Iron-ion-doped aluminum-based MOF (Metal Organic Framework) gas-phase capillary column as well as preparation method and application thereof

Abstract

The invention discloses an iron-ion-doped aluminum-based MOF (Metal Organic Framework) gas-phase capillary column as well as a preparation method and application thereof, and the preparation method comprises the following steps: injecting a NaOH aqueous solution into the capillary column, standing, and blowing out by using inert gas; continuously introducing inert gas, and drying at constant temperature for later use; dissolving aluminum nitrate nonahydrate, fumaric acid and sodium hydroxide in deionized water to obtain a first reaction solution, injecting the first reaction solution into a capillary column, and reacting at the constant temperature of 100-120 DEG C for 20-24 hours; aging at 250 DEG C for 4-8 hours under the protection of inert gas, and cooling to form a seed crystal layer in the capillary column; dissolving aluminum nitrate nonahydrate, ferric trichloride, fumaric acid and sodium hydroxide in deionized water to obtain a second reaction solution, injecting the second reaction solution into the capillary column containing the seed crystal layer, reacting for 10-12 hours at 90-100 DEG C, washing, and aging for 12-20 hours at 200 DEG C under the protection of inert gas to obtain an iron ion doped aluminum-based MOF gas phase capillary column; the coating in the capillary column is uniform in thickness, the coating is difficult to fall off, the column efficiency is high, the separation degree is good, the peak shape is good, and the separation effect is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of gas phase capillary columns, and in particular to an iron ion-doped aluminum-based MOF gas phase capillary column, a preparation method thereof, and applications thereof. Background Art

[0002] Gas phase analysis, a key branch of analytical chemistry, primarily studies the composition, concentration, and properties of gases or volatile substances. Its core goal is to separate, detect, and quantify gas components, providing critical data for environmental monitoring, industrial process control, food safety, and other fields. Gas phase analysis technology, characterized by high sensitivity, rapid response, and excellent selectivity, is widely used in scientific research and industrial production.

[0003] Refrigerants are the key working medium in refrigeration, air conditioning, and heat pump systems. Their composition and purity directly impact system performance and environmental friendliness. Gas phase analysis, due to its high sensitivity, high resolution, and excellent quantitative capabilities, has become the primary method for refrigerant composition analysis. Gas phase analysis methods play a central role in refrigerant analysis, with GC, GC-MS, and FTIR being the most commonly used techniques.

[0004] In the existing technology, the current standard GB / T 31400-2015 is often used to perform gas phase analysis of refrigerants. The imported Porapak Q 4m packed column used has average separation, poor peak shape, poor separation, and is expensive. The 60m capillary column used in the current standard GB / T 38100-2019 has problems such as extremely poor peak shape, severe tailing, and poor separation. In addition, commercially available imported chromatographic columns also have problems such as uneven coating thickness and easy falling off of the internal coating, which greatly reduces the separation of the chromatographic column. Summary of the Invention

[0005] The present invention provides an iron ion-doped aluminum-based MOF gas phase capillary column and a preparation method and application thereof to solve the above problems.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] A method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column comprises 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 it is neutral; place the capillary column in a constant temperature drying oven, continuously pass inert gas, dry it, and set aside;

[0009] S2: Aluminum nitrate nonahydrate, fumaric acid, and sodium hydroxide are dissolved in deionized water to obtain a first reaction solution, the first reaction solution is injected into the capillary column pretreated in S1, both ends of the capillary column are sealed, and the reaction is carried out at a constant temperature of 100-120° C. for 20-24 hours. After the reaction, the capillary column is rinsed with deionized water; then, the column is aged at 250° C. for 4-8 hours under inert gas protection, and cooled to room temperature to form a seed layer in the capillary column;

[0010] S3: Aluminum nitrate nonahydrate, ferric chloride, fumaric acid and sodium hydroxide are dissolved in deionized water to obtain a second reaction solution, and the second reaction solution is injected into the capillary column containing the seed layer prepared in S2. Both ends of the capillary column are sealed, and the reaction is carried out at 90-100°C for 10-12 hours. After the reaction is completed, the capillary column is rinsed with deionized water, and then aged at 200°C 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 the 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°C and the drying time is 3-4 hours.

