Metal organic framework material, preparation method and application thereof

Abstract

The application discloses a kind of metal organic framework materials and preparation method and application thereof.The metal organic framework material provided by the application includes metal ions and organic ligand, and the organic ligand is selected from the compound shown in formula I or formula II.The metal organic framework material of the application has excellent adsorption separation selectivity to p-xylene.The raw material for synthesizing the material is cheap and easy to obtain, the material preparation process is simple and low in cost, and the material has good regeneration and repetition performance, and can maintain the original adsorption effect after vacuum or heating regeneration, and has wide industrial application prospect.

Description

Technical Field

[0001] This invention relates to the technical field of adsorption materials and energy, and in particular to a metal-organic framework material, its preparation method and application. Background Technology

[0002] p-Xylene (PX) is primarily used in the production of purified terephthalic acid (PTA). PTA is then reacted with ethylene glycol to further produce polyethylene terephthalate (PET), which is ultimately used in the synthesis of polyester fibers and other materials. The industrial source of xylene isomers is the catalytic reforming of naphtha. Catalytic reforming yields a mixture of C8 aromatic isomers, primarily including p-xylene (PX), m-xylene (MX), o-xylene (OX), and ethylbenzene (EB). Because xylene isomers have almost identical boiling points, traditional separation techniques such as distillation require over 300 theoretical plates, resulting in enormous energy consumption. Therefore, separating PX from a highly similar mixture of C8 aromatic isomers is challenging. Currently, over 75% of industrially produced p-xylene is produced using simulated moving bed (SMB) technology, which employs FAU zeolite as an adsorbent and operates within a high temperature range of 393 to 523 K. However, the boiling points, configurations and other physicochemical properties of the C8 isomers are highly similar, and the molecular sieve structure has poor tunability, resulting in very low adsorption selectivity of the molecular sieve, with the selectivity of xylene to other isomers not exceeding 5.

[0003] Metal-organic frameworks (MOFs), also known as coordination polymers, possess extremely high specific surface areas and pore volumes. Furthermore, by altering the types of metal ions and ligands, as well as the synthesis conditions, porous structures with varying pore shapes and sizes can be obtained. Moreover, MOF structures exhibit unique molecular flexibility (including "door opening effects" or "breathing effects"), which gives MOFs significant technological advantages in the field of adsorption and separation.

[0004] However, most metal-organic frameworks (MOFs) exhibit low selectivity and poor stability, and lose their high selectivity at the high temperatures required for diffusion. Therefore, the low-cost preparation of MOFs with good stability, considerable p-xylene adsorption capacity, and high adsorption-separation selectivity presents a significant technical challenge. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention provides a new metal-organic framework material and a method for adsorbing and separating p-xylene from mixed C8 aromatic isomers using the metal-organic framework material as an adsorbent.

[0006] In a first aspect, the present invention provides a metal-organic framework material comprising a metal ion and an organic ligand, wherein the organic ligand is selected from compounds represented by Formula I or Formula II.

[0007]

[0008] In Formula I, X1 is N, X2 is CH, and X3 is selected from O, S, or NH; or X1 is CH, X2 is N, and X3 is selected from O, S, or NH; R1, R2, R3, and R4 are each independently selected from hydrogen, hydroxyl, halogen, carboxyl, amino, or C1-C4 alkyl, and at least one of R1, R2, R3, and R4 is selected from carboxyl.

[0009] In Formula II, R5 is selected from hydrogen, hydroxyl, halogen, carboxyl, amino, and C1-C4 alkyl; L is selected from single bond or C6-C10 arylene.

[0010] In some embodiments, in Formula I, X1 is N, X2 is CH, X3 is selected from O or NH, and R1, R2, R3 and R4 are each independently selected from hydrogen, hydroxyl, fluorine, chlorine, bromine, carboxyl, amino, methyl or ethyl, and only one of R1, R2, R3 and R4 is selected from carboxyl.

[0011] In some embodiments, in Formula I, X1 is CH, X2 is N, X3 is selected from NH, and R1, R2, R3 and R4 are each independently selected from hydrogen, hydroxyl, fluorine, chlorine, bromine, carboxyl, amino, methyl or ethyl, and only one of R1, R2, R3 and R4 is selected from carboxyl.

[0012] In some embodiments, in Formula II, R5 is selected from hydrogen, hydroxyl, fluorine, chlorine, bromine, carboxyl, amino, methyl or ethyl, and L is selected from single bond, phenylene or benzylene.

