A water-resistant monolithic VOCs catalytic oxidation catalyst, its preparation method and application

Abstract

This invention provides a water-resistant monolithic VOCs catalytic oxidation catalyst, its preparation method, and its application. The catalyst comprises a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a substrate with open channels and VOCs catalytic oxidation catalyst supported on the inner and outer surfaces of the substrate. The water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a porous metal oxide support and a noble metal active component supported on the support. The water-resistant protective layer comprises, from the inside out, an inner hydrophobic layer, a middle hydrophilic layer, and an outer hydrophobic layer. The inner and outer hydrophobic layers are made of pure silica molecular sieves and / or titanium silica molecular sieves, while the middle hydrophilic layer is made of fumed silica. The catalyst provided by this invention exhibits excellent catalytic oxidation activity for VOCs under high water content conditions.

Description

Technical Field

[0001] This invention relates to a water-resistant monolithic VOCs catalytic oxidation catalyst, its preparation method and application, belonging to the field of safety, environmental protection and energy-saving and water-saving technology. Background Technology

[0002] VOCs is an abbreviation for volatile organic compounds, which can harm human health and cause serious environmental pollution. The industrial application technologies used to treat VOCs mainly fall into the following categories: First, the biological method. This involves collecting VOC-containing waste gas and passing it through a biofilm filter bed. Water is sprayed onto the biofilm filter bed to keep the surface moist, simultaneously washing away the VOCs from the waste gas, allowing them to contact, react, and degrade in the biofilm. The VOCs are biologically decomposed into water and carbon dioxide, and the treated exhaust gas meets emission standards. The advantage of this method is its low treatment cost, but the disadvantage is that VOC degradation is incomplete; if it contains recalcitrant VOCs, the exhaust gas may not meet emission standards. Second, the regenerative thermal oxidizer (RTO) method. This involves collecting VOC-containing waste gas and sending it into a combustion chamber equipped with regenerative materials. Natural gas is then injected into the combustion chamber as a combustion aid, causing the VOCs to be burned and decomposed into water and carbon dioxide. The advantages of this method are thorough VOCs decomposition, but its disadvantages include high investment costs, reaction temperatures as high as 700-800℃, and high operating costs. It is suitable for treating large-volume, high-concentration organic waste gas. The third method is catalytic combustion, where VOCs-containing waste gas is collected, preheated to 400-500℃, and then sent to a combustion chamber equipped with a fixed-bed catalyst. Under the action of the catalyst, VOCs are decomposed into carbon dioxide and water. The advantages of this method are low reaction temperatures and relatively lower operating costs compared to regenerative combustion. The disadvantages are high investment costs and incomplete VOCs decomposition if the catalyst is not suitable.

[0003] Numerous studies have been conducted on catalytic oxidation catalysts. For example, CN106732605A discloses a non-precious metal oxide catalyst with a water-resistant protective layer and its preparation method. This catalyst uses nano-transition metal Fe / Co composite oxide as the active component and has a polymer porous film attached to its surface, giving it excellent water resistance. However, this catalyst is only suitable for treating easily removed toxic gases such as CO and formaldehyde (which require low reaction temperatures). The catalytic oxidation of VOCs, including propane, generally requires higher temperatures, and the polymer porous film on the catalyst surface will decompose or coke at high temperatures.

[0004] CN108772075A discloses a catalyst for removing volatile benzene-based pollutants and its preparation method. The catalyst consists of a noble metal active component and a support; wherein the noble metal active component is elemental platinum or platinum oxide; and the noble metal active component constitutes 0.01%-0.05% of the total catalyst mass based on the noble metal element. This catalyst cannot isolate water from itself, and under high temperature and high water content conditions, the aggregation of the noble metal active component is accelerated, reducing the catalyst's lifespan.

[0005] CN113856748A discloses a hollow ZSM-5 catalyst with a dual inner surface modified by atomic doping and metal clusters, and its preparation method. The catalyst has the general formula NOx@M-ZSM-5@Al-ZSM-5, where 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 monolithic catalyst with two inner layers, where the outer Al-ZSM-5 and the middle M-ZSM-5 are tightly bonded together as a whole. Although molecular sieves have good water resistance, molecular sieve-based catalysts are prone to coking and deactivation because their active centers are located in the molecular sieve channels or cages.

[0006] Therefore, providing a novel water-resistant monolithic VOCs catalytic oxidation catalyst, its preparation method, and its application has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] To address the aforementioned shortcomings and deficiencies, one objective of this invention is to provide a water-resistant monolithic VOCs catalytic oxidation catalyst.

[0008] Another object of the present invention is to provide a method for preparing the above-described water-resistant monolithic VOCs catalytic oxidation catalyst.

[0009] Another object of the present invention is to provide the application of the above-described water-resistant monolithic VOCs catalytic oxidation catalyst in the catalytic oxidation of VOCs.

[0010] To achieve the above objectives, in one aspect, the present invention provides a water-resistant monolithic VOCs catalytic oxidation catalyst, wherein the water-resistant monolithic VOCs catalytic oxidation catalyst comprises a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst comprises a substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst; the VOCs catalytic oxidation catalyst comprises a porous metal oxide support and a noble metal active component supported on the support.

[0011] The water-resistant protective layer comprises, from the inside out, an inner hydrophobic layer, an intermediate hydrophilic layer, and an outer hydrophobic layer. The materials of the inner and outer hydrophobic layers include pure silicon molecular sieves and / or titanium silicon molecular sieves, and the material of the intermediate hydrophilic layer includes fumed silica.

[0012] In the catalysts described above in this invention, "inner" and "outer" are relative to the VOCs catalytic oxidation catalyst. The side closer to the VOCs catalytic oxidation catalyst is "inner", and the side away from the VOCs catalytic oxidation catalyst is "outer".

[0013] In the catalyst described above in this invention, the noble metal active component comprises noble metal oxides and elemental noble metals. The VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, but the support of the VOCs catalytic oxidation catalyst must not block the open pores of the substrate, so that VOCs can smoothly pass through the open pores when the water-resistant monolithic VOCs catalytic oxidation catalyst is subsequently used for VOCs catalytic oxidation. The inner surface refers to the surface of the open pores of the substrate, and the outer surface includes the upper and lower surfaces of the substrate.

