CN110451521B - Preparation method of Beta molecular sieve and preparation method of SCR catalyst - Google Patents

Preparation method of Beta molecular sieve and preparation method of SCR catalyst Download PDF

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CN110451521B
CN110451521B CN201910540791.XA CN201910540791A CN110451521B CN 110451521 B CN110451521 B CN 110451521B CN 201910540791 A CN201910540791 A CN 201910540791A CN 110451521 B CN110451521 B CN 110451521B
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molecular sieve
beta molecular
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template agent
scr catalyst
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CN110451521A (en
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梁珂
许庆
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Hefei Paisen New Material Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/7049—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
    • B01J29/7057—Zeolite Beta
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
    • B01J29/74—Noble metals
    • B01J29/7415—Zeolite Beta
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
    • B01J29/76—Iron group metals or copper
    • B01J29/7615—Zeolite Beta
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/04—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof using at least one organic template directing agent, e.g. an ionic quaternary ammonium compound or an aminated compound
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area

Abstract

The invention belongs to the field of chemical catalytic synthesis, and particularly relates to a preparation method of a Beta molecular sieve and a preparation method of an SCR (selective catalytic reduction) catalyst. The preparation method comprises the following steps: mixing an aluminum source, inorganic alkali, water and seed crystals, then adding a mixed template agent and a silicon source to form gel, and obtaining the Beta molecular sieve through crystallization, ammonium exchange and roasting; wherein the mixed template agent comprises at least one diaminoalkane and at least one tetraethylammonium cation organic amine.

Description

Preparation method of Beta molecular sieve and preparation method of SCR catalyst
Technical Field
The invention belongs to the field of chemical catalytic synthesis, and particularly relates to a preparation method of a Beta molecular sieve and a preparation method of an SCR (selective catalytic reduction) catalyst.
Background
The Beta molecular sieve is a wide-pore and high-silicon microporous molecular sieve material and contains three-dimensional 12-membered pore channels. It is often used in catalytic reactions because of its high thermal, chemical, strong acid sites, hydrophobicity, and large pore size. However, the high synthesis cost limits the wide use of Beta molecular sieves.
The grain size of the Beta molecular sieve synthesized at present is generally small, so that the requirement on solid-liquid separation equipment in industrial production is strict, and the mass production of the Beta molecular sieve is restricted.
Patent US5164169 discloses a method for synthesizing a large-particle-size Beta molecular sieve, wherein a tertiary amine compound is used as a chelating agent to synthesize the large-particle-size Beta molecular sieve, but the tertiary amine compound is toxic, has poor water solubility, is extremely volatile, and is easy to damage the environment in the industrial production process.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of a Beta molecular sieve and a preparation method of an SCR catalyst.
According to an aspect of the present invention, there is provided a method for preparing a Beta molecular sieve, comprising the steps of:
mixing an aluminum source, inorganic alkali, water and seed crystals, then adding a mixed template agent and a silicon source to form gel, and obtaining the Beta molecular sieve through crystallization, ammonium exchange and roasting;
wherein the mixed template agent comprises at least one diaminoalkane and at least one tetraethylammonium cation organic amine.
According to one embodiment of the invention, the diaminoalkane is selected from one or more of pentanediamine, hexanediamine, heptanediamine or octanediamine.
According to one embodiment of the invention, the tetraethylammonium cationic organic amine is selected from one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride or tetraethylammonium iodide.
Further, the diaminoalkane is selected from one or more of hexamethylenediamine or heptamethylenediamine, and the tetraethyl amine cationic organic amine is selected from one or more of tetraethyl ammonium hydroxide or tetraethyl ammonium bromide.
According to an embodiment of the present invention, in the mixed template, the mass ratio of the tetraethylene amine cation organic amine to the diamine alkane is 1: (0.01-3).
Further, the mass ratio of the tetraethylene amine cation organic amine to the diamine alkane is 1: (0.5-1).
According to one embodiment of the present invention, the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; the silicon source is selected from one or more of alkaline silica sol, neutral silica sol, solid silica gel and water glass; the aluminum source is one or more selected from aluminum sulfate, aluminum nitrate, pseudo-boehmite, aluminum chloride, sodium metaaluminate and alumina.
According to one embodiment of the present invention, SiO is the silicon source2: al in aluminum source2O3The molar ratio of the inorganic alkali to the mixed template agent to the water is 1 (0.001-0.1), (0.005-0.2), (0.01-0.1) and (5-20).
According to one embodiment of the present invention, the crystallization process is: and heating the gel to 120-190 ℃ at a heating rate of 1-10 ℃/min, and crystallizing for 12-96 hours.
