A method for the synthesis of a chabazite zeolite having a CHA structure

Abstract

This invention discloses a method for synthesizing chabazite with a CHA structure. The method involves mixing a silicon source and an aluminum source, or a silicon source, an aluminum source, and a sodium source, aging the mixture, and then mixing the resulting NaY molecular sieve directing agent with the silicon and aluminum sources to form a gel. The gel is then mixed with potassium hydroxide, crystallized, separated, and washed to obtain chabazite with a CHA structure. The method specifies the molar ratio of the NaY molecular sieve directing agent and the gel, as well as the amount of potassium hydroxide added. This method provides a way to synthesize chabazite with a CHA structure in situ by limiting the timing and amount of potassium hydroxide addition, combined with the molar ratio of the NaY molecular sieve directing agent and the gel. It eliminates the need for adding organic substances, has a short crystallization time, low cost, and is easy to operate and control.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve preparation technology, and in particular to a method for synthesizing chamazolithium with a CHA structure. Background Technology

[0002] The large-scale capture, separation, and recycling of CO2 is one of the major concerns of human society and is also one of the "seven chemical separation problems that could change the world." Currently, the mature commercial method for CO2 separation is amine solution absorption, but this technology is highly corrosive to equipment, consumes a lot of energy for regeneration, and the amine adsorbent is prone to deactivation. Therefore, it is crucial to develop new technologies and materials that can efficiently and cost-effectively separate CO2.

[0003] Type A and Type X molecular sieves are widely used adsorbents. Although both exhibit high adsorption capacities for CO2, their selectivity for CO2 adsorption is not ideal in the presence of small molecules such as H2O, CH4, and N2. In the field of CO2 adsorption, small-pore molecular sieves, such as CHA and RHO, have received widespread attention and significant research and development in recent years. These 8-membered ring small-pore molecular sieves with cage-like topologies possess unique separation mechanisms for CO2 (size sieving, kinetic sieving, weak interactions based on physical adsorption, interactions based on chemisorption, molecular gate effect, etc.). Therefore, these zeolite molecular sieve materials have the effect of highly efficient CO2 separation.

[0004] For example, Chinese patent document CN201980019996.1 discloses a method for synthesizing zeolites with a CHA framework structure containing transition metals, which uses an organic template agent in the specific preparation process.

[0005] Chinese patent document CN202010797179.3 discloses a CHA-type chalcogenide molecular sieve, its synthesis method, and its application, belonging to the field of chemical synthesis technology and its application. Specifically, it uses N,N,N-trialkyl-N-phenyl quaternary ammonium salts or quaternary ammonium base compounds as organic template agents to synthesize CHA-type chalcogenide molecular sieves.

[0006] Chinese patent document CN201610480629.X discloses a method for direct hydrothermal synthesis of medium-silica-alumina ratio chalcogenide. In the hydrothermal synthesis reaction of chalcogenide, no organic template agent or chalcogenide seed crystal is added. Instead, a weakly alkaline inorganic salt is added to obtain aluminosilicate zeolite molecular sieve with a chalcogenide structure.

[0007] Chinese patent document CN201610480630.2 discloses a method for synthesizing zeolite molecular sieves with a chabazite structure. The preparation method is as follows: in the reaction of synthesizing chabazite under hydrothermal conditions, no organic template agent or chabazite seed crystal is added. Instead, an organic weak base is added to obtain aluminosilicate zeolite molecular sieve with a chabazite structure and a framework silicon-aluminum atom molar ratio in the range of 4-40.

[0008] Chinese patent document CN201810031149.4 discloses a method for preparing and using low silicon-to-aluminum ratio chabazite. The preparation method mainly involves using silicon source, aluminum source and alkali as raw materials, calcining (high energy consumption) or adding chabazite seed crystals without adding organic template agents, fluoride ions, etc., and crystallizing in a high-pressure reactor to obtain low silicon-to-aluminum ratio chabazite with a silicon-to-aluminum ratio of 1.0 to 2.2.

[0009] Chinese patent document CN201110290616 discloses a method for synthesizing chabazite, specifically using a traditional hydrothermal synthesis method, which prepares chabazite by seed-directed crystal method without the addition of organic template agents.

