Zirconium-based metal-organic framework material, its preparation method and application, adsorption and separation device and method

Abstract

The present invention provides a zirconium-based metal-organic framework material, a preparation method and an application thereof, an adsorption and separation device and a method. The chemical structural formula of the zirconium-based metal-organic framework material is [C 18 H6O 16 Zr3] n . The zirconium-based metal-organic framework material includes a zirconium element and an organic ligand that forms a coordination bond with the zirconium element. The organic ligand is ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid. The molecular structure of the zirconium-based metal-organic framework material of the present invention is a three-dimensional network structure with one-dimensional channels. By changing the aspect ratio of the organic ligand, the present invention precisely controls the size of the one-dimensional channels, enabling the zirconium-based metal-organic framework material to achieve efficient separation of hexane isomers through kinetic effects.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption separation, and particularly relates to a zirconium-based metal-organic framework material, a preparation method and an application thereof, an adsorption separation device and a method. Background Art

[0002] Industrial chemical separation processes are closely related to the national economy and social development, and are an indispensable important engine for promoting the modern development of mankind. However, the energy crisis and environmental pollution are two major problems faced by the world today. Currently, chemical separation mainly uses thermally driven separation technologies (such as distillation). The energy consumption related to the chemical separation process accounts for about 50% of industrial energy consumption and 10 - 15% of the world's total energy consumption. Moreover, this process releases a large amount of carbon dioxide and other harmful gases, having a serious impact on the environment. Therefore, it is extremely urgent to develop energy-saving and environment-friendly alternative technologies to reduce the energy consumption required in the chemical separation process in the chemical industry, reduce the release of harmful gases, and reduce environmental pollution.

[0003] High-octane gasoline has excellent anti-knock performance and is an important energy substance in today's society. Alkane isomers are one of the main components in the gasoline composition. The separation of alkane isomers (mainly pentane and hexane) is an indispensable important process in the petrochemical industry for preparing high-octane gasoline. In the petroleum refining process, catalytic isomerization reactions generate pentane and hexane isomers with different degrees of branching and separate them. The low-octane branched isomers (such as n-hexane, with an octane number of 30) are returned to the catalytic isomerization reactor for recycling, while the branched isomers with a higher octane number (such as 2,2-dimethylbutane, with an octane number of 92) can be used as gasoline raw materials. Currently, distillation technology is generally used in the industry to separate alkane isomers. However, due to the very close boiling points between alkane isomers, the distillation separation process is complex, has huge energy consumption, and requires high capital investment.

[0004] In order to reduce the energy consumption required for separation and lower the cost, it is urgent to develop more efficient, energy-saving and environment-friendly separation technologies. In recent years, many countries have conducted extensive explorations in the process of separating alkane isomers with different degrees of branching using solid porous materials as adsorbents to improve the octane number of gasoline components, and it has been proven to be feasible. However, up to now, the problem of efficient separation of hexane isomers, especially single-branched and double-branched hexanes, has not been well solved, and the separation process is complex and requires a large amount of energy consumption. Summary of the Invention

[0005] To solve the above technical problems, the first object of the present invention is to provide a zirconium-based metal-organic framework material and a preparation method thereof, so as to solve the problem that the existing separation technology cannot separate the mixture of hexane isomers; the second object of the present invention is to provide an adsorption separation device and an adsorption separation method, so as to solve the problem that the existing technology cannot efficiently separate hydrocarbon mixtures.

[0006] To achieve the above object, in the first aspect of the present invention, a zirconium-based metal-organic framework material (Zr-dpetc) is provided, and its chemical structural formula is [C 18 H 6 O 16 Zr 3 n , the zirconium-based metal-organic framework material includes zirconium element and an organic ligand that forms a coordination bond with the zirconium element, the organic ligand is ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid (English name: Diphenylethyne-3,3',5,5'-tetracarboxylic acid, abbreviated as dpetc), and the structural formula of this organic ligand is as follows:

[0007]

[0008] According to a specific embodiment of the present invention, preferably, the crystal structure of the above zirconium-based metal-organic framework material is as Figure 1a and Figure 1b shown, and the zirconium-based metal-organic framework material crystal belongs to the tetragonal system and the I4 / mmm space group.

[0009] Under the guidance of topology, the present invention finely regulates the pore size and shape of the metal-organic framework material by ligand screening, and then achieves a relatively high adsorption separation performance for hydrocarbon mixtures. The tetravalent metal ions (such as Zr 4+ ) used in the present invention have a small radius and a high charge, and the polarization ability is very strong. The coordination bond formed with the oxygen-containing ligand (such as carboxylic acid) has a large covalent component, forming a structure with strong chemical and thermal stability.

[0010] According to a specific embodiment of the present invention, preferably, the molecular structure of the above zirconium-based metal-organic framework material is a three-dimensional network structure with one-dimensional channels.

