CN114749202A - Core-shell SAPO-34@ ZSM-5 molecular sieve catalyst and preparation method thereof - Google Patents

Core-shell SAPO-34@ ZSM-5 molecular sieve catalyst and preparation method thereof Download PDF

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CN114749202A
CN114749202A CN202210310227.0A CN202210310227A CN114749202A CN 114749202 A CN114749202 A CN 114749202A CN 202210310227 A CN202210310227 A CN 202210310227A CN 114749202 A CN114749202 A CN 114749202A
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CN114749202B (en
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汪全华
范彬彬
李瑞丰
刘砚超
张丽晨
马晓森
白亚东
郑家军
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Taiyuan University of Technology
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    • B01J29/005—Mixtures of molecular sieves comprising at least one molecular sieve which is not an aluminosilicate zeolite, e.g. from groups B01J29/03 - B01J29/049 or B01J29/82 - B01J29/89
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    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
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    • B01J29/82—Phosphates
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Abstract

The invention provides a core-shell SAPO-34@ ZSM-5 zeolite catalyst and a preparation method thereof, which takes SAPO-34 microspheres (2 mu m) formed by stacking nano polycrystalline aggregates as a core, a layer of MCM-41 material is deposited on the outer surface of the SAPO-34 microspheres, and then a ZSM-5 seed crystal precursor solution is added to induce the MCM-41 in-situ zeolitization of the shell layer to form ZSM-5 zeolite particles (150 nm) by utilizing the traditional hydrothermal synthesis method. The core-shell type SAPO-34@ ZSM-5 zeolite catalyst prepared by the invention utilizes the deposited MCM-41 to modify the surface of the SAPO-34, and effectively solves the problem that SAPO-34 crystals are damaged in an alkaline environment system for synthesizing the SAPO-34@ ZSM-5. The preparation method has the advantages of easily obtained raw materials, simple process, relatively mild conditions and the like, can realize industrial application, and has wide application prospect in the aspect of solving the problem of energy shortage.

Description

Core-shell SAPO-34@ ZSM-5 molecular sieve catalyst and preparation method thereof
Technical Field
The invention belongs to the field of inorganic materials, and particularly relates to a core-shell type SAPO-34@ ZSM-5 molecular sieve catalyst and a preparation method thereof.
Background
Zeolite molecular sieves are a class of crystalline materials having a framework structure that have been widely used in the fields of catalysis, adsorptive separation, biotechnology, and the like, due to their unique microporous structure, tunable acidity, good thermal/hydrothermal stability, and chemical stability. Among them, SAPO-34 molecular sieve is one of the important members of SAPO series, SAPO-34 has CHA topology which is formed by SiO4,AlO4And PO4The tetrahedrons are connected with each other through oxygen bridges to form a three-dimensional cross pore channel structure. Has higher selectivity to ethylene and propylene in the MTO catalytic reaction. However, the mass transfer and diffusion of product molecules in micropores are severely limited by the narrow micropore pore canals (about 0.38 nm) of the traditional SAPO-34 zeolite, so that the polymerization, cyclization and hydrogen transfer probability of olefin molecules is greatly increased, the generation of carbon deposition precursors is accelerated, and the catalyst is quickly deactivated. The most common method for solving the problem of catalyst deactivation is to form hierarchical pores in the zeolite molecular sieve.
The methods reported in the literature at present mainly comprise a post-treatment method and a method for adding a mesoporous template. By adopting a post-treatment method (acid or alkali treatment), aluminum or silicon atoms in a zeolite framework are extracted to cause lattice defects, so that intragranular mesopores are generated in zeolite crystals, but the method easily causes the damage of the crystals, reduces the crystallinity of the zeolite, and the separated amorphous silicon and aluminum species easily block microporous channels. The adoption of the mesoporous template and the micromolecular organic amine (structure directing agent) can easily cause incompatibility between the templates in the growth process of the zeolite, and easily cause two-phase separation or mixed crystal. In addition, a large amount of waste gas generated in the process of removing the template agent is easy to cause environmental pollution. Whichever method is used, the skeleton acid center of the catalyst is weakened, so that the catalytic active sites of the catalyst in the reaction are greatly reduced, thereby further influencing the reaction performance of the catalyst. Moreover, the complicated synthesis procedure, the expensive price of the mesoporous template and the large time consumption severely limit the industrial application.
