A zsm-35 molecular sieve and a method for preparing the same

Abstract

This application discloses a ZSM-35 molecular sieve and its preparation method, belonging to the field of ZSM-35 molecular sieve synthesis technology. The ZSM-35 molecular sieve is a pure phase. In the X-ray powder diffraction pattern of the ZSM-35 molecular sieve: at 2θ angles of (9.3±2)°, (12.5±2)°, (12.7±2)°, (13.4±2)°, (22.3±2)°, (22.5±2)°, (23.1±2)°, (23.6±2)°, (24.4±2)°, (25.2±2)°, (… Characteristic diffraction peaks of ZSM-35 molecular sieve (9.3), (12.5), (12.7), (13.4), (22.3), (22.6), (23.2), (23.6), (24.4), (25.2), (25.6), and (29.4) were observed at (25.6±2)° and (29.4±2)°. The relative crystallinity of ZSM-35 molecular sieve is 95~180. The preparation method of ZSM-35 molecular sieve uses a template agent and a single alkali source, which shortens the synthesis time, produces ZSM-35 molecular sieve with high crystallinity, has good reproducibility, and is easy to industrialize; moreover, the raw materials used are inexpensive, reducing the synthesis cost.

Description

Technical Field

[0001] This application relates to a ZSM-35 molecular sieve and its preparation method, belonging to the field of ZSM-35 molecular sieve synthesis technology. Background Technology

[0002] ZSM-35 molecular sieves possess a FER topology, featuring one-dimensional ten-membered ring channels (0.42nm*0.54nm) and one-dimensional eight-membered ring channels (0.35nm*0.48nm), which intersect perpendicularly to form crucial sites for catalytic reactions. Highly crystalline ZSM-35 molecular sieves exhibit uniform particle size, regular channel dimensions, high specific surface area, well-developed micropore volume, and strong hydrothermal stability, making them widely applicable in the isomerization of straight-chain olefin skeletons, the carbonylation of dimethyl ethers, and NO... x Reactions such as selective catalytic reduction, aromatic benzylation, and naphtha modification.

[0003] Patent CN113998708A reports a method for synthesizing highly crystalline ZSM-35 molecular sieves without amines. The method involves first mixing an aluminum source with a seed crystal solution to obtain mixture A, then mixing a silicon source with a fluoride to obtain mixture B, and finally mixing mixture A and mixture B together and crystallizing to obtain ZSM-35 molecular sieves. This synthesis method introduces fluorides, which increases the environmental burden.

[0004] Patent CN1166563C reports a method for synthesizing ZSM-35 zeolite. This method involves adding seed crystals during the synthesis process, and the crystallization time is between 70 hours and 7 days. This method has a long synthesis cycle, requires the preparation of seed crystals, and has complicated production processes and high costs.

[0005] In summary, the synthesis of highly crystalline ZSM-35 molecular sieves currently requires the introduction of seed crystals or the addition of fluorine-containing reagents, resulting in a long synthesis cycle, complex production steps, high synthesis costs, and significant environmental pressure. Summary of the Invention

[0006] To address the aforementioned technical problems, this application provides a ZSM-35 molecular sieve and its preparation method. The ZSM-35 molecular sieve is a pure phase. In the X-ray powder diffraction pattern of the ZSM-35 molecular sieve: at 2θ angles of (9.3±2)°, (12.5±2)°, (12.7±2)°, (13.4±2)°, (22.3±2)°, (22.5±2)°, (23.1±2)°, (23.6±2)°, (24.4±2)°, (25.2±2)°, (… Characteristic diffraction peaks of ZSM-35 molecular sieve were observed at (9.3), (12.5), (12.7), (13.4), (22.3), (22.6), (23.2), (23.6), (24.4), (25.2), (25.6), and (29.4) at (25.6±2)° and (29.4±2)°, indicating a relative crystallinity of 95–180. The preparation method of ZSM-35 molecular sieve is simple, using a template agent and a single alkali source. By using different aluminum and silicon sources and changing the silicon-aluminum ratio, and by synergistically controlling the amount of template agent and alkali source added to the synthesis system, high-crystallinity, low-cost ZSM-35 molecular sieves can be synthesized within a short crystallization time, avoiding complex synthesis processes and the addition of multiple alkali metal ions.

