Application of pillared metal organic framework material in adsorbing and separating xylene isomer

Abstract

The invention discloses application of a pillared metal organic framework material in adsorption and separation of xylene isomers. Wherein the pillared metal organic framework material is used as an adsorbent to adsorb and separate mixed gas containing xylene isomers, the pillared metal organic framework material comprises metal ions and ligands, the ligands comprise main ligands and pillared ligands, the main ligands are selected from C6-C10 aromatic ring dicarboxylic acids containing or not containing substituent groups, the pillared ligands are selected from C6-C10 aromatic ring dicarboxylic acids containing or not containing substituent groups, and the pillared ligands are selected from C6-C10 aromatic ring dicarboxylic acids containing or not containing substituent groups. The substituent group is selected from one or more of C1-C5 alkyl groups, halogen, C1-C5 halogenated alkyl groups, amino groups, hydroxyl groups, cyano groups and C1-C5 alkoxy groups. The metal organic framework material provided by the invention is good in stability, developed in pore structure, large in BET (Brunauer, Emmett and Teller) specific surface area, high in adsorption capacity and high in adsorption separation selectivity when being applied to adsorption separation of xylene isomers.

Description

Technical Field

[0001] The invention belongs to the technical field of adsorption separation materials, and particularly relates to application of a pillared metal organic framework material in the adsorption separation of xylene isomers. Background Art

[0002] Xylene isomers, including o-xylene (OX), m-xylene (MX), p-xylene (PX), and ethylbenzene (EB), are important basic chemical raw materials for industries such as polyesters, plasticizers, dyes, coatings, and pharmaceuticals. They are in high demand and have broad market prospects. Currently, these isomers are primarily obtained through petroleum processing techniques such as toluene disproportionation, catalytic reforming, and aromatization of pyrolysis gasoline, ultimately forming a mixture of C8 aromatic hydrocarbons. In industrial production, to achieve high-value-added utilization, they must be further separated into individual isomers. However, due to the similar structures and close boiling points of the isomers (for example, MX and PX differ by only 0.75°C), conventional separation methods suffer from high energy consumption and poor selectivity, necessitating the development of efficient and economical separation and enrichment technologies.

[0003] Currently, the main separation methods used in industry include crystallization, simulated moving bed (SMB) technology, membrane separation technology, and adsorption separation technology. Crystallization achieves selective crystallization of different isomers by controlling temperature. For example, the multi-stage crystallization system proposed in US Patent No. 5,448,005 can significantly improve PX yield, but its process is complex, equipment investment is high, and operating costs are high. Simulated moving bed (SMB) is the most widely used xylene separation method in industry, represented by UOP's Parex process (Chem. Eng. Prog., 1970, 66:70-75.). This method achieves isomer separation through liquid-phase adsorption and can further improve separation efficiency by controlling bed temperature differences. However, this process has disadvantages such as complex equipment, dense equipment, extremely high packing uniformity requirements, and the necessary use of a desorbent (such as p-diethylbenzene), which have limited its further adoption. Membrane separation technology has demonstrated high selectivity in the laboratory, such as achieving a PX / OX separation factor of 200–480 using ZSM-5 zeolite membranes (Science, 2003, 300(5618):456-460). However, due to the difficulty in preparing membrane materials, high costs, and short service life, its application in industry remains at an exploratory stage.

[0004] Adsorption separation methods have become a research hotspot due to their advantages such as low energy consumption, simple equipment, and continuous operation. BP's MFI-type non-acidic molecular sieves can efficiently adsorb PX and EB at 200°C and 3–20 bar (US6600083B2). Furthermore, the multi-stage shape-selective modified adsorbent proposed in CN109529764A exhibits excellent selectivity for PX, but its preparation process is cumbersome, and there are cost and operational challenges.

