A method for separating and determining the content of antioxidants in aviation kerosene

Abstract

This disclosure relates to a method for separating and determining the content of antioxidants in jet fuel. The separation method includes the following steps: (1) packing a stationary phase into a solid-phase extraction column and adding the jet fuel sample to be tested to the stationary phase; (2) washing the stationary phase with a first eluent to obtain a first eluent; (3) washing the stationary phase obtained in step (2) with a second eluent to obtain a second eluent containing the antioxidant; wherein the stationary phase comprises silica gel and alumina, and the antioxidant is 2,6-di-tert-butyl-p-cresol. The method of this disclosure can effectively separate the antioxidant 2,6-di-tert-butyl-p-cresol from jet fuel, avoiding interference from hydrocarbons. The use of gas chromatography-mass spectrometry to determine the antioxidant content can improve the accuracy of content analysis.

Description

Technical Field

[0001] This disclosure relates to the petrochemical field, specifically to a method for separating antioxidants from aviation kerosene and a method for determining their content. Background Technology

[0002] Aviation kerosene (also known as jet fuel) is a product blended from straight-run fractions, hydrocracking, and hydrorefining components with necessary additives. It is primarily used as fuel for aircraft turbine engines. Trace amounts of additives can significantly improve jet fuel quality. Common jet fuel additives include antioxidants, metal passivators, anti-icing agents, antistatic agents, anti-wear agents, and thermal stability additives. The addition of antioxidants can reduce the amount of gum produced by fuel oxidation, delay fuel oxidation, and improve the storage stability of jet fuel. Common antioxidants include phenolic antioxidants, amine antioxidants, and phenol-amine antioxidants. 2,6-Di-tert-butyl-p-cresol (T501) is a commonly used phenolic antioxidant in my country, typically added to fuel oil at a level of 0.002%-0.005%. Antioxidants are gradually consumed over time; therefore, the determination of antioxidants in jet fuel is of great significance for jet fuel production, quality evaluation, and safe use.

[0003] Currently, the main methods for detecting antioxidants in jet fuel include electrochemical detection, high-performance liquid chromatography, gas chromatography, and mass spectrometry. Among these, electrochemical detection is easily affected by the hydrocarbon composition of jet fuel, resulting in low accuracy.

[0004] Currently, most domestic methods use the standard "RIPP 95-90 High Performance Liquid Chromatography for Direct Determination of 2,6-Di-tert-butyl-p-cresol Antioxidant Content in Jet Fuel" to determine the antioxidant content. However, this method suffers from severe peak tailing, large retention time drift, and poor repeatability in practical applications.

[0005] Xue Yan et al. [“Determination of Antioxidant Content in Jet Fuel by Reversed-Phase High Performance Liquid Chromatography-Mass Spectrometry.” Chromatography, 2004, 22(06): 661] used reversed-phase high performance liquid chromatography-mass spectrometry selected ion method to determine the antioxidant content in jet fuel. This method is simple, rapid and efficient, but the high performance liquid chromatography-mass spectrometry instrument is expensive and rarely used in petrochemical enterprises. Therefore, this method is difficult to promote in practical applications.

[0006] Tang Chengguo [“Analysis of Phenolic Antioxidants in Jet Fuel by GC / MS.” Journal of Mass Spectrometry, 2000, 21(1): 40-44] established a method for qualitative and quantitative analysis of antioxidants in jet fuel oil using GC / MS. This method employs single-ion scanning (SIM) to select characteristic ions for antioxidant quantification. However, this method is not applicable to all jet fuel samples. For more complex jet fuel samples, SIM quantification is still affected by hydrocarbon interference, and the quantitative detection error is relatively large for low-content additives.

[0007] Zhang Jianjian et al. [“Gas Chromatography-Mass Spectrometry Analysis of Phenolic Antioxidants in Jet Fuel.” Journal of Henan Normal University (Natural Science Edition), 2016, 44(1): 82-86] analyzed the content of various phenolic antioxidants in jet fuel using single-column gas chromatography-mass spectrometry (GC-MS) and two-dimensional GC-MS based on the center-cutting method, respectively. In the single-column GC-MS method, target substances such as T501 are easily interfered with by other components, so it is not applicable to the determination of T501 in jet fuel. The two-dimensional GC-MS method based on the center-cutting method can eliminate the interference of jet fuel components on target substances, but it requires the installation of a flow path control valve and a two-dimensional chromatographic column on the gas chromatograph and control by corresponding software, which is complicated to operate and difficult to promote in refineries.

[0008] Shi Dejun et al. used solid-phase extraction technology to separate and enrich antioxidants and anti-icing agents from aviation kerosene, and then used gas chromatography-mass spectrometry-flame ionization detector to perform qualitative and quantitative analysis of the separated antioxidants and anti-icing agents ("A method for separating, purifying and simultaneously determining antioxidants and anti-icing agents in aviation kerosene", Chinese Patent Application Publication No.: CN 111579654A). However, the antioxidant recovery rate obtained by this method is low, and the analysis time is long, with a single analysis time exceeding 25 minutes.

