Monolithic catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of post-treatment of exhaust gas discharged by a mobile source, and particularly relates to a monolithic catalyst as well as a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: fully mixing the raw materials, namely the molecular sieve, the soluble metal salt, the deionized water, the silane coupling agent, the zirconium silica sol, the dispersing agent, the deionized water and the pH regulator, and then putting the mixture into a circulating type stirring ball mill for one-step grinding and pulping; soaking a honeycomb ceramic carrier in the prepared slurry, repeating for multiple times, and then drying and roasting at high temperature; and placing the roasted monolithic catalyst in an activation atmosphere, and carrying out high-temperature activation treatment. Active metal elements in the prepared monolithic catalyst are uniformly distributed, the stability and activity of a catalytic coating are enhanced, and the monolithic catalyst can be widely applied to catalytic treatment of waste gas discharged by moving sources such as diesel vehicles and gasoline vehicles, and has important environmental protection significance and huge economic value.

Description

Technical Field

[0001] The present invention belongs to the technical field of post-treatment of exhaust gas from mobile sources, and particularly relates to a monolithic catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Green development, circular development, and low-carbon development have become the "direction signs" for the development path of China's civilization in the new era. Especially in the aspect of controlling automobile pollution emissions, in the past 20 years, the number of automobiles in China has increased by about 15 times in terms of ownership and production and sales volume, while the total emissions of automobile air pollutants are equivalent to those in 2000. This is inseparable from the development and progress of automobile emission control technology. The post-treatment technology is an indispensable way to solve the emissions of automobile exhaust pollutants, especially in the stage of National VI standards. The monolithic catalyst is the core component of the post-treatment system (device) for emissions, and it plays a key role in the catalytic purification of CO, HC, NOx, PM, etc. The monolithic catalyst usually consists of a catalytic coating and a honeycomb ceramic carrier, and its preparation process specifically includes pulping, coating, drying and calcination, etc.

[0003] To ensure the performance of the monolithic catalyst, the actual preparation often adopts the method of first preparing the catalyst powder and then preparing the slurry for coating. CN 106984357A discloses a SCR catalyst for denitrification purification of diesel vehicle exhaust gas and a preparation method thereof. Among them, the molecular sieve catalyst powder is first prepared, and then the slurry is adjusted and coated, which belongs to the conventional preparation process. To simplify the preparation process cycle, CN 110201708A discloses a SCR catalyst and a preparation method thereof, adopting a one-step pulping method, directly grinding and pulping the modified molecular sieve carrier and copper source, etc. for coating. More directly, CN 107362822 A discloses a preparation method of a monolithic molecular sieve SCR catalytic reactor. In this method, the molecular sieve and metal oxide are directly mixed into the preparation raw materials of the cordierite honeycomb ceramic carrier, and then the surface is modified with the molecular sieve catalyst after the cordierite is calcined and formed.

[0004] The binder determines the structural stability of the catalytic coating and directly affects the activity and durability of the monolithic catalyst. CN105363486A discloses a preparation method of a molecular sieve-based SCR catalyst. First, a zirconium-aluminum composite sol binder is prepared, and then molecular sieve and deionized water are added for ball milling and pulping, and finally obtained by repeated impregnation, drying, and calcination. CN 107597178 A discloses a monolithic molecular sieve type SCR catalyst and a preparation method thereof, and the binder used is α-Al2O3. The binder used in the preparation process of the monolithic denitrification catalyst disclosed in CN 114632537A is silica sol or aluminum sol;

[0005] Traditional silica sol, alumina sol and their modified composite sols, although having strong adhesiveness, have poor affinity for organic substances or organic interfaces. Moreover, the catalytic coating slurry has a complex composition and is extremely prone to sedimentation and aggregation of sol-like substances. Therefore, a substance that can connect the organic end and the inorganic end and simultaneously act as a binder is needed. Summary of the Invention

[0006] The object of the present invention is to provide a monolithic catalyst with excellent activity and durability, and its preparation method and application, so as to achieve efficient and continuous post-treatment of mobile source exhaust gas.

[0007] The monolithic catalyst provided by the present invention uses a silane coupling agent as a medium to connect organic and inorganic substances and simultaneously acts as a binder; among them, an in-situ pulping method is used to prepare the catalyst coating slurry, making the coating slurry more uniform and more stable; the coating slurry is coated on a carrier to prepare a monolithic catalyst.

