CN109876851B - HZSM-5 molecular sieve catalyst, preparation method and application thereof - Google Patents

HZSM-5 molecular sieve catalyst, preparation method and application thereof Download PDF

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CN109876851B
CN109876851B CN201910225681.4A CN201910225681A CN109876851B CN 109876851 B CN109876851 B CN 109876851B CN 201910225681 A CN201910225681 A CN 201910225681A CN 109876851 B CN109876851 B CN 109876851B
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李建伟
毛庆
张艳君
张佳瑾
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Beijing University of Chemical Technology
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Abstract

The invention relates to an HZSM-5 molecular sieve catalyst, a preparation method and application thereof, and the HZSM-5 molecular sieve catalyst is characterized by comprising the following raw materials: an organic silicon source, an aluminum source, a template agent M and water; wherein the molar ratio of the silicon source to the aluminum source is SiO2：Al2O3(10-200): 1; the molar ratio of the template agent M to the aluminum source is M: al (Al)2O3(2-10): 1; the molar ratio of the water to the aluminum source is H2O：Al2O3(1000-: 1. the HZSM-5 molecular sieve catalyst disclosed by the invention is an efficient and simple synthetic method, and can greatly save the synthetic cost, so that the preparation process is simple, the operation condition is friendly, extreme conditions such as high temperature, high pressure, high acid and high alkali are not required, the environmental pollution and the operation difficulty are reduced.

Description

HZSM-5 molecular sieve catalyst, preparation method and application thereof
Technical Field
The invention relates to the field of catalyst materials, in particular to an HZSM-5 molecular sieve catalyst, a preparation method and application thereof.
Background
The ZSM-5 molecular sieve has a unique three-dimensional cross pore channel structure, larger specific surface area and pore volume, and good thermal stability and hydrothermal stability, and is widely applied to the fields of catalysis, adsorption separation and the like. The HZSM-5 is generally synthesized by a hydrothermal method in industry by the following steps: putting raw materials such as a silicon source, an aluminum source, water, alkali, a template agent and the like into a crystallization kettle, aging at a certain temperature to form colloid, then crystallizing at a higher temperature, carrying out suction filtration, washing, drying and roasting processes to obtain NaZSM-5, and finally carrying out ion exchange, roasting and other processes to obtain HZSM-5. The process flow is complex, and the use of a large amount of water in the preparation process not only has low yield, but also has large discharge amount of waste liquid in the whole process. In molding, the synthesized molecular sieve powder usually needs to be added with a large amount of binder to prepare particles with certain mechanical strength and shape to adapt to various applications. The introduction of the binder can not only reduce the content of the effective molecular sieve, but also partially block the pore opening of the molecular sieve, thereby causing the problems of weakened adsorption capacity, lowered catalytic activity and selectivity and the like.
In order to overcome the above problems, some new synthesis methods were developed. For example, the dry gel method can effectively improve the synthesis yield of the molecular sieve, and the method adopts the steps of gelling, drying, then carrying out solid-liquid separation in a crystallization kettle, standing, crystallizing under the action of steam to obtain NaZSM-5, and then carrying out processes of ion exchange, roasting and the like to obtain HZSM-5. But the method is almost the same as a hydrothermal process in the aspects of waste liquid discharge, synthesis process and forming process except that the yield is improved.
CN105600804B discloses a method for directly preparing HZSM-5 molecular sieve and forming HZSM-5 molecular sieve, the preparation process is: taking a silicon source, an aluminum source, HZSM-5 seed crystals and a template agent as raw materials, grinding and fully mixing solid raw materials, adding a liquid raw material, mixing, putting into a crystallization kettle for crystallization, washing and drying an obtained sample, and roasting to obtain the HZSM-5 molecular sieve. The invention provides a method for preparing HZSM-5 molecular sieve and a method for preparing formed HZSM-5 molecular sieve, mainly solving the problems that the traditional synthesis process has longer route, more template agent dosage, more waste liquid discharge, longer route or influenced molecular sieve performance by the forming process and the like. However, the selectivity and yield of the HZSM-5 prepared by the method in the methanol aromatization reaction are still not ideal.
