Water-resistant VOCs catalytic oxidation catalyst as well as preparation method and application thereof

Abstract

The invention provides a water-resistant VOCs catalytic oxidation catalyst as well as a preparation method and application thereof. The water-resistant VOCs catalytic oxidation catalyst has a core-shell structure, a core body is a Co3O4-loaded metal oxide, a shell layer is silicon dioxide, the outer surface of the shell layer is subjected to hydrophobic modification, and roasted polydopamine is arranged between the core body and the shell layer. The water-resistant VOCs catalytic oxidation catalyst has excellent water resistance, still keeps high catalytic activity under the condition of high water content, and can avoid the problem of carbon deposition deactivation.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental catalysis, and specifically relates to a water-resistant VOCs catalytic oxidation catalyst and a preparation method and application thereof. Background Art

[0002] Volatile organic compounds (VOCs) are one of the important precursors of ozone and PM2.5. Among the many VOC treatment technologies, VOCs catalytic oxidation technology has been widely used in the oil refining, chemical, pharmaceutical and other industries due to its high removal rate and no secondary pollution. VOCs catalytic oxidation technology refers to the use of air to oxidize VOCs into CO at low temperature under the action of a catalyst. 2 and H 2 O. Its technical core is catalytic oxidation catalyst. Although precious metal catalysts are currently mainly used in industry, precious metals are expensive, so researchers have begun to develop non-precious metal catalysts. 3 O 4 Due to its unique spinel structure, it has a high reactivity to VOCs such as formaldehyde and CO. However, its water resistance is poor, and the catalyst performance is often affected by water and reduced. For this reason, it is necessary to prepare a water-resistant VOCs catalytic oxidation catalyst. Researchers have currently developed some VOCs catalytic oxidation catalysts with water-resistant effects.

[0003] Patent CN108772075A discloses a catalyst for removing volatile benzene pollutants and a preparation method thereof. The catalyst is composed of a precious metal active component and a carrier; wherein the precious metal active component is a single substance of platinum or platinum oxide; the precious metal active component is 0.01%-0.05% of the total mass of the catalyst in terms of precious metal elements. The advantages are: the catalyst has a high removal efficiency for various VOCs such as benzene, toluene, and xylene at a relatively low temperature. And the catalyst has excellent water resistance. However, the catalyst cannot isolate water from the catalyst. Under high temperature and high water content conditions, the agglomeration of the precious metal active component will be accelerated, reducing the life of the catalyst.

[0004] Patent CN113856748A discloses a hollow ZSM-5 catalyst with double modifications of atomic doping and metal clusters on the inner surface and a preparation method thereof. The general formula of the catalyst is NOx@M-ZSM-5@Al-ZSM-5. Al-ZSM-5 is a hierarchical porous molecular sieve with an MFI structure, and M and N are transition metal elements. This catalyst is a double-inner-layer monolithic catalyst. The external Al-ZSM-5 and the middle-layer M-ZSM-5 are tightly combined into a whole. In addition, M-ZSM-5 and NOx are tightly combined through strong metal-carrier interactions. This catalyst has a high specific surface area, mesoporous channels and diffusivity; this catalyst has high catalytic oxidation-reduction properties, sufficient surface active oxygen components and appropriate acidity. This catalyst exhibits high low-temperature catalytic activity and characteristics of resistance to sulfur, water and chlorine poisoning during the catalytic oxidation of VOCs, improving the stability of the catalyst. Although ZSM-5 (Zeolite Socony Mobil-5) molecular sieve has advantages such as adjustable hydrophobicity, controllable surface acidity and high thermal stability, and can achieve the purpose of appropriately improving the water resistance of the catalyst by increasing the silicon-aluminum ratio, molecular sieve-based catalysts have the drawback of being prone to coking deactivation. Summary of the Invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a water-resistant VOCs catalytic oxidation catalyst, its preparation method and application. This water-resistant VOCs catalytic oxidation catalyst has excellent water resistance, maintains high catalytic activity under high water content conditions, and can avoid the problem of carbon deposition deactivation.

[0006] To achieve the above purpose, the present invention provides a water-resistant VOCs catalytic oxidation catalyst, which has a core-shell structure. The core is a metal oxide loaded with Co 3 O 4 , and the shell is silica. The outer surface of the shell is hydrophobically modified. Between the core and the shell is polydopamine that has been calcined and removed.

[0007] The present invention also provides a preparation method of the above water-resistant VOCs catalytic oxidation catalyst, which includes the following steps:

[0008] (1) Immerse a cobalt precursor in a metal oxide support, and obtain the core after drying and calcination;

[0009] (2) Mix the core obtained in step (1) in water, adjust the pH to 8-10, disperse ultrasonically, then add dopamine hydrochloride, react at 0-40 °C for 1-24 h, and obtain the core coated with polydopamine after filtration, washing and drying;

[0010] (3) Dissolve the dispersant in an alcohol solvent, add the poly-dopamine-coated core obtained in step (2), ultrasonically disperse it, add the alcohol solution of the organosilicon source under stirring, control the pH to 7-12, react for 0.5-2 h, and after filtration, washing, drying, and calcination, obtain the core coated with a silica hollow shell;

[0011] (4) Disperse the core coated with a silica hollow shell obtained in step (3) in water, adjust the pH to 7-9, dropwise add the organosilicon compound, react at 20-90 °C for 0.5-4 h, and after filtration, washing, and drying, obtain the water-resistant VOCs catalytic oxidation catalyst.

[0012] According to a specific embodiment of the present invention, preferably, in step (1), the cobalt precursor includes one or a combination of two of cobalt nitrate and cobalt chloride.

[0013] According to a specific embodiment of the present invention, preferably, in step (1), the metal oxide includes γ-aluminum oxide.

