阅读说明：本技术 一种B掺杂Cu-SSZ-13分子筛及其制备方法和应用 (B-doped Cu-SSZ-13 molecular sieve and preparation method and application thereof ) 是由 焦卫勇 樊卫斌 吕文婷 董梅 白璞 李延峰 薛海霞 于 2021-09-26 设计创作，主要内容包括：本发明提供了一种B掺杂Cu-SSZ-13分子筛及其制备方法和应用,属于脱硝催化剂技术领域。本发明通过引入B原子,诱导产生了不同的骨架铝分布,双六元环中铝对含量显著增加,进而在负载铜离子过程中,铝对上连接的二价铜离子活性位点含量增加,从而使催化剂的催化活性增强。而且,在分子筛晶化过程中,B的调节作用使骨架铝优先落位于CHA笼上的八元环内,相比双六元环,CHA笼上的八元环在空间上更加开放,更有利于Al原子的均匀分布,从而在水热条件下减少了铝氧四面体的扭曲,因此大大提高了分子筛的水热稳定性。(The invention provides a B-doped Cu-SSZ-13 molecular sieve and a preparation method and application thereof, belonging to the technical field of denitration catalysts. According to the invention, different framework aluminum distributions are induced by introducing the B atom, the content of the aluminum pairs in the double six-membered ring is obviously increased, and further, in the process of loading copper ions, the content of the divalent copper ion active sites connected to the aluminum pairs is increased, so that the catalytic activity of the catalyst is enhanced. Moreover, in the crystallization process of the molecular sieve, the framework aluminum is preferentially positioned in the eight-membered ring on the CHA cage under the regulation action of B, and compared with a double six-membered ring, the eight-membered ring on the CHA cage is more open in space and more beneficial to the uniform distribution of Al atoms, so that the distortion of an aluminum tetrahedron is reduced under the hydrothermal condition, and the hydrothermal stability of the molecular sieve is greatly improved.)

1. A preparation method of a B-doped Cu-SSZ-13 molecular sieve comprises the following steps:

mixing a template agent, a silicon source, an aluminum source, an alkali metal hydroxide, a boron source and water to obtain initial sol; the silicon source is SiO₂Mole ofThe amount of the aluminum source is calculated by Al₂O₃The template agent, alkali metal hydroxide, Al₂O₃、SiO₂And the molar ratio of water to water is 0-0.2: 0.2-0.7: 0.2: 1: 15-80; b and SiO in the boron source₂The molar ratio of (A) is less than 0.8;

carrying out crystallization reaction on the initial sol, and carrying out first roasting on a solid product obtained by the crystallization reaction to obtain a B-doped SSZ-13 molecular sieve;

mixing the B-doped SSZ-13 molecular sieve with a solution containing ammonium ions, carrying out ammonium ion exchange, and carrying out second roasting on the exchanged molecular sieve to obtain a hydrogen-type B-doped SSZ-13 molecular sieve;

mixing the hydrogen type B doped SSZ-13 molecular sieve with a copper salt solution to carry out Cu²⁺And exchanging, and carrying out third roasting on the exchange reaction product to obtain the B-doped Cu-SSZ-13 molecular sieve.

2. The method of claim 1, wherein the template comprises N, N-trimethyl-1-adamantane ammonium hydroxide; the silicon source comprises one or more of FAU type molecular sieve, silica sol, silica gel and white carbon black; the alkali metal hydroxide comprises KOH or NaOH; the aluminum source comprises one or more of FAU type molecular sieve, aluminum hydroxide, sodium metaaluminate, aluminum sulfate and aluminum isopropoxide; the boron source comprises boric acid or sodium tetraborate.

3. The method according to claim 1, wherein the crystallization reaction is carried out at 150 ℃ for 3 to 8 days.

4. The method according to claim 1, wherein the first, second and third baking temperatures are independently 500 to 600 ℃ and the holding time is independently 6 to 10 hours.