[0009] In general, current methods for detecting antioxidants in jet fuel are easily affected by the composition of the jet fuel, impacting the accuracy of quantitative results; some methods also use instruments that are not universally applicable and not suitable for use in actual refineries. Therefore, it is necessary to develop suitable analytical methods to achieve accurate and rapid analysis of antioxidant content in jet fuel. Summary of the Invention

[0010] The purpose of this disclosure is to provide a method for separating and determining the content of antioxidants in jet fuel. This method can effectively separate the antioxidant 2,6-di-tert-butyl-p-cresol from jet fuel and perform rapid and accurate quantitative analysis of its content.

[0011] To achieve the above objectives, the first aspect of this disclosure provides a method for separating antioxidants from aviation kerosene, the method comprising the following steps:

[0012] (1) A stationary phase is packed into a solid phase extraction column, and the jet fuel sample to be tested is added to the stationary phase;

[0013] (2) The stationary phase is washed with the first eluent to obtain the first eluent;

[0014] (3) Rinse the stationary phase obtained in step (2) with the second eluent to obtain a second eluent containing an antioxidant;

[0015] The stationary phase comprises silica gel and alumina, and the antioxidant is 2,6-di-tert-butyl-p-cresol;

[0016] The first eluent includes a first elution component and a second elution component;

[0017] The first elution component includes one or more chloroalkanes having 2-4 chlorine atoms;

[0018] The second eluent component includes one or more of n-alkanes having 5-7 carbon atoms and cycloalkanes having 5-6 carbon atoms;

[0019] The second eluent comprises one or more of saturated monohydric alcohols having 1-3 carbon atoms and saturated monocarboxylic acids having 1-2 carbon atoms.

[0020] Optionally, the stationary phase is silica gel and alumina, and the silica gel content is 20-40% by weight, based on the total weight of the stationary phase.

[0021] Optionally, the specific surface area of ​​the silicone is 400-750 m². 2 / g, particle size 0.038-0.15mm, total pore volume 0.35-0.90cm³ 3 / g;

[0022] The specific surface area of ​​the alumina is 80-250 m². 2 / g, with a particle size of 0.038-0.15mm.

[0023] Optionally, the volume ratio of the first elution component to the second elution component is 1:(1-10);

[0024] Optionally, the chloroalkane having 2-4 chlorine atoms includes one or more of dichloromethane, trichloromethane, and tetrachloromethane;

[0025] Optionally, the n-alkane having 5-7 carbon atoms includes one or more of n-pentane, n-hexane, and n-heptane; the cycloalkane having 5-6 carbon atoms includes cyclopentane and / or cyclohexane.

[0026] Optionally, the second eluent comprises one or more of methanol, ethanol, isopropanol, formic acid, and acetic acid.

[0027] Optionally, the method further includes: drying the silica gel before step (1), wherein the drying conditions include: a temperature of 100-200°C and a time of 3-8 hours;

[0028] The method further includes: before step (1), calcining the alumina, wherein the calcination conditions include: a temperature of 300-500℃ and a time of 2-6h.

[0029] Optionally, in step (1), the weight ratio of the jet fuel sample to the stationary phase is 1:(2-20);

[0030] In step (2), the volume ratio of the jet fuel sample to be tested to the first eluent is 1:(1-50), and the volume ratio of the jet fuel sample to be tested to the second eluent is 1:(1-50).

[0031] A second aspect of this disclosure provides a method for determining the antioxidant content in aviation kerosene, the method comprising:

[0032] The second eluent is separated from the aviation kerosene sample to be tested using the separation method described in the first aspect of this disclosure;

[0033] The antioxidant content in the second eluent was determined by gas chromatography-mass spectrometry.

[0034] The quantitative method of the gas chromatography-mass spectrometry is the internal standard method.

[0035] Optionally, the internal standard used in the internal standard method is perfluorobiphenyl and / or deuterated hydrocarbon.

[0036] Optionally, the mass spectrometry method employs a selected ion scanning mode, and the selected ions include the molecular ion of the internal standard, the molecular ion of the antioxidant, and / or fragment ions.

[0037] Optionally, the content of 2,6-di-tert-butyl-p-cresol in the jet fuel sample to be tested is 5-100 mg / L.

[0038] Optionally, the test conditions for gas chromatography include: an injection port temperature of 200-300℃, an injection volume of 0.1-1.0 μL, and a split ratio of (1-20):1;

[0039] The mass spectrometry test conditions include: ionization method is electron bombardment ionization, electron energy is 70 eV, and ion source temperature is 200-250℃.

[0040] Through the above technical solution, this disclosure uses alumina and silica gel as the stationary phase to extract the antioxidant 2,6-di-tert-butyl-p-cresol from jet fuel. It employs 2-4 chlorinated alkanes, 5-7 carbon n-alkanes, and / or 5-6 carbon cycloalkanes as the first eluent to elute hydrocarbons. A second eluent, selected from 1-3 carbon saturated monohydric alcohols and 1-2 carbon saturated monocarboxylic acids, is used to elute the antioxidant. This method can separate the antioxidant from jet fuel, eliminating interference from hydrocarbons. Gas chromatography-mass spectrometry (GC-MS) can rapidly and accurately determine the antioxidant content in jet fuel. Furthermore, accurate measurement results can be obtained even when the antioxidant content in jet fuel is low.

[0041] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0042] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0043] Figure 1 This is the gas chromatography-mass spectrometry total ion chromatogram of sample D1, which does not contain T501 jet fuel, in Example 1 of this disclosure.

[0044] Figure 2 This is a gas chromatography-mass spectrometry selected ion flow chromatogram of sample D1, which does not contain T501 jet fuel, in Example 1 of this disclosure.

