A method for the synthesis of a zeolitic molecular sieve

Abstract

This invention discloses a method for synthesizing zeolite molecular sieves. A silicon source and an aluminum source, or a silicon source, an aluminum source, and sodium hydroxide are mixed and aged to obtain a NaY molecular sieve directing agent. This NaY agent is then mixed with a silicon source, an aluminum source, and a recycled mother liquor to form a gel. The gel is then mixed evenly with potassium hydroxide, crystallized, separated, and washed with water to obtain a solid zeolite molecular sieve with a CHA structure and a crystallization mother liquor. The crystallization mother liquor is mixed and stirred with an aluminum sulfate solution, separated, and washed with water to obtain a recycled mother liquor. This invention, by limiting the molar ratio of each substance in the NaY molecular sieve directing agent and the gel, as well as the amount of potassium hydroxide added, and by utilizing the raw materials in the recycled crystallization mother liquor, further improves the utilization rate of raw materials, reduces costs, and is environmentally friendly.

Description

Technical Field

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

[0002] In recent years, with the rapid development of industry, the greenhouse effect has become one of the most concerning environmental issues. The greenhouse effect leads to global warming, accelerated glacial melting, rising sea levels, increased pests and diseases, abnormal climate, and desertification, among other things. The main cause of the greenhouse effect is the large-scale emission of greenhouse gases (GHGs), with CO2 having the greatest impact on global climate change. Given the significant technological and economic challenges currently facing the development and application of new energy sources, experts generally predict that fossil fuels will remain the world's primary energy source for the next 50 years, and CO2 emissions will continue to increase. Therefore, issues related to CO2 emission reduction, recycling, fixation, and utilization are particularly important.

[0003] The internal pores of zeolite molecular sieves can adsorb molecules. Due to the cleanliness of these pores and the uniform pore size distribution, they can selectively adsorb molecules of a certain size while repelling larger molecules. Therefore, zeolite molecular sieves can be used to recover and reuse CO2; among them, chalcogenite, with its unique molecular gate effect, can efficiently adsorb and separate CO2.

[0004] Traditionally, chabazite is synthesized using organic templates. For example, Chinese patent document CN202010797179.3 discloses a CHA-type zeolite molecular sieve and its synthesis method and application. Specifically, it uses N,N,N-trialkyl-N-phenyl quaternary ammonium salts or quaternary ammonium base compounds as organic templates to synthesize CHA-type zeolite molecular sieves. Paul Webley et al. (Adsorption, 2005, 11: 173-177) synthesized CHA-type chabazite with a silicon-to-aluminum ratio of 2.4 by using a ratio of 0.16 (TMA): 6.67 Na2O: 2.2 K2O: 17.5 SiO2: Al2O3: 276 H2O under hydrothermal conditions at 85℃ for 4 days. Trimericic anhydride (TMA) was added during the synthesis process. However, the method of preparing chabazite using organic templates is not only environmentally polluting, but also involves expensive organic templates, which may even require high-temperature calcination to remove the template, resulting in high energy consumption.

[0005] To address the aforementioned problems associated with using organic templates, researchers have developed methods for synthesizing chalcogenide without template agents, by adding inorganic / organic additives or seed crystals. This not only avoids the use of expensive template agents but also solves the environmental problems caused by the calcination of template agents after synthesis. For example, Chinese patent document CN201610480629.X discloses a method for the direct hydrothermal synthesis of chalcogenide with a medium silica-to-alumina ratio. In the hydrothermal synthesis reaction of chalcogenide, no organic template agent or chalcogenide seed crystals are added; instead, a weakly basic inorganic salt is added to obtain an aluminosilicate zeolite molecular sieve with a chalcogenide structure. Chinese patent document CN201610480630.2 discloses a method for synthesizing zeolite molecular sieves with a chalcogenide structure. The preparation method involves: in the hydrothermal synthesis reaction of chalcogenide, no organic template agent or chalcogenide seed crystals are added; instead, a weak organic base is added to obtain an aluminosilicate zeolite molecular sieve with a chalcogenide structure and a framework silica-to-alumina molar ratio in the range of 4-40.

