Preparation method of large-particle-size 4A molecular sieve powder

Abstract

The preparation method of the large-particle-size 4A molecular sieve powder comprises the following steps: mixing reactants of an aluminum source and a silicon source for a synthetic reaction to obtain crystallized slurry; the crystallization slurry is subjected to at least two times of segmented heating treatment, the temperature of the previous heating treatment is lower than that of the next heating treatment, and heat preservation treatment is conducted on the crystallization slurry after each time of heating treatment; and carrying out solid-liquid separation and calcination on the crystallized slurry subjected to segmented heating treatment to obtain 4A molecular sieve powder with the particle size D50 not less than 4 microns. According to the method, the problem that the grain size is difficult to control in a traditional method is solved by accurately controlling the temperature and time in the synthesis process, and an effective technical means is provided for industrial production of the 4A molecular sieve powder.

Description

Technical Field

[0001] This application relates to the field of materials technology, and in particular to a method for preparing large-particle-size 4A molecular sieve powder. Background Technology

[0002] 4A molecular sieve is an important alkali metal aluminosilicate material with a uniform microporous cubic lattice structure, possessing a large specific surface area and pore volume, exhibiting excellent separation and selective adsorption capabilities. It also possesses high thermal stability, good chemical stability, a wide variety of types, and significant customization characteristics, making it a high-value-added novel functional material. Due to its widespread application in deep drying of gases and liquids, purification of natural gas and hydrogen, and purification of other chemical raw materials, 4A molecular sieve has become one of the most widely used adsorbent products. Furthermore, through ion exchange with potassium / calcium, 4A molecular sieve can also be formulated into 3A / 5A molecular sieves, further expanding its application range.

[0003] However, the particle size of 4A molecular sieve raw powder currently on the market is relatively small, resulting in a low bulk density of molded products. This limits the adsorbent loading capacity of adsorption separation equipment, leading to low equipment utilization and high operating costs. This cannot meet the high loading capacity requirements of some industrial equipment for 4A molecular sieve adsorbent. With rapid technological advancements, high-end molecular sieve products are largely monopolized by developed countries, posing a potential threat to the development of related industries and national security in key areas in my country. Therefore, developing key technologies for the industrialization of zeolite molecular sieve materials suitable for my country's resource characteristics, based on independent innovation, to synthesize large-particle-size 4A molecular sieves and improve their adsorption capacity and equipment utilization, has become an important issue that urgently needs to be addressed in my country. Summary of the Invention

[0004] This application provides a method for preparing large-particle-size 4A molecular sieve powder to solve the following technical problem: how to accurately control the single-crystal particle size of 4A molecular sieve powder.

[0005] This application provides a method for preparing large-particle-size 4A molecular sieve powder, including: The reactants from aluminum and silicon sources are mixed to carry out a synthesis reaction, resulting in a crystallized slurry; The crystallization slurry is subjected to at least two staged heating treatments, wherein the temperature of the first heating treatment is lower than the temperature of the second heating treatment, and the crystallization slurry is subjected to heat preservation treatment after each heating treatment. The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation and calcination to obtain 4A molecular sieve powder with a particle size D50 of not less than 4μm.

[0006] Optionally, the SiO2 / Al2O3 molar ratio of the reactants of the aluminum source and the silicon source is 1.5 to 2.5.

[0007] Optionally, the parameters of the synthesis reaction include: a temperature of 25–50°C and a time of 10–60 minutes.

[0008] Optionally, at least two of the segmented heating processes include three temperature stages: The first stage involves raising the temperature to 65–85℃ and holding it for 1–4 hours. The second stage involves raising the temperature to 80–95℃ and holding it at that temperature for 1–4 hours. The third stage involves raising the temperature to 90–110°C and holding it there for 2–5 hours.

[0009] Optionally, the solid-liquid separation method includes one of the following: pressure filtration, centrifugal separation, or filtration.

[0010] Optionally, the calcination parameters include: a calcination temperature of 300–800°C and a calcination time of 1–6 hours.

[0011] Optionally, the synthesis reaction process further includes: stirring the materials of the synthesis reaction at a stirring speed of 50 to 200 rpm.