CN107188195A discloses a preparation method and application of a hierarchical pore HZSM-5 molecular sieve, comprising the following steps: 1) dissolving an aluminum source in water, adding a tetrapropyl ammonium hydroxide solution, then adding a silicon source, and mixing to obtain a molecular sieve precursor; 2) pre-crystallizing a molecular sieve precursor; 3) adding cane sugar into the pre-crystallized molecular sieve precursor, mixing, and carrying out hydrothermal crystallization reaction; 4) after the crystallization reaction is finished, separating, washing, drying and roasting to obtain the hierarchical pore ZSM-5 molecular sieve; 5) and carrying out ion exchange on the hierarchical pore ZSM-5 molecular sieve and an ammonium salt solution, and separating, washing, drying and roasting to obtain the hierarchical pore HZSM-5 molecular sieve. The hierarchical pore HZSM-5 molecular sieve prepared by the preparation method can improve the aromatization capacity and the coking resistance in the biomass catalytic pyrolysis process. However, the selectivity and yield of the HZSM-5 prepared by this method in the methanol aromatization reaction are still not ideal.
In order to solve the above defects, it is a technical problem to be solved urgently that a catalyst with excellent performance, simple preparation method, friendly synthesis conditions, and especially good selectivity and yield in methanol aromatization is provided.
Disclosure of Invention
The invention provides an HZSM-5 molecular sieve catalyst, which has the advantages of simple preparation process, friendly operation conditions, no harsh operation conditions such as high temperature, high pressure, high acid, high alkali and the like and no serious pollution to the environment, and is particularly suitable for methanol aromatization reaction.
The invention provides an HZSM-5 molecular sieve catalyst, which comprises the following raw materials: an organic silicon source, an aluminum source, a template agent M and water; wherein the molar ratio of the silicon source to the aluminum source is SiO2：Al2O3(10-200): 1; the molar ratio of the template agent M to the aluminum source is M: al (Al)2O3(2-10): 1; the molar ratio of the water to the aluminum source is H2O：Al2O3＝(1000-1200)：1。
Further, the organic silicon source is any one or a combination of any two or more of 2-aminoethyl trimethoxysilane, aminomethyl trimethoxysilane, 3-aminopropyltrimethoxysilane, tetraethyl silicate, methylchlorosilane, phenylchlorosilane, ethyltrichlorosilane, propyltrichlorosilane and vinyltrichlorosilane.
Further, the aluminum source is any one or a combination of any two or more of aluminum isopropoxide, aluminum nitrate and sodium metaaluminate.
Further, the template agent M is any one or any combination of more than two of diethylamine, triethylamine, tetrapropylammonium bromide, ethanol, carbon nanotubes, hexadecyltrimethylammonium bromide and tetrapropylammonium hydroxide.
Further, the XRD spectrum of the HZSM-5 molecular sieve catalyst shows distinct characteristic peaks at 2 θ ═ 7.9 °, 8.7 °, 23.1 °, 23.7 °, and 24.4 °.
Further, the specific surface area S of the HZSM-5 molecular sieve catalystBET300-340m2/g。
The invention further provides a preparation method of the HZSM-5 molecular sieve catalyst, which comprises the following steps:
step 1), preparation of gel: weighing the raw materials according to the proportioning and using amount of the raw materials, preparing a part of water and the template M into a template solution, uniformly mixing, and keeping stirring in a water bath kettle at 25-35 ℃ for 15-50 min; preparing an aluminum source solution from the other part of the water and the aluminum source, adding the aluminum source solution into the template agent solution, uniformly mixing, and keeping stirring in a water bath kettle at the temperature of 25-35 ℃ for 10-50min to obtain a first mixed material; finally, adding the silicon source into the first mixed material, uniformly mixing, and aging for 2-4h under the condition of water bath at 25-35 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 48-96 hours at the temperature of 150-;
step 3), hydrogen type replacement: taking out the lower layer precipitate in the crystallized material, putting the lower layer precipitate into a centrifugal tube, and putting the centrifugal tube into the centrifugal tubeAdding deionized water, stirring uniformly, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper layer liquid, repeating the steps of adding deionized water, stirring uniformly, centrifuging and detecting the pH value until the pH value is 7, drying and roasting the obtained final precipitation product, wherein the drying condition is drying at 120 ℃ for 8-20h in an oven, and the roasting condition is roasting at 600 ℃ in a muffle furnace for 5-10h to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution, wherein the ion exchange condition is that the solution is stirred in water bath at 60-95 ℃ for 10-15h, washing the solid material obtained after the ion exchange to be neutral, continuing to carry out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at the temperature of 100 ℃ and 120 ℃ for 10-15h to obtain a hydrogen type displacement product;
step 4), removing the template agent: and transferring the hydrogen type displacement product to a muffle furnace, raising the temperature to 550 ℃ by a program, and roasting for 4-8h at 550 ℃ to obtain the HZSM-5 molecular sieve catalyst. Preferably, the temperature programming is to heat the muffle furnace from 30 ℃ to 200 ℃ over 60min, to maintain the temperature at 200 ℃ for 30min, to heat the muffle furnace from 200 ℃ to 450 ℃ over 100min, to maintain the temperature at 450 ℃ for 30min, and to heat the muffle furnace from 450 ℃ to 550 ℃ over 60 min.
