LSX molecular sieve low-dew-point adsorption material for deep dehumidification and preparation method of LSX molecular sieve low-dew-point adsorption material

Abstract

The invention relates to the technical field of adsorption materials, in particular to an LSX molecular sieve low-dew-point adsorption material for deep dehumidification and a preparation method of the LSX molecular sieve low-dew-point adsorption material. According to the adsorption material, a Na-LSX molecular sieve is used as a matrix, and is matched with lanthanum nitrate and rubidium chloride composite rare earth metal salt and compounded with a functionalized silane reagent to form a synergistic adsorption structure of the Na-LSX molecular sieve, the lanthanum nitrate and the rubidium chloride. The preparation process comprises the steps of synthesis of a rare earth-silane coordination precursor, reaction of a matrix and the precursor, gradient activation and the like, and is mild in process condition, free of complex equipment and easy to control. The material is high in adsorption capacity under extremely low humidity, low in regeneration temperature, low in energy consumption and excellent in cycling stability, extremely low dew point output can be stably achieved, and the strict deep dehumidification requirements in the fields of lithium battery production, aerospace and the like can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorption materials, and particularly relates to LSX molecular sieve low dew point adsorption material for deep dehumidification and a preparation method thereof. BACKGROUND

[0002] As a key supporting technology in the fields of high-end manufacturing, aerospace, electronic information, etc., the core requirement of deep dehumidification technology is to stably control the dew point of gas below-60 DEG C, so as to avoid the corrosion of equipment, product defects and performance degradation caused by water vapor. For example, in the production process of lithium batteries, the dew point of the dry environment of the pole piece needs to be lower than-70 DEG C, otherwise problems such as electrolyte decomposition and battery capacity decline will be caused; the strict requirement for low dew point of the storage and operation environment of aerospace precision instruments is directly related to the reliability and service life of the equipment. Adsorption dehumidification has become the mainstream technology in the field of deep dehumidification due to its relatively low energy consumption, precise dew point control and other advantages, and the performance of the adsorption material directly determines the dehumidification effect, operation cost and stability.

[0003] The low-silicon aluminum ratio X-type (LSX) molecular sieve has a silicon aluminum molar ratio of only 1.0-1.1, has rich cation sites and high specific surface area, and exhibits excellent adsorption selectivity and capacity for water vapor molecules, and is widely used as a substrate of deep dehumidification adsorption material. In order to further improve the dehumidification performance, the existing technology mainly optimizes the LSX molecular sieve through three types of modification paths: one is cation exchange modification, which introduces Li + , Ca 2+ , Ce 3+ and other cations to control the pore electric field and adsorption site strength, trying to improve the adsorption capacity under low humidity; two is composite carrier modification, which composites LSX molecular sieve with polymer resin, porous carbon material or loads hygroscopic salt, in order to balance the adsorption capacity and structural stability; three is pore structure regulation, which constructs multi-stage pores through template-assisted synthesis or post-processing process, and improves the water vapor diffusion efficiency.

[0004] However, the existing modification technology still has many defects that are difficult to overcome, which restricts the improvement of deep dehumidification performance and industrial application. In terms of extremely low humidity adsorption performance, the water vapor adsorption capacity of conventional modified LSX molecular sieves is generally low at a relative humidity of 10%, it is difficult to capture trace water vapor, and it is difficult to stably realize a low dew point output below-60℃. The core reason is that a single modification path cannot build adsorption sites with gradient binding energy, and it is difficult to match the capture needs of water vapor with different concentrations at extremely low humidity. In terms of regeneration energy consumption, the regeneration temperature of existing modified materials is mostly above 200℃, and some even exceed 250℃. High regeneration temperature leads to a sharp increase in dehumidification system energy consumption and high operating costs, which is closely related to the strong water molecule binding energy after cation exchange and the insufficient thermal stability of the composite carrier. In terms of cycle stability, cation exchange easily causes local collapse of the molecular sieve framework, and the active sites are severely lost after multiple adsorption-regeneration cycles; the carrier and the molecular sieve have weak binding force and are easy to peel off, resulting in rapid decay of adsorption performance. In addition, the high-performance Li + exchange modification requires multiple cycles to achieve the ideal exchange degree, and the high price of Li resources makes the material preparation cost high, which is difficult to scale up. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art, and to provide a LSX molecular sieve low dew point adsorption material for deep dehumidification and a preparation method thereof.

