A nano EUO type zeolite molecular sieve and its preparation method

Abstract

The present invention provides a nano EUO type zeolite molecular sieve and a preparation method thereof, and relates to the field of molecular sieve technology. The present invention mixes an aluminum source, an inorganic base, water and a template to obtain an aqueous phase; mixes a silicon source and an organic solvent to obtain an organic phase; and mixes the aqueous phase and the organic phase to perform a dynamic hydrothermal reaction to obtain the nano EUO type zeolite molecular sieve. The present invention adopts a phase transfer method, and by dissolving the aluminum source and the silicon source in different aqueous phases and organic phases, avoids direct contact between the two to form large-particle colloidal particles, and also avoids the direct conversion of large-particle colloidal particles into large-particle zeolite crystals; when the raw materials of the organic phase are slowly transferred to the aqueous phase, the growth process of the zeolite crystals is restricted, thereby obtaining a nanometer morphology. The EUO type zeolite molecular sieve synthesized by the phase transfer method of the present invention has a nanometer morphology (50 to 200 nm), a high degree of crystallinity, and the synthesis time of the method of the present invention is short.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a nano EUO type zeolite molecular sieve and a preparation method thereof. Background Art

[0002] Zeolite is a kind of inorganic microporous material with regular and uniform pore structure, which has a wide range of applications in adsorption, catalysis and ion exchange. Among them, EUO zeolite has a one-dimensional ten-membered ring pore structure with a pore size of about At the same time, there is a Due to its strong shape selectivity, EUO zeolite has a wide range of industrial applications, such as xylene isomerization and ethylbenzene disproportionation.

[0003] Chinese patent CN201911023722.8 discloses a method for synthesizing EUO-type zeolite using an organic structure-directing agent, the method comprising: preparing a gel containing a silicon source, an aluminum source, an organic template, an alkali and water, and then dynamically hydrothermally reacting the gel in an autoclave reactor under autogenous pressure, and then separating to obtain a zeolite product with an EUO topological structure. The morphology of the product is a block formed by stacking needle-like structures. Chinese patent CN202110269842.7 discloses a method for synthesizing EUO-type zeolite by crystallization using *MRE-type zeolite, the method comprising: preparing a gel containing *MRE-type zeolite, an aluminum source, an organic template, an alkali and water, and then dynamically hydrothermally reacting the gel in an autogenous pressure autoclave reactor, and then separating to obtain a zeolite product with an EUO topological structure. The EUO zeolite prepared by this method has large crystals in the micron range. A method for synthesizing high-silica micron-sized EUO is disclosed in the prior art (S. Hu, Y. Gong, Highly selective formation of propylene from methanol over high-silica EU-1 zeolite catalyst, Cataly. Commun., 28, 2012, 95-99). A method for synthesizing micron-sized EUO zeolite under hydrothermal conditions without an organic template and under seed-directed conditions is also disclosed in the prior art (C. Bian, H. Mao, Facile and seed-direct synthesis of pure EUO zeolite with enhanced catalytic performance, Mater. Res. Express, 6, 2019, 095529).

[0004] The EUO zeolite crystals disclosed in the above-mentioned technology are too large in size and cannot fully contact with the reactants, which is not conducive to the progress of the catalytic reaction. Therefore, it is very important to reduce the size of EUO zeolite crystals. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a nano EUO zeolite molecular sieve and a preparation method thereof. The present invention successfully synthesizes a nano EUO zeolite molecular sieve with a nano morphology.

[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 method for preparing a nano EUO zeolite molecular sieve, comprising the following steps:

[0008] mixing an aluminum source, an inorganic base, water, and a template to obtain an aqueous phase;

[0009] mixing a silicon source and an organic solvent to obtain an organic phase;

[0010] Mixing the aqueous phase and the organic phase to perform a dynamic hydrothermal reaction to obtain the nano EUO zeolite molecular sieve;

[0011] The inorganic base is calculated as M2O, wherein M is the metal element of the inorganic base, the silicon source is calculated as SiO2, and the aluminum source is calculated as Al2O3. The molar ratio of the inorganic base, water, template, aluminum source, silicon source and organic solvent is (7.35~25.3):(1270~4390):(8.33~28.7):1.0:(22.1~76.0):(167~575).

[0012] Preferably, the aluminum source includes one or more of sodium aluminate, pseudo-boehmite, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate and aluminum isopropoxide.