[0008] The preparation method of the monolithic catalyst provided by the present invention specifically comprises the following steps:

[0009] Step 1, slurry preparation; specifically, a one-step pulping method is adopted, that is, raw materials such as molecular sieve, soluble metal salt, deionized water, silane coupling agent, zirconium-silica sol, dispersant, deionized water and pH regulator are fully mixed, and then placed in a circulating stirring ball mill for one-step grinding and pulping. The grinding time is 18 - 24 hours, the slurry temperature is 80 - 100 °C, and the slurry pH value is 2 - 10, preferably 3 - 6; wherein, the molar ratio of the silane coupling agent to deionized water is 0.01 - 0.5, the molar ratio of the dispersant to the silane coupling agent is 0.05 - 15; the mass ratio of zirconium-silica sol to deionized water is 0.01 - 10, and the mass ratio of the metal element in the soluble metal salt to the molecular sieve is 0.01 - 0.5; the solid content of the slurry is 5 - 50% by mass; preferably, the solid content is 20 - 40% by mass;

[0010] Step 2, impregnation coating; the honeycomb ceramic carrier is impregnated in the slurry prepared in Step 1, taken out, and the residual liquid is removed by hot air spraying. The honeycomb ceramic carrier is turned over and impregnated again. This is repeated multiple times, and the number of repetitions is 2 - 4 times; taken out and dried at 120 °C - 250 °C; calcined at 400 - 750 °C;

[0011] Step 3, activation treatment; the calcined monolithic catalyst is placed in an activation atmosphere, the temperature is raised to 300 - 600 °C, and the activation treatment is carried out for 12 - 24 hours.

[0012] Furthermore, in Step 1:

[0013] The specific structural formula of the silane coupling agent is M-R-Si(OR)3, where M is an organic functional group with a molecular weight of 28-1000 (preferably 500-1000), and R is an alkyl group with 1-10 carbon atoms (preferably 5-8).

[0014] Preferably, the silane coupling agent is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, isobutyltriethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0015] The silane coupling agent described above functions as a binder in the coating slurry, making the catalytic coating have a certain viscosity and adhere to the surface of the carrier.

[0016] In the process of preparing the monolithic catalyst, the silane coupling agent forms silicon oxide, enabling the catalytic coating and the carrier to form a strong interaction with each other and inhibiting the separation between the catalytic coating and the carrier.

[0017] The silane coupling agent described above does not function for surface modification, does not play a role in reconciling the lipophilicity of the solution, and its purpose is not to remove free metal ions either.

[0018] The molecular sieve described above specifically includes at least one of AFX, AEI, BEA, CHA, ERI, FAU, LTA, MFI, RHO, OFF and their co-products according to the framework structure type.

[0019] Preferably, the framework structure type of the molecular sieve is selected from AFX, AEI, BEA, CHA, MFI. Among them:

[0020] The CHA structure molecular sieve has a CHA cage and a double six-membered ring structural unit. Preferably, the molecular sieves belonging to the CHA structure include at least one of SSZ-13, SAPO-34, ZK-4, SAPO-44;

[0021] The AFX structure molecular sieve has an AFT cage, a GME cage and a double six-membered ring structural unit. Preferably, the molecular sieves belonging to the AFX structure include at least one of MnAPSO-56, CoAPSO-56, SAPO-56, SSZ-16;

[0022] The AEI structure molecular sieve has a pear-shaped supercage formed by a double six-membered ring and its connected four-membered ring. Preferably, the molecular sieves belonging to the AFX structure include at least one of AlPO-18, SAPO-18, SSZ-39, SIZ-8;

[0023] The BEA-structured molecular sieve has a three-dimensional pore system with twelve-membered rings and a stacking fault structure formed by the stacking of two (or three) ordered structures. Preferably, the molecular sieves belonging to the BEA structure include BETA; the MFI-structured molecular sieve has structural units such as MOR cages, CAS cages, MFI cages, and MEL cages. Preferably, the molecular sieves with the MFI structure include at least one of ZSM-5 and Silicalite-1.

[0024] The soluble metal salt refers to a metal salt that can dissolve in a solvent containing water or ethanol or methanol. Among them, the types of metal cation elements specifically include at least one of Cu, Fe, Mn, Ce, Au, Ag, Pt, Pd, Rh, Cr, Ni, Nb, Ba, Mg, Ca, Sr, Co, V, and Sm. Correspondingly, the coordination anions specifically include Cl - , NO3 - , CO3 2- , HCO3 - , SO4 2- , HSO4 - , Br - , I - , F - , CH3COO - , CN - , SCN - and at least one of them.

[0025] The dispersants specifically include at least one of ethylene glycol, isopropyl alcohol, polyethylene glycol, sodium polyacrylate, sodium pyrophosphate, propylene glycol methyl ether, diethanolmonoisopropanolamine, acrylic polymer, starch, sodium carboxymethyl starch, gelatin, seaweed gum, and glucose;

[0026] The solid content of the silicon-zirconium sol ranges from 5 wt% to 50 wt%, and the proportion of zircon (total amount of silicon and zirconium elements) ranges from 0 to 100%.

