A method of determining the composition of a fischer-tropsch synthesis oil

Abstract

The application discloses a method for determining the composition of Fischer-Tropsch synthetic oil, and belongs to the technical field of analysis and detection, and comprises the following steps: obtaining detection data of a Fischer-Tropsch synthetic aviation kerosene distillate sample to be tested in a comprehensive two-dimensional gas chromatography mass spectrometry analysis; obtaining the retention time of a plurality of n-alkane standard samples with representative carbon numbers in the comprehensive two-dimensional gas chromatography mass spectrometry analysis; calculating the retention index of each spectrum peak according to the retention time of the plurality of n-alkane standard samples with representative carbon numbers, and obtaining a special standard retention index database according to the retention index of each spectrum peak; establishing a multi-dimensional qualitative discrimination rule for the hydrocarbon components of the aviation kerosene distillate; wherein, the multi-dimensional qualitative discrimination rule for the hydrocarbon components of the aviation kerosene distillate; based on the multi-dimensional qualitative discrimination rule for the hydrocarbon components of the aviation kerosene distillate, generating a full-component qualitative result report according to the detection data and the special standard retention index database; and calculating the mass fraction of each component in the full-component qualitative result report.

Description

Technical Field

[0001] This invention belongs to the field of analytical testing technology, and specifically relates to a method for determining the composition of Fischer-Tropsch synthetic oil. Background Technology

[0002] Fischer-Tropsch synthesis is an important process that converts syngas (CO and H2) into liquid hydrocarbons under the action of a catalyst. Among them, the preparation of aviation kerosene fractions from Fischer-Tropsch synthesis products through processes such as hydrorefining and hydroisomerization is an important direction for the high-value utilization of Fischer-Tropsch synthetic oils.

[0003] Fischer-Tropsch aviation kerosene fraction refers to the middle distillate extracted from the crude Fischer-Tropsch synthesis product, with a distillation range within the boiling range of aviation kerosene (typically approximately 140–300°C). The Fischer-Tropsch synthesis reaction is characterized by a complex product portfolio and a wide carbon number distribution. Because the carbon number distribution of the Fischer-Tropsch synthesis products follows the Anderson-Schul-Flory (ASF) distribution, the crude product inevitably contains heavy wax components ranging from C4 light hydrocarbons to C30+. Therefore, before distillation to obtain the aviation kerosene fraction, the actual carbon number distribution of the Fischer-Tropsch aviation kerosene fraction is typically C4–C30+, encompassing light hydrocarbons, middle distillates, and some heavy components, resulting in an extremely complex composition.

[0004] The hydrocarbon composition of Fischer-Tropsch aviation kerosene distillates has distinct characteristics: it is mainly composed of alkanes (n-alkanes and isoalkanes), while also containing a certain amount of cycloalkanes and alkenes (including terminal alkenes and a small amount of internal alkenes). Accurate analysis of the detailed composition of various hydrocarbon components within the C4–C30+ carbon range in Fischer-Tropsch aviation kerosene distillates is not only the core foundation for evaluating the performance of Fischer-Tropsch synthesis catalysts and optimizing hydroisomerization process conditions, but also a crucial technical support for improving the quality of aviation kerosene products and meeting the stringent requirements of aviation fuel regulations.

[0005] Currently, the analysis of hydrocarbon composition in Fischer-Tropsch synthesis jet fuel distillate mainly faces the following technical bottlenecks: First, there is a contradiction between the extremely wide carbon number distribution and the need for single-step analysis. The carbon number distribution of Fischer-Tropsch synthetic jet fuel oil typically extends from C4 to C30+, with significant differences in boiling points between different carbon number groups. The boiling points of light components (C4–C8) and heavy components (C20–C30+) can differ by more than 300°C. Existing gas chromatography methods mostly employ fractionation to analyze light and heavy components separately, which is cumbersome and prone to introducing errors. No method has yet been reported that can achieve single-step separation and analysis of the entire carbon number range from C4 to C30+.

[0006] Secondly, there is the challenge of distinguishing between isoalkanes and cycloalkanes. In Fischer-Tropsch synthesis jet fuel distillates, isoalkanes and monocyclic cycloalkanes show highly overlapping peak positions and extremely similar retention times in conventional one-dimensional gas chromatography. Although their molecular formulas differ (isoalkanes have C16-C16), they are distinct. n H2n+2, cycloalkanes are C n While both H2n and other hydrocarbons exhibit similar characteristic ion series in electron impact mass spectrometry (EIMS), they are difficult to distinguish accurately using traditional gas chromatography-mass spectrometry methods alone. Existing PONA analytical methods are mainly applicable to light naphtha fractions, and their effectiveness in distinguishing cycloalkanes and isoalkanes over a wide carbon number range in jet fuel fractions is limited.

[0007] Thirdly, there is the problem of misclassification between alkenes and isoalkanes. In Fischer-Tropsch synthesis jet fuel distillate, the peak positions of alkenes (including terminal and internal alkenes) and isoalkanes highly overlap in conventional one-dimensional gas chromatography, making accurate differentiation impossible. Although both exhibit characteristic ion series of alkane / alkene in mass spectra, existing analytical methods rely heavily on manual experience and lack quantitative distinguishing indicators. This easily leads to alkene peaks being incorrectly classified as isoalkanes or vice versa, severely impacting the accuracy of compositional analysis data. Fourth, there is a contradiction between the difficulty in obtaining standards and the need for qualitative analysis across the entire carbon number range. The hydrocarbon components in Fischer-Tropsch jet fuel distillate have a wide carbon number range and numerous isomers. Obtaining standards for each compound across the entire carbon number range for retention time calibration is neither economical nor practical. This is especially true for high-carbon-number (C20 and above) isoalkanes and cycloalkanes, where commercially available standards are unavailable for most compounds. Therefore, achieving high-accuracy qualitative analysis of components across the entire carbon number range using only a limited number of standards is a pressing technical challenge that needs to be addressed.