Further, during the ion exchange in the step 3, NH is added4NO3NH used in solution4NO3The solid is 1.2 times of the mass of the Na-type molecular sieve.
The invention also provides the application of the HZSM-5 molecular sieve catalyst synthesized by the invention in methanol aromatization reaction. Preferably, the HZSM-5 molecular sieve catalyst of the invention is used for 5 to 6 hours-1Under the harsh conditions of high space velocity, normal pressure and 450 ℃, the complete conversion life of the methanol is more than 10 hours and is between 0.5 and 1.5 hours-1The complete conversion life of the methanol is not less than 100h under the conditions of space velocity, normal pressure and 450 ℃.
The invention has the advantages of
1. The HZSM-5 molecular sieve catalyst disclosed by the invention is prepared by optimally combining the raw material formula and the preparation method, so that the preparation process is simple, the operation condition is friendly, extreme conditions such as high temperature, high pressure, high acid and high alkali are not needed, the environmental pollution and the operation difficulty are reduced, the HZSM-5 molecular sieve catalyst is an efficient and simple synthesis method, and the synthesis cost can be greatly saved;
2. the HZSM-5 molecular sieve catalyst prepared by the method has a moderate specific surface area distribution range and good pore texture distribution characteristics, is applied to methanol aromatization reaction, and has the characteristics of high aromatic hydrocarbon quality yield, long service life of the catalyst and the like.
Drawings
FIG. 1 is an XRD spectrum of an HZSM-5 molecular sieve catalyst obtained in examples 1 to 6 of the present invention;
FIG. 2N of HZSM-5 molecular sieve catalyst obtained in examples 1 to 6 of the present invention2Adsorption and desorption isothermal curves;
FIG. 3 is a graph of pore size distribution for HZSM-5 molecular sieve catalysts obtained in examples 1-6 of the present invention at different silica to alumina ratios;
FIG. 4 NH of HZSM-5 molecular sieve catalysts obtained in examples 1-6 of the present invention at different silica to alumina ratios3-a TPD spectrum;
FIG. 5 is an SEM image of the HZSM-5 molecular sieve catalyst obtained in examples 1-6 of the present invention.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention.
Example 1
A preparation method of an HZSM-5 molecular sieve catalyst comprises the following steps:
step 1), preparation of gel: according to the silicon-aluminum ratio Si of the raw materials, Al is 8, and a template agent M: al (Al)2O3＝6.8、H2O:Al2O3Each raw material was weighed 1149, the mass of the aluminum source was fixed, and 10g of H was weighed2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; another portion of the water and 0.297g of the aluminum source (i.e., NaAlO) was added2) Preparing an aluminum source solution, adding the aluminum source solution into the template agent solution, uniformly mixing, and then carrying out water treatment at 30 DEG CStirring in the bath kettle for 30min to obtain a first mixed material; finally, adding the silicon source (namely tetraethyl silicate) into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: and transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ through 60min by program heating, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ through 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ through 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain the HZSM-5 molecular sieve catalyst sample 1.
Example 2
A preparation method of an HZSM-5 molecular sieve catalyst comprises the following steps:
step 1), preparation of gel: according to the silicon-aluminum ratio Si: Al being 13. Template agent M: al (Al)2O3＝6.8、H2O:Al2O3Each raw material was weighed 1149, the mass of the aluminum source was fixed, and 10g of H was weighed2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; another portion of the water and 0.297g of the aluminum source (i.e., NaAlO) was added2) Preparing an aluminum source solution, adding the aluminum source solution into the template agent solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source (namely tetraethyl silicate) into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: and transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ through 60min by program heating, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ through 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ through 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain the HZSM-5 molecular sieve catalyst sample 2.