[0012] Optionally, the synthesis reaction process further includes: adding seed crystals to the materials of the synthesis reaction, wherein the seed crystals are 4A molecular sieve seed crystals, and the mass of the 4A molecular sieve seed crystals is 0.1% to 5% of the mass of the materials.

[0013] Optionally, the synthesis reaction process further includes: adding a template agent to the materials of the synthesis reaction, wherein the mass of the template agent is 0.01% to 1% of the mass of the materials, and the template agent includes at least one of the following: organic amine compounds, quaternary ammonium salt compounds, organophosphorus compounds, and polymeric template agents.

[0014] Optionally, the particle size D50 of the 4A molecular sieve powder is 4-10 μm, and the static saturated water adsorption capacity of the 4A molecular sieve powder is not less than 27%.

[0015] The technical solutions provided in this application have the following advantages compared with the prior art: This application provides a method for preparing large-particle-size 4A molecular sieve powder. First, through staged heating, the reactants from the aluminum and silicon sources begin to crystallize at a lower temperature, forming tiny crystal nuclei. This lower temperature promotes uniform nucleation and avoids defects. As the temperature gradually increases, the nuclei grow rapidly at higher energies, and the heat preservation treatment after each heating stage provides a stable growth environment for the crystals, allowing sufficient time to perfect their structure and release stress, thereby promoting grain growth. This combination of gradual heating and heat preservation ensures optimal growth conditions at different stages, ultimately resulting in crystals with larger particle sizes. Second, solid-liquid separation and calcination further optimize the product. Solid-liquid separation removes reaction impurities and unreacted raw materials, improving product purity; calcination removes template agents and organic impurities, optimizing the crystal structure and improving crystallinity and stability. Through these steps, high-quality 4A molecular sieve powder with a particle size D50 of not less than 4 μm is finally obtained. This method, by precisely controlling the temperature and time during the synthesis process, solves the problem of difficult grain size control in traditional methods, providing an effective technical means for the industrial production of 4A molecular sieve powder. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings necessary for the description of the embodiments or the prior art will be outlined below. Obviously, those skilled in the art can derive other related drawings based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating a method for preparing large-particle-size 4A molecular sieve powder, as provided in this application embodiment. Detailed Implementation

[0019] To more clearly illustrate the purpose, technical solutions, and advantages of the embodiments of this application, the technical solutions of this embodiment will be described in detail below with reference to the accompanying drawings. Please note that the embodiments described herein are merely exemplary and do not represent all possible implementation paths. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] The range descriptions used herein, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1~6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "including" and "contains" as used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships mentioned herein, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained through commercial purchase or prepared using existing methods.

[0021] Figure 1 A flowchart illustrating a method for preparing large-particle-size 4A molecular sieve powder, as provided in this application embodiment.

[0022] Please see Figure 1 This application provides a method for preparing large-particle-size 4A molecular sieve powder, comprising: S1. The reactants of aluminum source and silicon source are mixed to carry out a synthesis reaction to obtain a crystallized slurry; S2. The crystallization slurry is subjected to at least two staged heating treatments, wherein the temperature of the first heating treatment is lower than the temperature of the second heating treatment, and the crystallization slurry is subjected to heat preservation treatment after each heating treatment. S3. The crystallized slurry after segmented heating is subjected to solid-liquid separation and calcination to obtain 4A molecular sieve powder with a particle size D50 of not less than 4μm.

[0023] Aluminum source: Compounds that provide aluminum, such as sodium aluminate. Silicon source: Compounds that provide silicon, such as water glass. Crystallization slurry: A slurry containing molecular sieve crystals formed after the synthesis reaction. Particle size D50: Represents the median particle size distribution, meaning that half of the particles are smaller than this value, and the other half are larger.