5. The method according to claim 1, wherein the solution containing ammonium ions comprises an ammonium nitrate solution, an ammonium sulfate solution, or an ammonium chloride solution; the concentration of ammonium ions in the solution containing ammonium ions is 0.5-1 mol/L.

6. The method of claim 1, wherein the copper salt solution comprises a copper nitrate solution, a copper sulfate solution, or a copper acetate solution; the concentration of the copper salt solution is 0.05-0.1 mol/L.

7. The method of claim 1, wherein the temperature of the ammonium ion exchange and the Cu ion exchange are controlled by the temperature of the ammonium ion exchange²⁺The temperature of the exchange is independently 80-100 ℃.

8. The B-doped Cu-SSZ-13 molecular sieve prepared by the preparation method of any one of claims 1 to 7.

9. The use of the B-doped Cu-SSZ-13 molecular sieve of claim 8 as a catalyst in diesel exhaust denitration reactions.

10. The use according to claim 9, wherein the denitration reaction is carried out at a temperature of 200 to 550 ℃.

Technical Field

The invention relates to the technical field of denitration catalysts, and particularly relates to a B-doped Cu-SSZ-13 molecular sieve and a preparation method and application thereof.

Background

NO_xIs one of the main pollutants of automobile exhaust, and brings great harm to the atmospheric environment and human health. Among them, heavy diesel vehicles, which account for 7.8% of the vehicle's holding capacity, emit 69% of NO_xThis is because the diesel engine operates at a high air-fuel ratio under lean combustion conditions, in which combustion efficiency is highest and fuel consumption is low, but a large amount of NO accompanies the engine_xAnd (4) generating. In 2020, the emission standard of national six automobile exhaust for diesel vehicle NO_xHigher demands are made on emissions, and therefore, the control and elimination of NO in diesel exhaust_xBecomes critical. Diesel vehicle tail gas NO_xIs mainly achieved by means of a Selective Catalytic Reduction (SCR) device. Wherein NH₃SCR devices are considered to be the most effective at the present time and the most widely used for NO removal_xThe core problem of technology is high performance SCR catalysts. For NO_xThe gasoline vehicle mainly uses a three-way catalyst to simultaneously control CO, HC and NO_xAnd (5) purifying. While diesel vehicles have a combustion mode different from gasoline vehicles, the oxygen content in the exhaust gas is extremely high, and under such lean combustion conditions, NO_xThe reduction is extremely difficult and the traditional three-way catalyst can not meet the requirements. In recent years, small pore molecular sieves having the CHA structure, particularly SSZ-13 molecular sieves, have been proposed due to their excellent NH content₃SCR catalytic performance, which is unique among numerous catalysts, becomes the mainstream catalyst for diesel vehicle exhaust denitration.

Three important factors for evaluating catalytic performance of Cu-SSZ-13 molecular sieve are NH₃SCR activity, hydrothermal stability and N₂And (4) selectivity. A number of studies have shown that in NH₃In the SCR reaction, the Cu-SSZ-13 molecular sieve is used for N in a wide temperature range₂Has a selectivity of nearly 100%, while NO at low temperature (200-550 ℃ C.)_xThe conversion is still low and the catalytic activity is reduced after the high-temperature hydrothermal treatment. In practical application, the temperature of an exhaust pipe of an automobile in a starting stage is low, and the environment where an SCR catalyst is located generally has high temperature and humidity, so that continuous improvement of the low-temperature activity and hydrothermal stability of the Cu-SSZ-13 molecular sieve is a problem which needs to be paid attention to and solved at present.

