Capillary gas chromatography column for realizing baseline separation of xylene isomers, preparation method thereof and application thereof

Abstract

The present invention discloses a capillary gas chromatography column for realizing baseline separation of xylene isomers, and a preparation method and application thereof. The stationary phase of the capillary gas chromatography column is a nano material with a multi-level pore structure, and nano particles are uniformly embedded in the inner wall of the capillary column. The prepared nano material is dissolved in an organic solvent, dynamically coated in a capillary chromatography column at a constant flow rate, and finally cured at high temperature to obtain the capillary chromatography column. The capillary column is used for separation of xylene isomers, and the position / para position separation is as high as 15.2. At the same time, the prepared capillary gas chromatography column can achieve excellent separation effects for other benzene substituted isomers and alkane isomers, providing a new solution for the efficient separation of such isomers.

Description

Technical Field

[0001] The invention belongs to the technical field of chromatographic separation, and in particular relates to a capillary gas chromatographic column for realizing baseline separation of xylene isomers, and a preparation method and application thereof. Background Art

[0002] Xylene is an important chemical raw material, and is the raw material for the production of polyester resins, plasticizers, etc. It is widely used in organic solvents and synthetic medicines, coatings, resins, explosives and pesticides. At the same time, xylene is also one of the environmental pollutants. It mainly comes from wastewater and waste gas from organic synthesis, synthetic rubber, paints and dyes, synthetic fibers, petroleum processing, pharmaceuticals, cellulose and other production plants, as well as unsealed production equipment and workshop ventilation. It is a low-toxic chemical substance that is seriously toxic to the human hematopoietic system and nervous system. Inhaling high-concentration xylene vapor for a long time can cause acute poisoning. In industrial production, anti-corrosion coatings with xylene as the solvent are applied in closed storage tanks. Due to the lack of good ventilation, a large amount of xylene vapor accumulates, which can cause acute poisoning of workers. Therefore, the separation and identification of these structural isomers are of great significance in the fields of industry and environmental science.

[0003] Xylene isomers exist in the form of ortho, meta, and para. Since these isomers have similar properties and small boiling point differences, they are difficult to separate and determine using general physical and chemical methods. Capillary column gas chromatography (GC) has the advantages of strong separation ability, high sensitivity and accuracy, and environmental friendliness. It is one of the important methods for complex sample analysis and determination in the fields of chemistry, petrochemicals, food, medicine, and environmental monitoring. Currently, it is difficult to achieve baseline separation of xylene isomers using common commercial chromatographic columns such as HP-5 and VF-WAXMS. It is also difficult to achieve complete baseline separation using new porous materials such as metal organic frameworks MOFs, metal organic nanosheets MONs, and porous organic cages. Isomer separation is still a major challenge in the petrochemical industry. Therefore, it is urgent to develop a porous material gas chromatography column with sensitive nanospaces and selective binding sites to achieve baseline separation of xylene isomers and similar isomers. Summary of the invention

[0004] Purpose of the invention: To solve the above technical problems, the present invention provides a capillary gas chromatography column for achieving baseline separation of xylene isomers, and a preparation method and application thereof. The chromatographic column can achieve the highest separation degree of the current separation of three xylene isomers and ethylbenzene mixture, with a meta / para separation degree of up to 15.2, and also has good separation performance for other similar isomeric materials.

[0005] Technical solution: The stationary phase of a capillary gas chromatography column for achieving baseline separation of xylene isomers described in the present invention is an octahedral nanomaterial with a multi-level pore structure, and the nanoparticles are uniformly embedded in the inner wall of the capillary column. The material structure contains pores of different sizes formed by defects generated by trifluoroacetic acid as a regulator.

[0006] The present invention also provides a method for preparing a capillary column for realizing baseline separation of xylene isomers, wherein the prepared nano material is dissolved in an organic solvent, dynamically coated in a capillary chromatographic column at a constant flow rate, and finally cured at high temperature to obtain the capillary chromatographic column.

[0007] Specifically, the preparation method comprises the following steps:

[0008] (1) Synthesizing hierarchical porous nanomaterials as stationary phase: preparing a ZrCl4 solution of a certain concentration, mixing it with a terephthalic acid solution, and then adding a certain amount of trifluoroacetic acid to mix evenly, reacting at high temperature to obtain white UiO-66 nanomaterials, cooling, centrifuging, washing and drying to obtain hierarchical porous nanomaterials;

[0009] (2) Preparing a capillary gas chromatography column with a multi-level porous material coated on the inner wall: ultrasonically dispersing the multi-level porous nanomaterial obtained in step (1) in an organic solvent, pushing it into a pretreated capillary chromatography column at a uniform speed using a syringe pump to dynamically coat the inner wall of the capillary chromatography column, and then subjecting the capillary column to a programmed temperature aging treatment under an inert atmosphere. After cooling to room temperature, the capillary gas chromatography column is obtained, which is installed in a gas chromatograph to perform sensitive detection of benzene isomers or efficient separation of a mixture of benzene isomers.

