CN114132945B

CN114132945B - Preparation method and application of CHA molecular sieve catalyst with high-framework four-coordination aluminum structure

Info

Publication number: CN114132945B
Application number: CN202111422067.0A
Authority: CN
Inventors: 王志光; 李进; 王贤彬; 王炳春; 李小龙; 柳海涛
Original assignee: China Catalyst Holding Co ltd
Current assignee: China Catalyst Holding Co ltd
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2023-05-16
Anticipated expiration: 2041-11-26
Also published as: CN114132945A

Abstract

The invention discloses a preparation method and application of a CHA molecular sieve catalyst with a high-skeleton four-coordination aluminum structure, wherein the molar ratio of silicon dioxide to aluminum oxide of the CHA molecular sieve product is 5-80, and the grain size is 1-5 mu m; BET formula calculation total specific surface area is more than or equal to 500m ² Per gram, the total pore volume is more than or equal to 0.20ml/g, and the micropore volume is more than or equal to 0.12ml/g; the content of adjacent pairing Al of the CHA molecular sieve framework is more than 80 percent of the total amount, and after the raw powder is treated by saturated steam at 600-850 ℃, the amount of tetra-coordinated aluminum is more than or equal to 92 percent of the total aluminum. The CHA molecular sieve synthesis is characterized in that N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N' -mono/dicycloalkyl-N-alkyl pyrrolidinium salt/alkali compounds are used as a composite template agent. The CHA molecular sieve and copper ions are exchanged to form the SCR catalyst, so that the SCR catalyst has good denitration catalytic activity, high-temperature hydrothermal stability and better sulfur poisoning resistance, and the defects of poor low-temperature light-off activity and easy sulfur poisoning after the CHA molecular sieve loaded copper SCR catalyst is hydrothermal in the prior art are overcome.

Description

Preparation method and application of CHA molecular sieve catalyst with high-framework four-coordination aluminum structure

Technical Field

The invention relates to a method for synthesizing a CHA molecular sieve and a catalyst by using a composite template agent consisting of N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N' -mono/bicycloalkyl-N-alkyl pyrrolidinium salt/alkali, in particular to a method for synthesizing a SSZ-13 molecular sieve with a CHA topological structure, which is used for forming an SCR catalyst after being exchanged with transition metal and is applied to NOx selective catalytic reduction reaction, and belongs to the chemical synthesis technology and the application field thereof.

Background

With the progress of global industrialization, NOx generated by stationary pollution sources (such as thermal power generation) as well as mobile air pollution sources is considered to be a major air pollutant. The laws and regulations around the world become stricter, and the control of the emission of NOx has become a difficult problem to be solved in the field of catalytic purification at home and abroad. The NOx discharged by the tail gas of the diesel vehicle in China accounts for about 70% of the total amount of the mobile source. The external purification control technology of the nitrogen oxides of the diesel vehicle mainly comprises a NOx catalytic decomposition technology, a three-way catalytic (TWC), a NOx Storage Reduction (NSR) technology and a Selective Catalytic Reduction (SCR) technology, wherein the SCR technology is the most mature external purification technology of the tail gas of the diesel engine. The release of NOx from the tail gas of diesel vehicles by the national six-release standard promulgated by 07 and 01 in 2020 is 77% compared with the national five-standard. In the fifth stage, more vanadium-based catalysts are used, the low-temperature window characteristics of the vanadium-based catalysts are narrow, and the emission standards of the sixth and European VI cannot be met; the molecular sieve catalyst is a diesel NH3-SCR catalyst which can meet the ultra-low NOx emission requirements of the six-stage and the European VI-stage and the diesel particle catcher at present and actively regenerates the thermal shock requirement.

In the existing SCR method denitration technology, V2O ₅ /TiO ₂ Catalysts already have very efficient denitration efficiency, but the reaction usually needs to be carried out at a relatively high temperature (active temperature window between 320 and 450 ℃). In addition, the presence of active component V in such catalysts may convert SO ₂ Oxidation to SO ₃ The equipment is corroded, the V is easy to run off to cause secondary pollution, and the catalyst is easy to be poisoned and deactivated by ash in the reaction. Therefore, the low-temperature environment-friendly catalyst without the V group is widely researched in the denitration field at home and abroad. Based on the characteristics that the catalyst has both an acid site and an oxidation site in the SCR denitration process, the research on the low-temperature catalyst comprises a molecular sieve-based catalyst. The molecular sieve has excellent adsorption performance, proper surface acidity and flexibility, and the activation temperature of the catalyst can be generated by changing the types and the occurrence state of active components in the surface or the framework of the molecular sieve in the preparationThe activity temperature is controllable by corresponding change, and meanwhile, the poisoning resistance of the catalyst is improved, and the regeneration performance and the treatment capacity of the catalyst are greatly improved compared with those of the traditional catalyst. The international large-scale company has applied the technology to denitration treatment in the aspect of mobile sources such as heavy truck and the like, has good effect and has been gradually popularized. At present, copper-based molecular sieves used for diesel vehicle tail gas treatment research generally comprise Cu-beta, cu-ZSM-5, cu-SAPO-34, cu-SSZ-13 and the like. It was found that in NH ₃ In the SCR technology, the small-aperture molecular sieve Cu-SSZ-13 has higher catalytic activity, selectivity and hydrothermal stability than the macroporous molecular sieve Cu-beta and the mesoporous molecular sieve Cu-ZSM-5, and the Cu-SSZ-13 denitration performance is more excellent at 160-550 ℃ under the same reaction condition. The Cu-SSZ-13 molecular sieve catalyst becomes a research hot spot for removing NOx in tail gas of diesel vehicles by virtue of excellent catalytic activity, good hydrothermal stability and wide temperature window.

SSZ-13 molecular sieves were synthesized by the oil company Chevron (America Chevron) in 1985 using a hydrothermal method. SSZ-13 is a aluminosilicate molecular sieve with Chabazite (CHA) topological structure, has a three-dimensional pore structure and orthogonal symmetry, and a one-dimensional main pore canal is composed of double eight-membered rings, the pore size is 0.38nm and 30.38nm, the framework density is 14.5, and the specific surface can reach 700m ² And/g. Because of its unique pore structure, large specific surface area, good hydrothermal stability and shape selective function, SSZ-13 molecular sieves are of great interest in academia and industry. The CHA molecular sieve topological structure is characterized in that a double 6 circular ring (d 6 r) is connected through a 4-membered ring to form a CHA cage, a d6r crystal face faces towards the CHA cage, cu ions can be stabilized in the d6r at high temperature, and Cu ion migration is allowed, so that the CHA molecular sieve is also a unique physicochemical characteristic of the small-pore molecular sieve with SCR reaction potential. Cu is disclosed for the first time in literature (J.Phys.chem.C 2010,114,1633-1640) by analysis of dehydrated Cu-SSZ-13 molecular sieves by Rietveld structure refinement ²⁺ Uniquely present on the face of d6 r. Subsequent studies have also demonstrated that dehydrated Cu ions ([ CuOH) are located near the 8-membered ring]Presence of the +) active site. SSZ-13 and SSZ-62 molecular sieves are typically CHA structured aluminosilicate zeolite molecular sieves and can be used as cracking catalysts, MTO reaction catalysts, nitrogen oxide reduction catalysts, and as nitrogen utilizing Selective Catalytic Reduction (SCR)Oxide reduction catalysts are widely used.

Zones et al (US 4544538) synthesized a high silica alumina SSZ-13 molecular Sieve (SiO) having the CHA ratio by first using an ammonium salt including TMADaOH et al as an organic template ₂ /Al ₂ O ₃ >10). Under the optimized condition, TMADaOH is used as a template agent to synthesize the SSZ-13 product, and each CHA cage structure can contain at most one TMADa+ cation, but the template agent has long crystallization time and high price, so that the application cost of the SSZ-13 molecular sieve is increased. Researchers have developed benzyltrimethylammonium hydroxide (BTMA) (chem. Lett.,2008,37 (9): 908-909, cn101573293 a), alkylammonium hydroxide (chem. Commun.,2015,51 (49): 9965-9968, cn 107108242a), choline chloride (environ. Sci. Technology, 2014,48 (23): 13909-13916, cn 10360211a), cupramming complexes (chem. Commun.,2011,47 (35): 9789-9791) as templates to synthesize SSZ-13 molecular sieves, but these single templates are relatively inexpensive compared to conventional N, N-trimethyl-1-adamantammonium hydroxide templates, but the synthesized SSZ-13 molecular sieves have poor performance for SCR catalysts, and it is difficult to meet the effects of reducing synthesis cost and improving catalytic performance at the same time.