[0014] As a specific embodiment of the catalyst described above in this invention, the VOCs catalytic oxidation catalyst further includes an auxiliary metal oxide, which is supported on the support, and the content of the auxiliary metal oxide is 0.5%-20% based on the total weight of the support as 100%.

[0015] In one specific embodiment of the catalyst described above in this invention, the auxiliary metal oxide includes one or a combination of several of CeO2, MnO, CuO, and La2O3. In some preferred embodiments of this invention, the content of CeO2 can be up to 20%, while the contents of MnO, CuO, and La2O3 can each be up to 15%.

[0016] In one specific embodiment of the catalyst described above in this invention, the noble metal includes one or a combination of several of Pt, Pd, and Rh.

[0017] As a specific embodiment of the catalyst described above in this invention, the content of the noble metal active component, calculated as noble metal, is 0.5%-5% based on the total weight of the support (100%), that is, the mass ratio of the noble metal active component to the support is 0.5-5:100.

[0018] As a specific embodiment of the catalyst described above in this invention, the porous metal oxide support includes one or a combination of several of TiO2, SiO2, CeO2, ZrO2, cerium-zirconium solid solution and γ-Al2O3.

[0019] In one specific embodiment of the catalyst described above in this invention, the loading of the VOCs catalytic oxidation catalyst is 10%-20% based on the total weight of the substrate as 100%.

[0020] As a specific embodiment of the catalyst described above in this invention, the content of the water-resistant protective layer is 1%-20% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0021] In one specific embodiment of the catalyst described above in this invention, the pure silicon molecular sieve includes one or a combination of pure silicon MCM-41 molecular sieve, pure silicon β molecular sieve and Silicalite-1, and the titanium silicon molecular sieve includes TS-1 and / or TS-2, etc.

[0022] In the catalyst described above in this invention, the materials of the inner hydrophobic layer and the outer hydrophobic layer can be the same or different.

[0023] As a specific embodiment of the catalyst described above in this invention, the substrate includes two main categories: ceramic carriers and metal carriers. The ceramic carriers include cordierite honeycomb ceramics or silicon carbide honeycomb ceramics, etc., and the metal carriers include metal honeycomb carriers, such as iron-chromium-aluminum metal honeycomb carriers, etc.

[0024] On the other hand, the present invention also provides a method for preparing the above-described water-resistant monolithic VOCs catalytic oxidation catalyst, wherein the preparation method includes:

[0025] Step (1): The impregnation solution containing the noble metal precursor and the porous metal oxide support are mixed evenly and then impregnated. The impregnated product is then dried and calcined to obtain the VOCs catalytic oxidation catalyst.

[0026] Step (2): Mix the VOCs catalytic oxidation catalyst, binder, peptide, dispersant and water and ball mill to form a catalyst slurry;

[0027] Step (3): Immerse the substrate in the catalyst slurry, remove the substrate, dry and calcine it to obtain an integral VOCs catalytic oxidation catalyst;

[0028] Step (4): Mix pure silicon molecular sieve and / or titanium silicon molecular sieve, dispersant and water and ball mill to form molecular sieve slurry. Immerse the monolithic VOCs catalytic oxidation catalyst in the molecular sieve slurry. Take out the monolithic VOCs catalytic oxidation catalyst and dry and calcine it.

[0029] Step (5): Mix fumed silica, dispersant and water and ball mill to form fumed silica slurry. Immerse the product obtained after calcination in step (4) in fumed silica slurry. Take out the product and dry and calcinate it.

[0030] Step (6): Mix pure silicon molecular sieve and / or titanium silicon molecular sieve, dispersant and water and ball mill to form molecular sieve slurry. Immerse the product obtained after calcination in step (5) in molecular sieve slurry. Take out the product and dry and calcinate it to obtain water-resistant monolithic VOCs catalytic oxidation catalyst.

[0031] As a specific embodiment of the preparation method described above in this invention, when the VOCs catalytic oxidation catalyst further includes an auxiliary metal oxide, in step (1), the impregnation liquid containing the noble metal precursor and the auxiliary metal precursor and the porous metal oxide support are mixed evenly and then simultaneously impregnated. The impregnated product is dried and calcined to obtain the VOCs catalytic oxidation catalyst.

[0032] Alternatively, the impregnation solution containing the auxiliary metal precursor and the porous metal oxide support can be mixed evenly and then impregnated, dried and calcined, and then mixed evenly with the impregnation solution containing the noble metal precursor and impregnated, and then dried and calcined to obtain the VOCs catalytic oxidation catalyst.

[0033] Alternatively, the impregnation solution containing the noble metal precursor and the porous metal oxide support can be mixed evenly and then impregnated, dried and calcined, and then mixed evenly with the impregnation solution containing the auxiliary metal precursor and impregnated, and then dried and calcined to obtain the VOCs catalytic oxidation catalyst.

[0034] In one specific embodiment of the preparation method described above, the auxiliary metal precursor includes nitrates of the auxiliary metal. For example, when the auxiliary metal is cerium, manganese, copper, or lanthanum, the auxiliary metal precursor is cerium nitrate, manganese nitrate, copper nitrate, and lanthanum nitrate, respectively.

[0035] In one specific embodiment of the preparation method described above in this invention, the noble metal precursor includes nitrates of noble metals, etc.

[0036] In one specific embodiment of the preparation method described above in this invention, the dispersant includes polyvinyl alcohol and / or polyvinylpyrrolidone, etc. The dispersant used in steps (2) and (4)-(5) of the preparation method of this invention is used to stabilize and disperse the slurry and adjust the viscosity of the slurry. Furthermore, this invention does not specify the amount of the dispersant, and its amount can be reasonably adjusted according to the actual operational needs.

[0037] As a specific embodiment of the preparation method described above in this invention, the adhesive in step (2) includes boehmite, etc., and the adhesive solvent includes one or a combination of concentrated nitric acid, hydrochloric acid, acetic acid and citric acid, preferably nitric acid. This invention does not make specific requirements on the amount of the adhesive and the adhesive solvent, and their amounts can be reasonably adjusted according to the actual operation needs.

