Core-shell structure composite adsorbent, preparation method and application thereof
By preparing a core-shell structured composite adsorbent, the problem of the inability to remove multiple impurities from alcohols simultaneously in existing technologies has been solved, achieving efficient and environmentally friendly impurity removal while reducing energy consumption and improving regeneration performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FTSCI HUBEI BIOTECH CO LTD
- Filing Date
- 2026-04-09
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies cannot simultaneously and efficiently remove polar impurities, non-polar impurities, and metal ions from alcohols. Furthermore, the preparation process is not environmentally friendly and has poor regeneration performance, resulting in complex processes and high energy consumption.
A core-shell structured composite adsorbent is prepared by co-precipitation-hot soaking method using ZIF-8 nanocrystals as the core layer, sulfonated UiO-66-NH2 microspheres as the shell layer, and externally coated with a cross-linked polyvinyl alcohol layer. Combined with sulfonation and thermosetting treatment, a core-shell structured composite adsorbent is formed.
It achieves gradient capture of aldehydes, ketones, carboxylic esters, aromatic hydrocarbons and metal ions, simplifies the impurity removal process, reduces distillation energy consumption, and improves regeneration stability and adsorption capacity.
Abstract
Description
Technical Field
[0001] This invention relates to the field of impurity adsorption materials technology, specifically to core-shell structured composite adsorbents, their preparation methods, and applications. Background Technology
[0002] Ethanol and methanol, as important basic chemical raw materials, often require a purity of ≥99.99 wt% in fields such as pharmaceutical synthesis, electronic material cleaning, and fine chemical preparation. Trace impurities in these raw materials (mainly including aldehydes, ketones, carboxylic esters, aromatic hydrocarbons, and metal ions) can severely affect the performance of downstream products. For example, metal ions in electronic-grade methanol can cause short circuits in semiconductor devices, and aldehyde impurities in pharmaceutical-grade ethanol can trigger side reactions and affect product safety. Therefore, efficiently removing these trace impurities is a crucial step in the preparation of high-purity ethanol / methanol.
[0003] In the prior art, there have been relevant studies on adsorption materials and methods for alcohol purification, among which the use of metal-organic frameworks (MOFs) for purification has been widely reported. For example, US2018 / 0254830A1 discloses a silicon and MOF-based catalytic membrane for the removal of trace organic matter. This technology uses DMSO as a solvent to prepare the catalytic membrane, which is mainly aimed at single types of organic impurities and cannot simultaneously treat polar impurities, non-polar impurities, and metal ions. Moreover, the membrane structure has a large permeation resistance, limiting its applicability to certain systems. Chen proposed a synergistic adsorbent separation technology, but this technology is designed for ethylene purification. The composition ratio and adsorption mechanism of the adsorbent cannot be adapted to the multiple types of impurities in the alcohol system, especially lacking the ability to capture metal ions (Science, 2019, 366, 241-246).
[0004] Furthermore, the application of single MOF materials has significant limitations: ZIF-8 possesses hydrophobic channels and exhibits excellent adsorption performance for nonpolar impurities such as aromatic hydrocarbons and alkenes, but its adsorption capacity for polar impurities such as aldehydes and ketones, as well as metal ions, is extremely weak (Microporous and Mesoporous Materials, 2013, 173, 1-5). UiO-66-NH2 can form hydrogen bonds / π-π interactions with aldehydes and ketones through its amino groups, and its sulfonation modification enables it to capture metal ions, but its adsorption effect on nonpolar aromatic hydrocarbons is poor (Journal of Cleaner Production, 2019, 229, 470-479). Meanwhile, Pamela et al. disclosed a method for preparing PVA-coated MOF particles, but this method only coats single MOF particles and does not involve the composite of core-shell structured MOFs. Moreover, the adsorption selectivity and regeneration stability of the coated material are insufficient, which cannot meet the long-term use requirements of multi-impurity systems (Mater. Adv., 2022, 3, 6458-6465).
[0005] In summary, the existing technology has the following drawbacks: (1) A single adsorption material or catalytic membrane cannot simultaneously and efficiently remove polar impurities, non-polar impurities and metal ions from alcohols. A multi-step impurity removal process is required, which is complex and energy-intensive. (2) Existing MOF composite technology lacks adjustable gradient adsorption design, which limits adsorption selectivity and applicability; (3) Some technologies use harmful solvents such as DMSO, which are not environmentally friendly and have complex regeneration processes and insufficient cycle stability.
