CN103073019A - Hierarchical pore zeolite molecular sieve preparation method - Google Patents

Abstract

The invention relates to a hierarchical pore zeolite molecular sieve and a preparation method, which belongs to the fine chemical and inorganic material field. The invention relates to a ZSM-12 zeolite molecular sieve having intergranular mesoporous and macroporous and a preparation method, the invention is characterized in that a traditional template tetraethyl ammonium bromide TEABr or a tetraethyl ammonium hydroxide TEAOH synthesized by zeolite are taken as a template to synthesize the hierarchical pore zeolite molecular sieve, the problem that the synthesis of the hierarchical pore zeolite molecular sieve employs post-treatment or expensive hard template to prepare the mesoporous can be solved, according to the material, the diffusion path is substantially shortened and the acid site accessibility is enhanced, and the material has important utility value on fine chemical, catalysis of petroleum chemical, adsorption and separating.

Description

A kind of preparation method of hierarchical pore zeolite molecular sieve

technical field

The invention discloses a method for preparing a multi-level pore zeolite molecular sieve, which belongs to the field of fine chemicals and inorganic materials, and specifically relates to a method for preparing a ZSM-12 zeolite molecular sieve with intercrystalline mesopores or macropores.

Background technique

As a microporous material, zeolites are widely used in the fields of catalysis, adsorption and separation. This material has demonstrated unique acid-catalytic and shape-selective properties in the fields of oil refining, basic chemistry, and fine chemistry. In addition to providing shape-selective performance, the intricate pore system in the molecular size range (0.3-1.5nm) in zeolite not only restricts the diffusion of reactive molecules passing through its channels, but also, when the spatial size of the reactive molecules passing through the channels is in line with the Close pore sizes in zeolites also induce high back pressures in the flow system, limiting the transport rate of reacting molecules within the zeolite crystals. On the one hand, at a given temperature and pressure, it is almost impossible to increase the diffusion rate inside the zeolite crystal without changing the internal structure of the zeolite; on the other hand, the intricate pore structure inside the zeolite cannot make its acid sites Relatively large reactive molecules are fully utilized. Therefore, the synthesis of zeolite materials containing a considerable amount of intracrystalline or intercrystalline mesoporous or macroporous structures has become a research hotspot because it can improve the diffusion properties of materials and increase the acid site accessibility of catalysts. .

The method of combining mesopores and micropores on the same zeolite crystal can be produced by superheated steam, acid etching or alkaline etching. In recent years, the synthesis of hierarchically porous zeolites using the template method is also very effective. However, the post-treatment method to prepare mesoporous zeolite molecular sieves will reduce the acidity of the catalyst, and at the same time it is easy to form mesoporous channels that cannot penetrate the catalyst as a whole; the use of hard templates to synthesize mesoporous zeolites is very expensive due to the high cost of hard templates. It is difficult to realize its industrialization; in the past ten years, researchers have spent considerable energy to synthesize nano-sized zeolite crystals in order to improve the diffusion effect of zeolite. However, the synthesis and preparation of this nano-sized zeolite has encountered many difficulties in the actual research work. The most notable problem is that the solid-liquid mixture after synthesis is difficult to separate, which greatly limits the fine grain size. The application of zeolite in practice ( Langmuir.21 , 2005, 504).

There are few reports on the formation of mesopores on ZSM-12 single crystals. Wei et al. ( Micropor. Mesopor. Mater. , 97, 2006, 97) used alkali etching to treat the previously synthesized ZSM-12 zeolite with alkali. A mesoporous ZSM-12 zeolite molecular sieve with mesoporous pores distributed between 15 and 20 nanometers was prepared; Wei et al. ( Micropor. Mesopor. Mater. , 89, 2006, 170) also used carbon black as a template to synthesize pore Mesoporous ZSM-12 molecular sieve materials distributed in the range of 10 to 50 nanometers. Whether it is alkali treatment or carbon black as a hard template, mesopores are formed on large single crystals. The former is easy to form pores that cannot penetrate the entire crystal particle. The process is often accompanied by the release of aluminum species, which weakens the acid center of the catalyst framework; and the use of hard templates to synthesize mesoporous zeolites is difficult to achieve industrialization due to the extremely high cost of hard templates. Therefore, there is an urgent need for a simple, large-scale method to produce and prepare mesoporous zeolite materials.

Contents of the invention

The purpose of the preparation method of a kind of multi-stage pore zeolite molecular sieve of the present invention is, in order to solve the synthesis of the multi-stage pore zeolite molecular sieve material that exists in the above-mentioned prior art either through aftertreatment or utilize expensive hard templating agent to realize the manufacture of mesopores Problem, thereby disclosing a method for synthesizing hierarchically porous zeolite molecular sieves using traditional templates synthesized by zeolites, tetraethylammonium bromide TEABr or tetraethylammonium hydroxide TEAOH, as templates.

