Synthesis method of zeolite molecular sieve

Abstract

The invention discloses a synthesis method of a zeolite molecular sieve, which comprises the following steps: uniformly mixing a silicon source and an aluminum source, or uniformly mixing the silicon source, the aluminum source and sodium hydroxide, aging to obtain a NaY molecular sieve guiding agent, and mixing the NaY molecular sieve guiding agent with the silicon source, the aluminum source and mother liquor reuse glue to form gel; uniformly mixing the gel with potassium hydroxide, crystallizing, separating, and washing to obtain a zeolite molecular sieve solid with the CHA structure and a crystallization mother solution; mixing and stirring the crystallized mother liquor and an aluminum sulfate solution, separating, and washing to obtain mother liquor recycling glue. According to the invention, by limiting the molar ratio of the NaY molecular sieve guiding agent to each substance in the gel and the addition amount of potassium hydroxide, and combining and recycling the raw materials in the crystallization mother liquor, the synthesis utilization rate of the raw materials is further improved, the cost is reduced, and the method is environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieve preparation, and in particular to a method for synthesizing a zeolite molecular sieve. Background Art

[0002] With the rapid development of industry in recent years, the greenhouse effect has become the most concerning environmental issue. The greenhouse effect will lead to global warming, accelerated melting of glaciers, rising sea levels, increased pests and diseases, abnormal climate and land desertification, etc. The main cause of the greenhouse effect is the large-scale emission of greenhouse gases (GHG), and CO2 has the greatest impact on global climate change among GHGs. In view of the great challenges in the development and application of new energy in terms of technology and economy, experts generally predict that fossil fuels will still be the world's main energy source in the next 50 years, and CO2 emissions will continue to increase. Therefore, the issues related to CO2 emission reduction, recovery, fixation and utilization are particularly important.

[0003] The internal pores of zeolite molecular sieve can play a role in adsorbing molecules. Due to the cleanliness of the pores and the uniform distribution of the pore size of the molecular sieve, it can selectively adsorb molecules of a certain size and exclude molecules of larger substances. Therefore, zeolite molecular sieve can recycle CO2; among them, chabazite can efficiently adsorb and separate CO2 with its unique molecular gate effect.

[0004] Traditional chabazite is generally synthesized using an organic template, such as Chinese patent document CN202010797179.3, which discloses a CHA-type zeolite molecular sieve and its synthesis method and application. Specifically, N,N,N-trialkyl-N-phenyl quaternary ammonium salt or quaternary ammonium base compound is used as an organic template to synthesize CHA-type zeolite molecular sieve. Paul Webley et al. (Adsorption, 2005, 11: 173-177) synthesized CHA-type chabazite with a silicon-aluminum ratio of 2.4 according to the ratio of 0.16 (TMA): 6.67Na2O: 2.2K2O: 17.5SiO2: Al2O3: 276H2O under 85°C hydrothermal conditions for 4 days, and trimellitic anhydride TMA was added during the synthesis process. However, the method of preparing chabazite using an organic template not only pollutes the environment, but also the organic template is expensive, and even requires high-temperature roasting to remove the template, which consumes a lot of energy.

[0005] In order to solve the above-mentioned problems existing in the use of organic templates, researchers have developed a method for synthesizing chabazite without templates, adding inorganic / organic additives or seeds. It not only avoids the use of expensive templates, but also solves the environmental problems caused by the calcination of templates after synthesis. For example, Chinese patent document CN201610480629.X discloses a method for direct hydrothermal synthesis of chabazite with a medium silicon-aluminum ratio. In the reaction of synthesizing chabazite under hydrothermal conditions, no organic template is added, no chabazite seeds are added, and a weakly alkaline inorganic salt is added to obtain an aluminosilicate zeolite molecular sieve with a chabazite structure. Chinese patent document CN201610480630.2 discloses a method for synthesizing a zeolite molecular sieve with a chabazite structure. The preparation method is: in the reaction of synthesizing chabazite under hydrothermal conditions, no organic template is added, no chabazite seeds are added, and an organic weak base is added to obtain an aluminosilicate zeolite molecular sieve with a chabazite structure and a framework silicon-aluminum atomic 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 chabazite, the preparation method mainly comprises: using silicon source, aluminum source and alkali as raw materials, calcining (high energy consumption) or adding chabazite seeds without adding organic templates, fluoride ions, etc., and crystallizing in a high-pressure reactor to obtain low silicon-aluminum ratio chabazite with a silicon-aluminum ratio of 1.0 to 2.2. Chinese patent document CN201110290616 discloses a method for synthesizing chabazite, specifically using a traditional hydrothermal synthesis method, and preparing chabazite by a seed-guided method without adding an organic template.

