Modified porous microspheres, their preparation methods, separation devices, and applications

Abstract

This invention relates to the field of gas separation, and discloses modified porous microspheres, their preparation methods, separation devices, and their applications. The modified porous microspheres comprise a styrene-divinylbenzene-acrylonitrile copolymer with a surface modified by molybdenum oxide oxidation of the benzene ring. The modified porous microspheres of this invention have a simple composition and are easily obtained. Gas chromatography packed columns prepared using the modified porous microspheres of this invention can effectively separate trace amounts of NO and N₂O from polymer-grade propylene feedstock. The analysis process is completed within 15 minutes, and qualitative and quantitative analysis of the target analytes can be performed simultaneously, with a limit of detection of 100 ppb for quantitative analysis.

Description

Technical Field

[0001] This invention relates to the field of gas separation, specifically to a modified porous microsphere, a method for preparing the modified porous microsphere, the modified porous microsphere obtained by the method, a separation device, and the application of the modified porous microsphere or the separation device in separating NO and N2O from propylene feedstock or in determining the content of NO and N2O in propylene feedstock. Background Technology

[0002] Propylene is a basic organic feedstock in the petrochemical industry. Oil-based propylene uses naphtha as a feedstock to produce propylene monomers through steam cracking and catalytic cracking; coal-based propylene uses coal as a feedstock to produce propylene monomers through Fischer-Tropsch synthesis; and gas-based propylene uses propane as a feedstock to produce propylene monomers through dehydrogenation. The diversification of upstream feedstocks for propylene also makes the impurities in propylene monomers more complex, with NO and N2O being more prevalent in oil-based and gas-based propylene.

[0003] During steam cracking and dehydrogenation of crude oil and propane, nitrogen (N) reacts with oxygen (O2) in the air to produce NO and N2O, which enter the propylene monomer. The Mg / Ti active sites of the Zn catalyst in polypropylene are extremely sensitive to NO and N2O, easily leading to poisoning and decreased activity. When the NO and N2O content exceeds 100 ppb, the activity of the Zn catalyst drops to 80%, and when it exceeds 1 ppm, the activity is only 50%. Therefore, the process of producing propylene monomer from crude oil and propane must strictly control the NO and N2O content in propylene to reduce its toxicity to downstream polypropylene catalysts.

[0004] Trace amounts of NO and N₂O in propylene can be detected using a nitrogen chemiluminescence detector (NCD) or a mass spectrometer (MSD). The sensitivity of both detectors is sufficient for detecting NO and N₂O up to 100 ppb. Propylene has a critical temperature and pressure of approximately 92℃ and 4.6 MPa, and is generally gaseous at room temperature. NO has a boiling point of -151℃ at normal pressure, and N₂O has a boiling point of -88℃ at normal pressure. Low-boiling-point compounds are difficult to separate on general-purpose chromatographic columns due to their different boiling points; separation based on polarity and other chemical properties is necessary. If NO and N₂O cannot be completely separated on a chromatographic column, the requirement for detecting trace amounts down to 100 ppb cannot be met. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that currently available commercially available chromatographic columns cannot effectively separate NO and N2O in propylene, thus affecting the detection limit. This invention provides a modified porous microsphere, its preparation method, separation device, and their applications. The gas-phase packed chromatographic column produced by this modified porous microsphere can effectively separate NO and N2O.

[0006] To achieve the above objectives, a first aspect of the present invention provides a modified porous microsphere comprising a styrene-divinylbenzene-acrylonitrile copolymer with a surface modified by molybdenum oxide oxidation of benzene rings.

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

[0008] (1) Styrene, divinylbenzene and acrylonitrile are mixed with an initiator and a porogen to obtain a monomer solution;

[0009] (2) The monomer solution was mixed with a dispersed phase containing a dispersant and subjected to suspension polymerization to obtain porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer;

[0010] (3) The porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer were subjected to molybdenum acid treatment to obtain the modified porous microspheres.

[0011] A third aspect of the present invention provides modified porous microspheres prepared by the method described above.

[0012] A fourth aspect of the present invention provides a separation device, wherein the separation device is filled with the modified porous microspheres as described above.

[0013] The fifth aspect of the present invention provides the application of the modified porous microspheres as described above or the separation device as described above in separating NO and N2O from propylene feedstock or in determining the content of NO and N2O in propylene feedstock.

