KR101137985B1 - Process for producing binder-free ZSM-5 zeolite in small crystal size - Google Patents

Abstract

The present invention relates to a method for preparing a binder-free ZSM-5 zeolite having a small crystal size. The present invention is mainly used to solve the problems in practical use, for example, the problem that the zeolite powder is difficult to recover, easily inactivated and aggregated, and the effective surface area is reduced and diffusion limit occurs by adding a binder in the molding process. do. Integral ZSM with small crystal size by using diatomaceous earth or silica aerogel as the main starting material in this invention, adding seed crystal aligning agent, silica sol and sodium silicate for kneading and shaping, and then gas phase-solid crystallization with organic amine and water vapor The conversion to -5 solves the above problems better. This method can be used to industrially produce small crystal size ZSM-5 molecular sieve catalysts.

ZSM-5 Zeolite, Seed Crystal Alignment Agent, Binder

Description

Process for producing binder-free ZSM-5 zeolite with small crystal size {Process for producing binder-free ZSM-5 zeolite in small crystal size}

1 is an XRD spectrogram of the product of Example 3. FIG.

FIG. 2 is an SEM photograph of the surface layer of the creature of Example 3. FIG.

3 is a SEM photograph of the product of Example 6.

The present invention relates to a method for preparing a binder-free ZSM-5 zeolite having a small crystal size.

Zeolite molecular sieves are widely used in the field of catalysts because of their homogeneous and ordered micropores, their specific surface area and their excellent hydrothermal stability. Small crystal size zeolites have short interdiffusion pore channels and large external areas, which are advantageous in improving physical properties of zeolites by increasing the chance of contact between active sites and reactants in the micropores. The zeolites exhibit unique advantages in reactions such as selectivity to certain macromolecules, relatively high catalytic activity, longer catalyst life and the like. However, the size of the zeolite is too small to be practical for practical application. Moreover, these zeolites are difficult to recover and are easily inactivated and aggregated. It is necessary to add a binder during the molding process, which reduces the effective surface area and causes diffusion limitations. Binder-free zeolite molecular sieves are zeolite particles having a high zeolite content that do not contain an inert binder or contain a small amount of inert binder. They therefore have more effective surface area and better catalytic properties.

Diatomaceous earth is a mineral rich in aluminosilicates. Anderson is a secondary growth method, in which a diatomaceous earth supported in a zeolite seed crystal grows under the action of an external silica source and an alumina source to form a zeolite film on the surface of the diatomaceous earth. SM Holmes et al. Stud . Surf . Sci. Catal . , 2001, 135 , 296.]. Under the premise that diatomaceous earth has a characteristic multilevel pore structure, Wang has crystal transitioned the diatomaceous earth into a zeolite material having a multilevel pore structure [YJ Wang et al., J. Mater . Chem. , 2002, 12, 1812.]

Due to the unique pore channel structure and better crystallinity, ZSM-5 molecular sieves have become a very important form-selective catalyst material and are widely used for organic catalytic conversion. The binder conversion method is one of the methods used for preparing binder-free zeolite molecular sieves. Long Inkai mixes ZSM-5 type hydrophobic silicon zeolite powder with a binder containing silicon dioxide, molds the mixture, dries it, then crystallizes and calcines in an aqueous solution of organic amine or quaternary ammonium or in steam to make it binder-free. A method for producing a ZSM-5 type hydrophobic silicon zeolite is disclosed. Long. YC, Binder-Free Hydrophobic Silicon Zeolite Adsorbent and Preparation One Patent No: ZL 94112035 X]. US5665325 and US6458736 disclose a process for preparing binder-free MFI zeolites and use in hydrocarbon catalysis. The method comprises first preparing an MFI zeolite powder, shaping it into amorphous silicon oxide and converting the shaped product into MFI having a small crystal size by hydrothermal crystallization, where the newly formed zeolite phase has a large crystal size As it grows around the initial zeolite molecular sieve, they are interwoven together. In the process, the initial zeolite powder needs to be prepared first, mixed with a binder for shaping and then crystallized. As the main material, diatomaceous earth, carbon white or mixtures thereof are kneaded with a seed crystal orienting agent and an appropriate amount of silica sol or water glass to form. The molded product is then converted to an integrated ZSM-5 binder-free molded zeolite with small crystal size. In this way, silica and alumina materials are easily and simply converted to ZSM-5 binder-free zeolites with small crystal sizes. The method of the present invention can be an economical method for preparing zeolite molecular sieve catalyst materials. Furthermore, integrated ZSM-5 binder-free shaped zeolites with small crystal sizes have more macropore structures and can have a synergistic effect on the actual catalytic reaction with the micropores of the zeolite crystals. For example, micropores are used as reaction sites and macropores are used as transport channels for reaction molecules to remove diffusion limitations and effectively utilize zeolites.

