CN114130423A

CN114130423A - CHA molecular sieve with characteristic framework structure and synthesis method and application thereof

Info

Publication number: CN114130423A
Application number: CN202111424173.2A
Authority: CN
Inventors: 王志光; 李进; 王炳春; 李小龙; 王贤彬; 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: 2022-03-04

Abstract

The invention discloses a CHA molecular sieve with a characteristic framework structure and a synthesis method and application thereof. The molar ratio of silicon dioxide to aluminum oxide of the CHA molecular sieve product ranges from 8 to 80, and the grain size ranges from 1 to 5 mu m; the total specific surface area calculated by a BET formula is more than or equal to 520m²The total pore volume is more than or equal to 0.20ml/g, and the micropore volume is more than or equal to 0.12 ml/g; the content of adjacent paired Al of the CHA molecular sieve framework accounts for more than 80 percent of the total content, and the CHA molecular sieve has obvious characteristic peaks at 330 plus or minus 2cm-1 and 465 plus or minus 5cm-1 through ultraviolet-Raman spectrum analysis. The CHA molecular sieve of the inventionThe catalyst is formed after exchange with copper ions, has good denitration catalytic reaction activity, high-temperature hydrothermal stability and good sulfur poisoning resistance, and overcomes the defects of poor low-temperature ignition activity and easy sulfur poisoning of the SCR catalyst with the CHA molecular sieve loaded copper after hydrothermal reaction in the prior art.

Description

CHA molecular sieve with characteristic framework structure and synthesis method and application thereof

Technical Field

The invention relates to a CHA type molecular sieve synthesized by a composite template agent consisting of N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and polyalkyl imidazolinium salt/alkali and a preparation method of a catalyst, in particular to a synthesis method of an SSZ-13 molecular sieve with a CHA topological structure, which is used for a selective catalytic reduction reaction of nitrogen oxides NOx after being exchanged with transition metal to form an SCR catalyst, and belongs to the fields of chemical synthesis technology and application thereof.

Background

With the progress of global industrialization, NOx produced by stationary pollution sources (such as thermal power generation) as well as mobile air pollution sources is considered as a major air pollutant. The laws and regulations around the world become stricter and the control of the discharge amount of NOx becomes a difficult problem to be solved urgently in the field of catalytic purification at home and abroad. NOx discharged by diesel vehicle tail gas in China accounts for about 70% of the total amount of the mobile source. The diesel vehicle nitrogen oxide external purification control technology mainly comprises a NOx catalytic decomposition technology, a three-way catalyst (TWC), a NOx Storage Reduction (NSR) technology and a Selective Catalytic Reduction (SCR) technology, wherein the SCR technology is the most mature diesel engine tail gas external purification technology. The six national emission standards promulgated and implemented by the year 2020, month 07 and day 01 have a 77% stricter emission of NOx in tail gas of diesel vehicles relative to the five national standards. Vanadium-based catalysts are used mostly in the fifth stage of China, and the low-temperature window characteristics of the vanadium-based catalysts are narrow, so that the vanadium-based catalysts cannot meet the emission standards of the sixth and European standards VI of China; the molecular sieve catalyst is a diesel engine NH3-SCR catalyst which can meet the requirements of ultra-low NOx emission in the sixth and sixth Euro VI stages, a diesel particulate trap and the requirement of active regeneration thermal shock at present.

In the existing SCR denitration technology, the V2O5/TiO2 catalyst has very high denitration efficiency, but the reaction usually needs to be carried out at a higher temperature (the active temperature window is 320-450℃)Time) can be performed. In addition, SO can be converted by the presence of an active component V in such catalysts₂Oxidation to SO₃And the catalyst is easy to be poisoned and inactivated by soot in the reaction, and the like. Therefore, the application of the non-V-based low-temperature environment-friendly catalyst to the field of denitration is widely researched at home and abroad. Based on the characteristic 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 activity temperature of the catalyst can be correspondingly changed by changing the types and occurrence states of active components on the surface or in the framework of the molecular sieve in the preparation process, so that the activity temperature is controllable, 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 technology has been applied to denitration treatment of heavy truck and other mobile sources by international large companies, has good effect, and has been gradually popularized. At present, copper-based molecular sieves used for diesel vehicle tail gas treatment research are generally Cu-beta, Cu-ZSM-5, Cu-SAPO-34, Cu-SSZ-13 and the like. Researches show that in the NH3-SCR technology, the small-aperture molecular sieve Cu-SSZ-13 has higher catalytic activity, selectivity and hydrothermal stability than the large-aperture molecular sieve Cu-beta and the medium-aperture molecular sieve Cu-ZSM-5, and the Cu-SSZ-13 has more excellent denitration performance at 160-550 ℃ under the same reaction condition. The Cu-SSZ-13 molecular sieve catalyst becomes a research hotspot for removing NOx from tail gas of diesel vehicles by virtue of excellent catalytic activity, better hydrothermal stability and wider temperature window.

In 1985, the SSZ-13 molecular sieve was synthesized by Severo (Chevron) Petroleum company in USA by a hydrothermal method. SSZ-13 is a silicon-aluminium molecular sieve with Chabazite (CHA) topological structure, and has three-dimensional pore structure and orthogonal symmetry, and its one-dimensional main channel is formed from double eight-membered rings, and its pore size is 0.38nm x 0.38nm, skeleton density is 14.5, and specific surface area can be up to 700m²(ii) in terms of/g. Due to its unique pore structure, large specific surface area, good hydrothermal stability and shape-selective function, the SSZ-13 molecular sieve has received much attention in academia and industry. The CHA molecular sieve topology is formed by a double 6 ring (d6r) connected via a 4-membered ringThe formation of the cha big cage, the crystal face of the d6r faces the cha big cage, Cu ions can be stabilized in the d6r at high temperature, and Cu ions are allowed to migrate, which is also a unique physicochemical characteristic of the small-pore molecular sieve with the potential of SCR reaction. Analysis of dehydrated Cu-SSZ-13 molecular sieves by Rietveld structural refinement in the literature (J.Phys.chem.C 2010,114,1633-²⁺Unique to the face of d6 r. In subsequent studies dehydrated Cu ions ([ CuOH ] located near the 8-membered ring were also confirmed]⁺) The presence of active sites. The SSZ-13 and SSZ-62 molecular sieves are typical CHA-structure silicoaluminophosphate molecular sieves, and are widely used as cracking catalysts, MTO reaction catalysts, nitrogen oxide reduction catalysts, and as nitrogen oxide reduction catalysts using Selective Catalytic Reduction (SCR).

