A hierarchical pore EUO molecular sieve, a preparation method and application thereof

Abstract

The application discloses a kind of multi-level hole EUO molecular sieve and its preparation method and application, the morphology of the multi-level hole EUO molecular sieve is fusiform;With micropore and mesopore;The pore volume of micropore is 0.12~0.15cm 3 / g;The pore volume of mesopore is 0.14~0.25cm 3 / g.The synthesis route is prepared by the optimization of silicon-aluminum source and synthesis system ratio and the addition of seed crystal, and the high crystallinity multi-level hole EUO molecular sieve is prepared by one-step hydrothermal crystallization method.The EUO molecular sieve described in the application has excellent diffusion performance due to its larger mesopore pore volume, and has excellent reaction stability in meta-xylene isomerization reaction.

Description

Technical Field

[0001] This invention belongs to the technical field of materials chemistry; specifically, it relates to a hierarchical porous EUO molecular sieve, its preparation method, and its application. Background Technology

[0002] EUO molecular sieves are one-dimensional porous zeolites with one-dimensional ten-membered ring channels (0.41 × 0.54 nm). Due to their unique pore structure and acidic properties, they possess enormous application potential in multiple catalytic fields. In particular, they exhibit unique and excellent catalytic performance in reactions such as xylene isomerization, methanol conversion, and light hydrocarbon cracking.

[0003] One-dimensional molecular sieves generally face severe diffusion limitations, which greatly restricts their commercial applications and makes them highly susceptible to carbon deposition and deactivation. In recent years, improving the diffusion properties of EUO zeolites has received widespread attention. EUO molecular sieves with a SiO2 / Al2O3 molar ratio greater than 50 exhibit a spindle-shaped morphology, with mesopore volumes typically below 0.08 cm³. 3 The presence of / g (Mohamed HM Ahmed; Oki Muraza; Koji Miyake, Applied Catalysis A; General, 2015, 497, 127-134) introduces certain mass transfer resistance, thus requiring the introduction of mesopores to improve its diffusion performance.

[0004] Wang Zhiguang et al. (CN108946756A) synthesized hierarchical porous EUO molecular sieves by using long-chain silane compounds as crystallization aids and bis-quaternary ammonium salts with bis-six-membered heterocyclic groups replacing alkane structures as organic templates, which greatly improved its catalytic performance in the isomerization reaction of m-xylene.

[0005] US Patent 6377063 discloses a method for synthesizing EUO structured molecular sieves, which uses relatively safer and cheaper alkylated derivatives of methylene diamine ions as structure directing agents, reducing costs and being relatively safer and more environmentally friendly.

[0006] Wang Jing et al. (CN114433220A) disclosed a method for preparing multi-level porous EUO molecular sieves. The method involves acid-treating the EUO molecular sieves with phosphoric acid solution to obtain an acid-treated sample; then, the acid-treated sample is alkali-treated with sodium hydroxide solution to obtain an acid-alkali treated EUO molecular sieve, which greatly improves the mesopore volume of the EUO molecular sieve.

[0007] Ahamed et al. (Mohamed HM Ahmed; Oki Muraza; Koji Miyake, Applied Catalysis A; General, 2015, 497, 127-134) reported a method for preparing hierarchical porous EUO zeolite. They treated EUO molecular sieves with sodium hydroxide solutions of different concentrations to obtain alkali-treated samples. These samples were then washed with hydrochloric acid solution followed by acid washing with 4M nitric acid. The effect of alkali concentration on the mesopore volume of the EUO molecular sieves was investigated. They found that when the sodium hydroxide solution concentration was 0.5M, the treated samples exhibited a larger mesopore volume.

[0008] In summary, current methods for the direct synthesis of hierarchical porous EUO zeolites are complex and require expensive structure-directing agents, which limits their scale-up applications to some extent. Developing a green, economical, and efficient route for the preparation of hierarchical porous EUO molecular sieves is therefore essential. Summary of the Invention

[0009] According to one aspect of this application, a hierarchical porous EUO molecular sieve is provided, wherein the morphology of the hierarchical porous EUO molecular sieve is a spindle-shaped aggregate.