Disclosure of Invention

The invention aims to provide a B-doped Cu-SSZ-13 molecular sieve and a preparation method and application thereof, and the B-doped Cu-SSZ-13 molecular sieve prepared by the invention has good low-temperature activity and hydrothermal stability.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a preparation method of a B-doped Cu-SSZ-13 molecular sieve, which comprises the following steps:

mixing a template agent, a silicon source, an aluminum source, an alkali metal hydroxide, a boron source and water to obtain initial sol; the silicon source is SiO₂Based on the molar amount of the aluminum source, wherein the dosage of the aluminum source is Al₂O₃The template agent, alkali metal hydroxide, Al₂O₃、SiO₂And the molar ratio of water to water is 0-0.2: 0.2-0.7: 0.2: 1: 15-80; b and SiO in the boron source₂The molar ratio of (A) is less than 0.8;

carrying out crystallization reaction on the initial sol, and carrying out first roasting on a solid product obtained by the crystallization reaction to obtain a B-doped SSZ-13 molecular sieve;

mixing the B-doped SSZ-13 molecular sieve with a solution containing ammonium ions, carrying out ammonium ion exchange, and carrying out second roasting on the exchanged molecular sieve to obtain a hydrogen-type B-doped SSZ-13 molecular sieve;

mixing the hydrogen type B doped SSZ-13 molecular sieve with a copper salt solution to carry out Cu²⁺And exchanging, and carrying out third roasting on the exchange reaction product to obtain the B-doped Cu-SSZ-13 molecular sieve.

Preferably, the template agent comprises N, N, N-trimethyl-1-adamantane ammonium hydroxide; the silicon source comprises one or more of FAU type molecular sieve, silica sol, silica gel and white carbon black; the alkali metal hydroxide comprises KOH or NaOH; the aluminum source comprises one or more of FAU type molecular sieve, aluminum hydroxide, sodium metaaluminate, aluminum sulfate and aluminum isopropoxide; the boron source comprises boric acid or sodium tetraborate.

Preferably, the temperature of the crystallization reaction is 150 ℃ and the time is 3-8 days.

Preferably, the temperature of the first roasting, the temperature of the second roasting and the temperature of the third roasting are 500-600 ℃, and the heat preservation time is 6-10 hours.

Preferably, the solution containing ammonium ions comprises an ammonium nitrate solution, an ammonium sulfate solution or an ammonium chloride solution; the concentration of ammonium ions in the solution containing ammonium ions is 0.5-1 mol/L.

Preferably, the copper salt solution comprises a copper nitrate solution, a copper sulfate solution or a copper acetate solution; the concentration of the copper salt solution is 0.05-0.1 mol/L.

Preferably, the temperature of the ammonium ion exchange and Cu²⁺The temperature of the exchange is independently 80-100 ℃.

The invention provides the B-doped Cu-SSZ-13 molecular sieve prepared by the preparation method in the scheme.

The invention provides application of the B-doped Cu-SSZ-13 molecular sieve in the scheme as a catalyst in a diesel tail gas denitration reaction.

Preferably, the temperature of the denitration reaction is 200-550 ℃.

The invention provides a preparation method of a B-doped Cu-SSZ-13 molecular sieve, which comprises the following steps: mixing a template agent, a silicon source, an aluminum source, an alkali metal hydroxide, a boron source and water to obtain initial sol; the silicon source is SiO₂Based on the molar amount of the aluminum source, wherein the dosage of the aluminum source is Al₂O₃The template agent and the alkali metalOxide, Al₂O₃、SiO₂And the molar ratio of water to water is 0-0.2: 0.2-0.7: 0.2: 1: 15-80; b and SiO in the boron source₂The molar ratio of (A) is less than 0.8; carrying out crystallization reaction on the initial sol, and carrying out first roasting on a solid product obtained by the crystallization reaction to obtain a B-doped SSZ-13 molecular sieve; mixing the B-doped SSZ-13 molecular sieve with a solution containing ammonium ions, carrying out ammonium ion exchange, and carrying out second roasting on the exchanged molecular sieve to obtain a hydrogen-type B-doped SSZ-13 molecular sieve; mixing the hydrogen type B doped SSZ-13 molecular sieve with a copper salt solution to carry out Cu²⁺And exchanging, and carrying out third roasting on the exchange reaction product to obtain the B-doped Cu-SSZ-13 molecular sieve.

