CN106542545B - Step hole ZSM-5 zeolite and preparation method thereof - Google Patents

Abstract

The invention provides a stepped pore ZSM‑5 zeolite and a preparation method thereof. The preparation method comprises: mixing a template agent with water to obtain a solution; adding sodium hydroxide, an aluminum source, a short-chain alcohol, and a silicon source to the solution, and mixing to form a gel mixture, wherein the silicon source is calculated as SiO ₂ and the aluminum source is expressed as Al ₂ O ₃ meter, the molar ratio of sodium hydroxide, aluminum source, silicon source, templating agent, short-chain alcohol and water is (5-15):1:(30-100):(0.5-3):(70- 500): (1000‑8000); crystallize the gel mixture, separate, wash and dry the solid product to obtain ZSM‑5 zeolite raw powder; roast ZSM‑5 zeolite raw powder to obtain stepped hole ZSM‑5 Zeolite. The present invention also provides a stepped pore ZSM‑5 zeolite prepared by the above preparation method. The stepped pore ZSM‑5 zeolite provided by the invention has ordered large mesopores, which is beneficial to the effective diffusion and reaction of macromolecular compounds.

Description

A kind of stepped pore ZSM-5 zeolite and its preparation method

technical field

The invention relates to a zeolite and a preparation method thereof, in particular to an ordered mesoporous-micropore step-pore ZSM-5 zeolite and a preparation method thereof, belonging to the technical field of zeolite preparation.

Background technique

Microporous zeolites are widely used in petroleum refining and petrochemical fields due to their regularly arranged micropore channels, highly crystalline pore walls and a large number of evenly distributed active sites. In the 1970s, Mobil first developed ZSM zeolite by using organic additives to synthesize gels. HZSM-5 zeolite has an acid center and has hydrogenation performance after loading active metals, so it is widely used in petrochemical fields such as catalytic cracking and catalytic hydrogenation. However, conventional ZSM zeolites generally have small pore sizes, which prevent the mass transfer of molecules with large kinetic diameters, and cannot exhibit good catalytic performance.

The emergence of ordered mesoporous materials (2nm<diameter<50nm) has been highly valued by the material science community. For some catalytic reactions that do not require strong active centers and the molecular size of reactants and products is large, its catalytic activity is significantly higher than that of microporous zeolites. However, due to the amorphous pore wall of mesoporous materials, their hydrothermal stability and catalytic activity are poor, which limits their wide application.

In order to make up for the shortcomings of the small pore size of microporous zeolites and the poor hydrothermal stability and catalytic activity of ordered mesoporous molecular sieves, scientists have recently prepared step-pore zeolites through various methods, including desilication or dealumination of zeolites. mesoporous zeolite is produced by adding mesoporous template agent after precrystallization, and mesoporous zeolite is synthesized by hard template method. Compared with conventional zeolite, mesoporous zeolite obtained has higher Excellent catalytic activity and selectivity, longer catalytic life and stronger ability to resist carbon deposition.

Chinese patent application 201010010136.2 supports Keggin structure polyoxometalate (POM) on nano-scale ZSM-5 molecular sieve, and introduces nickel nitrate to improve the catalytic performance of the catalyst. The gasoline treated by this catalyst can greatly reduce the sulfur in gasoline content. However, nano-scale molecular sieves are easy to agglomerate, which shortens the life of the catalyst.

Lizama et al. (Applied Catalusis B:Environmental.82.2008.135) reported the use of mesoporous SBA-15 as a carrier to load phosphorus tungsten and phosphorus molybdenum, and 4,6-dimethyldibenzothiophene as a hydrodesulfurization reaction. needle molecule. The research results show that the larger pore diameter of the ordered mesoporous material can allow larger 4,6-dimethyldibenzothiophene molecules to enter the pores to react and achieve deep hydrodesulfurization. Fixed structure, poor stability, weak acidity.

Zhao Xiaobo et al. (Acta Petroleum Sinica, Petroleum Processing, 22, 2006, 20) reported the application of modified nano ZSM-5 zeolite in FCC gasoline upgrading. Their research results show that the nano-HZSM-5 catalyst modified by hydrothermal treatment and metal oxide combination has good desulfurization performance, but its stability still needs to be improved.