[0011] According to a specific embodiment of the present invention, preferably, in the above zirconium-based metal-organic framework material, the size of the one-dimensional pore channel

[0012] According to a specific embodiment of the present invention, preferably, in the above zirconium-based metal-organic framework material, the three-dimensional network structure is formed by connecting ZrO 6 octahedrons with organic ligands.​

[0013] According to a specific embodiment of the present invention, preferably, in the above-mentioned zirconium-based metal-organic framework material, the ZrO 6 octahedron contains six Zr atoms.

[0014] Under the guidance of topology, the present invention finely regulates the pore size and shape of the metal-organic framework material through ligand screening, and then achieves high adsorption and separation performance for hydrocarbon mixtures. The tetravalent metal ions (such as Zr 4+ ) used in the present invention have a small radius and a high charge, and a very strong polarization ability. The coordination bond formed with an oxygen-containing ligand (such as a carboxylic acid) has a large covalent component, forming a structure with strong chemical and thermal stability. The zirconium-based metal-organic framework material of the present invention is formed by connecting a ZrO 6 octahedron formed by six Zr atoms with an organic ligand (dpetc) to form a three-dimensional network structure with one-dimensional channels. The one-dimensional pore size is about which can allow n-hexane, mono-branched hexane, and di-branched hexane to enter the pores while forming a certain steric hindrance to inhibit the diffusion of larger molecules.

[0015] The zirconium-based metal-organic framework material (Zr-dpetc) of the present invention is a three-dimensional network structure based on octahedrally connected Zr 6 and bridged by a four-connected dpetc 4- organic ligand, having an scu topology structure, and the one-dimensional pore size is about This material connects six metal centers into a Zr 3 -O and μ 3 -OH to form a Zr 6 O 4 (OH) 4 metal-oxygen cluster octahedron. This octahedron has 12 external connection points and can be connected to up to 12 carboxyl groups through coordination bonds to form an ftw topology. However, the pore structure of the material can be adjusted by designing the geometric configuration of the ligand. The present invention changes the pore structure of the structure from the cage-like holes of the ftw topology to the one-dimensional channels of the scu topology by changing the aspect ratio of the organic ligand. The main effects of this design idea on the separation of alkane isomers are as follows: (1) The cage-like holes have a small window size, which will limit the diffusion of alkane molecules between the holes, resulting in a large influence on mass transfer during the separation process, and thus affecting the separation efficiency; (2) By changing the cage-like holes into one-dimensional channels, the pore size is effectively enlarged, and through the control of the ligand size, the pore size of the material is finally optimized to Due to the appropriate pore size, the material has high thermodynamic selectivity for single-branched / double-branched alkanes. At the same time, since the pore size is close to the size of the double-branched isomers, a certain restriction is formed on the diffusion of the double-branched alkanes, thus further improving the separation performance of the material. This is the first time to optimize the adsorption and separation performance of alkane isomers through dual regulation of pore structure and pore size under the guidance of topology.

[0016] According to a specific embodiment of the present invention, preferably, the specific surface area of the zirconium-based metal-organic framework material is 500-1000 m 2 / g.

[0017] According to a specific embodiment of the present invention, preferably, the thermal decomposition temperature of the zirconium-based metal-organic framework material is 350-500 °C.

[0018] According to a specific embodiment of the present invention, preferably, the zirconium-based metal-organic framework material is in the form of white powder crystals.

[0019] The zirconium-based metal-organic framework material of the present invention has excellent stability, and the decomposition temperature is close to 500 °C. Whether it is exposed to a high temperature of 120 °C for 7 days, exposed to air with a relative humidity of 90% for 7 days, or placed in hot water at 80 °C for 7 days, it can still maintain the integrity of the structure and the adsorption and separation performance does not decrease significantly.

[0020] The zirconium-based metal-organic framework material of the present invention can be used as an adsorbent material, which has the characteristics of purity, no impurities, regular morphology, etc., and can perform kinetic separation on the straight-chain, single-branched and double-branched isomers of hexane.

[0021] The second aspect of the present invention provides a preparation method of the above zirconium-based metal-organic framework material, which includes the following steps:

[0022] Mix zirconium salt, organic ligand, first solvent and acid in proportion, carry out solvothermal reaction or use microwave synthesis method to obtain a semi-finished product; then remove the solvent in the pores of the semi-finished product to obtain the finished zirconium-based metal-organic framework material.

[0023] According to a specific embodiment of the present invention, preferably, the above preparation method further includes: before removing the solvent in the pores of the semi-finished product, washing and drying the semi-finished product. Preferably, the washing is carried out with the first solvent, and the semi-finished product is dried after suction filtration.