[0006] To achieve the above purpose, the present application provides a LSX molecular sieve low dew point adsorption material for deep dehumidification, which comprises the following raw materials in parts by weight: Na-LSX molecular sieve base: 80-120 parts, rare earth metal salt: 5-12 parts, functional silane reagent: 8-12 parts. The preparation method of the Na-LSX molecular sieve base is as follows: Sodium aluminate and sodium hydroxide were added to deionized water and stirred for 30-60 min. Then sodium silicate was added and stirred to form a sol. The sol was then aged at 40-60℃ for 12-36 h. The sol was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and crystallized at 100-110℃ for 4-6 h. After filtration, washing and drying, the Na-LSX molecular sieve matrix was obtained. In this step, a well-structured zeolite framework with a low silica-to-alumina ratio was constructed through a stepwise reaction. First, sodium aluminate and sodium hydroxide are added to deionized water. Sodium hydroxide provides a strongly alkaline environment, promoting the dissociation of sodium aluminate to form aluminum-oxygen tetrahedral precursors, providing a stable aluminum source for the subsequent construction of the silicon-aluminum framework. Then, sodium silicate is added and stirred to form a sol. Sodium silicate, acting as a silicon source, dissociates into silicon-oxygen tetrahedra, which, through dehydration condensation, initially form an amorphous aluminosilicate gel. During aging at 40-60℃ for 12-36 hours, ions within the gel slowly diffuse and rearrange, gradually forming an ordered precursor structure, reducing defects in the subsequent crystallization process. Next, the gel is transferred to a high-pressure reactor for crystallization. The high temperature and pressure environment drives the amorphous gel to transform into X-type zeolite crystals with a regular three-dimensional porous structure. By controlling the molar ratio of sodium aluminate, sodium hydroxide, and sodium silicate, the silicon-aluminum molar ratio of the crystals is maintained in a low range of 1-1.1. + As cation sites occupying the zeolite framework as balancing cations, the Na-LSX molecular sieve matrix is ​​finally obtained through filtration, washing, and drying.

[0007] Preferably, the rare earth metal salt refers to a mixture of lanthanum nitrate and rubidium chloride in a weight ratio of 3-8:2-4.

[0008] Preferably, the functionalized silane reagent refers to a mixture of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in a molar ratio of 1:0.5-1.

[0009] Preferably, in the method for preparing the Na-LSX molecular sieve matrix, the molar ratio of sodium aluminate, sodium hydroxide, and sodium silicate is 1:0.1-0.3:1-1.1.

[0010] Preferably, in the method for preparing the Na-LSX molecular sieve matrix, sodium aluminate and deionized water are in a weight ratio of 1:30-40.

[0011] Furthermore, the present invention also provides a method for preparing LSX molecular sieve low dew point adsorption material for deep dehumidification, comprising the following steps: (1) Add the rare earth metal salt to deionized water and stir until dissolved. Add the functionalized silane reagent, adjust the pH to 5.5-6 with acetic acid-sodium acetate buffer, and stir the reaction at 50-60℃ for 1-2 hours to obtain a rare earth-silane coordination precursor solution. In this step, the rare earth metal salt (a mixture of lanthanum nitrate and rubidium chloride) dissociates into La after dissolving in deionized water. 3+ and Rb + Adding a functionalized silane reagent (a complex of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane), under a pH controlled by an acetate-sodium acetate buffer, the epoxy groups in the silane reagent react with La... 3+ , amino and Rb + Coordination reactions occur separately, while the alkoxy groups of silane undergo hydrolysis to generate silanol groups, ultimately forming a stable rare earth-silane coordination precursor solution. This process achieves the directional binding of rare earth ions and silane functional groups through pre-coordination, avoiding competitive adsorption between the two in subsequent reactions. (2) Add the Na-LSX molecular sieve matrix to the rare earth-silane coordination precursor solution, add a dispersant, heat to 70-80℃, react at 300-400 r / min for 4-5 h, cool to room temperature, filter, wash the collected solid product with deionized water for 5-10 min, and dry to obtain the adsorption material precursor; In this step, the Na-LSX molecular sieve matrix is ​​added to the precursor solution, and the abundant hydroxyl groups on the surface of the molecular sieve undergo a dehydration condensation reaction with the silanol groups of the silane precursor to form a strong Si-O-Si covalent bond, so that the rare earth-silane coordination structure is grafted onto the surface of the molecular sieve; The added dispersant sodium dodecylbenzenesulfonate reduces the surface tension of the system, prevents the precursor from agglomerating, and ensures that the coordination structure is uniformly distributed on the surface of the molecular sieve. After the reaction, the precursor is obtained by filtration, washing with water and drying. (3) The precursor of the adsorption material is placed in a tube furnace, heated to 100-200℃ at 1-3℃ / min and kept at 1-3h, then heated to 450-500℃ at 2-5℃ / min and activated for 2-4h, and cooled to room temperature under a nitrogen atmosphere to obtain LSX molecular sieve low dew point adsorption material for deep dehumidification.