[0014] The modified porous microspheres of this invention have simple composition, are easy to obtain, have low cost, are simple to prepare, have no environmental pollution, and produce separation devices (such as chromatographic columns) with high consistency.

[0015] The gas chromatography packed column prepared using the modified porous microspheres described in this invention can effectively separate trace amounts of NO and N2O from polymer-grade propylene feedstock. The analysis process is completed within 15 minutes, and it can simultaneously perform qualitative and quantitative analysis of the target analytes, with a limit of detection of 100 ppb for quantitative analysis. Polypropylene producers can use this chromatographic column to detect and control the content of NO and N2O in propylene feedstock, thereby ensuring the long-term operation of polyolefin catalysts. This is of great significance for reducing costs and increasing efficiency in polyolefin petrochemical enterprises and improving the quality of polyolefin resin products. Attached Figure Description

[0016] Figure 1 A schematic diagram of the structure of the modified porous microspheres described in this invention is shown.

[0017] Figure 2 The GC-MS chromatogram of NO and N2O separated from propylene in Example 1 is shown.

[0018] Figure 3 The GC-NCD chromatogram of NO and N2O separated from propylene in Example 2 is shown.

[0019] Figure 4 The GC-MS chromatogram of NO and N2O separated from propylene in Example 3 is shown.

[0020] Figure 5 The GC-MS chromatograms of NO and N2O separated from propylene in Comparative Example 1 are shown.

[0021] Figure 6 The GC-MS chromatograms of NO and N2O separated from propylene in Comparative Example 2 are shown.

[0022] Figure 7 The GC-NCD chromatograms of NO and N2O separated from propylene in Comparative Example 3 are shown. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of this invention provides a modified porous microsphere comprising a styrene-divinylbenzene-acrylonitrile copolymer with a surface modified by molybdenum oxide oxidation of benzene rings. Its structural schematic diagram is shown below. Figure 1 As shown.

[0025] Preferably, in the styrene-divinylbenzene-acrylonitrile copolymer, the weight ratio of styrene units, divinylbenzene units, and acrylonitrile units is (25-45, for example, 25, 30, 35, 40, 45, or any range between any two values): (20-40, for example, 20, 25, 30, 35, 40, or any range between any two values): (10-30, for example, 10, 15, 20, 25, 30, or any range between any two values).

[0026] Preferably, the modified porous microspheres contain 92-98 wt% styrene-divinylbenzene-acrylonitrile copolymer, for example, 92, 94, 96, 98 wt% or any range between any two values, preferably 94-96 wt%; and 2-8 wt% molybdate groups, for example, 2, 4, 6, 8 wt% or any range between any two values, preferably 4-6 wt%.

[0027] Preferably, the number average molecular weight of the styrene-divinylbenzene-acrylonitrile copolymer is 10,000-60,000 g / mol, for example, it can be 10,000, 20,000, 30,000, 40,000, 50,000, 60,000 g / mol and any range between any two values.

[0028] Preferably, the divinylbenzene unit is a p-divinylbenzene unit and / or a m-divinylbenzene unit.

[0029] Preferably, the mass ratio of the elements on the surface of the modified porous microspheres is C (46-74, for example, 46, 50, 54, 58, 62, 66, 70, 74, or any range between any two values): O (12-18, for example, 12, 13, 14, 15, 16, 17, 18, or any range between any two values): Mo (24-36, for example, 24, 26, 28, 30, 32, 34, 36, or any range between any two values). The inventors discovered that the product performs better when molybdenum acid forms a monolayer dispersion on the surface of the modified porous microspheres. X-ray fluorescence and X-ray diffraction were used to determine the content of each element; XRF detected the elemental content, and XRD detected molybdenum acid crystal peaks, indicating multilayer formation; no peaks were detected, indicating a monolayer.

[0030] Preferably, the modified porous microspheres have a particle size of 150-1000 μm.

[0031] Preferably, the pore size of the modified porous microspheres is 20-100 nm.

[0032] Preferably, the modified porous microspheres have a BET specific surface area of ​​30-40 m². 2 / g.

[0033] The above parameters can be determined using the BET method.

[0034] Preferably, the column packing density of the modified porous microspheres is 0.2-0.5 g / mL. The column packing density can be determined by weighing and measuring the packed column volume.

