Capillary gas chromatographic column for efficiently separating disubstituted benzene isomer and preparation method of capillary gas chromatographic column
By applying nano-porous materials with high BET specific surface area to the inner wall of the capillary gas chromatography column, the problem of difficult to efficiently separate disubstituted benzene isomers in the prior art, and efficient separation of multiple isomers is achieved , significantly improves separation efficiency and yield.
Patent Information
- Application Number
- CN202411484047.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2025-02-14
AI Technical Summary
The prior art is difficult to achieve efficient separation of disubstituted benzene isomers, resulting in high energy consumption and low yields required in industrial production. In particular, the separation of xylene isomers is considered a major challenge in chemical separation.
A nanoscale microporous material with a high BET specific surface area was designed as the stationary phase of a capillary gas chromatography column, and the baseline separation of the disubstituted benzene isomers was achieved by applying the material to the inner wall of the capillary column.
Efficient separation of a variety of disubstituted benzene isomers is achieved, especially the separation degree of orthoxylene/p-xylene is as high as 31.1, which significantly improves the separation efficiency and yield.
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Figure CN119425651A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of chromatographic separation, and particularly relates to a capillary gas chromatographic column for efficiently separating disubstituted benzene isomers and a preparation method thereof. Background Art
[0002] Benzene derivatives such as xylene, ethyltoluene, chlorotoluene, and dichlorobenzene isomers are important sources for the production of polymers, plastics, fibers, and fuel additives, and are closely related to the national economy. For example, p-xylene is one of the most important aromatic products, and can be used to synthesize polyesters through the intermediate terephthalic acid; o-chlorotoluene plays an important role in the fields of dyes and fragrances; and p-dichlorobenzene is an important raw material for the synthesis of polyphenylene sulfide. Since the physical and chemical properties of isomers are similar, for example, the boiling point difference of the three xylene isomers is less than 1K, and the difference in kinetic diameter is only 0.1nm; and in industrial production, single-component isomers are inevitably mixed, so conventional distillation separation not only requires high energy consumption and low yield, but also the separation of xylene isomers is recognized as one of the "seven major chemical separation challenges that will change the world."
[0003] Metal organic frameworks (MOFs) are a new type of adsorption and separation material, which are self-assembled from inorganic metal ions / metal clusters and organic ligands. They have properties such as high porosity, high specific surface area, and chemical designability. It is expected that the kinetic diffusion between disubstituted benzene isomers can be differentiated by rationally designing the topological structure of MOFs, thereby achieving size screening of guest molecules with different kinetic diameters and cross-sectional sizes. Gas chromatography has the advantages of high column efficiency, no need for fillers, and fast analysis speed, and is suitable as a separation and detection device. However, it is still difficult to achieve efficient separation of disubstituted benzene isomers with existing technologies, and isomer separation is still a major challenge in the petrochemical industry. Therefore, designing a gas chromatography capillary column to achieve efficient separation of disubstituted benzene isomers is of great significance and application prospects. 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 efficiently separating disubstituted benzene isomers and a preparation method thereof. The chromatographic column can achieve baseline separation of multiple isomers, among which the resolution of o-xylene / p-xylene is as high as 31.1.
[0005] Technical solution: The present invention provides a capillary gas chromatography column for efficiently separating disubstituted benzene isomers, wherein the stationary phase is a nano-scale microporous material with a high BET specific surface area, and the nano-material is coated on the inner wall of the capillary column, and has excellent performance of baseline separation of disubstituted benzene isomers. The disubstituted benzene isomers may be xylene isomers, ethyltoluene isomers, chlorotoluene isomers, and dichlorobenzene isomers.
[0006] The present invention also provides a method for preparing a capillary gas chromatography column for efficiently separating disubstituted benzene isomers, and the specific preparation steps are as follows:
[0007] (1) Synthesis of nanoporous materials with high BET specific surface area: Al(NO3)3·9H2O was dissolved in an organic solvent, 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-xylene was added to the obtained colorless solution, mixed evenly, and a certain amount of anhydrous formic acid was added as a regulator. After high temperature reaction for 20-30h, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a white powder, named GM-2;
[0008] (2) Preparation of a capillary gas chromatography column with nanomaterials embedded in the inner wall: The material prepared in step (1) is added to an organic solvent and stirred to obtain a mixed solution, which is injected into the inner wall of the pretreated capillary chromatography column at a flow rate of 1-2 mL / h using a syringe pump. After the coating is completed, the capillary column is placed in an inert atmosphere, and the column is aged by programmed temperature to remove unbonded materials and impurities. After cooling to room temperature, the preparation is completed.