[0008] Fifth, there is a lack of dedicated standard spectral databases covering the entire carbon number range. Currently, there are no reports of dedicated standard retention index databases or standard fingerprint databases for hydrocarbon components in the C4–C30+ carbon number range of Fischer-Tropsch synthetic jet fuel distillate, resulting in a lack of standardized analytical tools for process monitoring and batch consistency evaluation of jet fuel product quality.

[0009] Therefore, there is an urgent need for a method to determine the composition of Fischer-Tropsch synthetic oils in order to solve the problems existing in the prior art. Summary of the Invention

[0010] In view of this, the present invention provides a method for determining the composition of Fischer-Tropsch synthetic oil, which solves the problems in the existing analysis of hydrocarbon components in Fischer-Tropsch synthetic jet fuel oil, such as the difficulty in one-time analysis due to the wide carbon number range, the difficulty in distinguishing between isoalkanes and cycloalkanes, the cross-judgment of alkenes and isoalkanes, and the difficulty in obtaining full carbon number standards.

[0011] To achieve the above objectives, the present invention provides: 1. A method for determining the composition of Fischer-Tropsch synthetic oil, characterized by comprising the following steps: To obtain detection data of Fischer-Tropsch synthetic jet fuel oil samples by two-dimensional gas chromatography-mass spectrometry analysis; the detection data includes chromatographic data, mass spectrometry data, and detector response data. Obtain the retention times of several representative n-alkane standards with different carbon numbers during two-dimensional gas chromatography-mass spectrometry analysis; The retention index of each spectral peak is calculated based on the retention time of several representative n-alkane standards with different carbon numbers, and a dedicated standard retention index database is obtained based on the retention index of each spectral peak. Establish multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel distillate; among which, the multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel distillate include: discrimination rules for n-alkanes, discrimination rules for isoalkanes, discrimination rules for cycloalkanes, and discrimination rules for alkenes; Based on the multidimensional qualitative discrimination rules for hydrocarbon components in aviation kerosene distillate, a report on the qualitative results of all components is generated according to the detection data and a dedicated standard retention index database. Calculate the mass fraction of each component in the overall qualitative results report.

[0012] As an embodiment of the present invention, the retention index of each spectral peak is calculated based on the retention times of several representative n-alkane standards with different carbon numbers, and a dedicated standard retention index database is obtained based on the retention indices of each spectral peak, including: Based on linear interpolation or extrapolation methods, a standard curve for the retention time of n-alkanes across the entire carbon number range is established according to the retention times of several representative n-alkanes with different carbon numbers. The standard curve for the retention time of n-alkanes is a fitted curve with carbon number as the abscissa and retention time as the ordinate. The retention index of each chromatographic peak was calculated based on the standard curve of retention time and carbon number of n-alkanes, using the following formula: In the formula, Indicates the analyte The retention index, Indicates the analyte The number of carbon atoms in the nearest n-alkane before peak elution. Indicates the analyte Retention time, Indicates the number of carbon atoms. Retention time of n-alkanes The number of carbon atoms is Retention time of n-alkanes; A dedicated standard retention index database was constructed based on the retention time carbon number standard curve of n-alkanes, the retention index of each chromatographic peak, and the corresponding chemical formula, molecular weight, and typical mass spectrometry characteristic ions for each carbon number.

[0013] As an embodiment of the present invention, the discrimination rule for n-alkanes is that the mass spectrum shows a series of characteristic ions such as m / z 57, 71, 85, and 99, and the peak intensity of each characteristic ion shows a decreasing trend. The retention index of n-alkanes with each carbon number has a good linear relationship with the carbon number. The discrimination rule for isoalkanes is that the abundance of carbon number-weighted characteristic fragment ions in the mass spectrum has a specific distribution pattern, and the retention index of isoalkanes with the same number of carbons shifts within a specific range relative to the corresponding n-alkanes. The discrimination rules for isoparaffins also include: when the abundance ratio of m / z 55 to m / z 57 in the mass spectrum of the chromatographic peaks is... When the value is greater than 1.0, it is excluded from the possibility of being an isoparaffin and classified as an olefin. The discrimination rule for cycloalkanes is that the molecular ion peak in the mass spectrum has... The compositional characteristics are present, and characteristic cycloalkanes with m / z 67, 81, and 95 are present; in full two-dimensional chromatography, the two-dimensional retention time of cycloalkanes is 0.5–3.0 seconds longer than that of isoalkanes; The discrimination rule for alkenes is that the molecular ion peak is visible in the mass spectrum and there are characteristic alkene ions at m / z 55 and 69; in the full two-dimensional chromatography, the two-dimensional retention time of alkenes shows a characteristic distribution range between that of n-alkanes and cycloalkanes. The core distinguishing indicator between alkenes and isoalkanes is the abundance ratio of characteristic ions in mass spectrometry. This ratio is determined by the abundance of peaks at m / z 55 to m / z 57. When the abundance ratio is greater than 1.0, it is determined to be an olefin; when the abundance ratio of the chromatographic peak m / z 55 to m / z 57 is greater than 1.0, it is determined to be an olefin. When the abundance ratio is less than 0.8, it is determined to be an isoalkane; when the abundance ratio of the chromatographic peak at m / z 55 to m / z 57 is... When the value is between 0.8 and 1.0, a comprehensive judgment is made by combining the retention index offset and the two-dimensional retention time.

[0014] As an embodiment of the present invention, a full-component qualitative result report is generated based on detection data and a dedicated standard retention index database, including: The retention index of the Fischer-Tropsch synthetic jet fuel sample was calculated based on the test data. The detection data and retention index are matched with data in a dedicated standard retention index database according to a preset priority order to obtain a full-component qualitative result report; the preset priority order is retention index matching, mass spectrometry library matching, and characteristic ion verification.