Two different forms of Cu are present in the Cu-SSZ-13 molecular sieve²⁺One is Cu bonded to the aluminum pair²⁺The other is Cu connected with single aluminum²⁺. The two copper species have different catalytic activities, with Cu on the aluminum pair²⁺Cu with higher activity than single aluminum²⁺. According to the invention, different framework aluminum distributions are induced by introducing the B atom, the content of the aluminum pairs in the double six-membered ring is obviously increased, and further, in the process of loading copper ions, the content of the divalent copper ion active sites connected to the aluminum pairs is increased, so that the catalytic activity of the catalyst is enhanced. Moreover, in the crystallization process of the molecular sieve, the framework aluminum is preferentially dropped into the eight-membered ring on the CHA cage under the regulation action of B, and compared with a double six-membered ring, the eight-membered ring on the CHA cage is more open in space and more beneficial to the uniform distribution of Al atoms, so that the distortion of an aluminum tetrahedron is reduced under the hydrothermal condition, and the hydrothermal stability of the molecular sieve is greatly improved.

Drawings

FIG. 1 is an XRD pattern of the molecular sieves finally prepared in examples 1-6 and comparative examples 1-2;

FIG. 2 is an SEM image of the molecular sieve finally prepared in example 1;

FIG. 3 is an SEM image of the molecular sieve finally prepared in example 2;

FIG. 4 is an SEM image of the molecular sieve finally prepared in example 3;

FIG. 5 is an SEM image of the molecular sieve finally prepared in example 4;

FIG. 6 is an SEM image of the molecular sieve finally prepared in example 5;

FIG. 7 is an SEM image of the molecular sieve finally prepared in example 6;

FIG. 8 is an SEM image of the molecular sieve finally prepared in comparative example 1;

FIG. 9 is an SEM image of the molecular sieve finally prepared in comparative example 2;

FIG. 10 shows samples of comparative example 1, example 3, and examples 5 to 6 after hydrothermal treatment²⁷Al NMR chart;

FIG. 11 is an XRD pattern of samples of comparative example 1, example 3 and examples 5 to 6 after hydrothermal treatment.

Detailed Description

The invention provides a preparation method of a B-doped Cu-SSZ-13 molecular sieve, which comprises the following steps:

mixing a template agent, a silicon source, an aluminum source, an alkali metal hydroxide, a boron source and water to obtain initial sol; the silicon source is SiO₂Based on the molar amount of the aluminum source, wherein the dosage of the aluminum source is Al₂O₃The template agent, alkali metal hydroxide, Al₂O₃、SiO₂And the molar ratio of water to water is 0-0.2: 0.2-0.7: 0.2: 1: 15-80; b and SiO in the boron source₂The molar ratio of (A) is less than 0.8;

carrying out crystallization reaction on the initial sol, and carrying out first roasting on a solid product obtained by the crystallization reaction to obtain a B-doped SSZ-13 molecular sieve;

mixing the B-doped SSZ-13 molecular sieve with a solution containing ammonium ions, carrying out ammonium ion exchange, and carrying out second roasting on the exchanged molecular sieve to obtain a hydrogen-type B-doped SSZ-13 molecular sieve;

mixing the hydrogen type B doped SSZ-13 molecular sieve with a copper salt solution to carry out Cu²⁺And exchanging, and carrying out third roasting on the exchange reaction product to obtain the B-doped Cu-SSZ-13 molecular sieve.

In the present invention, the starting materials used are all commercially available products well known in the art, unless otherwise specified.

Mixing a template agent, a silicon source, an aluminum source, an alkali metal hydroxide, a boron source and water to obtain initial sol.