[0024] Reactants containing aluminum and silicon sources are mixed and synthesized to generate a crystallized slurry. Aluminum and silicon sources are the basic raw materials for synthesizing 4A molecular sieves. By controlling their mixing ratio and reaction conditions, the structure and performance of the molecular sieve can be affected. The crystallized slurry undergoes at least two staged heating treatments. After each heating, the slurry is held at the same temperature. This staged heating method promotes the growth of molecular sieve crystals, increasing their particle size. Specifically, the temperature of the first heating treatment is lower than that of the second heating treatment; this temperature increase helps the gradual growth and stabilization of the crystals. The crystallized slurry after staged heating treatment undergoes solid-liquid separation to remove excess liquid, and then calcined. The calcination process removes impurities such as organic template agents, making the molecular sieve structure more stable. The final 4A molecular sieve powder has a particle size D50 of not less than 4 μm. This large-particle-size molecular sieve has a higher adsorption capacity and equipment utilization rate. Particle size D50 is not less than 4μm: covering 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc.

[0025] In some embodiments, the SiO2 / Al2O3 molar ratio of the reactants of the aluminum source and the silicon source is 1.5 to 2.5.

[0026] The SiO2 / Al2O3 molar ratio of the aluminum and silicon source reactants is 1.5–2.5. By controlling this ratio, the Si / Al ratio of the molecular sieve can be adjusted, thereby affecting its adsorption performance and thermal stability. Specifically, when the SiO2 / Al2O3 molar ratio is 1.5, the molecular sieve has a relatively low Si / Al ratio and strong adsorption performance; while when the SiO2 / Al2O3 molar ratio is 2.5, the Si / Al ratio is relatively high and the thermal stability is better. This ratio range covers all individual values ​​from 1.5 to 2.5, including 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5, providing flexibility for synthesizing 4A molecular sieves with different performance requirements.

[0027] In some embodiments, the parameters of the synthesis reaction include: a temperature of 25–50°C and a time of 10–60 minutes.

[0028] The parameters for the synthesis reaction include a temperature of 25–50°C and a time of 10–60 minutes. Controlling the temperature and time can affect the crystallinity and particle size distribution of the molecular sieve. Specifically, the temperature range covers all individual values ​​between 25°C and 50°C, including 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, and 50°C. The time range covers all individual values ​​from 10 minutes to 60 minutes, including 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, 35 minutes, 36 minutes, 37 minutes, 38 minutes, 39 minutes, 40 minutes, 41 minutes, 42 minutes, 43 minutes, 44 minutes, 45 minutes, 46 minutes, 47 minutes, 48 ​​minutes, 49 minutes, 50 minutes, 51 minutes, 52 minutes, 53 minutes, 54 minutes, 55 minutes, 56 minutes, 57 minutes, 58 minutes, 59 minutes, and 60 minutes. By conducting synthesis reactions within these parameter ranges, 4A molecular sieve powders with different particle sizes and properties can be obtained.

[0029] In some implementations, the at least two staged heating processes comprise three temperature phases: The first stage involves raising the temperature to 65–85℃ and holding it for 1–4 hours. The second stage involves raising the temperature to 80–95℃ and holding it at that temperature for 1–4 hours. The third stage involves raising the temperature to 90–110°C and holding it there for 2–5 hours.

[0030] The at least two staged heating processes described above comprise three temperature phases: Phase 1: Heating to 65–85℃ and holding for 1–4 hours. The temperature range for this phase covers all individual values ​​between 65℃ and 85℃, including 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, and 85℃. The holding time ranges from 1 hour to 4 hours, including 1 hour, 2 hours, 3 hours, and 4 hours. This heating phase primarily aims to promote the initial growth of molecular sieve crystals, providing a foundation for subsequent growth.

[0031] The second stage involves heating to 80–95°C and holding at that temperature for 1–4 hours. The temperature range in this stage covers all individual values ​​between 80°C and 95°C, including 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, and 95°C. The holding time ranges the same as in the first stage, also from 1 hour to 4 hours. This heating process further promotes the growth of the molecular sieve crystals, causing their particle size to gradually increase.

