Modified porous microspheres, preparation method thereof, separation device and application of modified porous microspheres and preparation method thereof

Abstract

The invention relates to the field of gas separation, and discloses a modified porous microsphere, a preparation method thereof, a separation device and application of the modified porous microsphere and the separation device, and the modified porous microsphere comprises styrene-divinyl benzene-acrylonitrile copolymer with surface benzene ring molybdic acid modification. Components of the modified porous microspheres are simple and easy to obtain, a gas chromatography packed column prepared from the modified porous microspheres can effectively separate trace NO and N2O in a polymer grade propylene raw material, the analysis process is completed within 15 min, qualitative and quantitative analysis can be carried out on a target object at the same time, and the lowest detection limit of quantitative analysis is 100 ppb.

Description

Technical Field

[0001] The present invention relates to the field of gas separation, and in particular to a modified porous microsphere, a method for preparing the modified porous microsphere, the modified porous microsphere prepared by the method, a separation device, and application of the modified porous microsphere or the separation device in separating NO and N2O from propylene raw materials or in determining the contents of NO and N2O in propylene raw materials. Background Art

[0002] Propylene is a basic organic raw material for petrochemical industry. Oil-based propylene uses naphtha as raw material to produce propylene monomer through steam cracking and catalytic cracking; coal-based propylene uses coal as raw material to produce propylene monomer through Fischer-Tropsch synthesis; gas-based propylene uses propane as raw material to produce propylene monomer through dehydrogenation. The diversification of upstream raw materials for propylene also makes the impurities in propylene monomer more complex. NO and N2O in propylene are mostly present in oil-based and gas-based propylene.

[0003] During steam cracking and cracking dehydrogenation, the nitrogen element in crude oil and propane reacts with O2 in the air to generate NO and N2O, which enter the propylene monomer. The Mg / Ti active center of the polypropylene ZN catalyst is extremely sensitive to NO and N2O, and is prone to poisoning, resulting in decreased activity. When the NO and N2O content exceeds 100ppb, the activity of the ZN catalyst drops to 80%, and when the NO and N2O content exceeds 1ppm, the activity of the ZN catalyst is only 50%. Therefore, the process of producing propylene monomer using crude oil and propane as raw materials must strictly control the NO and N2O content in propylene to reduce the toxicity to the downstream polypropylene catalyst.

[0004] Trace amounts of NO and N2O in propylene can be detected using a nitrogen chemiluminescence detector (NCD) and a mass spectrometer detector (MSD). The sensitivity of the two detectors can meet the requirements for detecting 100ppb NO and N2O. The critical temperature and pressure of propylene are approximately 92°C and 4.6Mpa, and it is generally in a gaseous state at room temperature. The boiling point of NO at normal pressure is -151°C, and the boiling point of N2O at normal pressure is -88°C. Low-boiling point compounds are difficult to separate by different boiling points on a general chromatographic column, and need to be separated by the polarity and other chemical properties of the substance. If NO and N2O cannot be completely separated on the chromatographic column, it is difficult to meet the requirements for 100ppb trace detection. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that the currently available chromatographic columns cannot effectively separate NO and N2O in propylene, thereby affecting the detection limit, and to provide a modified porous microsphere and a preparation method, a separation device and their applications. The gas-filled chromatographic column produced by the modified porous microsphere can effectively separate NO and N2O.

[0006] In order to achieve the above object, the first aspect of the present invention provides a modified porous microsphere, wherein the modified porous microsphere comprises a styrene-divinylbenzene-acrylonitrile copolymer whose surface is modified by molybdenumation of benzene rings.

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

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

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

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

[0011] The 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] A fifth aspect of the present invention provides the use of the modified porous microspheres or the separation device described above in separating NO and N2O from a propylene feedstock or in determining the contents of NO and N2O in a propylene feedstock.

[0014] The modified porous microspheres of the present invention have simple components, are easy to obtain, are low in cost, have a simple preparation process, are environmentally friendly, and the prepared separation device (such as a chromatographic column) has high consistency.

