Qualitative and quantitative analysis method for polyolefin oxidation products
Through the combination of GC-MS and GC-FID, the problem of qualitative and quantitative analysis of polyolefin oxidation products was solved, efficient and accurate analysis results were achieved, and the progress of plastic recycling technology was promoted.
Patent Information
- Application Number
- CN202411387347.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-01
- Publication Date
- 2025-07-18
AI Technical Summary
The prior art is difficult to efficiently and at low cost to perform qualitative and quantitative analysis of polyolefin oxidation products, resulting in limited progress in plastic recycling technology.
After methylation of polyolefin oxidation products was methylated by GC-MS combined with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID), the molecular structure was qualitatively analyzed by GC-MS, and the product content was quantitatively analyzed by GC-FID, and CO2 and CO in gas phase products were quantified using GC-TCD.
It realizes efficient, accurate and quantitative analysis of polyolefin oxidation products, provides reliable product data support, and promotes the innovation and development of plastic recycling technology.
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Figure CN120334384A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of polyolefin oxidation product analysis, and particularly relates to a qualitative and quantitative analysis method for polyolefin oxidation products. Background Art
[0002] Polyolefins, including polyethylene (PE) and polypropylene (PP), account for half of the global annual plastic production. Due to their extensive use in disposable products, they also account for half of the plastic waste generated. The depolymerization process of polyolefins is challenging because these non-polar carbon-carbon bonds are not only thermodynamically stable but also have low reactivity. Coupled with the lack of available chemical functional groups in the polymer, depolymerization becomes even more difficult. The pyrolysis of polyolefins at high temperatures (usually above 400 °C) produces complex pyrolysis oils and a large amount of non-volatile and insoluble coke. Molecular recycling / upcycling of polyolefins at milder temperatures can produce more useful and targeted hydrocarbon product distributions. In the presence of excess hydrogen, treating polyolefins through catalytic hydrogenolysis and / or hydrocracking can produce liquid hydrocarbons suitable for use as fuels and lubricants. In the presence of excess oxygen, treating polyolefins through auto-oxidation or catalytic oxidation can produce high-value oxygenates. However, the oxidation process generally follows a peroxide or free radical chain reaction mechanism, resulting in extremely complex products, and the known types of oxidation products reach hundreds to thousands. When analyzing such complex mixtures, both qualitative and quantitative analyses face huge challenges.
[0003] To develop an efficient polyolefin oxidation system for preparing high-value oxygenates, accurate qualitative and quantitative analysis of oxidation products is crucial. Therefore, developing a low-cost, easy-to-operate, environmentally friendly, and efficient qualitative and quantitative analysis method for polyolefin oxidation products is of great significance for promoting the progress of plastic recycling technology. Summary of the Invention
[0004] The purpose of the present invention is to provide a qualitative and quantitative analysis method for polyolefin oxidation products, which accelerates the determination of product yields and helps directly compare the performance of different catalysts and reaction systems, thereby promoting the innovation and development of plastic recycling technology.
[0005] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:
[0006] A qualitative and quantitative analysis method for polyolefin oxidation products, which is a process of collecting, qualitatively and quantitatively analyzing the oxidation products obtained after the oxidation reaction of polyolefins in a high-pressure reactor, and specifically includes the following specific steps:
[0007] (1) Gas-phase product collection: After the oxidation reaction is completed and the reaction kettle is naturally cooled to room temperature, the gas-phase products collected at the top of the high-pressure reaction kettle are collected using an airbag, and a certain amount of internal standard is injected into the airbag for standby.
[0008] (2) Solid-liquid separation: After flushing the thermocouple and the quartz inner wall of the high-pressure reaction kettle with a solvent, the catalyst in the materials in the high-pressure reaction kettle is removed by filtration or centrifugation to obtain the reaction solution; the solvent is one of methanol, acetonitrile, acetone or tetrahydrofuran, or the solvent is a mixed solution of methanol and dichloromethane.
[0009] (3) Rotary evaporation: The reaction solution obtained in step (2) is concentrated by rotary evaporation to remove part of the solvent and obtain a concentrated product, that is, a concentrated solution of polyolefin oxidation product; during the rotary evaporation process, the system pressure is controlled at 60-100 hPa, and the water bath temperature is controlled at 50-70 °C.