[0010] The multi-level porous EUO molecular sieve has micropores and mesopores;

[0011] The pore volume of the micropores is 0.12–0.15 cm³. 3 / g;

[0012] The mesopore volume is 0.14–0.25 cm³. 3 / g.

[0013] The silica-to-alumina ratio of the multi-level porous EUO molecular sieve is greater than 50.

[0014] The size of the multi-level porous EUO molecular sieve is 0.5–2.5 μm.

[0015] It has a short diffusion path and excellent diffusion performance.

[0016] According to another aspect of this application, a method for preparing the above-mentioned hierarchical porous EUO molecular sieve is provided, comprising the following steps:

[0017] Raw materials containing silicon source, aluminum source, inorganic alkali, template agent, seed crystal and water are mixed and aged and crystallized in a sealed container to obtain the multi-level porous EUO molecular sieve.

[0018] Specifically, under stirring conditions, raw materials containing aluminum source, inorganic alkali, template agent and seed crystal are mixed with water, raw materials containing silicon source are added, and the mixture is aged and hydrothermally crystallized in a reaction vessel to obtain the EUO molecular sieve.

[0019] The silicon source is selected from at least one of silica, silica sol, tetraethyl orthosilicate, and water glass;

[0020] The aluminum source is selected from at least one of aluminum nitrate, aluminum sulfate, sodium aluminate, boehmite, and aluminum chloride;

[0021] The inorganic base is selected from at least one of sodium hydroxide, sodium carbonate, potassium hydroxide, lithium hydroxide, and ammonia water;

[0022] The template agent is at least one of hexamethylammonium bromide, hexamethylammonium chloride, and hexamethylammonium hydroxide;

[0023] The seed crystals are selected from molecular sieves with EUO and / or *MRE topologies.

[0024] The molar ratio of the inorganic base to the silicon source is 0.1 to 0.6;

[0025] The molar ratio of SiO2 / Al2O3 between the silicon source and the aluminum source is greater than 50;

[0026] The molar ratio of the template agent to the silicon source is 0.02 to 0.08;

[0027] The molar ratio of water to silicon source is 25 to 60;

[0028] The mass ratio of the seed crystal to the silicon source is 0.03 to 0.15;

[0029] The molar amount of the silicon source is calculated based on the molar amount of SiO2 in the silicon source;

[0030] The molar amount of the aluminum source is calculated based on the molar amount of Al2O3 in the aluminum source;

[0031] The molar amount of the template agent is calculated based on the molar amount of hexamethylammonium ions in the template agent;

[0032] The mass of the seed crystal is calculated based on the mass of SiO2 in the seed crystal.

[0033] The molar amount of the inorganic base is calculated based on the hydroxide ions in the base source.

[0034] The aging temperature is 30–120°C;

[0035] The aging time is 12 to 48 hours.

[0036] The crystallization is a hydrothermal dynamic crystallization carried out in a batch reactor within a rotating oven.

[0037] The crystallization temperature is 140–200°C;

[0038] The crystallization time is 48–168 hours;

[0039] The rotation speed of the rotary oven is 20-70 r / min.

[0040] The multi-level porous EUO molecular sieve is filtered, washed, and dried.

[0041] According to another aspect of this application, an application of the above-described hierarchical porous EUO molecular sieve is provided as a catalyst for the m-xylene isomerization reaction. It exhibits excellent diffusion properties and excellent reaction stability in the m-xylene isomerization reaction.

[0042] The beneficial effects that this application can produce include:

[0043] (1) The EUO molecular sieve described in this application has a regular spindle-shaped morphology and excellent diffusion properties; its length is 0.5–2.5 μm; and its micropore volume is 0.12–0.15 cm³. 3 / g, mesoporous pore volume is 0.14~0.25cm³ 3 / g;

[0044] (2) This synthesis route uses the optimization of the ratio of silicon-aluminum source to synthesis system and the addition of seed crystals to prepare highly crystalline hierarchical porous EUO molecular sieves by one-step hydrothermal crystallization.