[0035] A second aspect of the present invention provides a method for preparing modified porous microspheres, the method comprising:

[0036] (1) Styrene, divinylbenzene and acrylonitrile are mixed with an initiator and a porogen to obtain a monomer solution;

[0037] (2) The monomer solution was mixed with a dispersed phase containing a dispersant and subjected to suspension polymerization to obtain porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer;

[0038] (3) The porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer were subjected to molybdenum acid treatment to obtain the modified porous microspheres.

[0039] In this invention, styrene, divinylbenzene and acrylonitrile can all be commercially available and their purity can be higher than 90 wt%. Generally, before polymerization, the monomers need to be treated to remove polymerization inhibitors. The method for removing polymerization inhibitors is a conventional method in the art and will not be described in detail here.

[0040] Preferably, the divinylbenzene is p-divinylbenzene and / or m-divinylbenzene.

[0041] Preferably, in step (1), the initiator is a peroxide and / or an azo compound, preferably selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide and tert-butyl hydroperoxide.

[0042] Preferably, the pore-forming agent is selected from one or more of ethyl acetate, paraffin, gasoline, kerosene, and n-C12-C18 alkyl alcohols (such as n-dodecyl alcohol, n-tridecyl alcohol, n-hexadecyl alcohol, n-octadecyl alcohol, etc.).

[0043] Preferably, the ratio of styrene, divinylbenzene, acrylonitrile, initiator, and porogen by weight is (25-45, for example, 25, 30, 35, 40, 45, and any range between any two values): (20-40, for example, 20, 25, 30, 35, 40, and any range between any two values): (10-30, for example, 10, 15, 20, 25, 30, and any range between any two values): (0.5-3, for example, 0.5, 1, 1.5, 2, 2.5, 3, and any range between any two values): (0.5-3, for example, 0.5, 1, 1.5, 2, 2.5, 3, and any range between any two values).

[0044] Preferably, the solvent of the monomer solution is selected from at least one of toluene, p-xylene, and ethylbenzene.

[0045] Preferably, the amount of solvent used in the monomer solution is 3-20 parts by weight relative to the total weight of 1 part by weight of styrene, divinylbenzene and acrylonitrile, for example, it can be 3, 5, 10, 15, 20 parts by weight and any range between any two values.

[0046] Preferably, in step (2), the dispersant is preferably one or more of C12-C22 alkyltriC1-C6 alkylammonium halide, preferably dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltriethylammonium chloride, dodecyltriethylammonium bromide, tetradecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, tetradecyltriethylammonium chloride, tetradecyltriethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltriethylammonium chloride, hexadecyltriethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, octadecyltriethylammonium chloride and octadecyltriethylammonium bromide, more preferably one or more of dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltriethylammonium chloride, dodecyltriethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltriethylammonium chloride and hexadecyltriethylammonium bromide.

[0047] Preferably, the dispersed phase is an aqueous phase.

[0048] Preferably, the amount of water used is 3-20 parts by weight relative to the total weight of 1 part by weight of styrene, divinylbenzene and acrylonitrile, for example, it can be 3, 5, 10, 15, 20 parts by weight and any range between any two values, and the amount of dispersant used is 0.01-0.05 parts by weight, for example, it can be 0.01, 0.03, 0.05 parts by weight and any range between any two values.

[0049] The obtained modified porous microspheres can be sieved to obtain porous microspheres with the target particle size. The obtained porous microspheres can also be dried; the drying conditions are not particularly limited, as long as moisture is removed, for example, drying at 100-110℃ for 4-6 hours. The obtained porous microspheres can then undergo molybdenum acidification treatment, that is, molybdenum acidification modification of the benzene rings in the porous microspheres.

[0050] Preferably, in step (2), the conditions for suspension polymerization include: a temperature of 50-95°C and a time of 5-10 hours.

[0051] The suspension polymerization process preferably incorporates ultrasonic dispersion and stirring. The stirring conditions preferably include a rotation speed of 300-1500 rpm.

[0052] The suspension polymerization process preferably involves gradient heating. Specifically, the suspension polymerization is preferably carried out at 55-65°C for 0.5-1.5 hours, followed by a reaction at 80-90°C for 1-2 hours, and then further heated to 85-95°C for 3-5 hours.