[0006] Therefore, developing a composite adsorbent that can simultaneously treat multiple types of impurities, has an environmentally friendly preparation process, and exhibits excellent regeneration performance has significant practical application value. Summary of the Invention
[0007] This invention proposes a core-shell structured composite adsorbent and its preparation method, which at least solves one of the many defects of existing technologies, such as environmentally unfriendly preparation processes, difficulty in removing multiple impurities, and poor regeneration performance.
[0008] The technical solution of this invention is implemented as follows:
[0009] In a first aspect, the present invention provides a core-shell structured composite adsorbent comprising a core-shell structure with ZIF-8 nanocrystals as the core layer and sulfonated UiO-66-NH2 microspheres as the shell layer, wherein the outer layer of the core-shell structure is coated with a cross-linked polyvinyl alcohol layer.
[0010] Furthermore, the core-shell structure is obtained by co-precipitation and hot leaching of ZIF-8 and UiO-66-NH2 in an alcohol-water solution to obtain a core-shell structure precursor, which is then sulfonated.
[0011] Preferably, the mass ratio of ZIF-8 to UiO-66-NH2 is (1-3):(5:1).
[0012] Preferably, the sulfonation degree of the core-shell precursor is 0.8-1.2 mmol / g.
[0013] Furthermore, the thickness of the cross-linked polyvinyl alcohol layer is 5-30 μm.
[0014] A second aspect of the present invention is to provide a method for preparing the core-shell structured composite adsorbent described in the first aspect above, comprising:
[0015] S1. Disperse the zinc source, 2-methylimidazole, zirconium source and 2-aminoterephthalic acid into a solution;
[0016] S2. Heat to 80-95℃ and react for 3-5 hours to obtain the core-shell structured precursor;
[0017] S3. The core-shell structure precursor is sulfonated under the action of a sulfonating agent to obtain the core-shell structure;
[0018] S4. The core-shell structure is dispersed in a low-concentration polyvinyl alcohol solution, then dried to remove the solvent, and then thermocured to obtain a core-shell structured composite adsorbent.
[0019] Further, in step S3, the core-shell structure is obtained by mixing a core-shell structure precursor and a sulfonating agent in a molar ratio of (1-1.5):1, reacting at 60-80 °C for 2-3 h, and then washing and drying.
[0020] Further, in step S4, the concentration of the polyvinyl alcohol solution is 2-8%;
[0021] And / or, the thermosetting temperature is 110-130℃ and the time is 1.5-3h.
[0022] A third aspect of the present invention is to provide the application of the core-shell structured composite adsorbent described in the first aspect above, or the core-shell structured composite adsorbent prepared by the preparation method described in the second aspect, in the removal of impurities, wherein the impurities are selected from at least one of aldehydes, ketones, carboxylic acid esters, aromatic hydrocarbons, and metal ions.
[0023] Furthermore, the application is for the preparation of high-purity methanol or ethanol, and is particularly suitable for the purification of high-purity ethanol or methanol required in the pharmaceutical, electronics, and fine chemical industries.
[0024] Furthermore, in this application, the core-shell composite adsorbent is filled into the impurity removal unit, and the raw material feed flow rate is controlled at 0.5-1.0 BV·h. -1 The operating temperature is 25-40℃, and the operating pressure is atmospheric pressure -0.3 MPa. Under these conditions, the removal rates of acetone, acetaldehyde, benzene, and metal ions in the raw materials are no less than 97%, 96%, 99%, and 99%, respectively.
[0025] Furthermore, the application can combine the impurity removal unit with the distillation unit. The impurity removal unit can be a spiral or stacked fixed bed, equipped with a temperature sensor and flow rate monitoring instrument to control the impurity removal efficiency online. The fixed bed is integrated into the "pre-impurity removal box" at the top of the distillation reflux column. The inlet of the pre-impurity removal box is connected to the raw material storage tank, and the outlet is connected to the inlet of the distillation reflux column. Through the combination of impurity removal and distillation separation, ethanol or methanol with a purity of over 99.99% can be obtained.
[0026] The above-mentioned device integrates adsorption and purification with distillation processes. The raw material first passes through a pre-purification box to remove trace impurities in one go, and then enters the distillation column for distillation separation. This avoids the accumulation of impurities in the distillation column, significantly reduces distillation energy consumption by 15-20%, and improves the operational stability of the distillation column.