[0010] Wherein, the concentration of zirconium tetrachloride in the zirconium tetrachloride solution in step (1) is 8 mg / mL to 11 mg / mL, and the concentration of the terephthalic acid solution is 8 mg / mL to 11 mg / mL.

[0011] The pretreatment of the capillary chromatographic column in step (2) comprises the following steps: silanizing the inner wall of the capillary column with APTES and then maintaining it at 120° C. for 2-5 hours.

[0012] During the dynamic coating, the injection rate is 3 mL / h to 5 mL / h.

[0013] When the heat treatment is performed under the inert atmosphere, the inert atmosphere is one of nitrogen, helium or argon, or a mixture of several of them in any proportion.

[0014] The specific method of the programmed temperature aging treatment in step (2) is: under an inert atmosphere, the initial temperature is 20-50°C, the temperature is increased to 250°C at a rate of 2°C / min to 10°C / min, and maintained for 2-8h.

[0015] Finally, the present invention also provides the use of the capillary gas chromatography column in separating other isomers such as chlorotoluene isomers, dichlorobenzene isomers, hexane isomers, octane isomers or decane isomers.

[0016] Connect the capillary gas chromatography column to the gas chromatograph, set the starting temperature, heating rate, and temperature retention time, and use a micro-injector to inject a small amount of the separation target into the chromatographic column from the injection port. Click to start the test and the chromatographic peak of the corresponding separation will be obtained after a few minutes.

[0017] In the gas chromatography column preparation method of the present invention, ZrCl4 is used as a metal source, terephthalic acid is used as an organic ligand, and trifluoroacetic acid is used as a regulator. A white powdery multi-level porous material is prepared by a solvent thermal method, and the material is filled on the inner wall of a capillary in a dynamic coating manner as a stationary phase. The material has a regular and uniform morphology and is evenly embedded in the inner wall of a quartz capillary column. The stationary phase material contains abundant pores and can provide different adsorption sites. The obtained capillary column has a high column efficiency and excellent cyclic stability.

[0018] The gas chromatography column using the multi-level porous material prepared by the present invention as the stationary phase has the following advantages: 1) the highest separation degree of the current three xylene isomers and ethylbenzene mixture is achieved, and the meta / para separation degree is as high as 15.2; 2) the material used as the stationary phase has good stability, the structure will not be destroyed in acid, alkali and water environments, and it is resistant to high temperatures; 3) the material has pores with different pore sizes, and these pore structures are conducive to the transmission and diffusion of the separation target, and can provide corresponding pores and forces for targets of different sizes and properties, thereby realizing the separation of the mixture; 4) the material particles used as the stationary phase have a large specific surface area, which is conducive to the adsorption of the target; the stationary phase material is small and uniform in size, which improves the fineness of the filler in the capillary tube and greatly improves the column efficiency; 5) the prepared capillary chromatographic column has extremely high stability and repeatability.

[0019] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following significant advantages: the capillary gas chromatography column prepared by the present invention is coated with multi-level pore structure nanoparticles, which are used for gas chromatography separation, and the highest separation degree of separation of three xylene isomers and ethylbenzene mixture is achieved, and the meta / para separation degree can be as high as 15.2; the stationary phase material has a high yield, the nanoparticles are uniform in size, and are evenly embedded in the inner wall of the capillary column. The preparation operation of the capillary gas chromatography column is simple, the cost is low, the performance is excellent, and large-scale production can be achieved; at the same time, the capillary gas chromatography column can achieve excellent separation effects on other benzene substituted isomers and alkane isomers, and is a very potential gas chromatography separation material, which has broad application prospects in the analysis and detection of chemical pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a longitudinal section SEM spectrum of the capillary gas chromatography column prepared in Example 1 of the present invention;

[0021] Figure 2 is a cross-sectional enlarged SEM image of the capillary gas chromatography column prepared in Example 1 of the present invention;

[0022] Figure 3 This is a SEM spectrum of the stationary phase material of the capillary gas chromatography column prepared in Example 2 of the present invention;

[0023] Figure 4 This is the TEM spectrum of the stationary phase material of the capillary gas chromatography column prepared in Example 2 of the present invention;

[0024] Figure 5 is the TGA spectrum of the stationary phase material of the capillary gas chromatography column prepared in Example 3 of the present invention;

[0025] Figure 6 It is the nitrogen adsorption spectrum of the stationary phase material of the capillary gas chromatography column prepared in Example 3 of the present invention;

[0026] Figure 7 is the pore size distribution spectrum of the stationary phase material of the capillary gas chromatography column prepared in Example 3 of the present invention;