Further, the crystallization process is as follows: and heating the gel to 150-180 ℃ at a heating rate of 1-10 ℃/min, and crystallizing for 12-48 hours.
According to one embodiment of the invention, the ammonium exchange is carried out using an ammonium exchange reagent selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.
According to another aspect of the present invention, there is provided a Beta molecular sieve prepared by the method according to the present invention.
According to another aspect of the present invention, there is provided a method for preparing an SCR catalyst, wherein the Beta molecular sieve used is prepared by the method as described above.
According to one embodiment of the present invention, a method for preparing an SCR catalyst includes: and (3) loading metal ions on the Beta molecular sieve prepared by the method to obtain the SCR catalyst.
According to one embodiment of the present invention, the method of loading Beta molecular sieves with metal ions may be by mixing the Beta molecular sieves with a solution of metal ions.
According to one embodiment of the present invention, the metal ion solution contains one or more metal ions selected from divalent copper ions, divalent cobalt ions, divalent nickel ions, trivalent cerium ions, monovalent silver ions, and divalent palladium ions.
According to one embodiment of the present invention, the metal ion solution is a nitric acid solution of metal ions, a sulfuric acid solution of metal ions, or the like. For example, copper nitrate, cobalt nitrate, nickel nitrate, cerium nitrate, silver nitrate, palladium nitrate, copper sulfate, cobalt sulfate, nickel sulfate, cerium sulfate, silver sulfate, palladium sulfate, etc.
According to one embodiment of the present invention, the concentration of the metal ion solution is 0.1mol/L to 0.5 mol/L; in the SCR catalyst, the mass percentage of metal ions is 1-5%.
The invention has the following beneficial effects: by utilizing the preparation method, the Beta molecular sieve with large particle size and high specific surface area is obtained. The Beta molecular sieve prepared by the method has the specific surface area as high as 700-900 m2The grain diameter can reach more than 1 mu m, which is beneficial to the separation and washing of Beta molecular sieve slurry in the industrial production process.
The preparation method of the Beta molecular sieve has the advantages of reducing the synthesis cost, shortening the crystallization time and the like.
The SCR catalyst obtained by utilizing the Beta molecular sieve prepared by the invention has high hydrothermal stability and high tail gas catalytic performance.
Detailed Description
The present invention will now be described with reference to the following detailed description, which is to be construed as illustrative only and not limiting in any way.
The invention provides a preparation method of a Beta molecular sieve and a preparation method of an SCR (selective catalytic reduction) catalyst.
The invention provides a preparation method of a Beta molecular sieve, which comprises the following steps:
mixing an aluminum source, inorganic alkali, water and seed crystals, then adding a mixed template agent and a silicon source to form gel, and obtaining the Beta molecular sieve through crystallization, ammonium exchange and roasting;
wherein the mixed template agent comprises at least one diaminoalkane and at least one tetraethylammonium cation organic amine.
Specifically, the preparation method may include the steps of:
preparing gel: (a) tetraethyl amine cation organic amine and cheap diamine alkane are uniformly mixed according to a certain proportion to form a mixed template agent; (b) mixing an aluminum source, an inorganic base, water and seed crystals; (c) adding a mixed template agent and a silicon source to obtain aluminosilicate gel with a certain molar ratio;
and (3) crystallization: crystallizing the sample of the aluminosilicate gel, separating, washing and drying to obtain molecular sieve raw powder;
ammonium exchange: mixing the molecular sieve raw powder with an ammonium exchange reagent aqueous solution, heating, stirring, and then separating, washing and drying the sample after ion exchange to obtain a molecular sieve sample;
roasting: and roasting the molecular sieve sample to obtain a roasted Beta molecular sieve product.
In the preparation method of the present invention, the order of step (a) and step (b) may be interchanged during the preparation of the gel.
According to one embodiment of the invention, tetraethylammonium cationic organic amine and diaminoalkane are mixed at a temperature of between room temperature and 90 ℃ to form a mixed template. The mixing means may be stirring mixing, such as mechanical stirring, magnetic stirring, etc.
By utilizing the preparation method, the Beta molecular sieve with large particle size and high specific surface area is obtained. The Beta molecular sieve prepared by the method has the specific surface area as high as 700-900 m2The grain diameter can reach more than 1 mu m, which is beneficial to the separation and washing of Beta molecular sieve slurry in the industrial production process. The preparation method of the Beta molecular sieve has the advantages of reducing the synthesis cost, shortening the crystallization time and the like.
According to one embodiment of the invention, the diaminoalkane is selected from one or more of pentanediamine, hexanediamine, heptanediamine or octanediamine.
