CN111760590A - High-mesoporosity HZSM-5@ SiO2Preparation method of composite molecular sieve - Google Patents

High-mesoporosity HZSM-5@ SiO2Preparation method of composite molecular sieve Download PDF

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CN111760590A
CN111760590A CN202010703803.9A CN202010703803A CN111760590A CN 111760590 A CN111760590 A CN 111760590A CN 202010703803 A CN202010703803 A CN 202010703803A CN 111760590 A CN111760590 A CN 111760590A
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季东
程春晖
李红伟
李贵贤
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Lanzhou University of Technology
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Abstract

The invention provides a high-mesoporosity HZSM-5@ SiO2The preparation method of the composite molecular sieve comprises the following steps: mixing and stirring a mixed solution of an alkali metal solution and a pore-leading agent (PDSN), HZSM-5 to obtain slurry, stirring to form a gel mixed solution, cooling, filtering, washing and drying to obtain the high-mesopore-degree XZSM-5 molecular sieve, and mixing the high-mesopore-degree XZSM-5 molecular sieve with NH4NO3After the solution is mixed with ion exchange, the solution is dried and roasted for 2 to 3 hours to obtain the HZSM-5 molecule with high mesoporositySieving seed crystal, adding dispersant and silicon source, hydrothermal crystallizing, washing, drying and roasting to obtain high-mesopore-degree HZSM-5@ SiO2And (3) compounding the molecular sieve. The high-mesoporosity HZSM-5@ SiO prepared by the invention2The composite molecular sieve shows good catalytic performance and anti-carbon deposition capability in isomerization, alkylation and other reactions.

Description

High-mesoporosity HZSM-5@ SiO2Preparation of composite molecular sieveMethod of producing a composite material
Technical Field
The invention belongs to the technical field of composite molecular sieve synthesis, and particularly relates to high-mesoporosity HZSM-5@ SiO2A preparation method of the composite molecular sieve.
Background
HZSM-5 has two-dimensional 10-membered ring channels, one of which is a 10-membered ring straight channel, and the other is a 10-membered ring channel with a Zigzag shape: the pore channel structure is [100 ]]
Figure BDA0002593864860000011
[010]
Figure BDA0002593864860000012
Figure BDA0002593864860000013
The crystal structure of the orthorhombic system, Pnma,
Figure BDA0002593864860000014
the ZSM-5 molecular sieve not only provides a large number of inlet and outlet channels for reactants and products, but also provides a good space restriction effect for shape-selective catalysis by using a special pore channel structure.
HZSM-5 belongs to an orthorhombic crystal system, a molecular sieve (| Na) with an MFI type structuren(H2O)16∣[AlnSi96-nO192]) The silicon-aluminum ratio can be from 10 to the full silicon Silicalite-1. The HZSM-5 molecular sieve structure contains strong acid sites (B acid) and weak acid sites (L acid), and the acid center is an active center for initiating a catalytic reaction. The acidic catalytic performance of HZSM-5 is independent of the Si atom, but depends on the Al atoms with different oxygen coordination numbers in the skeleton, the low-coordination Al atom (i.e. the bidentate structure [ AlO ]2](iii) a three-coordinate structure of [ AlO ]3]) Form an L-acid center, a highly coordinated Al atom (i.e., a four-coordinate structure H [ AlO ]4](iii) a penta-coordinate structure H2[AlO5]Hexa-coordinate structure H3[A1O6]Forming a B acid center. The mutual conversion of the L acid center and the B acid center can be realized by adjusting the oxygen coordination number of the Al atom, so as to achieve the purpose of changing the catalytic performance.
The shape-selective catalysis of the HZSM-5 molecular sieve enables the HZSM-5 molecular sieve to have higher selectivity in specific reaction, but also enables the catalytic reaction of molecules with the size similar to or larger than that of the zeolite molecular sieve pore channel to be difficult to carry out, namely, the molecular diffusion in the reaction is limited, so that the reaction activity is greatly reduced, and meanwhile, the zeolite molecular sieve is easy to deposit carbon and deactivate in the reaction, and the service life is greatly reduced. The hierarchical pore material has the advantages of both microporous molecular sieve and mesoporous material, has high hydrothermal stability, strong acidity and mesoporous structure, and can provide excellent mass transfer performance while maintaining excellent shape selectivity when used as catalytic material.
As a simple and efficient method for introducing mesopores, alkali treatment is a means for increasing the external surface area of the molecular sieve and improving diffusion, which is widely used at present. Fathi et al (Fuel,2014,116(6):529-537) use different alkaline reagents NaOH and Na2CO3And CaCO3The ZSM-5 molecular sieve is treated to find Na2CO3The crystallinity of the treated mesoporous ZSM-5 molecular sieve catalyst is increased, and the mesoporous volume is from 0.101cm3Lifting the/g to 0.119cm3The acid content was reduced slightly from 0.8594mmol/g to 0.7587 mmol/g. However, the traditional alkali treatment using inorganic alkali such as NaOH as an alkali reagent is difficult to control the desilication rate, and is easy to cause excessive desilication, so that on one hand, the introduced mesoporous has large aperture, and a mesoporous system with concentrated and uniformly distributed aperture is difficult to construct in a molecular sieve crystal phase; on the other hand, excessive desilication can cause serious destruction of the framework structure, leading to the breakage of the molecular sieve crystal structure, and seriously affecting the catalytic effect (J.Mater. chem.,2006,16(22): 2121).