[0006] Chinese patent document CN201810031149.4 discloses a method for preparing and using low-silicon-aluminum-ratio chamazolithium. The preparation method mainly involves using silicon source, aluminum source, and alkali as raw materials, and calcining (high energy consumption) or adding chamazolithium seed crystals without adding organic template agents or fluoride ions, followed by crystallization in a high-pressure reactor to obtain low-silicon-aluminum-ratio chamazolithium with a silicon-aluminum ratio of 1.0 to 2.2. Chinese patent document CN201110290616 discloses a method for synthesizing chamazolithium, specifically employing a traditional hydrothermal synthesis method, preparing chamazolithium through a seed-directed method without adding organic template agents.

[0007] 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.

[0008] 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.

[0009] In summary, methods using inorganic / organic additives or seed crystals generally have certain requirements for the silicon source and require a relatively long crystallization time; moreover, the seed crystal method requires the prior preparation of CHA seed crystals, making the process cumbersome.

[0010] To address the problems associated with the aforementioned methods using inorganic / organic additives or seed crystals, researchers have also explored the preparation of chabazite via a crystallization method. For example, Yin Xiaoyan et al. published an experimental study on the crystallization preparation of CHA-type zeolite from FAU-type zeolite (Plastic Additives, 2018, No. 6), first preparing an octahedral zeolite molecular sieve FAU via hydrothermal synthesis, and then allowing it to crystallize to form a CHA-type zeolite molecular sieve. Che Shuai published a study on the successful synthesis of chabazite with a silicon-to-aluminum ratio of 2.25 using HY molecular sieve as raw material and maintaining a temperature of 95℃ for 15 days (Study on ion exchange modification and CO2 adsorption and separation performance of chabazite, Northeastern University, Doctoral Dissertation, 2013). Chinese patent document CN201010202727.X discloses the formation of pure chabazite through the permeation of heterogeneous T-type zeolite nuclei under conditions without organic template agents. 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.

[0011] It is evident that the crystal transformation method requires pre-prepared FAU zeolite and T-type zeolite crystals to be transformed into CHA crystal form under certain conditions, which involves cumbersome steps and high costs. Summary of the Invention

[0012] To address the existing problems and areas for improvement in the preparation of zeolite molecular sieves, this invention provides a method for preparing zeolite molecular sieves. This method allows for the reuse of nutrients from the crystallization mother liquor, offering advantages such as low cost, environmental friendliness, and no silicon-containing wastewater discharge. Furthermore, the method is performed at room temperature, is simple to operate, and is easy to control.

[0013] To achieve the above objectives, the present invention provides a method for synthesizing zeolite molecular sieves, comprising the following steps:

[0014] 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;

[0015] Step 2: Mix the silicon source, aluminum source, mother liquor recycled adhesive, and the NaY molecular sieve directing agent to form a gel;

[0016] Step 3: After mixing the gel with potassium hydroxide evenly, crystallize for 10-40 hours, then separate to obtain zeolite molecular sieve and crystallization mother liquor;

[0017] Step 4: Mix and stir the crystallization mother liquor with aluminum sulfate solution, filter and separate, and wash the obtained solid with water to obtain mother liquor reuse gel, which can be used in step 2 for the next synthesis;

[0018] The chabazite has a CHA structure.

[0019] The molar ratio of each substance in the NaY molecular sieve directing agent, calculated as oxides (silicon in the NaY molecular sieve directing agent as SiO2; aluminum in the NaY molecular sieve directing agent as Al2O3; sodium in the NaY molecular sieve directing agent as Na2O), is (10-18)SiO2:(0.7-1.3)Al2O3:(10-18)Na2O:(200-400)H2O;

[0020] The molar ratio of each substance in the gel is (1-6) Na2O: (0.7-1.3) Al2O3: (5-18) SiO2: (100-350) H2O, calculated by oxides (SiO2 is the amount of silicon in the gel in step 2, Al2O3 is the amount of aluminum in the gel, and Na2O is the amount of sodium in the gel).

