Hierarchical pore EUO molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses a hierarchical pore EUO molecular sieve as well as a preparation method and application thereof. The morphology of the hierarchical pore EUO molecular sieve is fusiform; the catalyst has micropores and mesopores; the pore volume of the micropores is 0.12 to 0.15 cm < 3 > / g; and the pore volume of the mesopores is 0.14-0.25 cm < 3 > / g. According to the synthetic route, the hierarchical pore EUO molecular sieve with high crystallinity is prepared by a one-step hydrothermal crystallization method through optimization of the ratio of a silicon-aluminum source to a synthetic system and addition of seed crystals. The EUO molecular sieve provided by the invention has a relatively large mesoporous volume, so that the EUO molecular sieve has excellent diffusion performance, and has excellent reaction stability in an isomerization reaction of m-xylene.

Description

Technical Field

[0001] The invention belongs to the technical field of material chemistry and specifically relates to a multi-level pore EUO molecular sieve and a preparation method and application thereof. Background Art

[0002] EUO molecular sieve is a one-dimensional pore zeolite with a one-dimensional ten-membered ring pore (0.41×0.54nm). Due to its unique pore structure and acid properties, it has great application potential in multiple catalytic fields. In particular, it exhibits 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 very easy to be deactivated by carbon deposition. In recent years, how to improve the diffusion performance of EUO zeolite has attracted extensive attention. EUO molecular sieves with a SiO2 / Al2O3 molar ratio greater than 50 have a spindle-shaped morphology, and the mesopore volume is generally less than 0.08 cm 3 / g(Mohamed HM Ahmed;Oki Muraza;Koji Miyake,Applied Catalysis A;General,2015,497,127-134), which brings certain mass transfer resistance, so it is necessary to introduce mesopores to improve its diffusion performance.

[0004] Wang Zhiguang et al. (CN108946756A) used long-chain silane compounds as crystallization aids and double quaternary ammonium salts of alkane structures substituted with double six-membered heterocyclic groups as organic templates to synthesize hierarchical pore EUO molecular sieves, which greatly improved its catalytic performance in the isomerization reaction of meta-xylene.

[0005] US6377063 patent discloses a method for synthesizing EUO structured molecular sieves, which uses relatively safer and cheaper alkylated derivatives of methylenediamine ions as structure directing agents, thereby reducing costs and being relatively safer and more environmentally friendly.

[0006] Wang Jing et al. (CN114433220A) disclosed a method for preparing a multi-level pore EUO molecular sieve, in which the EUO molecular sieve is acid-treated with a phosphoric acid solution to obtain an acid-treated sample; then the acid-treated sample is alkaline-treated with a sodium hydroxide solution to obtain an acid-base 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 a hierarchical pore EUO zeolite, using sodium hydroxide solutions of different concentrations to treat the EUO molecular sieve with alkali to obtain alkali-treated samples, and then using hydrochloric acid solution to pickle the alkali-treated samples with 4M nitric acid to investigate the effect of alkali solution concentration on the mesoporous volume of the EUO molecular sieve. It was found that when the concentration of the sodium hydroxide solution was 0.5M, the treated sample had a larger mesoporous volume.

[0008] In summary, the current method of preparing and synthesizing hierarchical EUO zeolites through a direct route is complex and requires the participation of expensive structure-directing agents, which to some extent limits its scale-up application. It is necessary to develop a green, economical, and efficient preparation route for hierarchical EUO molecular sieves. Summary of the invention

[0009] According to one aspect of the present application, a multi-level pore EUO molecular sieve is provided, wherein the morphology of the multi-level pore EUO molecular sieve is a spindle-shaped agglomerate;

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

[0011] The pore volume of the micropores is 0.12 to 0.15 cm 3 / g;

[0012] The pore volume of the mesopores is 0.14 to 0.25 cm 3 / g.

[0013] The silicon-to-aluminum ratio of the multi-level pore EUO molecular sieve is greater than 50.

[0014] The multi-level pore EUO molecular sieve has a size of 0.5 to 2.5 μm.

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

[0016] According to another aspect of the present application, a method for preparing the above-mentioned multi-level pore EUO molecular sieve is provided, comprising the following steps:

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

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

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

[0020] The aluminum source is selected from at least one of aluminum nitrate, aluminum sulfate, sodium aluminate, pseudo-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 seeds are selected from molecular sieves having EUO and / or *MRE topology.

