5 - 7 times; the temperature of the temperature-controlled drying is 80 - 85 °C.

[0024] Advantages of the present invention:

[0025] (1) The present invention selects sepiolite with a layered porous structure as the carrier. Since there are many acidic and basic centers on the surface of sepiolite, sepiolite has strong adsorption performance, which increases the speed of adsorbing VOCs. In addition, sepiolite is natural and has good stability and catalytic properties; on this basis, potassium permanganate and copper trifluoroacetate hydrate are used to increase the specific surface area of sepiolite, laying a foundation for loading zinc acetate dihydrate and platinum metal nanoparticles, effectively providing more sites as channels for VOCs molecules to flow rapidly in the catalyst, which is conducive to the mass transfer and degradation of VOCs molecules inside the catalyst. That is, during the treatment of VOCs, adsorption, mass transfer, and degradation occur simultaneously, and the raw materials complement each other, making the prepared catalyst have outstanding photocatalytic performance and durability.

[0026] (2) The present invention adds potassium permanganate, and the solution hydrolyzes to be acidic, the bonds in sepiolite break, and the internal channels are connected. At the same time, the microstructural structure of copper trifluoroacetate hydrate increases the pores and channels of the internal structure of sepiolite, resulting in changes in the internal structure of sepiolite. Thus, in cooperation with potassium permanganate, the specific surface area of sepiolite is further increased, enabling sepiolite to provide a large number of active sites, laying a foundation for the growth and attachment of zinc acetate dihydrate and platinum metal nanoparticles in the follow-up. In addition, the larger specific surface area can extend the residence time of VOCs in the catalyst region, that is, it lays a good foundation for the prepared catalyst to have excellent catalytic performance.

[0027] (3) The present invention adds stearic acid. The carboxyl group in stearic acid binds to the surface hydroxyl groups of sepiolite, reducing the surface tension of sepiolite, preventing its aggregation and caking, effectively improving the dispersion degree of sepiolite, making its function more significant, and further enhancing the catalytic performance during the use of the catalyst.

[0028] (4) The present invention loads zinc acetate dihydrate with sufficient active oxygen groups and a rich surface pore structure on sepiolite, ensuring that the prepared catalyst has a sufficient number of active oxygen groups to oxidize and degrade VOCs. At the same time, the rich pore structure provides more sites as channels for the rapid flow of VOCs molecules in the catalyst, facilitating the mass transfer of VOCs molecules inside the catalyst, thereby improving the photocatalytic efficiency. In addition, since zinc acetate dihydrate belongs to a wide-bandgap semiconductor and can utilize less sunlight, the present invention also adds chloroplatinic acid solution for surface modification as a bridge to induce the photo-generated electrons to jump from the valence band to the conduction band of zinc acetate dihydrate, thereby enhancing the photocatalytic effect of the catalyst. Specific embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0030] Example 1

[0031] A composite catalyst for degrading VOCs, the composite catalyst comprising the following raw materials in parts by weight:

[0032]

[0033]

[0034] The chloroplatinic acid solution is a chloroplatinic acid solution of an H2PtCl6-ethylene glycol mixed solution (20 mg Pt / 100 mL) prepared with ethylene glycol; the composite catalyst also includes deionized water, a sodium hydroxide solution with a concentration of 5 moL / L, absolute ethanol, and an ethanol solution of 6 wt% sodium borohydride.

[0035] The preparation method of the composite catalyst comprises the following steps:

[0036] S10. Pretreat sepiolite and potassium permanganate respectively:

[0037] S11. Mix sepiolite and deionized water at a dosage ratio of 1 g:11 mL and stir for 0.5 h. After stirring, separate the scum, filter, and dry at a controlled temperature of 70 °C. Grind the dried sepiolite, dry it at a controlled temperature of 75 °C, and sieve through a 300-mesh sieve to obtain pretreated sepiolite for later use.

[0038] S12. Mix potassium permanganate and deionized water at a dosage ratio of 1 g:69 mL and stir evenly to obtain mixed solution A for later use.

[0039] S20. While stirring, add the pretreated sepiolite prepared in step S11 to mixed solution A. Then, adjust the pH of the solution to 7.3 with sodium hydroxide solution and stir for 1 h. After stirring, let it stand at room temperature for 10 h. After standing, filter by suction, wash with ultrapure water 5 times, and dry at a controlled temperature of 100 °C to obtain intermediate material A. Mix intermediate material A and copper trifluoroacetate hydrate evenly, grind, and sieve through a 300-mesh sieve to obtain intermediate material B.