[0045] Figure 3 This is a gas chromatography-mass spectrometry selected ion chromatogram of the first eluent obtained from the separation of sample D1, which does not contain T501 jet fuel, in Example 1 of this disclosure.

[0046] Figure 4 This is a gas chromatography-mass spectrometry selected ion chromatogram of the first eluent obtained from the separation of T501 jet fuel sample D2 in Example 1 of this disclosure.

[0047] Figure 5 This is a gas chromatography-mass spectrometry selected ion chromatogram of the second eluent obtained from the separation of sample D1, which does not contain T501 jet fuel, in Example 1 of this disclosure.

[0048] Figure 6 This is a gas chromatography-mass spectrometry selected ion chromatogram of the second eluent obtained from the separation of T501 jet fuel sample D2 in Example 1 of this disclosure.

[0049] Figure 7 This is a chromatogram of the second eluent obtained from the separation of T501 jet fuel sample D2 in Comparative Example 1 of this disclosure.

[0050] Figure 8 This is a gas chromatography-mass spectrometry selected ion chromatogram of the first eluent b obtained from the separation of T501 jet fuel sample D2 in Comparative Example 2 of this disclosure.

[0051] Figure 9 This is the standard operating curve in Embodiment 2 of this disclosure.

[0052] Figure 10 This is a gas chromatography-mass spectrometry total ion chromatogram of petroleum-based jet fuel in Example 4 of this disclosure.

[0053] Figure 11 This is a gas chromatography-mass spectrometry total ion chromatogram of bio-based jet fuel in Example 4 of this disclosure.

[0054] Figure 12 This is a gas chromatography-mass spectrometry selected ion flow chromatogram of petroleum-based jet fuel in Example 4 of this disclosure.

[0055] Figure 13 This is a gas chromatography-mass spectrometry selected ion flow chromatogram of bio-based jet fuel in Example 4 of this disclosure.

[0056] Figure 14 This is a gas chromatography-mass spectrometry selected ion flow chromatogram of the second eluent of petroleum-based jet fuel in Example 4 of this disclosure.

[0057] Figure 15 This is a gas chromatography-mass spectrometry selected ion flow chromatogram of the second eluent of bio-based jet fuel in Example 4 of this disclosure.

[0058] Figure 16 This is a gas chromatography-mass spectrometry selected ion chromatogram of the first eluent obtained from the separation of T501 jet fuel sample D2 in Comparative Example 4 of this disclosure.

[0059] Figure 17 This is a gas chromatography-mass spectrometry selected ion chromatogram of the second eluent obtained from the separation of T501 jet fuel sample D2 in Comparative Example 4 of this disclosure. Detailed Implementation

[0060] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0061] The first aspect of this disclosure provides a method for separating antioxidants from aviation kerosene, the method comprising the following steps:

[0062] (1) A stationary phase is packed into a solid phase extraction column, and the jet fuel sample to be tested is added to the stationary phase;

[0063] (2) The stationary phase is washed with the first eluent to obtain the first eluent;

[0064] (3) Rinse the stationary phase obtained in step (2) with the second eluent to obtain a second eluent containing an antioxidant;

[0065] The stationary phase comprises silica gel and alumina, and the antioxidant is 2,6-di-tert-butyl-p-cresol;

[0066] The first eluent includes a first elution component and a second elution component;

[0067] The first elution component includes one or more chloroalkanes having 2-4 chlorine atoms;

[0068] The second eluent component includes one or more of n-alkanes having 5-7 carbon atoms and cycloalkanes having 5-6 carbon atoms;

[0069] The second eluent comprises one or more of saturated monohydric alcohols having 1-3 carbon atoms and saturated monocarboxylic acids having 1-2 carbon atoms.

[0070] In one embodiment of this disclosure, a first eluent is used to separate hydrocarbons from jet fuel. The volume ratio of the first eluent component to the second eluent component is 1:(1-10); preferably 1:(5-9), more preferably 1:(8-9). The chloroalkanes having 2-4 chlorine atoms include one or more of dichloromethane, trichloromethane, and tetrachloromethane; the n-alkanes having 5-7 carbon atoms include one or more of n-pentane, n-hexane, and n-heptane; and the cycloalkanes having 5-6 carbon atoms include cyclopentane and / or cyclohexane. Specifically, the first eluent can be, for example, a mixture of dichloromethane and n-hexane in a volume ratio of 1:9. Using the above solvent as the first eluent can effectively elute hydrocarbons from jet fuel, eliminating their interference with the determination of antioxidant content.

[0071] In one embodiment of this disclosure, a second eluent is used to separate antioxidants from jet fuel. For example, the second eluent comprises oxygen-containing organic matter, including one or more of a saturated monohydric alcohol having 1-3 carbon atoms and a saturated monohydric acid having 1-2 carbon atoms. Further, the second eluent contains one or more of methanol, ethanol, isopropanol, formic acid, and acetic acid; preferably methanol or ethanol. Using the above solvents as the second eluent can achieve better antioxidant elution results, which is beneficial for improving the accuracy of content determination.

[0072] In one embodiment of this disclosure, the stationary phase is alumina and silica gel. Based on the total weight of the stationary phase, the silica gel content is 20-40% by weight, preferably 20-30% by weight. A stationary phase meeting the above content range can avoid the problems of poor antioxidant adsorption due to excessive silica gel content and excessive adsorption due to insufficient silica gel content, which in turn leads to inaccurate measurement results.