[0021] In step 2, the mass ratio of potassium hydroxide to the gel is (2-15):100.

[0022] In the synthesis method of zeolite molecular sieves 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.

[0023] 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.

[0024] Optionally, in step 4 of the synthesis method of zeolite molecular sieve provided by the present invention, the crystallization mother liquor is calculated as SiO2, the aluminum sulfate solution is calculated as Al2O3, and the molar ratio of the crystallization mother liquor to the aluminum sulfate solution is 3 to 12. In order to achieve a silicon dioxide recovery rate of more than 90% in the crystallization mother liquor, the molar ratio of the crystallization mother liquor to the aluminum sulfate solution is preferably 6 to 9.

[0025] Optionally, in step 2 of the method for synthesizing zeolite molecular sieves provided by the present invention, the SiO2 in the mother liquor recycled gel accounts for 10% to 50% of the SiO2 in the gel.

[0026] Optionally, in step 3 of the synthesis method of zeolite molecular sieve 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.

[0027] Optionally, in step 3 of the synthesis method of zeolite molecular sieve 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.

[0028] Optionally, in the synthesis method of zeolite molecular sieve provided by the present invention, the crystallization time is 12-35 hours, and 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.

[0029] Optionally, in the synthesis method of zeolite molecular sieve provided by the present invention, the NaY molecular sieve directing agent and the gel are respectively calculated as Al2O3, and the mass ratio of the NaY molecular sieve directing agent to the gel is (3~30):100.

[0030] Optionally, in the synthesis method of zeolite molecular sieve 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.

[0031] Optionally, in the synthesis method of zeolite molecular sieve provided by the present invention, in step 2, after the silicon source, the mother liquor recycled gel 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.

[0032] Optionally, in the synthesis method of zeolite molecular sieve provided by the present invention, in step 2, the aluminum source can be added uniformly to the mixture of the silicon source and the mother liquor recycled adhesive within 0.5 to 4 hours. After the aluminum source is added, the NaY molecular sieve directing agent is added, and the mixture is homogenized to obtain the gel.

[0033] 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.

[0034] Optionally, in the synthesis method of zeolite molecular sieves 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 organic silicon source or inorganic silicon source. The present invention recommends inorganic silicon source, preferably at least one of water glass, silica sol and silica gel.

[0035] 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.

[0036] Optionally, in step 2 of the synthesis method of zeolite molecular sieve 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.

[0037] The synthesis method of zeolite molecular sieve provided by the present invention is that the zeolite molecular sieve has a CHA structure and an eight-membered ring structure. Moreover, the crystallization mother liquor containing a large amount of silicon material obtained in the synthesis process can be recycled, which greatly improves the utilization rate of raw materials, reduces costs and wastewater discharge in the synthesis process.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] The method for synthesizing zeolite molecular sieves provided by this invention first synthesizes a NaY molecular sieve directing agent with a specific ratio. Then, a mother liquor recycled gel prepared from the crystallization mother liquor generated in the previous batch synthesis is used as one of the raw materials to form a gel with a specific ratio. Finally, potassium hydroxide is added to the gel to directly synthesize the zeolite molecular sieve. The preparation of the mother liquor recycled gel through crystallization mother liquor significantly improves the utilization rate of various molecular sieve synthesis raw materials, resulting in a substantial reduction in wastewater discharge during the synthesis process. Furthermore, the mother liquor contains a small amount of chalcogenide microparticles, which can act as seed crystals to induce the growth of molecular sieves during crystallization, and also reduce the amount of potassium hydroxide used in the synthesis process. The synthesis method provided by this invention requires no additional crystallization or seed crystals, no addition of organic / inorganic substances, and features short crystallization time, low cost, and easy operation and control under normal pressure. Attached Figure Description