Disclosure of Invention
The invention aims to solve the technical problem of providing a high-mesoporosity HZSM-5@ SiO2Preparation method of composite molecular sieve, and high-mesopore-degree HZSM-5@ SiO prepared by method2The core of the composite molecular sieve has a large number of highly dispersed and strongly communicated micro-mesoporous structures, so that the diffusion and the reaction activity of molecules are greatly promoted; simultaneous inert SiO2The thin shell layer can well inhibit the secondary isomerization reaction of aromatic hydrocarbon, and can effectively modulate the pore size of HZSM-5 zeolite, thereby greatly improving the shape-selective catalytic capability of the zeolite. The method not only can accurately control the mesoporous specific surface area and the pore size of the catalyst core by adjusting the type and the dosage of the pore-forming agent (PDS); and the existence of the pore-leading agent (PDS) can effectively prevent disorder in the desilication process, furthest maintain the inherent property of the catalyst core, and have micro-mesoporous structures and connectivity of different layers. Then, by depositing modifiers with different sizes at the orifice of the high-mesopore HZSM-5 core and finely modulating the modifiers, the shape selectivity of reactants and products can be greatly improved.
In order to solve the technical problems, the invention adopts the technical scheme that: high-mesoporosity HZSM-5@ SiO2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing and stirring a mixed solution of an alkali metal solution and a pore-forming agent (PDSN) and HZSM-5 to obtain slurry;
the mixed solution of the alkali metal solution and the pore-leading agent PDAs is a mixture of an alkali metal hydroxide solution and the pore-leading agent PDAs with a molar ratio of 1 (1-5); the concentration of the alkali metal hydroxide solution is 0.1 mol/L-1 mol/L;
s2, stirring the slurry obtained in the S1 at the temperature of 50-90 ℃ for 2-6 hours to form a gel mixed solution, cooling to room temperature, and filtering, washing and drying to obtain the high-mesopore-degree XZSM-5 molecular sieve; x in the high-mesoporosity XZSM-5 molecular sieve represents alkali metal;
s3, mixing the high-mesoporosity XZSM-5 molecular sieve obtained in S2 with NH with the concentration of 0.5-1 mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 550-650 ℃ for 2-3 h to obtain high-mesoporous HZSM-5 molecular sieve seed crystals;
s4, adding a dispersing agent and a silicon source into the HZSM-5 molecular sieve seed crystal with high mesoporosity obtained in S3, carrying out hydrothermal crystallization at 100-200 ℃ for 12-38 h, washing,After drying, roasting for 2-3 h at the temperature of 550-650 ℃ to obtain the HZSM-5@ SiO with high mesoporosity2And (3) compounding the molecular sieve.
Preferably, the dosage ratio of the mixed solution of the alkali metal solution and the pore-directing agent PDAs in the slurry in S1 to HZSM-5 is (20-50) mL: 1g of the total weight of the composition.
Preferably, the alkali metal hydroxide solution in S1 is a sodium hydroxide solution or a potassium hydroxide solution; the pore guide agent PDAs are anionic surfactants, nonionic surfactants or cationic surfactants.
Preferably, the anionic surfactant is DS-(ii) a The nonionic surfactant is EDA, DAH, TAEA or DEA; the cationic surfactant is PTA+、TPA+、CTA+、DSA+、 HM2+、HDP+Or BA+；
The anionic surfactant DS-Molecular formula is CH3(CH2)11OSO3 -The structural formula is as follows:
Figure BDA0002593864860000031
the molecular formula of the non-ionic surfactant EDA is C2H4(NH2)2The structural formula is as follows:
Figure BDA0002593864860000041
the molecular formula of the non-ionic surfactant DAH is H2N(CH2)6NH2The structural formula is as follows:
Figure BDA0002593864860000042
the molecular formula of the nonionic surfactant TAEA is N (CH)2CH2NH2)3The structural formula is as follows:
Figure BDA0002593864860000043
the molecular formula of DEA of the nonionic surfactant is HN (CH)2CH3)2The structural formula is as follows:
Figure BDA0002593864860000044
the cationic surfactant PTA+The molecular formula is (CH)3)3N+C3H7The structural formula is as follows:
Figure BDA0002593864860000045
the cationic surfactant TPA+Molecular formula is N+(C3H7)4The structural formula is as follows:
Figure BDA0002593864860000046
the cationic surfactant CTA+The molecular formula is (CH)3)3N+C12H25The structural formula is as follows:
Figure BDA0002593864860000047
the cationic surfactant DSA+The molecular formula is (C)18H37)2N+(CH3)3The structural formula is as follows:
Figure BDA0002593864860000048
the cationic surfactant HM2+The molecular formula is (CH)3)3N+C6H12N+(CH3)3The structural formula is as follows:
Figure BDA0002593864860000051
the cationic surfactant HDP+Molecular formula C16H33N+C5H5The structural formula is as follows:
Figure BDA0002593864860000052
the cationic surfactant BA+Molecular formula C6H5CH2N+(CH3)2R，R＝C8H17to C16H33The structural formula is as follows:
Figure BDA0002593864860000053
preferably, the washing methods in S2 and S4 are both washing with distilled water several times to neutrality.