[0005] In recent years, metal-organic frameworks (MOFs) have been considered promising candidates for next-generation high-performance adsorbents due to their highly tunable structures, ultra-large surface areas, and highly controllable pore size distributions. MOFs are constructed through coordination chemistry, and their pore structures can be selectively matched to specific isomers, enabling efficient separations. Furthermore, MOFs can be further engineered to enhance separation selectivity and structural stability through the regulation of different metal centers and organic ligands. Building on this, pillared MOFs have emerged. These MOFs employ a dual-ligand construction strategy to introduce "pillars," forming highly ordered, rigid, three-dimensional frameworks with enhanced structural stability, pore size uniformity, and molecular recognition capabilities. However, research on pillared MOFs for xylene isomer separation remains relatively limited, and their structural design, selectivity mechanisms, and industrial feasibility have yet to be fully developed. Therefore, developing a novel, highly selective adsorbent material based on pillared MOFs would not only improve the separation efficiency of the target component but also possess excellent thermal stability, reproducibility, and potential for industrial application, thus possessing significant research significance and promising applications. Summary of the Invention

[0006] The purpose of the present invention is to provide an application of a pillared metal-organic framework material in the adsorption separation of xylene isomers. The metal-organic framework material provided by the present invention has good stability, a developed pore structure, and a large specific surface area. It has a high adsorption capacity and high adsorption separation selectivity when used in the adsorption separation of xylene isomers.

[0007] The present invention provides an application of a pillared metal-organic framework material in the adsorption and separation of xylene isomers, wherein the pillared metal-organic framework material is used as an adsorbent to adsorb and separate a mixed gas containing xylene isomers. The pillared MOF material includes metal ions and ligands, and the ligands include primary ligands and pillaring ligands. The primary ligands are selected from C6-C10 aromatic ring dicarboxylic acids with or without substituents, and the substituents are selected from one or more of C1-C5 alkyl, halogen, C1-C5 haloalkyl, amino, hydroxyl, cyano, and C1-C5 alkoxy.

[0008] In some embodiments, the xylene isomers are selected from at least two of ethylbenzene, p-xylene, m-xylene, and o-xylene.

[0009] In some embodiments, the metal ion is selected from cobalt ion or nickel ion.

[0010] In some embodiments, the C6-C10 aromatic ring dicarboxylic acid containing or not containing a substituent is selected from the benzene ring dicarboxylic acid containing or not containing a substituent. In some embodiments, the substituent is selected from one or more of methyl, ethyl, fluorine, chlorine, bromine, iodine, trifluoromethyl, amino, hydroxyl, cyano, and methoxy. In some embodiments, the substituent is amino.

[0011] In some embodiments, the primary ligand is isophthalic acid, terephthalic acid, 5-aminoisophthalic acid or 2-aminoterephthalic acid.

[0012] In some embodiments, the pillaring ligand is represented by Formula I:

[0013]

[0014] In formula I, R is independently selected from hydrogen, C1-C5 alkyl, halogen, C1-C5 haloalkyl, amino, hydroxy, cyano, and C1-C5 alkoxy.

[0015] In some embodiments, each R is independently selected from hydrogen, methyl, ethyl, fluorine, chlorine, bromine, iodine, trifluoromethyl, amino, hydroxyl, cyano, and methoxy; preferably, each R is hydrogen.

[0016] In some embodiments, the pillaring ligand is meso-α,β-di(4-pyridyl)ethylene glycol.

[0017] In some embodiments, the pore size of the pillared metal organic framework material is

[0018] In some embodiments, the specific surface area of ​​the pillared metal organic framework material is 400 to 500 m 2 / g, pore volume is 0.1~0.2cm 3 / g.

[0019] According to some embodiments of the present invention, the preparation method of the pillared metal-organic framework material includes dissolving a metal inorganic salt, a pillaring ligand, and a primary ligand in a solvent and performing a hydrothermal reaction. The hydrothermal reaction temperature affects crystal formation; either too high or too low a temperature will result in failure to form crystals. Therefore, the hydrothermal reaction temperature is 60-150°C, and the reaction time is 12-72 hours. More preferably, the temperature is 70-100°C, and the reaction time is 24-48 hours.