[0009] Preferably, the solvent of the Al(NO3)3·9H2O solution in step (1) is anhydrous N,N-dimethylformamide (DMF) treated with molecular sieves.
[0010] Preferably, the concentration of Al(NO3)3·9H2O in the organic solvent in step (1) is 5 mg / mL to 10 mg / mL.
[0011] Preferably, the volume ratio of anhydrous formic acid to organic solvent in step (1) is 0.15-0.3.
[0012] Preferably, the high temperature reaction in step (1) is carried out in an oven, and the temperature is raised from room temperature of 30°C to 150°C at a heating rate of 0.3-0.6°C / min, maintained at 150°C for 20-30h, and then cooled to 30°C at a cooling rate of 0.2°C / min.
[0013] More preferably, the heating rate is 0.4°C / min
[0014] Preferably, the chromatographic column in step (2) is treated with a reagent 3-aminopropyltriethoxysilane and maintained at 120° C. under an inert atmosphere for 3 hours, thereby modifying the amino groups on its inner wall.
[0015] Preferably, the inert atmosphere in step (2) is one of nitrogen, helium or argon, or an atmosphere formed by mixing several of them in any proportion.
[0016] Preferably, the temperature rising procedure in step (2) is to increase the temperature to 250°C at a heating rate of 5°C / min at a room temperature of 20-35°C, and maintain the temperature at 250°C for 4 hours.
[0017] The separation process of disubstituted benzene isomers is as follows: connect the capillary column to the gas chromatograph, set the heating program (starting temperature and retention time, heating rate, ending temperature and retention time, split ratio), use a micro-injection needle to absorb the vaporized disubstituted benzene isomer gas and inject it into the chromatographic column from the injection port, and click to start the test. Stop the test after all the chromatographic peaks have flowed out, and you can get the chromatogram of the corresponding analyte.
[0018] The preparation of the gas chromatography column stationary phase in the present invention is to use aluminum nitrate nonahydrate (Al(NO3)3·9H2O) as a metal source, 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-xylene (H4TCPB-Me2) as a ligand, N,N-dimethylformamide (DMF) as a solvent, and anhydrous formic acid as a regulator to obtain a white powder through a solvothermal method. The material has a high specific surface area, a large porosity, and a pore size of about 1nm. The gas chromatography column using it as the stationary phase has the following advantages: ① The material synthesis is simple and the experimental results are reproducible; ② The material has a large specific surface area, which is conducive to the adsorption of guest molecules; ③ The material has three pores of different sizes. The large pores are conducive to the mass transfer and diffusion of guest molecules, and the small pores can screen isomers of different sizes and provide them with corresponding forces, which is conducive to the separation of the mixture; ④ The obtained gas chromatography column achieves the highest separation degree of the three xylene isomer mixtures at present, among which the separation degree of o-xylene / p-xylene is 24.8, and the separation degree of m-xylene / p-xylene is as high as 31.1.
[0019] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following significant advantages: the stationary phase material prepared by the present invention has three pores that can amplify the differences in kinetic diameter and cross-sectional size between disubstituted benzene isomers, and realize the size screening of different guest molecules. The gas chromatography capillary column can realize the efficient separation of four disubstituted benzene isomers, among which the separation degree of o-xylene / p-xylene is as high as 31.1, the separation degree of o-ethyltoluene / p-ethyltoluene is as high as 32.5, the separation degree of o-chlorotoluene / p-chlorotoluene is as high as 23.0, and the separation degree of o-dichlorobenzene / p-dichlorobenzene is as high as 20.8. The above results show that the capillary column has excellent application potential in the analysis and detection of chemical raw materials. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is the XRD spectrum of the stationary phase material of the capillary gas chromatography column prepared in Examples 1-4 of the present invention;
[0021] Figure 2It is the SEM spectrum of the stationary phase material of the capillary gas chromatography column prepared in Examples 1-4 of the present invention;
[0022] Figure 3 is the TGA spectrum of the stationary phase material of the capillary gas chromatography column prepared in Example 3 of the present invention;
[0023] Figure 4 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;
[0024] Figure 5 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;
[0025] Figure 6 This is the gas chromatographic separation spectrum of a mixture of three xylene isomers using a capillary gas chromatographic column prepared in Example 3 of the present invention;
[0026] Figure 7 This is the gas chromatographic separation spectrum of a mixture of three ethyltoluene isomers using a capillary gas chromatographic column prepared in Example 3 of the present invention;
[0027] Figure 8 The capillary gas chromatography column prepared in Example 3 of the present invention is a gas chromatographic separation spectrum of three chlorotoluene isomers;
[0028] Fig. 9 This is the gas chromatographic separation spectrum of three dichlorobenzene isomers using the capillary gas chromatographic column prepared in Example 3 of the present invention. DETAILED DESCRIPTION
[0029] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments, but it is necessary to point out that the following embodiments are only used to describe the content of the invention and do not constitute a limitation on the protection scope of the present invention. Among them, the gas chromatograph used in the present invention is Agilent GC7890B, and the reagents used are analytical grade or chromatographic grade.