Preferably, the high-mesoporosity XZSM-5 molecular sieve in S3 is mixed with NH4NO3The amount ratio of the solution was 1g:40 mL.
Preferably, the dispersant in S4 is n-hexane or n-heptane; the silicon source is Si (OCH)3)4、Si(OC2H5)4Or SiCl4。
Preferably, the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal, the dispersing agent and the silicon source in S4 is (1-7): (12-28): (3-38).
Preferably, the high mesoporosity HZSM-5@ SiO in S42The specific surface area of the composite molecular sieve is 276m2/g～420m2Per g, the mesoporous volume is 0.23cm3/g～0.45cm3The pore diameter of most probable pores is 2 nm-30 nm.
Compared with the prior art, the invention has the following advantages:
1. the high-mesoporosity HZSM-5@ SiO prepared by the invention2The core of the composite molecular sieve has a large number of highly-dispersed and strongly-communicated micro-mesoporous structures, so that the diffusion and the reaction activity of molecules are greatly promoted; simultaneous inert SiO2Thin shell layer can be very thinThe secondary isomerization reaction of aromatic hydrocarbon is well inhibited, the pore size of HZSM-5 zeolite can be effectively modulated, and the shape-selective catalytic capability of zeolite is greatly improved. The method not only can accurately control the mesoporous specific surface area and the pore size of the catalyst core by adjusting the type and the dosage of the pore-forming agent (PDS); and the existence of the pore-leading agent (PDS) can effectively prevent disorder in the desilication process, furthest maintain the inherent property of the catalyst core, and have micro-mesoporous structures and connectivity of different layers. Then, modifiers with different sizes are deposited at the orifice of the high-mesoporosity HZSM-5 core, and the shape selection selectivity of reactants and products can be greatly improved by finely modulating the modifiers.
2. The high-mesoporosity HZSM-5@ SiO prepared by the invention2The composite molecular sieve has the through mesopores with uniform dispersion and concentrated aperture, and can effectively improve the contact between the active site of the catalyst and the reactant molecules and improve the mass transfer capacity of the catalyst; and a layer of thin shell SiO is covered on the surface of the crystal2The shape selectivity of the catalyst is significantly improved. Compared with the conventional microporous HZSM-5 zeolite, the high-mesoporosity HZSM-5@ SiO prepared by the invention2The composite molecular sieve shows good catalytic performance and anti-carbon deposition capability in isomerization, alkylation and other reactions.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 shows HZSM-5@ SiO with high mesoporosity prepared in example 12X-ray diffraction pattern of the composite molecular sieve.
FIG. 2 shows HZSM-5@ SiO with high mesoporosity prepared in example 12Nitrogen adsorption and desorption isotherm curves of the composite molecular sieve products.
FIG. 3 shows HZSM-5@ SiO with high mesoporosity prepared in example 12Electron microscope image of the composite molecular sieve.
FIG. 4 shows HZSM-5@ SiO with high mesoporosity prepared in example 12The ammonia gas of the composite molecular sieve is removed from the attached figure by temperature programming.
FIG. 5 shows HZSM-5@ SiO with high mesoporosity prepared in example 12Inactivation thermogram of composite molecule.
Detailed Description
Example 1
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is a sodium hydroxide solution with the concentration of 0.1 mol/L; the pore-guiding agent PDAs is a cationic surfactant TPA+；
The cationic surfactant TPA+Molecular formula is N+(C3H7)4The structural formula is as follows:
Figure BDA0002593864860000071
wherein Na+And TPA+In a molar ratio of 1: 1;
s2, stirring the slurry obtained in the step S1 at the temperature of 80 ℃ for 4 hours to form a gel mixed solution, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 1mol/L4NO3Mixing the solutions, performing ion exchange AT 80 ℃, drying, and roasting AT 550 ℃ for 3 hours to obtain a high-mesoporosity HZSM-5 molecular sieve crystal seed named AT-3; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-hexane) and a silicon source (Si (OC) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S32H5)4) Then carrying out hydrothermal crystallization for 12h at the temperature of 110 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 3h at the temperature of 550 ℃ to obtain the high-mesoporosity HZSM-5@ SiO2The composite molecular sieve is named as AT-4; the high-mesoporosity HZSM-5 molecular sieve seed crystal, a dispersing agent andthe mass ratio of the silicon source is 3: 17: 24; the high mesoporosity HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 276m2Per g, the mesoporous volume is 0.22cm3The pore diameter of the most probable pore is 4.59 nm.
Comparative example 1
HZSM-5@ SiO of this comparative example2The preparation method of the composite molecular sieve, the difference between the comparative example and the example 1 is that the slurry in S1 does not contain the guide hole agent PDAs and does not have the operation of the S4 step; the method comprises the following steps:
s1, mixing 100mL of 0.1mol/L sodium hydroxide solution and 5g of HZSM-5, and stirring to obtain slurry;
s2, S2 as in example 1;
s3, the same as S3 in example 1, to obtain HZSM-5 molecular sieve seed crystal named AT-1.
