Nano NON molecular sieve as well as preparation method and application thereof

Abstract

The invention discloses a nano NON molecular sieve as well as a preparation method and application thereof. The crystal morphology of the nano NON molecular sieve is a nano particle, and the average diameter of the crystal is 50-140 nm. The molecular sieve has the advantages of nano-particle morphology, uniform particle size and small size; the molecular sieve can be used as an adsorbent or a catalyst for conversion of organic compounds, and has good performance.

Description

Technical Field

[0001] This invention belongs to the field of NON molecular sieves, specifically relating to a nano NON molecular sieve, its preparation method, and its application. Background Technology

[0002] Molecular sieve materials are a class of microporous solid materials with regular pore systems, constructed from TO4 (T = Si, P, Al, Ge, Ti, etc.) tetrahedral structural units connected in different ways. The most important characteristics of molecular sieves are their adjustable pore diameter, varied pore shape, and controllable chemical composition. These excellent properties make them important in many fields such as adsorption and separation, catalysis, microelectronic devices, medical diagnostics, and drug delivery. Non-non-metallic molecular sieves, with their six-membered ring pore structure, have limited applications in macromolecular catalysis. However, their smaller pore size makes them advantageous for the adsorption and storage of radioactive materials and selective catalysis of small molecules, and they are generally widely used as adsorbents. Non-non-metallic molecular sieves can be used for water purification and contaminated soil remediation to lock and remove toxic heavy metal ions; they also hold promise for extracting useful trace metals from salt lake brine, which is of great significance for solving water shortage problems and promoting socio-economic development and ecological environment construction.

[0003] CN107473239A discloses a method for synthesizing NON-type molecular sieves using tetraethylammonium hydroxide and trimethylethylammonium bromide as organic structure directing agents, which exhibit good hydrogen storage performance. CN115304075A discloses a method for synthesizing one-dimensional strip-shaped, rod-shaped, or needle-shaped NON-type molecular sieves using 4-diaminopyridine and other organic structure directing agents, which exhibit good performance in organic compound conversion reactions.

[0004] In the above methods for synthesizing NON-type molecular sieves, the organic structure-directing agents used are either complex in structure and expensive, or multiple organic structure-directing agents need to be used simultaneously. Some NON-type molecular sieves require multi-stage crystallization in their synthesis process, making the operation complex. Furthermore, the average particle size of NON-type molecular sieves prepared by the above methods is generally 5–10 μm. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a nano-NON molecular sieve, its preparation method, and its applications. The molecular sieve possesses the advantages of nanoparticle morphology, uniform particle size, and small dimensions; the preparation method boasts high yield and low synthesis cost; the molecular sieve can be used as an adsorbent or a catalyst for the conversion of organic compounds, exhibiting excellent performance.

[0006] The first aspect of this invention provides a nano-NON molecular sieve. The crystal morphology of the molecular sieve is nanoparticles.

[0007] According to the present invention, the average diameter of the NON molecular sieve crystal is 50-140 nm.

[0008] According to the present invention, the NON molecular sieve has the following chemical composition nSiO2·Al2O3, wherein 50≤n≤100, preferably 66.7≤n≤100, in molar terms.

[0009] A second aspect of this invention provides a method for preparing nano-NON molecular sieves, comprising the following steps:

[0010] A silicon source, an aluminum source, a fluorine source, an organic structure directing agent, and water are mixed and then subjected to water distillation to obtain a crystallization raw material mixture; the crystallization raw material mixture is then subjected to a crystallization reaction to obtain the nano-NON molecular sieve.

[0011] The organic structure directing agent is selected from at least one of the following compounds, their quaternary ammonium salts or their quaternary ammonium bases;

[0012] The organic structure directing agent has the following structural formula:

[0013] Among them, R1 is selected from C 1-8 Alkyl groups, preferably selected from C 1-4 Alkyl groups, more preferably selected from C 1-2 Alkyl; R2 - For OH - At least one of the following: halogen anions.

[0014] According to the present invention, the molar ratio of silicon source (SiO2), aluminum source (Al2O3), fluorine source (F), organic structure directing agent (OSDA), and water in the feed is SiO2:Al2O3:OSDA:F:H2O = 1:(0.010~0.020):(0.05~1.0):(0.5~3.0):(8~30), preferably 1:(0.010~0.015):(0.05~0.8):(0.5~1.5):(8~25), more preferably 1:(0.010~0.015):(0.15~0.5):(0.5~1.0):(8~20).

