Modified polymer porous microspheres and preparation method and application thereof

Abstract

The present invention belongs to the field of analytical chemistry and relates to a modified polymer porous microsphere, its preparation method, and application. The modified polymer porous microsphere is prepared by suspension polymerization of styrene, divinylbenzene, and acrylonitrile, followed by surface modification by amination of the phenyl rings. The preparation process is simple and environmentally friendly, with readily available raw materials and low cost. A chromatographic column loaded with the modified polymer porous microsphere can effectively separate helium from hydrogen, while ensuring that the completely separated helium meets trace detection requirements at the ppm level, thereby ensuring the long-term operation of PEMFC.

Description

Technical Field

[0001] The present invention belongs to the field of analytical chemistry, and more specifically, relates to a modified polymer porous microsphere and a preparation method and application thereof. Background Art

[0002] As an efficient, clean, low-carbon, and environmentally friendly secondary energy source, hydrogen is widely used in the new energy vehicle industry and is an ideal solution for replacing petroleum fuels. Hydrogen fuel cell vehicles (FCVs) utilize proton exchange membrane fuel cells (PEMFCs). These fuels convert chemical energy into electricity through a catalyst-driven reaction between hydrogen and oxygen, with water as the final product. This results in zero-emission, pollution-free, and environmentally friendly new energy vehicles. The quality of hydrogen, as a fuel, directly determines the performance and lifespan of fuel cells. Currently, hydrogen produced from fossil fuels is a key source of hydrogen. However, the production process inevitably contains helium impurities, a major factor affecting fuel cell durability. Therefore, unlike refinery hydrogen, FCV hydrogen requires not only purity requirements but also the control of critical trace impurities, which can severely impact the efficiency and lifespan of the cells.

[0003] Analysis of impurity components in PEMFC hydrogen is typically performed at trace levels below 1 part per million (ppm). Trace amounts of helium in hydrogen can be detected using a thermal conductivity detector (TCD), whose sensitivity meets the requirements for detecting trace helium at the ppm level. However, the boiling points of hydrogen at atmospheric pressure are -252.77°C, and helium at atmospheric pressure is -268.93°C. These ultra-low-boiling-point compounds are virtually impossible to separate using boiling point analysis on conventional chromatographic columns. Separation requires the use of weak bonding and other chemical properties. If the helium in hydrogen cannot be completely separated on a chromatographic column, it will be difficult to meet the requirements for ppm-level trace detection. Therefore, there is an urgent need to develop a gas chromatography column that can effectively separate hydrogen and helium, so that the completely separated helium can meet the requirements for ppm-level trace detection. Summary of the Invention

[0004] The purpose of the present invention is to provide a modified polymer porous microsphere and its preparation method and application, so as to achieve effective separation of helium from hydrogen, and at the same time make the completely separated helium meet the trace detection requirements of ppm level, thereby ensuring the long-term operation of PEMFC.

[0005] In order to achieve the above object, the first aspect of the present invention provides a modified polymer porous microsphere. The modified polymer porous microsphere is prepared by suspension polymerization of styrene, divinylbenzene and acrylonitrile, followed by amino modification.

[0006] According to the present invention, preferably, the specific surface area of ​​the modified polymer porous microspheres is 300 to 400 m 2 / g, and the pore diameter of the modified polymer porous microspheres is 2 to 10 nm.

[0007] A second aspect of the present invention provides a method for preparing the modified polymer porous microspheres, the method comprising:

[0008] 1) mixing styrene, divinylbenzene, and acrylonitrile that have been optionally pretreated with an initiator and a porogen and performing suspension polymerization to obtain styrene-divinylbenzene-acrylonitrile copolymer porous microspheres;

[0009] 2) The polymer porous microspheres obtained in step 1) are sequentially dried, nitrated, and aminated to obtain the modified polymer porous microspheres.

[0010] In the above step 1), the purity of the styrene, divinylbenzene and acrylonitrile used is greater than 90%. The pretreatment of styrene, divinylbenzene and acrylonitrile is generally to remove the polymerization inhibitor in styrene, divinylbenzene and acrylonitrile.

[0011] According to the present invention, preferably, the mass ratio of styrene, divinylbenzene, acrylonitrile, initiator and porogen is 30-35:25-30:10-20:1-3:1-3; the initiator is a peroxide and / or an azo compound; the porogen is at least one of toluene, paraffin, ethyl acetate, gasoline, kerosene, n-dodecanol and n-octadecanol; the reaction temperature of the suspension polymerization is 60-90° C., the reaction time is 6-9 hours, and the reaction method is ultrasonic dispersion gradient heating stirring.

[0012] More preferably, the styrene is a comonomer styrene; the divinylbenzene is para-divinylbenzene; and the initiator is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and tert-butyl hydroperoxide. The use of para-divinylbenzene can help improve the regularity of the copolymerized polymer beads.