Zones et al (US4544538) firstly used ammonium salt including TMADAOH and the like as an organic template to synthesize the SSZ-13 molecular Sieve (SiO) with high silica-alumina ratio and CHA type₂/Al₂O₃>10). Under optimized conditions, the SSZ-13 product synthesized by using TMADAOH as template can contain at most one TMADA in each CHA cage structure⁺But the template agent has long crystallization time and high price, thus increasing the application cost of the SSZ-13 molecular sieve. Researchers have developed benzyl trimethyl ammonium hydroxide (BTMA) (chem.lett.,2008,37(9): 908-.

The patent CN201611070989 discloses the synthesis of a molecular sieve material with CHA topological structure by using alkyl ammonium hydroxide and adamantyl ammonium hydroxide as a dual template agent, the Si/Al molar ratio is between 4 and 8, and the BET specific surface area is 400 to 800m²A grain size of 0.8 to 20 μm/g. And patent CN201780032379 discloses a CHA-type zeolite having a silica/alumina molar ratio of 10.0 to 55.0, which is synthesized using an N, N, N-trialkyladamantylammonium salt and an N, N, N-trialkylcyclohexylammonium salt as composite templates. Both of the above documents adopt a dual template, but both involve a relatively expensive organic template, N-trialkyl adamantyl ammonium salt, which is difficult to achieve the requirements of reducing the cost and improving the catalyst performance.

Influence degree of sulfur poisoning on Cu/CHA catalyst activity, sulfur oxide species and atmosphere (SO)₂、SO₃、H₂O or NH₃Etc.) and temperature, the Cu/CHA catalyst may form sulfur species [ H ] during sulfidation₂SO₄、(NH₄)₂SO₄、CuHSO₃、Cu SO₄And Al₂(SO₄)₃]And the like. The catalyst had copper sulfate formation accompanied by a 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 activity decline after sulfidation for the Cu/SSZ-13 catalyst is related to the Cu-S species generated at the active sites. And under sulfidation conditions, active Cu (OH) in Cu/SSZ-13 catalyst⁺Phase contrast Cu²⁺Is more easily mixed with SO₂The reaction forms sulfate. When NH is present₃In the presence of SO₂The effect of the thiamine species is not negligible when the sulfiding atmosphere is in progress. The research on the common vulcanization of Cu/SAPO-34 thiamine in the literature (Applied Catalysis B: Environmental,2017,204: 239-249; Applied Catalysis B: Environmental,2017,219:142-154) shows that a large amount of ammonium sulfate is generated at the 250 ℃ active site, while only copper sulfate is generated at 350 ℃, and further that the reduction of the isolated Cu2 active site is the main cause of the activity reduction regardless of the sulfate generated at the active site through TOF. The Cu/SSZ-13 catalyst produces mainly ammonium sulfate under the condition of 200 ℃ sulfur-ammonia co-vulcanization, and produces mainly copper sulfate at 400 ℃.

The synthesis of SSZ-13 molecular sieves having the CHA structure and their catalytic performance as SCR catalysts are disclosed in many of the above literature documents, indicating that it is preferable to obtain catalysts having good thermal stability and good dispersion of the supported metal. The prior conventional method adopts N, N, N-trialkyl-1-adamantyl ammonium salt and alkaline compound thereof as a template agent, which has high price, low utilization rate and difficult recovery and treatment, and wastewater generated by molecular sieve synthesis is difficult to carry out biochemical treatment, thus causing the problem of great reduction pollution; and the conventionally synthesized CHA molecular sieve can obviously reduce the activity of an SCR catalyst in tail gas containing sulfur oxides, so that a template agent with low cost, easy post-treatment and strong structure-oriented ability is needed to synthesize the CHA-type silicon-aluminum zeolite molecular sieve with large specific surface area, large pore volume, good thermal stability and strong sulfur poisoning resistance.

Disclosure of Invention

The invention aims to provide a CHA type SSZ-13 molecular sieve synthesized by a composite organic template agent and containing N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N, N, N, 1-tetraalkyl-4-piperidine ammonium onium salt/alkali compound and a preparation method of a corresponding SCR catalyst, wherein the molecular sieve is used as a catalyst carrier for removing NOx by selective reduction, has high Al content, small grain size, large specific surface area and pore volume, can provide more ion exchange site number and solid acid amount, and forms the SCR catalyst after copper ion exchange. The present invention relates to removal of nitrogen oxides emitted from internal combustion engines, and provides a nitrogen oxide removal catalyst composed of a silicoaluminophosphate zeolite molecular sieve having a CHA structure, a production method of the catalyst, and a nitrogen oxide removal method in which nitrogen oxides are reacted with at least one of ammonia water, urea, and an organic amine using the catalyst.

The invention aims to solve the technical problem of overcoming the defect that the activity of an SCR catalyst for synthesizing a molecular sieve by using copper loaded in the prior art is lower at low temperature through a hydrothermal durability test, and provides a copper-based SCR catalyst which still has higher activity at low temperature after hydrothermal durability and sulfur aging tests and a preparation method thereof.

The invention discloses a method for synthesizing a CHA-type molecular sieve by using a double template agent, which is characterized by comprising the following steps of: comprises the crystallization reaction of raw materials of a silicon source, an aluminum source and a template agent under the crystallization condition; the template agent is N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N, N, N, 1-tetraalkyl-4-piperidine ammonium oniumThe method comprises the following steps of (1) mixing a salt/alkali compound to form a double-template agent to synthesize a CHA-type zeolite molecular sieve, wherein the molar ratio of silicon dioxide to aluminum oxide of a CHA molecular sieve product ranges from 8 to 80, and the grain size ranges from 1 to 5 mu m; the total specific surface area calculated by a BET formula is more than or equal to 520m²The total pore volume is more than or equal to 0.20ml/g, and the micropore volume is more than or equal to 0.12 ml/g; the CHA molecular sieve passes diffuse reflection ultraviolet-visible spectrum (DR UV-vis spectrum) Co²⁺The content of the Al in the adjacent pairing of the skeleton is quantitatively represented by the coordination peak separation accounts for more than 80% of the total amount; the CHA molecular sieve is analyzed by ultraviolet-Raman spectroscopy at 330 +/-2 cm^-1And 465. + -.5 cm^-1Has obvious characteristic peaks. After the CHA molecular sieve raw powder is treated by saturated steam at the temperature of 600-850 ℃, the four-coordination aluminum accounts for more than or equal to 92% of the total aluminum, and the six-coordination aluminum accounts for less than or equal to 8% of the total aluminum.