Disclosure of Invention
In view of the above situation, the present invention aims to provide a core-shell type SAPO-34@ ZSM-5 molecular sieve catalyst and a preparation method thereof, wherein in an MTO reaction, the SAPO-34 (core) and ZSM-5 (shell) act synergistically to increase the service life of the catalyst and obtain high olefin selectivity.
In order to realize the purpose, the technical scheme adopted by the invention is as follows: provides a core-shell type SAPO-34@ ZSM-5 molecular sieve catalyst and a preparation method thereof.
A core-shell SAPO-34@ ZSM-5 zeolite catalyst is characterized in that a zeolite catalytic material takes SAPO-34 microspheres (2 mu m) formed by stacking nano polycrystalline aggregates as a core, a layer of MCM-41 material is deposited on the outer surfaces of the SAPO-34 microspheres, and then a ZSM-5 zeolite particle (150 nm) is formed by adding a ZSM-5 seed crystal precursor solution to induce in-situ zeolization of MCM-41 on a shell layer by using a traditional hydrothermal synthesis method.
The preparation method of the core-shell SAPO-34@ ZSM-5 comprises the following steps:
(1) preparation of SAPO-34 polycrystalline aggregates: the mole components for preparing the SAPO-34 zeolite by using a traditional microporous template as a Structure Directing Agent (SDA) are as follows: al (Al)2O3:SiO2:P2O5:SDA:H2O =1.00: 0.45-1.93: 1.00-4.14: 0.72-5.17: 100.34-300.76; and sequentially adding an aluminum source, SDA, a silicon source and a phosphorus source into the aqueous solution. Stirring uniformly, and then putting the mixture into an oven for hydrothermal crystallization at the temperature of 160-200 ℃ for 24-96 h. Washing the crystallized sample to be neutral, and drying overnight to obtain solid powder;
(2) Preparation of SAPO-34@ MCM-41: and (2) adding the SAPO-34 powder synthesized in the step (1) into distilled water, and stirring to form a uniform milky solution, wherein the weight percentage of the surfactant, organic alcohol and organic alkali: the preparation method comprises the following steps of adding a silicon source, namely water, into an aqueous solution at a molar ratio of 1.00: 100.34-600.25: 20.30-150.12: 1.51-9.85: 1253.41-3000.23, sequentially adding a surfactant, organic alcohol, organic alkali and the silicon source into the aqueous solution, stirring to form a uniform solution, then putting the uniform solution into a water bath kettle, hydrolyzing at 30-80 ℃ for 1-5 hours, washing and drying a hydrolyzed product to obtain solid powder;
(3) preparation of ZSM-5 seed crystal precursor solution: dissolving a silicon source, an aluminum source, tetrapropylammonium hydroxide and absolute ethyl alcohol in water according to a molar ratio of the silicon source to the aluminum source to tetrapropylammonium hydroxide to absolute ethyl alcohol to water = 120.20-300: 1.02-3.04: 8.34-62.45: 450.02-1200.00: 1000.14-3000.56, stirring and dissolving, wherein the crystallization temperature is 100-180 ℃;
(4) preparation of SAPO-34@ ZSM-5: and (3) adding the SAPO-34@ MCM-41 powder synthesized in the step (2) into a ZSM-5 precursor solution (the solid/liquid mass ratio = 1-7), fully and uniformly stirring, then putting into a stainless steel autoclave for hydrothermal crystallization at 100-180 ℃ for 24-72 h, washing a crystallized sample to be neutral, and drying overnight to obtain solid powder.
Further, the aluminum source used for synthesizing the SAPO-34 zeolite molecular sieve is aluminum isopropoxide, pseudo-boehmite, aluminum hydroxide or gamma-Al2O3One of (a) and (b); the silicon source is one of gas-phase silicon dioxide, ethyl orthosilicate or silica sol; the phosphorus source is one of phosphoric acid, ammonium dihydrogen phosphate or ammonium monohydrogen phosphate; the structure directing agent is one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide or diethylamine.