[0040] Figure 1 This is an electron microscope image of the zeolite molecular sieve synthesized in Example 1 of the present invention;

[0041] Figure 2 This is an electron microscope image of the zeolite molecular sieve synthesized in Example 2 of the present invention;

[0042] Figure 3 This is an electron microscope image of the zeolite molecular sieve synthesized in Example 3 of the present invention;

[0043] Figure 4 This is an electron microscope image of the zeolite molecular sieve synthesized in Example 4 of the present invention;

[0044] Figure 5 This is an electron microscope image of the zeolite molecular sieve synthesized in Example 5 of the present invention;

[0045] Figure 6 This is an electron microscope image of the zeolite molecular sieve synthesized in Comparative Example 1 of the present invention.

[0046] Figure 7 The image shows the XRD pattern of the zeolite molecular sieve synthesized in Example 1 of this invention.

[0047] Figure 8 The image shows the XRD pattern of the zeolite molecular sieve synthesized in Example 2 of this invention.

[0048] Figure 9 The image shows the XRD pattern of the zeolite molecular sieve synthesized in Example 3 of this invention.

[0049] Figure 10 The XRD pattern of the zeolite molecular sieve synthesized in Example 4 of this invention;

[0050] Figure 11 The image shows the XRD pattern of the zeolite molecular sieve synthesized in Example 5 of this invention.

[0051] Figure 12 The image shows the XRD pattern of the zeolite molecular sieve synthesized in Comparative Example 1 of this invention. Detailed Implementation

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Evaluation and analysis methods:

[0056] 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°.

[0057] 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.

[0058] Example 1

[0059] This embodiment provides a zeolite molecular sieve, and the specific synthesis method is as follows:

[0060] Preparation of mother liquor recycled adhesive:

[0061] 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.

[0062] 2) Weigh 660g of water glass, add 90g of the above-mentioned NaY molecular sieve directing agent, mix well, and then add 156g of aluminum sulfate solution at a uniform rate over 1 hour. Then add 44g of low-alkalinity sodium aluminate to adjust the proportion of each component. After homogenizing and stirring for 1 hour, a gel is obtained. The ratio of each substance in the gel is 5.4Na2O:1.25Al2O3:18.0SiO2:323H2O.

[0063] 3) Add 100g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization tank; crystallize at 100℃ for 15h, filter, and wash with 394g of water. The resulting liquid is the crystallization mother liquor, and the solid is chalcogenide with CHA structure.

[0064] 4) Take 252 mL of crystallization mother liquor and add it to 103 mL of aluminum sulfate. Stir for 30 min, filter and wash with water. The solid obtained is the mother liquor reuse gel. The molar ratio of SiO2 provided by the mother liquor to Al2O3 provided by aluminum sulfate is 5.5.

[0065] Preparation of zeolite molecular sieves:

[0066] 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.

[0067] 2) Weigh 165g of water glass, add 240g of the above-mentioned mother liquor recycled adhesive and 62g of the above-mentioned NaY molecular sieve directing agent, mix well, add 78g of aluminum sulfate solution at a uniform rate for 45min, and finally add 42g 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:1.0Al2O3:7.4SiO2:170H2O.

[0068] 3) Add 18g of potassium hydroxide solid to the above gel, stir for 15min, put it into a sealed crystallization tank, crystallize at 94℃ for 15h, filter, wash the obtained solid with 350g of water to obtain zeolite molecular sieve, and the obtained liquid (the mixture of the filtered liquid and the washed liquid) is the crystallization mother liquor.