According to one embodiment of the invention, the tetraethylammonium cationic organic amine is selected from one or more of tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride or tetraethylammonium iodide.
Further, the diaminoalkane is selected from one or more of hexamethylenediamine or heptamethylenediamine, and the tetraethyl amine cationic organic amine is selected from one or more of tetraethyl ammonium hydroxide or tetraethyl ammonium bromide.
According to an embodiment of the present invention, in the mixed template, the mass ratio of the tetraethylene amine cation organic amine to the diamine alkane is 1: (0.01-3).
Further, the mass ratio of the tetraethylene amine cation organic amine to the diamine alkane is 1: (0.5-1).
The applicants have found that Beta molecular sieves cannot be obtained using a process according to the present invention when only diaminoalkanes are used as templating agents.
According to one embodiment of the present invention, the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; the silicon source is selected from one or more of alkaline silica sol, neutral silica sol, solid silica gel and water glass; the aluminum source is one or more selected from aluminum sulfate, aluminum nitrate, pseudo-boehmite, aluminum chloride, sodium metaaluminate and alumina.
According to one embodiment of the present invention, SiO is the silicon source2: al in aluminum source2O3: inorganic base: mixing a template agent: the molar ratio of water is 1 (0.001-0.1): (0.005-0.2): (0.01-0.1): 5-20). In the present invention, the amount of water is the total amount of all water in the system.
According to one embodiment of the present invention, the crystallization process is: and heating the gel to 120-190 ℃ at a heating rate of 1-10 ℃/min, and crystallizing for 12-96 hours.
Further, the crystallization process is as follows: and heating the gel to 150-180 ℃ at a heating rate of 1-10 ℃/min, and crystallizing for 12-48 hours. According to an embodiment of the present invention, the crystallization time is, for example, 12 hours, 15 hours, 18 hours, 20 hours, 24 hours, 28 hours, 30 hours, 36 hours, 40 hours, 45 hours, 48 hours, or the like.
According to one embodiment of the invention, the ammonium exchange is carried out using an ammonium exchange reagent selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.
The invention also provides a Beta molecular sieve which is prepared by the method.
The invention also provides a preparation method of the SCR catalyst, wherein the Beta molecular sieve is prepared by the method.
According to one embodiment of the present invention, a method for preparing an SCR catalyst includes: and (3) loading metal ions on the Beta molecular sieve prepared by the method to obtain the SCR catalyst.
According to one embodiment of the present invention, the method of loading Beta molecular sieves with metal ions may be by mixing the Beta molecular sieves with a solution of metal ions.
According to one embodiment of the present invention, the metal ion solution contains one or more metal ions selected from divalent copper ions, divalent cobalt ions, divalent nickel ions, trivalent cerium ions, monovalent silver ions, and divalent palladium ions.
According to one embodiment of the present invention, the metal ion solution is a nitric acid solution of metal ions, a sulfuric acid solution of metal ions, or the like. For example, copper nitrate, cobalt nitrate, nickel nitrate, cerium nitrate, silver nitrate, palladium nitrate, copper sulfate, cobalt sulfate, nickel sulfate, cerium sulfate, silver sulfate, palladium sulfate, etc.
According to one embodiment of the present invention, the concentration of the metal ion solution is 0.1mol/L to 0.5 mol/L; in the SCR catalyst, the mass percentage of metal ions is 1-5%.
The SCR catalyst obtained by utilizing the Beta molecular sieve prepared by the invention has high hydrothermal stability and high tail gas catalytic performance.
The embodiments of the present invention will be further explained and illustrated with reference to the following examples.
In the invention, the hydrothermal stability of the molecular sieve is tested through a hydrothermal aging experiment, and the tail gas purification effect of the SCR catalyst is evaluated in a tail gas purification evaluation device.
Example 1
First, 0.46g NaOH and 1g sodium metaaluminate are stirred in water at 25 ℃ and then 5.16g mixed template agent (the mass ratio of tetraethylammonium hydroxide to hexamethylenediamine is 1: 1) and 0.3g seed crystal are added, and then 27g silica gel is added while stirring and transferred into a stainless steel reaction kettle. And heating to 140 ℃, uniformly stirring and crystallizing for 48 hours, collecting, washing, drying, exchanging ammonium and roasting to obtain the Beta molecular sieve.
The Beta molecular sieve is characterized by SEM, BET and the like, wherein D50 is 0.5 mu m, and the specific surface area is 898m2(ii) in terms of/g. The Beta molecular sieve and a copper nitrate solution (with the concentration of 0.15mol/L) are mixed to obtain the SCR catalyst loaded with Cu ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the conversion rate of NO is more than 85% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by only 6% after aging for 20 hours at 800 ℃.
