CN116022809A - Method for preparing metal doped integral hierarchical pore nano beta zeolite - Google Patents

Abstract

The invention discloses a method for preparing metal-doped integral multistage-pore nano beta zeolite, which relates to the technical field of beta zeolite synthesis and potassium salt extraction from illite, and comprises the following steps: in a solid-like phase system, depolymerizing natural illite clay by acid steam, and extracting potassium element which is rich in the natural illite clay to obtain active silicon and aluminum species with high activity; the solid silicon-aluminum species generated by depolymerizing illite is used as a raw material to prepare a synthesis precursor of the integral multi-level pore nano beta zeolite; in the solid-like phase system, an organic template agent is added into the synthesized precursor to obtain the nano beta zeolite with an integral multi-level pore structure. Because of the high chemical activity of the active silicon aluminum species formed after clay depolymerization, the crystallization time is greatly shortened, the use of an organic template agent is reduced, and the active silicon aluminum species can be firmly bonded with Fe or Ti, so that the green synthesis of the integral multistage pore nano beta zeolite with low cost and high efficiency is realized.

Description

Method for preparing metal-doped monolithic hierarchical porous nano-beta zeolite

technical field

The invention relates to the technical field of synthesis of beta zeolite and extraction of potassium salt from illite, in particular to a method for preparing metal-doped monolithic multi-level porous nanometer beta zeolite.

Background technique

Illite is a 2:1 layered silicate mica-like clay mineral, which has been regarded as a potential source of potassium fertilizer because of its potassium-rich characteristics. However, the inherent layered structure of illite is stable in the natural state. In order to efficiently extract the abundant potassium components in illite and obtain the silicon-alumina raw material suitable for the synthesis of high-silicon-aluminum ratio zeolite molecular sieves, it is often necessary to extract illite High-temperature activation, followed by acid/alkali washing to destroy its inherent structure, can destroy its stable lattice structure, realize high-yield extraction of potassium components in its components, and obtain silicon-aluminum raw materials with high chemical activity. However, this process has huge energy consumption and acid-base discharge, which is not conducive to large-scale industrial production. Therefore, how to achieve low-temperature depolymerization of illite with high efficiency and low energy consumption, while extracting the potassium component of illite, is a great challenge to obtain high chemical activity and high silicon-aluminum ratio solid silicon-aluminum raw materials.

In recent years, due to its high hydrothermal stability, good shape selectivity and acidity, Beta zeolite molecular sieves have shown excellent catalytic performance in a series of catalytic reactions such as isomerization and hydrocracking. Especially Ti-beta zeolite and Fe-Beta zeolite have attracted more and more attention due to their good catalytic activity and selectivity in NH ₃ -SCR reaction.

Traditional Ti-beta zeolite is obtained in a hydrothermal environment, using chemical raw materials (such as white carbon black, etc.) as raw materials, and strictly controlling the synthesis conditions and synthesis ratio. At the same time, there are also problems such as environmental pollution caused by the discharge of synthetic waste liquid, which is not conducive to its industrial scale production. In addition, the Ti-beta zeolite molecular sieve produced by traditional synthesis technology is affected by the size of the inherent pores, which has severe diffusion limitations in macromolecular catalytic reactions. Therefore, it is very important to explore a low-cost green route to prepare Ti-beta zeolite with high catalytic performance for its industrial scale production.

The invention patent (CN 110422855 B) discloses a synthesis method of Ti-beta molecular sieve nanocrystals. The low-cost synthesis of nano Ti-beta molecular sieves was realized in a short time without using F ions and seeds. The invention patent (CN113731485 A) discloses a preparation method of a loaded multi-level porous titanium-silicon molecular sieve. A monolithic zeolite with micropore, mesopore and carrier channel structure is successfully prepared by using a porous material as a carrier, which solves the industrial The recovery and separation of nano-zeolite catalysts in the production process is difficult. However, the synthetic raw material chemical raw materials, synthetic technology and the improvement of the catalytic performance of the synthetic product used in the above-mentioned disclosed technology all need to be further developed. If the low-cost, green and sustainable preparation of Ti-beta zeolite molecular sieve catalyst with high catalytic performance is of great significance for its industrial scale production and utilization.

The catalytic activity of traditional Fe-Beta zeolites will be affected by the dual loading of iron species and the diffusion properties of zeolite molecular sieves. In addition, the introduction process of iron species would seriously interfere with the crystallization process of Fe-Beta zeolite. Therefore, how to prepare Fe-Beta zeolite with high crystallinity and high catalytic activity in a low-cost and green way has always been a hot issue in the field of industrial catalysis.