[0032] The third stage involves heating to 90–110℃ and holding at that temperature for 2–5 hours. The temperature range for this stage covers all individual values ​​between 90℃ and 110℃, including 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, 96℃, 97℃, 98℃, 99℃, 100℃, 101℃, 102℃, 103℃, 104℃, 105℃, 106℃, 107℃, 108℃, 109℃, and 110℃. The holding time ranges from 2 hours to 5 hours, including 2 hours, 3 hours, 4 hours, and 5 hours. This heating stage is crucial for the growth of molecular sieve crystals. The higher temperatures and longer holding times allow the molecular sieve crystals to grow sufficiently to reach the desired particle size range.

[0033] This segmented heating process allows for precise control of the molecular sieve crystal growth, resulting in a more uniform particle size distribution and ultimately producing large-particle-size 4A molecular sieve powder with a D50 of not less than 4 μm. This large-particle-size molecular sieve exhibits higher adsorption capacity and equipment utilization, meeting the demands of industrial equipment for high-volume adsorbent loading.

[0034] In some embodiments, the solid-liquid separation method includes one of the following: pressure filtration, centrifugal separation, or filtration.

[0035] Solid-liquid separation methods include: pressure filtration, centrifugation, and filtration. Different solid-liquid separation methods have their own characteristics and applicable scenarios. Pressure filtration: By applying pressure, liquid flows through a filter medium (such as filter cloth), while the solid molecular sieve is retained on the filter medium. Pressure filtration is suitable for processing larger volumes of slurry and has high separation efficiency. Centrifugal separation: Utilizes centrifugal force to separate the solid molecular sieve from the liquid. Centrifugal separation is suitable for processing smaller volumes of slurry, with good separation effect and can obtain relatively pure solid molecular sieves. Filtration: Separates the solid molecular sieve from the liquid through the interception effect of the filter medium. Filtration is simple to operate, low in cost, and suitable for large-scale production.

[0036] Choosing the right solid-liquid separation method can be adjusted according to actual production needs and equipment conditions to ensure the production of high-quality 4A molecular sieve powder.

[0037] In some embodiments, the calcination parameters include: a calcination temperature of 300–800°C and a calcination time of 1–6 hours.

[0038] Calcination temperature: refers to the highest temperature reached by the material during the calcination process, measured in degrees Celsius (°C). Calcination time: refers to the time the material remains at a high temperature during the calcination process, measured in hours (h).

[0039] The calcination temperature directly affects the thermal and structural stability of molecular sieves. Lower calcination temperatures (e.g., 300℃) may not completely remove impurities such as organic template agents, while higher calcination temperatures (e.g., 800℃) may lead to over-sintering of the molecular sieve structure, affecting its adsorption performance. Calcination temperatures between 300 and 800℃ ensure structural stability of the molecular sieve while removing impurities, improving its thermal stability and adsorption performance. The calcination time also affects the performance of molecular sieves. Shorter calcination times (e.g., 1 hour) may not completely remove impurities, while longer calcination times (e.g., 6 hours) may lead to over-sintering of the molecular sieve structure, affecting its adsorption performance. Calcination times between 1 and 6 hours ensure complete removal of impurities while avoiding over-sintering. Calcination temperatures of 300–800℃ include 300℃, 400℃, 500℃, 600℃, 700℃, and 800℃. Calcination times of 1–6 hours include 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, and 6 hours.

[0040] In some embodiments, the synthesis reaction process further includes stirring the materials involved in the synthesis reaction at a stirring speed of 50–200 rpm. Stirring speed refers to the number of times the stirrer rotates per unit time, measured in revolutions per minute (rpm). The stirring speed directly affects the uniformity of mixing of the reactants and the reaction rate. A lower stirring speed (e.g., 50 rpm) may not adequately mix the reactants, leading to an uneven reaction. A higher stirring speed (e.g., 200 rpm) ensures thorough mixing of the reactants, improving the reaction rate and uniformity, but excessively high stirring speeds may result in energy waste and equipment wear. A stirring speed of 50–200 rpm ensures thorough mixing of the reactants while avoiding energy waste and equipment wear. The stirring speed range of 50–200 rpm encompasses 50 rpm, 100 rpm, 150 rpm, 200 rpm, etc.