[0024] According to a specific embodiment of the present invention, preferably, the above preparation method includes the following steps:

[0025] (1) Mix zirconium salt, organic ligand dpetc, first solvent and acid in proportion, dissolve them by ultrasonic or stirring, and then put them into a reaction kettle or glass bottle or other closed container for solvothermal reaction or microwave synthesis;

[0026] (2) After the solvothermal reaction or microwave synthesis is completed, wash it several times with the first solvent, and the semi-finished product can be obtained through suction filtration and drying.

[0027] (3) Remove the reaction solvent molecules existing in the pores of the semi-finished product structure by vacuum drying or through solvent exchange followed by vacuum drying to obtain the finished zirconium-based metal-organic framework material.

[0028] According to a specific embodiment of the present invention, preferably, in the above preparation method, the molar ratio of the zirconium salt, organic ligand, first solvent, and acid is 10:(1 - 100):(1 - 100):(2 - 200).

[0029] According to a specific embodiment of the present invention, preferably, in the above preparation method, the zirconium salt is selected from at least one of zirconium nitrate, zirconium chloride, zirconium aluminum oxide, and zirconium sulfate.

[0030] According to a specific embodiment of the present invention, preferably, in the above preparation method, the organic ligand is ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid.

[0031] According to a specific embodiment of the present invention, preferably, in the above preparation method, the first solvent is selected from at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and N,N-diethylformamide (DEF).

[0032] According to a specific embodiment of the present invention, preferably, in the above preparation method, the acid is selected from at least one of formic acid, acetic acid, hydrochloric acid, and benzoic acid.

[0033] According to a specific embodiment of the present invention, preferably, when the above preparation method adopts a solvothermal reaction, the reaction temperature of the solvothermal reaction is 80 - 200 °C, and the reaction time is 12 - 72 h.

[0034] According to a specific embodiment of the present invention, preferably, when the above preparation method adopts a microwave synthesis method, the reaction temperature is 80 - 180 °C, and the reaction time is 1 - 60 min.

[0035] According to a specific embodiment of the present invention, preferably, in the above preparation method, the method for removing the solvent in the pores of the semi-finished product is: performing vacuum drying on the semi-finished product, or impregnating the semi-finished product in a second solvent for solvent exchange, and then performing vacuum drying.

[0036] According to a specific embodiment of the present invention, preferably, in the above preparation method, the second solvent is selected from at least one of methanol, dichloromethane, ethanol, and acetone.

[0037] The preparation method of the zirconium-based metal-organic framework material of the present invention has good repeatability, and the obtained adsorbent uses raw materials with low prices, mild conditions, a simple synthesis process, pure products, and can be prepared rapidly on a large scale.

[0038] The third aspect of the present invention provides an application of the zirconium-based metal-organic framework material in separating alkane isomers.

[0039] According to a specific embodiment of the present invention, preferably, in the above application, the zirconium-based metal-organic framework material serves as an adsorbent.

[0040] According to a specific embodiment of the present invention, preferably, in the above application, the alkane isomers are hexane isomers;

[0041] According to a specific embodiment of the present invention, preferably, in the above application, the adsorption priority order of the zirconium-based metal-organic framework material for the hexane isomers is: n-hexane, single-branched hexane, double-branched hexane.

[0042] High-octane gasoline has excellent anti-knock performance and is an important energy substance in today's society. Alkane isomers are one of the main components in the gasoline composition. The kinetic radii and octane numbers of alkane (mainly pentane and hexane) isomers are shown in Table 1 below:

[0043] Table 1 Comparison of kinetic radii and octane numbers of hexane isomers

[0044]

[0045] The zirconium-based metal-organic framework material of the present invention is formed by connecting ZrO6 octahedrons formed by six Zr atoms with an organic ligand (dpetc) to form a three-dimensional network structure with one-dimensional channels. The one-dimensional pore size is about It can enable n-hexane, single-branched hexane, and double-branched hexane to enter the pores while forming a certain steric hindrance to inhibit the diffusion of larger molecules; in addition, due to different interaction forces between different isomers and the pore wall, in the order of hexane alkane > single-branched hexane > double-branched hexane, the adsorption trends for the three types of components are in the order of n-hexane > single-branched hexane > double-branched hexane, thereby realizing the separation of n-hexane, single-branched hexane, and double-branched hexane isomers.

[0046] The fourth aspect of the present invention provides an adsorption separation device for alkane isomers, including an adsorbent, and the adsorbent is the above-mentioned zirconium-based metal-organic framework material.

[0047] According to a specific embodiment of the present invention, preferably, the above adsorption separation device includes an adsorption column, and the adsorbent is filled in the adsorption column.

[0048] According to a specific embodiment of the present invention, preferably, in terms of the operation mode, the adsorption mode of the adsorption separation device is selected from any one of fixed-bed gas-phase adsorption, simulated moving-bed adsorption, and moving-bed adsorption, and fixed-bed gas-phase adsorption is preferred.