[0012] Preferably, in (1), the rare earth metal salt and deionized water are in a weight ratio of 1:40-60.

[0013] Preferably, the concentration of the acetate-sodium acetate buffer solution in (1) is 0.1 mol / L.

[0014] Preferably, in (2), the Na-LSX molecular sieve matrix and the dispersant are in a weight ratio of 1:0.02-0.05, and the dispersant refers to sodium dodecylbenzenesulfonate.

[0015] Preferably, the flow rate of nitrogen gas in (3) is 80-120 ml / min.

[0016] Preferably, the working mechanism of the LSX molecular sieve low dew point adsorption material used for deep dehumidification in this invention is as follows: First, the Na-LSX molecular sieve matrix provides the basic structural support for deep dehumidification. This matrix, prepared through a specific process, possesses a low silicon-to-aluminum ratio and a regular three-dimensional pore structure, with abundant Na in its framework. + The cation sites can serve as initial adsorption sites, capturing water vapor molecules through electrostatic attraction. Meanwhile, the high surface hydroxyl density resulting from the low silica-alumina ratio not only provides covalent binding sites for subsequent grafting of functionalized silane reagents, but also assists in adsorption through hydrogen bonding between hydroxyl groups and water molecules, laying the structural foundation for deep dehumidification. Secondly, the coordination active sites formed by the composite rare earth ions and functionalized silane reagents are the core of achieving efficient water vapor capture. During the preparation process, La... 3+ Rb undergoes a coordination reaction with the epoxy group of γ-(2,3-epoxypropoxy)propyltrimethoxysilane. + It forms a stable coordination structure with the amino group of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and the two coordination sites exhibit different binding energies: La 3+ -The epoxy group has a moderate coordination energy, which can efficiently capture trace amounts of water vapor molecules in extremely low humidity environments; Rb + -Amino coordination sites enhance the adsorption capacity for water molecules through hydrogen bonds. The two work together to cover the adsorption needs of water vapor at different concentrations in the low humidity range, providing an active guarantee for reducing the dew point to an extremely low level. Furthermore, the compound system of functionalized silane reagents also plays a role in regulating the adsorption-desorption balance, achieving low regeneration energy consumption. After the two silane reagents are stably combined with the Na-LSX molecular sieve matrix through Si-O-Si bonds, the alternating hydrophobic and hydrophilic surface structure formed by their molecular chains can, on the one hand, reduce the aggregation of water molecules in the pores and accelerate the diffusion of water vapor to the active sites; on the other hand, the hydrophobic segments of the silane molecules can weaken the excessive binding of water molecules with the adsorption material, avoiding the problem of excessively high regeneration temperature caused by excessive adsorption in traditional materials. At the same time, the gradient activation process further optimizes the stability of the silane-rare earth coordination structure, ensuring that the active sites do not fall off during adsorption. Only a low temperature is needed to achieve efficient desorption of water molecules, balancing deep dehumidification effect and energy economy. Ultimately, the synergistic effect of the above three elements constructs a complete dehumidification pathway of "rapid diffusion - efficient capture - gentle desorption": the pores of the Na-LSX molecular sieve enable the directional transport of water vapor, the rare earth-silane coordination sites complete the precise capture of trace amounts of water vapor, and the silane complex structure regulates the adsorption intensity to reduce regeneration energy consumption. The combined effect of the three elements enables the adsorbent material to still have a high adsorption capacity in extremely low humidity environments and stable regeneration performance.

[0017] The beneficial effects of this invention are: 1. This invention constructs a synergistic adsorption system by combining rare earth ions with functionalized silanes, La 3+ It forms a precise coordination site with the epoxy group of γ-(2,3-epoxypropoxy)propyltrimethoxysilane, Rb + The adsorption of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane is enhanced by hydrogen bonding. Combined with the surface hydroxyl groups and regular pores of the Na-LSX molecular sieve matrix, it can efficiently capture trace amounts of water vapor with a relative humidity as low as 10%, stably reducing the gas dew point to an extremely low level, meeting the stringent requirements of lithium battery production, aerospace and other fields for extremely dry environments.

[0018] 2. In this invention, the compounded silane forms a hydrophobic-hydrophilic alternating structure on the material surface, which can weaken the excessive binding of water molecules to the material; at the same time, the coordination bond between rare earth ions and silane ensures adsorption efficiency and avoids excessive energy required for desorption. In addition, the optimized structural stability of the gradient activation process significantly reduces the material regeneration temperature, eliminating the need for a high-grade heat source, effectively reducing the energy consumption of the dehumidification system and lowering the cost input in industrial applications.