[0013] In some embodiments, the organic ligand is selected from one or more of benzimidazole-5-carboxylic acid, benzimidazole-4-carboxylic acid, benzoxazole-5-carboxylic acid, indazole-5-carboxylic acid, isonicotinic acid, 3-aminoisonicotinic acid, 2-aminoisonicotinic acid, and 4-pyridinebenzoic acid.

[0014] In some embodiments, the metal ion is selected from one or more transition metal ions and alkaline earth metal ions.

[0015] In some embodiments, the metal ion is selected from one or more of calcium ions, molybdenum ions, chromium ions, iron ions, cobalt ions, nickel ions, copper ions, magnesium ions, and manganese ions.

[0016] In some embodiments, the metal ion of the metal-organic framework material is cobalt or nickel ion, and the organic ligand is benzimidazole-5-carboxylic acid, isonicotinic acid, or 3-aminoisonicotinic acid.

[0017] In some embodiments, the metal ion of the metal-organic framework material is a nickel ion, and the organic ligand is benzimidazole-5-carboxylic acid.

[0018] In some embodiments, the pores of the metal-organic framework material are square or rhomboid. In some embodiments, the pore size of the metal-organic framework material is 4-10 angstroms.

[0019] In some embodiments, the pores of the metal-organic framework material are square or rhomboid, with a pore size of 4-6 angstroms.

[0020] In some embodiments, the metal-organic framework material is in the shape of a cube, rod, particle, or column.

[0021] In a second aspect, the present invention provides a method for preparing the metal-organic framework material described in the first aspect, which includes reacting a metal inorganic salt, an organic ligand, and optionally a C1-C4 organic acid in a solvent to produce a metal-organic framework material.

[0022] In some embodiments, the metal inorganic salt is selected from one or more of the following: chloride salts, nitrate salts, acetate salts, carbonate salts, sulfate salts, or perchlorate salts of metal ions.

[0023] In some embodiments, the inorganic metal salt is selected from nickel chloride, nickel nitrate, cobalt chloride, cobalt nitrate, manganese chloride, or manganese nitrate.

[0024] In some embodiments, the C1-C4 organic acid is selected from formic acid and / or acetic acid.

[0025] In some embodiments, the solvent includes an organic solvent and water. In some embodiments, the organic solvent is selected from acetonitrile, methanol, ethanol, acetone, N,N-dimethylformamide, or N,N-dimethylacetamide.

[0026] In some embodiments, the volume ratio of the organic solvent to water is 1:(0.5-3), for example, 1:1, 1:1.5, 1:2 or 1:2.5.

[0027] In some embodiments, the molar ratio of the metal inorganic salt to the organic ligand is 1:(0.5-10), for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:7, 1:8, 1:9, or any value between them. In some embodiments, the molar ratio of the metal inorganic salt to the organic ligand is 1:(0.5-3). In some embodiments, the molar ratio of the metal inorganic salt to the organic ligand is 1:(1-1.5).

[0028] In some embodiments, the molar ratio of the metal inorganic salt to the C1-C4 organic acid is 1:(0.01-10), for example, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:7, 1:8, 1:9, or any value between them. In some embodiments, the molar ratio of the metal inorganic salt to the C1-C4 organic acid is 1:(0.5-3.5). In some embodiments, the molar ratio of the metal inorganic salt to the C1-C4 organic acid is 1:(0.5-2).

[0029] Changing the ratio of metal salt, organic ligand, and C1-C4 organic acid such as formic acid will alter the crystal size, crystal form, regularity, etc., and will also affect the adsorption capacity and selective adsorption separation performance of the material for p-xylene, m-xylene, o-xylene, and ethylbenzene.

[0030] In some embodiments, the reaction temperature is 100°C-220°C, for example, 110°C, 130°C, 150°C, 160°C, 170°C, or 200°C. In some embodiments, the reaction temperature is 120°C-180°C.

[0031] In some embodiments, the reaction time is 12h-112h, for example 24h, 36h, 48h, 60h, 72h, 84h, 96h, or 108h. In some embodiments, the reaction time is 24h-100h.

[0032] In some embodiments, the metal-organic framework material is prepared by the following method:

[0033] (1) Mix inorganic salt, organic ligand, formic acid, acetonitrile and deionized water in proportion, stir to dissolve, and then put into an atmospheric pressure or high pressure reactor for reaction; the inorganic salt is a chloride, nitrate, acetate, carbonate, sulfate or perchlorate of metal ions.

[0034] (2) After the hydrothermal reaction is completed, wash with deionized water several times and then vacuum dry to obtain the product.