[0014] According to a specific embodiment of the present invention, preferably, in step (1), the equal-volume impregnation method is used for impregnation.

[0015] According to a specific embodiment of the present invention, preferably, in step (1), based on cobalt tetroxide, the mass ratio of the cobalt precursor to the metal oxide support is 5-20:100.

[0016] According to a specific embodiment of the present invention, preferably, in step (2), the mass ratio of dopamine hydrochloride to the core is 5-50:100.

[0017] According to a specific embodiment of the present invention, preferably, in step (3), the dispersant includes one or a combination of two or more of polyvinylpyrrolidone and polyethylene glycol 4000.

[0018] According to a specific embodiment of the present invention, preferably, in step (3), the mass ratio of the dispersant to the alcohol solvent is 0.5-10:100.

[0019] According to a specific embodiment of the present invention, preferably, in step (3), the mass ratio of the poly-dopamine-coated core to the alcohol solvent is 5-40:100.

[0020] According to a specific embodiment of the present invention, preferably, in step (3), the organosilicon source includes one or a combination of two or more of tetraethyl orthosilicate, tetrabutyl orthosilicate, tetra-isopropyl orthosilicate, and methyl orthosilicate.

[0021] According to a specific embodiment of the present invention, preferably, in step (3), the mass ratio of the organosilicon source (calculated as silicon dioxide) to the poly-dopamine-coated core is 5-40:100.

[0022] According to a specific embodiment of the present invention, preferably, in step (3), the calcination condition is calcination at 450-700 °C for 2-10 h.

[0023] According to a specific embodiment of the present invention, preferably, in step (4), the organosilicon compound includes one or a combination of two or more of methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, n-octyltriethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, dimethyldichlorosilane, dimethyldimethoxysilane, dimethyldiethoxysilane, ethyldimethoxysilane, diethyldiethoxysilane, trimethylchlorosilane, hexamethyldisiloxane, and hexamethyldisilazane.

[0024] According to a specific embodiment of the present invention, preferably, in step (4), the mass ratio of the organosilicon compound to the core coated with a silica hollow shell is 0.5-2:1.

[0025] According to a specific embodiment of the present invention, the above preparation method includes the following specific steps:

[0026] 1. Core preparation:

[0027] (1) Take a certain amount of the metal oxide support γ-alumina, impregnate it with an appropriate amount of cobalt nitrate by the equal-volume impregnation method, and obtain the core, i.e., Co 3 O 4 / γ-alumina after drying and calcination;

[0028] 2. Poly-dopamine coating:

[0029] (2) Take a certain amount of the above Co 3 O 4 / γ-alumina catalyst and put it into a beaker, add an appropriate amount of water, adjust the pH to 8-10 with ammonia water, disperse it by ultrasonic wave, then add a certain amount of dopamine hydrochloride, place the beaker in a water bath at 0-40 °C and stir for 1-24 h, filter, wash with clear water, and dry to obtain the poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst;

[0030] 3. Silica coating:

[0031] (3) First dissolve a certain amount of dispersant in absolute ethanol, and add the above poly-dopamine-coated Co 3 O 4 / γ-aluminum oxide, oscillate and disperse under ultrasound to obtain a dispersion of cobalt coated with polydopamine 3 O 4 / γ-aluminum oxide dispersion;

[0032] (4) Transfer the cobalt coated with polydopamine 3 O 4 / γ-aluminum oxide dispersion to a container, and under stirring conditions, uniformly dropwise add a certain amount of anhydrous ethanol solution of organosilicon source. During the dropping process, control the pH to 7-12 by adding ammonia in batches to cause the hydrolysis of the organosilicon source to form silica precipitate;

[0033] (5) After the dropping is completed, continue to react for 0.5-2 h;

[0034] (6) After the reaction is completed, filter the reaction solution and wash it with deionized water until neutral. Then, dry and calcine the filter cake to obtain cobalt 3 O 4 / γ-aluminum oxide@hollow SiO 2 ;

[0035] 4. Hydrophobic modification:

[0036] (7) Disperse the cobalt 3 O 4 / γ-aluminum oxide@SiO 2 obtained in step (6) in water, adjust the pH of the dispersion to 7-9, and then slowly dropwise add organosilicon compound. Stir at a constant temperature of 20-90 °C for 0.5-4 h. The organosilicon compound will undergo hydrolysis reaction with water in the solution to generate organosilanol, and then undergo dehydration condensation reaction with the hydroxyl groups on the surface of the silica shell layer, and be anchored on the surface of the silica shell layer in the form of Si-O-Si bonds. After filtration, washing with ethanol to remove the excess organosilicon compound, and drying, a water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica can be obtained.

[0037] The present invention also provides the application of the above water-resistant VOCs catalytic oxidation catalyst in the treatment of VOCs.

[0038] The present invention has the following beneficial effects:

[0039] 1. The catalyst loads cobalt 3 O 4 on γ-aluminum oxide. On the one hand, it can increase the specific surface area of the catalyst and the contact area between the catalyst and VOCs. On the other hand, it can improve the stability of the active component cobalt 3 O 4 ;

[0040] 2. Coating a layer of polydopamine on the surface of the original metal oxide catalyst, and then in-situ synthesizing and coating a layer of SiO 2 , to form a core-shell structure. Then, through chemical modification, the silica shell layer is hydrophobically modified using organosilicate (the organosilicate will undergo a hydrolysis reaction with water in the solution to generate organosilanol, and then undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the silica shell layer, and be anchored on the surface of the silica shell layer in the form of Si-O-Si bonds, changing the hydrophilic group -OH to an organosilicate with a hydrophobic organic group), which can isolate the moisture in the waste gas from the internal catalyst, enabling the catalyst to have excellent water resistance and still maintain high catalytic activity under high water content conditions. Moreover, by changing the ratio of the catalyst to the silicon source and the type and content of the organosilicate, the hydrophobic effect of the catalyst can be adjusted, which can cope with different reaction conditions such as different water contents and different space velocities. Detailed implementation method