[0015] As an embodiment of the present invention, calculating the mass fraction of each component in the full-component qualitative results report includes: The effective carbon number of each component in the full component qualitative results report is determined as follows: In the formula, Indicates the effective carbon number, Indicates the actual number of carbon atoms. This represents the weakening coefficient of the ring structure. Indicates the number of ring structures. This represents the double bond attenuation coefficient. Indicates the number of double bonds; The correction factor for each component is obtained based on the effective carbon number of each component; The mass fraction of each component was calculated based on the correction factor for each component, as shown below: In the formula, This indicates that the first [item] in the Fischer-Tropsch synthesis jet fuel distillate sample is [the first item]. Mass fraction of each component Indicates the first Peak area of ​​each component Indicates the first Correction factors for each component This represents the sum of the corrected peak areas of all identified components.

[0016] The beneficial effects of this invention are as follows: This invention addresses the characteristic of the extremely wide carbon number distribution of jet fuel fraction oil synthesized by Fischer-Tropsch synthesis. It adopts full two-dimensional gas chromatography technology, combined with optimized fourth- or fifth-order temperature program conditions and high-temperature chromatographic columns, to achieve one-time full-component testing and analysis from C4 light components to C30+ heavy components. No fraction cutting is required, and the operation is simple and efficient.

[0017] Based on full two-dimensional gas chromatography, this invention comprehensively utilizes multi-dimensional information such as fine classification of retention index offset, differences in mass spectrometry characteristic ions, and two-dimensional retention time distribution characteristics to effectively solve the technical problem of distinguishing and identifying isoalkanes and cycloalkanes under conventional chromatographic conditions.

[0018] This invention, while retaining the index offset discrimination, introduces a quantitative threshold for the abundance ratio of characteristic ions at m / z 55 and m / z 57 as a hard discrimination index (greater than 1.0 indicates alkenes, less than 0.8 indicates isoalkanes, and the intermediate range is determined by combining other information). This fundamentally avoids the cross-judgment of alkenes and isoalkanes caused by the overlap of the retained index range, ensuring the authenticity and reliability of the compositional analysis data.

[0019] This invention only requires selecting a few representative n-alkane standards with carbon numbers in the range of C4 to C30+ to establish a retention index benchmark. The retention time of other carbon numbers is obtained by linear interpolation or extrapolation of the carbon number retention time standard curve of n-alkane. It does not require preparing standards for all compounds in the full carbon number range one by one, thus overcoming the technical difficulties of obtaining high carbon number compound standards and high costs. This makes the method economical and scalable.

[0020] The invention establishes a dedicated standard retention index database and a three-level matching algorithm for the full carbon number range of C4 to C30+, which enables batch automatic qualitative analysis of chromatographic peaks, significantly improving the qualitative efficiency compared to traditional manual qualitative methods.

[0021] Other advantages, objectives, and features of the invention will be set forth in the following description and will be apparent to those skilled in the art in some respects, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0022] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0023] like Figure 1 As shown, the present invention provides 1. a method for determining the composition of Fischer-Tropsch synthetic oil, characterized by comprising the following steps: To obtain detection data of Fischer-Tropsch synthetic jet fuel oil samples by two-dimensional gas chromatography-mass spectrometry analysis; the detection data includes chromatographic data, mass spectrometry data, and detector response data. Obtain the retention times of several representative n-alkane standards with different carbon numbers during two-dimensional gas chromatography-mass spectrometry analysis; The retention index of each spectral peak is calculated based on the retention time of several representative n-alkane standards with different carbon numbers, and a dedicated standard retention index database is obtained based on the retention index of each spectral peak. Establish multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel distillate; among which, the multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel distillate include: discrimination rules for n-alkanes, discrimination rules for isoalkanes, discrimination rules for cycloalkanes, and discrimination rules for alkenes; Based on the multidimensional qualitative discrimination rules for hydrocarbon components in aviation kerosene distillate, a report on the qualitative results of all components is generated according to the detection data and a dedicated standard retention index database. Calculate the mass fraction of each component in the overall qualitative results report.