[0013] Preferably, the inorganic base includes one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.

[0014] Preferably, the template comprises hexamethonium hydroxide and / or hexamethonium bromide.

[0015] Preferably, the silicon source includes one or more of sodium silicate, white carbon black, water glass, silica sol and tetraethyl orthosilicate.

[0016] Preferably, the organic solvent includes one or more of cyclohexane, n-dodecane and toluene.

[0017] Preferably, the molar ratio of the inorganic base, water, template, aluminum source, silicon source and organic solvent is (10.5-19.5):(1820-3380):(11.9-22.1):1.0:(31.5-58.5):(238-442).

[0018] Preferably, the temperature of the dynamic hydrothermal reaction is 130-200° C., the time is 10 h-9 d, and the rotation speed is 10-100 rpm.

[0019] The present invention provides a nano EUO zeolite molecular sieve prepared by the preparation method described in the above technical solution.

[0020] Preferably, the particle size of the nano EUO zeolite molecular sieve is 50 to 200 nm.

[0021] The present invention provides a preparation method of a nano EUO type zeolite molecular sieve, comprising the following steps: mixing an aluminum source, an inorganic base, water and a template to obtain an aqueous phase; mixing a silicon source and an organic solvent to obtain an organic phase; mixing the aqueous phase and the organic phase to carry out a dynamic hydrothermal reaction to obtain the nano EUO type zeolite molecular sieve; the inorganic base is calculated as M2O, wherein M is a metal element of the inorganic base, the silicon source is calculated as SiO2, and the aluminum source is calculated as Al2O3; and the molar ratio of the inorganic base, water, template, aluminum source, silicon source and organic solvent is (7.35-25.3):(1270-4390):(8.33-28.7):1.0:(22.1-76.0):(167-575). The present invention utilizes a phase transfer method to dissolve the aluminum and silicon sources in separate aqueous and organic phases, preventing direct contact between the two, thereby forming large colloidal particles and preventing the direct conversion of these large colloidal particles into large zeolite crystals. As the organic phase raw materials slowly transfer to the aqueous phase, the growth of the zeolite crystals is restricted, resulting in a nanometer morphology. The EUO zeolite molecular sieve synthesized by this phase transfer method exhibits a nanometer morphology (50-200 nm), high crystallinity, and a short synthesis time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The X-ray diffraction (PXRD) patterns of the zeolite molecular sieve products prepared in Examples 1 to 3 and Comparative Examples 3 to 7 are shown;

[0023] Figure 2 This is a scanning electron microscope (SEM) image of the EUO zeolite molecular sieve product H1 prepared in Example 1;

[0024] Figure 3 This is a scanning electron microscope image of the EUO zeolite molecular sieve product H2 prepared in Example 2;

[0025] Figure 4 This is a scanning electron microscope image of the EUO zeolite molecular sieve product H3 prepared in Example 3;

[0026] Figure 5 This is a scanning electron microscope image of product H4 prepared in Comparative Example 1;

[0027] Figure 6 This is a scanning electron microscope image of product H5 prepared in Comparative Example 2;

[0028] Figure 7 This is a scanning electron microscope image of product H8 prepared in comparative example 5. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a nano EUO zeolite molecular sieve, comprising the following steps:

[0030] mixing an aluminum source, an inorganic base, water, and a template to obtain an aqueous phase;

[0031] mixing a silicon source and an organic solvent to obtain an organic phase;

[0032] Mixing the aqueous phase and the organic phase to perform a dynamic hydrothermal reaction to obtain the nano EUO zeolite molecular sieve;

[0033] The inorganic base is calculated as M2O, wherein M is the metal element of the inorganic base, the silicon source is calculated as SiO2, and the aluminum source is calculated as Al2O3. The molar ratio of the inorganic base, water, template, aluminum source, silicon source and organic solvent is (7.35~25.3):(1270~4390):(8.33~28.7):1.0:(22.1~76.0):(167~575).

[0034] In the present invention, unless otherwise specified, the raw materials involved are commercially available products well known to those skilled in the art.