[0027] The specifications of the silicon-zirconium sol include acidic, neutral, and basic, and preferably the pH value of the sol is 3 - 5.

[0028] The pH regulator is used to adjust the acidity and alkalinity of the coating slurry, specifically referring to acidic pH regulators and basic pH regulators. After adding the pH regulator, the pH value of the slurry does not exceed 10. Preferably, the pH value of the adjusted slurry ranges from 3 to 6.

[0029] Among them, the acidic pH regulators specifically include at least one of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, citric acid, malic acid, sulfamic acid, and oxalic acid; the basic pH regulators specifically include caustic alkali, ammonia water, and amino organic bases with a molecular weight lower than 1000 and soluble in water.

[0030] The so-called one-step pulping, also known as in-situ pulping or one-pot pulping, is used to efficiently combine active metal elements with the carrier molecular sieve and silicon and zirconium oxides in the coating while preparing the coating slurry.

[0031] The above-mentioned efficient combination of the active metal and the carrier occurs during the mixing and grinding pulping process in the preparation of the coating slurry. The chemical reactions involved in the efficient combination include one or more of ion exchange, chemical deposition, electrostatic adsorption, impregnation, and solid-phase grinding reaction processes.

[0032] In the process of step one in the cyclic pulping, the temperature of the slurry will rise. Through heat transfer, the temperature of the slurry is controlled not to exceed 100 °C.

[0033] After the above-mentioned active metal is dried and calcined, or the final chemical existence state in the monolithic catalyst includes one or more of ionic state, combined state, and elemental state.

[0034] The combined state of the above-mentioned final chemical state specifically includes one or more of the following: oxides formed by bonding with oxygen, aluminates, silicates, and aluminosilicates formed by bonding with aluminum and silicon elements, and compounds formed by bonding with the surface hydroxyl groups, carbonyl functional groups, ion exchange sites, and chemical adsorption sites of the above-mentioned carrier.

[0035] The above-mentioned active metal is distributed in the molecular sieve, binder, and honeycomb ceramic carrier. At the same time, the distribution of the active metal elements directly affects the performance of the catalyst.

[0036] The active metal elements are specifically distributed in one or more of the outer surface, microporous channels, and molecular sieve cages of the molecular sieve; the active metal is also specifically distributed in one or more of the surface, interior, and even lattice of the binder.

[0037] The final chemical state of the above-mentioned binder in the monolithic catalyst is one or more of single oxides, multi-metal oxides of two or more kinds, fixed-structure composite oxides, and supported composite oxides formed by bonding silicon, zirconium, aluminum, magnesium, cerium, manganese, iron, copper, barium, calcium, gold, silver, platinum, rhodium, and palladium elements with oxygen.

[0038] Furthermore:

[0039] In step two, impregnation coating is carried out to adhere the coating slurry to the honeycomb ceramic carrier. Among them, the impregnation coating feed specifically includes at least one of up-feed and down-feed; the methods of impregnation coating include at least one of vacuum extraction, impregnation lifting, natural immersion, atomization spraying, high-temperature cooking, and in-situ growth.

[0040] For the above-mentioned impregnation coating, the solid content of the slurry is controlled at 5-50%, preferably 20-40%.

[0041] The above-mentioned flipped honeycomb ceramic carrier is impregnated again, and the purpose is to ensure the coating uniformity of the monolithic catalyst.

[0042] The above-mentioned re-impregnation is beneficial to improving the loading rate of the catalytic coating and beneficial to the uniform distribution of the coating, but it will increase the risk of pore blockage.

[0043] The number of times of the above-mentioned repeated impregnation does not exceed 5 times; after each impregnation and coating cycle, hot air is blown to remove the residual liquid in the honeycomb ceramic pores.

[0044] Furthermore:

[0045] In step three, the activation treatment aims to make the final chemical states of the active components, carriers, binders, and honeycomb ceramic carriers in the monolithic catalyst more stable as monomers and compounds, and on the other hand, to improve the activity of the monolithic catalyst.

[0046] The temperature of the above-mentioned activation treatment is 300-600°C, and the treatment time of the activation atmosphere does not exceed 24h.

[0047] The above-mentioned activation atmosphere specifically includes reducing atmosphere, oxidizing atmosphere, and neutral atmosphere.

