Preparation method of polycation structure-directing agent and ZSM-11 / ZSM-5 symbiotic molecular sieve

Abstract

The invention provides a preparation method of a polycation structure-directing agent and a ZSM-11 / ZSM-5 symbiotic molecular sieve, and relates to the technical field of molecular sieves. The polycation structure directing agent provided by the invention is a quaternary ammonium type cationic polymer with a long-chain structure. The ZSM-11 / ZSM-5 symbiotic molecular sieve (with a fixed symbiotic proportion) with controllable ZSM-11 content can be prepared by adopting the polycation structure-directing agent, a hierarchical porous structure (including micropores and mesopores) with better diffusion performance is formed in the synthesis process, and the grain size is 150-300nm; the polycation structure directing agent can guide the generation of the ZSM-11 / ZSM-5 symbiotic molecular sieve in a relatively wide silica-alumina ratio window (50-infinity); in addition, the polycation structure directing agent is a single directing agent, the proportion of all directing agents does not need to be controlled like a common template method, and a pore-forming agent does not need to be added when the hierarchical pore structure is formed.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieves, and in particular to a method for preparing a polycationic structure directing agent and a ZSM-11 / ZSM-5 symbiotic molecular sieve. Background Art

[0002] Molecular sieve is made of TO 4 (T=Si, Al or P, etc.) tetrahedrons form microporous aluminosilicate crystals with a skeleton structure by sharing O atoms. This structure gives it good ion exchange, hydrothermal stability, strong acidity, and unique molecular selective adsorption and shape-selective catalytic properties. In recent decades, symbiotic molecular sieves have gradually attracted widespread attention from academia and industry. The competitive growth of different crystals will lead to the frequent appearance of stacking defects of various topological structures, while the stacking order between phase layers is prone to symbiosis; symbiotic molecular sieve crystals show unique synergistic effects and catalytic advantages in the fields of adsorption, separation and catalysis.

[0003] As very important members of the five-membered ring zeolite family, the skeleton structures of ZSM-5 (MFI) and ZSM-11 (MEL) molecular sieves are closely related to each other and can be described by different stacking modes of the same five-membered ring chain. The adjacent five-membered ring chains in the ZSM-5 structure are connected to each other by centrosymmetry, while the five-membered ring chains in the ZSM-11 structure are connected by mirror symmetry. The subtle difference in pore structure makes it possible to prepare ZSM-11 / ZSM-5 symbiotic molecular sieves, which was first reported by Mobil Oil Company in 1979. At present, ZSM-11 / ZSM-5 symbiotic molecular sieves have been commercially applied in the gas-phase alkylation process of catalytic cracking tail gas and benzene to produce ethylbenzene. At the same time, they also show excellent catalytic performance in the catalytic cracking of n-decane and methanol to hydrocarbons.

[0004] Due to its unique catalytic and adsorption properties, the preparation of the symbiotic structure of ZSM-11 / ZSM-5 has aroused widespread interest among researchers. ZSM-11 / ZSM-5 symbiotic molecular sieves are often synthesized using tetrabutylammonium (TBA) and tetrapropylammonium (TPA) as structure-directing agents, that is, using the co-template method. However, since the ZSM-5 lattice is more stable, its structure often becomes the dominant polymorph, and the ZSM-11 structure will not appear until the TBA content is greater than 90%. Since the ratio of tetrabutylammonium and tetrapropylammonium needs to be adjusted during the synthesis process, the synthesis process is not easy to control, the symbiotic ratio of ZSM-11 and ZSM-5 is unstable, and the ZSM-11 content is low. In addition, the ZSM-11 / ZSM-5 symbiotic molecular sieve obtained by this method is a single microporous structure, and its diffusion performance is limited, which affects its catalytic performance; and the introduction of general pore-forming agents will affect the formation of the symbiotic structure, making the synthesis of symbiotic multi-level pore molecular sieves a major challenge. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing a polycationic structure directing agent and a ZSM-11 / ZSM-5 symbiotic molecular sieve. The polycationic structure directing agent provided by the present invention can be used to prepare a ZSM-11 / ZSM-5 symbiotic molecular sieve with controllable ZSM-11 content, and a multi-level pore structure with better diffusion performance is formed during the synthesis process.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a polycationic structure directing agent having a structure shown in Formula I:

[0008]

[0009] In the structure shown in formula I, X is Br or OH, and n is an integer of 5 to 20.

[0010] The present invention provides a method for preparing the polycationic structure directing agent described in the above technical solution, comprising the following steps:

[0011] Di-n-butylamine, suberyl chloride and an organic solvent are mixed to undergo a nucleophilic addition reaction to obtain N,N,N',N'-tetrabutyl-1,8-suberylamide;

[0012] The N,N,N',N'-tetrabutyl-1,8-octanediamine is mixed with lithium aluminum hydride and an organic solvent for reduction reaction to obtain N,N,N',N'-tetrabutyl-1,8-octanediamine;

[0013] The N,N,N',N'-tetrabutyl-1,8-octanediamine is mixed with 1,8-dibromooctane and an organic solvent to carry out a nucleophilic substitution polymerization reaction to obtain a polycationic structure directing agent having a structure shown in Formula I when X is Br;

[0014] The polycationic structure directing agent with the structure shown in formula I when X is Br is subjected to ion exchange through a strong alkaline anion exchange resin to obtain a polycationic structure directing agent with the structure shown in formula I when X is OH.