Comparative example 2
The HZSM-5 molecular sieve seed crystal of the comparative example is prepared, and the difference between the comparative example and the example 1 is that the alkali metal solution and the guiding hole agent PDS (TPA) in the example 1+) The mixed solution of (2) is changed into a TPAOH solution, the slurry in S1 does not contain a pore-forming agent (PDS), and the operation of the step S4 is not performed; the method comprises the following steps:
s1, mixing 100mL of TPAOH solution with the concentration of 0.1mol/L and 5g of HZSM-5, and stirring to obtain slurry;
s2, S2 as in example 1;
s3, the same as S3 in example 1, to obtain HZSM-5 molecular sieve seed crystal named AT-2.
Comparative example 3
The preparation method of the HZSM-5 molecular sieve seed crystal of the comparative example is different from the preparation method of the example 1 in the operation without the step of S4; the method comprises the following steps:
s1, S1 as in example 1;
s2, S2 as in example 1;
s3, the same as S3 in example 1, to obtain HZSM-5 molecular sieve seed crystal named AT-3.
FIG. 1 shows the HZSM-5 raw material and the HZSM-5@ SiO with high mesoporosity prepared in example 12Composite molecular sieve (AT-4) and comparative examples 1 to 3The X-ray diffraction patterns of AT-1, AT-2 and AT-3 show that all samples show typical characteristic MFI topological diffraction peaks AT 2 θ 7-10 ° and 2 θ 22.5-25 °. The intensity of the characteristic AT-1 peak is significantly reduced compared to HZSM-5, because the crystal structure is severely destroyed by excessive desilication of sodium hydroxide. The increase in the intensity of the diffraction peak of AT-3 compared to that of AT-1 indicates the addition of the channeling agent, PDAs (TPA) to the sodium hydroxide solution+) And then, the framework structure of the HZSM-5 molecular sieve can be effectively improved, the existence of the pore-guiding agent PDAs can effectively prevent disorder in the desilication process, and the inherent properties of the catalyst core, namely the structure and connectivity of micro-mesopores with different layers, are maintained to the maximum extent. AT-2 treated with TPAOH alone has an increased intensity of diffraction peaks compared to AT-3, further demonstrating TPA+Protective desilication of (1). AT-4 has a slightly lower intensity of the characteristic diffraction peak of MFI than AT-3 without the characteristic diffraction peak of silica, which is likely to be that amorphous silica is highly dispersed on the outer surface of the molecular sieve, but the crystal structure is not changed, while inert SiO2The thin shell layer can well inhibit the secondary isomerization reaction of aromatic hydrocarbon, effectively regulate the pore size of the HZSM-5 zeolite and greatly improve the shape-selective catalytic capability of the HZSM-5 zeolite.
FIG. 2 shows the HZSM-5 raw material and the HZSM-5@ SiO with high mesoporosity prepared in example 12The nitrogen adsorption desorption isotherms of the composite molecular sieve (AT-4) and AT-1, AT-2 and AT-3 of comparative examples 1 to 3 were shown in Table 1 as physical characteristic parameters. As can be seen from FIG. 1, except that the raw powders HZSM-5 and AT-2 show type I adsorption isotherms, which are typical microporous materials, the samples all show type I and type IV composite adsorption isotherms, which indicates that mesoporous structures are formed in AT-1, AT-3 and AT-4. At p/p0>0.4, the hysteresis loops of AT-3 and AT-4 belong to the H2 type, compared with the hysteresis loop H3 type of AT-1, which indicates that the mesopores in AT-1 are irregular in shape, while the mesopores of AT-3 and AT-4 are more concentrated and ordered. As is clear from Table 1, AT-4 has a reduced specific surface area of 276m compared with AT-12The material is mainly thin shell SiO coated on the surface of the molecular sieve2So that the core of the catalyst is not affected; simultaneous mediatorThe pore volume and the most probable pore diameter of the pores are increased by nearly one time compared with HZSM-5 and are respectively increased to 0.22cm3The concentration of the carbon is 4.59nm, which greatly improves the diffusion path, greatly promotes the diffusion and the reaction activity of molecules and reduces the carbon deposition rate.
TABLE 1 physical Property parameters of HZSM-5 and AT-1 to AT-4
Figure BDA0002593864860000091
FIG. 3 shows HZSM-5 as the raw material and HZSM-5@ SiO with high mesoporosity as prepared in example 12Electron micrographs of composite molecular sieves (AT-4) and AT-1, AT-2 and AT-3 of comparative examples 1-3; as can be seen from the figure, the powder is different from the original powder HZSM-5, the surface of which is smooth and the crystal grains are complete, and the AT-1 surface is rough, and a large number of deeper holes exist. AT-3 appeared densely and uniformly bright spots in vivo and the surface was also smooth compared to AT-1 due to the guiding agent TPA+The ionic radius is larger than the micropore diameter of the molecular sieve, so that TPA+Na with small radius for protecting surrounding Si from being dissolved+Ions do not have a protective effect and cause OH-Is easier to attack and dissolve to form mesopores. Thus, introducing the guiding agent TPA+The desiliconization process has more controllability and selectivity, and the pore size, the number and the pore size distribution of mesopores formed in the crystal phase are determined. The external surface of AT-4 is provided with a layer of transparent amorphous SiO compared with AT-32While the internal structure is not affected, which is consistent with the characterization results of the X-ray diffraction pattern and the nitrogen adsorption desorption isotherm.