The patented technology (CN112536066B) discloses a method for preparing a mesoporous Fe-Beta molecular sieve catalyst with a core-shell structure. Aiming at the problems existing in the post-modification and application of Fe-Beta molecular sieves in the prior art, they first prepared the Fe-C-Al precursor with a core-shell structure, and then prepared a mesoporous Fe-Beta molecular sieve catalyst with a core-shell structure strategy. A core-shell Fe-Beta zeolite with high specific surface area, rich mesopores, uniform iron distribution and high catalytic performance was prepared. Patent technology (CN 111943222 B) discloses a Fe-beta molecular sieve for NOx removal, its synthesis method and application technology. In the hydrothermal reaction, they used silicon source, organic template agent, inorganic base, aluminum source and part of iron source to stir the gel as the precursor, and used two-stage crystallization technology (first long-term low-temperature aging, and then adding iron source , and then through high-temperature crystallization, oxalic acid or ammonium oxalate treatment) to obtain Fe-beta zeolite. Using the above technology, the content of iron in Fe-beta molecular sieve was successfully increased, and the iron species existed in the form of monomer iron, reducing iron oxide groups The formation of clusters makes the prepared Fe-beta have excellent NOx denitrification activity. Though above-mentioned technology has remedied some problems in existing Fe-beta molecular sieve synthetic technology, has improved its catalytic performance, yet, the intrinsic property (such as crystal size, Pore properties, acid distribution) and other aspects need to be further developed. If the process can be simple, low-cost, green and sustainable, the preparation of Fe-beta molecular sieve catalyst with high catalytic performance is of great significance for its industrial scale production and utilization.

Contents of the invention

In order to overcome problems such as low Fe or Ti content in the existing synthesis technology, uneven Fe or Ti elements in the synthesized product, high synthesis cost, long process cycle and harsh synthesis conditions, and poor catalytic performance of the synthesized product, the invention provides The method of preparing metal-doped monolithic hierarchical porous nano-beta zeolite is based on the low energy consumption environment, green and high value-added development of illite resources, on the basis of high-efficiency extraction of potassium in illite components, and at the same time The depolymerized silica-alumina components are used as raw materials to directly prepare metal-doped illite clay-based monolithic hierarchical porous nano-beta zeolites; and the following effects can be obtained:

In order to solve the problem of high energy consumption caused by activation in the traditional process of extracting potassium from illite, in a solid-like system, the natural illite clay is directly depolymerized by using acid vapor, and high activity is obtained by depolymerizing the illite lattice structure. At the same time as silicon and aluminum precursors, high-efficiency extraction of the rich potassium elements can be achieved, providing cheap raw materials for the production of agricultural potassium fertilizers;

In order to overcome the problems of long synthesis period of beta zeolite, harsh synthesis conditions, and complicated process of introducing Fe element into zeolite, and further improve the catalytic performance of beta zeolite, solve the problem of high synthesis cost, ungreen synthesis process and synthetic product in the traditional synthesis process of beta zeolite. Low efficiency hinders its industrialized large-scale preparation and poor mass transfer performance, and the introduction of Fe or Ti is less and easy to agglomerate and cause poor catalytic performance. In the phase system, the active silicon and aluminum species formed by the depolymerization of natural illite clay with acid vapor were used as raw materials, and the metal-doped illite clay-based monolithic hierarchical porous nanostructures were directly prepared by adding a very small amount of organic template agent (TEAOH). beta zeolite method.

The present invention realizes through following technical scheme:

The method for preparing metal-doped monolithic hierarchically porous nano-beta zeolite, the specific steps are as follows:

Step 1: In a solid-like system, use acid steam to depolymerize natural illite clay to obtain active silicon and aluminum species with a high silicon-aluminum ratio. The specific steps are as follows:

1-1. Ball mill the natural illite to 80 mesh;

1-2. Place the illite powder in the polytetrafluoroethylene lining of the hydrothermal reactor, and react at 210 °C for 24 hours. The solid-to-liquid ratio of the solvent in the polytetrafluoroethylene lining to the illite powder is 15 mL/g;

1-3. The reaction product is taken out, and the solid product obtained by washing and filtering is illite-based highly active silicon and aluminum species; the obtained filtrate is a mixed solution of potassium chloride, ferric chloride, and ferrous chloride;

Step 2: Prepare the synthetic precursor of monolithic hierarchical porous nano-beta zeolite, the specific steps are as follows:

2-1. Weigh 200 g of highly active silicon and aluminum species obtained in Step 1 and place them in 1 L of titanium sulfate or ferrous chloride solution with a concentration of 0.05 mol/L, then transfer the solution to a microwave digestion tank, and then Put the microwave digestion tank in the microwave digestion apparatus, and carry out microwave irradiation treatment under the environment of 60-90 °C; after 15-30 cycles of irradiation, take out the raw materials in the digestion tank, and stand and age for 0.5 h to obtain pretreatment liquid;

2-2. Suction filter the solution aged in step (2-1), and take the solid precipitate obtained after suction filtration and dry it completely in an oven at 80°C to obtain the monolithic multi-level porous nano-beta Synthetic precursors for zeolites;

Step 3: In the solid-like system, the preparation of the metal-doped monolithic hierarchical porous nano-beta zeolite is prepared, and the specific steps are as follows:

3-1. Mix the organic template agent tetraethylammonium hydroxide (TEAOH) with the synthetic precursor prepared in step 2 according to the molar ratio of TEAOH:SiO ₂ = 0.125-0.165:1, and grind in a mortar Uniform, to obtain a synthetic precursor;

3-2. Place the evenly ground mixture in the polytetrafluoroethylene lining of the hydrothermal reaction kettle, raise the temperature to 110-140°C, and crystallize for 1-3 hours;

3-3. Take out the hydrothermal reaction kettle, wait for its temperature to drop to room temperature, suction filter the synthesized solid product until it is neutral, and dry it to obtain a metal-doped monolithic hierarchically porous nano-beta zeolite.