[0045] (3) The EUO molecular sieve described in this application has excellent diffusion performance due to its large mesoporous pore volume and excellent reaction stability in the m-xylene isomerization reaction. Attached Figure Description

[0046] Figure 1 X-ray diffraction (XRD) patterns of samples prepared for Comparative Example 1 and Examples 1-5;

[0047] Figure 2 The N2 adsorption-desorption curves and pore size distribution curves of the sample prepared for Comparative Example 1 were obtained.

[0048] Figure 3 The N2 adsorption-desorption curves and pore size distribution curves of the sample prepared in Example 1;

[0049] Figure 4 The diagram shows the effect of the m-xylene isomerization reaction of the EUO molecular sieve catalysts provided in Example 1 and Comparative Example 1 of this invention.

[0050] Figure 5 The image shown is an SEM image of the sample prepared in Example 1, with a scale of 2 μm and a spindle-shaped aggregate size of approximately 1.5 μm. Detailed Implementation

[0051] The present invention will be further illustrated by the following examples, but the examples do not limit the scope of the present invention.

[0052] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0053] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0054] The specific information of the various substances used in the examples is as follows:

[0055] Silica sol (Qingdao Marine Chemical Co., Ltd., 30wt% SiO2);

[0056] Silica (Maclean, 95wt% SiO2);

[0057] Tetraethyl orthosilicate (TEOS) (Comio, >98wt%);

[0058] Al2(SO4)3·18H2O (Sinopharm Group, 98wt%)

[0059] Al(NO3)3·9H2O (Sinopharm Group, 99wt%)

[0060] Boehmite (Maclean, 66 wt% Al2O3, 33 wt% H2O);

[0061] NaOH (Sinopharm Group, >96wt%)

[0062] KOH (Komeo, 85wt%);

[0063] HMBr (Aladdin, 98wt%)

[0064] HMOH (Aladdin, 98 wt%)

[0065] EUO seed crystals (Nankai Catalyst Factory)

[0066] Deionized water (homemade)

[0067] m-Xylene (Aladdin, >99wt%)

[0068] Comparative Example 1:

[0069] Under stirring conditions, 0.62 g Al2(SO4)3·18H2O, 2.15 g HMBr, and 0.77 g NaOH were dissolved in 29.82 g H2O. After complete dissolution, 14.63 g silica sol was added dropwise under stirring conditions. The solution was transferred to a stainless steel reactor and placed in a rotary oven for hydrothermal crystallization at 170 °C and 40 r / min for 168 h. After crystallization, the solution was rapidly cooled to room temperature with cold water, filtered, washed, and dried to obtain sodium-type molecular sieve powder. The XRD pattern of the obtained product is shown below. Figure 1 The image shown is a pure-phase EUO molecular sieve. (The text appears to be incomplete and requires further context.) Figure 2 It can be seen that the adsorption and desorption results of nitrogen gas ( Figure 2 It can be determined that the micropore volume is 0.14 cm³. 3 / g, mesoporous pore volume is 0.20cm³ 3 / g.

[0070] Example 1:

[0071] Under stirring conditions, 0.62 g Al2(SO4)3·18H2O, 0.81 g HMBr, 0.77 g NaOH, and 0.25 g EUO seed crystals were added to 29.82 g H2O and placed in a stainless steel reactor. 14.63 g silica sol was added dropwise under stirring conditions. The reactor was then placed in a rotary oven and aged at 90 °C and 40 r / min for 24 h, followed by hydrothermal crystallization at 150 °C and 40 r / min for 72 h. After crystallization, the mixture was rapidly cooled to room temperature with cold water, filtered, washed, and dried to obtain sodium-type molecular sieve powder. The XRD pattern of the obtained product is shown below. Figure 1 The image shows a pure-phase EUO molecular sieve. The results of nitrogen adsorption-desorption are shown. Figure 3 It can be determined that the micropore volume is 0.14 cm³. 3 / g, mesoporous pore volume is 0.20cm³ 3 / g. From Figure 5 It can be seen that the product has a regular spindle shape and a size of about 1.5 μm.