[0030] Example 1
[0031] A method for preparing a capillary gas chromatography column for efficiently separating disubstituted benzene isomers comprises the following steps:
[0032] (1) Synthesis of nanoporous materials with high BET specific surface area: Weigh 15 mg of Al(NO3)3·9H2O white solid and ultrasonically disperse it in 2 mL of anhydrous DMF. Add 8.8 mg of 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-xylene to the resulting colorless solution. Mix well and then add 300 μL of anhydrous formic acid. Transfer the resulting solution to a 5 mL polytetrafluoroethylene-lined autoclave, heat the temperature from 30°C to 150°C at a rate of 0.4°C / min, maintain at 150°C for 24 h, and then cool it down to 30°C at a rate of 0.2°C / min. After the oven cools to room temperature, centrifuge the material at 15,000 rpm, wash with DMF and methanol, and dry naturally to obtain a white powder.
[0033] (2) Preparation of a capillary gas chromatography column with nanomaterials embedded in the inner wall: Weigh 1 mg of the material prepared in step (1), add it to 1 mL of methanol and disperse it ultrasonically, and inject it into the inner wall of the pretreated capillary chromatography column at a flow rate of 1.5 mL / h using a syringe pump. After the coating is completed, the capillary column is placed in a nitrogen atmosphere, and the temperature is increased from room temperature to 250°C at a rate of 5°C / min, and maintained at 250°C for 4 hours. After cooling to room temperature, the capillary gas chromatography column is obtained.
[0034] Example 2
[0035] A method for preparing a capillary gas chromatography column for efficiently separating disubstituted benzene isomers comprises the following steps:
[0036] (1) Synthesis of nanoporous materials with high BET specific surface area: Weigh 15 mg of Al(NO3)3·9H2O white solid and ultrasonically disperse it in 2 mL of anhydrous DMF. Add 8.8 mg of 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-xylene to the resulting colorless solution. Mix well and then add 400 μL of anhydrous formic acid. Transfer the resulting solution to a 5 mL polytetrafluoroethylene-lined autoclave, heat the temperature from 30°C to 150°C at a rate of 0.4°C / min, maintain at 150°C for 24 h, and then cool it down to 30°C at a rate of 0.2°C / min. After the oven cools to room temperature, centrifuge the material at 15,000 rpm, wash with DMF and methanol, and dry naturally to obtain a white powder.
[0037] (2) Preparation of a capillary gas chromatography column with nanomaterials embedded in the inner wall: Weigh 1 mg of the material prepared in step (1), add it to 1 mL of methanol and disperse it ultrasonically, and inject it into the inner wall of the pretreated capillary chromatography column at a flow rate of 1.5 mL / h using a syringe pump. After the coating is completed, the capillary column is placed in a nitrogen atmosphere, and the temperature is increased from room temperature to 250°C at a rate of 5°C / min, and maintained at 250°C for 4 hours. After cooling to room temperature, the capillary gas chromatography column is obtained.
[0038] Example 3
[0039] A method for preparing a capillary gas chromatography column for efficiently separating disubstituted benzene isomers comprises the following steps:
[0040] (1) Synthesis of nanoporous materials with high BET specific surface area: Weigh 15 mg of Al(NO3)3·9H2O white solid and ultrasonically disperse it in 2 mL of anhydrous DMF. Add 8.8 mg of 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-xylene to the resulting colorless solution, mix well, and then add 500 μL of anhydrous formic acid. Transfer the resulting solution to a 5 mL polytetrafluoroethylene-lined autoclave, and heat the temperature from 30°C to 150°C at a rate of 0.4°C / min, maintain at 150°C for 24 h, and then cool it down to 30°C at a rate of 0.2°C / min. After the oven cools to room temperature, centrifuge the material at 15,000 rpm, wash with DMF and methanol, and dry naturally to obtain a white powder;
[0041] (2) Preparation of a capillary gas chromatography column with nanomaterials embedded in the inner wall: Weigh 1 mg of the material prepared in step (1), add it to 1 mL of methanol and disperse it ultrasonically, and inject it into the inner wall of the pretreated capillary chromatography column at a flow rate of 1.5 mL / h using a syringe pump. After the coating is completed, the capillary column is placed in a nitrogen atmosphere, and the temperature is increased from room temperature to 250°C at a rate of 5°C / min, and maintained at 250°C for 4 hours. After cooling to room temperature, the capillary gas chromatography column is obtained.
