Layered molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a layered molecular sieve and a preparation method and application thereof, and belongs to the technical field of molecular sieves. An aluminum source, water, a template agent, an alkali source and a silicon source are mixed, the template agent is 1, 5-pentane ethane dibromide, stirring is carried out, obtained silica-alumina gel and seed crystals are mixed, aging and crystallization are carried out in sequence, and the novel layered molecular sieve is obtained. The novel layered molecular sieve is synthesized by adopting a seed crystal auxiliary method, is high in crystallinity and can be applied to hydroisomerization reaction, and the variety and the application range of the layered molecular sieve are widened.

Description

Technical Field

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

[0002] Due to their unique pore structure and excellent stability, molecular sieves have been widely used in catalysis, separation, adsorption, and ion exchange. Currently, there are 260 molecular sieve structure codes awarded by the International Molecular Sieve Association, of which more than 20 have been industrially applied. For example, the Y (FA U structure) molecular sieve developed for use in catalytic cracking processes has sparked a revolution in the oil refining industry; the SAPO-34 (CHA) molecular sieve developed for use in the methanol-to-olefins process has revolutionized the coal chemical industry. Currently, the pursuit of the creation of molecular sieves with new structures has always been a research hotspot in the molecular sieve field.

[0003] Layered molecular sieves, as a very important type of molecular sieve, can improve the accessibility of catalytic active centers and improve the diffusion performance of macromolecular reactants or products in their pores, thereby expanding the application range or performance of related molecular sieves. They have received widespread attention in recent years. The currently developed MCM-22 (MWW structure) molecular sieve has been industrially applied in the alkylation process. Recently, researchers have also done a lot of work on the development of new layered molecular sieves. The prior art (Layered Zeolite for Assembly of Two-Dimensional Separation Membranes for Hydrogen Purification, Wang J, et al., Angewandte Chemie, 2023, 135 (25). DOI: 10.1002 / ange.202304734) reported an expanded layered zeolite ECNU-28 with an SZR topology and eight-membered ring pores. It can be easily peeled off to construct a two-dimensional membrane with extremely high hydrogen selectivity for natural gas, and has great prospects in hydrogen purification and greenhouse gas capture. Prior art (Dual-template Synthesis of Thinner-layered MCM-49 Zeolite to Boost its Alkylation Performance, Cao S, et al., Molecular Catalysis, 2022, 524, 112333. DOI: 10.1016 / j.mcat.2022.112333) synthesized a layered MCM-49 molecular sieve with more acidic sites on the outside. Due to its thinner layered structure, the selectivity of ethylbenzene in the alkylation reaction is greatly improved. The present invention is committed to developing a new layered molecular sieve to broaden the types and applications of molecular sieves. Summary of the Invention

[0004] The purpose of the present invention is to provide a layered molecular sieve and a preparation method and application thereof to solve the above problems.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a layered molecular sieve, comprising the following steps:

[0007] An aluminum source, water, a template, an alkali source, and a silicon source are mixed and stirred to obtain a silica-alumina gel;

[0008] Mixing the molecular sieve seed crystals with the silica-alumina gel, and sequentially performing an aging reaction and a crystallization reaction to obtain a layered molecular sieve;

[0009] The template agent includes 1,5-pentaneethane dibromide;

[0010] Calculated based on Al2O3 in the aluminum source, Na2O in the alkali source, and SiO2 in the silicon source, the molar ratio of the aluminum source, water, template, alkali source, and silicon source is 0.004-0.016:33:0.065-0.098:0.08-0.165:1;

[0011] The molecular sieve seed crystals include ZSM-57 molecular sieve or a first layered molecular sieve;

[0012] When the molecular sieve seed crystal is ZSM-57 molecular sieve, a first layered molecular sieve is obtained;

[0013] When the molecular sieve seed crystal is a first layered molecular sieve, a second layered molecular sieve is obtained;

[0014] The layered molecular sieve includes a first layered molecular sieve or a second layered molecular sieve.

[0015] Preferably, the aluminum source includes sodium aluminate, and the mass fraction of Al2O3 in the sodium aluminate is ≥41.0%.

[0016] Preferably, the alkali source comprises sodium hydroxide.

[0017] Preferably, the silicon source comprises 30.5 wt% silica sol aqueous solution.

[0018] Preferably, the mass ratio of the molecular sieve seed crystal to the silicon source is 0.02 to 0.1:1, calculated based on SiO2 in the silicon source.

[0019] Preferably, the aging reaction temperature is 25 to 80° C., and the time is 6 to 96 hours.