[0053] Preferably, in step (3), the molybdenum acidification treatment includes: contacting the porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer with molybdate and phosphorus pentoxide in a mixed solution of sulfuric acid and nitric acid, and performing molybdenum acidification treatment to obtain the modified porous microspheres.

[0054] In this process, porous microspheres can be dispersed (e.g., by ultrasound) into a mixed solution of sulfuric acid and nitric acid, and then molybdate and phosphorus pentoxide are added under stirring conditions.

[0055] Preferably, in the mixed solution of sulfuric acid and nitric acid, the concentration of sulfate is 15-40 wt%, for example, it can be 15, 20, 25, 30, 35, 40 wt% or any range between any two values, more preferably 20-30 wt%, and the concentration of nitrate is 30-65 wt%, for example, it can be 30, 35, 40, 45, 50, 55, 60, 65 wt% or any range between any two values, more preferably 40-50 wt%.

[0056] Preferably, the weight ratio of the mixed solution of sulfuric acid and nitric acid to the porous microspheres is 5-15:1, for example, it can be 5:1, 7:1, 9:1, 11:1, 13:1, 15:1, or any range between any two values.

[0057] Preferably, compared to 100 parts by weight of porous microspheres, the amount of molybdate used is 1-20 parts by weight, for example, it can be 1, 2, 4, 8, 10, 12, 14, 16, 18, 20 parts by weight or any range between any two values, and the amount of phosphorus pentoxide used is 1-20 parts by weight, for example, it can be 1, 2, 4, 8, 10, 12, 14, 16, 18, 20 parts by weight or any range between any two values.

[0058] Preferably, the molybdate is sodium molybdate and / or potassium molybdate.

[0059] Preferably, the conditions for the molybdenum acid treatment include: a vacuum degree of less than 0.1 MPa (e.g., 0.01 MPa, 0.02 MPa, 0.04 MPa, 0.06 MPa, 0.08 MPa, 0.09 MPa, 0.095 MPa, 0.098 MPa, or any range between any two values), and a time of 6-12 hours (e.g., 6, 7, 8, 9, 10, 11, 12 hours, or any range between any two values). The molybdenum acid treatment can be carried out at 20-40°C.

[0060] The molybdenum acidification process generates heat. When the material temperature drops to room temperature, the resulting product can be repeatedly washed with ethanol and centrifuged. The final separated product is dried to obtain molybdenum acidified microsphere powder, which is the modified porous microsphere described in this invention. The obtained modified porous microsphere can also be sieved using a sieve with a certain mesh size (e.g., 20-100 mesh) to obtain modified porous microspheres with a specific particle size.

[0061] A third aspect of the present invention provides modified porous microspheres prepared by the method described above.

[0062] The parameters of the modified porous microspheres can be found in the first aspect, and will not be repeated here.

[0063] A fourth aspect of the present invention provides a separation device, wherein the separation device is filled with the modified porous microspheres as described above.

[0064] Preferably, the separation device is a chromatographic column.

[0065] Preferably, the column packing density of the modified porous microspheres is 0.2-0.5 g / mL.

[0066] The method for preparing the chromatographic column can be a conventional method in the art, and those skilled in the art can prepare the chromatographic column as needed.

[0067] For example, when choosing a chromatographic column, you can choose a glass tube, stainless steel tube, or plastic tube with a uniform inner diameter and appropriate length. For example, the inner diameter of a packed column can be 1.2-4 mm, the length can be 0.5-3 m, and the shape can be U-shaped or spiral.

[0068] Before use, the column tube can be rinsed directly with clean water for about 20 minutes. Then, dilute acid or dilute alkali (generally 0.05-0.2 mol / L nitric acid, hydrochloric acid, or sodium hydroxide) is poured into the column tube and allowed to soak for more than 2 hours. Then, it is rinsed with clean water until the eluent is neutral. Then, ethanol or acetone is injected in the same way and soaked for more than 2 hours. Then, it is rinsed with distilled water and ethanol in sequence and dried in an oven.

[0069] The volume of microspheres required for the chromatographic column is estimated based on V = Lπr. 2 , where r is the inner radius of the column (cm); L is the length of the column (cm); and V is the volume of the column (mL).