In the present invention, the template preferably comprises N, N, N-trimethyl-1-adamantane ammonium hydroxide (TMADAOH); the silicon source preferably comprises one or more of FAU type molecular sieve, silica sol, silica gel and white carbon black, and more preferably FAU type molecular sieve; in the present invention, the silica sol is preferably a silica sol having a mass concentration of 25%. In the present invention, the alkali metal hydroxide preferably comprises KOH or NaOH, more preferably KOH; the aluminum source preferably comprises one or more of FAU type molecular sieve, aluminum hydroxide, sodium metaaluminate, aluminum sulfate and aluminum isopropoxide, more preferably FAU type molecular sieve and aluminum hydroxide; the boron source preferably comprises boric acid or sodium tetraborate. In the present invention, the FAU-type molecular sieve serves as both a boron source and an aluminum source. In the invention, the silicon-aluminum ratio of the FAU type molecular sieve is preferably 1.06-17. The invention has no special requirement on the specific type of the FAU type molecular sieve, and the FAU type molecular sieve well known in the field can be adopted. In an embodiment of the present invention, the FAU type molecular sieve is specifically a Y type molecular sieve.

In the invention, the silicon source is used as SiO₂Based on the molar amount of the aluminum source, wherein the dosage of the aluminum source is Al₂O₃The template agent, alkali metal hydroxide, Al₂O₃、SiO₂And the molar ratio of water to water is 0-0.2: 0.2-0.7: 0.2: 1: 15 to 80, preferably 0.05 to 0.2: 0.3-0.6: 0.2: 1: 20 to 70, more preferably 0.1 to 0.15: 0.4-0.5: 0.2: 1: 30-60 parts of; b and SiO in the boron source₂The molar ratio of (a) to (b) is less than 0.8, more preferably 0.1 to 0.4.

The invention has no special requirement on the mixing process of the template agent, the silicon source, the aluminum source, the alkali metal hydroxide, the boron source and the water, and can adopt the mixing process well known in the field.

After the initial sol is obtained, the initial sol is subjected to crystallization reaction, and a solid product obtained by the crystallization reaction is subjected to first roasting to obtain the B-doped SSZ-13 molecular sieve.

The initial sol is preferably stirred at room temperature and then placed in a hydrothermal reaction kettle for crystallization reaction.

The present invention has no special requirement on the rotation speed of the stirring, and the stirring speed which is well known in the field can be adopted. In the invention, the stirring time is preferably 2-48 h, more preferably 10-40 h, and further preferably 15-30 h. The invention utilizes stirring to fully mix the reactants, simultaneously quickly dissolve the Y-shaped molecular sieve, and fully hydrolyze the silicon source and the aluminum source to form silicate and aluminate.

In the invention, the temperature of the crystallization reaction is preferably 150 ℃, and the time is preferably 3 to 8 days, more preferably 4 to 7 days, and further preferably 5 to 6 days. In the crystallization reaction process, molecular sieve nucleation, conversion from an amorphous phase to a crystalline phase and conversion from a monomolecular state to a polymeric state occur.

After the crystallization reaction is completed, the solid product obtained by the reaction is preferably washed and dried by deionized water, and then is subjected to first roasting to obtain the B-doped SSZ-13 molecular sieve.

The present invention has no special requirement for the washing and drying process of deionized water, and the washing and drying process well known in the art can be adopted. In the invention, the temperature of the first roasting is preferably 500-600 ℃, more preferably 520-580 ℃, and further preferably 540-560 ℃; the heat preservation time is preferably 6-10 h, and more preferably 6-8 h.

In the first roasting process, the template is removed to obtain the B-doped SSZ-13 molecular sieve which is marked as B/Al-SSZ-13 raw powder.

In the invention, B and Al belong to the same group elements and have the same coordination, a proper amount of heteroatom B is introduced, B enters an SSZ-13 molecular sieve framework and occupies a part of Al, the distribution of aluminum in a double six-membered ring and an eight-membered ring in the SSZ-13 molecular sieve framework is effectively modulated, and the content of aluminum pairs in the framework is obviously increased.

After the B-doped SSZ-13 molecular sieve is obtained, the B-doped SSZ-13 molecular sieve is mixed with a solution containing ammonium ions for ammonium ion exchange, and the molecular sieve obtained after the exchange is subjected to second roasting to obtain the hydrogen type B-doped SSZ-13 molecular sieve.