Further, the organic alcohol used for synthesizing the SAPO-34@ MCM-41 is one of n-propanol, isopropanol, ethanol or n-butanol; the surfactant is one of cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide or dodecyl trimethyl ammonium bromide; the organic base being NH3.H2O, triethylamine, diethylamine or n-butylamine; the silicon source is ethyl orthosilicate, propyl orthosilicate, silica sol or sodium silicateOne kind of the medicine.
Further, the silicon source used for synthesizing the ZSM-5 precursor solution is tetraethoxysilane, sodium silicate, silica sol or gas-phase SiO2One of (1); the aluminum source is one of aluminum hydroxide, sodium aluminate or aluminum isopropoxide.
Further, the crystallization time of the ZSM-5 precursor solution is 24-96 h.
The core-shell SAPO-34@ ZSM-5 zeolite catalytic material with the SAPO-34 microsphere of the nano polycrystalline aggregate prepared by the invention as the core and the ZSM-5 zeolite (150 nm) as the shell.
The invention adopts a surface modification method, firstly, SAPO-34 nano polycrystalline aggregates with spherical morphology are prepared under the condition of not adding a secondary template agent, then the SAPO-34 is taken as a core, under the condition of organic alkali and a surfactant, a silicon source of the SAPO-34 nano polycrystalline aggregates is hydrolyzed on the surface of the SAPO-34, silicon hydroxyl is directionally assembled on the organic template agent micelle surfactant to form a MCM-41 material with a highly ordered two-dimensional hexagonal mesoporous structure, thus the SAPO-34@ MCM-41 with a core-shell structure is obtained, and finally, a pre-prepared ZSM-5 seed crystal precursor solution is added in a hydrothermal crystallization system to induce the in-situ zeolization of the MCM-41 with the shell layer, thereby the SAPO-34 ZSM-5 zeolite catalytic material is obtained.
The invention has the beneficial effects that: the core-shell SAPO-34@ ZSM-5 zeolite catalyst prepared by the invention utilizes the deposited MCM-41 to modify the surface of the SAPO-34, and effectively solves the problem that the SAPO-34 crystals are damaged in the alkaline environment system for synthesizing the SAPO-34@ ZSM-5 at present. In addition, the MCM-41 forms shell layer ZSM-5 zeolite crystal grains after in-situ zeolitization, and the problem of two-phase separation is effectively avoided. The invention obviously improves the service life of the catalyst in the MTO catalytic reaction, and obtains higher selectivity of the low-carbon olefin at the same time. The preparation method has the advantages of easily obtained raw materials, simple process, relatively mild conditions and the like, can realize industrial application, and has wide application prospect in solving the problem of energy shortage.
Drawings
FIG. 1 is a flow chart of a process for preparing a material prepared in accordance with an embodiment of the present invention;
FIG. 2 is a wide angle XRD pattern (a) of a SAPO-34@ ZSM-5 catalytic material prepared according to the present invention;
FIG. 3 is a small angle XRD pattern (b) of SAPO-34@ ZSM-5 catalytic material prepared according to the present invention;
FIG. 4 is an SEM image (c and d) of SAPO-34 diagram (a), SAPO-34@ MCM-41 diagram (b) and SAPO-34@ ZSM-5 materials prepared according to the invention;
FIG. 5 is a graph showing the trend of methanol conversion with reaction time for SAPO-34@ ZSM-5 catalytic material prepared according to the present invention.
FIG. 6 is a graph showing the variation trend of the low carbon olefins (ethylene and propylene) of the SAPO-34@ ZSM-5 catalytic material prepared according to the present invention with the reaction time.
Detailed Description
The following examples further describe embodiments of the present invention. The following examples are only for illustrating the technical solutions of the present invention more clearly, and do not limit the scope of the present invention. Various changes, modifications, substitutions and alterations to these embodiments will be apparent to those skilled in the art without departing from the principles and spirit of this invention.