In patent CN201611070989, molecular sieve materials of CHA topology are disclosed which are synthesized using alkylammonium hydroxide and adamantylammonium hydroxide as dual templates, with Si/Al molar ratios between 4 and 8, BET specific surface areas between 400 and 800m ² And/g, the grain size is 0.8-20 mu m. In patent CN201780032379, the CHA zeolite having a silica to alumina molar ratio of 10.0 to 55.0 is synthesized using an N, N-trialkyl adamantyl ammonium salt and an N, N-trialkyl cyclohexyl ammonium salt as the composite templating agent. Both of these documents use dual templates, but involve relatively expensive organic templates, such as N, N-trialkyladamantylammonium salts, which are difficult to achieve with reduced cost and improved catalyst performance.

The degree of influence of sulfur poisoning on Cu/CHA catalyst activity and sulfur oxide species, atmosphere (SO ₂ 、SO ₃ 、H ₂ O or NH ₃ Etc.) and temperature, the Cu/CHA catalyst may form sulfur species [ H ] during sulfiding ₂ SO ₄ 、(NH ₄ ) ₂ SO ₄ 、CuHSO ₃ 、Cu SO ₄ And Al ₂ (SO ₄ ) ₃ ]Etc. The catalyst had copper sulfate formation with a concomitant decrease in the number of active sites, indicating that the decrease in active sites was due to sulfate formation and that the decrease in catalyst SCR activity was linearly related to the decrease in active sites. The decrease in activity after sulfiding for the Cu/SSZ-13 catalyst is related to the Cu-S species generated at the active site. And under sulfiding conditions, active Cu (OH) in the Cu/SSZ-13 catalyst ⁺ Compared with Cu ²⁺ Is easier to be combined with SO ₂ The reaction forms sulfate. When NH ₃ Exists in SO ₂ The effect of the sulfur ammonia species is not negligible when in a sulfiding atmosphere. Co-sulfidation studies of Cu/SAPO-34 sulfur ammonia in literature (Applied Catalysis B: environmental,2017,204:239-249;Applied Catalysis B:Environmental,2017,219:142-154) revealed that ammonium sulfate was largely formed at 250 ℃ active site, whereas copper sulfate was only formed at 350 ℃, further demonstrating by TOF that the reduction of isolated Cu2 active site is the main cause of activity reduction regardless of the sulfate formed at the active site. The Cu/SSZ-13 catalyst produces mainly ammonium sulfate under 200 ℃ sulfur ammonia co-sulfiding conditions, while 400 ℃ produces mainly copper sulfate.

The above documents disclose a method for synthesizing SSZ-13 molecular sieve having CHA structure and its catalytic performance as SCR catalyst, and indicate that it is preferable to obtain a catalyst having good thermal stability and good dispersion of supported metal. The conventional N, N, N-trialkyl-1-adamantyl ammonium salt and alkaline compound thereof are adopted as a template agent, so that the cost is high, the utilization rate is low, the recovery and treatment are difficult, the waste water generated by the synthesis of the molecular sieve is difficult to biochemically treat, and the problem of great reduction pollution is caused; moreover, the activity of the SCR catalyst can be obviously reduced in the tail gas containing the sulfur oxide by the conventional synthesized CHA molecular sieve, so that the CHA silicon-aluminum zeolite molecular sieve with large specific surface area, large pore volume, good thermal stability and strong sulfur poisoning resistance is synthesized by a template agent with low cost, easy post-treatment and strong structure guiding capability.

Disclosure of Invention

The invention aims to provide a CHA-13 molecular sieve synthesized by a composite organic template agent formed by N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N' -mono/bicycloalkyl-N-alkyl pyrrolidinium salt/alkali and a preparation method of a corresponding SCR catalyst, which are used as catalyst carriers for removing NOx by selective reduction. The present invention relates to the removal of nitrogen oxides emitted from internal combustion engines and provides a nitrogen oxide removal catalyst composed of a aluminosilicate zeolite molecular sieve having the CHA structure, a process for producing the catalyst and a nitrogen oxide removal process in which nitrogen oxides are reacted with at least one of ammonia, urea and an organic amine using the catalyst.

The invention aims to solve the technical problem that the SCR catalyst using the synthetic molecular sieve loaded with copper in the prior art has lower activity at low temperature through a hydrothermal endurance test, and provides a copper-based SCR catalyst still having higher activity at low temperature after the hydrothermal endurance test and a preparation method thereof.

The invention discloses a method for synthesizing CHA molecular sieve by a double template agent, which comprises the steps of crystallizing raw materials of silicon source, aluminum source and template agent under crystallization condition; the template agent is N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N' -mono/dicycloalkyl-N-alkyl pyrrolidinium salt/alkali compound which are mixed to form a double template agent for synthesizing the CHA zeolite molecular sieve, the molar ratio of silicon dioxide to aluminum oxide of the CHA zeolite molecular sieve product is 5-80, and the grain size is 1-5 mu m; BET formula calculation total specific surface area is more than or equal to 500m ² Per gram, the total pore volume is more than or equal to 0.20ml/g, and the micropore volume is more than or equal to 0.12ml/g; the CHA molecular sieve was prepared by diffusely reflecting ultraviolet-visible spectrum (DR UV-vis spectrum) Co ²⁺ The coordination peak-dividing quantitative characterization skeleton adjacent pairing Al content accounts for more than 80 percent of the total number; the CHA molecular sieve was analyzed by UV-Raman spectroscopy at 330+ -2 cm ^-1 And 465+ -5 cm ^-1 Obvious characteristic peaks are arranged at the positions; after saturated steam treatment is carried out on the CHA molecular sieve raw powder within the temperature range of 600-850 ℃, tetra-coordinated aluminum accounts for more than or equal to 92 percent of the total aluminum,the hexacoordinated aluminum accounts for less than or equal to 8 percent of the total aluminum.

Further, the N, N, N-trialkyl cyclohexyl quaternary ammonium salt/base and N' -mono/bicycloalkyl-N-alkylpyrrolidinium salt/base compounds described in the above technical schemes are characterized by the structural formulas:

R1 and R2 are independently selected from methyl or deuterated methyl, C2-C5 straight-chain or branched-chain alkyl; R3-R7 are independently selected from C1-C5 straight chain or branched alkyl; x-is a counter anion of a quaternary ammonium onium ion, including any of hydroxide, chloride, bromide, iodide, sulfate, bisulfate, carbonate, nitrate, bicarbonate, oxalate, acetate, phosphate, carboxylate;

further, in the technical scheme, the synthetic method comprises the steps of 1) fully dissolving and dispersing the zeolite molecular sieve raw material to be converted, naOH and deionized water in a molar ratio range of 2-40 of silicon dioxide to aluminum oxide to obtain a slurry component with a molar ratio of nNa ₂ O:nSiO ₂ :nAl ₂ O ₃ nH2 O= (0.5-2.5) 1.0 (0.025-0.5) and (5-20), aging in a crystallization kettle at 50-120 ℃ for 6-36 hours to obtain silica-alumina gel; step 2) adding a silicon source, N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali OSDA1, N' -mono/bicycloalkyl-N-alkyl pyrrolidinium salt/alkali OSDA2 and deionized water into the mixed silica-alumina gel mixture in step 1), fully and uniformly mixing, and mixing the components in a molar ratio of nNa ₂ O:nSiO ₂ :nA1 ₂ O ₃ :nOSDA1:nOSDA2:nH ₂ O= (0.005-0.5) 1.0 (0.0125-0.20) (0.01-0.5) (0.005-0.5) (5-100); adding acid solution to control alkali hydroxyl OH & lt- & gt and SiO in the mixed slurry ₂ Molar ratio nOH-/nSiO ₂ =0.1 to 1.0; the molar ratio of the two templates nOSDA1: nOSDA 2= (0.05-100): 1; step 3) stirring the mixture in the step 2), transferring the mixture into a hydrothermal crystallization reaction kettle, crystallizing the mixture for 8 to 120 hours under the autogenous pressure at the temperature of between 125 and 200 ℃, and filtering, washing, drying and roasting the crystallized productObtaining molecular sieve raw powder; step 4) mixing the molecular sieve raw powder obtained in the step 3) with ammonium salt solution with the concentration of 0.1-5.0 mol/L according to the solid-liquid mass ratio of 1: (5-50) carrying out ion exchange at 60-100 ℃ for 0.5-6 hours each time, and repeatedly exchanging the obtained filter cake with the ammonium salt solution for 1-3 times until the Na content in the molecular sieve is lower than 500ppm; and filtering to separate out solid product, washing with deionized water repeatedly to neutrality, drying the filter cake at 100-150 deg.c for 12-48 hr and roasting at 400-600 deg.c for 2-16 hr to obtain CHA type chabazite molecular sieve.