[0007] According to a first aspect of this application, a ZSM-35 molecular sieve is provided.

[0008] A ZSM-35 molecular sieve, wherein the ZSM-35 molecular sieve is a pure phase, and the X-ray powder diffraction pattern of the ZSM-35 molecular sieve shows the following 2θ angles: (9.3±2)°, (12.5±2)°, (12.7±2)°, (13.4±2)°, (22.3±2)°, (22.5±2)°, (23.1±2)°, (23.6±2)°, (24.4±2)°, (25.2)°. Characteristic diffraction peaks of ZSM-35 molecular sieve (9.3), (12.5), (12.7), (13.4), (22.3), (22.6), (23.2), (23.6), (24.4), (25.2), (25.6), and (29.4) were observed at (25.6±2)°, (25.6±2)°, and (29.4)°. The relative crystallinity of the ZSM-35 molecular sieve is 95~180.

[0009] Optionally, the relative crystallinity of the ZSM-35 molecular sieve is any value or a range between any two of 95, 100, 105, 110, 115, 120, 122, 125, 130, 135, 140, 142, 145, 150, 155, 160, 165, 170, 175, 179, and 180.

[0010] The ZSM-35 molecular sieve has high crystallinity.

[0011] Optionally, the silicon-to-aluminum ratio of the ZSM-35 molecular sieve is 25-47.

[0012] Optionally, the silica-alumina ratio of the ZSM-35 molecular sieve is any value among 25, 27, 29, 31, 32, 33, 35, 37, 39, 41, 43, 45, and 47, or a range between any two.

[0013] The silicon-to-aluminum ratio was determined by X-ray fluorescence spectroscopy (XRF).

[0014] The ZSM-35 molecular sieve has a FER topology, which consists of one-dimensional ten-membered ring channels and one-dimensional eight-membered ring channels that are vertically interspersed.

[0015] According to a second aspect of this application, a method for preparing ZSM-35 molecular sieve is provided.

[0016] A method for preparing ZSM-35 molecular sieve, the method comprising the following steps: S1. Dissolve the silicon source, aluminum source, template agent and alkali source in water, mix and stir to obtain a homogeneous mixed solution; S2. The homogeneous mixed solution is hydrothermally crystallized, and then washed, dried and calcined in sequence to obtain the ZSM-35 molecular sieve.

[0017] Optionally, in S1, the silicon source is at least one of silica sol and water glass.

[0018] Optionally, in S1, the aluminum source is at least one of boehmite, aluminum hydroxide, sodium aluminate, aluminum sulfate, and aluminum sol.

[0019] Optionally, in S1, the template agent is cyclohexylamine.

[0020] Optionally, in S1, the alkali source is sodium hydroxide.

[0021] Optionally, in S1, the molar ratio of the silicon source, the aluminum source, the template agent, the alkali source, and the water is 1:(20~70):(3~11):(1~5):(400~1200), wherein the molar amount of the silicon source is SiO2, the molar amount of the aluminum source is Al2O3, and the molar amount of the alkali source is Na2O.

[0022] Optionally, in S1, the alkalinity OH in the homogeneous mixed solution is... - / SiO2 is 0.06~0.3.

[0023] Optionally, in S1, the alkalinity OH in the homogeneous mixed solution is... - / SiO2 can be any value from 0.06, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.25, 0.28, 0.3 or a range between any two.

[0024] Optionally, in step S1, the acid source is also dissolved in water.

[0025] Optionally, the acid source is sulfuric acid.

[0026] Optionally, the molar ratio of the silicon source to the acid source is 1:(0~6.5).