Example 1: preparation of SAPO-34@ ZSM-5
(1) 6.12g of aluminum isopropoxide was weighed and dissolved in a solution of 30.3mL of distilled water and 35.3mL of tetrapropylammonium hydroxide, and stirred until completely dissolved, and then 3.6mL of ethyl orthosilicate and 4.0mL of phosphoric acid were sequentially added. After being mixed evenly, the mixture is transferred into a stainless steel reaction kettle with the volume of 100mL, and is hydrothermally crystallized at 180 ℃ for 3 days. Washing the crystallized sample to be neutral, and drying the sample at 80 ℃ overnight to obtain solid powder;
(2) Placing 160g of distilled water, 1.6g of hexadecyl trimethyl ammonium bromide, 40mL of isopropanol, 1mL of ammonia water, 1.6mL of tetraethoxysilane and 2g of SAPO-34 molecular sieve obtained in the step (1) into the solution, stirring the solution for 3 hours at 30 ℃, washing the final product with distilled water, and drying the product at 80 ℃ overnight to obtain core-shell type SAPO-34@ MCM-41;
(3) weighing 10.98g of tetraethoxysilane, 10.37g of tetrapropylammonium hydroxide, 0.06g of aluminum isopropoxide, 15g of water and 9.11g of absolute ethyl alcohol, stirring for 4 hours, and putting the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining for crystallization for 3 days at 100 ℃ to obtain a precursor solution of ZSM-5 zeolite seed crystals;
(4) and (3) uniformly mixing and stirring the SAPO-34@ MCM-41 obtained in the step (2) and the ZSM-5 zeolite seed crystal precursor solution obtained in the step (3) according to a solid/liquid (mass ratio) =1:2, then putting the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining, crystallizing at 180 ℃, standing for 3 days, washing the obtained product with distilled water, and drying at 80 ℃ overnight to obtain the SAPO-34@ ZSM-5 zeolite catalytic material.
Example 2
Preparation of SAPO-34@ ZSM-5, step (1), 7.01g of monoammonium phosphate, and the remainder of example 1.
Example 3
Preparation of SAPO-34@ ZSM-5, step (1), 4.23g of ammonium monohydrogen phosphate, as in example 1.
Example 4
SAPO-34@ ZSM-5 was prepared, and in step (1), hydrothermal crystallization was carried out at 160 ℃ as in example 1.
Example 5
Preparation of SAPO-34@ ZSM-5:
(1) 5.08g of pseudoboehmite was weighed and dissolved in a solution of 30.3mL of distilled water and 35.3mL of tetrapropylammonium hydroxide, stirred until completely dissolved, and then 3.6mL of silica sol and 4.0mL of phosphoric acid were added in this order. After being mixed evenly, the mixture is transferred into a stainless steel reaction kettle with the volume of 100mL, and is hydrothermally crystallized at 180 ℃ for 3 days. Washing the crystallized sample to be neutral, and drying the sample at 60 ℃ overnight to obtain solid powder;
(2) 160g of distilled water, 1.6g of tetradecyl trimethyl ammonium bromide, 40mL of n-propanol, 1mL of n-butylamine and 2g of propyl orthosilicate are put into the SAPO-34 molecular sieve obtained in the step (1), stirred for 3 hours at 30 ℃, and the final product is washed by distilled water and dried overnight at 80 ℃ to obtain core-shell SAPO-34@ MCM-41;
(3) weighing 10.98g of ethyl orthosilicate, 10.37g of tetrapropylammonium hydroxide, 0.06g of aluminum isopropoxide, 15g of water and 9.71g of absolute ethyl alcohol, stirring for 4 hours, and putting the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining for crystallization for 3 days at 120 ℃ to obtain a precursor solution of the ZSM-5 zeolite seed crystal;
(4) and (3) uniformly mixing and stirring the SAPO-34@ MCM-41 obtained in the step (2) and the precursor solution of the ZSM-5 zeolite seed crystal obtained in the step (3) according to a solid/liquid (mass ratio) =1:4, then putting the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining, crystallizing at 180 ℃, drying for 3 days, washing the obtained product with distilled water, drying at 80 ℃ overnight, and roasting the obtained sample at 550 ℃ for 6 hours to obtain the SAPO-34@ ZSM-5 zeolite catalytic material.
