阅读说明：本技术 一种O-Si-Al-Zr三元骨架AEI分子筛及其合成方法 (O-Si-Al-Zr ternary framework AEI molecular sieve and synthesis method thereof ) 是由 王莉 李森 孙浩 于 2021-09-02 设计创作，主要内容包括：本发明公开了一种O-Si-Al-Zr三元骨架AEI分子筛及其合成方法。本发明以氢氧化六甲双铵为模板剂,锆溶胶为第三元骨架元素,经水热法合成D-(50)＝2～3微米左右的三元AEI分子筛。在AEI分子筛骨架中,采用锆来替代部分元素硅,其中锆以锆氧四面体替代了部分硅氧四面体进入分子筛的骨架,而不是像铜离子那样,只是通过离子交换与分子筛主体形成类似于盐的化合物。上述三元AEI分子筛经离子交换法加铜后,在尾气净化测试中,表现比二元AEI分子筛更好的热稳定性,对高温段去除氮氧化物有显著的改善。(The invention discloses an O-Si-Al-Zr ternary framework AEI molecular sieve and a synthesis method thereof. The invention takes hexamethonium hydroxide as a template agent and zirconium sol as a third element of framework, and D is synthesized by a hydrothermal method 50 The ternary AEI molecular sieve is about 2-3 microns. In the AEI molecular sieve framework, zirconium is used in place of a portion of the elemental silicon, wherein zirconium replaces a portion of the silicon oxygen tetrahedra with zirconium oxygen tetrahedra into the framework of the molecular sieve, rather than forming a salt-like compound with the molecular sieve body by ion exchange, as with copper ions. After the ternary AEI molecular sieve is added with copper by an ion exchange method, the ternary AEI molecular sieve has better thermal stability than the binary AEI molecular sieve in a tail gas purification test, and has obvious improvement on removal of nitrogen oxides at a high-temperature section.)

1. An O-Si-Al-Zr ternary framework AEI molecular sieve is characterized in that zirconium in the O-Si-Al-Zr ternary framework AEI molecular sieve enters the framework of the molecular sieve in a zirconium-oxygen tetrahedron; the composite material is prepared by taking hexamethonium hydroxide as a template agent and zirconium sol as a third skeleton element through a hydrothermal method.

2. The method for synthesizing the O-Si-Al-Zr ternary skeleton AEI molecular sieve according to claim 1, wherein the molecular sieve is a molecular sieve having a ternary skeleton of O-Si-Al-Zr,

the raw materials and the weight ratio thereof are as follows:

template agent: hexamethonium hydroxide;

silicon source: ammonium silica sol;

an aluminum source: aluminum hydroxide;

a zirconium source: zirconium sol;

alkali source: sodium hydroxide;

the weight ratio is as follows: SiO 2₂:Al₂O₃:ZrO₂:Na₂O:C₁₂H₃₂N₂O₂＝100:(6～8.5):(0.2～3.5):(4～5.3):(31～43)；

The synthesis method specifically comprises the following steps:

1) forming a colloidal slurry

Heating aluminum hydroxide and a sodium hydroxide aqueous solution for reaction to generate sodium metaaluminate, cooling to normal temperature, adding a template agent of hexamethonium hydroxide, and stirring and uniformly mixing for later use;

mixing zirconium sol and ammonium silica sol, and stirring and uniformly mixing by using a high-shear emulsifier for later use;

2) hydrothermal reaction

Adding the two mixed solutions into a high-pressure reaction kettle, sealing, starting stirring, heating to 160 ℃, stopping heating, and carrying out heat preservation reaction for 36-72 hours;

3) post-treatment

After the reaction is finished, the temperature is reduced to normal temperature, and the ternary AEI molecular sieve is obtained by filtering, washing and roasting.

3. The method for synthesizing the O-Si-Al-Zr ternary framework AEI molecular sieve according to claim 2, wherein the stirring speed of the high-pressure reaction kettle in the step 2) is 200-300 rpm.

4. The method for synthesizing the AEI molecular sieve with the ternary framework of O-Si-Al-Zr according to claim 2, wherein the SiO of the ammonium silica sol₂The content is 30-40%; na of the aqueous sodium hydroxide solution₂The content of O is 25-30%; ZrO of the zirconium sol₂The content is 12-15%.

5. The method for synthesizing the O-Si-Al-Zr ternary framework AEI molecular sieve of claim 2, wherein the weight ratio of the raw materials is as follows:

SiO₂:Al₂O₃:ZrO₂:Na₂O:C₁₂H₃₂N₂O₂＝100:(7～8.5):(3～3.5):(4～5.3):(35～43)。

6. the method of claim 2, wherein the molecular sieve after calcination contains sodium, and is soaked with ammonium bicarbonate to obtain ammonium type molecular sieve, and the molecular sieve is calcined again to remove ammonia to obtain hydrogen type AEI molecular sieve.