[0010] Chinese patent document CN202210257343.0 discloses a method for preparing CHA zeolite from bleaching clay. Specifically, the method involves using powdered bleaching clay and CHA seed crystals to undergo a hydrothermal crystallization reaction to obtain CHA molecular sieve. The method includes: (1) selecting powdered bleaching clay; (2) preparing a KOH solution; (3) calcining the bleaching clay at high temperature to obtain amorphous powder; (4) adding the calcined bleaching clay to the prepared KOH solution, then adding 1-5% by mass of CHA seed crystals and mixing them uniformly to obtain a new reaction mixture; (5) adding the reaction mixture to a hydrothermal reactor for hydrothermal crystallization reaction; (6) removing the mixture after the reaction and filtering it, then drying the solid obtained after filtration to obtain the product CHA molecular sieve.

[0011] Chinese patent document CN201610497784.2 discloses a medium silicon-to-aluminum ratio aluminosilicate chabazite, wherein the silicon-to-aluminum atomic molar ratio of the aluminosilicate chabazite is 20-40. The aluminosilicate chabazite is prepared by mixing aluminum-source and silicon-source compounds with sodium hydroxide, potassium hydroxide, and a buffer in a molar ratio of Na2O:K2O:buffer:Al2O3:SiO2:H2O = (2-20):(2-20):(2-20):1:(40-80):(300-800). Specifically, the aluminum-source and silicon-source compounds are mixed evenly with sodium hydroxide, potassium hydroxide, and the buffer in the stated molar ratio; the mixture is allowed to stand at room temperature for 0.1-16 hours; then hydrothermally crystallized at 120-150 degrees Celsius for 2 to 5 days; and finally separated and washed to obtain the aluminosilicate chabazite.

[0012] Yin Xiaoyan et al. published an experimental study on the preparation of CHA-type zeolite by FAU-type zeolite transformation (Plastic Additives, No. 6, 2018). They first prepared octahedral zeolite molecular sieve FAU by hydrothermal synthesis, and then allowed it to transform into CHA-type zeolite molecular sieve.

[0013] Che Shuai published a paper on the successful synthesis of chabazite with a silicon-to-aluminum ratio of 2.25 using HY molecular sieve as raw material and holding at 95℃ for 15 days (Study on chabazite ion exchange modification and CO2 adsorption and separation performance, Northeastern University, Doctoral Dissertation, 2013).

[0014] Chinese patent document CN201010202727.X discloses the formation of pure chalcogenide through the permeation of heterogeneous T-type zeolite in the absence of organic template agents.

[0015] Chinese patent document CN202210612836.1 discloses a method for preparing low-silicon CHA-type molecular sieves. Specifically, potassium source, sodium source, silicon source, aluminum source and water are mixed to obtain an initial gel; then the initial gel is subjected to static hydrothermal crystallization at 140-180℃ for 2-6 days to obtain low-silicon CHA-type molecular sieves.

[0016] Chinese patent document CN202210392986.6 discloses a method for in-situ preparation of high-silicon CHA molecular sieve membranes. The method involves mixing a silicon source, an alkali source, an aluminum source, an organic structure-directing agent (OSDA), and water, and aging the mixture at room temperature to form a sol. A porous support is then immersed in the OSDA solution, and after drying, OSDA adheres to the surface of the porous support. The porous support is placed in a high-pressure reactor lined with polytetrafluoroethylene containing the aforementioned sol, and a crystallization reaction is performed under microwave heating. After cleaning, drying, and calcination, a high-silicon CHA molecular sieve membrane is obtained. However, the organic structure-directing agent OSDA volatilizes during the gelation process, and the synthesized molecular sieve must undergo a calcination process to remove the template agent before it can have a porous structure. The calcination process is generally carried out at high temperatures, resulting in high costs and the release of organic matter and CO2. Furthermore, the microwave heating method is difficult to operate and requires sophisticated equipment.