Example 6
Preparation of SAPO-34@ ZSM-5:
(1) 6.08g of aluminum hydroxide was weighed and dissolved in a solution of 30.3mL of distilled water and 25.3mL of tetraethylammonium hydroxide, stirred until completely dissolved, and then 3.6mL of silica sol and 4.0mL of phosphoric acid were added in this order. After being mixed evenly, the mixture is transferred into a stainless steel reaction kettle with the volume of 100mL, and is hydrothermally crystallized at 180 ℃ for 3 days. The crystallized sample was washed to neutrality and dried overnight at 60 ℃ to give a solid powder. Then roasting for 6 hours at 550 ℃ to obtain the SAPO-34 molecular sieve with the spherical morphology of the nano polycrystalline aggregates;
(2) 160g of distilled water, 1.6g of dodecyl trimethyl ammonium bromide, 40mL of n-propanol, 1mL of ammonia water and 2g of propyl orthosilicate are put into the SAPO-34 molecular sieve obtained in the step (1), stirred at 30 ℃ for 3 hours, and the final product is washed with distilled water and dried at 80 ℃ overnight to obtain core-shell SAPO-34@ MCM-41;
(3) weighing 10.98g of ethyl orthosilicate, 10.37g of tetrapropylammonium hydroxide and 0.06g of gamma-Al2O3Stirring 15g of water and 9.71g of absolute ethyl alcohol for 4 hours, and putting the mixed solution into a stainless steel high-pressure kettle with a polytetrafluoroethylene lining for crystallization for 3 days at 140 ℃ to obtain a precursor solution of the ZSM-5 zeolite seed crystal;
(4) and (3) uniformly mixing and stirring the SAPO-34@ MCM-41 obtained in the step (2) and the precursor solution of the ZSM-5 zeolite seed crystal obtained in the step (3) according to a solid/liquid (mass ratio) =1:4, then putting the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining, crystallizing at 180 ℃, drying for 3 days, washing the obtained product with distilled water, drying at 80 ℃ overnight, and roasting the obtained sample at 550 ℃ for 6 hours to obtain the SAPO-34@ ZSM-5 zeolite catalytic material.
Example 7
Preparation of SAPO-34@ ZSM-5:
(1) 6.08g of aluminum isopropoxide was weighed and dissolved in a solution of 30.3mL of distilled water and 25.3mL of tetrabutylammonium hydroxide, stirred until completely dissolved, and then 3.6mL of silica sol and 4.0mL of phosphoric acid were added in this order. After being mixed evenly, the mixture is transferred into a stainless steel reaction kettle with the volume of 100mL, and is hydrothermally crystallized at 180 ℃ for 3 days. The crystallized sample was washed to neutrality and dried overnight at 60 ℃ to give a solid powder. Then roasting for 6 hours at 550 ℃ to obtain the SAPO-34 molecular sieve with the spherical morphology of the nano polycrystalline aggregates;
(2) 160g of distilled water, 1.6g of decaalkyltrimethylammonium bromide, 40mL of ethanol, 1mL of ammonia water and 2g of propyl orthosilicate are put into the SAPO-34 molecular sieve obtained in the step (1), the mixture is stirred for 5 hours at 30 ℃, the final product is washed by distilled water, and the mixture is dried overnight at 90 ℃ to obtain the core-shell type SAPO-34@ MCM-41 catalytic material;
(3) 10.98g of ethyl orthosilicate, 10.37g of tetrabutylammonium hydroxide and 0.06g of gamma-Al are weighed2O3Stirring 15g of water and 9.71g of absolute ethyl alcohol for 4 hours, and putting the mixed solution into a stainless steel high-pressure kettle with a polytetrafluoroethylene lining for crystallization for 3 days at 140 ℃ to obtain a precursor solution of the ZSM-5 zeolite seed crystal;
(4) and (3) uniformly mixing and stirring the SAPO-34@ MCM-41 obtained in the step (2) and the precursor solution of the ZSM-5 zeolite seed crystal obtained in the step (3) according to the solid/liquid (mass ratio) =1:2, then putting the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining, crystallizing at 180 ℃, drying for 3 days, washing the obtained product with distilled water, drying at 80 ℃ overnight, and roasting the obtained sample at 550 ℃ for 8 hours to obtain the SAPO-34@ ZSM-5 zeolite catalytic material.