[0070] The column packing method is as follows: Connect a small funnel to the outlet of the washed and dried column, and gradually add the prepared microspheres into the column while gently tapping the column wall continuously until the column is filled to 1.5 cm from the inlet. Move the glass funnel to the column inlet, and plug the outlet end with a small wad of silanized glass wool, wrapped with a thin layer of cotton or two layers of gauze. Connect this to a vacuum pump via a rubber tube, turn on the vacuum pump, and continue to slowly add the prepared packing material through the funnel, gently tapping the column wall continuously to ensure uniform and tight packing. After packing, plug the inlet end with another small wad of silanized glass wool and press it down appropriately to prevent the packing material from shifting.

[0071] Before use, the obtained chromatographic column can be aged. The specific method is as follows: connect the column inlet to the vaporization chamber, do not connect the detector to the outlet end, introduce carrier gas (N2) at a flow rate of 15 mL / min, raise the temperature to 250℃ in stages, and age at this temperature for at least 24 hours.

[0072] The chromatographic column described in this invention can be connected to a gas chromatograph and the contents of NO and N2O can be determined using an MSD detector or an NCD detector. The control, recording, qualitative and quantitative analysis of the chromatographic separation system are completed by a chromatography workstation.

[0073] The fifth aspect of the present invention provides the application of the modified porous microspheres as described above or the separation device as described above in separating NO and N2O from propylene feedstock or in determining the content of NO and N2O in propylene feedstock.

[0074] The operating conditions of the chromatographic column may include: helium as the carrier gas, a carrier gas flow rate of 0.8-15 mL / min, a carrier gas pressure of 0.3-0.6 MPa, a quantitative loop of 0.2-3 mL, a split ratio of 1:1-1:10, and a column temperature of 40-100℃.

[0075] The present invention will be described in detail below through examples.

[0076] Unless otherwise specified, all reagents and materials used are commercially available.

[0077] In the following examples, the concentration of sulfuric acid in the mixed solution of nitric acid and sulfuric acid was 23.3 wt%, and the concentration of nitric acid was 46.7 wt%.

[0078] In the following examples, the polymer-grade propylene feedstock was taken from the feedstock storage tank of the polyolefin production unit, and the propylene feedstock was detected by chromatography via a gas valve.

[0079] Example 1

[0080] This embodiment illustrates the preparation method of the modified porous microspheres and chromatographic column described in this invention, as well as the method for determining the content of the analyte by gas chromatography.

[0081] 1. Preparation of porous microspheres

[0082] In 100 mL of p-xylene, 7 g of styrene, 6 g of m-divinylbenzene and 4 g of acrylonitrile (after the polymerization inhibitor was removed) were mixed with 0.2 g of benzoyl peroxide and 0.2 g of n-octadecyl alcohol, and nitrogen was passed through to remove oxygen, resulting in a monomer phase solution.

[0083] 0.3 g of hexadecyltrimethylammonium bromide was mixed with 100 ml of distilled water. After purging with nitrogen to remove oxygen, an aqueous solution was obtained. This aqueous solution was then mixed with the monomer solution and ultrasonically dispersed for 30 min. The mixture was transferred to a three-necked flask, purged with nitrogen for 10 min to remove oxygen, and then heated. The mixture was stirred at 1040 r / min, heated to 60 °C, and reacted for 60 min. The temperature was then increased to 85 °C and reacted for 90 min. Finally, the mixture was heated to 90 °C and reacted for 4 h, after which heating was stopped. After the material cooled to room temperature, steam distillation was performed to remove n-octadecyl alcohol. The filtered product was placed in a fat extractor and extracted with toluene to remove the chain polymers. The remaining solid was dried and then sieved to obtain 70-80 mesh porous microspheres.

[0084] 2. Modification of porous microspheres

[0085] 10g of the solid porous microspheres obtained in step 1 were ultrasonically dispersed in 100mL of a mixed solution of nitric acid and sulfuric acid. Then, 1g of sodium molybdate and 1g of phosphorus pentoxide were added and stirred continuously. A vacuum was continuously applied using a circulating water pump, and the molybdenum acidification reaction was carried out at 25℃ for 10h. When the mixed solution cooled to room temperature, the product was repeatedly washed with ethanol and centrifuged. The final separated product was dried to obtain the molybdenum acid-modified porous microspheres. Modified porous microspheres with a mesh size of 70-80 were selected for later use, resulting in modified porous microspheres with a pore size of 20-100nm and a specific surface area of ​​30-40m². 2 / g.