[0038] As a specific embodiment of the preparation method described above in this invention, in step (3), the substrate is immersed in the catalyst slurry, and after the substrate is taken out, it is dried and calcined. The above operation (i.e., immersion, drying and calcination) is repeated 2-4 times until the loading of VOCs catalytic oxidation catalyst is 10%-20% based on the total weight of the substrate as 100%, and an integral VOCs catalytic oxidation catalyst is obtained.

[0039] As a specific embodiment of the preparation method described above in this invention, the calcination temperature in steps (1) and (3)-(6) is 400-750℃.

[0040] This invention does not impose specific requirements on the drying conditions, such as temperature and time, in the preparation method described above. The drying temperature and time can be reasonably adjusted according to the actual operation needs, as long as the target material can be dried.

[0041] As a specific embodiment of the preparation method described above in this invention, in steps (3) to (5), the immersion time is 10-30 min.

[0042] In another aspect, the present invention also provides the application of the above-described water-resistant monolithic VOCs catalytic oxidation catalyst in the catalytic oxidation of VOCs.

[0043] In some specific embodiments of the present invention, the VOCs may be, for example, VOCs contained in exhaust gas, and the exhaust gas has a high water content, such as a water content of not less than 10 wt%.

[0044] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0045] This invention obtains a water-resistant monolithic VOCs catalytic oxidation catalyst by setting a water-resistant protective layer on the surface of the monolithic VOCs catalytic oxidation catalyst. The water-resistant protective layer includes an inner hydrophobic layer, an intermediate hydrophilic layer and an outer hydrophobic layer from the inside out. The materials of the inner hydrophobic layer and the outer hydrophobic layer include pure silicon molecular sieve and / or titanium silicon molecular sieve, and the material of the intermediate hydrophilic layer includes fumed silica. The inner and outer hydrophobic layers are made of materials with strong hydrophobic properties, which can separate the moisture in the exhaust gas from the monolithic VOCs catalytic oxidation catalyst inside the water-resistant monolithic VOCs catalytic oxidation catalyst, preventing them from coming into contact. This avoids the problem of reduced efficiency or even deactivation of the catalyst due to the aggregation of precious metal active components under high temperature and high water content conditions, thus extending the life of the catalyst under water content conditions. The middle hydrophilic layer is made of hydrophilic fumed silica. Its main function is to guide some of the water vapor that passes through the outer hydrophobic layer laterally (referring to the direction perpendicular to the open pore direction of the substrate) through its longitudinal direction (referring to the direction parallel to the open pore direction of the substrate). By combining water blocking and water guiding, i.e., a combination of blocking and dredging, the aggregation and deactivation of precious metal active components under high temperature and high water content conditions is reduced.

[0046] In summary, compared with conventional monolithic VOCs catalytic oxidation catalysts, the water-resistant monolithic VOCs catalytic oxidation catalyst provided by this invention solves the problem of catalyst efficiency decline caused by water molecules in the waste gas competing with VOCs (such as low-carbon alkanes like propane) for adsorption on the catalyst surface, thus improving the catalyst's catalytic oxidation activity for VOCs under high water content conditions. Detailed Implementation

[0047] It should be noted that the term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0048] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0049] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0050] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0051] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0052] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the appendices and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0054] Example 1

[0055] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0056] Step (1): Dissolve 20g of cerium nitrate hexahydrate (calculated as CeO2) and 2g of platinum nitrate (calculated as Pt) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and dry it in an oven at 120℃ for 4 hours. Then take it out and grind it into powder. Place it in a muffle furnace and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0057] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0058] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.5g) in the catalyst slurry. After 10 minutes, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4 hours. After that, put it in a muffle furnace and calcine it at 500℃ for 4 hours. Repeat the immersion, blowing, drying and calcination three times until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 15%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0059] Step (4): Take 20g of Silicalite-1 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 10min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 500℃ for 2h.

[0060] Step (5): Take 20g of fumed silica, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 400℃ for 2h.

[0061] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 400°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0062] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and CeO2 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of Silicalite-1, and the middle hydrophilic layer is made of fumed silica.

[0063] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, namely CeO2, is 20%, the content of the Pt active component, calculated as Pt, is 2%, the loading of the VOCs catalytic oxidation catalyst is 15% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 5.4% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0064] Example 2

[0065] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0066] Step (1): Dissolve 20g of cerium nitrate hexahydrate (calculated as CeO2) and 5g of platinum nitrate (calculated as Pt) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0067] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0068] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 h. After that, put it in a muffle furnace and calcine it at 500°C for 4 h. Repeat the immersion, blowing, drying and calcination twice until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 10%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0069] Step (4): Take 50g of Silicalite-1 molecular sieve, 6g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 10min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 400℃ for 2h.

[0070] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 600℃ for 2h.

[0071] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 500°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0072] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and CeO2 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of Silicalite-1, and the middle hydrophilic layer is made of fumed silica.

[0073] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, namely CeO2, is 20%, the content of the Pt active component, calculated as Pt, is 5%, the loading of the VOCs catalytic oxidation catalyst is 10% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 17% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0074] Example 3

[0075] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0076] Step (1): Take 15g of 50wt% manganese nitrate solution (calculated as MnO) and 5g of palladium nitrate (calculated as Pd) and dissolve them in 35g of water. After complete dissolution, pour the resulting impregnation solution into 100g of SiO2 and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0077] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0078] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 h. After that, put it in a muffle furnace and calcine it at 500°C for 4 h. Repeat the immersion, blowing, drying and calcination twice until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 10%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0079] Step (4): Take 60g of Silicalite-1 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 650℃ for 2h.

[0080] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 600℃ for 2h.

[0081] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 650°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0082] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pd active components (including Pd and its oxides) and MnO supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer, and an outer hydrophobic layer from the inside out. The inner hydrophobic layer and the outer hydrophobic layer are both made of Silicalite-1, and the middle hydrophilic layer is made of fumed silica.

