An iron ion-doped aluminum-based MOF gas-phase capillary column and a preparation method and application thereof

Abstract

This invention discloses an iron-doped aluminum-based MOF gas-phase capillary column, its preparation method, and its application. The preparation method includes the following steps: injecting NaOH aqueous solution into the capillary column, allowing it to stand, and then blowing it out with inert gas; continuously introducing inert gas and drying at a constant temperature for later use; dissolving aluminum nitrate nonahydrate, fumaric acid, and sodium hydroxide in deionized water to obtain a first reaction solution, injecting it into the capillary column, and reacting it at a constant temperature of 100-120℃ for 20-24 hours; and aging it at 250℃ for 4-8 hours under inert gas protection. After cooling, a seed layer is formed inside the capillary column. Aluminum nitrate nonahydrate, ferric chloride, fumaric acid, and sodium hydroxide are dissolved in deionized water, and the resulting second reaction solution is injected into the capillary column containing the seed layer. The reaction is carried out at 90-100℃ for 10-12 hours. After rinsing, the column is aged at 200℃ for 12-20 hours under inert gas protection to obtain an iron-doped aluminum-based MOF gas-phase capillary column. The coating thickness inside this capillary column is uniform, the coating is difficult to peel off, the column efficiency is high, the separation degree is good, the peak shape is good, and the separation effect is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of gas phase capillary column technology, and in particular to an iron ion-doped aluminum-based MOF gas phase capillary column, its preparation method, and its application. Background Technology

[0002] Gas phase analysis is an important branch of analytical chemistry, primarily studying the composition, concentration, and properties of gases or volatile substances. Its core objective is to provide crucial data for environmental monitoring, industrial process control, food safety, and other fields by separating, detecting, and quantifying gas components. Gas phase analysis techniques are characterized by high sensitivity, rapid response, and good selectivity, and are widely used in scientific research and industrial production.

[0003] Refrigerants are critical working media in refrigeration, air conditioning, and heat pump systems, and their composition and purity directly affect system performance and environmental friendliness. Gas phase analysis techniques, due to their high sensitivity, high resolution, and excellent quantitative capabilities, have become the primary method for refrigerant composition analysis. Gas phase analysis methods occupy a core position in refrigerant composition analysis, with GC, GC-MS, and FTIR being the most commonly used techniques.

[0004] In existing technologies, the current standard GB / T 31400-2015 is commonly used for gas chromatography analysis of refrigerants. The imported Porapak Q 4m packed column used has poor resolution, poor peak shape, and is expensive. The current standard GB / T 38100-2019 uses a 60m capillary column, which has extremely poor peak shape, severe tailing, and poor resolution. In addition, commercially available imported chromatographic columns have problems such as uneven coating thickness and easy peeling of the internal coating, which greatly reduces the resolution of the chromatographic column. Summary of the Invention

[0005] This invention provides an iron-doped aluminum-based MOF gas-phase capillary column, its preparation method, and its application, in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing an iron-doped aluminum-based MOF vapor-phase capillary column includes the following steps:

[0008] S1: Inject NaOH aqueous solution into the capillary column, let it stand, blow it out with inert gas, and then rinse it until neutral; place the capillary column in a constant temperature drying oven, continuously pass in inert gas, dry it, and set it aside for later use;

[0009] S2: Dissolve aluminum nitrate nonahydrate, fumaric acid, and sodium hydroxide in deionized water to obtain the first reaction solution. Inject the first reaction solution into the pretreated capillary column in S1. Seal both ends of the capillary column and react at a constant temperature of 100-120℃ for 20-24 hours. After the reaction is completed, rinse the capillary column with deionized water. Then age it at 250℃ for 4-8 hours under inert gas protection and cool it to room temperature to form a seed layer inside the capillary column.

[0010] S3: Dissolve aluminum nitrate nonahydrate, ferric chloride, fumaric acid and sodium hydroxide in deionized water to obtain a second reaction solution. Inject the second reaction solution into the capillary column containing the seed layer prepared in S2. Seal both ends of the capillary column and react at 90-100℃ for 10-12 hours. After the reaction is completed, rinse the capillary column with deionized water and then age it at 200℃ for 12-20 hours under inert gas protection to obtain the iron ion-doped aluminum-based MOF gas phase capillary column.