[0086] XRF and XRD analyses showed that the mass ratio of the elements on the surface of the modified porous microspheres was C 55:O 15:Mo 30, and no molybdate crystals were found, indicating that molybdate was dispersed in a monolayer on the surface of the modified porous microspheres.

[0087] 3. Preparation of Gas Chromatography Column

[0088] A U-shaped stainless steel chromatographic column with an inner diameter of 1.2 mm and a length of 2 m was selected. First, the column was rinsed with water for 20 minutes. Then, 0.1 mol / L sodium hydroxide was poured into the column and soaked for 2 hours. The column was then rinsed with water until the eluent was neutral. Ethanol was then injected into the column and soaked for 2 hours using the same method. The column was then rinsed sequentially with distilled water and ethanol. Finally, the column was dried in an oven.

[0089] Place the funnel at one end of the dried U-shaped chromatographic column and fill it with the modified porous microspheres prepared in step 2 in portions through the funnel while gently tapping the column wall continuously until it is filled to 1.5 cm from the column opening. Remove the funnel and insert glass wool wrapped in a thin layer of cotton into the opening. Finally, connect this end of the U-shaped chromatographic column to the vacuum pump through a rubber tube.

[0090] Place the funnel at the other end of the U-shaped chromatographic column. After turning on the vacuum pump, continue to fill the U-shaped chromatographic column with the prepared modified porous microspheres through the funnel. Gently tap the column wall continuously to ensure uniform and tight filling until the column is filled to 1.5 cm from the column opening. Remove the funnel and insert a thin layer of cotton-wrapped silanized glass wool into the opening. Press the glass wool firmly to prevent the packing material from moving. The packing density of the modified porous microspheres is 0.3 g / mL.

[0091] Connect the column inlet to the vaporization chamber, and initially leave the outlet unconnected to the detector. Introduce carrier gas N2 at a flow rate of 15 mL / min. Gradually increase the temperature to 250 °C and age the column at 250 °C for 24 h to obtain the gas chromatographic column.

[0092] 4. Application of chromatographic columns (GC-MS)

[0093] The Agilent 8890B(GC) gas chromatograph with a 5977B(MSD) detector was used. The control and recording of the chromatographic separation system were performed by the MassHunter workstation, while qualitative and quantitative analysis was performed by custom software.

[0094] Separation chromatographic column: The gas chromatographic column prepared in step 3 was used, with a length of 2m and a diameter of 1.2mm.

[0095] Heating conditions: constant temperature of 40℃.

[0096] Flow rate: 1.0 mL / min constant flow.

[0097] Injection volume: 1.0 mL

[0098] Flow split ratio: 1:5

[0099] Mass spectrometry conditions: Selected ion mode (SIM) 30 / 44

[0100] Carrier gas: Helium / hydrogen (99.9999%).

[0101] The obtained GC-MS chromatogram is as follows Figure 2 As shown.

[0102] Example 2

[0103] The operation is performed according to the method described in Example 1, with the following differences:

[0104] 3. Preparation of chromatographic column

[0105] A U-shaped stainless steel chromatographic column with an inner diameter of 1.5 mm and a length of 3 m was selected.

[0106] 4. Application of chromatographic columns

[0107] The Agilent 7890B(GC) gas chromatograph, with a nitrogen chemiluminescence (NCD) detector, has its chromatographic separation system controlled and recorded by a CDS workstation. Qualitative and quantitative analyses are performed using custom software.

[0108] Separation chromatographic column: The preparative phase chromatographic column of this invention is used. The column is 3m long and 1.5mm in diameter.

[0109] Heating conditions: constant temperature of 50℃.

[0110] Flow rate: 10 mL / min constant flow.

[0111] Injection volume: 0.25 mL

[0112] Flow split ratio: 1:10

[0113] Carrier gas: Helium (99.9999%).

[0114] The obtained GC-NCD chromatogram is as follows Figure 3 As shown.