[0083] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, i.e., MnO, is 15%, the content of the Pd active component, calculated as Pd, is 5%, the loading of the VOCs catalytic oxidation catalyst is 10% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 20% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0084] Example 4

[0085] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0086] Step (1): Dissolve 15g of copper nitrate (calculated as CuO) and 5g of rhodium nitrate (calculated as Rh) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of CeO2 and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0087] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0088] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.3g) in the catalyst slurry. After 10 minutes, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4 hours and then place it in a muffle furnace and calcine it at 500℃ for 4 hours. Repeat the immersion, blowing, drying and calcination process 3 times until the loading of the VOCs catalytic oxidation catalyst is 14.9% based on the total weight of the cordierite honeycomb ceramic, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0089] Step (4): Take 55g of pure silicon β molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain pure silicon β molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 750℃ for 2h.

[0090] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 750℃ for 2h.

[0091] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and use compressed air to blow away the slurry residue on the inner surface of the cordierite honeycomb ceramic pores to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 750°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0092] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Rh active components (including Rh and its oxides) and CuO supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of pure silicon β molecular sieve, and the middle hydrophilic layer is made of fumed silica.

[0093] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, i.e., CuO, is 15%, the content of the Rh active component (calculated as Rh) is 5%, the loading of the VOCs catalytic oxidation catalyst is 14.9% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 18% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0094] Example 5

[0095] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0096] Step (1): Dissolve 15g of lanthanum nitrate (calculated as La2O3) and 3g of palladium nitrate (calculated as Pd) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of TiO2 and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and dry it in an oven at 120℃ for 4 hours. Then take it out and grind it into powder. Place it in a muffle furnace and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0097] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0098] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.7g) in the catalyst slurry. After 10 minutes, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4 hours. After that, put it in a muffle furnace and calcine it at 500℃ for 4 hours. Repeat the immersion, blowing, drying and calcination three times until the loading of VOCs catalytic oxidation catalyst is 15.2% based on the total weight of cordierite honeycomb ceramic, and obtain the monolithic VOCs catalytic oxidation catalyst.

[0099] Step (4): Take 43g of TS-1 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain TS-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 550℃ for 2h.

[0100] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 550℃ for 2h.

[0101] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 550°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0102] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pd active components (including Pd and its oxides) and La2O3 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of TS-1 molecular sieve, and the middle hydrophilic layer is made of fumed silica.

[0103] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, namely La2O3, is 15%, the content of the Pd active component, calculated as Pd, is 3%, the loading of the VOCs catalytic oxidation catalyst is 15.2% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 15% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0104] Example 6

[0105] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0106] Step (1): Dissolve 15g of lanthanum nitrate (calculated as La2O3) and 3g of palladium nitrate (calculated as Pd) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of ZrO2 and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder. Put it into a muffle furnace and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0107] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0108] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.9 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 h. After that, put it in a muffle furnace and calcine it at 500°C for 4 h. Repeat the immersion, blowing, drying and calcination three times until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 15%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0109] Step (4): Take 45g of TS-2 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain TS-2 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 550℃ for 2h.

[0110] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 550℃ for 2h.

[0111] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 550°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0112] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pd active components (including Pd and its oxides) and La2O3 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of TS-2 molecular sieve, and the middle hydrophilic layer is made of fumed silica.

[0113] Specifically, based on the total weight of the carrier (100%), the content of the auxiliary metal oxide, namely La2O3, is 15%, the content of the Pd active component (calculated as Pd) is 3%, the loading of the VOCs catalytic oxidation catalyst is 15% based on the total weight of the substrate (100%), and the content of the water-resistant protective layer is 15.3% based on the total weight of the monolithic VOCs catalytic oxidation catalyst (100%).

[0114] Example 7

[0115] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0116] Step (1): Take 10g of cerium nitrate hexahydrate (calculated as CeO2), 3g of lanthanum nitrate (calculated as La2O3), 1g of platinum nitrate (calculated as Pt), and 1.5g of palladium nitrate (calculated as Pd) and dissolve them in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of cerium-zirconium solid solution and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into a 120℃ oven to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0117] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0118] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110 °C for 4 h. After that, put it in a muffle furnace and calcine it at 500 °C for 4 h. Repeat the immersion, blowing, drying and calcination process 4 times until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 20%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0119] Step (4): Take 35g of Silicalite-1 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 600℃ for 2h.

[0120] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 500℃ for 2h.

[0121] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 600°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0122] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and Pd active components (including Pd and its oxides) supported on the support, as well as CeO2 and La2O3. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of Silicalite-1 molecular sieve, and the middle hydrophilic layer is made of fumed silica.

[0123] Specifically, based on the total weight of the carrier (100%), the contents of the auxiliary metal oxides, namely La2O3 and CeO2, are 3% and 10%, respectively; the contents of the Pd active component (calculated as Pd) and the Pt active component (calculated as Pt) are 1.5% and 1%, respectively; based on the total weight of the substrate (100%), the loading of the VOCs catalytic oxidation catalyst is 20%; and based on the total weight of the monolithic VOCs catalytic oxidation catalyst (100%), the content of the water-resistant protective layer is 10.7%.

[0124] Example 8

[0125] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0126] Step (1): Dissolve 10g of cerium nitrate hexahydrate (calculated as CeO2), 3g of lanthanum nitrate (calculated as La2O3), 1g of platinum nitrate (calculated as Pt), and 1.5g of palladium nitrate (calculated as Pd) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and dry it in an oven at 120℃ for 4 hours. Then take it out and grind it into powder. Place it in a muffle furnace and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0127] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0128] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.4 g by weight) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110 °C for 4 h. After that, put it in a muffle furnace and calcine it at 500 °C for 4 h. Repeat the immersion, blowing, drying and calcination process 4 times until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 20%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0129] Step (4): Take 5g of Silicalite-1 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 600℃ for 2h.

[0130] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 500℃ for 2h.

[0131] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 600°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0132] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and Pd active components (including Pd and its oxides) supported on the support, as well as CeO2 and La2O3. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of Silicalite-1 molecular sieve, and the middle hydrophilic layer is made of fumed silica.