Example 3
A preparation method of an HZSM-5 molecular sieve catalyst comprises the following steps:
step 1), preparation of gel: according to the silicon-aluminum ratio Si of the raw materials, Al is 25, and a template agent M: al (Al)2O3＝6.8、H2O:Al2O3Each raw material was weighed 1149, the mass of the aluminum source was fixed, and 10g of H was weighed2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; another portion of the water and 0.297g of the aluminum source (i.e., NaAlO) was added2) Preparing an aluminum source solution, adding the aluminum source solution into the template agent solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source (namely tetraethyl silicate) into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3The solution is subjected to ion exchange (converted into ammonium nitrate solid)The adding amount is 1.2 times of that of the Na-type molecular sieve), the ion exchange condition is that the solid material obtained after the ion exchange is stirred for 12 hours in water bath at the temperature of 80 ℃, the solid material obtained after the ion exchange is washed to be neutral, the centrifugation and the washing are continuously carried out until the material obtained after the ion exchange is neutral, and the treated material is dried for 12 hours at the temperature of 100-;
step 4), removing the template agent: and transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ through 60min by program heating, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ through 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ through 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain the HZSM-5 molecular sieve catalyst sample 3.
Example 4
A preparation method of an HZSM-5 molecular sieve catalyst comprises the following steps:
step 1), preparation of gel: according to the raw material Si-Al ratio Si, Al is 38, and a template agent M: al (Al)2O3＝6.8、H2O:Al2O3Each raw material was weighed 1149, the mass of the aluminum source was fixed, and 10g of H was weighed2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; another portion of the water and 0.297g of the aluminum source (i.e., NaAlO) was added2) Preparing an aluminum source solution, adding the aluminum source solution into the template agent solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source (namely tetraethyl silicate) into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower layer precipitate in the crystallized material, putting the lower layer precipitate into a centrifugal tube, adding deionized water into the centrifugal tube, uniformly stirring, and continuing to performCentrifuging, detecting the pH value of the centrifuged upper layer liquid, repeatedly adding deionized water, stirring uniformly, centrifuging and detecting the pH value until the pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ in an oven for 12 hours, the roasting condition is roasting at 550 ℃ in a muffle furnace for 6 hours to obtain the Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: and transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ through 60min by program heating, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ through 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ through 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain the HZSM-5 molecular sieve catalyst-sample 4.
Example 5
A preparation method of an HZSM-5 molecular sieve catalyst comprises the following steps:
step 1), preparation of gel: according to the raw material Si-Al ratio Si, Al is 58, and a template agent M: al (Al)2O3＝6.8、H2O:Al2O3Each raw material was weighed 1149, the mass of the aluminum source was fixed, and 10g of H was weighed2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; another portion of the water and 0.297g of the aluminum source (i.e., NaAlO) was added2) Preparing an aluminum source solution, adding the aluminum source solution into the template agent solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source (namely tetraethyl silicate) into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: and transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ through 60min by program heating, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ through 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ through 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain the HZSM-5 molecular sieve catalyst sample 5.
Example 6
A preparation method of an HZSM-5 molecular sieve catalyst comprises the following steps:
step 1), preparation of gel: according to the raw material Si-Al ratio Si, Al is 80, and a template agent M: al (Al)2O3＝6.8、H2O:Al2O3Each raw material was weighed 1149, the mass of the aluminum source was fixed, and 10g of H was weighed2Preparing a template agent solution from the O and the template agent M, and uniformly mixingStirring in 30 deg.C water bath for 30 min; another portion of the water and 0.297g of the aluminum source (i.e., NaAlO) was added2) Preparing an aluminum source solution, adding the aluminum source solution into the template agent solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source (namely tetraethyl silicate) into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: and transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ through 60min by program heating, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ through 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ through 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain the HZSM-5 molecular sieve catalyst-sample 6.
Data sheet for sample 1-sample 6 well Structure parameters
Figure BDA0002005096170000111
As can be seen from the above pore structure parameter data table, the specific surface area of the molecular sieve is the smallest and the external specific surface area of the molecular sieve is the smallest when n (si)/n (al) is 58, and the specific surface area and the external specific surface area of the molecular sieve are slightly larger than those of the molecular sieves synthesized under the conditions of n (si)/n (al) 58 and are lower than those of the other sample molecular sieves. According to the BJH pore size distribution diagram and the SEM characterization result, the molecular sieves of the two samples are large in size and reach the micron level, the outer surfaces of the molecular sieves are smooth, and obvious rough nano-crystalline grains do not exist, so that the specific surface area and the outer specific surface area of the molecular sieves are small. Although the surface of the molecular sieve is smooth when the silica-alumina ratio is larger, the difference between the total specific surface area and the specific surface area when the silica-alumina ratio is smaller is not large, and the reason may be that the molecular sieves with the silica-alumina ratios of 8, 13 and 25 have more mesopores, so that the specific surface area is reduced, and when the silica-alumina ratio is larger, micropores are mainly used. The pore volume of the molecular sieve tends to increase and decrease with the increase of the ratio of silicon to aluminum, and is larger at the ratio of silicon to aluminum of 8, 13 and 25 and smaller at the ratio of silicon to aluminum of 38, 8 and 80.