Example 8
Preparation of SAPO-34@ ZSM-5:
(1) 6.08g of aluminum isopropoxide was weighed and dissolved in a solution of 30.3mL of distilled water and 25.3mL of tetrabutylammonium hydroxide, stirred until completely dissolved, and then 3.6mL of silica sol and 4.0mL of phosphoric acid were added in this order. After being mixed evenly, the mixture is transferred into a stainless steel reaction kettle with the volume of 100mL, and is hydrothermally crystallized at 180 ℃ for 3 days. The crystallized sample was washed to neutrality and dried overnight at 60 ℃ to give a solid powder. Then roasting for 6 hours at 550 ℃ to obtain the SAPO-34 molecular sieve with the spherical morphology of the nano polycrystalline aggregates;
(2) putting 160g of distilled water, 1.6g of dodecyl trimethyl ammonium bromide, 40mL of ethanol, 1mL of diethylamine and 2g of propyl orthosilicate into the SAPO-34 molecular sieve obtained in the step (1), stirring for 5 hours at 30 ℃, washing the final product with distilled water, and drying at 90 ℃ overnight to obtain core-shell SAPO-34@ MCM-41;
(3) 10.98g of silica sol, 10.37g of tetrapropylammonium hydroxide and 0.10g of gamma-Al were weighed2O315g of water and 9.71g of absolute ethyl alcohol are stirred for 4 hours, and the mixed solution is put into a stainless steel autoclave with a polytetrafluoroethylene lining
Crystallizing for 3 days at 140 ℃ to obtain a precursor solution of ZSM-5 zeolite seed crystals;
(4) and (3) uniformly mixing and stirring the SAPO-34@ MCM-41 obtained in the step (2) and the precursor solution of the ZSM-5 zeolite seed crystal obtained in the step (3) according to the solid/liquid (mass ratio) =1:5, then putting the mixed solution into a stainless steel autoclave with a polytetrafluoroethylene lining, crystallizing at 180 ℃, drying for 3 days, washing the obtained product with distilled water, drying at 80 ℃ overnight, and roasting the obtained sample at 550 ℃ for 4 hours to obtain the SAPO-34@ ZSM-5 zeolite catalytic material.
The preparation method of the core-shell SAPO-34@ ZSM-5 zeolite catalyst utilizes the raw materials synthesized by the traditional zeolite. Under the condition of not adding a secondary template agent, firstly synthesizing the SAPO-34 zeolite microspheres with spherical morphology of nano polycrystalline aggregates. Then, the surface of the SAPO-34 is modified, and a hydrolyzed silicon source is directionally assembled on the surface of the SAPO-34 zeolite under the action of a surfactant micelle to obtain the core-shell type SAPO-34@ MCM-41 material. And finally, inducing in-situ zeolitization of a shell MCM-41 on the surface by using a seed crystal ZSM-5 zeolite precursor solution to form the core-shell SAPO-34@ ZSM-5 zeolite.
As shown in figure 1, a flow chart of a preparation process of the SAPO-34@ ZSM-5 zeolite catalytic material prepared by the invention is shown, polycrystalline aggregates SAPO-34 zeolite microspheres are prepared firstly, then MCM-41 is uniformly laminated on the surfaces of the SAPO-34 microspheres, and then the shell MCM-41 is subjected to in-situ zeolitization to form the SAPO-34@ ZSM-5 zeolite catalytic material.
FIGS. 2 and 3 are X-ray diffraction patterns (XRD) of SAPO-34@ ZSM-5 material prepared by the invention, wherein the prepared material can be seen to belong to typical SAPO-34 characteristic diffraction peaks in FIG. 2, and can also be seen to be characteristic diffraction peaks of ZSM-5, and a sample can show one characteristic diffraction peak at 2 theta =2.5 in FIG. 3, which proves that the sample is MCM-41 material with ordered mesoporous channels.