[0040] S30. Mix intermediate material B and absolute ethanol at a dosage ratio of 1 g:65 mL evenly. Then, add zinc acetate dihydrate and chloroplatinic acid solution in sequence and ultrasonically disperse for 25 min. After dispersion, adjust the pH of the solution to 7.0 with sodium hydroxide solution, add stearic acid, and then stir at a controlled speed of 320 r / min for 1.5 h to obtain mixed solution B.

[0041] S40. Add sodium borohydride solution to mixed solution B and stir evenly. Then, carry out an oil bath at a controlled temperature of 90 °C for 4 h. After the oil bath, centrifuge, wash with deionized water 5 times, and dry at a controlled temperature of 80 °C to obtain the composite catalyst.

[0042] The dosage ratio of the mixed solution B and the sodium borohydride solution is 1 g:25 mL.

[0043] Example 2

[0044] A composite catalyst for degrading VOCs, the composite catalyst comprising the following raw materials in parts by weight:

[0045]

[0046] The chloroplatinic acid solution is a chloroplatinic acid solution of an H2PtCl6-ethylene glycol mixed solution (20 mg Pt / 100 mL) prepared with ethylene glycol; the composite catalyst also includes deionized water, a sodium hydroxide solution with a concentration of 5 moL / L, absolute ethanol, and a 6 wt% sodium borohydride ethanol solution.

[0047] The preparation method of the composite catalyst comprises the following steps:

[0048] S10. Pretreat sepiolite and potassium permanganate respectively:

[0049] S11. Mix sepiolite and deionized water at a dosage ratio of 1 g: 10.5 mL and stir for 1 h. After stirring, separate the scum, filter, dry at a controlled temperature of 60 °C, grind the dried sepiolite, dry at a controlled temperature of 80 °C, and pass through a 300-mesh sieve to obtain pretreated sepiolite for later use;

[0050] S12. Mix potassium permanganate and deionized water at a dosage ratio of 1 g: 72 mL and stir evenly to obtain mixed solution A for later use;

[0051] S20. Add the pretreated sepiolite prepared in step S11 to mixed solution A while stirring. Then, adjust the pH of the solution to 7.5 with sodium hydroxide solution and stir for 2 h. After stirring, let it stand at room temperature for 11 h. After standing, filter by suction, wash with ultrapure water 4 times, dry at a controlled temperature of 103 °C to obtain intermediate material A. Mix intermediate material A and copper trifluoroacetate hydrate evenly, grind, and pass through a 300-mesh sieve to obtain intermediate material B;

[0052] S30. Mix intermediate material B and absolute ethanol at a dosage ratio of 1 g: 68 mL evenly. Then, add zinc acetate dihydrate and chloroplatinic acid solution in sequence and ultrasonically disperse for 20 min. After dispersion, adjust the pH of the solution to 7.0 with sodium hydroxide solution, add stearic acid, and then stir at a controlled speed of 300 r / min for 2 h to obtain mixed solution B;

[0053] S40. Add sodium borohydride solution to mixed solution B and stir evenly. Then, carry out an oil bath at a controlled temperature of 95 °C for 3 h. After the oil bath, centrifuge, wash with deionized water 6 times, and dry at a controlled temperature of 83 °C to obtain the composite catalyst;

[0054] The dosage ratio of the mixed solution B to the sodium borohydride solution is 1 g: 20 mL.

[0055] Example 3

[0056] A composite catalyst for degrading VOCs, and the composite catalyst comprises raw materials in the following parts by weight:

[0057]

[0058] The chloroplatinic acid solution is a chloroplatinic acid solution of an H2PtCl6-ethylene glycol mixed solution (20 mg Pt / 100 mL) prepared with ethylene glycol; the composite catalyst also comprises deionized water, a sodium hydroxide solution with a concentration of 5 moL / L, absolute ethanol, and an ethanol solution of 6 wt% sodium borohydride.

[0059] The preparation method of the composite catalyst comprises the following steps:

[0060] S10. Pretreat sepiolite and potassium permanganate respectively:

[0061] S11. Mix sepiolite and deionized water at a dosage ratio of 1 g:10 mL and stir for 1 h. After stirring, separate the scum, filter, and dry at a controlled temperature of 65 °C. Grind the dried sepiolite, dry it at a controlled temperature of 78 °C, and sieve through a 300-mesh sieve to obtain pretreated sepiolite for standby.

[0062] S12. Mix potassium permanganate and deionized water at a dosage ratio of 1 g:70.5 mL and stir evenly to obtain mixed solution A for standby.