[0048] The reducing atmosphere refers to a gas containing a substance that can convert a high-valence active metal element into a low-valence state, specifically including one or more of hydrogen, carbon monoxide, alkanes with less than 10 carbon atoms, alkenes with less than 10 carbon atoms, alkynes with less than 10 carbon atoms, hydrogen sulfide, ammonia, nitric oxide, sulfur monoxide, hydrazine hydrate; the oxidizing atmosphere refers to a gas containing a substance that can convert a low-valence active metal element into a high-valence state, specifically including one or more of oxygen, ozone, nitrogen oxides, chlorine; the neutral atmosphere specifically includes one or more of compressed air, inert gas, nitrogen, steam-containing air, and steam-containing neutral atmosphere.

[0049] After the activation treatment, one or more of the valence state change, chemical bonding state change, distribution and dispersion state change, and binding position and chemical state change with the carrier of the active metal element in the monolithic catalyst occur, thereby realizing the improvement of catalytic activity.

[0050] The monolithic catalyst prepared by the method of the present invention has excellent low-temperature catalytic activity and a wide activity temperature window. The light-off temperature can reach as low as 85°C at the lowest, and the activity temperature window can reach as wide as 120-650°C, and it can be used for the catalytic reaction of efficient and continuous post-treatment of mobile source exhaust emissions.

[0051] The exhaust gas emitted by the mobile source includes gaseous pollutants such as nitrogen oxides, carbon monoxide, methane, volatile organic compounds, hydrocarbons, etc.

[0052] Specifically, the monolithic copper-based SCR catalyst prepared in the embodiments of the present invention can be used for selectively catalytically reducing and eliminating nitrogen oxides in exhaust gas. Among them, the carrier carrying the active copper species is preferably one or more of the molecular sieves with CHA, AEI, and AFX structures.

[0053] In the preparation of the monolithic copper-based SCR catalyst, adding one or more of the elements Mn, Ce, La, Y, Sm, and Fe in the one-step pulping step can improve the NH3-SCR performance of the monolithic copper-based SCR catalyst. The test results in a micro fixed-bed reactor are specifically manifested as a lower ignition temperature of nitrogen oxides and a wider active temperature window. Test conditions: 500 ppm NO, 500 ppm NH3, 10% H2O, 10% O2, N2 as the balance gas, the total flow rate is 1,000 ml / min, and the reaction space velocity is 30,000 h -1 。

[0054] For another example, the noble metal molecular sieve catalyst prepared in the embodiments of the present invention can be used for low-temperature adsorption of nitrogen oxides, as well as deep catalytic oxidation of carbon monoxide, methane, volatile organic compounds, and hydrocarbons.

[0055] Similarly, one or more of the elements Pt, Pd, Rh, Ru, Au, Ag, Ce, Mn, Sn, and Ni can be introduced in the one-step pulping step to prepare an improved noble metal molecular sieve catalyst.

[0056] The above copper-based SCR catalyst and noble metal molecular sieve catalyst are used to eliminate gaseous pollutants in exhaust gas.

[0057] Compared with the prior art, the monolithic catalyst provided by the present invention has the following advantages:

[0058] (1) The silane coupling agent coating slurry provided by the present invention can connect substances at both the organic end and the inorganic end, avoiding the use of silica sol / alumina sol with high viscosity, easy sedimentation, and poor affinity, and ensuring the stability of the coating slurry;

[0059] (2) The one-step pulping technology provided by the present invention realizes the efficient combination of the active metal and the carrier during the cyclic grinding pulping process, shortens the process cycle, and ensures the uniform distribution of the active metal elements.

[0060] (3) The monolithic catalyst preparation method provided by the present invention enhances the stability and activity of the catalytic coating after activation atmosphere treatment.

[0061] (4) The monolithic catalyst preparation method provided by the present invention is not only applicable to the preparation of catalysts such as diesel vehicle DOC, CDPF, ASC, and SCR, but also applicable to the preparation of catalysts such as gasoline vehicle TWC and CGPF, and has wide versatility. Description of the Drawings

[0062] Figure 1 They are the catalytic coating loading rates during single coating and double coating in Examples 1 - 3. As can be seen from the figure, when dip - coating is carried out once, the loading rate is about 10 - 15%, and when double - coating is carried out, the loading rate is 25 - 30%.

[0063] Figure 2 They are the particle size distributions of the slurries in Examples 1 - 3, which are concentrated in the range of 2 - 10 microns.

[0064] Figure 3 The microscopic morphology of the monolithic catalyst coating in Example 1.

[0065] Figure 4 The microscopic morphology of the monolithic catalyst coating in Example 1.

[0066] Figure 5 The microscopic morphology of the monolithic catalyst coating in Example 1.