[0027] Furthermore, the application also includes the regeneration of core-shell structured composite adsorbents, including: 1) Removal of polar impurities: The adsorbent is rinsed with low-pressure steam at 60-90℃ to remove adsorbed aldehydes, ketones and carboxylic acid esters; 2) Removal of nonpolar impurities: A mixture of nitrogen and hydrogen is introduced, and thermal desorption is performed at 120-160℃ under vacuum for 10-30 min to remove adsorbed aromatic hydrocarbon impurities. 3) Cool to room temperature to obtain the regenerated core-shell composite adsorbent.
[0028] The regeneration method described above is simple to operate and requires no complex equipment. After 12 cycles of regeneration, the adsorption capacity of the adsorbent still maintains more than 90% of the initial capacity, with a decay of less than 10%, which is significantly better than the regeneration stability of existing technologies.
[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: The core-shell composite adsorbent of this invention is prepared using a one-step co-precipitation-hot soaking process with ZIF-8 and UiO-66-NH2, followed by sulfonation modification, dispersion in a polyvinyl alcohol solution, drying, and then thermosetting to complete the coating. This preparation process is environmentally friendly and efficient, enabling gradient capture of aldehydes, ketones, carboxylic esters, aromatic hydrocarbons, and metal ions. During regeneration, the core-shell composite adsorbent is purged using a combination of low-pressure steam and a hydrogen / nitrogen mixture. After multiple cycles, the adsorption capacity decays minimally, overcoming the limitations of existing single MOF materials or adsorption technologies that cannot simultaneously remove polar, non-polar impurities, and metal ions. It also avoids the application limitations of existing catalytic membranes or single coating technologies, demonstrating promising prospects for industrial applications. Detailed Implementation
[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0031] Example 1: Preparation of composite adsorbent (ZIF-8:UiO-66-NH2=3:1)
[0032] 1) Mixing raw materials: Weigh 0.744g Zn(NO3)2·6H2O (2.5 mmol), 0.821g 2-methylimidazole (10 mmol), 0.233g ZrCl4 (1.0 mmol), and 0.332g 2-aminoterephthalic acid (2.0 mmol), mix them in 50 mL of a mixed solvent with an ethanol / water volume ratio of 1:1, and stir for 30 min until uniformly dispersed.
[0033] 2) Formation of core-shell structure: The mixed system was transferred to a 100 mL reactor, heated to 90 °C, and reacted at a constant temperature for 4 h. After the reaction was completed, the mixture was centrifuged (8000 r / min, 10 min), washed three times with ethanol, and dried at 80 °C for 12 h to obtain the ZIF-8 / UiO-66-NH2 core-shell structure precursor.
[0034] 3) Sulfonation modification: Weigh 2.0 g of the core-shell structure precursor, add 50 mL of anhydrous ethanol, stir and disperse, then add 0.184 g of chlorosulfonic acid (1.5 mmol), heat to 70 ℃, and react for 2.5 h; after the reaction, wash with deionized water until the pH of the filtrate is 7, and dry at 80 ℃ for 8 h to obtain the sulfonated core-shell structure; the degree of sulfonation of sulfonated UiO-66-NH2 was 1.0 mmol / g.
[0035] 4) Coating and curing: The sulfonated core-shell structure was dispersed in 40 mL of 5% PVA solution and ultrasonically dispersed for 30 min; it was dried using a spray dryer with an inlet temperature of 120℃ and an outlet temperature of 60℃ to obtain spherical particles with a diameter of 1~3 mm; the spherical particles were placed in an oven and heat-cured at 120℃ for 2 h to obtain the composite adsorbent product.
[0036] Example 2 Preparation of composite adsorbent (ZIF-8:UiO-66-NH2=1:3)
[0037] 1) Mixing raw materials: Weigh 0.248g Zn(NO3)2·6H2O (0.83 mmol), 0.274g 2-methylimidazole (3.33 mmol), 0.699g ZrCl4 (3.0 mmol), and 0.996g 2-aminoterephthalic acid (6.0 mmol), mix them in 50mL of a mixed solvent with an ethanol / water volume ratio of 1:1, and stir for 30 min until uniformly dispersed.