[0042] Example 4
[0043] A method for preparing a capillary gas chromatography column for efficiently separating disubstituted benzene isomers comprises the following steps:
[0044] (1) Synthesis of nanoporous materials with high BET specific surface area: Weigh 15 mg of Al(NO3)3·9H2O white solid and ultrasonically disperse it in 2 mL of anhydrous DMF. Add 8.8 mg of 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-xylene to the resulting colorless solution, mix well, and then add 600 μL of anhydrous formic acid. Transfer the resulting solution to a 5 mL polytetrafluoroethylene-lined autoclave, and heat the temperature from 30°C to 150°C at a rate of 0.4°C / min, maintain at 150°C for 24 h, and then cool it down to 30°C at a rate of 0.2°C / min. After the oven cools to room temperature, centrifuge the material at 15,000 rpm, wash with DMF and methanol, and dry naturally to obtain a white powder;
[0045] (2) Preparation of a capillary gas chromatography column with nanomaterials embedded in the inner wall: Weigh 1 mg of the material prepared in step (1), add it to 1 mL of methanol and disperse it ultrasonically, and inject it into the inner wall of the pretreated capillary chromatography column at a flow rate of 1.5 mL / h using a syringe pump. After the coating is completed, the capillary column is placed in a nitrogen atmosphere, and the temperature is increased from room temperature to 250°C at a rate of 5°C / min, and maintained at 250°C for 4 hours. After cooling to room temperature, the capillary gas chromatography column is obtained.
[0046] The structure, morphology, thermal stability and pore structure of the stationary phase material prepared in the above embodiment were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), specific surface area and pore size analyzer technology. Figure 1 ) shows that its crystallinity is related to the amount of formic acid added as a regulator. The materials prepared in Examples 2 and 4 with formic acid amounts of 400 μL and 600 μL respectively have poor crystallinity and rough baselines; the material prepared in Example 1 with formic acid amounts of 300 μL has a more severe peak broadening and an unclear characteristic peak; the material prepared in Example 3 with formic acid amounts of 500 μL has a sharper peak and a flatter baseline, indicating that it has good crystallinity. SEM image of the stationary phase material ( Figure 2 ) shows that the size of the obtained materials is about 1 μm. The materials obtained in Example 1 and Example 2 with formic acid amounts of 300 μL and 400 μL respectively are interlaced nanoblocks; the materials obtained in Example 3 and Example 4 with formic acid amounts of 500 μL and 600 μL respectively are relatively uniform in size and have a flake-like morphology. TGA graph of the material obtained in Example 3 with formic acid amount of 500 μL ( Figure 3 ) shows that the skeleton is still intact and does not collapse at a temperature of 400°C, and has good thermal stability. Figure 4 ) shows that when the relative pressure (p / p0) = 1, the adsorption capacity of the material is 450cm 3 / g, BET specific surface area is 1,141.1720m 2 / g, indicating a higher porosity. The pore size distribution diagram of the material obtained in Example 3 ( Figure 5 ) showed that the material contained three micropores of different sizes, namely 0.68nm, 0.93nm and 1.17nm.
[0047] The gas chromatogram of the capillary gas chromatographic column prepared in Example 3 for separating xylene, ethyltoluene, chlorotoluene and dichlorobenzene isomers is as follows: Figure 6-Figure 9 shown. Figure 6 It shows that the obtained material has a separation degree of m-xylene / p-xylene of 24.9 and a separation degree of o-xylene / p-xylene of 31.1. Figure 7It shows that the obtained material has a separation degree of 23.2 for m-ethyltoluene / p-ethyltoluene and a separation degree of 32.5 for o-ethyltoluene / p-ethyltoluene. Figure 8 It shows that the obtained material has a separation degree of m-chlorotoluene / p-chlorotoluene of 17.2 and a separation degree of o-chlorotoluene / p-chlorotoluene of 23.0. Fig. 9 The results show that the separation degree of the obtained material for m-dichlorobenzene / p-dichlorobenzene is as high as 17.1, and the separation degree of o-dichlorobenzene / p-dichlorobenzene is as high as 20.8. Under the same conditions, the commercial column HP-5 (30m) is used to replace the capillary gas chromatography column prepared in Example 3 to separate xylene, ethyltoluene, chlorotoluene, and dichlorobenzene isomers. The specific separation degrees are shown in Table 1. The above results show that the capillary column has good application potential in the field of separating disubstituted benzene isomers.