[0007] Chinese patent document CN202210257343.0 discloses a method for preparing CHA zeolite from bleaching earth, specifically, using powdered bleaching earth, under the action of CHA seed crystals, to obtain the product CHA molecular sieve through hydrothermal crystallization reaction. It includes: (1) selecting powdered bleaching earth; (2) preparing KOH solution; (3) roasting the bleaching earth at high temperature to obtain amorphous powder; (4) adding the roasted bleaching earth to the prepared KOH solution, then adding 1-5% by mass of CHA seed crystals, and uniformly mixing to obtain a new reaction mixture; (5) adding the reaction mixture to a hydrothermal reactor for hydrothermal crystallization reaction; (6) taking out the mixture after the reaction and filtering it, and drying the solid obtained after filtration to obtain the product CHA molecular sieve.

[0008] Chinese patent document CN201610497784.2 discloses an aluminosilicate chabazite with a medium silicon-aluminum ratio, wherein the silicon-aluminum atomic molar ratio of the aluminosilicate chabazite is 20-40, and the aluminosilicate chabazite is prepared from compounds of an aluminum source and a silicon source and 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 compounds of an aluminum source and a silicon source are uniformly mixed with sodium hydroxide, potassium hydroxide, and a buffer in the molar ratio; aged at room temperature for 0.1-16 hours; then hydrothermally crystallized at 120-150 degrees Celsius for 2 to 5 days; and separated and washed to obtain the aluminosilicate chabazite.

[0009] In summary, the method of using inorganic / organic additives or seed crystal synthesis generally has certain requirements for the silicon source, and the crystallization time is also relatively long; and the seed crystal method also requires the pre-preparation of CHA seeds, and the steps are cumbersome.

[0010] In response to the problems of the above-mentioned methods using inorganic / organic additives or seed crystal synthesis, researchers have also carried out research on the preparation of chabazite by crystallization. For example, Yin Xiaoyan et al. published an experimental study on the preparation of CHA zeolite by crystallization of FAU zeolite (Plastic Additives, Issue 6, 2018). First, the eight-sided zeolite molecular sieve FAU was prepared by hydrothermal synthesis, and then it was crystallized to form CHA zeolite molecular sieve. Che Shuai published a study on the successful synthesis of chabazite with a silicon-aluminum ratio of 2.25 using HY molecular sieve as raw material and keeping it at 95°C for 15 days (Study on ion exchange modification of chabazite and CO2 adsorption and separation performance, Northeastern University, doctoral dissertation, 2013). Chinese patent document CN201010202727.X discloses the formation of pure chabazite by permeation of heterogeneous crystal nucleus T-type zeolite in the absence of organic templates. Chinese patent document CN202210612836.1 discloses a method for preparing a low-silicon CHA-type molecular sieve, specifically, mixing a potassium source, a sodium source, a silicon source, an aluminum source and water to obtain an initial gel; then the initial gel is subjected to static hydrothermal crystallization at 140-180°C for 2-6 days to obtain a low-silicon CHA-type molecular sieve.

[0011] It can be seen that the crystallization method requires the pre-prepared FAU zeolite and T-type zeolite crystals to be crystallized under certain conditions to convert them into CHA crystal form, which has the problems of complicated steps and high cost. Summary of the invention

[0012] In view of the problems existing in the existing preparation of zeolite molecular sieves and the directions for improvement, the present invention provides a method for preparing zeolite molecular sieves. The method can realize the reuse of nutrients for synthesizing molecular sieves in crystallization mother liquor, has the advantages of low cost, environmental protection, and no silicon-containing wastewater discharge. In addition, the method is synthesized at room temperature, is simple to operate, and is easy to control.