Further, the molar ratio of SiO ₂ to Al ₂ O ₃ in illite-based highly active silicon and aluminum species obtained in step 1 is 330:1.

Further, the cycle conditions of single microwave irradiation in step 2 are as follows: 250w irradiation for 15s, 300w irradiation for 15s, 350w irradiation for 15s, stop for 30s.

Further, the solid-like system described in step 1 and step 3 means that the material in the polytetrafluoroethylene lining of the hydrothermal reactor is isolated from the reaction solvent, and the reaction process only depends on the steam generated by the evaporation of the solvent. as a reaction medium.

Further, the solvent described in step (1-2) is a hydrochloric acid solution with a concentration of 4 mol/L. The organic template agent tetraethylammonium hydroxide (TEAOH) used in step (3-1) is an aqueous solution with a mass concentration of 35%; in step (3-2), no additional liquid solvent is used in the system, but still needs to use A spacer isolates the synthesis precursors from the PTFE-lined substrate to facilitate a complete monolithic structure.

Compared with prior art, advantage of the present invention is as follows:

First, compared with the current method of depolymerizing natural clay to obtain highly active silicon and aluminum species for beta zeolite, in a solid-like system, by directly depolymerizing natural illite clay with acid vapor, the high temperature of the clay can be directly avoided. Activation steps to achieve the purpose of energy saving. At the same time, different from the depolymerization behavior of natural clay in an alkaline environment, this technology can preserve the basic unit structure in the illite crystal structure to the greatest extent while destroying the crystal structure of illite clay, thus endowing it with excellent crystallization efficiency. Ultra-high chemical activity for the beta zeolite process. At the same time, after the depolymerization of illite clay is completed, by adding a small amount of acid solution to the used acid solution, the acid solution can be used multiple times, thus avoiding the discharge of acid solution and the loss of potassium element solution. Enrichment.

Secondly, the surface of highly active silicon and aluminum species obtained by depolymerizing natural illite clay with acid steam has more defect sites, which can easily form a uniform and stable bonding relationship with Fe or Ti elements. This can avoid the phenomenon that in the traditional zeolite molecular sieve synthesis process, the introduced Fe or Ti elements will be gradually repelled to the surface of the synthesized zeolite and agglomerated during the crystallization process, which is very important for obtaining Fe- beta zeolite or Ti-beta zeolite, and then it is very important to realize the regulation of the acid center distribution of the synthetic product. In addition, more importantly, the presence of Fe or Ti elements will hinder the crystallization behavior of zeolites, and the amount of Fe or Ti elements introduced is directly critical to the improvement of its catalytic performance. For chemical silicon-aluminum raw materials, the introduction of Fe or Ti elements is extremely complicated and compared with the low amount of introduction, the presence of a large number of defect sites in the active silicon-alumina species formed after clay depolymerization happens to make the introduction of Fe or Ti easier. Easy (in the present invention, it is easy to control the content of Fe or Ti in the molecular sieve by changing the microwave irradiation conditions and the number of cycles), and the introduction of Fe or Ti elements will interfere with the crystallization behavior of zeolite, which is beneficial to the formation of nano-zeolite , but due to the higher activity of synthetic raw materials (due to the basic structure of some natural clays). Therefore, the combination of the two results in that the synthetic raw material can be recrystallized into Fe-beta zeolite crystals with a particle size of about 50 nm with high crystallinity through in-situ reconstitution in an extremely fast time even without long-term aging. This avoids the process of aging the synthetic precursor at low temperature for a long time in the traditional process of synthesizing nano-zeolite.

Thirdly, the highly active silicon and aluminum species used for zeolite synthesis obtained by depolymerizing natural clay have part of the basic structure of natural clay (its role is similar to that of zeolite seeds, that is, it has the effect of inducing zeolite nucleation, which is beneficial to the formation of zeolite. generation), showing ultra-high chemical activity in the macroscopic aspect. Therefore, Fe-beta zeolite or Ti-beta zeolite can be obtained with high efficiency under the use of a very small amount of organic template (tetraethylammonium hydroxide, TEAOH). From this point of view, the use of organic template is greatly reduced. A great reduction in synthesis cost is achieved.