Further, in the above technical scheme, the CHA zeolite molecular sieve of the present invention is characterized in that: the XRD phase analysis pattern shows at least one XRD diffraction peak in each of the following tables in the range of 4 to 40 ° 2θ and has the features described in the following table:

* The relative intensity is the intensity relative to the peak intensity of 2θ=20.40 to 20.90

Further, in the above technical scheme, in the step 1) of the synthesis method, the zeolite molecular sieve raw material having a molar ratio of silica to alumina ranging from 2 to 40 is any one of FAU-type zeolite, MFI-type zeolite, BEA-type zeolite, MOR-type zeolite, LTA-type zeolite, and EMT-type zeolite, preferably any one of FAU-type zeolite, MFI-type zeolite, BEA-type zeolite, and MOR-type zeolite, and more preferably any one of X-type zeolite, Y-type zeolite, and USY-type zeolite having a FAU-type structure; the silicon source in the step 2) is selected from one or more of silica sol, water glass, white carbon black, sodium metasilicate, column chromatography silica gel, macroporous silica gel, coarse pore silica gel, fine pore silica gel, amorphous silica gel, B-type silica gel, methyl silicate, ethyl silicate, propyl silicate, butyl silicate, superfine silica powder, activated clay, organic silicon, diatomite and gas phase method silica gel, preferably one or more of silica sol, water glass, column chromatography silica gel, white carbon black, macroporous silica gel, coarse pore silica gel, fine pore silica gel, amorphous silica, B-type silica gel, methyl silicate and ethyl silicate.

Further, in the above technical scheme, the acid solution in the step 2) of the synthesis method is selected from any one or more of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, propionic acid, citric acid, lithocarbonic acid, oxalic acid and benzoic acid.

Further, in the above technical scheme, the ammonium salt is a mixture of any one, two or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carbonate and ammonium acetate in any proportion.

The invention provides an SCR catalyst for denitration, which is characterized in that a CHA zeolite molecular sieve is subjected to ion exchange with a soluble copper salt solution, then forms slurry with a binder and deionized water, wherein the solid content of the slurry is 25.0-48.0 wt%, and is coated on a porous regular material or a carrier of an integral filter substrate to form a proper coating so as to obtain the SCR catalyst of the metal-promoted CHA molecular sieve.

Further, in the above technical solution, the present invention provides an SCR catalyst, which is characterized in that: the soluble metal salt is selected from one or a combination of several soluble salts of copper, iron, cobalt, tungsten, nickel, zinc, molybdenum, vanadium, tin, titanium, zirconium, manganese, chromium, niobium, bismuth, antimony, ruthenium, germanium, palladium, indium, platinum, gold or silver, preferably any one or two of copper salt and ferric salt, further preferably copper salt; the copper salt is one or more of copper nitrate, copper chloride, copper acetate or copper sulfate; the concentration of copper ions in the copper salt aqueous solution is 0.1-0.5 mol/L.

Further, in the above technical solution, the present invention is characterized in that: the binder is selected from one or more of silica sol, alumina sol or pseudo-boehmite; the porous regular material or the integral filter base material is prepared from any one of cordierite, alpha-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia or zirconium silicate.

The application of the SCR catalyst disclosed by the invention is characterized in that: the method is applied to the selective catalyst reduction process of nitrogen oxides in the tail gas of an internal combustion engine and the purification of gas containing nitrogen oxides generated in the refining industrial process, and the purification treatment of gas containing nitrogen oxides from a refining heater and a boiler, a furnace, a chemical processing industry, a coke oven, a municipal waste treatment device and an incinerator.

The nitrogen oxides (NOx) of the present invention include various compounds, such as nitrous oxide (N) ₂ O), nitric Oxide (NO), nitrogen dioxide (NO ₂ ) Dinitrogen trioxide (N) ₂ O ₃ ) Dinitrogen tetroxide (N) ₂ O ₄ ) And dinitrogen pentoxide (N) ₂ O ₅ ) Etc.

The method of treating a gas stream comprising NOx, wherein the NOx is metered to 100 wt% of NO prior to contacting the catalyst with the gas stream ₂ The content is 80% by weight or less based on the total amount of the NO contained therein, preferably 5 to 70% by weight, more preferably 10 to 60% by weight, still more preferably 15 to 55% by weight, even more preferably 20 to 50% by weight ₂ The content is as follows. An oxidation catalyst located upstream of the catalyst oxidizes nitric oxide in the gas to nitrogen dioxide and then mixes the resulting gas with a nitrogenous reductant before the mixture is added to the zeolite catalyst, wherein the oxidation catalyst is adapted to produce a gas stream entering the zeolite catalyst, the gas stream having a ratio of 4:1 to 1:3 NO: NO2 volume ratio.

Reducing agents (urea, NH) ₃ Etc.), several chemical reactions occur, all of which represent reactions that reduce NOx to elemental nitrogen. In particular, the dominant reaction mechanism at low temperature is represented by formula (1).

4NO+4NH ₃ +O ₂ →4N ₂ +6H ₂ O (1)

Nonselective reaction with competing oxygen, or formation of 2-fold products, or non-productive consumption of NH ₃ . As such a non-selective reaction, for example, NH represented by formula (2) ₃ Is a complete oxidation of (c).

4NH ₃ +5NO ₂ →4NO+6H ₂ O (2)

Furthermore, NO present in NOx ₂ With NH ₃ The reaction of (2) is considered to be carried out by means of the reaction formula (3).

3NO ₂ +4NH ₃ →(7/2)N ₂ +6H ₂ O (3)

While NH is ₃ With NO and NO ₂ The reaction therebetween is represented by reaction formula (4).

NO+NO ₂ +2NH ₃ →2N ₂ +3H ₂ O (4)

The reaction rates of the reactions (1), (3) and (4) vary greatly depending on the reaction temperature and the kind of the catalyst used, and the reaction rate of the reaction (4) is usually 2 to 10 times the reaction rate of the reactions (1), (3).

In the SCR catalyst, in order to improve the NOx purifying ability at low temperature, it is necessary to make the reaction of the formula (4) dominant instead of the reaction of the formula (1). At low temperatures, the reaction of formula (4) predominates, preferably by increasing NO ₂ As is evident.

Therefore, copper has excellent adsorption ability to NO at low temperature of 150-300 ℃ and has stronger ability to oxidize NO. The oxidation reaction of NO is represented by formula (5).

NO+1/2O ₂ →NO ₂ (5)

The SCR catalyst for denitration is an SCR catalyst for carrying out ion exchange on synthetic silicon-aluminum zeolite molecular sieve raw powder and soluble metal salt solution to obtain a metal-promoted SSZ-13 eutectic molecular sieve.

The soluble copper salt used in the preparation process of the catalyst is one or more selected from copper nitrate, copper chloride, copper acetate or copper sulfate; the concentration of copper ions in the copper salt aqueous solution is 0.1-1.5 mol/L.

