A composite adsorbent and its preparation method

Abstract

The present invention discloses a composite adsorbent and a preparation method thereof. First, a molecular sieve, a binder, p-diphenol, a carbonate and a formate are co-molded, and the binder blocked in the adsorbent pores is dissolved by a strong base formed by high-temperature hydrolysis of urea, thereby forming a smooth pore. At the same time, the organic ligand 2,5-dimethyl terephthalic acid is generated in situ by decomposition to form a CO2 atmosphere. The organic ligand in the molded body is then coordinated with the metal to anchor the MOFs in situ in a fixed position, ensuring that the MOFs are evenly dispersed on the molecular sieve surface and in the pores. The composite adsorbent prepared by the inventive method has a high mass transfer rate and solves the problem of difficult powder recovery.

Description

Technical Field

[0001] The invention belongs to the field of adsorbent synthesis, and particularly relates to a composite adsorbent and a preparation method thereof. Background Art

[0002] With the continued rapid economic development and increasingly stringent environmental protection requirements, there is an urgent need to develop sustainable, clean energy sources to replace traditional ones. Hydrogen, as a clean, efficient, and excellent energy carrier, has attracted considerable attention. Currently, my country's hydrogen production technology is relatively mature, with fossil fuel hydrogen and industrial byproduct hydrogen remaining the primary sources. However, these hydrogen contain small amounts of CH4, N2, CO, and other impurities, making them difficult to meet the purity requirements of automotive fuel cells. Therefore, pressure swing adsorption (PSA) technology is needed to remove these impurities.

[0003] Adsorbents, as key components of the pressure swing adsorption process, directly influence the development of pressure swing adsorption technology. Molecular sieves have a uniform, regular pore structure and a large specific surface area. As polar adsorbents, they have a stronger adsorption capacity for highly polar and unsaturated molecules, as well as some easily polarized non-polar molecules. Therefore, they are widely used in the adsorption field. Furthermore, MOFs, as a new type of porous metal-organic material, combine inorganic metal atoms and organic ligands through coordination. Their organic framework can accept almost all cations in the periodic table, and the pore size and specific surface area can be adjusted by adjusting the binding with organic ligands.

[0004] CN106902746A discloses a metal-organic framework / molecular sieve composite adsorption material. The composite adsorption material is loaded onto a carrier via a binder for use. CN109012606A discloses a MOF-Zn@molecular sieve composite material, its preparation method, and its application in cigarettes. In this method, an organic ligand compound, a metal zinc salt, and activated SBA-15 are reacted at a constant temperature for a predetermined time using N,N-dimethylformamide (DMF) as a solvent, followed by cooling and separation. The resulting product is the MOF-Zn@SBA-15 composite material.

[0005] Most MOFs adsorbents exist in powder form, making industrial applications difficult. Therefore, they must be molded. Molding MOFs individually can easily damage their structure and has poor mechanical strength, making them less feasible. Currently, there is much research on loading MOFs onto supports, but this has led to issues such as uneven distribution. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for preparing a molecular sieve and MOF-74 composite adsorbent.

[0007] A method for preparing a high-efficiency composite adsorbent comprises the following steps:

[0008] (1) taking 85-95 parts by weight of molecular sieve, 5-15 parts by weight of activated binder, 2-10 parts by weight of bonding aid, 10-25 parts by weight of hydroquinone, and 1-10 parts by weight of carbonate, mechanically mixing and then forming;

[0009] (2) drying the molecular sieve formed body obtained in step (1) and calcining it at a low temperature in an inert gas atmosphere;

[0010] (3) adding the formed body obtained in step (2) to a urea aqueous solution for reaction, and washing to obtain an intermediate;

[0011] (4) Add the intermediate obtained in step (3) and the metal salt to N,N-dimethylformamide and stir evenly, then transfer it to a reactor and react at 100-160°C for 24-72 hours;

[0012] (5) The product obtained after filtration, washing, drying and calcination is the composite adsorbent.

[0013] Furthermore, the molecular sieve in step (1) may be one or more of type A molecular sieve, X molecular sieve or Y molecular sieve; the binder is generally selected from one or more of kaolin, attapulgite and bentonite; the bonding aid is generally selected from one or more of sesbania powder, carboxymethyl cellulose and silica sol; the carbonate may be one or more of potassium carbonate, sodium carbonate and lithium carbonate; and the molding method may be strip, spherical or granular.