[0063] S20. Add the pretreated sepiolite prepared in step S11 to the mixed solution A while stirring. Then, adjust the pH of the solution to 7.0 with sodium hydroxide solution and stir for 1.5 h. After stirring, let it stand at room temperature for 12 h. After standing, filter by suction, wash with ultrapure water 3 times, and dry at a controlled temperature of 105 °C to obtain intermediate A. Mix intermediate A and copper trifluoroacetate hydrate evenly, grind, and sieve through a 300-mesh sieve to obtain intermediate B.

[0064] S30. Mix intermediate B and absolute ethanol at a dosage ratio of 1 g:70 mL evenly. Then, add zinc acetate dihydrate and chloroplatinic acid solution in sequence and disperse them by ultrasonic wave for 30 min. After dispersion, adjust the pH of the solution to 7.0 with sodium hydroxide solution, add stearic acid, and then stir at a controlled speed of 310 r / min for 2 h to obtain mixed solution B.

[0065] S40. Add sodium borohydride solution to the mixed solution B and stir evenly. Then, carry out an oil bath at a controlled temperature of 100 °C for 3.5 h. After the oil bath, centrifuge, wash with deionized water 7 times, and dry at a controlled temperature of 85 °C to obtain the composite catalyst.

[0066] The dosage ratio of the mixed solution B to the sodium borohydride solution is 1 g:23 mL.

[0067] Comparative Example 1-2

[0068] Compared with Example 1, the difference is that the weight parts of potassium permanganate and copper trifluoroacetate hydrate in Comparative Examples 1-2 are shown in Table 1, and the remaining operation steps and raw material addition amounts remain unchanged.

[0069] Table 1

[0070] Potassium permanganate (parts by weight) Copper trifluoroacetate hydrate (parts by weight) Comparative Example 1 0 4 Comparative Example 2 4 0

[0071] Comparative Example 3

[0072] Compared with Example 1, the difference is that stearic acid is not added in Comparative Example 3, and the remaining operation steps and raw material addition amounts remain unchanged.

[0073] Comparative Example 4

[0074] Compared with Example 1, the difference is that zinc acetate dihydrate is not added in Comparative Example 4, and the remaining operation steps and raw material addition amounts remain unchanged.

[0075] Comparative Example 5

[0076] Compared with Example 1, the difference is that in Comparative Example 5, chloroplatinic acid solution is not added, and the remaining operation steps and raw material addition amounts remain unchanged.

[0077] Test Example

[0078] (1) Use a closed glass reactor with quartz glass at the top, equipped with a gas inlet, a gas outlet, a gas sampling port, and a temperature sensor, and an internal volume of 100 mL. Simulate the sunlight source with a 300 W xenon lamp. Drop 2 mL of deionized water into the bottom of the closed glass reactor, and then place a quartz reactor (d = 20 mm, h = 30 mm) containing 50 mg of the composite catalyst at the bottom of the closed glass reactor. Introduce pure O2 (2 atm) to remove the air in the device. Use a microsyringe to inject 3 μL of toluene / formaldehyde solution into the closed glass reactor. At the same time, place the closed glass reactor in the dark for 30 min to establish an adsorption-desorption equilibrium between the sample and toluene / formaldehyde. Then turn on the xenon lamp for photocatalytic degradation reaction. Every 20 min, use a glass syringe to take out 500 μL of the reacted gas sample from the sampling port for quantitative analysis until 80 min. In this way, the photocatalytic effects of the composite catalysts prepared in Examples 1-3 and Comparative Examples 1-5 are detected. Among them, the initial concentrations of toluene and formaldehyde are 0.8 mg / L and 0.16 mg / L, respectively. The test results are shown in Table 2.

[0079] (2) Use the same test method to cycle test each composite catalyst in Test (1). Observe the number of times when the removal rate of toluene or formaldehyde by Examples 1-3 and Comparative Examples 1-5 is lower than 90% at the 120th min, so as to reflect the durability of the composite catalyst. The test results are shown in Table 3.

[0080] Table 2

[0081]

[0082]

[0083] As can be seen from Table 2, the composite catalyst prepared by the present invention has excellent VOCs removal rate. Specifically, from Comparative Examples 1-2, it can be seen that the potassium permanganate and copper trifluoroacetate hydrate added in the present invention can increase the specific surface area of sepiolite, enabling it to provide a large number of active sites, laying a foundation for the growth and attachment of zinc acetate dihydrate and platinum metal nanoparticles subsequently. In addition, the larger specific surface area can extend the residence time of VOCs in the catalyst region, that is, it lays a good foundation for the excellent catalytic performance of the prepared catalyst; from Comparative Example 3, it can be seen that the stearic acid added in the present invention reduces the surface tension of sepiolite, preventing its aggregation and caking, effectively improving the dispersion degree of sepiolite, making its role more significant, that is, further strengthening the catalytic performance during the use of the catalyst; from Comparative Examples 4-5, it can be seen that the zinc acetate dihydrate and chloroplatinic acid solution added in the present invention are the reasons why the prepared composite catalyst has excellent VOCs removal rate.