[0073] In one embodiment of this disclosure, the specific surface area of ​​the silicone is 400-750 m². 2 / g, preferably 500-650m 2 / g; particle size of 0.038-0.15mm, preferably 0.074-0.15mm; total pore volume of 0.35-0.90cm³. 3 / g, preferably 0.35-0.50cm 3 / g; the specific surface area of ​​alumina is 80-250m². 2 / g, preferably 90-200m 2 / g; particle size is 0.038-0.15mm, preferably 0.074-0.15mm.

[0074] In a preferred embodiment, prior to step (1), the silica gel is dried under the following conditions: a temperature of 100-200°C for 3-8 hours; more preferably, the drying conditions include a temperature of 150-200°C for 5-8 hours. Prior to step (1), the alumina is calcined under the following conditions: a temperature of 300-500°C for 2-6 hours; more preferably, the calcination conditions include a temperature of 350-450°C for 4-6 hours. This is conventional in the art.

[0075] In one embodiment of this disclosure, in step (1), the weight ratio of the jet fuel sample to the stationary phase is 1:(2-20); preferably 1:(2-10), and more preferably 1:(4-6).

[0076] In one embodiment of this disclosure, in step (2), the volume ratio of the jet fuel sample to be tested to the first eluent is 1:(1-50), preferably 1:(5-30), and more preferably 1:(6-10); the volume ratio of the jet fuel sample to be tested to the second eluent is 1:(1-50), preferably 1:(5-30), and more preferably 1:(8-10).

[0077] The separation method disclosed herein can be used for different types of jet fuel, such as petroleum-based jet fuel and / or bio-based jet fuel.

[0078] A second aspect of this disclosure provides a method for determining the antioxidant content in aviation kerosene, the method comprising:

[0079] The second eluent is separated from the aviation kerosene sample to be tested using the separation method described in the first aspect of this disclosure;

[0080] The antioxidant content in the second eluent was determined by gas chromatography-mass spectrometry.

[0081] The quantitative method described in the gas chromatography-mass spectrometry is the internal standard method.

[0082] In one embodiment of this disclosure, the internal standard used in the internal standard method is perfluorobiphenyl and / or deuterated hydrocarbon.

[0083] In one embodiment of this disclosure, the mass spectrometry employs a selected ion scanning method, and the selected ions include the molecular ions of internal standards, the molecular ions of antioxidants, and / or fragment ions.

[0084] In one embodiment of this disclosure, the content of 2,6-di-tert-butyl-p-cresol in the jet fuel sample to be tested is 5-100 mg / L.

[0085] In one embodiment of this disclosure, the gas chromatography test conditions include: an injection port temperature of 200-300℃, preferably 250-300℃; an injection volume of 0.1-1.0μL, preferably 0.5-1.0μL; a split ratio of (1-20):1, preferably (1-10):1; further, the gas chromatography temperature program can be set as follows: an initial temperature of 40-100℃, held for 1-5 min, and then increased to 200-300℃ at a heating rate of 5-40℃ / min, with a carrier gas flow rate of 0.5-1.5mL / min, preferably 0.8-1.5mL / min.

[0086] In one embodiment of this disclosure, the mass spectrometry testing conditions include: ionization mode is electron bombardment ionization; electron energy is 70 eV; and ion source temperature is 200-250℃, preferably 220-230℃.

[0087] In one specific embodiment of this disclosure, the determination of the antioxidant 2,6-di-tert-butyl-p-cresol in jet fuel using selected ion mass spectrometry with internal standard method further includes the step of establishing a standard working curve:

[0088] S1 uses the following steps to prepare a series of standard working solutions containing different concentrations of antioxidants, each standard working solution containing the same amount of internal standard;

[0089] S2 used gas chromatography-mass spectrometry to determine the mass spectra of the standard working solutions, and calculated the peak area (A) of the antioxidant and the peak area (A) of the internal standard. sThe ratio of the peak area of ​​the antioxidant to the peak area of ​​the internal standard is plotted on the x-axis, and the ratio of the corresponding content of the antioxidant to the internal standard is plotted on the y-axis to obtain the standard working curve and the correlation formula.

[0090] Further, step S1 includes:

[0091] A. Dissolve the antioxidant in a first solvent to prepare an antioxidant standard stock solution; the first solvent includes one or more of toluene, methanol, ethanol and isopropanol, for example, toluene;

[0092] B. Add an internal standard solution to the antioxidant standard stock solution to prepare 4-6 standard working solutions with different antioxidant concentrations, and the content of the internal standard in each standard working solution is the same; the concentration of antioxidant in the standard working solution is 0.1-100 mg / L, preferably 0.5-50 mg / L;

[0093] In a further embodiment, the antioxidant content in the second eluent is determined using the following steps:

[0094] a. Add internal standard solution to the second eluent to obtain the second eluent to be tested;

[0095] b. Measure the mass spectrum of the second eluent using gas chromatography-mass spectrometry (GC-MS), and calculate the peak area (A1) of the antioxidant and the peak area (A2) of the internal standard. s 1) Then, based on the standard working curve, determine the antioxidant content in the aviation kerosene sample to be tested;

[0096] In this standard working curve, the horizontal axis represents the peak area (A) of the antioxidant and the peak area (A) of the internal standard. s The ratio of antioxidant content (m) to internal standard content (m) is given by the standard working curve, with the ordinate of the curve representing the ratio of antioxidant content (m) to internal standard content (m). s The ratio of )

[0097] The internal standard solution includes an internal standard and a second solvent, and the amount of internal standard solution added is 100-200 μL; the concentration of the internal standard in the internal standard solution is 1-100 mg / L.