[0020] According to some embodiments of the present invention, in the above-mentioned preparation method, after the hydrothermal reaction is completed, the generated solid is washed and dried. According to some embodiments of the present invention, after the hydrothermal reaction is completed, the solid is washed sequentially with N,N-dimethylformamide and anhydrous methanol, and then naturally dried in air; the drying time is 6 to 24 hours. According to some embodiments of the present invention, the product after the hydrothermal reaction is washed with N,N-dimethylformamide and centrifuged several times to displace the alkaline solution and inorganic salts remaining in the pores, and then washed with anhydrous methanol and centrifuged several times to displace the organic ligands and water remaining in the pores, thereby completing the purification of the adsorbent.

[0021] According to some embodiments of the present invention, in the above preparation method, the solvent is a mixture of N-dimethylformamide and methanol.

[0022] According to some embodiments of the present invention, in the above preparation method, the metal inorganic salt is selected from chlorides, nitrates, acetates, carbonates, sulfates or perchlorates of metal ions.

[0023] According to some embodiments of the present invention, in the above preparation method, the molar ratio of the metal inorganic salt to the pillaring ligand is 1:(1-3).

[0024] According to some embodiments of the present invention, in the above preparation method, the molar ratio of the inorganic salt, the pillaring ligand and the main ligand is 1:(1.5-2):1, and most preferably 1:1.5:1.

[0025] According to some embodiments of the present invention, the temperature of the adsorption separation is -5 to 300°C, for example, -5°C, 0°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 150°C, 160°C, 170°C, 200°C, etc. According to some embodiments of the present invention, the temperature of the adsorption separation is 15 to 120°C. According to some embodiments of the present invention, the temperature of the adsorption separation is 20 to 90°C.

[0026] According to some embodiments of the present invention, the total pressure of the mixed gas is 100-1000 kPa, for example, 100 kPa, 200 kPa, 300 kPa, 400 kPa, 500 kPa, 600 kPa, 700 kPa, 800 kPa, 900 kPa, etc. According to some embodiments of the present invention, the total pressure of the mixed gas is 100-400 kPa.

[0027] According to some embodiments of the present invention, the temperature for adsorption separation is 50-70° C., and the total pressure of the mixed gas is 100 kPa.

[0028] According to some embodiments of the present invention, the temperature of the adsorption separation is 60° C., and the total pressure of the mixed gas is 100 kPa.

[0029] The metal-organic framework materials provided by this invention are a series of MOFs with uniform pore sizes. Using different metals and ligands can produce materials with varying pore sizes. The pillared MOFs used in this invention are constructed from two types of ligands: primary ligands (also called base ligands) that coordinate with metal ions to form a layered structure, and pillaring ligands that act as connectors between the layers.

[0030] The preparation process of this metal-organic framework material uses inexpensive and readily available symmetrical carboxylic acids as pillaring ligands or primary ligands, which undergo a hydrothermal reaction with a series of metal inorganic salts. This material is prepared using low-cost raw materials, mild synthesis conditions, simple operation, easy post-processing, and low material synthesis cost. In the method of the present invention, the metal-organic framework material exhibits high adsorption and separation selectivity for xylene isomers, and the material structure and adsorption properties are stable, with good stability, promising promising prospects for industrial application.

[0031] The metal-organic framework material used in this invention as an adsorbent can be regenerated after adsorption saturation by simply heating to 50-150°C under vacuum or an inert atmosphere such as nitrogen for 2-10 hours. Excessively high temperatures or prolonged regeneration can damage the adsorbent structure, while excessively low temperatures or short regeneration times may prevent the complete removal of residual adsorbates.

[0032] The adsorbent prepared by the preferred method of the present invention has stable structure and performance, and has high selectivity and adsorption capacity for xylene isomers.

[0033] Preferably, the flow rate of the mixed gas through the adsorbent is 1 to 50 mL / min.

[0034] Preferably, the mixed gas comprises two or more of p-xylene, m-xylene, o-xylene and ethylbenzene. The raw gas composition range of the present invention is very wide and various concentrations are applicable, ranging from 50 ppm to 95%.