[0017] Therefore, existing methods for synthesizing CHA molecular sieves mainly employ organic templates, seed crystal methods, crystal transformation, and the use of organic weak bases or inorganic weak base salts. However, the use of organic templates is environmentally polluting, and organic templates are expensive, sometimes requiring high-temperature calcination to remove the template agent, resulting in high energy consumption. The crystal transformation method requires pre-prepared FAU zeolite and T-type zeolite crystals to be transformed into the CHA crystal form under specific conditions. Although it eliminates the need for organic template agents, the process is cumbersome and costly. Methods using inorganic / organic additives or seed crystals generally have certain requirements for the silicon source, and the crystallization time is relatively long; moreover, the seed crystal method requires the pre-preparation of CHA seeds, making the process cumbersome. Summary of the Invention

[0018] The purpose of this invention is to address the shortcomings of existing methods for preparing CHA molecular sieves, such as high raw material costs, lack of environmental friendliness, or long crystallization times. This invention provides a method for synthesizing chalcogenide with a CHA structure. This method produces CHA molecular sieves with eight-membered ring structural units in situ without the need for adding organic substances. Moreover, it has a short crystallization time, low cost, and is easy to operate and control.

[0019] To achieve the above objectives, the present invention provides a method for synthesizing chabazite with a CHA structure, comprising the following steps:

[0020] Step 1: Mix silicon source and aluminum source, or silicon source, aluminum source and sodium hydroxide, and then age to obtain NaY molecular sieve directing agent;

[0021] Step 2: Mix the silicon source, aluminum source, and NaY molecular sieve directing agent to form a gel;

[0022] Step 3: After the gel is mixed evenly with potassium hydroxide, it is crystallized, separated and washed to obtain the chalcogenide with the CHA structure;

[0023] In step 1, the molar ratio of each substance in the NaY molecular sieve directing agent is (10-18) SiO2 : (0.7-1.3) Al2O3 : (10-18) Na2O : (200-400) H2O, calculated as oxides (silicon in NaY molecular sieve directing agent as SiO2; aluminum in NaY molecular sieve directing agent as Al2O3; sodium in NaY molecular sieve directing agent as Na2O).

[0024] The molar ratio of each substance in the gel, calculated as oxides (silicon in the gel as SiO2, aluminum in the gel as Al2O3, and sodium in the gel as Na2O), is (1-6) Na2O:(0.7-1.3) Al2O3:(5-18) SiO2:(100-350) H2O.

[0025] The mass ratio of potassium hydroxide to the gel is (6-25):100.

[0026] In the synthesis method of chalcogenide with a CHA structure provided by this invention, when controlling the molar ratio of the NaY molecular sieve directing agent and the various substances in the gel, if necessary (e.g., when using standard industrial raw materials, since the concentrations are limited, it is impossible to accurately control the proportion of each material), low-alkalinity sodium aluminate or high-alkalinity sodium aluminate can be added to adjust the ratio of each material. If formulated raw materials are used, the adjustment of low-alkalinity sodium aluminate or high-alkalinity sodium aluminate is not required.

[0027] Both low-alkalinity sodium aluminate and high-alkalinity sodium aluminate are currently raw materials for the industrial synthesis of NaY molecular sieves. Their compositions are both Na2O and Al2O3, but the concentrations of low-alkalinity sodium aluminate and high-alkalinity sodium aluminate are different.

[0028] Optionally, in the method for synthesizing chamazolithium with a CHA structure provided by the present invention, the potassium hydroxide is a solid or an aqueous solution thereof, and solid potassium hydroxide is preferred to improve the yield.

[0029] Optionally, in step 3 of the synthesis method of chamazolithium with CHA structure provided by the present invention, in order to ensure the uniform dispersion of potassium hydroxide in the gel, the gel and potassium hydroxide are mixed and stirred for at least 10 minutes.

[0030] Optionally, in the synthesis method of chamazolithium with a CHA structure provided by the present invention, the crystallization time is 12-35 hours.

[0031] Optionally, in the synthesis method of chamazolithium with a CHA structure provided by the present invention, the crystallization temperature is 85–110°C. The crystallization is carried out in a closed container. If the closed container is pressure-resistant, the crystallization temperature can be increased to 110°C; if the closed container is not pressure-resistant, the crystallization temperature is controlled at 85–100°C.

[0032] Optionally, in the method for synthesizing chamazolithium with a CHA structure provided by the present invention, the NaY molecular sieve directing agent and the gel are calculated as Al2O3 respectively, and the mass ratio of the NaY molecular sieve directing agent to the gel is (3-30):100.

[0033] Optionally, in the synthesis method of chamazolithium with CHA structure provided by the present invention, in step 1, the aging temperature is 25-40°C and the time is 6-42 hours, preferably 15-40 hours.