[0024] The working principle and beneficial effects of the above technical solution are as follows: Before detection, the sample is pretreated by taking the Fischer-Tropsch synthesis jet fuel oil sample, diluting it to a predetermined concentration with an organic solvent, dehydrating it with anhydrous sodium sulfate, and filtering it for later use. Simultaneously, a two-dimensional gas chromatography-mass spectrometry (GC-MS) analysis is performed. The pretreated sample is injected into the GC-MS instrument for analysis, where the one-dimensional column is a non-polar or weakly polar capillary column, and the two-dimensional column is a moderately polar or polar capillary column. Separation is performed using multi-stage temperature programming conditions optimized for the entire C4–C30+ carbon number range. Then, during the GC-MS analysis, chromatographic data, mass spectrometric data, and detector response data are simultaneously acquired. Next, several representative n-alkane standards with carbon numbers within the C4–C30+ range are selected and analyzed under the same chromatographic conditions as described above. The analysis involved determining the retention times of selected n-alkane standards and establishing a carbon number standard curve for retention times of n-alkanes using linear interpolation or extrapolation. The carbon number continuity was extended to the full C4–C30+ range, and the retention index of each chromatographic peak was calculated. Then, multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel oil were established: rules for n-alkanes, isoalkanes, cycloalkanes, and alkenes were established separately. The retention indices of the collected chromatographic peaks (i.e., the detection data) were matched with a standard retention index database. Automatic qualitative analysis was performed according to the priority order of retention index matching, mass spectrometry library matching, and characteristic ion verification. For chromatographic peaks that failed to match, carbon number retention value patterns were introduced for trend extrapolation. Finally, correction factors were used to quantify the identified hydrocarbon components, obtaining the mass fraction of each component. The organic solvent is at least one of n-hexane, isooctane, carbon disulfide, or dichloromethane; the dilution factor is 5 to 50 times; the dehydration treatment with anhydrous sodium sulfate is carried out at room temperature for 1 to 4 hours; the two-dimensional gas chromatography-mass spectrometry (GC×GC) system is a GC×GC coupled with time-of-flight mass spectrometry (TOFMS) or quadrupole mass spectrometry (qMS) system; the one-dimensional chromatographic column is a non-polar or weakly polar chromatographic column, including HP-1, DB-1, DB-5, HP-5 MS, MTX-1, or Rxi-5Sil. MS, column length 30–60 m, inner diameter 0.18–0.32 mm, stationary phase film thickness 0.10–1.00 μm; the two-dimensional chromatographic column is a medium polarity or polarity column, including DB-17, DB-1701, HP-88, ZB-WAX or DB-WAX, column length 1–5 m, inner diameter 0.10–0.32 mm, stationary phase film thickness 0.10–0.50 μm; the multi-stage temperature program is a four- or five-stage temperature program, with the following parameters: initial temperature 30–50 °C, hold for 1–3 min; increase to 100–150 °C at a rate of 2–6 °C / min; then increase at a rate of 1–4 °C / min. The temperature was increased at a rate of 200–250 °C; then increased to 300–350 °C at a rate of 2–6 °C / min; finally increased to 360–400 °C at a rate of 1–3 °C / min and held for 5–50 min; the carrier gas was high-purity helium or high-purity argon with a purity ≥99.999% and a flow rate of 0.8–2.5 mL / min; the injection volume was 0.1–1.0 μL and the split ratio was 20:1–100:1; the injection port temperature was 280–380 °C; the mass spectrometry conditions were: EI ionization mode, electron energy 70 eV, ion source temperature 200–280 °C, transfer line temperature 280–350 °C, and mass-to-charge ratio scan range m / z 35–800. It is worth noting that the carbon number range of Fischer-Tropsch synthetic jet fuel distillate is C4 to C30+; the hydrocarbon compounds in Fischer-Tropsch synthetic jet fuel distillate include n-alkanes, isoalkanes, monocyclic cycloalkanes and alkenes, and the alkenes include terminal alkenes and internal alkenes. This method classifies the two into the olefin category without making any distinction. The above technical solution addresses the challenges in current Fischer-Tropsch synthesis jet fuel fraction hydrocarbon component analysis, including difficulties in single-analysis due to the wide carbon number range, indistinguishability between isoalkanes and cycloalkanes, cross-identification between alkenes and isoalkanes, and difficulties in obtaining full-carbon standard samples. It achieves a single-analysis of all components from C4 light components to C30+ heavy components, taking advantage of the extremely wide carbon number distribution of Fischer-Tropsch synthesis jet fuel fractions. This is accomplished using full two-dimensional gas chromatography (GC), combined with optimized fourth- or fifth-order temperature programs and high-temperature columns, eliminating the need for fraction cutting and offering simplified and efficient operation. Building upon GC, it comprehensively utilizes multi-dimensional information such as fine fractionation of retention index shifts, differences in characteristic ions from mass spectrometry, and two-dimensional retention time distribution characteristics to effectively solve the technical challenge of distinguishing isoalkanes from cycloalkanes under conventional chromatographic conditions. Furthermore, based on retention index shift discrimination, m / z 55 and m / z... The quantitative threshold of the abundance ratio of 57 characteristic ions is used as a hard discrimination index (greater than 1.0 indicates alkenes, less than 0.8 indicates isoalkanes, and the intermediate range is determined by combining other information). This fundamentally avoids cross-judgment of alkenes and isoalkanes due to overlapping retention index ranges, ensuring the authenticity and reliability of compositional analysis data. Only a few representative n-alkanes with carbon numbers in the C4 to C30+ range need to be selected to establish a retention index benchmark. The retention times of other carbon numbers are obtained by linear interpolation or extrapolation of the carbon number retention time standard curve of n-alkanes. It is not necessary to prepare standards for all compounds in the full carbon number range one by one, overcoming the technical difficulties of obtaining high carbon number compound standards and high costs. This makes the method economical and scalable. The established dedicated standard retention index database for the full carbon number range of C4 to C30+ and the three-level matching algorithm realize the batch automatic qualitative analysis of chromatographic peaks, which significantly improves the qualitative efficiency compared with traditional manual qualitative methods.

[0025] In one embodiment, the retention index of each spectral peak is calculated based on the retention times of several representative n-alkane standards with different carbon numbers, and a dedicated standard retention index database is obtained based on the retention indices of each spectral peak, including: Based on linear interpolation or extrapolation methods, a standard curve for the retention time of n-alkanes across the entire carbon number range is established according to the retention times of several representative n-alkanes with different carbon numbers. The standard curve for the retention time of n-alkanes is a fitted curve with carbon number as the abscissa and retention time as the ordinate. The retention index of each chromatographic peak was calculated based on the standard curve of retention time and carbon number of n-alkanes, using the following formula: In the formula, Indicates the analyte The retention index, Indicates the analyte The number of carbon atoms in the nearest n-alkane before peak elution. Indicates the analyte Retention time, Indicates the number of carbon atoms. Retention time of n-alkanes The number of carbon atoms is Retention time of n-alkanes; A dedicated standard retention index database was constructed based on the retention time carbon number standard curve of n-alkanes, the retention index of each chromatographic peak, and the corresponding chemical formula, molecular weight, and typical mass spectrometry characteristic ions for each carbon number.

[0026] The working principle and beneficial effects of the above technical solution are as follows: Select several representative n-alkane standards with carbon numbers ranging from C4 to C30+, prepare mixed standard solutions, and analyze them under the same chromatographic conditions as in step (2) to determine the retention time of each selected n-alkane standard; use the retention time and carbon number of each selected n-alkane standard as a benchmark, establish a standard curve of n-alkane retention time and carbon number by linear interpolation or extrapolation, and extend the continuity of carbon number to the full range of C4 to C30+; among them, for chromatographic peaks with elution times earlier than the selected n-alkane standard with the lowest carbon number, the retention time and carbon number standard curve of n-alkane is extended to the lower carbon number range. After obtaining the retention time for the corresponding carbon number through linear extrapolation in the direction of carbon number, the retention index is calculated. For chromatographic peaks with elution times later than the selected highest carbon number n-alkane standard, the retention time for the corresponding carbon number is obtained by linear extrapolating the carbon number retention time standard curve of n-alkane towards the direction of higher carbon number, and the retention index is calculated. The one-dimensional retention index, two-dimensional retention time, and mass spectrometry information of each chromatographic peak are matched with the NIST / Wiley standard mass spectrometry library, and preliminary qualitative analysis is performed based on the carbon number retention value pattern. A dedicated standard retention index database is established, which includes the standard retention index, chemical formula, molecular weight, and typical mass spectrometry characteristic ions of each component in the full carbon number range of C4 to C30+ jet fuel oil. The representative n-alkane standards are selected from at least four carbon numbers from C5, C6, C7, C8, C9, C10, C12, C14, C16, C18, C20, C22, C24, C26, C28, and C30, preferably at least eight carbon numbers, and the selected carbon numbers are uniformly distributed in the range of C4 to C30+; the concentration of each n-alkane standard is 50 to 500 μg / mL; the carbon number retention time standard curve of n-alkane is as follows: a fitting curve is established with carbon number as the abscissa and retention time as the ordinate. For the carbon number between two adjacent n-alkane standards, the retention time is determined by linear interpolation, and for the part exceeding the carbon number range of the selected standards, the retention time is determined by linear extrapolation.