[0011] Furthermore, in S2, the mass ratio of aluminum nitrate nonahydrate to fumaric acid and sodium hydroxide is 0.2251:0.07:0.07.

[0012] Furthermore, in S3, the mass ratio of aluminum nitrate nonahydrate to ferric chloride, fumaric acid, and sodium hydroxide is 0.2026:0.0162:0.07:0.0344.

[0013] Furthermore, in S1, the drying temperature is 100-120℃ and the time is 3-4 hours.

[0014] Furthermore, ultrasonic dissolution is performed before the first and second reaction solutions are injected into the capillary column.

[0015] Furthermore, the inert gas used in S1, S2 and S3 is high-purity nitrogen.

[0016] In another aspect, the present invention provides an iron-doped aluminum-based MOF gas-phase capillary column prepared by the aforementioned method for preparing an iron-doped aluminum-based MOF gas-phase capillary column.

[0017] In another aspect, the present invention provides the application of the iron-doped aluminum-based MOF gas-phase capillary column described above in the separation of fluorinated refrigerants.

[0018] Further, the fluorinated refrigerant includes difluoromethane, 1,1,1-trifluoroethane, difluorochloromethane, 1,1-difluoroethane, pentafluoroethane, 1,1,2,3,3,3-hexafluoropropene, 1,1,1,2-tetrafluoroethane, 1,1,1,2,2-pentafluoropropane, 1,1-difluoro-1-chloroethane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1,2-tetrafluoro-2-chloroethane, 1,1,1,3 The analytical conditions for the separation of ,3,3-hexafluoropropane were as follows: a flame ionization detector was used; the hydrogen flow rate was 35-45 ml / min; the air flow rate was 350-450 ml / min; and the combined flow rate of the tail purge and column was 35-45 ml / min. The initial column temperature was 40℃; the heating rate was 10℃ / min; the endpoint temperature was 150℃ and held for 10 min; the column split ratio was 7:1; and the column flow rate was 5-15 ml / min.

[0019] The beneficial effects of this invention are:

[0020] This invention discloses a method for preparing an iron-doped aluminum-based MOF gas-phase capillary column. First, the inner wall of the capillary column is treated with NaOH aqueous solution to achieve hydroxylation of the inner wall surface through alkaline etching. The resulting sodium silanol hydroxide (Si-ONa) provides high-density anchoring sites for the subsequent MOF seed layer. Then, Al3+ released from aluminum nitrate nonahydrate forms coordination bonds with the carboxylate ions dissociated from fumaric acid, constructing an Al-carboxylic acid periodic network structure. Al3+ and column wall hydroxyl groups are fixed to the MOF crystals through Al-O-Si covalent bonds, forming a robust seed layer. Finally, Fe3+ is introduced... + Metal nodes, through heterometallic coordination with Al3+, construct a heterometallic coordination network. The internal material of the resulting capillary column is a trivalent iron ion-doped aluminum-based metal-organic framework (Fe-AlMOF), which has the characteristics of ultra-large specific surface area and functionalizable structure. In addition, the coating thickness inside the capillary column is uniform and the coating is difficult to fall off, resulting in high column efficiency, good separation, good peak shape, and ensuring separation effect. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a SEM image of an iron-doped aluminum-based MOF vapor phase capillary column disclosed in Embodiment 1 of the present invention.

[0023] Figure 2This is a SEM image of an iron-doped aluminum-based MOF vapor phase capillary column inner coating disclosed in Embodiment 1 of the present invention.

[0024] Figure 3 This is a SEM image of the thickness of the inner coating of an iron-doped aluminum-based MOF vapor phase capillary column disclosed in Embodiment 1 of the present invention.

[0025] Figure 4 This is a gas chromatogram of twelve refrigerants separated by an iron-doped aluminum-based MOF gas phase capillary column as disclosed in Example 1 of the present invention.