[0034] Optionally, in the method for synthesizing chamazolithium with a CHA structure provided by the present invention, in step 2, after the silicon source and the NaY molecular sieve directing agent are mixed, an aluminum source is added at a uniform rate within 0.5 to 4 hours. After the aluminum source is completely added, the mixture is homogenized to obtain the gel.

[0035] Optionally, in the method for synthesizing chamazolithium with a CHA structure provided by the present invention, in step 2, the aluminum source can be added to the silicon source at a uniform rate within 0.5 to 4 hours. After the aluminum source is completely added, the NaY molecular sieve directing agent is added, and the mixture is homogenized to obtain the gel.

[0036] The homogenization methods and parameters described above are not specifically limited; any methods and parameters commonly used in the industry that can mix the substances evenly are acceptable. If stirring is chosen, mix for 0.5 to 4 hours until homogeneous.

[0037] Optionally, in the synthesis method of chamazolithium with CHA structure provided by the present invention, the silicon source can be any conventional one in the industry and is not specifically limited. For example, it can be selected from an organic silicon source or an inorganic silicon source. The present invention recommends an inorganic silicon source, preferably at least one of water glass, silica sol and silica gel.

[0038] The aluminum source can be any commonly used in the industry and is not specifically limited. It can be selected from organic or inorganic aluminum sources. This invention recommends inorganic aluminum sources, preferably at least one of aluminum sulfate, sodium aluminate and sodium aluminate.

[0039] Optionally, in step 2 of the synthesis method of chamazolithium with CHA structure provided by the present invention, when the silicon source is silica gel, it needs to be dissolved with sodium hydroxide solution. The concentration of silica gel and the concentration of sodium hydroxide solution are not specifically limited, as long as the molar ratio of each substance in the gel is met.

[0040] The method for synthesizing chamazolithium with a CHA structure provided by this invention produces chamazolithium with an eight-membered ring structure, and the synthesis time is short and the cost is lower.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] The present invention provides a method for synthesizing chalcogenide with a CHA structure. First, a NaY molecular sieve directing agent with a specific ratio is synthesized. Then, a gel with a specific ratio is formed. Finally, potassium hydroxide is added to the gel to directly synthesize a CHA molecular sieve with an eight-membered ring structure. The NaY molecular sieve directing agent added during gel synthesis introduces a specific crystal nucleus structure, while the addition of potassium hydroxide in step 3... + After ionization, the crystal nuclei are directed to form an eight-membered ring structure, ultimately resulting in chabazite with a CHA structure. The synthesis method provided by this invention requires no crystallization or seed crystals, no organic substances, and has a short crystallization time, low cost, and is easy to operate and control. If the proportions of the materials in the NaY molecular sieve directing agent or gel are not within the specified range, or if the amount of potassium hydroxide added is not within the specified range, the final product will not be chabazite with a CHA structure. Attached Figure Description

[0043] Figure 1 This is an electron microscope image of the chamaezig with a CHA structure synthesized in Example 1 of the present invention;

[0044] Figure 2 This is an electron microscope image of the chamaezig with a CHA structure synthesized in Example 2 of the present invention;

[0045] Figure 3 This is an electron microscope image of the chamaezig with a CHA structure synthesized in Example 3 of the present invention;

[0046] Figure 4 This is an electron microscope image of the chamaezig with a CHA structure synthesized in Example 4 of the present invention;

[0047] Figure 5 This is an electron microscope image of the chamaestone with a CHA structure synthesized in Example 5 of the present invention;

[0048] Figure 6 This is an electron microscope image of the NaY zeolite with FAU structure synthesized in Comparative Example 1 of this invention.

[0049] Figure 7 This is an electron microscope image of the zeolite sample synthesized in Comparative Example 4 of the present invention.

[0050] Figure 8 The image shows the XRD pattern of the chamaezig with a CHA structure synthesized in Example 1 of this invention.

[0051] Figure 9 The image shows the XRD pattern of the chamaezig with a CHA structure synthesized in Example 2 of this invention.

[0052] Figure 10 The image shows the XRD pattern of the chamaezig with a CHA structure synthesized in Example 3 of this invention.

[0053] Figure 11 The image shows the XRD pattern of the chamaezig with a CHA structure synthesized in Example 4 of this invention.

[0054] Figure 12 The image shows the XRD pattern of the chamaezig with a CHA structure synthesized in Example 5 of this invention.