[0027] In one embodiment, the discrimination rule for n-alkanes is that the mass spectrum shows a series of characteristic ions such as m / z 57, 71, 85, and 99, and the peak intensity of each characteristic ion shows a decreasing trend. The retention index of n-alkanes with each carbon number has a good linear relationship with the carbon number. The discrimination rule for isoalkanes is that the abundance of carbon number-weighted characteristic fragment ions in the mass spectrum has a specific distribution pattern, and the retention index of isoalkanes with the same number of carbons shifts within a specific range relative to the corresponding n-alkanes. The discrimination rules for isoparaffins also include: when the abundance ratio of m / z 55 to m / z 57 in the mass spectrum of the chromatographic peaks is... When the value is greater than 1.0, it is excluded from the possibility of being an isoparaffin and classified as an olefin. The discrimination rule for cycloalkanes is that the molecular ion peak in the mass spectrum has... The compositional characteristics are present, and characteristic cycloalkanes with m / z 67, 81, and 95 are present; in full two-dimensional chromatography, the two-dimensional retention time of cycloalkanes is 0.5–3.0 seconds longer than that of isoalkanes; The discrimination rule for alkenes is that the molecular ion peak is visible in the mass spectrum and there are characteristic alkene ions at m / z 55 and 69; in the full two-dimensional chromatography, the two-dimensional retention time of alkenes shows a characteristic distribution range between that of n-alkanes and cycloalkanes. The core distinguishing indicator between alkenes and isoalkanes is the abundance ratio of characteristic ions in mass spectrometry. This ratio is determined by the abundance of peaks at m / z 55 to m / z 57. When the abundance ratio is greater than 1.0, it is determined to be an olefin; when the abundance ratio of the chromatographic peak m / z 55 to m / z 57 is greater than 1.0, it is determined to be an olefin. When the abundance ratio is less than 0.8, it is determined to be an isoalkane; when the abundance ratio of the chromatographic peak at m / z 55 to m / z 57 is... When the value is between 0.8 and 1.0, a comprehensive judgment is made by combining the retention index offset and the two-dimensional retention time. The working principle and beneficial effects of the above technical solution: Establishment of multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel distillate: Based on the multidimensional information differences among four types of hydrocarbon components—n-alkanes, isoalkanes, cycloalkanes, and alkenes—the following discrimination rules are established respectively; Given that jet fuel distillate from Fischer-Tropsch synthesis usually requires subsequent hydroisomerization or hydrocracking, and alkenes are converted to corresponding alkanes under hydrogenation conditions, this method unifies terminal alkenes and internal alkenes into the olefin category without further distinction: Discrimination rule for n-alkanes: The m / z ratio is presented in the mass spectrum. Characteristic ions of series 57, 71, 85, and 99 show a decreasing trend in peak intensity; the retention index of n-alkanes with different carbon numbers exhibits a good linear relationship with the carbon number; the discrimination rules for isoalkanes are: the abundance of carbon number-weighted characteristic fragment ions in the mass spectrum has a specific distribution pattern; the retention index of isoalkanes with the same carbon number shifts within a specific range relative to the corresponding n-alkanes; the correlation between the retention time and isomerism degree of isoalkanes in the two-dimensional direction of the full two-dimensional chromatography is used for auxiliary discrimination; the discrimination of isoalkanes also requires the following exclusion condition: when the abundance ratio of m / z 55 to m / z 57 in the mass spectrum of the chromatographic peak is greater than 1.0, it is excluded from the possibility of being an isoalkan and classified as an alkene; the discrimination rules for cycloalkanes are: the molecular ion peak in the mass spectrum has a specific distribution pattern; the retention index of isoalkanes with different carbon numbers shows ... The compositional characteristics of cycloalkanes are present, and characteristic ions of cycloalkanes such as m / z 67, 81, and 95 are present. In full two-dimensional chromatography, the two-dimensional retention time of cycloalkanes is 0.5–3.0 seconds longer than that of isoalkanes. Cycloalkanes of different ring sizes show regular differences in retention index shift and two-dimensional retention time. The discrimination rule for alkenes is that the molecular ion peak is visible in the mass spectrum, and characteristic ion of alkenes such as m / z 55 and 69 are present. In full two-dimensional chromatography, the two-dimensional retention time of alkenes shows a characteristic distribution range between that of n-alkanes and cycloalkanes. The core distinguishing indicator between alkenes and isoalkanes is the abundance ratio of characteristic ions in mass spectrometry: when the abundance ratio of m / z 55 to m / z 57 of the chromatographic peak is ( When the ratio is greater than 1.0 (preferably greater than 1.2), it is identified as an olefin; when the ratio is less than 0.8, it is identified as an isoparaffin; when the ratio is between 0.8 and 1.0, a comprehensive judgment is made by combining the retention index offset and the two-dimensional retention time; no further distinction is made between the end groups and end-position isomers of olefins, and they are uniformly classified into olefin categories; this classification method is compatible with the process characteristics of Fischer-Tropsch synthesis jet fuel distillate oil, in which olefins are converted into corresponding alkanes during subsequent hydroisomerization or hydrocracking treatment; The retention index shift of cycloalkanes varies depending on the ring size and the degree of alkyl substitution; the more alkyl substituents and the longer the carbon chain, the greater the shift. The two-dimensional retention time distribution characteristics of alkenes in full two-dimensional chromatography are as follows: under the same one-dimensional retention index conditions, the two-dimensional retention time of alkenes is slightly longer than that of n-alkanes and slightly shorter than that of cycloalkanes, exhibiting a characteristic distribution range between the two. The specific method for determining the abundance ratio of m / z 55 to m / z 57 is as follows: extract the mass spectrum at the peak apex of the chromatogram, read the ion abundance values ​​of m / z 55 and m / z 57 respectively, and calculate the ratio; when the ratio is greater than 1.0, it is determined to be an alkene; when the ratio is less than 0.8, it is determined to be an isoalkan; when the ratio is between 0.8 and 1.0, a comprehensive determination is made by combining the retention index shift and the two-dimensional retention time.

