CN118059923A - Mo-atom-doped Cu-SSZ-13 molecular sieve catalyst and preparation method and application thereof - Google Patents

Mo-atom-doped Cu-SSZ-13 molecular sieve catalyst and preparation method and application thereof Download PDF

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CN118059923A
CN118059923A CN202410196609.4A CN202410196609A CN118059923A CN 118059923 A CN118059923 A CN 118059923A CN 202410196609 A CN202410196609 A CN 202410196609A CN 118059923 A CN118059923 A CN 118059923A
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molecular sieve
ssz
ammonium
atoms
framework
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苏怡
缪嵩松
张鼎
杨微微
廖建辉
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Changchun Institute of Applied Chemistry of CAS
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Changchun Institute of Applied Chemistry of CAS
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Abstract

The invention provides a Cu-SSZ-13 molecular sieve catalyst doped with Mo atoms, and a preparation method and application thereof. The molecular sieve catalyst comprises a molecular sieve framework and Cu 2+ dispersed outside the molecular sieve framework, wherein the molecular sieve framework is an SSZ-13 molecular sieve framework containing framework Mo atoms. According to the invention, mo atoms are introduced to replace part of Si and Al atoms in the SSZ-13 molecular sieve framework, so that the finally obtained molecular sieve catalyst has good framework stability. According to the invention, the Cu-SSZ-13 molecular sieve doped with Mo atoms is used for NH 3 -SCR denitration reaction and is used as a catalyst, and the result shows that the catalyst has higher NH 3 -SCR denitration activity, can realize high-efficiency denitration in a wider temperature window (150-600 ℃), and has higher high-temperature hydrothermal stability.

Description

Mo-atom-doped Cu-SSZ-13 molecular sieve catalyst and preparation method and application thereof
Technical Field
The invention belongs to the technical field of molecular sieves, and particularly relates to a Cu-SSZ-13 molecular sieve catalyst doped with Mo atoms, and a preparation method and application thereof.
Background
Nitrogen oxides (NO x) are one of the main atmospheric pollutants, endangering the ecological environment and affecting the physical and mental health of humans. With the implementation of more severe emission standards of NO x in diesel vehicles, development of more efficient and durable exhaust gas treatment systems for fuel vehicles is urgent, and the core problem is the high performance denitration catalyst.
In many NH 3 -SCR denitration catalysts, copper-based CHA small pore molecular sieves (namely Cu-SSZ-13 molecular sieves) have been commercially used in the field of diesel vehicle exhaust treatment due to excellent catalytic activity and hydrothermal stability, however, the Cu-SSZ-13 molecular sieves have low NO x conversion rate at low temperature and reduced activity after hydrothermal aging.
In recent years, a great deal of research focused on improving the low-temperature activity and the anti-hydrothermal aging capability of the Cu-SSZ-13 molecular sieve at home and abroad is continuously emerging. Representative catalyst modification schemes include: constructing a metal oxide-molecular sieve composite catalyst, modifying rare earth cations, constructing a core-shell structure and the like. The above-mentioned various researches focus on the post-treatment modification of SSZ-13 molecular sieve, and the catalyst preparation process is relatively complex.
Disclosure of Invention
In view of the above, the present invention aims to provide a Cu-SSZ-13 molecular sieve doped with Mo atoms, and a preparation method and application thereof. According to the invention, the Cu-SSZ-13 molecular sieve catalyst doped with Mo atoms is obtained through isomorphous substitution of the molybdenum atoms, and has higher NH 3 -SCR denitration activity, high-efficiency denitration can be realized in a wider temperature window, and higher hydrothermal stability is realized.
In order to achieve the purpose, the invention adopts the following technical scheme:
In a first aspect, the invention provides a Mo atom doped Cu-SSZ-13 molecular sieve catalyst, which comprises a molecular sieve framework and Cu 2+ dispersed outside the molecular sieve framework, wherein the molecular sieve framework is an SSZ-13 molecular sieve framework containing framework Mo atoms;
The SSZ-13 molecular sieve framework comprises silicon atoms and aluminum atoms.