[0041] In some embodiments, the synthesis reaction process further includes adding seed crystals to the materials of the synthesis reaction, wherein the seed crystals are 4A molecular sieve seed crystals, and the mass of the 4A molecular sieve seed crystals is 0.1% to 5% of the mass of the materials (the mass ratio of seed crystals is 0.1% to 5%).

[0042] Seed crystals: These can be synthesized in-house or purchased from chemical reagent suppliers, such as Sinopharm Chemical Reagent Co., Ltd., model AR (analytical grade). The addition of seed crystals can significantly affect the crystallization process of molecular sieves. A lower seed crystal mass ratio (e.g., 0.1%) may not effectively guide crystallization, resulting in a slower crystallization rate. A higher seed crystal mass ratio (e.g., 5%) can accelerate the crystallization process but may lead to crystal aggregation, affecting the particle size distribution. A seed crystal mass ratio of 0.1% to 5% ensures efficient crystallization while avoiding crystal aggregation. Seed crystal mass ratios of 0.1% to 5% include 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, and 5.0%.

[0043] In some embodiments, the synthesis reaction process further includes: adding a template agent to the materials of the synthesis reaction, wherein the mass of the template agent is 0.01% to 1% of the mass of the materials (the mass ratio of the template agent is 0.01% to 1%), and the template agent includes at least one of the following: organic amine compounds, quaternary ammonium salt compounds, organophosphorus compounds, and polymeric template agents.

[0044] Template agents: These can be synthesized in-house or purchased from chemical reagent suppliers, such as Sinopharm Chemical Reagent Co., Ltd., model AR (analytical grade). The addition of template agents can significantly affect the crystallization process and pore structure of molecular sieves. A lower template agent mass ratio (e.g., 0.01%) may not effectively guide crystallization, resulting in an uneven pore structure. A higher template agent mass ratio (e.g., 1%) can better guide the crystallization process, but may lead to template agent residue, affecting the final performance of the molecular sieve. An appropriate template agent mass ratio can ensure efficient crystallization while avoiding template agent residue. Different types of template agents (e.g., organic amine compounds, quaternary ammonium salt compounds, organophosphorus compounds, polymer template agents) can provide different crystallization environments, affecting the pore structure and adsorption performance of molecular sieves. Template agent mass ratios of 0.01%–1% include 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1.0%.

[0045] In some embodiments, the particle size D50 of the 4A molecular sieve powder is 4 to 10 μm, and the static saturated water adsorption capacity of the 4A molecular sieve powder is not less than 27%.

[0046] Static saturated water adsorption capacity: Under specific conditions, the maximum amount of water adsorbed by a molecular sieve, usually expressed as a percentage, reflects the adsorption performance of the molecular sieve. Larger particle sizes (e.g., 10 μm) can increase the adsorption capacity of the molecular sieve, but may lead to reduced equipment utilization. Smaller particle sizes (e.g., 4 μm) can increase equipment utilization, but the adsorption capacity may be lower. A particle size D50 of 4A molecular sieve powder of 4–10 μm ensures an optimal balance between adsorption capacity and equipment utilization. A static saturated water adsorption capacity of 4A molecular sieve powder of not less than 27% indicates good adsorption performance, suitable for applications such as deep drying, and ensures good adsorption effects in practical applications. Particle size D50 4–10 μm: covers 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc. Static saturated water adsorption capacity not less than 27%: covers 27%, 28%, 29%, 30%, etc.

[0047] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0048] Example 1 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.9 and a synthesis reaction was carried out at a reaction temperature of 35°C for 15 minutes to obtain a crystallized slurry.

[0049] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 75℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 95℃ and hold for 3 hours.

[0050] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by pressure filtration) and then calcined at 500℃ for 3 hours.

[0051] Finally, 4A molecular sieve powder with a particle size D50 of 4-8 μm was obtained.

[0052] Example 2 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.91 and a synthesis reaction was carried out at a reaction temperature of 38°C for 15 minutes to obtain a crystallized slurry.

[0053] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 75℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 95℃ and hold for 3 hours.

[0054] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by centrifugation) and then calcined at 550℃ for 3 hours.