[0115] Example 3

[0116] The procedure is the same as in Example 1, except that the modification steps are different. The specific modification method is as follows:

[0117] 2. Modification of porous microspheres

[0118] 10g of the solid porous microspheres obtained in step 1 were ultrasonically dispersed in 100mL of a mixed solution of nitric acid and sulfuric acid. Then, 5g of sodium molybdate and 3g of phosphorus pentoxide were added and stirred continuously. A vacuum (30kPa-40kPa) was continuously applied using a circulating water pump, and the molybdenum acidification reaction was carried out at 25℃ for 24h. When the mixed solution cooled to room temperature, the product was repeatedly washed with ethanol and centrifuged. The final separated product was dried to obtain the molybdenum acid-modified porous microspheres. Modified porous microspheres with a mesh size of 70-80 were selected for later use, resulting in modified porous microspheres with a pore size of 50-200nm and a specific surface area of ​​5-20m². 2 / g.

[0119] XRF analysis revealed that the mass ratio of elements on the surface of the modified porous microspheres was C 34:O 22:Mo 44. XRD analysis showed diffraction peaks of sodium molybdate crystals on the modified porous microspheres, indicating that molybdate is dispersed in a multilayered state on the surface of the modified porous microspheres. The obtained GC-MS chromatogram is shown below. Figure 4 As shown.

[0120] Comparative Example 1

[0121] The difference from Example 1 is that a Gaspro gas chromatography column was used, and the resulting chromatogram is as follows: Figure 5 As shown.

[0122] Comparative Example 2

[0123] The difference from Example 1 is that an unmolybdenum-treated porous microsphere column was used, and the resulting chromatogram is as follows. Figure 6 As shown.

[0124] Comparative Example 3

[0125] The difference from Example 2 is that a polymethylsiloxane porous microsphere column HP-1 was used, and the resulting GC-NCD chromatogram is as follows. Figure 7 As shown.

[0126] As shown in Example 1 and Comparative Examples 1-2, the gas chromatography column prepared by the modified porous microspheres of the present invention can effectively separate ppb-level NO and N2O in propylene feedstock using GC-MS. The retention time of N2O is 6.080 min, and the retention time of NO is 7.823 min. The resolution of NO and N2O is greater than 1.5, achieving complete baseline separation. However, the chromatographic column using bonded silica gel as the stationary phase described in Comparative Example 1 cannot effectively separate ppb-level NO and N2O in propylene feedstock. NO and N2O are interfered with by the propylene bulk, resulting in peak shapes that are "bun-like" (a type of peak shape), which greatly reduces the detection sensitivity of NO and N2O. The resolution of NO and N2O using the unmolybdenum-acidified porous microsphere column is less than 1.5, failing to achieve complete baseline separation and affecting the accurate quantification of NO and N2O.

[0127] As shown in Example 2 and Comparative Example 3, the gas chromatography column prepared by the modified porous microspheres of the present invention can effectively separate ppb-level NO and N2O in propylene feedstock on a GC-NCD, with a retention time of 4.928 min for N2O and 5.779 min for NO. The resolution of NO and N2O is greater than 1.5, achieving complete baseline separation. In contrast, the polymethylsiloxane porous microsphere column produces severe peak tailing for both NO and N2O, making qualitative and quantitative analysis of NO and N2O impossible.

[0128] A comparison of Examples 1 and 3 shows that the molybdenum acid in the microspheres modified by the non-preferred molybdenum acid modification method is in a multilayered dispersion state, which affects the separation of NO and N2O.

[0129] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A modified porous microsphere, characterized in that, The modified porous microspheres comprise a styrene-divinylbenzene-acrylonitrile copolymer with a surface modified by molybdenum oxide oxidation of benzene rings.

2. The modified porous microspheres according to claim 1, wherein, In the styrene-divinylbenzene-acrylonitrile copolymer, the weight ratio of styrene units, divinylbenzene units, and acrylonitrile units is (25-45):(20-40):(10-30); and / or The number-average molecular weight of the styrene-divinylbenzene-acrylonitrile copolymer is 10,000-60,000 g / mol.

3. The modified porous microspheres according to claim 2, wherein, The divinylbenzene unit is a p-divinylbenzene unit and / or a meta-divinylbenzene unit; and / or The surface element mass ratio of the modified porous microspheres is C (46-74):O (12-18):Mo (24-36).