7. A catalyst material for an exhaust gas purifier for a vehicle, characterized in that the hydrogen-form AEI molecular sieve prepared in claim 6 is further doped with copper ions by ion exchange to prepare a catalyst material for an exhaust gas purifier for a vehicle.

Technical Field

The invention relates to an AEI molecular sieve and a synthesis method thereof, belonging to the technical field of inorganic catalytic materials.

Background

The AEI molecular sieve is a branch similar to an SSZ-13 molecular sieve structure, is a microporous molecular sieve with a three-dimensional pore structure and is formed by eight-membered ring pores, and the unique pore structure enables the AEI molecular sieve to have wide application prospects in the field of catalyst gas adsorption separation in recent years. In recent years, AEI molecular sieves are mainly used as catalysts for manufacturing automobile exhaust purifiers, and have better heat resistance and catalytic effect than SSZ-13 molecular sieves. Generally, AEI molecular sieves used for exhaust gas purification are AEI copper formed by combining bronsted acids and copper ions by ion exchange.

The principle of tail gas purification is to rapidly reduce nitrogen oxides into nitrogen and oxidize incompletely combusted organic residues into CO₂. The rate of the catalytic reaction is critical because the oxidation-reduction reaction must be completed in a moment because the speed of the automobile exhaust gas as it passes through the purifier is fast. The method for improving the catalytic performance mainly comprises the following two ways, namely changing the doped metal ions and changing the framework element of the molecular sieve, namely aluminum or silicon, so that part of the aluminum or silicon is replaced by other elements. Regarding the AEI molecular sieve catalyst, CN108786912A discloses an AEI molecular sieve catalyst containing copper and iron bi-metals and a preparation method thereof, wherein Cu and/or Fe are simultaneously or stepwise loaded on an AEI molecular sieve by means of ion exchange, and the AEI molecular sieve catalyst containing copper and iron bi-metals is prepared and obtained. CN108786911A discloses a Cu-AEI molecular sieve catalyst containing rare earth and a preparation method thereof, wherein the AEI molecular sieve containing rare earth elements and a salt solution of Cu are subjected to ion exchange to obtain the Cu-AEI molecular sieve catalyst containing rare earth elements. In the synthesis process, the rare earth elements are introduced into the molecular sieve in situ, so that the preparation process is simplified, and the stability of the molecular sieve can be improved. The above patent documents are all compounds which are similar to salt and formed with the molecular sieve main body by an ion exchange mode, and no report of introducing zirconium-oxygen tetrahedron into the framework material of the AEI molecular sieve is found.

Meanwhile, at present, N-diethyl-2, 6-dimethylpiperidinium hydroxide is almost used as a template agent when a binary AEI molecular sieve is synthesized, but the binary AEI molecular sieve is very few in suppliers and expensive, so that the binary AEI molecular sieve is difficult to purchase.

Disclosure of Invention

The present invention overcomes the deficiencies of the prior art described above,an O-Si-Al-Zr ternary skeleton AEI molecular sieve and its synthesis are disclosed. The invention uses hexamethonium hydroxide (C)₁₂H₃₂N₂O₂) Is taken as a template agent, zirconium sol is taken as a third element of framework, and D is synthesized by a hydrothermal method₅₀The ternary AEI molecular sieve is about 2-3 microns. In the AEI molecular sieve framework, zirconium is used in place of a portion of the elemental silicon, wherein zirconium replaces a portion of the silicon oxygen tetrahedra with zirconium oxygen tetrahedra into the framework of the molecular sieve, rather than forming a salt-like compound with the molecular sieve body by ion exchange, as with copper ions. After the ternary AEI molecular sieve is added with copper by an ion exchange method, the ternary AEI molecular sieve has better thermal stability than the binary AEI molecular sieve in a tail gas purification test, and has obvious improvement on removal of nitrogen oxides at a high-temperature section.

The technical scheme of the invention is as follows: an O-Si-Al-Zr ternary framework AEI molecular sieve is characterized in that zirconium in the O-Si-Al-Zr ternary framework AEI molecular sieve enters the framework of the molecular sieve in a zirconium-oxygen tetrahedron; the composite material is prepared by taking hexamethonium hydroxide as a template agent and zirconium sol as a third skeleton element through a hydrothermal method.