[0035] The metal organic framework material used in the present invention can be prepared into spherical, columnar, granular and other adsorption separation materials through different processing techniques or made into membrane materials according to existing conventional technologies for separation of xylene isomers.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] The metal organic framework adsorbent prepared by the present invention is a metal organic framework material with a uniform pore structure. The pore size of the adsorbent material is close to the kinetic diameter range of xylene isomers (ethylbenzene: Paraxylene: Meta-Xylene: o-Xylene: ), which is suitable for the separation of xylene isomers. Xylene molecules with larger kinetic sizes (such as m-xylene and o-xylene) diffuse into the pores more slowly, while p-xylene and ethylbenzene molecules with smaller kinetic sizes diffuse into the pores more quickly. It is worth noting that although the kinetic diameters of ethylbenzene molecules are comparable to those of p-xylene molecules, the three-dimensional dimensions of ethylbenzene are slightly larger than those of p-xylene. Therefore, the material can separate xylene isomers based on differences in kinetic diffusion rates. In addition, the aromatic carboxylic acid ligands impart aromatic properties to the pores, which can produce effective π-π stacking effects with the benzene rings of xylene isomers. Smaller molecules can produce more effective π-π stacking with the benzene rings of the pores. Therefore, the material can also achieve effective separation of xylene isomers based on differences in thermodynamic affinity.

[0038] The ligands and metal salts used in the preparation of the metal-organic framework materials of the present invention are both inexpensive and readily available, the synthesis conditions are mild, the purification steps are simple, and they are easy to operate and scale up. The metal-organic framework materials of the present invention have a stable structure and performance, exhibit high adsorption capacity for xylene isomers, and can achieve efficient separation of xylene isomers even at extremely low concentrations. Furthermore, after repeated adsorption and regeneration cycles, the adsorption performance remains unchanged. The adsorbent prepared by the present invention is far superior to most solid adsorbents in terms of xylene isomer separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is the isotherm of the single-component vapor adsorption of xylene isomers in Example 1.

[0040] Figure 2 This is a diagram of the penetration experiment of the xylene isomer mixed gas (equal proportions) in Example 1.

[0041] Figure 3 This is a diagram of the penetration experiment of the xylene isomer mixed gas (actual industrial ratio) in Example 1. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the scope of protection of the present invention.

[0043] In this application, the terms "C8 aromatic isomers" and "xylene isomers" are used interchangeably to refer to aromatic hydrocarbons with the molecular formula C8H10, examples of which include p-xylene, m-xylene, o-xylene, and ethylbenzene.

[0044] Measurement method

[0045] 1. Aperture measurement method:

[0046] The pore size of the adsorbent material described in the present invention is analyzed based on the CIF file obtained from the single crystal structure test using the structure measurement tool in the Material Studio software. The specific method is: measure the distance between the two closest atomic centers on either side of the pore in the corresponding crystal direction. If the distance between the two closest atomic centers measured in the x (or a) direction is The closest interatomic center distance measured in the y (or b) direction is The pore diameter of the channel is defined as

[0047] 2. Measurement method of specific surface area:

[0048] The specific surface area of ​​the materials described in the present invention is measured by nitrogen adsorption-desorption isotherm testing at 77K. The test samples are pre-degassed under vacuum or inert atmosphere to remove surface impurities. The specific surface area of ​​the material is then calculated based on the nitrogen adsorption data in the relative pressure range of P / P0 = 0.05 to 0.30 according to the BET (Brunauer–Emmett–Teller) model, and the unit is m 2 / g.

[0049] 3. Pore volume measurement method:

[0050] The pore volume of the materials described in the present invention was determined using nitrogen adsorption-desorption isotherms at 77 K. The total pore volume of the material was calculated based on the adsorption capacity at a relative pressure P / P0≈0.99, assuming that the pores are completely filled with liquid nitrogen under this condition. The adsorption capacity is based on the density of liquid nitrogen (approximately 0.808 g / cm 3 ) is converted to obtain the pore volume per unit mass of the material in cm 3 / g.

