CN115784254A - A preparation method of a mesoporous-rich fly ash-based MFI structure nano zeolite - Google Patents

Abstract

The invention discloses a method for preparing a mesoporous-rich fly ash-based MFI structure nano zeolite, which belongs to the technical field of resource utilization of industrial solid waste and zeolite synthesis. The zeolite disclosed and prepared by the invention has an MFI framework topology, a grain size of 100-500 nm, and a mesopore ratio of 64-85%. The present invention not only synthesizes a mesoporous-rich nano-zeolite molecular sieve, but also realizes the utilization of silicon-aluminum resources in fly ash, and provides a high-yield, simple preparation method of fly ash-based MFI structure nano-zeolite . Compared with traditional molecular sieves, mesopores can effectively reduce the limitation of micropores on mass transfer, and nanoscale can increase the specific surface area of porous materials, thereby expanding their applications in the fields of catalysis, adsorption, and separation.

Description

A preparation method of a mesoporous-rich fly ash-based MFI structure nano zeolite

technical field

The invention belongs to the technical field of resource utilization of industrial solid waste and zeolite synthesis, and in particular relates to a preparation method of a fly ash-based MFI structure nano zeolite rich in mesopores.

Background technique

Due to the rapid development of China's economy in recent decades, power consumption has also continued to increase, which has directly led to the increase of solid waste fly ash in coal-fired power plants. Fly ash will not only occupy a large amount of land resources, increase management costs, but also It has caused serious damage to the ecological environment, so we urgently need to find a reasonable treatment method. Zeolite is a kind of crystal composed of aluminosilicate with specific pore structure, which is widely used in the fields of catalysis, adsorption and ion exchange. Since the fly ash contains a large amount of SiO ₂ and Al ₂ O ₃ , it can replace the silicon and aluminum sources in chemicals, thereby greatly reducing the production cost of molecular sieves and realizing the value-added utilization of solid waste. Therefore, using fly ash as raw material to prepare zeolite is one of the effective ways for high-value utilization of solid waste.

Common zeolites synthesized from fly ash include topologies such as LTA, FAU, FER, and MFI, and the methods used are mainly hydrothermal synthesis. Usually, the active components such as silicon and aluminum in the fly ash are extracted, separated and purified by grinding, high-temperature roasting, acid leaching, alkali dissolution, neutralization and other steps, and then the obtained two Silicon oxide and aluminum oxide are used as silicon source and aluminum source, and organic template agent, inorganic alkali and water are added, and then zeolite is prepared by hydrothermal synthesis method. By adjusting the raw material ratio of the initial sol, the type of organic template and the hydrothermal crystallization process conditions, zeolite products with different structure types can be obtained. The MFI structure zeolite synthesized by the traditional process is a microporous material with a large particle size, and produces a large amount of acid and alkali waste water, forming secondary pollution.

The MFI structure zeolite is composed of TO ₄ tetrahedron as the basic structural unit. TO ₄ shares oxygen bridges to form a five-membered ring, and then the structural units composed of eight five-membered rings are connected through common edges to form a Pentasil chain. The chain and The chains are reconnected to form a three-dimensional skeleton, which is often used as solid acid catalysts, adsorbents, and membrane separation materials such as alkylation, disproportionation, isomerization, and catalytic cracking. At present, the raw materials used in the artificial synthesis of MFI zeolite are usually chemical reagents such as silicon salts, aluminum salts, inorganic bases, and organic templates. The synthesis methods used mainly include hydrothermal synthesis, solid-phase synthesis, and xerogel synthesis. .

At present, the MFI structure zeolite synthesized from fly ash is usually a microporous zeolite with a particle size of micron. Although microporous zeolite has significant advantages in adsorption, ion exchange, and partial catalytic reactions, due to the limitation of its single pore, it hinders the contact of reactants and adsorbates with larger molecular sizes with the active sites on the inner surface of the material, and the intermediary Pores can effectively reduce the restriction of micropores on mass transfer. At the same time, nano-sized molecular sieves have a larger outer surface area than micron-sized molecular sieves, as well as more active centers on the outer surface, and shorter and regular channels, which means that reactants can have more accessible active sites. It tends to have better anti-coking ability and stability in catalytic applications.

