CN112705248A - Core-shell MFI/MFI molecular sieve and preparation method thereof - Google Patents

Core-shell MFI/MFI molecular sieve and preparation method thereof Download PDF

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CN112705248A
CN112705248A CN201911019744.7A CN201911019744A CN112705248A CN 112705248 A CN112705248 A CN 112705248A CN 201911019744 A CN201911019744 A CN 201911019744A CN 112705248 A CN112705248 A CN 112705248A
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molecular sieve
mfi
shell
layered silicate
core
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CN112705248B (en
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袁志庆
陶伟川
赵胜利
刘松霖
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • C07C2/86—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon
    • C07C2/862—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms
    • C07C2/864—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation between a hydrocarbon and a non-hydrocarbon the non-hydrocarbon contains only oxygen as hetero-atoms the non-hydrocarbon is an alcohol
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/16—After treatment, characterised by the effect to be obtained to increase the Si/Al ratio; Dealumination
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2529/00—Catalysts comprising molecular sieves
    • C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
    • C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • C07C2529/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention provides a core-shell MFI/MFI molecular sieve, which comprises an MFI structure molecular sieve, a layered silicate material, a template agent R and an optional reaction product of alkali and water. The MFI/MFI type core-shell molecular sieve prepared by the invention has better molecular shape selectivity in catalytic reaction, can be used in catalytic reaction with higher requirement on reaction selectivity, such as the production of paraxylene and the production of ethylbenzene, and has higher selectivity and conversion rate.

Description

Core-shell MFI/MFI molecular sieve and preparation method thereof
Technical Field
The invention relates to the field of molecular sieves, in particular to a core-shell MFI/MFI molecular sieve and a preparation method thereof.
Background
The MFI type zeolite represented by ZSM-5 has a unique three-dimensional ten-membered ring pore channel structure and easily-regulated solid acid property, so that the MFI type zeolite is widely applied to petrochemical processes of catalytic cracking, alkylation, isomerization, disproportionation, dewaxing, etherification and the like of hydrocarbons. However, as the petrochemical industry advances, the selectivity of molecular sieves in reaction is more and more demanding, and therefore it is desirable to perform more reactions inside the shape selective channels while minimizing the side reactions occurring on the outer surface of the molecular sieve. To achieve the purpose, the general solution is to perform post-treatment modification on the molecular sieve to reduce the acid amount on the outer surface and the acid strength, and the common methods include high-temperature water vapor treatment, acid dealumination, organic passivation and the like, but on one hand, the modification methods easily cause the blockage of the molecular sieve pore channel and pore opening, thereby greatly reducing the catalytic activity, and on the other hand, the methods are difficult to accurately control, so that the repeatability in industrial application is poor.
The MFI/MFI core-shell zeolite molecular sieve is a composite molecular sieve with MFI structures in a core phase and a shell phase, and a shell layer molecular sieve covers the outer surface of the core phase molecular sieve, so that the probability of reaction on the outer surface of the core phase molecular sieve (which often has high acid catalytic activity) is greatly reduced, and the shape selection function of the molecular sieve is improved on the premise of not influencing the channel diffusivity and the acid property of the core phase molecular sieve. The traditional method for synthesizing the composite molecular sieve is an embedding method, namely, the molecular sieve serving as a nuclear phase is put into a hydrothermal synthesis system of a shell layer molecular sieve, and the composite molecular sieve is obtained after crystallization. For example, chinese patent CN 101723402 provides a method for synthesizing a ZSM-5/ZSM-5 core-shell zeolite molecular sieve, wherein ZSM-5 is used as a seed crystal, and a shell phase molecular sieve uses a silicon source, an aluminum source and a template agent which are usually used in hydrothermal synthesis of ZSM-5. Chinese patent CN 102259018 provides a method for synthesizing a P-ZSM-5/Silicalite-1 composite molecular sieve. Chinese patent CN 105268472 provides a ZSM-5/silicalite-1 molecular sieve with shell-layer oriented epitaxial intergrowth, Bouzi Y and the like [ chem. Mater,2006,18(20): 4959-. U.S. Pat. No. 4,988,605 and U.S. Pat. No. 4,988,374 also successfully utilize direct epitaxy to grow ZSM-5/Silicalite-1 molecular sieves. However, the above conventional methods all require a certain amount of strong base to activate the outer surface of the core phase molecular sieve, thereby causing aluminum loss of the core phase molecular sieve, and simultaneously, the aluminum content of the shell phase molecular sieve is increased, so that the application effect of the core-shell molecular sieve is reduced.