[0035] The preparation of this metal-organic framework material involves the reaction of organic ligands with a series of metal inorganic salts in water and acetonitrile. The raw materials used in this preparation are inexpensive, the synthesis conditions are mild, the operation is simple, post-processing is easy, and the material synthesis cost is low. In this invention, the metal-organic framework material exhibits high adsorption and separation selectivity for p-xylene, m-xylene, o-xylene, and ethylbenzene. Furthermore, the material has a stable structure and adsorption performance, good high-temperature resistance, and shows promising prospects for industrial application.

[0036] In some embodiments, the molar ratio of the inorganic salt, organic ligand, and formic acid is 1:(0.5–3):(0–3.5). Water and acetonitrile are used as solvents and are evaporated during the subsequent drying process. More preferably, when the inorganic salt is a nickel salt and the organic ligand is benzimidazole-5-carboxylic acid, the molar ratio of the inorganic salt, ligand, and formic acid is 1:(1–1.5):(0–2). Most preferably, when the inorganic salt is a nickel salt, the amount of formic acid added is 1, and the molar ratio of the inorganic salt to the organic ligand is 1:1.

[0037] Most preferably, the inorganic salt is nickel nitrate hexahydrate, the organic ligand is benzimidazole-5-carboxylic acid, and the ratio of metal salt, organic ligand and formic acid is 1 mmol:1 mmol:1 mmol.

[0038] In some embodiments, the stirring step involves stirring at 500–1000 rpm for an appropriate time to mix the solution evenly. Incomplete mixing can lead to irregular crystal structures in the resulting crystals.

[0039] In some embodiments, the hydrothermal reaction is carried out at a temperature of 100–220°C for 12–112 hours.

[0040] Preferably, the reaction is carried out at 120–180°C for 24–100 hours;

[0041] The optimal reaction temperature is 160°C for 48 hours. The reaction temperature affects crystal formation; too high or too low a temperature will prevent crystal formation.

[0042] The product after the hydrothermal reaction is washed and centrifuged several times with water to replace the residual ligands, alkaline solutions and residual inorganic salts in the pores.

[0043] More preferably, the vacuum drying temperature is 25–150°C and the time is 10–24 hours.

[0044] Thirdly, the present invention provides the application of the metal-organic framework material described in the first aspect or the metal-organic framework material prepared by the preparation method described in the second aspect in the separation of mixed C8 aromatic isomers.

[0045] In some embodiments, the mixed C8 aromatic isomers are in a gaseous or liquid state.

[0046] In some embodiments, the mixed C8 aromatic isomers include at least two of p-xylene, ethylbenzene, o-xylene, and m-xylene.

[0047] In some embodiments, the mixed C8 aromatic isomers include ethylbenzene, p-xylene, o-xylene, and m-xylene.

[0048] According to some embodiments, the mixed C8 aromatic isomers contain p-xylene, the content of which can be 5-95%. According to some embodiments of the invention, the volume percentage of p-xylene in the mixed C8 aromatic isomers is 5% to 95%. Preferably, the volume percentage of p-xylene in the mixed vapor or mixed liquid of the mixed C8 aromatic isomers is 10% to 85%. According to some embodiments, the volume percentage of p-xylene in the mixed C8 aromatic isomers is 5%, 15%, 25%, 35%, 50%, 60%, 70%, 80%, or 90%.

[0049] In some embodiments, the application includes separating the C8 aromatic isomers by adsorption separation using an adsorbent comprising a metal-organic framework material as described in the first aspect or a metal-organic framework material prepared according to the preparation method described in the second aspect.

[0050] Fourthly, the present invention provides a method for separating p-xylene from a mixture of C8 aromatic isomers, comprising adsorbing and separating the mixture of C8 aromatic isomers with an adsorbent comprising a metal-organic framework material as described in the first aspect or a metal-organic framework material prepared according to the preparation method described in the second aspect, thereby separating p-xylene.

[0051] In some embodiments, the mixed C8 aromatic isomers are in a gaseous or liquid state.

[0052] In some embodiments, the mixed C8 aromatic isomers include p-xylene and one or more C8 aromatic isomers selected from ethylbenzene, o-xylene, and m-xylene.

[0053] In some embodiments, the mixed C8 aromatic isomers include ethylbenzene, p-xylene, o-xylene, and m-xylene.