[0072] Example 2:

[0073] Under stirring conditions, 0.62 g Al2(SO4)3·18H2O, 0.81 g HMCl, 0.77 g NaOH, and 0.25 g EUO seed crystals were added to 29.82 g H2O and placed in a stainless steel reactor. 14.63 g silica sol was added dropwise under stirring conditions. The reactor was then placed in a rotary oven and aged at 120 °C and 40 r / min for 12 h, followed by hydrothermal crystallization at 140 °C and 40 r / min for 84 h. After crystallization, the mixture was rapidly cooled to room temperature with cold water, filtered, washed, and dried to obtain sodium-type molecular sieve powder. The XRD pattern of the obtained product is shown below. Figure 1 As shown, this is a pure-phase EUO molecular sieve.

[0074] Example 3:

[0075] Under stirring conditions, 0.20 g of boehmite, 0.52 g of HMOH, 0.77 g of NaOH, and 0.30 g of EUO seed crystals were added to 29.82 g of H2O and placed in a stainless steel reactor. 14.63 g of silica sol was added dropwise under stirring conditions. The reactor was then placed in a rotary oven and aged at 60 °C and 40 r / min for 36 h, followed by hydrothermal crystallization at 160 °C and 20 r / min for 120 h. After crystallization, the mixture was rapidly cooled to room temperature with cold water, filtered, washed, and dried to obtain sodium-type molecular sieve powder. The XRD pattern of the obtained product is shown below. Figure 1 As shown, this is a pure-phase EUO molecular sieve.

[0076] Example 4:

[0077] Under stirring conditions, 0.62 g Al2(SO4)3·18H2O, 0.52 g HMOH, 0.77 g KOH, and 0.30 g *MRE seed crystals were added to 29.82 g H2O and placed in a stainless steel reactor. 14.63 g silica sol was added dropwise under stirring conditions. The reactor was then placed in a rotary oven and aged at 120℃ and 40 r / min for 48 h, followed by hydrothermal crystallization at 200℃ and 30 r / min for 144 h. After crystallization, the product was rapidly cooled to room temperature with cold water, filtered, washed, and dried to obtain sodium-type molecular sieve powder. The XRD pattern of the obtained product is shown below. Figure 1 As shown, this is a pure-phase EUO molecular sieve.

[0078] Example 5:

[0079] Under stirring conditions, 0.62 g Al2(SO4)3·18H2O, 2.15 g HMBr, 0.68 g KOH, and 0.25 g EUO seed crystals were added to 29.82 g H2O and placed in a stainless steel reactor. 14.63 g silica sol was added dropwise under stirring conditions. The reactor was then placed in a rotary oven and aged at 30 °C and 40 r / min for 24 h, followed by hydrothermal crystallization at 180 °C and 60 r / min for 96 h. After crystallization, the mixture was rapidly cooled to room temperature with cold water, filtered, washed, and dried to obtain sodium-type molecular sieve powder. The XRD pattern of the obtained product is shown below. Figure 1 As shown, this is a pure-phase EUO molecular sieve.

[0080] Application Example 1

[0081] The samples obtained in Comparative Example 1 and Example 1 were exchanged several times with 1 mol / L NH4NO3 solution, filtered, dried, calcined, and tableted. Samples with a size of 20–40 mesh were then subjected to m-xylene (MX) isomerization reactions in a fixed-bed reactor with an inner diameter of 9 mm. The reaction temperature was 370 °C and the space velocity was 10 h⁻¹. -1 V N2 :V MX When the ratio is 300:1, the reaction result is as follows: Figure 4 As shown, the sample obtained in Example 1 exhibits significantly higher catalytic stability for xylene isomerization than that in Comparative Example 1.