FIG. 4 is a Scanning Electron Microscope (SEM) image of the SAPO-34@ ZSM-5 catalytic material obtained in example 1, from FIG. 4(a) it can be seen that the prepared material is formed by stacking nanocrystals, the average diameter of the SAPO-34 zeolite microspheres is 2 μm, and from FIG. 4(b) it can be seen that the surface of SAP0-34 is covered with a layer of MCM-41 material, so that the surface is smooth. As can be seen from the graph 4(c and d), ZSM-5 particles (150 nm) are uniformly coated on the surface of the SAPO-34 zeolite microspheres to form the SAPO-34@ ZSM-5 zeolite catalytic material with the SAPO-34 as a core and the ZSM-5 as a shell.
The samples prepared above were used as catalysts for MTO reaction, and the catalytic performance of the catalysts was examined.
The evaluation of the catalytic reaction performance was carried out on a normal-pressure mini-fixed-bed reactor, into which 0.79g of the catalyst was charged. Firstly, N with the flow rate of 50mL/min is introduced into the reactor2Heating from room temperature to reaction temperature (400 deg.C) at a rate of 5 deg.C/min, activating the catalyst for 1 hr, and maintaining N2The flow rate was then measured by passing methanol through a micro-metering pump, the feed rate was controlled to 1mL/h, and the product after the reaction was analyzed on a gas chromatograph equipped with a Flame Ionization Detector (FID).
The catalysis results of the graphs 5 and 6 show that compared with SAPO-34 and a mechanically mixed SAPO-34+ ZSM-5 catalyst, the SAPO-34@ ZSM-5 catalytic material still has a methanol conversion rate of over 60% after reaction for 60 hours, and the selectivity of ethylene and propylene is maintained at over 50%, which shows that the catalytic material has high methanol reaction activity, stability and low carbon olefin selectivity.

Claims (9)

1. A core-shell type SAPO-34@ ZSM-5 zeolite catalyst is characterized in that: in particular to a core-shell type SAPO-34@ ZSM-5 zeolite catalyst which takes SAPO-34 microspheres of nano polycrystalline aggregates as a core and ZSM-5 zeolite (150 nm) as a shell;
the zeolite catalyst takes SAPO-34 microspheres (-2 μm) formed by stacking nano polycrystalline aggregates as a core, a layer of MCM-41 material is deposited on the outer surface of the SAPO-34 microspheres, and then a ZSM-5 seed crystal precursor solution is added to induce in-situ zeolitization of MCM-41 on a shell layer to form ZSM-5 zeolite particles (-150 nm) by using a traditional hydrothermal synthesis method.
2. The core-shell type SAPO-34@ ZSM-5 zeolite catalyst of claim 1, wherein: the thickness of the shell MCM-41 is 50-100 nm.
3. A preparation method of a core-shell type SAPO-34@ ZSM-5 zeolite catalyst is characterized by comprising the following steps: the method specifically comprises the following steps:
(1) preparation of SAPO-34 zeolite microspheres: according to Al2O3:SiO2:P2O5:SDA:H2O = 1.00: 0.45-1.93: 1.00-4.14: 0.72-5.17: 100.34-300.76, and an aluminum source, a Structure Directing Agent (SDA), a silicon source and a phosphorus source are sequentially added into the aqueous solution; uniformly stirring, and then putting the mixture into an oven for hydrothermal crystallization at the temperature of 160-200 ℃ for 24-96 h; washing the crystallized sample to be neutral, and drying overnight to obtain solid powder;
(2) Preparation of SAPO-34@ MCM-41: weighing 1-3 g of the synthesized SAPO-34 powder, adding the SAPO-34 powder into distilled water, and stirring to form a uniform milky solution, wherein the weight ratio of the surfactant to the organic alcohol to the organic base is as follows: the preparation method comprises the following steps of adding a silicon source, namely water, in a molar ratio of = 1.00: 100.34-600.25: 20.30-150.12: 1.51-9.85: 1253.41-3000.23, sequentially adding a surfactant, organic alcohol, organic alkali and the silicon source, stirring to form a uniform solution, then putting the solution into a water bath kettle, hydrolyzing at 30-80 ℃ for 1-5 hours, washing and drying a hydrolyzed product to obtain solid powder;
(3) preparation of a ZSM-5 seed crystal precursor solution: dissolving a silicon source, an aluminum source, tetrapropylammonium hydroxide and absolute ethyl alcohol in water according to a molar ratio of the silicon source to the aluminum source to tetrapropylammonium hydroxide to absolute ethyl alcohol to water = 120.20-300.00: 1.02-3.04: 8.34-62.45: 450.02-1200.00: 1000.14-3000.56, stirring and dissolving, and carrying out hydrothermal crystallization at 100-180 ℃ for 24-96 hours;
(4) preparation of SAPO-34@ ZSM-5: adding the synthesized SAPO-34@ MCM-41 powder into a ZSM-5 precursor solution (the solid/liquid mass ratio = 1-7), fully and uniformly stirring, and then putting into a stainless steel autoclave for hydrothermal crystallization at 100-180 ℃; washing the crystallized sample to be neutral, and drying the sample overnight; then roasting the obtained sample at 550 ℃ to obtain the SAPO-34@ ZSM-5 zeolite catalytic material.