[0041] In order to have a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0042] Catalyst evaluation method: On a fixed-bed reactor manufactured by Boluming (Beijing Science and Technology) Co., Ltd., the catalytic activity of the catalyst sample is tested. That is, 4 g of 40-60 mesh catalyst is placed in the reactor; taking formaldehyde as the object, formaldehyde gas is mixed with air and water vapor to form a mixed gas with a formaldehyde content of 100 mg / m 3 and a water content of 4% wt, and the mixed gas enters the fixed-bed catalytic reactor at a fixed space velocity of 10000 ml / g / h. Under the condition of programmed temperature rise, an 8860-type gas chromatograph manufactured by Agilent Co., Ltd. is used to detect the formaldehyde content of the mixed feed gas and the tail gas, and the formaldehyde removal rate at different temperatures is calculated. The temperature at which formaldehyde is 100% converted is used to measure the catalyst activity. The lower the temperature, the higher the catalyst activity. And it is compared with a comparative sample (a Co 3 O 4 / γ-alumina catalyst sample without a hydrophobic silica shell).

[0043] Example 1

[0044] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0045] (1) Dissolve cobalt nitrate calculated as 0.5 g of cobalt tetroxide in 30 ml of water, take 10 g of γ-alumina and pour it in for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ - alumina catalyst core

[0046] (2) Take 10 g of the above - mentioned Co 3 O 4 / γ - alumina catalyst core and put it into a beaker, add 100 g of water, adjust the pH to 10 with ammonia water, disperse it ultrasonically, then add 0.5 g of dopamine hydrochloride, put the beaker into a 0 °C water bath and stir for 24 h, filter, wash with clear water, and dry to obtain the Co 3 O 4 / γ - alumina catalyst core coated with polydopamine;

[0047] (3) Dissolve 1 g of polyvinylpyrrolidone in 200 g of absolute ethanol, add 10 g of the obtained Co 3 O 4 / γ - alumina catalyst core coated with polydopamine, and disperse it under ultrasonic oscillation for 1 h. Transfer the obtained dispersion to a three - necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate calculated as 0.5 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three - necked flask. Add ammonia water in batches during the dropping process to control the pH of the solution in the three - necked flask to 9. After the dropping is completed, continue to react for 0.5 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain the catalyst Co 3 O 4 / γ - alumina@hollow SiO 2 ;

[0048] (4) Take 8 g of the obtained Co 3 O 4 / γ - alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 7, then add 4 g of methyltrichlorosilane, stir at a constant temperature of 20 °C for 0.5 h, filter and dry to obtain the water - repellent silica - coated water - resistant VOCs catalytic oxidation catalyst.

[0049] The comparative sample 1 was prepared by the following steps:

[0050] Dissolve cobalt nitrate calculated as 0.5 g of cobalt tetroxide in 30 ml of water, take 10 g of γ - alumina and pour it in for impregnation. After impregnation for 2 h, put it into an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain the Co 3 O 4 / γ - alumina catalyst.

[0051] The evaluation results show that the temperature at which the catalyst completely converts formaldehyde is 96 °C, and that of the comparative sample 1 is 111 °C.

[0052] Example 2

[0053] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0054] (1) Dissolve cobalt chloride equivalent to 2 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst core;

[0055] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker, add 100 g of water, adjust the pH to 9 with ammonia water, disperse it ultrasonically, then add 5 g of dopamine hydrochloride, place the beaker in a water bath at 40 °C and stir for 1 h, filter, wash with clear water, and dry to obtain Co coated with polydopamine 3 O 4 / γ-alumina catalyst core;

[0056] (3) Dissolve 3 g of polyvinylpyrrolidone in 150 g of absolute ethanol, add 10 g of the obtained Co coated with polydopamine 3 O 4 / γ-alumina catalyst core, and disperse it by shaking under ultrasonic for 1 h. Transfer the obtained dispersion to a three-necked flask, and adjust the pH to 9 with ammonia water. Take methyltrimethoxysilane equivalent to 1 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process to control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue to react for 1 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain a catalyst Co with a hollow silica shell coating 3 O 4 / γ-alumina@hollow SiO 2 ;

[0057] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 8, then add 16 g of methyltrimethoxysilane, stir at a constant temperature of 30 °C for 2 h, filter and dry to obtain a water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica.

[0058] The comparative sample 2 is prepared by the following steps:

[0059] Dissolve cobalt chloride equivalent to 2 g of cobalt tetroxide in 30 ml of water. Take 10 g of γ-alumina and pour it in for impregnation. After 2 h of impregnation, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst;

[0060] The evaluation results show that the temperature at which the catalyst completely converts formaldehyde is 99 °C, and that of Comparative Sample 2 is 109 °C.

[0061] Example 3

[0062] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0063] (1) Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water. Take 10 g of γ-alumina and pour it in for impregnation. After 2 h of impregnation, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst core;

[0064] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker. Add 100 g of water, adjust the pH to 9 with ammonia water, disperse it ultrasonically, then add 2 g of dopamine hydrochloride, place the beaker in a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain Co 3 O 4 / γ-alumina catalyst core coated with polydopamine;

[0065] (3) Dissolve 6 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained Co 3 O 4 / γ-alumina catalyst core coated with polydopamine, and disperse it under ultrasonic oscillation for 1 h. Transfer the obtained dispersion liquid to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetra-isopropyl orthosilicate equivalent to 3 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process to control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue the reaction for 1 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain a catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0066] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of methyltriethoxysilane, stir at a constant temperature of 50 °C for 4 h, and filter and dry to obtain a water-repellent silica-coated water-resistant VOCs catalytic oxidation catalyst.