[0049] The fifth aspect of the present invention provides a method for adsorptive separation of alkane isomers, including: passing a gas mixture or liquid mixture containing hexane isomers through an adsorption column filled with an adsorbent, successively collecting each component of the isomers, and performing desorption treatment on the adsorbent after the collection is completed; the adsorbent is the above-mentioned zirconium-based metal-organic framework material.

[0050] According to a specific embodiment of the present invention, preferably, in the above-mentioned adsorptive separation method, the desorption is carried out by one or more of heating, vacuum treatment, and inert gas purging.

[0051] In the present invention, hexane isomers include straight-chain hexane (n-hexane), single-branched hexane (2-methylpentane, 3-methylpentane), and double-branched (2,2-dimethylbutane, 2,3-dimethylbutane), and the gas mixture or liquid mixture contains 2-5 components of hexane isomers. In the adsorptive separation method of the present invention, double-branched hexane preferentially penetrates through the adsorption column, then single-branched hexane penetrates through the adsorption column, and straight-chain hexane penetrates through the adsorption column last. The double-branched and single-branched alkanes are successively collected to obtain a product with a high octane number and high purity; after the straight-chain alkane penetrates, the straight-chain components adsorbed in the adsorbent can be eluted by heating, vacuum treatment, inert gas purging, or a combination of multiple desorption methods to obtain high-purity C6 straight-chain gas. The adsorbent of the present invention can be regenerated only after desorption treatment.

[0052] According to a specific embodiment of the present invention, preferably, in the above-mentioned adsorptive separation method, the adsorption temperature is 0-200°C, more preferably 20-150°C.

[0053] According to a specific embodiment of the present invention, preferably, in the above-mentioned adsorptive separation method, the total pressure of the gas mixture during adsorption is 0-5 bar, more preferably 0.5-1 bar.

[0054] According to a specific embodiment of the present invention, preferably, in the above-mentioned adsorptive separation method, the desorption temperature is 100-200°C.

[0055] According to a specific embodiment of the present invention, preferably, in the above-mentioned adsorptive separation method, the total pressure of the gas mixture during desorption is 0.05-1 bar.

[0056] According to a specific embodiment of the present invention, preferably, in the above-mentioned adsorptive separation method, the total amount of the hexane isomers accounts for 70-90% of the total mass of the gas mixture or liquid mixture.

[0057] According to a specific embodiment of the present invention, preferably, in the above adsorption separation method, the mixed gas further includes one or more of impurity gases such as methane in n-pentane, isopentane, oxygen, nitrogen, helium, carbon dioxide, and water vapor.

[0058] According to a specific embodiment of the present invention, preferably, in the above adsorption separation method, the mixed liquid further includes one or more of n-pentane, isopentane, water, etc.

[0059] Compared with the currently commonly used cryogenic distillation method, the adsorption separation method of alkane isomers of the present invention has the advantages of low cost, energy conservation and environmental protection, simple operation, etc., and can bring improvements in quality and economic benefits to petrochemical enterprises in the preparation of high-octane gasoline blending components.

[0060] Compared with the prior art, the zirconium-based metal-organic framework material, its preparation method and application involved in the present invention have the following beneficial effects:

[0061] (1) The molecular structure of the zirconium-based metal-organic framework material of the present invention is a three-dimensional network structure with one-dimensional channels. By changing the aspect ratio of the organic ligand, the size of the one-dimensional channel is precisely controlled, enabling the zirconium-based metal-organic framework material to achieve efficient separation of hexane isomers through kinetic effects, especially the efficient separation of single-branched hexane and double-branched hexane, thereby obtaining high-octane alkane products;

[0062] (2) Compared with the current hexane isomer separation materials, the zirconium-based metal-organic framework material of the present invention can obtain n-hexane, single-branched hexane and double-branched hexane respectively under mild conditions through simple operation steps; the obtained double-branched hexane can be used as a high-octane gasoline additive component, high-purity n-hexane is used for ethylene cracking or solvents, and single-branched hexane is returned to the isomerization reactor for reaction, thereby realizing the full utilization of oil components;

[0063] (3) The zirconium-based metal-organic framework material of the present invention does not contain impurities, has a pure material, regular morphology, has outstanding advantages such as good stability and high adsorption selectivity under harsh environments, and has good industrial application prospects, and can be applied to the petrochemical industry to prepare high-octane gasoline. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1a It is a schematic diagram of the crystal three-dimensional structure of the zirconium-based metal-organic framework material Zr-dpetc of the present invention;

[0065] Figure 1b It is a schematic diagram of the crystal plane structure of the zirconium-based metal-organic framework material Zr-dpetc of the present invention;

[0066] Figure 2X-ray diffraction patterns of the Zr-dpetc samples A-F obtained in Example 1 of the present invention after stability tests;

[0067] Figure 3 TG curves of the Zr-dpetc samples A and B obtained in Example 1;

[0068] Figure 4 N₂ adsorption-desorption isotherm of the Zr-dpetc sample C obtained in Example 1 at 77K;