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

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

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

[0027] The molar ratio of the water to the 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 is calculated based on the molar amount of hexamethylammonium in the template;

[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 in the alkali source.

[0034] The aging temperature is 30 to 120° C.

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

[0036] The crystallization is hydrothermal dynamic crystallization, which is carried out in a tank reactor in a rotary oven.

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

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

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

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

[0041] According to another aspect of the present application, there is provided an application of the multi-level pore EUO molecular sieve as a catalyst for isomerization of meta-xylene, which has excellent diffusion performance and excellent reaction stability in the isomerization of meta-xylene.

[0042] The beneficial effects of this application include:

[0043] (1) The EUO molecular sieve described in this application has a regular spindle-shaped morphology and excellent diffusion performance; the length is 0.5 to 2.5 μm; the micropore volume is 0.12 to 0.15 cm 3 / g, and the mesopore volume is 0.14~0.25cm 3 / g;

[0044] (2) This synthetic route uses a one-step hydrothermal crystallization method to prepare a high-crystallinity multi-level pore EUO molecular sieve by optimizing the ratio of silicon aluminum source to the synthetic system and adding seed crystals.

[0045] (3) The EUO molecular sieve described in the present application has excellent diffusion performance due to its large mesopore volume, and has excellent reaction stability in the isomerization reaction of m-xylene. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0047] Figure 2 N2 adsorption-desorption curve and pore size distribution curve of the sample prepared in Comparative Example 1;

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

[0049] Figure 4 This is a diagram showing the effect of the isomerization reaction of m-xylene using the EUO molecular sieve catalyst provided in Example 1 of the present invention and Comparative Example 1.

[0050] Figure 5 This is a SEM electron microscope photograph of the sample prepared in Example 1. The scale is 2 μm, and the size of the spindle-shaped agglomerates is about 1.5 μm. DETAILED DESCRIPTION

[0051] The present invention is further described below with examples, but the examples are not intended to limit the present invention.

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

[0053] Unless otherwise specified, the raw materials and catalysts in the examples of this application were purchased through commercial channels.

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

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

[0056] White carbon (McLean, 95wt% SiO2);

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

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

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

[0060] Pseudoboehmite (McLean, 66%wtAl2O3, 33wt%H2O);

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

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

[0063] HMBr (Aladdin, 98 wt%);

[0064] HMOH (Aladdin, 98 wt%);

[0065] EUO Seed (Nankai Catalyst Factory)

[0066] Deionized water (homemade)

[0067] Meta-xylene (Aladdin, >99wt%)

[0068] Comparative Example 1:

[0069] Under stirring conditions, 0.62g Al2(SO4)3·18H2O, 2.15g HMBr, and 0.77g NaOH were dissolved in 29.82g H2O. After complete dissolution, 14.63g silica sol was added dropwise under stirring conditions. The mixture was transferred to a stainless steel reactor and placed in a rotary oven. The mixture was hydrothermally crystallized at 170°C and 40r / min for 168h. After crystallization, the mixture was cooled to room temperature with cold water, filtered, washed, and dried to obtain the sodium-type molecular sieve raw powder. The XRD spectrum of the obtained product is shown in the figure below. Figure 1 As shown, it is a pure phase EUO molecular sieve. Figure 2 It can be seen from the nitrogen adsorption and desorption results ( Figure 2 ) It can be seen that the micropore volume is 0.14cm 3 / g, and the mesopore volume is 0.20cm 3 / g.

[0070] Embodiment 1:

[0071] Under stirring conditions, 0.62g Al2(SO4)3·18H2O, 0.81g HMBr, 0.77g NaOH, and 0.25g EUO seed were added to 29.82g H2O, placed in a stainless steel reactor, and 14.63g silica sol was added dropwise under stirring conditions. The stainless steel reactor was placed in a rotary oven and aged at 90°C and 40r / min for 24h, and then hydrothermally crystallized at 150°C and 40r / min for 72h. After crystallization, it was cooled to room temperature with cold water, filtered, washed, and dried to obtain the sodium-type molecular sieve raw powder. The XRD spectrum of the obtained product is as follows: Figure 1 As shown, it is a pure phase EUO molecular sieve. The nitrogen adsorption and desorption results ( Figure 3 ) It can be seen that the micropore volume is 0.14cm 3 / g, and the mesopore volume is 0.20cm 3 / g. By Figure 5 It can be seen that the morphology of the product is a regular spindle shape with a size of about 1.5 μm.