Preferably, the mole ratio of Mo atoms to silicon atoms in the SSZ-13 molecular sieve framework is (0.001-0.5): 1.
Preferably, the molar ratio of Cu 2+ to silicon atoms in the SSZ-13 molecular sieve framework is (0-0.05): 1.
In a second aspect, the invention provides a preparation method of the Mo atom doped Cu-SSZ-13 molecular sieve catalyst, which comprises the following steps:
S1: performing hydrothermal crystallization treatment on a mixture of an alkaline substance, an aluminum source, an organic structure directing agent, a molybdenum source, a silicon source and water to obtain an Mo atom doped SSZ-13 molecular sieve;
s3: and roasting the obtained Mo-doped SSZ-13 molecular sieve, and then sequentially carrying out ammonium ion exchange and copper ion exchange to obtain the Mo-atom-doped Cu-SSZ-13 molecular sieve.
Preferably, the alkaline substance is selected from sodium hydroxide and/or potassium hydroxide.
Preferably, the aluminum source is selected from any one or more of aluminum hydroxide, aluminum isopropoxide, aluminum sulfate or sodium metaaluminate.
Preferably, the organic structure directing agent is selected from N, N-trimethyl-1-adamantylammonium hydroxide and/or choline chloride.
Preferably, the molybdenum source is selected from any one or more of sodium molybdate, ammonium molybdate, silicomolybdic acid, ammonium silicomolybdate or sodium silicomolybdate.
Preferably, the silicon source is selected from any one or more of white carbon black, silica sol, tetraethoxysilane or sodium silicate.
Preferably, the mole ratio of Mo atoms to silicon atoms in the mixture is (0.001 to 0.5): 1.
Preferably, the molar ratio of the silicon source to the aluminum source to the alkaline substance to the organic structure directing agent to the water is 1 (0.025-0.05): 0.2-0.8): 0.1-0.3): 10-20.
Preferably, the temperature of the hydrothermal crystallization treatment is 140-160 ℃ and the time is 48-144 h.
Preferably, the roasting temperature is 540-600 ℃ and the time is 4-10 h.
Preferably, the ammonium ion exchange is treated with an ammonium salt selected from any one or more of ammonium sulfate, ammonium chloride or ammonium nitrate.
Preferably, the concentration of ammonium ions in the ammonium salt is 0.5 to 1.0mol/L.
Preferably, the temperature of the ammonium ion exchange is 70-90 ℃ and the time is 3-6 h.
Preferably, the copper ion exchange is treated with a soluble copper salt selected from any one or more of copper sulfate, copper nitrate or copper acetate.
Preferably, the concentration of copper ions in the soluble copper salt is 0.002-0.025 mol/L.
Preferably, the temperature of the copper ion exchange is 25-80 ℃ and the time is 4-24 h.
In a third aspect, the invention provides an application of a Mo atom doped Cu-SSZ-13 molecular sieve catalyst in NH 3 -SCR denitration reaction.
Compared with the prior art, the invention has the beneficial effects that:
The method directly starts from the element composition of the SSZ-13 molecular sieve catalyst skeleton, and designs and prepares the Cu-SSZ-13 molecular sieve catalyst with isomorphous substitution of molybdenum atoms, namely the Cu-SSZ-13 molecular sieve catalyst doped with Mo atoms. According to the invention, mo atoms are introduced to replace part of Si and Al atoms in the SSZ-13 molecular sieve framework, and the finally obtained molecular sieve catalyst has good framework stability by virtue of the improvement of oxidation-reduction capability and the improvement of acidity, hydrothermal stability, adsorption and other performances caused by the Mo atoms. According to the invention, the Cu-SSZ-13 molecular sieve catalyst doped with Mo atoms is used for NH 3 -SCR denitration reaction, and the result shows that the catalyst has higher NH 3 -SCR denitration activity, can realize high-efficiency denitration in a wider temperature window (150-600 ℃), has higher high-temperature hydrothermal stability, still has excellent NH 3 -SCR denitration activity after hydrothermal aging for 16 hours at 750 ℃, and can realize high-efficiency denitration. Therefore, mo atoms introduced in the invention can obviously improve the low-temperature and high-temperature catalytic activity of the Cu-SSZ-13 molecular sieve and improve the hydrothermal stability of the Cu-SSZ-13 molecular sieve.
