Integral catalyst body, its preparation method and application

Abstract

The present invention discloses an integral catalyst body, its preparation method and application, which solve the technical problems of difficult coating, poor coating stability and poor low-temperature catalytic activity in the prior art. The integral catalyst body includes a support skeleton and layers sequentially loaded on the surface of the support skeleton: a transition layer, which is formed by coating and drying a transition slurry including a first binder, a curing agent and a modifier; a first catalytic layer, which is formed by coating and drying a first catalytic slurry including a second binder, activated carbon and a first active metal precursor; and a second catalytic layer, which is formed by coating and drying a second catalytic slurry including a second binder, activated carbon and a second active metal precursor.

Description

Technical Field

[0001] The present invention relates to the technical field of monolithic catalysts and purification of volatile organic compounds (VOCs), and more particularly, to a monolithic catalyst green body, a preparation method thereof, and an application thereof. Background Art

[0002] In the tail-end treatment technology of VOCs, the catalytic oxidation method has the advantages of high purification efficiency and strong adaptability, and has been widely used in industry. However, the vast majority of VOCs catalysts on the market are noble metal-based at present. The noble metals are expensive and are prone to sintering in high-temperature environments, and their low-temperature activity is not very ideal. Therefore, it is particularly important to develop a VOCs catalyst with low cost, excellent low-temperature catalytic activity, and applicable working conditions.

[0003] If base metals are used instead of noble metals, the cost can be greatly reduced. Moreover, traditional powder or granular VOCs catalysts are restricted in industrial applications due to large pressure loss, pulverization and blockage, etc. The monolithic catalyst can well adapt to the working conditions at the tail end of VOCs.

[0004] Carbon-based materials have a rich pore structure and can provide a large number of adsorption and active sites, and have always been considered as ideal carrier materials for base metals in low-temperature VOCs catalysts. Coating base metals and carbon-based materials onto a porous skeleton to form a monolithic catalyst can meet the requirements of VOCs catalysts in terms of cost, low-temperature activity, working condition adaptability, etc.

[0005] However, carbon-based materials are difficult to coat, and the bonding force between the coating and the porous skeleton is weak, resulting in low structural strength and poor coating stability of the formed coating, and it is prone to pulverization, and even structural collapse and shedding in industrial applications. Therefore, it is very difficult to prepare a monolithic catalyst, and the low-temperature catalytic activity is still not ideal. Summary of the Invention

[0006] The main object of the present invention is to provide a monolithic catalyst green body, a preparation method thereof, and an application thereof, so as to solve the technical problems of difficult coating of carbon-based materials, poor coating stability, and poor low-temperature catalytic activity in the prior art.

[0007] To achieve the above object, according to the first aspect of the present invention, a monolithic catalyst green body is provided, and the technical solution is as follows:

[0008] The monolithic catalyst green body includes a support skeleton and the following sequentially loaded on the surface of the support skeleton:

[0009] A transition layer, which is formed by coating and drying a transition slurry including a first binder, a curing agent, and a modifier;

[0010] The first catalytic layer is formed by coating and drying a first catalytic slurry comprising a second binder, activated carbon, and a first active metal precursor;

[0011] The second catalytic layer is formed by coating and drying a second catalytic slurry comprising a second binder, activated carbon, and a second active metal precursor.

[0012] As a further improvement of the first aspect of the present invention: the support skeleton is cordierite; the first binder is any several of silica sol, alumina sol, zirconia sol, and clay; the curing agent is any several of glass fiber, silica powder, asphalt, and kaolin; the modifier is any several of citric acid, oxalic acid, nitric acid, hydrochloric acid, and acetic acid; the second binder is any several of silica sol, alumina sol, coal tar, asphalt, and clay; the first active metal precursor and / or the second active metal precursor contains at least two metal salts, and the metal types in the first active metal precursor and the second active metal precursor are completely different or partially the same.

[0013] As a further improvement of the first aspect of the present invention: the second active metal precursor has more metal types than the first active metal precursor; and / or, the molar content of the second active metal precursor in the second catalytic layer is greater than the molar content of the first active metal precursor in the first catalytic layer.

