Zeolite molecular sieve adsorption material modified by carboxylic acid organic compound as well as preparation method and application of zeolite molecular sieve adsorption material

Abstract

The invention discloses a carboxylic acid organic compound modified zeolite molecular sieve adsorption material as well as a preparation method and application thereof, and belongs to the technical field of molecular sieve adsorption materials. The preparation method comprises the following steps: adding a calcined zeolite molecular sieve into a carboxylic acid organic compound solution, carrying out excessive impregnation at room temperature for 12-48 hours, filtering, and drying to obtain a modified zeolite molecular sieve adsorption material; the mass ratio of the zeolite molecular sieve to the carboxylic acid organic compound solution is 1: 5-1: 20; the carboxylic acid organic compound used in the invention is loaded to the surface and pore channels of the zeolite molecular sieve material in a dipping manner, so the pore size, surface functional groups and polar environment of the zeolite molecular sieve material are effectively adjusted, and enrichment of methane component in ventilation air methane can be effectively promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular sieve adsorption materials, and particularly relates to a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound, a preparation method and an application thereof. The adsorption material is used for enriching ventilation air methane (VAM). Background Art

[0002] Coal is the main fossil energy in China. During the coal mining process, in order to ensure the safety of the mine, a large amount of ventilation is usually required to ensure that the gas concentration in the mine is relatively low. This gas is usually called ventilation air methane (VAM). Since the concentration of VAM is low, it cannot be directly utilized and is generally discharged. The VAM emission in China is huge, which not only wastes resources but also pollutes the environment. Therefore, the resource utilization of VAM is imperative.

[0003] In order to reduce the greenhouse effect caused by the discharge of VAM and realize the resource utilization of methane, in recent years, the attention to the enrichment of VAM in coal mines has been increasing. The biggest challenge in the enrichment of VAM in coal mines is the separation of methane molecules and nitrogen molecules. Their physical properties are similar (Table 1), so it is very difficult to enrich VAM.

[0004] Currently, the separation technologies for VAM enrichment include cryogenic distillation separation technology, hydrate separation technology, membrane separation technology, pressure swing adsorption separation technology, etc. The pressure swing adsorption separation technology has the advantages of simple process flow, mature technology, low energy consumption, strong operability, etc., and is considered to be a separation technology with very good application prospects. The pressure swing adsorption method is to use the differences in the adsorption strength of each component of the gas mixture by the adsorption material, the kinetic effect of diffusion inside and outside the adsorption material particles, or the steric effect of the pores in the adsorption material on the gas as the separation driving force, and realize the concentration or purification of one or more components through the cyclic change of pressure. The key to the pressure swing adsorption separation technology lies in the selection of the adsorption material.

[0005] The pressure swing adsorption materials include zeolite molecular sieves, metal-organic framework materials and porous carbon materials. Among them, the metal-organic framework materials have the advantages of high adsorption capacity and high selectivity, but due to the high cost of the metal-organic framework materials, industrial production cannot be realized. Although the porous carbon materials are cheap in cost and simple in process, due to their complex pore structure and wide pore size distribution, especially the biomass carbon materials are extremely dependent on the selection of raw materials and do not have high separation selectivity. The zeolite molecular sieve has a mature production process, and has the advantages of rich and regular pores, large specific surface area, and adjustable internal chemical environment, and is widely used in the fields of adsorption separation, catalysis, etc.

[0006] Due to its unique three-dimensional twelve-membered ring pore structure, Beta zeolite has good adsorption performance. This structure is conducive to the diffusion of molecules in the pores, thereby improving the adsorption efficiency. Secondly, in the current literature on methane enrichment, the key pore size range for methane adsorption is mentioned to be between 0.4 and 0.6 nm, and Beta zeolite is close to this separation size. Through modification strategies, precise regulation of the pore size can be achieved. Currently, the molecular sieves for separating methane / nitrogen mixtures focus on ultra-microporous molecular sieves such as 8-membered ring and 10-membered ring, and there is little research on 12-membered ring molecular sieves. The present invention provides a new possibility for molecular sieve to adsorb methane and broadens the selection types of molecular sieves for methane adsorption. Summary of the Invention

[0007] The present invention overcomes the deficiencies of existing materials for methane enrichment and provides a carboxylic acid organic compound-modified zeolite molecular sieve adsorption material, its preparation method and application.

[0008] The present invention is achieved through the following technical solutions: A preparation method of a carboxylic acid organic compound-modified zeolite molecular sieve adsorption material, adding calcined zeolite molecular sieve to a carboxylic acid organic compound solution, impregnating excessively at room temperature for 12 - 48 h and then filtering and drying to obtain the modified zeolite molecular sieve adsorption material; the mass ratio of zeolite molecular sieve to carboxylic acid organic compound solution is 1:5 - 1:20.