[0019] 3. In this invention, the functionalized silane is firmly bonded to the Na-LSX molecular sieve matrix through Si-O-Si covalent bonds, while rare earth ions form coordination bonds with silane functional groups. The two intertwine to construct a three-dimensional stable network of "matrix-silane-rare earth", which can prevent the active sites from falling off during the cycle. The adsorption performance of the material remains stable after multiple cycles, reducing the cost and operational burden caused by frequent material replacement.

[0020] 4. The preparation process of this invention does not require complex equipment; the Na-LSX molecular sieve matrix can be obtained through stepwise crystallization without the need for special high-temperature or high-pressure conditions; at the same time, it abandons the traditional high-cost Li + Multiple exchange modifications, mild reaction conditions, readily available and controllable raw materials, avoid the limitations of expensive reagents or complex processes on large-scale production, making it suitable for industrial batch preparation.

[0021] 5. The material of this invention can not only achieve deep dehumidification at room temperature and pressure, but also flexibly adapt to the low dew point requirements of different fields, from electronics manufacturing to aerospace, by adjusting the ratio of rare earth and silane and the activation process according to the humidity and temperature requirements of different application scenarios. There is no need to redesign the material formula for specific scenarios, which has strong environmental adaptability and practicality, and broadens the application range of LSX molecular sieve adsorption materials. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0023] Preparation Example 1: The specific preparation method of Na-LSX molecular sieve includes the following steps: 100g of sodium aluminate and 4.88g of sodium hydroxide were added to 3kg of deionized water and stirred for 30min. Then, 148.87g of sodium silicate was added and stirred to form a sol. The sol was then aged at 40℃ for 12h. The sol was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and crystallized at 100℃ for 4h. After filtration, washing and drying, the Na-LSX molecular sieve matrix was obtained.

[0024] Preparation Example 2: The specific preparation method of Na-LSX molecular sieve includes the following steps: 100g of sodium aluminate and 9.76g of sodium hydroxide were added to 3.5kg of deionized water and stirred for 45min. Then, 156.35g of sodium silicate was added and stirred to form a sol. The sol was then aged at 50℃ for 24h. The sol was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and crystallized at 105℃ for 5h. After filtration, washing and drying, the Na-LSX molecular sieve matrix was obtained.

[0025] Preparation Example 3: The specific preparation method of Na-LSX molecular sieve includes the following steps: 100g of sodium aluminate and 14.64g of sodium hydroxide were added to 4kg of deionized water and stirred for 60min. Then, 163.8g of sodium silicate was added and stirred to form a sol. The sol was then aged at 60℃ for 36h. The sol was then transferred to a high-pressure reactor lined with polytetrafluoroethylene and crystallized at 110℃ for 6h. After filtration, washing and drying, the Na-LSX molecular sieve matrix was obtained.

[0026] Example 1: A specific preparation method for LSX molecular sieve low dew point adsorption material for deep dehumidification, including the following steps: (1) Add 3g of lanthanum nitrate and 2g of rubidium chloride to 200g of deionized water and stir until dissolved. Add 8g of functionalized silane reagent (a mixture of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in a molar ratio of 1:0.5). Adjust the pH to 5.5-6 with 0.1mol / L acetate-sodium acetate buffer solution. Heat to 50℃ and stir for 1h to obtain rare earth-silane coordination precursor solution. (2) Add 80g of the Na-LSX molecular sieve matrix prepared according to Preparation Example 1 to the rare earth-silane coordination precursor solution, and then add 1.6g of sodium dodecylbenzenesulfonate. Heat to 70℃ and react at 300r / min for 4h. After cooling to room temperature, filter, wash the collected solid product with deionized water for 5min, and dry to obtain the adsorption material precursor. (3) The adsorption material precursor was placed in a tube furnace, heated to 100℃ at 1℃ / min and kept at 1h for 1h, then heated to 450℃ at 2℃ / min for 2h for activation, and cooled to room temperature under a nitrogen flow atmosphere at a flow rate of 80ml / min to obtain LSX molecular sieve low dew point adsorption material for deep dehumidification.