[0014] To achieve the above object, according to the second aspect of the present invention, a method for preparing a monolithic catalyst green body is provided, and the technical solution is as follows:

[0015] The method for preparing a monolithic catalyst green body includes the following steps:

[0016] (1) Prepare a transition slurry; then coat the transition slurry onto the support skeleton along a first direction, and then dry to form a transition layer;

[0017] (2) Prepare a first catalytic slurry; then coat the first catalytic slurry onto the transition layer along a second direction, and then dry to form a first catalytic layer;

[0018] (2) Prepare a second catalytic slurry; then coat the second catalytic slurry onto the first catalytic layer along a third direction, and then dry to form a second catalytic layer, thus obtaining the monolithic catalyst green body.

[0019] As a further improvement of the second aspect of the present invention:

[0020] In step (1), 20 - 35 g of the first binder, 2 - 4 g of the curing agent, 4 - 6 mL of the modifier, and 2 - 4 mL of deionized water are ball-milled and dispersed to obtain the transition slurry, and the dry loading of the transition layer is 32 - 38 g / L;

[0021] In step (2), 25-35 g of activated carbon, 8-20 mL of water, 20-24 mmol of the first active metal precursor, and 15-25 g of the second binder are ball-milled and dispersed to obtain the first catalytic slurry, and the dry loading of the first catalytic layer is 20-50 g / L;

[0022] In step (3), 25-35 g of activated carbon, 8-20 mL of water, 25-40 mmol of the second active metal precursor, and 15-25 g of the second binder are ball-milled and dispersed to obtain the second catalytic slurry, and the dry loading of the second catalytic layer is 40-70 g / L.

[0023] As a further improvement in the second aspect of the present invention:

[0024] The drying in step (1) and step (2) is carried out at 65-75 °C for 8-12 minutes;

[0025] The drying in step (3) is divided into three stages. First, it is dried at 65-75 °C for 8-16 hours, then at 80-90 °C for 8-16 hours, and finally at 100-120 °C under airtight conditions for 8-16 hours.

[0026] As a further improvement in the second aspect of the present invention: The first direction and the second direction are not the same, and / or the second direction and the third direction are not the same.

[0027] To achieve the above object, according to the third aspect of the present invention, a method for preparing a monolithic catalyst is provided, and the technical solution is as follows:

[0028] A method for preparing a monolithic catalyst, comprising the following steps:

[0029] Obtain the monolithic catalyst green body described in the first aspect above; or obtain the monolithic catalyst green body prepared by the preparation method described in the second aspect above;

[0030] Perform a calcination treatment on the monolithic catalyst green body to obtain the monolithic catalyst.

[0031] As a further improvement in the third aspect of the present invention: Place the dried monolithic catalyst green body in a porcelain container with an open upper end, fill the void part with fine sand, and place it in an inert gas atmosphere furnace for calcination.

[0032] As a further improvement in the third aspect of the present invention: The calcination treatment is carried out in a nitrogen atmosphere, the calcination temperature is 400-500 °C, and the calcination duration is 2-4 hours.

[0033] To achieve the above object, according to the fourth aspect of the present invention, a monolithic catalyst is provided, and the technical solution is as follows:

[0034] The monolithic catalyst is prepared by the preparation method described in the third aspect above.

[0035] In order to achieve the above object, according to the fifth aspect of the present invention, a method for purifying VOCs is provided, and the technical solution is as follows:

[0036] The method for purifying VOCs uses the monolithic catalyst described in the fourth aspect above to adsorb and catalytically oxidize VOCs at low temperature for decomposition.

[0037] The present invention has the following advantages:

[0038] First of all, the provided transition layer can generate a porous anchoring special structure, which can well embed the porous skeleton and the carbon-containing catalytic layer firmly together, and has an obvious promoting effect on the adhesion stability of the carbon-containing catalytic layer, and can significantly reduce the pulverization rate and the shedding rate. It has been verified that the shedding rate of the catalytic layer of the monolithic catalyst provided with a transition layer is as low as 2.05%, which is reduced by more than 25% compared with the shedding rate of the catalytic layer of the monolithic catalyst without a transition layer.