[0069] Figure 5 Adsorption isotherms of the Zr-dpetc sample C obtained in Example 1 for n-hexane (nHEX), 3-methylpentane (3MP), and 2,2-dimethylbutane (22DMB) at 30 °C;

[0070] Figure 6 Adsorption kinetic curves of the Zr-dpetc sample C obtained in Example 1 for n-hexane (nHEX), 3-methylpentane (3MP), and 2,2-dimethylbutane (22DMB) at 30 °C;

[0071] Figure 7 Multi-component breakthrough curves of the Zr-dpetc sample C obtained in Example 1 for the ternary mixture of n-hexane (nHEX), 3-methylpentane (3MP), and 2,2-dimethylbutane (22DMB), where the curve RON represents the octane number of the eluate;

[0072] Figure 8 Multi-component breakthrough curves of the Zr-dpetc sample C obtained in Example 1 for the penta-component mixture of n-hexane (nHEX), 2-methylpentane (2MP), 3-methylpentane (3MP), 2,2-dimethylbutane (22DMB), and 2,3-dimethylbutane (23DMB), where the curve RON represents the octane number of the eluate. Detailed implementation manners

[0073] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the implementable scope of the present invention.

[0074] Example 1

[0075] This example provides a preparation method of a zirconium-based metal-organic framework material and a test on the adsorption and separation performance of alkane isomers, specifically as follows:

[0076] 0.17 mmol of zirconium chloride and 0.06 mmol of dpetc were added to a mixed solution composed of 6 mL of formic acid and 4 mL of N,N-dimethylformamide. After stirring for 30 min, it was transferred to a 20 mL glass bottle. After tightening the lid, it was placed in an oven at 120 °C for reaction for 72 hours. After cooling, white powder crystals A were obtained by filtration.

[0077] The filtered material was soaked in methanol solution for 48 hours to fully replace the N,N-dimethylformamide solvent with a higher boiling point inside the material pores with methanol with a lower boiling point. Then, the material after solvent exchange was filtered to obtain material B. The X-ray diffraction patterns of white powder crystals A and material B are as Figure 2 shown, and its thermogravimetric curve is as Figure 3 shown.

[0078] In order to test the specific surface area of the above-synthesized adsorbent, material B was degassed under vacuum at 120 °C for 12 hours to obtain zirconium-based metal-organic framework material C with the solvent removed from the pores, and its nitrogen adsorption-desorption isotherm was tested at 77 K. The results are as Figure 4 shown. After testing, the specific surface area of this material C is 630 m 2 / g.

[0079] In order to test the stability of the above adsorption material, the above adsorbent B was placed in an oven at 120 °C, in water at 80 °C, and in air with a humidity of 90% respectively. After being placed for 7 days, materials (D, E, F) were obtained for X-ray diffraction analysis and testing. As Figure 2 shown, the test results show that D, E, and F still maintain a complete crystal structure, indicating good stability.

[0080] In order to test the adsorption and separation performance of the above-synthesized adsorbent, the above desorbed adsorbent C was used to test the single-component adsorption isotherms of n-hexane, 3-methylpentane, and 2,2-dimethylbutane respectively. As Figure 5 shown, under the test conditions of a temperature of 30 °C and a pressure of 0.9 bar, the adsorption amount of n-hexane is 85 mg / g, the adsorption amount of 3-methylpentane is 72 mg / g, and the adsorption amount of 2,2-dimethylbutane is 86 mg / g.

[0081] An equimolar ternary mixture of n-hexane, 3-methylpentane, and 2,2-dimethylbutane was passed through an adsorption column filled with the adsorbent with helium as the carrier gas. As Figure 6 shown, at a temperature of 30 °C, a pressure of 1 bar, and a mixed gas flow rate of 1 mL / min, 2,2-dimethylbutane began to break through at the 10th minute. At the 25th minute, 3-methylpentane began to break through, and n-hexane began to break through at the 35th minute. As Figure 7As shown, gasoline blending components with an octane number higher than 95 can be obtained by this method.

[0082] A five-component mixture of equimolar amounts of n-hexane, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, and 2,2-dimethylbutane was passed through an adsorption column filled with C using helium as the carrier gas at a temperature of 30 °C, a pressure of 1 bar, and a mixed gas flow rate of 1 mL / min. After testing, as Figure 8 shown, 2,2-dimethylbutane penetrated at the 5th minute, 2,3-dimethylbutane penetrated at the 13th minute, 2-methylpentane and 3-methylpentane penetrated at the 24th minute. The components before the penetration of the monomethyl components were collected and condensed to obtain a product with an octane number as high as 95. n-Hexane penetrated at the 47th minute. The components before the penetration of n-hexane were collected and condensed to obtain monobranched alkanes. After the penetration of n-hexane, the gas supply was stopped, and the adsorption column was heated to 150 °C for desorption to collect a product with a n-hexane content greater than 80%.