[0027] Optionally, in step S1, the stirring is magnetic stirring, and the magnetic stirring time is 60~120 minutes.

[0028] Optionally, in step S2, hydrothermal crystallization of the homogeneous mixed solution includes: placing the homogeneous mixed solution into a high-pressure reactor, and then placing the high-pressure reactor into a homogeneous reaction oven for hydrothermal crystallization.

[0029] Optionally, in S2, the hydrothermal crystallization is dynamic crystallization, and the rotational speed of the hydrothermal crystallization is 10~30 rpm.

[0030] Optionally, in S2, the temperature of the hydrothermal crystallization is 110~170°C, and the time of the hydrothermal crystallization is 24-48h.

[0031] Optionally, in step S2, the calcination temperature is 550~650°C, and the calcination time is 2~4 hours.

[0032] The beneficial effects that this application can produce include: The preparation method provided in this application is simple, employing a template agent and a single alkali source. By using different aluminum and silicon sources, changing the silicon-aluminum ratio, and synergistically controlling the addition amounts of template agent and alkali source in the synthesis system, high-crystallinity, low-cost ZSM-35 molecular sieves can be synthesized within a short crystallization time, avoiding complex synthesis processes and the addition of multiple alkali metal ions. This method provides a new route for preparing low-cost, high-crystallinity pure-phase ZSM-35 molecular sieves, and it exhibits good reproducibility and is easily industrialized. Attached Figure Description

[0033] Figure 1 The image shows the X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Example 1. Figure 2 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Example 2; Figure 3 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Example 3; Figure 4 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Example 4; Figure 5 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Example 5; Figure 6 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Example 6; Figure 7 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Comparative Example 1 is shown. Figure 8 The image shows the X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Comparative Example 2. Detailed Implementation

[0034] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0035] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0036] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0037] In the embodiments of this application, XRD refers to X-ray powder diffraction; XRF refers to X-ray fluorescence spectroscopy.

[0038] Example 1 Weigh 20.07g of deionized water, add 0.38g of boehmite and stir until homogeneous. Then add 1.5g of cyclohexylamine to the mixture and continue stirring for 10min. While stirring, add 0.41g of sodium hydroxide solid and then add 18.24g of 25% silica sol dropwise. After stirring for 60min, place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30rpm for 48 hours for hydrothermal reaction.

[0039] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0040] XRD analysis showed that the solid product was pure phase ZSM-35 with a relative crystallinity of 179; XRF analysis showed that the silicon-to-aluminum ratio was 25.

[0041] Example 2 Weigh 12.51g of deionized water, add 1.06g of aluminum sol and stir until well mixed. Then add 1.5g of cyclohexylamine to the mixture and continue stirring for 10 minutes. While stirring, add 0.47g of sodium hydroxide solid and then add 18.24g of 25% silica sol dropwise. After stirring for 60 minutes, place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30rpm for 48 hours for hydrothermal reaction.

[0042] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0043] XRD analysis showed that the solid product was pure phase ZSM-35 with a relative crystallinity of 142; XRF analysis showed that the silicon-to-aluminum ratio was 32.

[0044] Example 3 Weigh 14.79g of deionized water, add 1.06g of aluminum sol and stir until well mixed. Then add 1.25g of cyclohexylamine to the mixture and continue stirring for 10 minutes. While stirring, add 0.47g of sodium hydroxide solid and then add 18.24g of 25% silica sol dropwise. After stirring for 60 minutes, place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30 rpm for 48 hours for hydrothermal reaction.

[0045] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0046] XRD analysis showed that the solid product was pure phase ZSM-35 with a relative crystallinity of 122; XRF analysis showed that the silicon-to-aluminum ratio was 31.

[0047] Example 4 Weigh 20.07g of deionized water, add 0.38g of boehmite and stir until homogeneous. Then add 1.5g of cyclohexylamine to the mixture and continue stirring for 10min. While stirring, add 0.41g of sodium hydroxide solid and then add 18.24g of 25% silica sol dropwise. After stirring for 60min, place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30rpm for a hydrothermal reaction for 36 hours.