In the present invention, the solution containing ammonium ions preferably includes an ammonium nitrate solution, an ammonium sulfate solution, or an ammonium chloride solution; the concentration of ammonium ions in the solution containing ammonium ions is 0.5-1 mol/L. In the invention, the volume ratio of the mass of the B-doped SSZ-13 molecular sieve to the volume of the solution containing ammonium ions is preferably 1g: 5-80 mL, and more preferably 1g: 10-60 mL. The invention preferably adds the B-doped SSZ-13 molecular sieve into water, and then adds the substance containing ammonium ions to carry out ammonium ion exchange. In the invention, the temperature of ammonium ion exchange is preferably 80-100 ℃, the time is preferably 4-6 h, and two times of ammonium ion exchange are preferably carried out in the invention. The time of the ammonium ion exchange refers to the time of a single ammonium ion exchange. The ammonium ion exchange is preferably carried out in a water bath with stirring. In the ammonium ion exchange process, NH is added₄ ⁺And K⁺(or Na)⁺) And carrying out exchange.

After the ammonium ion exchange is completed, the invention preferably washes the solid product thoroughly with deionized water and dries, followed by a second calcination to obtain the hydrogen form B-doped SSZ-13 molecular sieve.

In the invention, the temperature of the second roasting is preferably 500-600 ℃, more preferably 520-580 ℃, and further preferably 540-560 ℃; the heat preservation time is preferably 6-10 h, and more preferably 7-9 h. The invention thermally decomposes ammonium ions into H by secondary roasting⁺Obtaining hydrogen type B doped SSZ-13 molecular sieve (marked as H-B/Al-SSZ-13), H⁺As attachment points for active copper species.

After the hydrogen type B doped SSZ-13 molecular sieve is obtained, the hydrogen type B doped SSZ-13 molecular sieve is mixed with a copper salt solution to carry out Cu²⁺And exchanging, and carrying out third roasting on the exchange reaction product to obtain the B-doped Cu-SSZ-13 molecular sieve.

In the present invention, the copper salt solution preferably includes a copper nitrate solution, a copper sulfate solution or a copper acetate solution; the concentration of the copper salt solution is preferably 0.05-0.1 mol/L. In the present invention, the ratio of the mass of the hydrogen form B doped SSZ-13 molecular sieve to the volume of the copper salt solution is preferably 1g:40 ℃100mL, more preferably 1g: 50-80 mL. In the present invention, the Cu²⁺The temperature of the exchange is preferably 80-100 ℃, the time is preferably 4-6 h, and the Cu is preferably carried out for 1 or two times in the invention²⁺And (4) exchanging. When Cu is performed twice²⁺When exchanging, the above Cu²⁺The time of the exchange refers to a single Cu²⁺The time of the exchange. The invention preferably carries out Cu in water bath and stirring condition²⁺And (4) exchanging. The invention is in Cu²⁺In the exchange process, Cu²⁺And H⁺And carrying out exchange.

Completing the Cu²⁺After the exchange, the invention preferably uses deionized water to fully wash the solid product and dry, and then carries out third roasting to obtain the B-doped Cu-SSZ-13 molecular sieve.

In the invention, the temperature of the third roasting is preferably 500-600 ℃, more preferably 520-580 ℃, and further preferably 540-560 ℃; the heat preservation time is preferably 6-10 h, and more preferably 7-9 h. In the third roasting process, the active site Cu species are activated.

The invention provides the B-doped Cu-SSZ-13 molecular sieve prepared by the preparation method in the scheme. In the invention, the content of Cu in the B-doped Cu-SSZ-13 molecular sieve is preferably 2.5-3.5 wt%; the molar ratio of B to Si is preferably 0.01-0.2: 1; the Si/Al molar ratio is preferably 3-4: 1. In the B-doped Cu-SSZ-13 molecular sieve, Cu is positioned at an acid position of the molecular sieve, and B replaces the position of part of Al in the molecular sieve.

The invention provides application of the B-doped Cu-SSZ-13 molecular sieve in the scheme as a catalyst in a diesel tail gas denitration reaction.