[0020] Preferably, the crystallization reaction temperature is 160-220° C., the time is 18-72 h, and the rotation speed is 40-50 rpm.

[0021] The present invention provides a layered molecular sieve prepared by the above preparation method.

[0022] The present invention provides the application of the layered molecular sieve in a hydrogenation isomerization reaction.

[0023] Beneficial effects of the present invention:

[0024] The present invention relates to the synthesis of a novel layered molecular sieve using a seed-assisted route. An aluminum source, water, a template, an alkali source, and a silicon source are mixed, wherein the template is 1,5-pentaneethane dibromide. The mixture is stirred, and the resulting silica-alumina gel is mixed with molecular sieve seed crystals. The mixture is then aged and crystallized to obtain the novel layered molecular sieve. The present invention utilizes a seed-assisted method, employing the synergistic effect of a gel system prepared in a specific ratio and an organic template to synthesize a novel layered molecular sieve with high crystallinity, which can be used in hydroisomerization reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The XRD spectrum of the layered molecular sieve obtained in Example 2;

[0026] Figure 2 This is a SEM image of the layered molecular sieve obtained in Example 2;

[0027] Figure 3 This is the nitrogen adsorption spectrum of the layered molecular sieve obtained in Example 2. DETAILED DESCRIPTION

[0028] The present invention provides a method for preparing a layered molecular sieve, comprising the following steps:

[0029] An aluminum source, water, a template, an alkali source, and a silicon source are mixed and stirred to obtain a silica-alumina gel;

[0030] Mixing the molecular sieve seed crystals with the silica-alumina gel, and sequentially performing an aging reaction and a crystallization reaction to obtain a layered molecular sieve;

[0031] The template agent includes 1,5-pentaneethane dibromide;

[0032] Calculated based on Al2O3 in the aluminum source, Na2O in the alkali source, and SiO2 in the silicon source, the molar ratio of the aluminum source, water, template, alkali source, and silicon source is 0.004-0.016:33:0.065-0.098:0.08-0.165:1;

[0033] The molecular sieve seed crystal is ZSM-57 molecular sieve or a first layered molecular sieve;

[0034] When the molecular sieve seed crystal is ZSM-57 molecular sieve, a first layered molecular sieve is obtained;

[0035] When the molecular sieve seed crystal is a first layered molecular sieve, a second layered molecular sieve is obtained;

[0036] The layered molecular sieve is a first layered molecular sieve or a second layered molecular sieve.

[0037] In the present invention, unless otherwise specified, the raw materials required for preparation are all commercially available products well known to those skilled in the art.

[0038] In the present invention, the aluminum source and water are preferably mixed evenly, and a template, an alkali source and a silicon source are added in sequence and stirred to obtain a silica-alumina gel.

[0039] In the present invention, the aluminum source preferably includes sodium aluminate, and the mass fraction of Al2O3 in the sodium aluminate is preferably ≥41.0%.

[0040] In the present invention, the template preferably includes 1,5-pentaneethane dibromide, denoted as OSDA.

[0041] In the present invention, the alkali source preferably includes sodium hydroxide.

[0042] In the present invention, the silicon source preferably comprises 30.5 wt % of a silica sol aqueous solution.

[0043] In the present invention, based on Al2O3 in the aluminum source, Na2O in the alkali source and SiO2 in the silicon source, the molar ratio of the aluminum source, water, template, alkali source and silicon source is preferably 0.004-0.016:33:0.065-0.098:0.08-0.165:1, and more preferably 0.0043-0.0059:33:0.065:0.08-0.1:1.

[0044] In the present invention, the stirring time is preferably 2 hours.

[0045] The present invention preferably mixes the molecular sieve seed crystals with the silica-alumina gel, and after the aging reaction is completed, the silica-alumina gel is placed in a high-pressure reactor to perform a crystallization reaction. The product is filtered and dried to obtain a layered molecular sieve.

[0046] In the present invention, the molecular sieve seed crystal is preferably ZSM-57 molecular sieve or the first layered molecular sieve; when the molecular sieve seed crystal is ZSM-57 molecular sieve, the first layered molecular sieve is preferably obtained; when the molecular sieve seed crystal is the first layered molecular sieve, the second layered molecular sieve is preferably obtained.

[0047] In the present invention, based on SiO2 in the silicon source, the mass ratio of the molecular sieve seed crystal to the silicon source is preferably 0.02 to 0.10:1, more preferably 0.06 to 0.08:1.

[0048] In the present invention, the temperature of the aging reaction is preferably 25 to 80° C., more preferably 50 to 80° C., and the time is preferably 6 to 96 hours, more preferably 48 hours.