[0013] In the above step 2), preferably, the drying is carried out at a temperature of 100-110°C for 4-6 hours; the nitration treatment is carried out for 4-5 hours at a temperature of 60-70°C; and the amination reduction treatment is carried out for 2-3 hours at a temperature of 60-70°C.

[0014] The nitration treatment is to disperse the dried polymer porous microspheres obtained in step 1) into a mixed acid of nitric acid and sulfuric acid, wherein the mass ratio of nitric acid to sulfuric acid is 2:1 to 5:1, and the mass ratio of the mixed acid to the polymer microspheres is 2:1 to 5:1.

[0015] The amination reduction is to add sodium sulfite to the polymer porous microspheres that have completed the nitration treatment to modify the phenyl ring of the styrene-divinylbenzene-acrylonitrile copolymer polymer porous microspheres by amination, wherein the mass ratio of sodium sulfite to the polymer microspheres is 1:2 to 1:10.

[0016] A third aspect of the present invention provides a chromatographic column for separating helium from hydrogen, the chromatographic column comprising a chromatographic column tube and the modified polymer porous microspheres loaded in the chromatographic column tube.

[0017] The shape of the chromatographic column tube in the present invention has no particular requirements and can be U-shaped or spiral-shaped. The material can also be glass, stainless steel, or plastic. The inner diameter of the chromatographic column tube is 1.2 to 4 mm and the length is 0.5 to 3 m. Preferably, the packing density of the chromatographic column is 0.2 to 0.5 g / mL, and the mesh size of the modified polymer porous microspheres is 20 to 100 mesh.

[0018] The separation mechanism of the chromatographic column is primarily based on the interaction between the molecular pores within the modified polymer porous microspheres and the gas analysis adsorption. As hydrogen and helium molecules pass through the pores, helium, being inert and unresponsive to the chemicals within, is the first to exit through the pores. Hydrogen, however, due to its acidic nature, undergoes chemical affinity adsorption with the amino-alkaline molecules of the modified chemicals within the pores, increasing the hydrogen's residence time within the pores and achieving effective separation.

[0019] A fourth aspect of the present invention provides use of the above-mentioned chromatographic column in gas chromatography detection.

[0020] According to the present invention, preferably, the operating conditions of the chromatographic column are: the carrier gas is nitrogen, the carrier gas flow rate is 5-30 mL / min, the carrier gas pressure is 0.3-0.6 MPa, the quantitative loop is 0.2-3 mL, and the split ratio is 1:10-1:50.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The raw materials for preparing the modified polymer porous microspheres disclosed in the present invention are simple and easily available, and the cost is low. The preparation process is simple and environmentally friendly, and the prepared modified polymer porous microspheres have high consistency.

[0023] 2) The chromatographic column filled with modified polymer porous microspheres disclosed in the present invention can effectively separate trace helium from hydrogen used in PEMFC, and the analysis time is short. The entire analysis process can be completed within 3 minutes, and the minimum detection limit is as low as 10 ppm, effectively ensuring the long-term operation of PEMFC.

[0024] 3) The chromatographic column filled with modified polymer porous microspheres disclosed in the present invention is suitable for use in various gas chromatographs and has a wide range of applications.

[0025] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0027] Figure 1 A schematic diagram of the synthesis of modified polymer porous microspheres in Example 1 of the present invention is shown.

[0028] Figure 2 The figure shows the structure of the U-shaped chromatographic column in Example 1 of the present invention.

[0029] Figure 3 The chromatogram of separating helium from hydrogen in Example 1 of the present invention is shown.

[0030] Figure 4 The chromatogram of separating helium from hydrogen in Comparative Example 1 of the present invention is shown.

[0031] Figure 5 The chromatogram of separating helium from hydrogen in Comparative Example 2 of the present invention is shown.

[0032] Figure 6 The chromatogram of separating helium from hydrogen in Comparative Example 3 of the present invention is shown.

[0033] Description of reference numerals:

[0034] 1. U-shaped chromatographic column tube; 2. Modified polymer porous microspheres. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0036] Example 1

[0037] 1) Preparation of toluene solution

[0038] 6 g of comonomer styrene, 5 g of divinylbenzene and 2 g of acrylonitrile from which the polymerization inhibitor was removed were mixed with 0.2 g of benzoyl peroxide and 0.2 g of n-octadecyl alcohol in 40 mL of toluene, and nitrogen was passed through the mixture to remove oxygen, thereby obtaining a toluene solution.

[0039] 2) Preparation of mixed solution

[0040] 0.3 g of hexadecyltrimethylammonium bromide was mixed with an appropriate amount of distilled water, and after deoxygenation through nitrogen, it was mixed with the toluene solution obtained in step 1), and ultrasonically dispersed for 30 minutes to obtain a mixed solution.