[0067] Figure 6 The microscopic morphology of the monolithic catalyst coating in Example 1.

[0068] Figure 7 The microscopic morphology of the monolithic catalyst coating in Example 1.

[0069] Figure 8 The microscopic morphology of the monolithic catalyst coating in Example 1.

[0070] Figure 9 The catalytic activity test results of the monolithic catalyst samples in Example 1 and Comparative Examples 1 - 3. As can be seen from the figure, Example 1 has more excellent low - temperature activity and temperature window. Detailed implementation mode

[0071] The technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0072] In the present invention, the simulated flue gas composition used for NH3 - SCR performance test is: 500 ppm NO, 500 ppm NH3, 10% H2O, 10% O2, with N2 as the balance gas, the total flow rate is 1,000 ml / min, and the reaction space velocity is 30,000 h -1 .

[0073] In the present invention, the low - temperature performance index is T 50 , which represents the temperature corresponding to when the NO X conversion rate reaches 50%; the temperature window index T 90 , which represents the temperature corresponding to when the NO XThe temperature range corresponding to a conversion rate exceeding 90%.

[0074] The present invention will be further described below in conjunction with embodiments.

[0075] Unless otherwise indicated, all numbers appearing in the present invention, such as values of temperature, time, and mass percentage of slurry feeding, etc., should not be understood as absolute exact values, and these values are within the error range allowed by those of ordinary skill in the art and known technologies.

[0076] Example 1

[0077] Take 950 ml of deionized water, add 86 g of copper nitrate trihydrate thereto, stir until dissolved and clear, and add nitric acid to adjust the pH to about 3. Subsequently, add 460 g of SSZ-13 molecular sieve and 32 g of ethylene glycol, and grind in a circulating stirring ball mill for 2 h. Slowly add 58 g of aminopropyltriethoxysilane and 90 g of silica-zirconia sol to the slurry, and continue grinding and stirring for 4 h.

[0078] After the pulping is completed, carry out coating. Immerse the honeycomb ceramic carrier in the above slurry for 10 s, take it out, use hot air to blow out and remove the residual liquid, turn it over and immerse it again. After repeating 2 times, take it out, carry out air drying treatment at 150 °C, and calcine at 550 °C for 6 h.

[0079] Use air containing 10% water vapor as the active atmosphere, carry out activation treatment at a purging rate of 1000 ml / min, keep the temperature constant at 500 °C for 5 h, and obtain the monolithic copper-based SCR catalyst.

[0080] Example 2

[0081] Take 1000 ml of deionized water, add 71 g of copper acetate, 35 g of ethylene glycol, 88 g of silica-zirconia sol, 90 g of aminopropyltriethoxysilane, and 530 g of SSZ-13 molecular sieve, stir well, and add glacial acetic acid dropwise to adjust the pH to about 5. Subsequently, grind in a circulating stirring ball mill for 6 h.

[0082] After the pulping is completed, carry out coating. Immerse the honeycomb ceramic carrier in the above slurry for 10 s, take it out, use hot air to blow out and remove the residual liquid, turn it over and immerse it again. After repeating 2 times, take it out, carry out air drying treatment at 150 °C, and calcine at 550 °C for 6 h.

[0083] Use air containing 10% water vapor as the active atmosphere, carry out activation treatment at a purging rate of 1000 ml / min, keep the temperature constant at 500 °C for 5 h, and obtain the monolithic copper-based SCR catalyst.

[0084] Example 3

[0085] Different from Example 2, an equimolar amount of 3-(2,3-epoxypropoxy)propyltrimethoxysilane was selected as the silane coupling agent.

[0086] Example 4

[0087] Different from Example 1, during the process of cyclic stirring for pulping, manganese nitrate and cerium nitrate were added to the slurry according to the molar ratio of Cu:Mn:Ce = 1:0.25:0.25 to introduce Mn and Ce elements, and a modified copper-based SCR catalyst was prepared.

[0088] Example 5

[0089] Different from Example 1, the impregnation coating was repeated 3 times.

[0090] Example 6

[0091] Take 1000 ml of deionized water, add 13 g of palladium nitrate, 60 g of ethylenediamine, 75 g of silica-zirconia sol, 90 g of aminopropyltriethoxysilane, and 500 g of SSZ-13 molecular sieve thereto, and stir well. Then, nitric acid was added dropwise to adjust the pH to about 5. Subsequently, it was ground in a cyclic stirring ball mill for 6 h.

[0092] After the pulping was completed, the coating was applied. The honeycomb ceramic carrier was immersed in the above slurry for 10 s, taken out, and the residual liquid was removed by hot air spraying, and then turned over and impregnated again. After repeating 2 times, it was taken out and dried by blowing air at 150 °C and calcined at 550 °C for 6 h.