The invention has no special requirements on the specific composition of the diesel tail gas, and the diesel tail gas well known in the field can be used. In an embodiment of the present invention, the diesel exhaust gas comprises: 500ppm NO, 500ppm NH₃、5vol％O₂The balance being N₂Balancing qi.

In the invention, the temperature of the denitration reaction is preferably 200-550 ℃, and more preferably 250-500 ℃; the invention has no special requirement on the volume space velocity of the denitration reaction, and adopts the volume well known in the fieldThe airspeed is just. In the embodiment of the invention, the volume space velocity of the denitration reaction is 200000h^-1。

The following examples are provided to illustrate the B-doped Cu-SSZ-13 molecular sieve and its preparation method and application in detail, but they should not be construed as limiting the scope of the invention.

Example 1

According to the template agent, KOH, Al₂O₃、SiO₂And the molar ratio of B to water in the boron source is 0.2: 0.2: 0.2: 1: 0.32: 40, dissolve type 1gY (Si/Al ═ 17) molecular sieve in 10mL deionized water, add 0.34g KOH to the system and stir for 5 minutes, continue to add 2.5g template TMADAOH (25%) and 0.41g Al (OH) to the solution₃And finally 0.12g of NaB was added thereto₄O₇Stirring at room temperature for 2h, transferring the obtained sol into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and crystallizing at 150 ℃ for 5 days. And after crystallization is finished, cooling to room temperature, fully washing with deionized water, drying, and then roasting at 550 ℃ for 6 hours to remove the template agent, thereby obtaining the B/Al-SSZ-13 raw powder.

Adding 2g of B/Al-SSZ-13 raw powder into 100mL of deionized water, then adding 8g of ammonium nitrate, stirring for 6H under the condition of 80 ℃ water bath for ammonium ion exchange, repeating the exchange steps, fully washing and drying with deionized water after the exchange is finished, and then roasting for 6H at 550 ℃ to obtain the H-SSZ-13 molecular sieve.

Taking 1g of the H-SSZ-13 molecular sieve and adding 0.1mol/L of Cu (NO)₃)₂And (3) carrying out copper ion exchange in the solution for 6h under the condition of water bath at 80 ℃, fully washing and drying by using deionized water after the exchange is finished, and then roasting for 6h at 550 ℃ to obtain the Cu-B/Al-SSZ-13 molecular sieve.

Example 2

The only difference from example 1 is that 0.29g NaB was added₄O₇B and SiO in boron source₂The molar ratio of (A) to (B) is 0.8, and the Cu-B/Al-SSZ-13 molecular sieve is obtained.

Example 3

The difference from example 1 was only that 0.019g of water was added H₃BO₃B and SiO in boron source₂The molar ratio of (A) to (B) is 0.04, and the Cu-B/Al-SSZ-13 molecular sieve is obtained.

Example 4

Differs from example 1 only in that 0.047g H is added₃BO₃B and SiO in boron source₂The molar ratio of (A) to (B) is 0.1, and the Cu-B/Al-SSZ-13 molecular sieve is obtained.

Example 5

The only difference from example 1 is that 0.094g H was added₃BO₃B and SiO in boron source₂The molar ratio of (A) to (B) is 0.2, and the Cu-B/Al-SSZ-13 molecular sieve is obtained.

Example 6

The difference from example 1 is only that 0.188g H is added₃BO₃B and SiO in boron source₂The molar ratio of (A) to (B) is 0.4, and the Cu-B/Al-SSZ-13 molecular sieve is obtained.

Comparative example 1

The only difference from example 1 is that NaB was not added₄O₇And obtaining the Cu-SSZ-13 molecular sieve.

Comparative example 2

The only difference from example 1 is that 0.376g H was added₃BO₃B and SiO in boron source₂The molar ratio of (A) to (B) is 0.8, and the Cu-B/Al-SSZ-13 molecular sieve is obtained.