[0015] Preferably, the molar ratio of di-n-butylamine to suberyl chloride is 4:1, the temperature of the nucleophilic addition reaction is room temperature, and the time is 24 to 48 hours.

[0016] Preferably, the molar ratio of the N,N,N',N'-tetrabutyl-1,8-octanediamide to lithium aluminum hydride is 1:3, the temperature of the reduction reaction is 60-100° C., and the time is 24-48 hours.

[0017] Preferably, the molar ratio of the N,N,N',N'-tetrabutyl-1,8-octanediamine to 1,8-dibromooctane is 1:1, and the temperature of the nucleophilic substitution polymerization reaction is 60-100° C., and the time is 24-96 hours.

[0018] The present invention provides a method for preparing a ZSM-11 / ZSM-5 symbiotic molecular sieve, comprising the following steps:

[0019] A structure directing agent, a silicon source, an aluminum source, an alkali source and water are mixed for hydrothermal crystallization to obtain a crystallized product; the structure directing agent is the polycationic structure directing agent described in the above technical solution, the alkali source is an alkali metal hydroxide; the silicon source is SiO 2 Aluminum source is Al 2 O 3 The molar ratio of the silicon source, the aluminum source, the structure directing agent, the alkali source and the water is 1:(0-0.04):(0.05-0.50):(0.02-0.50):(10-150);

[0020] The crystallized product is calcined to obtain the ZSM-11 / ZSM-5 intergrowth molecular sieve.

[0021] Preferably, the silicon source includes one or more of tetraethyl orthosilicate, sodium silicate, fumed silica, silica sol and white carbon black; the aluminum source includes one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium aluminate, pseudo-boehmite and aluminum isopropoxide; the alkali source includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0022] Preferably, the hydrothermal crystallization temperature is 110-190° C., and the time is 3-14 days.

[0023] Preferably, the ZSM-11 / ZSM-5 intergrowth molecular sieve has micropores and mesopores, a particle size of 150 to 300 nm, and a silicon-aluminum molar ratio greater than or equal to 50.

[0024] Preferably, the symbiotic ratio of ZSM-11 molecular sieve to ZSM-5 molecular sieve in the ZSM-11 / ZSM-5 symbiotic molecular sieve is 80:20.

[0025] The present invention provides a polycationic structure directing agent having a structure shown in Formula I. The polycationic structure directing agent provided by the present invention is a quaternary ammonium cationic polymer having a long-chain structure. The polycationic structure directing agent is used to prepare a ZSM-11 / ZSM-5 symbiotic molecular sieve. The polycationic structure directing agent is used as a structure directing agent to prepare a ZSM-11 / ZSM-5 symbiotic molecular sieve with controllable ZSM-11 content (having a fixed symbiotic ratio), and a multi-level pore structure (including micropores and mesopores) with better diffusion performance can be generated during the synthesis process. The size of the obtained symbiotic molecular sieve can be reduced to 150-300nm, and the mass transfer is better; and the polycationic structure directing agent can guide the generation of the ZSM-11 / ZSM-5 symbiotic molecular sieve in a wider silicon-aluminum ratio (50-∞) window; in addition, the polycationic structure directing agent is a single directing agent, and there is no need to control the ratio between the directing agents as in the co-template method, because it can also be used as a pore-forming agent to support the mesoporous structure, and there is no need to add an additional pore-forming agent to form the mesoporous structure, the process of synthesizing the molecular sieve is easier to control, and the microstructure of the obtained molecular sieve is uniform and controllable.

[0026] The invention provides a method for preparing a ZSM-11 / ZSM-5 symbiotic molecular sieve. The ZSM-11 / ZSM-5 symbiotic molecular sieve is prepared by the method. The prepared ZSM-11 / ZSM-5 symbiotic molecular sieve has a fixed symbiotic ratio (the symbiotic ratio of the ZSM-11 molecular sieve to the ZSM-5 molecular sieve is 80:20), and has a multi-level pore structure (including micropores and mesopores), and the grain size is between 150 and 300 nm. The multi-level pore structure has better diffusion performance, which will be beneficial to improving the catalytic activity, selectivity and anti-carbon deposition performance of the catalyst; in addition, the silicon-aluminum ratio window of the ZSM-11 / ZSM-5 symbiotic molecular sieve is large (50 to ∞). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 For the N,N,N',N'-tetrabutyl-1,8-octanediamide prepared in 1 1 H NMR spectra (a) and 13 C NMR spectrum (b);

[0028] Figure 2 The N,N,N',N'-tetrabutyl-1,8-octanediamine prepared in Example 1 1 H NMR spectra (a) and 13 C NMR spectrum (b);

[0029] Figure 3 The polycationic structure directing agent [(Bu) 2 -C 8 ] n (Br) 1H NMR spectra (a) and 13 C NMR spectrum (b);

[0030] Figure 4 This is the XRD pattern of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 3. Figure 4 From left to right in the figure, the second and third small pictures are partial enlarged pictures of the first small picture;

[0031] Figure 5 FE-SEM images of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 3 at different magnifications (the scale bars in the figure are 5 μm, 2 μm, 1 μm, and 500 nm, respectively);

[0032] Figure 6 This is the XRD pattern of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 4. Figure 6 From left to right in the figure, the second and third small pictures are partial enlarged pictures of the first small picture;