[0054] According to some embodiments, the mixed C8 aromatic isomers contain p-xylene, the content of which can be 5-95%. According to some embodiments of the invention, the volume percentage of p-xylene in the mixed C8 aromatic isomers is 5% to 95%. Preferably, the volume percentage of p-xylene in the mixed vapor or mixed liquid of the mixed C8 aromatic isomers is 10% to 85%. According to some embodiments, the volume percentage of p-xylene in the mixed C8 aromatic isomers is 5%, 15%, 25%, 35%, 50%, 60%, 70%, 80%, or 90%.

[0055] In this invention, the term "mixed C8 aromatic isomers" refers to a mixture containing two or more C8 aromatic isomers. In addition to C8 aromatic isomers, "mixed C8 aromatic isomers" may also include components such as n-hexane, 2-pentane, 3-pentane, 2,2-dimethylbutane, 2,3-dimethylbutane, toluene, and methylcyclohexane.

[0056] The adsorbent used in this invention, once saturated, can be regenerated simply by maintaining a temperature of 25–200°C under vacuum or nitrogen inert atmosphere for 10–48 hours. Excessive temperature or time will damage the adsorbent structure; excessively low temperature or short time will prevent the complete removal of residual adsorbate.

[0057] The adsorption separation process of the present invention is simple. Mixed C8 aromatic isomer vapors under a certain pressure are passed through an adsorption tower or adsorption column filled with the adsorbent. Furthermore, the adsorption tower can also be composed of multiple components, and separation can be achieved through existing simulated moving bed technology.

[0058] Preferably, the adsorption separation temperature is -5 to 300°C, and the total vapor pressure of the mixed C8 aromatic isomers is 1 to 1000 kPa;

[0059] More preferably, the adsorption separation temperature is 30–200°C, and the total pressure of the mixed steam is 1–100 kPa;

[0060] Most preferably, the adsorption separation temperature is 120℃ and the total pressure of the mixed steam is 1.2kPa.

[0061] In some embodiments, during the adsorption separation, the adsorbent and the mixed C8 aromatic isomers are at temperatures ranging from -5°C to 300°C, preferably from 25°C to 250°C, and more preferably from 30°C to 150°C. According to some embodiments, the adsorbent and the mixed C8 aromatic isomers are at temperatures of 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C.

[0062] According to some embodiments of the present invention, mixed C8 aromatic isomers are separated by adsorption in the form of mixed C8 aromatic isomer vapor or liquid. According to some embodiments of the present invention, in the adsorption separation, the adsorbent and the mixed C8 aromatic isomer vapor are at a pressure of 1-1000 kPa, preferably 10-800 kPa. According to some embodiments, the adsorbent and the mixed C8 aromatic isomer vapor are at a pressure of 100-600 kPa. According to some embodiments, the adsorbent and the mixed C8 aromatic isomer liquid are at a pressure of 1.1-2.5 MPa.

[0063] According to some embodiments of the present invention, the mixed C8 aromatic isomer vapor consists of mixed C8 aromatic isomers and a support. According to some embodiments, the carrier gas is nitrogen and / or helium.

[0064] In some embodiments, the adsorption separation of the present invention is carried out using a fixed bed, wherein the adsorbent is filled in the fixed bed adsorption column, preferably including the following steps:

[0065] (1) The vapor of mixed C8 aromatic isomers formed by mixing C8 aromatic isomers and carrier gas is passed through a fixed bed adsorption column. The strongly adsorbed p-xylene in the mixed xylene is adsorbed on the adsorbent, and the weakly adsorbed C8 aromatic isomers in the mixed xylene permeate the adsorption column to obtain weakly adsorbed C8 aromatic isomers.

[0066] (2) Desorb the strongly adsorbed p-xylene from the adsorbent to obtain strongly adsorbed p-xylene.

[0067] In some embodiments, the flow rate of the mixed C8 aromatic isomer vapor through the fixed-bed adsorption column is 20-200 mL / min / g adsorbent.

[0068] In some embodiments, the adsorption separation of the present invention is carried out using a simulated moving bed, wherein the adsorbent is filled in the adsorption zone of the simulated moving bed, preferably including the following steps:

[0069] The mixed C8 aromatic isomer liquid is separated by adsorption using a liquid-phase simulated moving bed, thereby extracting p-xylene, o-xylene and / or m-xylene, and ethylbenzene into different bed layers.

[0070] In some embodiments, the simulated moving bed has 4-32 adsorbent beds, and the ratio of adsorption zone bed to desorption zone bed is 1.0-1.5.