[0014] Furthermore, the activated binder in step (1) refers to a binder activated by high-temperature calcination, the calcination temperature is generally 550-800°C, and the calcination time is 2-6 hours.

[0015] Furthermore, the drying in step (2) is carried out under conventional conditions in the art, with a drying temperature of 80-120° C. and a drying time of 10-48 h.

[0016] Furthermore, in step (2), the low-temperature calcination temperature is 100-300°C, the calcination time is 2-8 hours, and the calcination atmosphere is an inert gas atmosphere such as N2 or Ar. Preferably, the low-temperature calcination temperature is 120-200°C, and the calcination time is 2-4 hours.

[0017] Furthermore, in step (3), the liquid-to-solid ratio of the urea aqueous solution to the intermediate adsorbent is 3 to 10 mL / g. The concentration of the urea aqueous solution is generally 0.2 to 0.6 mol / L. The reaction temperature is generally 110 to 160°C, and the reaction time is 5 to 15 hours. Preferably, the reaction temperature is 120 to 150°C, and the reaction time is 8 to 12 hours.

[0018] Furthermore, the metal salt in step (4) is selected from one of soluble salts of Ni, Co or Zn. The metal salt concentration is 0.05-5 mol / L, and the liquid-to-solid ratio is 10-30 mL / g.

[0019] Furthermore, vacuum drying is preferably used in step (5). The drying temperature is generally 80-150°C for 12-48 hours. Calcination is carried out in an inert atmosphere such as N2 or Ar at a temperature of 150-250°C for 2-4 hours.

[0020] According to the second aspect of the present invention, the present invention also provides a composite adsorbent, which is prepared by the method described above.

[0021] The composite adsorbent prepared by the method of the present invention is a composite adsorbent of molecular sieve and MOF-74. The composite adsorbent contains 75-95% molecular sieve by weight and 5-25% MOF-74 by weight. The composite adsorbent is primarily composed of a porous molecular sieve, with MOFs material inserted and anchored within the pores of the molecular sieve adsorbent, forming a network of interconnected channels. This adsorbent combines the adsorption advantages of both molecular sieves and MOF-74, achieving both microporous screening and high strength, while also enabling efficient utilization of the highly adsorbent MOF-74.

[0022] The composite adsorbent can be applied to the adsorption separation of gases, and is particularly suitable for the adsorption separation process of hydrogen.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Urea is used as an alkali source. The urea solution is neutral at low temperature. When the solution reaches a certain temperature, the urea decomposes to gradually increase the pH value of the solution. This characteristic replaces the traditional strong base sodium hydroxide. The hydroxyl ions produced by the hydrolysis of urea can react with the clay blocked in the pores and dissolve it, so as to achieve smooth flow of the adsorbent pores, solve the problem of clay blocking the pores of the molded adsorbent, and thus improve the mass transfer rate of the molded adsorbent.

[0025] 2. The hydroquinone in the molded body reacts with the CO2 released during the urea hydrolysis process to generate MOFs organic ligands, which can further coordinate with metal ions to generate MOFs. Its binding force is stronger than that of direct growth on the molecular sieve surface. At the same time, it can anchor the metal ions in a fixed position, ensuring that MOFs are evenly dispersed on the molecular sieve surface and in the pores.

[0026] 3. The molecular sieve in the composite adsorption material plays a protective and supporting role for MOFs, acting as a carrier for MOFs. At the same time, it also improves the utilization rate of MOFs and solves the problem of difficult powder recovery during the preparation process of MOFs. DETAILED DESCRIPTION

[0027] The technical content and effects of the present invention are further illustrated below with reference to the embodiments, but the present invention is not limited to the scope of the embodiments. Example 1

[0028] 90 parts by weight of type A molecular sieve, 10 parts by weight of activated kaolin, 5 parts by weight of carboxymethyl cellulose, 20 parts by weight of hydroquinone, and 8 parts by weight of sodium carbonate were mechanically mixed and then formed. The mixture was then dried and calcined at 180°C in an N2 atmosphere for 2 hours to obtain a shaped body. The shaped body was then added to a 0.4 mol / L aqueous urea solution at a liquid-to-solid ratio of 8 mL / g. The mixture was reacted at 140°C for 10 hours and washed to obtain an intermediate.