Drawings
FIG. 1 is an XRD spectrum of the product obtained in comparative preparation example 1;
FIG. 2 is an XRD spectrum of the product obtained in preparation example 1;
FIG. 3 is an XRD spectrum of the product obtained in preparation example 2;
FIG. 4 is an SEM image of the product obtained in comparative preparation example 1;
FIG. 5 is an SEM image of the product obtained in preparation example 1;
FIG. 6 is an SEM image of the product obtained in preparation example 2;
FIG. 7 is an SEM image of the product obtained in preparation example 3;
FIG. 8 is an SEM image of the product obtained in preparation example 5;
FIG. 9 is a mapping image of HAADF STEM and each element of the product obtained in example 1.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Term interpretation:
(1) NH 3 -SCR, an abbreviation for NH 3 SELECTIVE CATALYTIC Reduction, refers to an ammonia selective catalytic Reduction reaction;
(2) The SSZ-13 molecular sieve is a small-pore silicon-aluminum molecular sieve, the framework is silicon-aluminum oxygen atoms, the framework is electronegative, the electronegativity is balanced by cations in pore channels of the molecular sieve, the cations can be modulated by ion exchange between the molecular sieve and a cation-containing aqueous solution, and the molecular sieve has higher hydrothermal stability; the method of writing SSZ-13 according to the present invention is not limited to the cation, and may be Na + ion, H +, or both Na + and H +;
(3) The Cu-SSZ-13 molecular sieve is a product obtained by exchanging an NH 4 + with an SSZ-13 molecular sieve to obtain an ammonium type NH 4 -SSZ-13 molecular sieve and then exchanging Cu 2+ with a solution containing copper ions with a certain concentration, and part of ammonium ions are replaced by Cu 2+.
Among the numerous NH 3 -SCR denitration catalysts, cu-SSZ-13, which is a copper-based CHA small pore molecular sieve, has been commercially applied in the field of diesel vehicle exhaust treatment due to its excellent catalytic activity and hydrothermal stability. But still faces the problems of low catalytic activity at low temperature and reduced activity after hydrothermal aging. In order to improve the performance of the catalyst, the prior art generally adopts post-treatment modification of a Cu-SSZ-13 molecular sieve, but generally has the problem of complex experimental process, and has lower catalytic activity and still needs to be improved in high-temperature hydrothermal stability, so the invention provides a Mo atom doped Cu-SSZ-13 molecular sieve catalyst which comprises a molecular sieve framework and Cu 2+ dispersed outside the molecular sieve framework. In the invention, the molecular sieve framework is an SSZ-13 molecular sieve framework containing framework Mo atoms, and the Mo atoms are introduced to replace part of silicon atoms or aluminum atoms on the SSZ-13 molecular sieve framework, so that the finally formed SSZ-13 molecular sieve framework comprises the Mo atoms, the Al atoms and the silicon atoms, and the introduced Mo atoms can improve the oxidation-reduction property, the acidity, the hydrothermal stability, the adsorption and other performances of the Cu-SSZ-13 molecular sieve framework finally obtained through copper ion exchange. As described above, the Cu 2+ is dispersed outside the framework, i.e., in the pores formed by the SSZ-13 molecular sieve framework containing framework Mo atoms.
In the present invention, the molar ratio of the Mo atom to the silicon atom in the SSZ-13 molecular sieve skeleton is (0.001 to 0.5): 1, preferably (0.005 to 0.3): 1, and more preferably (0.01 to 0.1): 1. The molar ratio of Cu 2+ to silicon in the SSZ-13 molecular sieve framework is (0.05-0.05): 1, preferably (0.01-0.04): 1, more preferably (0.02-0.03): 1.