[0051] Example 1

[0052] 0.37mmol meso-α,β-di(4-pyridyl)ethylene glycol (DPG) and 0.56mmol cobalt nitrate hexahydrate were dissolved in a mixed solution of DMF / anhydrous methanol (15mL each), followed by the addition of 0.37mmol isophthalic acid (IPA). After complete dissolution, the mixture was placed in a 70°C oven for reaction for 36h. After the reaction was completed and cooled to room temperature, the solid product was collected by filtration, washed three times with DMF and methanol respectively, and dried naturally in air to obtain a sample. The pore size of the material is BET specific surface area is 453m 2 / g, pore volume is 0.15cm 3 The purified adsorbent was degassed at 150° C. under vacuum for 24 hours to obtain a desolventized adsorbent, which was then subjected to gas adsorption.

[0053] In order to test the adsorption and separation performance of the metal organic framework material prepared in this example, a single component vapor adsorption experiment of xylene isomers was carried out using the above adsorbent. 100 mg of the adsorbent was taken and the adsorption temperature was set to 60°C. The test showed that at 60°C and 1 kPa, the adsorption amounts of p-xylene, ethylbenzene, m-xylene, and o-xylene were 147.8 mg / g, 125.5 mg / g, 101.9 mg / g, and 72.2 mg, respectively. The adsorption isotherms are shown in Figure 2. Figure 1 .

[0054] In order to verify the actual separation effect of the above-mentioned metal-organic framework material on xylene isomers, a penetration experiment of a xylene isomer mixed gas was carried out using the above-mentioned synthesized adsorbent. The specific method is to prepare a mixed solution of PX, EB, MX, OX and other components in a volume ratio of 1:1:1:1, and then use nitrogen as the bubbling gas to generate a xylene isomer mixed gas through the above-mentioned mixed solution for a penetration experiment. The penetration temperature is 60°C, the pressure is 0.1MPa, and the nitrogen flow rate is 20mL / min. After testing, OX penetrated at 196min / g, MX penetrated at 664min / g, EB penetrated at 1048min / g, and PX penetrated at 1773min / g. The penetration curve is shown in FIG. Figure 2 .

[0055] In order to verify the actual separation effect of the xylene isomer mixture of the above-mentioned industrial actual components of the metal-organic framework material, a penetration experiment of the xylene isomer mixed gas was carried out using the above-mentioned synthesized adsorbent. The specific method is to prepare a mixed solution of PX, EB, MX, OX and other components in a volume ratio of 22:6:50:22, and then use nitrogen as the bubbling gas to generate a xylene isomer mixed gas through the above-mentioned mixed solution for a penetration experiment. The penetration temperature is 60°C, the pressure is 0.1MPa, and the nitrogen flow rate is 20mL / min. After testing, OX penetrated at 205min / g, MX penetrated at 750min / g, EB penetrated at 2025min / g, and PX penetrated at 2739min / g. The penetration curve is shown in FIG. Figure 3 .

[0056] Example 2

[0057] The metal organic framework synthesized in Example 1 was purified and degassed at 150° C. under vacuum for 24 hours to obtain a desolvated adsorbent, which was then subjected to gas adsorption.

[0058] Single-component vapor adsorption experiments of xylene isomers were conducted using the above-mentioned adsorbent. 100 mg of the adsorbent was taken and the adsorption temperature was set at 30°C. At 30°C and 1 kPa, the adsorption capacities of p-xylene, ethylbenzene, m-xylene, and o-xylene were 180.7 mg / g, 159.6 mg / g, 149.8 mg / g, and 132.9 mg, respectively.

[0059] Using the synthesized adsorbent, a xylene isomer gas mixture was tested for penetration. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 1:1:1:1. Nitrogen was then used as the bubbling gas to generate a xylene isomer gas mixture through the mixed solution for penetration testing. The penetration temperature was 30°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX and MX achieved penetration at 312 min / g, EB at 688 min / g, and PX at 1442 min / g.

[0060] To verify the separation performance of a mixture of p-xylene isomers, a practical industrial component of the metal-organic framework, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 22:6:50:22. Nitrogen was then used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 30°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 190 min / g, MX at 195 min / g, EB at 1945 min / g, and PX at 2518 min / g.

[0061] Example 3

[0062] The metal organic framework synthesized in Example 1 was purified and degassed at 150° C. under vacuum for 24 hours to obtain a desolvated adsorbent, which was then subjected to gas adsorption.