In recent years, people try to prepare MFI structure zeolite with special structure and morphology by using fly ash as raw material. CN112194150A uses fly ash as raw material and utilizes microwave-ultrasonic-ultraviolet light synergistic activation technology to replace the traditional high-energy-consumption alkali fusion technology to synthesize a multi-stage channel MFI structure zeolite, but the synthesized zeolite has a large particle size and mesoporous Relatively few, and this method is difficult to realize industrialized production; CN103435064B discloses a kind of method utilizing fly ash to prepare nanoscale ZSM-5 molecular sieve, although the nanoscale ZSM-5 molecular sieve prepared by its microwave-assisted hydrothermal synthesis has good crystallinity, but The lack of mesopores limits its application field, and it is difficult to realize industrial production and application; CN111646486B discloses a pretreatment operation that does not require any pretreatment and does not require any extraction of aluminum and silicon, only by adding templates and silicon source materials Form dry glue, and further undergo steam crystallization treatment and high-temperature calcination to directly synthesize the required ZSM-5 molecular sieve. Although this synthesis method is simple, the product molecular sieve has few mesopores and large particle size, and its application field has certain limitations.

So far, there is no report on the synthesis of MFI zeolite with nanometer particle size and rich mesoporous channels using fly ash as raw material.

Contents of the invention

In view of this, the present invention provides a method for preparing fly ash-based MFI structure zeolite with nanometer particle size and rich in mesoporous channels.

It should be noted that the present invention uses fly ash solid waste rich in silicon and aluminum as raw materials to realize the simultaneous utilization of silicon and aluminum resources in fly ash, and finds a method for synthesizing pulverized coal by adding co-auxiliary PL The preparation method of gray-based MFI nano zeolite, on the one hand, the synthesized zeolite has a smaller particle size, which leads to a larger specific surface area than ordinary zeolite, so that more active centers can be exposed; on the other hand, the Zeolite is rich in mesoporous channels. Compared with traditional molecular sieves, mesoporous can effectively reduce the limitation of micropores on mass transfer, making it easier for reactants to contact the active centers on the inner surface of the catalyst, thereby improving the catalytic activity of the material. The invention has obvious economic value by transforming fly ash from solid waste into high value-added inorganic material.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for preparing a mesoporous-rich fly ash-based MFI structure nano zeolite, specifically comprising the steps of:

(1) Grinding: the fly ash is ground to reach the standard of third-grade ash;

(2) Pickling: Mix the fly ash obtained in step (1) with water and fully dissolve and stir at a stirring speed of 500 rpm, add a certain amount of concentrated hydrochloric acid, continue stirring for 2 to 4 hours, and set aside;

(3) Calcination: Calcining the fly ash obtained in step (2) at high temperature in a muffle furnace, the calcination temperature is 600-850°C, the heating rate is 3°C/min-5°C/min, and the calcination time is 4-6h;

(4) Alkali fusion activation: the fly ash obtained in step (3) is mixed with the inorganic base, by calculation, according to the mol ratio of silicon dioxide in the fly ash and the inorganic base is 0.13～0.26, evenly mixed, fully ground, Put it in a muffle furnace and roast at 550-800°C for 2-6 hours, the heating rate is 3°C/min-5°C/min, after cooling, grind it to get activated fly ash;

(5) Initial sol configuration: the activated fly ash obtained in step (4) is mixed with organic template agent (SDA), inorganic base, co-auxiliary PL and water in a certain proportion and fully dissolved and stirred, and the stirring rate is kept constant. Add a certain amount of silica sol to obtain the initial sol;

(6) Hydrothermal crystallization: Stir and age the initial sol obtained in step (5) at room temperature for 2 to 6 hours at a stirring speed of 1000 to 2000 rpm, and place it in a polytetrafluoroethylene-lined stainless steel reaction kettle after aging. Reactor dynamic rotating crystallization, the rotation speed is 8~16rpm, the crystallization temperature is 140~200℃, and the crystallization time is 48~120h;

(7) Calcination: After the crystallization is completed, the product is cooled to room temperature, filtered, washed and dried, and finally calcined at a high temperature of 450-580°C for 4-8 hours, and the heating rate is 3°C/min-5°C/min. That is, the fly ash-based MFI structure zeolite is obtained.

Specifically, fly ash was pretreated by grinding, pickling, calcination and alkali fusion activation, and was used as the sole source of aluminum and part of the source of silicon in zeolite products. By adding silica sol to adjust the initial sol-silicon-aluminum ratio, by adding organic amine as a structure-directing agent, and adding a co-auxiliary PL composed of water-soluble polyamide and water-soluble organic small molecules, and adjusting the initial sol The silicon-aluminum ratio, Composition and dosage of co-auxiliary PL, MFI structure zeolite was synthesized by constant temperature hydrothermal crystallization under autogenous pressure.