[0067] Comparative sample 3 was prepared by the following steps:

[0068] Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst;

[0069] The evaluation results show that: the temperature at which the catalyst completely converts formaldehyde is 91 °C, and that of comparative sample 3 is 104 °C.

[0070] Example 4

[0071] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0072] (1) Dissolve cobalt nitrate calculated as 2 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain a Co 3 O 4 / γ-alumina catalyst core;

[0073] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker, add 100 g of water, adjust the pH to 9 with ammonia water, disperse it ultrasonically, then add 3 g of hydrochloric acid dopamine, place the beaker in a water bath at 15 °C and stir for 10 h, filter, wash with clear water, and dry to obtain a polydopamine-coated Co 3 O 4 / γ-alumina catalyst core;

[0074] (3) Dissolve 4 g of polyvinylpyrrolidone in 50 g of absolute ethanol, add 10 g of the obtained polydopamine-coated Co 3 O 4The γ-aluminum oxide catalyst core was shaken and dispersed under ultrasound for 1 h. The obtained dispersion was transferred to a three-necked flask, and the pH was adjusted to 9 with ammonia water. Tetrabutyl orthosilicate calculated based on 1 g of silicon dioxide was dissolved in 50 ml of anhydrous ethanol and added dropwise to the three-necked flask. During the dropping process, ammonia water was added in batches to control the pH of the solution in the three-necked flask to 9. After the dropping was completed, the reaction was continued for 2 h. Then, the reaction solution was filtered by suction and washed with deionized water until neutral. After that, the filter cake was dried at 120 °C for 4 h and calcined at 550 °C for 4 h to obtain the catalyst Co coated with a hollow silica shell. 3 O 4 / γ-aluminum oxide@hollow SiO 2 ;

[0075] (4) 8 g of the obtained Co 3 O 4 / γ-aluminum oxide@hollow SiO 2 was dispersed in 200 ml of water, the pH of the dispersion was adjusted to 9, then 7 g of ethyltrimethoxysilane was added, and the mixture was stirred at a constant temperature of 50 °C for 4 h. After filtration and drying, the water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica could be obtained.

[0076] The comparative sample 4 was prepared by the following steps:

[0077] Cobalt nitrate calculated based on 2 g of cobalt tetroxide was dissolved in 30 ml of water. 10 g of γ-aluminum oxide was taken and poured in for impregnation. After impregnation for 2 h, it was placed in an oven at 120 °C and dried for 4 h. Then, it was taken out, ground into powder, and placed in a muffle furnace and calcined at 550 °C for 2 h to obtain the Co 3 O 4 / γ-aluminum oxide catalyst;

[0078] The evaluation results showed that the temperature at which formaldehyde was completely converted by the catalyst was 94 °C, and that of the comparative sample 4 was 109 °C.

[0079] Example 5

[0080] This example provides a water-resistant VOCs catalytic oxidation catalyst, which was prepared by the following steps:

[0081] (1) Cobalt nitrate calculated based on 2 g of cobalt tetroxide was dissolved in 30 ml of water. 10 g of γ-aluminum oxide was taken and poured in for impregnation. After impregnation for 2 h, it was placed in an oven at 120 °C and dried for 4 h. Then, it was taken out, ground into powder, and placed in a muffle furnace and calcined at 550 °C for 2 h to obtain the Co 3 O 4 / γ-aluminum oxide catalyst core;

[0082] (2) 10 g of the above-mentioned Co 3 O 4Put the Co 3 O 4 / γ-alumina catalyst core into a beaker, add 100 g of water, adjust the pH to 8 with ammonia water, disperse ultrasonically, then add 4 g of dopamine hydrochloride, put the beaker into a water bath at 20 °C and stir for 3 h, filter, wash with clear water, and dry to obtain the Co

[0083] (3) Dissolve 2.5 g of polyvinylpyrrolidone in 25 g of absolute ethanol, add 10 g of the obtained Co 3 O 4 / γ-alumina catalyst core, and disperse it by shaking under ultrasonic for 1 h. Transfer the obtained dispersion to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetrabutyl orthosilicate calculated as 2 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process, and control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue the reaction for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain the catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0084] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of n-octyltriethoxysilane, stir at a constant temperature of 90 °C for 4 h, filter and dry to obtain the water-repellent silica-coated water-resistant VOCs catalytic oxidation catalyst.

[0085] The comparative sample 5 was prepared by the following steps:

[0086] Dissolve cobalt nitrate calculated as 2 g of cobalt tetroxide in 30 ml of water, take 10 g of γ-alumina and pour it in for impregnation. After impregnation for 2 h, put it into an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain the Co 3 O 4 / γ-alumina catalyst.

[0087] The evaluation results show that: the temperature at which the catalyst completely converts formaldehyde is 91 °C, and that of the comparative sample 5 is 109 °C.

[0088] Example 6

[0089] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0090] (1) Dissolve cobalt nitrate equivalent to 2 g of cobalt tetroxide in 30 ml of water. Take 10 g of γ-alumina and pour it in for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst core;

[0091] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker. Add 100 g of water, and adjust the pH to 9 with ammonia water. Disperse it ultrasonically. Then add 5 g of dopamine hydrochloride. Place the beaker in a water bath at 35 °C and stir for 16 h. Filter, wash with clear water, and dry to obtain Co 3 O 4 / γ-alumina catalyst core coated with polydopamine;

[0092] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol. Add 10 g of the obtained Co 3 O 4 / γ-alumina catalyst core coated with polydopamine, and disperse it by shaking under ultrasonic for 1 h. Transfer the obtained dispersion liquid to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetrabutyl orthosilicate equivalent to 4 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drip it into the three-necked flask. Add ammonia water in batches during the dripping process, and control the pH of the solution in the three-necked flask to 9. After the dripping is completed, continue the reaction for 2 h. Then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain a catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0093] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion liquid to 9. Then add 4.2 g of 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, stir at a constant temperature of 90 °C for 4 h, filter and dry to obtain a water-repellent silica-coated anti-water VOCs catalytic oxidation catalyst.