[0083] Example 2

[0084] This example provides a preparation method of a zirconium-based metal-organic framework material and a test for the adsorption and separation performance of alkane isomers, which are specifically as follows:

[0085] 0.35 mmol of zirconium chloride and 0.12 mmol of dpetc were added to a mixed solution composed of 3 mL of acetic acid and 2 mL of N,N-dimethylacetamide (DMA). After ultrasonic treatment for 30 min, it was transferred to a glass tube of a 10 mL microwave synthesizer, the bottle cap was tightened, and then the glass tube was placed in the microwave synthesizer and heated at 100 °C for 5 minutes. After cooling, a white powder was obtained by filtration. The white powder was soaked in dichloromethane solution for 48 hours, and the exchanged sample was obtained by filtration. The exchanged sample was degassed under vacuum at 80 °C for 15 hours to obtain a desorbed sample. A mixed gas with a molar ratio of components of n-hexane: 2-methylpentane: 3-methylpentane: 2,3-dimethylbutane: 2,2-dimethylbutane: oxygen = 19:19:19:19:19:5 was passed through an adsorption column filled with the desorbed sample at a temperature of 30 °C, a pressure of 0.5 bar, and a mixed gas flow rate of 2 mL / min. Oxygen penetrated first, and then 2,2-dimethylbutane and 2,3-dimethylbutane penetrated. A product with an octane number of 96 was obtained by condensation; 2-methylpentane and 3-methylpentane penetrated subsequently, and n-hexane penetrated last. After penetration, the gas inlet was stopped, and the adsorption column was purged with helium. After condensation of the purge gas, n-hexane with a purity of 85% was obtained.

[0086] Example 3

[0087] This example provides a preparation method of a zirconium-based metal-organic framework material and a test for the adsorption and separation performance of alkane isomers, which are specifically as follows:

[0088] 0.35 mmol of zirconium aluminum oxide and 0.40 mmol of dpetc were added to a mixed solution composed of 3 mL of formic acid and 2 mL of N,N - diethylformamide (DEF). After ultrasonic treatment for 30 min, it was transferred to a 25 - mL stainless - steel reactor with a Teflon liner. The reactor lid was tightened, and then the reactor was placed in an oven at 150 °C for reaction for 24 hours. After cooling, it was filtered to obtain white powder A. A was soaked in n - hexane solution for 48 hours and then filtered to obtain material B. B was degassed under vacuum at 150 °C for 8 hours to obtain C. A mixed gas with a molar ratio of components: n - hexane: 2 - methylpentane: 2,3 - dimethylbutane: 2,2 - dimethylbutane: nitrogen: helium = 20:20:20:20:5:5 was passed through an adsorption column filled with the desorbed sample at a temperature of 40 °C, a pressure of 1 bar, and a mixed - gas flow rate of 4 mL / min. Nitrogen and helium penetrated first, followed by 2,2 - dimethylbutane and 2,3 - dimethylbutane. A product with an octane number of 95 was obtained through condensation; 2 - methylpentane then penetrated, and n - hexane penetrated last. After penetration, the gas inlet was stopped, and the adsorption column was purged with helium. After condensation of the purge gas, n - hexane with a purity of 82% was obtained.

[0089] Example 4

[0090] This example provides a preparation method of a zirconium - based metal - organic framework material and a test on the adsorption and separation performance of alkane isomers, as follows:

[0091] 0.35 mmol of zirconium sulfate and 0.12 mmol of dpetc were added to a mixed solution composed of 3 mL of hydrochloric acid and 10 mL of N,N - dimethylformamide. After ultrasonic treatment for 30 min, it was transferred to a glass tube of a 10 - mL microwave synthesizer. The bottle cap was tightened, and then the glass tube was placed in the microwave synthesizer and heated at 160 °C for 50 minutes. The white powder was soaked in an ethanol solution for 48 hours and then filtered. The filtered sample was degassed under vacuum at 200 °C for 6 hours to obtain the desorbed sample. An equimolar five - component mixture of n - hexane, 2 - methylpentane, 3 - methylpentane, 2,3 - dimethylbutane, and 2,2 - dimethylbutane was passed through an adsorption column filled with the desorbed sample with helium as the carrier gas at a temperature of 100 °C, a pressure of 1 bar, and a mixed - gas flow rate of 2 mL / min. 2,2 - dimethylbutane and 2,3 - dimethylbutane penetrated first, and a product with an octane number of 97 was obtained through condensation; 2 - methylpentane and 3 - methylpentane then penetrated, and n - hexane penetrated last. After penetration, the gas inlet was stopped, and the adsorption column was purged with helium. After condensation of the purge gas, n - hexane with a purity of 86% was obtained.