[0039] Secondly, the carbon-containing catalytic layer includes a first catalytic layer and a second catalytic layer, and a synergistic catalytic effect is generated between the first catalytic layer and the second catalytic layer, which can promote the catalytic effect, especially the catalytic oxidation of VOCs, and improve the low-temperature catalytic performance. It has been verified that the T90 (temperature when the conversion rate reaches 90%) of the monolithic catalyst of the present invention for catalytic combustion and decomposition of toluene is as low as 189°C, showing excellent low-temperature catalytic activity.

[0040] The following further describes the present invention in conjunction with the drawings and specific embodiments. The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings forming a part of the present invention are used to assist in understanding the present invention. The content provided in the drawings and the related descriptions in the present invention can be used to explain the present invention, but do not constitute an improper limitation to the present invention. In the drawings:

[0042] Figure 1 It is a schematic structural diagram of the catalytic activity test device of the catalyst of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The following clearly and completely describes the present invention in conjunction with the drawings. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the drawings, it should be particularly noted that:

[0044] In the present invention, the technical solutions and technical features provided in each part including the following description can be combined with each other without conflict.

[0045] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0046] Regarding the terms and units in the present invention. The terms "comprising", "having" and any variations thereof in the specification, claims and relevant parts of the present invention are intended to cover non-exclusive inclusion.

[0047] Example 1

[0048] The preparation method of the monolithic catalyst in this embodiment is specifically as follows:

[0049] (1) Prepare the transition slurry: Weigh 30 g of silica sol with a mass fraction of 17%, 3 g of glass fiber powder, 5 mL of citric acid solution with a mass fraction of 20% and 3 mL of deionized water, mix them, and obtain the transition layer slurry after ball milling and dispersing for 10 minutes.

[0050] (2) Prepare the first catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the first active metal precursor solution (dissolving 3.25 g of cerium nitrate (Ce(NO3)3·6H2O) and 4.45 g of cobalt nitrate (Co(NO3)2·6H2O), totaling 22.8 mmol)), mix and ball mill for 10 minutes, then add 10 g of coal tar and 5 g of asphalt, mix and ball mill for 10 minutes to obtain the first catalytic slurry.

[0051] (3) Prepare the second catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the second active metal precursor solution (dissolving 3.31 g of manganese acetate (C4H6MnO4), 3.25 g of cerium nitrate and 2.96 g of cobalt nitrate, totaling 36.8 mmol)), mix and ball mill for 15 minutes, then add 10 g of coal tar and 5 g of asphalt, mix and ball mill for 15 minutes to obtain the second catalytic slurry.

[0052] (4) First, use the dip coating method to coat the transition slurry along the first direction onto the cordierite with a mesh number of 200 cell / in 2 , control the dry loading to be 32 - 38 g / L (that is, 32 - 38 g of the dry transition layer material is loaded per liter of cordierite), and dry at 70 °C for 10 minutes to form the transition layer;

[0053] Next, continue to use the dip - coating method to coat the first catalytic slurry onto the cordierite containing the transition layer along the second direction, where the second direction is opposite to the first direction. Control the dry loading to be 32 - 38 g / L, and dry at 70 °C for 10 minutes to form the first catalytic layer.

[0054] Next, continue to use the dip - coating method to coat the second catalytic slurry onto the cordierite containing the first catalytic layer along the third direction, where the third direction is opposite to the second direction (the third direction is the same as the first direction). Control the dry loading to be 47 - 53 g / L, and then dry at 70 °C for 12 hours, 90 °C for 12 hours, and 120 °C under air - isolated conditions for 12 hours respectively to form the second catalytic layer, obtaining the monolithic catalyst blank.

[0055] (5) Place the monolithic catalyst blank in a porcelain container with an open upper end, fill the void part with fine sand, and calcine at 450 °C for 3 h under a nitrogen atmosphere to obtain the monolithic carbon - based catalyst, marked as S1.

[0056] It is verified that the specific surface area of the catalytic coating (including the first catalytic layer and the second catalytic layer) in S1 is 1306 m 2 / g, the T90 of S1 for catalyzing toluene is 189 °C, and the coating shedding rate obtained from the coating stability test is 2.25%.

[0057] Example 2

[0058] Compared with Example 1, the difference in the preparation method of the monolithic catalyst in this example is:

[0059] (1) Prepare the transition slurry: Weigh 20 g of silica sol with a mass fraction of 17%, 5 g of glass fiber powder, 5 mL of citric acid solution with a mass fraction of 20%, and 3 mL of deionized water, mix them, and obtain the transition layer slurry after ball - milling and dispersing for 10 minutes.