In the disclosure of prior art ZSM-5 binder-free shaped zeolites, a significant amount of zeolite initial powder needs to be incorporated into precursor preparation. Thus, some problems are complicated: manufacturing method; Pollutants such as wastewater can be produced by hydrothermal crystallization; There may be a problem that the crystallite size of the resulting zeolite may be limited for some applications. In order to solve the above problems of the prior art, a new method for producing a small crystal size ZSM-5 zeolite is provided. The method is simple in the manufacturing process, produces no waste, uses readily available materials and has a zeolite particle size adjusted to fall within the submicron level. Moreover, the above production method can be used to convert the starting material into a binder-free ZSM-5 zeolite with a small crystal size in a one-off way, and the product has the advantage of not containing an inert binder. .

In order to solve the above technical problem, the following technical solution is used in the present invention. The ZSM-5 zeolite manufacturing method having a small crystal size uses diatomaceous earth or carbon white as the silica source, and aluminum oxide, aluminum salt or aluminate as the aluminum raw material, and a seed crystal aligning agent and an extrusion aid as silica sol or water. Used in amounts necessary for kneading and shaping with glass to obtain a precursor mixture having a weight ratio of X Na ₂ O: Y Al ₂ O ₃ : 100 SiO ₂ , where X is greater than 0 and less than 16 and Y is greater than 0 and less than 6 And then gas phase-solid crystallization with organic amine and water vapor to convert to a binder-free ZSM-5 shaped zeolite having a small crystal size, wherein the crystallization is carried out at 120-200 ° C. for 48-240 hours, The seed crystallization agent was obtained by aging a mixture of (TPA) ₂ O, SiO ₂ and H ₂ O having a molecular ratio (molar ratio) of 1: 2-10: 60-150 at 50-100 ° C. for 12-240 hours. Where TPA is La shows a profile ammonium.

In the above technical solution the seed crystal aligning agent is preferably a colloidal liquid-containing nano ZSM-5 zeolite or ZSM-5 primary structure and is added in an amount of 1.0-50% by weight of the precursor mixture. The organic amine is preferably at least one selected from the group consisting of ethylamine, n-propylamine, n-butylamine, ethylenediamine, triethylamine and hexanediamine. Vapor-solid phase crystallization here is preferably carried out at 140-180 ° C. for 72-180 hours. ZSM-5 zeolites having a small crystal size preferably have a particle size of less than 1 μm. The extrusion aid is also at least one selected from the group consisting of sesbania powder, starch, activated carbon, polyethylene glycol, polyacrylamide and polyvinyl alcohol and preferably 0.1-4% by weight of the precursor cp mixture.