[0055] Figure 13 The image shows the XRD pattern of the NaY zeolite with FAU structure synthesized in Comparative Example 1 of this invention.

[0056] Figure 14 The image shows the XRD pattern of the synthesized sample of Comparative Example 2 of this invention.

[0057] Figure 15 The image shows the XRD pattern of the synthesized sample of Comparative Example 3 of this invention.

[0058] Figure 16 The image shows the XRD pattern of the synthesized sample of Comparative Example 4 of this invention. Detailed Implementation

[0059] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0060] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0061] The grade of the raw materials mentioned below is not limited; any chemical raw materials of industrial grade or higher can meet the requirements of the technical solution of this invention. All raw materials used in the following embodiments and comparative examples are of industrial grade.

[0062] Evaluation and analysis methods:

[0063] Phase analysis conditions (X-ray diffraction analysis): Light source CuKα, tube voltage 40kV, tube current 20mA. Scanning speed 10° / min, scanning range 2θ = 4°-45°.

[0064] Electron microscopy testing conditions: Crystal morphology analysis was performed using a scanning electron microscope (model JSM-IT200) manufactured by Nippon Electron Ltd. JSM-IT200: The dried and ground sample was placed on conductive adhesive, and then the treated sample was placed under a vacuum of 10... -2 The sample was purified under the condition of pa, and then a scanning test was performed under the conditions of accelerating voltage of 5kV and working distance of 10mm.

[0065] Example 1

[0066] This embodiment provides a chalcogenide with a CHA structure, and the specific synthesis method is as follows:

[0067] 1) Weigh 162g of water glass, add 119g of high-alkalinity sodium aluminate, stir evenly, and then age at 35℃ for 16h to obtain NaY molecular sieve directing agent; the ratio of each substance in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317H2O.

[0068] 2) Weigh 165g of water glass, add 33g of the above-mentioned NaY molecular sieve directing agent, then add 70g of aluminum sulfate solution at a uniform rate over 45min, and finally add 35g of low-alkalinity sodium aluminate to adjust the proportion of each component. After homogenizing and stirring for 1h, a gel is obtained. The ratio of each substance in the gel is 2.1Na2O:1.0Al2O3:7.4SiO2:155H2O.

[0069] 3) Add 24g of potassium hydroxide solid to the above gel, stir for 15min, put it into a sealed crystallization jar, crystallize at 94℃ for 15h, filter, and wash with water to obtain sample S-1.

[0070] Example 2

[0071] This embodiment provides a chalcogenide with a CHA structure, and the specific synthesis method is as follows:

[0072] 1) Weigh 142g of water glass, add 105g of high-alkalinity sodium aluminate, stir evenly, and then age at 38℃ for 16h to obtain NaY molecular sieve directing agent. The ratio of each substance in the NaY molecular sieve directing agent is 12.6Na2O:0.8Al2O3:11.4SiO2:252.8H2O.

[0073] 2) Weigh 165g of water glass, add 24g of the above-mentioned NaY molecular sieve directing agent, add 46g of aluminum sulfate solution at a uniform rate over 45min, and then add 26g of low-alkalinity sodium aluminate to adjust the proportion of each component. After homogenizing and stirring for 1h, a gel is obtained; the ratio of each substance in the gel is 3.6Na2O:1.1Al2O3:11.6SiO2:221.7H2O.

[0074] 3) Add 30g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization jar; crystallize at 100℃ for 32h, filter, and wash with water to obtain sample S-2.

[0075] Example 3

[0076] This embodiment provides a chalcogenide with a CHA structure, and the specific synthesis method is as follows:

[0077] 1) Weigh 178g of water glass, add 121g of high-alkalinity sodium aluminate, stir evenly, and then age at 28℃ for 40h to obtain NaY molecular sieve directing agent. The ratio of each substance in the NaY molecular sieve directing agent is 17.6Na2O:1.1Al2O3:17.0SiO2:361.6H2O.

[0078] 2) 139g of aluminum sulfate solution was added to 165g of water glass at a uniform rate over 1.5h, followed by the addition of 26g of low-alkalinity sodium aluminate. After stirring for 30min, 140g of the aforementioned NaY molecular sieve directing agent was added, and the mixture was homogenized and stirred for 1h to obtain a gel. The ratio of substances in the gel was 1.7Na₂O:1.0Al₂O₃:6.1SiO₂:154.2H₂O:

[0079] 3) Add 52g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization jar; crystallize at 88℃ for 32h, filter, and wash with water to obtain sample S-3.