[0133] Specifically, based on the total weight of the carrier (100%), the contents of the auxiliary metal oxides, namely La2O3 and CeO2, are 3% and 10%, respectively; the contents of the Pd active component (calculated as Pd) and the Pt active component (calculated as Pt) are 1.5% and 1%, respectively; based on the total weight of the substrate (100%), the loading of the VOCs catalytic oxidation catalyst is 20%; and based on the total weight of the monolithic VOCs catalytic oxidation catalyst (100%), the content of the water-resistant protective layer is 1%.

[0134] Example 9

[0135] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0136] Step (1): Dissolve 20g of cerium nitrate hexahydrate (calculated as CeO2) and 5g of platinum nitrate (calculated as Pt) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0137] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0138] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 h. After that, put it in a muffle furnace and calcine it at 500°C for 4 h. Repeat the immersion, blowing, drying and calcination twice until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 10%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0139] Step (4): Take 50g of Silicalite-1 molecular sieve, 6g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 10min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 400℃ for 2h.

[0140] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 600℃ for 2h.

[0141] Step (6): Take 50g of pure silicon β molecular sieve, 6g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain pure silicon β molecular sieve slurry, which is called the third slurry. Immerse the catalyst obtained after calcination in step (5) in the third slurry. After 30min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h. After that, put it in a muffle furnace and calcinate it at 500℃ for 2h to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0142] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and CeO2 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out. The materials of the inner hydrophobic layer and the outer hydrophobic layer are Silicalite-1 and pure silicon β molecular sieve, respectively, and the material of the middle hydrophilic layer is fumed silica.

[0143] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, namely CeO2, is 20%, the content of the Pt active component, calculated as Pt, is 5%, the loading of the VOCs catalytic oxidation catalyst is 10% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 17% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0144] Example 10

[0145] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0146] Step (1): Dissolve 20g of cerium nitrate hexahydrate (calculated as CeO2) and 5g of platinum nitrate (calculated as Pt) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0147] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0148] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 h. After that, put it in a muffle furnace and calcine it at 500°C for 4 h. Repeat the immersion, blowing, drying and calcination twice until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 10%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0149] Step (4): Take 50g of TS-2 molecular sieve, 6g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain TS-2 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 10min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 400℃ for 2h.

[0150] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 600℃ for 2h.

[0151] Step (6): Mix 50g of TS-1 molecular sieve, 6g of polyvinyl alcohol and 300g of water, and ball mill for 30min to obtain TS-1 molecular sieve slurry, which is referred to as the third slurry. Immerse the catalyst obtained after calcination in step (5) in the third slurry. After 30min, remove it and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h, and then place it in a muffle furnace and calcine at 500℃ for 2h to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0152] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and CeO2 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer, and an outer hydrophobic layer from the inside out. The materials of the inner hydrophobic layer and the outer hydrophobic layer are TS-2 and TS-1, respectively, and the material of the middle hydrophilic layer is fumed silica.

[0153] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, namely CeO2, is 20%, the content of the Pt active component, calculated as Pt, is 5%, the loading of the VOCs catalytic oxidation catalyst is 10% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 17% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0154] Example 11

[0155] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0156] Step (1): Dissolve 20g of cerium nitrate hexahydrate (calculated as CeO2) and 5g of platinum nitrate (calculated as Pt) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0157] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0158] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 h. After that, put it in a muffle furnace and calcine it at 500°C for 4 h. Repeat the immersion, blowing, drying and calcination twice until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 10%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0159] Step (4): Take 50g of TS-1 molecular sieve, 6g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain TS-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 10min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 400℃ for 2h.

[0160] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 600℃ for 2h.

[0161] Step (6): Mix 50g of pure silicon β molecular sieve, 6g of polyvinyl alcohol and 300g of water, and ball mill for 30min to obtain a pure silicon β molecular sieve slurry, which is referred to as the third slurry. Immerse the catalyst obtained after calcination in step (5) in the third slurry. After 30min, remove it and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h, and then place it in a muffle furnace and calcine at 500℃ for 2h to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0162] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and CeO2 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out. The materials of the inner hydrophobic layer and the outer hydrophobic layer are TS-1 molecular sieve and pure silicon β molecular sieve, respectively, and the material of the middle hydrophilic layer is fumed silica.

[0163] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, namely CeO2, is 20%, the content of the Pt active component, calculated as Pt, is 5%, the loading of the VOCs catalytic oxidation catalyst is 10% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 17% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0164] Example 12

[0165] This embodiment provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0166] Step (1): Dissolve 20g of cerium nitrate hexahydrate (calculated as CeO2) and 0.5g of platinum nitrate (calculated as Pt) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and put it into an oven at 120℃ to dry for 4 hours. Then take it out and grind it into powder, put it into a muffle furnace, and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0167] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0168] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 h. After that, put it in a muffle furnace and calcine it at 500°C for 4 h. Repeat the immersion, blowing, drying and calcination twice until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 10%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0169] Step (4): Take 50g of TS-1 molecular sieve and pure silicon β molecular sieve, 6g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain a slurry of TS-1 pure silicon and β molecular sieve, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 10min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 400℃ for 2h.

[0170] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 600℃ for 2h.

[0171] Step (6): Take 50g of Silicalite-1 molecular sieve and TS-2 molecular sieve, 6g of polyvinyl alcohol and 300g of water, mix them, and ball mill for 30min to obtain a mixed slurry of Silicalite-1 molecular sieve and TS-2 molecular sieve, which is referred to as the third slurry. Immerse the catalyst obtained after calcination in step (5) in the third slurry, take it out after 30min, and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h, and then put it in a muffle furnace and calcinate it at 500℃ for 2h to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0172] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this embodiment includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and CeO2 supported on the support. The water-resistant protective layer includes an inner hydrophobic layer, an intermediate hydrophilic layer and an outer hydrophobic layer from the inside out. The inner hydrophobic layer is made of TS-1 molecular sieve and pure silicon β molecular sieve, the outer hydrophobic layer is made of Silicalite-1 molecular sieve and TS-2 molecular sieve, and the intermediate hydrophilic layer is made of fumed silica.