Magadiite and Kenyaite are typical layered silicate minerals, are easily available in sources, and are easy to crystallize under mild conditions to obtain the zeolite molecular sieve, and no research on obtaining the core-shell composite molecular sieve by using layered silicate crystal transformation is reported in the literature at present.
Disclosure of Invention
The invention provides a core-shell MFI/MFI molecular sieve and a preparation method thereof, aiming at the problems of high pH value, large using amount of a template agent and low silica-alumina ratio of a shell layer molecular sieve in the prior art.
The invention is realized by comparing the silicon-aluminum ratio (SiO)2/Al2O3) MFI structure molecular sieve of 20-400, silicon-aluminum ratio (SiO)2/Al2O3) The core-shell MFI/MFI molecular sieve is prepared by mixing a layered silicate material with a content of more than or equal to 200, a small amount of alkali or even no alkali and water according to a certain proportion, and then crystallizing the mixture at 130-200 ℃ for 5-120 hours in a closed system.
In a first aspect, the present invention provides a core-shell MFI/MFI molecular sieve comprising an MFI structure molecular sieve, a layered silicate material, a templating agent R, and optionally a reaction product of a base and water.
According to some embodiments of the invention, the core-shell MFI/MFI molecular sieve comprises a reaction product of an MFI structure molecular sieve, a layered silicate material, a template R, and water.
According to some embodiments of the invention, the core-shell MFI/MFI molecular sieve comprises an MFI structure molecular sieve, a layered silicate material, a templating agent R, a reaction product of a base and water.
According to some embodiments of the present invention, the MFI structure molecular sieve has a silica to alumina ratio, calculated as Si/Al, of from 20 to 400.
According to a preferred embodiment of the present invention, the MFI structure molecular sieve has a silica to alumina ratio, calculated as Si/Al, of from 40 to 200.
According to some embodiments of the present invention, the layered silicate has a silicon to aluminum ratio ≧ 200 in terms of Si/Al.
According to a preferred embodiment of the invention, the phyllosilicate has a silicon to aluminium ratio ≥ 400 in terms of Si/Al.
According to some embodiments of the invention, the mass ratio of the MFI structure molecular sieve to the layered silicate material is from 0.1 to 50.
According to a preferred embodiment of the invention, the mass ratio of the MFI structure molecular sieve to the layered silicate material is between 1 and 10.
According to some embodiments of the invention, the molar ratio of the templating agent R to the framework elements in the layered silicate material, calculated as R/Si, is from 0.01 to 2.
According to a preferred embodiment of the present invention, the molar ratio of the templating agent R to the framework elements in the layered silicate material, calculated as R/Si, is between 0.02 and 2.
According to some embodiments of the invention, the OH-Calculated by/Si, the molar ratio of the alkali to the framework elements in the phyllosilicate material is 0-2.
According to a preferred embodiment of the invention, with OH-Calculated as/Si, the molar ratio of the alkali to the framework elements in the phyllosilicate material is 0.
According to some embodiments of the invention, H2And the molar ratio of the water to the framework elements in the layered silicate material is 10-200 calculated by O/Si.
According to some embodiments of the invention, the framework element is selected from at least one of silicon and aluminum.
According to some embodiments of the invention, the at least one compound is selected from the group consisting of LiOH, NaOH, KOH, RbOH, and CsOH.
According to a preferred embodiment of the invention, the base is selected from NaOH and/or KOH.
According to some embodiments of the invention, the templating agent is selected from at least one of alkyl amine compounds, alkyl quaternary ammonium compounds, and alkyl quaternary ammonium base compounds.
According to a preferred embodiment of the invention, the templating agent is selected from tetrapropylammonium bromide and/or tetrapropylammonium hydroxide.
According to some embodiments of the invention, the phyllosilicate material is selected from at least one of magadiite, boehmite, disilstoseite and magadiite.
According to some embodiments of the present invention, the phyllosilicate material may be obtained from mineral products or may be obtained synthetically.
According to a preferred embodiment of the invention, the phyllosilicate material is magadiite.
According to some embodiments of the invention, the MFI structure molecular sieve is ZSM-5.