[0009] Preferably, the carboxylic acid organic compound solution is prepared by dissolving a carboxylic acid organic compound in one of the solvents of methanol, ethanol, N,N-dimethylformamide.

[0010] Preferably, the carboxylic acid organic compound is one or any combination of fumaric acid, isonicotinic acid, trans-1,4-cyclohexanedicarboxylic acid, 5-aminoisophthalic acid, 4,4'-sulfonyldibenzoic acid.

[0011] Preferably, the silica-alumina ratio of the zeolite molecular sieve is 25 - 350.

[0012] Preferably, the zeolite molecular sieve is Beta zeolite molecular sieve.

[0013] Preferably, the mass fraction of the carboxylic acid organic compound solution is 5% - 50%.

[0014] Preferably, the drying temperature is 80 - 100 °C and the drying time is 12 - 24 h.

[0015] A carboxylic acid organic compound-modified zeolite molecular sieve adsorption material prepared by using the preparation method of a carboxylic acid organic compound-modified zeolite molecular sieve adsorption material.

[0016] A zeolite molecular sieve adsorbent material modified by a carboxylic acid organic compound is used for the enrichment of ventilation air methane.

[0017] The beneficial effects of the present invention compared with the prior art are as follows: The present invention preferably selects organic ligands with carboxylic acid structures used in metal-organic framework materials. These functionalized organic ligands can effectively change the polarity of the surface and the interior of the pore channels of the adsorbent material, have a strong attraction to non-polar methane molecules, and have an extremely strong adsorption effect on methane molecules. However, due to the high cost of metal-organic framework materials themselves, they are not suitable for large-scale production. Molecular sieves themselves have regular pore channels and mature manufacturing processes. The present invention combines the advantages of molecular sieve materials and metal-organic framework materials to achieve the functionalization of molecular sieve materials. The introduction of carboxylic acid organic compounds can effectively improve the adsorption capacity and selectivity of zeolite molecular sieves, and maintain the advantage of molecular sieve materials being conducive to industrial production.

[0018] The carboxylic acid organic compound reagent used in the present invention is loaded onto the surface and pore channels of the molecular sieve by impregnation, which can effectively adjust the pore diameter of the molecular sieve, and the carboxylic acid organic compound can form an interaction with methane to achieve effective adsorption of methane. Since different organic reagents have different relative molecular weights and kinetic radii, the effective adjustment of the pore diameter and the effective adjustment of the surface polarity of the molecular sieve can be achieved by controlling the impregnation temperature and time. The adsorbent material prepared by this invention has the advantages of large adsorption capacity, high selectivity, wide universality, and can be used for large-scale production.

[0019] Specifically: 1. By impregnating zeolite molecular sieve adsorbent materials with different silicon-aluminum ratios with different organic reagents and then drying, a modified zeolite molecular sieve adsorbent material can be obtained.

[0020] 2. The carboxylic acid organic compound used in the present invention can be loaded onto the surface and pore channels of the molecular sieve by impregnation, and change the surface polarity of the molecular sieve to achieve effective adsorption of methane.

[0021] 3. Since the molecular structures, relative molecular weights and other physical and chemical properties of different carboxylic acid organic compounds are different, the loading amount can be effectively adjusted by controlling the impregnation modification time, mass ratio, etc.

[0022] 4. The present invention combines the advantages of molecular sieve materials and metal-organic framework materials to achieve the functionalization of molecular sieve materials. The introduction of carboxylic acid organic compounds can effectively improve the adsorption capacity and selectivity of zeolite molecular sieves.

[0023] 5. The operation of the present invention is simple, the pore diameter and functional groups of the adsorbent material are adjustable, the adsorption capacity is large, the selectivity is high, and it is easy to realize industrial production. Description of the Drawings

[0024] Figure 1 This is the XRD pattern of the unmodified Beta zeolite with a silica-alumina ratio of 25 in Comparative Example 1 of the present invention.

[0025] Figure 2 This is the XRD pattern of the isonicotinic acid-modified Beta zeolite with a silica-alumina ratio of 25 in Example 8 of the present invention.

[0026] Figure 3 This is the FT-IR spectrum of the isonicotinic acid-modified Beta zeolite with a silica-alumina ratio of 25 in Example 8 of the present invention.

[0027] Figure 4 This is the FT-IR spectrum of the isonicotinic acid-modified Beta zeolite with a silica-alumina ratio of 350 in Example 11 of the present invention. Detailed implementation manners

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below in conjunction with examples and drawings. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention. The technical solutions of the present invention will be described in detail below in conjunction with examples and drawings, but the protection scope is not limited hereby.