[0173] Of which, based on the total weight of the carrier as 100%, the content of the auxiliary metal oxide, namely CeO2, is 20%, the content of the Pt active component, calculated as Pt, is 0.5%, the loading of the VOCs catalytic oxidation catalyst is 10% based on the total weight of the substrate as 100%, and the content of the water-resistant protective layer is 17% based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%.

[0174] Comparative Example 1

[0175] This comparative example provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0176] Step (1): Dissolve 10g of cerium nitrate hexahydrate (calculated as CeO2), 3g of lanthanum nitrate (calculated as La2O3), 1g of platinum nitrate (calculated as Pt), and 1.5g of palladium nitrate (calculated as Pd) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and dry it in an oven at 120℃ for 4 hours. Then take it out and grind it into powder. Place it in a muffle furnace and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0177] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0178] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110 °C for 4 h. After that, put it in a muffle furnace and calcine it at 500 °C for 4 h. Repeat the immersion, blowing, drying and calcination process 4 times until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 20%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0179] Step (4): Take 35g of Silicalite-1 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 600℃ for 2h.

[0180] Step (5): Take 20g of Silicalite-1 molecular sieve, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 500℃ for 2h.

[0181] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 600°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0182] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this comparative example includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and Pd active components (including Pd and its oxides) supported on the support, as well as CeO2 and La2O3. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophobic layer, and an outer hydrophobic layer from the inside out, wherein the material of the inner hydrophobic layer, the middle hydrophobic layer, and the outer hydrophobic layer is Silicalite-1 molecular sieve.

[0183] Specifically, based on the total weight of the carrier (100%), the contents of the auxiliary metal oxides, namely La2O3 and CeO2, are 3% and 10%, respectively; the contents of the Pd active component (calculated as Pd) and the Pt active component (calculated as Pt) are 1.5% and 1%, respectively; based on the total weight of the substrate (100%), the loading of the VOCs catalytic oxidation catalyst is 20%; and based on the total weight of the monolithic VOCs catalytic oxidation catalyst (100%), the content of the water-resistant protective layer is 10.7%.

[0184] Comparative Example 2

[0185] This comparative example provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0186] Step (1): Dissolve 10g of cerium nitrate hexahydrate (calculated as CeO2), 3g of lanthanum nitrate (calculated as La2O3), 1g of platinum nitrate (calculated as Pt), and 1.5g of palladium nitrate (calculated as Pd) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and dry it in an oven at 120℃ for 4 hours. Then take it out and grind it into powder. Place it in a muffle furnace and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0187] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0188] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110 °C for 4 h. After that, put it in a muffle furnace and calcine it at 500 °C for 4 h. Repeat the immersion, blowing, drying and calcination process 4 times until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 20%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0189] Step (4): Take 65g of Silicalite-1 molecular sieve, 2g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain Silicalite-1 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcine at 600℃ for 2h.

[0190] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 500℃ for 2h.

[0191] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 600°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0192] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this comparative example includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and Pd active components (including Pd and its oxides) supported on the support, as well as CeO2 and La2O3. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer and an outer hydrophobic layer from the inside out, wherein the inner hydrophobic layer and the outer hydrophobic layer are both made of Silicalite-1 molecular sieve, and the middle hydrophilic layer is made of fumed silica.

[0193] Specifically, based on the total weight of the carrier (100%), the contents of the auxiliary metal oxides, namely La2O3 and CeO2, are 3% and 10%, respectively; the contents of the Pd active component (calculated as Pd) and the Pt active component (calculated as Pt) are 1.5% and 1%, respectively; based on the total weight of the substrate (100%), the loading of the VOCs catalytic oxidation catalyst is 20%; and based on the total weight of the monolithic VOCs catalytic oxidation catalyst (100%), the content of the water-resistant protective layer is 22%.

[0194] Comparative Example 3

[0195] This comparative example provides a water-resistant monolithic VOCs catalytic oxidation catalyst, which is prepared by a method including the following specific steps:

[0196] Step (1): Dissolve 10g of cerium nitrate hexahydrate (calculated as CeO2), 3g of lanthanum nitrate (calculated as La2O3), 1g of platinum nitrate (calculated as Pt), and 1.5g of palladium nitrate (calculated as Pd) in 50g of water. After complete dissolution, pour the resulting impregnation solution into 100g of γ-alumina and stir evenly for impregnation. After impregnation for 2 hours, take out the impregnation product and dry it in an oven at 120℃ for 4 hours. Then take it out and grind it into powder. Place it in a muffle furnace and calcine it at 550℃ for 2 hours to obtain a powdered VOCs catalytic oxidation catalyst.

[0197] Step (2): Place 100g of the obtained powdered VOCs catalytic oxidation catalyst, 10g of pseudoboehmite, 7.5g of concentrated nitric acid, 250g of water, and 1g of polyvinyl alcohol into a ball mill jar and add 300g of grinding balls. After ball milling for 2 hours, the catalyst slurry is obtained.

[0198] Step (3): Immerse the acid-treated cordierite honeycomb ceramic (21.6 g in mass) in the catalyst slurry. After 10 min, remove it and blow the residual slurry in the pores of the cordierite honeycomb ceramic with compressed air to avoid clogging the pores. Then dry it at 110 °C for 4 h. After that, put it in a muffle furnace and calcine it at 500 °C for 4 h. Repeat the immersion, blowing, drying and calcination process 4 times until the total weight of the cordierite honeycomb ceramic is 100% and the loading of the VOCs catalytic oxidation catalyst is 20%, thus obtaining the monolithic VOCs catalytic oxidation catalyst.

[0199] Step (4): Take 35g of ordinary ZSM-5 molecular sieve with Si / Al (molar ratio) of 100, 2g of polyvinyl alcohol and 300g of water, mix them, and ball mill for 30min to obtain ZSM-5 molecular sieve slurry, which is called the first slurry. Immerse the obtained monolithic VOCs catalytic oxidation catalyst in the first slurry. After 15min, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110℃ for 4h, and then put it in a muffle furnace and calcine at 600℃ for 2h.