Further, the structural formulas of the compound containing N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N, N, N, 1-tetraalkyl-4-piperidine ammonium salt/alkali in the technical scheme are respectively characterized in that:

r1, R2 and R3 are independent from each other and are selected from methyl or deuterated methyl, C2-C5 straight-chain or branched-chain alkyl; r4 is selected from any one of hydrogen, methyl or deuterated methyl, C2-C3 straight-chain or branched-chain alkyl; R5-R7 are independently selected from C1-C5 straight chain or branched chain alkyl; x-is a counter anion of quaternary ammonium onium ion, including any one of hydroxide, chloride, bromide, iodide, sulfate, bisulfate, carbonate, nitrate, bicarbonate, oxalate, acetate, phosphate and carboxylate;

further, in the technical scheme, in the step 1) of the synthesis method, the molar ratio of silicon dioxide to aluminum oxide is 2-40, the zeolite molecular sieve raw material to be crystallized, NaOH and deionized water are fully dissolved and dispersed, and then the slurry with the molar ratio of nNa is obtained₂O:nSiO₂:nAl₂O₃:nOH^-:nH₂O (0.5-2.5): 1.0 (0.025-0.5): 1.0-5.0: (5-20), aging in a crystallization kettle at 50-120 ℃ for 6-36 hours to obtainTo silica-alumina gel; step 2) adding a silicon source, N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali OSDA1, 1-alkyl-1-alkyl/cycloalkyl piperazinium salt/alkali OSDA2 and deionized water into the mixed silicon-aluminum gel mixture obtained in the step 1), fully and uniformly mixing, and adding an acid solution to control the molar ratio nOH-/nSiO2 of alkali hydroxyl OH < - > to SiO2 in the mixed slurry to be within the range of 0.1-1.0; the component molar ratio of the mixed slurry is nNa₂O:nSiO₂:nA1₂O₃:nOH^-:nOSDA1:nOSDA2:nH₂O is (0.05-0.5): 1.0, (0.0125-0.125): 0.1-1.0), (0.01-0.5): 0.05-0.5): 5-100); the molar ratio of the two templates nOSDA 1: nOSDA2 (0.05-100): 1; step 3) stirring the mixture obtained in the step 2), transferring the mixture into a hydrothermal crystallization reaction kettle, crystallizing for 8-120 hours at the self-generated pressure and the temperature of 125-200 ℃, and filtering, washing, drying and roasting the obtained crystallized product to obtain molecular sieve raw powder; step 4), mixing the molecular sieve raw powder obtained in the step 3) with an 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 ℃, wherein each time of exchange is 0.5-6 hours, 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 500 ppm; and then filtering and separating out a solid product, repeatedly washing the solid product by using deionized water until the solid product is neutral, drying a filter cake at the temperature of 100-150 ℃ for 12-48 hours, and roasting the filter cake at the temperature of 400-600 ℃ for 2-16 hours to obtain the CHA type chabazite molecular sieve.

Further, in the above technical solution, the CHA zeolite molecular sieve of the present invention is characterized in that: an XRD phase analysis pattern showing at least one XRD diffraction peak in each of the following tables in the range of 4 to 40 DEG 2 theta and having the characteristics set out in the following tables:

relative intensity is intensity relative to peak intensity of 20.40-20.90 [ theta ]

Further, in the above technical solution, in the synthesis method step 1), the zeolite molecular sieve raw material having a silica-alumina molar ratio in a range of 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 molecular sieve, Y molecular sieve, and USY molecular sieve having FAU-type structure; in the step 2), the silicon source 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, B-type silica gel, methyl silicate, ethyl silicate, propyl silicate, butyl silicate, ultrafine silica powder, activated clay, organic silicon, kieselguhr and gas phase method silica gel, and any 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 are preferred.

Further, in the above technical solution, the acid solution in 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, carbolic acid, oxalic acid, and benzoic acid.

In the above technical solution, the ammonium salt of the present invention is a mixture of any one, two or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carbonate and ammonium acetate mixed at any ratio.

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 the solid content of 25.0-48.0 wt% with a binder and deionized water, and is coated on a proper coating formed on a carrier of a porous regular material or an integral filter substrate to obtain the metal-promoted SCR catalyst of the CHA molecular sieve.

Further, in the above technical solution, the present invention provides an SCR catalyst, characterized in that: the soluble metal salt is selected from one or a combination of more of 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 iron salt, and 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 any one or mixture of silica sol, aluminum sol or pseudo-boehmite; the porous regular material or the monolithic 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 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, the purification of gas containing nitrogen oxides generated in the industrial process of refining, and the purification treatment of gas containing nitrogen oxides from refining heaters and boilers, furnaces, chemical processing industry, coke ovens, municipal waste treatment devices and incinerators.

Nitrogen oxides (NOx) according to the present invention include a variety of compounds, such as nitrous oxide (N)₂O), Nitric Oxide (NO), nitrogen dioxide (NO)₂) Dinitrogen trioxide (N)₂O₃) Dinitrogen tetroxide (N)₂O₄) And dinitrogen pentoxide (N)₂O₅) And the like.

The process for treating a gas stream comprising NOx wherein prior to contacting the catalyst with the gas stream, NO2 is present in an amount of 80 wt.% or less, based on NOx, based on 100 wt.% and preferably comprising 5 to 70 wt.%, more preferably 10to 60 wt.%, more preferably 15 to 55 wt.%, even more preferably 20 to 50 wt.% NO₂And (4) content. An oxidation catalyst located upstream of the catalyst oxidizes nitrogen monoxide in the gas to nitrogen dioxide and then mixes the resulting gas with a nitrogenous reductant prior to the mixture being 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: NO₂Volume ratio.

Reducing agents (urea, NH) are generally used₃Etc.) of a compoundIn the contact reduction (SCR) system, several chemical reactions take place, 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+4NH₃+O₂→4N₂+6H₂O (1)

Non-selective reaction with competing oxygen, or formation of 2-fold products, or non-productive consumption of NH₃. As such a non-selective reaction, for example, NH represented by the formula (2)₃Is completely oxidized.

4NH₃+5NO₂→4NO+6H₂O (2)

Furthermore, NO present in NOx₂And NH₃The reaction of (3) is considered to proceed by means of the reaction formula.

3NO₂+4NH₃→(7/2)N₂+6H₂O (3)

And NH₃With NO and NO₂The reaction between (a) and (b) is represented by the reaction formula (4).

NO+NO₂+2NH₃→2N₂+3H₂O (4)

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

In the SCR catalyst, in order to improve NOx purification ability at low temperature, it is necessary to make the reaction of formula (4) dominant, not the reaction of formula (1). The reaction of formula (4) is dominant at low temperatures, preferably increasing NO₂This is obvious.