4. The modified porous microspheres according to any one of claims 1-3, wherein, The modified porous microspheres have a pore size of 20-100 nm; and / or The modified porous microspheres have a particle size of 150-1000 μm; and / or The modified porous microspheres have a BET specific surface area of ​​30-40 m². 2 / g; and / or The column packing density of the modified porous microspheres is 0.2-0.5 g / mL.

5. A method for preparing modified porous microspheres according to any one of claims 1-4, characterized in that, The method includes: (1) Styrene, divinylbenzene and acrylonitrile are mixed with an initiator and a porogen to obtain a monomer solution; (2) The monomer solution was mixed with a dispersed phase containing a dispersant and subjected to suspension polymerization to obtain porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer; (3) The porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer were subjected to molybdenum acid treatment to obtain the modified porous microspheres; In step (3), the molybdenum acidification treatment includes: contacting the porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer with molybdate and phosphorus pentoxide in a mixed solution of sulfuric acid and nitric acid, and performing molybdenum acidification treatment to obtain the modified porous microspheres.

6. The method according to claim 5, wherein, In step (1), the initiator is a peroxide and / or an azo compound; and / or The pore-forming agent is selected from one or more of ethyl acetate, paraffin wax, gasoline, kerosene, and n-C12-C18 alkyl alcohols; and / or The divinylbenzene is p-divinylbenzene and / or m-divinylbenzene.

7. The method according to claim 6, wherein, The initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and tert-butyl hydroperoxide; and / or The weight ratio of styrene, divinylbenzene, acrylonitrile, initiator, and porogen is (25-45):(20-40):(10-30):(0.5-3):(0.5-3); and / or The solvent of the monomer solution is selected from at least one of toluene, p-xylene, and ethylbenzene.

8. The method according to claim 5, wherein, In step (2), the dispersant is a C12-C22 alkyltriC1-C6 alkylammonium halide; and / or The dispersed phase is an aqueous phase.

9. The method according to claim 8, wherein, In step (2), the dispersant is one or more of the following: dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltriethylammonium chloride, dodecyltriethylammonium bromide, tetradecyltrimethylammonium chloride, tetradecyltrimethylammonium bromide, tetradecyltriethylammonium chloride, tetradecyltriethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltriethylammonium chloride, hexadecyltriethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, octadecyltriethylammonium chloride, and octadecyltriethylammonium bromide; and / or Compared to the total weight of 1 part by weight of styrene, divinylbenzene and acrylonitrile, the amount of water used is 3-20 parts by weight, and the amount of dispersant used is 0.01-0.05 parts by weight.

10. The method according to claim 9, wherein, In step (2), the dispersant is one or more of the following: dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, dodecyltriethylammonium chloride, dodecyltriethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, hexadecyltriethylammonium chloride, and hexadecyltriethylammonium bromide.

11. The method according to any one of claims 5-10, wherein, In step (2), the conditions for suspension polymerization include: a temperature of 50-95℃ and a time of 5-10h.

12. The method according to claim 11, wherein, The suspension polymerization is carried out by reacting at 55-65℃ for 0.5-1.5h, then at 80-90℃ for 1-2h, and then at 85-95℃ for 3-5h.

13. The method according to claim 5, wherein, In the mixed solution of sulfuric acid and nitric acid, the concentration of sulfate is 15-40 wt% and the concentration of nitrate is 30-65 wt%; and / or The weight ratio of the sulfuric acid and nitric acid mixture to the porous microspheres is 5-15:1; and / or Compared to 100 parts by weight of porous microspheres, the amount of molybdate used is 1-20 parts by weight, and the amount of phosphorus pentoxide used is 1-20 parts by weight. and / or The molybdate is sodium molybdate and / or potassium molybdate; and / or The conditions for the molybdenum acidification treatment include: a vacuum degree of less than 0.1 MPa and a time of 6-12 hours.

14. The method according to claim 13, wherein, In the mixed solution of sulfuric acid and nitric acid, the concentration of sulfate is 20-30 wt% and the concentration of nitrate is 40-50 wt%.

15. A separation device, characterized in that, The separation device is filled with the modified porous microspheres as described in any one of claims 1-4.

16. The separation device according to claim 15, wherein, The separation device is a chromatographic column.

17. The application of the modified porous microspheres according to any one of claims 1-4 or the separation device according to claim 15 or 16 in separating NO and N2O from propylene feedstock or in determining the content of NO and N2O in propylene feedstock.

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