Data tables corresponding to FIG. 4 for samples 1-6
Figure BDA0002005096170000121
Fig. 4 shows the data table, which shows the area ratio of strong acid desorption peak to weak acid desorption peak of HZSM-5 molecular sieve prepared under different silica/alumina ratio conditions. The analysis of the data in the table shows that the acid amount of the molecular sieve is in a trend of increasing firstly and then decreasing, when the silicon-aluminum ratio is 38, the ratio of strong acid to weak acid is 0.049, which is the minimum value, and the peak area of the weak acid is obviously larger than that of other samples by combining a desorption curve, which indicates that the molecular sieve is mainly weak acid.
As can be seen from FIG. 5, the morphology of the HZSM-5 molecular sieve catalyst prepared by the present invention is greatly changed with the increase of the silica-alumina ratio, and when the silica-alumina ratio is 8, the morphology of the molecular sieve catalyst is uniform in size, is in the shape of a regular and rough-surfaced fuzzy ball with the particle size range of 400-800nm, and is formed by stacking the particles with the particle size of 2-40 nm; when the silica-alumina ratio is 13 to 25, the surface of the molecular sieve catalyst is in an ellipsoid shape with uniform size and 400-600nm particle size, and compared with the molecular sieve catalyst with the silica-alumina ratio of 8, the surface is rougher; when the silicon-aluminum ratio is increased to 38 and 58, the molecular sieves have different shapes, smooth surfaces and larger particles, and are mostly hexagonal columns with unclear edges and corners; when the Si/Al ratio is 80, the molecular sieve is in a regular hexagonal column shape and has uniform size, and the particle size range is 400-600 nm.
As can be seen from fig. 1, in XRD patterns of molecular sieve catalysts with different silica-alumina ratios, characteristic diffraction peaks of ZSM-5 appear at 2 θ ═ 7.9 °, 8.7 °, 23.1 °, 23.7 °, and 24.4 ° in all 6 samples, and no other miscellaneous peaks exist, indicating that the synthesized samples are ZSM-5 molecular sieves. The figure shows that the characteristic diffraction peak intensity changes with the change of the silicon-aluminum ratio, and the diffraction peak intensity at a low silicon-aluminum ratio below 25 is obviously lower than that of the diffraction peak intensities with the silicon-aluminum ratios of 38, 58 and 80, which indicates that the change of the silicon-aluminum ratio influences the crystallinity of the molecular sieve.
As can be seen from FIG. 2, in order to investigate the influence of Si/Al ratio on the pore structure and specific surface area of a molecular sieve, BET test was performed thereon, and FIG. 2 shows N of HZSM-5 molecular sieve2Adsorption and desorption isotherms. It can be seen from the figure that the HZSM-5 molecular sieve catalyst of six groups of samples is in the low pressure section (P/P) within the range of the silicon-aluminum ratio explored by the invention0<0.1) all have higher adsorption capacity, which indicates that all molecular sieve catalysts have certain micropore structures.
When Si/Al is 8, 13, 25, N2The adsorption and desorption isotherms belong to IV-type isotherms, cannot be superposed due to the coagulation effect of capillaries, have hysteresis, and conform to an H3 hysteresis loop, which indicates that a sample has crack holes accumulated in a particle form, namely that the synthesized molecular sieve has a certain mesoporous structure. When Si/Al is 38, 58, 80, N2The adsorption and desorption isotherms belong to the type I isotherm and have no obvious hysteresis loop, which indicates that the molecular sieve is mainly microporous.
As can be seen from fig. 3, in order to investigate whether the hysteresis loop of the molecular sieve represents the existence of a mesoporous structure of the molecular sieve, the BJH pore size distribution diagram of ZSM-5 shown in fig. 3 is plotted. It can be seen from the figure that when Si/Al is 8, 13, 25, the molecular sieve has smaller mesopore diameter of the largest possible pore diameter, and in the vicinity of 3.8nm, it indicates that all three molecular sieve samples contain a certain amount of mesopore structure, which is similar to N2The adsorption and desorption curve conclusion corresponds to that when Si/Al is 38, 58 and 80, in the range of 2-50nm, three molecular sieve samples have no obvious mesopore distribution and no obvious mesopore and pore diameter, which indicates that the molecular sieve mainly takes micropores as the main part, and the conclusion is in line with the conclusion that the molecular sieve has the most probable pore diameter2The adsorption and desorption curves are consistent in conclusion.