[0038] 2.2 The core-shell structure formation, sulfonation modification, coating and curing steps are the same as in Example 1, wherein the amount of sulfonating agent used is 0.552 g chlorosulfonic acid (4.5 mmol); the degree of sulfonation of sulfonated UiO-66-NH2 was tested to be 0.9 mmol / g.
[0039] Example 3 Preparation of composite adsorbent (ZIF-8:UiO-66-NH2=5:1)
[0040] 1) Mixing raw materials: Weigh 0.992g Zn(NO3)2·6H2O (3.33 mmol), 1.096g 2-methylimidazole (13.33 mmol), 0.155g ZrCl4 (0.67 mmol), and 0.221g 2-aminoterephthalic acid (1.33 mmol), mix them in 50 mL of a mixed solvent with an ethanol / water volume ratio of 1:1, and stir for 30 min until uniformly dispersed.
[0041] 3.2 The core-shell structure formation, sulfonation modification, coating and curing steps are the same as in Example 1, wherein the amount of sulfonating agent used is 0.123 g chlorosulfonic acid (1.0 mmol); the degree of sulfonation of sulfonated UiO-66-NH2 was tested to be 1.1 mmol / g.
[0042] Comparative Example 1
[0043] The single ZIF-8 adsorbent (without UiO-66-NH2 composite and PVA coating) was prepared by mixing 0.744g Zn(NO3)2·6H2O and 0.821g 2-methylimidazole in 50 mL of ethanol, reacting at 90 °C for 4 h, and then drying to obtain ZIF-8 particles.
[0044] Comparative Example 2
[0045] The preparation method of the single sulfonated UiO-66-NH2 adsorbent (without ZIF-8 composite and PVA coating) is as follows: 0.233g ZrCl4 and 0.332g 2-aminoterephthalic acid are mixed in 50 mL ethanol / water 1:1, reacted at 90 ℃ for 4 h, and then dried after sulfonation modification.
[0046] Comparative Example 3
[0047] We provide commercial 5A molecular sieves (Sigma-Aldrich, pellets, 1.6mm, activated before use), which are commonly used for alcohol dehydration and adsorption of some impurities.
[0048] Performance testing
[0049] 1. Impurity Removal Performance Test
[0050] The adsorbents obtained in Examples 1-3 and Comparative Examples 1-3 were respectively packed into 10cm×1.5cm spiral fixed beds with a packing amount of 5 g. The fixed beds were integrated into the pre-removal box at the top of the distillation reflux column. The raw material was 1 L of methanol containing 12 ppm acetone, 8 ppm acetaldehyde, 4 ppm methyl acetate, 0.4% benzene, and 5 ppm Fe. 3+ The feed flow rate is controlled at 0.8 BV·h. -1 The operating temperature is 30 ℃ and the operating pressure is atmospheric pressure. After impurity removal, the raw material enters the distillation column. The operating conditions of the distillation column are: top pressure 0.1MPa, reflux ratio 5:1, and bottom temperature 65 ℃.
[0051] The results of the impurity removal effect and product purity test are shown in Table 1.
[0052] Table 1: Adsorbent Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Acetone removal rate (%) 98.5 99.1 97.2 20.2 99.0 46.3 Acetaldehyde removal rate (%) 97.8 98.5 96.5 23.5 98.2 43.7 Methyl acetate removal rate (%) 96.3 97.6 95.1 27.1 97.5 35.5 Benzene removal rate (%) 99.2 97.3 99.5 98.8 40.6 65.2 <![CDATA[Fe 3+ Removal rate (%) 99.5 99.7 99.3 8.1 99.7 63.9 Product purity (wt%) 99.993 99.991 99.992 99.5 99.8 99.0 Energy consumption reduction rate of distillation (%) 18.5 17.2 19.1 5.1 8.3 3.0
[0053] 2. Regeneration performance test
[0054] Using the core-shell composite adsorbent prepared in Example 1 as the subject, a regeneration cycle test was conducted. The regeneration steps are as follows:
[0055] 1) Removal of polar impurities: The fixed bed was flushed with low-pressure steam at 80 ℃ and 0.15 MPa for 30 min.
[0056] 2) Removal of nonpolar impurities: A mixture of nitrogen and hydrogen in a volume ratio of 3:1 is introduced at a flow rate of 1.5 BV·h. -1 Thermal desorption was performed at 150 °C and 0.085 MPa vacuum for 20 min.