[0071] The principle of adsorption separation in this invention is as follows: The pores of this type of metal-organic framework material are square or rhomboid, with a pore size of 4-10 angstroms, for example, 4.5-5.5 angstroms. This size is similar to the molecular size of the molecules to be separated, resulting in excellent separation performance. Furthermore, the material is designed with a pore shape that perfectly matches the cross-sectional shape of the PX molecule, thereby achieving optimal thermodynamic selectivity. In addition, the material possesses a unique flexibility, amplifying the minute force differences between the C8 aromatic isomers and the material through framework deformation. Both thermodynamic and kinetic factors result in significant differences in the adsorption amounts of the four isomers on the material surface, thus achieving highly efficient adsorption separation of the aforementioned molecules.

[0072] The adsorbent prepared by the preferred method described above in this invention has stable structure and performance, regular particle shape, and suitable pore size. It exhibits high selectivity and considerable adsorption capacity for the adsorption and separation of C8 aromatic isomers such as p-xylene, m-xylene, o-xylene, and ethylbenzene.

[0073] The metal-organic framework materials used in this invention can be prepared into spherical, columnar, or granular adsorption and separation materials through different processing techniques, or made into membrane materials according to existing conventional technologies for the membrane separation of C8 aromatic isomers such as p-xylene, m-xylene, o-xylene, and ethylbenzene.

[0074] Compared with the prior art, the present invention has the following advantages:

[0075] The metal salts used in the preparation of the metal-organic framework materials involved in this invention are abundant in nature, the ligands are inexpensive and readily available, the synthesis conditions are mild, the purification steps are simple, and the process is easy to operate and scale up. The metal-organic framework materials involved in this invention have stable structures and properties, exhibiting very high adsorption selectivity for p-xylene / m-xylene / o-xylene / ethylbenzene, and maintaining their original adsorption performance even after repeated adsorption-regeneration cycles. In the adsorption and separation of these mixed C8 aromatic isomers, the adsorbent prepared in this invention is far superior to most solid adsorbents. Attached Figure Description

[0076] Figure 1 The image shows the XRD pattern used to investigate the stability of the metal-organic framework material prepared in Example 1.

[0077] Figure 2 The vapor adsorption curves of the metal-organic framework material prepared in Example 1 for p-xylene, m-xylene, o-xylene and ethylbenzene at 120 °C are shown.

[0078] Figure 3 The vapor breakthrough curves of the metal-organic framework material prepared in Example 7 for p-xylene, m-xylene, o-xylene, and ethylbenzene at 120°C are shown. Detailed Implementation

[0079] The following embodiments further illustrate the present invention, but the content of the present invention is not limited to these embodiments at all.

[0080] Example 1

[0081] 0.1 mmol nickel nitrate hexahydrate, 0.1 mmol benzimidazole-5-carboxylic acid, 3 mL deionized water, and 3 mL acetonitrile were mixed, and 0.2% v / v formic acid was added. The mixture was placed in a 25 mL hydrothermal reactor and stirred for 60 minutes, then reacted at 160 °C for 48 hours. After the reaction was complete, the reactor was cooled, and the mixture was washed multiple times with pure water to obtain the purified metal-organic framework material. The purified adsorbent was then degassed under vacuum at 150 °C for 12 hours to obtain the solvent-free adsorbent.

[0082] To test the stability of the samples, they were exposed to air at a relative humidity of 60% for three months and immersed in PX at 30℃ and 120℃ for 7 days respectively. XRD analysis of the adsorbent under each condition was then performed. See details below. Figure 1 The results show that the XRD patterns of the adsorbent remained consistent with those of the freshly synthesized material after immersion in PX at 30°C and 120°C for 7 days or after exposure to air with a relative humidity of 60% for 3 months, indicating the excellent stability of the material.

[0083] To test the adsorption and separation performance of the synthesized metal-organic framework material, single-component adsorption isotherms for p-xylene, m-xylene, o-xylene, and ethylbenzene were obtained using the aforementioned adsorbent. The isotherms are detailed below. Figure 2 Take an appropriate amount of adsorbent and set the adsorption temperature to 120℃.

[0084] At 120℃ and a single-component saturated vapor pressure of 1.2 kPa, the adsorption capacity of p-xylene reached 1.9 mmol / g, m-xylene 0.08 mmol / g, o-xylene 0.06 mmol / g, and ethylbenzene 1.1 mmol / g. At high temperatures, the adsorption capacity of this material for p-xylene differed significantly from that of other isomers, indicating that this material has excellent adsorption and separation effects on p-xylene, a C8 aromatic isomer, at high temperatures.

