Preparation method of nano GME type molecular sieve

Abstract

The application discloses a preparation method of nano GME molecular sieve. The method comprises the following steps: placing a mixture containing a silicon source, an aluminum source, sodium hydroxide and water into a sealed container, and crystallizing to obtain the nano GME molecular sieve. The method does not use seeds and Y zeolite, and a cheap template agent pyrrolidine is used, so that the synthesis method has low cost and simple synthesis process, and has a good application prospect.

Description

Technical Field

[0001] This application relates to a method for preparing nano-GME-type molecular sieves, belonging to the field of molecular sieve synthesis. Background Technology

[0002] Zeolite molecular sieves are a class of microporous materials with regular channel structures, and they have wide applications in adsorption, catalysis, and ion exchange. GME molecular sieve is a type of molecular sieve with a 12*8 three-dimensional channel structure.

[0003] Currently, the synthesis of GME molecular sieves often employs complex organic structure-directing agents, or requires the addition of seed crystals in purely inorganic systems. References such as *Microporous Mesoporous Mater.* 1999, 33, 197-207 use complex DABCO polymers as template agents, *Angew. Chem. Int. Ed.* 2017, 56, 13475–13478 uses cis-tetramethyl-N,N,3,5-pyridinium ions as template agents, and patent CN109694081A uses polyethylene glycol as a template agent. Patents CN113233474A, US009364782B1, and US6187283B1, which use purely inorganic systems, require the use of Y molecular sieves as seed crystals or raw materials for synthesis. These methods, using complex organic structure-directing agents or requiring seed crystals in inorganic systems, inevitably result in cumbersome synthesis steps, high synthesis costs, and environmental pollution. Summary of the Invention

[0004] To address the issues of expensive template agents and high costs in the synthesis of nano-GMEs, and the need for seed crystals and Y zeolite in inorganic system synthesis, this application provides a low-cost synthesis method that does not require the addition of seed crystals or other molecular sieves such as Y. This synthesis method is low-cost and simple.

[0005] A method for preparing nano-GME molecular sieves includes the following steps:

[0006] A mixture containing silicon source, aluminum source, sodium hydroxide and water is placed in a sealed container and crystallized to obtain the nano-GME molecular sieve.

[0007] Optionally, the mixture further includes the template agent pyrrolidine, and the molar ratio of each raw material is as follows:

[0008] SiO2:Al2O3:NaOH:pyrr:H2O=1: (0.03-0.1): (0.7-1): (0-2): (20-40);

[0009] The silicon source is calculated based on the number of moles of SiO2 it contains;

[0010] The aluminum source is calculated based on the number of moles of Al2O3 it contains;

[0011] NaOH is calculated based on its own mole count;

[0012] pyrr represents the template agent pyrrolidine, calculated based on its own molar number;

[0013] Water is measured in moles.

[0014] Optionally, the molar ratio of each raw material in the mixture is as follows:

[0015] SiO2:Al2O3:NaOH:pyrr:H2O=1: (0.05-0.1):(0.75-1):(0-2):(20-35).

[0016] In this invention, the template agent pyrrolidine may or may not be added. When the template agent pyrrolidine is added, the pyrrolidine is located in the GME cage of the GME molecular sieve, which plays a role in filling and stabilizing the structure. The protonated pyrrolidine can balance the negative charge of the framework.

[0017] Optionally, the silicon source is selected from at least one of silica sol, fumed silica, and tetraethylsilane. Preferably, it is selected from at least one of silica sol and fumed silica.

[0018] Optionally, the aluminum source is selected from at least one of sodium aluminate, aluminum isopropoxide, and aluminum nitrate. Preferably, it is selected from at least one of sodium aluminate and aluminum isopropoxide.

[0019] Optionally, the crystallization conditions are:

[0020] The crystallization temperature is 80℃~160℃, and the crystallization time is 12-120 hours.

[0021] Optionally, the crystallization conditions are:

[0022] The crystallization temperature is 90℃~140℃, and the crystallization time is 24-96 hours.

[0023] Optionally, the crystallization conditions are:

[0024] The crystallization temperature is 100℃~120℃, and the crystallization time is 24-96 hours.

[0025] Optionally, the crystallization temperature is independently selected from any value or a range between 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, and 160°C.

[0026] Optionally, the crystallization time is independently selected from any value of 12 hours, 24 hours, 36 hours, 48 ​​hours, 60 hours, 72 hours, 84 hours, 96 hours, 108 hours, and 120 hours, or a range between any two.

[0027] Optionally, the nano-GME molecular sieve is a nanoparticle with a size of 20-300 nm.