[0063] Single-component vapor adsorption experiments of xylene isomers were conducted using the above-mentioned adsorbent. 100 mg of the adsorbent was taken and the adsorption temperature was set at 30°C. At 90°C and 1 kPa, the adsorption capacities of p-xylene, ethylbenzene, m-xylene, and o-xylene were 120.2 mg / g, 101.9 mg / g, 79.7 mg / g, and 30.4 mg, respectively.

[0064] Using the synthesized adsorbent, a xylene isomer gas mixture was tested for penetration. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 1:1:1:1. Nitrogen was then used as the bubbling gas to generate a xylene isomer gas mixture through the mixed solution for penetration testing. The penetration temperature was 90°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 107 min / g, MX at 1095 min / g, and EB and PX almost simultaneously at 1700 min / g.

[0065] To verify the separation performance of a mixture of p-xylene isomers, a practical industrial component of the metal-organic framework, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 22:6:50:22. Nitrogen was then used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 90°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 102 min / g, MX at 370 min / g, EB at 2070 min / g, and PX at 2219 min / g.

[0066] Example 4

[0067] 0.37mmol meso-α,β-di(4-pyridyl)ethylene glycol (DPG) and 0.56mmol cobalt nitrate hexahydrate were dissolved in a mixed solution of DMF / anhydrous methanol (15mL each), followed by the addition of 0.37mmol terephthalic acid (bdc). After complete dissolution, the mixture was placed in a 70℃ oven for reaction for 36h. After the reaction was completed and cooled to room temperature, the solid product was collected by filtration, washed three times with DMF and methanol respectively, and dried naturally in air to obtain a sample. The pore size of the material is BET specific surface area is 482m 2 / g, pore volume is 0.17cm 3 The purified adsorbent was degassed at 150° C. under vacuum for 24 hours to obtain a desolventized adsorbent, which was then subjected to gas adsorption.

[0068] To test the adsorption and separation performance of the metal-organic framework prepared in this example, a single-component vapor adsorption experiment of xylene isomers was conducted using the adsorbent. 100 mg of the adsorbent was used, and the adsorption temperature was set at 60°C. At 60°C and 1 kPa, the adsorption capacities of p-xylene, ethylbenzene, m-xylene, and o-xylene were 149.8 mg / g, 127.1 mg / g, 104.3 mg / g, and 89.2 mg, respectively.

[0069] To verify the effectiveness of the metal-organic framework for separating xylene isomers, a gaseous penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 1:1:1:1. Nitrogen was then used as the bubbling gas to generate a gaseous xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved a penetration of 288 min / g, MX achieved a penetration of 634 min / g, EB achieved a penetration of 1061 min / g, and PX achieved a penetration of 1801 min / g.

[0070] To verify the separation performance of a mixture of p-xylene isomers, a practical industrial component of the metal-organic framework, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 22:6:50:22. Nitrogen was then used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 249 min / g, MX at 753 min / g, EB at 2017 min / g, and PX at 2414 min / g.

[0071] Example 5

[0072] 0.37mmol meso-α,β-di(4-pyridyl)ethylene glycol (DPG) and 0.56mmol cobalt nitrate hexahydrate were dissolved in a mixed solution of DMF / anhydrous methanol (15mL each), followed by the addition of 0.37mmol 5-aminoisophthalic acid (IPA-NH2). After complete dissolution, the mixture was placed in a 70°C oven for reaction for 36h. After the reaction was completed and cooled to room temperature, the solid product was collected by filtration, washed three times with DMF and methanol respectively, and dried naturally in air to obtain a sample. The pore size of the material is BET specific surface area is 387m 2 / g, pore volume is 0.13cm 3 The purified adsorbent was degassed at 150° C. under vacuum for 24 hours to obtain a desolventized adsorbent, which was then subjected to gas adsorption.