[0027] Example 2: A specific preparation method for LSX molecular sieve low dew point adsorbent material for deep dehumidification, including the following steps: (1) Add 5g of lanthanum nitrate and 3g of rubidium chloride to 400g of deionized water and stir until dissolved. Add 10g of functionalized silane reagent (a mixture of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in a molar ratio of 1:0.8). Adjust the pH to 5.5-6 with 0.1mol / L acetate-sodium acetate buffer solution. Heat to 55℃ and stir for 1.5h to obtain rare earth-silane coordination precursor solution. (2) 100g of the Na-LSX molecular sieve matrix prepared according to Preparation Example 2 was added to the rare earth-silane coordination precursor solution, and then 3g of sodium dodecylbenzenesulfonate was added. The temperature was raised to 75℃ and the reaction was carried out at a speed of 350r / min for 4.5h. After cooling to room temperature, the mixture was filtered, and the collected solid product was washed with deionized water for 8min. After drying, the adsorption material precursor was obtained. (3) The precursor of the adsorption material is placed in a tube furnace, heated to 150°C at 2°C / min and kept at 2h for 2h, then heated to 480°C at 3°C / min for 3h for activation, and cooled to room temperature under a nitrogen flow atmosphere at a flow rate of 100ml / min to obtain LSX molecular sieve low dew point adsorption material for deep dehumidification.

[0028] Example 3: A specific preparation method for LSX molecular sieve low dew point adsorbent material for deep dehumidification, including the following steps: (1) Add 8g of lanthanum nitrate and 4g of rubidium chloride to 720g of deionized water and stir until dissolved. Add 12g of functionalized silane reagent (a mixture of γ-(2,3-epoxypropoxy)propyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane in a molar ratio of 1:1). Adjust the pH to 5.5-6 with 0.1mol / L acetate-sodium acetate buffer solution. Heat to 60℃ and stir for 2h to obtain rare earth-silane coordination precursor solution. (2) 120g of the Na-LSX molecular sieve matrix prepared according to Preparation Example 3 was added to the rare earth-silane coordination precursor solution, and then 6g of sodium dodecylbenzenesulfonate was added. The temperature was raised to 80℃ and the reaction was carried out at 400r / min for 5h. After cooling to room temperature, the mixture was filtered, and the collected solid product was washed with deionized water for 10min. After drying, the adsorption material precursor was obtained. (3) The precursor of the adsorption material is placed in a tube furnace, heated to 200℃ at 3℃ / min and kept at 3h for 3h, then heated to 500℃ at 5℃ / min for 4h for activation, nitrogen flow at 120ml / min, and cooled to room temperature under the atmosphere to obtain LSX molecular sieve low dew point adsorption material for deep dehumidification.

[0029] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that lanthanum nitrate is not added.

[0030] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that rubidium chloride is not added.

[0031] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that lanthanum nitrate and rubidium chloride are not added.

[0032] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that γ-(2,3-epoxypropoxy)propyltrimethoxysilane is not added.

[0033] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane was not added.

[0034] Comparative Example 6: The difference between Comparative Example 6 and Example 3 is that no functionalized silane reagents are added, that is, γ-(2,3-epoxypropoxy)propyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane are added.

[0035] Comparative Example 7: The difference between Comparative Example 7 and Example 3 is that the Na-LSX molecular sieve matrix prepared according to Preparation Example 3 was replaced with commercially available ordinary LSX molecular sieve.

[0036] Performance testing: 1. Water vapor adsorption capacity test under extremely low humidity: The static gravimetric adsorption method was used for testing. The test objects included the adsorption materials of Examples 1-3 and Comparative Examples 1-7. First, each test sample was placed in a vacuum drying oven at 120℃ for 24 hours to remove surface physically adsorbed water and residual impurities. After cooling to room temperature, the sample mass was accurately weighed (recorded as m0, with an accuracy of 0.0001g). Then, the sample was placed in the sample cell of the adsorption instrument. The test temperature was set to 25℃, and nitrogen gas (purity ≥99.99%) precisely controlled by a humidity generator was introduced to stabilize the relative humidity of the adsorption environment at 5% (simulating an extremely low humidity scenario). The test environment was kept at constant temperature and humidity, and the change in sample mass was continuously monitored until the sample mass change rate was ≤0.1% within 1 hour, which was considered to have reached adsorption equilibrium. The sample mass at this time was recorded (recorded as m1). According to the formula: Adsorption capacity (mg·g) -1 The water vapor adsorption capacity of each sample is calculated as (m1 - m0) × 1000 / m0. The experimental results are shown in Table 1.

[0037] 2. Regeneration Temperature and Desorption Efficiency Tests: A simultaneous thermal analyzer was used for testing, and the regeneration performance was analyzed using thermogravimetric-differential thermal (TG-DSC) curves. Approximately 10 mg of each test sample (Examples 1-3, Comparative Examples 1-7) was taken and adsorbed to equilibrium in an environment of 25℃ and RH=5%, then placed in the crucible of the thermal analyzer. The test atmosphere was set to nitrogen (flow rate 100 ml / min), and the programmed temperature rise parameters were: from room temperature to 300℃ at a rate of 10℃ / min. The sample mass loss rate and heat flow changes were recorded in real time throughout the process. The regeneration temperature was determined by the temperature at which 90% of the adsorbed water was desorbed from the sample. Simultaneously, the energy consumption per unit mass of sample during desorption was calculated. The experimental results are shown in Table 1.