[0015] The gas chromatography packed column prepared by the modified porous microspheres of the present invention can effectively separate trace NO and N2O in polymerization-grade propylene raw materials. The analysis process is completed within 15 minutes, and the target can be qualitatively and quantitatively analyzed at the same time. The minimum detection limit of the quantitative analysis is 100ppb. Polypropylene production enterprises can use this chromatographic column to detect NO and N2O in propylene raw materials and control their content, thereby ensuring the long-term operation of polyolefin catalysts, which is of great significance for reducing costs and increasing efficiency for polyolefin petrochemical enterprises and improving the quality of polyolefin resin products. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic structural diagram of the modified porous microspheres of the present invention is shown.

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

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

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

[0020] Figure 5 The GC-MS chromatogram of separation of NO and N2O in propylene in Comparative Example 1 is shown.

[0021] Figure 6 The GC-MS chromatogram of separation of NO and N2O in propylene in Comparative Example 2 is shown.

[0022] Figure 7 The GC-NCD chromatogram of separation of NO and N2O in propylene in Comparative Example 3 is shown. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] The first aspect of the present invention provides a modified porous microsphere, wherein the modified porous microsphere comprises a styrene-divinylbenzene-acrylonitrile copolymer whose surface is modified by molybdenum acidification of benzene rings. The schematic diagram of the structure can be shown as follows Figure 1 shown.

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

[0026] Preferably, in the modified porous microspheres, the content of styrene-divinylbenzene-acrylonitrile copolymer is 92-98wt%, for example, it can be 92, 94, 96, 98wt% and any range between any two values, preferably 94-96wt%; the content of molybdic acid groups is 2-8wt%, for example, it can be 2, 4, 6, 8wt% and any range between any two values, preferably 4-6wt%.

[0027] Preferably, the number average molecular weight of the styrene-divinylbenzene-acrylonitrile copolymer is 10000-60000 g / mol, for example, it can be 10000, 20000, 30000, 40000, 50000, 60000 g / mol and any range between any two values.

[0028] Preferably, the divinylbenzene units are p-divinylbenzene units and / or m-divinylbenzene units.

[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 and any range between any two values): O (12-18, for example, 12, 13, 14, 15, 16, 17, 18 and any range between any two values): Mo (24-36, for example, 24, 26, 28, 30, 32, 34, 36 and any range between any two values). The inventors found that when molybdic acid forms a monolayer dispersion on the surface of the modified porous microspheres, the product effect is better. X-ray fluorescence and X-ray diffraction were used for determination, and the content of each element was detected by XRF. The molybdic acid crystal peak detected by XRD is a multilayer, and no single layer was detected.

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

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

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

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

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

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

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

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

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

[0039] In the present invention, styrene, divinylbenzene and acrylonitrile can be obtained commercially, and the purity thereof can be higher than 90wt%. Generally speaking, before polymerization, the monomers need to be treated to remove the polymerization inhibitor, and the method for removing the polymerization inhibitor 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 at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide and tert-butyl hydroperoxide.

[0042] Preferably, the porogen is selected from one or more of ethyl acetate, paraffin, gasoline, kerosene, normal C12-C18 alkyl alcohols (such as n-dodecyl alcohol, n-tridecanol, n-hexadecanol, n-octadecyl alcohol, etc.).

[0043] Preferably, by weight, the amount ratio of styrene, divinylbenzene, acrylonitrile, initiator and porogen 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, compared to 1 part by weight of the total weight of styrene, divinylbenzene and acrylonitrile, the amount of the solvent in the monomer solution is 3-20 parts by weight, for example, 3, 5, 10, 15, 20 parts by weight and any range between any two values.

[0046] Preferably, in step (2), the dispersant is preferably a C12-C22 alkyl tri-C1-C6 alkyl ammonium halide, preferably one or more of 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, compared to 1 part by weight of the total weight of styrene, divinylbenzene and acrylonitrile, the amount of water is 3-20 parts by weight, for example, 3, 5, 10, 15, 20 parts by weight and any range between any two values, and the amount of dispersant is 0.01-0.05 parts by weight, for example, 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 a target particle size. The obtained porous microspheres can also be dried, and the drying conditions are not particularly limited as long as the moisture can be removed, such as drying at 100-110° C. for 4-6 hours. The obtained porous microspheres can be molybdate treated, that is, the benzene rings of the porous microspheres are molybdate modified.