[0080] Example 4

[0081] This embodiment provides a chalcogenide with a CHA structure, and the specific synthesis method is as follows:

[0082] 1) Weigh 15g of sodium hydroxide and add it to 127g of silica sol. Then add 119g of highly alkaline sodium aluminate to the mixture. After stirring evenly, let it stand at 30℃ for 30h to obtain NaY molecular sieve directing agent. The ratio of each substance in the NaY molecular sieve directing agent is 16.4Na2O:0.9Al2O3:13.6SiO2:238.5H2O.

[0083] 2) Weigh 165g of silica sol, add 60g of the above-mentioned NaY molecular sieve directing agent, add 95g of aluminum sulfate solution at a uniform rate for 1h, then add 36g of low-alkalinity sodium aluminate, and stir homogenously for 2h to obtain a gel; the ratio of each substance in the gel is 3.0Na2O:1.2Al2O3:9.8SiO2:171.2H2O.

[0084] 3) Add 25g of potassium hydroxide solid to the above gel, stir for 30min, and then put it into a sealed crystallization jar; crystallize at 105℃ for 10h, filter, and wash with water to obtain sample S-4.

[0085] Example 5

[0086] This embodiment provides a chalcogenide with a CHA structure, and the specific synthesis method is as follows:

[0087] 1) Weigh 162g of water glass, add 119g of highly alkaline sodium aluminate, stir evenly, and then age at 35℃ for 24h to obtain NaY molecular sieve directing agent; the ratio of each substance in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317.0H2O;

[0088] 2) Weigh 165g of water glass, add 55g of the above-mentioned NaY molecular sieve directing agent, add 68g of aluminum sulfate solution at a uniform rate over 1 hour, then add 23g of low-alkalinity sodium aluminate to adjust the proportion of each component, stir homogenously for 1 hour, and obtain a gel; the ratio of each substance in the gel is 2.0Na2O:0.75Al2O3:6.6SiO2:139.2H2O;

[0089] 3) Add 45g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization jar; crystallize at 100℃ for 15h, filter, and wash with water to obtain sample S-5.

[0090] Example 6

[0091] This embodiment provides a chalcogenide with a CHA structure, and the specific synthesis method is as follows:

[0092] 1) Weigh 86g of water glass, add 60g of high-alkalinity sodium aluminate, stir evenly, and then age at 35℃ for 24h to obtain NaY molecular sieve directing agent; the ratio of each substance in the NaY molecular sieve directing agent is 17.6Na2O:1.1Al2O3:16.7SiO2:355.0H2O.

[0093] 2) Weigh 330g of water glass, add 45g of the above-mentioned NaY molecular sieve directing agent, add 78g of aluminum sulfate solution at a uniform rate over 1 hour, then add 22g of low-alkalinity sodium aluminate to adjust the proportion of each component, stir homogenously for 1 hour, and obtain a gel; the ratio of each substance in the gel is 5.4Na2O:1.25Al2O3:18.0SiO2:323H2O;

[0094] 3) Add 100g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization jar; crystallize at 100℃ for 15h, filter, and wash with water to obtain sample S-6.

[0095] Comparative Example 1

[0096] This comparative example provides a zeolite, and the specific synthesis method is as follows:

[0097] 1) Weigh 162g of water glass, add 119g of high-alkalinity sodium aluminate, stir evenly, and then age at 35℃ for 16h to obtain NaY molecular sieve directing agent; the ratio of each substance in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317H2O.

[0098] 2) Weigh 165g of water glass, add 33g of the above molecular sieve directing agent, add 70g of aluminum sulfate solution at a uniform rate over 45min, and then add 35g of low-alkalinity sodium aluminate to adjust the proportion of each component. After homogenizing and stirring for 1h, a gel is obtained; the ratio of each substance in the gel is 2.1Na2O:1.0Al2O3:7.4SiO2:155H2O.

[0099] 3) The above gel was placed into a sealed crystallization vessel; crystallized at 94°C for 28 hours, filtered, and washed with water to obtain sample C-1.