[0069] 4) Take 252 mL of crystallization mother liquor and add it to 52 mL of aluminum sulfate. Stir for 30 min, filter, and wash with water. The solid obtained is the mother liquor reuse gel. The molar ratio of SiO2 provided by the mother liquor to Al2O3 provided by aluminum sulfate is 11.0.

[0070] Example 2

[0071] This embodiment provides a zeolite molecular sieve, 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 125g of the mother liquor recycled adhesive prepared in Example 1 and 93g of the above-mentioned NaY molecular sieve directing agent, mix well, and then add 62g of aluminum sulfate solution at a uniform rate for 45min. After homogenization and stirring for 1h, a gel is obtained; the ratio of each substance in the gel is 3.6Na2O:1.1Al2O3:11.6SiO2:217H2O.

[0074] 3) Add 30g of potassium hydroxide solid to the above gel, stir for 15min, put it into a sealed crystallization tank, crystallize at 100℃ for 32h, filter, wash the obtained solid with 266g of water to obtain zeolite molecular sieve, and the liquid (the mixture of the filtered liquid and the washed liquid) is the crystallization mother liquor.

[0075] 4) Take 251 mL of crystallization mother liquor and add it to 87 mL of aluminum sulfate. Stir for 30 min, filter, and wash with water to obtain mother liquor reuse gel. The molar ratio of SiO2 provided by the crystallization mother liquor to Al2O3 provided by aluminum sulfate is 6.5.

[0076] Example 3

[0077] This embodiment provides a zeolite molecular sieve, and the specific synthesis method is as follows:

[0078] 1) Weigh 162g of water glass, add 119g of high-alkalinity sodium aluminate, stir evenly, and then age at 37℃ for 8h 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;

[0079] 2) Weigh 165g of water glass, add 32g of the above-mentioned NaY molecular sieve directing agent and 65g of the mother liquor recycled adhesive prepared in Example 2, mix well, add 73g of aluminum sulfate solution at a uniform rate for 1 hour, then add 50g of low-alkalinity sodium aluminate to adjust the proportion of each component, stir homogenously for 1 hour to obtain a gel; the ratio of each substance in the gel is 2.0Na2O:1.0Al2O3:6.6SiO2:159.2H2O;

[0080] 3) Add 52g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization tank; crystallize at 105℃ for 12h, filter, and wash with 231g of water to obtain zeolite molecular sieve. The liquid (the mixture of the filtered liquid and the washed liquid) is the crystallization mother liquor.

[0081] 4) Take 251 mL of crystallization mother liquor and add it to 76 mL of aluminum sulfate. Stir for 30 min, filter, and wash with water to obtain mother liquor reuse gel. The molar ratio of SiO2 provided by the crystallization mother liquor to Al2O3 provided by aluminum sulfate is 7.5.

[0082] Example 4

[0083] This embodiment provides a zeolite molecular sieve, and the specific synthesis method is as follows:

[0084] 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.

[0085] 2) 84g of aluminum sulfate solution was added at a constant rate to a mixture of 165g of water glass and 165g of the mother liquor recycled adhesive prepared in Example 3 over 1.5 hours. Then, 63g of low-alkalinity sodium aluminate was added, and the mixture was stirred for 30 minutes. After stirring for 1 hour, 32g of the aforementioned NaY molecular sieve directing agent was added, and the mixture was homogenized and stirred for 1 hour to obtain a gel. The ratio of the substances in the gel was 1.7 Na₂O: 1.0 Al₂O₃: 6.1 SiO₂: 152H₂O:

[0086] 3) Add 42g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization tank; crystallize at 88℃ for 32h, filter, and wash with 305g of water to obtain zeolite molecular sieve. The liquid (the mixture of the filtered liquid and the washed liquid) is the crystallization mother liquor.

[0087] 4) Take 251 mL of crystallization mother liquor and add it to 67 mL of aluminum sulfate. Stir for 30 min, filter, and wash with water to obtain mother liquor reuse gel. The molar ratio of SiO2 provided by the crystallization mother liquor to Al2O3 provided by aluminum sulfate is 8.5.