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

NO+1/2O₂→NO₂ (5)

The invention relates to an SCR catalyst for denitration, which is an SCR catalyst for obtaining a metal-promoted SSZ-13 eutectic molecular sieve by carrying out ion exchange on synthesized silicon-aluminum zeolite molecular sieve raw powder and a soluble metal salt solution.

The soluble copper salt used in the preparation process of the catalyst is selected from 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 0.1-1.5 mol/L.

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

In certain embodiments of the invention, the washcoat of a molecular sieve SCR catalyst is preferably a solution, suspension or slurry that is applied to a porous structured material (i.e., a honeycomb monolithic catalyst support structure having a plurality of parallel channels running axially through the entire assembly) or a monolithic filter substrate such as a wall-flow filter, etc., with suitable coatings including a surface coating, a coating that penetrates a portion of the substrate, a coating that penetrates the substrate, or some combination thereof.

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

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

The catalyst in the embodiments of the invention shows that high NOx conversion is obtained in a much wider temperature window. The temperature range for improving the conversion efficiency may be about 150 to 650 ℃, preferably 200 to 500 ℃, more preferably 200 to 450 ℃, or most significantly 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 ℃) can be greater than 55% to 100%, more preferably greater than 90% efficiency, and even more preferably greater than 95% efficiency.

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

The molecular sieve has more reasonably distributed acidity and good hydrothermal stability, overcomes the limitations of the components, and has excellent NOx reducibility particularly at low temperature after the provided SCR catalyst is subjected to durable treatment at high temperature in the atmosphere containing hydrothermal steam. Better meets the requirements of industrial application and has wide application prospect.

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

Drawings

The invention is further described with reference to the following figures and examples:

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

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

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

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

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

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

Detailed Description

The embodiments and the effects of the present invention are further illustrated by examples and comparative examples, but the scope of the present invention is not limited to the contents listed in the examples.

In the Powder method using X-ray Diffraction (X-ray Diffraction) analysis according to the present invention, the lattice plane spacing (d) is obtained from the XRD pattern, and the obtained Data is identified by comparison with Data collected from the XRD database of the International society for synthetic zeolites or the PDF (Powder Diffraction File) of ICDD (International centre for Diffraction Data). As XRD measurement conditions in the embodiment of the present invention, the following conditions may be mentioned: irradiating with PANALYTICAL X' Pert diffractometer with CuK alpha monochromatic light, tube voltage 45kV, current 40mA, and CuK alpha ray lambda 1.540598; measurement mode: step scan 2 θ step scan scale: 0.02626 °, measurement range: 2 theta is 5-60 degrees.

The pore structure of the molecular sieve was determined using a Micromeritics ASAP 2460 model static nitrogen adsorber. And (3) testing conditions are as follows: the sample was placed in a sample handling system and evacuated to 1.33X 10 at 350 deg.C^-2Pa, keeping the temperature and the pressure for 15h, and purifying the sample. Measuring the specific pressure p/p of the purified sample at-196 deg.C under liquid nitrogen₀And (3) obtaining a nitrogen adsorption-desorption isothermal curve according to the adsorption quantity and the desorption quantity of the nitrogen under the condition. Then, the BET total specific surface area (S) is calculated using the BET equation_BET) Calculating the specific surface area (S) of the sample micropore by adopting a t-plot method_micro) And micropore volume (V)_micro) Total pore volume in P/P₀Calculated as adsorption at 0.98: specific surface area of outer pores (S)_exter)＝S_BET–S_micro(ii) a External pore volume (V)_exter)＝V_total-V_micro)。

The method for measuring the content of Al in adjacent paired frameworks comprises the following steps: mixing Co²⁺Ion exchange on CHA molecular sieve, 500 deg.C under high vacuum condition (<10^-1Pa) roasting for 5 hours at room temperature to obtain a relevant diffuse reflection ultraviolet-visible spectrum (DR UV-vis spectrum), and measuring Co by ICP²⁺Co in CHA molecular sieve after ion exchange²⁺Molar amount of ion [ 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 phase adjacent skeleton Al_close]，[Al_isolated]＝[Al_total]-2×[Co_max]，[Al_close]＝[Al_pairs]+[Al_unpairs]When the silicon-aluminum ratio of the CHA molecular sieve is more 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 balances out two Al atoms (called Al) close to each other_close) The negative charge generated is located in the secondary structure ring (Al)_pairs) Middle or two adjacent rings (Al)_unpairs) But not to balance (Al) having a long distance from each other_isolated) The charge generated by a single Al atom.

Ultraviolet Raman spectrum determination: the spectroscopic system used a SPEX Triplemate T64000 type three-grating monochromator (Jobin-Yvon Corp.), with a spectral resolution of 2cm^-1The detector uses a liquid nitrogen cooled Spectrum One CCD 2000 photoelectric coupling detector, and the excitation light source adopts an IK-3351-G He-Cd laser (325nm) and 266nm ultraviolet laser generated by frequency doubling of 532nm laser generated by a DPSS 532Model 200 laser.

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

The molar ratio of silica to alumina of the CHA molecular sieve product obtained by the inventive process described belowThe range is 8-80, and the grain size is 1-5 μm; the total specific surface area calculated by a BET formula is more than or equal to 520m²The total pore volume is more than or equal to 0.20ml/g, and the micropore volume is more than or equal to 0.12 ml/g; the CHA molecular sieve passes diffuse reflection ultraviolet-visible spectrum (DR UV-vis spectrum) Co²⁺The content of the Al in the adjacent pairing of the skeleton is quantitatively represented by the coordination peak separation accounts for more than 80% of the total amount; the CHA molecular sieve is analyzed by ultraviolet-Raman spectroscopy at 330 +/-2 cm^-1And 465. + -.5 cm^-1Has obvious characteristic peaks. After the CHA molecular sieve raw powder is treated by saturated steam at the temperature of 600-850 ℃, the four-coordination aluminum accounts for more than or equal to 92% of the total aluminum, and the six-coordination aluminum accounts for less than or equal to 8% of the total aluminum.