[0085] Example 2

[0086] 0.1 mmol nickel chloride hexahydrate, 0.1 mmol benzimidazole-5-carboxylic acid, 3 mL deionized water, and 3 mL acetonitrile were mixed, and 0.2% v / v formic acid was added. The mixture was placed in a 25 mL hydrothermal reactor and stirred for 60 minutes, then reacted at 160 °C for 48 hours. After the reaction was complete, the reactor was cooled, and the material was washed multiple times with pure water to obtain the purified metal-organic framework material. The purified adsorbent was degassed under vacuum at 150 °C for 12 hours to obtain the solvent-free adsorbent, which was then subjected to adsorption separation.

[0087] To test the adsorption and separation performance of the synthesized metal-organic framework material, single-component adsorption isotherms for p-xylene, m-xylene, o-xylene, and ethylbenzene were obtained using the above adsorbent. An appropriate amount of adsorbent was used, and the adsorption temperature was set to 120℃.

[0088] At 120 °C and a single-component saturated vapor pressure of 1.2 kPa, the adsorption capacity of p-xylene reached 1.9 mmol / g, the adsorption capacity of m-xylene reached 0.1 mmol / g, the adsorption capacity of o-xylene reached 0.05 mmol / g, and the adsorption capacity of ethylbenzene reached 1.6 mmol / g.

[0089] Example 3

[0090] 0.1 mmol cobalt chloride hexahydrate, 0.1 mmol benzimidazole-5-carboxylic acid, 3 mL deionized water, and 3 mL acetonitrile were mixed, and 0.2% v / v formic acid was added. The mixture was placed in a 100 mL hydrothermal reactor and stirred for 60 minutes, then reacted at 160 °C for 48 hours. After the reaction was complete, the reactor was cooled, and the material was washed multiple times with pure water to obtain the purified metal-organic framework material. The purified adsorbent was degassed under vacuum at 150 °C for 12 hours to obtain the solvent-free adsorbent, which was then subjected to adsorption separation.

[0091] To test the adsorption and separation performance of the synthesized metal-organic framework material, single-component adsorption isotherms for p-xylene, m-xylene, o-xylene, and ethylbenzene were obtained using the above adsorbent. An appropriate amount of adsorbent was used, and the adsorption temperature was set to 120℃.

[0092] At 120 °C and a single-component saturated vapor pressure of 1.2 kPa, the adsorption capacity of p-xylene reached 0.5 mmol / g, the adsorption capacity of m-xylene reached 0.2 mmol / g, the adsorption capacity of o-xylene reached 0.06 mmol / g, and the adsorption capacity of ethylbenzene reached 0.3 mmol / g.

[0093] Example 4

[0094] 0.1 mmol manganese chloride hexahydrate, 0.1 mmol benzimidazole-5-carboxylic acid, 3 mL deionized water, and 3 mL acetonitrile were mixed, and 0.2% v / v formic acid was added. The mixture was placed in a 100 mL hydrothermal reactor and stirred for 60 minutes, then reacted at 160 °C for 48 hours. After the reaction was complete, the reactor was cooled, and the material was washed multiple times with pure water to obtain the purified metal-organic framework material. The purified adsorbent was degassed under vacuum at 150 °C for 12 hours to obtain the solvent-free adsorbent, which was then subjected to adsorption separation.

[0095] To test the adsorption and separation performance of the synthesized metal-organic framework material, single-component adsorption isotherms for p-xylene, m-xylene, o-xylene, and ethylbenzene were obtained using the above adsorbent. An appropriate amount of adsorbent was used, and the adsorption temperature was set to 120℃.

[0096] At 120 °C and a single-component saturated vapor pressure of 1.2 kPa, the adsorption capacity of p-xylene reached 0.9 mmol / g, the adsorption capacity of m-xylene reached 0.3 mmol / g, the adsorption capacity of o-xylene reached 0.07 mmol / g, and the adsorption capacity of ethylbenzene reached 0.4 mmol / g.

[0097] Example 5

[0098] 0.1 mmol nickel nitrate hexahydrate, 0.1 mmol isonicotinic acid, 3 mL deionized water, and 3 mL acetonitrile were mixed, and 0.2% v / v formic acid was added. The mixture was placed in a 100 mL hydrothermal reactor and stirred for 60 minutes, then reacted at 150 °C for 48 hours. After the reaction was complete, the reactor was cooled, and the material was washed multiple times with pure water to obtain the purified metal-organic framework material. The purified adsorbent was degassed under vacuum at 150 °C for 12 hours to obtain the solvent-free adsorbent, which was then subjected to adsorption separation.

[0099] To test the adsorption and separation performance of the synthesized metal-organic framework material, single-component adsorption isotherms for p-xylene, m-xylene, o-xylene, and ethylbenzene were obtained using the above adsorbent. An appropriate amount of adsorbent was used, and the adsorption temperature was set to 120℃.