[0026] Figure 5 This is a gas chromatogram of R407c refrigerant separated by an iron-doped aluminum-based MOF gas phase capillary column as disclosed in Embodiment 1 of the present invention.

[0027] Figure 6 This is a gas chromatogram of R415b refrigerant separated by an iron-doped aluminum-based MOF gas phase capillary column as disclosed in Example 1 of the present invention.

[0028] Figure 7 This is a SEM image of the gas chromatography column prepared in Comparative Example 1 of the present invention;

[0029] Figure 8 The above is a gas chromatogram of twelve fluorinated refrigerants separated by a gas chromatographic column prepared in Comparative Example 1 of the present invention.

[0030] Figure 9 This is a SEM image of a commercially available gas phase capillary column used in Comparative Example 2 of this invention.

[0031] Figure 10 This is a SEM image of the coating inside a commercially available vapor phase capillary column in Comparative Example 2 of this invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1:

[0034] like Figure 1-2 The figure shows a method for preparing an iron-doped aluminum-based MOF vapor-phase capillary column according to this embodiment, including the following steps:

[0035] S1: Inject a 5-10% NaOH aqueous solution into a quartz capillary column (30m × 0.53mm), let it stand for 4-6 hours, then purge it with high-purity nitrogen gas, followed by rinsing with deionized water until neutral. Place the capillary column in a constant temperature drying oven, continuously purge with high-purity nitrogen gas, and dry at 100-120℃ for 3-4 hours for later use.

[0036] S2: Weigh 0.2251 g of aluminum nitrate nonahydrate, 0.07 g of fumaric acid, and 0.0344 g of sodium hydroxide, dissolve them in 10 mL of deionized water, and sonicate until clear and transparent to obtain the first reaction solution. Inject the first reaction solution into the pretreated capillary column, seal both ends, and react at 100°C for 20 hours. After the reaction is complete, rinse the column with deionized water for 10 min, then age it at 250°C for 5 hours under a nitrogen atmosphere, and allow it to cool naturally to room temperature to obtain a capillary column containing a seed layer.

[0037] S3: Weigh 0.2026 g of aluminum nitrate nonahydrate, 0.0162 g of ferric chloride, 0.07 g of fumaric acid and 0.0344 g of sodium hydroxide, dissolve them in 10 mL of deionized water, and sonicate to dissolve them to obtain the second reaction solution; inject the second reaction solution into the above-mentioned capillary column containing the seed layer, seal both ends, react at 90 °C for 10 hours, after the reaction is completed, rinse the column with 30 mL of deionized water, and age it at 200 °C for 15 hours under nitrogen protection to obtain an iron ion-doped aluminum-based MOF gas phase capillary column.

[0038] SEM scans were performed on the prepared iron-doped aluminum-based MOF gas-phase capillary column, and the results are as follows: Figure 1-2 As shown, from Figure 1-2 It can be seen that the prepared gas-phase capillary column has no breaks on its wall, and the coating thickness inside the capillary column is uniformly distributed, exhibiting a clustered petal-like structure. Figure 3 As shown, the thickness of the internal coating of the prepared gas phase capillary column is in the range of 500-700 nm.

[0039] 1. Refrigerant separation performance test of the gas-phase capillary column prepared in this embodiment:

[0040] (1) The test method is as follows: the prepared capillary column is connected to the gas chromatograph, Agilent 6890;

[0041] The configuration and operating conditions of the gas chromatograph are as follows:

[0042] Vaporization chamber temperature: 200℃, FID detector temperature: 260℃, hydrogen flow rate: 35ml / min, air flow rate: 350ml / min, combined tail purge and column flow rate: 35ml / min; initial column oven temperature: 40℃; heating rate: 10℃ / min, final temperature: 150℃, held for 10min; column flow rate: 10ml / min, split ratio: 7:1.