Example 1

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

1) mixing 45.59g HY molecular sieve (Si/Al to nSiO)₂/nAl₂O₃5.20 dry basis, 78.1 percent of dry basis), 26.68g of NaOH flake caustic soda and 69.98g of deionized water are fully dissolved and dispersed to obtain slurry with the molar ratio of nNa₂O:nSiO₂:nAl₂O₃:nOH^-:nH₂Aging at 85 deg.C for 36 hr to obtain silica-alumina gel;

2) to the mixed silica-alumina gel mixture in 1) was added 507.51g of silica gel solution (Na 2O: 0.24 wt% SiO₂: 30.36 wt%), 173.23g N, N, N-dimethylethylcyclohexylammonium hydroxide (concentration 20 wt%, expressed as OSDA1, CAS: 105197-93-1), 27.94g of N, N, N, 1-tetramethyl-4-piperidinium hydroxide (concentration 25% by weight, expressed as OSDA2, CAS: 1379151-27-5), 56.31g of NaOH flake caustic soda and 216.79g of deionized water are fully and evenly stirred and mixed by ultrasonic, and 5 percent of HCl solution is added to adjust the nOH in the system^-/nSiO₂Ratio of the components of the mixed slurry to each other

nNa₂O:nSiO₂:nAl₂O₃:nOH^-:nOSDA1:nOSDA2:nH₂O ═ 0.35:1.0:0.0286:0.78:0.0667:0.0133: 15; stirring the above mixture, transferring into hydrothermal crystallization reaction kettle, crystallizing at 140 deg.C under autogenous pressure for 36 hr, quenching to stop crystallization, filtering, washing to neutral pH, oven drying at 120 deg.C for 12 hr, and baking at 540 deg.CBurning for 4 hours to obtain SSZ-13 molecular sieve raw powder;

3) performing 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 for 2 hours at 70 ℃ according to the solid-liquid mass ratio of 1:10, and then repeatedly exchanging the filter cake obtained by filtering with a fresh ammonium nitrate solution twice under the same condition so as to enable the Na ion content in the sample to be lower than 500 ppm. The filter cake obtained by subsequent filtration is dried at 110 ℃ overnight to obtain ammonium type molecular sieve NH₄Heating to 450 ℃ and roasting for 16 hours to obtain the H-type SSZ-13 molecular sieve.

4) Adding 50.0g of the H-type SSZ-13 molecular sieve obtained in the step 3) into a copper nitrate aqueous solution with the concentration of 0.15mol/L, dropwise adding dilute nitric acid into the solution to adjust the pH value to 6.5, uniformly stirring, putting into a heat-resistant container, and putting into a dryer with a pressure reducing valve; vacuumizing the pressure in the dryer to be below 10Torr by using a vacuum pump, degassing at room temperature for 1 hour, heating to 90 ℃, drying for 12 hours, and roasting the dried sample at the temperature of 500 ℃ for 4 hours under normal atmospheric pressure; the copper-modified SSZ-13 molecular sieve was obtained, and the catalyst prepared according to XRF analysis results had copper (II) ions accounting for 2.8% of the total weight of the molecular sieve catalyst, i.e., copper loading was 2.8 wt%.

5) 40.0g of the copper-modified molecular sieve obtained in the above 4) was mixed with 20.0g of silica sol (SiO2 content: 30.0 wt%) and 78.97g of deionized water are uniformly mixed to prepare catalyst slurry with the solid content of 33.1 wt%, the catalyst slurry is coated on a honeycomb-shaped porous regular material (#400cpsi, the diameter of 20mm and the length of 40mm) made of cordierite through an impregnation method, redundant slurry drops are blown off by compressed air, the catalyst is dried for 24 hours at 105 ℃, the catalyst is coated for 2 times under the same condition and is calcined for 2 hours at 500 ℃ to prepare the SCR catalyst, the loading on the regular material is 219.5g/L (the weight of the weight increased by the regular material after calcination is divided by the space volume occupied by the regular material, the definitions of the subsequent examples and comparative examples on the loading are the same), and the obtained SCR catalyst is marked as A, and relevant preparation parameters and material types are shown in tables 1, 2, 3 and 4.

Example 2

Synthesis of CHA-type SSZ-13 the process of molecular sieve is similar to example 1 except that the molar ratio of the mixed sol, the type of organic template, the type of silicon source, the type of transgranular zeolite and the silica-alumina ratio, the crystallization temperature and the crystallization time in step 1) and step 2) are the same, 50.0g of H-type SSZ-13 molecular sieve is taken in step 3), different soluble metal salt types, concentrations, solution volumes and metal loading amounts are adopted, and 4) 40.0g of copper modified CHA-type SSZ-13 molecular sieve and 20.0g of silica Sol (SiO) (SiO 0 g) are taken in step 4)₂The content is as follows: 30.0 wt%) and 104.29g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 28.0 wt%, and the catalyst slurry was coated on a cordierite structured material by an impregnation method. Specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 3

The process for synthesizing the CHA-type SSZ-13 molecular sieve is similar to example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the crystal transition zeolite, the silicon-aluminum ratio, the crystallization temperature, the crystallization time and the like in the steps 1) and 2), 50.0g of the H-type SSZ-13 molecular sieve is taken in the step 3), different soluble metal salt types, concentrations, solution volumes and metal loading amounts are adopted, and 4) 40g of the copper-modified CHA-type SSZ-13 molecular sieve and 20.0g of silica Sol (SiO) are taken in the step 4₂The content is as follows: 30.0 wt%) and 76.50g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 33.7 wt%, which was coated on a cordierite structured material by an impregnation method. Specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 4

The process for synthesizing the CHA-type SSZ-13 molecular sieve is similar to example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the crystal transition zeolite, the silicon-aluminum ratio, the crystallization temperature, the crystallization time and the like in the steps 1) and 2), 50.0g of the H-type SSZ-13 molecular sieve is taken in the step 3), different soluble metal salt types, concentrations, solution volumes and metal loading amounts are adopted, and 4) 40g of the copper-modified CHA-type SSZ-13 molecular sieve and 20.0g of silica Sol (SiO) are taken in the step 4₂The content is as follows: 30.0 wt.%) and 80.24g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 32.8 wt.%, and the catalyst slurry was impregnated with the catalyst slurryThe impregnation method is used for coating on the cordierite structured material. Specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 5

The process for synthesizing the CHA-type SSZ-13 molecular sieve is similar to example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the crystal transition zeolite, the silicon-aluminum ratio, the crystallization temperature, the crystallization time and the like in the steps 1) and 2), 50.0g of the H-type SSZ-13 molecular sieve is taken in the step 3), different soluble metal salt types, concentrations, solution volumes and metal loading amounts are adopted, and 4) 40g of the copper-modified CHA-type SSZ-13 molecular sieve and 30.0g of the aluminum sol (Al) are taken in the step 4)₂O₃The content is as follows: 20.0 wt%) and 122.16g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 25.5 wt%, and the catalyst slurry was coated on a cordierite structured material by an impregnation method. Specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 6