[0041] 3) Preparation of polymer porous microspheres

[0042] The mixed solution was transferred to a three-necked flask and purged with nitrogen for 10 minutes to remove oxygen. Heating was then started. The temperature was raised to 60°C with a stirring speed of 1040 r / min, followed by a reaction for 60 minutes. The temperature was then raised to 80-85°C for a reaction of 90 minutes. The temperature was then raised to 85-90°C for a reaction of 4 hours before stopping heating. After the solution cooled to room temperature, it was steam distilled to remove the n-octadecyl alcohol. After filtration, the filter cake was placed in a fat extractor and extracted with toluene to remove the chain polymer. The remaining solid was dried and sieved to obtain solid polymer porous microspheres with a mesh size of 20-100.

[0043] 4) Modification of polymer porous microspheres

[0044] Ultrasonic dispersion of 10g of the solid polymer porous microspheres obtained in step 3) is carried out in 100mL of a mixed acid of nitric acid and sulfuric acid, the mass ratio of nitric acid to sulfuric acid being 2:1, and a circulating water pump is used to continuously evacuate and release the vacuum, so that the external pressure varies within the range of 0.08 to 0.1Mpa, and the nitration reaction is carried out at a temperature of 60°C for 4h. Then 1g of hydrated sodium sulfite is added and stirred continuously, and the amino reduction is carried out at 60°C for 2h. When the mixed solution is cooled to room temperature, it is washed with acetone repeatedly and centrifuged, and the separated product is finally dried to obtain amino-modified polymer porous microspheres. Screen the modified polymer porous microspheres with a mesh size of 20 to 100 for use. The synthesis process of the modified polymer porous microspheres is as follows: Figure 1 As shown in the figure, the pore size of the modified polymer porous microspheres is 2-10 nm and the specific surface area is 300-400 m 2 / g.

[0045] 5) Preparation of chromatographic columns

[0046] A U-shaped stainless steel chromatographic column with an inner diameter of 2mm and a length of 3m was selected. The column was first rinsed with clean water for 20 minutes. 0.1mol / L sodium hydroxide was then poured into the column and allowed to soak for 2 hours. The column was then rinsed with clean water until the eluate was neutral. Ethanol was then injected into the column using the same method and allowed to soak for 2 hours. The column was then rinsed with distilled water and then ethanol. Finally, the column was dried in an oven.

[0047] Place the funnel at one end of the dried U-shaped chromatographic column tube 1, and fill the modified polymer porous microspheres 2 prepared in step 4) in portions through the funnel while continuously tapping the column wall until it is filled to 1.5 cm from the column mouth. Remove the funnel and plug the port with silanized glass wool wrapped in a thin layer of cotton. Finally, connect this end of the U-shaped chromatographic column tube 1 to the vacuum pump through a rubber tube.

[0048] Place the funnel at the other end of the U-shaped chromatographic column tube 1, turn on the vacuum pump, and continue to fill the modified polymer porous microspheres 2 prepared in step 4) into the U-shaped chromatographic column tube 1 through the funnel, and keep tapping the column wall to make it fill evenly and tightly until it is filled to 1.5 cm from the column mouth. Remove the funnel and insert silanized glass wool wrapped with a thin layer of cotton at the port, and press the glass wool to prevent the filling in the column from moving. The U-shaped chromatographic column tube 1 filled with modified polymer porous microspheres 2 is as shown in FIG. Figure 2 As shown, the packing density is 0.2 to 0.5 g / mL.

[0049] Connect the column inlet to the vaporizer, leaving the outlet unconnected to a detector, and introduce N2 carrier gas at a flow rate of 15 mL / min. Raise the temperature to 250°C in stages and age at 250°C for 24 h.

[0050] 6) Application of chromatographic columns

[0051] An Agilent 8890B gas chromatograph with a thermal conductivity TCD detector was used, and the chromatographic separation system was controlled and recorded by a CDS workstation.

[0052] The operating conditions of the chromatograph were as follows: a constant temperature of 70° C., a constant flow rate of 15 mL / min, an injection volume of 0.25 mL, a split ratio of 1:15, a carrier gas of 0.5 MPa nitrogen (99.9999%), and a quantitative loop of 0.25 mL.

[0053] The hydrogen from the hydrogen storage tank for PEMFC enters the GC-TCD through the gas valve for separation and detection. The resulting chromatogram is as follows: Figure 3 shown.

[0054] Comparative Example 1

[0055] The difference from Example 1 is that a polyethylene glycol polymer porous microsphere chromatographic column is used, and the chromatogram obtained is as follows Figure 4 shown.