[0015] According to the present invention, the silicon source is selected from at least one of silicic acid, silica gel, silica sol, tetraethyl silicate, and water glass; the aluminum source is selected from at least one of aluminum hydroxide, aluminum oxide, aluminum isopropoxide, aluminum salt, and aluminum tetraalkoxy; and the fluorine source is at least one of hydrofluoric acid and ammonium fluoride.

[0016] The crystallization raw material mixture according to the present invention does not contain alkali metals or alkaline earth metals. No alkali source is added in the preparation method of the molecular sieve. The alkali source can be, for example, an alkaline substance other than silicon sources, aluminum sources, and organic structure directing agents; specifically, any alkali source conventionally used in the art for the purpose of making the system alkaline; more specifically, inorganic bases with alkali metals or alkaline earth metals as cations, particularly sodium hydroxide and potassium hydroxide. Here, "not containing an alkali source" means that no alkali source is intentionally or actively introduced into the mixture.

[0017] According to the present invention, in the method for preparing the molecular sieve, the raw materials do not contain seed crystals, that is, no seed crystals are added.

[0018] According to the present invention, the method of water treatment is rotary evaporation or open heating for water removal; the open heating treatment conditions are heating and stirring at 40 to 100°C, preferably at 45 to 80°C.

[0019] According to the present invention, in the crystallized raw material mixture obtained after water distillation, the molar ratio of silicon source (SiO2) to water is 1:(3-7), preferably 1:(4-6).

[0020] According to the present invention, the crystallization conditions are as follows: crystallization at 110–180°C for 5–15 days, preferably at 130–170°C for 6–14 days, and more preferably at 140–160°C for 7–13 days. Crystallization is preferably performed at a rotation speed of 15–50 rpm. After crystallization, washing can be performed until the pH value is near neutral (pH = 7–8).

[0021] According to the present invention, drying is required after crystallization. The drying conditions are 50–160°C for 6–36 hours.

[0022] According to the present invention, the molecular sieve can be calcined as needed to remove template agents and any present moisture. The calcination can be carried out in any manner conventionally known in the art, for example, the calcination temperature is generally 300–900°C, preferably 400–700°C, more preferably 450–600°C; the calcination time is generally 2–9 hours, preferably 3–6 hours. Furthermore, the calcination is carried out in an oxygen-containing atmosphere, such as air or an oxygen atmosphere.

[0023] A third aspect of the present invention provides a NON molecular sieve composition comprising any of the aforementioned nano NON molecular sieves or nano NON molecular sieves prepared according to any of the aforementioned preparation methods, and a binder.

[0024] The fourth aspect of the present invention provides the application of any of the aforementioned nano-NON molecular sieves or NON molecular sieve compositions, or nano-NON molecular sieves prepared according to any of the aforementioned preparation methods, as adsorbents and / or catalysts.

[0025] Compared with the prior art, the main advantages of the present invention include:

[0026] 1. The nano-NON molecular sieve of the present invention has a nanoparticle morphology with an average crystal diameter of 50–140 nm. The molecular sieve of the present invention has a unique crystal morphology, uniform particle size, and small dimensions. Preferably, the chemical composition of the NON-type molecular sieve of the present invention is nSiO2·Al2O3, where 50 ≤ n ≤ 100. Compared with existing NON-type molecular sieves, the silicon content in the molecular sieve is increased, classifying it as a high-silicon molecular sieve.

[0027] 2. In the preparation method of the nano-NON molecular sieve of the present invention, a specific organic structure directing agent OSDA is used. Preferably, the feed ratio is further limited. The preparation method of the molecular sieve of the present invention has high yield and low synthesis cost; the molecular sieve prepared by the method can be used as an adsorbent or a catalyst for the conversion of organic compounds, and has good performance.

[0028] 3. The nano-NON molecular sieve provided by this invention can be used as an adsorbent or a catalyst for the conversion of organic compounds. Attached Figure Description

[0029] Figure 1 The X-ray diffraction (XRD) pattern of the sample in Example 1;

[0030] Figure 2 The image shown is a scanning electron microscope (SEM) image of the sample in Example 1.