In summary, it is an urgent problem to be solved in this field to provide a ZSM-5 zeolite with high catalytic activity and good stability.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a kind of stepped pore ZSM-5 zeolite and preparation method thereof, the ZSM-5 zeolite obtained by the preparation method has crystallized micropore walls, abundant ordered mesopores, and has The larger specific surface area and pore volume are conducive to the effective diffusion and reaction of macromolecular compounds.

In order to achieve the above object, the invention provides a kind of preparation method of step hole ZSM-5 zeolite, and this preparation method comprises the following steps:

Step 1: mixing the template agent with water to obtain a solution;

Step 2: Add sodium hydroxide, aluminum source, short-chain alcohol and silicon source to the solution, and mix to form a gel mixture, wherein the molar ratio of sodium hydroxide, aluminum source, silicon source, templating agent, short-chain alcohol and water is (5-15):1:(30-100):(0.5-3):(70-500):(1000-8000), the silicon source is calculated as _SiO2 , and the aluminum source is calculated as _{Al2O3 ;}

Step 3: crystallize the gel mixture, separate, wash and dry the solid product to obtain ZSM-5 zeolite raw powder;

Step 4: Roasting the ZSM-5 zeolite raw powder to obtain the stepped pore ZSM-5 zeolite.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, in step 2, sodium hydroxide is added to the solution and stirred evenly, then the aluminum source is added to stir evenly, and finally the mixture of short-chain alcohol and silicon source is added, Stir to form a gel mixture, wherein the molar ratio of Si in the silicon source to short-chain alcohols is 1:(1-50).

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the mixing temperature in step 1 and step 2 is 20°C-60°C.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the crystallization temperature in step 3 is 120°C-250°C, and the crystallization time is 12h-240h.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the calcination temperature in step 4 is 500°C-650°C, and the calcination time is 4h-12h.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the preparation method also includes the step of ammonium exchange, after the ZSM-5 zeolite raw powder is roasted in step 4, ammonium exchange is carried out, and then after pumping filtering, washing, drying and roasting to obtain the stepped pore ZSM-5 zeolite.

According to a specific embodiment of the present invention, ammonium exchange is performed to convert Na-type stepped-pore ZSM-5 zeolite into H-type stepped-pore ZSM-5 zeolite, wherein the drying temperature is 120° C., and the drying time is 6 hours; the roasting temperature is 500° C. -650℃, the roasting time is 4h-12h.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the template used comprises a gemini type polyquaternium surfactant; Polyquaternium salts are formed with multiple cationic polyquaternium salts. Wherein, the gemini-type polyquaternium surfactant can be formed by double-head cationic polyquaternium salts and multi-head cationic polyquaternium salts in any ratio.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the multi-head cationic polyquaternium salt used is selected from trimer quaternary ammonium salt, tetramer quaternary ammonium salt and poly-polyquaternium salt, multi-head cationic polyquaternium salt The hydrophobic chain of the polyquaternium salt is a C ₈ -C ₂₂ alkyl chain, and the linking group of the polyquaternium salt is a C ₂ -C ₁₀ alkyl chain.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the gemini type polyquaternium surfactant used is CH ₃ (CH ₂ ) ₁₅ N(CH ₃ ) ₂ (CH ₂ ) ₆ N( CH ₃ ) ₂ (CH ₂ ) ₁₅ CH ₃ Br ₂ and CH ₃ (CH ₂ ) ₁₅ [N(CH ₃ ) ₂ (CH ₂ ) ₆ ] _n-1 N(CH ₃ ) ₂ (CH ₂ ) ₁₅ CH ₃ Br _n , n is an integer of 3-5.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the aluminum source used includes one or more combinations of inorganic aluminum source and organic aluminum source; more preferably, the inorganic aluminum source used includes Aluminum sulfate and sodium aluminate. The organic aluminum source includes C ₂ -C ₅ tri-secondary alkoxide aluminum; most preferably, the organic aluminum source used includes aluminum isopropoxide and aluminum isobutoxide.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the silicon source used includes one or more combinations of inorganic silicon source and organic silicon source; more preferably, the inorganic silicon source used includes Water glass, silica sol, sodium silicate, the organosilicon source is C ₂ -C ₅ alkyl silicate; most preferably, the organosilicon source used includes ethyl orthosilicate and propyl orthosilicate.