The amount of Cu in the copper-based SCR molecular sieve catalyst is 0.03-20 wt%, based on the weight of the copper-based SCR catalyst, wherein the amount of Cu is preferably 0.2-15 wt%, more preferably 0.5-10 wt%, more preferably 1.0-8.0 wt%, more preferably 1.5-5.0 wt%, more preferably 2.0-4.0 wt%, more preferably 2.5-3.5 wt%, more preferably 2.7-3.3 wt%, more preferably 2.9-3.1 wt%.

In certain embodiments of the invention, the washcoat of the molecular sieve SCR catalyst is preferably a solution, suspension or slurry that is applied to a porous monolith material (i.e., a honeycomb monolith catalyst support structure having a plurality of parallel channels extending axially through the entire component) or monolith filter substrate, such as a wall-flow filter, or the like, and suitable coatings that are formed include surface coatings, coatings that penetrate a portion of the substrate, coatings that penetrate the substrate, or some combination thereof.

The porous regular material comprises a honeycomb flow-through type regular carrier, and is prepared from cordierite, alpha-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia or zirconium silicate materials; the support is preferably a cordierite porous honeycomb flow-through monolith support having a loading of 170 to 270g/L.

The two most common substrate designs to which the SCR catalysts of the present invention can be applied are plate-like and honeycomb-like. Preferred substrates, particularly for mobile applications, include flow-through monoliths having a so-called honeycomb geometry, comprising a plurality of adjacent, parallel channels which are open at both ends and which generally extend from the inlet face to the outlet face of the substrate and which produce a high surface area to volume ratio. For certain applications, the honeycomb flow-through monolith preferably has a high cell density, for example, about 600 to 800 cells per square inch, and/or an average inner wall thickness of about 0.18 to 0.35mm, preferably about 0.20 to 0.25mm. For certain other applications, the honeycomb flow-through monolith preferably has a low cell density of about 150 to 600 cells per square inch, more preferably about 200 to 400 cells per square inch.

The catalysts in embodiments of the present invention exhibit high NOx conversion over a much wider temperature window. The temperature range for increasing the conversion efficiency may be about 150 to 650 ℃, preferably 200 to 500 ℃, more preferably 200 to 450 ℃, or most notably 200 to 400 ℃. Within these temperature ranges, the conversion efficiency after exposure to a reducing atmosphere, even after exposure to a reducing atmosphere and high temperatures (e.g., up to 850 ℃) may be greater than 55% to 100%, more preferably greater than 90% efficiency, even more preferably greater than 95% efficiency.

The SCR catalyst prepared by the CHA structure molecular sieve provided by the invention has better hydrothermal stability and wider ignition activity window temperature (200-500 ℃), has good low temperature and high Wen Qiran activity, has more proper pore channel structure and grain size distribution, is favorable for diffusing NOx molecules, enhances the adhesion of metal copper ions, and reduces the possibility of aggregation caused by the hydrothermal action of the metal copper ions.

The molecular sieve provided by the invention has more reasonably distributed acidity and good hydrothermal stability, overcomes the limitations of the components thereof, and has excellent NOx reduction performance after durable treatment at high temperature under the atmosphere containing hydrothermal steam, especially at low temperature. Better meets the requirements of industrial application and has wide application prospect.

The aluminosilicate zeolite molecular sieve of the present invention is more suitable for a catalyst or a CHA-type zeolite having high crystallinity of a catalyst carrier, particularly a CHA-type zeolite suitable for a nitrogen oxide reduction catalyst or a carrier thereof, and further suitable for a nitrogen oxide reduction catalyst or a carrier thereof in the presence of ammonia or urea, than conventional CHA-type zeolite.

Drawings

The invention is further described below with reference to the accompanying drawings and examples:

FIG. 1 is an XRD diffraction pattern of the SSZ-13 molecular sieve synthesized in example 1;

FIG. 2 is an XRD diffraction pattern of the SSZ-13 molecular sieve synthesized in example 2;

FIG. 3 is an XRD diffraction pattern of the SSZ-13 molecular sieve synthesized in example 3;

FIG. 4 is an SEM image of the synthesized SSZ-13 molecular sieve grains of example 1;

FIG. 5 is an SEM image of the synthesized SSZ-13 molecular sieve grains of example 2;

FIG. 6 is an SEM image of the synthesized SSZ-13 molecular sieve grains of example 3.

Detailed Description

Embodiments of the present invention and the effects produced are further illustrated by examples and comparative examples, but the scope of the present invention is not limited to what is shown in the examples.

The present invention uses a powder method of X-ray Diffraction (X-ray Diffraction) analysis to determine the lattice plane spacing (d) from the XRD pattern, and identifies the lattice plane spacing by comparison with the data collected in the XRD database of the International synthetic Zeolite Association or in the PDF (Powder Diffraction File; powder Diffraction file) of ICDD (International Centrefor Diffraction Data; international center for Diffraction data). As XRD measurement conditions in the embodiment of the present invention, the following conditions are given: using a PANalyticalX' Pert diffractometer to radiate with CuK alpha monochromatic light, wherein the tube voltage is 45kV, the current is 40mA, and the CuK alpha rays lambda= 1.540598; measurement mode: step-scan 2θ step-scan scale: 0.02626 °, measurement range: 2θ=5° to 60 °.

The pore structure of the molecular sieve was determined using a Micromeritics ASAP 2460 static nitrogen adsorber. Test conditions: placing the sample in a sample processing system, and vacuumizing to 1.33310 at 350deg.C ^-2 Pa, maintaining the temperature and the pressure for 15h, and purifying the sample. At the temperature of liquid nitrogen of-196 ℃, the purified sample is measured at different specific pressures p/p ₀ And (3) obtaining the adsorption quantity and desorption quantity of nitrogen under the condition to obtain a nitrogen adsorption-desorption isothermal curve. Then calculate the BET total specific surface area using the BET formula (S _BET ) The specific surface area of the sample micropore is calculated by adopting a t-plot method (S _micro ) And micropore volume (V) _micro ) Total pore volume in P/P ₀ Adsorption amount calculation at=0.98: specific surface area of outer hole (S) _exter )＝S _BET –S _micro The method comprises the steps of carrying out a first treatment on the surface of the External pore volume (V) _exter )＝V _total -V _micro )。

The content determination method of the framework adjacent pairing Al comprises the following steps: co is to be ²⁺ Ion exchange to CHA molecular sieve at 500 deg.c and high vacuum condition<10 ^-1 Pa) is baked for 5 hours, then room temperature test is carried out to obtain related diffuse reflection ultraviolet-visible spectrum (DR UV-vis spectrum), and C is measured by ICP ^o2+ Co in CHA molecular sieves after ion exchange ²⁺ Ion molar mass [ Co ] _max ]The molar amount of total Al [ Al ] can also be determined _total ]By the formula [ Al ] _close ]＝2×[Co _max ]Calculating the mole number of Al of the nearest neighbor framework _close ]，[Al _isolated ]＝[Al _total ]-2×[Co _max ]，[Al _close ]＝[Al _pairs ]+[Al _unpairs ]When (when)The CHA molecular sieve has a silica to alumina ratio greater than 10 (Si/Al>5) Then [ Al _close ]≈[Al _pairs ]Carrying out peak separation treatment through DR UV-vis spectrum to obtain the content of single six-membered ring sigma, the content of eight-membered ring tau and the content of double six-membered ring omega; the co2+ ion balance is formed by two Al atoms (called Al _close ) The negative charge generated is located in the secondary structural ring (Al _pairs ) In or two adjacent rings (Al _unpairs ) But cannot balance the difference between the two (Al _isolated ) The charge generated by a single Al atom.

²⁷ Al MAS NMR test method: superconducting nuclear magnetic resonance apparatus model VARIAN INOVA 300M, ²⁷ the resonance frequency of the Al detection core is 78.155MHz, the sampling time is 0.02s, the pulse width is 0.3 mu s, the cycle delay time is 1s, the scanning is 400 times, and the Al (NO) ₃ ) ₃ 29H ₂ The chemical shift of O is a reference external standard. Pretreatment of the product to be analyzed: placing the powder sample of the molecular sieve SSZ-13 from which the template agent is removed into a glass tube, connecting the glass tube to a vacuum system, heating the glass tube at a speed of about 1-2 ℃ per minute while vacuumizing, respectively staying at 120 ℃ and 300 ℃ for 30min, and finally reaching 400 ℃. And sealing the sample tube after the vacuum degree reaches 1310-3Pa and is maintained for more than 5 hours, so as to prepare the sample to be measured.