[0082] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A hierarchical porous EUO molecular sieve, characterized in that, The morphology of the hierarchical porous EUO molecular sieve is spindle-shaped; The multi-level porous EUO molecular sieve has micropores and mesopores; The micropores have a pore volume of 0.12 to 0.15 cm 3 / g; the mesopores have a pore volume of 0.14 to 0.25 cm 3 / g; The size of the hierarchical porous EUO molecular sieve is 0.5~2.5μm; The hierarchical porous EUO molecular sieve is prepared by a method comprising the following steps: Raw materials containing silicon source, aluminum source, inorganic alkali, template agent, seed crystal and water are mixed, aged and crystallized in a sealed container to obtain the multi-level porous EUO molecular sieve. wherein the seed is selected from the group consisting of EUO and / or MRE topological structure molecular sieve; The template agent is at least one of hexamethylammonium bromide, hexamethylammonium chloride, and hexamethylammonium hydroxide; The mass ratio of the seed crystal to the silicon source is 0.03 to 0.15; The molar amount of the silicon source is calculated based on the molar amount of SiO2 in the silicon source; The mass of the seed crystal is calculated based on the mass of SiO2 in the seed crystal. The molar ratio of the inorganic base to the silicon source is 0.1 to 0.6; The molar ratio of SiO2 / Al2O3 between the silicon source and the aluminum source is greater than 50; The molar ratio of the template agent to the silicon source is 0.02~0.08; The molar ratio of water to silicon source is 25-60; The molar amount of the silicon source is calculated based on the molar amount of SiO2 in the silicon source; The molar amount of the aluminum source is calculated based on the molar amount of Al2O3 in the aluminum source; The molar amount of the template agent is calculated based on the molar amount of hexamethylammonium ions in the template agent; The molar amount of the inorganic base is calculated based on the hydroxide ions in the inorganic base.

2. The multi-level porous EUO molecular sieve according to claim 1, characterized in that, The silica-to-alumina ratio of the multi-level porous EUO molecular sieve is greater than 50.

3. A method for preparing a hierarchical porous EUO molecular sieve according to any one of claims 1 to 2, characterized in that, Includes the following steps: Raw materials containing silicon source, aluminum source, inorganic alkali, template agent, seed crystal and water are mixed, aged and crystallized in a sealed container to obtain the multi-level porous EUO molecular sieve. the seed is selected from the group consisting of molecular sieves having EUO and / or MRE topology; The template agent is at least one of hexamethylammonium bromide, hexamethylammonium chloride, and hexamethylammonium hydroxide.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the seed crystal to the silicon source is 0.03 to 0.15; The molar amount of the silicon source is calculated based on the molar amount of SiO2 in the silicon source; The mass of the seed crystal is calculated based on the mass of SiO2 in the seed crystal.

5. The preparation method according to claim 3, characterized in that, The silicon source is selected from at least one of silica, silica sol, tetraethyl orthosilicate, and water glass; The aluminum source is selected from at least one of aluminum nitrate, aluminum sulfate, sodium aluminate, boehmite, and aluminum chloride; The inorganic base is selected from at least one of sodium hydroxide, sodium carbonate, potassium hydroxide, lithium hydroxide, and ammonia water.

6. The preparation method according to claim 3, characterized in that, The molar ratio of the inorganic base to the silicon source is 0.1 to 0.6; The molar ratio of SiO2 / Al2O3 between the silicon source and the aluminum source is greater than 50; The molar ratio of the template agent to the silicon source is 0.02~0.08; The molar ratio of water to silicon source is 25-60; The molar amount of the silicon source is calculated based on the molar amount of SiO2 in the silicon source; The molar amount of the aluminum source is calculated based on the molar amount of Al2O3 in the aluminum source; The molar amount of the template agent is calculated based on the molar amount of hexamethylammonium ions in the template agent; The molar amount of the inorganic base is calculated based on the hydroxide ions in the inorganic base.

7. The preparation method according to claim 3, characterized in that, The temperature of the aging is 30~120 C; The aging time is 12-48 hours.

8. The preparation method according to claim 3, characterized in that, The crystallization is hydrothermal dynamic crystallization; The temperature of the crystallization is 140 to 200 C; The crystallization time is 48~168 h.

9. An application of the hierarchical porous EUO molecular sieve according to any one of claims 1 to 2, characterized in that, It is used as a catalyst in the isomerization reaction of m-xylene.

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