It is worth noting that even without using the periodic interval progressive method, the synthetic precursor can be prepared directly by microwave irradiation technology, but in actual experiments, it is found that the periodic interval progressive method can make Fe or Ti element and acid vapor The active silicon-aluminum raw materials produced by the treatment have a stronger binding effect, because microwaves can not only further act on the chemical bonds in the silicon-aluminum raw materials, causing them to further break and produce more defect sites, but also make the Fe or Ti elements in the system The effective collision probability with the solid silicon-aluminum raw material increases, so that relatively more Fe or Ti elements remain on the surface of the solid raw material; at the same time, the effective collision probability between the elements in the system and the solid silicon-aluminum raw material increases, avoiding the Fe or Ti element The aggregation of Ti makes relatively more Fe or Ti retained on the surface of solid raw materials. At the same time, through this loading method, it is also possible to identify whether Fe or Ti is physically loaded or chemically loaded; in addition, due to the use of steroids in the synthesis process Phase synthesis system, and adopts the technical characteristics of steam-assisted, material and reactor separation synthesis. Therefore, the centrifugation process of the synthetic raw materials in the traditional hydrothermal synthesis is completely avoided, so the synthesis method has an ultra-high synthesis yield, and there is no environmental pollution problem caused by the discharge of the synthesis solution. In particular, based on this special synthesis system, the obtained product has a monolithic hierarchical porous structure, which not only leads to a further increase in its diffusion performance, but also avoids the problem of molding powdered catalysts in industrial catalytic reactions. In conclusion, the present invention has good industrial application value.

Description of drawings

In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the description of the specific embodiments or the prior art. Throughout the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, elements or parts are not necessarily drawn in actual scale.

Figure 1 is the XRD pattern of the illite raw material and the product after acid steam treatment for 24 h;

Fig. 2 is the TEM figure of product after illic acid vapor treatment 24 h;

Fig. 3 is the XRD pattern of embodiment 1-4 synthetic sample;

Fig. 4 is the ²⁹ Si MAS-NMR figure of the illite raw material and the solid raw material obtained after acid steam treatment for 24 hours;

Fig. 5 is the TEM figure of the synthetic sample of embodiment 5;

Fig. 6 is the XRD pattern of the synthetic sample of embodiment 5-8.

Detailed ways

In order to clearly and completely describe the technical solution of the present invention and its specific working process, in conjunction with the accompanying drawings, the specific implementation of the present invention is as follows:

The material composition of raw material illite powder of the present invention is as follows:

Al ₂ O ₃ : 35.16%; SiO ₂ : 52.28%; K ₂ O: 8.04%; TiO ₂ : 0.48%; Fe ₂ O ₃ : 3.13%;

Example 1 This example provides a method for directly preparing illite clay-based monolithic hierarchical porous nano Ti-beta zeolite, and the specific steps of the method are as follows:

Step 1: In a solid-like system, use acid steam to depolymerize natural illite clay to obtain active silicon and aluminum species with a high silicon-aluminum ratio (SiO ₂ /Al ₂ O ₃ molar ratio). The specific steps are as follows:

1-1. Ball mill the natural illite to 80 mesh;

1-2. Place the illite powder in the polytetrafluoroethylene lining of the hydrothermal reactor, and react at 210 °C for 24 hours. The solid-to-liquid ratio of the solvent in the polytetrafluoroethylene lining to the illite powder is 15 mL/g;

1-3. The reaction product is taken out, and the solid product obtained after washing and filtering is the illite-based highly active silicon and aluminum species (the molar ratio of the product: SiO ₂ :Al ₂ O ₃ = 330:1); the obtained filtrate is chlorine Potassium chloride, ferric chloride, the mixed solution of ferrous chloride;

Step 2: Prepare the synthetic precursor of monolithic hierarchical porous nano Ti-beta zeolite, the specific steps are as follows:

2-1. Weigh 200 g of highly active silicon and aluminum species obtained in Step 1 and place them in 1 L of titanium sulfate solution with a concentration of 0.05 mol/L, then transfer the solution to a microwave digestion tank, and then place the microwave digestion tank in In a microwave digestion apparatus, microwave irradiation treatment was carried out in an environment of 90°C. The conditions for one cycle of microwave irradiation are: 250w irradiation for 15s, 300w irradiation for 15s, 350w irradiation for 15s, and stop for 30s. After 30 cycles of irradiation each time, the raw materials in the digestion tank were taken out and left to age for 0.5 h to obtain the pretreatment solution;

2-2. Suction filter the solution after aging in step 1, and take the solid precipitate obtained after suction filtration and completely dry it in an oven at 80°C to obtain the monolithic hierarchical porous nano Ti-beta zeolite. synthetic precursors;

Step 3: In the solid-like system, prepare the monolithic hierarchical porous nano Ti-beta zeolite, the specific steps are as follows:

3-1. Mix the organic template agent (tetraethylammonium hydroxide, TEAOH) and the synthetic precursor according to the material molar ratio of TEAOH:SiO ₂ = 0.125:1, and grind them evenly in a mortar to obtain the synthetic precursor body;

3-2. Place the evenly ground mixture in the polytetrafluoroethylene lining of the hydrothermal reaction kettle, raise the temperature to 140°C, and crystallize for 1 hour;

3-3. Take out the hydrothermal reaction kettle, wait for its temperature to drop to room temperature, suction filter the synthesized solid product to neutrality, and dry it to obtain monolithic hierarchical porous nano Ti-beta zeolite.