This method not only synthesizes a zeolite molecular sieve with nanometer particle size and rich mesoporous channels, but also realizes the simultaneous utilization of silicon and aluminum resources in fly ash, and provides a high-yield, low-emission, simple fly ash The MFI-based zeolite not only realizes the reuse of waste resources, but also reduces the production cost of the MFI-structure zeolite, which has high economic value. At the same time, the synthesized zeolite has a larger specific surface area and mesopore volume, which is conducive to catalysis Reactivity and Adsorption Properties.

Preferably, in the pickling step (2), the concentration of the hydrochloric acid is 5%-10%, and the solid-liquid ratio (g/ml) of the fly ash to the pickling solution is 1: (10-40).

Preferably, the inorganic base used in the step (4) alkali fusion activation can be one of sodium hydroxide, sodium carbonate and sodium bicarbonate.

Preferably, in step (5), the organic template is a combination of one or more organic amine templates, and the organic amine template is tetramethylammonium hydroxide, tetraethylammonium hydroxide or Tetrapropylammonium hydroxide;

The co-adjuvant PL is composed of water-soluble polyamide and water-soluble organic small molecules, and the water-soluble polyamide is polyvinylpyrrolidone, nitrogen methylpyrrolidone, N-vinylpyrrolidone, N-ethylpyrrolidone One or more mixtures; the water-soluble small organic molecule is one of arginine, histidine, lysine, ethylenediaminetetraacetic acid and polyvinyl alcohol.

Further, the mass ratio of the water-soluble polyamide to the water-soluble small organic molecule is (0.2-3.6):1; the mass ratio of the co-adjuvant PL to the added water is (0.03-0.12):1.

Further, the organic template is tetrapropylammonium hydroxide, the water-soluble polyamide is polyvinylpyrrolidone, and the water-soluble small organic molecule is lysine.

Preferably, the molar ratio of each component in the initial sol is SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.033～0.02:0.15～0.5:0.2～0.5:0.02～0.25:10 ~30.

It can be seen from the above-mentioned technical scheme that, compared with the prior art, a method for preparing a mesoporous-rich fly ash-based MFI structure nano-zeolite has the following excellent effects:

1. The present invention uses the waste fly ash of a coal-fired power plant as a raw material, and then obtains an MFI structure zeolite through dynamic hydrothermal crystallization after grinding, refining, pickling and alkali melting to activate the silicon-aluminum element in the fly ash. It not only realizes the high value of fly ash, but also synthesizes the MFI structure zeolite that can be widely used in catalysis and adsorption.

2. In the present invention, by adding a co-auxiliary agent composed of water-soluble polyamide and water-soluble organic small molecules in the concentrated sol, it also plays the role of introducing mesoporous channels in the crystal while reducing the grain size of the molecular sieve; The method disclosed in the invention can prepare molecular sieves with MFI structure with nano particle size and rich in mesoporous channels.

3. The present invention provides a method for preparing a fly ash-based MFI structure zeolite with a nanometer particle size and rich in mesoporous channels by adding a co-auxiliary PL. On the one hand, the synthesized zeolite has a smaller particle size, This allows more active centers to be exposed; on the other hand, the zeolite is rich in mesoporous channels. Compared with traditional molecular sieves, mesopores can effectively reduce the restriction of micropores on mass transfer, making reactants more accessible to the catalyst. The surface active centers thus enhance the catalytic activity of the material.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is the XRD figure of MFI type zeolite in embodiment 1.

Fig. 2 is the SEM figure of MFI type zeolite in embodiment 1.

Fig. 3 is the BET figure of MFI type zeolite in embodiment 1.

FIG. 4 is an XRD pattern of MFI zeolite in Comparative Example 2.

Figure 5 is the XRD pattern of the MFI type zeolite in Example 3.

Figure 6 is the XRD pattern of the MFI type zeolite in Example 4.

Figure 7 is the XRD pattern of the MFI type zeolite in Example 5.

Figure 8 is the XRD pattern of the MFI type zeolite in Example 6.

FIG. 9 is an XRD pattern of MFI zeolite in Comparative Example 1.

FIG. 10 is a SEM image of the MFI zeolite in Comparative Example 1.

FIG. 11 is a BET diagram of the MFI type zeolite in Comparative Example 1.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The embodiment of the invention discloses a preparation method of a fly ash-based MFI structure nano zeolite rich in mesoporous.