[0028] In one embodiment, a full-component qualitative result report is generated based on detection data and a dedicated standard retention index database, including: The retention index of the Fischer-Tropsch synthetic jet fuel sample was calculated based on the test data. The detection data and retention index are matched with data in a dedicated standard retention index database according to a preset priority order to obtain a full-component qualitative result report; the preset priority order is retention index matching, mass spectrometry library matching, and characteristic ion verification.

[0029] The working principle and beneficial effects of the above technical solution are as follows: The retention indices of each collected chromatographic peak are matched with the standard retention index database. Automatic qualitative analysis is performed according to the priority order of retention index matching, mass spectrometry library matching, and characteristic ion verification. For chromatographic peaks that fail to match, the carbon number retention value regularity is introduced for trend extrapolation. The automatic qualitative analysis is implemented by an automated data processing program, which can read raw chromatographic data in batches, calculate retention indices, call the database for matching, and automatically generate a full component qualitative result report. In one embodiment, calculating the mass fraction of each component in the full-component qualitative results report includes: The effective carbon number of each component in the full component qualitative results report is determined as follows: In the formula, Indicates the effective carbon number, Indicates the actual number of carbon atoms. This represents the weakening coefficient of the ring structure. Indicates the number of ring structures. This represents the double bond attenuation coefficient. Indicates the number of double bonds; The correction factor for each component is obtained based on the effective carbon number of each component; The mass fraction of each component was calculated based on the correction factor for each component, as shown below: In the formula, This indicates that the first [item] in the Fischer-Tropsch synthesis jet fuel distillate sample is [the first item]. Mass fraction of each component Indicates the first Peak area of ​​each component Indicates the first Correction factors for each component This represents the sum of the corrected peak areas of all identified components.

[0030] The working principle and beneficial effects of the above technical solution: The correction factor is calculated using the effective carbon number method. For alkanes, the effective carbon number equals the actual carbon number; for cycloalkanes, the effective carbon number is the actual carbon number minus the response attenuation factor caused by the ring structure; for alkenes, the effective carbon number is the actual carbon number minus the response attenuation factor caused by the double bond; it is worth noting that... For effective carbon number, This represents the actual carbon number. The ring structure weakening coefficient (with a value of 0.10 to 0.30) The number of rings (in monocyclic alkanes) = 1), The double bond weakening coefficient (with a value of 0.05 to 0.15) The number of double bonds (in alkenes) = 1).

[0031] In one embodiment, Sample source: The crude oil produced by a Fischer-Tropsch synthesis industrial unit and the Fischer-Tropsch synthesis distillate oil without any subsequent processing were used as the test sample. The carbon number distribution of the sample is C4 to C35, and it mainly contains n-alkanes, isoalkanes, cycloalkanes and alkenes, which is consistent with the typical composition characteristics of Fischer-Tropsch synthesis jet fuel oil.

[0032] Instrumentation: An Agilent 7890B gas chromatograph coupled with an Agilent 5977B mass spectrometer detector, and a ZX-type cold spray modulator were used to construct a fully two-dimensional gas chromatography (GC×GC) system. The one-dimensional column was an HP-5 MS capillary column (60m × 0.25mm × 0.25μm), and the two-dimensional column was a DB-17 capillary column (2.5m × 0.15mm × 0.15μm).

[0033] Standards: Select n-alkanes with eight carbon numbers (C5, C6, C7, C8, C10, C12, C14, and C16) as standards (each component concentration 100 μg / mL, solvent carbon disulfide).

[0034] Pretreatment steps: Take 1 mL of Fischer-Tropsch synthesis jet fuel oil sample to be tested, add 10 mL of carbon disulfide for dilution, dehydrate with anhydrous sodium sulfate at room temperature for 1.5 hours, filter through a 0.45 μm organic filter membrane and seal for later use.

[0035] Chromatographic conditions: Carrier gas was high-purity helium (99.999% purity), constant flow mode, flow rate was 1.0 mL / min. Injector temperature was 320℃, split injection was used with a split ratio of 80:1, and the injection volume was 0.2 μL. One-dimensional column oven temperature program: initial temperature 40℃, hold for 2 min; increase to 120℃ at a rate of 4℃ / min; increase to 220℃ at a rate of 2℃ / min; increase to 320℃ at a rate of 4℃ / min; increase to 370℃ at a rate of 2℃ / min, hold for 30 min. The two-dimensional column oven temperature program was the same as the one-dimensional column oven. Modulation periods were 5 s (C4–C12 segment) and 8 s (C13–C30+ segment).

[0036] Mass spectrometry conditions: EI ionization mode, electron energy 70 eV, ion source temperature 250℃, transfer line temperature 320℃, full scan mode, scan range m / z 35~800, solvent delay 2 min.