[0033] Figure 7 FE-SEM images of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 4 at different magnifications (5 μm, 2 μm, 1 μm, 500 nm);

[0034] Figure 8 This is the XRD pattern of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 5. Figure 8 From left to right in the figure, the second and third small pictures are partial enlarged pictures of the first small picture;

[0035] Fig. 9 FE-SEM images of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 5 at different magnifications (the scale bars in the figure are 5 μm, 2 μm, 1 μm, and 500 nm, respectively);

[0036] Fig.10 This is the XRD pattern of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 6. Fig.10 From left to right in the figure, the second and third small pictures are partial enlarged pictures of the first small picture;

[0037] Fig.11 FE-SEM images of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 6 at different magnifications (the scale bars in the figure are 5 μm, 2 μm, 1 μm, and 500 nm, respectively);

[0038] Fig.12 N of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 6 2 Physical adsorption isotherm (inset shows pore size distribution);

[0039] Fig.13 This is the mercury injection curve of the ZSM-11 / ZSM-5 intergrowth molecular sieve prepared in Example 6 (the inset is the pore size distribution. DETAILED DESCRIPTION

[0040] The present invention provides a polycationic structure directing agent having a structure shown in Formula I:

[0041]

[0042] In the structure shown in formula I, X is Br or OH, and n is an integer of 5 to 20.

[0043] In the present invention, n may be 5, 10, 12, 15 or 20.

[0044] In the present invention, when X is Br, the chemical formula of the polycationic structure directing agent of the structure shown in Formula I is [-N + (CH 2 CH 2 CH 2 CH 3 ) 2 -(CH 2 ) 8 -] n [Br - ] n (Abbreviated as [(Bu) 2 -C 8 ] n (Br)), and when X is OH, the chemical formula of the polycationic structure-directing agent represented by Formula I is [-N + (CH 2 CH 2 CH 2 CH 3 ) 2 -(CH 2 ) 8 -] n [OH - ] n (Abbreviated as [(Bu) 2 -C 8 ] n (OH)).

[0045] The polycationic structure-directing agent provided by the present invention is a quaternary ammonium cationic polymer with a long-chain structure, wherein the single quaternary ammonium salt structural unit has a TBA (tetrabutylammonium)-like structure, and the overall structure is equivalent to a linear polymeric cation formed by connecting the TBA-like structure through a CC chemical bond. The polycationic structure-directing agent can construct a multi-level structure while controlling the generation of a ZSM-5 / ZSM-11 symbiotic structure.

[0046] The present invention provides a method for preparing the polycationic structure directing agent described in the above technical solution, comprising the following steps:

[0047] Di-n-butylamine, suberyl chloride and an organic solvent are mixed to undergo a nucleophilic addition reaction to obtain N,N,N',N'-tetrabutyl-1,8-suberylamide;

[0048] The N,N,N',N'-tetrabutyl-1,8-octanediamine is mixed with lithium aluminum hydride and an organic solvent for reduction reaction to obtain N,N,N',N'-tetrabutyl-1,8-octanediamine;

[0049] The N,N,N',N'-tetrabutyl-1,8-octanediamine is mixed with 1,8-dibromooctane and an organic solvent to carry out a nucleophilic substitution polymerization reaction to obtain a polycationic structure directing agent having a structure shown in Formula I when X is Br;

[0050] The polycationic structure directing agent with the structure shown in formula I when X is Br is subjected to ion exchange through a strong alkaline anion exchange resin to obtain a polycationic structure directing agent with the structure shown in formula I when X is OH.

[0051] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well known in the art.

[0052] The invention mixes di-n-butylamine, suberyl chloride and an organic solvent to carry out a nucleophilic addition reaction to obtain N,N,N',N'-tetrabutyl-1,8-suberylamide.

[0053] In the present invention, the molar ratio of di-n-butylamine to suberyl chloride is preferably 4:1; the organic solvent is preferably ether, and the present invention has no special requirements for the amount of the organic solvent, as long as the raw materials are fully dissolved. In the present invention, the method of mixing di-n-butylamine, suberyl chloride and organic solvent is preferably: adding the organic solvent and di-n-butylamine to the reaction container, ice bathing for 1 hour, and then slowly adding suberyl chloride thereto. In the present invention, the temperature of the nucleophilic addition reaction is preferably room temperature, and the time is preferably 24 to 48 hours, which can be 24, 36 or 48 hours; the nucleophilic addition reaction is preferably carried out under stirring. In the present invention, the reaction formula of the nucleophilic addition reaction is shown in Formula A (compound R1 in Formula A is N,N,N',N'-tetrabutyl-1,8-suberamide):

[0054]

[0055] After the nucleophilic addition reaction is completed, the present invention preferably filters the obtained reaction solution to obtain a clear solution, using 5wt% NaHCO 3The obtained clear solution was washed three times with the solution, dried over anhydrous magnesium sulfate for 24 h, and then the solvent was removed by rotary evaporation to obtain N,N,N',N'-tetrabutyl-1,8-octanediamide.

[0056] After obtaining N,N,N',N'-tetrabutyl-1,8-octanediamide, the present invention mixes the N,N,N',N'-tetrabutyl-1,8-octanediamide with lithium aluminum hydride and an organic solvent for reduction reaction to obtain N,N,N',N'-tetrabutyl-1,8-octanediamine.