[0029] The intermediate product and nickel nitrate were added to N,N-dimethylformamide and stirred thoroughly. The mixture was then transferred to a reactor and reacted at 120°C for 30 hours. After washing, the composite adsorbent was dried in an oven at 120°C for 14 hours and calcined at 250°C under a nitrogen atmosphere for 3 hours. The performance evaluation results are shown in Table 1. Example 2

[0030] 85 parts by weight of type A molecular sieve, 15 parts by weight of activated kaolin, 10 parts by weight of carboxymethyl cellulose, 25 parts by weight of hydroquinone, and 10 parts by weight of sodium carbonate were mechanically mixed, then molded, dried, and calcined at 200°C in an Ar atmosphere for 2 hours to obtain a molded body. The molded body was then added to a 0.2 mol / L aqueous urea solution at a liquid-to-solid ratio of 10 mL / g, reacted at 150°C for 12 hours, and washed to obtain an intermediate.

[0031] The intermediate product and cobalt nitrate were added to N,N-dimethylformamide and stirred thoroughly. The mixture was then transferred to a reactor and reacted at 160°C for 72 hours. After washing, the composite adsorbent was dried in an oven at 150°C for 12 hours and calcined at 200°C for 2 hours under an Ar atmosphere. The performance evaluation results are shown in Table 1. Example 3

[0032] 95 parts by weight of type A molecular sieve, 5 parts by weight of activated kaolin, 2 parts by weight of carboxymethyl cellulose, 10 parts by weight of hydroquinone, and 5 parts by weight of sodium carbonate were mechanically mixed, then molded, dried, and calcined at 120°C under a nitrogen atmosphere for 4 hours to obtain a molded body. The molded body was then added to a 0.6 mol / L aqueous urea solution at a liquid-to-solid ratio of 3 mL / g, reacted at 140°C for 8 hours, and washed to obtain an intermediate.

[0033] The intermediate product and zinc nitrate were added to N,N-dimethylformamide and stirred evenly. The mixture was then transferred to a reactor and reacted at 100°C for 72 hours. After washing, the mixture was dried in an oven at 80°C for 48 hours and calcined at 150°C under an Ar atmosphere for 4 hours to obtain a composite adsorbent. The performance evaluation results are shown in Table 1. Example 4

[0034] 88 parts by weight of type A molecular sieve, 12 parts by weight of activated kaolin, 6 parts by weight of carboxymethyl cellulose, 10 parts by weight of hydroquinone, and 1 part by weight of sodium carbonate were mechanically mixed, then molded, dried, and calcined at 150°C in an Ar atmosphere for 4 hours to obtain a shaped body. The shaped body was then added to a 0.4 mol / L aqueous urea solution at a liquid-to-solid ratio of 6 mL / g, reacted at 120°C for 12 hours, and washed to obtain an intermediate.

[0035] The intermediate product and nickel nitrate were added to N,N-dimethylformamide and stirred thoroughly. The mixture was then transferred to a reactor and reacted at 140°C for 48 hours. After washing, the composite adsorbent was dried in an oven at 100°C for 36 hours and calcined at 200°C under a nitrogen atmosphere for 4 hours. The performance evaluation results are shown in Table 1. Example 5

[0036] 90 parts by weight of type A molecular sieve, 10 parts by weight of activated kaolin, 6 parts by weight of carboxymethyl cellulose, 10 parts by weight of hydroquinone, and 1 part by weight of sodium carbonate were mechanically mixed, then molded, dried, and calcined at 180°C in an N2 atmosphere for 3 hours to obtain a molded product. The molded product was then added to a 0.5 mol / L aqueous urea solution at a liquid-to-solid ratio of 9 mL / g, reacted at 150°C for 10 hours, and washed to obtain an intermediate.

[0037] The intermediate product and nickel nitrate were added to N,N-dimethylformamide and stirred thoroughly. The mixture was then transferred to a reactor and reacted at 130°C for 48 hours. After washing, the composite adsorbent was dried in an oven at 120°C for 24 hours and calcined at 220°C under a nitrogen atmosphere for 3 hours. The performance evaluation results are shown in Table 1.