[0093] Using argon containing 3% hydrogen as the active atmosphere, activation treatment was carried out at a purge rate of 1000 ml / min, and it was kept at a constant temperature of 500 °C for 5 h to obtain a noble metal molecular sieve catalyst.

[0094] Example 7

[0095] Different from Example 6, according to Pt:Pd = 1:3, chloroplatinic acid was added to introduce Pt element, and an improved noble metal molecular sieve catalyst was prepared.

[0096] Example 8

[0097] Different from Example 7, according to the molar ratio of Pt:Pd:Rh = 1:3:1, chloroplatinic acid and rhodium chloride were added to introduce Pt and Rh simultaneously, and an improved noble metal molecular sieve catalyst was prepared.

[0098] Example 9

[0099] Different from Example 6, according to the molar ratio of Pd:Ce = 1:1, cerium nitrate was added to introduce the non-noble metal Ce, and an improved noble metal molecular sieve catalyst was prepared.

[0100] Example 10

[0101] Different from Example 1, the amount of water added is controlled so that the solid content of the slurry is about 30%.

[0102] Example 11

[0103] Different from Example 1, the total molar amount of the silane coupling agent in the slurry remains unchanged, and a mixture of aminopropyltriethoxysilane and isobutyltriethoxysilane is selected as the silane coupling agent.

[0104] Example 12

[0105] Different from Example 1, AFX structure molecular sieve is selected.

[0106] Example 13

[0107] Take 1000 ml of deionized water, add 123 g of ferric nitrate, 15 g of polyethylene glycol, 65 g of silica-zirconia sol, 90 g of aminopropyltriethoxysilane, and 500 g of beta molecular sieve thereto, and stir well. Then, add nitric acid to adjust the pH to about 5. Subsequently, grind and process in a circulating stirring ball mill for 6 h.

[0108] After the pulping is completed, coating is carried out. Immerse the honeycomb ceramic carrier in the above slurry for 10 s, take it out, remove the residual liquid by hot air spraying, turn it over and immerse it again. After repeating 2 times, take it out, dry it by blowing air at 150 °C, and calcine it at 550 °C for 6 h.

[0109] Use air containing 10% water vapor as the active atmosphere, carry out activation treatment at a purge rate of 1000 ml / min, keep the temperature constant at 500 °C for 5 h, and obtain a monolithic iron-based molecular sieve catalyst.

[0110] Example 14

[0111] Different from Example 6, pure silica MFI structure molecular sieve is selected.

[0112] Comparative Example 1

[0113] Take 950 ml of deionized water, add 86 g of copper nitrate trihydrate thereto, stir until dissolved and clear, and add nitric acid to adjust the pH to about 3. Subsequently, add 460 g of SSZ-13 molecular sieve and 32 g of ethylene glycol, and grind and process in a circulating stirring ball mill for 2 h. Slowly add 148 g of silica sol to the slurry, and continue to grind and stir for 4 h.

[0114] After the pulping is completed, coating is carried out. Immerse the honeycomb ceramic carrier in the above slurry for 10 s, take it out, remove the residual liquid by hot air spraying, turn it over and immerse it again. After repeating 2 times, take it out, dry it by blowing air at 150 °C, and calcine it at 550 °C for 6 h.

[0115] Using air containing 10% water vapor as the active atmosphere, activation treatment was carried out at a purge rate of 1000 ml / min, and the temperature was kept constant at 500 °C for 5 h to obtain a monolithic copper-based SCR catalyst.

[0116] Comparative Example 2

[0117] According to the raw material ratio in Example 1, the difference is that only mechanical stirring treatment was carried out for 6 h.

[0118] Comparative Example 3

[0119] According to the raw material ratio in Example 1, the difference is that no silane coupling agent was added.

[0120] Comparative Example 4

[0121] Different from Example 1, the solid content of the slurry exceeds 50%.

[0122] Table 1 Particle size distribution of the slurry and test results of the sedimentation stability of the slurry for 24 h

[0123] Number D10 D50 D90 Whether it settles Whether the coating clogs the holes Example 1 1.46 3.58 5.13 No No Example 2 1.63 3.72 5.52 No No Example 3 1.52 3.62 5.68 No No Example 4 1.74 3.99 4.89 No No Example 5 1.90 3.02 4.74 No No Example 6 1.95 3.25 4.87 No No Example 7 1.44 3.18 4.97 No No Example 8 1.87 3.35 5.09 No No Example 9 1.97 3.48 5.73 No No Example 10 1.94 3.13 4.94 No No Example 11 2.03 3.78 5.02 No No Example 12 1.77 3.52 4.96 No No Example 13 1.61 3.32 5.00 No No Example 14 1.76 3.13 4.86 No No Comparative Example 1 3.75 6.28 9.52 No Yes Comparative Example 2 5.64 9.89 11.32 Yes Yes Comparative Example 3 1.02 3.18 3.21 Yes No Comparative Example 4 4.23 7.19 10.72 Yes Yes 。