[0098] The concentration of antioxidant in the standard stock solution is 10-20 g / L;

[0099] The internal standard includes perfluorobiphenyl and / or deuterated hydrocarbons, wherein the deuterated hydrocarbons are selected from one or more of deuterated terphenyl, deuterated chlorobenzene, and deuterated n-tetracosane; specifically, the internal standard is perfluorobiphenyl.

[0100] The second solvent includes one or more of methanol, ethanol, and isopropanol; for example, it can be methanol.

[0101] The formula for calculating the antioxidant content is as follows:

[0102] C1=(A1 / A s 1×k+b)×C s ×V s 1 / V1 (1)

[0103] Wherein, C1 represents the antioxidant content in the sample to be tested, in mg / L;

[0104] A1 represents the peak area of ​​the quantitative antioxidant ions in the sample to be tested;

[0105] A s 1 represents the peak area of ​​the internal standard ion in the sample to be tested;

[0106] k—the slope of the linear equation in the standard curve;

[0107] b—The intercept of the linear equation in the standard curve;

[0108] C s —Internal standard concentration, mg / L;

[0109] V s 1—Volume of internal standard added, μL;

[0110] V1 — Volume of sample added, μL.

[0111] The recovery rate was determined using a jet fuel sample containing a known antioxidant concentration. The actual concentration was obtained according to formula (1), and the recovery rate was calculated using formula (2).

[0112] R = C1 / C2 × 100% (2)

[0113] Where R is the antioxidant recovery rate, %;

[0114] C1 represents the antioxidant content in the sample to be tested, in mg / L;

[0115] C2 represents the known antioxidant concentration in the sample to be tested, in mg / L.

[0116] In one embodiment of this disclosure, the mass-to-charge ratio of the antioxidant is 220, and the mass-to-charge ratio of the internal standard is 334.

[0117] The following examples illustrate the method for separating and determining the antioxidant 2,6-di-tert-butyl-p-cresol in aviation kerosene according to this application.

[0118] The silica gel used in the examples and comparative examples was produced by the Qingdao Marine Chemical Plant Branch, with a particle size of 0.074-0.150 mm, a total pore volume of 0.36 mL / g, and a specific surface area of ​​635 m². 2 / g.

[0119] The alumina is neutral alumina for column chromatography, produced by Sinopharm Chemical Reagent Co., Ltd. Particle size is 0.074-0.150 mm, and specific surface area is 152 m². 2 / g, loss on ignition ≤8.0%.

[0120] The instrument used for analysis was a gas chromatograph-mass spectrometer, model 7890GC / 5975MS.

[0121] Gas chromatography conditions: injection port temperature 300℃, injection volume 1μL, split ratio 10:1, column oven temperature program set to initial temperature 100℃, hold for 1 min, increase to 300℃ at 40℃ / min, carrier gas flow rate 1.5mL / min.

[0122] The mass spectrometry conditions were electron impact ionization with an electron energy of 70 eV, an ion source temperature of 220 °C, and a solvent delay of 2 min. Characteristic ions of the desired compounds were selected for selective ion detection. The selected ions used were: antioxidant with a mass-to-charge ratio m / z = 220 (2,6-di-tert-butyl-p-cresol) and internal standard with a mass-to-charge ratio m / z = 334 (internal standard was perfluorobiphenyl).

[0123] In the examples and comparative examples, in the gas chromatography-mass spectrometry total ion chromatogram and gas chromatography-mass spectrometry selected ion chromatogram, the vertical axis represents the relative adsorption amount and the horizontal axis represents the retention time, in min.

[0124] Example 1

[0125] The stationary phase was prepared using the following steps:

[0126] Silica gel was dried at 150℃ for 5 hours to obtain activated silica gel, which was then stored in a desiccator for later use. Alumina was calcined at 400℃ for 4 hours to obtain activated alumina. Activated silica gel and activated alumina were weighed, mixed evenly, and used to form a stationary phase, which was then stored in a desiccator for later use.

[0127] The following steps are used to separate antioxidants from jet fuel:

[0128] Sample D1 is petroleum-based jet fuel free of 2,6-di-tert-butyl-p-cresol (T501). The jet fuel sample was provided by the Research Institute of Petroleum Processing, Sinopec. Its gas chromatography-mass spectrometry total ion chromatogram and selected ion chromatogram are shown below. Figure 1 and Figure 2 As shown, sample D2 is jet fuel with 100 mg / L of 2,6-di-tert-butyl-p-cresol (T501) added.

[0129] 3g of stationary phase was packed into a solid-phase extraction (SPE) column. Based on the total weight of the stationary phase, the silica gel content was 20% by weight. 0.5mL of each of the above jet fuel samples D1 and D2 (jet fuel to stationary phase weight ratio 1:6) were added to the SPE column. After the jet fuel samples were completely adsorbed by the stationary phase, the SPE column was washed with 4mL of a mixed solvent of n-hexane and dichloromethane (volume ratio 9:1) as the first eluent to obtain the first eluent. The volume ratio of jet fuel samples to the first eluent was 1:8.