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

[0014] Step 1, mixing a silicon source and an aluminum source, or a silicon source, an aluminum source and sodium hydroxide, and aging the mixture to obtain a NaY molecular sieve directing agent;

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

[0016] Step 3, after uniformly mixing the gel and potassium hydroxide, crystallizing for 10 to 40 hours, separating to obtain zeolite molecular sieve and crystallization mother liquor;

[0017] Step 4, mixing the crystallization mother liquor with the aluminum sulfate solution, filtering and separating, washing the obtained solid with water, and obtaining the mother liquor as a recycled glue, so as to be used in step 2 in the next synthesis;

[0018] Wherein, the chabazite has a CHA structure,

[0019] Calculated in terms of oxides (calculated in terms of SiO2 for silicon in the NaY molecular sieve directing agent; in terms of Al2O3 for aluminum in the NaY molecular sieve directing agent; in terms of Na2O for sodium in the NaY molecular sieve directing agent), 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;

[0020] Calculated in terms of oxides (silicon in the gel in step 2 is calculated in terms of SiO2, aluminum in the gel is calculated in terms of Al2O3, and sodium in the gel is calculated in terms of Na2O), the molar ratio of the substances in the gel is (1-6) Na2O: (0.7-1.3) Al2O3: (5-18) SiO2: (100-350) H2O;

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

[0022] In the synthesis method of the zeolite molecular sieve provided by the present invention, when controlling the molar ratio of the NaY molecular sieve directing agent and each substance in the gel, if necessary (for example, when all industrial standard raw materials are used, since the concentrations are limited, it is impossible to accurately control the proportion of each material), low-basicity sodium aluminate or high-basicity sodium aluminate can be added to adjust the ratio of each material. If the prepared raw materials are used, low-basicity sodium aluminate or high-basicity sodium aluminate is not required for adjustment.

[0023] Low basicity sodium aluminate and high basicity sodium aluminate are both raw materials for the current industrial synthesis of NaY molecular sieves. Their compositions are both Na2O and Al2O3, and the concentrations of low basicity sodium aluminate and high basicity sodium aluminate are different.

[0024] Optionally, in step 4 of the method for synthesizing zeolite molecular sieves provided by the present invention, the molar ratio of the crystallization mother liquor to the aluminum sulfate solution is 3 to 12, with SiO2 being the crystallization mother liquor and Al2O3 being the aluminum sulfate solution. 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 sieve provided by the present invention, SiO2 in the mother liquor recycled gel accounts for 10% to 50% of SiO2 in the gel.

[0026] Optionally, in step 3 of the method for synthesizing zeolite molecular sieve provided by the present invention, the potassium hydroxide is solid or its aqueous solution. To increase the yield, solid potassium hydroxide is preferred.

[0027] Optionally, in step 3 of the method for synthesizing zeolite molecular sieve provided by the present invention, in order to ensure the uniformity of dispersion of the potassium hydroxide in the gel, the gel and the 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 to 35 hours, and the crystallization temperature is 85 to 110° C. The crystallization is carried out in a closed container, and if the closed container is resistant to high pressure, the crystallization temperature can be increased to 110° C.; if the closed container is not resistant to high pressure, the crystallization temperature is controlled at 85 to 100° C.

[0029] Optionally, in the synthesis method of the zeolite molecular sieve provided by the present invention, the mass ratio of the NaY molecular sieve directing agent and the gel, calculated as Al2O3, 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 mixing the silicon source, the mother liquor recycled gel and the NaY molecular sieve directing agent, an aluminum source is added at a uniform speed within 0.5 to 4 hours, and after the aluminum source is added, homogenization is performed 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 also be added to the mixture of the silicon source and the mother liquor recycled gel at a uniform speed within 0.5 to 4 hours, and after the aluminum source is added, the NaY molecular sieve directing agent is added and homogenized to obtain the gel.

[0033] The above homogenization method and parameters are not specifically limited, and conventional methods and parameters in the industry can be used to mix the various substances uniformly. For example, stirring can be selected, and the mixture is stirred for 0.5 to 4 hours until the mixture is uniformly mixed.