In the preparation method of the stepped pore ZSM-5 zeolite provided by the present invention, preferably, the short-chain alcohol used includes one or a combination of ethanol and C ₃ -C ₅ secondary alcohols.

The present invention also provides a stepped pore ZSM-5 zeolite, which is prepared by the above preparation method.

In the preparation method of the present invention, a gemini-type polyquaternium surfactant is used as a template. The Gemini polyquaternium surfactant reacts with the silicon source and the Al source, leading to the formation of the ZSM-5 structure, while the long alkyl chain in the Gemini polyquaternium surfactant prevents the formation of silicon-oxygen tetrahedrons and The role of alumina tetrahedron growth, after the reaction is completed, the template is removed by calcination to form micropores and mesoporous channels.

The formation of the mesoporous structure of the stepped pore ZSM-5 zeolite in the present invention is through the following two methods: one is formed by accumulation of highly crystallized small grains, and the other is generated by roasting to remove hydrophobic alkyl chains.

The preparation method provided by the invention uses the novel gemini type polyquaternium surfactant as a template to synthesize the stepped pore ZSM-5 zeolite. The zeolite has a hierarchical pore structure, which can allow macromolecules of the guest to enter the pores to react, and has more acid active sites and stronger acid strength.

Description of drawings

Fig. 1 is the small-angle XRD figure of the different pore structure ZSM-5 zeolites that comparative example 1 and embodiment 1-4 make;

Fig. 2 is the large-angle XRD pattern of the different pore structure ZSM-5 zeolites that comparative example 1 and embodiment 1-4 make;

Fig. 3 is the N of the different pore structure ZSM-5 zeolites that comparative example 1 and embodiment 1-4 make _; Adsorption-desorption isotherm curve figure;

Fig. 4 is the ammonia gas temperature-programmed desorption curves of ZSM-5 zeolites with different pore structures prepared in Comparative Example 1 and Examples 1-4.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

Comparative example 1

This comparative example provides a kind of ZSM-5 zeolite, and it is prepared through the following steps:

Mix 70.0g of deionized water, 0.5g of sodium hydroxide, 0.3g of aluminum sulfate octadecahydrate, and 2.7g of tetrapropylammonium bromide, and add 6.6g of tetrapropylammonium bromide dropwise and stir at 60°C for 4-6h get the gel;

The gel was transferred to a polytetrafluoroethylene-lined stainless steel reactor, hydrothermally crystallized at 150°C for 4 days, the hydrothermally crystallized product was suction-filtered, washed with deionized water until pH<9, and then placed in Drying at 120°C for 12 hours, and then calcining in a muffle furnace at 550°C to remove the template agent to obtain Na-type conventional ZSM-5 zeolite;

The above-mentioned Na-type conventional ZSM-5 zeolite was subjected to ammonium exchange, then suction filtered, washed, dried at 120°C for 6 hours, and calcined at 500°C for 4 hours to obtain H-type conventional ZSM-5 zeolite, which was designated as Z-0.

The powder XRD test result of the ZSM-5 zeolite Z-0 that this comparative example obtains is as shown in Figure 1 and Figure ₂ , N The adsorption-desorption isotherm curve is as shown in Figure 3, and the ammonia gas temperature-programmed desorption curve is shown in Figure 4 shown.

Example 1

This embodiment provides a kind of stepped pore ZSM-5 zeolite, which is prepared through the following steps:

Mix 50g of deionized water, 1.45g of three-head polyquaternium C ₁₆ C ₆ C ₆ C ₁₆ Br ₃ and 0.38g of double-head polyquaternium C ₁₆ C ₆ C ₁₆ Br ₂ to obtain a solution;

Add 0.7g of sodium hydroxide to the solution, stir evenly, add 0.6g of aluminum sulfate octadecahydrate, then add a mixture of 12.4g of ethanol and 8.2g of ethyl orthosilicate, stir at 40-60°C for 4-6h to obtain a condensate glue mixture;

The gel mixture was transferred to a polytetrafluoroethylene-lined stainless steel reactor, and hydrothermally crystallized at 150°C for 4 days;

The product obtained by hydrothermal crystallization was suction-filtered, washed with deionized water until pH<9, then dried at 120°C for 12h, and the dried sample was put into a muffle furnace for calcination at 550°C for 4h to obtain Na-type ZSM- 5 zeolites;

The Na-type ZSM-5 zeolite was subjected to ammonium exchange, then suction filtered, washed, dried at 120°C for 6 hours and calcined at 500°C for 4 hours to obtain the H-type stepped-pore ZSM-5 zeolite, which was designated as Z-1.