[0130] The solid-phase extraction column was then rinsed with 5 mL of methanol as the second eluent to obtain the second eluent. The volume ratio of jet fuel sample to the second eluent was 1:10.

[0131] 100 μL of internal standard solution was added to the first and second eluents respectively for gas chromatography-mass spectrometry analysis.

[0132] The internal standard solution used perfluorobiphenyl as an internal standard dissolved in methanol, with a concentration of 20.0 mg / L.

[0133] Samples D1 and D2 were separated by solid-phase extraction. The gas chromatography-mass spectrometry selected ion chromatograms of the first eluent are shown below. Figure 3 and Figure 4 As shown, the gas chromatography-mass spectrometry selected ion chromatograms of the obtained second eluent are as follows: Figure 5 and Figure 6 As shown.

[0134] according to Figure 3 , Figure 4 , Figure 5 and Figure 6 It can be seen that the first eluent contains no antioxidant, and the second eluent, apart from the internal standard peak, does not contain any obvious hydrocarbon peaks. This indicates that the method of this application can effectively separate the antioxidant 2,6-di-tert-butyl-p-cresol (T501) from jet fuel, avoiding interference from hydrocarbons.

[0135] Comparative Example 1

[0136] The second eluent after adding the internal standard solution in Example 1 was analyzed by gas chromatography-flame ionization detector (GC-FID) for the detection of the antioxidant 2,6-di-tert-butyl-p-cresol (T501). Figure 7 This is a chromatogram of the detection results.

[0137] contrast Figure 6It can be observed that when using gas chromatography-flame ionization detector (GC-FID) to detect the antioxidant 2,6-di-tert-butyl-p-cresol (T501), there is still significant interference from hydrocarbon compounds, resulting in low detection accuracy. This indicates that the GC-MS-selective scanning method used in this invention can largely avoid interference from hydrocarbon compounds in the determination of the antioxidant 2,6-di-tert-butyl-p-cresol (T501), thereby improving the accuracy of the determination of the antioxidant 2,6-di-tert-butyl-p-cresol (T501) in jet fuel.

[0138] Comparative Example 2

[0139] 3g of stationary phase was packed into a solid-phase extraction column. Based on the total weight of the stationary phase, the silica gel content was 20% by weight. 0.5mL of the above jet fuel sample D2 (jet fuel sample to stationary phase weight ratio of 1:6) was added to the solid-phase extraction column. After the jet fuel sample was completely adsorbed by the stationary phase, the solid-phase extraction column was washed sequentially with a mixed solvent of 4mL n-hexane and 4mL n-hexane and dichloromethane (volume ratio of 9:1) as the first eluent to obtain the first eluent a and the first eluent b.

[0140] Then, the solid-phase extraction column was rinsed with 5 mL of methanol as the second eluent to obtain the second eluent.

[0141] 100 μL of internal standard solution was added to the first eluent a, the first eluent b, and the second eluent, respectively, for gas chromatography-mass spectrometry analysis.

[0142] The internal standard solution used perfluorobiphenyl as an internal standard dissolved in methanol, with a concentration of 20.0 mg / L.

[0143] The gas chromatography-mass spectrometry selected ion chromatogram of the first eluent b obtained from solid-phase extraction is shown below. Figure 8 As shown.

[0144] according to Figure 8 It is evident that hydrocarbon components remain in the solid-phase chromatography column after elution with only n-hexane. This indicates that the elution method using n-hexane as the first eluent has a significantly weaker elution ability for hydrocarbon components than the method using the mixed solvent as the first eluent. This demonstrates that the first eluent used in this method has a better effect on the separation of hydrocarbons and the antioxidant 2,6-di-tert-butyl-p-cresol, thereby reducing the interference of hydrocarbon components on 2,6-di-tert-butyl-p-cresol (T501) and improving the accuracy of 2,6-di-tert-butyl-p-cresol (T501) determination.

[0145] Example 2

[0146] This embodiment illustrates that the determination method provided by the present invention can accurately determine the antioxidant content in aviation kerosene.

[0147] (1) Establishing a standard curve

[0148] A certain amount of 2,6-di-tert-butyl-p-cresol (T501) was dissolved in toluene to prepare an antioxidant standard stock solution with a concentration of 10.0 mg / mL. Using the standard stock solution, standard working solutions with concentrations of 0.5 mg / L, 1 mg / L, 2 mg / L, 5 mg / L, and 10 mg / L were prepared, and an internal standard solution with a concentration of 2.0 mg / L was added.

[0149] Standard working solutions of different concentrations were analyzed by gas chromatography-mass spectrometry. The tests were repeated three times, and the average value was used for calculation.

[0150] The ion detection peak area (A) and the internal standard peak area (A) of T501 are used as the bases for the detection peak. s The ratio of T501 content m (mg) to internal standard content m is used as the x-axis, and the ratio of T501 content m (mg) to internal standard content m is used as the y-axis. s Plot a standard working curve with the ratio of (mg) as the ordinate, such as... Figure 9 As shown.

[0151] The results showed that T501 had a good linear response in the concentration range of 0.05-10 mg / L, with a linear correlation coefficient greater than 0.997.