[0057] In the present invention, the molar ratio of the N,N,N',N'-tetrabutyl-1,8-octanediamide to lithium aluminum hydride is preferably 1:3; the organic solvent is preferably tetrahydrofuran, and the present invention has no special requirements for the amount of the organic solvent, as long as the raw materials are fully dissolved. In the present invention, the method of mixing the N,N,N',N'-tetrabutyl-1,8-octanediamide with lithium aluminum hydride and the organic solvent is preferably: adding the organic solvent and N,N,N',N'-tetrabutyl-1,8-octanediamide to a reaction container, and adding lithium aluminum hydride thereto after ice bathing for 1 hour.

[0058] In the present invention, the temperature of the reduction reaction is preferably 60 to 100°C, and may be 60, 70, 80, 90 or 100°C, and the time is preferably 24 to 48 hours, and may be 24, 36 or 48 hours. In the present invention, the reaction formula of the reduction reaction is shown in Formula B (compound R2 in Formula B is N,N,N',N'-tetrabutyl-1,8-octanediamine):

[0059]

[0060] After the reduction reaction is completed, the present invention preferably cools the obtained reaction solution, adds methanol, deionized water and anhydrous magnesium sulfate thereto, stirs for 1 hour, filters to obtain a clear liquid, and evaporates the obtained clear liquid to remove the solvent to obtain N,N,N',N'-tetrabutyl-1,8-octanediamine. In the present invention, the mass ratio of the methanol, deionized water and anhydrous magnesium sulfate is preferably 1:1:1.

[0061] After obtaining N,N,N',N'-tetrabutyl-1,8-octanediamine, the present invention mixes the N,N,N',N'-tetrabutyl-1,8-octanediamine with 1,8-dibromooctane and an organic solvent to carry out a nucleophilic substitution polymerization reaction to obtain a polycationic structure directing agent with a structure shown in formula I when X is Br.

[0062] In the present invention, the molar ratio of the N,N,N',N'-tetrabutyl-1,8-octanediamine to 1,8-dibromooctane is preferably 1:1; the organic solvent is preferably methanol, and the present invention has no special requirements for the amount of the organic solvent, as long as the raw materials are fully dissolved; in an embodiment of the present invention, the ratio of the total molar amount of the N,N,N',N'-tetrabutyl-1,8-octanediamine and 1,8-dibromooctane to the volume of the organic solvent is 0.20mol:100mL. The present invention preferably adds the organic solvent and N,N,N',N'-tetrabutyl-1,8-octanediamine to the reaction vessel, and then adds 1,8-dibromooctane thereto.

[0063] In the present invention, the temperature of the nucleophilic substitution polymerization reaction is preferably 60 to 100°C, and can be 60, 70, 80, 90 or 100°C, and the time is preferably 24 to 96 hours, and can be 24, 36, 48 or 96 hours; the nucleophilic substitution polymerization reaction is preferably carried out under stirring and reflux conditions. In the present invention, the reaction formula of the nucleophilic substitution polymerization reaction is shown in Formula C:

[0064]

[0065] After the nucleophilic substitution polymerization reaction is completed, the present invention preferably performs rotary evaporation on the obtained reaction solution to remove the solvent, and then washes with n-hexane to obtain a polycationic structure directing agent (viscous liquid) with a structure shown in formula I when X is Br; in the present invention, the role of the n-hexane washing is to remove residual raw materials and solvents.

[0066] In the present invention, the polycationic structure directing agent with the structure shown in formula I when X is Br is subjected to ion exchange through a strong alkaline anion exchange resin to obtain the polycationic structure directing agent with the structure shown in formula I when X= is OH.

[0067] In the present invention, the strong base anion exchange resin is preferably Amberlite IRA402 strong base anion exchange resin, specifically Amberlite IRA402 (chloride type) is exchanged into OH type in NaOH solution, and the concentration of the NaOH solution is preferably 1 mol / L. In the present invention, the role of the ion exchange is to replace the halogen anion with the hydroxide anion to obtain a polycationic structure directing agent of the structure shown in Formula I when X=OH.

[0068] In the present invention, the specific operation of the ion exchange is preferably:

[0069] The polycationic structure directing agent having the structure of Formula I when X is Br is dissolved in water, a strong basic anion exchange resin is added thereto, and the mixture is stirred and filtered in sequence, and the filtrate is collected;

[0070] The filtrate is subjected to rotary evaporation to obtain a polycationic structure directing agent having a structure shown in Formula I when X is OH.

[0071] In the present invention, the water is preferably deionized water, and when X is Br, the mass ratio of the polycationic structure directing agent of the structure shown in Formula I to water is preferably 1:2-10, and can be 1:5 or 1:6; when X is Br, the mass ratio of the polycationic structure directing agent of the structure shown in Formula I to the strong basic anion exchange resin is preferably 1:1-5, and can be 1:2.5 or 1:3.5. In the present invention, the stirring time (i.e., the ion exchange time) is preferably 8-24h, and can be 10 or 12h. In the present invention, the filtrate is an aqueous solution of the polycationic structure directing agent of the structure shown in Formula I when X is OH. The present invention has no special requirements for the conditions of the rotary evaporation, and the water in the filtrate can be removed.