The invention also provides a preparation method of the Mo atom doped Cu-SSZ-13 molecular sieve catalyst, which comprises the following steps:
S1: performing hydrothermal crystallization treatment on a mixture of an alkaline substance, an aluminum source, an organic structure directing agent, a molybdenum source, a silicon source and water to obtain an Mo atom doped SSZ-13 molecular sieve;
S2: and roasting the obtained Mo-doped SSZ-13 molecular sieve, and then sequentially carrying out ammonium ion exchange and copper ion exchange to obtain the Mo-atom-doped Cu-SSZ-13 molecular sieve catalyst.
According to the present invention, a mixture of an alkaline substance, an aluminum source, an organic structure directing agent, a molybdenum source, a silicon source, and water is first provided. In some embodiments of the invention, the alkaline substance, the aluminium source, the organic structure directing agent, the molybdenum source, and water are preferably mixed, preferably under stirring, and then the resulting mixture is mixed with the silicon source, also under stirring, to obtain the final mixture, i.e. the initial sol-gel. Wherein the alkaline material is selected from sodium hydroxide and/or potassium hydroxide for providing alkalinity to ensure the formation of an initial sol gel; the aluminum source is selected from any one or more of aluminum hydroxide, aluminum isopropoxide, aluminum sulfate or sodium metaaluminate; the organic structure directing agent is selected from N, N, N-trimethyl-1-adamantylammonium hydroxide and/or choline chloride, preferably N, N, N-trimethyl-1-adamantylammonium hydroxide, to form a better molecular sieve framework structure; the molybdenum source is selected from any one or more of sodium molybdate, ammonium molybdate, silicon molybdic acid, ammonium silicomolybdate or sodium silicomolybdate; the silicon source is selected from any one or more of white carbon black, silica sol, tetraethoxysilane or sodium silicate. In the present invention, the molar ratio of Mo atoms to silicon atoms in the final mixture, i.e., the initial sol-gel, is controlled to be (0.001 to 0.5): 1, preferably (0.005 to 0.3): 1, and more preferably (0.01 to 0.1): 1. In some embodiments of the invention, the silicon source, aluminum source, alkaline material, organic structure directing agent, and water are added to the system, preferably in a molar ratio of 1 (0.025-0.05): (0.2-0.8): (0.1-0.3): (10-20), preferably 1 (0.03-0.04): (0.3-0.5): (0.1-0.2): (15-20), to form the initial sol-gel.
After the initial sol-gel is obtained, the initial sol-gel is subjected to hydrothermal crystallization treatment according to the invention, and the Mo-doped SSZ-13 molecular sieve is obtained. In some embodiments of the invention, the initial sol-gel is preferably transferred to an autoclave lined with polytetrafluoroethylene for a hydrothermal crystallization treatment at a temperature of 140 to 160 ℃, preferably 145 to 155 ℃, for a time of 48 to 144 hours, preferably 72 to 120 hours.
The Mo-doped SSZ-13 molecular sieve is then calcined to remove the organic structure directing agent. In some preferred embodiments of the present invention, the Mo-doped SSZ-13 molecular sieve is preferably washed, dried, and then calcined. The roasting temperature is 540-600 ℃, preferably 550-580 ℃, and the time is 4-10h, preferably 5-8 h.
After the roasting is completed, the obtained product is preferably subjected to ammonium ion exchange to obtain the ammonium type Mo atom doped SSZ-13 molecular sieve. The ammonium ion exchange is carried out by adopting ammonium salt, the ammonium salt is selected from any one or more of ammonium sulfate, ammonium chloride or ammonium nitrate, and the concentration of ammonium ions in the ammonium salt is 0.5-1.0 mol/L, preferably 0.6-0.8 mol/L. In some embodiments of the invention, the calcined product is preferably mixed with a solution of ammonium salt for an ammonium ion exchange, preferably not less than 2 times, preferably 2 times, at a temperature of 70 to 90 ℃, preferably 75 to 80 ℃, for a period of 3 to 6 hours, preferably 4 to 5 hours.