[0200] Step (5): Take 20g of fumed silica, 3g of polyvinyl alcohol and 300g of water and mix them. Ball mill for 30min to obtain fumed silica slurry, which is called the second slurry. Immerse the catalyst obtained after calcination in step (4) in the second slurry. Take it out after 10min and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic channel with compressed air to avoid clogging the channel. Then dry it at 110℃ for 4h and then put it in a muffle furnace and calcin at 500℃ for 2h.

[0201] Step (6): Immerse the catalyst obtained after calcination in step (5) in the first slurry. After 30 minutes, take it out and blow the slurry residue on the inner surface of the cordierite honeycomb ceramic pores with compressed air to avoid clogging the pores. Then dry it at 110°C for 4 hours and then put it in a muffle furnace and calcinate it at 600°C for 2 hours to obtain the water-resistant monolithic VOCs catalytic oxidation catalyst.

[0202] The water-resistant monolithic VOCs catalytic oxidation catalyst obtained in this comparative example includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a cordierite honeycomb ceramic substrate with open channels and a VOCs catalytic oxidation catalyst, wherein the VOCs catalytic oxidation catalyst is supported on the inner and outer surfaces of the substrate, and the water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a γ-alumina support and Pt active components (including Pt and its oxides) and Pd active components (including Pd and its oxides) supported on the support, as well as CeO2 and La2O3. The water-resistant protective layer includes an inner hydrophobic layer, a middle hydrophilic layer, and an outer hydrophobic layer from the inside out. The inner hydrophobic layer and the outer hydrophobic layer are both made of ZSM-5 molecular sieve, and the middle hydrophilic layer is made of fumed silica.

[0203] Specifically, based on the total weight of the carrier (100%), the contents of the auxiliary metal oxides, namely La2O3 and CeO2, are 3% and 10%, respectively; the contents of the Pd active component (calculated as Pd) and the Pt active component (calculated as Pt) are 1.5% and 1%, respectively; based on the total weight of the substrate (100%), the loading of the VOCs catalytic oxidation catalyst is 20%; and based on the total weight of the monolithic VOCs catalytic oxidation catalyst (100%), the use of ordinary ZSM-5 molecular sieve instead of pure silicon molecular sieve, and the content of the water-resistant protective layer is 10.7%.

[0204] Catalyst performance evaluation example 1

[0205] In this embodiment, the catalytic activity of the monolithic VOCs catalytic oxidation catalysts (catalyst samples without a water-resistant protective layer in Examples 1-8, denoted as DC1-DC8), the water-resistant monolithic VOCs catalytic oxidation catalysts (denoted as C1-C12), and the water-resistant monolithic VOCs catalytic oxidation catalysts (denoted as D1C7-D3C7) provided in Examples 1-3 were tested on a fixed-bed catalytic reactor manufactured by Bolumin (Beijing Technology) Co., Ltd. Specifically, the tests included:

[0206] Three identical catalyst samples (each measuring 16×16×50mm) were loaded into a square reactor with a side length of 18mm in the aforementioned fixed-bed catalytic reactor. Using propane as the target, propane (a product of Dalian Date Gas Co., Ltd.) was mixed with air and water vapor to form a propane content of 500mg / m³. 3 A mixed feed gas with a water content of 10 wt% was used to make the mixed gas flow at a rate of 16000 h⁻¹. -1The gas enters the fixed-bed catalytic reactor at a fixed space velocity. Under programmed temperature rise, the catalyst catalytically oxidizes propane. The propane content in the mixed feed gas and tail gas is detected by an Agilent Technologies 8860 gas chromatograph. The propane removal rate at different temperatures is calculated. The catalyst activity is measured by the temperature at which 98% of the propane is converted (T98). The lower the T98, the higher the catalyst activity.

[0207] In this embodiment, the T98 values ​​of DC1-DC8 and C1-C8 are shown in Table 1 below, the T98 values ​​of C2, DC2 and C9-C12 are shown in Table 2 below, and the T98 values ​​of C7, DC7 and D1C7-D3C7 are shown in Table 3 below.

[0208] Table 1

[0209] catalyst T98 / ℃ C1 280 DC1 336 C2 334 DC2 363 C3 357 DC3 366 C4 321 DC4 342 C5 328 DC5 342 C6 333 DC6 347 C7 254 DC7 297 C8 296 DC8 297

[0210] Table 2

[0211] catalyst T98 / ℃ C2 334 DC2 363 C9 348 C10 337 C11 350 C12 430

[0212] Table 3

[0213] catalyst T98 / ℃ C7 254 DC7 297 D1C7 280 D2C7 305 D3C7 342

[0214] As can be seen from Table 1, compared with the monolithic VOCs catalytic oxidation catalyst samples without a water-resistant protective layer provided in each embodiment, the water-resistant monolithic VOCs catalytic oxidation catalyst provided in the corresponding embodiment has a lower T98. This indicates that setting a water-resistant protective layer on the monolithic VOCs catalytic oxidation catalyst in the embodiments of the present invention can improve the catalytic activity of the catalyst for propane under high water content conditions.

[0215] As shown in Table 2, compared to C2 prepared using Silicalite-1 molecular sieves for both the inner and outer hydrophobic layers in Example 2, the T98 values ​​of C2 and C11 prepared using pure silica β molecular sieves for the outer hydrophobic layers in Examples 9 and 11 are significantly higher. This is mainly because the pores of pure silica β molecular sieves are relatively large, resulting in relatively poor performance in preventing water vapor from entering. The T98 of C10 prepared in Example 10 is not significantly different from that in Example 2, because TS-1, TS-2, and Silicalite-1 molecular sieves all have MFI topologies and similar pore sizes. The T98 of C12 provided in Example 12 is higher, at 430°C, mainly because the content of noble metal active components in the catalyst is lower.

[0216] As can be seen from Table 3, compared with D1C7 provided by Comparative Example 1 without an intermediate hydrophilic layer, the water resistance activity of C7 provided by Example 7 is significantly improved. This indicates that the introduction of an intermediate hydrophilic layer helps to improve the water resistance activity of the catalyst. Compared with DC7 without a water-resistant protective layer, D2C7 has a water-resistant protective layer content of more than 20%, but its T98 temperature actually increases. This indicates that the water-resistant protective layer content cannot be too high, otherwise it will hinder the contact between propane and the internal catalyst, resulting in a decrease in activity. Comparative Example 3 uses ordinary ZSM-5 molecular sieve to prepare D3C7. Not only does it fail to improve the water resistance of the catalyst, but because ordinary ZSM-5 molecular sieve adsorbs more water vapor and contacts the catalyst, the catalyst activity is significantly lower than that of DC-7 without a water-resistant protective layer.