In this example, the solid-like system described in step (1-2) and step (3-2) means that the material and reaction solvent in the polytetrafluoroethylene lining of the hydrothermal reactor are in an isolated state , the reaction process only relies on the steam generated by the evaporation of the solvent as the reaction medium;

In this example, the solvent described in step (1-2) is hydrochloric acid solution with a concentration of 4 mol/L; the organic template (tetraethylammonium hydroxide, TEAOH) used in step (3-1) is An aqueous solution with a mass concentration of 35%.

In this example, in step (3-2), no additional liquid solvent is used in the system, but it is still necessary to use a spacer to isolate the synthetic precursor from the bottom of the PTFE inner substrate, so as to obtain a complete monolithic structure .

The illite clay-based monolithic hierarchical porous nano Ti-beta zeolite prepared by the method described in this example is formed by stacking Ti-beta single crystals with a grain size of about 50 nm, and the Ti element in the grains is in the The elements in zeolite are evenly distributed.

Example 2 This example provides a method for directly preparing illite clay-based monolithic hierarchical porous nano Ti-beta zeolite. The specific steps of the method are as follows:

Step 1: In a solid-like system, use acid steam to depolymerize natural illite clay to obtain active silicon and aluminum species with a high silicon-aluminum ratio (SiO ₂ /Al ₂ O ₃ molar ratio). The specific steps are as follows:

1-1. Ball mill the natural illite to 80 mesh;

1-2. Place the illite powder in the polytetrafluoroethylene lining of the hydrothermal reactor, and react at 210 °C for 24 hours. The solid-to-liquid ratio of the solvent in the polytetrafluoroethylene lining to the illite powder is 15 mL/g;

1-3. The reaction product is taken out, and the solid product obtained after washing and filtering is the illite-based highly active silicon and aluminum species (the molar ratio of the product: SiO ₂ :Al ₂ O ₃ = 330:1); the obtained filtrate is chlorine Potassium chloride, ferric chloride, the mixed solution of ferrous chloride;

Step 2: Prepare the synthetic precursor of monolithic hierarchical porous nano Ti-beta zeolite, the specific steps are as follows:

2-1. Weigh 200 g of highly active silicon and aluminum species obtained in Step 1 and place them in 1 L of titanium sulfate solution with a concentration of 0.05 mol/L, then transfer the solution to a microwave digestion tank, and then place the microwave digestion tank in the microwave In the digestion instrument, microwave irradiation treatment is carried out in an environment of 60°C; the conditions for one cycle of microwave irradiation are: 250w irradiation for 15s, 300w irradiation for 15s, 350w irradiation for 15s, stop for 30s; each irradiation 15 cycles Finally, take out the raw material in the digestion tank, leave it to stand and age for 0.5 h to obtain the pretreatment liquid;

2-2. Suction filter the solution after aging in step 1, and take the solid precipitate obtained after suction filtration and completely dry it in an oven at 80°C to obtain the monolithic hierarchical porous nano Ti-beta zeolite. synthetic precursors;

Step 3: In the solid-like system, prepare the monolithic hierarchical porous nano Ti-beta zeolite, the specific steps are as follows:

3-1. Mix the organic template agent (tetraethylammonium hydroxide, TEAOH) and the synthetic precursor according to the material molar ratio of TEAOH:SiO ₂ = 0.125:1, and grind them evenly in a mortar to obtain the synthetic precursor body;

3-2. Place the evenly ground mixture in the polytetrafluoroethylene lining of the hydrothermal reaction kettle, raise the temperature to 110°C, and crystallize for 3 hours;

3-3. Take out the hydrothermal reaction kettle, wait for its temperature to drop to room temperature, suction filter the synthesized solid product to neutrality, and dry it to obtain monolithic hierarchical porous nano Ti-beta zeolite.

The solid-like system described in step (1-2) and step (3-2) means that the material in the polytetrafluoroethylene lining of the hydrothermal reactor is isolated from the reaction solvent, and the reaction process only depends on the solvent The steam generated by heating and evaporating is used as the reaction medium.

The solvent described in step (1-2) is a hydrochloric acid solution with a concentration of 4 mol/L. The organic template agent (tetraethylammonium hydroxide, TEAOH) used in step (3-1) is an aqueous solution with a mass concentration of 35%.

In step (3-2), no additional liquid solvent is used in the system, but a spacer is still required to isolate the synthetic precursor from the bottom of the PTFE inner substrate, so as to obtain a complete monolithic structure.