FIG. 4 shows NH of molecular sieves synthesized under different Si/Al ratios3-TPD spectrum. As shown in the figure: NH of 6 samples in the spectrogram3The TPD curves are typically bimodal, respectively a low temperature peak at around 200 ℃ and a high temperature peak at around 500 ℃, representing weak acid sites and strong acid sites in the molecular sieve. It can be seen from the figure that as the silicon-aluminum ratio increases, the desorption peak position of the weak acid starts to move towards the low temperature direction, and the desorption peak position of the strong acid also tends to move towards the low temperature direction and the desorption peak gradually becomes less obvious, which indicates that the acidity degree of the molecular sieve can be properly reduced by increasing the silicon-aluminum ratio. In the range of examination, the area of the strong acid peak is increased and then decreased along with the increase of the silicon-aluminum ratio, which shows that the surface acidity distribution of the molecular sieve can be properly adjusted by adjusting the feeding silicon-aluminum ratio in the synthesis process.
Example 7
The evaluation of the methanol aromatization reaction performance with the aforementioned sample 1 comprises the steps of:
2.815g of HZSM-5 molecular sieve catalyst of sample 1 respectively, crushing and sieving to 40-60 meshes, firstly activating the catalyst for 6h, then filling the catalyst into a fixed bed differential reactor, taking methanol (analytically pure) as a raw material, setting the temperature at 450 ℃ under normal pressure and the mass space velocity of the raw material at 5.06h-1Performing methanol aromatization reaction, condensing and separating the product at the outlet of the fixed bed differential reactor by a condenser, and separating the gas-phase product (namely low-carbon hydrocarbon) and the liquid-phase product (C)5 +Hydrocarbon) is separated, then, after separating a water layer and an oil layer in the liquid phase product, the oil layer product is subjected to quantitative analysis and then is extracted and separated to obtain the target product aromatic hydrocarbon.
The performance of the methanol aromatization reaction was evaluated on the molecular sieve catalysts of samples 2-6 using the same method as described above, and the data obtained are shown in table 1.
Table 1 evaluation data of methanol aromatization reaction performance of sample 1 to sample 6
Figure BDA0002005096170000141
Figure BDA0002005096170000151
Example 8
Comparing the service life of the catalyst, the HZSM-5 molecular sieve catalyst synthesized by the invention and the HZSM-5 molecular sieve catalyst of the commercial Nankai catalyst factory are used for carrying out methanol aromatization reaction under the same conditions, and the reaction time and the yield data of aromatic hydrocarbon products are shown in Table 2.
TABLE 2 catalyst Life comparison Table
Mass yield of south Keohio powder% Mass yield of Si/Al 13 molecular sieve raw powder%
0.5h 16.46454204 17.66050426
1h 15.55800827 15.63987832
2h 14.36457406 14.7319562
3h 9.516535802 14.43679184
4h 5.743621686 14.09958094
5h 13.26568172
6h 13.02472925
7h 12.85320847
8h 12.46148699
9h 12.12463529
Therefore, the HZSM-5 molecular sieve catalyst produced by the method has obvious advantages in service life compared with the commercial products.
All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Claims (5)

1. A preparation method of an HZSM-5 molecular sieve catalyst is characterized by comprising the following steps:
step 1), preparation of gel: al =8, a template M: al (Al)2O3=6.8、H2O:Al2O3=1149 weigh each raw material, fix the mass of the aluminium source, weigh 10g of H2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; preparing an aluminum source solution from the other part of the water and 0.297g of the aluminum source, adding the aluminum source solution into the template solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, stirring uniformly, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper layer liquid, and repeating the steps of adding deionized water, stirring uniformly, centrifuging and detecting the pH value until the pH value is detectedDetecting the obtained pH value to be 7, drying and roasting the obtained final precipitation product, wherein the drying condition is drying at 120 ℃ for 12h in a drying oven, and the roasting condition is roasting at 550 ℃ in a muffle furnace for 6h to obtain the Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution, wherein the ion exchange condition is stirring in a water bath at 80 ℃ for 12h, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 120 ℃ for 12h to obtain a hydrogen-type displacement product;
step 4), removing the template agent: transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ after 60min by programmed temperature raising, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ after 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ after 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain an HZSM-5 molecular sieve catalyst;
wherein the aluminum source is NaAlO2The silicon source is tetraethyl silicate; the HZSM-5 molecular sieve catalyst has n (Si)/n (Al) of 8 and SBETIs 318.38m2 g-1、SmicIs 269.2m2 g-1、SextIs 49.18m2 g-1、VtotalIs 0.232cm3 g-1、VmicIs 0.103cm3 g-1、VmesIs 0.129cm3 g-1；NH3-peak position of weak acid at 199 ℃, peak position of strong acid at 556 ℃, peak area of weak acid at 88.6%, peak area of strong acid at 11.4%, and peak/weak acid at 0.129% in TPD spectrogram; the mass percent of the aromatic hydrocarbon yield was 15.55%, the mass percent of the BTX yield was 12.79%, the mole percent of the aromatic hydrocarbon selectivity was 36.06%, and the mole percent of the BTX selectivity was 30.84%.