The process for synthesizing the CHA-type SSZ-13 molecular sieve is similar to example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the crystal transition zeolite, the silicon-aluminum ratio, the crystallization temperature, the crystallization time and the like in the steps 1) and 2), 50.0g of the H-type SSZ-13 molecular sieve is taken in the step 3), different soluble metal salt types, concentrations, solution volumes and metal loading amounts are adopted, and 4) 40g of the copper-modified CHA-type SSZ-13 molecular sieve and 30.0g of the aluminum sol (Al) are taken in the step 4)₂O₃The content is as follows: 20.0 wt%) and 71.98g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 32.4 wt%, and the catalyst slurry was coated on a cordierite structured material by an impregnation method. Specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 7

The process for synthesizing the CHA-type SSZ-13 molecular sieve is similar to that of example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the transgranular zeolite, the silicon-aluminum ratio, the crystallization temperature, the crystallization time and the like in the steps 1) and 2), 50.0g of the H-type SSZ-13 molecular sieve is taken in the step 3), and different soluble metal salt types, concentrations, solution volumes and crystallization times are adoptedLoading of metal, and 4) taking 40g of copper modified CHA type SSZ-13 molecular sieve and 30.0g of aluminum sol (Al)₂O₃The content is as follows: 20.0 wt%) and 57.07g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 36.2 wt%, and the catalyst slurry was coated on a cordierite structured material by an impregnation method. Specific parameters in this example are shown in tables 1, 2, 3 and 4.

Example 8

The process for synthesizing the CHA-type SSZ-13 molecular sieve is similar to example 1, except that the molar ratio of the mixed sol, the type of the organic template, the type of the silicon source, the type of the crystal transition zeolite, the silicon-aluminum ratio, the crystallization temperature, the crystallization time and the like in the steps 1) and 2), 50.0g of the H-type SSZ-13 molecular sieve is taken in the step 3), different soluble metal salt types, concentrations, solution volumes and metal loading amounts are adopted, and 4) 40g of the copper-modified CHA-type SSZ-13 molecular sieve and 30.0g of the aluminum sol (Al) are taken in the step 4)₂O₃The content is as follows: 20.0 wt%) and 62.95g of deionized water were mixed uniformly to prepare a catalyst slurry having a solid content of 34.6 wt%, and the catalyst slurry was coated on a cordierite structured material by an impregnation method. Specific parameters in this example are shown in tables 1, 2, 3 and 4.

TABLE 1 selection of parameters in the Synthesis of molecular sieves step 1)

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

TABLE 3 tables of molecular sieve performance parameters obtained in examples 1 to 8

*: by Co²⁺After the ions are fully exchanged on the CHA molecular sieve, the diffuse reflection ultraviolet-visible spectrum and ICP (inductively coupled plasma) are used for measuring the related data and calculating the result

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

Comparative example 1

SSZ-13 molecular sieve is synthesized and SCR catalyst is prepared according to the method in CN 109195911A

Mixing 25 wt% aqueous DMECHAOH (N, N-dimethylethylcyclohexylammonium hydroxide), 25 wt% aqueous TMAdOH (N, N-trimethyl-1-adamantylammonium hydroxide), 48% aqueous sodium hydroxide, 48 wt% aqueous potassium hydroxide, deionized water, and amorphous aluminum silicate (SiO2/Al2O3 ═ 25.7) to give 50.0g of a mixture having a molar composition:

0.1Na:0.1K:SiO₂:0.0389Al₂O₃:0.2OH^-:0.04DMECHAOH:0.04TMAdOH:15.0H₂O

the raw material composition was charged into a closed container having an internal volume of 80mL, and the container was reacted at 170 ℃ for 48 hours while rotating and stirring at 55 rpm. And (3) carrying out solid-liquid separation on the obtained product, washing the product by using deionized water, drying the product at 110 ℃, and roasting the product at 540 ℃ for 4 hours to obtain the SSZ-13 molecular sieve raw powder. The molecular sieve raw powder and ammonium nitrate solution with the concentration of 1.0mol/L are subjected to ion exchange for 2 hours at the temperature of 80 ℃ according to the solid-liquid mass ratio of 1:10, and then filter cakes obtained by filtration are repeatedly exchanged with fresh ammonium nitrate solution twice under the same condition, so that the Na ion content is lower than 500 ppm. And then drying the filter cake obtained by filtering at 110 ℃ overnight to obtain an ammonium type molecular sieve NH4-SSZ-13, and then heating to 450 ℃ to roast for 16 hours to obtain the H type SSZ-13 molecular sieve.

Adding 10g of SSZ-13 molecular sieve raw powder into 100g of Cu (NO3) 2.3H 2O aqueous solution with the concentration of 0.3mol/L, dropwise adding dilute nitric acid into the solution to adjust the pH value to 5.8, and uniformly stirring. After stirring was stopped for 1 hour, the supernatant was siphoned off when SSZ-13 zeolite settled. The exchange with fresh copper nitrate solution was repeated once, and finally the exchanged SSZ-13 zeolite was filtered and washed with deionized water. Drying at 90 ℃ for 12 hours under the low pressure of 10Torr, and then roasting at 500 ℃ for 4 hours under normal atmospheric pressure to obtain the copper modified SSZ-13 molecular sieve powder. According to XRF analysis, copper (II) ions accounted for 2.9% of the total weight of the molecular sieve catalyst.

15g of the obtained copper modified SSZ-13 molecular sieve is uniformly mixed with 5.56g of silica sol (30 wt% of SiO2) and 22.80g of deionized water to prepare catalyst slurry with the solid content of 38.44 wt%, the catalyst slurry is coated on a honeycomb-shaped porous regular material (400 cpsi, the diameter of 20mm and the length of 40mm) prepared from cordierite through an immersion method, redundant slurry drops are blown off by compressed air, the drying is carried out for 12 hours at 110 ℃, then, slurry is coated again, the SCR catalyst is prepared after the calcination is carried out for 2 hours at 500 ℃, and the measured catalyst loading capacity on the regular material is 212.5g/L and is recorded as VS-1.

Comparative example 2

SSZ-13 molecular sieve is synthesized and SCR catalyst is prepared according to the method in CN108602056A

1) 530.71g N, N, N-trimethylcyclohexylammonium hydroxide (20% by weight H)₂O solution) with 66.74 g of aluminum triisopropoxide and 215.66g of ethyltrimethylammonium hydroxide (20% by weight H)₂O solution) were mixed. Thereafter, 686.93g of Ludox-AS40 (at H)₂40 wt% colloidal solution in O) and 11.49g cha seeds were added to the stirred mixture. The resulting gel was placed in a stirred autoclave having a total volume of 2.5L. The autoclave was heated to 170 ℃ over 7 hours, the temperature being kept constant for 72 hours. After this time the autoclave was cooled to room temperature, the solid was isolated by filtration and washed vigorously until the wash water pH was 7. The solid was finally dried at 120 ℃ for 10 hours. And roasting the solid product at 550 ℃ for 5 hours to obtain SSZ-13 molecular sieve raw powder.

