A molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification and a preparation method thereof

Abstract

The application discloses a kind of molecular sieve-aluminum fumarate metal MOF composite adsorbing material for rotary dehumidification and preparation method thereof, comprising: first, preparing aluminum fumarate MOF powder;Second step, molecular sieve, the aluminum fumarate MOF powder, silica sol, water and organic binder are uniformly mixed to form composite slurry;By prefabricated aluminum fumarate MOF powder again composite slurry is made, avoid aluminum fumarate MOF particle migration, local enrichment and structure uneven, the steps of preparing aluminum fumarate MOF powder are as follows: first, fumaric acid is dissolved in water with sodium hydroxide to form a homogeneous solution;Second step, then the solution is added to aluminum sulfate solution;Third step, under the condition of 50~70 ℃, reaction 0.5~2h;Fourth step, after reaction, the obtained solid is dried at 80~120 ℃ for 6~12h, then ground, to obtain aluminum fumarate MOF powder with particle size of 1~10 μm.

Description

Technical Field

[0001] This invention relates to the field of composite adsorption materials technology, specifically a molecular sieve-aluminum fumarate metal MOF composite adsorption material for rotary dehumidification and its preparation method. Background Technology

[0002] Rotary dehumidifier technology is widely used in air conditioning, drying, and air treatment, and its core lies in the adsorption capacity of the adsorbent material for moisture in the air. Traditional rotary dehumidifier materials mainly include inorganic porous materials such as silica gel and molecular sieves. Among them, molecular sieves have excellent adsorption performance under low humidity conditions, but they are prone to rapid saturation under high humidity conditions, resulting in limited adsorption capacity; while silica gel has a high adsorption capacity under high humidity conditions, its adsorption performance decreases significantly under low humidity conditions. Therefore, it is difficult for a single adsorbent material to achieve efficient adsorption simultaneously over a wide humidity range.

[0003] In recent years, metal-organic frameworks (MOFs) have attracted attention due to their high specific surface area, tunable pore structure, and excellent water adsorption performance. Among them, aluminum fumarate MOFs (such as MIL-53(Al)-FA) exhibit good hydrothermal stability and stepwise adsorption-desorption characteristics, showing potential application in rotary dehumidifiers. Existing technologies have explored combining molecular sieves with MOF materials to achieve synergistic adsorption effects.

[0004] However, existing methods for preparing composite adsorbent materials mostly employ in-situ synthesis routes, where MOF precursors react to generate MOF crystals in the presence of molecular sieves or supports. This approach has the following drawbacks: First, the random nucleation and growth of MOF crystals in solution easily leads to particle migration, localized enrichment, and structural inhomogeneity, affecting the adsorption uniformity of the composite material. Second, to stabilize the reaction system, large amounts of additives or a high-viscosity environment are usually required, increasing process complexity and additive usage. Third, the in-situ crystallization process is greatly affected by fluctuations in reaction conditions, making batch stability and repeatability difficult to guarantee, which is detrimental to continuous industrial production. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a composite adsorbent material with uniform dispersion, controllable process, good batch stability and excellent adsorption performance, and its preparation method, which can solve the problems in the prior art.

[0006] This invention is achieved through the following technical solution: A method for preparing a molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification, comprising: a first step, preparing aluminum fumarate MOF powder; a second step, uniformly mixing the molecular sieve, the aluminum fumarate MOF powder, silica sol, water, and organic binder to form a composite slurry; by pre-preparing the aluminum fumarate MOF powder before preparing the composite slurry, migration, local enrichment, and structural inhomogeneity of the aluminum fumarate MOF particles are avoided.

[0007] A further technical solution involves the following steps for preparing aluminum fumarate MOF powder: First, fumarate and sodium hydroxide are dissolved in water to form a homogeneous solution; second, this solution is then added to an aluminum sulfate solution; third, the reaction is carried out at 50–70°C for 0.5–2 h; fourth, after the reaction is completed, the mixture is filtered, and the resulting solid is dried at 80–120°C for 6–12 h, followed by grinding to obtain aluminum fumarate MOF powder with a particle size of 1–10 μm.

[0008] In a further technical solution, in the first step, the mass ratio of fumaric acid, sodium hydroxide and water is 1:1:(8-15).

[0009] In a further technical solution, in the second step, the mass ratio of aluminum sulfate to water is 1:(3-6).

[0010] A further technical solution is provided, wherein the composite slurry comprises molecular sieve: 30-60 parts, MOF powder: 10-40 parts, silica sol: 10-30 parts, water: 50-150 parts, and organic binder: 0.5-3 parts. The solid content of the slurry is 25%-45%, and the viscosity is 500-1500 mPa·s.

[0011] In a further technical solution, the organic binder includes one or more of chitosan, polyvinyl alcohol, or carboxymethyl cellulose.

[0012] A method for preparing a moisture-absorbing material from a composite slurry of molecular sieve-metal alumina fumarate (MOF) for rotary dehumidification: First, immerse a blank preform in the above slurry for 5 minutes and then remove it; Second, lift the immersed blank preform and then blow away excess slurry from the pores with an air knife; Third, dry the blown blank preform with hot air at 120°C for 1 hour to obtain a blocky composite moisture-absorbing material.