[0035] In the present invention, an aluminum source, an inorganic base, water, and a template are mixed to obtain an aqueous phase. In the present invention, the aluminum source preferably includes one or more of sodium aluminate, pseudo-boehmite, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate, and aluminum isopropoxide, more preferably aluminum hydroxide. In the present invention, the inorganic base preferably includes one or more of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide, more preferably sodium hydroxide. In the present invention, the water is preferably deionized water. In the present invention, the template preferably includes hexamethonium hydroxide and / or hexamethonium bromide, and the hexamethonium hydroxide is preferably added as a 25% aqueous solution.

[0036] In the present invention, the mixing of the aluminum source, inorganic base, water and template is preferably carried out at room temperature and in a closed condition, and the mixing method is preferably stirring and mixing, and the stirring and mixing is based on uniform mixing of the aluminum source, inorganic base, water and template.

[0037] The present invention mixes a silicon source and an organic solvent to obtain an organic phase. In the present invention, the silicon source preferably includes one or more of sodium silicate, white carbon black, water glass, silica sol, and tetraethyl orthosilicate, more preferably tetraethyl orthosilicate (TEOS, SiO2 28% by mass). In the present invention, the organic solvent preferably includes one or more of cyclohexane, n-dodecane, and toluene, more preferably toluene.

[0038] In the present invention, the mixing of the silicon source and the organic solvent is preferably carried out at room temperature and in a closed condition. The mixing method is preferably stirring and mixing, and the stirring and mixing is based on uniform mixing of the silicon source and the organic solvent.

[0039] After obtaining the aqueous phase and the organic phase, the present invention mixes the aqueous phase and the organic phase to carry out a dynamic hydrothermal reaction to obtain the nano EUO type zeolite molecular sieve.

[0040] In the present invention, the inorganic base is calculated as M2O, wherein M is the metal element of the inorganic base, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the molar ratio of the inorganic base, water, template, aluminum source, silicon source and organic solvent is (7.35-25.3):(1270-4390):(8.33-28.7):1.0:(22.1-76.0):(167-575) (expressed as M2O:H2O:R1:Al2O3:SiO2:R2=( 7.35~25.3):(1270~4390):(8.33~28.7):1.0:(22.1~76.0):(167~575), wherein R1 represents a template and R2 represents an organic solvent), preferably (10.5~19.5):(1820~3380):(11.9~22.1):1.0:(31.5~58.5):(238~442), more preferably 15:2600:17:1.0:45:340.

[0041] In the present invention, the aqueous phase and the organic phase are preferably sequentially charged into a reaction kettle with a polytetrafluoroethylene liner, and then transferred to an oven for dynamic hydrothermal reaction.

[0042] In the present invention, the temperature of the dynamic hydrothermal reaction is preferably 130-200°C, more preferably 150-195°C, the time is preferably 10 hours to 9 days, more preferably 3-7 days, and the rotation speed is preferably 10-100 rpm, more preferably 45-60 rpm. The present invention adopts a dynamic hydrothermal reaction, which allows the two immiscible phases to be fully mixed into an emulsion, and the migration of materials between the two phases is more uniform and sufficient.

[0043] After the dynamic hydrothermal reaction is completed, the present invention preferably sequentially performs solid-liquid separation, solid-phase washing, and drying on the resulting crystallization reaction solution to obtain a nano EUO zeolite molecular sieve (nanosphere EUO zeolite). In the present invention, the solid-liquid separation method is preferably centrifugation, the solid-phase washing is preferably water washing, the drying temperature is preferably 75-100°C, and the drying time is preferably 6-12 hours.

[0044] The present invention provides a nano-EUO zeolite molecular sieve prepared using the preparation method described in the above technical solution. In the present invention, the nano-EUO zeolite molecular sieve has a particle size of 50 to 200 nm. In an embodiment of the present invention, the prepared nano-EUO zeolite molecular sieve has a particle size of approximately 100 nm. The present invention successfully synthesizes a highly crystalline EUO zeolite with a nanospherical morphology.

[0045] In order to further illustrate the present invention, the nano EUO zeolite molecular sieve and its preparation method provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of protection of the present invention.

[0046] Example 1

[0047] Preparation of nano EUO zeolite molecular sieve:

[0048] 0.0726 g of sodium hydroxide, 2.82 mL of distilled water, 0.364 g of hexamethonium bromide powder, and 0.00930 g of aluminum hydroxide were added to a reaction vessel and stirred uniformly under sealed conditions at room temperature to obtain a phase transfer reaction solution A-1 (i.e., the aqueous phase);

[0049] 0.554 g of tetraethyl orthosilicate (TEOS) and 1.82 g of toluene were added to a reaction container, and stirred evenly under sealed conditions at room temperature to obtain a phase transfer reaction liquid B-1 (ie, an organic phase).