Example 2
0.56g of NaOH and 2g of sodium metaaluminate are added into 30.9g of water at 25 ℃ and fully stirred, 9.16g of mixed template agent (the mass ratio of tetraethylammonium bromide to heptanediamine is 1: 1) and 0.3g of seed crystal are added, 27g of silica gel is added while stirring, and the mixture is transferred into a stainless steel reaction kettle. Heating to 160 ℃, stirring at a constant speed, carrying out uniform stirring crystallization for 36 hours, collecting, washing, drying, carrying out ammonium exchange, and roasting to obtain the Beta molecular sieve.
The Beta molecular sieve is characterized by SEM, BET and the like, wherein D50 is 0.63 mu m, and the specific surface area 833m2/g。
The Beta molecular sieve is mixed with a nickel sulfate solution (with the concentration of 0.2mol/L) to obtain the SCR catalyst loaded with Ni ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 86% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 4% after aging for 20 hours at 800 ℃.
Example 3
0.56g of NaOH and 2g of sodium metaaluminate are added into 30.9g of water at 25 ℃ and fully stirred, 5.16g of mixed template agent (the mass ratio of tetraethylammonium hydroxide to hexamethylene diamine is 1:0.5) and 0.3g of seed crystal are added, 27g of silica gel is added while stirring, and the mixture is transferred into a stainless steel reaction kettle. And heating to 160 ℃, uniformly stirring and crystallizing for 36 hours, collecting, washing, drying, exchanging ammonium and roasting to obtain the Beta molecular sieve.
The Beta molecular sieve is characterized by XRF, BET, particle size analyzer and the like, wherein D50 is 0.84 mu m, and the specific surface area is 788m2(ii) in terms of/g. The Beta molecular sieve and a copper nitrate solution (with the concentration of 0.3mol/L) are mixed to obtain the SCR catalyst loaded with Cu ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 84% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 3% after aging for 20 hours at 800 ℃.
Example 4
0.56g of NaOH and 2g of sodium metaaluminate are added into 30.9g of water at 25 ℃ and fully stirred, 5.16g of mixed template agent (the mass ratio of tetraethylammonium bromide to hexamethylenediamine is 1: 2) and 0.3g of seed crystal are added, 27g of silica gel is added while stirring, and the mixture is transferred into a stainless steel reaction kettle. And heating to 180 ℃, uniformly stirring and crystallizing for 12 hours, collecting, washing, drying, exchanging ammonium and roasting to obtain the Beta molecular sieve.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 1.33 mu m, and the specific surface area is 718m2(ii) in terms of/g. The Beta molecular sieve is mixed with silver nitrate solution (the concentration is 0.25mol/L) to obtain the SCR catalyst loaded with Ag ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 83% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 5 percent after aging for 20 hours at 800 ℃.
Example 5
The same as example 1, except that tetraethylammonium chloride and heptanediamine (mass ratio of 1:0.5) were used as the mixed template.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 0.53 mu m, and the specific surface area is 883m2(ii) in terms of/g. The Beta molecular sieve and a cerium nitrate solution (with the concentration of 0.4mol/L) are mixed to obtain the Ce ion-loaded SCR catalyst, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 86% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 4% after aging for 20 hours at 800 ℃.
Example 6
The same as example 1, except that tetraethylammonium iodide and octanediamine (mass ratio of 1:1.5) are used as mixed templates.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 0.52 mu m, and the specific surface area is 892m2(ii) in terms of/g. The Beta molecular sieve and a copper nitrate solution (with the concentration of 0.5mol/L) are mixed to obtain the SCR catalyst loaded with Cu ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 85% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 5 percent after aging for 20 hours at 800 ℃.
Example 7
The same as example 1, except that tetraethylammonium chloride and hexamethylene diamine (mass ratio of 1:2.5) were used as mixed templates.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 0.51 mu m, and the specific surface area is 895m2(ii) in terms of/g. The Beta molecular sieve is mixed with silver nitrate solution (the concentration is 0.2mol/L) to obtain the SCR catalyst loaded with Ag ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 84% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 5 percent after aging for 20 hours at 800 ℃.
Example 8
The same as example 1, except that tetraethylammonium iodide and hexamethylenediamine (1: 0.1 by mass ratio) were used as the mixed template.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 0.48 mu m, and the specific surface area is 902m2(ii) in terms of/g. The Beta molecular sieve and a cobalt nitrate solution (with the concentration of 0.15mol/L) are mixed to obtain the SCR catalyst loaded with Co ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 86% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 4% after aging for 20 hours at 800 ℃.