In a second aspect, the present invention provides a process for the preparation of a core-shell MFI/MFI molecular sieve comprising:
step A: mixing an MFI structure molecular sieve, a layered silicate material, a template agent R and optional alkali with water to obtain a mixed solution;
and B: crystallizing the mixed solution to obtain a crystallized product;
and C: and washing, drying and roasting the crystallized product to obtain the core-shell MFI/MFI molecular sieve.
According to some embodiments of the present invention, the step a is mixing the MFI structure molecular sieve, the layered silicate material, the template R and water to obtain a mixed solution.
According to some embodiments of the present invention, the step a is mixing the MFI structure molecular sieve, the layered silicate material, the template R, the base, and water to obtain a mixed solution.
According to some embodiments of the present invention, the MFI structure molecular sieve has a silica to alumina ratio, calculated as Si/Al, of from 20 to 400.
According to a preferred embodiment of the present invention, the MFI structure molecular sieve has a silica to alumina ratio, calculated as Si/Al, of from 40 to 200.
According to some embodiments of the present invention, the layered silicate has a silicon to aluminum ratio ≧ 200 in terms of Si/Al.
According to a preferred embodiment of the invention, the phyllosilicate has a silicon to aluminium ratio ≥ 400 in terms of Si/Al.
According to some embodiments of the invention, the mass ratio of the MFI structure molecular sieve to the layered silicate material is from 0.1 to 50.
According to a preferred embodiment of the invention, the mass ratio of the MFI structure molecular sieve to the layered silicate material is between 1 and 10.
According to some embodiments of the invention, the molar ratio of the templating agent R to the framework elements in the layered silicate material, calculated as R/Si, is from 0.01 to 2.
According to a preferred embodiment of the present invention, the molar ratio of the templating agent R to the framework elements in the layered silicate material, calculated as R/Si, is between 0.02 and 2.
According to some embodiments of the invention, the OH-Calculated by/Si, the molar ratio of the alkali to the framework elements in the phyllosilicate material is 0-2.
According to a preferred embodiment of the invention, with OH-Calculated as/Si, the molar ratio of the alkali to the framework elements in the phyllosilicate material is 0.
According to some embodiments of the invention, H2And the molar ratio of the water to the framework elements in the layered silicate material is 10-200 calculated by O/Si.
According to some embodiments of the invention, the framework element is selected from at least one of silicon and aluminum.
According to some embodiments of the invention, the at least one compound is selected from the group consisting of LiOH, NaOH, KOH, RbOH, and CsOH.
According to a preferred embodiment of the invention, the base is selected from NaOH and/or KOH.
According to some embodiments of the invention, the templating agent is selected from at least one of alkyl amine compounds, alkyl quaternary ammonium compounds, and alkyl quaternary ammonium base compounds.
According to a preferred embodiment of the invention, the templating agent is selected from tetrapropylammonium bromide and/or tetrapropylammonium hydroxide.
According to some embodiments of the invention, the phyllosilicate material is selected from at least one of magadiite, boehmite, disilstoseite and magadiite.
According to some embodiments of the present invention, the phyllosilicate material may be obtained from mineral products or may be obtained synthetically.
According to a preferred embodiment of the invention, the phyllosilicate material is magadiite.
According to some embodiments of the invention, the MFI structure molecular sieve is ZSM-5.
According to some embodiments of the invention, the temperature of the crystallization is 130-.
According to some embodiments of the invention, the temperature of the crystallization is 130-.
According to some embodiments of the invention, the crystallization time is 5 to 120 hours.
According to some embodiments of the invention, the crystallization time is 10 to 48 hours.
In a third aspect, the present invention provides the use of a molecular sieve according to the first aspect or obtained by the method of preparation according to the second aspect in a catalytic reaction.
According to some embodiments of the invention, the catalytic reaction is selected from the group consisting of catalytic cracking, alkylation, isomerization, disproportionation, dewaxing and etherification reactions.
According to some embodiments of the present invention, the catalyst provided by the present invention can be used in catalytic reactions of selective disproportionation of toluene, alkylation of toluene and methanol, alkylation of benzene and ethylene, olefin production from methanol, olefin production from cracking of carbon tetraolefin, and the like.
In the molecular sieve prepared according to the invention, only a small amount of alkali needs to be added or even not added, the dissociation of the alkali to silicon and aluminum on the seed crystal is less, and the seed crystal cannot be consumed, so that the deviation of the silicon-aluminum ratio of the shell and the fed silicon-aluminum ratio is smaller, and the aim of passivating the outer surface of the nuclear phase molecular sieve is more easily achieved; in addition, since the amount of the alkali added is small, the metal on the case is not likely to form a metal oxide, and the case more likely to contain a large amount of metal ions.