FIG. 4 shows HZSM-5 as the raw material and HZSM-5@ SiO with high mesoporosity as prepared in example 12Ammonia programmed temperature desorption of composite molecular sieve (AT-4) and AT-1, AT-2 and AT-3 of comparative examples 1-3, table 2 shows the acid amount distribution. As can be seen in fig. 4, all samples exhibited two desorption peaks at 190 ℃ and 430 ℃, which are respectively weak and strong acids of the HZSM-5 molecular sieve. Different treatment methods have obvious influence on the weak acid strength of the molecular sieve, and the position of a desorption peak is AT-1>AT-3>HASM-5≈AT-2>AT-4 decreases in turn, indicating inert SiO2Can be effectiveAnd reduces the surface acid strength of the molecular sieve. As can be seen from Table 2, the total acid content of the alkali-treated samples is significantly increased, which may be due to the exposed portion of the framework aluminum in the desilication of the molecular sieves, according to AT-1>AT-3>HZSM-5 is approximately equal to AT-2 and approximately equal to AT-4 is reduced in sequence, and the further supplementary evidence of precipitation of amorphous SiO on the AT-3 surface2(i.e., AT-4) can passivate the mesopores and the outer acid sites.
TABLE 2 acid amount distribution of HZSM-5 and AT-1 to AT-4
Figure BDA0002593864860000101
FIG. 5 shows HZSM-5 as the raw material and HZSM-5@ SiO with high mesoporosity as prepared in example 12As can be seen from FIG. 5, the thermogravimetric graphs of the composite molecular sieve (AT-4) and the deactivated catalysts of AT-1, AT-2 and AT-3 of comparative examples 1 to 3 show that the carbon deposition amount and carbon deposition rate of AT-4 are remarkably reduced compared with AT-1, which indicates that the stability and service life of the catalyst are greatly improved.
Table 3 shows the HZSM-5 raw material, the HZSM-5@ SiO with high mesoporosity prepared in example 12Evaluation table of performance of composite molecular sieve (AT-4) and AT-1, AT-2 and AT-3 of comparative examples 1 to 3 for methanol aromatization when used as a catalyst. As can be seen from Table 3, the selectivity for light aromatic hydrocarbons (benzene, toluene and xylene) is according to AT-4>AT-3>AT-2≈AT-1>HZSM-5 is reduced in sequence, and meanwhile, the light aromatic hydrocarbon of AT-4 accounts for 66.73% AT the highest, and the heavy aromatic hydrocarbon is 21.41% AT the lowest, which shows that the high-dispersion and strong-communication micro-mesoporous structure introduced into the AT-4 body effectively improves the diffusion property of the pore channel, so that the generated light aromatic hydrocarbon product can be desorbed rapidly, the accumulation in the micropore is avoided, and the phenomenon that the heavy aromatic hydrocarbon blocks the pore channel to further isomerize into coke is reduced. Simultaneously depositing amorphous inert SiO on the surface of the catalyst2On the one hand, under the condition of not influencing the inner pore canal of the catalyst, the acid sites on the outer surface of the catalyst are covered, so that the accumulation of coke on the active sites can be slowed down; on one hand, the effective pore diameter of the zeolite is regulated and controlled, and the shape selective separation capability of the catalyst is improved.
TABLE 3 evaluation of catalytic Performance when HZSM-5 and AT-1 to AT-4 were used as catalysts
Figure BDA0002593864860000111
In summary, the high mesoporosity HZSM-5@ SiO prepared in example 12The core of the composite molecular sieve has a large number of highly dispersed and strongly communicated micro-mesoporous structures, so that the diffusion and the reaction activity of molecules are greatly promoted; simultaneous inert SiO2The thin shell layer can well inhibit the secondary isomerization reaction of aromatic hydrocarbon, and can effectively modulate the pore size of HZSM-5 zeolite, thereby greatly improving the shape-selective catalytic capability of the zeolite. The method not only can accurately control the mesoporous specific surface area and the pore size of the catalyst core by adjusting the type and the dosage of the pore-forming agent (PDS); and the existence of the pore-leading agent (PDS) can effectively prevent disorder in the desilication process, furthest maintain the inherent property of the catalyst core, and have micro-mesoporous structures and connectivity of different levels. Then, by depositing modifiers with different sizes at the orifice of the high-mesopore HZSM-5 core and finely modulating the modifiers, the shape selectivity of reactants and products can be greatly improved. Compared with the conventional microporous HZSM-5 zeolite, the high-mesopore HZSM-5@ SiO prepared by the invention2The composite molecular sieve shows good catalytic performance and anti-carbon deposition capability in isomerization, alkylation and other reactions.
Example 2
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 2g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is a sodium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is an anionic surfactant DS-；
The anionic surfactant DS-Molecular formula is CH3(CH2)11OSO3 -The structural formula is as follows:
Figure BDA0002593864860000121
wherein Na+And DS-In a molar ratio of 1: 2;
s2, stirring the slurry obtained in the step S1 at the temperature of 50 ℃ for 6 hours to form a gel mixed solution, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 1mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 650 ℃ for 2 hours to obtain HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-hexane) and a silicon source (Si (OCH) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S33)4) Then hydrothermal crystallizing for 38h at 100 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 2h at 650 ℃ to obtain the high-mesopore-degree HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 1: 12: 3; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 330m2Per g, the mesoporous volume is 0.25cm3The pore diameter of the most probable pore is 2 nm.