[0034] Optionally, in the synthesis method of zeolite molecular sieve provided by the present invention, the silicon source can be any conventional one in the industry without specific limitation, such as 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;

[0035] The aluminum source can be any conventional aluminum source in the industry without specific limitation, and can be selected from an organic aluminum source or an inorganic aluminum source. The present invention recommends an inorganic aluminum source, preferably at least one of aluminum sulfate, sodium aluminate and sodium metaaluminate.

[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 can be satisfied.

[0037] The zeolite molecular sieve synthesis method provided by the present invention has a CHA structure and an octagonal ring structure, and the crystallization mother liquor containing a large amount of silicon substance obtained during the synthesis process can be recycled, which greatly improves the utilization rate of raw materials and reduces the cost and wastewater discharge during the synthesis process.

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

[0039] The synthesis method of the zeolite molecular sieve provided by the present invention first synthesizes a NaY molecular sieve directing agent with a specific ratio, and then uses the mother liquor recycling glue prepared by the crystallization mother liquor produced by the previous batch synthesis as one of the raw materials to form a gel with a specific ratio, and finally potassium hydroxide is added to the gel to directly synthesize a zeolite molecular sieve. Wherein, the mother liquor recycling glue is prepared by the crystallization mother liquor recycling, which can greatly improve the utilization rate of various molecular sieve synthesis raw materials, so that the wastewater discharge during the synthesis process is greatly reduced, and in the mother liquor, containing a small amount of chabazite microparticles, it can be used as a seed for the growth of the molecular sieve during the crystallization process. There is a certain induction effect, and the use of potassium hydroxide in the synthesis process can also be reduced. The synthesis method provided by the present invention does not require additional crystal conversion or addition of seed crystals during the whole process, and does not require the addition of organic / inorganic substances, and the crystallization time is short, the cost is low, and the atmospheric synthesis is easy to operate and control. BRIEF DESCRIPTION OF THE DRAWINGS

[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 This is the XRD pattern of the zeolite molecular sieve synthesized in Example 1 of the present invention;

[0047] Figure 8 The XRD pattern of the zeolite molecular sieve synthesized in Example 2 of the present invention;

[0048] Fig. 9 This is the XRD pattern of the zeolite molecular sieve synthesized in Example 3 of the present invention;

[0049] Fig.10 The XRD pattern of the zeolite molecular sieve synthesized in Example 4 of the present invention;

[0050] Fig.11 This is the XRD pattern of the zeolite molecular sieve synthesized in Example 5 of the present invention;

[0051] Fig.12 This is the XRD diagram of the zeolite molecular sieve synthesized in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0052] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0053] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0054] The grades of the raw materials involved below are not limited, and chemical raw materials above industrial grade can meet the implementation of the technical solution of the present invention. The raw materials involved in the following embodiments and comparative examples are all industrial grade.

[0055] Evaluation and analysis methods:

[0056] Phase test 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 microscope test conditions: The crystal morphology analysis was performed using a scanning electron microscope (model JSM-IT200) produced by Japan Electronics Co., Ltd. JSM-IT200: The dried and ground sample was placed on the conductive glue, and then the processed sample was placed in a vacuum of 10 -2 The sample was purified under the condition of pa, and then the scanning test was carried out under the conditions of acceleration voltage 5kV and working distance 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 glue:

[0061] 1) Weigh 86g of water glass, add 60g of high-basicity sodium aluminate thereto, stir evenly, and age at 35°C for 24h to obtain a NaY molecular sieve directing agent; the ratio of the substances in the NaY molecular sieve directing agent is 17.6Na2O: 1.1Al2O3: 16.7SiO2: 355.0H2O;

[0062] 2) Weigh 660 g of water glass, add 90 g of the above-mentioned NaY molecular sieve directing agent, mix well, add 156 g of aluminum sulfate solution at a constant speed over 1 hour, and then add 44 g of low-basicity 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 100 g of potassium hydroxide solid to the above gel, stir for 15 min, and then put into a sealed crystallization tank; crystallize at 100° C. for 15 h, filter, and wash with 394 g of water. The obtained liquid is the crystallization mother liquor, and the solid is chabazite with a CHA structure.