[0152] (2) Determination of the content of antioxidant T501 in aviation kerosene

[0153] Using jet fuel samples without T501, T501 was added to prepare jet fuel samples with T501 concentrations of 10 mg / L, 20 mg / L, and 100 mg / L. The recovery rate and precision were then tested.

[0154] The jet fuel sample containing a known concentration of T501 prepared above was subjected to solid-phase extraction according to the method described in Example 1. After adding 100 μL of internal standard solution to the second eluent obtained, gas chromatography-mass spectrometry (GC-MS) analysis was performed. Based on the selected ion chromatogram, the peak area (A1) of T501 and the peak area (A2) of the internal standard were measured. s 1) Quantitative analysis was performed using a standard working curve. The analysis was repeated 6 times, and the results are shown in Table 1.

[0155] The internal standard solution used perfluorobiphenyl as an internal standard dissolved in methanol, with a concentration of 20.0 mg / L.

[0156] Table 1

[0157]

[0158] According to the data in Table 1, the recovery rate of T501 was 81.0-108.5% and the relative standard deviation (RSD) was 4.94-6.53% within the concentration range of 10-100 mg / L. This indicates that the quantitative determination method of the present invention has good accuracy and can accurately measure the content of antioxidant T501 in aviation kerosene, meeting the requirements of routine analysis.

[0159] Comparative Example 3

[0160] The method of Example 2 was adopted, except that acetonitrile was used as the second eluent, and the solid phase extraction column was washed three times to obtain second eluent a, second eluent b and second eluent c.

[0161] The results showed that the recoveries of 2,6-di-tert-butyl-p-cresol (T501) in the second eluent a, second eluent b, and second eluent c were 53.5%, 29.5%, and 9.8%, respectively.

[0162] Based on the data above, it can be seen that when using acetonitrile as the second elution solvent, 12 mL is required to achieve an elution effect comparable to that of methanol, indicating that using methanol as the second elution solvent has a better elution effect on antioxidants.

[0163] Comparative Example 4

[0164] 1 g of neutral alumina was packed into a solid-phase extraction (SPE) column, and the column was moistened with a 0.5 mL mixture of methyl tert-butyl ether (MTBE) and n-hexane (0.33:1, v / v). 0.5 mL of jet fuel sample D2 containing 100 mg / L T501 was added to the SPE column. After the jet fuel sample was completely adsorbed by the stationary phase, the SPE column was washed with 2 mL of the MTBE and n-hexane mixture (0.33:1, v / v) to obtain the first eluent. Then, the SPE column was washed with 2 mL of the methanol and dichloromethane mixture (0.11:1, v / v) to obtain the second eluent. 100 μL of internal standard solution was added to each of the first and second eluents, and gas chromatography-mass spectrometry (GC-MS) was used for analysis. The selected ion chromatograms were as follows: Figure 16 and Figure 17 .

[0165] The results showed that some T501 was eluted into the first eluent, indicating that the solid-phase extraction conditions could not separate the hydrocarbon compounds from the antioxidant T501.

[0166] Example 3

[0167] The recovery rate of antioxidant in a jet fuel sample with a T501 concentration of 100 mg / L was tested using the method in Example 2, the only difference being that the weight of the stationary phase was 0.5 g and the weight ratio of jet fuel sample to stationary phase was 1:1. The results showed that the recovery rate of T501 in the second eluent was only 62%, with some T501 being eluted into the first eluent.

[0168] Within the range of a preferred weight ratio of the jet fuel sample to the stationary phase of 1:(2-20), the separation of antioxidant T501 is well achieved.

[0169] Example 4

[0170] This embodiment illustrates that the determination method provided by the present invention can be used to quantitatively analyze antioxidants in different types of aviation kerosene.

[0171] Petroleum-based and bio-based jet fuel were used as samples, both provided by the Research Institute of Petroleum Processing, Sinopec. Their gas chromatography-mass spectrometry total ion chromatograms were as follows: Figure 10 and Figure 11 Their selected ion chromatograms are respectively Figure 12 and Figure 13 The two jet fuel samples were subjected to T501 separation and content determination according to the method in Example 2. The gas chromatography-mass spectrometry selected ion chromatograms of the resulting second eluent are shown below. Figure 14 and Figure 15 As shown.

[0172] The results showed that, apart from the internal standard peak, the second eluent did not contain any obvious hydrocarbon peaks. This indicates that the method of this application can be used to determine antioxidants in different types of jet fuel samples.

[0173] Example 5

[0174] The recovery rate of antioxidant in aviation kerosene samples with a T501 concentration of 100 mg / L was tested using the method of Example 2. The only difference was that, based on the total weight of the stationary phase, the content of silica gel was 15% by weight, and the content of T501 in the second eluent was calculated. The results showed that the recovery rate of T501 in the second eluent was only 56.5%.

[0175] Based on the above data, it can be seen that when the silica gel content in the stationary phase is not within the preferred range of 20-40% by weight (silica gel content less than 15% by weight), due to the strong adsorption of antioxidants by the stationary phase, solid-phase extraction cannot separate hydrocarbon compounds from T501 in jet fuel. The recovery rate of T501 in the second eluent is significantly lower than the measurement results when the silica gel content is within the preferred range of 20-40% by weight. This indicates that a stationary phase meeting the above preferred content range is beneficial for the separation of antioxidants in jet fuel and improves the accuracy of the measurement results.