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

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

[0052] Gradient heating is preferred during the suspension polymerization process. Specifically, the suspension polymerization is preferably carried out at 55-65° C. for 0.5-1.5 h, then at 80-90° C. for 1-2 h, and then heated to 85-95° C. for 3-5 h.

[0053] Preferably, in step (3), the molybdate treatment comprises: 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 molybdate treatment to obtain the modified porous microspheres.

[0054] The porous microspheres may be dispersed (eg, by ultrasound) into the mixed solution of sulfuric acid and nitric acid, and then molybdate and phosphorus pentoxide are added thereto under stirring.

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

[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 and any range between any two values.

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

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

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

[0060] Heat is generated during the molybdate process. When the material temperature drops to room temperature, the obtained product can be repeatedly washed with ethanol and centrifuged, and the separated product is finally dried to obtain a molybdate-treated microsphere powder, i.e., the modified porous microspheres of the present invention. The obtained modified porous microspheres can also be sieved using a sieve with a certain mesh number (e.g., 20-100 mesh) to obtain modified porous microspheres with a specific particle size.

[0061] The 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 described in detail 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 chromatographic column packing density of the modified porous microspheres is 0.2-0.5 g / mL.

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

[0067] For example, regarding the selection of chromatographic column tubes, glass tubes, stainless steel tubes or plastic tubes with uniform inner diameters and appropriate lengths can be selected. For example, the inner diameter of the filling 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 directly rinsed with clean water for about 20 minutes, and then a dilute acid or a dilute alkali (generally 0.05-0.2 mol / L nitric acid, hydrochloric acid or sodium hydroxide) is poured into the column tube, and it is allowed to soak for more than 2 hours, and then rinsed with clean water until the eluate is neutral, and then ethanol or acetone is injected in the same way, soaked for more than 2 hours, and then rinsed with distilled water and ethanol in turn, 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 column length (cm); and V is the column volume (mL).

[0070] The filling method of the chromatographic column can be: connect a small funnel to the outlet of the washed and dried chromatographic column, fill the prepared microspheres into the column in batches, and tap the column wall continuously until it is filled to 1.5 cm from the column mouth. Move the glass funnel to the entrance of the chromatographic column, plug a small ball of silanized glass wool at the outlet, and wrap it with a thin layer of cotton or 2 layers of gauze, connect it to the vacuum pump through a rubber tube, turn on the vacuum pump, and continue to slowly add the prepared filler from the funnel, and tap the column wall continuously to make it filled evenly and tightly. After filling, also plug a small ball of silanized glass wool at the entrance, and press it appropriately to keep the filler in the column from moving.

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

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

[0073] A fifth aspect of the present invention provides the use of the modified porous microspheres or the separation device described above in separating NO and N2O from a propylene feedstock or in determining the contents of NO and N2O in a propylene feedstock.

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

[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, in the mixed solution of nitric acid and sulfuric acid, the concentration of sulfuric acid is 23.3 wt %, and the concentration of nitric acid is 46.7 wt %.

[0078] In the following examples, the polymerization-grade propylene raw material was taken from the raw material storage tank of the polyolefin production device, and the propylene raw material was introduced into the chromatographic detection through a gas valve.

[0079] Example 1

[0080] This example is used to illustrate the preparation method of the modified porous microspheres and chromatographic columns and the method of determining the content of the components to be measured by gas chromatography according to the present invention.

[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 from which the polymerization inhibitor has been removed are mixed with 0.2 g of benzoyl peroxide and 0.2 g of n-octadecyl alcohol, and nitrogen is passed through to deoxygenate, thereby obtaining a monomer phase solution.