[0073] To test the adsorption and separation performance of the metal-organic framework prepared in this example, a single-component vapor adsorption experiment of xylene isomers was conducted using the adsorbent. 100 mg of the adsorbent was used, and the adsorption temperature was set at 60°C. At 60°C and 1 kPa, the adsorption capacities of p-xylene, ethylbenzene, m-xylene, and o-xylene were 143.8 mg / g, 124.5 mg / g, 100.9 mg / g, and 82.2 mg, respectively.

[0074] To verify the actual separation effect of the metal-organic framework material on xylene isomers, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 1:1:1:1. Then, nitrogen was used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 196 min / g, MX at 264 min / g, EB at 1005 min / g, and PX at 1173 min / g.

[0075] To verify the separation performance of a mixture of p-xylene isomers, a practical industrial component of the metal-organic framework, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 22:6:50:22. Nitrogen was then used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 177 min / g, MX at 682 min / g, EB at 1972 min / g, and PX at 2319 min / g.

[0076] Example 6

[0077] 0.37mmol meso-α,β-di(4-pyridyl)ethylene glycol (DPG) and 0.56mmol cobalt nitrate hexahydrate were dissolved in a mixed solution of DMF / anhydrous methanol (15mL each), followed by the addition of 0.37mmol 2-aminoterephthalic acid (bdc-NH2). After complete dissolution, the mixture was placed in a 70°C oven for reaction for 36h. After the reaction was completed and cooled to room temperature, the solid product was collected by filtration, washed three times with DMF and methanol respectively, and dried naturally in air to obtain a sample. The pore size of the material is BET specific surface area is 413m 2 / g, pore volume is 0.14cm 3 The purified adsorbent was degassed at 150° C. under vacuum for 24 hours to obtain a desolventized adsorbent, which was then subjected to gas adsorption.

[0078] To test the adsorption and separation performance of the metal-organic framework prepared in this example, a single-component vapor adsorption experiment of xylene isomers was conducted using the adsorbent described above. 100 mg of the adsorbent was used, and the adsorption temperature was set at 60°C. At 60°C and 1 kPa, the adsorption capacities of p-xylene, ethylbenzene, m-xylene, and o-xylene were 141.1 mg / g, 118.1 mg / g, 97.4 mg / g, and 88.2 mg, respectively.

[0079] To verify the actual separation effect of the metal-organic framework material on xylene isomers, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 1:1:1:1. Then, nitrogen was used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 228 min / g, MX at 424 min / g, EB at 1004 min / g, and PX at 1583 min / g.

[0080] To verify the separation performance of a mixture of p-xylene isomers, a practical industrial component of the metal-organic framework, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 22:6:50:22. Nitrogen was then used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 240 min / g, MX at 635 min / g, EB at 1968 min / g, and PX at 2124 min / g.

[0081] Example 7

[0082] 0.37mmol meso-α,β-di(4-pyridyl)ethylene glycol (DPG) and 0.56mmol nickel nitrate hexahydrate were dissolved in a mixed solution of DMF / anhydrous methanol (15mL each), followed by the addition of 0.37mmol isophthalic acid (IPA). After complete dissolution, the mixture was placed in a 70°C oven for reaction for 36h. After the reaction was completed and cooled to room temperature, the solid product was collected by filtration, washed three times with DMF and methanol respectively, and dried naturally in air to obtain a sample. The pore size of the material is BET specific surface area is 494m 2 / g, pore volume is 0.18cm 3The purified adsorbent was degassed at 150° C. under vacuum for 24 hours to obtain a desolventized adsorbent, which was then subjected to gas adsorption.

[0083] To test the adsorption and separation performance of the metal-organic framework prepared in this example, a single-component vapor adsorption experiment of xylene isomers was conducted using the adsorbent. 100 mg of the adsorbent was used, and the adsorption temperature was set at 60°C. At 60°C and 1 kPa, the adsorption capacities of p-xylene, ethylbenzene, m-xylene, and o-xylene were 149.8 mg / g, 137.5 mg / g, 104.9 mg / g, and 81.1 mg, respectively.

[0084] To verify the actual separation effect of the metal-organic framework material on xylene isomers, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 1:1:1:1. Then, nitrogen was used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 218 min / g, MX at 594 min / g, EB at 1053 min / g, and PX at 1609 min / g.