The synthesis method of the O-Si-Al-Zr ternary framework AEI molecular sieve is characterized in that,

the raw materials and the weight ratio thereof are as follows:

template agent: hexamethonium hydroxide (C)₁₂H₃₂N₂O₂)；

Silicon source: ammonium silica sol;

an aluminum source: aluminum hydroxide;

a zirconium source: zirconium sol;

alkali source: sodium hydroxide;

the weight ratio is as follows: SiO 2₂:Al₂O₃:ZrO₂:Na₂O:C₁₂H₃₂N₂O₂＝100:(6～8.5):(0.2～3.5):(4～5.3):(31～43)；

The synthesis method specifically comprises the following steps:

1) forming a colloidal slurry

Heating aluminum hydroxide and a sodium hydroxide aqueous solution for reaction to generate sodium metaaluminate, cooling to normal temperature, adding a template agent of hexamethonium hydroxide, and stirring for 10-20 minutes for later use;

mixing zirconium sol and ammonium silica sol, and stirring for 60-90 minutes by using a high-shear emulsifier for later use;

2) hydrothermal reaction

Adding the two mixed solutions into a high-pressure reaction kettle, sealing, starting stirring at the rotating speed of 200-300 rpm, heating to 160 ℃, stopping heating, and carrying out heat preservation reaction for 36-72 hours;

3) post-treatment

And after the reaction is finished, cooling to normal temperature, filtering, washing and roasting (the roasting temperature is 450-550 ℃) to obtain the ternary AEI molecular sieve.

Further, the baked molecular sieve contains sodium, and is soaked by ammonium bicarbonate to obtain an ammonium type molecular sieve, and the ammonium type molecular sieve is baked again to remove ammonia to obtain the hydrogen type molecular sieve.

The hydrogen type molecular sieve can be further doped with copper ions through ion exchange (the hydrogen type molecular sieve and copper acetate perform ion exchange reaction together, and the copper ions enter the molecular sieve), and finally the catalyst material of the automobile tail gas purifier is formed.

Further, SiO of the ammonium silica sol₂The content is 30-40% (the rest water and ammonia); al of the aluminum hydroxide₂O₃The content is 63-66%; na of the aqueous sodium hydroxide solution₂The content of O is 25-30% (the rest water); ZrO of the zirconium sol₂The content of the water is 12-15% (the rest water); the template agent contains hexamethonium hydroxide 25 wt% and water for the rest.

Preferably, the weight ratio of the raw materials is as follows: SiO 2₂:Al₂O₃:ZrO₂:Na₂O:C₁₂H₃₂N₂O₂＝100:(7～8.5):(3～3.5):(4～5.3):(35～43)。

The O-Si-Al-Zr ternary skeleton AEI molecular sieve produced by the method has the granularity D₅₀2 to 3 μm, specific surface area 550 to 600m²The volume of pores is 0.3cc/g, and the micrograph is shown in FIG. 1.

The invention has the beneficial effects that:

1. adopts hexamethonium hydroxide as a template agent and zirconium sol as a third element of framework elements to synthesize D for the first time by a hydrothermal method₅₀The molecular sieve is an O-Si-Al-Zr ternary AEI molecular sieve with the particle size of about 2-3 microns. Although the chemical composition of the molecular sieve contains 3-3.6% of ZrO₂However, the XRD pattern has no shift or hetero-phase peak (see the comparison between FIG. 3 and FIG. 2), and it is considered that zirconium replaces part of silicon oxygen tetrahedron with zirconium oxygen tetrahedron, and is a novel derivative of AEI molecular sieve.

2. At present, N-diethyl-2, 6-dimethylpiperidinium hydroxide is used as a template agent mainly used in the synthesis of an AEI molecular sieve, and due to the great synthesis difficulty, a suitable supplier can not be found at home, the selling price is high, and the cost of the molecular sieve is difficult to reduce; and after the hexamethonium hydroxide is adopted, the cost price is greatly reduced, and the method is suitable for industrial production.

3. After the ternary AEI molecular sieve is added with copper by an ion exchange method, the ternary AEI molecular sieve has better thermal stability than binary AEI in a tail gas purification test, and has obvious improvement on removal of nitrogen oxides at a high temperature section (the catalytic performance of the binary AEI molecular sieve is reduced along with the temperature rise from 500 ℃, and the ternary AEI molecular sieve can be well maintained).

Drawings

FIG. 1 is a photomicrograph of an O-Si-Al-Zr ternary framework AEI molecular sieve (hydrogen form);

FIG. 2 is an XRD pattern of a binary framework AEI molecular sieve (hydrogen form);

FIG. 3 is an XRD pattern of an O-Si-Al-Zr ternary framework AEI molecular sieve (hydrogen form);

FIG. 4 is an XRD diagram of an O-Si-Al-Zr ternary framework AEI molecular sieve (hydrogen form) with a larger (5%) zirconium loading.

Detailed Description

Raw materials used in the examples: ammonium type silica sol, SiO₂40%; aluminum hydroxide, Al₂O₃65 percent; sodium hydroxide solution, Na₂O is 30 percent; zirconium sol: ZrO (ZrO)₂15 percent; the content of hexamethonium hydroxide in the template agent is 25 percent.