And (3) structural and performance characterization:

1. XRD characterization is performed on the finally prepared molecular sieves of examples 1-6 and comparative examples 1-2, and the result is shown in FIG. 1. As can be seen from FIG. 1, all of the examples and comparative examples synthesized molecular sieves of pure phase CHA structure.

2. The molecular sieves finally prepared in examples 1 to 6 and comparative examples 1 to 2 were observed by a scanning electron microscope, and the results are sequentially shown in fig. 2 to 9. As can be seen from FIG. 2, the molecular sieves of examples 1 to 6 and comparative examples 1 to 2 are all cubic masses with uniform morphology and rough surface.

3. The results of elemental analysis of the molecular sieves of comparative examples 1 to 2, example 3 and examples 5 to 6 are shown in Table 1. As can be seen from Table 1, the Si/Al molar ratios of the comparative examples and examples before and after addition of B did not change much, but the Cu content increased significantly after introduction of B; in addition, due to the weak binding force between B and the skeleton, most of B is lost in the exchange process, and the content of B in the finally obtained sample is very small.

TABLE 1 results of elemental analysis of molecular sieves of comparative examples 1-2, example 3, and examples 5-6

4. The prepared molecular sieve is used as a catalyst for ammonia selective catalytic reduction (NH)₃-SCR) reaction. The method comprises the following specific steps: 0.1g of catalyst is placed in a quartz tube reactor with the inner diameter of 8mm, and 500ppm NO and 500ppm NH are introduced₃，5％O₂，N₂The activity evaluation is carried out on the reaction gas of the balance gas, the gas flow rate is 800mL/min, and the volume space velocity is 200000h^-1. The temperature rise rate during evaluation was 5 ℃/min, the temperature was maintained at 25 ℃ for 0.5 hour intervals and the concentration of each component in the tail gas was measured. The results are shown in Table 2.

TABLE 2 NH3-SCR results for molecular sieves of examples 1-6 and comparative examples 1-2

In table 2, conversion rate ═ (NO inlet concentration-outlet concentration)/NO inlet concentration ═ 100

As can be seen from Table 2, the activity of the sample increased after introducing a certain amount of B, but when the B/Si exceeded 0.8 (i.e., comparative example 2), the activity decreased compared to comparative example 1.

5. Hydrothermal stability tests were performed on a portion of the molecular sieves prepared in examples and comparative example 1, as follows: introducing nitrogen containing 10% of water vapor into a molecular sieve at 800 ℃, wherein the space velocity is 50000h^-1And the treatment time is 12h, and the test results are shown in Table 3.

Table 3 results of hydrothermal stability test of part of examples and comparative example 1 molecular sieves

As can be seen from Table 3, the activity of the sample without B introduced in comparative example 1 is reduced after the hydrothermal treatment, but the activity of the sample after B introduction after the hydrothermal treatment is higher than that of the sample after comparative example 1, which shows that the doping of B can improve the hydrothermal stability of the Cu-SSZ-13 molecular sieve.

FIG. 10 shows samples of comparative example 1, example 3, and examples 5 to 6 after hydrothermal treatment²⁷Al NMR chart. As can be seen from fig. 10, after the hydrothermal treatment, more pentacoordinate non-framework aluminum was formed in the sample without B addition, while the framework aluminum of the sample with B addition was more stable during the hydrothermal treatment.

FIG. 11 is an XRD pattern of samples of comparative example 1, example 3 and examples 5 to 6 after hydrothermal treatment. As can be seen in fig. 11, the crystallinity of the sample of comparative example 1 without B addition was significantly reduced and lower than that of the sample with B addition after the hydrothermal treatment. The results show that the addition of a proper amount of B is beneficial to improving the hydrothermal stability of the Cu-SSZ-13 molecular sieve.

As can be seen from the above examples and comparative examples, the invention provides a B-doped Cu-SSZ-13 molecular sieve, a preparation method and an application thereof, and the B-doped Cu-SSZ-13 molecular sieve prepared by the invention has good low-temperature activity and hydrothermal stability.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.