[0100] At 120 °C and a single-component saturated vapor pressure of 1.2 kPa, the adsorption capacity of p-xylene reached 0.4 mmol / g, the adsorption capacity of m-xylene reached 0.03 mmol / g, the adsorption capacity of o-xylene reached 0.09 mmol / g, and the adsorption capacity of ethylbenzene reached 0.07 mmol / g.

[0101] Example 6

[0102] 0.1 mmol nickel nitrate hexahydrate, 0.1 mmol 3-aminoisonicotinic acid, 3 mL deionized water, and 3 mL acetonitrile were mixed, and 0.2% v / v formic acid was added. The mixture was placed in a 100 mL hydrothermal reactor and stirred for 60 minutes, then reacted at 150 °C for 48 hours. After the reaction was complete, the reactor was cooled, and the material was washed multiple times with pure water to obtain the purified metal-organic framework material. The purified adsorbent was degassed under vacuum at 150 °C for 12 hours to obtain the solvent-free adsorbent, which was then subjected to adsorption separation.

[0103] To test the adsorption and separation performance of the synthesized metal-organic framework material, single-component adsorption isotherms for p-xylene, m-xylene, o-xylene, and ethylbenzene were obtained using the above adsorbent. An appropriate amount of adsorbent was used, and the adsorption temperature was set to 120℃.

[0104] At 120 °C and a single-component saturated vapor pressure of 1.2 kPa, the adsorption capacity of p-xylene reached 1.7 mmol / g, the adsorption capacity of m-xylene reached 0.07 mmol / g, the adsorption capacity of o-xylene reached 0.02 mmol / g, and the adsorption capacity of ethylbenzene reached 1.1 mmol / g.

[0105] At high temperatures, the adsorption capacity of this material for p-xylene differs significantly from that of other isomers, indicating that this material has a good adsorption and separation effect on p-xylene among C8 aromatic isomers at high temperatures.

[0106] Example 7

[0107] 1 mmol nickel nitrate hexahydrate, 1 mmol benzimidazole-5-carboxylic acid, 30 mL deionized water, and 30 mL acetonitrile were mixed, and 0.2% v / v formic acid was added. The mixture was placed in a 100 mL hydrothermal reactor and stirred for 60 minutes, then reacted at 160 °C for 48 hours. After the reaction was complete, the reactor was cooled, and the material was washed multiple times with pure water to obtain the purified metal-organic framework material. The purified adsorbent was degassed under vacuum at 150 °C for 12 hours to obtain the solvent-free adsorbent, which was then subjected to adsorption separation.

[0108] To test the dynamic adsorption and separation performance of the synthesized metal-organic framework material, multi-component dynamic breakthrough curves for p-xylene, m-xylene, o-xylene, and ethylbenzene were obtained using the above adsorbent. The breakthrough curves are shown in the figure. Figure 3 .

[0109] Take 0.4 g of adsorbent and pack it into an adsorption column with an inner diameter of 4.6 mm and a length of 3 cm. After activation with nitrogen at 150 °C for 24 h, a mixed vapor with a composition of 22(PX) / 50(MX) / 22(OX) / 6(EB) (total pressure of 1.2 kPa) is introduced into the adsorption column at 120 °C, finally obtaining the following... Figure 3 The breakthrough curves are shown. The selectivity of this adsorbent material for the mixed C8 aromatic isomers, calculated from the integrated area, is 116.9(PX) / 1.3(MX) / 1(OX) / 36.5(EB)(S). PX / MX =90,S PX / OX =117,S PX / EB =3.2), exceeding the vast majority of C8 aromatic adsorbent materials, and the adsorption and separation effect is very good.

[0110] The above description is merely a specific implementation example of this invention patent, but the technical features of this invention patent are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of this invention are covered by the patent scope of this invention.

Claims

1. The application of a metal-organic framework material in the separation of mixed C8 aromatic isomers, the metal-organic framework material comprising a metal ion and an organic ligand, wherein the organic ligand is selected from one or more of benzimidazole-5-carboxylic acid, benzimidazole-4-carboxylic acid, isonicotinic acid, 3-aminoisonicotinic acid and 2-aminoisonicotinic acid, the metal ion is selected from transition metal ions, and the pores of the metal-organic framework material are rhomboid with a pore size of 4 Å to 10 Å.