[0094] The comparative sample 6 was prepared by the following steps:

[0095] Dissolve cobalt nitrate equivalent to 2 g of cobalt tetroxide in 30 ml of water. Take 10 g of γ-alumina and pour it in for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst.

[0096] The evaluation results show that the temperature at which the catalyst achieves complete conversion of formaldehyde is 95 °C, while that of the comparative sample 6 is 109 °C.

[0097] Example 7

[0098] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0099] (1) Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water. Take 10 g of γ-alumina and pour it in for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain a Co 3 O 4 / γ-alumina catalyst core;

[0100] (2) Take 10 g of the above-mentioned Co 3 O 4 / γ-alumina catalyst core and put it into a beaker. Add 100 g of water, adjust the pH to 8 with ammonia water, disperse it ultrasonically, then add 2.5 g of dopamine hydrochloride, place the beaker in a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain a poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core;

[0101] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core, and disperse it by shaking under ultrasonic waves for 1 h. Transfer the obtained dispersion to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate equivalent to 2 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process to control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue the reaction for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain a catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0102] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 8 g of dimethyldichlorosilane, stir at a constant temperature of 60 °C for 2 h, filter and dry to obtain a water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica.

[0103] The comparative sample 7 was prepared by the following steps:

[0104] Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C to dry for 4 h, then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst.

[0105] The evaluation results show that: the temperature at which the catalyst completely converts formaldehyde is 86, and that of the comparative sample 7 is 104 °C.

[0106] Example 8

[0107] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0108] (1) Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C to dry for 4 h, then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain a Co 3 O 4 / γ-alumina catalyst core;

[0109] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker, add 100 g of water, adjust the pH to 8 with ammonia water, disperse it ultrasonically, then add 2.5 g of hydrochloric acid dopamine, place the beaker in a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain a Co 3 O 4 / γ-alumina catalyst core coated with polydopamine;

[0110] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained Co 3 O 4The γ-aluminum oxide catalyst core was shaken and dispersed under ultrasound for 1 h. The obtained dispersion was transferred to a three-necked flask, and the pH was adjusted to 9 with ammonia water. Tetraethyl orthosilicate calculated as 2 g of silicon dioxide was dissolved in 50 ml of absolute ethanol and added dropwise to the three-necked flask. During the dropping process, ammonia water was added in batches to control the pH of the solution in the three-necked flask to 9. After the dropping was completed, the reaction was continued for 2 h. Then, the reaction solution was filtered by suction and washed with deionized water until neutral. After that, the filter cake was dried at 120 °C for 4 h and calcined at 550 °C for 4 h to obtain the catalyst Co coated with a hollow silica shell. 3 O 4 / γ-aluminum oxide@hollow SiO 2 ;

[0111] (4) Take 8 g of the obtained Co 3 O 4 / γ-aluminum oxide@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of dimethyldimethoxysilane, stir at a constant temperature of 60 °C for 2 h, and filter and dry to obtain a water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica.

[0112] The comparative sample 8 was prepared by the following steps:

[0113] Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-aluminum oxide into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain the Co 3 O 4 / γ-aluminum oxide catalyst.

[0114] The evaluation results show that the temperature at which the catalyst completely converts formaldehyde is 90 °C, and that of the comparative sample 8 is 104 °C.

[0115] Example 9

[0116] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0117] (1) Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-aluminum oxide into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain the Co 3 O 4 / γ-aluminum oxide catalyst core;

[0118] (2) Take 10 g of the above Co 3 O 4Put the Co / γ-aluminum oxide catalyst core into a beaker, add 100 g of water, adjust the pH to 8 with ammonia water, disperse it ultrasonically, then add 2.5 g of dopamine hydrochloride, put the beaker into a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain the Co / γ-aluminum oxide catalyst core coated with polydopamine. 3 O 4 / γ-aluminum oxide catalyst core;

[0119] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained Co / γ-aluminum oxide catalyst core coated with polydopamine, and disperse it by shaking ultrasonically for 1 h. Transfer the obtained dispersion to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate calculated as 2 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and add it dropwise to the three-necked flask. Add ammonia water in batches during the dropping process, and control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue to react for 2 h, then filter the reaction solution, wash it with deionized water until neutral, and then dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain the catalyst Co / γ-aluminum oxide@hollow SiO₂. 3 O 4 / γ-aluminum oxide@hollow SiO₂; 3 O 4 / γ-aluminum oxide@hollow SiO₂; 2 ;

[0120] (4) Disperse 8 g of the obtained Co / γ-aluminum oxide@hollow SiO₂ in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of dimethyldiethoxysilane, stir at a constant temperature of 60 °C for 2 h, filter and dry to obtain the water-repellent silica-coated anti-water VOCs catalytic oxidation catalyst. 3 O 4 / γ-aluminum oxide@hollow SiO₂; 2 The comparative sample 9 was prepared by the following steps:

[0121] Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water, take 10 g of γ-aluminum oxide and pour it in for impregnation. After impregnation for 2 h, put it in an oven at 120 °C and dry for 4 h, then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain the Co / γ-aluminum oxide catalyst.

[0122] The evaluation results show that the temperature at which the catalyst completely converts formaldehyde is 92 °C, and that of the comparative sample 9 is 104 °C. 3 O 4 / γ-aluminum oxide catalyst.