[0049] In the present invention, the crystallization reaction temperature is preferably 160-220° C., more preferably 210-220° C., the time is preferably 18-72 h, more preferably 20-30 h, and the rotation speed is preferably 40-50 rpm, more preferably 45-50 rpm.

[0050] In the present invention, the layered molecular sieve is preferably the first layered molecular sieve or the second layered molecular sieve.

[0051] The present invention also provides a layered molecular sieve prepared by the above preparation method, which exhibits relevant characteristic peaks at 4.28°, 9.09°, 12.42°, 14.47°, 18.11° and 26.3°.

[0052] The present invention also provides the use of the layered molecular sieve in a hydrogenation isomerization reaction.

[0053] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1

[0055] 0.062g of sodium aluminate (n(Al2O3)=2.6×10 -4 mol) and 7.64g water (n = 0.42mol) were mixed evenly, and 0.47g 1,5-pentaneethane dibromide (n = 1.1×10 -3 mol), 0.22 g of sodium hydroxide (n(Na2O) = 0.00275 mol), and 3.33 g of silica sol (n(SiO2) = 0.017 mol), and stirred for 2 h to obtain silica-alumina gel. The molar ratio of the effective raw materials in the silica-alumina gel is: 1.0SiO2: 0.016Al2O3: 0.065OSDA: 0.165Na2O: 33H2O;

[0056] The silica-alumina gel was mixed with 0.02 g of ZSM-57 molecular sieve seed crystals and subjected to an aging reaction. After aging at 25° C. for 6 h, the silica-alumina gel was transferred to a high-pressure reactor for a crystallization reaction. The crystallization reaction was carried out at 160° C. and 50 rpm for 72 h. The product was filtered and dried to obtain a first layered molecular sieve.

[0057] Example 2:

[0058] 0.0159 g of sodium aluminate (n(Al2O3)=6.7×10 -5 mol) and 7.64g water (n = 0.42mol) were mixed evenly, and 0.47g 1,5-pentaneethane dibromide (n = 1.1×10 -3 mol), 0.1 g sodium hydroxide (n(Na2O) = 0.00125 mol), 3.33 g silica sol (n(SiO2) = 0.017 mol), and stirred for 2 h to obtain silica-alumina gel. The molar ratio of the effective raw materials in the silica-alumina gel is: 1.0SiO2: 0.004Al2O3: 0.065OSDA: 0.08Na2O: 33H2O;

[0059] The silica-alumina gel was mixed with 0.06 g of the first layered molecular sieve prepared in Example 1 and subjected to an aging reaction. After aging at 80°C for 48 h, the silica-alumina gel was transferred to a high-pressure reactor for a crystallization reaction. The crystallization reaction was carried out at 210°C and 50 rpm for 20 h. The product was filtered and dried to obtain the layered molecular sieve of Example 2.

[0060] Example 3:

[0061] The only difference from Example 2 is:

[0062] The mass of sodium aluminate is 0.0169 g (n(Al2O3) = 7.2 × 10 -5 mol), the mass of sodium hydroxide is 0.13g (n(Na2O)=0.001625mol);

[0063] The molar ratio of the effective raw materials in the silica-alumina gel is as follows:

[0064] 1.0SiO2:0.0043Al2O3:0.065OSDA:0.1Na2O:33H2O;

[0065] The layered molecular sieve of Example 3 was obtained.

[0066] Example 4:

[0067] The only difference from Example 2 is:

[0068] The mass of 1,5-pentaneethane dibromide is 0.704 g (n = 0.0016 mol), and the mass of sodium hydroxide is 0.13 g (n (Na2O) = 0.001625 mol);

[0069] The molar ratio of the effective raw materials in the silica-alumina gel is as follows: 1.0SiO2:0.004Al2O3:0.098OSD A:0.1Na2O:33H2O;

[0070] The layered molecular sieve of Example 4 was obtained.

[0071] Example 5:

[0072] The only difference from Example 2 is:

[0073] The mass of sodium aluminate is 0.0231 g (n(Al2O3)=9.8×10 -5 mol);

[0074] The molar ratio of the effective raw materials in the silica-alumina gel is as follows:

[0075] 1.0SiO2:0.0059Al2O3:0.065OSDA:0.08Na2O:33H2O;

[0076] The layered molecular sieve of Example 5 was obtained.

[0077] Example 6:

[0078] The only difference from Example 2 is:

[0079] The aging reaction time is 96h;

[0080] The crystallization reaction temperature was 190 °C and the time was 30 h;

[0081] The molar ratio of the effective raw materials in the silica-alumina gel is as follows:

[0082] 1.0SiO2:0.004Al2O3:0.065OSDA:0.08Na2O:33H2O;

[0083] The layered molecular sieve of Example 6 was obtained.