[0050] The reaction solutions A-1 and B-1 were sequentially charged into a polytetrafluoroethylene-lined reactor and subjected to dynamic crystallization at 180°C at a rotation speed of 60 rpm for 3 days.

[0051] After the hydrothermal reaction was completed, a centrifugal device was used to separate the solid and liquid. The solid product was washed with water and dried in an oven at 75°C for 12 hours to obtain a product, which was recorded as H1.

[0052] Figure 1 The middle curve H1 is the X-ray diffraction pattern of EUO-type zeolite molecular sieve product H1. By comparing it with the standard diffraction pattern published by the International Zeolite Association, it can be seen that H1 is a zeolite with EUO structure.

[0053] Figure 2 This is a scanning electron microscope image of EUO type zeolite molecular sieve product H1. H1 has a nano-spherical structure and a small particle size of about 100nm.

[0054] Example 2

[0055] Preparation of nano EUO zeolite molecular sieve:

[0056] 1.4 g of sodium hydroxide, 56 mL of distilled water, 7.2 g of hexamethonium bromide powder, and 0.186 g of aluminum hydroxide were added to a reaction vessel and stirred uniformly under sealed conditions at room temperature to obtain a phase transfer reaction solution A-2;

[0057] 11.1 g of tetraethyl orthosilicate (TEOS) and 36.4 g of toluene were added to a reaction container, and stirred evenly under sealed conditions at room temperature to obtain a phase transfer reaction liquid B-2.

[0058] The reaction solutions A-2 and B-2 were sequentially charged into a polytetrafluoroethylene-lined reactor and subjected to dynamic crystallization at 195°C with a rotation speed of 45 rpm for 7 days.

[0059] After the hydrothermal reaction was completed, a centrifugal device was used to separate the solid and liquid. The solid product was washed with water and dried in an oven at 100°C for 8 hours to obtain the product, which was recorded as H2.

[0060] Figure 1 The middle curve H2 is the X-ray diffraction pattern of EUO-type zeolite molecular sieve product H2. By comparing it with the standard diffraction pattern published by the International Zeolite Association, it can be seen that H2 is a zeolite with EUO structure.

[0061] Figure 3 This is a scanning electron microscope image of EUO type zeolite molecular sieve product H2. H2 has a nano-spherical structure and a particle size of about 100nm.

[0062] Example 3

[0063] Preparation of nano EUO zeolite molecular sieve:

[0064] 0.36 g of sodium hydroxide, 14 mL of distilled water, 1.8 g of hexamethonium bromide powder, and 0.046 g of aluminum hydroxide were added to a reaction vessel and stirred evenly under closed conditions at room temperature to obtain a phase transfer reaction solution A-3;

[0065] 2.5 g of tetraethyl orthosilicate (TEOS) and 9.2 g of toluene were added to a reaction container, and stirred evenly under sealed conditions at room temperature to obtain a phase transfer reaction liquid B-3.

[0066] The reaction solutions A-3 and B-3 were sequentially charged into a polytetrafluoroethylene-lined reactor and subjected to dynamic crystallization at 150° C. at a rotation speed of 50 rpm for 9 days.

[0067] After the hydrothermal reaction was completed, a centrifugal device was used to separate the solid and liquid. The solid product was washed with water and dried in an oven at 80°C for 6 hours to obtain a product, which was recorded as H3.

[0068] Figure 1 The middle curve H3 is the X-ray diffraction pattern of EUO-type zeolite molecular sieve product H3. By comparing it with the standard diffraction pattern published by the International Zeolite Association, it can be seen that H3 is a zeolite with EUO structure.

[0069] Figure 4 This is a scanning electron microscope image of EUO type zeolite molecular sieve product H3. H3 has a nano-spherical structure with a particle size of about 100nm.

[0070] Comparative Example 1

[0071] The product was synthesized according to the method shown in the literature (S. Hu, Y. Gong, Highly selective formation of propylene from methanol over high-silica EU-1zeolite catalyst, Cataly. Commun., 28, 2012, 95-99), and the obtained product was recorded as H4.