A preparation method of a multi-stage pore zeolite molecular sieve of the present invention is characterized in that a traditional template synthesized by zeolite, tetraethylammonium bromide TEABr or tetraethylammonium hydroxide TEAOH, is used as a template to synthesize a multi-stage pore zeolite The method of molecular sieve, concrete steps are:

1 At room temperature, 1.28g of sodium metaaluminate, 1.89g of sodium hydroxide, 18ml of silica sol with a mass percent concentration of 40% and 54ml of distilled water were mixed and stirred into a uniform white jelly, and put into a stainless steel reaction kettle at 170 Hydrothermal treatment at ℃ for 8~24h, then vacuum filtration, and keep the filtrate for later use;

II Take 50~100ml of the above-mentioned filtrate, add 10~19.3g template agent in the filtrate, the template agent is tetraethylammonium bromide TEABr or tetraethylammonium hydroxide TEAOH, 5~18ml mass percentage concentration is 25% Ammonia water and 3~15ml of silica sol with a mass percentage concentration of 40% are stirred evenly, crystallized at 140~180 degrees Celsius for 4~7 days, then cooled to room temperature with tap water, the product is washed with distilled water until neutral, filtered, and 100℃ After drying in a special oven for 12 hours, it was calcined in a muffle furnace at 550°C for 4-6 hours under the condition of ventilation to obtain a ZSM-12 hierarchically porous zeolite molecular sieve with intergranular mesopores or macropores. .

The advantage of the preparation method of a multi-stage zeolite molecular sieve of the present invention is that the primary and secondary structural units of the zeolite present in the precursor after the first step of precrystallization are used to accelerate the nucleation of ZSM-12 zeolite and induce the acquisition of A kind of hierarchically porous ZSM-12 zeolite molecular sieve formed by stacking nano crystal grains; Compared with the traditional post-processing method of making mesopores on single crystals, the present invention can obtain through mesoporous channels; In terms of soft and hard templates to prepare multi-stage zeolite molecular sieves, the present invention utilizes traditional zeolite synthesis templates, i.e. cheap tetraethylammonium bromide or tetraethylammonium hydroxide as templates to synthesize multi-stage Porous zeolite molecular sieve, low cost and easy to realize industrialization; compared with porous zeolite molecular sieve materials formed on single crystals (Micropor. Mesopor. Mater., 97, 2006, 97; Micropor. Mesopor. Mater., 89, 2006, 170) The mesoporous channel in the aggregate composed of small crystal grains is the outer surface of the small crystal grain zeolite, which is connected with the micropores of the zeolite, and because the outer surface of the zeolite is all aluminum-rich places, so this multi- Compared with the intracrystalline pores, the mesoporous channels of crystal aggregates are rich in acid centers, which will inevitably bring different acid catalytic properties to the catalyst; The diffusion rate of nanocrystalline particles has been greatly improved due to the shortening of the diffusion path, and it has also solved the difficulty of separating the solid-liquid mixture after the synthesis of single nanocrystalline zeolite molecular sieves (Langmuir. 21 , 2005, 504); through the synthesis Conditions such as the control of crystallization time to change the particle size of nanocrystals in polycrystalline aggregates can effectively adjust the size of mesoporous channels in aggregates.

The small-grained nano-zeolite has a high outer surface, and the zeolite catalyst has more pore entrances per unit weight, so its acid site accessibility is greatly improved. shortening, the diffusion restriction of reaction molecules in the material pores is greatly reduced, effectively increasing the diffusion rate of reaction and product molecules in the internal pores of the material, so that the reaction product releases faster in the pores of the zeolite material, greatly reducing the secondary The probability of the reaction occurring. the

Description of drawings

Figure 1 is the XRD diffraction pattern of a hierarchically porous ZSM-12 zeolite sample.

Figure 2 is the SEM image of the hierarchically porous ZSM-12 zeolite sample.

Figure 3 is the _N adsorption diagram of the hierarchically porous ZSM-12 zeolite sample.