[0010] (4) An esterification reagent is added to the concentrated solution of polyolefin oxidation product obtained in step (3) for an esterification reaction to obtain a methyl esterification solution; the addition amount of the esterification reagent is 10-20 mL, the esterification reagent is a methanol solution of acetyl chloride (the volume fraction of acetyl chloride is 10-20 vol.%), the esterification reaction temperature is 50-80 °C, and the esterification reaction time is 1-3 h. The specific dosage, reaction temperature and time are selected according to the input amount of the reaction substrate; through the esterification reaction, the polyolefin oxidation product is methyl esterified and converted into a methyl ester derivatized product.
[0011] (5) The methyl ester derivatized product (methyl esterification solution) obtained in step (4) is fixed to a certain volume with a constant volume solvent and 4-heptanone as the internal standard is added to obtain a liquid sample to be measured; the constant volume solvent is methanol, acetone, tetrahydrofuran, acetonitrile or dichloromethane; the internal standard is 4-heptanone.
[0012] (6) A certain amount of the liquid sample to be measured obtained in step (5) is taken, and the structure of the product is qualitatively analyzed by gas chromatography-mass spectrometry (GC-MS), the product is quantitatively analyzed by gas chromatography-flame ionization detector (GC-FID), and the product yield is calculated by the effective carbon number method (Science, 2016, 354(6310), 329-333; J Chromatogr Sci, 1985, 23(8), 333-340).
[0013] (7) A certain amount of the gas-phase product with internal standard in the airbag in step (1) is taken, and CO2 and CO in the gas-phase product are quantitatively analyzed by gas chromatography-thermal conductivity detector (GC-TCD) by internal standard method.
[0014] Further, in the gas chromatography-mass spectrometry (GC-MS), the selected chromatographic column is TG-5MS.
[0015] The chromatographic conditions of GC-MS are as follows: the inlet temperature is 280 - 360 °C; the split ratio is (20 - 50):1, the flow rate is 0.8 - 1.2 mL / min, and the chromatographic column temperature program is: the initial temperature is 50 °C, held for 1 min, then increased to 320 °C at a rate of 10 °C / min and held for 20 min;
[0016] The mass spectrometric conditions of GC-MS are as follows: the ion source temperature is 280 - 320 °C, the ion transfer line temperature is 280 - 320 °C, the mass scanning range is 30 - 550 amu, and the dwell or scan time is 0.2 s.
[0017] Furthermore, in the gas chromatography - flame ionization detector (GC-FID) technique, the chromatographic column used is HP-5;
[0018] The chromatographic conditions of GC-FID are as follows: the inlet temperature is 280 - 360 °C; the split ratio is (20 - 50):1, the flow rate is 0.8 - 1.2 mL / min; the chromatographic column temperature program is: the initial temperature is 50 °C, held for 1 min, then increased to 320 °C at a rate of 10 °C / min and held for 20 min.
[0019] Furthermore, the product is quantified according to the following calculation formulas (1)-(4) (the product yield is calculated by the effective carbon number method):
[0020]
[0021] n 产品 = n 甲酯衍生化产品 (2);
[0022]
[0023] In the above formulas: n 4-庚酮 represents the amount of substance of the internal standard added in each analysis, with the unit mmol; W 4-庚酮 represents the mass of the internal standard added in each analysis, with the unit mg; MW 4-庚酮 represents the molecular mass of 4-heptanone (its value is 114 mg mmol-1); n 产品 represents the amount of substance of the product in each analysis (unit mmol); n 甲酯衍生化产品 represents the amount of substance of the methyl ester derivative product in each analysis (unit mmol); A 甲酯衍生化产品 represents the peak area of the methyl ester derivative product in the GC-FID chromatogram; A 4-庚酮 represents the peak area of 4-heptanone in the GC-FID chromatogram; ECN 4-庚酮 represents the effective carbon number of the internal standard 4-heptanone (its value is 6); ECN 甲酯衍生化产品 represents the effective carbon number of the methyl ester derivative product; Y产品 represents the product yield; N 产品中碳子数 represents the number of carbon atoms in the product; MW 碳 represents the molar mass of carbon atoms (12 mg mmol -1 ); C 底物 represents the carbon content in the substrate.