[0048] Table 1 Separation of four disubstituted benzene isomers by different capillary columns
[0049] GM-2 column Commercial column HP-5 (30m) o-Xylene / m-Xylene 7.4 5.2 Meta-Xylene / Para-Xylene 24.9 0 o-Xylene / p-Xylene 31.1 5.2 o-ethyltoluene / m-ethyltoluene 11.9 / m-Ethyltoluene / p-Ethyltoluene 23.2 / o-Ethyltoluene / p-Ethyltoluene 32.5 / o-Chlorotoluene / m-Chlorotoluene 6.7 0 m-Chlorotoluene / p-Chlorotoluene 17.2 0 o-Chlorotoluene / p-Chlorotoluene 23.0 0 o-Dichlorobenzene / m-Dichlorobenzene 3.7 4.7 m-dichlorobenzene / p-dichlorobenzene 17.1 1.4 o-Dichlorobenzene / p-Dichlorobenzene 20.8 6.1
Claims
1. A capillary gas chromatography column for efficiently separating disubstituted benzene isomers, characterized in that: The stationary phase of the capillary gas chromatography column is a nanometer-scale microporous material with a high BET specific surface area, and the nanometer material is coated on the inner wall of the capillary column.
2. The method for preparing a capillary gas chromatography column according to claim 1, characterized in that: The following steps are involved: (1) Synthesis of nanoporous materials with high BET specific surface area: Al(NO3)3·9H2O was dissolved in an organic solvent, 1,2,4,5-tetrakis(4-carboxyphenyl)-3,6-xylene was added to the obtained colorless solution, mixed evenly, and a certain amount of anhydrous formic acid was added as a regulator. After high temperature reaction for 20-30h, the mixture was cooled to room temperature, filtered, washed, and dried to obtain a white powder, named GM-2; (2) Preparation of a capillary gas chromatography column with nanomaterials embedded in the inner wall: The material prepared in step (1) is added to an organic solvent and mixed evenly to obtain a mixed solution, which is injected into the inner wall of the pretreated capillary chromatography column at a flow rate of 1-2 mL / h using a syringe pump. After the coating is completed, the capillary column is placed in an inert atmosphere, and the column is aged by programmed temperature to remove unbonded materials and impurities. After cooling to room temperature, the preparation is completed.
3. The method for preparing a capillary gas chromatography column according to claim 2, characterized in that: The solvent of the Al(NO3)3·9H2O solution in step (1) is anhydrous DMF treated with molecular sieves.
4. The method for preparing a capillary gas chromatography column according to claim 2, characterized in that: The concentration of Al(NO3)3·9H2O in the organic solvent in step (1) is 5 mg / mL to 10 mg / mL.
5. The method for preparing a capillary gas chromatography column according to claim 2, characterized in that: The volume ratio of anhydrous formic acid to organic solvent in step (1) is 0.15-0.
3.
6. The method for preparing a capillary gas chromatography column stationary phase according to claim 2, characterized in that: The high temperature reaction in step (1) is carried out in an oven, and the temperature is raised from room temperature of 30°C to 150°C at a heating rate of 0.3-0.6°C / min.
7. The method for preparing a capillary gas chromatography column according to claim 2, characterized in that: The chromatographic column in step (2) is treated with a reagent 3-aminopropyltriethoxysilane and maintained at 120° C. under an inert atmosphere for 3 hours to modify the amino groups on its inner wall.
8. The method for preparing a capillary gas chromatography column according to claim 2, 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.
9. The method for preparing a capillary gas chromatography column according to claim 2, characterized in that: The temperature rising program in step (2) is to increase the temperature to 250°C at a heating rate of 5°C / min at a room temperature of 20-35°C, and maintain it at 250°C for 4 hours.
10. The capillary gas chromatography column for efficiently separating disubstituted benzene isomers according to claim 1, characterized in that: The disubstituted benzene isomers are xylene isomers, ethyltoluene isomers, chlorotoluene isomers, and dichlorobenzene isomers.