For a better understanding of the present invention, the present invention will be further specifically described below through the following examples, but it should not be construed as a limitation of the present invention. For some non-essential improvements and adjustments made by those skilled in the art according to the above-mentioned content of the invention, It is also considered to fall within the protection scope of the present invention.

In the following, the technical solutions of the present invention will be further described in conjunction with specific embodiments.

At the same time, the prepared MFI type zeolite was tested for its morphology and structure, as follows:

Figure 1, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, and Figure 9 are obtained by using a German BRUKER D8 Focus X-ray diffractometer (XRD), Cu-Kα is the radiation source, the tube voltage is 40KV, and the tube current is 40mA , the scan rate is 2°/min, and the scan angle is scanned at 2θ=5°-50°.

Figure 2 and Figure 10 are tested by JSM-6490LV scanning electron microscope (SEM) of JEOL Ltd. The accelerating voltage is 10-20kV. Before the test, the sample molecular sieve is fully dispersed in the ethanol solution.

Figures 3 and 11 are based on China’s 3H-2000PM1 BEST specific surface area and pore size analyzer (BET). Before the test, they were degassed at 200°C for 4 hours. The specific surface area was calculated using the BET method, and the mesopore ratio was calculated using the BJH method.

Example 1

Embodiment 1 of the present invention discloses a method for preparing a mesoporous-rich fly ash-based MFI nano-zeolite, which specifically includes the following steps:

(1) Use a powder machine to refine the fly ash powder, and screen the finer fly ash through a 200-mesh screen;

(2) In a 500mL three-neck flask, add 10.0g of fly ash material, then add 190.0ml of deionized water and 10.0ml of concentrated hydrochloric acid to fully dissolve and stir at a stirring speed of 500rpm, and continue stirring for 2h; after that, the fly ash Dry after washing;

(3) Calcining the obtained fly ash at a high temperature in a muffle furnace, the calcination temperature is 800°C, and the calcination time is 4h;

(4) Take 1.0 g of calcined fly ash, mix it with 1.2 g of NaOH, grind it fully with an agate mortar, then place it in a muffle furnace for 4 h at 550 ° C, then cool and grind it to obtain activated powder coal ash material;

(5) In a 250mL three-necked flask, add 2.2g of activated fly ash material, then add 18.6ml of deionized water and 27.2ml of tetrapropylammonium hydroxide, and add polyvinylpyrrolidone 1.5g and lysine 2.5 g, start to stir vigorously, the specific speed is 1200rpm, keep the stirring rate constant, add 22.2mL silica sol during stirring, so that the molar ratio of the mixture is SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.02:0.4:0.4:0.16:20, thereby obtaining initial sol;

(6) Stir and age the initial sol at room temperature for 4 hours, the aging stirring speed is 1500rpm, then transfer the initial sol to a polytetrafluoroethylene-lined stainless steel reactor, and the reactor dynamically rotates and crystallizes, and the rotation speed is 12rpm, Crystallized at 175°C for 72h.

(7) After the crystallization, the product was cooled to room temperature, filtered, washed and dried, and finally calcined at 550° C. for 6 hours to obtain the MFI structure zeolite.

The product was characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM). It can be seen from the XRD spectrum that 2θ=7.9°, 8.9°, 23.1°, 23.9° and 24.4° are the characteristic diffraction peaks of the MFI topology, and have higher peak intensities.

Compared with Comparative Example 1 (preparation of MFI zeolite without adding co-adjuvant PL), adding a certain amount of co-adjuvant PL, it can be determined that the obtained sample is still MFI zeolite, with a relative crystallinity of 63.82% and a yield of 72.53%. SEM The picture shows that the sample is evenly dispersed, in the shape of a cuboid or ellipsoid, and the crystal size is about 100-300nm. N ₂ adsorption-desorption experiments show that the specific surface area of the sample is 354.24m ² /g, and the proportion of mesopores reaches 75.61%. From the N ₂ adsorption-desorption curve, it can be seen that the product synthesized by adding co-adjuvant has obvious hysteresis loop , indicating that the product is rich in mesoporous structure.

Example 2

To reduce the silicon-aluminum ratio of ingredients, Embodiment 2 of the present invention discloses a preparation method of a fly ash-based MFI structure zeolite, which specifically includes the following steps:

(1) Use a powder machine to refine the fly ash powder, and screen the finer fly ash through a 200-mesh screen;

(2) In a 500mL three-neck flask, add 10.0g of fly ash material, then add 190.0ml of deionized water and 10ml of concentrated hydrochloric acid to fully dissolve and stir at a stirring speed of 500rpm, and continue stirring for 2h. The fly ash is then washed and dried.