[0029] Example 1 This example provides a carboxylic acid organic compound-modified zeolite molecular sieve adsorption material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of fumaric acid with a mass fraction of 5%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:5, impregnate at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0030] Example 2 This example provides a carboxylic acid organic compound-modified zeolite molecular sieve adsorption material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of isonicotinic acid with a mass fraction of 5%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:5, impregnate at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0031] Example 3 This example provides a carboxylic acid organic compound-modified zeolite molecular sieve adsorption material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of 5-aminoisophthalic acid with a mass fraction of 5%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:5. Immerse at room temperature for 24 h, filter, and place in an oven at 80 °C to dry for 12 h to obtain the modified Beta zeolite.

[0032] Example 4 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of trans-1,4-cyclohexanedicarboxylic acid with a mass fraction of 5%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:5. Immerse at room temperature for 24 h, filter, and place in an oven at 80 °C to dry for 12 h to obtain the modified Beta zeolite.

[0033] Example 5 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of 4,4'-sulfonyldibenzoic acid with a mass fraction of 5%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:5. Immerse at room temperature for 24 h, filter, and place in an oven at 80 °C to dry for 12 h to obtain the modified Beta zeolite.

[0034] Example 6 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of isonicotinic acid with a mass fraction of 20%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:5. Immerse at room temperature for 24 h, filter, and place in an oven at 80 °C to dry for 12 h to obtain the modified Beta zeolite.

[0035] Example 7 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of isonicotinic acid with a mass fraction of 50%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:5. Immerse at room temperature for 24 h, filter, and place in an oven at 80 °C to dry for 12 h to obtain the modified Beta zeolite.

[0036] Example 8 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of isonicotinic acid with a mass fraction of 20%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:10, impregnate at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0037] Example 9 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of isonicotinic acid with a mass fraction of 20%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:20, impregnate at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0038] Example 10 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of isonicotinic acid with a mass fraction of 20%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:20, impregnate at room temperature for 48 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0039] Example 11 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an ethanol solution of isonicotinic acid with a mass fraction of 20%. Add Beta zeolite with a silica-alumina ratio of 350 according to a solid-liquid mass ratio of 1:20, impregnate at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0040] Example 12 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare a methanol solution of isonicotinic acid with a mass fraction of 20%. Add Beta zeolite with a silica-alumina ratio of 350 according to a solid-liquid mass ratio of 1:20, impregnate at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0041] Example 13 This example presents a carboxylic acid organic compound-modified zeolite molecular sieve adsorbent material and its preparation method. The specific steps are as follows: Prepare an N,N-dimethylformamide solution containing 20% isonicotinic acid by mass. Add Beta zeolite with a silica-alumina ratio of 350 according to a solid-liquid mass ratio of 1:20. Immerse at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0042] In Examples 1 to 13, the room temperature mentioned is 25 °C.

[0043] Comparative Example 1 Commercially available Beta zeolite molecular sieve powder with a silica-alumina ratio of 25 was purchased as the adsorbent material.

[0044] Comparative Example 2 Prepare a manganese nitrate solution with a mass fraction of 20%. Add Beta zeolite with a silica-alumina ratio of 25 according to a solid-liquid mass ratio of 1:10. Immerse at room temperature for 24 h, filter, and place in an oven at 80 °C for drying for 12 h to obtain the modified Beta zeolite.

[0045] Comparative Example 3 Mix 0.2 mmol of copper sulfate tetrahydrate solution with 0.1 mmol of isonicotinic acid in a mixed solution of 500 mL of ethanol and deionized water (volume ratio 1:1). Stir for 12 h, place the mixed solution in a hydrothermal autoclave, and heat in an oven at 80 °C for 10 h. After filtration and washing, place in a vacuum drying oven at 130 °C for drying for 12 h to obtain the MOF material Cu(INA). 2 。

[0046] In the FT-IR spectra of Example 8 and Example 11, stretching vibration peaks of C=C bonds, C=O bonds, and -OH bonds appeared, and they were all the stretching vibration characteristic peaks of isonicotinic acid, proving the successful loading of isonicotinic acid on the Beta zeolite. A stronger interaction occurred between the functional groups and methane molecules, promoting the separation of methane / nitrogen. In addition, the XRD patterns of Comparative Example 1 and Example 8 showed that the crystal form of the carboxylic acid-impregnated Beta zeolite was similar to that of the commercially available Beta zeolite. Therefore, the isonicotinic acid impregnation did not change the crystal form of the Beta zeolite.

[0047] Evaluation of the performance of the adsorbent material For the zeolite molecular sieve adsorbent materials prepared in Examples 1 to 11 and Comparative Examples 1 to 3, a self-built adsorption device was used to measure the breakthrough curve at normal temperature and pressure. High-purity N 2 and CH 4 were used to prepare a mixed gas with a CH 4 content of 0.39%. The flow rate was controlled at 50 mL / min with a mass flow meter, and the partial pressure of the pressure gauge was 0.1 MPa. 5 g of the adsorbent material was added to the adsorption column, and a suction-type infrared methane concentration detector was used at the outlet to measure the instantaneous concentration change of methane.