2) And carrying out ion exchange on the SSZ-13 molecular sieve raw powder and an ammonium nitrate solution with the concentration of 1.0mol/L for 2 hours at 90 ℃ according to the solid-liquid mass ratio of 1:10, and then repeatedly exchanging the filter cake obtained by filtering with a fresh ammonium nitrate solution twice under the same condition so as to enable the Na ion content to be lower than 500 ppm. And then drying the filter cake obtained by filtering at 110 ℃ overnight to obtain an ammonium type molecular sieve NH4-SSZ-13, and then heating to 450 ℃ to roast for 16 hours to obtain the H type SSZ-13 molecular sieve.

3) 10g of SSZ-13 molecular sieve raw powder was added to 100g of Cu (NO) having a concentration of 0.3mol/L₃)₂·3 H₂And (3) dripping dilute nitric acid into the O aqueous solution to adjust the pH value to 5.8, and uniformly stirring. After stirring was stopped for 1 hour, the supernatant was siphoned off when SSZ-13 zeolite settled. The exchange with fresh copper nitrate solution was repeated once, and finally the exchanged SSZ-13 zeolite was filtered and washed with deionized water. Drying at 90 ℃ for 12 hours under the low pressure of 10Torr, and then roasting at 500 ℃ for 4 hours under normal atmospheric pressure to obtain the copper modified SSZ-13 molecular sieve powder. According to XRF analysis, copper (II) ions accounted for 3.0% of the total weight of the molecular sieve catalyst.

4) 15g of the obtained copper modified SSZ-13 molecular sieve is uniformly mixed with 5.56g of silica sol (30 wt% of SiO2) and 22.80g of deionized water to prepare catalyst slurry with the solid content of 38.44 wt%, the catalyst slurry is coated on a honeycomb-shaped porous regular material (400 cpsi, the diameter of 20mm and the length of 40mm) prepared from cordierite through an immersion method, redundant slurry drops are blown off by compressed air, the drying is carried out for 12 hours at 110 ℃, then, slurry is coated again, the SCR catalyst is prepared after the calcination is carried out for 2 hours at 500 ℃, and the catalyst loading capacity on the regular material is 207.4g/L and is recorded as VS-2.

Examples 9 to 24

Testing of the SCR catalyst:

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

In (1), contains 500ppm of NO and 500ppm of NH ₃10% by volume of O₂160mL/min of a mixed gas stream containing 5 vol% of steam and Ar as an equilibrium gas was passed through a preheater (set at 250 ℃ C.) and then fed into the SCR reactor. Reaction temperature of 150-650 ℃ and reaction temperature of 48000h^-1The test specimens were tested at a volumetric gas hourly space velocity. The temperature is monitored by an internal thermocouple located at the sample site.

The used fresh SCR catalysts of the above examples and comparative examples were subjected to a hydrothermal durability treatment under the conditions of the hydrothermal durability treatment test to obtain aged SCR catalysts:

space velocity SV: 30000/h, temperature: 800 ℃, time: 16 hours, water concentration: 10%, oxygen concentration: 10%, nitrogen concentration: and (4) balancing.

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

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

The SCR catalyst activity laboratory evaluation device described above was used to evaluate the selective catalytic reduction performance of NOx on the Cu-supported SCR catalysts prepared in examples and comparative examples, and the results are shown in table 5.

TABLE 5 evaluation indexes for NOx Selective reduction Performance of catalysts prepared in examples 1 to 6 and comparative examples 1 to 2

800 ℃ in an atmosphere of 10% moisture + 10% oxygen concentration, at a space velocity of 30000/h, for 16 hours.

As can be seen from Table 5, the evaluation of the Cu-SSZ-13 or Fe-SSZ-13 catalysts obtained in examples 1 to 6 in examples 9 to 14 shows that the catalysts have better low-temperature ignition performance, high-temperature activity and wider temperature conversion window, and the SCR activity is obviously better than the catalytic performance of the catalysts VS-1 and VS-2 obtained in comparative example 1 in examples 15 to 16, no matter the 'fresh' state or 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 the catalysts obtained therewith have improved SCR catalytic activity, especially at low conversion temperatures characteristic of cold start conditions when treating NOx, for example, in diesel locomotive applications.

Sulfur poisoning resistance SCR catalytic test:

SCR catalysts of VS-1, VS-2 and A-F prepared in comparative examples 1-2 and examples 1-6, totaling 8, were placed in a reactor

In (1), SO₂The gas flow is introduced into the gas flow containing NOx at regular intervals, so that the gas flow has the composition of 500ppm NO and 500ppm NH₃、200ppmSO₂10% by volume of O₂The combined gas stream of 5 vol% steam and Ar as the balance gas, 160mL/min, first passed through a preheater set at 250 ℃ and then into the SCR reactor. Reaction temperature at 200 ℃ and based on 48000h^-1Carrying out sulfur poisoning resistant SCR reaction test on the sample at a volume gas hourly space velocity, and introducing or stopping SO₂The results of the evaluation of the NOx conversion of the SCR catalysts in the examples and comparative examples at 200 ℃ after different aging times of the atmosphere are shown in table 6.

TABLE 6

The NOx conversion on the SCR catalysts prepared in the examples remained above 86% after 5min of the SO 2-containing exhaust gas, while the NOx conversion on the SCR catalysts VS-1 and VS-2 in the comparative examples decreased to below 70%; 30min after the SO2 tail gas had been passed, the NOx conversion on 6 SCR catalysts A-F in the examples dropped abruptly to below 65%, but remained substantially above 63%, while the NOx conversion on the SCR catalysts VS-1 and VS-2 of the comparative examples dropped to below 55%. Introducing SO₂After 60min and 100min of the exhaust gas, the NOx conversion on 6 SCR catalysts A-F in the examples, although continuing to decrease, remained substantially above 60%, while the NOx conversion on VS-1 and VS-2 in the comparative SCR catalystsThere is also a reduction, but below 50%. 10min after stopping the introduction of SO2, the NOx conversion rate on 6 SCR catalysts of A-F in the example is recovered to be more than 61%, and the NOx conversion rate on VS-1 and VS-2 of the SCR catalysts of the comparative example is also slightly recovered to be only about 49% at most. From the comparison of the above data, it can be seen that the SCR catalysts prepared in the examples have significant resistance to sulfur poisoning, 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 rates to be maintained in a sulfur-containing atmosphere, thus allowing for high energy efficiency treatment of NOx-containing exhaust gases at comparable conversion rates.