2. A preparation method of an HZSM-5 molecular sieve catalyst is characterized by comprising the following steps:
step 1), preparation of gel: al =13, template M: al (Al)2O3=6.8、H2O:Al2O3=1149 weigh each raw material, fix the mass of the aluminium source, weigh 10g of H2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; preparing an aluminum source solution from the other part of the water and 0.297g of the aluminum source, adding the aluminum source solution into the template solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ after 60min by programmed temperature raising, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ after 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ after 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain an HZSM-5 molecular sieve catalyst;
wherein the aluminum source is NaAlO2The silicon source is tetraethyl silicate; the HZSM-5 molecular sieve catalyst has n (Si)/n (Al) of 13 and SBETIs 309.28m2 g-1、SmicIs 256.07m2 g-1、SextIs 53.21m2 g-1、VtotalIs 0.265cm3 g-1、VmicIs 0.126cm3 g-1、VmesIs 0.139cm3 g-1；NH3-the weak acid peak position in the TPD spectrum is 194 ℃, the strong acid peak position is 526 ℃, the weak acid peak area is 88.19%, the strong acid peak area is 11.81%, and the strong acid/weak acid is 0.134%; the mass percent of the aromatic hydrocarbon yield was 17.66%, the mass percent of the BTX yield was 14.41%, the mole percent of the aromatic hydrocarbon selectivity was 41.39%, and the mole percent of the BTX selectivity was 35.45%.
3. A preparation method of an HZSM-5 molecular sieve catalyst is characterized by comprising the following steps:
step 1), preparation of gel: al =25, template M: al (Al)2O3=6.8、H2O:Al2O3=1149 weigh each raw material, fix the mass of the aluminium source, weigh 10g of H2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; preparing an aluminum source solution from the other part of the water and 0.297g of the aluminum source, adding the aluminum source solution into the template solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ after 60min by programmed temperature raising, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ after 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ after 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain an HZSM-5 molecular sieve catalyst;
wherein the aluminum source is NaAlO2The silicon source is tetraethyl silicate; the HZSM-5 molecular sieve catalyst has n (Si)/n (Al) of 25 and SBETIs 334.73m2 g-1、SmicIs 286.24m2 g-1、SextIs 48.49m2 g-1、VtotalIs 0.286cm3 g-1、VmicIs 0.127cm3 g-1、VmesIs 0.159cm3 g-1；NH3-TPD spectrum with weak acid peak position 190 ℃, strong acid peak position 481 ℃, weak acid peak area 83.37%, strong acid peak area 16.63%, and strong acid/weak acid 0.199(ii) a The mass percent of the aromatic hydrocarbon yield was 16.65%, the mass percent of the BTX yield was 13.45%, the mole percent of the aromatic hydrocarbon selectivity was 38.88%, and the mole percent of the BTX selectivity was 33.1%.
4. A preparation method of an HZSM-5 molecular sieve catalyst is characterized by comprising the following steps:
step 1), preparation of gel: al =38 of raw material Si/Al ratio, and a template agent M: al (Al)2O3=6.8、H2O:Al2O3=1149 weigh each raw material, fix the mass of the aluminium source, weigh 10g of H2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; preparing an aluminum source solution from the other part of the water and 0.297g of the aluminum source, adding the aluminum source solution into the template solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3The solution is subjected to ion exchange (the adding amount of ammonium nitrate solid is 1.2 times of that of Na-type molecular sieve), and the ion exchange condition is thatStirring in water bath at 80 ℃ for 12h, washing the solid material obtained after ion exchange to be neutral, continuously centrifuging and washing until the material obtained after ion exchange is neutral, and drying the treated material at 120 ℃ for 12h to obtain a hydrogen-type displacement product;
step 4), removing the template agent: transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ after 60min by programmed temperature raising, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ after 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ after 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain an HZSM-5 molecular sieve catalyst;
wherein the aluminum source is NaAlO2The silicon source is tetraethyl silicate; the HZSM-5 molecular sieve catalyst has n (Si)/n (Al) of 38 and SBETIs 307.47m2 g-1、SmicIs 294.99m2 g-1、SextIs 12.48m2 g-1、VtotalIs 0.197cm3 g-1、VmicIs 0.154cm3 g-1、VmesIs 0.043cm3 g-1；NH3-peak position of weak acid at 172 ℃, peak position of strong acid at 576 ℃, peak area of weak acid at 95.34%, peak area of strong acid at 4.66%, and peak area of strong acid/weak acid at 0.049 in TPD spectrogram; the mass percent of the aromatic hydrocarbon yield was 15.35%, the mass percent of the BTX yield was 13.84%, the mole percent of the aromatic hydrocarbon selectivity was 35.87%, and the mole percent of the BTX selectivity was 33.65%.