[0083] 0.3g of hexadecyltrimethylammonium bromide was mixed with 100ml of distilled water, and the aqueous phase solution was obtained after nitrogen deoxygenation, and the aqueous phase solution was mixed with the monomer phase solution and ultrasonically dispersed for 30min. The mixed material was transferred to a three-necked flask, and the nitrogen was passed for 10min to deoxygenate, and then heating was started. At a stirring speed of 1040r / min, the temperature was raised to 60℃ and the reaction was carried out for 60min, and then the temperature was raised to 85℃ and the reaction was carried out for 90min. After the temperature was raised to 90℃ and the reaction was carried out for 4h, the heating was stopped. After the material temperature was cooled to room temperature, steam distillation was carried out to remove n-octadecyl alcohol. After filtering, the filter cake was placed in a fat extractor, and the chain polymer was extracted with toluene to remove the chain polymer. The remaining solid was dried and then sieved to obtain 70-80 mesh solid porous microspheres.

[0084] 2. Modification of porous microspheres

[0085] Ultrasonic dispersion of 10g of the solid porous microspheres obtained in step 1 is carried out in a 100mL mixed solution of nitric acid and sulfuric acid, and then 1g of sodium molybdate and 1g of phosphorus pentoxide are added and stirred continuously, and the vacuum is continuously drawn and released with a circulating water pump, and the molybdate reaction is carried out at 25°C for 10h. When the mixed solution is cooled to room temperature, the product is repeatedly washed with ethanol and centrifuged, and the final separated product is dried to obtain molybdate modified porous microspheres. Screen the modified porous microspheres with a mesh size of 70-80 for use, and the obtained modified porous microspheres have a pore size of 20-100nm and a specific surface area of ​​30-40m 2 / g.

[0086] Through XRF and XRD analysis, the mass ratio of the elements on the surface of the modified porous microspheres was C 55:O15:Mo 30, and no molybdic acid crystals were found, which indicated that molybdic acid was dispersed in a single layer on the surface of the modified porous microspheres.

[0087] 3. Preparation of gas chromatography column

[0088] Select a U-shaped stainless steel chromatographic column tube with an inner diameter of 1.2mm and a length of 2m. First rinse the chromatographic column tube with clean water for 20 minutes, then pour 0.1mol / L sodium hydroxide into the chromatographic column tube and soak it for 2 hours, then rinse it with clean water until the eluent is neutral. In the same way, inject ethanol into the chromatographic column tube and soak it for 2 hours, then rinse it with distilled water and ethanol in turn, and finally place the chromatographic column tube in an oven to dry.

[0089] Place the funnel at one end of the dried U-shaped chromatographic column tube, and fill the modified porous microspheres prepared in step 2 in portions through the funnel while constantly 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 with a thin layer of cotton. Finally, connect this end of the U-shaped chromatographic column tube to the vacuum pump through a rubber tube.

[0090] Place the funnel at the other end of the U-shaped chromatographic column tube, turn on the vacuum pump, and continue to fill the prepared modified porous microspheres into the U-shaped chromatographic column tube through the funnel, and keep tapping the column wall to make it filled 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 into the port, and press the glass wool to keep the filling in the column from being moved. The packing density of the modified porous microspheres is 0.3 g / mL.

[0091] The inlet of the chromatographic column was connected to the vaporization chamber, and the outlet was not connected to the detector, and the carrier gas N2 was introduced at a flow rate of 15 mL / min. The temperature was raised to 250°C in stages, and aged at 250°C for 24 hours to obtain a gas chromatographic column.

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

[0093] Agilent 8890B (GC) gas chromatograph, 5977B (MSD) detector, the control and recording of the chromatographic separation system are completed by MassHunter workstation, and qualitative and quantitative analysis are completed by customized software.

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

[0095] Heating conditions: 40℃ constant temperature,

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

[0097] Injection volume: 1.0mL,

[0098] 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 shown.

[0102] Example 2

[0103] The operation was carried out according to the method described in Example 1, except that:

[0104] 3. Preparation of chromatographic columns

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

[0106] 4. Application of chromatographic columns

[0107] Agilent 7890B (GC) gas chromatograph, nitrogen chemiluminescence (NCD) detector, the control and recording of the chromatographic separation system are completed by CDS workstation. Qualitative and quantitative analysis are completed by customized software.

[0108] Separation chromatographic column: The stationary preparative phase chromatographic column of the present invention was used, with a column length of 3 m and a diameter of 1.5 mm.