[0043] The samples consisted of twelve refrigerants: difluoromethane (R32), 1,1,1-trifluoroethane (R143a), difluorochloromethane (R22), 1,1-difluoroethane (R152a), pentafluoroethane (R125), 1,1,2,3,3,3-hexafluoropropene (R1216), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1,2,2-pentafluoropropane (R245cb), 1,1-difluoro-1-chloroethane (R142b), 1,1,1,2,3,3,3-heptafluoropropane (R227ea), 1,1,1,2-tetrafluoro-2-chloroethane (R124), and 1,1,1,3,3,3-hexafluoropropane (R236fa).

[0044] The injection volume was 20 μL.

[0045] (2) The results are as follows Figure 4 As shown in Table 1;

[0046] Table 1. Results of performance tests on the gas-phase capillary column prepared in Example 1 for twelve refrigerants.

[0047]

[0048]

[0049] Combining Table 1 and Figure 4 As can be seen, the gas phase capillary column of Example 1 of this application can separate 12 components in the refrigerant, the chromatogram baseline is straight and the chromatographic peaks have no obvious tailing phenomenon, and the overall analysis time is relatively short.

[0050] 2. Refrigerant separation performance test of the gas-phase capillary column prepared in this embodiment:

[0051] (1) The test method is as follows: the prepared capillary column is connected to the gas chromatograph, Agilent 6890;

[0052] The configuration and operating conditions of the gas chromatograph are as follows:

[0053] Vaporization chamber temperature: 150℃, FID detector temperature: 220℃, hydrogen flow rate: 35ml / min, air flow rate: 350ml / min, combined tail purge and column flow rate: 35ml / min; column oven temperature: 100℃; column flow rate: 5ml / min, split ratio: 7:1;

[0054] The sample is R407c refrigerant, which is a mixed refrigerant composed of R32, R125, and R134a.

[0055] The injection volume was 20 μL.

[0056] (2) The results are as follows Figure 5 As shown in Table 2;

[0057] Table 2. Results of R407c refrigerant separation performance tests on the gas phase capillary column prepared in Example 1.

[0058] Retention time Component Name Symmetry factor Half peak width Theoretical number of plates Resolution 0.849 R32 0.851 0.008 62737.42 1.761 R125 0.504 0.022 35620.85 2.074 2.046 R143a 0.656 0.024 38791.45 1.162

[0059] Combine Table 2 and Figure 5 As can be seen, the gas phase capillary column of Example 1 of this application can separate different components in the mixed refrigerant, the chromatogram baseline is straight and the chromatographic peaks have no obvious tailing phenomenon, and the overall analysis time is relatively short.

[0060] 3. Refrigerant separation performance test of the gas-phase capillary column prepared in this embodiment:

[0061] (1) The test method is as follows: the prepared capillary column is connected to the gas chromatograph, Agilent 6890;

[0062] The configuration and operating conditions of the gas chromatograph are as follows:

[0063] Vaporization chamber temperature: 150℃, FID detector temperature: 220℃, hydrogen flow rate: 35ml / min, air flow rate: 350ml / min, combined tail purge and column flow rate: 35ml / min; column oven temperature: 100℃; column flow rate: 5ml / min, split ratio: 7:1;

[0064] The sample is R415b refrigerant. R407c refrigerant is a mixed refrigerant composed of R32 and R152a.

[0065] The injection volume was 20 μL.

[0066] (2) The results are as follows Figure 6 As shown in Table 3;

[0067] Table 3. Results of R407c refrigerant separation performance tests on the gas phase capillary column prepared in Example 1.

[0068] Retention time Component Name Symmetry factor Half peak width Theoretical number of plates Resolution 1.516 R32 0.588 0.018 39591.42 1.728 R152a 0.614 0.019 45978.85 1.140

[0069] Combined with Table 3 and Figure 6 As can be seen, the gas phase capillary column of Example 1 of this application can separate different components in the mixed refrigerant, the chromatogram baseline is straight and the chromatographic peaks have no obvious tailing phenomenon, and the overall analysis time is relatively short.

[0070] Comparative Example

[0071] Comparative Example 1:

[0072] The following is a method for preparing a gas-phase capillary column:

[0073] S1: Same as the steps in Example 1;

[0074] S2: Same as the steps in Example 1;

[0075] No S3 step.