2. The application according to claim 1, characterized in that, The metal ion is selected from one or more of molybdenum ions, chromium ions, iron ions, cobalt ions, nickel ions, copper ions, and manganese ions; and / or, the mixed C8 aromatic isomers include at least two of p-xylene, ethylbenzene, o-xylene, and m-xylene.

3. The application according to claim 1, characterized in that, The metal-organic framework material is cubic, rod-shaped, or granular; and / or, the mixed C8 aromatic isomers include ethylbenzene, p-xylene, o-xylene, and m-xylene.

4. The application according to any one of claims 1-3, characterized in that, The method for preparing the metal-organic framework material includes: reacting a metal inorganic salt, an organic ligand, and optionally a C1-C4 organic acid in a solvent to produce a metal-organic framework material.

5. The application according to claim 4, characterized in that, The inorganic metal salt is selected from one or more of the following: chloride, nitrate, acetate, carbonate, sulfate, or perchlorate salts of metal ions; and / or The C1-C4 organic acid is selected from formic acid and / or acetic acid; and / or The solvent includes an organic solvent and water, wherein the organic solvent is selected from acetonitrile, methanol, ethanol, acetone, N,N-dimethylformamide, or N,N-dimethylacetamide; and / or The molar ratio of the metal inorganic salt to the organic ligand is 1:(0.5-10); the molar ratio of the metal inorganic salt to the C1-C4 organic acid is 1:(0.01-10); and / or The reaction temperature is 100℃-220℃, and the reaction time is 12h-112h.

6. The application according to claim 5, characterized in that, The volume ratio of the organic solvent to water is 1:(0.5-3); and / or the molar ratio of the metal inorganic salt to the organic ligand is 1:(0.5-3); the molar ratio of the metal inorganic salt to the C1-C4 organic acid is 1:(0.5-3.5).

7. The application according to claim 1, characterized in that, The pores of the metal-organic framework material are square, and / or the mixed C8 aromatic isomers contain p-xylene, which occupies 5% to 95% of the volume.

8. A method for separating p-xylene from a mixture of C8 aromatic isomers, comprising adsorbing the mixture of C8 aromatic isomers with an adsorbent comprising a metal-organic framework material to separate p-xylene; wherein the metal-organic framework material is the metal-organic framework material used in any one of claims 1-7.

9. The method according to claim 8, characterized in that, The mixed C8 aromatic isomers are in a gaseous or liquid state, including p-xylene and one or more C8 aromatic isomers selected from ethylbenzene, o-xylene and m-xylene; and / or the adsorption separation temperature is from -5°C to 300°C; and / or the total vapor pressure of the mixed C8 aromatic isomers is 1 kPa to 1000 kPa.

10. The method according to claim 9, characterized in that, The mixed C8 aromatic isomers include ethylbenzene, p-xylene, o-xylene, and m-xylene; and / or the adsorption separation temperature is from 25°C to 250°C.

11. The method according to claim 9, characterized in that, The adsorption separation temperature is from 30°C to 150°C.

12. The method according to any one of claims 8-11, characterized in that, The adsorption separation is carried out using a fixed bed, wherein the adsorbent is filled in the fixed bed adsorption column; or, the adsorption separation is carried out using a simulated moving bed, wherein the adsorbent is filled in the adsorption zone of the simulated moving bed.

13. The method according to claim 12, characterized in that, The adsorption separation includes the following steps: (1) The vapor of mixed C8 aromatic isomers formed by mixing C8 aromatic isomers and carrier gas is passed through a fixed bed adsorption column. The strongly adsorbed p-xylene in the mixed C8 aromatic isomers is adsorbed on the adsorbent, and the weakly adsorbed other C8 aromatic isomers in the mixed C8 aromatic isomers permeate the adsorption column to obtain the weakly adsorbed other C8 aromatic isomers. (2) Desorb the strongly adsorbed p-xylene from the adsorbent to obtain strongly adsorbed p-xylene; Alternatively, the adsorption separation includes the following steps: The mixed C8 aromatic isomer liquid is separated by adsorption using a liquid-phase simulated moving bed, thereby extracting p-xylene, o-xylene and / or m-xylene, and ethylbenzene into different bed layers.

14. The method according to claim 13, characterized in that, The flow rate of the mixed C8 aromatic isomer vapor through the fixed-bed adsorption column is 20-200 mL / min / g adsorbent; the simulated moving bed has 4-32 adsorbent beds, and the ratio of adsorption zone bed to desorption zone bed is 1.0-1.

5.

15. The method according to claim 9, characterized in that, In the mixed C8 aromatic isomers, p-xylene accounts for 5% to 95% of the volume.

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