[0072] In the present invention, since ion exchange cannot guarantee a 100% exchange rate, the polycation structure directing agent obtained needs to be titrated with an acid after the rotary evaporation to determine the concentration of the OH-type polycation structure directing agent, and then added according to the amount of the OH-type polycation during the subsequent synthesis of the molecular sieve. In the present invention, the acid is preferably 0.1 mol / L hydrochloric acid.

[0073] In the present invention, the degree of polymerization of the polycationic structure directing agent is measured by gel permeation chromatography (GPC); the molecular weight of the polycationic structure directing agent is determined on a WATERS 2414 differential refractive index detector using a WATERS ULtrahydrogel×3 gel column; the mobile phase is a 0.10M sodium nitrate aqueous solution; polyethylene glycol is used as a standard sample; the column temperature and the detector temperature are both 313K.

[0074] The present invention provides a method for preparing a ZSM-11 / ZSM-5 symbiotic molecular sieve, comprising the following steps:

[0075] A silicon source, an aluminum source, an alkali source, a structure directing agent and water are mixed for hydrothermal crystallization to obtain a crystallized product; the structure directing agent is the polycationic structure directing agent described in the above technical solution, the alkali source is an alkali metal hydroxide; the silicon source is SiO 2 Aluminum source is Al 2 O 3 The molar ratio of the silicon source, the aluminum source, the structure directing agent, the alkali source and the water is 1:(0.00-0.04):(0.05-0.50):(0.02-0.50):(10-150);

[0076] The crystallized product is calcined to obtain the ZSM-11 / ZSM-5 intergrowth molecular sieve.

[0077] The present invention mixes a silicon source, an aluminum source, an alkali source, a structure directing agent and water to perform hydrothermal crystallization to obtain a crystallized product.

[0078] In the present invention, the silicon source preferably includes one or more of tetraethyl orthosilicate (TEOS), sodium silicate, fumed silica, silica sol and white carbon black; the aluminum source preferably includes one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium aluminate, pseudo-boehmite and aluminum isopropoxide; the alkali source preferably includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide; the water is preferably deionized water.

[0079] In the present invention, the silicon source is SiO 2 Aluminum source is Al 2 O 3 The alkali source is calculated as alkali metal elements, and the structure directing agent is calculated as structural units (i.e., [(Bu) 2 -C 8 ]), the molar ratio of the silicon source, aluminum source, structure directing agent, alkali source and water is 1: (0-0.04): (0.05-0.50): (0.02-0.50): (10-150), can be 1: (0-0.01): (0.10-0.30): (0.10-0.20): (30-60), further can be 1: (0.0025-0.01): (0.10-0.20): (0.10-0.15): (40-50). In the present invention, the Si / Al ratio can be adjusted by adjusting the amount of the silicon source and the aluminum source, thereby achieving the acidity adjustment of the molecular sieve, and the higher the Si / Al ratio, the lower the acid density.

[0080] In the present invention, the mixing is preferably carried out under stirring conditions. The present invention has no special requirements for the stirring conditions, as long as the components are mixed evenly. The mixing can be carried out at room temperature, i.e., no additional heating or cooling is required.

[0081] In the present invention, the temperature of the hydrothermal crystallization is preferably 110-190°C, and may be 120, 130, 140, 150, 160, 170 or 180°C, and the time is preferably 3-14 days, and may be 5, 7 or 10 days. In the present invention, the hydrothermal crystallization may be carried out under static or dynamic conditions, and the dynamic condition is preferably stirring, and the stirring rate may be 30 rpm.

[0082] After the hydrothermal crystallization is completed, the present invention sequentially performs solid-liquid separation, solid phase washing and drying on the obtained crystallization reaction liquid to obtain a crystallized product. The present invention has no special requirements for the solid-liquid separation method, and methods well known to those skilled in the art can be used, such as filtration and suction filtration. In the present invention, the washing agent used for the washing is preferably deionized water and / or ethanol; the drying temperature is preferably 40 to 250°C, and can be 60, 100 or 150°C, and the time is preferably 8 to 30 hours, and can be 8, 10 or 20 hours. The drying can be carried out under normal pressure or under reduced pressure.

[0083] After obtaining the crystallized product, the present invention calcines the crystallized product to obtain the ZSM-11 / ZSM-5 intergrowth molecular sieve.

[0084] In the present invention, the calcination temperature is preferably 300-800°C, and may be 400, 500, 550 or 650°C, and the time is preferably 1-10 hours, and may be 5, 6 or 8 hours; the calcination is preferably carried out in an oxygen-containing atmosphere, and the oxygen-containing atmosphere may be air or oxygen. The present invention removes the structure directing agent through the calcination to obtain a ZSM-11 / ZSM-5 intergrowth molecular sieve, specifically a sodium-type, potassium-type or lithium-type ZSM-11 / ZSM-5 intergrowth molecular sieve.

[0085] After the calcination, the present invention can also sequentially perform ammonium exchange (or ammonium ion exchange) and secondary calcination on the obtained molecular sieve to obtain a hydrogen-type ZSM-11 / ZSM-5 intergrowth molecular sieve.