Example 3
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is a sodium hydroxide solution with the concentration of 0.1 mol/L; the pore-guiding agent PDAs are nonionic surfactants EDA;
the molecular formula of the non-ionic surfactant EDA is C2H4(NH2)2The structural formula is as follows:
Figure BDA0002593864860000131
wherein Na+And EDA in a 2:3 molar ratio;
s2, stirring the slurry obtained in the step S1 at the temperature of 90 ℃ for 2 hours to form gel mixed liquid, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 0.5mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 650 ℃ for 2 hours to obtain HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-heptane) and a silicon source (SiCl) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S34) Then carrying out hydrothermal crystallization for 14h at the temperature of 200 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 2h at the temperature of 650 ℃ to obtain the high-mesoporosity HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 2: 14: 5; the high mesoporosity HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 380m2Per g, the mesoporous volume is 0.35cm3The pore diameter of most probable pore is 22 nm.
Example 4
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is potassium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is a nonionic surfactant DAH;
the molecular formula of the non-ionic surfactant DAH is H2N(CH2)6NH2The structural formula is as follows:
Figure BDA0002593864860000141
wherein K+And DS-In a molar ratio of 3: 4;
s2, stirring the slurry obtained in the step S1 at the temperature of 50 ℃ for 6 hours to form a gel mixed solution, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree KZSM-5 molecular sieve;
s3, mixing the high-mesoporosity KZSM-5 molecular sieve obtained in S2 and NH with the concentration of 1mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 550 ℃ for 3 hours to obtain the HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity KZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-hexane) and a silicon source (SiCl) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S34) Then hydrothermally crystallizing for 38h at 110 ℃, washing the crystal with distilled water for many times to be neutral, drying the crystal, and roasting the crystal for 2.5h at 600 ℃ to obtain the high-mesoporosity HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 2:15: 10; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 360m2Per g, the mesoporous volume is 0.30cm3The pore diameter of the most probable pore is 25 nm.
Example 5
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 2g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is potassium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is a nonionic surfactant TAEA;
the molecular formula of the nonionic surfactant TAEA is N (CH)2CH2NH2)3The structural formula is as follows:
Figure BDA0002593864860000151
wherein K+And TAEA in a 3:5 molar ratio;
s2, stirring the slurry obtained in the step S1 for 3 hours at the temperature of 60 ℃ to form gel mixed liquid, cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree KZSM-5 molecular sieve;
s3, mixing the high-mesoporosity KZSM-5 molecular sieve obtained in S2 and NH with the concentration of 0.5mol/L4NO3Mixing the solutions, performing ion exchange at 80 ℃, drying, and roasting at 550 ℃ for 3h to obtain HZSM-5 molecular sieve seed crystals with high mesopores; the high-mesoporosity KZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-heptane) and a silicon source (Si (OCH) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S33)4) Then carrying out hydrothermal crystallization for 20h at the temperature of 150 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 3h at the temperature of 550 ℃ to obtain the high-mesoporosity HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 3: 18: 7; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 400m2Per g, the mesoporous volume is 0.42cm3The pore diameter of the most probable pore is 8 nm.
Example 6
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is potassium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is a nonionic surfactant DEA;
the molecular formula of DEA of the nonionic surfactant is HN (CH)2CH3)2The structural formula is as follows:
Figure BDA0002593864860000161
wherein K+And DEA in a molar ratio of 4: 5;
s2, stirring the slurry obtained in the step S1 at the temperature of 90 ℃ for 2 hours to form gel mixed liquid, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 0.5mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 550 ℃ for 3 hours to obtain the HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-heptane) and a silicon source (Si (OC) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S32H5)4) Then carrying out hydrothermal crystallization for 16h at the temperature of 120 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 3h at the temperature of 550 ℃ to obtain the high-mesoporosity HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 2: 18: 15; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 400m2Per g, the mesoporous volume is 0.28cm3The pore diameter of the most probable pore is 12 nm.
Example 7
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is a sodium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is a cationic surfactant PTA+；
The cationic surfactant PTA+The molecular formula is (CH)3)3N+C3H7The structural formula is as follows:
Figure BDA0002593864860000171
wherein Na+And PTA+In a molar ratio of 2: 5;
s2, stirring the slurry obtained in the step S1 at the temperature of 80 ℃ for 5 hours to form gel mixed liquid, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 0.5mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 550 ℃ for 3 hours to obtain the HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-heptane) and a silicon source (SiCl) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S34) Then hydrothermally crystallizing at 170 ℃ for 30h, washing with distilled water for multiple times to neutrality, drying, and roasting at 580 ℃ for 2.4h to obtain the high-mesoporosity HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 4: 25: 18; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 410m2Per g, the mesoporous volume is 0.33cm3The pore diameter of the most probable pore is 18 nm.