[0038] 3. Adsorption-Regeneration Cycle Stability Test: A cycle test system was built based on a static adsorbent and a muffle furnace to test the performance degradation of each sample (Examples 1-3, Comparative Examples 1-7) after 50 adsorption-regeneration cycles. The single cycle procedure is as follows: ① Adsorption stage: Adsorption was performed under the conditions of "Water Vapor Adsorption Capacity Test under Extremely Low Humidity", and the equilibrium adsorption capacity was recorded; ② Regeneration stage: The adsorption-saturated sample was placed in a tube furnace, under a nitrogen atmosphere, at a flow rate of 100 ml / min, and heated to the regeneration temperature and held for 2 hours for desorption and regeneration; ③ Cooling stage: After natural cooling to 25℃, the next cycle began. After 50 cycles, the equilibrium adsorption capacity of the sample was tested again under the conditions of 25℃ and RH=5%, and the adsorption capacity decay rate was calculated. The experimental results are shown in Table 1.

[0039] 4. Minimum Dew Point Output Test: A dynamic continuous dehumidification test device was used to simulate the working conditions and test the actual dehumidification dew point level of each sample (Examples 1-3, Comparative Examples 1-7). The test device consisted of an air compressor, a dehumidifier, a humidity regulator, a sample adsorption column (inner diameter 20 mm, height 100 mm, filled with 5 g of sample), a dew point meter (accuracy ±0.1℃, measurement range -100℃-20℃), and a gas flow meter. Before the test, the sample was pretreated at 120℃ for 2 hours and then loaded into the adsorption column. The inlet conditions were set as follows: room temperature (25℃), initial relative humidity 30%, and gas flow rate 50 ml / min. The airflow was continuously introduced, and the dew point temperature of the gas at the outlet of the adsorption column was monitored in real time using the dew point meter. The value from the start of the test until the dew point stabilized (fluctuation ≤0.5℃ within 30 minutes) was recorded as the minimum dew point output value of the sample. The experimental results are shown in Table 1.

[0040] Table 1 Performance Test Results Performance Analysis: As can be seen from the experimental data in Table 1, the adsorbent materials prepared by the present invention in Examples 1-3 are significantly better than those in Comparative Examples 1-7 in terms of water vapor adsorption capacity, regeneration temperature and energy consumption control, cycle stability and minimum dew point output. Moreover, with the optimization of rare earth and silane dosages and the improvement of activation process during preparation, the performance shows a gradual improvement trend, with Example 3 showing the best overall performance.

[0041] Example 3 exhibits a higher water vapor adsorption capacity at extremely low humidity, which may be due to the La content in the composite rare earth element. 3+ It forms stable coordination bonds with the epoxy groups of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560). The empty orbitals of this coordination structure can precisely capture water molecules and form weak coordination interactions, while Rb + The adsorption of water molecules by the amino group of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792) is enhanced through hydrogen bonding. These two effects synergistically cover adsorption sites with different binding energy requirements under extremely low humidity conditions. Simultaneously, the low silica-to-alumina ratio of the Na-LSX matrix results in a higher density of hydroxyl groups on its surface. These hydroxyl groups form secondary hydrogen bonds with water molecules, further aiding adsorption. Furthermore, the porous structure of the matrix itself provides directional channels for water vapor diffusion, reducing mass transfer resistance. Compared to Example 3, Comparative Example 1 lacks La... 3+ The precise capture sites formed by epoxy group coordination are lost, resulting in a reduction in the number of adsorption sites; Comparative Example 2 lacks Rb. + The enhanced adsorption effect of amino hydrogen bonds disappears, relying solely on single coordination interactions, resulting in a decrease in adsorption capacity; Comparative Example 3 contains no rare earth elements and lacks rare earth-silane coordination active sites, relying solely on the Na+ of the Na-LSX matrix itself. +Adsorption and hydrogen bonding with hydroxyl groups; insufficient adsorption sites at extremely low humidity levels lead to a significant decrease in adsorption capacity; Comparative Example 4 lacks KH560, thus failing to form La. 3+ -Epoxy group coordination, retaining only Rb + -Amino adsorption, with a single site type; Comparative Example 5 lacks KH792 and Rb. + -Amino adsorption is lost, only La remains. 3+ - Epoxy groups coordinate, resulting in insufficient adsorption strength; Comparative Example 6 uses unfunctionalized silane, where rare earth ions cannot form stable bonds with the matrix, easily agglomerate, leading to the failure of active sites and a sharp drop in adsorption capacity; Comparative Example 7 uses commercially available ordinary LSX matrix, with a lower surface hydroxyl density than Na-LSX matrix, making it difficult to form uniform adsorption sites, resulting in significantly lower adsorption capacity.