Since the self-made seed crystal aligning agent is added during the kneading and forming of the reactants, the seed crystal aligning agent prepared according to the present invention contains a considerable amount of ZSM-5 primary and secondary structural units. The seed crystal aligning agent may be uniformly distributed in the molded material during the kneading and forming process. In gas phase-solid crystallization, the ZSM-5 zeolite primary and secondary structural units become crystal nuclei of ZSM-5 zeolite for crystallization. Although the seed crystal aligning agent is small, it plays an important role in inducing the growth of silica alumina material on its surface, eliminating nucleation growth period, increasing conversion speed, shortening crystallization time, and stray ) Production of crystals can be suppressed and the particle size of the crystals can be reduced. Moreover, the zeolite crystals growing around the crystal nuclei can be intertwined due to spatial limitations so that the seed crystallization agent can improve the strength of the resulting integrated binder-free ZSM-5 zeolite to favor practical applications and have better technical effects. Can be achieved.

1 shows that the product of Example 3 is ZSM-5 zeolite.

2 shows that ZSM-5 zeolite has a crystal size of about 200 nm.

3 shows that the starting materials in the product, ie diatomaceous earth, carbon white and binder-silica sol, are converted to ZSM-5 zeolite particles of 100-500 nm particle size, showing that the zeolite particles are intertwined with each other.

The present invention will be described in more detail with reference to the following examples.

Example 1

A mixture of a tetrapropylammonium hydroxide (TPAOH) solution, tetraethyl orthosilicate (TEOS) and a molar ratio of (TPA) ₂ O: 5.5 TEOS: 90 H ₂ O) of water was mixed homogeneously. After three days of aging, the mixture was refluxed at 80 ° C. to obtain a seed crystal aligning agent.

Examples 2-4

20 g of the seed crystal aligning agent prepared in Example 1 and 15 g (40 wt%) of silica sol were 300 g of diatomaceous earth (87.74 wt% of SiO ₂ , 1.44 wt% of Al, 0.18 wt% of Ca, 0.80 wt% of Fe, K 0.24 wt%, Mg 0.30 wt%, and 0.09 wt% Na). Then the mixture was kneaded to form a cylinder by adding 120 g of water.

A mixture of 5 g of triethylamine, 10 g of ethylenediamine and 15 g of distilled water was previously added to the reaction vessel. 30 g of the cylindrical product obtained above was placed on a stainless steel screen in a reaction vessel. The gas phase-solid treatment was performed at 180 ° C. for 3, 5 and 7 days after sealing the reaction vessel. The obtained product was removed, washed with distilled water, dried and calcined in air at 550 ° C. XRD spectrogram of the product after 3 days treatment indicated that ZSM-5 zeolite crystals were produced. The crystallinity of the product after 5 days of treatment was greatly increased and the diatomaceous earth was completely converted. SEM images of the surface layer of the formed zeolite showed that the ZSM-5 zeolite crystals had a width of about 200 nm, while SEM images of the cross-section showed that the ZSM-5 zeolite crystals had a width of about 200-500 nm and the nitrogen adsorption at low temperature. When measured, it showed that it had a surface area of about 225 m ² / g. After 7 days of treatment the crystallinity of the product no longer increased.

Example 5-7

7.5 g of sesbania powder and 20 g of aluminum sulfate solution (formed by dissolving 20 g of Al ₂ (SO ₄ ) ₃ .18H ₂ O) in 50 g of water) and 33 g of the seed crystal aligning agent prepared in Example 1 were used for 80 g of diatomaceous earth and 120 g of silica aerosol. Was added to the mixture. 225 g of silica sol (40 wt.%) Was then added to knead the mixture into a cylinder.

A mixture of 10 g of triethylamine, 12.5 g of ethylenediamine, and 8 g of distilled water was previously added to the reaction vessel. 50 g of the cylindrical product prepared above was placed on a stainless steel screen in a reaction vessel. The gas phase-solid treatment was performed at 180 ° C. for 3, 5 and 7 days after sealing the reaction vessel. The reaction product was removed, washed with distilled water, dried and calcined at 550 ° C. in air. The XRD spectrogram showed that all of the products were ZSM-5 zeolites, and the molded zeolites showed a crystal size of less than 500 nm.