After the ammonium ion exchange is completed, the present invention preferably carries out copper ion exchange on the obtained product. In some embodiments of the invention, the resulting product is preferably washed with deionized water multiple times, preferably 1 to 3 times, before copper ion exchange. The copper ion exchange is carried out by adopting soluble copper salt, the soluble copper salt is selected from any one or more of copper sulfate, copper nitrate or copper acetate, and the concentration of copper ions in the soluble copper salt is 0.002-0.025 mol/L, preferably 0.005-0.01 mol/L. In some embodiments of the invention, the product after ammonium ion exchange is preferably mixed with a solution of a soluble copper salt for copper ion exchange at a temperature of 25 to 80 ℃, preferably 40 to 60 ℃, for a time of 4 to 24 hours, preferably 8 to 12 hours.
In some preferred embodiments of the present invention, the resulting product is preferably washed, dried and calcined after copper ion exchange is complete to yield the final Mo atom doped Cu-SSZ-13 molecular sieve catalyst. The calcination treatment is preferably performed at 550 to 600℃for 3 to 6 hours, more preferably at 560 to 580℃for 4 to 5 hours. The step of roasting is to convert ammonium ions in the pore channels of the molecular sieve into hydrogen ions.
The preparation method provided by the invention is designed in the aspect of element composition of the molecular sieve framework, mo atoms are directly introduced to replace part of Si atoms or Al atoms in the framework, and the preparation method is simple and convenient to realize, and compared with the prior art, the preparation method does not need complex post-treatment of the Cu-SSZ-13 molecular sieve so as to improve the service performance of the Cu-SSZ-13 molecular sieve.
The invention also provides application of the Mo atom doped Cu-SSZ-13 molecular sieve in NH 3 -SCR denitration reaction. According to the invention, the Cu-SSZ-13 molecular sieve doped with Mo atoms is used as a catalyst for NH 3 -SCR denitration reaction, and the result shows that the catalyst has higher NH 3 -SCR denitration activity, can realize high-efficiency denitration in a wider temperature window (150-600 ℃), has higher high-temperature hydrothermal stability, still has excellent NH 3 -SCR denitration activity after hydrothermal aging for 16 hours at 750 ℃, and can realize high-efficiency denitration. Therefore, mo atoms introduced in the invention can obviously improve the low-temperature and high-temperature catalytic activity of the Cu-SSZ-13 molecular sieve and improve the hydrothermal stability of the Cu-SSZ-13 molecular sieve.
In order to further illustrate the present invention, the following examples are provided. The experimental materials used in the following examples of the present invention are all generally commercially available.
Comparative preparation example 1
0.8G of sodium hydroxide was dissolved in 28.6g of water, and then 12.0g of an aqueous solution (25 wt%) of N, N-trimethyl-1-adamantylammonium hydroxide and 0.4g of aluminum hydroxide (76.5 wt%) were added, followed by stirring for 1 hour, and then 7.3g of 40wt% silica sol was added, followed by stirring for 3 hours to obtain an initial sol. The initial sol is transferred into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and is placed in an oven at 160 ℃ for static crystallization for 5 days. And after crystallization, cooling the reaction kettle by tap water, washing and drying the obtained solid product, and finally roasting in a muffle furnace at 600 ℃ for 8 hours to remove the organic structure directing agent, thereby obtaining the SSZ-13 molecular sieve.
The obtained product was subjected to XRD test, and the result is shown in fig. 1.
Preparation example 1
0.8G of sodium hydroxide is dissolved in 28.6g of deionized water, then 12.0g of N, N-trimethyl-1-adamantyl ammonium hydroxide aqueous solution (25 wt%) is added, after stirring for 5min, 0.4g of aluminum hydroxide (76.5 wt%) and 0.015g of sodium molybdate are added, stirring is carried out for 30min, then 7.3g of silica sol (40 wt%) is added, after stirring for 3h, the reaction raw material is added into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallization is carried out at 160 ℃ for 120h. And (3) filtering, washing and drying the solid product, and roasting in a muffle furnace at 600 ℃ for 6 hours to remove the organic structure directing agent to obtain the product.
The obtained product was subjected to XRD test, and the result is shown in fig. 2.