[0092] Example 5

[0093] This example provides a method for preparing a zirconium-based metal-organic framework material and a test on the adsorption and separation performance of alkane isomers, as follows:

[0094] 0.35 mmol of zirconium chloride and 0.12 mmol of dpetc were added to a mixed solution composed of 8 mL of benzoic acid and 2 mL of N,N-dimethylformamide. After ultrasonic treatment for 30 min, it was transferred to a 25-mL stainless-steel reaction kettle with a Teflon liner. The kettle lid was tightened, and then the reaction kettle was placed in an oven at 200 °C for reaction for 160 hours. After cooling, white powder was obtained by filtration. The white powder was soaked in an ethanol solution for 48 hours and then filtered. The filtered sample was degassed under vacuum at 160 °C for 8 hours to obtain a desorbed sample. An equimolar five-component mixed liquid of n-hexane, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, and 2,2-dimethylbutane was passed through an adsorption column filled with the desorbed sample at a temperature of 30 °C, a pressure of 5 bar, and a mixed liquid flow rate of 1 mL / min. 2,2-Dimethylbutane and 2,3-dimethylbutane penetrated first, and the product had an octane number of 96; 2-methylpentane and 3-methylpentane penetrated subsequently, and n-hexane penetrated last. After penetration, the feed gas was stopped, and the adsorption column was heated to 200 °C and purged with nitrogen. The gas purged out was condensed and collected to obtain n-hexane with a purity of 82%.

[0095] Comparative Example 1

[0096] This comparative example provides a method for adsorbing and separating hexane isomers using 5A molecular sieve, as follows:

[0097] An equimolar five-component mixture of n-hexane, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, and 2,2-dimethylbutane was passed through an adsorption column filled with activated 5A molecular sieve with helium as the carrier gas at a temperature of 100 °C, a pressure of 1 bar, and a mixed gas flow rate of 2 mL / min. 2,2-Dimethylbutane, 2,3-dimethylbutane, 2-methylpentane, and 3-methylpentane penetrated first, and the product with an octane number of 88 was obtained by condensation; subsequently, n-hexane penetrated last. After penetration, the gas inlet was stopped, and the adsorption column was purged with helium. The purged gas was condensed to obtain n-hexane with a purity of 85%. 5A molecular sieve is a one-dimensional pore solid adsorbent with a diameter of about The pore diameter is between the kinetic diameters of straight-chain hexane and branched-chain hexane. Coupled with the relatively rigid structural characteristics of the molecular sieve, 5A molecular sieve can only adsorb straight-chain alkane isomers and does not adsorb all branched isomers. Therefore, 5A molecular sieve can only separate hexane isomers with straight-chain and branched-chain structures and cannot separate hexane isomers with single-branched and double-branched structures.

[0098] Comparative Example 2

[0099] This comparative example provides a method for adsorptive separation of hexane isomers using UiO-66(Zr) metal-organic framework material. UiO-66(Zr) is a three-dimensional pore structure formed by coordination of metal Zr and terephthalic acid, which contains octahedral cages and tetrahedral cages with diameters of 1.1 nm and 0.8 nm respectively, and its pore windows are about 0.5 - 0.7 nm. The adsorptive separation method is as follows:

[0100] A pentamix of equimolar amounts of n-hexane, 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane and 2,2-dimethylbutane was introduced into an adsorption column filled with activated UiO-66 with helium as the carrier gas at a temperature of 100 °C, a pressure of 1 bar, and a flow rate of the mixed gas of 2 mL / min. First, n-hexane, 2-methylpentane, and 3-methylpentane broke through, and a product with an octane number of 56 was obtained by condensation; subsequently, 2,3-dimethylbutane and 2,2-dimethylbutane broke through. After breakthrough, the gas inlet was stopped, and the adsorption column was purged with helium. After condensation of the purge gas, a mixture containing 2,2-dimethylbutane and 2,3-dimethylbutane was obtained, and this mixture also included the remaining n-hexane, 2-methylpentane, and 3-methylpentane. In this mixture, the total amount of the two alkanes, 2,2-dimethylbutane and 2,3-dimethylbutane, accounted for 52% of the total mixture, and the octane number of the mixture was 74. The separation method of this comparative example cannot obtain a product with a higher octane number.

[0101] The above are the specific embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A zirconium-based metal-organic framework material, characterized in that, The zirconium-based metal-organic framework material is used for separating hexane isomers, and its chemical structural formula is [C 18 H 6 O 16 Zr 3 n . The zirconium-based metal-organic framework material includes a zirconium element and an organic ligand that forms a coordination bond with the zirconium element, and the organic ligand is ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid;​ the zirconium-based metal-organic framework material crystal belongs to the tetragonal system and the I4 / mmm space group; the molecular structure of the zirconium-based metal-organic framework material is a three-dimensional network structure with one-dimensional pores, and the size of the one-dimensional pores is 5-7 Å.

2. The zirconium-based metal-organic framework material according to claim 1, characterized in that, The three-dimensional network structure is formed by the connection of ZrO 6 octahedra and organic ligands.