[0176] Example 6

[0177] The recovery rate of antioxidant in aviation kerosene samples with a T501 concentration of 100 mg / L was tested using the method of Example 2. The only difference was that, based on the total weight of the stationary phase, the content of silica gel was 50% by weight, and the content of T501 in the second eluent was calculated. The results showed that the recovery rate of T501 in the second eluent was only 70.1%, and some T501 was eluted into the first eluent.

[0178] Based on the above data, it can be seen that when the silica gel content in the stationary phase is not within the preferred range of 20-40% by weight (silica gel content is greater than 40% by weight), solid-phase extraction cannot separate hydrocarbon compounds from T501 in jet fuel, and some T501 is eluted into the first eluent. The recovery rate of T501 in the second eluent is less than 70%, significantly lower than the measurement results when the silica gel content is within the preferred range of 20-40% by weight. This indicates that a stationary phase meeting the above preferred content range is beneficial for the separation of antioxidants in jet fuel and improves the accuracy of measurement results.

[0179] As can be seen from the above embodiments and comparative examples, this application uses alumina and silica gel as the stationary phase, and chloroalkanes with 2-4 chlorine atoms, n-alkanes with 5-7 carbon atoms, and / or cycloalkanes with 5-6 carbon atoms as the first eluent to elute hydrocarbons. A second eluent, selected from saturated monohydric alcohols with 1-3 carbon atoms and saturated monocarboxylic acids with 1-2 carbon atoms, is used to elute the antioxidant. This method can effectively separate the antioxidant T501, avoiding interference from hydrocarbons, and its content can be accurately determined by gas chromatography-mass spectrometry. When the silica gel content in the stationary phase is in the range of 20-40% by weight, even more accurate content test results can be obtained. Furthermore, accurate measurement results can also be obtained when the antioxidant content in jet fuel is low.

[0180] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0181] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0182] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for separating antioxidants from aviation kerosene, characterized in that, The method includes the following steps: (1) A stationary phase is packed into a solid phase extraction column, and the jet fuel sample to be tested is added to the stationary phase; (2) The stationary phase is washed with the first eluent to obtain the first eluent; (3) Rinse the stationary phase obtained in step (2) with the second eluent to obtain a second eluent containing an antioxidant; The antioxidant is 2,6-di-tert-butyl-p-cresol; The first eluent includes a first elution component and a second elution component; The first elution component includes one or more chloroalkanes having 2-4 chlorine atoms; The second eluent component includes one or more of n-alkanes having 5-7 carbon atoms and cycloalkanes having 5-6 carbon atoms; The second eluent comprises one or more of a saturated monohydric alcohol having 1-3 carbon atoms and a saturated monocarboxylic acid having 1-2 carbon atoms; The chloroalkanes having 2-4 chlorine atoms include one or more of dichloromethane, trichloromethane, and tetrachloromethane; The n-alkanes having 5-7 carbon atoms include one or more of n-pentane, n-hexane, and n-heptane; The cycloalkanes having 5-6 carbon atoms include cyclopentane and / or cyclohexane; The second eluent comprises one or more of methanol, ethanol, isopropanol, formic acid, and acetic acid; The stationary phase is silica gel and alumina, and the silica gel content is 20-40% by weight, based on the total weight of the stationary phase. The volume ratio of the first elution component to the second elution component is 1:(1-10); The volume ratio of the jet fuel sample to the first eluent is 1:(8-10), and the volume ratio of the jet fuel sample to the second eluent is 1:(8-10). The weight ratio of the jet fuel sample to the stationary phase is 1:(2-20).

2. The separation method according to claim 1, wherein, The specific surface area of ​​the silicone is 400-750 m². 2 / g, particle size 0.038-0.15mm, total pore volume 0.35-0.90cm³ 3 / g; The specific surface area of ​​the alumina is 80-250 m². 2 / g, with a particle size of 0.038-0.15mm.

3. The separation method according to claim 1, wherein, The method further includes: drying the silica gel before step (1), wherein the drying conditions include: a temperature of 100-200℃ and a time of 3-8h; The method further includes: before step (1), calcining the alumina, wherein the calcination conditions include: a temperature of 300-500℃ and a time of 2-6h.

4. A method for determining the antioxidant content in aviation kerosene, characterized in that, The method includes: The second eluent is separated from the aviation kerosene sample to be tested using the separation method described in any one of claims 1-3; The antioxidant content in the second eluent was determined by gas chromatography-mass spectrometry. The quantitative method of the gas chromatography-mass spectrometry is the internal standard method.

5. The method according to claim 4, wherein, The internal standard method uses perfluorobiphenyl and / or deuterated hydrocarbons as internal standards.

6. The method according to claim 4, wherein, The mass spectrometry method employs a selected ion scanning mode, and the selected ions include the molecular ions of the internal standard, the molecular ions of the antioxidant, and / or fragment ions.

7. The method according to claim 4, wherein, The content of 2,6-di-tert-butyl-p-cresol in the jet fuel sample to be tested was 5-100 mg / L.

8. The method according to claim 4, wherein, The gas chromatography test conditions include: an injection port temperature of 200-300℃, an injection volume of 0.1-1.0μL, and a split ratio of (1-20):1; The mass spectrometry test conditions include: ionization method is electron bombardment ionization, electron energy is 70 eV, and ion source temperature is 200-250℃.

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