[0013] The beneficial effects of this invention are as follows: First, it reduces the use of additives: Because this invention uses a pre-formed MOF powder system, there is no need to stabilize the reaction system. Therefore, it avoids the problems of particle migration, local enrichment, and structural inhomogeneity caused by random nucleation and growth of crystals in solution, fundamentally reducing the system's dependence on high-viscosity environments. Compared to existing technologies that require a large amount of additives to stabilize the reaction system, this invention achieves stable dispersion simply by controlling the slurry solids content and the basic binding system, thereby significantly reducing the amount of additives used.

[0014] II. Strong process controllability: MOF powder is prepared independently, avoiding the uncertainty of the in-situ crystallization process and improving batch stability and repeatability.

[0015] III. Excellent adsorption performance: The synergistic effect of molecular sieve and MOF enables wide-range and efficient adsorption under both low and high humidity conditions.

[0016] IV. Suitable for continuous production: The slurry system is stable and can be directly applied to coating or impregnation production lines, making it suitable for the industrial preparation of rotary dehumidification materials. Attached Figure Description

[0017] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0018] Figure 1 This is a schematic diagram of the process for preparing a molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification and its preparation method, according to the present invention. Figure 2 The graph shows the change in water vapor adsorption rate of each sample over time. Figure 3 Nitrogen adsorption-desorption isotherms for each sample; Figure 4 This is the first SEM image of the molecular sieve-aluminum fumarate metal MOF composite adsorbent material. Figure 5 This is the second SEM image of the molecular sieve-aluminum fumarate metal MOF composite adsorbent material. Figure 6 This is the third SEM image of the molecular sieve-aluminum fumarate metal MOF composite adsorbent material. Detailed Implementation

[0019] like Figures 1-6 As shown, the present invention will be described in detail. For ease of description, the directions mentioned below are defined as follows: the directions of up, down, left, right, front, and back mentioned below are the same as... Figure 1 The directions of the projection relationship are consistent in all directions: up, down, left, right, front, and back.

[0020] Example 1: A molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification and its preparation method, comprising the following steps: Step 1, Preparation of aluminum fumaric acid MOF powder: Fumaric acid, sodium hydroxide and water are mixed in a mass ratio of 1:1:10 and added to aluminum sulfate solution (mass ratio of 1:4). The mixture is reacted at 55℃ for 1 hour. After filtration, it is dried at 100℃ for 8 hours and then ground to obtain MOF powder. The second step is the preparation of aluminum fumaric acid MOF powder and molecular sieve impregnation solution: 20 parts by mass of silica sol, 50 parts by mass of molecular sieve, 50 parts by mass of aluminum fumaric acid MOF powder, 100 parts by mass of water and 1 part by mass of chitosan are stirred for 1 hour to obtain a slurry with a viscosity of about 1000 mPa·s. The third step is the preparation of the moisture-absorbing material: the blank preform is immersed in the above slurry for 5 minutes, then taken out and lifted out. The excess slurry in the pores is blown away with an air knife, and then dried with hot air at 120°C for 1 hour to obtain the blocky composite moisture-absorbing material.

[0021] At 25°C and 70% humidity, the moisture absorption rate of the saturated mass of the moisture-absorbing material is 15%.

[0022] At 25°C and 20% humidity, the moisture absorption rate of the saturated mass of the moisture-absorbing material is 10%.

[0023] Comparative Example 1: No molecular sieve was added in the second step.

[0024] At 25°C and 70% humidity, the moisture absorption rate of the saturated mass of the moisture-absorbing material is 14%.

[0025] At 25°C and 20% humidity, the moisture absorption rate of the saturated mass of the moisture-absorbing material is 5%.

[0026] Comparative Example 2: The first step was omitted, and aluminum fumarate MOF powder was not added in the second step.

[0027] At 25℃ and 70% humidity, the moisture absorption rate of the saturated mass of the moisture-absorbing material is 10%.

[0028] At 25°C and 20% humidity, the moisture absorption rate of the saturated mass of the moisture-absorbing material is 8%.

[0029] Example 4: According to the formulation of this patent application, the mass percentage content of the organic binder can be calculated in the following way: Total proportions of each component: Molecular sieve: 30-60 parts, MOF powder: 10-40 parts, silica sol: 10-30 parts, water: 50-150 parts, organic binder: 0.5-3 parts, the solid content of the slurry is 25%-45%; Minimum total number of portions: 30 + 10 + 10 + 50 + 0.5 = 100.5 portions; Maximum total number of portions: 60 + 40 + 30 + 150 + 3 = 283 portions; The content of organic binder in the wet slurry is approximately 0.50% to 1.06%. The patent document with publication number "CN110523380B" employs an in-situ synthesis route, and its system only involves the formation process of aluminum-fumaric acid MOF on a honeycomb ceramic matrix, without addressing the synergistic dispersion of multiple adsorbent materials. In contrast, this application presents a molecular sieve-aluminum fumaric acid MOF composite system, in which the molecular sieve and MOF exhibit significant differences in particle size, specific surface area, and surface chemical properties, belonging to a typical multiphase solid composite dispersion system. Such systems in existing technologies typically require the introduction of multiple additives such as dispersants, thickeners, and stabilizers to prevent agglomeration and phase separation.