[0100] Comparative Example 2

[0101] This comparative example provides a zeolite, and the specific synthesis method is as follows:

[0102] 1) Weigh 162g of water glass, add 119g of high-alkalinity sodium aluminate, stir evenly, and then age at 35℃ for 16h to obtain NaY molecular sieve directing agent; the ratio of each substance in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317H2O.

[0103] 2) Weigh 165g of water glass, add 33g of the above-mentioned NaY molecular sieve directing agent, add 24g of potassium hydroxide solid, stir for 15min, then add 70g of aluminum sulfate solution at a uniform rate for 45min, and then add 35g of low-alkalinity sodium aluminate to adjust the proportion of each component. After homogenizing and stirring for 1h, a gel is obtained. The ratio of each substance in the gel is 2.1Na2O:1.0Al2O3:7.4SiO2:155H2O:3.2K2O. The gel is placed in a sealed crystallization jar and crystallized at 94℃ for 15h. After filtration and washing with water, sample C-2 is obtained.

[0104] Comparative Example 3

[0105] This comparative example provides a zeolite, and the specific synthesis method is as follows:

[0106] 1) Weigh 162g of water glass, add 119g of high-alkalinity sodium aluminate, stir evenly, and then age at 35℃ for 16h to obtain NaY molecular sieve directing agent; the ratio of each substance in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317H2O.

[0107] 2) Weigh 234g of water glass, add 39g of the above-mentioned NaY molecular sieve directing agent, then add 35g of aluminum sulfate solution at a uniform rate over 45min, and finally add 39g of low-alkalinity sodium aluminate to adjust the proportion of each component. After homogenizing and stirring for 1h, a gel is obtained; the ratio of each substance in the gel is 9.0Na2O:1.3Al2O3:20.0SiO2:320H2O.

[0108] 3) Add 12g of potassium hydroxide solid to the above gel, stir for 15min, put it into a sealed crystallization jar, crystallize at 94℃ for 15h, filter, and wash with water to obtain sample C-3.

[0109] Comparative Example 4

[0110] This comparative example provides a zeolite, and the specific synthesis method is as follows:

[0111] 1) Weigh 162g of water glass, add 119g of high-alkalinity sodium aluminate, stir evenly, and then age at 35℃ for 16h to obtain NaY molecular sieve directing agent; the ratio of each substance in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317H2O.

[0112] 2) Weigh 165g of water glass, add 33g of the above-mentioned NaY molecular sieve directing agent, then add 70g of aluminum sulfate solution at a uniform rate over 45min, and finally add 35g of low-alkalinity sodium aluminate to adjust the proportion of each component. After homogenizing and stirring for 1h, a gel is obtained; the ratio of each substance in the gel is 2.1Na2O:1.0Al2O3:7.4SiO2:155H2O.

[0113] 3) Add 7.5g of potassium hydroxide solid to the above gel, stir for 15min, put it into a sealed crystallization jar, crystallize at 94℃ for 15h, filter, and wash with water to obtain sample C-4.

[0114] The samples prepared in the above embodiments and comparative examples were scanned by electron microscopy, specifically as follows: Figure 1-7 As shown, by Figure 1-5 It can be seen that the zeolite sample provided by this invention has a spherical crystal structure, an outer surface resembling a ball of yarn, non-agglomerated grains, and a size of 2-3 μm, indicating that it is a chalcogenide zeolite with a CHA structure. Figure 6 It can be seen that the zeolite is a Y-type molecular sieve of octahedral zeolite, with a crystal size of 300-400 nm. This indicates that the sample prepared in Comparative Example 1 is a NaY zeolite with a FAU structure, not a chamazolithite with a CHA structure. Therefore, it can be concluded that without the addition of potassium hydroxide, under the same conditions, it is impossible to prepare a chamazolithite with a CHA structure. Figure 7 It can be seen that the crystals of the zeolite molecular sieve obtained in Comparative Example 4 contain both the crystal morphology of Y-type molecular sieve and the crystals of chalcogenide, indicating that when the amount of potassium hydroxide added is low, the obtained molecular sieve is not a pure phase of chalcogenide.