Comparative example 1
The same procedure as in example 1 was followed, except that 5.16g of tetraethylammonium hydroxide was used as the template and that the crystallization time was 72 hours.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 0.3 mu m, and the specific surface area is 918m2(ii) in terms of/g. The Beta molecular sieve and a copper nitrate solution (with the concentration of 0.15mol/L) are mixed to obtain the SCR catalyst loaded with Cu ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the conversion rate of NO is more than 80% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 44 percent after aging for 20 hours at 800 ℃.
Comparative example 2
The same procedure as in example 2 was followed, except that 9.16g of tetraethylammonium bromide was used as the template and the crystallization time was 72 hours.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 0.6 mu m, and the specific surface area is 842m2(ii) in terms of/g. The Beta molecular sieve is mixed with a nickel nitrate solution (with the concentration of 0.2mol/L) to obtain the SCR catalyst loaded with Ni ions, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 80% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 41 percent after aging for 20 hours at 800 ℃.
Comparative example 3
The same procedure as in example 5 was followed, except that 5.16g of tetraethylammonium chloride was used as the template and the crystallization time was 72 hours.
The Beta molecular sieve is characterized by SEM, XRF, BET and the like, wherein D50 is 0.51 mu m, and the specific surface area is 887m2(ii) in terms of/g. The Beta molecular sieve and a cerium nitrate solution (with the concentration of 0.4mol/L) are mixed to obtain the Ce ion-loaded SCR catalyst, the catalytic performance of the SCR catalyst is detected by an exhaust gas purification evaluation device, and the results show that the NO conversion rate is more than 80% at 200 ℃ and 600 ℃. The hydrothermal aging stability is detected in a hydrothermal aging device, and the overall catalytic performance of the catalyst is reduced by 47 percent after aging for 20 hours at 800 ℃.
According to the comparison between the embodiment of the invention and the comparative embodiment, it can be seen that the beta molecular sieve prepared by the mixed template of the invention has large particle size, higher specific surface area, better hydrothermal stability and higher catalytic performance of tail gas.
Comparative example 4
The same procedure as in example 1, except that 5.16g of tetraethylammonium hydroxide and hexamethylenediamine were used as the templating agent in a mass ratio of greater than 1: 3.
the sample is characterized by SEM, XRF, BET and the like, and is a mixed crystal containing ZSM-22 and ZSM-5 molecular sieves, wherein D50 is about 1.54 mu m, and the specific surface area is less than or equal to 514m2(ii) in terms of/g. The catalytic performance of the loaded sample is detected in a tail gas purification evaluation device, the result shows that the conversion rate of NO is less than 55% at 200 ℃ and 600 ℃, the hydrothermal aging stability is detected in a hydrothermal aging device, and the total catalytic performance is reduced by about 48% after aging for 20 hours at 800 DEG CAnd (4) right.
In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims (2)

1. The preparation method of the Beta molecular sieve is characterized by comprising the following steps:
mixing an aluminum source, inorganic alkali, water and seed crystals, then adding a mixed template agent and a silicon source to form gel, and obtaining the Beta molecular sieve through crystallization, ammonium exchange and roasting;
wherein the mixed template agent comprises at least one diaminoalkane and at least one tetraethylammonium cation organic amine;
the diaminoalkane is selected from one or more of pentanediamine, hexanediamine, heptanediamine or octanediamine;
the cationic organic amine of the tetraethylene amine is selected from one or more of tetraethyl ammonium hydroxide, tetraethyl ammonium bromide, tetraethyl ammonium chloride or tetraethyl ammonium iodide;
in the mixed template agent, the mass ratio of the tetraethylene amine cation organic amine to the diamine alkane is 1: (0.01-3);
the inorganic alkali is selected from one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; the silicon source is selected from one or more of alkaline silica sol, neutral silica sol, solid silica gel and water glass; the aluminum source is selected from one or more of aluminum sulfate, aluminum nitrate, pseudo-boehmite, aluminum chloride, sodium metaaluminate and alumina;
SiO in silicon source2: al in aluminum source2O3The molar ratio of the inorganic alkali to the mixed template agent to the water is 1 (0.001-0.1) to 0.005-0.2):(0.01～0.1):(5～20)；
The crystallization process comprises the following steps: and heating the gel to 120-190 ℃ at a heating rate of 1-10 ℃/min, and crystallizing for 12-96 hours.
2. The preparation method according to claim 1, wherein the mass ratio of the tetraethylene amine cation organic amine to the diamine alkane in the mixed template agent is 1: (0.5-1).
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