[0024] When calculating the product yield by the effective carbon number method, the effective carbon number contributions of different groups or atoms are as follows: the contribution of aliphatic carbon is 1, the contribution of carbon in alkenes is 0.95, the contribution of carbonyl carbon is 0, and the contribution of methyl esters is 0.5 (Science, 2016, 354(6310), 329 - 333; J Chromatogr Sci, 1985, 23(8), 333 - 340).
[0025] Furthermore, in step (7), the main components of the gaseous products analyzed by GC - TCD are CO2 and CO, and the internal standard used for the gaseous products is CH4 or He, and the added amount is 10 - 30 mL.
[0026] The present invention has the following advantages:
[0027] The present invention provides a qualitative and quantitative method for preparing oxygen - containing compound products by polyolefin oxidation, which is convenient to operate, accurate in detection, can accurately reflect the contents of different types of oxygen - containing compounds in the products, and thus provides reliable data support for product production.
[0028] 1. Qualitative analysis: Through hard - ionization electron - impact mass spectrometry (EI - MS), the products derivatized with methyl esters are bombarded into molecular ions and fragment ions, thereby providing detailed information about the molecular structure and providing favorable support for the qualitative analysis of the products.
[0029] 2. Quantitative analysis:
[0030] (1) Fatty acids are usually not easily volatile and are difficult to directly analyze by gas chromatography (GC). Through methylation, fatty acids are converted into fatty acid methyl esters, and these derivatives have higher volatility, which is convenient for GC analysis. Moreover, the separated effect of the fatty acid methyl esters after methylation on the chromatographic column is better and has a better detector response, the chromatographic peak shape is sharper, reducing the peak tailing phenomenon, which helps to improve the accuracy and repeatability of the analysis.
[0031] (2) Using a flame ionization detector (FID) combined with the effective carbon number method (Effective Carbon Number, ECN) for quantitative analysis can shorten the analysis time and improve work efficiency because it is not necessary to establish a calibration curve for each fatty acid separately; and it reduces the demand for multiple standards, thereby reducing the analysis cost. Description of the Drawings
[0032] Figure 1 It is the GC-TCD chromatogram in Example 1.
[0033] Figure 2 It is the GC-FID chromatogram of the HDPE catalytic oxidation product in Example 1.
[0034] Figure 3 It is the reaction performance diagram of HDPE catalytic oxidation in Example 1 (the column height in the figure represents the yield of the corresponding product).
[0035] Figure 4 It is the reaction performance diagram and error bars of the three-time thermal oxidation of HDPE in Example 2.
[0036] Figure 5 It is the recovery rate of C7-C15 aliphatic dibasic acids under different esterification reaction conditions in Example 4. Detailed implementation manners
[0037] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the following further details the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. The methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products unless otherwise specified.
[0038] The present invention uses gas chromatography-mass spectrometry (GC-MS) to qualitatively analyze liquid products and reveal their molecular structures; while gas chromatography-flame ionization detector (GC-FID) is used for quantitative analysis, and the product yield is calculated by the effective carbon number method. The gas products are quantitatively analyzed by gas chromatography-thermal conductivity detector (GC-TCD). The method of the present invention provides detailed information about the molecular structure through GC-MS, significantly improves the performance of oxygen-containing compounds in chromatographic analysis through methyl ester derivatization treatment, and finally improves the analysis efficiency by means of the effective carbon number method, providing an efficient and accurate technical means for the qualitative and quantitative analysis of polyolefin oxidation products, thereby promoting the progress of plastic recycling technology.
[0039] In the specification and drawings, the fatty dibasic acid refers to the aliphatic dibasic acid.
[0040] Example 1
[0041] This example is for the qualitative and quantitative analysis of the HDPE catalytic oxidation product.
[0042] The HDPE catalytic oxidation process is as follows:
[0043] Take 100 mg of HDPE (Mw ~ 80 kDa) and 100 mg of the catalyst in a 100 mL quartz inner liner. After adding 15 mL of water, oscillate in ultrasonic for 2 min to fully disperse the catalyst. Transfer the quartz inner liner containing the catalyst and the substrate to a high-pressure reactor, and displace the reactor with oxygen 5 times. Then react at a reaction temperature of 160 °C and an oxygen pressure of 1.0 MPa for 4 h to fully convert the HDPE (Mw ~ 80 kDa) plastic. After the oxidation reaction is completed, the reactor cools naturally to the ambient temperature.