[0064] 4) Take 252 mL of the crystallization mother liquor and add it into 103 mL of aluminum sulfate. After stirring for 30 min, filter and wash with water. The obtained solid is the mother liquor recycling gum, in which the molar ratio of SiO2 provided by the mother liquor and 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-basicity sodium aluminate thereto, stir evenly, and age at 35°C for 16h to obtain a NaY molecular sieve directing agent; the ratio of the substances in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317H2O.

[0067] 2) Weigh 165 g of water glass, add 240 g of the above-mentioned mother liquor recycling glue and 62 g of the above-mentioned NaY molecular sieve directing agent, mix well, add 78 g of aluminum sulfate solution at a uniform speed of 45 min, and finally add 42 g 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 2.1Na2O:1.0Al2O3:7.4SiO2:170H2O.

[0068] 3) Add 18 g of potassium hydroxide solid to the above gel, stir for 15 min, put into a closed crystallization tank, crystallize at 94 ° C for 15 h, filter, and wash the obtained solid with 350 g of water to obtain a zeolite molecular sieve. The obtained liquid (a 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 into 52 mL of aluminum sulfate. After stirring for 30 min, filter and wash with water. The obtained solid is the mother liquor recycling gum, in which 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-basicity sodium aluminate thereto, stir evenly, and age at 38°C for 16h to obtain a NaY molecular sieve directing agent, wherein the ratio of each substance in the NaY molecular sieve directing agent is 12.6Na2O:0.8Al2O3:11.4SiO2:252.8H2O;

[0073] 2) Weigh 165 g of water glass, add 125 g of the mother liquor recycled gel prepared in Example 1 and 93 g of the above-mentioned NaY molecular sieve directing agent, mix well, add 62 g of aluminum sulfate solution at a constant speed over 45 min, stir homogenously for 1 h, and obtain a gel; the ratio of the substances in the gel is 3.6 Na2O: 1.1 Al2O3: 11.6 SiO2: 217 H2O.

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

[0075] 4) Take 251 mL of the crystallization mother liquor and add it into 87 mL of aluminum sulfate. After stirring for 30 min, filter and wash with water to obtain the mother liquor recycling glue, wherein 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-basicity sodium aluminate thereto, stir evenly, and age at 37°C for 8h to obtain a NaY molecular sieve directing agent; the ratio of the substances in the NaY molecular sieve directing agent is 15.8Na2O: 1.0Al2O3: 14.4SiO2: 317.0H2O;

[0079] 2) Weigh 165 g of water glass, add 32 g of the above-mentioned NaY molecular sieve directing agent and 65 g of the mother liquor recycled glue prepared in Example 2, mix well, add 73 g of aluminum sulfate solution at a uniform speed for 1 hour, and then add 50 g of low-basicity sodium aluminate to adjust the proportion of each component, and 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 52 g of potassium hydroxide solid to the above gel, stir for 15 min, and then put into a closed crystallization tank; crystallize at 105° C. for 12 h, filter, and wash with 231 g of water to obtain a zeolite molecular sieve. The liquid (a mixture of the liquid obtained by filtration and the liquid obtained by washing) is the crystallization mother liquor.

[0081] 4) Take 251 mL of the crystallization mother liquor and add it into 76 mL of aluminum sulfate. After stirring for 30 min, filter and wash with water to obtain the mother liquor recycling glue, wherein 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-basicity sodium aluminate thereto, stir evenly, and age at 28°C for 40h to obtain a NaY molecular sieve directing agent, wherein the ratio of each substance in the NaY molecular sieve directing agent is 17.6Na2O:1.1Al2O3:17.0SiO2:361.6H2O;

[0085] 2) 84 g of aluminum sulfate solution was uniformly added to a mixture of 165 g of water glass and 165 g of the mother liquor recycled glue prepared in Example 3 for 1.5 h, and then 63 g of low-basicity sodium aluminate was added. After stirring for 30 min, 32 g of the above-mentioned NaY molecular sieve directing agent was added. After homogenizing and stirring for 1 h, a gel was obtained; the ratio of each substance in the gel was 1.7 Na2O: 1.0 Al2O3: 6.1 SiO2: 152 H2O:

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

[0087] 4) Take 251 mL of the crystallization mother liquor and add it into 67 mL of aluminum sulfate. After stirring for 30 min, filter and wash with water to obtain the mother liquor recycling glue, wherein 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 high-basicity sodium aluminate to the mixture, stir evenly, and age at 30°C for 30h to obtain a 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 165 g of water glass, add 48 g of the above-mentioned NaY molecular sieve directing agent and 250 g of the mother liquor recycled glue prepared in Example 4, mix well, add 4.1 g of aluminum sulfate solution at a constant speed over 4 hours, and then add 12 g of low-basicity sodium aluminate to adjust the proportion of each component, and stir homogenously for 1 hour to obtain a gel; the ratio of each substance in the gel is 5.5 Na2O: 1.3 Al2O3: 17.6 SiO2: 303.5 H2O;

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

[0093] 4) Take 125 mL of the crystallization mother liquor and add it into 14 mL of aluminum sulfate. After stirring for 30 min, filter and wash with water to obtain the mother liquor recycling glue, wherein 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-basicity sodium aluminate thereto, stir evenly, and age at 35°C for 16h to obtain a NaY molecular sieve directing agent; the ratio of the substances in the NaY molecular sieve directing agent is 15.8Na2O:1.0Al2O3:14.4SiO2:317H2O.

[0097] 2) Weigh 165 g of water glass, add 33 g of the above-mentioned NaY molecular sieve directing agent, then add 70 g of aluminum sulfate solution at a uniform speed over 45 minutes, and finally add 35 g 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 2.1Na2O:1.0Al2O3:7.4SiO2:155H2O.

[0098] 3) Add 24 g of potassium hydroxide solid to the above gel, stir for 15 min, put into a sealed crystallization tank, crystallize at 94° C. for 15 h, filter, and wash with water to obtain a 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-basicity sodium aluminate thereto, stir evenly, and age at 38°C for 16h to obtain a NaY molecular sieve directing agent, wherein the ratio of each substance in the NaY molecular sieve directing agent is 12.6Na2O:0.8Al2O3:11.4SiO2:252.8H2O;

[0102] 2) Weigh 165 g of water glass, add 50 g of the above-mentioned NaY molecular sieve directing agent, add 53 g of aluminum sulfate solution at a constant speed of 45 min, and then add 13 g of low-basicity sodium aluminate to adjust the ratio of each component. After homogenizing and stirring for 1 hour, a gel is obtained, in which the ratio of each substance in the gel is 3.6 Na2O: 1.1 Al2O3: 11.6 SiO2: 221.7 H2O;

[0103] 3) Add 30g of potassium hydroxide solid to the gel, stir for 15min, and then put into a sealed crystallization tank; crystallize at 100°C 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 high-basicity sodium aluminate thereto, stir evenly, and age at 35°C for 24h to obtain a NaY molecular sieve directing agent; the ratio of the substances in the NaY molecular sieve directing agent is 15.8Na2O: 1.0Al2O3: 14.4SiO2: 317.0H2O;

[0107] 2) Weigh 165 g of water glass, add 27 g of the above-mentioned NaY molecular sieve directing agent, add 70 g of aluminum sulfate solution at a uniform rate over 1 hour, and then add 47 g of low-basicity 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 2.0 Na2O: 1.0 Al2O3: 6.6 SiO2: 149.2 H2O;

[0108] 3) Add 45 g of potassium hydroxide solid to the above gel, stir for 15 min, and then put into a sealed crystallization tank; crystallize at 88° C. for 32 h, filter, and wash with water to obtain a 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-basicity sodium aluminate thereto, stir evenly, and age at 28°C for 40h to obtain a NaY molecular sieve directing agent, wherein 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 speed for 1.5h, and then 50g of low-alkalinity sodium aluminate was added. After stirring for 30min, 20g of the above-mentioned NaY molecular sieve directing agent was added. After homogenous stirring for 1h, a gel was obtained; the proportion of each substance in the gel was 1.7Na2O:1.0Al2O3:6.1SiO2:142.8H2O:

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

[0114] The zeolite molecular sieves prepared in the above-mentioned embodiments and comparative example 1 were respectively subjected to electron microscope scanning. Figure 1-6 As shown by Figure 1-6 It can be seen that the crystal structures of the zeolite molecular sieve prepared by the preparation method provided by the present invention and the zeolite molecular sieve prepared in Comparative Example 1 are both spherical, with an outer surface similar to a ball of wool, the grains are basically not agglomerated, and the size is 2 to 3 μm, indicating that they are both chabazite.