[0076] The prepared gas-phase capillary column was scanned by SEM, and the results are as follows: Figure 7 As shown, from Figure 7 It can be seen that the uniformity of the coating thickness on the wall of the prepared gas-phase capillary column is very poor.

[0077] The gas-phase capillary column prepared in this comparative example was tested for the separation performance of twelve refrigerants:

[0078] 1) The test method is the same as that in the separation performance test of Example 1:

[0079] 2) Results are as follows Figure 8 As shown in Table 4;

[0080] Table 4 shows the results of the gas-phase capillary column prepared in Comparative Example 1 for the separation performance of twelve refrigerants.

[0081]

[0082]

[0083] From Table 4 and Figure 8 As can be seen, mixed peaks appeared, indicating separation failure. The gas-phase capillary column prepared in this comparative example could not be accurately qualitatively and quantitatively analyzed, which greatly affected the accuracy of the test results.

[0084] Comparative Example 2:

[0085] SEM scanning was performed on the commercially available Plot Q gas chromatography capillary column (Agient HP-PLOT-Q), and the results are as follows: Figure 9 and Figure 10 As shown in the figure, the coating thickness on the inner wall of the gas phase capillary column is uneven, and the adsorbent in the coating is not firmly adhered and is easy to fall off, which will lead to a significant decrease in separation efficiency.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The application of an iron-doped aluminum-based MOF gas-phase capillary column in the separation of fluorinated refrigerants, characterized in that, The fluorinated refrigerant is difluoromethane, 1,1,1-trifluoroethane, difluorochloromethane, 1,1-difluoroethane, pentafluoroethane, 1,1,2,3,3,3-hexafluoropropene, 1,1,1,2-tetrafluoroethane, 1,1,1,2,2-pentafluoropropane, 1,1-difluoro-1-chloroethane, 1,1,1,2,3,3,3-heptafluoropropane, 1,1,1,2-tetrafluoro-2-chloroethane, or 1,1,1,3,3,3-hexafluoropropane; The method for preparing the iron ion-doped aluminum-based MOF gas-phase capillary column includes the following steps: S1: Inject 5-10% NaOH aqueous solution into the capillary column, let it stand, blow it out with inert gas, and then rinse it until neutral; place the capillary column in a constant temperature drying oven, continuously pass in inert gas, dry it, and set it aside for later use. S2: Dissolve aluminum nitrate nonahydrate, fumaric acid, and sodium hydroxide in deionized water to obtain the first reaction solution. Inject the first reaction solution into the pretreated capillary column in S1. Seal both ends of the capillary column and react at a constant temperature of 100-120℃ for 20-24 hours. After the reaction is completed, rinse the capillary column with deionized water. Then age it at 250℃ for 4-8 hours under inert gas protection and cool it to room temperature to form a seed layer inside the capillary column. S3: Dissolve aluminum nitrate nonahydrate, ferric chloride, fumaric acid and sodium hydroxide in deionized water to obtain a second reaction solution. Inject the second reaction solution into the capillary column containing the seed layer prepared in S2. Seal both ends of the capillary column and react at 90-100℃ for 10-12 hours. After the reaction is completed, rinse the capillary column with deionized water and then age it at 200℃ for 12-20 hours under inert gas protection to obtain the iron ion-doped aluminum-based MOF gas phase capillary column.

2. The application according to claim 1, characterized in that, In S2, the mass ratio of aluminum nitrate nonahydrate to fumaric acid and sodium hydroxide is 0.2251:0.07:0.

07.

3. The application according to claim 1, characterized in that, In S3, the mass ratio of aluminum nitrate nonahydrate to ferric chloride, fumaric acid, and sodium hydroxide is 0.2026:0.0162:0.07:0.0344.

4. The application according to claim 1, characterized in that, In S1, the drying temperature is 100-120℃ and the time is 3-4 hours.

5. The application according to claim 1, characterized in that, Before the first and second reaction solutions are injected into the capillary column, ultrasonic dissolution is performed.

6. The application according to claim 1, characterized in that, The inert gas used in S1, S2 and S3 is high-purity nitrogen.

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