(3) Calcining the obtained fly ash at a high temperature in a muffle furnace, the calcination temperature is 800°C, and the calcination time is 4h;

(4) Take 1.0 g of calcined fly ash, mix it with 1.2 g of NaOH, grind it fully with an agate mortar, then place it in a muffle furnace for 4 h at 550 ° C, then cool and grind it to obtain activated powder coal ash material;

(5) In a 250mL three-necked flask, add 2.2g of activated fly ash material, then add 26.2ml of deionized water and 22.4ml of tetrapropylammonium hydroxide, and add 1.5g of polyvinylpyrrolidone and 2.5g of lysine g, start to stir vigorously, the specific speed is 1200rpm, keep the stirring rate constant, add 16.3mL silica sol during stirring, so that the molar ratio of the mixture is SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.033:0.4:0.4:0.16:20, thereby obtaining initial sol;

(6) Stir and age the initial sol at room temperature for 4 hours, the rotating speed of the aging stirring is 1200rpm, then transfer the initial sol to a polytetrafluoroethylene-lined stainless steel reactor, and the reactor dynamically rotates and crystallizes, and the rotation speed is 12rpm, Crystallized at 175°C for 72h.

(7) After the crystallization, the product was cooled to room temperature, filtered, washed and dried, and finally calcined at 550° C. for 6 hours to obtain the MFI structure zeolite.

The product was characterized by XRD and SEM.

Compared with Comparative Example 1 (no addition of co-adjuvant PL to prepare MFI zeolite), the product is still MFI zeolite when the co-adjuvant PL is added and the silicon-aluminum ratio is reduced to 30, the relative crystallinity is 50.73%, and the yield is 79.67% %, the sample is ellipsoidal, the crystal size is about 200-400nm, the specific surface area of the sample is 326.51m ² /g, and the proportion of mesopores reaches 71.35%.

Example 3

To reduce the amount of auxiliary agent PL in the initial gel, embodiment 3 of the present invention discloses a preparation method of a fly ash-based MFI structure zeolite, which specifically includes the following steps:

(1) Use a powder machine to refine the fly ash powder, and screen the finer fly ash through a 200-mesh screen;

(2) In a 500mL three-neck flask, add 10.0g of fly ash material, then add 190.0ml of deionized water and 10.0ml of concentrated hydrochloric acid to fully dissolve and stir at a stirring speed of 500rpm, and continue stirring for 2h. The fly ash is then washed and dried.

(3) Calcining the obtained fly ash at a high temperature in a muffle furnace, the calcination temperature is 800°C, and the calcination time is 4h;

(4) Take 1.0 g of calcined fly ash, mix it with 1.2 g of NaOH, grind it fully with an agate mortar, then place it in a muffle furnace for 4 h at 550 ° C, then cool and grind it to obtain activated powder coal ash material;

(5) In a 250mL three-necked flask, add 2.2g of activated fly ash material, then add 18.6ml of deionized water and 28.0ml of tetrapropylammonium hydroxide, and add 1.0g of polyvinylpyrrolidone and 1.6 g, start to stir vigorously, the specific speed is 1200rpm, keep the stirring rate constant, add 27.2mL silica sol during stirring, so that the molar ratio of the mixture is SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.02:0.4:0.5:0.1:20, thereby obtaining initial sol;

(6) Stir and age the initial sol at room temperature for 4 hours, the rotating speed of the aging stirring is 1200rpm, then transfer the initial sol to a polytetrafluoroethylene-lined stainless steel reactor, and the reactor dynamically rotates and crystallizes, and the rotation speed is 12rpm, Crystallized at 175°C for 72h.

(7) After the crystallization, the product was cooled to room temperature, filtered, washed and dried, and finally calcined at 550° C. for 6 hours to obtain the MFI structure zeolite.

The product was characterized by XRD and SEM.

Compared with Comparative Example 1 (no addition of co-adjuvant PL to prepare MFI zeolite), it is found that the product is still MFI zeolite when the ratio of initial gel co-auxiliary PL and silicon is increased to 0.1, the relative crystallinity is 64.11%, and the yield is 65.16%, the sample is ellipsoidal, the crystal size is about 300-700nm, the specific surface area of the sample is 301.97m ² /g, and the proportion of mesopores reaches 62.31%.