[0124] The particle size distribution of the solid substances in the slurry within a reasonable range is a necessary but not sufficient condition for the slurry to maintain stability and not easily settle, and not easily block pores during coating. The particle size distributions of Examples 1-14 are all relatively reasonable, better than those of the four comparative examples, and the slurries of the comparative examples are prone to sedimentation and pore blockage.

[0125] Examples for verifying catalytic performance

[0126] The monolithic catalysts of Example 1 and Comparative Examples 1-3 of the present invention were made into small samples of Φ20 mm × 25 mm according to T / CAEPI 12.2-2017, and the NH3-SCR catalytic performance evaluations were carried out on a micro fixed-bed reactor respectively. The heating rate of the evaluation test was 5 °C / min. The simulated atmosphere composition: 500 ppm NO, 500 ppm NH3, 5% O2, 10% H2O, N2 as the balance gas, the total flow rate was 1,000 ml / min, and the reaction space velocity was 30,000 h -1 。

[0127] The test results are shown in Figure 9 , the NO ignition temperature of Example 1 was 136 °C, and the temperature window was 173-485 °C, far superior to Comparative Examples 1-3 in terms of low-temperature activity and temperature window. The NOx ignition temperatures of Comparative Examples 1-3 were 142, 153, and 162 °C respectively; the temperature windows were 210-415 °C, 220-435 °C, and 210-445 °C respectively.

Claims

1. A preparation method of an integral catalyst, characterized in that, The specific steps are as follows: Step 1: Slurry preparation; Specifically, the one-step pulping method is adopted, that is, the raw materials such as molecular sieve, soluble metal salt, deionized water, silane coupling agent, zirconium silicate sol, dispersant, deionized water and pH regulator are fully mixed, and then placed in a circulating stirring ball mill for one-step grinding and pulping. The grinding time is 18 - 24h, the slurry temperature is 80 - 100°C, and the slurry pH value is 2 - 10; Among them, the molar ratio of the silane coupling agent to deionized water is 0.01 - 0.5, the molar ratio of the dispersant to the silane coupling agent is 0.05 - 15; The mass ratio of zirconium silicate sol to deionized water is 0.01 - 10, and the mass ratio of the metal element in the soluble metal salt to the molecular sieve is 0.01 - 0.5; The solid content of the slurry is 5 - 50% by mass; Step 2: Impregnation coating; The honeycomb ceramic carrier is impregnated in the slurry prepared in Step 1, taken out, and the residual liquid is removed by hot air spraying. The honeycomb ceramic carrier is turned over and impregnated again, and this is repeated 2 - 4 times; Take out; Dry at 120°C - 250°C; Then calcine at 400 - 750°C; Step 3: Activation treatment; The calcined monolithic catalyst is placed in an activation atmosphere, heated to 300 - 600°C, and activated for 12 - 24h.

2. The preparation method according to claim 1, characterized in that, In Step 1: The specific structural formula of the silane coupling agent is M-R-Si(OR)3, where M is specifically an organic functional group with a molecular weight of 28 - 1000, and R is an alkyl group with 1 - 10 carbon atoms; The molecular sieve, according to the framework structure type, specifically includes at least one of AFX, AEI, BEA, CHA, ERI, FAU, LTA, MFI, RHO, OFF; The soluble metal salt refers to a metal salt that can dissolve in a solvent containing water or ethanol or methanol; The zirconium silicate sol has a solid content of 5wt% - 50wt%, and the mass ratio of zirconium is 1 - 99%; The pH regulator is used to adjust the acidity and alkalinity of the coating slurry, including acidic pH regulators and basic pH regulators.