Example 1: (3.5% ZrO)₂)

1) Forming a slurry

Heating 25.2 g of aluminum hydroxide and 30.0 g of sodium hydroxide aqueous solution for reaction at 100 ℃ to generate sodium metaaluminate, cooling to normal temperature, adding 303 g of template agent hexamethonium hydroxide, and stirring for 10 minutes for later use;

482.1 g of ammonium type silica sol and 45.0 g of zirconium sol are added into a beaker and stirred for 90 minutes by a high-shear emulsifier for standby;

2) adding the two mixed solutions into a high-pressure reaction kettle, sealing, starting stirring at the rotating speed of 280rpm, heating to raise the temperature (the temperature raising speed is 0.8 ℃/min), stopping heating when the temperature is 160 ℃, and preserving heat for 72 hours;

3) post-treatment

After the reaction is finished, the temperature is reduced to normal temperature, and the ternary AEI molecular sieve (hydrogen type) is obtained after the reaction is filtered, washed, dried and roasted (roasting temperature is 500 ℃), the roasted molecular sieve contains sodium, the ammonium molecular sieve is soaked by 65g/l of ammonium bicarbonate to obtain the ammonium molecular sieve, and the ammonium molecular sieve is roasted again to remove ammonia (roasting temperature is 400 ℃).

The ternary AEI molecular sieve (hydrogen type) prepared by the method comprises the following components in percentage by weight of SiO₂:85.81％、Al₂O₃:10.42％、ZrO₂3.77%, particle size D₅₀3 microns, specific surface area: 550 to 600m²The volume of pores is 0.3cc/g, the micrograph is shown in figure 1, and the XRD characteristics are shown in figure 3. Compared with the binary AEI molecular sieve shown in FIG. 2, the XRD pattern of the binary AEI molecular sieve has no shift or hetero-phase peak, and zirconium replaces part of silicon oxygen tetrahedron with zirconium oxygen tetrahedron, so that the binary AEI molecular sieve is a novel derivative of the AEI molecular sieve.

Comparative example: (5% ZrO)₂)

1) Forming a slurry

Heating 25.2 g of aluminum hydroxide and 30.0 g of sodium hydroxide aqueous solution for reaction at 100 ℃ to generate sodium metaaluminate, cooling to normal temperature, adding 303 g of template agent, and stirring for 10 minutes for later use;

482.1 g of silica sol and 64.3 g of zirconium sol are added into a beaker and stirred for 90 minutes by a high-shear emulsifier for standby;

2) adding the two mixed solutions into a high-pressure reaction kettle, sealing, starting stirring at the rotating speed of 280rpm, heating to raise the temperature (the temperature raising speed is 0.8 ℃/min), stopping heating when the temperature is 160 ℃, and preserving heat for 72 hours;

3) post-treatment

After the reaction is finished, cooling to normal temperature, filtering, washing, drying, roasting (roasting temperature is 500 ℃), soaking the roasted molecular sieve containing sodium in 65g/l ammonium bicarbonate to obtain an ammonium type molecular sieve, and roasting again to remove ammonia (roasting temperature is 400 ℃) to obtain the ternary AEI molecular sieve (hydrogen type). The XRD pattern is shown in FIG. 4.

As can be seen from fig. 4: in comparison with FIG. 3, when the amount of Zr added to the molecular sieve is too large (example 5%), a hetero-peak appears at about 18 ℃ and small changes appear elsewhere, indicating that all Zr does not enter the crystal lattice and some Zr is dissociated. Thus, the amount of zirconium substituted for silicon is limited.

Example 2: (3.07% ZrO)₂)

1) Forming a slurry

Heating 25.2 g of aluminum hydroxide and 30.0 g of sodium hydroxide aqueous solution for reaction at 100 ℃ to generate sodium metaaluminate, cooling to normal temperature, adding 303 g of template agent hexamethonium hydroxide, and stirring for 10 minutes for later use;

482.1 g of ammonium type silica sol and 39.5 g of zirconium sol are added into a beaker and stirred for 80 minutes by a high-shear emulsifier for standby;

2) adding the two mixed solutions into a high-pressure reaction kettle, sealing, starting stirring at the rotating speed of 280rpm, heating to raise the temperature (the temperature raising speed is 0.8 ℃/min), stopping heating when the temperature is 160 ℃, and preserving the temperature for 60 hours;

3) post-treatment

Cooling to normal temperature after reaction, filtering, washing, drying, roasting (roasting temperature 500 deg.C), soaking the roasted molecular sieve containing sodium in 65g/l ammonium bicarbonate to obtain ammonium type molecular sieve, roasting again to remove ammonia (roasting temperature 400 deg.C) to obtain ternary AEI molecular sieve (hydrogen type), with particle size D₅₀2.4 microns.