The powder XRD test result of the step hole ZSM-5 zeolite Z-1 that the present embodiment obtains is as shown in Figure 1 and Figure ₂ , N Adsorption-desorption isotherm is as shown in Figure 3, and ammonia temperature programming desorption curve is as shown in Figure 3 Figure 4 shows.

Example 2

This embodiment provides a kind of stepped pore ZSM-5 zeolite, which is prepared through the following steps:

The preparation method is generally the same as in Example 1, the difference is that the template agent is replaced by 1.77g four-head cationic polyquaternary ammonium surfactant and 0.38g double-head cationic surfactant, and other conditions remain unchanged, and the prepared H-type The stepped pore ZSM-5 zeolite is denoted as Z-2.

The powder XRD test result of the step hole ZSM-5 zeolite Z-2 that the present embodiment obtains is as shown in Figure 1 and Figure ₂ , N The adsorption-desorption isotherm is as shown in Figure 3, and the ammonia gas temperature-programmed desorption curve is shown in Figure 3 Figure 4 shows.

Example 3

This embodiment provides a kind of stepped pore ZSM-5 zeolite, which is prepared through the following steps:

The preparation method is generally the same as that in Example 1, except that the template agent is replaced with 1.94 g of three-head cationic polyquaternium salt, and other conditions remain unchanged, and the prepared H-type stepped pore ZSM-5 zeolite is recorded as Z-3.

The powder XRD test result of the step hole ZSM-5 zeolite Z-3 that the present embodiment obtains is as shown in Figure 1 and Figure ₂ , N The adsorption-desorption isotherm is as shown in Figure 3, and the ammonia gas temperature-programmed desorption curve is shown in Figure 3 Figure 4 shows.

Example 4

This embodiment provides a kind of stepped pore ZSM-5 zeolite, which is prepared through the following steps:

The preparation method is generally the same as that of Example 1, except that 1.54 g of double-headed cationic polyquaternium salt is used as the template, and the other conditions remain unchanged. The prepared H-type stepped-pore ZSM-5 zeolite is recorded as Z-4.

The powder XRD test result of the step hole ZSM-5 zeolite Z-4 that the present embodiment obtains is as shown in Figure 1 and Figure ₂ , N The adsorption-desorption isotherm is as shown in Figure 3, and the ammonia gas temperature-programmed desorption curve is shown in Figure 3 Figure 4 shows.

Example 5

This embodiment carries out structural analysis to the ZSM-5 zeolite of the different structure that embodiment 1-4 and comparative example 1 obtain, and analysis result is as shown in table 1, and table 1 is the ZSM that embodiment 1-4 and comparative example 1 obtain Pore structure parameters of -5 zeolites.

Table 1

As can be seen from Table 1, in the step hole ZSM-5 zeolite that preparation method provided by the present invention makes, adding gemini type polyquaternium surfactant all can lead to the formation of step hole ZSM-5 zeolite, adopt multi-head Compared with conventional ZSM-5 zeolite, the stepped pore ZSM-5 zeolite synthesized by quaternary ammonium salt can greatly increase its specific surface area, pore volume and pore size, especially the external specific surface area is significantly increased, and the multi-head cationic polyquaternary The ammonium salt is similar in structure to the double-headed cationic polyquaternary ammonium salt surfactant, and has good compounding performance. The number of mesopores can be increased by mixing the two, so as to adjust the mesopores and micropores of the stepped pore ZSM-5 zeolite. Proportion.

In addition, it can be seen from Fig. 3 that the ZSM-5 zeolite prepared by adding the gemini type polyquaternium surfactant has obvious hysteresis ring, indicating that the new multi-head polyquaternium can be used to simultaneously guide the ZSM-5 zeolite structure and mesoporous structure, and it can be seen from Fig. 1 and Fig. 2 that the mesopores of the ZSM-5 zeolite prepared by the present invention tend to be ordered.