[0048] The full-automatic specific surface area analyzer was used to measure the saturated adsorption capacity of the material for CH 4 and N 2 Before the test, 200 mg of the sample was weighed and placed in a quartz sample tube, and vacuum degassed at 300 o °C for more than 5 h. After cooling to room temperature, the adsorption isotherms of different samples for CH 4 and N 2 were tested. After processing them, the saturated adsorption capacity of single-component gases of methane and nitrogen was obtained, and the CH 4 / N 2 selectivity was obtained by calculation. The specific data are shown in Table 2.

[0049] It can be seen that the breakthrough time of the zeolite molecular sieve impregnated and modified with carboxylic acid organic compounds is much longer than that of the directly purchased commercial zeolite molecular sieve, indicating that the zeolite molecular sieve modified with carboxylic acid organic compounds has significantly improved methane adsorption capacity and selectivity for methane. Through a series of experiments, it can be found that by using carboxylic acid organic compounds to modify zeolite molecular sieve materials, effective separation of methane and nitrogen can be achieved. And the smaller the molecular size, the better the adsorption effect of the molecular sieve modified with carboxylic acid organic compounds with unsaturated cyclic structures, specifically: isonicotinic acid > 5-aminoisophthalic acid > 4,4'-sulfonyldibenzoic acid > trans-1,4-cyclohexanedicarboxylic acid > fumaric acid. This is because isonicotinic acid belongs to a bifunctional ligand, and the carboxylic acid and pyridine functional groups provide a favorable environment for methane affinity, improving the selectivity while ensuring the pore channels of the zeolite molecular sieve itself. The physical properties of carboxylic acid organic compounds are shown in Table 3.

[0050] In addition, due to the mismatch between the pore diameter of the molecular sieve and the diameter of the carboxylic acid organic compound, most functional groups cannot enter the interior of the molecular sieve. Isonicotinic acid itself has a smaller pore diameter and can enter the interior of the pore diameter, realizing the loading of functional groups inside the molecular sieve, increasing the polarity on the surface and inside the pore channels of the molecular sieve, and realizing the effective adsorption of methane molecules. The surface potential of the high-silica-alumina ratio Beta molecular sieve is relatively high, which can achieve the effective adsorption of methane molecules. Therefore, using a Beta molecular sieve with a relatively high silica-alumina ratio and impregnating it with a suitable carboxylic acid organic compound is beneficial to further improving the adsorption performance of the molecular sieve.

[0051] It can be found from Comparative Example 3 that the method adopted in the present invention effectively avoids the problems of high cost of metal-organic framework materials and inability to achieve industrial production, and the adsorption capacity of the Beta molecular sieve impregnated and modified with carboxylic acid organic compounds exceeds that of the original Cu(INA) 2, which not only realizes the effective adsorption of methane molecules, but also has the prospect of industrial production.

[0052] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited to this. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the premise of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the scope of patent protection determined by the claims submitted by the present invention.

Claims

1. A method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound, characterized in that: The calcined zeolite molecular sieve is added to the carboxylic acid organic compound solution, and then the zeolite molecular sieve is filtered and dried after excessive impregnation for 12 to 48 hours at room temperature to obtain a modified zeolite molecular sieve adsorption material; the mass ratio of the zeolite molecular sieve to the carboxylic acid organic compound solution is 1: 5 to 1:

20.

2. The method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound according to claim 1, characterized in that: The carboxylic acid organic compound solution is prepared by dissolving the carboxylic acid organic compound in a solvent selected from the group consisting of methanol, ethanol and N,N-dimethylformamide.

3. The method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound according to claim 2, characterized in that: The carboxylic acid organic compound is one or any combination of fumaric acid, isonicotinic acid, trans-1,4-cyclohexanedicarboxylic acid, 5-aminoisophthalic acid, and 4,4'-sulfonyldibenzoic acid.

4. The method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound according to claim 1, characterized in that: The silicon-aluminum ratio of the zeolite molecular sieve is 25-350.

5. The method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound according to claim 4, characterized in that: The zeolite molecular sieve is Beta zeolite molecular sieve.

6. The method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound according to claim 1, characterized in that: The mass fraction of the carboxylic acid organic compound solution is 5% to 50%.

7. The method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound according to claim 1, characterized in that: The drying temperature is 80-100° C. and the drying time is 12-24 hours.

8. A zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound, characterized in that: The material is prepared by the method for preparing a zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound as described in any one of claims 1 to 7.

9. The zeolite molecular sieve adsorption material modified by a carboxylic acid organic compound as claimed in claim 8 is used for enrichment of exhaust gas.

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