[0084] Table 3

[0085] Number of uses when the toluene or formaldehyde removal rate is less than 90% (times) Example 1 8 Example 2 8 Example 3 8 Comparative Example 1 7 Comparative Example 2 6 Comparative Example 3 7 Comparative Example 4 3 Comparative Example 5 4

[0086] As can be seen from Table 3, the composite catalyst prepared by the present invention has outstanding durability and still maintains a toluene or formaldehyde removal rate of not less than 90% after 7 cycles.

[0087] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0088] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods to substitute, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A composite catalyst for degrading VOCs, characterized in that, The composite catalyst comprises raw materials in the following parts by weight:

2. The composite catalyst for degrading VOCs according to claim 1, wherein The composite catalyst further comprises deionized water, sodium hydroxide solution, absolute ethanol and sodium borohydride solution.

3. A preparation method of the composite catalyst for degrading VOCs as described in claim 2, characterized in that, The preparation method of the composite catalyst comprises the following steps: S10. Respectively pre-treat sepiolite and potassium permanganate to obtain pretreated sepiolite and mixture A, and set aside; S20. Add the pretreated sepiolite to mixture A, adjust the pH of the solution and stir. After stirring is completed, let it stand, filter by suction, wash, and dry under controlled temperature to obtain intermediate material A. Mix intermediate material A and copper trifluoroacetate hydrate evenly, grind, and screen to obtain intermediate material B; S30. Mix intermediate material B and absolute ethanol evenly, successively add zinc acetate dihydrate and chloroplatinic acid solution for ultrasonic dispersion, adjust the pH of the solution, add stearic acid, and stir at a controlled speed to obtain mixture B; S40. Add sodium borohydride solution to mixture B, stir evenly, then carry out oil bath under controlled temperature, then centrifuge, wash, and dry under controlled temperature to obtain the composite catalyst.

4. The preparation method of the composite catalyst for degrading VOCs according to claim 3, characterized in that, The specific steps of S10 are as follows: S11. Mix sepiolite and deionized water and stir, separate the floating slag, filter, and dry under controlled temperature. Grind the dried sepiolite, dry under controlled temperature, and screen to obtain pretreated sepiolite, and set aside; S12. Mix potassium permanganate and deionized water and stir evenly to obtain mixture A, and set aside.

5. The preparation method of the composite catalyst for degrading VOCs according to claim 4, characterized in that, In S11, the dosage ratio of sepiolite to deionized water is 1 g: 10 - 11 mL; the stirring time is 0.5 - 1 h; the temperature of drying under controlled temperature is 60 - 70 °C; the temperature of drying under controlled temperature is 75 - 80 °C; the screening is through a 300-mesh sieve.

6. The preparation method of the composite catalyst for degrading VOCs according to claim 4, wherein, In S12, the dosage ratio of potassium permanganate to deionized water is 1 g: 69 - 72 mL.

7. The preparation method of the composite catalyst for degrading VOCs according to claim 3, wherein, In S20, the method of adding the pretreated sepiolite is to add it while stirring; the adjustment of the pH of the solution and stirring specifically means: use sodium hydroxide solution to adjust the pH of the solution to 7.0 - 7.5 and stir for 1 - 2 h.

8. The preparation method of the composite catalyst for degrading VOCs according to claim 3, characterized in that, In S20, the standing is at room temperature for 10 - 12 h; the washing is with ultrapure water for 3 - 5 times; the temperature of drying under controlled temperature is 100 - 105 °C; the screening is through a 300-mesh sieve.

9. The preparation method of the composite catalyst for degrading VOCs according to claim 3, wherein, In S30, the dosage ratio of intermediate material B to absolute ethanol is 1 g: 65 - 70 mL; the ultrasonic dispersion time is 20 - 30 min; the adjustment of the pH of the solution is to use sodium hydroxide solution to adjust the pH of the solution to 7.0; the speed of stirring at a controlled speed is 300 - 320 r / min, and the time is 1.5 - 2 h.

10. The preparation method of the composite catalyst for degrading VOCs according to claim 3, characterized in that, In S40, the dosage ratio of mixture B to sodium borohydride solution is 1 g: 20 - 25 mL; the temperature of the oil bath under controlled temperature is 90 - 100 °C, and the time is 3 - 4 h; the washing is with deionized water for 5 - 7 times; the temperature of drying under controlled temperature is 80 - 85 °C.

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