[0044] The catalyst used in this example is a supported manganese catalyst, which is formed by loading the active component of manganese oxide (MnO X ) on the SiO2 support. The expression of manganese oxide is MnO X where X = 1 - 3.5; the loading amount of manganese on the support is 1.0 - 100 wt.%.
[0045] The preparation process of the supported manganese catalyst used in this example is as follows:
[0046] Take 7.1233 g of Mn(NO3)2·4H2O in a 10 mL volumetric flask, make up the volume to 10 mL with deionized water, and oscillate in ultrasonic to fully dissolve the Mn salt to obtain an aqueous solution of Mn(NO3)2·4H2O. Take 200 μL of the obtained manganese salt aqueous solution and 2 mL of deionized water in a beaker, and oscillate in ultrasonic for 10 min to obtain an impregnation solution. Weigh 500 mg of nano-silica and slowly add it to the above impregnation solution under vigorous stirring. Then stir at room temperature for 12 h first, then raise the temperature to 60 °C and stir until the water is completely evaporated to obtain a catalyst precursor. Heat the precursor to 600 °C at a heating rate of 2 °C / min and calcine for 3 h to obtain the supported manganese catalyst (MnO x / SiO2).
[0047] The qualitative and quantitative analysis process of the HDPE catalytic oxidation product is as follows:
[0048] Use an air bag to collect the gas-phase product in the headspace of the reactor and inject 30 mL of CH4 as an internal standard. Next, clean the thermocouple and the quartz inner liner wall of the reactor with methanol and separate the solid catalyst by centrifugation to recover the reaction solution. By rotary evaporation technology, at a system pressure of 80 hPa and a water bath temperature of 60 °C, remove part of the solvent in the reaction solution to obtain a concentrated solution of polyolefin oxidation products. Then, add 10 mL of a pre-prepared methanol solution of acetyl chloride (acetyl chloride accounts for 10 vol.%) to the concentrated solution and carry out an esterification reaction at 60 °C for 2 h to obtain a methyl esterification solution, and convert the polyolefin oxidation product into a methyl esterified derivative product through the esterification reaction.
[0049] After the esterification reaction was completed, the obtained methyl esterified solution was made up to 25 mL with methanol, and one drop of 4-heptanone was added as an internal standard to obtain the liquid sample to be measured.
[0050] Finally, a small amount of the liquid sample to be measured was taken into a chromatographic vial, and gas chromatography-mass spectrometry (GC-MS) technology was used to qualitatively analyze different product structures, and the peak areas of different methyl esterified derivatives were measured by gas chromatography-flame ionization detector (GC-FID). The yields of CO2 and CO in the gas-phase products were measured by gas chromatography-thermal conductivity detector (GC-TCD).
[0051] Preparation of the above-mentioned methanol solution of acetyl chloride: 1 mL of acetyl chloride was taken into a 10-mL volumetric flask, and then methanol was added dropwise with shaking in an ice-water bath to the 10-mL scale line, and finally shaken well and mixed evenly for use.
[0052] The chromatographic conditions and mass spectrometry conditions during GC-MS analysis were as follows:
[0053] The chromatographic conditions of GC-MS were as follows: the chromatographic column was TG-5MS, the inlet temperature was 350 °C, the split ratio was 30:1, the flow rate was 1.0 mL / min, and the chromatographic column temperature program was: the initial temperature was 50 °C and held for 1 min, then it was heated to 320 °C at a rate of 10 °C / min and held for 20 min.
[0054] The mass spectrometry conditions of GC-MS were as follows: the ion source temperature was 320 °C, the ion transfer line temperature was 300 °C, the mass scanning range was 30-550 amu, and the dwell or scan time was 0.2 s.
[0055] The chromatographic conditions during GC-FID analysis were as follows: the chromatographic column was HP-5, the inlet temperature was 350 °C, the split ratio was 30:1, the flow rate was 1.0 mL / min, and the chromatographic column temperature program was: the initial temperature was 50 °C and held for 1 min, then it was heated to 320 °C at a rate of 10 °C / min and held for 20 min.