[0037] Retention index benchmark establishment: A mixed standard of n-alkanes with eight carbon numbers (C5-C16) was injected and analyzed under the above chromatographic conditions, and the retention times of n-alkanes with each carbon number were recorded. A standard curve was established with carbon number as the x-axis and retention time as the y-axis. Linear interpolation was used between adjacent carbon numbers, and linear extrapolation was used between C4 and C5 and above C16 to obtain the retention times of n-alkanes in the full range of carbon numbers (C4-C30+), which served as the benchmark for calculating the retention index.

[0038] Analysis Results: Under optimized conditions, all C4-C35 hydrocarbon components in the Fischer-Tropsch synthesis jet fuel oil were completely separated within 130 min, with a stable chromatographic baseline and good resolution. A total of 427 chromatographic peaks were collected, and 401 of them were successfully identified by automated qualitative analysis, with a qualitative accuracy of 93.9%. The quantitative results of each carbon group are shown in Table 1.

[0039] Table 1. Qualitative and quantitative results of hydrocarbon components in Fischer-Tropsch synthetic jet fuel distillate. In one embodiment, Sample source: The crude oil produced by a Fischer-Tropsch synthesis industrial unit and the Fischer-Tropsch synthesis distillate oil without any subsequent processing were used as the test sample. The carbon number distribution of the sample is C4 to C38, and it mainly contains n-alkanes, isoalkanes, cycloalkanes and alkenes, which is consistent with the typical composition characteristics of Fischer-Tropsch synthesis jet fuel oil.

[0040] Instrumentation: An Agilent 7890B gas chromatograph coupled with an Agilent 5977B mass spectrometer detector, and a ZX-type cold spray modulator were used to construct a fully two-dimensional gas chromatography (GC×GC) system. The one-dimensional column was an MTX-1 capillary column (60m × 0.25mm × 0.32μm), and the two-dimensional column was a DB-17 capillary column (2.5m × 0.15mm × 0.15μm).

[0041] Standards: Select n-alkanes with 10 carbon atoms, namely C5, C6, C8, C10, C12, C14, C16, C18, C20, and C22 (each component concentration 100 μg / mL, solvent n-hexane).

[0042] Pretreatment steps: Take 1 mL of Fischer-Tropsch synthesis jet fuel oil sample to be tested, add 5 mL of n-hexane for dilution, dehydrate with anhydrous sodium sulfate at room temperature for 2 hours, filter through a 0.45 μm organic filter membrane and seal for later use.

[0043] Chromatographic conditions: Carrier gas was high-purity helium (99.999% purity), constant flow mode, flow rate was 1.0 mL / min. Injector temperature was 320℃, split injection was used with a split ratio of 50:1, and the injection volume was 0.2 μL. One-dimensional column oven temperature program: initial temperature 40℃, hold for 2 min; increase to 120℃ at a rate of 4℃ / min; increase to 220℃ at a rate of 2℃ / min; increase to 320℃ at a rate of 4℃ / min; increase to 370℃ at a rate of 2℃ / min, hold for 50 min. The two-dimensional column oven temperature program was the same as the one-dimensional column oven. Modulation periods were 5 s (C4–C12 segment) and 8 s (C13–C30+ segment).

[0044] Mass spectrometry conditions: EI ionization mode, electron energy 70 eV, ion source temperature 250℃, transfer line temperature 320℃, full scan mode, scan range m / z 35~800, solvent delay 2 min.

[0045] Retention index benchmark establishment: A mixed standard of n-alkanes with 10 carbon numbers (C5 to C22) was injected and analyzed under the above chromatographic conditions, and the retention times of n-alkanes with each carbon number were recorded. A standard curve was established with carbon number as the x-axis and retention time as the y-axis. Linear interpolation was used between adjacent carbon numbers, and linear extrapolation was used between C4 and C5 and above C22 to obtain the retention times of n-alkanes in the full range of C4 to C30+ carbon numbers, which served as the benchmark for calculating the retention index.

[0046] Analysis results: Under optimized conditions, all C4-C38 hydrocarbon components in the Fischer-Tropsch synthesis jet fuel oil were completely separated within 150 min, with a stable chromatographic baseline and good resolution. A total of 442 chromatographic peaks were collected, and 410 of them were successfully identified by automated qualitative analysis, with a qualitative accuracy of 92.8%. The quantitative results of each carbon group are shown in Table 2.

[0047] Table 2. Qualitative and quantitative results of hydrocarbon components in Fischer-Tropsch synthetic jet fuel distillate. The gas chromatographic identification method for hydrocarbon components in Fischer-Tropsch synthesis jet fuel distillate provided by this invention is simple to operate, rapid in analysis, accurate in qualitative analysis, and highly automated. Furthermore, it requires only a limited number of n-alkane standards to establish a retention index benchmark covering the entire carbon number range, without relying on expensive and difficult-to-obtain full-carbon number standards, thus exhibiting good economic efficiency and scalability. This invention can be widely applied in process research, catalyst performance evaluation, product quality control, process monitoring, and jet fuel product quality improvement in the fields of Fischer-Tropsch synthesis jet fuel distillate.

[0048] This invention also provides a method for constructing a standard fingerprint database for identifying jet fuel fractions in Fischer-Tropsch synthesis, comprising the following steps: Representative Fischer-Tropsch synthetic jet fuel standard samples were selected and analyzed according to the aforementioned determination method to obtain the full two-dimensional gas chromatograms of the standard samples and the qualitative results of each component. The chromatograms of standard samples were segmented according to carbon number, and the relative retention index and relative peak area of ​​each carbon group from C4 to C30+ were extracted as characteristic parameters. With carbon number as the x-axis and retention index as the y-axis, standard curves for the retention index of n-alkanes, the distribution ranges for the retention index of isoalkanes, the distribution ranges for the retention index of cycloalkanes, and the distribution ranges for the retention index of alkenes were constructed respectively. All characteristic parameters are integrated to form a standard fingerprint database for aviation kerosene distillate oil, which includes standard chromatograms and a qualitative database.