[0038] Comparative Example 1

[0039] The preparation and evaluation of the adsorbent were the same as in Example 1, except that no MOFs were grown outside the molecular sieve. Reference agent B1 was prepared, and its performance evaluation results are shown in Table 1.

[0040] Comparative Example 2

[0041] The preparation and evaluation of the adsorbent were the same as in Example 1, except that MOF precursors and ligands were added according to conventional methods, and MOFs were grown directly on the molecular sieve surface. Reference agent B2 was prepared, and its performance evaluation results are shown in Table 1.

[0042] In the embodiments and comparative examples of the present invention, the specific surface area was measured using nitrogen as the adsorbate, and the N2 adsorption amount was measured using a volumetric adsorption instrument.

[0043] Table 1 Performance evaluation results

[0044] Sample name <![CDATA[Specific surface area (m 2 / g)]]> Adsorption capacity (mL / g) Desorption time / adsorption time Example 1 602 13.2 1.03 Example 2 585 12.2 1.10 Example 3 593 12.7 1.07 Example 4 589 12.5 1.09 Example 5 596 12.9 1.05 Comparative Example 1 576 12.0 1.12 Comparative Example 2 587 12.3 1.09

Claims

1. A method for preparing a composite adsorbent, comprising the following steps: (1) taking 85-95 parts by weight of molecular sieve, 5-15 parts by weight of activated binder, 2-10 parts by weight of bonding aid, 10-25 parts by weight of hydroquinone, and 1-10 parts by weight of carbonate, mechanically mixing and then forming; (2) drying the molecular sieve formed body obtained in step (1) and calcining it at a low temperature in an inert gas atmosphere; (3) adding the formed body obtained in step (2) to a urea aqueous solution for reaction, and washing to obtain an intermediate; (4) Add the intermediate obtained in step (3) and the metal salt to N,N-dimethylformamide and stir evenly, then transfer it to a reactor and react at 100-160°C for 24-72 hours; (5) The product obtained after filtration, washing, drying and calcination is the composite adsorbent; in, The carbonate in step (1) is selected from one or more of potassium carbonate, sodium carbonate, and lithium carbonate; In step (2), the low-temperature calcination temperature is 100-300°C and the calcination time is 2-8 hours; The liquid-to-solid ratio of the urea aqueous solution to the intermediate adsorbent in step (3) is 3 to 10 mL / g; the concentration of the urea aqueous solution is 0.2 to 0.6 mol / L; the reaction temperature of step (3) is 110 to 160°C; The metal salt in step (4) is selected from one of the soluble salts of Ni, Co or Zn.

2. The preparation method according to claim 1, characterized in that: The molecular sieve in step (1) is one or more of type A molecular sieve, X molecular sieve or Y molecular sieve.

3. The preparation method according to claim 1, characterized in that: The activated binder refers to a binder that has been activated by high-temperature calcination, wherein the calcination temperature is 550-800° C. and the calcination time is 2-6 hours; the binder is selected from one or more of kaolin, attapulgite, and bentonite.

4. The preparation method according to claim 1, characterized in that The bonding aid is selected from one or more of sesbania powder, carboxymethyl cellulose, and silica sol.

5. The preparation method according to claim 1, characterized in that: The drying conditions in step (2) are: drying temperature is 80~120℃, and the drying time is 10~48h.

6. The preparation method according to claim 1, characterized in that: The temperature of low-temperature roasting in step (2) is 120-200° C., and the roasting time is 2-4 hours.

7. The preparation method according to claim 1, characterized in that: The reaction time of step (3) is 5 to 15 hours.

8. The preparation method according to claim 7, characterized in that: The reaction temperature of step (3) is 120-150°C, and the reaction time is 8-12 hours.

9. The preparation method according to claim 1, characterized in that: The drying in step (5) is performed by vacuum drying.

10. The preparation method according to claim 1, characterized in that: The calcination in step (5) is carried out in an inert atmosphere at a temperature of 150-250° C. for 2-4 hours.

11. The composite adsorbent obtained by the preparation method according to any one of claims 1 to 10.

12. The composite adsorbent according to claim 11, characterized in that The molecular sieve content is 75-95% and the MOF-74 content is 5-25% based on the weight of the adsorbent.