[0060] (2) Prepare the first catalytic slurry: Weigh 30 g of activated carbon powder and 10 mL of the first active metal precursor solution (dissolving 3.25 g of cerium nitrate and 4.45 g of cobalt nitrate, totaling 22.8 mmol), mix and ball - mill for 10 minutes, then add 10 g of coal tar and 5 g of pitch, mix and ball - mill for 10 minutes to obtain the first catalytic slurry.

[0061] (3) Prepare the second catalytic slurry: Weigh 30 g of activated carbon powder and 10 mL of the second active metal precursor solution (dissolving 3.31 g of manganese acetate, 3.25 g of cerium nitrate, and 2.96 g of cobalt nitrate, totaling 36.8 mmol), mix and ball - mill for 15 minutes, then add 10 g of coal tar and 5 g of pitch, mix and ball - mill for 15 minutes to obtain the second catalytic slurry.

[0062] (4) The dry loading of the first catalytic layer is 32 - 38 g / L, and the dry loading of the second catalytic layer is 57 - 63 g / L.

[0063] The obtained monolithic carbon-based catalyst is labeled as S2.

[0064] It is verified that the specific surface area of the catalytic layer in S2 is 1052 m 2 / g, the T90 of S2 for catalyzing toluene is 210 °C, and the coating shedding rate is 2.38%.

[0065] Example 3

[0066] Compared with Example 1, the difference in the preparation method of the monolithic catalyst in this example is:

[0067] (1) Prepare the transition slurry: Weigh 30 g of aluminum sol with a mass fraction of 17%, 3 g of glass fiber powder, 5 mL of citric acid solution with a mass fraction of 20%, and 3 mL of deionized water, mix them, and obtain the transition layer slurry after ball milling and dispersing for 10 minutes.

[0068] (2) Prepare the first catalytic slurry: Weigh 30 g of activated carbon powder and 10 mL of the first active metal precursor solution (dissolving 2.79 g of cerium nitrate and 4.45 g of cobalt nitrate, totaling 21.7 mmol), mix and ball mill for 15 minutes, then add 20 g of aluminum sol with a mass fraction of 17% and mix and ball mill for 10 minutes to obtain the first catalytic slurry.

[0069] (3) Prepare the second catalytic slurry: Weigh 30 g of activated carbon powder and 10 mL of the second active metal precursor solution (dissolving 2.83 g of manganese acetate, 3.25 g of cerium nitrate, and 3.7 g of cobalt nitrate, totaling 36.6 mmol), mix and ball mill for 10 minutes, then add 20 g of aluminum sol with a mass fraction of 17% and mix and ball mill for 10 minutes to obtain the second catalytic slurry.

[0070] (4) The dry loadings of both the first catalytic layer and the second catalytic layer are 37 - 43 g / L.

[0071] The obtained monolithic carbon-based catalyst is labeled as S3.

[0072] It is verified that the specific surface area of the catalytic layer in S3 is 1327 m 2 / g, the T90 of S3 for catalyzing toluene is 214 °C, and the coating shedding rate is 2.05%.

[0073] Comparative Example 1

[0074] Compared with Example 1, the difference in this comparative example is: The molar content of the second active metal precursor in the second catalytic layer is less than that of the first active metal precursor in the first catalytic layer. Specifically:

[0075] Prepare the first catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the first active metal precursor solution (dissolving 3.25 g of cerium nitrate and 6.78 g of cobalt nitrate, totaling 30.8 mmol), mix and ball-mill for 10 minutes. Then add 10 g of coal tar and 5 g of pitch, mix and ball-mill for 10 minutes to obtain the first catalytic slurry.

[0076] Prepare the second catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the second active metal precursor solution (dissolving 1.7 g of manganese acetate, 2.25 g of cerium nitrate, and 3.45 g of cobalt nitrate, totaling 26.5 mmol), mix and ball-mill for 15 minutes. Then add 10 g of coal tar and 5 g of pitch, mix and ball-mill for 15 minutes to obtain the second catalytic slurry.