The above-mentioned embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for synthesizing a CHA molecular sieve with a characteristic framework structure is characterized by comprising the following steps:

comprises the crystallization reaction of raw materials of a silicon source, an aluminum source and a template agent under the crystallization condition;

the template is N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N, N, N, 1-tetraalkyl-4-piperidine ammonium salt/alkali compound to form a double template for synthesizing the CHA type zeolite molecular sieve;

the CHA molecular sieve passes diffuse reflection ultraviolet-visible spectrum Co²⁺The content of the Al in the adjacent pairing of the skeleton is quantitatively represented by the coordination peak separation accounts for more than 80% of the total amount; the CHA molecular sieve is analyzed by ultraviolet-Raman spectroscopy at 330 +/-2 cm^-1And 465. + -.5 cm^-1Has obvious characteristic peaks.

The structural formula of the compound containing N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali and N, N, N, 1-tetraalkyl-4-piperidine ammonium salt/alkali is as follows:

r1, R2 and R3 are respectively and independently selected from methyl or deuterated methyl, C2-C5 straight-chain or branched-chain alkyl; r4 is selected from any one of hydrogen, methyl or deuterated methyl, C2-C3 straight-chain or branched-chain alkyl; R5-R7 are respectively and independently selected from C1-C5 straight chain or branched chain alkyl; x^-The counter anion of the quaternary ammonium onium ion comprises any one of hydroxide, chloride, bromide, iodide, sulfate, hydrogen sulfate, carbonate, nitrate, hydrogen carbonate, oxalate, acetate, phosphate and carboxylate.

2. The CHA molecular sieve synthesis process of claim 1, wherein:

1) fully dissolving and dispersing a zeolite molecular sieve raw material, NaOH and deionized water in a molar ratio of 2-40 between silicon dioxide and aluminum oxide, and ageing the slurry to obtain silicon-aluminum gel;

2) adding a silicon source, N, N, N-trialkyl cyclohexyl quaternary ammonium salt/alkali OSDA1, 1-alkyl-1-alkyl/cycloalkyl piperazinium salt/alkali OSDA2 and deionized water into the mixed silicon-aluminum gel mixture in the step 1), fully and uniformly mixing, and adding an acid solution to control alkali hydroxyl OH in the mixed slurry^-With SiO₂In a molar ratio of nOH^-/nSiO₂The content is 0.1-1.0; the molar ratio of the two templates nOSDA 1: nOSDA2 (0.05-100): 1;

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

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

3. The CHA molecular sieve synthesis process of claim 2, wherein:

in the step 1), the components of the slurry are in molThe mixture ratio is nNa₂O:nSiO₂:nAl₂O₃:nOH^-:nH₂O (0.5-2.5): 1.0 (0.025-0.5): 1.0-5.0): 5-20 under the aging condition of aging at 50-120 ℃ for 6-36 hours;

in the step 2), the molar ratio of the components of the mixed slurry is nNa₂O:nSiO₂:nA1₂O₃:nOH^-:nOSDA1:nOSDA2:nH₂O＝(0.05～0.5):1.0:(0.0125～0.125):(0.1～1.0):(0.01～0.5):(0.05～0.5):(5～100)；

In the step 4), the molecular sieve raw powder and the ammonium salt solution with the concentration of 0.1-5.0 mol/L are mixed according to the solid-liquid mass ratio of 1: (5-50) carrying out ion exchange at 60-100 ℃, wherein each time of exchange is 0.5-6 hours, 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 500 ppm; and then filtering and separating out a solid product, repeatedly washing the solid product by using deionized water until the solid product is neutral, drying a filter cake at the temperature of 100-150 ℃ for 12-48 hours, and roasting the filter cake at the temperature of 400-600 ℃ for 2-16 hours to obtain the CHA type chabazite molecular sieve.

4. The method of synthesis according to claim 2, characterized in that: the zeolite molecular sieve raw material with the mole ratio of the silicon dioxide to the aluminum oxide in the step 1) being in the range of 2-40 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 further preferably any one of an X molecular sieve, a Y molecular sieve and a USY molecular sieve with FAU type structure; in the step 2), the silicon source 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, B-type silica gel, methyl silicate, ethyl silicate, propyl silicate, butyl silicate, ultrafine silica powder, activated clay, organic silicon, kieselguhr and gas phase method silica gel, and any 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 are preferred.

5. The method of synthesis according to claim 2, 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, carbolic acid, oxalic acid and benzoic acid.

6. The method of synthesis according to claim 2, wherein: the ammonium salt in the step 4) is a mixture formed by mixing any one, two or more than two of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carbonate and ammonium acetate in any proportion.

7. The CHA molecular sieve obtained by the preparation method of any one of claims 1 to 6, which is characterized in that: the molar ratio of silicon dioxide to aluminum oxide of the CHA molecular sieve product ranges from 8 to 80, and the grain size ranges from 1 to 5 mu m; the total specific surface area calculated by a BET formula is more than or equal to 520m²The total pore volume is more than or equal to 0.20ml/g, and the micropore volume is more than or equal to 0.12 ml/g.

8. The CHA molecular sieve of claim 7, characterized in that: an XRD phase analysis pattern showing at least one XRD diffraction peak in each of the following tables in the range of 4 to 40 DEG 2 theta and having the characteristics set out in the following tables:

the relative intensity is an intensity relative to a peak intensity of 20.40 to 20.90 in terms of 2 θ.

9. An SCR catalyst for denitration, characterized in that: the CHA-type zeolite molecular sieve of claim 7 or 8 is subjected to ion exchange with a soluble copper salt solution, then forms a slurry with a solid content of 25.0-48.0 wt% with a binder and deionized water, and is coated on a proper coating formed on a carrier of a porous regular material or an integral filter substrate to obtain the SCR catalyst of the metal-promoted CHA molecular sieve.

10. The SCR catalyst of claim 9, wherein: the soluble metal salt is selected from one or a combination of more of 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 iron salt, and 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.

11. The catalyst of claim 9, wherein: the binder is selected from any one or mixture of silica sol, aluminum sol or pseudo-boehmite; the porous regular material or the monolithic 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 the SCR catalyst of any one of claims 9 to 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, the purification of gas containing nitrogen oxides generated in the refining industry process, and the purification treatment of gas containing nitrogen oxides from refining heaters and boilers, furnaces, chemical processing industry, coke ovens, municipal waste treatment devices and incinerators.