[0086] In the present invention, the ammonium exchange is preferably carried out in an ammonium salt solution, that is, the molecular sieve obtained after the calcination is immersed in an ammonium salt solution; the ammonium salt in the ammonium salt solution preferably includes one or more of ammonium chloride, ammonium nitrate, ammonium carbonate and ammonium sulfate, and the concentration of ammonium ions in the ammonium salt solution is preferably 0.1-1 mol / L, which can be 0.2 or 0.5 mol / L; the solid-liquid mass ratio of the molecular sieve obtained after the calcination to the ammonium salt solution is preferably 1:5-1:20, which can be 1:15 or 1:20. In the present invention, the temperature of the ammonium exchange is preferably 30-80°C, which can be 55 or 65°C, the ammonium exchange is preferably carried out multiple times, the number of ammonium exchanges is preferably 1-3 times, and the time of a single ammonium exchange is preferably 1-8h, which can be 3 or 5h. After the ammonium exchange is completed, the present invention preferably dries the obtained ammonium type ZSM-11 / ZSM-5 symbiotic molecular sieve, and the drying temperature is preferably 100°C and the time is preferably 8h.

[0087] In the present invention, the temperature of the secondary calcination is preferably 500-600°C, and may be 550°C, and the time is preferably 5-8 hours, and may be 6 hours. The secondary calcination is preferably carried out in air. After the secondary calcination, a hydrogen-type ZSM-11 / ZSM-5 intergrowth molecular sieve is obtained.

[0088] In the present invention, the ZSM-11 / ZSM-5 intergrowth molecular sieve has micropores and mesopores, and also has macropores, a particle size of 150 to 300 nm, and a silicon-aluminum molar ratio (Si / Al) greater than or equal to 50, specifically 50 to 200 (i.e., SiO 2 / Al 2 O 3 The molar ratio is 100 to 400). In the present invention, the symbiotic ratio of ZSM-11 molecular sieve to ZSM-5 molecular sieve in the ZSM-11 / ZSM-5 symbiotic molecular sieve is 80:20.

[0089] The present invention provides a method for preparing a ZSM-11 / ZSM-5 symbiotic molecular sieve that is simple to operate and feasible. The method uses the polycationic structure directing agent for direct synthesis, and the synthesized molecular sieve has a wide range of silicon-aluminum ratio (50-∞), and the acid properties are adjustable; and the prepared ZSM-11 / ZSM-5 symbiotic molecular sieve has a fixed symbiotic ratio, and has a multi-level pore structure with better diffusion performance, and has excellent performance. The method for synthesizing a multi-level pore ZSM-11 / ZSM-5 symbiotic molecular sieve using polycations as structure directing agents has not been reported before.

[0090] To further illustrate the present invention, the preparation method of the polycationic structure directing agent and ZSM-11 / ZSM-5 symbiotic molecular sieve provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0091] In the embodiment, the structure of the ZSM-11 / ZSM-5 intergrowth molecular sieve is determined by an X-ray diffraction spectrum (XRD), and the X-ray diffraction spectrum (XRD) is determined by an X-ray powder diffractometer (model Panalytical XPERPRO, Cu Kα ray source Nickel filter, 2θ scanning range 3-50°, operating voltage 40kV, current 40mA, scanning rate 5° / min). Before the sample test, a scanning electron microscope (SEM, model S-4800II field emission scanning electron microscope) was used to observe the crystallization of the molecular sieve sample to confirm that the sample morphology was uniform. On this basis, an XRD test was performed to ensure that there were no interference peaks of other crystals in the diffraction peaks in the XRD spectrum.

[0092] Example 1

[0093] Preparation of polycationic structure directing agent having structure (X=Br) shown in formula Ⅰ:

[0094] Add 400 mL of ether and 67.2 g (0.52 mol) of di-n-butylamine to a 1000 mL flask; after an ice bath for 1 h, slowly add 25.0 g (0.13 mol) of suberyl chloride to the solution; stir the mixture at room temperature for 24 h; after the reaction is completed, filter the mixture to obtain a clear solution, and use 150 mL of NaHCO 3 The solution (5 wt%) was washed three times, dried with anhydrous magnesium sulfate for 24 h, and then the ether was removed by rotary evaporation to obtain N,N,N',N'-tetrabutyl-1,8-octanediamide;

[0095] N,N,N',N'-tetrabutyl-1,8-octanediamide 13 C. 1 H NMR test, the results are as follows Figure 1 shown.

[0096] Add 400 mL of tetrahydrofuran and 20.0 g (0.05 mol) of N,N,N',N'-tetrabutyl-1,8-octanediamide into a 1000 mL flask, place in an ice bath for 1 hour, add 5.7 g (0.15 mol) of lithium aluminum hydride, and then reflux the mixture at 60°C for 48 hours. After cooling the reaction solution, slowly add 11 g of methanol, 11 g of deionized water, and 11 g of anhydrous magnesium sulfate. After stirring for 1 hour, filter to obtain a clear liquid, and evaporate the solvent to obtain N,N,N',N'-tetrabutyl-1,8-octanediamine.

[0097] N,N,N',N'-tetrabutyl-1,8-octanediamine 13 C. 1 H NMR test, the results are as follows Figure 2 shown.

[0098] In a 500 mL flask, 200 mL of methanol and 36.8 g (0.10 mol) of N,N,N',N'-tetrabutyl-1,8-octanediamine were added, followed by 27.2 g (0.10 mol) of 1,8-dibromooctane. The mixture was stirred and refluxed at 60 ° C for 96 h, and the solvent was removed by rotary evaporation and washed with n-hexane to obtain a polycationic structure directing agent [-N + (CH 2 CH 2 CH 2 CH 3 ) 2 -(CH 2 ) 8 -] n [Br - ] n (Abbreviated as [(Bu) 2 -C 8 ]n (Br)), with an average degree of polymerization of 11.