[0072] Figure 5 This is a scanning electron microscope image of H4, which has a blocky structure and a particle size of 0.8 to 2 μm.

[0073] Comparative Example 2

[0074] The product was synthesized according to the method shown in Example 1 of patent CN201911023722.8 and was denoted as H5.

[0075] Figure 6 This is a scanning electron microscope image of H5, which is a large block structure formed by the accumulation of needle-like structures with a particle size of 5μm.

[0076] Comparative Example 3

[0077] Compared with Example 1, in Comparative Example 3, no organic solvent toluene was added, and the remaining procedures were the same as in Example 1 to prepare a comparative product, which was recorded as H6.

[0078] Figure 1The curve H6 in the figure is the PXRD pattern of product H6. It can be seen that H6 is not EUO type zeolite comparative example 4.

[0079] Compared with Example 2, the template agent hexamethonium bromide was not added in Comparative Example 4, and the remaining scheme was the same as Example 2 to prepare a comparative product, which was recorded as H7.

[0080] Figure 1 Curve H7 in FIG is the PXRD pattern of product H7, and it can be seen that H7 is not EUO type zeolite.

[0081] Comparative Example 5

[0082] Compared with Example 2, static crystallization was used instead of dynamic crystallization in Comparative Example 5, and the rest of the scheme was the same as that of Example 2 to prepare a comparative product, which was recorded as H8.

[0083] Figure 1 Curve H8 in FIG is the PXRD pattern of product H8, and it can be seen that H8 is pure EUO zeolite.

[0084] Figure 7 This is a scanning electron microscope image of product H8. H8 is a mixture of small block structures and large block structures, and the particle size is uneven.

[0085] Comparative Example 6

[0086] Compared with Example 2, in Comparative Example 6, crystallization was performed at 100° C., and the rest of the procedures were the same as in Example 2, to prepare a comparative product, which was designated as H9.

[0087] Figure 1 Curve H9 in FIG. 1 is the PXRD pattern of product H9, from which it can be seen that H9 is not EUO type zeolite.

[0088] Comparative Example 7

[0089] Compared with Example 2, the crystallization time in Comparative Example 7 was 5 h, and the rest of the scheme was the same as Example 2, and a comparative product was prepared, which was recorded as H10.

[0090] Figure 1 Curve H10 in FIG is the PXRD pattern of product H10. It can be seen that H10 is not a pure EUO zeolite.

[0091] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing nano EUO zeolite molecular sieve, characterized in that: The following steps are involved: mixing an aluminum source, an inorganic base, water, and a template to obtain an aqueous phase; Mixing a silicon source and an organic solvent to obtain an organic phase; the organic solvent is one or more of cyclohexane, n-dodecane and toluene; Mixing the aqueous phase and the organic phase to perform a dynamic hydrothermal reaction to obtain the nano EUO zeolite molecular sieve; The inorganic base is calculated as M2O, wherein M is the metal element of the inorganic base, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, and the molar ratio of the inorganic base, water, template, aluminum source, silicon source and organic solvent is (7.35-25.3):(1270-4390):(8.33-28.7):1.0:(22.1-76.0):(167-575); The nano EUO zeolite molecular sieve has a nano spherical morphology and a particle size of 50 to 200 nm.

2. The preparation method according to claim 1, characterized in that The aluminum source includes one or more of sodium aluminate, pseudo-boehmite, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate and aluminum isopropoxide.

3. The preparation method according to claim 1, characterized in that The inorganic base includes one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.

4. The preparation method according to claim 1, characterized in that The template agent includes hexamethonium hydroxide and / or hexamethonium bromide.

5. The preparation method according to claim 1, characterized in that The silicon source includes one or more of sodium silicate, white carbon black, water glass, silica sol and tetraethyl orthosilicate.

6. The preparation method according to any one of claims 1 to 5, characterized in that The molar ratio of the inorganic base, water, template, aluminum source, silicon source and organic solvent is (10.5-19.5):(1820-3380):(11.9-22.1):1.0:(31.5-58.5):(238-442).

7. The preparation method according to claim 1, characterized in that The temperature of the dynamic hydrothermal reaction is 130-200° C., the time is 10 h-9 d, and the rotation speed is 10-100 rpm.

8. The nano EUO zeolite molecular sieve prepared by the preparation method according to any one of claims 1 to 7.

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