As can be seen from Figure 4, the ammonia gas temperature-programmed desorption curve of the ZSM-5 zeolite prepared by adding the gemini-type polyquaternium surfactant corresponds to the low-temperature desorption peak (150°C-225°C) of the weak acid center and the high-temperature desorption peak (300°C-450°C) corresponding to the strong acid center are significantly higher than the conventional ZSM-5 zeolite; and its weak acid position shifts backward, indicating that the ZSM- Zeolite 5 has a higher acid number and acid strength.

It can be seen from the above examples that the stepped pore ZSM-5 zeolite prepared by the preparation method provided by the present invention has an ordered mesoporous structure, which allows guest macromolecules to enter the pores and react, and is a very good mesoporous material.

Claims (12)

1. a kind of preparation method of step hole ZSM-5 zeolite, the preparation method include the following steps：

Step 1：Template and water are mixed to get solution；

Step 2：Sodium hydroxide, silicon source, short chain alcohol, silicon source are added into solution, is mixed to form gel mixture, wherein hydrogen-oxygen The molar ratio for changing sodium, silicon source, silicon source, template, short chain alcohol and water is (5-15):1:(30-100):(0.5-3):(70-500): (1000-8000), the silicon source is with SiO₂Meter, silicon source is with Al₂O₃Meter；Wherein, the template includes double type polyquaternium table Face activating agent；The double type polyquaternium surfactant is by double end cationic polyquaternium and bull cationic poly What quaternary ammonium salt was formed；

Step 3：Crystallization is carried out to gel mixture, by solid product separation, washing, drying, obtains ZSM-5 zeolite original powder；

Step 4：ZSM-5 zeolite original powder is roasted, step hole ZSM-5 zeolite is obtained.

2. preparation method according to claim 1, wherein in step 2, sodium hydroxide is added into solution and stirs evenly Afterwards, it adds silicon source to stir evenly, is eventually adding the mixture of short chain alcohol and silicon source, stir and form gel mixture, in silicon source Si and short chain alcohol molar ratio be 1:(1-50).

3. preparation method according to claim 1, wherein the mixing temperature in step 1 and step 2 is 20 DEG C -60 DEG C； Crystallization temperature in step 3 is 120 DEG C -250 DEG C, crystallization time 12h-240h；Maturing temperature in step 4 is 500 DEG C- 650 DEG C, calcining time 4h-12h.

4. preparation method according to claim 1, wherein further include the steps that ammonium exchanges in the preparation method, step 4 In ZSM-5 zeolite original powder is roasted after, carry out ammonium exchange and by suction filtration, washing, drying and roasting obtain step hole ZSM-5 zeolite.

5. preparation method according to claim 1, wherein the bull cationic polyquaternium is selected from three polyquaternary amines Salt, four polyquaterniums and poly quaternary ammonium salt, the hydrophobic chain of the bull cationic polyquaternium are C₈-C₂₂Alkyl chain, institute The connecting group for stating polyquaternium is C₂-C₁₀Alkyl chain；The double type polyquaternium surfactant is CH₃(CH₂)₁₅N (CH₃)₂(CH₂)₆N(CH₃)₂(CH₂)₁₅CH₃Br₂And CH₃(CH₂)₁₅[N(CH₃)₂(CH₂)₆]_n-1N(CH₃)₂(CH₂)₁₅CH₃Br_n, n is The integer of 3-5.

6. preparation method according to claim 1, wherein source of aluminium includes one of inorganic silicon source and organic silicon source Or several combination.

7. preparation method according to claim 6, wherein the inorganic silicon source includes aluminum sulfate, sodium aluminate, described organic Silicon source includes C₂-C₅Three secondary aluminum alkoxides.

8. preparation method according to claim 6, wherein organic silicon source includes aluminium isopropoxide, isobutanol aluminum.

9. preparation method according to claim 1, wherein the silicon source includes one of inorganic silicon source and organic silicon source Or several combination.

10. preparation method according to claim 9, wherein the inorganic silicon source includes waterglass, silica solution, sodium metasilicate, The organic silicon source is C₂-C₅Alkyl silicate.

11. preparation method according to claim 9, wherein the organic silicon source includes ethyl orthosilicate, positive silicic acid third Ester.

12. preparation method according to claim 1 or 2, wherein the short chain alcohol includes ethyl alcohol and C₃-C₅Secondary alcohol in One or more of combinations.