[0077] The obtained monolithic carbon-based catalyst is labeled as B1.

[0078] Verified, the specific surface area and coating shedding rate of B1 and S1 have little difference, but the T90 of B1 rises to 265 °C, indicating that the molar content of the active metal on the surface layer has a more obvious effect on the catalytic activity. To a certain extent, increasing the molar content of the active metal on the surface layer and reducing the molar content of the active metal on the inner layer can effectively reduce the raw material input cost.

[0079] Comparative Example 2

[0080] Compared with Example 1, the difference of this comparative example is that both the first active metal precursor and the second active metal precursor contain two metal salts, but the types of the two metal salts are different, specifically:

[0081] Prepare the first catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the first active metal precursor solution (dissolving 3.25 g of cerium nitrate and 4.45 g of cobalt nitrate, totaling 22.8 mmol), mix and ball-mill for 10 minutes. Then add 10 g of coal tar and 5 g of pitch, mix and ball-mill for 10 minutes to obtain the first catalytic slurry.

[0082] Prepare the second catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the second active metal precursor solution (dissolving 3.25 g of cerium nitrate and 5.07 g of manganese acetate, totaling 36.8 mmol), mix and ball-mill for 15 minutes. Then add 10 g of coal tar and 5 g of pitch, mix and ball-mill for 15 minutes to obtain the second catalytic slurry.

[0083] The obtained monolithic carbon-based catalyst is labeled as B2.

[0084] It has been verified that the specific surface areas and coating shedding rates of B2 and S1 have little difference, but the T90 of B2 has increased to 228 °C, indicating that the type of active metal on the surface layer has a more obvious effect on the catalytic activity, and to a certain extent, enriching the types of active metals on the surface layer and reducing the types of active metals in the inner layer can effectively reduce the raw material input cost.

[0085] Comparative Example 3

[0086] Compared with Comparative Example 2, the difference of this comparative example is: the first active metal precursor and the second active metal precursor contain two identical metal salts, specifically:

[0087] Prepare the first catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the first active metal precursor solution (dissolving 3.25 g of cerium nitrate and 4.45 g of cobalt nitrate, totaling 22.8 mmol), mix and ball-mill for 10 minutes, then add 10 g of coal tar and 5 g of pitch, mix and ball-mill for 10 minutes to obtain the first catalytic slurry.

[0088] Prepare the second catalytic slurry: Weigh 30 g of activated carbon powder and 15 mL of the second active metal precursor solution (dissolving 3.25 g of cerium nitrate and 8.53 g of cobalt nitrate, totaling 36.8 mmol), mix and ball-mill for 15 minutes, then add 10 g of coal tar and 5 g of pitch, mix and ball-mill for 15 minutes to obtain the second catalytic slurry.

[0089] The obtained monolithic carbon-based catalyst is labeled as B3.

[0090] It has been verified that the specific surface areas and coating shedding rates of B3 and S1 have little difference, but the T90 of B3 has increased to 241 °C, indicating that there is a synergistic effect between the first catalytic layer and the second catalytic layer with different active metal types, which helps to improve the catalytic activity.

[0091] Comparative Example 4

[0092] Compared with Example 1, the difference of this comparative example is: it only contains one catalytic layer, specifically:

[0093] Prepare the catalytic slurry: Weigh 60 g of activated carbon powder and 30 mL of the active metal precursor solution (dissolving 6.5 g of cerium nitrate, 7.41 g of cobalt nitrate and 3.31 g of manganese acetate), mix and ball-mill for 10 minutes, then add 20 g of coal tar and 10 g of pitch, mix and ball-mill for 10 minutes to obtain the catalytic slurry.

[0094] Coat the catalytic slurry along the second direction onto the cordierite containing the transition layer, control the dry loading to be 77 - 83 g / L, and then dry at 70 °C for 12 hours, 90 °C for 12 hours, and dry in an airtight manner at 120 °C for 12 hours to form the catalytic layer, obtaining the monolithic catalyst blank.

[0095] The obtained monolithic carbon-based catalyst is labeled as B4.