Ultraviolet raman spectrometry: the spectroscopic system used a SPEX Triplemate T64000 type tri-grating monochromator (Jobin-Yvon Co.) with a spectral resolution of 2cm-1, the detector used a liquid nitrogen cooled Spectrum One CCD 2000 type photo-coupled detector, and the excitation light source used an IK-3351-G type He-Cd laser (325 nm) and 266nm ultraviolet laser generated by doubling the frequency of 532nm laser generated by a DPSS 532model 200 laser.

Diffuse reflectance ultraviolet-visible spectrum (DR-UV-vis) data acquisition was performed with an agilent Cary 5000 ultraviolet-visible-near infrared (UV-vis-NIR) spectrophotometer equipped with a polytetrafluoroethylene integrating sphere.

The molar ratio of the CHA molecular sieve product silicon dioxide to aluminum oxide obtained by the method is 5-80, and the grain size is 1-5 mu m; BET formula calculation total specific surface area is more than or equal to 500m ² Per gram, the total pore volume is more than or equal to 0.20ml/g,the micropore volume is more than or equal to 0.12ml/g; the CHA molecular sieve was prepared by diffusely reflecting ultraviolet-visible spectrum (DR UV-vis spectrum) Co ²⁺ The coordination peak-dividing quantitative characterization skeleton adjacent pairing Al content accounts for more than 80 percent of the total number; the CHA molecular sieve has obvious characteristic peaks at 330+/-2 cm < -1 > and 465+/-5 cm < -1 > through ultraviolet-Raman spectrum analysis; after saturated steam treatment is carried out on the CHA molecular sieve raw powder at the temperature of 600-850 ℃, the total aluminum content of tetra-coordinated aluminum is more than or equal to 92%, and the total aluminum content of hexa-coordinated aluminum is less than or equal to 8%.

Example 1

A CHA type SSZ-13 molecular sieve and a catalyst preparation method are provided:

1) 45.59g of HY molecular sieve (silicon-aluminum ratio nSiO ₂ /nAl ₂ O ₃ After=5.20, 78.1% dry basis, 26.68g NaOH flake alkali and 69.98g deionized water are fully dissolved and dispersed, the molar ratio of the slurry components is nNa ₂ O:nSiO ₂ :nAl ₂ O ₃ :nOH ^- :nH ₂ O=0.75:1.0:0.192:1.5:10, aging in a crystallization kettle at 85 ℃ for 36 hours to obtain silica-alumina gel;

2) To the mixed silica alumina gel mixture of 1) was added 507.51g of a silica gel solution (Na 2O:0.24wt%, siO2:30.36 wt%), 173.23g of N, N-dimethylethylcyclohexylammonium hydroxide (concentration 20wt%, expressed as OSDA1, CAS: 105197-93-1), 29.71g of N-cyclohexyl-N-methylpyrrolidinium hydroxide (concentration 25% by weight, expressed as OSDA2, CAS: 1892548-62-7), 56.31g of NaOH caustic soda flakes and 215.47g of deionized water are fully and uniformly stirred and mixed by ultrasonic, and 5% of HCl solution is added to regulate nOH in the system ^- /nSiO ₂ Ratio of the components of the mixed slurry to the molar ratio nNa ₂ O:nSiO ₂ :nA1 ₂ O ₃ :nOH ^- :nOSDA:nH ₂ O=0.35:1.0:0.0286:0.78:0.08:15; stirring the mixture, transferring the mixture into a hydrothermal crystallization reaction kettle, crystallizing for 36 hours at the self-generated pressure and 140 ℃, quenching to stop crystallization, filtering and washing the product until the pH value is nearly neutral, drying for 12 hours at 120 ℃, and roasting for 4 hours at 540 ℃ to obtain SSZ-13 molecular sieve raw powder;

3) Separating SSZ-13 molecular sieve raw powder in the step 2) and 1.0mol/L ammonium nitrate solution according to the solid-liquid mass ratio of 1:10 at 70 DEG CSub-exchange for 2 hours, and then the filter cake obtained by filtration is repeatedly exchanged with fresh ammonium nitrate solution for two times under the same condition, so that the Na ion content in the sample is lower than 500ppm. The filter cake obtained by the subsequent filtration is dried overnight at 110 ℃ to obtain the ammonium molecular sieve NH ₄ SSZ-13 is heated to 450 ℃ and baked for 16 hours to obtain the H-type SSZ-13 molecular sieve.

4) 50.0g of the H-type SSZ-13 molecular sieve obtained in the step 3) is added into a copper nitrate aqueous solution with the concentration of 0.15mol/L, diluted nitric acid is added into the solution dropwise to adjust the pH value to 6.5, and the mixture is placed into a heat-resistant container after being stirred uniformly and then placed into a dryer with a pressure reducing valve; pumping the pressure in the dryer to below 10Torr by a vacuum pump, performing degassing treatment at room temperature for 1 hour, heating to 90 ℃ and drying for 12 hours, and roasting the dried sample at 500 ℃ for 4 hours under normal atmospheric pressure; the copper modified SSZ-13 molecular sieve is obtained, and in the catalyst prepared according to the XRF analysis result, copper (II) ions account for 3.4% of the total weight of the molecular sieve catalyst, namely, the copper load is 3.4% by weight.

5) 40.0g of the copper-modified molecular sieve obtained in 4) above was mixed with 20.0g of silica sol (SiO 2 content: 30.0 wt%) and 110.37g of deionized water were uniformly mixed to prepare a catalyst slurry having a solid content of 27.0wt%, and coated on a cordierite-made honeycomb porous structured material (# 400cpsi, diameter 20mm, length 40 mm) by an impregnation method, excess slurry droplets were blown off with compressed air, dried at 105 deg.c for 24 hours, and coated under the same conditions for 2 times, and baked at 500 deg.c for 2 hours to prepare an SCR catalyst having a structured material loading of 230.9g/L (the mass of the structured material weight gain after baking divided by the space occupied by the structured material, and the definitions of the subsequent examples and comparative examples were the same), and the obtained SCR catalyst was designated as a, and the relevant preparation parameters and substance types are shown in tables 1, 2, 3 and 4.

Example 2

The process for the synthesis of CHA-type SSZ-13 molecular sieves is similar to example 1, except that the mole ratio of the mixed sols in step 1) and step 2), the type of organic template, the type of silicon source, the type of transcrystalline zeolite and the silicon to aluminum ratio, crystallizationTemperature and crystallization time, etc., step 3) 50.0g of H-type SSZ-13 molecular sieve is taken, different soluble metal salt types, concentrations, solution volumes and metal loading amounts are adopted, and step 4) 40.0g of copper-modified CHA-type SSZ-13 molecular sieve is taken, and 20.0g of silica sol (SiO ₂ The content is as follows: 30.0 wt%) and 52.20g deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 41.0wt%, which was coated on the cordierite regular material by dipping. The specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 3

The process for the synthesis of CHA-type SSZ-13 molecular sieves is similar to example 1, except that the mole ratio of the mixed sol, the type of organic template, the type of silicon source, the type of transcrystalline zeolite and the silicon to aluminum ratio, the crystallization temperature and crystallization time, etc. in step 1) and step 2), step 3) 50.0g of H-type SSZ-13 molecular sieve is taken, different soluble metal salt types, concentrations, solution volumes and metal loadings are used, and step 4) 40g of copper-modified CHA-type SSZ-13 molecular sieve is taken, and 20.0g of silica sol (SiO ₂ The content is as follows: 30.0 wt%) and 61.69g deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 37.8wt% which was coated on the cordierite regular material by dipping. The specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 4