[0031] Figure 3 The X-ray diffraction (XRD) pattern of the sample in Example 2;

[0032] Figure 4 The image shown is a scanning electron microscope (SEM) image of the sample in Example 2.

[0033] Figure 5 The X-ray diffraction (XRD) pattern of the sample in Comparative Example 1 is shown.

[0034] Figure 6 The image shows the X-ray diffraction (XRD) pattern of the sample in Comparative Example 2. Detailed Implementation

[0035] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments.

[0036] In this invention, the structure of the molecular sieve is determined by X-ray diffraction (XRD), which is measured using an X-ray powder diffractometer with a Cu-Kα ray source and a nickel filter. Before sample testing, the crystallization of the molecular sieve sample is observed using a scanning electron microscope (SEM) to confirm that the sample contains only one type of crystal, i.e., the molecular sieve sample is a pure phase. Based on this, XRD testing is then performed to ensure that there are no interfering peaks from other crystals in the diffraction patterns of the XRD spectrum.

[0037] In this invention, the scanning electron microscope (SEM) used for observing the molecular sieves in the following examples and comparative examples is a model S-4800II field emission scanning electron microscope. The molecular sieves were observed using this SEM at a magnification of 40,000x. A randomly selected field of view was used to calculate the average diameter of all crystals within that field of view, and this operation was repeated a total of 10 times. The average of the sums of the 10 calculations was taken as the average crystal diameter.

[0038] In this invention, the room temperature in each example is 20°C.

[0039] In this invention, the organic structure directing agent OSDA used in each embodiment has the following structural formula:

[0040]

[0041] In Examples 1, 2, and 4, R1 is ethyl, and R2 is... - For OH - ;

[0042] In Example 3, R1 is methyl, and R2 is... - For OH - .

[0043] In Example 5, R1 is ethyl, and R2 is... - For Cl - .

[0044] Example 1

[0045] Deionized water, organic structure-directing agent OSDA, silica sol, aluminum hydroxide, and hydrofluoric acid were mixed evenly. The amount of organic structure-directing agent OSDA in the feed was 0.05 mol; the molar ratio of the materials was: Al₂O₃ / SiO₂ = 0.01, OSDA / SiO₂ = 0.5, F / SiO₂ = 0.8, and H₂O / SiO₂ = 20.

[0046] After stirring at room temperature for 5 hours, the raw material liquid was stirred in an open container at 80°C, and then treated with water distillation to obtain a mixture. The molar ratio of H₂O / SiO₂ in the mixture was 6.

[0047] The mixture was placed in a stainless steel reactor and crystallized for 8 days at 160℃ and 40 rpm. After crystallization, the mixture was centrifuged and washed until the pH value was near neutral (pH = 7-8), and then dried in an oven at 110℃ for 16 hours to obtain the molecular sieve.

[0048] The XRD pattern of the molecular sieve is as follows: Figure 1 The image shown is of a non-non molecular sieve with a yield of 88 wt%. The SEM image of the molecular sieve is shown below. Figure 2 As shown, the molecular sieve has a nanoparticle morphology with an average crystal diameter of 130 nm.

[0049] Example 2

[0050] Deionized water, organic structure-directing agent OSDA, silica sol, aluminum hydroxide, and hydrofluoric acid were mixed evenly. The amount of organic structure-directing agent OSDA in the feed was 0.05 mol; the molar ratio of the materials was: Al₂O₃ / SiO₂ = 0.015, OSDA / SiO₂ = 0.5, F / SiO₂ = 0.6, and H₂O / SiO₂ = 15.

[0051] After stirring at room temperature for 5 hours, the raw material liquid was stirred in an open container at 80°C, and then treated with water distillation to obtain a mixture. In the mixture, the molar ratio of H2O / SiO2 = 4.

[0052] The mixture was placed in a stainless steel reactor and crystallized for 10 days at 150°C and 30 rpm. After crystallization, the mixture was centrifuged and washed until the pH value was near neutral (pH = 7-8), and then dried in an oven at 120°C for 8 hours to obtain the molecular sieve.

[0053] The XRD pattern of the molecular sieve is as follows: Figure 3 The image shown is of a non-non molecular sieve with a yield of 80 wt%. The SEM image of the molecular sieve is shown below. Figure 4 As shown, the molecular sieve has a nanoparticle morphology with an average crystal diameter of 120 nm.