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

[0015] Furthermore, the inert gases used in S1, S2 and S3 are all high-purity nitrogen.

[0016] Another aspect of the present invention provides an iron ion-doped aluminum-based MOF gas-phase capillary column prepared by the method for preparing an iron ion-doped aluminum-based MOF gas-phase capillary column.

[0017] Another aspect of the present invention provides a use of the iron ion-doped aluminum-based MOF gas phase capillary column in separating fluorine-containing refrigerants.

[0018] Furthermore, the fluorine-containing refrigerant includes difluoromethane, 1,1,1-trifluoroethane, difluorochloromethane, 1,1-difluoroethane, pentafluoroethane, 1,1,2,3,3,3-hexafluoropropylene, 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 detection conditions for the separation of 3,3-hexafluoropropane are as follows: using a hydrogen flame ionization detector, a hydrogen flow rate of 35-45ml / min, an air flow rate of 350-450ml / min, and a tail blow and column flow rate of 35-45ml / min in total; the initial temperature of the column box is 40°C; the heating rate is 10°C / min, the end temperature is 150°C, and it is maintained for 10 minutes; the chromatographic column split ratio is 7:1, and the column flow rate is 5-15ml / min.

[0019] The beneficial effects of the present invention are:

[0020] The present invention discloses a method for preparing an iron ion-doped aluminum-based MOF gas-phase capillary column. First, the inner wall of the capillary column is treated with a NaOH aqueous solution, and the inner wall surface is hydroxylated by alkaline etching. The generated sodium silanol (Si-ONa) provides high-density anchoring points for the subsequent MOF seed layer. Then, Al3+ released by aluminum nitrate nonahydrate is used to form a coordination bond with the carboxylate ions dissociated from fumaric acid to construct an Al-carboxylic acid periodic network structure, in which Al3+ and the column wall hydroxyl groups are fixed to the MOF crystals through Al-O-Si covalent bonds to form a solid seed layer. Finally, Fe3 + The metal node constructs a heterometallic coordination network with Al3+ through heterometallic coordination. The internal material of the capillary column is an aluminum-based metal-organic framework (Fe-AlMOF) doped with trivalent iron ions, which has the characteristics of ultra-large specific surface area and structural functionalization. The coating thickness inside the capillary column is uniform and the coating is difficult to fall off. The column efficiency is high, the separation degree is good, and the peak shape is good, ensuring the separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a SEM image of an iron ion-doped aluminum-based MOF gas phase capillary column disclosed in Example 1 of the present invention;

[0023] Figure 2This is a SEM image of the inner coating of an aluminum-based MOF gas phase capillary column doped with iron ions disclosed in Example 1 of the present invention;

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

[0025] Figure 4 This is a gas chromatogram of the separation of twelve refrigerants using an iron ion-doped aluminum-based MOF gas capillary column disclosed in Example 1 of the present invention;

[0026] Figure 5 This is a gas chromatogram of the separation of R407c refrigerant using an iron ion-doped aluminum-based MOF gas phase capillary column disclosed in Example 1 of the present invention;

[0027] Figure 6 This is a gas chromatogram of the separation of R415b refrigerant using an iron ion-doped aluminum-based MOF gas phase capillary column 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 This is a gas chromatogram of the gas chromatography column prepared in Comparative Example 1 of the present invention for separating twelve fluorine-containing refrigerants;

[0030] Figure 9 This is a SEM image of a commercially available gas phase capillary column in Comparative Example 2 of the present invention;

[0031] Figure 10 This is a SEM image of the inner coating of a commercially available gas phase capillary column in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1:

[0034] like Figure 1-2 The method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column provided in this embodiment includes the following steps:

[0035] S1: Inject a 5-10% NaOH aqueous solution into a quartz capillary column (30 m x 0.53 mm). Allow to stand for 4-6 hours, then purge with high-purity nitrogen. Rinse with deionized water until neutral. Place the capillary column in a constant-temperature drying oven, continuously flowing with high-purity nitrogen, and dry at 100-120°C for 3-4 hours before 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 in 10 mL of deionized water, and sonicate until clear and transparent to obtain a first reaction solution. Inject the first reaction solution into a 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 minutes, then age at 250°C under a nitrogen atmosphere for 5 hours. 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 ultrasonically dissolve them to obtain a second reaction liquid; inject the second reaction liquid into the above-mentioned capillary column containing the seed layer, seal both ends, and react at 90°C for 10 hours. After the reaction is completed, rinse the column tube with 30 mL of deionized water, and age it at 200°C under nitrogen protection for 15 hours to obtain an iron ion-doped aluminum-based MOF gas phase capillary column.