The process for the synthesis of CHA-type SSZ-13 molecular sieves is similar to example 1, except that the mole ratio of the mixed sol, the type of organic template, the type of silicon source, the type of transcrystalline zeolite and the silicon to aluminum ratio, the crystallization temperature and crystallization time, etc. in step 1) and step 2), step 3) 50.0g of H-type SSZ-13 molecular sieve is taken, different soluble metal salt types, concentrations, solution volumes and metal loadings are used, and step 4) 40g of copper-modified CHA-type SSZ-13 molecular sieve is taken, and 20.0g of silica sol (SiO ₂ The content is as follows: 30.0 wt%) and 51.56g deionized water were uniformly mixed to prepare a catalyst slurry having a solid content of 41.2wt%, and coated on the cordierite regular material by dipping. The specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 5

SynthesisThe process for the CHA type SSZ-13 molecular sieves was similar to that of example 1 except that the mole ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the transcrystalline zeolite, the silica-alumina ratio, the crystallization temperature, the crystallization time, etc. in step 1) and step 2), 50.0g of the H-type SSZ-13 molecular sieve was taken, the type of soluble metal salt, the concentration, the solution volume and the metal loading were varied, and 40g of the copper-modified CHA type SSZ-13 molecular sieve was taken in step 4) and 30.0g of the alumina sol (Al ₂ O ₃ The content is as follows: 20.0 wt%) and 124.44g deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 25.2wt% which was coated on the cordierite structured material by dipping. The specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 6

The process for the synthesis of CHA-type SSZ-13 molecular sieves is similar to example 1, except that the mole ratio of the mixed sol, the type of organic template, the type of silicon source, the type of transcrystalline zeolite and the silicon to aluminum ratio, the crystallization temperature and crystallization time, etc. in step 1) and step 2), step 3) 50.0g of H-type SSZ-13 molecular sieve is taken, different soluble metal salt types, concentrations, solution volumes and metal loadings are used, and step 4) 40g of copper-modified CHA-type SSZ-13 molecular sieve is taken, and 30.0g of aluminum sol (Al ₂ O ₃ The content is as follows: 20.0 wt%) and 76.03g deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 31.5wt%, which was coated on the cordierite regular material by dipping. The specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 7

The process for the synthesis of CHA-type SSZ-13 molecular sieves is similar to example 1, except that the mole ratio of the mixed sol, the type of organic template, the type of silicon source, the type of transcrystalline zeolite and the silicon to aluminum ratio, the crystallization temperature and crystallization time, etc. in step 1) and step 2), step 3) 50.0g of H-type SSZ-13 molecular sieve is taken, different soluble metal salt types, concentrations, solution volumes and metal loadings are used, and step 4) 40g of copper-modified CHA-type SSZ-13 molecular sieve is taken, and 30.0g of aluminum sol (Al ₂ O ₃ The content is as follows: 20.0wt percent) and 51.69g deionized water are mixed uniformly to prepare the solid contentThe catalyst slurry in an amount of 37.8wt% was coated on the cordierite structured material by an impregnation method. The specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 8

The process for the synthesis of CHA-type SSZ-13 molecular sieves is similar to example 1, except that the mole ratio of the mixed sol, the type of organic template, the type of silicon source, the type of transcrystalline zeolite and the silicon to aluminum ratio, the crystallization temperature and crystallization time, etc. in step 1) and step 2), step 3) 50.0g of H-type SSZ-13 molecular sieve is taken, different soluble metal salt types, concentrations, solution volumes and metal loadings are used, and step 4) 40g of copper-modified CHA-type SSZ-13 molecular sieve is taken, and 30.0g of aluminum sol (Al ₂ O ₃ The content is as follows: 20.0 wt%) and 40.84g deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 41.5wt%, which was coated on the cordierite regular material by dipping. The specific parameters in this example are shown in tables 1, 2, 3 and 4.

TABLE 1 molecular sieve Synthesis step 1) selection of parameters

TABLE 2 selection of parameters in molecular sieve Synthesis step 2)

TABLE 3 molecular sieve Performance parameter Table obtained in examples 1-8

* : by Co ²⁺ After the ion is fully exchanged on the CHA molecular sieve, the diffuse reflection ultraviolet is usedCalculation of the correlation data measured in the visible spectrum and in ICP (inductively coupled plasma)

* *: after 16 hours of steam heat treatment at 800 ℃, the sample was tested for aluminum ratio using 27Al MAS NMR solid nuclear magnetism.

Table 4 preparation of SCR catalyst metal ion parameters and metal loadings in examples 1-8

Comparative example 1

According to the SCR catalyst preparation method in patent CN 112429749A:

1) 593.72g of silica sol (Na ₂ O：0.24wt％，SiO ₂ :30.36wt percent) and 196.99g of deionized water are added into the mixture and evenly mixed under ultrasonic stirring, 11.50g of pseudo-boehmite (77.0 wt percent on a dry basis) molecular sieve serving as an aluminum source and 58.69g of NaOH flake alkali are fully and evenly stirred to form silica-alumina gel, and 241.42g of N, N-dimethyl-N' -ethyl- (decalin-1-yl) ammonium hydroxide (with the concentration of 20wt percent and expressed as OSDA 1) and 27.73g of N, N-dimethyl ethyl-cyclohexyl ammonium hydroxide (with the concentration of 25wt percent and expressed as OSDA 2) are respectively added into the mixture and evenly stirred; then adding 8.85g of NaCl (99 wt%) as metal salt M into the solution respectively, and mixing them completely and uniformly; finally adding 5% HCl solution to regulate nOH in the system ^- /nSiO ₂ Ratio of the mixed slurry components to molar ratio

nNa ₂ O:nSiO ₂ :nA1 ₂ O ₃ :nOH ^- :nOSDA1:nOSDA2:nNaCl:nH ₂ O=0.25:1.0:0.0286:0.58:0.0667:0.0133:0.050:15; adding SiO into the mixed slurry ₂ With A1 ₂ O ₃ 9.72g of CHA molecular sieve accounting for 5.0 percent of the total mass is used as seed crystal;

2) The mixture in the step 1) is stirred and then transferred into a hydrothermal crystallization reaction kettle, stirred under autogenous pressure and at a speed of 80rpm, crystallized for 24 hours at 140 ℃, and then heated to 170 ℃ for crystallization for 72 hours. After crystallization is completed, the sudden cooling of the product stops crystallization, and the SSZ-13 molecular sieve raw powder is obtained through suction filtration separation, washing to pH value of 8.0-9.0, drying at 120 ℃ for 12 hours and roasting at 540 ℃ for 4 hours.

3) And (2) carrying out ion exchange on the SSZ-13 molecular sieve raw powder in the step (2) and an ammonium nitrate solution with the concentration of 1.0mol/L according to the solid-liquid mass ratio of 1:10 for 2 hours at the temperature of 70 ℃, and then repeatedly exchanging the filtered filter cake with the fresh ammonium nitrate solution for two times under the same condition, so that the Na ion content in a sample is lower than 500ppm. And then drying the filter cake obtained by filtering overnight at 110 ℃ to obtain an ammonium type molecular sieve NH4-SSZ-13, and then heating to 500 ℃ to bake for 8 hours to obtain an H type SSZ-13 molecular sieve, namely the CHA molecular sieve.

5) 40.0g of the copper-modified molecular sieve obtained in 4) above was mixed with 20.0g of silica sol (SiO 2 content: 30.0 wt%) and 121.82g of deionized water were uniformly mixed to prepare a catalyst slurry having a solid content of 25.3wt%, and the catalyst slurry was coated on a cordierite-made honeycomb porous structured material (# 400cpsi, diameter 20mm, length 40 mm) by an immersion method, excess slurry droplets were blown off with compressed air, dried at 105 ℃ for 24 hours, and coated under the same conditions for 2 times, and baked at 500 ℃ for 2 hours to prepare an SCR catalyst having a structured material loading of 232.7g/L (the mass of the structured material weight gain after baking divided by the space volume occupied by the structured material, and the definition of the subsequent examples and comparative examples with respect to the loading was the same), and the obtained SCR catalyst was designated as VS-1.