[0115] The zeolite molecular sieves prepared in the above-mentioned embodiments and comparative example 1 were subjected to X-ray diffraction analysis (XRD) test. Figure 7-12 As shown. Figure 7-12 It can be seen that 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° of the zeolite molecular sieve prepared by the preparation method provided by the present invention and the zeolite molecular sieve prepared in Comparative Example 1 are all typical diffraction peaks of CHA structure chabazite, which is consistent with the results of electron microscope scanning, indicating that the zeolite molecular sieves prepared by the method provided by the present invention and Comparative Example 1 are chabazite with CHA structure.

[0116] The mass of fresh water glass raw material, the mass of the prepared gel, the mass ratio of water glass to gel, and the proportion of silicon source provided by the mother liquor recycled gel in the gel preparation process (i.e., step 2)) in each embodiment and comparative example are shown in Table 1 below. The silicon source in the gel is provided by fresh water glass and mother liquor recycled gel, and the proportion of silicon source provided by the mother liquor recycled gel refers to the proportion of silicon source in the mother liquor recycled gel to silicon source in the gel.

[0117] Table 1

[0118]

[0119]

[0120] The zeolite molecular sieves prepared in the embodiments and comparative examples of the present invention are all CHA structured. It can be seen from the data in the above table that, compared with comparative examples 1-4 in which no mother liquor recycled glue is added and all fresh water glass is used as the source of silicon source in the gel, the mother liquor recycled glue is used in the present invention, so that the proportion of fresh water glass is significantly reduced, indicating that the preparation method provided by the present invention can improve the utilization rate of the silicon source.

[0121] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for synthesizing a zeolite molecular sieve, characterized in that: The steps include: Step 1, mixing a silicon source and an aluminum source, or a silicon source, an aluminum source and sodium hydroxide, and aging the mixture to obtain a NaY molecular sieve directing agent; Step 2, mixing the silicon source, the aluminum source, the mother liquor recycled gel and the NaY molecular sieve directing agent to form a gel; Step 3, after uniformly mixing the gel and potassium hydroxide, crystallizing for 10 to 40 hours, separating to obtain zeolite molecular sieve and crystallization mother liquor; Step 4, mixing the crystallization mother liquor with the aluminum sulfate solution, separating, and washing with water to obtain the mother liquor recycling glue; Wherein, the zeolite molecular sieve has a CHA structure; Calculated as 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; Calculated as oxides, the molar ratio of the substances in the gel is (1-6) Na2O: (0.7-1.3) Al2O3: (5-18) SiO2: (100-350) H2O; The mass ratio of the potassium hydroxide to the gel is (2-15):

100.

2. The synthesis method according to claim 1, characterized in that In step 4, the molar ratio of the crystallization mother solution to the aluminum sulfate solution is 3 to 12, preferably 6 to 9, based on SiO2 and Al2O3.

3. The synthesis method according to 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 to 110° C., and the crystallization time is 12 to 35 hours.

5. The synthesis method according to claim 1, characterized in that The mass ratio of the NaY molecular sieve directing agent and the gel is (3-30):100, calculated based on Al2O3.

6. The synthesis method according to claim 1, characterized in that The aging temperature is 25-40° C., and the aging time is 6-42 hours, preferably 15-40 hours.

7. The synthesis method according to claim 1, characterized in that In step 2, after the silicon source, the mother liquor recycled gel and the NaY molecular sieve directing agent are mixed, the aluminum source is added at a uniform speed within 0.5 to 4 hours, and after the aluminum source is added, homogenization is performed to obtain the gel.

8. The synthesis method according to claim 1, characterized in that The silicon source is selected from an organic silicon source or an inorganic silicon source, preferably an inorganic silicon source, and more preferably at least one of water glass, silica sol and silica gel.

9. The synthesis method according to claim 1, characterized in that The aluminum source is selected from an organic aluminum source or an inorganic aluminum source, preferably an inorganic aluminum source, and more preferably at least one of aluminum sulfate, sodium aluminate and sodium metaaluminate.

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