Preparation example 2
0.8G of sodium hydroxide is dissolved in 28.6g of deionized water, then 12.0g of N, N-trimethyl-1-adamantyl ammonium hydroxide aqueous solution (25 wt%) is added, after stirring for 5min, 0.4g of aluminum hydroxide (76.5 wt%) and 0.01g of sodium molybdate are added, stirring is carried out for 30min, then 7.3g of silica sol (40 wt%) is added, after stirring for 3h, the reaction raw material is added into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallization is carried out at 160 ℃ for 120h. And (3) filtering, washing and drying the solid product, and roasting in a muffle furnace at 600 ℃ for 6 hours to remove the organic structure directing agent to obtain the product.
The obtained product was subjected to XRD test, and the result is shown in fig. 3.
From a comparison of FIGS. 1-3, it can be seen that the structure of the SSZ-13 molecular sieve is not affected by the present invention after Mo atoms are introduced into the SSZ-13 molecular sieve.
Preparation example 3
1.12G of sodium hydroxide was weighed and dissolved in 40.0g of deionized water, then 16.8g of an aqueous solution (25 wt%) of N, N-trimethyl-1-adamantylammonium hydroxide was added, after stirring for 5min, 1.1217g of aluminum isopropoxide was added, stirring was carried out for 1h, then 0.2806g of sodium molybdate was added, after stirring for 2h, 10.22g of silica sol (40 wt%) was added and stirring was continued for 3h. The reaction raw materials are added into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallized for 120 hours at 160 ℃. And (3) filtering, washing and drying the solid product, and roasting in a muffle furnace at 600 ℃ for 6 hours to remove the organic structure directing agent to obtain the product.
Preparation example 4
0.8G of sodium hydroxide is dissolved in 33.0g of deionized water, then 12.0g of N, N-trimethyl-1-adamantyl ammonium hydroxide aqueous solution (25 wt%) is added, after stirring for 5min, 0.4g of aluminum hydroxide (76.5 wt%) and 0.02g of sodium molybdate are added, stirring is carried out for 30min, then 2.92g of white carbon black is added, after stirring for 3h, the reaction raw material is added into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallization is carried out at 160 ℃ for 120h. And (3) filtering, washing and drying the solid product, and roasting in a muffle furnace at 600 ℃ for 6 hours to remove the organic structure directing agent to obtain the product.
Preparation example 5
0.8G of sodium hydroxide is dissolved in 28.6g of deionized water, then 12.0g of N, N-trimethyl-1-adamantyl ammonium hydroxide aqueous solution (25 wt%) is added, after stirring for 5min, 0.8g of aluminum hydroxide (76.5 wt%) and 0.05g of sodium molybdate are added, stirring is carried out for 30min, then 7.3g of silica sol (40 wt%) is added, after stirring for 3h, the reaction raw material is added into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallization is carried out at 160 ℃ for 120h. And (3) filtering, washing and drying the solid product, and roasting in a muffle furnace at 600 ℃ for 6 hours to remove the organic structure directing agent to obtain the product.
Preparation example 6
0.8G of sodium hydroxide is dissolved in 33.0g of deionized water, then 12.0g of N, N-trimethyl-1-adamantyl ammonium hydroxide aqueous solution (25 wt%) is added, after stirring for 5min, 0.4g of aluminum hydroxide (76.5 wt%) is added, stirring is carried out for 30min, then 2.92g of white carbon black is added, after stirring for 3h, 0.02g of sodium molybdate is added, stirring is continued for 1h, the reaction raw material is added into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallization is carried out at 160 ℃ for 120h. And (3) filtering, washing and drying the solid product, and roasting in a muffle furnace at 600 ℃ for 6 hours to remove the organic structure directing agent to obtain the product.
Preparation example 7
0.8G of sodium hydroxide is dissolved in 35.8g of deionized water, 1.36g of choline chloride is added, after stirring for 5min, 0.4g of aluminum hydroxide (76.5 wt%) and 0.01g of sodium molybdate are added, stirring is carried out for 30min, then 7.3g of silica sol (40 wt%) are added, after stirring for 3h, the reaction raw materials are added into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallization is carried out for 120h at 160 ℃. And (3) filtering, washing and drying the solid product, and roasting in a muffle furnace at 600 ℃ for 8 hours to remove the organic structure directing agent to obtain the product.