[0109] Heating conditions: 50℃ constant temperature,

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

[0111] Injection volume: 0.25mL,

[0112] Split ratio: 1:10

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

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

[0115] Example 3

[0116] The method of Example 1 was followed, except that the modification steps were different. The specific modification method was as follows:

[0117] 2. Modification of porous microspheres

[0118] Ultrasonic dispersion of 10g of the solid porous microspheres obtained in step 1 is carried out in a 100mL mixed solution of nitric acid and sulfuric acid, and then 5g of sodium molybdate and 3g of phosphorus pentoxide are added and stirred continuously, and a circulating water pump is used to continuously evacuate and release the vacuum (vacuum degree is 30kPa-40kPa), and the molybdate reaction is carried out at 25°C for 24h. When the mixed solution is cooled to room temperature, the product is repeatedly washed with ethanol and centrifuged, and the product after final separation is dried to obtain molybdate modified porous microspheres. Screen the modified porous microspheres of 70-80 mesh for use, and the pore size of the obtained modified porous microspheres is 50-200nm and the specific surface area is 5-20m 2 / g.

[0119] After XRF analysis, the mass ratio of the elements on the surface of the modified porous microspheres is C 34:O 22:Mo44. After XRD analysis, it is found that the modified porous microspheres have sodium molybdate crystal diffraction peaks, which indicates that molybdic acid is dispersed in multiple layers on the surface of the modified porous microspheres. The obtained GC-MS chromatogram is as follows: Figure 4 shown.

[0120] Comparative Example 1

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

[0122] Comparative Example 2

[0123] The difference from Example 1 is that: a non-molybdate-treated porous microsphere chromatographic column is used, and the chromatogram obtained is as follows Figure 6 shown.

[0124] Comparative Example 3

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

[0126] It can be seen from Example 1 and Comparative Examples 1-2 that the gas chromatography column prepared by the modified porous microspheres of the present invention can effectively separate ppb-level NO and N2O in propylene raw materials on GC-MS, with N2O retention time of 6.080min and NO retention time of 7.823min. The separation degree of NO and N2O is greater than 1.5, and the baseline is completely separated. However, the bonded silica gel described in Comparative Example 1 as the stationary phase chromatographic column cannot effectively separate ppb-level NO and N2O in propylene raw materials. NO and N2O are interfered by the main body of propylene, and the peak shape is a steamed bun peak, which greatly reduces the detection sensitivity of NO and N2O; the separation degree of NO and N2O using the porous microsphere chromatographic column that is not molybdate is less than 1.5, and the baseline cannot be completely separated, which affects the accurate quantification of NO and N2O.

[0127] It can be seen from Example 2 and Comparative Example 3 that the gas chromatography column prepared by the modified porous microspheres of the present invention can effectively separate ppb-level NO and N2O in propylene raw materials on GC-NCD, with a retention time of 4.928 min for N2O and 5.779 min for NO. The separation degree of NO and N2O is greater than 1.5, and the baseline is completely separated. However, the NO and N2O peaks of the polymethylsiloxane porous microsphere chromatographic column are both bun-shaped and have serious tailing, and qualitative and quantitative analysis of NO and N2O cannot be performed.

[0128] From the comparison between Example 1 and Example 3, it can be seen that the molybdic acid in the microspheres modified by the non-preferred molybdate modification method is in a multi-layer dispersion state, which affects the separation of NO and N2O.

[0129] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A modified porous microsphere, characterized in that: The modified porous microspheres contain styrene-divinylbenzene-acrylonitrile copolymers with surface benzene rings molybdate-modified.

2. The modified porous microsphere 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 10000-60000 g / mol; and / or Preferably, the divinylbenzene units are p-divinylbenzene units and / or m-divinylbenzene units; Preferably, the mass ratio of the elements on the surface of the modified porous microspheres is C (46-74): O (12-18): Mo (24-36).

3. The modified porous microsphere according to claim 1 or 2, wherein: The pore size of the modified porous microspheres is 20-100 nm; and / or The particle size of the modified porous microspheres is 150-1000 μm; and / or The BET specific surface area of ​​the modified porous microspheres is 30-40 m 2 / g; and / or The chromatographic column packing density of the modified porous microspheres is 0.2-0.5 g / mL.