The MFI/MFI type core-shell molecular sieve prepared by the invention has better molecular shape selectivity in catalytic reaction, can be used in catalytic reaction with higher requirement on reaction selectivity, such as the production of paraxylene and the production of ethylbenzene, and has higher selectivity and conversion rate.
Drawings
FIG. 1 is an XRD pattern of a ZSM-5 molecular sieve used in example 1 according to the present invention.
FIG. 2 is an SEM picture of a ZSM-5 molecular sieve used in example 1 according to the invention.
Fig. 3 is an XRD pattern of magadiite used in example 1 according to the present invention.
Fig. 4 is an SEM image of magadiite used in example 1 according to the present invention.
FIG. 5 is an XRD pattern of an MFI/MFI core-shell molecular sieve prepared according to example 1 of the present invention.
FIG. 6 is an SEM image of an MFI/MFI core-shell molecular sieve prepared according to example 1 of the present invention.
Detailed Description
The invention is further illustrated by the following specific examples. The following illustrative examples are provided to further illustrate the present invention and are not intended to limit the scope of the invention.
[ example 1 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al ═ 120) (XRD and SEM are shown in fig. 1 and fig. 2, respectively), 0.5 g of magadiite (Si/Al ═ 400) (XRD and SEM are shown in fig. 3 and fig. 4, respectively), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein the molar ratio of tetrapropylammonium bromide to silicon in magadiite (expressed as R/Si) was set to be equal toShown as the same below) was 0.05, and the molar ratio of water to silicon in magadiite (as H)2O/Si, the same below) is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein XRD and SEM are respectively shown in fig. 5 and fig. 6. The silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is within the range of 360-420, and is close to the silicon-aluminum ratio of the charged magadiite.
[ example 2 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide, 0.03 g of NaOH and 25 ml of water, wherein R/Si 0.05, the molar ratio of NaOH to silicon in magadiite (expressed as OH-/Si, the same applies hereinafter) was 0.09, H was 0.09, and2and (2) the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 331-379.
[ example 3 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide, 0.06 g of NaOH and 25 ml of water, wherein R/Si 0.05, OH—0.18 of/Si, H2And the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 325-380.
[ example 4 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 400), 2.5 g of tetrapropylammonium hydroxide and 25 ml of water, wherein R/Si is 0.05, and H is 0.052The O/Si is 167, the mixed solution is crystallized in a closed system at the temperature of 160 ℃ for 32 hours, and the obtained product is washed, dried and roasted according to a conventional method to obtain the MFI/MFI core-shell molecular sieveThe silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 326-378.
[ example 5 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si is 0.05, and H is 0.052And (2) the O/Si is 167, crystallizing the mixed solution in a closed system at 140 ℃ for 60 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 331-379.
[ example 6 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si is 0.05, and H is 0.052And the O/Si is 167, crystallizing the mixed solution in a closed system at 180 ℃ for 24 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 331-379.
[ example 7 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.2 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si 0.125, H2And (2) the O/Si ratio is 167, the mixed solution is crystallized in a closed system at 160 ℃ for 32 hours, the obtained product is washed, dried and roasted according to a conventional method, and the MFI/MFI core-shell molecular sieve is obtained, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is within the range of 236-308.
[ example 8 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (all-silica), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si 0.05, H2167% of O/Si, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the productThe MFI/MFI core-shell molecular sieve has the silicon-aluminum ratio range of 399-510 in different areas of the shell of the core-shell molecular sieve.
[ example 9 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 200), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si is 0.05, and H is 0.052And the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 157-182.
[ example 10 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 60), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si is 0.05, and H is 0.052And the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product by a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is in a range of 346-395.
[ example 11 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 60), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide, 0.06 g of NaOH and 25 ml of water, wherein R/Si 0.05, OH—0.18 of/Si, H2And (2) the O/Si ratio is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 304-361.
[ example 12 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al ═ 60), 0.5 g of magadiite (all-silica), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si ═ 0.05, H and H were contained2The O/Si is 167, the mixed solution is crystallized for 32 hours at 160 ℃ in a closed system, and the preparation methodAnd washing, drying and roasting the obtained product by a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different regions of the shell of the core-shell molecular sieve is in a range of 377-456.
[ example 13 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al ═ 400), 0.5 g of magadiite (all-silica), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si ═ 0.05, H and H were mixed2And the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product by a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 418-499.