3. The zirconium-based metal-organic framework material according to claim 2, characterized in that, The ZrO 6 octahedron contains six Zr atoms.

4. The zirconium-based metal-organic framework material according to claim 1, characterized in that, The specific surface area of the zirconium-based metal-organic framework material is 500-1000 m 2 / g.

5. The zirconium-based metal-organic framework material according to claim 1, characterized in that, the thermal decomposition temperature of the zirconium-based metal-organic framework material is 350-500 °C.

6. The zirconium-based metal-organic framework material according to claim 1, characterized in that, the zirconium-based metal-organic framework material is a white powder crystal.

7. The zirconium-based metal-organic framework material according to claim 1, characterized in that, when used for separating hexane isomers, the zirconium-based metal-organic framework material is used as an adsorbent.

8. The zirconium-based metal-organic framework material according to claim 1, characterized in that, when used for separating hexane isomers, the adsorption priority order of the zirconium-based metal-organic framework material for the hexane isomers is: n-hexane, single-branched hexane, double-branched hexane.

9. A preparation method of the zirconium-based metal-organic framework material according to any one of claims 1-8, characterized in that, it includes the following steps: (1) Mix zirconium salt, organic ligand, first solvent and acid in proportion, and carry out solvothermal reaction or use microwave synthesis method to obtain a semi-finished product; wherein the organic ligand is ethynylbiphenyl-3,3',5,5'-tetracarboxylic acid; (2) Then remove the solvent in the pores of the semi-finished product to obtain the finished zirconium-based metal-organic framework material.

10. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the preparation method further includes: before removing the solvent in the pores of the semi-finished product, washing and drying the semi-finished product.

11. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the molar ratio of the zirconium salt, organic ligand, first solvent and acid is 10:(1-100):(1-100):(2-200).

12. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the zirconium salt is selected from at least one of zirconium nitrate, zirconium chloride, zirconium aluminum oxide, zirconium sulfate.

13. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the first solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide.

14. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the acid is selected from at least one of formic acid, acetic acid, hydrochloric acid, benzoic acid.

15. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the reaction temperature of the solvothermal reaction is 80 - 200 °C, and the reaction time is 12 - 72 h.

16. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the reaction temperature of the microwave synthesis method is 80 - 180 °C, and the reaction time is 1 - 60 min.

17. The preparation method of the zirconium-based metal-organic framework material according to claim 9, characterized in that, the method for removing the solvent in the pores of the semi-finished product is: performing vacuum drying on the semi-finished product, or impregnating the semi-finished product in a second solvent for solvent exchange and then performing vacuum drying.

18. The preparation method of the zirconium-based metal-organic framework material according to claim 17, characterized in that, the second solvent is selected from at least one of methanol, dichloromethane, ethanol, and acetone.

19. An adsorption separation device for alkane isomers, characterized in that, it includes an adsorbent, and the adsorbent is the zirconium-based metal-organic framework material according to any one of claims 1 - 8.

20. The adsorption separation device for alkane isomers according to claim 19, characterized in that, the adsorption separation device includes an adsorption column, and the adsorbent is filled in the adsorption column.

21. The adsorption separation device for alkane isomers according to claim 19, characterized in that, the adsorption method of the adsorption separation device is selected from any one of fixed-bed gas-phase adsorption, simulated moving-bed adsorption, and moving-bed adsorption.

22. An adsorption separation method for alkane isomers, characterized in that, it includes: passing a mixed gas or mixed liquid containing hexane isomers through an adsorption column filled with an adsorbent, sequentially collecting each component isomer, and performing desorption treatment on the adsorbent after collection; the adsorbent is the zirconium-based metal-organic framework material according to any one of claims 1 - 8.

23. The adsorption separation method for alkane isomers according to claim 22, characterized in that, the desorption adopts one or more of heating, vacuum treatment, and inert gas purging.

24. The adsorption separation method for alkane isomers according to claim 22, characterized in that, the adsorption temperature is 0 - 200 °C.

25. The adsorption separation method for alkane isomers according to claim 24, characterized in that, the adsorption temperature is 20 - 150 °C.

26. The adsorption separation method for alkane isomers according to claim 22, characterized in that, the total pressure of the mixed gas during adsorption is 0 - 5 bar.

27. The adsorption separation method for alkane isomers according to claim 26, characterized in that, the total pressure of the mixed gas during adsorption is 0.5 - 1 bar.

28. The adsorption separation method for alkane isomers according to claim 22, characterized in that, the desorption temperature is 100 - 200 °C.

29. The adsorption separation method for alkane isomers according to claim 22, characterized in that, The total pressure of the mixed gas in the desorption is 0.05 - 1 bar.

30. The adsorption separation method of alkane isomers according to claim 22, characterized in that the total amount of the hexane isomers accounts for 70 - 90% of the total mass of the mixed gas or mixed liquid.

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