SEM tests were performed on the products obtained in comparative preparation example 1 and preparation examples 1,2, 3, 5, and the results are shown in fig. 4 to 8, and fig. 5 to 8 are compared with fig. 4, and the molecular sieves obtained by adding Mo source are present in the form of molecular sieve polycrystalline aggregates, while their crystal particle size is larger.
It should be noted, however, that the organic structure directing agent is more preferably N, N-trimethyl-1-adamantylammonium hydroxide because of the higher crystallinity of the molecular sieve crystals obtained using the former as compared to choline chloride.
Examples 1 to 7
Carrying out twice NH 4 + ion exchange (80 ℃ for 5 hours) on the Mo-SSZ-13 molecular sieves obtained in preparation examples 1-7 by using 1.0mol/L ammonium nitrate solution, and then carrying out suction filtration and washing with deionized water for many times to obtain NH 4 -SSZ-13; then carrying out ion exchange (25 ℃ for 24 hours) with 0.004mol/L copper acetate solution, carrying out suction filtration to obtain solid, washing the solid with deionized water for a plurality of times, drying, and roasting the dried solid in a muffle furnace at 550 ℃ for 6 hours to finally obtain the corresponding Mo atom doped Cu-SSZ-13 molecular sieve catalyst.
EDS test was performed on the Mo-SSZ-13 molecular sieve obtained in example 1, and the result is shown in FIG. 9, it can be seen that Mo atoms are indeed present, indicating that the Mo atoms were successfully doped in the Cu-SSZ-13 molecular sieve.
Comparative example 1
For the molecular sieves obtained in comparative preparation example 1 and preparation example 1, NH 4 + ion-exchange was performed twice (80 ℃ C., 5 h) with 1.0mol/L ammonium nitrate solution, followed by suction filtration and washing with deionized water multiple times to obtain NH 4 -SSZ-13; then carrying out ion exchange (25 ℃ for 24 hours) with 0.004mol/L copper acetate solution, carrying out suction filtration to obtain solid, washing the solid with deionized water for a plurality of times, drying, and roasting the dried solid in a muffle furnace at 550 ℃ for 6 hours to finally obtain the corresponding Cu-SSZ-13 and Mo-doped Cu-SSZ-13 molecular sieve catalyst.
Evaluation of Performance
The molecular sieve catalysts obtained in preparation example 1 and comparative preparation example 1 were subjected to NH 3 -SCR denitration catalytic performance evaluation. In addition, after the obtained molecular sieve catalyst is subjected to hydrothermal aging treatment, NH 3 -SCR denitration catalytic performance evaluation is performed. Wherein, the hydrothermal aging conditions are: the corresponding catalyst was hydrothermally aged in an air stream containing 12.5% water at 750 ℃ for 16h.
In the invention, denitration catalytic performance test is evaluated by a set of conventional fixed bed reaction system, a catalyst is placed in a quartz tube, the temperature is controlled by a tube furnace, gas passing through a catalyst bed is detected by an on-line mass spectrometer, and the test is carried out at 150-600 ℃.
The specific test method is as follows:
Before the corresponding catalyst is subjected to reaction evaluation, the catalyst can be pressed and ground into particles with 40-60 meshes, mixed with a proper amount of quartz sand and filled in a quartz tube. Reaction conditions: the catalyst dosage is 50mg,500ppm NO,500ppmNH3,5vol%O 2,5vol％H2 O, ar is balance gas, the total gas flow is 200mL/min, and the reaction space velocity is 240000 mL.g -1·h-1. The concentrations of reactants and products were detected by an on-line mass spectrometer. The conversion of NO in the reaction temperature range is shown in table 1.