5. A preparation method of an HZSM-5 molecular sieve catalyst is characterized by comprising the following steps:
step 1), preparation of gel: al =58, template M: al (Al)2O3=6.8、H2O:Al2O3=1149 weigh each raw material, fix the mass of the aluminium source, weigh 10g of H2Preparing a template agent solution from the O and the template agent M, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30 min; formulating another portion of said water and 0.297g of said aluminum source into an aluminum source solution, and subjecting said aluminum source solution to a heat treatmentAdding an aluminum source solution into the template solution, uniformly mixing, and keeping stirring in a water bath kettle at 30 ℃ for 30min to obtain a first mixed material; finally, adding the silicon source into the first mixed material, uniformly mixing, and aging for 3 hours under the condition of water bath at the temperature of 30 ℃ to obtain a gel material;
step 2), hydrothermal crystallization synthesis: transferring the gel material obtained in the step 1) into a static synthesis reaction kettle with a polytetrafluoroethylene lining, putting the static synthesis reaction kettle into an oven, and crystallizing for 72 hours at 180 ℃ to obtain a crystallized material;
step 3), hydrogen type replacement: taking out the lower-layer precipitate in the crystallized material, putting the precipitate into a centrifuge tube, adding deionized water into the centrifuge tube, uniformly stirring, continuing to perform centrifugal operation, detecting the pH value of the centrifuged upper-layer liquid, repeatedly adding deionized water, uniformly stirring, centrifuging and detecting the pH value until the detected pH value is 7, drying and roasting the obtained final precipitate product, wherein the drying condition is drying at 120 ℃ for 12 hours in an oven under the condition of 100 plus materials and roasting at 550 ℃ in a muffle furnace for 6 hours to obtain a Na-type molecular sieve, and then mixing the Na-type molecular sieve with 0.8ml/L NH4NO3Carrying out ion exchange on the solution (the addition amount of ammonium nitrate solid is 1.2 times of that of the Na-type molecular sieve), stirring the solution in water bath at 80 ℃ for 12 hours under the ion exchange condition, washing the solid material obtained after the ion exchange to be neutral, continuously carrying out centrifugation and washing until the material obtained after the ion exchange is neutral, and drying the treated material at 100-120 ℃ for 12 hours to obtain a hydrogen-type displacement product;
step 4), removing the template agent: transferring the hydrogen type displacement product into a muffle furnace, raising the temperature of the muffle furnace from 30 ℃ to 200 ℃ after 60min by programmed temperature raising, keeping the temperature at 200 ℃ for 30min, raising the temperature from 200 ℃ to 450 ℃ after 100min, keeping the temperature at 450 ℃ for 30min, raising the temperature from 450 ℃ to 550 ℃ after 60min, and keeping the temperature at 550 ℃ for roasting for 6h to obtain an HZSM-5 molecular sieve catalyst;
wherein the aluminum source is NaAlO2The silicon source is tetraethyl silicate; the HZSM-5 molecular sieve catalyst has n (Si)/n (Al) of 58 and SBETIs 301.09m2 g-1、SmicIs 291.21m2 g-1、SextIs 9.88m2 g-1、VtotalIs 0.189cm3 g-1、VmicIs 0.151cm3 g-1、VmesIs 0.038cm3 g-1；NH3-peak position of weak acid at 188 ℃, peak position of strong acid at 527 ℃, peak area of weak acid 86.39%, peak area of strong acid at 13.61%, and peak area of strong acid/weak acid at 0.158% in TPD spectrogram; the mass percent of the aromatic hydrocarbon yield was 17.6%, the mass percent of the BTX yield was 15.4%, the mole percent of the aromatic hydrocarbon selectivity was 41.14%, and the mole percent of the BTX selectivity was 38.46%.
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