[0099] The prepared polycationic structure directing agent [(Bu) 2 -C 8 ] n (Br) 13 C. 1 H NMR test, the results are as follows Figure 3 shown.

[0100] Example 2

[0101] Preparation of polycationic structure directing agent having the structure shown in formula I (X is OH):

[0102] 20.0 g of the polycationic structure directing agent [(Bu) 2 -C 8 ] n (Br) was dissolved in 100.0 g of deionized water, and 50 g of Amberlite IRA402 strong base anion exchange resin (Amberlite IRA402 (chloride type) was exchanged into OH type in 1 mol / L NaOH solution) was added, stirred for 12 h, filtered, and the filtrate was collected; the filtrate was evaporated to remove water, and titrated with 0.1 mol / L hydrochloric acid to obtain a polycationic structure directing agent [-N] having a structure shown in formula I (X is OH) + (CH 2 CH 2 CH 2 CH 3 ) 2 -(CH 2 ) 8 -] n [OH - ] n (Abbreviated as [(Bu) 2 -C 8 ] n (OH)).

[0103] Example 3

[0104] 8.10g deionized water, 0.52g [(Bu) 2 -C 8 ] n (OH) (SDA, prepared in Example 2), 0.06 g of sodium hydroxide, 0.01 g of sodium aluminate (content 80 wt%), and 2.09 g of TEOS were stirred at room temperature for 24 h to obtain a mixture. The final molar ratio of the mixture was: SiO 2 / Al 2 O 3=200, NaOH / SiO 2 =0.15,SDA / SiO 2 =0.20, H 2 O / SiO 2 =45, where SDA is in structural units (Bu) 2 -C 8 -(OH) meter;

[0105] The mixture was placed in a stainless steel reactor and heated for crystallization at 160° C. for 5 days. After the crystallization, the mixture was filtered, washed, dried in an oven at 100° C. for 8 hours, and calcined in air at 550° C. for 6 hours to obtain a ZSM-11 / ZSM-5 symbiotic molecular sieve sample.

[0106] The X-ray diffraction pattern (XRD pattern) of the sample prepared in Example 3 is as follows: Figure 4 As shown, it is a ZSM-11 / ZSM-5 symbiotic molecular sieve, and the symbiotic ratio of ZSM-11 to ZSM-5 is 80:20; the FE-SEM image of the sample is shown in Figure 5 As shown, the particle size is between 150 and 300 nm, and the symbiotic microstructure has good uniformity.

[0107] Example 4

[0108] 8.10g deionized water, 0.52g [(Bu) 2 -C 8 ] n (OH) (SDA, prepared in Example 2), 0.06 g of sodium hydroxide, and 2.09 g of TEOS were stirred at room temperature for 24 h to obtain a mixture. The final molar ratio of the mixture was: SiO 2 / Al 2 O 3 =∞, NaOH / SiO 2 =0.15,SDA / SiO 2 =0.20, H 2 O / SiO 2 =45, where SDA is in structural units (Bu) 2 -C 8 -(OH) meter;

[0109] The mixture was placed in a stainless steel reactor and heated for crystallization at 160° C. for 5 days. After the crystallization, the mixture was filtered, washed, dried in an oven at 100° C. for 8 hours, and calcined in air at 550° C. for 6 hours to obtain a ZSM-11 / ZSM-5 symbiotic molecular sieve sample.

[0110] The X-ray diffraction pattern (XRD pattern) of the sample prepared in Example 4 is as follows: Figure 6As shown, it is a pure silicon ZSM-11 / ZSM-5 symbiotic molecular sieve, and the symbiotic ratio of ZSM-11 to ZSM-5 is 80:20; the FE-SEM image of the sample is shown in Figure 7 As shown, the particle size is between 150 and 300 nm.

[0111] Example 5

[0112] 8.10g deionized water, 0.52g [(Bu) 2 -C 8 ] n (OH) (SDA, prepared in Example 2), 0.04 g of sodium hydroxide, 0.02 g of sodium aluminate (content 80 wt%), and 2.09 g of TEOS were stirred at room temperature for 24 h to obtain a mixture. The final molar ratio of the mixture was: SiO 2 / Al 2 O 3 =100, NaOH / SiO 2 =0.10,SDA / SiO 2 =0.20, H 2 O / SiO 2 =45, where SDA is in structural units (Bu) 2 -C 8 -(OH) meter;

[0113] The mixture was placed in a stainless steel reactor and heated for crystallization at 160° C. for 5 days. After the crystallization, the mixture was filtered, washed, dried in an oven at 100° C. for 8 h, and calcined in air at 550° C. for 6 h to obtain a ZSM-11 / ZSM-5 symbiotic molecular sieve sample.

[0114] The X-ray diffraction pattern (XRD pattern) of the sample prepared in Example 5 is as follows: Figure 8 As shown, it is a ZSM-11 / ZSM-5 symbiotic molecular sieve, and the symbiotic ratio of ZSM-11 to ZSM-5 is 80:20; the FE-SEM image of the sample is shown in Fig. 9 As shown, the particle size is between 150 and 300 nm.