[0085] To verify the separation performance of a mixture of xylene isomers, a practical industrial component of the metal-organic framework, a penetration test of a xylene isomer mixture was conducted using the synthesized adsorbent. Specifically, a mixed solution of PX, EB, MX, and OX was prepared at a volume ratio of 22:6:50:22. Nitrogen was then used as the bubbling gas to generate a xylene isomer mixture through the mixed solution for penetration testing. The penetration temperature was 60°C, the pressure was 0.1 MPa, and the nitrogen flow rate was 20 mL / min. OX achieved penetration at 231 min / g, MX at 603 min / g, EB at 2047 min / g, and PX at 2423 min / g.

[0086] The specific implementation methods described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above is only the most preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of a pillared metal organic framework material in the adsorption separation of xylene isomers, wherein: The pillared metal organic framework material is used as an adsorbent to adsorb and separate a mixed gas containing xylene isomers. The pillared MOF material includes metal ions and ligands. The ligands include main ligands and pillaring ligands. The main ligands are selected from C6-C10 aromatic ring dicarboxylic acids with or without substituents, and the substituents are selected from one or more of C1-C5 alkyl, halogen, C1-C5 haloalkyl, amino, hydroxyl, cyano, and C1-C5 alkoxy.

2. The use according to claim 1, characterized in that The metal ions are selected from cobalt ions or nickel ions; and the xylene isomers are selected from at least two of ethylbenzene, p-xylene, m-xylene and o-xylene.

3. The use according to claim 1 or 2, characterized in that The C6-C10 aromatic ring dicarboxylic acid containing or not containing a substituent is selected from the benzene ring dicarboxylic acid containing or not containing a substituent; Preferably, the substituent is selected from one or more of methyl, ethyl, fluorine, chlorine, bromine, iodine, trifluoromethyl, amino, hydroxyl, cyano, and methoxy; Preferably, the primary ligand is selected from one or more of isophthalic acid, terephthalic acid, 5-aminoisophthalic acid, and 2-aminoterephthalic acid.

4. The use according to any one of claims 1 to 3, characterized in that The pillaring ligand is shown in Formula I: In formula I, R is independently selected from hydrogen, C1-C5 alkyl, halogen, C1-C5 haloalkyl, amino, hydroxy, cyano, C1-C5 alkoxy; Preferably, R is independently selected from hydrogen, methyl, ethyl, fluorine, chlorine, bromine, iodine, trifluoromethyl, amino, hydroxyl, cyano, methoxy; preferably, each R is hydrogen; More preferably, the pillaring ligand is meso-α,β-di(4-pyridyl)ethylene glycol.

5. The use according to any one of claims 1 to 4, characterized in that The pore size of the pillared metal organic framework material is 6. The use according to any one of claims 1 to 5, characterized in that The BET specific surface area of ​​the pillared metal organic framework material is 400 to 500 m 2 / g, pore volume is 0.1~0.2cm 3 / g.

7. The use according to any one of claims 1 to 6, characterized in that The preparation method of the pillared MOF material comprises: dissolving a metal inorganic salt, a pillaring ligand and a main ligand in a solvent, performing a hydrothermal reaction at 60 to 150° C. for 12 to 72 hours, and optionally washing and drying the generated solid.

8. The use according to claim 7, characterized in that The solvent is a mixture of N-dimethylformamide and methanol; The metal inorganic salt is selected from chlorides, nitrates, acetates, carbonates, sulfates or perchlorates of metal ions; The molar ratio of the metal inorganic salt to the pillaring ligand is 1:(1-3).

9. The use according to claim 7 or 8, characterized in that The molar ratio of the metal inorganic salt, the pillaring ligand and the main ligand is 1:(1.5-2):1, and most preferably 1:1.5:

1.

10. The use according to any one of claims 1 to 9, characterized in that The temperature of the adsorption separation is -5 to 300° C., and the total pressure of the mixed gas is 100 to 1000 kPa; preferably, the temperature of the adsorption separation is 15 to 120° C., and the total pressure of the mixed gas is 100 to 400 kPa.

Images