3. The preparation method according to claim 2, characterized in that, In Step 1: The silane coupling agent is selected from vinyltrimethoxysilane, vinyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, isobutyltriethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane; The molecular sieve, its framework structure type is selected from AFX, AEI, BEA, CHA, MFI; Among them: The CHA structure molecular sieve is specifically selected from SSZ-13, SAPO-34, ZK-4, SAPO-44; The AFX structure molecular sieve is specifically selected from MnAPSO-56, CoAPSO-56, SAPO-56, SSZ-16; The AEI structure molecular sieve is specifically selected from AlPO-18, SAPO-18, SSZ-39, SIZ-8; The BEA structure molecular sieve is specifically BETA; The MFI-structured molecular sieve is specifically selected from ZSM-5 and Silicalite-1; The soluble metal salt, and the types of metal cation elements are specifically selected from Cu, Fe, Mn, Ce, Au, Ag, Pt, Pd, Rh, Cr, Ni, Nb, Ba, Mg, Ca, Sr, Co, V, Sm; correspondingly, the coordinating anions are selected from Cl - , NO3 - , CO3 2- , HCO3 - , SO4 2- , HSO4 - , Br - , I - , F - , CH3COO - , CN - , SCN - ; The dispersant is specifically selected from ethylene glycol, isopropyl alcohol, polyethylene glycol, sodium polyacrylate, sodium pyrophosphate, propylene glycol methyl ether, diethanolmonoisopropanolamine, acrylic polymer, starch, sodium carboxymethyl starch, gelatin, seaweed glue, and glucose; The pH value of the silicon-zirconium sol is 3-5; Among the pH regulators, the acidic pH regulators are selected from nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, citric acid, malic acid, sulfamic acid, and oxalic acid; the basic pH regulators are selected from caustic alkali, ammonia water, and amino organic bases with a molecular weight lower than 1000 and soluble in water.

4. The preparation method according to claim 3, wherein In Step 1: The one-step pulping is to complete the efficient combination of the active metal element with the carrier molecular sieve and the silicon and zirconium oxides in the coating while preparing the coating slurry; The above-mentioned efficient combination of the active metal and the carrier occurs during the mixing and grinding pulping process in the preparation of the coating slurry. The chemical reactions involved in the efficient combination include one or several of ion exchange, chemical deposition, electrostatic adsorption, impregnation, and solid-phase grinding reaction processes; During the cyclic pulping process, the temperature of the slurry rises to achieve heat transfer, and the temperature of the slurry is controlled not to exceed 100 °C.

5. The preparation method according to claim 4, characterized in that, In Step 2, the impregnation coating method includes up-feeding and / or down-feeding; the impregnation coating methods include at least one of vacuum extraction, dip coating, natural immersion, spray coating, high-temperature cooking, and in-situ growth.

6. The preparation method according to claim 5, characterized in that, In Step 3, in the activation treatment, the activation atmosphere includes a reducing atmosphere, an oxidizing atmosphere, or a neutral atmosphere; among them: The reducing atmosphere refers to a gas that can convert the active metal element in the high valence state to the low valence state, specifically selected from hydrogen, carbon monoxide, alkanes with less than 10 carbon atoms, alkenes with less than 10 carbon atoms, alkynes with less than 10 carbon atoms, hydrogen sulfide, ammonia, nitric oxide, sulfur monoxide, and hydrazine hydrate; The oxidizing atmosphere refers to a gas that can convert the active metal element in the low valence state to the high valence state, specifically selected from oxygen, ozone, nitrogen oxide, and chlorine; The neutral atmosphere is specifically selected from compressed air, inert gas, nitrogen, air containing water vapor, and a neutral atmosphere containing water vapor; For the monolithic catalyst after activation treatment, one or several of the valence state change, chemical bonding state change, distribution and dispersion state change, and binding position and chemical state change with the carrier of the active metal element occur, thereby realizing the improvement of catalytic activity.

7. The preparation method according to claim 6, characterized in that, The final chemical existence state of the monolithic catalyst includes one or several of ionic state, combined state, and elemental state; among them: The combined state of the final chemical state specifically includes one or several of the following: oxides formed by bonding with oxygen, aluminates, silicates, and aluminosilicates formed by bonding with aluminum and silicon elements, and compounds formed by bonding with the surface hydroxyl groups, carbonyl functional groups, ion exchange sites, and chemical adsorption sites of the above carriers; The active metal is distributed on the molecular sieve, binder, and honeycomb ceramic carrier; The active metal element is specifically distributed on one or several of the outer surface, micropore channels, and molecular sieve cages of the molecular sieve; the active metal is also distributed on one or several of the surface, inside, and even the crystal lattice of the binder; The final chemical state of the binder in the monolithic catalyst is one or several of single oxides, multi-metal oxides of two or more kinds, fixed-structure composite oxides, and supported composite oxides formed by the bonding of silicon, zirconium, aluminum, magnesium, cerium, manganese, iron, copper, barium, calcium, gold, silver, platinum, rhodium, and palladium elements with oxygen.

8. The monolithic catalyst obtained by the preparation method according to any one of claims 1-7.

9. The application of the monolithic catalyst according to claim 8 in the post-treatment of exhaust gas from mobile sources.

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