[0072] Embodiment 2:

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

[0074] Embodiment 3:

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

[0076] Embodiment 4:

[0077] Under stirring conditions, 0.62g Al2(SO4)3·18H2O, 0.52g HMOH, 0.77g KOH, and 0.30g*MRE seed crystals were added to 29.82g H2O and placed in a stainless steel reactor. 14.63g silica sol was added dropwise under stirring conditions. The stainless steel reactor was placed in a rotary oven and aged at 120°C, 40r / min for 48h, and then hydrothermally crystallized at 200°C, 30r / min for 144h. After crystallization, it was quenched to room temperature with cold water, filtered, washed, and dried to obtain sodium-type molecular sieve raw powder. The XRD spectrum of the obtained product is as follows: Figure 1 Shown is a pure phase EUO molecular sieve.

[0078] Embodiment 5:

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

[0080] Application Example 1

[0081] The samples obtained in Comparative Example 1 and Example 1 were exchanged with 1 mol / L NH4NO3 solution for several times, filtered, dried, roasted, and pressed into tablets. Samples with a size of 20 to 40 mesh were selected and subjected to isomerization experiments of m-xylene (MX) in a fixed bed reactor with an inner diameter of 9 mm. When the reaction temperature was 370°C and the air velocity was 10 h -1 , V N2 :V MX =300:1, the reaction results are as follows Figure 4 As shown: It can be seen that the catalytic stability of the sample obtained in Example 1 for xylene isomerization reaction is much higher than that of Comparative Example 1.

[0082] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A multi-level pore EUO molecular sieve, characterized in that: The morphology of the multi-level pore EUO molecular sieve is spindle-shaped; The multi-level pore EUO molecular sieve has micropores and mesopores; The pore volume of the micropores is 0.12 to 0.15 cm 3 / g; The pore volume of the mesopores is 0.14 to 0.25 cm 3 / g.

2. The multi-level pore EUO molecular sieve according to claim 1, characterized in that: The silicon-to-aluminum ratio of the multi-level pore EUO molecular sieve is greater than 50.

3. The multi-level pore EUO molecular sieve according to claim 1, characterized in that: The multi-level pore EUO molecular sieve has a size of 0.5 to 2.5 μm.

4. A method for preparing the multi-level pore EUO molecular sieve according to any one of claims 1 to 3, characterized in that: The following steps are involved: The raw materials containing silicon source, aluminum source, inorganic base, template agent, seed crystal and water are mixed, aged and crystallized in a sealed container to obtain the multi-level pore EUO molecular sieve.

5. The preparation method according to claim 4, characterized in that: The seed crystals are selected from molecular sieves having EUO and / or *MRE topological structures; 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.

6. The preparation method according to claim 4, characterized in that: The silicon source is selected from at least one of white carbon black, silica sol, ethyl orthosilicate and water glass; The aluminum source is selected from at least one of aluminum nitrate, aluminum sulfate, sodium aluminate, pseudo-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; The template agent is at least one of hexamethylammonium bromide, hexamethylammonium chloride and hexamethylammonium hydroxide.

7. The preparation method according to claim 4, characterized in that: The molar ratio of the inorganic base to the silicon source is 0.1 to 0.6; The SiO2 / Al2O3 molar ratio of the silicon source to the aluminum source is greater than 50; The molar ratio of the template to the silicon source is 0.02 to 0.08; The molar ratio of the water to the silicon source is 25 to 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 is calculated based on the molar amount of hexamethylammonium in the template; The molar amount of the inorganic base is calculated based on the hydroxide in the alkali source.

8. The preparation method according to claim 4, characterized in that: The aging temperature is 30 to 120° C. The aging time is 12 to 48 hours.

9. The preparation method according to claim 4, characterized in that: The crystallization is hydrothermal dynamic crystallization; The crystallization temperature is 140-200°C; The crystallization time is 48 to 168 hours.

10. An application of the multi-level pore EUO molecular sieve according to any one of claims 1 to 3, characterized in that: As a catalyst, it is used in the isomerization reaction of meta-xylene.

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