Example 8-11

10 g of sesbania powder and aluminum sulfate solution [formed by dissolving 27.8 g of Al ₂ (SO ₄ ) ₃ .18H ₂ O) in 50 g of water] and 40 g of the seed crystal aligning agent prepared in Example 1 were added to 250 g of silica aerosol. . 470 g of silica sol (40 wt%) was then added to kneaded the mixture to form.

A mixture of 5 g of triethylamine, 7 g of ethylenediamine, and 10.5 g of distilled water was previously added to the reaction vessel. 50 g of the cylindrical product prepared above was placed on a stainless steel screen in a reaction vessel. The gas phase-solid treatment was performed at 180 ° C. for 2, 3, 5 and 7 days after sealing the reaction vessel. The reaction product was removed, washed with distilled water, dried and calcined at 550 ° C. in air. The XRD spectrogram showed that all of the products were ZSM-5 zeolites, and the molded zeolites showed a crystal size of less than 600 nm.

 Example 12

A mixture of a tetrapropylammonium bromide (TPABr) solution and a molar ratio of (TPA) ₂ O: 4 SiO ₂ : 100 H ₂ O) of silica sol was stirred at room temperature for 24 hours. The pH was adjusted to 12 with ammonia water. The mixture was then aged at 60 ° C. for 140 hours to form a seed crystal aligning agent.

Example 13-15

12 g of sesbania powder and aluminum sulfate solution [formed by dissolving 27.8 g of Al ₂ (SO ₄ ) ₃ .18H ₂ O) in 50 g of water] and 80 g of the seed crystal aligning agent prepared in Example 12 were added to 250 g of silica aerosol. . Then, 400 g of silica sol (40 wt%) was added to kneaded the mixture to form a cylinder.

A mixture of 8 g of triethylamine, 7 g of ethylenediamine, and 8 g of distilled water was previously added to the reaction vessel. 50 g of the cylindrical product prepared above was placed on a stainless steel screen in a reaction vessel. The gas phase-solid treatment was performed at 200 ° C. for 4, 6 and 9 days after sealing the reaction vessel. The reaction product was removed, washed with distilled water, dried and calcined at 550 ° C. in air. The XRD spectrogram showed that all of the products were ZSM-5 zeolites and the molded zeolites exhibited a crystal size of less than 800 nm.

Example 16-17

8.0 g of sesbania powder and an aluminum sulfate solution [formed by dissolving 18 g of Al ₂ (SO ₄ ) ₃ .18H ₂ O) in 50 g of water] and 40 g of the seed crystal aligning agent prepared in Example 1 were used with 80 g of diatomaceous earth, silica aerosol and To 120 g of carbon white was added. Then, 220 g of silica sol (40 wt%) was added to kneaded the mixture and molded.

A mixture of 8 g of triethylamine and 7 g of distilled water was previously added to the reaction vessel. 50 g of the cylindrical product prepared above was placed on a stainless steel screen in a reaction vessel. After sealing the reaction vessel, gas-phase treatment was performed at 160 ° C. for 4 and 6 days. The reaction product was removed, washed with distilled water, dried and calcined at 550 ° C. in air. The XRD spectrogram showed that all of the products were ZSM-5 zeolites and the molded zeolites exhibited a crystal size of less than 500 nm.

Example 18-19

10 g of sesbania powder and sodium aluminate solution (formed by dissolving 39.1 g of NaAlO ₂ (Al ₂ O ₃ is present in an amount greater than 43% by weight) in 80 g of water) and 40 g of the seed crystal aligning agent prepared in Example 1 To 180 g of silica aerosol was added. 275 g of silica sol (40% by weight) was then added to kneaded the mixture to form.

A mixture of 35 g of ethylenediamine and 5 g of distilled water was previously added to the reaction vessel. 150 g of the cylindrical product prepared above was placed on a stainless steel screen in a reaction vessel. The gas phase-solid treatment was performed at 160 ° C. for 5 and 7 days after sealing the reaction vessel. The reaction product was removed, washed with distilled water, dried and calcined at 550 ° C. in air. The XRD spectrogram showed that all of the products were ZSM-5 zeolites, and the molded zeolites showed a crystal size of less than 500 nm.