TABLE 1 NH 3 -SCR denitration Properties of different catalysts before and after hydrothermal aging
As can be seen from the data in Table 1, compared with a single Cu-SSZ-13 molecular sieve, the Mo atom doped Cu-SSZ-13 molecular sieve catalyst provided by the invention has higher NH 3 -SCR catalytic activity and higher hydrothermal stability, which indicates that the Mo atom introduced in the invention can obviously improve the low-temperature and high-temperature catalytic activity of the Cu-SSZ-13 molecular sieve and improve the high-temperature hydrothermal stability of the Cu-SSZ-13 molecular sieve.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. The Mo atom doped Cu-SSZ-13 molecular sieve catalyst is characterized by comprising a molecular sieve framework and Cu 2+ dispersed outside the molecular sieve framework, wherein the molecular sieve framework is an SSZ-13 molecular sieve framework containing framework Mo atoms;
The SSZ-13 molecular sieve framework comprises silicon atoms and aluminum atoms.
2. The Mo atom doped Cu-SSZ-13 molecular sieve catalyst according to claim 1, wherein the molar ratio of Mo atoms to silicon atoms in the SSZ-13 molecular sieve framework is (0.001 to 0.5): 1.
3. Mo atom doped Cu-SSZ-13 molecular sieve catalyst according to claim 1 or 2, characterized in that the molar ratio of Cu 2+ to silicon atoms in the SSZ-13 molecular sieve framework is (0-0.05): 1.
4. A method for preparing the Mo atom doped Cu-SSZ-13 molecular sieve catalyst according to any one of claims 1 to 3, comprising the steps of:
S1: performing hydrothermal crystallization treatment on a mixture of an alkaline substance, an aluminum source, an organic structure directing agent, a molybdenum source, a silicon source and water to obtain an Mo atom doped SSZ-13 molecular sieve;
S2: and roasting the obtained Mo-doped SSZ-13 molecular sieve, and then sequentially carrying out ammonium ion exchange and copper ion exchange to obtain the Mo-atom-doped Cu-SSZ-13 molecular sieve catalyst.
5. The method according to claim 4, wherein the alkaline substance is selected from sodium hydroxide and/or potassium hydroxide;
the aluminum source is selected from any one or more of aluminum hydroxide, aluminum isopropoxide, aluminum sulfate or sodium metaaluminate;
the organic structure directing agent is selected from N, N, N-trimethyl-1-adamantyl ammonium hydroxide and/or choline chloride;
the molybdenum source is selected from any one or more of sodium molybdate, ammonium molybdate, silicon molybdic acid, ammonium silicomolybdate or sodium silicomolybdate;
the silicon source is selected from any one or more of white carbon black, silica sol, tetraethoxysilane or sodium silicate.
6. The method according to claim 4 or 5, wherein the molar ratio of Mo atoms to silicon atoms in the mixture is (0.001-0.5): 1;
the molar ratio of the silicon source to the aluminum source to the alkaline substance to the organic structure directing agent to the water is 1 (0.025-0.05), 0.2-0.8, 0.1-0.3 and 10-20.
7. The method according to claim 4, wherein the hydrothermal crystallization treatment is carried out at a temperature of 140 to 160 ℃ for 48 to 144 hours;
the roasting temperature is 540-600 ℃ and the roasting time is 4-10 h.
8. The method according to claim 4, wherein the ammonium ion exchange is performed with an ammonium salt selected from any one or more of ammonium sulfate, ammonium chloride, and ammonium nitrate;
The concentration of ammonium ions in the ammonium salt is 0.5-1.0 mol/L;
The temperature of the ammonium ion exchange is 70-90 ℃ and the time is 3-6 h.
9. The preparation method according to claim 4, wherein the copper ion exchange is performed by using a soluble copper salt selected from any one or more of copper sulfate, copper nitrate and copper acetate;
The concentration of copper ions in the soluble copper salt is 0.002-0.025 mol/L;
the temperature of the copper ion exchange is 25-80 ℃ and the time is 4-24 h.
10. Use of the Mo atom doped Cu-SSZ-13 molecular sieve catalyst according to any one of claims 1 to 3 or the Mo atom doped Cu-SSZ-13 molecular sieve catalyst prepared according to the preparation method according to any one of claims 4 to 9 in NH 3 -SCR denitration reactions.
CN202410196609.4A 2024-02-22 2024-02-22 Mo-atom-doped Cu-SSZ-13 molecular sieve catalyst and preparation method and application thereof Pending CN118059923A (en)

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