[0123] Example 10

[0124] This example provides an anti-water VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0125] This example provides an anti-water VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0126] (1) Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water. Take 10 g of γ-alumina and pour it in for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain the Co 3 O 4 / γ-alumina catalyst core;

[0127] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker. Add 100 g of water, and adjust the pH to 8 with ammonia water. Disperse it ultrasonically, then add 2.5 g of dopamine hydrochloride. Place the beaker in a water bath at 25 °C and stir for 10 h. Filter, wash with clear water, and dry to obtain the Co 3 O 4 / γ-alumina catalyst core coated with polydopamine;

[0128] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol. Add 10 g of the obtained Co 3 O 4 / γ-alumina catalyst core coated with polydopamine, and disperse it under ultrasonic oscillation for 1 h. Transfer the obtained dispersion to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate equivalent to 2 g of silica, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process, and control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue the reaction for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain the catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0129] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of ethyl dimethoxysilane, stir at a constant temperature of 60 °C for 2 h, filter and dry to obtain the water-repellent silica-coated anti-water VOCs catalytic oxidation catalyst.

[0130] Comparative sample 10 was prepared by the following steps:

[0131] Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water. Pour 10 g of γ-alumina into it for impregnation. After 2 h of impregnation, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst.

[0132] The evaluation results show that the temperature at which the catalyst completely converts formaldehyde is 90 °C, while that of Comparative Sample 10 is 104 °C.

[0133] Example 11

[0134] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0135] (1) Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water. Pour 10 g of γ-alumina into it for impregnation. After 2 h of impregnation, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain a Co 3 O 4 / γ-alumina catalyst core;

[0136] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker. Add 100 g of water, adjust the pH to 8 with ammonia water, disperse it ultrasonically, then add 2.5 g of dopamine hydrochloride, place the beaker in a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain a poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core;

[0137] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core, and disperse it by shaking under ultrasonic waves for 1 h. Transfer the obtained dispersion liquid to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate equivalent to 2 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process to control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue the reaction for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain a catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0138] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of diethyldiethoxysilane, stir at a constant temperature of 60 °C for 2 h, filter and dry to obtain a water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica.

[0139] Comparative sample 11 was prepared by the following steps:

[0140] Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst.

[0141] The evaluation results show that: the temperature at which the catalyst completely converts formaldehyde is 88 °C, and that of comparative sample 11 is 104 °C.

[0142] Example 12

[0143] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0144] (1) Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain a Co 3 O 4 / γ-alumina catalyst core;

[0145] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker, add 100 g of water, adjust the pH to 8 with ammonia water, ultrasonically disperse it, then add 2.5 g of hydrochloric acid dopamine, place the beaker in a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain a Co 3 O 4 / γ-alumina catalyst core coated with polydopamine;

[0146] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained Co 3 O 4The γ-aluminum oxide catalyst core was shaken and dispersed under ultrasound for 1 h. The obtained dispersion was transferred to a three-necked flask, and the pH was adjusted to 9 with ammonia water. Tetraethyl orthosilicate calculated based on 2 g of silicon dioxide was dissolved in 50 ml of absolute ethanol and added dropwise to the three-necked flask. During the dropping process, ammonia water was added in batches to control the pH of the solution in the three-necked flask to 9. After the dropping was completed, the reaction was continued for 2 h. Then, the reaction solution was suction filtered and washed with deionized water until neutral. After that, the filter cake was dried at 120 °C for 4 h and calcined at 550 °C for 4 h to obtain the catalyst Co coated with a hollow silica shell. 3 O 4 / γ-aluminum oxide@hollow SiO 2 ;

[0147] (4) 8 g of the obtained Co 3 O 4 / γ-aluminum oxide@hollow SiO 2 was dispersed in 200 ml of water, the pH of the dispersion was adjusted to 9, then 6 g of trimethylchlorosilane was added, and the mixture was stirred at a constant temperature of 60 °C for 2 h. After filtration and drying, the water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica could be obtained.

[0148] The comparative sample 12 was prepared by the following steps:

[0149] Cobalt nitrate calculated based on 1 g of cobalt tetroxide was dissolved in 30 ml of water. 10 g of γ-aluminum oxide was taken and poured for impregnation. After impregnation for 2 h, it was put into an oven at 120 °C for drying for 4 h. Then, it was taken out and ground into powder, and put into a muffle furnace for calcination at 550 °C for 2 h to obtain the Co 3 O 4 / γ-aluminum oxide catalyst.

[0150] The evaluation results showed that the temperature at which formaldehyde was completely converted by the catalyst was 83 °C, and that of the comparative sample 12 was 104 °C.

[0151] Example 13

[0152] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0153] (1) Cobalt nitrate calculated based on 1 g of cobalt tetroxide was dissolved in 30 ml of water. 10 g of γ-aluminum oxide was taken and poured for impregnation. After impregnation for 2 h, it was put into an oven at 120 °C for drying for 4 h. Then, it was taken out and ground into powder, and put into a muffle furnace for calcination at 550 °C for 2 h to obtain the Co 3 O 4 / γ-aluminum oxide catalyst core;

[0154] (2) 10 g of the above Co 3 O 4The Co / γ-aluminum oxide catalyst core is placed in a beaker, 100 g of water is added, and the pH is adjusted to 8 with ammonia water, followed by ultrasonic dispersion. Then, 2.5 g of dopamine hydrochloride is added, and the beaker is placed in a 25 °C water bath and stirred for 10 h. After filtration, washing with clear water, and drying, the Co / γ-aluminum oxide catalyst core coated with polydopamine is obtained. 3 O 4 / γ-aluminum oxide catalyst core;