[0028] Optionally, the crystallization process may also include washing and drying steps.

[0029] The beneficial effects that this application can produce include:

[0030] The method for preparing nano-GME molecular sieves provided in this application does not use seed crystals or Y zeolite, and the template agent pyrrolidine used is inexpensive. This synthesis method is low-cost, simple in process, and has good application prospects. Attached Figure Description

[0031] Figure 1 This is the X-ray powder diffraction (XRD) pattern of the product obtained in Example 1 of this invention.

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the product obtained in Example 1 of the present invention, with a scale of 3 μm. Detailed Implementation

[0033] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0034] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0035] The analysis method in the embodiments of this application is as follows:

[0036] Phase analysis of the samples was performed using X-ray powder diffraction (XRD) with a Cu target and a Kα light source. The instrument used was an X'Pert PRO X-ray diffractometer from PANalytical, Netherlands. Tested under conditions of 40KV voltage and 40mA current.

[0037] The XRF analysis of the samples was performed using an X-ray fluorescence analyzer from PANalytical, a Dutch company.

[0038] Sample morphology analysis was performed using a scanning electron microscope (SEM) with the instrument being a Hitachi SU8020 field emission scanning electron microscope.

[0039] Example 1: Preparation of Sample 1

[0040] Preparation of nano-GME molecular sieve sample 1:

[0041] 5.390 g of silica sol (27.34%), 0.337 g of sodium aluminate, 0.730 g of sodium hydroxide, 2.669 g of pyrrolidine, and 9.335 g of water were mixed in a molar ratio of SiO2:Al2O3:NaOH:pyrrolidine:H2O = 1:0.07:0.9:1.5:30. After thorough mixing, the mixture was transferred to a stainless steel high-pressure reactor and crystallized at 100°C for 72 hours. After crystallization, the solid product was centrifuged, washed, and dried in air at 100°C to obtain the GME molecular sieve, designated as Sample 1. The X-ray powder diffraction (XRD) pattern of Sample 1 is shown below. Figure 1 As shown, sample 1 is a silica-alumina molecular sieve with a GME framework structure. XRF analysis revealed a silica-alumina atomic ratio of 2.5. Scanning electron microscopy (SEM) images are shown below. Figure 2 The image shows a nanoparticle sample with a particle size of approximately 100 nm.

[0042] Preparation of Samples 2-9 in Examples 2-9

[0043] The preparation process for Examples 2-9 is the same as that for Example 1. The specific proportions and crystallization conditions are shown in Table 1. The XRD patterns and SEM images of the obtained samples are similar to those of Sample 1 prepared in Example 1. The phase identification results of the obtained samples are shown in Table 1.

[0044] Table 1. Raw material types, proportions, and crystallization conditions for Examples 2-9

[0045]

[0046] The molar ratios of the raw materials in Examples 2-9 are calculated as shown in Table 2 below.

[0047] Table 2

[0048]

[0049]

[0050] 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 method for preparing nano-GME molecular sieves, characterized in that, Includes the following steps: A mixture containing a silicon source, an aluminum source, sodium hydroxide, a template agent pyrrolidine, and water is placed in a sealed container and crystallized to obtain the nano-GME molecular sieve. The molar ratios of the raw materials in the mixture are as follows: SiO2∶Al2O3∶NaOH∶pyrr∶H2O =1∶(0.03-0.1)∶(0.7-1)∶(1-2)∶(20-40); The silicon source is calculated based on the number of moles of SiO2 it contains; The aluminum source is calculated based on the number of moles of Al2O3 it contains; NaOH is calculated based on its own mole count; pyrr represents the template agent pyrrolidine, calculated based on its own molar number; Water is measured in moles. The nano-GME molecular sieve is composed of nanoparticles with a size of 20~300nm.

2. The preparation method according to claim 1, characterized in that, The molar proportions of the raw materials in the mixture are as follows: SiO2∶Al2O3∶NaOH∶pyrr∶H2O =1∶(0.05-0.1)∶(0.75-1)∶(1-2)∶(20-35).

3. The preparation method according to claim 1, characterized in that, The silicon source is selected from at least one of silica sol, silica, and tetraethylsilane.

4. The preparation method according to claim 1, characterized in that, The aluminum source is selected from at least one of sodium aluminate, aluminum isopropoxide, and aluminum nitrate.

5. The preparation method according to claim 1, characterized in that, The conditions for crystallization are: The crystallization temperature is 80℃~160℃, and the crystallization time is 12-120 hours.

6. The preparation method according to claim 1, characterized in that, The conditions for crystallization are as follows: The crystallization temperature is 90℃~140℃, and the crystallization time is 24-96 hours.

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