[0038] The prepared iron ion doped aluminum-based MOF gas phase capillary column was scanned by SEM, and the results were as follows: Figure 1-2 As shown, from Figure 1-2 It can be seen that there are no breakpoints on the wall of the prepared gas phase capillary column, and the coating thickness inside the capillary column is evenly distributed, showing clusters of petal-like structures. Figure 3 As shown, the thickness of the inner coating of the prepared gas phase capillary column is in the range of 500-700 nm.

[0039] 1. The gas phase capillary column prepared in this example was subjected to a refrigerant separation performance test 1:

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

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

[0042] Vaporizer temperature: 200°C, FID detector temperature: 260°C, hydrogen flow rate: 35 ml / min, air flow rate: 350 ml / min, tail gas and column flow rate: 35 ml / min combined; column oven initial temperature: 40°C; heating rate: 10°C / min, endpoint temperature: 150°C, hold: 10 min; column flow rate: 10 ml / min, split ratio: 7:1;

[0043] The samples are twelve refrigerants: difluoromethane (R32), 1,1,1-trifluoroethane (R143a), difluorochloromethane (R22), 1,1-difluoroethane (R152a), pentafluoroethane (R125), 1,1,2,3,3,3-hexafluoropropylene (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] Injection volume: 20 μL.

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

[0046] Table 1 Test results of separation performance of twelve refrigerants using the gas phase capillary column prepared in Example 1

[0047]

[0048]

[0049] Combined with Table 1 and Figure 4 It can be seen that the gas phase capillary column of Example 1 of the present application can separate 12 components in the refrigerant, the chromatogram baseline is straight and the chromatographic peak has no obvious tailing phenomenon, and the overall analysis time is short.

[0050] 2. The gas phase capillary column prepared in this example was subjected to the second refrigerant separation performance test:

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

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

[0053] Vaporizer temperature: 150°C, FID detector temperature: 220°C, hydrogen flow rate 35 ml / min, air flow rate 350 ml / min, tail gas and column flow rate 35 ml / min combined; column oven temperature 100°C; column flow rate 5 ml / min, split ratio 7:1;

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

[0055] Injection volume: 20 μL.

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

[0057] Table 2 Test results of R407c refrigerant separation performance of the gas phase capillary column prepared in Example 1

[0058] Retention time Component name Symmetry Factor Half-peak width Theoretical plates Separation 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] Combined with Table 2 and Figure 5 It can be seen that the gas phase capillary column of Example 1 of the present application is capable of separating different components in the mixed refrigerant, the chromatogram baseline is straight and the chromatographic peak has no obvious tailing phenomenon, and the overall analysis time is short.

[0060] 3. The gas phase capillary column prepared in this example was subjected to the refrigerant separation performance test 3:

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

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

[0063] Vaporizer temperature: 150°C, FID detector temperature: 220°C, hydrogen flow rate 35 ml / min, air flow rate 350 ml / min, tail gas and column flow rate 35 ml / min combined; column oven temperature 100°C; column flow rate 5 ml / min, split ratio 7:1;

[0064] The samples are: R415b refrigerant, R407c refrigerant is a mixed refrigerant composed of R32 and R152a;

[0065] Injection volume: 20 μL.

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

[0067] Table 3 Test results of R407c refrigerant separation performance of the gas phase capillary column prepared in Example 1

[0068] Retention time Component name Symmetry Factor Half-peak width Theoretical plates Separation 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 It can be seen that the gas phase capillary column of Example 1 of the present application is capable of separating different components in the mixed refrigerant, the chromatogram baseline is straight and the chromatographic peak has no obvious tailing phenomenon, and the overall analysis time is short.

[0070] Comparative Example

[0071] Comparative Example 1:

[0072] The method for preparing a gas phase capillary column is as follows:

[0073] S1: The same steps as in Example 1;

[0074] S2: The same steps as in Example 1;

[0075] No S3 step.