[ example 14 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al ═ 400), 0.5 g of magadiite (all-silica), 0.1 g of tetrapropylammonium bromide, 0.03 g of NaOH, and 25 ml of water, wherein R/Si ═ 0.05, OH —/Si was 0.09, H ═ H2And (2) the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product by a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different regions of the shell of the core-shell molecular sieve is 391-467.
[ example 15 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetraethylammonium bromide (R) and 25 ml of water, wherein R/Si 0.06, H2And the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 363-400.
[ example 16 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of magadiite (Si/Al 400), 0.1 g of tetrapropylammonium bromide, 0.03 g of potassium hydroxide and 25 ml of water, wherein R/Si 0.05, OH ═ Si 0.08,H2and the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is 372-405.
[ example 17 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of kenyaite (Si/Al 400), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si 0.05, H2And the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is within the range of 297-380.
[ example 18 ]
A mixed solution was obtained by mixing 1.0 g of ZSM-5 molecular sieve (Si/Al 120), 0.5 g of kenyaite (all-silica), 0.1 g of tetrapropylammonium bromide and 25 ml of water, wherein R/Si 0.05, H2And the O/Si is 167, crystallizing the mixed solution in a closed system at 160 ℃ for 32 hours, washing, drying and roasting the obtained product according to a conventional method to obtain the MFI/MFI core-shell molecular sieve, wherein the silicon-aluminum ratio of different areas of the shell of the core-shell molecular sieve is between 313 and 387.
[ example 19 ]
Taking 1.0 g of the core-shell molecular sieve obtained in the example 1, tabletting, crushing, taking out 0.5 g of molecular sieve particles with 200-400 meshes, and carrying out catalytic performance evaluation on a toluene methanol alkylation reaction under the following reaction conditions: the reaction raw material is a mixed solution of toluene and methanol (the molar ratio of toluene to methanol is 2), the reaction pressure is 0.5 MPa, the reaction temperature is 420 ℃, and the space velocity of the volume of the fed liquid is 4h-1The hydrogen to hydrocarbon ratio was 3. the results of the sample analysis at the stage of the reaction stage were 21% conversion of toluene and 90% selectivity to p-xylene.
Comparative example 1
2.5 g of ethyl orthosilicate, 6 g of tetrapropylammonium hydroxide solution (25 wt%) and 100 g of water are mixed and stirred for 6 hours, then 12 g of ZSM-5 nuclear phase molecular sieve with Si/Al of 120 is added, the mixture is put into a 200 ml stainless steel reaction kettle with a polyethylene lining of a polytetra-reactor, the stainless steel reaction kettle is sealed and placed in a rotary oven, the rotation speed is 20 revolutions per minute, the crystallization temperature is 160 ℃, and the crystallization time is 32 hours. After crystallization, washing, drying and roasting at 550 ℃ for 6 hours to obtain the MFI/MFI core-shell molecular sieve, and element analysis shows that the range of the silicon-aluminum ratio (Si/Al) of different areas of the shell of the core-shell molecular sieve is about 200-280.
Comparative example 2
Taking 1.0 g of ZSM-5 molecular sieve (Si/Al is 120), tabletting and then crushing, taking out 0.5 g of molecular sieve particles with 200-400 meshes, and carrying out catalytic performance evaluation on a toluene methanol alkylation reaction, wherein the reaction conditions are the same as those in example 20, and the result of sampling analysis at the stage of a reaction platform is that the conversion rate of toluene is 13%, and the selectivity of p-xylene is 32%.
Comparative example 3
Taking 1.0 g of the core-shell molecular sieve obtained in the comparative example 1, tabletting, crushing, taking out 0.5 g of molecular sieve particles with 200-400 meshes, and carrying out catalytic performance evaluation on a toluene methanol alkylation reaction, wherein the reaction conditions are the same as those in the example 20, and the results of sampling analysis in the stage of a reaction platform are that the conversion rate of toluene is 15% and the selectivity of p-xylene is 56%.
[ example 20 ]
Taking 1.0 g of the core-shell molecular sieve obtained in the example 8, tabletting, crushing, taking out 0.5 g of molecular sieve particles with 200-400 meshes, and carrying out catalytic performance evaluation on a toluene methanol alkylation reaction under the following reaction conditions: the reaction raw material is a mixed solution of toluene and methanol (the molar ratio of toluene to methanol is 2), the reaction pressure is 0.5 MPa, the reaction temperature is 420 ℃, and the space velocity of the volume of the fed liquid is 4h-1The hydrogen to hydrocarbon ratio was 3. the results of the sample analysis at the stage of the reaction stage showed a toluene conversion of 19% and a p-xylene selectivity of 92%.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.