Example 8
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 2g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is a sodium hydroxide solution with the concentration of 1 mol/L; the pore-leading agent (PDSA) is a cationic surfactant CTA+；
The cationic surfactant CTA+The molecular formula is (CH)3)3N+C12H25The structural formula is as follows:
Figure BDA0002593864860000181
wherein Na+And CTA+In a molar ratio of 1: 1;
s2, stirring the slurry obtained in the step S1 for 2 to 6 hours (4) at the temperature of 50 to 90 ℃ (80) to form a gel mixed solution, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 0.5mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 580 ℃ for 2.5 hours to obtain high-mesoporosity HZSM-5 molecular sieve seed crystals; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-hexane) and a silicon source (Si (OCH) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S33)4) Then carrying out hydrothermal crystallization for 18h at the temperature of 130 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 2.2h at the temperature of 570 ℃ to obtain the HZSM-5@ SiO with high mesoporous degree2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 4: 15: 37; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 340m2Per g, the mesoporous volume is 0.28cm3The pore diameter of the most probable pore is 8 nm.
Example 9
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 2g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is potassium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is a cationic surfactant DSA+；
The cationic surfactant DSA+The molecular formula is (C)18H37)2N+(CH3)3The structural formula is as follows:
Figure BDA0002593864860000191
wherein K+And DSA+In a molar ratio of 1: 5;
s2, stirring the slurry obtained in the step S1 at the temperature of 80 ℃ for 4 hours to form gel mixed liquid, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree KaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity KZSM-5 molecular sieve obtained in S2 and NH with the concentration of 1mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 550 ℃ for 3 hours to obtain the HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity KZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-hexane) and a silicon source (Si (OC) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S32H5)4) Then hydrothermally crystallizing at 170 ℃ for 30h, washing with distilled water for multiple times to neutrality, drying, and roasting at 560 ℃ for 2.5h to obtain the high-mesopore-degree HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 5: 17: 38; the high mesoporous HZSM-5@ SiO2Composite molecular sieve ratio tableArea is 340m2Per g, the mesoporous volume is 0.33cm3The pore diameter of most probable pore is 20 nm.
Example 10
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is potassium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is a cationic surfactant HM2+；
The cationic surfactant HM2+The molecular formula is (CH)3)3N+C6H12N+(CH3)3The structural formula is as follows:
Figure BDA0002593864860000201
wherein K+And HM2+In a molar ratio of 5: 7;
s2, stirring the slurry obtained in the step S1 at the temperature of 60 ℃ for 3 hours to form a gel mixed solution, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree KZSM-5 molecular sieve;
s3, mixing the high-mesoporosity KZSM-5 molecular sieve obtained in S2 and NH with the concentration of 1mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 650 ℃ for 2 hours to obtain HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity KZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-heptane) and a silicon source (SiCl) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S34) Then carrying out hydrothermal crystallization for 22h at the temperature of 150 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 3h at the temperature of 550 ℃ to obtain the high-mesoporosity HZSM-5@ SiO2Compounding molecular sieve; the high porosity HZSThe mass ratio of the M-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 5: 28: 32, a first step of removing the first layer; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 420m2Per g, the mesoporous volume is 0.45cm3The pore diameter of the most probable pore is 30 nm.
Example 11
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is a sodium hydroxide solution with the concentration of 1 mol/L; the pore-guiding agent PDAs is a cationic surfactant HDP+；
The cationic surfactant HDP+Molecular formula C16H33N+C5H5The structural formula is as follows:
Figure BDA0002593864860000211
wherein Na+And HDP+In a molar ratio of 3: 8;
s2, stirring the slurry obtained in the step S1 at the temperature of 80 ℃ for 5 hours to form gel mixed liquid, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 1mol/L4NO3Mixing the solutions, performing ion exchange at the temperature of 80 ℃, drying, and roasting at the temperature of 550 ℃ for 3 hours to obtain the HZSM-5 molecular sieve crystal seeds with high mesopores; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-hexane) and a silicon source (SiCl) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S34) Then hydrothermal crystallizing at 190 deg.C for 14 hr, and subjecting to crystallizationWashing with distilled water for multiple times to neutrality, drying, and calcining at 550 deg.C for 3 hr to obtain high-mesopore HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 6: 17: 33; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 370m2Per g, the mesoporous volume is 0.32cm3The pore diameter of the most probable pore is 18 nm.