Comparative example 2

Synthesis of SSZ-13 molecular sieves and preparation of SCR catalysts according to the method in CN 109195911A

25wt% of DMECHAOH (N, N, N-dimethylethylcyclohexylammonium hydroxide) aqueous solution, 25wt% of TMADOH (N, N, N-trimethyl-1-adamantylammonium hydroxide) aqueous solution, 48wt% of sodium hydroxide aqueous solution, 48wt% of potassium hydroxide aqueous solution, deionized water, and amorphous aluminum silicate (SiO 2/Al2 O3=25.7) were mixed to obtain 50.0g of a mixture having a molar composition of:

0.1Na:0.1K:SiO ₂ :0.0389Al ₂ O ₃ :0.2OH ^- :0.04DMECHAOH:0.04TMAdOH:15.0H ₂ O

The raw material composition was filled into a closed container having an internal volume of 80mL, and the container was stirred at 55rpm while being rotated, and reacted at 170℃for 48 hours. And (3) carrying out solid-liquid separation on the obtained product, cleaning with deionized water, drying at 110 ℃, and roasting at 540 ℃ for 4 hours to obtain SSZ-13 molecular sieve raw powder. The molecular sieve raw powder and 1.0mol/L ammonium nitrate solution are subjected to ion exchange for 2 hours at 80 ℃ according to the solid-liquid mass ratio of 1:10, and then the filter cake obtained by filtration is repeatedly exchanged with the fresh ammonium nitrate solution for two times under the same condition, so that the Na ion content is lower than 500ppm. The filter cake obtained by the subsequent filtration is dried overnight at 110 ℃ to obtain the ammonium molecular sieve NH ₄ SSZ-13 is heated to 450 ℃ and baked for 16 hours to obtain the H-type SSZ-13 molecular sieve.

10g of SSZ-13 molecular sieve raw powder was added to 100g of Cu (NO) with a concentration of 0.3mol/L ₃ ) ₂ ·3H ₂ And (3) in the O aqueous solution, dropwise adding dilute nitric acid into the solution to adjust the pH to 5.8, and uniformly stirring. After stopping stirring for 1 hour, the supernatant was siphoned off when SSZ-13 zeolite settled. And (3) repeatedly exchanging the copper nitrate solution once, and finally filtering and washing the exchanged SSZ-13 zeolite by deionized water. Drying at 90 ℃ for 12 hours under 10Torr low pressure, and roasting at 500 ℃ for 4 hours under normal atmospheric pressure to obtain the copper modified SSZ-13 molecular sieve powder. Based on the results of the XRF analysis, The copper (II) ions account for 2.9% of the total weight of the molecular sieve catalyst.

15g of the resulting copper-modified SSZ-13 molecular sieve were taken together with 5.56g of a silica sol (30 wt% SiO) ₂ ) And 22.80g deionized water are uniformly mixed to prepare catalyst slurry with the solid content of 38.44wt%, the catalyst slurry is coated on a cordierite honeycomb porous structured material (# 400cpsi, diameter 20mm and length 40 mm) by an immersion method, redundant slurry drops are blown off by compressed air, the mixture is dried for 12 hours at 110 ℃, then the slurry is coated again, the catalyst slurry is baked for 2 hours at 500 ℃ to prepare the SCR catalyst, and the catalyst loading on the structured material is measured to be 212.5g/L and is marked as VS-2.

Examples 9 to 24

SCR catalyst test:

SCR catalysts prepared in examples 1 to 6 and comparative examples 1 to 2 were placed in a reactor

Comprises 500ppm NO, 500ppm NH ₃ A mixed gas stream of 160mL/min, 10% O2 by volume, 5% steam by volume and Ar as balance gas, was passed through a preheater (set at 250 ℃ C.) and then into the SCR reactor. At a reaction temperature of 150 to 650 ℃ and based on 48000h ^-1 The test pieces were tested at a volumetric air hourly space velocity. The temperature is monitored by means of a thermocouple located at the sample location.

The fresh SCR catalyst of each of the above examples and comparative examples, which had been used, was subjected to hydrothermal durability treatment to obtain an aged SCR catalyst, and the conditions of the hydrothermal durability treatment test were:

Space velocity SV:30000/h, temperature: 800 ℃ for the time of: 16 hours, moisture concentration: 10%, oxygen concentration: 10%, nitrogen concentration: balance.

After hydrothermal aging treatment is carried out according to the parameters, the catalyst is continuously used as an SCR catalyst for evaluating and testing the NOx catalytic reduction reaction:

the NO conversion or "denox" activity was determined under steady state conditions by measuring the NOx, NH3 and N2O concentrations at the outlet using a Bruker EQUINOX model 55 FT-IR spectrometer.

The Cu-supported SCR catalysts prepared in examples and comparative examples were evaluated for selective catalytic reduction performance of NOx using the above-described SCR catalyst activity laboratory evaluation apparatus, and the results are shown in table 5.

TABLE 5 preparation of catalyst NOx Selective reduction Performance evaluation indicators for examples 1 to 6 and comparative examples 1 to 2

* 800 ℃ was aged for 16 hours at a space velocity of 30000/h under an atmosphere of 10% moisture concentration +10% oxygen concentration.

As can be seen from Table 5, the Cu-SSZ-13 or Fe-SSZ-13 catalysts obtained in examples 1-6, evaluated in examples 9-14, showed better light-off at low temperatures and high temperature activity, with SCR activity significantly superior to the catalytic performance shown in examples 15-16 for the catalysts VS-1 and VS-2 obtained in comparative example 1, both in the "fresh" state and in the "aged" state. Thus, the results obtained from examples 9-14 clearly show that the Cu-SSZ-13 or Fe-SSZ-13 catalyst materials of the present invention and catalysts obtained therewith have improved SCR catalytic activity, especially at low conversion temperatures typical of cold start conditions when treating NOx in, for example, diesel locomotive applications.

Sulfur poisoning resistant SCR catalytic test:

SCR catalysts of the sum 8 of VS-1, VS-2 and A-F prepared in comparative examples 1 to 2 and examples 1 to 6 were charged in a reactor

In (2) SO2 was fed into the NOx-containing gas stream at a timing such that the gas stream had a composition of 500ppm NO, 500ppm NH3, 200ppm SO2, 10% O2 by volume, 5% steam by volume and Ar as an equilibrium gas mixture stream of 160mL/min, passed through a preheater (set at 250 ℃ C.) and then into the SCR reactor. At 200℃and based on 48000h ^-1 The test pieces were subjected to sulfur poisoning resistance SCR reaction test at the volume gas hourly space velocity, and the evaluation results are shown in table 8.

TABLE 8 introduction or stopping SO ₂ SCR catalyst NOx conversion at 200 ℃ after different aging times in atmosphere in examples and comparative examples

The NOx conversion on the SCR catalyst prepared in the example remained above 86% after 5min of SO 2-containing tail gas, while the NOx conversion on the SCR catalysts VS-1 and VS-2 in the comparative example was reduced below 70%; after 10min of SO2 tail gas introduction, the NOx conversion over 6 of the A-F SCR catalysts in the examples was suddenly reduced to below 66%, but was maintained at substantially above 62%, while the NOx conversion over the comparative SCR catalysts VS-1 and VS-2 was reduced to below 55%. After 60min and 100min of SO2 tail gas introduction, the NOx conversion on the 6 SCR catalysts A-F in the examples remained substantially above 60% although continuing to be reduced, while the NOx conversion on the comparative SCR catalysts VS-1 and VS-2 was also reduced but reduced below 50%. Stopping introducing SO ₂ After 10 minutes, the NOx conversion rate of 6 SCR catalysts A-F in the example is recovered to be more than 61%, and the NOx conversion rates of the comparative SCR catalysts VS-1 and VS-2 are slightly recovered, and the maximum is only about 49%. From the comparison of the above data, it can be seen that the SCR catalyst prepared in the examples has a significant sulfur poisoning resistance, which also increases the service life of the catalyst. For other SCR applications, the Cu-SSZ-13 or Fe-SSZ-13 catalyst materials of the present invention allow for higher conversion to be maintained in a sulfur-containing atmosphere, thus allowing for high energy efficiency treatment of NOx-containing exhaust gases at comparable conversion.

The above-mentioned embodiments are merely for illustrating the technical concept and features of the present invention, and are not intended to limit the scope of the present invention to those skilled in the art to understand the present invention and implement the same. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.