[0027] Figure 8 The gas chromatographic separation spectrum of a mixture of three xylene isomers and ethylbenzene by the capillary gas chromatographic column prepared in Example 1 of the present invention;

[0028] Fig. 9 This is the gas chromatographic separation spectrum of a mixture of three chlorotoluene isomers using a capillary gas chromatographic column prepared in Example 2 of the present invention;

[0029] Fig.10 This is the gas chromatographic separation spectrum of three dichlorobenzene isomers by the capillary gas chromatographic column prepared in Example 3 of the present invention;

[0030] Fig.11 The gas chromatographic separation spectrum of a mixture of n-hexane, n-heptane, n-octane, n-nonane and n-decane by the capillary gas chromatographic column prepared in Example 4 of the present invention;

[0031] Fig.12 is a gas chromatographic separation spectrum of a mixture of three hexane isomers using a capillary gas chromatographic column prepared in Example 5 of the present invention;

[0032] Fig.13 This is the gas chromatographic separation spectrum of a mixture of three octane isomers using the capillary gas chromatographic column prepared in Example 6 of the present invention;

[0033] Fig.14 Gas chromatographic separation spectrum of a mixture of three decane isomers by the capillary gas chromatographic column prepared in Example 7 of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0035] The technical solution of the present invention is further described in detail below through specific examples, but it is necessary to point out that the following examples are only used to describe the content of the invention and do not constitute a limitation on the protection scope of the present invention. The gas chromatograph used in the present invention is Agilent GC7890B, and the reagents used are analytical grade or chromatographic grade.

[0036] Example 1

[0037] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0038] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.00 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0039] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 2°C / min in a nitrogen atmosphere, and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0040] Example 2

[0041] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0042] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.50 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0043] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 2°C / min in a nitrogen atmosphere, and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0044] Example 3

[0045] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0046] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.00 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.40 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, the final product was obtained by centrifugation and washing three times with N,N-dimethylformamide;

[0047] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 2°C / min in an argon atmosphere and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0048] Example 4

[0049] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0050] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 44.70 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 49.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0051] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 2°C / min in a nitrogen atmosphere, and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0052] Example 5

[0053] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0054] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.80 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 51.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0055] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 2°C / min in a nitrogen atmosphere, and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0056] Example 6

[0057] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0058] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.00 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0059] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.0 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 2°C / min in a nitrogen atmosphere and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0060] Example 7

[0061] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0062] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.00 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0063] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 5.0 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 2°C / min in a nitrogen atmosphere, and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0064] Example 8

[0065] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0066] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.00 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0067] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 5°C / min in a nitrogen atmosphere and maintained at this temperature for 2 hours to obtain the capillary gas chromatography column.

[0068] Example 9

[0069] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0070] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.00 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0071] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 4.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 10°C / min in a nitrogen atmosphere and maintained at this temperature for 4 hours to obtain the capillary gas chromatography column.

[0072] Example 10

[0073] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0074] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.00 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.00 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0075] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 5°C / min in a nitrogen atmosphere, and maintained at this temperature for 6 hours to obtain the capillary gas chromatography column.

[0076] Embodiment 11

[0077] A method for preparing a gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps:

[0078] 1) Preparation of hierarchical porous UiO-66 nanomaterials: Weigh 45.30 mg of ZrCl4, dissolve it in 5 mL of N,N-dimethylformamide, dissolve 50.90 mg of terephthalic acid in 5 mL of N,N-dimethylformamide, mix the prepared ZrCl4 solution with the terephthalic acid solution, add 0.5 mL of trifluoroacetic acid, and mix by ultrasonic. The resulting mixture was transferred to an upright glass vial with a volume of 20 mL and reacted at a constant temperature of 120°C for 72 hours. After cooling to room temperature, centrifuge and wash three times with N,N-dimethylformamide to obtain the final product;

[0079] 2) Preparation of a capillary chromatographic column with a multi-level porous material on the inner wall: ultrasonically disperse 2.3 mg of the prepared material in 1 mL of methanol, and use a syringe pump to uniformly push it into a pretreated capillary chromatographic column at an injection rate of 3.5 mL / h. After the injection of the material is completed, the capillary column is heated to 250°C at a rate of 10°C / min in a nitrogen atmosphere and maintained at this temperature for 8 hours to obtain the capillary gas chromatography column.