4. A method for preparing modified porous microspheres, characterized in that: The method includes: (1) mixing styrene, divinylbenzene and acrylonitrile with an initiator and a porogen to obtain a monomer solution; (2) mixing the monomer solution with a dispersed phase containing a dispersant and performing suspension polymerization to obtain porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer; (3) The porous microspheres of styrene-divinylbenzene-acrylonitrile copolymer are subjected to molybdate treatment to obtain the modified porous microspheres.

5. The method according to claim 4, wherein: In step (1), the initiator is a peroxide and / or an azo compound, preferably at least one selected from azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide and tert-butyl hydroperoxide; and / or The porogen is selected from one or more of ethyl acetate, paraffin, gasoline, kerosene, and normal C12-C18 alkyl alcohol; and / or The divinylbenzene is p-divinylbenzene and / or m-divinylbenzene; Preferably, by weight, the ratio of styrene, divinylbenzene, acrylonitrile, initiator and porogen is (25-45):(20-40):(10-30):(0.5-3):(0.5-3); Preferably, the solvent of the monomer solution is selected from at least one of toluene, p-xylene and ethylbenzene.

6. The method according to claim 4 or 5, wherein: In step (2), the dispersant is a C12-C22 alkyl tri-C1-C6 alkyl ammonium halide, preferably one or more of dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, dodecyl triethyl ammonium chloride, dodecyl triethyl ammonium bromide, tetradecyl trimethyl ammonium chloride, tetradecyl trimethyl ammonium bromide, tetradecyl triethyl ammonium chloride, tetradecyl triethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, hexadecyl triethyl ammonium chloride, hexadecyl triethyl ammonium bromide, octadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium bromide, octadecyl triethyl ammonium chloride and octadecyl triethyl ammonium bromide, more preferably one or more of dodecyl trimethyl ammonium chloride, dodecyl trimethyl ammonium bromide, dodecyl triethyl ammonium chloride, dodecyl triethyl ammonium bromide, hexadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, hexadecyl triethyl ammonium chloride and hexadecyl triethyl ammonium bromide; and / or The dispersed phase is an aqueous phase; Preferably, compared to 1 part by weight of the total weight of styrene, divinylbenzene and acrylonitrile, the amount of water used is 3-20 parts by weight, and the amount of the dispersant used is 0.01-0.05 parts by weight.

7. The method according to any one of claims 4 to 6, wherein: In step (2), the conditions of the suspension polymerization include: temperature of 50-95° C. and time of 5-10 h; Preferably, the suspension polymerization is carried out by reacting at 55-65° C. for 0.5-1.5 h, then reacting at 80-90° C. for 1-2 h, and then heating to 85-95° C. for 3-5 h.

8. The method according to claim 4, wherein: In step (3), the molybdate treatment comprises: 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 molybdate treatment to obtain the modified porous microspheres; Preferably, in the mixed solution of sulfuric acid and nitric acid, the concentration of sulfate is 15-40wt%, more preferably 20-30wt%, and the concentration of nitrate is 30-65wt%, more preferably 40-50wt%; Preferably, the weight ratio of the mixed solution of sulfuric acid and nitric acid to the porous microspheres is 5-15:1; Preferably, compared to 100 parts by weight of the porous microspheres, the amount of the molybdate is 1-20 parts by weight, and the amount of the phosphorus pentoxide is 1-20 parts by weight; Preferably, the molybdate is sodium molybdate and / or potassium molybdate; Preferably, the molybdate treatment conditions include: vacuum degree less than 0.1 MPa, and time of 6-12 h.

9. Modified porous microspheres prepared by the method according to any one of claims 4 to 8.

10. A separation device, characterized in that: The separation device is filled with the modified porous microspheres according to any one of claims 1 to 3 and 9; Preferably, the separation device is a chromatographic column.

11. Use of the modified porous microspheres according to any one of claims 1 to 3 and 9 or the separation device according to claim 10 for separating NO and N2O from propylene raw materials or for determining the contents of NO and N2O in propylene raw materials.

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