[0054] Example 3

[0055] Deionized water, organic structure directing agent OSDA, silica sol, aluminum hydroxide, and hydrofluoric acid were mixed evenly. The amount of organic structure directing agent OSDA in the feed was 0.05 mol; the molar ratio of the materials was: Al₂O₃ / SiO₂ = 0.01, OSDA / SiO₂ = 0.5, F / SiO₂ = 0.6, and H₂O / SiO₂ = 18.

[0056] After stirring at room temperature for 5 hours, the raw material liquid was stirred in an open container at 80°C, and then treated with water distillation to obtain a mixture. In the mixture, the molar ratio of H2O / SiO2 = 5.

[0057] The mixture was placed in a stainless steel reactor and crystallized for 10 days at 150°C and 30 rpm. After crystallization, the mixture was centrifuged and washed until the pH value was near neutral (pH = 7-8), and then dried in an oven at 130°C for 6 hours to obtain the molecular sieve.

[0058] The XRD pattern of the molecular sieve and Figure 1 Similarly, this is a non-non molecular sieve, with a yield of 78 wt%; the SEM image of the molecular sieve is similar to... Figure 2 Similarly, molecular sieves have a nanoparticle morphology with an average crystal diameter of 120 nm.

[0059] Example 4

[0060] Deionized water, organic structure-directing agent OSDA, silica sol, aluminum hydroxide, and hydrofluoric acid were mixed evenly. The amount of organic structure-directing agent OSDA in the feed was 0.03 mol; the molar ratio of the materials was: Al₂O₃ / SiO₂ = 0.015, OSDA / SiO₂ = 0.3, F / SiO₂ = 1, and H₂O / SiO₂ = 10.

[0061] After stirring at room temperature for 5 hours, the raw material liquid was stirred in an open container at 80°C, and then treated with water distillation to obtain a mixture. In the mixture, the molar ratio of H2O / SiO2 = 5.

[0062] The mixture was placed in a stainless steel reactor and crystallized for 12 days at 140°C and 30 rpm. After crystallization, the mixture was centrifuged and washed until the pH value was near neutral (pH = 7-8), and then dried in an oven at 110°C for 10 hours to obtain the molecular sieve.

[0063] The XRD pattern of the molecular sieve and Figure 1 Similarly, this is a non-non molecular sieve, with a yield of 85 wt%; the SEM image of the molecular sieve is similar to... Figure 2 Similarly, molecular sieves have a nanoparticle morphology with an average crystal diameter of 110 nm.

[0064] Example 5

[0065] The main difference from Example 1 lies in the different organic structure-directing agent. In this example, the organic structure-directing agent OSDA is used, with the following structural formula:

[0066]

[0067] R1 is ethyl, R2 - For Cl - .

[0068] Deionized water, organic structure directing agent OSDA, silica sol, aluminum hydroxide, and hydrofluoric acid were mixed evenly. The amount of organic structure directing agent OSDA in the feed was 0.05 mol; the molar ratio of the materials was: Al₂O₃ / SiO₂ = 0.01, OSDA / SiO₂ = 0.5, F / SiO₂ = 0.8, and H₂O / SiO₂ = 18.

[0069] After stirring at room temperature for 5 hours, the raw material liquid was stirred in an open container at 80°C, and then treated with water distillation to obtain a mixture. The molar ratio of H₂O / SiO₂ in the mixture was 6.

[0070] The mixture was placed in a stainless steel reactor and crystallized for 8 days at 160℃ and 40 rpm. After crystallization, the mixture was centrifuged and washed until the pH value was near neutral (pH = 7-8), and then dried in an oven at 110℃ for 16 hours to obtain the molecular sieve.

[0071] The XRD pattern of the molecular sieve and Figure 1 Similarly, this is a non-non molecular sieve, with a yield of 70 wt%; the SEM image of the molecular sieve is similar to... Figure 2 Similarly, molecular sieves have a nanoparticle morphology with an average crystal diameter of 135 nm.

[0072] Comparative Example 1

[0073] The raw materials and preparation steps are the same as in Example 1, except that the raw material ratios are adjusted. During feeding, the organic structure-directing agent OSDA is 0.5 mol. The molar ratios of the materials are: Al2O3 / SiO2 = 0.1, OSDA / SiO2 = 0.5; F / SiO2 = 0.8; H2O / SiO2 = 25.