Example 4

To increase the amount of auxiliary agent PL in the initial gel, embodiment 4 of the present invention discloses a preparation method of a fly ash-based MFI structure zeolite, which specifically includes the following steps:

(1) Use a powder machine to refine the fly ash powder, and screen the finer fly ash through a 200-mesh screen;

(2) In a 500mL three-neck flask, add 10.0g of fly ash material, then add 190.0ml of deionized water and 10.0ml of concentrated hydrochloric acid to fully dissolve and stir at a stirring speed of 500rpm, and continue stirring for 2h. The fly ash is then washed and dried.

(3) Calcining the obtained fly ash at a high temperature in a muffle furnace, the calcination temperature is 800°C, and the calcination time is 4h;

(4) Take 1.0 g of calcined fly ash, mix it with 1.2 g of NaOH, grind it fully with an agate mortar, then place it in a muffle furnace for 4 h at 550 ° C, then cool and grind it to obtain activated powder coal ash material;

(5) In a 250mL three-necked flask, add 2.2g of activated fly ash material, then add 18.6ml of deionized water and 22.4ml of tetrapropylammonium hydroxide, and add 2.0g of polyvinylpyrrolidone and 3.1g of lysine g, start to stir vigorously, the specific speed is 1200rpm, keep the stirring rate constant, add 27.2mL silica sol during stirring, so that the molar ratio of the mixture is SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.02:0.4:0.4:0.2:20, thereby obtaining initial sol;

(6) Stir and age the initial sol at room temperature for 4 hours, the rotating speed of the aging stirring is 1200rpm, then transfer the initial sol to a polytetrafluoroethylene-lined stainless steel reactor, and the reactor dynamically rotates and crystallizes, and the rotation speed is 12rpm, Crystallized at 175°C for 72h.

(7) After the crystallization, the product was cooled to room temperature, filtered, washed and dried, and finally calcined at 550° C. for 6 hours to obtain the MFI structure zeolite.

The product was characterized by XRD.

Compared with Comparative Example 1 (no addition of co-adjuvant PL to prepare MFI zeolite), it is found that the product is still MFI zeolite when the ratio of initial gel co-adjuvant PL to silicon is increased to 0.2. The product is still MFI zeolite, and the relative crystallinity decreases to 39.27%, the yield was 76.59%, the crystal size was about 300-500nm, the specific surface area of the sample was 276.85m ² /g, and the proportion of mesopores reached 65.43%.

Example 5

Only adding polyvinylpyrrolidone in the co-adjuvant PL, embodiment 5 of the present invention discloses a preparation method of a fly ash-based MFI structure zeolite, which specifically includes the following steps:

(1) Use a powder machine to refine the fly ash powder, and screen the finer fly ash through a 200-mesh screen;

(2) In a 500mL three-neck flask, add 10.0g of fly ash material, then add 190.0ml of deionized water and 10.0ml of concentrated hydrochloric acid to fully dissolve and stir at a stirring speed of 500rpm, and continue stirring for 2h. The fly ash is then washed and dried.

(3) Calcining the obtained fly ash at a high temperature in a muffle furnace, the calcination temperature is 800°C, and the calcination time is 4h;

(4) Take 1.0 g of calcined fly ash, mix it with 1.2 g of NaOH, grind it fully with an agate mortar, then place it in a muffle furnace for 4 h at 550 ° C, then cool and grind it to obtain activated powder coal ash material;

(5) In a 250mL three-necked flask, add 2.2g of activated fly ash material, then add 18.6ml of deionized water and 22.4ml of tetrapropylammonium hydroxide, and add 1.5g of polyvinylpyrrolidone, and start vigorously stirring, The specific rotation speed is 1200rpm, and the stirring rate is kept constant. During the stirring process, 27.2mL of silica sol is added, so that the molar ratio of the mixture is SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.025: 0.4:0.4:0.0000125:20 to obtain the initial sol;

(6) Stir and age the initial sol at room temperature for 4 hours, the rotating speed of the aging stirring is 1200rpm, then transfer the initial sol to a polytetrafluoroethylene-lined stainless steel reactor, and the reactor dynamically rotates and crystallizes, and the rotation speed is 12rpm, Crystallized at 175°C for 72h.

(7) After the crystallization, the product was cooled to room temperature, filtered, washed and dried, and finally calcined at 550° C. for 6 hours to obtain the MFI structure zeolite.

The product was characterized by XRD.

Compared with Comparative Example 1 (no co-adjuvant PL was added to prepare MFI zeolite), the product was still MFI zeolite when the co-adjuvant PL only added polyvinylpyrrolidone, the relative crystallinity was 69.20%, the yield was 67.32%, and the crystal size was about 500-800nm, the specific surface area of the sample is 267.58m ² /g, and the proportion of mesopores reaches 52.33%.