[0155] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, and add 10 g of the obtained Co / γ-aluminum oxide catalyst core coated with polydopamine, and disperse it by shaking under ultrasonic for 1 h. Transfer the obtained dispersion to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate calculated as 2 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. During the dropping process, ammonia water is added in batches to control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue the reaction for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain the catalyst Co / γ-aluminum oxide@hollow SiO2. 3 O 4 / γ-aluminum oxide@hollow SiO 3 O 4 / γ-aluminum oxide@hollow SiO 2 ;

[0156] (4) Take 8 g of the obtained Co / γ-aluminum oxide@hollow SiO2 and disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of hexamethyldisiloxane, stir at a constant temperature of 60 °C for 2 h, and filter and dry to obtain the water-repellent silica-coated water-resistant VOCs catalytic oxidation catalyst. 3 O 4 / γ-aluminum oxide@hollow SiO 2 The comparative sample 13 is prepared by the following steps:

[0157] Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water, take 10 g of γ-aluminum oxide and pour it in for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, and place it in a muffle furnace and calcine it at 550 °C for 2 h to obtain the Co / γ-aluminum oxide catalyst.

[0158] The evaluation results show that the temperature at which the catalyst completely converts formaldehyde is 96 °C, and that of the comparative sample 13 is 104 °C. 3 O 4 / γ-aluminum oxide catalyst.

[0159] Example 14

[0160] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0161] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0162] (1) Dissolve cobalt nitrate calculated as 1 g of cobalt tetroxide in 30 ml of water. Take 10 g of γ-alumina and pour it in for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst core;

[0163] (2) Take 10 g of the above Co 3 O 4 / γ-alumina catalyst core and put it into a beaker. Add 100 g of water, adjust the pH to 8 with ammonia water, disperse it ultrasonically, then add 2.5 g of dopamine hydrochloride, place the beaker in a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core;

[0164] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core, and disperse it by shaking under ultrasonic for 1 h. Transfer the obtained dispersion liquid to a three-necked flask, and adjust the PH to 9 with ammonia water. Take tetraethyl orthosilicate calculated as 2 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process, and control the PH of the solution in the three-necked flask to be 9. After the dropping is completed, continue the reaction for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain a catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0165] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion liquid to 9, then add 6 g of hexamethyldisilazane, stir at a constant temperature of 60 °C for 2 h, filter and dry to obtain a water-repellent silica-coated anti-water VOCs catalytic oxidation catalyst.

[0166] The comparative sample 14 was prepared by the following steps:

[0167] Evaluation: Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water. Pour 10 g of γ-alumina into it for impregnation. After 2 h of impregnation, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst.

[0168] The evaluation results show that the temperature at which the catalyst achieves complete conversion of formaldehyde is 83 °C, while that of Comparative Sample 14 is 104 °C.

[0169] Example 15

[0170] This example provides a water-resistant VOCs catalytic oxidation catalyst, which is prepared by the following steps:

[0171] (1) Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water. Pour 10 g of γ-alumina into it for impregnation. After 2 h of impregnation, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain a Co 3 O 4 / γ-alumina catalyst core;

[0172] (2) Take 10 g of the above-mentioned Co 3 O 4 / γ-alumina catalyst core and put it into a beaker. Add 100 g of water, adjust the pH to 8 with ammonia water, disperse it ultrasonically, then add 2.5 g of hydrochloric acid dopamine, place the beaker in a water bath at 25 °C and stir for 10 h, filter, wash with clear water, and dry to obtain a poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core;

[0173] (3) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the obtained poly-dopamine-coated Co 3 O 4 / γ-alumina catalyst core, and disperse it by ultrasonic oscillation for 1 h. Transfer the obtained dispersion liquid to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate equivalent to 2 g of silicon dioxide, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. Add ammonia water in batches during the dropping process to control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue the reaction for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry the filter cake at 120 °C for 4 h and calcine it at 550 °C for 4 h to obtain a catalyst Co 3 O 4 / γ-alumina@hollow SiO 2 ;

[0174] (4) Take 8 g of the obtained Co 3 O 4 / γ-alumina@hollow SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of hexamethyldisilazane, stir at a constant temperature of 60 °C for 2 h, and filter and dry to obtain a water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica.

[0175] The comparative sample 15 was prepared by the following steps:

[0176] Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain Co 3 O 4 / γ-alumina catalyst.

[0177] The evaluation results show that: the temperature at which formaldehyde is completely converted by the catalyst is 88 °C, and that of the comparative sample 15 is 104 °C.

[0178] Comparative Example 1

[0179] This comparative example provides a water-resistant VOCs catalytic oxidation catalyst coated with hydrophobic silica, which is prepared by the following steps:

[0180] (1) Dissolve cobalt nitrate equivalent to 1 g of cobalt tetroxide in 30 ml of water, pour 10 g of γ-alumina into it for impregnation. After impregnation for 2 h, place it in an oven at 120 °C and dry for 4 h. Then take it out, grind it into powder, put it into a muffle furnace, and calcine it at 550 °C for 2 h to obtain a Co 3 O 4 / γ-alumina catalyst core;

[0181] (2) Dissolve 2 g of polyvinylpyrrolidone in 100 g of absolute ethanol, add 10 g of the above-mentioned Co 3 O 4 / γ-alumina catalyst core, and disperse it under ultrasonic oscillation for 1 h. Transfer the obtained dispersion to a three-necked flask, and adjust the pH to 9 with ammonia water. Take tetraethyl orthosilicate equivalent to 2 g of silica, dissolve it in 50 ml of absolute ethanol, and drop it into the three-necked flask. During the dropping process, add ammonia water in batches to control the pH of the solution in the three-necked flask to 9. After the dropping is completed, continue to react for 2 h, then filter the reaction solution, wash it with deionized water until neutral. Then, dry and calcine the filter cake to obtain a catalyst Co 3 O 4 / γ-alumina@SiO 2 ;

[0182] (3) Take 8 g of the obtained catalyst Co 3 O 4 / γ-aluminum oxide SiO 2 Disperse it in 200 ml of water, adjust the pH of the dispersion to 9, then add 6 g of hexamethyldisilazane, stir at a constant temperature of 60 °C for 2 h, filter and dry to obtain a water-repellent VOCs catalytic oxidation catalyst coated with hydrophobic silica.