[0056] The yields of various products were calculated by the following calculation formulas (1)-(4), and the relevant results are shown in Figures 1-3 .
[0057]
[0058] n 产品 =n 甲酯衍生化产品 (2);
[0059]
[0060] In the above formula: n 4-庚酮 represents the amount of substance of the internal standard added in each analysis, with the unit of mmol; W 4-庚酮Mass of the internal standard added in each analysis, unit mg; MW 4-庚酮 Molecular mass of 4-heptanone (value is 114 mg mmol-1); n 产品 Amount of substance of the product in each analysis (unit mmol); n 甲酯衍生化产品 Amount of substance of the methyl ester derivative product in each analysis (unit mmol); A 甲酯衍生化产品 Peak area of the methyl ester derivative product in the GC-FID chromatogram; A 4-庚酮 Peak area of 4-heptanone in the GC-FID chromatogram; ECN 4-庚酮 Effective carbon number of the internal standard 4-heptanone (value is 6); ECN 甲酯衍生化产品 Effective carbon number of the methyl ester derivative product; Y 产品 Product yield; N 产品中碳子数 Number of carbon atoms in the product; MW 碳 Molar mass of carbon atom (12 mg mmol -1 ); C 底物 Carbon content in the substrate.
[0061] Taking one of the products (succinic acid) as an example, calculate the yield by the effective carbon number method:
[0062]
[0063] n 产品 = n 甲酯衍生化产品
[0064]
[0065] Example 2
[0066] This example is a repeated experiment on the qualitative and quantitative analysis of HDPE thermal oxidation products.
[0067] The HDPE thermal oxidation process is as follows:
[0068] Take 100 mg of HDPE (Mw ~ 80 kDa) in a 100 mL quartz inner liner, and add 15 mL of water. Transfer the quartz inner liner containing the substrate to a high-pressure reactor, and displace the reactor with oxygen 5 times. Then react at a reaction temperature of 160 °C and an oxygen pressure of 1.0 MPa for 4 h to fully convert the HDPE (Mw ~ 80 kDa) plastic. After the reaction is completed, the reactor is naturally cooled to ambient temperature.
[0069] The process of qualitative and quantitative analysis of HDPE thermal oxidation products is as follows:
[0070] The gaseous products in the headspace of the reactor were collected using an airbag, and 30 mL of CH4 was injected as an internal standard. Next, the thermocouple and the quartz inner wall of the reactor were washed with methanol to obtain the reaction solution. By rotary evaporation technology, part of the solvent in the reaction solution was removed at a system pressure of 80 hPa and a water bath temperature of 60 °C, thereby obtaining a concentrated solution of polyolefin oxidation products. After that, 10 mL of a methanol solution of acetyl chloride (acetyl chloride accounted for 10 vol.%) prepared in advance was added to the concentrated solution, and esterification reaction was carried out at 60 °C for 2 h to obtain a methyl esterification solution. Through the esterification reaction, the polyolefin oxidation products were converted into methyl esterified derivative products.
[0071] After the esterification reaction was completed, the obtained methyl esterification solution was made up to 25 mL with methanol, and one drop of 4-heptanone was added as an internal standard to obtain the liquid sample to be measured.
[0072] Finally, a small amount of the liquid sample to be measured was taken into a chromatographic vial, and gas chromatography-mass spectrometry (GC-MS) technology was used to qualitatively analyze different product structures, and the peak areas of different methyl esterified derivative products were measured by gas chromatography-flame ionization detector (GC-FID). The yields of CO2 and CO in the gaseous products were measured by gas chromatography-thermal conductivity detector (GC-TCD).
[0073] The above-mentioned acetyl chloride-methanol solution was prepared in the same way as in Example 1.
[0074] The chromatographic conditions and mass spectrometry conditions during GC-MS analysis were as follows:
[0075] The chromatographic conditions of GC-MS were: the chromatographic column was TG-5MS, the inlet temperature was 350 °C, the split ratio was 30:1, the flow rate was 1.0 mL / min, and the chromatographic column temperature programming was: the initial temperature was maintained at 50 °C for 1 min and then increased to 320 °C at a rate of 10 °C / min and maintained for 20 min.