[0115] Example 6

[0116] 16.20g deionized water, 1.03g [(Bu) 2 -C 8 ] n (OH) (SDA, prepared in Example 2), 0.12 g of sodium hydroxide, 0.01 g of sodium aluminate (content 80 wt%), and 4.17 g of TEOS were stirred at room temperature for 24 h to obtain a mixture. The final molar ratio of the mixture was: SiO 2 / Al 2 O3 =400, NaOH / SiO 2 =0.15,SDA / SiO 2 =0.20, H 2 O / SiO 2 =45, where SDA is a structural monomer (Bu) 2 -C 8 -(OH) meter;

[0117] The mixture was placed in a stainless steel reactor and heated for crystallization at 160° C. for 5 days. After the crystallization, the mixture was filtered, washed, dried in an oven at 100° C. for 8 h, and calcined in air at 550° C. for 6 h to obtain a ZSM-11 / ZSM-5 symbiotic molecular sieve sample.

[0118] The X-ray diffraction pattern (XRD pattern) of the sample prepared in Example 6 is as follows: Fig.10 As shown, it is a ZSM-11 / ZSM-5 symbiotic molecular sieve, and the symbiotic ratio of ZSM-11 to ZSM-5 is 80:20; the FE-SEM image of the sample is shown in Fig.11 As shown, the particle size is between 150 and 300 nm.

[0119] Fig.12 N is the N of the sample prepared in Example 6 2 Physical adsorption isotherm (inset is pore size distribution), Fig.13 The mercury injection curve of the sample prepared in Example 6 (the inset is the pore size distribution, with a peak value of 60 nm). Figures 12-13 It can be seen that in addition to micropores, the molecular sieve also has a mesopore distribution, and the pore size is mainly concentrated in 40-70 nm.

[0120] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A polycationic structure directing agent, characterized in that: It has the structure shown in formula I: In the structure shown in formula I, X is Br or OH, and n is an integer of 5 to 20.

2. The method for preparing the polycationic structure directing agent according to claim 1, characterized in that: The following steps are involved: Di-n-butylamine, suberyl chloride and an organic solvent are mixed to undergo a nucleophilic addition reaction to obtain N,N,N',N'-tetrabutyl-1,8-suberylamide; The N,N,N',N'-tetrabutyl-1,8-octanediamide is mixed with lithium aluminum hydride and an organic solvent for reduction reaction to obtain N,N,N',N'-tetrabutyl-1,8-octanediamine; The N,N,N',N'-tetrabutyl-1,8-octanediamine is mixed with 1,8-dibromooctane and an organic solvent to carry out a nucleophilic substitution polymerization reaction to obtain a polycationic structure directing agent with a structure shown in Formula I when X is Br; The polycationic structure directing agent with the structure shown in formula I when X is Br is subjected to ion exchange through a strong alkaline anion exchange resin to obtain a polycationic structure directing agent with the structure shown in formula I when X is OH.

3. The preparation method according to claim 2, characterized in that: The molar ratio of di-n-butylamine to suberyl chloride is 4:1, the temperature of the nucleophilic addition reaction is room temperature, and the time is 24 to 48 hours.

4. The preparation method according to claim 2, characterized in that: The molar ratio of the N,N,N',N'-tetrabutyl-1,8-octanediamide to lithium aluminum hydride is 1:3, the temperature of the reduction reaction is 60-100° C., and the time is 24-48 hours.

5. The preparation method according to claim 2, characterized in that: The molar ratio of the N,N,N',N'-tetrabutyl-1,8-octanediamine to 1,8-dibromooctane is 1:1, the temperature of the nucleophilic substitution polymerization reaction is 60-100° C., and the time is 24-96 hours.

6. A method for preparing a ZSM-11 / ZSM-5 symbiotic molecular sieve, characterized in that: The following steps are involved: A structure directing agent, a silicon source, an aluminum source, an alkali source and water are mixed for hydrothermal crystallization to obtain a crystallized product; the structure directing agent is the polycationic structure directing agent according to claim 1, and the alkali source is an alkali metal hydroxide; the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the alkali source is calculated as an alkali metal element, and the structure directing agent is calculated as a structural unit, and the molar ratio of the silicon source, the aluminum source, the structure directing agent, the alkali source and the water is 1:(0-0.04):(0.05-0.50):(0.02-0.50):(10-150); The crystallized product is calcined to obtain the ZSM-11 / ZSM-5 intergrowth molecular sieve.

7. The preparation method according to claim 6, characterized in that: The silicon source includes one or more of tetraethyl orthosilicate, sodium silicate, fumed silica, silica sol and white carbon black; the aluminum source includes one or more of aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum hydroxide, sodium metaaluminate, pseudo-boehmite and aluminum isopropoxide; the alkali source includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

8. The preparation method according to claim 6, characterized in that: The temperature of the hydrothermal crystallization is 110-190° C., and the time is 3-14 days.

9. The preparation method according to claim 6, characterized in that: The ZSM-11 / ZSM-5 intergrowth molecular sieve has micropores and mesopores, a particle size of 150 to 300 nm, and a silicon-aluminum molar ratio of greater than or equal to 50.

10. The preparation method according to claim 6 or 9, characterized in that: The symbiotic ratio of ZSM-11 molecular sieve to ZSM-5 molecular sieve in the ZSM-11 / ZSM-5 symbiotic molecular sieve is 80:20.

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