[0074] After stirring at room temperature for 5 hours, the raw material liquid was stirred in an open container at 80°C, and then treated with water distillation to obtain a mixture. The molar ratio of H₂O / SiO₂ in the mixture was 6.

[0075] The mixture was placed in a stainless steel reactor and crystallized for 8 days at 160℃ and 40 rpm. After crystallization, the mixture was filtered, washed to near neutral pH (pH = 7-8), and dried in an oven at 110℃ for 16 hours. The XRD pattern of the obtained product is shown below. Figure 5 As shown, the sample is uncrystallized, has an amorphous structure, and is not a NON molecular sieve.

[0076] Comparative Example 2

[0077] The difference from Example 1 lies in the directing agent; in this example, tetraethylammonium hydroxide is used instead of the organic directing agent OSDA in Example 1. Other steps are the same as in Example 1. A molecular sieve is thus obtained.

[0078] The XRD pattern of the molecular sieve is as follows: Figure 6As shown, the sample is an MFI type molecular sieve, not a NON molecular sieve.

[0079] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A nano-NON molecular sieve characterized by, The NON molecular sieve has a crystal morphology of nanoparticles, and the average diameter of the crystal is 50-140 nm.

2. The molecular sieve of claim 1, wherein, The NON molecular sieve has a chemical composition of nSiO2·Al2O3, wherein 50≤n≤100, preferably 66.7≤n≤100, in terms of moles.

3. A preparation method of the nano NON molecular sieve, comprising the following steps: mixing a silicon source, an aluminum source, a fluorine source, an organic structure directing agent and water, and then performing steam treatment to obtain a crystallization raw material mixture; and then performing a crystallization reaction on the crystallization raw material mixture to obtain the nano NON molecular sieve; the organic structure directing agent is selected from at least one of the following compounds, quaternary ammonium salts thereof or quaternary ammonium bases thereof; The organic structure-directing agent has a structural formula: wherein R1is selected from C 1-8 alkyl, preferably selected from C 1-4 alkyl, more preferably selected from C 1-2 alkyl; R2 - is OH - at least one of a halide anion.

4. The preparation method according to claim 3, characterized in that, the molar ratio of the silicon source (in terms of SiO2), the aluminum source (in terms of Al2O3), the fluorine source (in terms of F), the organic structure directing agent (OSDA) and water in the raw material is SiO2:Al2O3:OSDA:F:H2O = 1:(0.010-0.020):(0.05-1.0):(0.5-3.0):(8-30), preferably 1:(0.010-0.015):(0.05-0.8):(0.5-1.5):(8-25), and more preferably 1:(0.010-0.015):(0.15-0.5):(0.5-1.0):(8-20).

5. The preparation method according to claim 3, characterized in that, the silicon source is selected from at least one of silicic acid, silica gel, silica sol, tetraethyl silicate and water glass; and / or the aluminum source is selected from at least one of aluminum hydroxide, aluminum oxide, aluminum isopropoxide, aluminum salts and tetraalkoxyaluminum; and / or the fluorine source is at least one of hydrofluoric acid and ammonium fluoride.

6. The preparation method according to claim 3, characterized in that, The crystallization raw material mixture does not contain alkali metals or alkaline earth metals.

7. The preparation method according to claim 3, characterized in that, The preparation method of the nano NON molecular sieve does not add seeds.

8. The preparation method according to claim 3, characterized in that, After the steam treatment, the molar ratio of the silicon source (in terms of SiO2) and water in the crystallization raw material mixture is 1:(3-7), preferably 1:(4-6).

9. The preparation method according to claim 3, characterized in that, The crystallization conditions are 110-180 ℃ for 5-15 days, preferably 130-170 ℃ for 6-14 days, and more preferably 140-160 ℃ for 7-13 days; and the crystallization is preferably performed under rotation at 15-50 rpm.

10. A NON molecular sieve composition, comprising the nano NON molecular sieve according to claim 1 or 2, or prepared according to any one of the preparation methods of claims 3-9, and a binder.

11. Use of the molecular sieve according to claim 1 or 2, or the NON molecular sieve composition according to claim 10, or the nano NON molecular sieve prepared according to any one of the preparation methods of claims 3-9, as an adsorbent and / or a catalyst.

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