[0080] The capillary column and the stationary phase multi-level porous nanomaterial prepared in the above examples were physically characterized by SEM, TGA and other methods. Figure 1 , 2) shows that the multi-level porous nanoparticles are uniformly embedded in the inner wall of the capillary column. From the SEM of the stationary phase multi-level porous nanomaterial ( Figure 3 ) and TEM( Figure 4 ) It is known that the material has uniform size and is three-dimensional particles at the nanoscale. TGA spectrum ( Figure 5 ) shows that this stationary phase nanomaterial is still stable at higher temperatures, and the calculated defect number is 2.79. Figure 6 The nitrogen adsorption spectrum shows that the material has a large specific surface area and high porosity, with a BET specific surface area value of 835.86 m 2 / g, strong adsorption capacity. According to the pore size distribution spectrum of the material ( Figure 7 ) It can be seen that the sample has rich pores and contains micropores of different pore sizes. Figure 8 This is a gas chromatogram obtained by separating a mixture of xylene and ethylbenzene using the capillary gas chromatography column prepared in Example 3, which achieves the highest separation degree reported so far, with a meta / para separation degree of up to 15.2. Fig. 9 This is a gas chromatogram obtained by separating a chlorotoluene mixture using the capillary gas chromatography column prepared in Example 5, and the meta / para separation degree is as high as 10.62. Fig.10 This is a gas chromatogram obtained by separating a dichlorobenzene mixture using the capillary gas chromatography column prepared in Example 6, and the meta / para separation is 11.20. This capillary column not only achieves a very high separation degree for benzene isomers, but also has an extremely excellent separation ability for alkane mixtures. Fig.11 This is a gas chromatogram obtained by separating a mixture of C6-C10 straight-chain alkanes using the capillary gas chromatography column prepared in Example 4. Fig.12 This is a gas chromatogram obtained by separating a hexane isomer mixture using the capillary gas chromatography column prepared in Example 2. The separation degree of 3-methylpentane / n-hexane is as high as 46.38. Fig.13 This is a gas chromatogram obtained by separating an octane isomer mixture using the capillary gas chromatography column prepared in Example 8, and the separation degree of 2,4-dimethylhexane / n-octane is 7.01. Fig.14 This is a gas chromatogram obtained by separating a mixture of decane isomers using the capillary gas chromatography column prepared in Example 10, and the separation degree of 3,3-dimethyloctane / n-decane is 6.61. The above results all indicate that the capillary column has a good application prospect for separating isomers.

[0081] Table 1 Separation of several benzene isomers by different capillary columns

[0082] Xylene isomers Chlorotoluene isomers Dichlorobenzene isomers This UiO-66 capillary column 15.20 10.62 11.20 Commercial column VF-WAXMS 0.47 0 1.32 Commercial column HP-5MS 0 0.62 0.93

Claims

1. Application of a capillary gas chromatography column in achieving baseline separation of xylene isomers, characterized in that: The stationary phase of the capillary gas chromatography column is a nano material with a multi-level pore structure, and the nano particles are uniformly embedded in the inner wall of the capillary gas chromatography column; The method for preparing a capillary gas chromatographic column for achieving baseline separation of xylene isomers comprises the following steps: (1) Synthesis of hierarchical porous nanomaterials as stationary phase: prepare a ZrCl4 solution of a certain concentration, mix it with a terephthalic acid solution, then add a certain amount of trifluoroacetic acid and mix evenly, react at high temperature to obtain white UiO-66 nanomaterials, cool it, wash it by centrifugation and dry it, and obtain hierarchical porous nanomaterials; (2) Preparing a capillary gas chromatography column with a multi-level porous material coated on the inner wall: ultrasonically dispersing the multi-level porous nanomaterial obtained in step (1) in an organic solvent, pushing the multi-level porous nanomaterial into a pretreated capillary gas chromatography column at a uniform speed using a syringe pump to dynamically coat the capillary gas chromatography column on the inner wall, and then subjecting the capillary gas chromatography column to a programmed temperature aging treatment in an inert atmosphere, and cooling it to room temperature to obtain the capillary gas chromatography column; The concentration of ZrCl4 in the ZrCl4 solution in step (1) is 8 mg / mL to 11 mg / mL, and the concentration of the terephthalic acid solution is 8 mg / mL to 10 mg / mL; The pretreatment of the capillary gas chromatography column in step (2) is to perform silanization treatment on the inner wall of the capillary gas chromatography column with APTES and then maintain it at 120 degrees Celsius for 2-5 hours.

2. The use of the capillary gas chromatography column according to claim 1 in achieving baseline separation of xylene isomers, characterized in that: The ZrCl4 solution and the terephthalic acid solution solvents in step (1) are both N,N-dimethylformamide.

3. The use of the capillary gas chromatography column according to claim 1 in achieving baseline separation of xylene isomers, characterized in that: The inert atmosphere in step (2) is one of nitrogen, helium or argon, or a mixture of several of them in any proportion.

4. The use of the capillary gas chromatography column according to claim 1 in achieving baseline separation of xylene isomers, characterized in that: The specific method of the programmed temperature aging treatment in step (2) is: the initial temperature is 20-50 degrees Celsius, the temperature is increased to 250 degrees Celsius at a rate of 2-10 degrees Celsius / minute, and maintained for 2-8 hours.

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