[0183] Compared with Example 15, this comparative example is exactly the same as Example 15 in all steps except that polydopamine coating is not carried out. The evaluation results of Comparative Example 1 show that the temperature at which formaldehyde is completely converted by the catalyst is 95 °C, which is higher than 88 °C of the sample in Example 15.

[0184] Perform long-term evaluation on Example 15 and Comparative Example 1. The long-term evaluation method of the catalyst is as follows: On a fixed-bed reactor manufactured by Boluming (Beijing Science and Technology) Co., Ltd., test the catalytic activity of the catalyst sample. That is, put 4 g of 40-60 mesh catalyst into the reactor; take formaldehyde as the object, mix formaldehyde gas with air and water vapor to form a mixed gas with a formaldehyde content of 100 mg / m 3 , and the water content is 4% wt. Let the mixed gas enter the fixed-bed catalytic reactor at a fixed space velocity of 10,000 ml / g / h, set the reactor temperature to 100 °C, and use an 8860-type gas chromatograph manufactured by Agilent Company to detect the formaldehyde content of the mixed raw material gas and the tail gas, and calculate the formaldehyde removal rate at different temperatures.

[0185] Table 1

[0186] Removal rate 5h 10h 50h 100h 150h 200h Example 15 100％ 100％ 100％ 100％ 100％ 100％ Comparative Example 1 100％ 100％ 100％ 98％ 80％ 53％

[0187] The results of the 200-h long-term evaluation show that for the catalyst in Example 15 during the 200-h evaluation, the formaldehyde removal rate is always 100%, while for the catalyst in Comparative Example 1, the formaldehyde removal rate starts to decline at 100 h and is only 53% at 200 h.

[0188] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

Claims

1. A water-resistant VOCs catalytic oxidation catalyst with a core-shell structure, where the core is a metal oxide loaded with Co 3 O 4 , the shell layer is silica, the outer surface of the shell layer is hydrophobically modified, and between the core and the shell layer is polydopamine that has been calcined and removed.

2. The preparation method of the water-resistant VOCs catalytic oxidation catalyst according to claim 1, wherein it comprises the following steps: (1) Impregnate a cobalt precursor on a metal oxide support, and obtain a core body through drying and calcination; (2) Mix the core body obtained in step (1) in water, adjust the pH to 8-10, after ultrasonic dispersion, add dopamine hydrochloride, react at 0-40 °C for 1-24 h, and obtain a core body coated with polydopamine after filtration, washing, and drying; (3) Dissolve a dispersant in an alcohol solvent, add the core body coated with polydopamine obtained in step (2), perform ultrasonic dispersion, add an alcohol solution of an organosilicon source under stirring, control the pH to 7-12, react for 0.5-2 h, and obtain a core body coated with a silica hollow shell after filtration, washing, drying, and calcination; (4) Disperse the core body coated with the silica hollow shell obtained in step (3) in water, adjust the pH to 7-9, dropwise add an organosilicon compound, react at 20-90 °C for 0.5-4 h, and obtain the water-resistant VOCs catalytic oxidation catalyst after filtration, washing, and drying.

3. According to the preparation method described in claim 2, wherein in step (1), the cobalt precursor includes one or a combination of two of cobalt nitrate and cobalt chloride; Preferably, in step (1), the metal oxide includes γ-alumina; Preferably, in step (1), the equal-volume impregnation method is used for impregnation.

4. According to the preparation method described in claim 2, wherein in step (1), based on cobalt tetroxide, the mass ratio of the cobalt precursor to the metal oxide support is 5-20:

100.

5. According to the preparation method described in claim 2, wherein in step (2), the mass ratio of dopamine hydrochloride to the core body is 5-50:

100.

6. According to the preparation method described in claim 2, wherein in step (3), the dispersant includes one or a combination of two of polyvinylpyrrolidone and polyethylene glycol 4000; Preferably, in step (3), the mass ratio of the dispersant to the alcohol solvent is 0.5-10:100; Preferably, in step (3), the mass ratio of the core body coated with polydopamine to the alcohol solvent is 5-40:100; Preferably, in step (3), the organosilicon source includes one or a combination of two or more of tetraethyl orthosilicate, tetrabutyl orthosilicate, tetraisopropyl orthosilicate, and methyl orthosilicate; Preferably, in step (3), the calcination conditions are calcination at 450-700 °C for 2-10 h.

7. According to the preparation method described in claim 2, wherein in step (3), based on silica, the mass ratio of the organosilicon source to the core body coated with polydopamine is 5-40:

100.

8. According to the preparation method described in claim 2, wherein In step (4), the organosilicon compound includes one or a combination of two or more of methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, n-octyltriethoxysilane, 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane, dimethyldichlorosilane, dimethyldimethoxysilane, dimethyldiethoxysilane, ethyldimethoxysilane, diethyldiethoxysilane, trimethylchlorosilane, hexamethyldisiloxane, and hexamethyldisilazane.

9. The preparation method according to claim 2, wherein, in step (4), the mass ratio of the organosilicon compound to the core body coated with the silica hollow shell is 0.5-2:

1.

10. Application of the water-resistant VOCs catalytic oxidation catalyst according to claim 1 in the treatment of VOCs.