[0076] The mass spectrometry conditions of GC-MS were: the ion source temperature was 320 °C, the ion transfer line temperature was 300 °C, the mass scanning range was 30 - 550 amu, and the dwell or scan time was 0.2 s.
[0077] The chromatographic conditions during GC-FID analysis were: the chromatographic column was HP-5, the inlet temperature was 350 °C, the split ratio was 30:1, the flow rate was 1.0 mL / min, and the chromatographic column temperature programming was: the initial temperature was maintained at 50 °C for 1 min, then heated to 320 °C at a rate of 10 °C / min and maintained for 20 min.
[0078] The yields of various products were calculated by formulas (1)-(4), and the experiment was repeated three times and quantitative analysis was carried out. The relevant results are shown in Figure 4 .
[0079] Example 3
[0080] This example is for verifying the accuracy of the effective carbon number calculation.
[0081] To verify the rationality of the contribution values of the effective carbon numbers of the selected methyl ester group, carbonyl carbon, and aliphatic carbon (0.5, 0, and 1 respectively), the following experiment was conducted: First, weigh about 7 mg of dimethyl succinate, dimethyl adipate, dimethyl suberate, and dimethyl azelate, accurately record the mass of the weighed substances, place them in a volumetric flask, and add about 7 mg of 4-heptanone as an internal standard, accurately record the mass of the internal standard. Subsequently, use methanol to make the solution up to the mark. After preparing the sample, analyze the sample using gas chromatography-flame ionization detector (GC-FID) to obtain the response factors of the substrate and the internal standard. Calculate the mass of each substance according to the calculation formulas (1)-(4), and compare it with the actual weighed mass of the substrate. The relevant analysis data are summarized in Table 1 below. It can be seen that the error in calculating the yield using the effective carbon number method adopted in the present invention is relatively small.
[0082] Table 1 Effective carbon number verification experiment
[0083]
[0084] Example 4
[0085] Exploration of the optimal esterification reaction conditions for the reaction system:
[0086] To determine the optimal esterification conditions suitable for this reaction system, a series of condition screening experiments were carried out. The experimental steps are as follows: First, accurately weigh about 10 mg of C7-C15 aliphatic dibasic acids in an eggplant-shaped flask, accurately record the mass, and then add 10 mL of a 10% (V%) methanol solution of acetyl chloride. Carry out the esterification reaction under different set temperature and time conditions, specifically: react for 1 h at 50 °C, react for 2 h at 60 °C, and react for 2 h at 80 °C. Through these experiments, the recovery rate (the ratio of the calculated result to the actual added substrate mass) data of aliphatic dibasic acids with different carbon numbers were obtained, and the results are summarized in Figure 5 It can be seen that the most suitable esterification condition for this system is to react at 60 °C for 2 h.
[0087] The above does not intend to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A qualitative and quantitative analysis method for polyolefin oxidation products, characterized in that: This method is a process for collecting, qualitatively and quantitatively analyzing the oxidation products obtained after the oxidation reaction of polyolefins in a high-pressure reactor, and specifically includes the following steps: (1) Collection of gas-phase products: The gas-phase products at the top of the high-pressure reactor are collected using an airbag, and a certain amount of internal standard is injected into the airbag for standby; (2) Solid-liquid separation: After flushing the thermocouple and the quartz inner wall of the high-pressure reactor with a solvent, the catalyst in the material in the high-pressure reactor is removed by filtration or centrifugation to obtain a reaction solution; (3) Rotary evaporation: The reaction solution obtained in step (2) is subjected to rotary evaporation technology to remove part of the solvent therein, thereby obtaining a concentrated solution of polyolefin oxidation products; (4) Esterification treatment: An esterification reagent is added to the concentrated solution of polyolefin oxidation products obtained in step (3), and an esterification reaction is carried out at a set temperature and time to obtain a methyl esterification solution; Through the esterification reaction, the polyolefin oxidation products are converted into methyl ester derivatives; (5) Volume fixing and analysis: The methyl esterification solution obtained after the reaction in step (5) is fixed to a certain volume using a volume-fixing solvent and an internal standard is added to obtain a liquid sample to be measured; (6) Take an appropriate amount of the liquid sample to be measured obtained in step (5), and use gas chromatography-mass spectrometry (GC-MS) to qualitatively analyze the product to determine its molecular structure; At the same time, gas chromatography-flame ionization detector (GC-FID) technology is used for quantitative analysis, and the yield of the product is calculated using the effective carbon number method; (7) Take an appropriate amount of the gas-phase product with an internal standard in the airbag in step (1) and perform quantitative analysis by internal standard method using gas chromatography-thermal conductivity detector (GC-TCD).