[0042] Example 3 shows a lower regeneration temperature and lower energy consumption, possibly because the molecular chains formed by the compounded silanes KH560 and KH792 construct an alternating hydrophobic-hydrophilic structure on the matrix surface. The hydrophobic segments weaken the excessive binding of water molecules to the surface of the adsorbent material, reducing the energy required for water molecule desorption; simultaneously, La 3+ -Epoxy group, Rb + The coordination bonds of the -amino group ensure the capture capacity during adsorption while avoiding the need for excessively high energy to break the bonds during desorption. Furthermore, the gradient activation process fully condenses the Si-O-Si covalent bonds, making the rare earth-silane coordination structure more stable and reducing the additional energy consumption caused by structural loosening during desorption. Comparative Examples 1-2, lacking a single rare earth element, have incomplete coordination structures, uneven distribution of water molecule binding energy, and some excessively strong binding interactions, requiring higher temperatures for desorption and thus increasing energy consumption. Comparative Example 3 lacks rare earth-silane coordination; water molecules mainly form strong hydrogen bonds with the matrix hydroxyl groups and Na+. + The electrostatic adsorption of the rare earth elements in Example 3 is high, requiring higher temperatures for desorption and significantly increasing energy consumption. Comparative Examples 4-5, lacking a single silane, have incomplete hydrophobic-hydrophilic alternating structures, weakening their control over the binding energy of water molecules. Therefore, the desorption temperatures and energy consumption are higher than in Example 3. In Comparative Example 6, without silane, rare earth ions easily form strong interactions with water molecules after binding, and without the hydrophobic control of silane, desorption is extremely difficult, resulting in the highest regeneration temperature and energy consumption. In Comparative Example 7, the commercially available LSX matrix has weaker binding force with rare earth-silane, and some modified components easily detach with water molecules during desorption. To ensure complete desorption, the temperature needs to be increased, leading to increased energy consumption.

[0043] Example 3 exhibits superior cycling stability, likely because the functionalized silane is firmly bonded to the hydroxyl groups on the Na-LSX matrix surface via Si-O-Si covalent bonds, while rare earth ions form coordination bonds with silane functional groups. These two types of chemical bonds intertwine to construct a three-dimensional network of matrix-silane-rare earth, a structure that is less prone to breakage during cyclic adsorption-desorption, making it difficult for active sites to detach. Comparative Examples 1-2, lacking a single rare earth element, have defective three-dimensional network structures, preventing the formation of some coordination bonds. During cycling, the remaining active sites are easily degraded due to thermal stress, leading to increased decay rates. Comparative Example 3 lacks rare earth-silane coordination and relies solely on the matrix material... In the case of adsorption, after multiple cycles, the matrix pores are prone to collapse due to the expansion and contraction caused by repeated adsorption and desorption of water vapor, resulting in a significant decrease in adsorption capacity. In Comparative Examples 4-5, the absence of a single silane leads to incomplete covalent bonding in the three-dimensional network, reduced structural stability, and easy detachment of active sites during cycling. In Comparative Example 6, without silane, rare earth ions only adhere to the matrix surface through weak interactions, resulting in a large number of detachments during cycling, a sharp reduction in active sites, and the highest decay rate. In Comparative Example 7, the commercially available LSX matrix has low crystallinity and insufficient covalent bonding sites with silane, resulting in an unstable three-dimensional network structure that is easily damaged during cycling, with a higher decay rate than in Example 3.

[0044] Example 3 achieves a lower dew point output because the rare earth-silane coordination active sites can effectively capture trace amounts of water vapor in the airflow, even in extremely low humidity environments, through La 3+ - Precise coordination of epoxides and Rb + The hydrogen bonding of the -amino group reduces the residual water vapor content to an extremely low level. Simultaneously, the directional transport effect of the matrix pores accelerates the diffusion of water vapor to the active sites, preventing water vapor from lingering within the pores and ensuring continuous removal of water vapor from the outlet gas. Comparative Examples 1-2, lacking a single rare earth element, have a lower active site density, making it unable to completely capture trace amounts of water vapor, resulting in more residual water vapor in the outlet gas and a higher dew point than Example 3. Comparative Example 3, lacking rare earth-silane coordination, has limited adsorption capacity, making it difficult to remove extremely low concentrations of water vapor, leading to a significant increase in the dew point. Comparative Examples 4-5, lacking a single silane, have incomplete active site types, resulting in decreased capture efficiency for trace amounts of water vapor and a higher dew point. Comparative Example 6, without silane, has extremely poor adsorption capacity, failing to meet the requirements for deep dehumidification, and has the highest dew point. Comparative Example 7, with its commercially available LSX matrix and modifier, has poor compatibility, uneven distribution of active sites, and some trace amounts of water vapor cannot be captured, resulting in a higher dew point than Example 3.