[0055] Finally, 4A molecular sieve powder with a particle size D50 of 4-8 μm was obtained.

[0056] Example 3 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.93 and a synthesis reaction was carried out at a reaction temperature of 35°C for 20 minutes to obtain a crystallized slurry.

[0057] The crystallization slurry is subjected to staged heating treatment: Stage 1: Heat to 78℃ and hold for 2 hours; Stage 2: Heat to 88℃ and hold for 2 hours; Stage 3: Heat to 98℃ and hold for 3 hours.

[0058] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by filtration) and then calcined at 600℃ for 3 hours.

[0059] Finally, 4A molecular sieve powder with a particle size D50 of 4-8 μm was obtained.

[0060] Example 4 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.90 and a synthesis reaction was carried out at a reaction temperature of 34°C for 25 minutes to obtain a crystallized slurry.

[0061] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 75℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 93℃ and hold for 3 hours.

[0062] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by pressure filtration) and then calcined at 500℃ for 3 hours.

[0063] Finally, 4A molecular sieve powder with a particle size D50 of 4-8 μm was obtained.

[0064] Example 5 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.92 and a synthesis reaction was carried out at a reaction temperature of 35°C for 15 minutes to obtain a crystallized slurry.

[0065] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 73℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 98℃ and hold for 3 hours.

[0066] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by centrifugation) and then calcined at 550℃ for 3 hours.

[0067] Finally, 4A molecular sieve powder with a particle size D50 of 4-8 μm was obtained.

[0068] Example 6 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.93 and a synthesis reaction was carried out at a reaction temperature of 35°C for 25 minutes to obtain a crystallized slurry.

[0069] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 78℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 93℃ and hold for 3.5 hours.

[0070] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by filtration) and then calcined at 600℃ for 3 hours.

[0071] Finally, 4A molecular sieve powder with a particle size D50 of 4-8 μm was obtained.

[0072] Comparative Example 1 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.4 and a synthesis reaction was carried out at a reaction temperature of 35°C for 15 minutes to obtain a crystallized slurry.

[0073] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 75℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 95℃ and hold for 3 hours.

[0074] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by pressure filtration) and then calcined at 500℃ for 3 hours.

[0075] Finally, 4A molecular sieve powder with a particle size D50 of 2-4 μm was obtained.

[0076] Comparative Example 2 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 2.6 and a synthesis reaction was carried out at a reaction temperature of 35°C for 15 minutes to obtain a crystallized slurry.

[0077] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 75℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 95℃ and hold for 3 hours.

[0078] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by centrifugation) and then calcined at 550℃ for 3 hours.

[0079] Finally, 4A molecular sieve powder with a particle size D50 of 3-5 μm was obtained.

[0080] Comparative Example 3 An aluminum source (sodium aluminate) and a silicon source (water glass) were mixed at a SiO2 / Al2O3 molar ratio of 1.9 and a synthesis reaction was carried out at a reaction temperature of 20°C for 10 minutes to obtain a crystallized slurry.

[0081] The crystallization slurry is subjected to staged heating treatment: First stage: heat up to 75℃ and hold for 2 hours; Second stage: heat up to 85℃ and hold for 2 hours; Third stage: heat up to 95℃ and hold for 3 hours.

[0082] The crystallized slurry after segmented heating treatment is subjected to solid-liquid separation (by filtration) and then calcined at 300℃ for 1 hour.

[0083] Finally, 4A molecular sieve powder with a particle size D50 of 2-4 μm was obtained.

[0084] Effect data: The effect data of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0085] Experimental methods for obtaining effect data: 1. Determination of particle size D50: The particle size distribution of the prepared 4A molecular sieve powder was tested using a laser particle size analyzer (model: Malvern Mastersizer 3000).

[0086] Disperse the sample in deionized water and sonicate for 10 minutes to ensure uniform dispersion.

[0087] The particle size distribution was measured using a laser particle size analyzer, and the D50 value was recorded.

[0088] 2. Determination of static saturated water adsorption capacity: The prepared 4A molecular sieve powder sample was dried at 110℃ for 2 hours, cooled to room temperature, and then weighed (referred to as W1).