[0096] It has been verified that the specific surface areas of B4 and S1 have little difference, but the coating shedding rate of B4 increases to 3.5%, and the T90 increases to 261 °C, indicating that a single catalytic layer will slightly reduce the coating stability, and the catalytic activity of the single catalytic coating is poor. By applying the two catalytic layers step by step and in the reverse direction, the catalytic activity can be improved and the coating shedding rate of the catalytic layer can be reduced.

[0097] Comparative Example 5

[0098] Compared with Example 1, the difference of this comparative example is that the first direction, the second direction and the third direction are all the same. The obtained monolithic carbon-based catalyst is labeled as B5.

[0099] It has been verified that the specific surface areas and catalytic activities of B5 and S1 have little difference, but the coating shedding rate of B5 increases to 2.8%, indicating that the reverse coating of the catalytic layer can reduce the coating shedding rate to a certain extent.

[0100] Comparative Example 6

[0101] Compared with Example 1, the difference of this comparative example is that the transition slurry does not contain a modifier. The obtained monolithic carbon-based catalyst is labeled as B6.

[0102] It has been verified that the specific surface areas and catalytic activities of B6 and S1 have little difference, but the coating shedding rate of B6 increases to 3.9%, indicating that the modifier can improve the connection strength of the transition layer, thereby reducing the coating shedding rate.

[0103] Comparative Example 7

[0104] Compared with Example 1, the difference of this comparative example is that there is no transition layer, and the first catalytic slurry is directly coated on cordierite. The obtained monolithic carbon-based catalyst is labeled as B7.

[0105] It has been verified that the catalytic activities of B7 and S1 have little difference, and the specific surface area has a certain increase, but the coating shedding rate of B7 increases to 27.15%, indicating that the transition layer has a very obvious strengthening effect on the connection between the porous skeleton and the catalytic layer.

[0106] The above-mentioned catalytic activity is measured by Figure 1 the catalyst evaluation device shown.

[0107] As Figure 1As shown in the figure, the catalyst evaluation device is used as follows: place the monolithic carbon-based catalyst in a quartz reactor, and the mixed gas formed by mixing water, oxygen, nitrogen, and toluene in a mixer reacts with the catalyst in the quartz reactor heated by an electric furnace. The test temperature range is 50 - 300 °C, and the space velocity (GHSV) is 10000 h -1 , and then use a detector (such as a chromatograph) to measure the concentration of toluene in the gas after the reaction. The measured tail gas is discharged after treatment.

[0108] Then calculate the toluene conversion efficiency = (C in - C out ) / C in * 100%, where C in and C out are the toluene concentrations in the gas before and after the reaction, respectively, with the unit of ppm, and C in = 500 ± 50 ppm.

[0109] The test method for the above-mentioned coating shedding rate (coating stability) is as follows: place a monolithic catalyst with a known dry loading C0 (unit: g / L) and a volume of V0 (unit: L) in an aqueous medium. After ultrasonic oscillation for 15 minutes, take out the monolithic catalyst, filter the aqueous solution after ultrasonic treatment to separate the solid particles, dry the solid particles in an airtight manner at 120 °C for 24 hours, and weigh the mass m1 (unit: g) of the shed particles after drying.

[0110] Then calculate the coating shedding rate = m1 / (C0 * V0) * 100%.

[0111] The preparation process of the above-mentioned activated carbon is as follows: weigh 500 g of waste leather powder crushed and sieved through 60 mesh, add 1000 mL of 1 - 5 mol / L hydrochloric acid solution and stir for 1 - 5 hours, then filter and wash with water until neutral, and dry at 105 °C for 24 hours. Carbonize the pretreated leather powder under a nitrogen atmosphere. The carbonization conditions are to stay at 120 °C for 1 hour, 400 - 500 °C for 1 hour, and 550 - 650 °C for 3 hours in sequence, with a heating rate of 1 °C / minute. Then add 500 mL of 1 mol / L nitric acid to the carbonized leather carbon and boil for 1 hour. After the reaction is completed, filter and wash until the pH is neutral, and then dry at 105 °C for 24 hours. Then add 500 mL of 20% potassium hydroxide solution to the carbonized leather carbon and stir rapidly for 1 hour. After the reaction is completed, filter and wash until neutral. Then add potassium hydroxide solid powder (the ratio of alkali to carbon is 1:1 - 5:1) to the obtained leather carbon and mix evenly, and then activate at 750 - 850 °C under a nitrogen atmosphere for 3 - 6 hours to obtain porous leather activated carbon. The present invention uses activated carbon prepared from leather powder as raw material, realizing the high-value recycling and utilization of waste leather resources.