[0084] Example 7:

[0085] The only difference from Example 2 is:

[0086] The crystallization reaction temperature was 220 °C and the time was 18 h;

[0087] The molar ratio of the effective raw materials in the silica-alumina gel is as follows:

[0088] 1.0SiO2:0.004Al2O3:0.065OSDA:0.08Na2O:33H2O;

[0089] The layered molecular sieve of Example 7 was obtained.

[0090] Characterization and performance testing

[0091] 1. The layered molecular sieve obtained in Example 2 was scanned by an X-ray diffraction analyzer and a scanning electron microscope, and the layered molecular sieve obtained in Example 2 was subjected to a BET test by a gas analyzer. The results are shown in FIG. Figures 1 to 3 ;in Figure 1 is the XRD spectrum of the layered molecular sieve obtained in Example 2, Figure 2 This is the SEM image of the layered molecular sieve obtained in Example 2. Figure 3 This is the nitrogen adsorption spectrum of the layered molecular sieve obtained in Example 2.

[0092] like Figure 1 As shown, the structure of the layered molecular sieve is analyzed by X-ray diffraction. Figure 2 A clear lamellar phase can be seen; Figure 3 The nitrogen adsorption spectrum shows a typical Langmuir curve, indicating that the layered molecular sieve obtained in Example 2 has a certain pore volume, and its specific surface area and pore volume are 126.47m 2 / g and 0.33cm 3 / g.

[0093] 2. Application Example 1

[0094] The layered molecular sieve obtained in Example 2 was used to prepare a catalytic sample by an equal amount impregnation method with H2PtC l6 The aqueous solution is used as a metal precursor, loaded with 1.26wt% Pt, impregnated and ultrasonicated for 2 hours and allowed to stand for 12 hours, fried at 60℃ and finally calcined at 550℃ for 6 hours to obtain a layered molecular sieve with a loading of 1.26wt% Pt;

[0095] The obtained 1.26 wt% Pt-layered molecular sieve is used as a catalyst to catalyze the n-dodecane hydrogenation isomerization reaction, and the catalytic reaction is carried out in the range of 240-400 DEG C and 20-45 bar.

[0096] The results show that the layered molecular sieve with a Pt loading of 1.26wt% has good catalytic activity in the hydroisomerization reaction of n-dodecane, with the highest selectivity reaching 68.7% at 370℃, and the corresponding conversion rate and yield are 50.4% and 34.6%, respectively.

[0097] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a layered molecular sieve, characterized in that: The following steps are involved: An aluminum source, water, a template, an alkali source, and a silicon source are mixed and stirred to obtain a silica-alumina gel; Mixing the molecular sieve seed crystals with the silica-alumina gel, and sequentially performing an aging reaction and a crystallization reaction to obtain a layered molecular sieve; The template agent includes 1,5-pentaneethane dibromide; Calculated based on Al2O3 in the aluminum source, Na2O in the alkali source, and SiO2 in the silicon source, the molar ratio of the aluminum source, water, template, alkali source, and silicon source is 0.004-0.016:33:0.065-0.098:0.08-0.165:1; The molecular sieve seed crystal is a ZSM-57 molecule or a first layered molecular sieve; When the molecular sieve seed crystal is ZSM-57 molecular sieve, a first layered molecular sieve is obtained; When the molecular sieve seed crystal is a first layered molecular sieve, a second layered molecular sieve is obtained; The layered molecular sieve is a first layered molecular sieve or a second layered molecular sieve.

2. The preparation method according to claim 1, characterized in that The aluminum source includes sodium aluminate, and the mass fraction of Al2O3 in the sodium aluminate is ≥41.0%.

3. The preparation method according to claim 1, characterized in that The alkaline source includes sodium hydroxide.

4. The preparation method according to claim 1, characterized in that The silicon source includes 30.5 wt % of a silica sol aqueous solution.

5. The preparation method according to claim 1, characterized in that Calculated based on SiO2 in the silicon source, the mass ratio of the molecular sieve seed crystal to the silicon source is 0.02 to 0.1:

1.

6. The preparation method according to claim 1, characterized in that The aging reaction temperature is 25 to 80° C., and the time is 6 to 96 hours.

7. The preparation method according to claim 1, characterized in that The crystallization reaction temperature is 160-220° C., the time is 18-72 hours, and the rotation speed is 40-50 rpm.

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

9. Use of the layered molecular sieve according to claim 8 in a hydroisomerization reaction.

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