[0056] Comparative Example 2

[0057] The difference from Example 1 is that the prepared polymer porous microspheres were not modified by amino, and the chromatogram obtained is as follows: Figure 5 shown.

[0058] Comparative Example 3

[0059] The difference from Example 1 is that a polymethylsiloxane polymer porous microsphere chromatographic column is used, and the chromatogram obtained is as follows: Figure 6 shown.

[0060] It can be seen from Example 1 and Comparative Examples 1 to 3 that the modified polymer porous microsphere chromatographic column can effectively separate ppm-level helium from hydrogen, wherein the retention time of hydrogen is 2.272 min, the retention time of helium is 1.782 min, and the separation degree of hydrogen and helium is greater than 1.5, achieving complete baseline separation.

[0061] However, chromatographic columns using other polymer porous microspheres cannot effectively separate ppm-level helium from hydrogen. Among them, the retention time of hydrogen using polyethylene glycol polymer porous microsphere chromatographic columns is 1.935 min, and the retention time of helium is 1.583 min. The separation degree of hydrogen and helium is less than 1.5, and baseline separation cannot be achieved. The retention time of hydrogen using styrene-divinylbenzene-acrylonitrile copolymer polymer porous microspheres that have not been amino-modified is 2.414 min, and the retention time of helium is 2.305 min. The separation degree of hydrogen and helium is less than 1.5, and baseline separation cannot be achieved. The retention time of hydrogen using polymethylsiloxane polymer porous microsphere chromatographic columns is 0.977 min, and the retention time of helium is 0.869 min. The separation degree of hydrogen and helium is less than 1.5, and baseline separation cannot be achieved.

[0062] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A chromatographic column for separating helium from hydrogen, characterized in that: The chromatographic column comprises a chromatographic column tube and modified polymer porous microspheres filled in the chromatographic column tube; the specific surface area of ​​the modified polymer porous microspheres is 300-400 m 2 / g, pore size is 2~10nm, The preparation method of the modified polymer porous microspheres comprises: 1) mixing optionally pretreated styrene, divinylbenzene, and acrylonitrile with an initiator and a porogen and subjecting the mixture to suspension polymerization to obtain styrene-divinylbenzene-acrylonitrile copolymer porous microspheres; wherein the mass ratio of styrene, divinylbenzene, acrylonitrile, initiator, and porogen is 30-35:25-30:10-20:1-3:1-3; 2) sequentially drying, nitration, and amination reduction the polymer porous microspheres obtained in step 1) to obtain the modified polymer porous microspheres; The nitration comprises dispersing the dried polymer porous microspheres obtained in step 1) into a mixed acid of nitric acid and sulfuric acid, wherein the mass ratio of the nitric acid to the sulfuric acid is 2:1 to 5:1, and the mass ratio of the mixed acid to the polymer porous microspheres is 2:1 to 5:1; The amination comprises mixing sodium sulfite with nitrated styrene-divinylbenzene-acrylonitrile copolymerized polymer porous microspheres, wherein the mass ratio of the sodium sulfite to the styrene-divinylbenzene-acrylonitrile copolymerized polymer porous microspheres is 1:2-1:

10.

2. The chromatographic column according to claim 1, characterized in that In step 1), The pretreatment is to remove the polymerization inhibitors in the styrene, divinylbenzene and acrylonitrile respectively; The initiator is a peroxide and / or an azo compound; The porogen is at least one of toluene, paraffin, ethyl acetate, gasoline, kerosene, n-dodecyl alcohol and n-octadecyl alcohol; The reaction temperature of the suspension polymerization is 60-90° C., the reaction time is 6-9 hours, and the reaction method is ultrasonic dispersion gradient heating and stirring.

3. The chromatographic column according to claim 2, characterized in that The divinylbenzene is para-divinylbenzene; The initiator is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide and tert-butyl hydroperoxide.

4. The chromatographic column according to claim 1, characterized in that In step 2), The drying step is to dry the product at a temperature of 100-110° C. for 4-6 hours; The nitration treatment time is 4-5 hours and the temperature is 60-70°C; The amination reduction is carried out for 2 to 3 hours at a temperature of 60 to 70°C.

5. The chromatographic column according to claim 1, characterized in that The packing density of the chromatographic column is 0.2-0.5 g / mL, and the mesh number of the modified polymer porous microspheres is 20-100 mesh.

6. Use of the chromatographic column according to any one of claims 1 to 5 in gas chromatography detection.

7. The use according to claim 6, characterized in that The operating conditions of the chromatographic column are as follows: the carrier gas is nitrogen, the carrier gas flow rate is 5-30 mL / min, the carrier gas pressure is 0.3-0.6 MPa, the quantitative loop is 0.2-3 mL, and the split ratio is 1:10-1:50.

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