[0049] In addition, the present invention also provides a quality control method for Fischer-Tropsch synthetic jet fuel distillate, comprising the following steps: The Fischer-Tropsch synthetic jet fuel sample was analyzed according to the above determination method to obtain its full component qualitative and quantitative results and full two-dimensional gas chromatogram. The gas chromatograms were compared with the standard chromatograms in the standard fingerprint database constructed above. When the similarity is lower than a preset threshold, the sample to be tested is judged to be of abnormal quality.

[0050] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for determining the composition of Fischer-Tropsch synthetic oil, characterized in that, Includes the following steps: To obtain detection data of the Fischer-Tropsch synthetic jet fuel oil sample by two-dimensional gas chromatography-mass spectrometry analysis; the detection data includes: chromatographic data, mass spectrometry data and detector response data; Obtain the retention times of several representative n-alkane standards with different carbon numbers during two-dimensional gas chromatography-mass spectrometry analysis; The retention index of each spectral peak is calculated based on the retention time of several representative n-alkane standards with different carbon numbers, and a dedicated standard retention index database is obtained based on the retention index of each spectral peak. Establish multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel distillate; among which, the multidimensional qualitative discrimination rules for hydrocarbon components in jet fuel distillate include: discrimination rules for n-alkanes, discrimination rules for isoalkanes, discrimination rules for cycloalkanes, and discrimination rules for alkenes; Based on the multidimensional qualitative discrimination rules for hydrocarbon components in aviation kerosene distillate, a report on the qualitative results of all components is generated according to the detection data and a dedicated standard retention index database. Calculate the mass fraction of each component in the overall qualitative results report.

2. The method for determining the composition of Fischer-Tropsch synthetic oil according to claim 1, characterized in that, The retention indices of each spectral peak are calculated based on the retention times of several representative n-alkane standards with different carbon numbers. A dedicated database of standard retention indices is then compiled based on these indices, including: Based on linear interpolation or extrapolation methods, a standard curve for the retention time of n-alkanes across the entire carbon number range is established according to the retention times of several representative n-alkanes with different carbon numbers. The standard curve for the retention time of n-alkanes is a fitted curve with carbon number as the abscissa and retention time as the ordinate. The retention index of each chromatographic peak was calculated based on the standard curve of retention time and carbon number of n-alkanes, using the following formula: In the formula, Indicates the analyte The retention index, Indicates the analyte The number of carbon atoms in the nearest n-alkane before peak elution. Indicates the analyte Retention time, Indicates the number of carbon atoms Retention time of n-alkanes The number of carbon atoms is Retention time of n-alkanes; A dedicated standard retention index database was constructed based on the retention time carbon number standard curve of n-alkanes, the retention index of each chromatographic peak, and the corresponding chemical formula, molecular weight, and typical mass spectrometry characteristic ions for each carbon number.

3. The method for determining the composition of Fischer-Tropsch synthetic oil according to claim 1, characterized in that, The discrimination rule for n-alkanes is that the mass spectrum shows a series of characteristic ions such as m / z 57, 71, 85, and 99, and the peak intensity of each characteristic ion shows a decreasing trend. The retention index of n-alkanes with different carbon numbers has a good linear relationship with the carbon number. The discrimination rule for isoalkanes is that the abundance of carbon number-weighted characteristic fragment ions in the mass spectrum has a specific distribution pattern, and the retention index of isoalkanes with the same number of carbons shifts within a specific range relative to the corresponding n-alkanes. The discrimination rules for isoparaffins also include: when the abundance ratio of m / z 55 to m / z 57 in the mass spectrum of the chromatographic peaks... When the value is greater than 1.0, it is excluded from the possibility of being an isoparaffin and classified as an olefin. The discrimination rule for cycloalkanes is that the molecular ion peak in the mass spectrum has... The compositional characteristics are present, and characteristic cycloalkanes with m / z 67, 81, and 95 are present; in full two-dimensional chromatography, the two-dimensional retention time of cycloalkanes is 0.5–3.0 seconds longer than that of isoalkanes; The discrimination rule for alkenes is that the molecular ion peak is visible in the mass spectrum and there are characteristic alkene ions at m / z 55 and 69; in the full two-dimensional chromatography, the two-dimensional retention time of alkenes shows a characteristic distribution range between that of n-alkanes and cycloalkanes. The core distinguishing indicator between alkenes and isoalkanes is the abundance ratio of characteristic ions in mass spectrometry. This ratio is determined by the abundance of peaks at m / z 55 to m / z 57. When the value is greater than 1.0, it is classified as an olefin; When the abundance ratio of the chromatographic peak at m / z 55 to m / z 57 When the abundance ratio is less than 0.8, it is determined to be an isoalkane; when the abundance ratio of the chromatographic peak at m / z 55 to m / z 57 is... When the value is between 0.8 and 1.0, a comprehensive judgment is made by combining the retention index offset and the two-dimensional retention time.

4. The method for determining the composition of Fischer-Tropsch synthetic oil according to claim 1, characterized in that, A full-component qualitative results report is generated based on the test data and a dedicated standard retention index database, including: The retention index of the Fischer-Tropsch synthetic jet fuel sample was calculated based on the test data. The detection data and retention index are matched with data in a dedicated standard retention index database according to a preset priority order to obtain a full-component qualitative result report; the preset priority order is retention index matching, mass spectrometry library matching, and characteristic ion verification.

5. The method for determining the composition of Fischer-Tropsch synthetic oil according to claim 1, characterized in that, Calculate the mass fraction of each component in the overall qualitative results report, including: The effective carbon number of each component in the full component qualitative results report is determined as follows: In the formula, Indicates the effective carbon number, Indicates the actual number of carbon atoms. This represents the weakening coefficient of the ring structure. Indicates the number of ring structures. This represents the double bond attenuation coefficient. Indicates the number of double bonds; The correction factor for each component is obtained based on the effective carbon number of each component; The mass fraction of each component was calculated based on the correction factor for each component, as shown below: In the formula, This indicates that the first [item] in the Fischer-Tropsch synthetic jet fuel distillate sample is [the first item]. Mass fraction of each component Indicates the first Peak area of ​​each component Indicates the first Correction factors for each component This represents the sum of the corrected peak areas of all identified components.

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