Example 6

Only add lysine in the co-adjuvant PL, the embodiment of the present invention 6 discloses a preparation method of a fly ash-based MFI structure zeolite, which specifically includes the following steps:

(1) Use a powder machine to refine the fly ash powder, and screen the finer fly ash through a 200-mesh screen;

(2) In a 500mL three-neck flask, add 10.0g of fly ash material, then add 190.0ml of deionized water and 10.0ml of concentrated hydrochloric acid to fully dissolve and stir at a stirring speed of 500rpm, and continue stirring for 2h. The fly ash is then washed and dried.

(3) Calcining the obtained fly ash at a high temperature in a muffle furnace, the calcination temperature is 800°C, and the calcination time is 4h;

(4) Take 1.0 g of calcined fly ash, mix it with 1.2 g of NaOH, grind it fully with an agate mortar, then place it in a muffle furnace for 4 h at 550 ° C, then cool and grind it to obtain activated powder coal ash material;

(5) In a 250mL three-necked flask, add 2.2g of activated fly ash material, then add 18.6ml of deionized water and 22.4ml of tetrapropylammonium hydroxide, and add 2.5g of lysine, and start vigorously stirring, The specific rotation speed is 1200rpm, and the stirring rate is kept constant. During the stirring process, 27.2mL of silica sol is added, so that the molar ratio of the mixture is SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.02: 0.4:0.4:0.16:20 to obtain the initial sol;

(6) The initial sol was stirred and aged at room temperature for 4 hours, and the rotating speed of the aging stirring was 1200rpm, and then the initial sol was transferred to a polytetrafluoroethylene-lined stainless steel reactor, and the reactor was dynamically rotated and crystallized, and the rotational speed was 12rpm. Crystallized at 175°C for 72h.

(7) After the crystallization, the product was cooled to room temperature, filtered, washed and dried, and finally calcined at 550° C. for 6 hours to obtain the MFI structure zeolite.

The product was characterized by XRD.

Compared with Comparative Example 1 (no co-adjuvant PL was added to prepare MFI zeolite), the product was still MFI zeolite when the co-auxiliary PL only added lysine, the relative crystallinity was 74.18%, the yield was 74.23%, and the crystal size was about 500-800nm, the specific surface area of the sample is 274.68m ² /g, and the proportion of mesopores reaches 53.45%.

Comparative example 1

Comparative example 1 of the present invention directly prepared MFI structure zeolite by adopting the method without adding co-auxiliary PL, specifically comprising the following steps:

(1) Use a powder machine to refine the fly ash powder, and screen the finer fly ash through a 200-mesh screen;

(2) In a 500mL three-neck flask, add 10.0g of fly ash material, then add 190.0ml of deionized water and 10.0ml of concentrated hydrochloric acid to fully dissolve and stir at a stirring speed of 500rpm, and continue stirring for 2h. The fly ash is then washed and dried.

(3) Calcining the obtained fly ash at a high temperature in a muffle furnace, the calcination temperature is 800°C, and the calcination time is 4h;

(4) Take 1 g of calcined fly ash, mix it with 1.2 g of NaOH, grind it thoroughly with an agate mortar, then place it in a muffle furnace for 4 h at 550 ° C, then cool and grind it to obtain activated pulverized coal gray material;

(5) In a 250mL three-necked flask, add 2.2g of activated fly ash material, then add 18.6ml of deionized water and 22.4ml of tetrapropylammonium hydroxide, start stirring vigorously, the specific speed is 1800rpm, and maintain the stirring rate Invariably, 27.2 mL of silica sol was added during stirring so that the molar ratio of the mixture was SiO ₂ :Al ₂ O ₃ :NaOH:SDA:H ₂ O=1:0.02:0.4:0.4:20, thereby obtaining the initial sol ;

(6) Stir and age the initial sol at room temperature for 4 hours, the rotating speed of the aging stirring is 1800rpm, then transfer the initial sol to a stainless steel reaction kettle lined with polytetrafluoroethylene, and the reaction kettle dynamically rotates and crystallizes, and the rotation speed is 12rpm, Crystallized at 175°C for 72h.

(7) After the crystallization, the product was cooled to room temperature, filtered, washed and dried, and finally calcined at 550° C. for 6 hours to obtain the MFI structure zeolite.

The products were characterized by XRD, SEM and BET.