[0088] Example 5

[0089] This embodiment provides a zeolite molecular sieve, and the specific synthesis method is as follows:

[0090] 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.

[0091] 2) Weigh 165g of water glass, add 48g of the above-mentioned NaY molecular sieve directing agent and 250g of the mother liquor recycled adhesive prepared in Example 4, mix well, add 4.1g of aluminum sulfate solution at a uniform rate over 4 hours, then add 12g of low-alkalinity sodium aluminate to adjust the proportion of each component, stir homogenously for 1 hour to obtain a gel; the ratio of each substance in the gel is 5.5Na2O:1.3Al2O3:17.6SiO2:303.5H2O;

[0092] 3) Add 48g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization tank; crystallize at 96℃ for 22h, filter, and wash with 275g of water to obtain zeolite molecular sieve. The liquid (the mixture of the filtered liquid and the washed liquid) is the crystallization mother liquor.

[0093] 4) Take 125 mL of crystallization mother liquor and add it to 14 mL of aluminum sulfate. Stir for 30 min, filter, and wash with water to obtain mother liquor reuse gel. The molar ratio of SiO2 provided by the crystallization mother liquor to Al2O3 provided by aluminum sulfate is 3.5.

[0094] Comparative Example 1

[0095] This comparative example provides a zeolite molecular sieve, and the specific synthesis method is as follows:

[0096] 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.

[0097] 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.

[0098] 3) Add 24g of potassium hydroxide solid to the above gel, stir for 15min, put it into a sealed crystallization tank, crystallize at 94℃ for 15h, filter, and wash with water to obtain solid zeolite molecular sieve.

[0099] Comparative Example 2

[0100] This comparative example provides a zeolite, and the specific synthesis method is as follows:

[0101] 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.

[0102] 2) Weigh 165g of water glass, add 50g of the above-mentioned NaY molecular sieve directing agent, add 53g of aluminum sulfate solution at a uniform rate over 45min, and then add 13g 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.

[0103] 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 a solid zeolite molecular sieve.

[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 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;

[0107] 2) Weigh 165g of water glass, add 27g of the above-mentioned NaY molecular sieve directing agent, add 70g of aluminum sulfate solution at a uniform rate over 1 hour, then add 47g 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:1.0Al2O3:6.6SiO2:149.2H2O;

[0108] 3) Add 45g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization tank; crystallize at 88℃ for 32h, filter, and wash with water to obtain solid zeolite molecular sieve.

[0109] Comparative Example 4

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

[0111] 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.

[0112] 2) 75g of aluminum sulfate solution was added to 165g of water glass at a uniform rate over 1.5 hours. Then, 50g of low-alkalinity sodium aluminate was added, and the mixture was stirred for 30 minutes. Afterward, 20g of the aforementioned NaY molecular sieve directing agent was added, and the mixture was homogenized and stirred for 1 hour to obtain a gel. The ratio of substances in the gel was 1.7Na₂O:1.0Al₂O₃:6.1SiO₂:142.8H₂O:

[0113] 3) Add 42g of potassium hydroxide solid to the above gel, stir for 15min, and then put it into a sealed crystallization tank; crystallize at 94℃ for 22h, filter, and wash with water to obtain solid zeolite molecular sieve.

[0114] The zeolite molecular sieves prepared in the above embodiments and Comparative Example 1 were respectively subjected to electron microscopy scanning, such as... Figure 1-6 As shown, by Figure 1-6 It can be seen that the zeolite molecular sieves prepared by the preparation method provided by the present invention and the zeolite molecular sieves prepared by Comparative Example 1 both have spherical crystal structures, with an outer surface resembling a ball of yarn. The crystal grains are basically non-agglomerated and have a size of 2-3 μm, indicating that they are both chalcogenide.