Claims (10)

1. A core-shell MFI/MFI molecular sieve comprises an MFI structure molecular sieve, a layered silicate material, a template R and an optional reaction product of alkali and water.
2. The molecular sieve of claim 1, wherein the MFI structure molecular sieve has a silica to alumina ratio, calculated as Si/Al, of 20 to 400, preferably 40 to 200, and the layered silicate has a silica to alumina ratio of 200 or more, preferably 400 or more.
3. The molecular sieve of claim 1 or 2, wherein the mass ratio of the MFI structure molecular sieve to the layered silicate material is from 0.1 to 50, preferably from 1 to 10; and/or
The molar ratio of the template agent R to the framework elements in the layered silicate material is 0.01-2, preferably 0.02-2 in terms of R/Si; and/or
With OH-In terms of/Si, the molar ratio of the alkali to the framework elements in the phyllosilicate material is 0-2, preferably 0; and/or
With H2The molar ratio of the water to the framework elements in the phyllosilicate material is 10-200 in terms of O/Si,
preferably, the framework element is selected from at least one of silicon and aluminum.
4. The molecular sieve according to any one of claims 1 to 3, wherein the base is selected from at least one of LiOH, NaOH, KOH, RbOH and CsOH, preferably from NaOH and/or KOH; and/or
The template agent is selected from at least one of alkyl amine compounds, alkyl quaternary ammonium salt compounds and alkyl quaternary ammonium base compounds, and is preferably selected from tetrapropyl ammonium bromide and/or tetrapropyl ammonium hydroxide; and/or
The layered silicate material is selected from at least one of magadiite, boehmite, hydrosilashe stone and magadiite, and is preferably magadiite; and/or
The MFI structure molecular sieve is ZSM-5.
5. A preparation method of a core-shell MFI/MFI molecular sieve comprises the following steps:
step A: mixing an MFI structure molecular sieve, a layered silicate material, a template agent R and optional alkali with water to obtain a mixed solution;
and B: crystallizing the mixed solution to obtain a crystallized product;
and C: and washing, drying and roasting the crystallized product to obtain the core-shell MFI/MFI molecular sieve.
6. The preparation method according to claim 5, wherein the MFI structure molecular sieve has a Si/Al ratio of 20 to 400, preferably 40 to 200, and the layered silicate has a Si/Al ratio of 200 or more, preferably 400 or more.
7. The production method according to claim 5 or 6, wherein the mass ratio of the MFI structure molecular sieve to the layered silicate material is 0.1 to 50, preferably 1 to 10; and/or
The molar ratio of the template agent R to the framework elements in the layered silicate material is 0.01-2, preferably 0.02-2 in terms of R/Si; and/or
With OH-In terms of/Si, the molar ratio of the alkali to the framework elements in the phyllosilicate material is 0-2, preferably 0; and/or
With H2The mol ratio of the water to the framework elements in the layered silicate material is 10-200 calculated by O/Si, and preferably, the framework elements are selected fromFrom at least one of silicon and aluminum.
8. The method according to any one of claims 5 to 7, wherein the base is selected from at least one of LiOH, NaOH, KOH, RbOH and CsOH, preferably from NaOH and/or KOH; and/or
The template agent is selected from at least one of alkyl amine compounds, alkyl quaternary ammonium salt compounds and alkyl quaternary ammonium base compounds, and is preferably selected from tetrapropyl ammonium bromide and/or tetrapropyl ammonium hydroxide; and/or
The layered silicate material is selected from at least one of magadiite, boehmite, hydrosilashe stone and magadiite, and is preferably magadiite; and/or
The MFI structure molecular sieve is ZSM-5.
9. The preparation method according to any one of claims 5 to 8, wherein the crystallization temperature is 130-200 ℃, preferably 130-180 ℃; and/or the crystallization time is 5 to 120 hours, preferably 10 to 48 hours.
10. Use of a molecular sieve according to any one of claims 1 to 4 or obtained by a process according to any one of claims 5 to 9 in catalytic reactions, in particular in catalytic cracking, alkylation, isomerization, disproportionation, dewaxing and etherification reactions.
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