[0030] Comparing with the patent document with publication number "CN 120132805 A", its synthesis system is similar to that of this application, which clearly adopts a compound system of film-forming agent and thickener, and the total content of its additives reaches 1 to 3.5 wt.%; in contrast, this application only uses 0.50% to 1.06% organic binder, and combines it with an inorganic binder system to achieve stable dispersion and molding, and the overall amount and types of additives are significantly reduced.

[0031] The nucleation and composite processes of MOF crystals are carried out separately: As described in the specification, this application first synthesizes aluminum fumarate MOF powder in an independent system, and obtains stable particles with a particle size of 1–10 μm through filtration, drying, and grinding. In the subsequent preparation of the composite slurry, MOF precursors (such as metal salts and organic ligands) are no longer present in the system, thus the chemical conditions for crystal nucleation and growth to occur again are not met, eliminating the prerequisite for "random nucleation in solution" from a mechanistic perspective.

[0032] The composite stage is a physical dispersion process rather than a chemical reaction process: the second step of this application only involves the mixing and dispersion of molecular sieves, MOF powder, silica sol, and organic binders, which is a typical solid-liquid dispersion system. In this process, MOF exists in the form of pre-formed particles, and its spatial distribution is only controlled by the rheology of the slurry and the uniformity of dispersion, without being driven by crystal growth. Therefore, there will be no particle migration or local enrichment problems caused by continuous crystal growth.

[0033] Particle size pre-control: This application controls the particle size of MOF powder within the range of 1–10 μm through grinding. This particle size is on the same order of magnitude as molecular sieve particles, which is beneficial for forming a stable multiphase dispersion system and reducing sedimentation, stratification, and local enrichment caused by density or particle size differences. This is fundamentally different from systems where nano / submicron crystals are generated in situ and are prone to migration.

[0034] Process results verify structural uniformity: The composite material in the examples in the specification exhibits stable and synergistic adsorption performance under different humidity conditions (e.g., the adsorption capacity at low and high humidity is better than that of a single component). The application effect shows that the internal structure of the material is uniformly distributed; otherwise, it would be difficult to achieve stable synergistic adsorption behavior.

[0035] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without creative effort should be included within the scope of protection of the present invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for preparing a molecular sieve-aluminum fumarate metal MOF composite adsorbent for rotary dehumidification, characterized in that, include: The first step is to prepare aluminum fumarate MOF powder; the second step is to mix molecular sieve, aluminum fumarate MOF powder, silica sol, water and organic binder evenly to form a composite slurry; by pre-preparing aluminum fumarate MOF powder and then making the composite slurry, the migration, local enrichment and structural inhomogeneity of aluminum fumarate MOF particles can be avoided.

2. The preparation method of a molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification according to claim 1, characterized in that: The steps for preparing aluminum fumaric acid MOF powder are as follows: First, fumaric acid and sodium hydroxide are dissolved in water to form a homogeneous solution; second, the solution is then added to an aluminum sulfate solution; third, the reaction is carried out at 50–70°C for 0.5–2 hours. Fourth step: After the reaction is completed, the solid is filtered and dried at 80-120℃ for 6-12 hours. Then it is ground to obtain aluminum fumarate MOF powder with a particle size of 1-10 μm.

3. The method for preparing a molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification according to claim 2, characterized in that: In the first step, the mass ratio of fumaric acid, sodium hydroxide and water is 1:1:(8-15).

4. The method for preparing a molecular sieve-aluminum fumarate metal MOF composite adsorbent for rotary dehumidification according to claim 2, characterized in that: In the second step, the mass ratio of aluminum sulfate to water is 1:(3-6).

5. A method for preparing a molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification according to any one of claims 1-4, characterized in that: The composite slurry comprises 30-60 parts of molecular sieve, 10-40 parts of MOF powder, 10-30 parts of silica sol, 50-150 parts of water, and 0.5-3 parts of organic binder. The solid content of the slurry is 25%-45%, and the viscosity is 500-1500 mPa·s.

6. The method for preparing a molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification according to claim 5, characterized in that: The organic binder includes one or more of chitosan, polyvinyl alcohol, or carboxymethyl cellulose.

7. A method for preparing a moisture-absorbing material using the preparation method of the molecular sieve-aluminum fumarate metal MOF composite adsorbent material for rotary dehumidification as described in claim 5, characterized in that: The first step is to immerse the blank preform in the composite slurry for 5 minutes and then remove it. The second step is to lift out the impregnated blank preform and then blow away the excess slurry in the pores with an air knife; the third step is to dry the blown blank preform with hot air at 120°C for 1 hour to obtain a blocky composite moisture-absorbing material.

Images