The illite clay-based monolithic hierarchical porous nano Ti-beta zeolite prepared in this example is formed by stacking Ti-beta single crystals with a grain size of about 50 nm, and the element distribution of the Ti element in the grains in the zeolite uniform.

Example 3 The rest is the same as Example 2, except that in step (3-1) the molar ratio of the template agent (tetraethylammonium hydroxide, TEAOH) and the synthetic precursor is TEAOH:SiO ₂ = 0.165:1 .

Example 4 The rest is the same as Example 2, except that the temperature in step (3-2) is increased to 130° C., and the crystallization takes 2 hours.

Figure 1 is the XRD pattern of the illite raw material and the product after acid steam treatment for 24 h; it can be seen from the figure that the crystal structure of illite is depolymerized before and after acid steam treatment, showing an amorphous structure;

Figure 2 is the TEM image of the product after illite acid steam treatment for 24 hours; it can be seen from the figure that the raw material after illite depolymerization actually retains its elementary structure, that is, the depolymerization process does not completely present the atomic state, but In the case of broken crystal unit fragments, only the original crystal lattice is destroyed;

Fig. 3 is the XRD pattern of embodiment 1-4 synthetic sample; As can be seen from the figure, can obtain the Ti-beta zeolite of high crystallinity;

Figure 4 is the ²⁹ Si MAS-NMR image of illite raw materials and solid raw materials obtained after acid steam treatment for 24 hours; illite has an obvious resonance peak signal at δ = -89 ppm, which is the layered silicate clay at Q ³ ( Typical characteristic peaks in the environment of [Si(SiO) ₃ (OH)]). For SIR-24, there is an extremely broad signal peak around δ = 112 ppm, indicating that the Si atoms in this sample are Q ³ ([Si(SiO) ₃ ( Al)]) and Q ⁴ ([Si(SiO) ₄ ]) silicon species exist. Generally, under alkaline conditions, the high-polymeric Q ³ ([Si(SiO) ₃ (OH)]) species in the natural clay crystal structure will migrate to the low-polymeric Q ² ([Si(SiO) ₂ (OH) ₂ ] ), Q ¹ ([Si(SiO) ₁ (OH) ₃ ]) and Q ⁰ ([Si(OH) ₄ ]) species undergo transformation, which is manifested in the gradual transformation of the long-range ordered crystalline structure into an amorphous structure. However, in acidic environment, the acid steam treatment failed to transform the Q ³ silicon species in the illite clay crystal structure not to the oligomeric state, but to the higher polymeric Q ⁴ silicon species, implying that the SIR-24 The spatial structure of the structure changes from two-dimensional layered to three-dimensional cross-linked three-dimensional.

Example 5 This example provides a method for directly preparing illite clay-based monolithic hierarchical porous nano-Fe-beta zeolite, and the specific steps of the method are as follows:

Step 1: In a solid-like system, use acid steam to depolymerize natural illite clay to obtain active silicon and aluminum species with a high silicon-aluminum ratio (SiO ₂ /Al ₂ O ₃ molar ratio). The specific steps are as follows:

1-1. Ball mill the natural illite to 80 mesh;

1-2. Place the illite powder in the polytetrafluoroethylene lining of the hydrothermal reactor, and react at 210 °C for 24 hours. The solid-to-liquid ratio of the solvent in the polytetrafluoroethylene lining to the illite powder is 15 mL/g;

1-3. The reaction product is taken out, and the solid product obtained after washing and filtering is the illite-based highly active silicon and aluminum species (the molar ratio of the product: SiO ₂ :Al ₂ O ₃ = 330:1); the obtained filtrate is chlorine Potassium chloride, ferric chloride, the mixed solution of ferrous chloride;

Step 2: Prepare the synthetic precursor of monolithic hierarchical porous nano Fe-beta zeolite, the specific steps are as follows:

2-1. Weigh 200 g of highly active silicon and aluminum species obtained in step (1) and place them in 1 L of ferrous chloride solution with a concentration of 0.05 mol/L, then transfer the solution to a microwave digestion tank, and then microwave The digestion tank was placed in a microwave digestion apparatus, and microwave irradiation treatment was carried out in an environment of 90°C. The conditions for one cycle of microwave irradiation are: 250w irradiation for 15s, 300w irradiation for 15s, 350w irradiation for 15s, stop for 30s. After 30 cycles of irradiation each time, the raw materials in the digestion tank were taken out and left to age for 0.5 h to obtain the pretreatment solution;

2-2. Suction filter the solution after aging in step 1, and take the solid precipitate obtained after suction filtration and dry it completely in an oven at 80°C to obtain the monolithic hierarchical porous nano Fe-beta zeolite. synthetic precursors;

Step 3: In the solid phase system, the preparation of monolithic hierarchical porous nano Fe-beta zeolite, the specific steps are as follows:

3-1. Mix the organic template agent (tetraethylammonium hydroxide, TEAOH) and the synthetic precursor according to the molar ratio of TEAOH:SiO ₂ = 0.165:1, and grind them evenly in a mortar to obtain the synthetic precursor body;

3-2. Place the uniformly ground mixture in the polytetrafluoroethylene lining of the hydrothermal reaction kettle, raise the temperature to 140°C, and crystallize for 1 hour.