2. The qualitative and quantitative analysis method for polyolefin oxidation products according to claim 1, characterized in that: In step (2), the solvent used for flushing is one of methanol, acetonitrile, acetone and tetrahydrofuran, or the solvent used for flushing is a mixed solution of methanol and dichloromethane.
3. The qualitative and quantitative analysis method for the oxidation product of polyolefin according to claim 1, characterized in that: During the rotary evaporation process in step (3), the system pressure is controlled at 60-100 hPa, and the water bath temperature is controlled at 50-70 °C.
4. The qualitative and quantitative analysis method for polyolefin oxidation products according to claim 1, characterized in that: In step (4), the esterification reagent is a methanol solution of acetyl chloride, and the volume fraction of acetyl chloride is 5-20 vol.%; The dosage of the esterification reagent is 10-20 mL, the temperature of the esterification reaction is 50-80 °C, and the reaction time is 1-3 h. The specific dosage, reaction temperature and time are selected according to the input amount of the reaction substrate.
5. The qualitative and quantitative analysis method for the oxidation product of polyolefin according to claim 1, characterized in that: In step (5), the volume-fixing solvent is methanol, acetone, acetonitrile, tetrahydrofuran or dichloromethane; The internal standard is 4-heptanone.
6. The qualitative and quantitative analysis method for polyolefin oxidation products according to claim 1, characterized in that: In the gas chromatography-mass spectrometry (GC-MS) technology, the selected chromatographic column is TG-5MS; The chromatographic conditions of GC-MS are: the inlet temperature is 280-360 °C; The split ratio is (20-50):1, the flow rate is 0.8-1.2 mL / min, and the chromatographic column temperature programming is: the initial temperature is 50 °C, hold for 1 min, and rise to 320 °C at a rate of 10 °C / min and hold for 20 min. The mass spectrometry conditions of GC-MS are: the ion source temperature is 280-320 °C, the ion transfer line temperature is 280-320 °C, the mass scanning range is 30-550 amu, and the dwell or scan time is 0.2 s.
7. The qualitative and quantitative analysis method for the oxidation product of polyolefin according to claim 1, characterized in that: In the gas chromatography-flame ionization detector (GC-FID) technology, the chromatographic column used is HP-5; The chromatographic conditions of GC-FID are as follows: the inlet temperature is 280-360 °C; the split ratio is (20-50):1, and the flow rate is 0.8-1.2 mL / min; the chromatographic column temperature programming is: the initial temperature is 50 °C, held for 1 min, heated to 320 °C at a rate of 10 °C / min and held for 20 min.
8. The qualitative and quantitative analysis method for polyolefin oxidation products according to claim 1, characterized in that: When calculating the product yield by the effective carbon number method, the effective carbon number contributions of different groups or atoms are as follows: the contribution of aliphatic carbon is 1, the contribution of carbon in alkenes is 0.95, the contribution of carbonyl carbon is 0, and the contribution of methyl ester is 0.
5.
9. The qualitative and quantitative analysis method for polyolefin oxidation products according to claim 1, characterized in that: In step (7), the GC-TCD quantitative analysis of the gaseous products is mainly CO2 and CO. The internal standard used for the gaseous products is CH4 or He, and the addition amount is 10-30 mL.
10. The qualitative and quantitative analysis method for polyolefin oxidation products according to claim 1, characterized in that: The oxidation reaction of the polyolefin includes catalytic oxidation and / or thermal oxidation, and the oxidation products are gaseous products (mainly CO2 and CO) and liquid products (aliphatic organic dibasic acids, methyl ketonic acids, γ-ketodibasic acids, and lactonic acids).