Detailed ways

Implementation mode 1:

Step 1: At room temperature, mix 1.28g sodium metaaluminate, 1.89g sodium hydroxide, 18ml silica sol and 54ml distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 24 hours , then vacuum filtration, and retain the filtrate for subsequent use;

Step 2: Take 55ml of the above-mentioned filtrate, add 12.5g template agent tetraethylammonium bromide TEABr, 6ml ammonia water and 3ml silica sol to the filtrate, stir evenly, crystallize at 140 degrees Celsius for 7 days, then cool with tap water To room temperature, the product was washed with distilled water until neutral, filtered, dried in an oven at 100°C for 12 hours, and calcined in a muffle furnace at 550°C for 6 hours under the condition of ventilation to obtain the final sample. The XRD and SEM analysis showed that the obtained sample was a ZSM-12 polycrystalline aggregate of about 10 microns in size composed of nano-sized grains, and the N ₂ analysis showed that there were intergranular mesopores with a pore distribution of about 3-5 nm.

the

Implementation mode 2:

Step 1: At room temperature, mix 1.28g sodium metaaluminate, 1.89g sodium hydroxide, 18ml silica sol and 54ml distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 24 hours , then vacuum filtration, and retain the filtrate for subsequent use;

The second step: take 50ml of the above-mentioned filtrate, add 10g template agent tetraethylammonium bromide TEABr, 5ml ammonia water and 15ml silica sol to the filtrate, stir evenly, crystallize at 170 degrees Celsius for 4 days, then cool with tap water to At room temperature, the product was washed with distilled water until neutral, filtered, dried in an oven at 100°C for 12 hours, and calcined in a muffle furnace at 550°C for 4 hours under air ventilation to obtain the final sample. XRD and SEM analysis showed that the obtained sample was a ZSM-12 polycrystalline aggregate of about 50 microns overall composed of nano-sized grains, and N ₂ analysis showed that there were intergranular mesopores with a pore distribution of about 5-10 nm.

the

Implementation mode 3:

Step 1: At room temperature, mix 1.28g sodium metaaluminate, 1.89g sodium hydroxide, 18ml silica sol and 54ml distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 24 hours , then vacuum filtration, and retain the filtrate for subsequent use;

Step 2: Take 72ml of the above-mentioned filtrate, add 19.3g template agent tetraethylammonium bromide TEABr, 5ml ammonia water and 5ml silica sol to the filtrate, stir evenly, crystallize at 180 degrees Celsius for 5 days, then cool with tap water To room temperature, the product was washed with distilled water until neutral, filtered, dried in an oven at 100°C for 12 hours, and calcined in a muffle furnace at 550°C for 5 hours under air ventilation to obtain the final sample. The results of XRD characterization show that the characteristic diffraction peak of ZSM-12 is obviously broadened, as shown in Figure 1, it is precisely because of the smaller crystal grains; SEM analysis shows that the obtained sample is composed of nano-sized crystal grains with an overall size of about 10-15 microns ZSM -12 polycrystalline aggregates, _N2 analysis shows the presence of intergranular mesopores with a pore distribution of about 4~8nm.

the

Implementation mode 4:

Step 1: At room temperature, mix 1.28g sodium metaaluminate, 1.89g sodium hydroxide, 18ml silica sol and 54ml distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 12 hours , then vacuum filtration, and retain the filtrate for subsequent use;

Step 2: Take 100ml of the above-mentioned filtrate, add 10g template agent tetraethylammonium bromide TEABr, 13.5ml ammonia water and 9ml silica sol to the filtrate, stir evenly, crystallize at 170 degrees Celsius for 4 days, then cool with tap water To room temperature, the product was washed with distilled water until neutral, filtered, dried in an oven at 100°C for 12 hours, and calcined in a muffle furnace at 550°C for 5 hours under air ventilation to obtain the final sample. The results of XRD characterization show that the characteristic diffraction peak of ZSM-12 is broadened because of the smaller crystal grains; SEM analysis shows that the obtained sample is an overall about 100 micron ZSM-12 polycrystalline aggregate composed of nano-sized crystal grains. _N2 analysis indicated the presence of intergranular mesopores with a pore distribution of about 10–15 nm.

the

Implementation mode 5:

Step 1: At room temperature, mix 1.28g sodium metaaluminate, 1.89g sodium hydroxide, 18ml silica sol and 54ml distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 12 hours , then vacuum filtration, and retain the filtrate for subsequent use;

The second step: take 65ml of the above-mentioned filtrate, add 15.7g template agent tetraethylammonium bromide TEABr, 18ml ammonia water and 3.5ml silica sol to the filtrate, stir evenly, crystallize at 170 degrees Celsius for 4 days, and then use The tap water was cooled to room temperature, the product was washed with distilled water until neutral, filtered, dried in an oven at 100°C for 12 hours, and calcined in a muffle furnace at 550°C for 5 hours under the condition of ventilation to obtain the final sample. The results of XRD characterization show that the characteristic diffraction peak of ZSM-12 is broadened; SEM analysis shows that the obtained sample is a ZSM-12 polycrystalline aggregate of about 50 microns overall composed of small nano-sized grains, as shown in Figure 2; N ₂ analysis shows that there are about Intergranular mesopores with 4~9nm pore distribution.

the

Implementation mode 6:

Step 1: At room temperature, mix 1.28g sodium metaaluminate, 1.89g sodium hydroxide, 18ml silica sol and 54ml distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 12 hours , then vacuum filtration, and retain the filtrate for subsequent use;

Step 2: Take 70ml of the above-mentioned filtrate, add 13.5g template agent tetraethylammonium hydroxide TEAOH, 15ml ammonia water and 4ml silica sol to the filtrate, stir evenly, crystallize at 160 degrees Celsius for 4 days, and then use tap water Cool to room temperature, wash the product with distilled water until neutral, filter, dry in an oven at 100°C for 12 hours, and bake in a muffle furnace at 550°C for 5 hours under air ventilation to obtain the final sample. The XRD characterization results show that the characteristic diffraction peak of ZSM-12 is broadened; SEM analysis shows that the obtained sample is a ZSM-12 polycrystalline aggregate of about 50 microns overall composed of small nano-sized grains; the _N2 adsorption isotherm of the sample is at p/ There is a large hysteresis loop between p0=0.4~0.8, as shown in Figure 3, which is attributed to the intergranular mesoporous channels formed by the accumulation of small grains.

the

Implementation mode 7:

Step 1: At room temperature, mix 1.28g of sodium metaaluminate, 1.89g of sodium hydroxide, 18ml of silica sol and 54ml of distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 8 hours , then vacuum filtration, and retain the filtrate for subsequent use;

Step 2: Take 82ml of the above-mentioned filtrate, add 19g template agent tetraethylammonium hydroxide TEAOH, 13ml ammonia water and 12ml silica sol to the filtrate, stir evenly, crystallize at 160 degrees Celsius for 7 days, then cool with tap water To room temperature, the product was washed with distilled water until neutral, filtered, dried in an oven at 100°C for 12 hours, and calcined in a muffle furnace at 550°C for 5 hours under air ventilation to obtain the final sample. The results of XRD characterization show that it is ZSM-12 zeolite molecular sieve; the N ₂ adsorption isotherm of the sample has a hysteresis loop between p/p0=0.4~0.8, which is attributed to the intergranular mesoporous channels formed by the accumulation of crystal grains.

Implementation mode 8:

Step 1: At room temperature, mix 1.28g of sodium metaaluminate, 1.89g of sodium hydroxide, 18ml of silica sol and 54ml of distilled water to form a uniform white jelly, put it into a stainless steel reaction kettle, and conduct hydrothermal treatment at 170°C for 8 hours , then vacuum filtration, and retain the filtrate for subsequent use;

Step 2: Take 72ml of the above-mentioned filtrate, add 19g template agent tetraethylammonium hydroxide TEAOH, 13ml ammonia water and 5ml silica sol to the filtrate, stir evenly, crystallize at 150 degrees Celsius for 4 days, then cool with tap water To room temperature, the product was washed with distilled water until neutral, filtered, dried in an oven at 100°C for 12 hours, and calcined in a muffle furnace at 550°C for 5 hours under air ventilation to obtain the final sample. The results of XRD characterization show that it is ZSM-12 zeolite molecular sieve; the N ₂ adsorption isotherm of the sample has a large hysteresis loop between p/p0=0.8~1, which is attributed to the large pores between crystal grains formed by the accumulation of crystal grains.

Claims (1)

1. A method for preparing a multi-stage pore zeolite molecular sieve, characterized in that it is a traditional template tetraethylammonium bromide TEABr or tetraethylammonium hydroxide TEAOH that utilizes zeolite synthesis to synthesize a multi-stage pore zeolite as a template The method of molecular sieve, concrete steps are: 1 At room temperature, 1.28g of sodium metaaluminate, 1.89g of sodium hydroxide, 18ml of silica sol with a mass percent concentration of 40% and 54ml of distilled water were mixed and stirred into a uniform white jelly, and put into a stainless steel reaction kettle at 170 Hydrothermal treatment at ℃ for 8~24h, then vacuum filtration, and keep the filtrate for later use; II Take 50~100ml of the above-mentioned filtrate, add 10~19.3g template agent in the filtrate, the template agent is tetraethylammonium bromide TEABr or tetraethylammonium hydroxide TEAOH, 5~18ml mass percentage concentration is 25% Ammonia water and 3~15ml of silica sol with a mass percentage concentration of 40% are stirred evenly, crystallized at 140~180 degrees Celsius for 4~7 days, then cooled to room temperature with tap water, the product is washed with distilled water until neutral, filtered, and 100℃ After drying in a special oven for 12 hours, it was calcined in a muffle furnace at 550°C for 4-6 hours under the condition of ventilation to obtain a ZSM-12 hierarchically porous zeolite molecular sieve with intergranular mesopores or macropores. .

Images