The yield of the MFI molecular sieve prepared without adding co-auxiliary PL was 80.49%. It can be observed from the SEM electron microscope pictures that the sample is irregular in shape and different in size. The particle size of the sample is 200-1000nm. N ₂ adsorption-desorption experiments show that the specific surface area of the sample is 319.22m ² /g, and the proportion of mesopores is 36.85%. From the N ₂ adsorption-desorption curve, it can be seen that the product without co-adjuvant has no obvious hysteresis loop , indicating that the product has less mesopores.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. a kind of preparation method of the fly ash base MFI structure nano zeolite that is rich in mesoporous, is characterized in that, specifically comprises the steps: (1) Grinding: the fly ash is ground to reach the standard of third-grade ash; (2) Pickling: Mix the fly ash obtained in step (1) with water and fully dissolve and stir, then add concentrated hydrochloric acid, continue stirring for 2 to 4 hours, and set aside; (3) calcining: calcining the fly ash obtained in step (2) at high temperature; (4) Alkali fusion activation: the fly ash obtained in step (3) is mixed with an inorganic base, fully ground and roasted to obtain activated fly ash; (5) Initial sol configuration: Mix the activated fly ash obtained in step (4) with organic template SDA, inorganic base, co-auxiliary PL and water and fully dissolve and stir, then add silica sol under the premise of maintaining the stirring rate , to obtain the initial sol; (6) Hydrothermal crystallization: Stir and age the initial sol obtained in step (5) at room temperature for 2 to 6 hours, and then place it in a reactor for dynamic rotational crystallization; (7) Calcination: After the crystallization in step (6), the product is cooled to room temperature, filtered, washed and dried, and finally calcined at a high temperature to obtain the mesoporous-rich fly ash-based MFI nano-zeolite. 2. the preparation method of a kind of mesoporous-rich fly ash base MFI structure nano zeolite according to claim 1 is characterized in that, in step (2) pickling, the concentration of described hydrochloric acid is 5%～10 %, the solid-to-liquid ratio of fly ash to pickling solution is 1: (10-40). 3. the preparation method of a kind of mesoporous-rich fly ash base MFI structure nano zeolite according to claim 1, is characterized in that, the calcination temperature in step (3) is 600 ℃～850 ℃, and the calcination time is 4～6h, the calcining temperature in step (4) is 550°C～800°C, the calcining time is 2～6h, the calcining temperature in step (7) is 450°C～580°C, and the calcining time is 4～8h; The heating rate in the steps is 3° C./min to 5° C./min. 4. the preparation method of a kind of mesopore-rich fly ash base MFI structure nano zeolite according to claim 1 is characterized in that, in step (4), described inorganic base is sodium hydroxide, sodium carbonate or Sodium bicarbonate, and according to the molar ratio of silicon dioxide in fly ash to inorganic base (0.13-0.26): 1, mix evenly. 5. the preparation method of a kind of mesoporous-rich fly ash base MFI structure nano zeolite according to claim 1, is characterized in that, in step (5), described organic template is one or more organic A combination of amine templates, wherein the organic amine templates are tetramethylammonium hydroxide, tetraethylammonium hydroxide or tetrapropylammonium hydroxide; The co-adjuvant PL is composed of water-soluble polyamide and water-soluble organic small molecules, and the water-soluble polyamide is polyvinylpyrrolidone, nitrogen methylpyrrolidone, N-vinylpyrrolidone, N-ethylpyrrolidone One or more mixtures; the water-soluble small organic molecule is one of arginine, histidine, lysine, ethylenediaminetetraacetic acid and polyvinyl alcohol. 6. according to claim 1 or 5 described a kind of preparation method of the fly ash base MFI structure nano zeolite that is rich in mesoporous, it is characterized in that, in step (5), the mol ratio of each composition in the described initial sol SiO ₂ :Al ₂ O ₃ :NaOH:SDA:PL:H ₂ O=1:0.033～0.02:0.15～0.5:0.2～0.5:0.02～0.25:10～30. 7. the preparation method of a kind of mesopore-rich fly ash base MFI structure nano zeolite according to claim 5, is characterized in that, the mass ratio of described water-soluble polyamide and described water-soluble organic small molecule is (0.2-3.6):1; the mass ratio of the co-adjuvant PL to the added water is (0.03-0.12):1. 8. the preparation method of a kind of mesoporous-rich fly ash base MFI structure nano zeolite according to claim 1, is characterized in that, the aging stirring speed in step (6) is 1000～2000r/min, dynamic rotation The crystallization speed is 8-16r/min; the crystallization temperature is 140°C-200°C, and the crystallization time is 48-120h.

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