[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low dew point adsorbent material for use in deep dehumidification, characterized in that, The application relates to a preparation method of a low dew point adsorption material for deep dehumidification, which comprises the following raw materials in parts by weight: a Na-LSX molecular sieve matrix: 80-120 parts, a rare earth metal salt: 5-12 parts, and a functional silane reagent: 8-12 parts. The preparation method of the Na-LSX molecular sieve matrix is as follows: Sodium metaaluminate and sodium hydroxide are added into deionized water, stirred for 30-60 min, then sodium silicate is added, and a sol is formed after stirring; the sol is aged at 40-60 DEG C for 12-36 h, then is transferred into a high-pressure reaction kettle provided with a polytetrafluoroethylene lining, crystallized at 100-110 DEG C for 4-6 h, filtered, washed and dried to obtain the Na-LSX molecular sieve matrix.

2. The LSX molecular sieve low dew point adsorbent material for deep dehumidification according to claim 1, characterized in that, The rare earth metal salt refers to a mixture of lanthanum nitrate and rubidium chloride in a weight ratio of 3-8:2-4.

3. The LSX molecular sieve low dew point adsorbent material for deep dehumidification according to claim 1, characterized in that, The functional silane reagent refers to a mixture of gamma-(2,3-epoxypropoxy) propyl trimethoxysilane and N-(beta-aminoethyl)-gamma-aminopropyl trimethoxysilane in a molar ratio of 1:0.5-1.

4. The LSX molecular sieve low dew point adsorbent material for deep dehumidification according to claim 1, characterized in that, In the preparation method of the Na-LSX molecular sieve matrix, the molar ratio of sodium metaaluminate, sodium hydroxide and sodium silicate is 1:0.1-0.3:1-1.

1.

5. The LSX molecular sieve low dew point adsorbent material for deep dehumidification according to claim 1, characterized in that, In the preparation method of the Na-LSX molecular sieve matrix, the weight ratio of sodium metaaluminate and deionized water is 1:30-40.

6. The method of claim 1-5, wherein the LSX molecular sieve low dew point adsorbent material for deep dehumidification is prepared by the following steps: The application further discloses a preparation method of the low dew point adsorption material for deep dehumidification. (1) the rare earth metal salt is added into deionized water and stirred until dissolved, the functional silane reagent is added, an acetic acid-sodium acetate buffer solution is used to adjust the pH to 5.5-6, and the mixture is stirred at 50-60 DEG C for 1-2 h to obtain a rare earth-silane coordination precursor solution; (2) the Na-LSX molecular sieve matrix is added into the rare earth-silane coordination precursor solution, a dispersing agent is further added, the mixture is reacted at 70-80 DEG C for 4-5 h under the condition of a rotating speed of 300-400 r / min, and after cooling to room temperature, the collected solid product is washed with deionized water for 5-10 min, and then dried to obtain an adsorption material precursor; (3) the adsorption material precursor is placed in a tube furnace, heated at a speed of 1-3 DEG C / min to 100-200 DEG C and kept for 1-3 h, then heated at a speed of 2-5 DEG C / min to 450-500 DEG C and activated for 2-4 h, and cooled to room temperature in a nitrogen flow atmosphere to obtain the LSX molecular sieve low dew point adsorption material for deep dehumidification.

7. The method of claim 6, wherein the LSX molecular sieve low dew point adsorbent material for deep dehumidification is prepared by the steps of: In the step (1), the weight ratio of the rare earth metal salt and deionized water is 1:40-60.

8. The method of claim 6, wherein the LSX molecular sieve low dew point adsorbent material for deep dehumidification is prepared by the steps of: In the step (1), the concentration of the acetic acid-sodium acetate buffer solution is 0.1 mol / L.

9. The method of claim 6, wherein the LSX molecular sieve low dew point adsorbent material for deep dehumidification is prepared by the steps of: In the step (2), the weight ratio of the Na-LSX molecular sieve matrix and the dispersing agent is 1:0.02-0.05, and the dispersing agent is sodium dodecyl benzene sulfonate.

10. The method of claim 6, wherein the LSX molecular sieve low dew point adsorbent material for deep dehumidification is prepared by the steps of: In the step (3), the flow rate of the nitrogen flow is 80-120 ml / min.

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