 Example 20-21

10 g of sesbania powder and an aluminum sulfate solution (formed by dissolving 109 g of Al ₂ (SO ₄ ) ₃ .18H ₂ O) in 140 g of water) and 40 g of the seed crystal aligning agent prepared in Example 1 were added to 180 g of the silica aerosol. Then 200 g of waterglass (where silicon dioxide was present in an amount of 30% by weight and Na ₂ O was present in an amount of 7.0% by weight) was kneaded and molded.

A mixture of 35 g of ethylenediamine and 5 g of distilled water was previously added to the reaction vessel. 150 g of the cylindrical product prepared above was placed on a stainless steel screen in a reaction vessel. The gas phase-solid treatment was performed at 160 ° C. for 4 and 6 days after sealing the reaction vessel. The reaction product was removed, washed with distilled water, dried and calcined at 550 ° C. in air. The XRD spectrogram showed that all of the products were ZSM-5 zeolites, and the molded zeolites showed a crystal size of less than 500 nm.

Comparative Example 1-3

80 g of silica sol (40 wt%) was added to 300 g of diatomaceous earth to obtain a mixture. Then an appropriate amount of water was added to knead the mixture.

A mixture of 4 g of triethylamine, 5 g of ethylenediamine, and 4 g of distilled water was previously added to the reaction vessel. 30 g of the cylindrical product prepared above was placed on a stainless steel screen in a reaction vessel. The gas phase-solid treatment was performed at 180 ° C. for 3, 5 and 7 days after sealing the reaction vessel. The reaction product was removed, washed with distilled water, dried and calcined at 550 ° C. in air. The XRD spectrogram showed that no ZSM-5 zeolite crystals were produced, indicating that the seed crystal orientation has the necessary inducing effect in the method of the present invention.

The production method of the present invention makes it possible to economically and simply produce a binder-free ZSM-5 zeolite having a small crystal size without generating waste.

Claims (7)

Diatomaceous earth or carbon white is used as the silica source and aluminum oxide, aluminum salt or aluminate is used as the aluminum source, and kneading and molding is carried out to obtain a precursor mixture in a weight ratio of X Na ₂ O: Y Al ₂ O ₃ : 100 SiO ₂ . Add the seed crystal aligning agent and the extrusion aid with silica sol or water glass in the required amount, where X is greater than 0 and less than 16 and Y is greater than 0 and less than 6 and gas phase-solid crystallization with organic amine and water vapor Converting to a small binder-free ZSM-5 shaped zeolite, wherein the crystallization is carried out at 120-200 ° C. for 48-240 hours and the seed crystal aligning agent has a molar ratio of 1: 2-10: 60-150 A mixture of (TPA) ₂ O, SiO ₂ and H ₂ O is obtained by aging at 50-100 ° C. for 12-240 hours, where TPA represents tetrapropylammonium with a small crystal size binder-free ZSM -5 zeolite manufacturing method. The method of claim 1 wherein the seed crystal aligning agent is added in an amount of 1.0-50% by weight of the precursor mixture. The method of claim 1 wherein the organic amine is selected from the group consisting of ethylamine, n-propylamine, n-butylamine, ethylenediamine, triethylamine and hexanediamine. A process according to claim 1, wherein the gas phase-solid crystallization is performed at 140-180 ° C. The method of claim 1 wherein the vapor-solid crystallization lasts for 72-180 hours. The method of claim 1, wherein the small crystal size ZSM-5 zeolite has a particle size of less than 1 μm. The method of claim 1, wherein the extrusion aid is at least one selected from the group consisting of sesbania powder, starch, activated carbon, polyethylene glycol, polyacrylamide and polyvinyl alcohol, in an amount of 0.1-4% by weight of the precursor mixture Characterized by being present.

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