3-3. Take out the hydrothermal reaction kettle, wait for its temperature to drop to room temperature, suction filter the synthesized solid product to neutrality, and dry it to obtain monolithic hierarchical porous nano-Fe-beta zeolite.

The solid-like system described in step (1-2) and step (3-2) means that the material in the polytetrafluoroethylene lining of the hydrothermal reactor is isolated from the reaction solvent, and the reaction process only depends on the solvent The steam generated by heating and evaporating is used as the reaction medium;

The solvent described in step (1-2) is a hydrochloric acid solution with a concentration of 4 mol/L. The organic template agent (tetraethylammonium hydroxide, TEAOH) used in the step (3-1) is an aqueous solution with a mass concentration of 35%;

In step (3-2), no additional liquid solvent is used in the system, but a spacer is still required to isolate the synthetic precursor from the bottom of the PTFE inner substrate, so as to obtain a complete monolithic structure.

The illite clay-based monolithic hierarchical porous nano Fe-beta zeolite prepared by the method described in this example is formed by the accumulation of Fe-beta single crystals with a grain size of about 50 nm, and the Fe element in the grains is in the The elements in zeolite are evenly distributed.

Example 6 This example provides a method for directly preparing illite clay-based monolithic hierarchical porous nano Fe-beta zeolite, the specific steps of the method are as follows:

Step 1: In a solid-like system, use acid steam to depolymerize natural illite clay to obtain active silicon and aluminum species with a high silicon-aluminum ratio (SiO ₂ /Al ₂ O ₃ molar ratio). The specific steps are as follows:

1-1. Ball mill the natural illite to 80 mesh;

1-2. Place the illite powder in the polytetrafluoroethylene lining of the hydrothermal reactor, and react at 210 °C for 24 hours. The solid-to-liquid ratio of the solvent in the polytetrafluoroethylene lining to the illite powder is 15 mL/g;

1-3. The reaction product is taken out, and the solid product obtained after washing and filtering is the illite-based highly active silicon and aluminum species (the molar ratio of the product: SiO ₂ :Al ₂ O ₃ = 330:1); the obtained filtrate is chlorine Potassium chloride, ferric chloride, the mixed solution of ferrous chloride;

Step 2: Prepare the synthetic precursor of monolithic hierarchical porous nano Fe-beta zeolite, the specific steps are as follows:

2-1. Weigh 200 g of highly active silicon and aluminum species obtained in step (1) and place them in 1 L of ferrous chloride solution with a concentration of 0.05 mol/L, then transfer the solution to a microwave digestion tank, and then microwave The digestion tank was placed in a microwave digestion apparatus, and microwave irradiation treatment was carried out in an environment of 60°C. The conditions for one cycle of microwave irradiation are: 250w irradiation for 15s, 300w irradiation for 15s, 350w irradiation for 15s, stop for 30s. After 15 cycles of irradiation each time, the raw materials in the digestion tank were taken out and left to age for 0.5 h to obtain the pretreatment solution;

2-2. Suction filter the solution after aging in step 1, and take the solid precipitate obtained after suction filtration and dry it completely in an oven at 80°C to obtain the monolithic hierarchical porous nano Fe-beta zeolite. synthetic precursors;

Step 3: the preparation of monolithic hierarchical porous nano Fe-beta zeolite, the specific steps are as follows:

3-1. Mix the organic template agent (tetraethylammonium hydroxide, TEAOH) and the synthetic precursor according to the material molar ratio of TEAOH:SiO ₂ = 0.125:1, and grind them evenly in a mortar to obtain the synthetic precursor body;

3-2. Place the evenly ground mixture in the polytetrafluoroethylene lining of the hydrothermal reaction kettle, raise the temperature to 110°C, and crystallize for 3 hours;

3-3. Take out the hydrothermal reaction kettle, wait for its temperature to drop to room temperature, suction filter the synthesized solid product to neutrality, and dry it to obtain monolithic hierarchical porous nano-Fe-beta zeolite.

The solid-like system described in step (1-2) and step (3-2) means that the material in the polytetrafluoroethylene lining of the hydrothermal reactor is isolated from the reaction solvent, and the reaction process only depends on the solvent The steam generated by heating and evaporating is used as the reaction medium;

The solvent described in step (1-2) is a hydrochloric acid solution with a concentration of 4 mol/L. The organic template agent (tetraethylammonium hydroxide, TEAOH) used in the step (3-1) is an aqueous solution with a mass concentration of 35%;

In step (3-2), no additional liquid solvent is used in the system, but a spacer is still required to isolate the synthetic precursor from the bottom of the PTFE inner substrate, so as to obtain a complete monolithic structure.