[0115] The zeolite samples prepared in the above examples and comparative examples were subjected to X-ray diffraction (XRD) analysis and testing, specifically as follows: Figures 8-16 As shown. By Figures 8-12 It can be seen that the samples prepared by the method provided in this invention have 2θ = 8.6-9.0°, 12.6-13.0°, 17.7-2-17.1°, 20.4-20.8°, 21.9-22.3°, 28.4-28.8°, 24.7-25.1°, and 38.8-39.2°, all of which are typical diffraction peaks of CHA-structured chabazite, indicating that they all possess a CHA structure, which is consistent with the results of electron microscopy. Figure 13 It can be seen that 2θ = 6.2°, 10.1°, 11.9°, 15.6°, 18.7°, 20.4°, 23.6°, 27.0°, 31.4°, 34.8°, and 37.9° are typical XRD diffraction peaks of Y-type molecular sieves, indicating that the sample prepared in Comparative Example 1 is NaY zeolite with a FAU structure, which is consistent with... Figure 6 The results are consistent. (By...) Figure 14 and Figure 15 As can be seen, the XRD test results show no characteristic diffraction peaks, indicating that they are all amorphous structures without any crystal form. This suggests that the samples prepared in Comparative Examples 2-3 are not chalcogenide and do not possess a CHA structure. Figure 16 It can be seen that the XRD results show that the characteristic diffraction peaks of the sample prepared in Comparative Example 4 include both Y-type zeolite and chalcogenide, and the obtained sample has a mixed-crystal molecular sieve structure.

[0116] Example 6 used the same method to perform electron microscopy and XRD tests, and the results of electron microscopy were consistent with... Figure 1-5 Essentially the same: the crystal structure is spherical, the outer surface resembles a ball of yarn, the grains do not agglomerate, and the size is 2–3 μm; XRD test results are similar to... Figure 8-12 The diffraction peaks are basically the same, and the product obtained in Example 6 is a chamazolithium with a CHA structure.

[0117] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for the synthesis of a chabazite zeolite having a CHA structure, characterized in that, Includes the following steps: Step 1: Mix silicon source and aluminum source, or silicon source, aluminum source and sodium hydroxide, and then age to obtain NaY molecular sieve directing agent; Step 2: Mix the silicon source, aluminum source, and NaY molecular sieve directing agent to form a gel; Step 3: After mixing the gel with potassium hydroxide evenly, crystallize for 10-40 hours, separate and wash to obtain the chalcogenide with CHA structure; Based on oxides, the molar ratio of each substance in the NaY molecular sieve directing agent is (10~18) SiO2:(0.7~1.3)Al2O3:(10~18) Na2O:(200~400) H2O; Based on oxides, the molar ratio of each substance in the gel is (1~6) Na2O:(0.7~1.3) Al2O3:(5~18) SiO2:(100~350) H2O; The mass ratio of potassium hydroxide to the gel is (6~25):100; The synthesis method yields CHA molecular sieves with eight-membered ring structural units in situ.

2. The method of synthesis of claim 1, wherein, The crystallization time is 10~35h.

3. The method of synthesis of claim 1, wherein, The crystallization temperature is 85~110℃.

4. The method of synthesis of claim 1, wherein, The NaY molecular sieve directing agent and the gel are calculated based on Al2O3, and the mass ratio of the NaY molecular sieve directing agent to the gel is (3~30):

100.

5. The synthesis method according to claim 1, characterized in that, In step 1, the aging temperature is 25~40℃ and the time is 6~42h.

6. The synthesis method according to claim 1, characterized in that, In step 2, after the silicon source and the NaY molecular sieve directing agent are mixed evenly, the aluminum source is added at a uniform rate over a period of 0.5 to 4 hours. After the aluminum source has been added, the mixture is homogenized to obtain the gel.

7. The synthesis method according to claim 1, characterized in that, The silicon source is selected from organic silicon sources or inorganic silicon sources.

8. The synthesis method according to claim 1, characterized in that, The aluminum source is selected from organic aluminum sources or inorganic aluminum sources.

9. The synthesis method as described in claim 5, characterized in that, In step 1, the aging time is 15-40 hours.

10. The synthesis method according to claim 7, characterized in that, The silicon source is selected from inorganic silicon sources.

11. The synthesis method according to claim 7, characterized in that, The silicon source is selected from at least one of water glass, silica sol, and silica gel.

12. The synthesis method according to claim 8, characterized in that, The aluminum source is selected from inorganic aluminum sources.

13. The synthesis method as described in claim 8, characterized in that, The aluminum source is selected from at least one of aluminum sulfate, sodium aluminate, and sodium metaaluminate.

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