[0115] The zeolite molecular sieves prepared in the above embodiments and Comparative Example 1 were subjected to X-ray diffraction (XRD) analysis, as follows: Figure 7-12 As shown. By Figure 7-12 It can be seen that the 2θ values ​​of the zeolite molecular sieves prepared by the method provided in this invention and the zeolite molecular sieves prepared in Comparative Example 1 are 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°, which are typical diffraction peaks of chabazite with a CHA structure. This is consistent with the results of electron microscopy, indicating that the zeolite molecular sieves prepared by the methods provided in this invention and Comparative Example 1 are chabazite with a CHA structure.

[0116] Table 1 shows the following parameters for the gel preparation process (i.e., step 2) in each embodiment and comparative example: the mass of fresh water glass raw material used, the mass of the gel obtained, the mass ratio of water glass to gel, and the proportion of silicon source provided by the recycled mother liquor. The silicon source in the gel is provided by fresh water glass and recycled mother liquor; the proportion of silicon source provided by the recycled mother liquor refers to the proportion of silicon source in the recycled mother liquor to the total silicon source in the gel.

[0117] Table 1

[0118]

[0119]

[0120] The zeolite molecular sieves with CHA structure obtained in all embodiments and comparative examples of this invention are shown in the table above. Compared with comparative examples 1-4, which did not add mother liquor recycled gel and used fresh water glass as the source of silicon in the gel, this invention uses mother liquor recycled gel, which significantly reduces the proportion of fresh water glass. This indicates that the preparation method provided by this invention can improve the utilization rate of silicon source.

[0121] 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 zeolitic molecular sieve, 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, mother liquor recycled adhesive, and the NaY molecular sieve directing agent to form a gel; Step 3: After mixing the gel with potassium hydroxide evenly, crystallize for 10-40 hours, then separate to obtain zeolite molecular sieve and crystallization mother liquor; Step 4: Mix and stir the crystallization mother liquor with aluminum sulfate solution, separate, wash with water, and obtain mother liquor reuse adhesive; The zeolite molecular sieve has a 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 (2~15):100; The zeolite microparticles in the mother liquor recycled adhesive are used to induce the growth of zeolite molecular sieves during the crystallization process.

2. The synthesis method according to claim 1, characterized in that, In step 4, the crystallization mother liquor is calculated as SiO2, and the aluminum sulfate solution is calculated as Al2O3. The molar ratio of the crystallization mother liquor to the aluminum sulfate solution is 3~12.

3. The synthesis method as described in claim 1, characterized in that, In step 2, the SiO2 in the mother liquor recycled gel accounts for 10% to 50% of the SiO2 in the gel.

4. The synthesis method according to claim 1, characterized in that, The crystallization temperature is 85~110℃, and the crystallization time is 12~35h.

5. The synthesis method according to claim 1, characterized in that, 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.

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

7. The synthesis method according to claim 1, characterized in that, In step 2, the silicon source, the mother liquor recycled adhesive, and the NaY molecular sieve directing agent are mixed evenly, and 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.

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

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

10. The synthesis method according to claim 2, characterized in that, In step 4, the crystallization mother liquor is calculated as SiO2, and the aluminum sulfate solution is calculated as Al2O3. The molar ratio of the crystallization mother liquor to the aluminum sulfate solution is 6~9.

11. The synthesis method according to claim 6, characterized in that, The aging time is 15-40 hours.

12. The synthesis method as described in claim 8, characterized in that, The silicon source is selected from inorganic silicon sources.

13. The synthesis method as described in claim 8, characterized in that, The silicon source is selected from at least one of water glass, silica sol, and silica gel.

14. The synthesis method as described in claim 9, characterized in that, The aluminum source is selected from inorganic aluminum sources.

15. The synthesis method as described in claim 9, characterized in that, The aluminum source is selected from at least one of aluminum sulfate, sodium aluminate, and sodium metaaluminate.

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