The illite clay-based monolithic hierarchical porous nano Fe-beta zeolite prepared by the method described in this example is formed by the accumulation of Fe-beta single crystals with a grain size of about 50 nm, and the Fe element in the grains is in the The elements in zeolite are evenly distributed.

Example 7 The rest is the same as Example 5, except that in step (3-2), the temperature is increased to 140°C and crystallized for 3 h.

Example 8 The rest is the same as Example 5, except that the microwave irradiation cycle in step (2-1) is 30 cycles.

Figure 5 is a TEM image of the sample synthesized in Example 1; as can be seen from the figure, the pores of the sample are highly penetrating and clear, indicating that the synthetic product has very high crystallinity;

Figure 6 is the XRD pattern of the synthesized sample in Example 5-6, which shows that the synthesized sample is highly crystalline Fe-beta zeolite.

The preferred embodiment of the present invention has been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the specific details of the above embodiment, within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, These simple modifications all belong to the protection scope of the present invention.

In addition, it should be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way if there is no contradiction. The combination method will not be described separately.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Claims (5)

1. prepare the method for the monolithic hierarchical porous nano-beta zeolite of metal doping, it is characterized in that, the concrete steps of described method are as follows: Step 1: In a solid-like system, use acid steam to depolymerize natural illite clay to obtain active silicon and aluminum species with a high silicon-aluminum ratio. The specific steps are as follows: 1-1. Ball mill the natural illite to 80 mesh; 1-2. Place the illite powder in the polytetrafluoroethylene lining of the hydrothermal reactor, and react at 210 °C for 24 hours. The solid-to-liquid ratio of the solvent in the polytetrafluoroethylene lining to the illite powder is 15 mL/g; 1-3. The reaction product is taken out, and the solid product obtained by washing and filtering is illite-based highly active silicon and aluminum species; the obtained filtrate is a mixed solution of potassium chloride, ferric chloride, and ferrous chloride; Step 2: Prepare the synthetic precursor of monolithic hierarchical porous nano-beta zeolite, the specific steps are as follows: 2-1. Weigh 200 g of highly active silicon and aluminum species obtained in step 1 and place them in 1 L of titanium sulfate or ferrous chloride solution with a concentration of 0.05 mol/L, then transfer the solution to a microwave digestion tank, and then The microwave digestion tank is placed in a microwave digestion apparatus, and microwave irradiation treatment is carried out in an environment of 60-90 ° C; after 15-30 cycles of irradiation, the raw materials in the digestion tank are taken out, and the pretreatment solution is obtained by standing and aging for 0.5 h ; 2-2. Suction filter the solution aged in step (2-1), and take the solid precipitate obtained after suction filtration and dry it completely in an oven at 80°C to obtain the monolithic multi-level porous nano-beta Synthetic precursors for zeolites; Step 3: In the solid-like system, the preparation of the metal-doped monolithic hierarchical porous nano-beta zeolite is prepared, and the specific steps are as follows: 3-1. Mix the organic template agent tetraethylammonium hydroxide TEAOH with the synthetic precursor prepared in step 2 in a molar ratio of TEAOH:SiO ₂ = 0.125-0.165:1, and grind them evenly in a mortar. Obtain synthetic precursors; 3-2. Place the evenly ground mixture in the polytetrafluoroethylene lining of the hydrothermal reaction kettle, raise the temperature to 110-140°C, and crystallize for 1-3 hours; 3-3. Take out the hydrothermal reaction kettle, wait for its temperature to drop to room temperature, suction filter the synthesized solid product to neutrality, and dry it to obtain monolithic hierarchical porous nano-beta zeolite. 2. The method for preparing metal-doped monolithic hierarchically porous nano-beta zeolites as claimed in claim 1, characterized in that the illite-based highly active silicon and aluminum species obtained in step 1 are SiO ₂ and Al ₂ O ₃ at a molar ratio of 330:1. 3. the method for the monolithic hierarchical porous nano-beta zeolite of preparation metal doping as claimed in claim 1, is characterized in that, the cycle condition of single microwave irradiation in step 2 is as follows: 250w irradiation 15s, 300w irradiation 15s , 350w irradiation for 15s, stop for 30s. 4. the method for the monolithic hierarchical porous nano-beta zeolite of preparation metal doping as claimed in claim 1, is characterized in that, the class solid phase system described in step 1 and step 3, refers to in hydrothermal reactor The material in the PTFE lining is isolated from the reaction solvent, and the reaction process only relies on the steam generated by the evaporation of the solvent as the reaction medium. 5. the method for preparing the monolithic hierarchical porous nano-beta zeolite of metal doping as claimed in claim 1, is characterized in that, the solvent described in step (1-2) is hydrochloric acid solution, and concentration is 4 mol/ L; The organic template tetraethylammonium hydroxide TEAOH used in step (3-1) is an aqueous solution with a mass concentration of 35%. In step (3-2), no additional liquid solvent is used in the system, but a spacer is still required The synthesis precursors are isolated from the PTFE-lined substrate to facilitate a complete monolithic structure.

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