Example 12
The high mesoporosity HZSM-5@ SiO of the present example2The preparation method of the composite molecular sieve comprises the following steps:
s1, mixing 100mL of mixed solution of alkali metal solution and pore-directing agent PDAs and 5g of HZSM-5, and stirring to obtain slurry;
the alkali metal hydroxide solution is a sodium hydroxide solution with the concentration of 0.1 mol/L; the pore-guiding agent PDAs is a cationic surfactant BA+；
The cationic surfactant BA+Molecular formula C6H5CH2N+(CH3)2R，R＝C8H17to C16H33The structural formula is as follows:
Figure BDA0002593864860000221
wherein Na+And DS-In a molar ratio of 4: 5;
s2, stirring the slurry obtained in the step S1 at the temperature of 80 ℃ for 5 hours to form gel mixed liquid, then cooling to room temperature, filtering, washing with distilled water for multiple times to be neutral, and drying to obtain the high-mesopore-degree NaZSM-5 molecular sieve;
s3, mixing the high-mesoporosity NaZSM-5 molecular sieve obtained in S2 and NH with the concentration of 1mol/L4NO3Mixing the solutions, performing ion exchange at 80 ℃, drying, and roasting at 550 ℃ for 3h to obtain HZSM-5 molecular sieve seed crystals with high mesopores; the high-mesoporosity NaZSM-5 molecular sieve and NH4NO3The dosage ratio of the solution is 1g to 40 mL;
s4, adding a dispersing agent (n-heptane) and a silicon source (Si (OCH) into the high-mesoporosity HZSM-5 molecular sieve seed crystal obtained in S33)4) Then hydrothermal crystallizing for 38h at 100 ℃, washing the product with distilled water for many times to be neutral, drying the product, and roasting the product for 3h at 550 ℃ to obtain the high-mesoporosity HZSM-5@ SiO2Compounding molecular sieve; the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal to the dispersing agent to the silicon source is 7: 21: 35; the high mesoporous HZSM-5@ SiO2The specific surface area of the composite molecular sieve is 400m2Per g, the mesoporous volume is 0.25cm3The pore diameter of most probable pore is 20 nm.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, change and equivalent changes of the above embodiments according to the technical essence of the invention are still within the protection scope of the technical solution of the invention.

Claims (9)

1. High-mesoporosity HZSM-5@ SiO2The preparation method of the composite molecular sieve is characterized by comprising the following steps:
s1, mixing and stirring a mixed solution of an alkali metal solution and a pore-forming agent (PDSN) and HZSM-5 to obtain slurry;
the mixed solution of the alkali metal solution and the pore-leading agent (PDS) is a mixture of an alkali metal hydroxide solution and the pore-leading agent (PDS) with a molar ratio of 1 (1-5); the concentration of the alkali metal hydroxide solution is 0.1 mol/L-1 mol/L;
s2, stirring the slurry obtained in the S1 at the temperature of 50-90 ℃ for 2-6 hours to form a gel mixed solution, cooling to room temperature, and filtering, washing and drying to obtain the high-mesopore-degree XZSM-5 molecular sieve; x in the high-mesoporosity XZSM-5 molecular sieve represents alkali metal;
s3, mixing the high-mesoporosity XZSM-5 molecular sieve obtained in S2 with NH with the concentration of 0.5-1 mol/L4NO3Mixing the solutions, performing ion exchange at 80 ℃, drying, and roasting at 550-650 ℃ for 2-3 hObtaining high-mesoporosity HZSM-5 molecular sieve seed crystal;
s4, adding a dispersing agent and a silicon source into the high-mesopore-degree HZSM-5 molecular sieve seed crystal obtained in S3, carrying out hydrothermal crystallization at 100-200 ℃ for 12-38 h, washing, drying, and roasting at 550-650 ℃ for 2-3 h to obtain the high-mesopore-degree HZSM-5@ SiO2And (3) compounding the molecular sieve.
2. The high mesoporosity HZSM-5@ SiO of claim 12The preparation method of the composite molecular sieve is characterized in that the dosage ratio of the mixed solution of the alkali metal solution and the pore-directing agent PDAs in the slurry in S1 to HZSM-5 is (20-50) mL: 1g of the total weight of the composition.
3. The high mesoporosity HZSM-5@ SiO of claim 12The preparation method of the composite molecular sieve is characterized in that the alkali metal hydroxide solution in S1 is sodium hydroxide solution or potassium hydroxide solution; the pore guiding agent PDAs are anionic surfactants, nonionic surfactants or cationic surfactants.
4. The high mesoporosity HZSM-5@ SiO of claim 32The preparation method of the composite molecular sieve is characterized in that the anionic surfactant is DS-(ii) a The nonionic surfactant is EDA, DAH, TAEA or DEA; the cationic surfactant is PTA+、TPA+、CTA+、DSA+、HM2+、HDP+Or BA+。
5. The high mesoporosity HZSM-5@ SiO of claim 12The preparation method of the composite molecular sieve is characterized in that washing methods in S2 and S4 are both washing for multiple times by using distilled water until the materials are neutral.
6. The high mesoporosity HZSM-5@ SiO of claim 12The preparation method of the composite molecular sieve is characterized in that,the high-mesoporosity XZSM-5 molecular sieve in S3 and NH4NO3The amount ratio of the solution was 1g:40 mL.
7. The high mesoporosity HZSM-5@ SiO of claim 12The preparation method of the composite molecular sieve is characterized in that the dispersing agent in S4 is n-hexane or n-heptane; the silicon source is Si (OCH)3)4、Si(OC2H5)4Or SiCl4。
8. The HZSM-5@ SiO of claim 1 or 7 having a high mesoporosity2The preparation method of the composite molecular sieve is characterized in that the mass ratio of the high-mesoporosity HZSM-5 molecular sieve seed crystal, the dispersing agent and the silicon source in S4 is (1-7): (12-28): (3-38).
9. The high mesoporosity HZSM-5@ SiO of claim 12The preparation method of the composite molecular sieve is characterized in that the high mesoporosity HZSM-5@ SiO in S42The specific surface area of the composite molecular sieve is 276m2/g～420m2Per g, the mesoporous volume is 0.23cm3/g～0.45cm3The pore diameter of most probable pores is 2 nm-30 nm.
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