[0217] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A water-resistant monolithic VOCs catalytic oxidation catalyst, characterized in that, The water-resistant monolithic VOCs catalytic oxidation catalyst includes a monolithic VOCs catalytic oxidation catalyst and a water-resistant protective layer. The monolithic VOCs catalytic oxidation catalyst includes a substrate with open channels and VOCs catalytic oxidation catalyst supported on the inner and outer surfaces of the substrate. The water-resistant protective layer covers the VOCs catalytic oxidation catalyst. The VOCs catalytic oxidation catalyst includes a porous metal oxide support and a noble metal active component supported on the support. The water-resistant protective layer comprises, from the inside out, an inner hydrophobic layer, an intermediate hydrophilic layer, and an outer hydrophobic layer. The materials of the inner hydrophobic layer and the outer hydrophobic layer include pure silicon molecular sieves and / or titanium silicon molecular sieves, and the material of the intermediate hydrophilic layer includes fumed silica. Based on the total weight of the monolithic VOCs catalytic oxidation catalyst as 100%, the content of the water-resistant protective layer is 1%-20%.

2. The catalyst according to claim 1, characterized in that, The VOCs catalytic oxidation catalyst also includes an auxiliary metal oxide, which is supported on the support. The content of the auxiliary metal oxide is 0.5%-20% based on the total weight of the support (100%).

3. The catalyst according to claim 2, characterized in that, The auxiliary metal oxide includes one or a combination of several of CeO2, MnO, CuO and La2O3.

4. The catalyst according to claim 1, characterized in that, The precious metals include one or a combination of Pt, Pd and Rh.

5. The catalyst according to claim 1 or 4, characterized in that, Based on the total weight of the carrier (100%), the content of the precious metal active component, calculated as precious metal, is 0.5%-5%.

6. The catalyst according to any one of claims 1-4, characterized in that, The porous metal oxide support includes one or a combination of several of TiO2, SiO2, CeO2, ZrO2, cerium-zirconium solid solution and γ-Al2O3.

7. The catalyst according to any one of claims 1-4, characterized in that, Based on the total weight of the substrate as 100%, the loading of the VOCs catalytic oxidation catalyst is 10%-20%.

8. The catalyst according to any one of claims 1-4, characterized in that, The pure silicon molecular sieve includes one or a combination of pure silicon MCM-41 molecular sieve, pure silicon β molecular sieve and Silicalite-1, and the titanium silicon molecular sieve includes TS-1 and / or TS-2.

9. The catalyst according to any one of claims 1-4, characterized in that, The substrate includes cordierite honeycomb ceramics, silicon carbide honeycomb ceramics, or metal honeycomb carriers.

10. A method for preparing the water-resistant monolithic VOCs catalytic oxidation catalyst according to any one of claims 1-9, characterized in that, The preparation method includes: Step (1): The impregnation solution containing the noble metal precursor and the porous metal oxide support are mixed evenly and then impregnated. The impregnated product is then dried and calcined to obtain the VOCs catalytic oxidation catalyst. Step (2): Mix the VOCs catalytic oxidation catalyst, binder, peptide, dispersant and water and ball mill to form a catalyst slurry; Step (3): Immerse the substrate in the catalyst slurry, remove the substrate, dry and calcine it to obtain an integral VOCs catalytic oxidation catalyst; Step (4): Mix pure silicon molecular sieve and / or titanium silicon molecular sieve, dispersant and water and ball mill to form molecular sieve slurry. Immerse the monolithic VOCs catalytic oxidation catalyst in the molecular sieve slurry. Take out the monolithic VOCs catalytic oxidation catalyst and dry and calcine it. Step (5): Mix fumed silica, dispersant and water and ball mill to form fumed silica slurry. Immerse the product obtained after calcination in step (4) in fumed silica slurry. Take out the product and dry and calcinate it. Step (6): Mix pure silicon molecular sieve and / or titanium silicon molecular sieve, dispersant and water and ball mill to form molecular sieve slurry. Immerse the product obtained after calcination in step (5) in molecular sieve slurry. Take out the product and dry and calcinate it to obtain water-resistant monolithic VOCs catalytic oxidation catalyst.

11. The preparation method according to claim 10, characterized in that, When the VOCs catalytic oxidation catalyst also includes an auxiliary metal oxide, in step (1), the impregnation liquid containing the noble metal precursor and the auxiliary metal precursor and the porous metal oxide support are mixed evenly and then simultaneously impregnated. The impregnated product is dried and calcined to obtain the VOCs catalytic oxidation catalyst. Alternatively, the impregnation solution containing the auxiliary metal precursor and the porous metal oxide support can be mixed evenly and then impregnated, dried and calcined, and then mixed evenly with the impregnation solution containing the noble metal precursor and impregnated, and then dried and calcined to obtain the VOCs catalytic oxidation catalyst. Alternatively, the impregnation solution containing the noble metal precursor and the porous metal oxide support can be mixed evenly and then impregnated, dried and calcined, and then mixed evenly with the impregnation solution containing the auxiliary metal precursor and impregnated, and then dried and calcined to obtain the VOCs catalytic oxidation catalyst.

12. The preparation method according to claim 11, characterized in that, Additive metal precursors include nitrates of additive metals.

13. The preparation method according to claim 10 or 11, characterized in that, Precious metal precursors include nitrates of precious metals.

14. The preparation method according to claim 10 or 11, characterized in that, The dispersant includes polyvinyl alcohol and / or polyvinylpyrrolidone.

15. The preparation method according to claim 10 or 11, characterized in that, In steps (1), (3) to (6), the roasting temperature is 400-750℃.

16. The application of the water-resistant monolithic VOCs catalytic oxidation catalyst according to any one of claims 1-9 in the catalytic oxidation of VOCs.