[0112] The above has described the relevant content of the present invention. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Based on the above content of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. Monolithic catalyst body, including a support skeleton, characterized in that: It also includes those successively loaded on the surface of the support skeleton: A transition layer, which is formed by coating and drying a transition slurry including a first binder, a curing agent, and a modifier; A first catalytic layer, which is formed by coating and drying a first catalytic slurry including a second binder, activated carbon, and a first active metal precursor; the first active metal precursor is cerium nitrate and cobalt nitrate; A second catalytic layer, which is formed by coating and drying a second catalytic slurry including a second binder, activated carbon, and a second active metal precursor; the second active metal precursor is manganese acetate, cerium nitrate, and cobalt nitrate; The molar content of the second active metal precursor in the second catalytic layer is greater than that of the first active metal precursor in the first catalytic layer.

2. The monolithic catalyst green body according to claim 1, characterized in that: The support skeleton is cordierite; the first binder is any several of silica sol, alumina sol, zirconia sol, and clay; the curing agent is any several of glass fiber, silica powder, asphalt, and kaolin; the modifier is any several of citric acid, oxalic acid, nitric acid, hydrochloric acid, and acetic acid; the second binder is any several of silica sol, alumina sol, coal tar, asphalt, and clay.

3. The method for preparing the integral catalyst body according to claim 1 or 2, characterized in that: It includes the following steps: (1) Prepare the transition slurry; then coat the transition slurry onto the support skeleton along the first direction, and then dry to form the transition layer; (2) Prepare the first catalytic slurry; then coat the first catalytic slurry onto the transition layer along the second direction, and then dry to form the first catalytic layer; (3) Prepare the second catalytic slurry; then coat the second catalytic slurry onto the first catalytic layer along the third direction, and then dry to form the second catalytic layer, thus obtaining the monolithic catalyst green body.

4. The preparation method of the monolithic catalyst green body as described in claim 3, wherein: In step (1), 20 - 35 g of the first binder, 2 - 4 g of the curing agent, 4 - 6 mL of the modifier, and 2 - 4 mL of deionized water are ball-milled and dispersed to obtain the transition slurry, and the dry loading of the transition layer is 32 - 38 g / L; In step (2), 25 - 35 g of activated carbon, 8 - 20 mL of water, 20 - 24 mmol of the first active metal precursor, and 15 - 25 g of the second binder are ball-milled and dispersed to obtain the first catalytic slurry, and the dry loading of the first catalytic layer is 20 - 50 g / L; In step (3), 25 - 35 g of activated carbon, 8 - 20 mL of water, 25 - 40 mmol of the second active metal precursor, and 15 - 25 g of the second binder are ball-milled and dispersed to obtain the second catalytic slurry, and the dry loading of the second catalytic layer is 40 - 70 g / L.

5. The preparation method of the monolithic catalyst green body as described in claim 4, wherein: The drying in step (1) and step (2) is drying at 65 - 75 °C for 8 - 12 minutes; The drying in step (3) is divided into three stages. First, dry at 65 - 75 °C for 8 - 16 hours, then dry at 80 - 90 °C for 8 - 16 hours, and finally dry under airtight conditions at 100 - 120 °C for 8 - 16 hours.

6. The preparation method of the monolithic catalyst green body according to claim 3, characterized in that: The first direction and the second direction are not the same, and / or, the second direction and the third direction are not the same.

7. Preparation method of the monolithic catalyst, characterized in that: It includes the following steps: Obtain the monolithic catalyst green body described in claim 1 or 2; Or obtain the monolithic catalyst green body prepared by the preparation method described in any one of claims 3-6; Perform a calcination treatment on the monolithic catalyst green body, and then the monolithic catalyst is obtained.

8. Monolithic catalyst, characterized in that: Prepared by the preparation method described in claim 7.

9. A method for purifying VOCs, characterized in that: Use the monolithic catalyst described in claim 8 to adsorb and catalytically oxidize VOCs decomposition at low temperature.

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