[0048] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0049] XRD analysis showed that the solid product was pure phase ZSM-35 with a relative crystallinity of 180; XRF analysis showed that the silicon-to-aluminum ratio was 27.

[0050] Example 5 Weigh 6.67g of deionized water, add 9.39g of 15% aluminum sulfate solution and 11.43g of 20% sulfuric acid, and stir to dissolve for 10 minutes. While stirring, add 8.89g of cyclohexylamine and stir to mix evenly. Then add 0.71g of 30% sodium hydroxide solution and 29.9g of water glass and continue stirring for 60 minutes. Place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30 rpm for a hydrothermal reaction for 36 hours.

[0051] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0052] XRD analysis showed that the solid product was pure phase ZSM-35 with a relative crystallinity of 140; XRF analysis showed that the silicon-to-aluminum ratio was 33.

[0053] Example 6 Weigh 8.02g of deionized water, add 0.38g of boehmite and stir until homogeneous. Then add 1.5g of cyclohexylamine to the mixture and continue stirring for 10min. While stirring, add 0.41g of sodium hydroxide solid and then add 25.3g of 30% silica sol dropwise. After stirring for 60min, place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30rpm for 48 hours for hydrothermal reaction.

[0054] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0055] XRD analysis showed that the solid product was pure phase ZSM-35 with a relative crystallinity of 95%; XRF analysis showed that the silicon-to-aluminum ratio was 47.

[0056] Comparative Example 1 The raw materials used in Comparative Example 1 and Example 1 are the same. The difference is that Comparative Example 1 uses static aging followed by hydrothermal reaction to prepare the crystallized product.

[0057] The specific experimental steps for Comparative Example 1 are as follows: Weigh 20.07g of deionized water, add 0.38g of boehmite and stir until homogeneous. Then add 1.5g of cyclohexylamine to the mixture and continue stirring for 10min. While stirring, add 0.41g of sodium hydroxide solid and then add 18.24g of 25% silica sol dropwise. After stirring for 60min, statically crystallize at 40℃ for 3h. Then, place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30rpm for 48 hours for hydrothermal reaction.

[0058] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0059] XRD analysis showed that the solid product was a mixed crystal; XRF analysis showed that the silicon-to-aluminum ratio was 25.

[0060] Comparative Example 2 The raw materials used in Comparative Example 2 and Example 5 are the same, except that the amount of alkali used in Comparative Example 2 is higher.

[0061] The specific experimental steps for Comparative Example 2 are as follows: Weigh 10.02g of deionized water, add 9.51g of 15% aluminum sulfate solution and 7.48g of 20% sulfuric acid, and stir to dissolve for 10 minutes. While stirring, add 9.00g of cyclohexylamine and stir to mix evenly. Then add 0.72g of 30% sodium hydroxide solution and 30.27g of water glass and continue stirring for 60 minutes. Then, place the mixture in a hydrothermal crystallization reactor at a reaction temperature of 170℃ and a stirring speed of 30rpm for a hydrothermal reaction for 36 hours.

[0062] After the crystallization reaction is completed, the obtained crystallized product is centrifuged and recovered, washed with deionized water until the pH is 7-8, and dried at 120°C. The dried crystallized product is placed in a muffle furnace and calcined at 550°C for 4 hours in a flowing air atmosphere to obtain ZSM-35 molecular sieve raw powder.

[0063] XRD analysis showed that the solid product was a mixed crystal; XRF analysis showed that the silicon-to-aluminum ratio was 32.

[0064] Characterization: Figures 1-6 The X-ray powder diffraction patterns of the ZSM-35 molecular sieves prepared in Examples 1 to 6 are shown respectively. The characteristic diffraction peaks of ZSM-35 molecular sieves at 2θ angles of (9.3)°, (12.5)°, (12.7)°, (13.4)°, (22.3)°, (22.5)°, (23.1)°, (23.6)°, (24.4)°, (25.2)°, (25.6)° and (29.4)° are observed.