4. The method for preparing the core-shell type SAPO-34@ ZSM-5 zeolite catalyst of claim 3, wherein the method comprises the following steps: in the step (1), the aluminum source is aluminum isopropoxide, pseudo-boehmite, aluminum hydroxide or gamma-Al2O3Any one of the above; the silicon source is any one of gas-phase silicon dioxide, ethyl orthosilicate or silica sol; the phosphorus source is any one of phosphoric acid, ammonium dihydrogen phosphate or ammonium monohydrogen phosphate; the structure directing agent is any one of tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide or diethylamine.
5. The method for preparing the core-shell type SAPO-34@ ZSM-5 zeolite catalyst of claim 3, wherein the core-shell type SAPO-34@ ZSM-5 zeolite catalyst comprises: in the step (2), the surfactant is any one of cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide or dodecyl trimethyl ammonium bromide; the organic alcohol is one of n-propanol, isopropanol, ethanol or n-butanol; the silicon source is any one of ethyl orthosilicate, propyl orthosilicate, silica sol or sodium silicate.
6. The method for preparing the core-shell type SAPO-34@ ZSM-5 zeolite catalyst of claim 3, wherein the core-shell type SAPO-34@ ZSM-5 zeolite catalyst comprises: in the step (3) of preparing the ZSM-5 precursor solution, the silicon source is tetraethoxysilane, sodium silicate, silica sol or gas-phase SiO 2One of (a) and (b); the aluminum source is one of aluminum hydroxide, sodium aluminate or aluminum isopropoxide.
7. The method for preparing the core-shell type SAPO-34@ ZSM-5 zeolite catalyst of claim 3, wherein the method comprises the following steps: the hydrothermal crystallization time is 24-72 h.
8. The method for preparing the core-shell type SAPO-34@ ZSM-5 zeolite catalyst of claim 3, wherein the core-shell type SAPO-34@ ZSM-5 zeolite catalyst comprises: the preparation method of the SAPO-34 zeolite microspheres is to form the SAPO-34 zeolite microspheres with the size of 2 mu m by stacking nanocrystals.
9. The method for preparing the core-shell type SAPO-34@ ZSM-5 zeolite catalyst of claim 3, wherein the core-shell type SAPO-34@ ZSM-5 zeolite catalyst comprises: the roasting time of the SAPO-34@ ZSM-5 zeolite is 4-8 h.
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CN109174174A (en) * 2018-08-20 2019-01-11 太原理工大学 A kind of HZSM-5/SAPO-5 core-shell molecular sieve and its preparation method and application
CN113385215A (en) * 2021-06-11 2021-09-14 洛阳市科创石化科技开发有限公司 Preparation method and application of catalyst for preparing propane by hydro-upgrading

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008019586A1 (en) * 2006-08-08 2008-02-21 Dalian Institute Of Chemical Physics, Chinese Academy Of Sciences An insitu synthesis method of a microsphere catalyst used for converting oxygen compound to olefine
CN106268933A (en) * 2016-07-21 2017-01-04 中国科学院广州能源研究所 Application in hud typed ZSM 5/SAPO 5 composite molecular sieve film and preparation method thereof and biomass gas purifying
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