[0057] 3) Cooling for later use: Introduce nitrogen gas until the adsorbent cools to room temperature.
[0058] After each regeneration, the impurity removal performance was tested under the same conditions as the impurity removal performance test described above. The test results after 12 cycles are shown in Table 2.
[0059] Table 2: Loop count 1 6 12 Acetone removal rate (%) 98.5 98.1 97.3 Acetaldehyde removal rate (%) 97.8 97.3 96.2 Benzene removal rate (%) 99.2 98.9 98.5 <![CDATA[Fe 3+ Removal rate (%) 99.5 99.4 99.2 Adsorption capacity retention rate (%) 100 96.7 93.0
[0060] The above Comparative Examples 1-3 were regenerated and cycled according to the above method. The adsorption capacity retention rate (%) after 5 cycles was 75.2% for Comparative Example 1, 78.6% for Comparative Example 2, and 85.3% for Comparative Example 3.
[0061] The performance test results above show that the composite adsorbent provided by this invention achieves efficient and simultaneous removal of all five types of impurities through the synergistic effect of its core-shell structure. In contrast, single-material adsorbents have functional limitations; while traditional adsorbents have a certain broad spectrum of effectiveness, they are inefficient and have poor regenerability.
[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A core-shell structured composite adsorbent, characterized by, It includes a core-shell structure with ZIF-8 nanocrystals as the core layer and sulfonated UiO-66-NH2 microspheres as the shell layer, wherein the outer layer of the core-shell structure is coated with a cross-linked polyvinyl alcohol layer.
2. The composite adsorbent as described in claim 1, characterized in that, The core-shell structure is obtained by co-precipitation and hot leaching of ZIF-8 and UiO-66-NH2 in an alcohol-water solution to obtain a core-shell structure precursor, which is then sulfonated.
3. The composite adsorbent as described in claim 2, characterized in that, The mass ratio of ZIF-8 to UiO-66-NH2 is (1-3):(5:1). And / or, the degree of sulfonation of the core-shell precursor is 0.8-1.2 mmol / g.
4. The composite adsorbent as described in claim 1, characterized in that, The thickness of the cross-linked polyvinyl alcohol layer is 5-30 μm.
5. A method for preparing the core-shell structured composite adsorbent according to any one of claims 1-4, characterized in that, include: S1. Disperse the zinc source, 2-methylimidazole, zirconium source and 2-aminoterephthalic acid into a solution; S2. Heat to 80-95℃ and react for 3-5 hours to obtain the core-shell structured precursor; S3. The core-shell structure precursor is sulfonated under the action of a sulfonating agent to obtain the core-shell structure; S4. The core-shell structure is dispersed in a low-concentration polyvinyl alcohol solution, then dried to remove the solvent, and then thermocured to obtain a core-shell structured composite adsorbent.
6. The preparation method according to claim 5, characterized in that, In step S3, the core-shell structure is obtained by mixing a core-shell structure precursor with a sulfonating agent in a molar ratio of (1-1.5):1, reacting at 60-80 °C for 2-3 h, and then washing and drying.
7. The preparation method according to claim 5, characterized in that, In step S4, the concentration of the polyvinyl alcohol solution is 2-8%; And / or, the thermosetting temperature is 110-130℃ and the time is 1.5-3h.
8. The application of the core-shell structured composite adsorbent according to any one of claims 1-4, or the core-shell structured composite adsorbent prepared by the preparation method according to claims 5-7, in the removal of impurities, wherein the impurities are selected from at least one of aldehydes, ketones, carboxylic acid esters, aromatic hydrocarbons and metal ions.
9. The application as described in claim 8, characterized in that, The application is for preparing high-purity methanol or ethanol.
10. The application as described in claim 8, characterized in that, The application also includes the regeneration of core-shell composite adsorbents, including: 1) Removal of polar impurities: The adsorbent is rinsed with low-pressure steam at 60-90℃ to remove adsorbed aldehydes, ketones and carboxylic acid esters; 2) Removal of nonpolar impurities: A mixture of nitrogen and hydrogen is introduced, and thermal desorption is performed at 120-160℃ under vacuum for 10-30 min to remove adsorbed aromatic hydrocarbon impurities. 3) Cool to room temperature to obtain the regenerated core-shell composite adsorbent.