Claims

1. A preparation method of a CHA molecular sieve catalyst with a high-skeleton four-coordination aluminum structure is characterized by comprising the following steps of: comprises crystallization reaction of raw materials of silicon source, aluminum source and template agent under crystallization condition;

The template agent is CHA zeolite molecular sieve synthesized by mixing N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N' -mono/dicycloalkyl-N-alkyl pyrrolidinium salt/alkali compound;

the CHA molecular sieve reflects ultraviolet-visible spectrum Co by diffusion ²⁺ The coordination peak-dividing quantitative characterization skeleton adjacent pairing Al content accounts for more than 80 percent of the total number; the CHA molecular sieve was analyzed by UV-Raman spectroscopy at 330+ -2 cm ^-1 And 465+ -5 cm ^-1 Obvious characteristic peaks are arranged at the positions; after saturated steam treatment is carried out on the CHA molecular sieve raw powder within the temperature range of 600-850 ℃, the total aluminum content of tetra-coordinated aluminum is more than or equal to 92%, and the total aluminum content of hexa-coordinated aluminum is less than or equal to 8%;

the structural formulas of the N, N, N-trialkyl cyclohexyl quaternary ammonium salt/base and the N' -mono/dicycloalkyl-N-alkyl pyrrolidinium salt/base compound are as follows:

，/>

，/>

，/>

，/>

；

wherein R1 and R2 are independently selected from methyl or deuterated methyl, C2-C5 straight-chain or branched alkyl; r3 to R7 are independent from each other and are selected from C1-C5 straight-chain or branched-chain alkyl; x-is a counter anion of a quaternary ammonium onium ion, including any of hydroxide, chloride, bromide, iodide, sulfate, bisulfate, carbonate, nitrate, bicarbonate, oxalate, acetate, phosphate, carboxylate;

The CHA molecular sieve synthesis method is characterized by comprising the following steps of:

1) Fully dissolving and dispersing a zeolite molecular sieve raw material to be subjected to crystal transformation, naOH and deionized water in a molar ratio range of 2-40 of silicon dioxide to aluminum oxide, and aging the slurry to obtain silica-alumina gel;

2) Adding silicon source, N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali OSDA1, N' -mono/bicycloalkyl-N-alkyl pyrrolidinium salt/alkali OSDA2 and deionized water into the mixed silica-alumina gel mixture in the step 1), fully and uniformly mixing, adding acid solution to control alkali hydroxyl OH in the mixed slurry ^- With SiO ₂ Molar ratio nOH of (C) ^- /nSiO ₂ In the range of=0.1 to 1.0; the molar ratio of the two templates nOSDA1: nOSDA 2= (0.05-100): 1;

3) Stirring the mixture in the step 2), transferring the mixture into a hydrothermal crystallization reaction kettle, crystallizing the mixture for 8 to 120 hours at the autogenous pressure and the temperature of 125 to 200 ℃, and filtering, washing, drying and roasting the crystallized product to obtain molecular sieve raw powder;

4) Ion exchange is carried out on the molecular sieve raw powder obtained in the step 3) and the ammonium salt solution until the Na content in the molecular sieve is lower than 500ppm; and filtering to separate out a solid product, washing, drying and roasting to obtain the CHA chabazite molecular sieve.

2. The method of manufacture of claim 1, wherein:

In the step 1), the molar ratio of the slurry components is nNa ₂ O: nSiO ₂ : nAl ₂ O ₃ : nH ₂ O= (0.5-2.5) 1.0 (0.025-0.5) 5-20, and aging at 50-120 ℃ for 6-36 hours in a crystallization kettle;

the molar ratio nNa of the components of the mixed slurry in the step 2) ₂ O: nSiO ₂ : nA1 ₂ O ₃ : nOSDA1: nOSDA2: nH ₂ O=(0.005~0.5):1.0: (0.0125~0.20): (0.01~0.5): (0.005~0.5): (5~100)；

In the step 4), the solid-liquid mass ratio of the molecular sieve raw powder to the ammonium salt solution with the concentration of 0.1-5.0 mol/L is 1: (5-50) carrying out ion exchange at 60-100 ℃ for 0.5-6 hours each time, and repeatedly exchanging the obtained filter cake with an ammonium salt solution for 1-3 times until the Na content in the molecular sieve is lower than 500ppm; and filtering to separate out a solid product, repeatedly washing with deionized water to neutrality, drying a filter cake at 100-150 ℃ for 12-48 hours, and roasting at 400-600 ℃ for 2-16 hours to obtain the CHA chabazite molecular sieve.

3. The method of manufacturing according to claim 1, characterized in that: the molar ratio of the silicon dioxide to the aluminum oxide in the step 1) ranges from 2 to 40; the zeolite molecular sieve raw material is any one of FAU type zeolite, MFI type zeolite, BEA type zeolite, MOR type zeolite, LTA type zeolite and EMT type zeolite; the silicon source in the step 2) is selected from one or more of silica sol, water glass, white carbon black, sodium metasilicate, column chromatography silica gel, macroporous silica gel, coarse pore silica gel, fine pore silica gel, amorphous silica gel, B-type silica gel, methyl silicate, ethyl silicate, propyl silicate, butyl silicate, superfine silica powder, activated clay, organic silicon, diatomite and gas phase method silica gel.

4. The method of manufacturing according to claim 1, characterized in that: the acid solution in the step 2) is selected from any one or more of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, propionic acid, citric acid, lithocarbonic acid, oxalic acid and benzoic acid.

5. The method of manufacture of claim 1, wherein: and (3) mixing any one or two or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carbonate and ammonium acetate in any proportion to obtain the ammonium salt in the step (4).

6. The CHA molecular sieve obtained by any one of the preparation methods of claims 1 to 5, wherein: the molar ratio of silicon dioxide to aluminum oxide of the CHA molecular sieve product ranges from 5 to 80, and the crystal grain size is determined1-5 μm in size; BET formula calculation total specific surface area is more than or equal to 500m ² Per gram, the total pore volume is more than or equal to 0.20ml/g, and the micropore volume is more than or equal to 0.12ml/g.

7. The CHA molecular sieve of claim 6, wherein: the XRD phase analysis pattern shows at least one XRD diffraction peak in each of the following tables in the range of 4-40 DEG 2 theta, and has the characteristics described in the following tables:

* The relative intensity is an intensity relative to the peak intensity of 2θ=20.40 to 20.90.

8. An SCR catalyst for denitration, which is prepared by performing ion exchange between the CHA-type zeolite molecular sieve according to claim 6 or 7 and a soluble copper salt solution, forming slurry with a binder and deionized water to a solid content of 25.0-48.0wt%, and coating the slurry on a carrier of a porous regular material or a monolithic filter substrate to form a proper coating.

9. The SCR catalyst according to claim 8, wherein: the soluble metal salt is selected from one or a combination of several soluble salts of copper, iron, cobalt, tungsten, nickel, zinc, molybdenum, vanadium, tin, titanium, zirconium, manganese, chromium, niobium, bismuth, antimony, ruthenium, germanium, palladium, indium, platinum, gold or silver.

10. The SCR catalyst according to claim 8, wherein: the soluble metal salt is selected from any one or two of copper salt and ferric salt; the copper salt is one or more of copper nitrate, copper chloride, copper acetate or copper sulfate; the concentration of copper ions in the copper salt aqueous solution is 0.1-0.5 mol/L.

11. The catalyst of claim 8, wherein: the binder is selected from one or more of silica sol, alumina sol or pseudo-boehmite; the porous regular material or the integral filter base material is prepared from any one of cordierite, alpha-alumina, silicon carbide, aluminum titanate, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia or zirconium silicate.

12. Use of an SCR catalyst according to any one of claims 8-11, characterized in that: the method is applied to the selective catalyst reduction process of nitrogen oxides in the tail gas of an internal combustion engine and the purification of gas containing nitrogen oxides generated in the refining industry process, and the purification treatment of gas containing nitrogen oxides from a refining heater and a boiler, a furnace, a chemical processing industry, a coke oven, a municipal waste treatment device and an incinerator.