[0065] Figure 7 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Comparative Example 1 shows the characteristic diffraction peaks of ZSM-35 molecular sieve at 2θ angles of (9.3)°, (12.5)°, (12.7)°, (13.4)°, (22.3)°, (22.5)°, (23.1)°, (23.6)°, (24.4)°, (25.2)°, (25.6)° and (29.4)°.

[0066] Figure 8 The X-ray powder diffraction pattern of the ZSM-35 molecular sieve prepared in Comparative Example 2 shows the characteristic diffraction peaks of ZSM-35 molecular sieve at 2θ angles of (9.3)°, (12.5)°, (12.7)°, (13.4)°, (22.3)°, (22.5)°, (23.1)°, (23.6)°, (24.4)°, (25.2)°, (25.6)° and (29.4)°.

[0067] 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 ZSM-35 molecular sieve, characterized in that, The ZSM-35 molecular sieve is a pure phase. In the X-ray powder diffraction pattern of the ZSM-35 molecular sieve: at 2θ angles of (9.3±2)°, (12.5±2)°, (12.7±2)°, (13.4±2)°, (22.3±2)°, (22.5±2)°, (23.1±2)°, (23.6±2)°, (24.4±2)°, (25.2±2)°, (… Characteristic diffraction peaks of ZSM-35 molecular sieve (9.3), (12.5), (12.7), (13.4), (22.3), (22.6), (23.2), (23.6), (24.4), (25.2), (25.6), and (29.4) were observed at (25.6±2)° and (29.4±2)°. The relative crystallinity of the ZSM-35 molecular sieve is 95~180.

2. The ZSM-35 molecular sieve according to claim 1, characterized in that, The silicon-to-aluminum ratio of the ZSM-35 molecular sieve is 25-47.

3. A method for preparing the ZSM-35 molecular sieve according to claim 1 or 2, characterized in that, The preparation method includes the following steps: S1. Dissolve the silicon source, aluminum source, template agent and alkali source in water, mix and stir to obtain a homogeneous mixed solution; S2. The homogeneous mixed solution is hydrothermally crystallized, and then washed, dried and calcined in sequence to obtain the ZSM-35 molecular sieve.

4. The preparation method according to claim 3, characterized in that, In S1, the silicon source is at least one of silica sol and water glass; Preferably, in S1, the aluminum source is at least one of boehmite, aluminum hydroxide, sodium aluminate, aluminum sulfate, and aluminum sol. Preferably, in S1, the template agent is cyclohexylamine; Preferably, in S1, the alkali source is sodium hydroxide.

5. The preparation method according to claim 3, characterized in that, In S1, the molar ratio of the silicon source, the aluminum source, the template agent, the alkali source, and the water is 1:(20~70):(3~11):(1~5):(400~1200), wherein the molar amount of the silicon source is SiO2, the molar amount of the aluminum source is Al2O3, and the molar amount of the alkali source is Na2O.

6. The preparation method according to claim 3, characterized in that, In S1, the alkalinity OH in the homogeneous mixed solution - / SiO2 is 0.06~0.

3.

7. The preparation method according to claim 3, characterized in that, In step S1, the acid source is also dissolved in water; Preferably, the acid source is sulfuric acid.

8. The preparation method according to claim 7, characterized in that, The molar ratio of the silicon source to the acid source is 1:(0~6.5).

9. The preparation method according to claim 3, characterized in that, In S2, the hydrothermal crystallization is dynamic crystallization, and the rotational speed of the hydrothermal crystallization is 10~30 rpm; Preferably, in step S2, the temperature of the hydrothermal crystallization is 110~170°C, and the time of the hydrothermal crystallization is 24-48h.

10. The preparation method according to claim 3, characterized in that, In step S2, the calcination temperature is 550~650°C, and the calcination time is 2~4 hours.

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