[0089] The sample was placed in a constant temperature and humidity chamber at 25°C and 50% relative humidity. After adsorption for 24 hours, it was taken out and weighed immediately (recorded as W2).

[0090] The formula for calculating the static saturated water adsorption capacity is:

[0091] Table 1

[0092] The above effect data table provides a clear comparison of the differences between various embodiments and comparative examples. The following conclusions can be drawn: 1. Comparison of particle size D50: Examples 1 to 6: The particle size D50 of the 4A molecular sieve powder in all examples was in the range of 4–8 μm. This indicates that the preparation method of this application can stably prepare large-particle-size 4A molecular sieve powder.

[0093] Comparative Examples 1 to 3: The particle size D50 of Comparative Examples 1 and 3 was 2–4 μm, and the particle size D50 of Comparative Example 2 was 3–5 μm. The particle sizes of these comparative examples are all smaller than the particle size range of the embodiments of this application, indicating that large-particle-size 4A molecular sieve powder cannot be prepared under these conditions.

[0094] 2. Comparison of static saturated water adsorption capacity: Examples 1 to 6: The static saturated water adsorption capacity of all examples was greater than 27%. This indicates that the preparation method of this application can significantly improve the adsorption performance of 4A molecular sieve.

[0095] Comparative Examples 1 to 3: The static saturated water adsorption capacity of Comparative Examples 1 and 3 was 25%, and the static saturated water adsorption capacity of Comparative Example 2 was 26%. The adsorption capacity of these comparative examples was lower than that of the embodiments of the present invention, indicating that the adsorption performance requirements of this application could not be met under these conditions.

[0096] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a 4A molecular sieve powder with a large particle size, comprising: mixing reactants of an aluminum source and a silicon source to perform a synthesis reaction, to obtain a crystallization slurry; performing at least two segmented temperature rising treatments on the crystallization slurry, wherein the temperature of the first temperature rising treatment is lower than the temperature of the last temperature rising treatment, and a holding treatment is performed on the crystallization slurry after each temperature rising treatment; performing a solid-liquid separation and calcination on the crystallization slurry after the segmented temperature rising treatments, to obtain a 4A molecular sieve powder with a particle size D50 not less than 4 μm.

2. The production method according to claim 1, characterized by, The SiO2 / Al2O3 molar ratio of the reactants of the aluminum source and the silicon source is 1.5-2.

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3. The production method according to claim 1, characterized by, The parameters of the synthesis reaction include: a temperature of 25-50 ℃ and a time of 10-60 minutes.

4. The method of claim 1, wherein, The at least two segmented temperature rising treatments include three temperature stages: the first stage is rising to 65-85 ℃ and holding for 1-4 hours; the second stage is rising to 80-95 ℃ and holding for 1-4 hours; the third stage is rising to 90-110 ℃ and holding for 2-5 hours.

5. The method of claim 1, wherein, The solid-liquid separation mode includes one of the following: pressure filtration, centrifugal separation, and filtration.

6. The method of claim 1, wherein, The parameters of the calcination include: a calcination temperature of 300-800 ℃ and a calcination time of 1-6 hours.

7. The preparation method according to claim 1, characterized in that, The synthesis reaction process further includes: stirring the material of the synthesis reaction, and the stirring speed is 50-200 revolutions per minute.

8. The method of claim 1, wherein, The synthesis reaction process further includes: adding seeds to the material of the synthesis reaction, the seeds are 4A molecular sieve seeds, and the mass of the 4A molecular sieve seeds is 0.1%-5% of the mass of the material.

9. The method of claim 1, wherein, The synthesis reaction process further includes: adding a template agent to the material of the synthesis reaction, the mass of the template agent is 0.01%-1% of the mass of the material, and the template agent includes at least one of the following: an organic amine compound, a quaternary ammonium salt compound, an organic phosphine compound, and a polymer template agent.

10. The method of claim 1, wherein, The particle size D50 of the 4A molecular sieve powder is 4-10 μm, and the static saturated water adsorption capacity of the 4A molecular sieve powder is not less than 27%.

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