[0076] The prepared gas phase capillary column was scanned by SEM, and the results were as follows: Figure 7 As shown, from Figure 7 It can be seen that the thickness uniformity of the coating 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 separation performance of twelve refrigerants:

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

[0079] 2) The results are as follows Figure 8 and as shown in Table 4;

[0080] Table 4 Comparative Example 1 prepared gas phase capillary column for twelve refrigerant separation performance test results

[0081]

[0082]

[0083] From Table 4 and Figure 8 It can be seen that a mixed peak appeared, that is, the separation failed. The gas phase capillary column prepared in this comparative example could not be accurately qualitatively and quantitatively determined, which greatly affected the accuracy of the test results.

[0084] Comparative Example 2:

[0085] The SEM scan of the commercially available Plot Q gas phase capillary column (Agient HP-PLOT-Q) was performed, and the results were as follows: Figure 9 and Figure 10 As shown in the figure, it can be seen that the coating thickness on the inner wall of the gas phase capillary column is uneven, the adsorbent on 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, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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. A method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column, characterized in that: The following steps are involved: 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 it is neutral; place the capillary column in a constant temperature drying oven, continuously pass inert gas, dry it, and set aside; S2: Aluminum nitrate nonahydrate, fumaric acid, and sodium hydroxide are dissolved in deionized water to obtain a first reaction solution, the first reaction solution is injected into the capillary column pretreated in S1, both ends of the capillary column are sealed, and the reaction is carried out at a constant temperature of 100-120° C. for 20-24 hours. After the reaction, the capillary column is rinsed with deionized water; then, the column is aged at 250° C. for 4-8 hours under inert gas protection, and cooled to room temperature to form a seed layer in the capillary column; S3: Aluminum nitrate nonahydrate, ferric chloride, fumaric acid and sodium hydroxide are dissolved in deionized water to obtain a second reaction solution, and the second reaction solution is injected into the capillary column containing the seed layer prepared in S2. Both ends of the capillary column are sealed, and the reaction is carried out at 90-100°C for 10-12 hours. After the reaction is completed, the capillary column is rinsed with deionized water, and then aged at 200°C for 12-20 hours under inert gas protection to obtain the iron ion-doped aluminum-based MOF gas phase capillary column.

2. The method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column according to claim 1, characterized in that: In S2, the mass ratio of the aluminum nitrate nonahydrate to fumaric acid and sodium hydroxide is 0.225 1:0.07:0.

07.

3. The method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column 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 method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column according to claim 1, characterized in that: In S1, the drying temperature is 100-120°C and the drying time is 3-4 hours.

5. The method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column according to claim 1, characterized in that: Before the first reaction liquid and the second reaction liquid are injected into the capillary column, ultrasonic dissolution treatment is performed.

6. The method for preparing an iron ion-doped aluminum-based MOF gas phase capillary column according to claim 1, characterized in that: The inert gas used in S1, S2 and S3 is high-purity nitrogen.

7. An iron ion-doped aluminum-based MOF gas-phase capillary column prepared by the method for preparing an iron ion-doped aluminum-based MOF gas-phase capillary column according to claim 1.

8. Use of the iron ion-doped aluminum-based MOF gas phase capillary column according to claim 7 in separating fluorine-containing refrigerants.

9. Use of an iron ion-doped aluminum-based MOF gas phase capillary column in separating fluorine-containing refrigerants according to claim 8, characterized in that: The fluorine-containing refrigerants include difluoromethane, 1,1,1-trifluoroethane, difluorochloromethane, 1,1-difluoroethane, pentafluoroethane, 1,1,2,3,3,3-hexafluoropropylene, 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, 1,1,1,3,3,3 The analytical detection conditions for separation of 3-hexafluoropropane are as follows: using a hydrogen flame ionization detector, a hydrogen flow rate of 35-45 ml / min, an air flow rate of 350-450 ml / min, and a total tail blow and column flow rate of 35-45 ml / min; the initial column box temperature is 40°C; the heating rate is 10°C / min, the end point temperature is 150°C, and it is maintained for 10 minutes; the chromatographic column split ratio is 7:1, and the column flow rate is 5-15 ml / min.

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