A method for detecting C10-C150 paraffins in petroleum and petrochemical complex base organic matter

Abstract

The present application relates to the technical field of analytical detection, and particularly relates to a detection method of C10-C150 alkane in complex base organic matter of petroleum and petrochemical, comprising: A) separating the complex base organic matter by column chromatography or thin layer chromatography to obtain saturated fraction; B) after removing the solvent in the saturated fraction, the obtained saturated fraction is redissolved in a non-polar solution; C) the obtained solution is analyzed by HPLC-APCI MS or UHPLC-APCI MS; the HPLC analysis condition is isocratic elution; the mobile phase is limited; the column temperature is 15-40 DEG C, the flow rate is 0.1-1.5 mL / min; the MS analysis adopts APCI mode, the automatic gain control target is 4.0-5.0e5, the maximum injection time is 100 ms, the micro scanning is 1, and the mass scanning range is 100-2000. 150 .

Description

Technical Field

[0001] This invention relates to the field of analytical detection technology, and in particular to a method for detecting C10 to C150 alkanes in complex organic matter from petroleum and petrochemical industries. Background Technology

[0002] Alkanes are not only key components of petroleum products but also important biomarkers in geochemistry. In refining, alkanes influence various properties of different petroleum products and distillate oils, including octane number, cetane number, viscosity-temperature, and pour point. In geochemistry, the carbon number distribution of n- and isoalkanes is used to evaluate crude oil maturity. Furthermore, long-chain alkanes are the simplest biomarkers in the molecular structure of leaf waxes from terrestrial higher plants and are frequently used to reconstruct paleoclimate and paleovegetation. Therefore, molecular composition analysis of alkanes is crucial for exploring the relationship between molecular composition and chemical properties and for gaining a deeper understanding of geochemical evolution.

[0003] In the refining and geochemical fields, GC-MS is commonly used to detect alkanes in crude oil or source rock extracts. However, due to the limitations of gas chromatography instruments in terms of temperature and separation capacity, it can currently only detect alkanes with fewer than 35 carbon atoms in light distillate oils. As the carbon number of alkanes increases, the boiling point also increases, and GC-MS cannot detect alkanes in the full range of samples (especially alkanes with more than 35 carbon atoms).

[0004] UHRMS analysis based on "petromics" is an ideal method for detecting alkanes in a full range of complex matrices. However, since alkanes have low polarity and do not have polar functional groups, commonly used electrospray ionization sources (ESI) cannot directly ionize them.

[0005] Ruthenium ion-catalyzed derivatization combined with ESI provides a feasible method for ESI analysis of saturated hydrocarbons. However, this reaction is time-consuming and complex. After the reaction, alkanes are converted into alcohols, and the ionization response under negative mode ESI is still not high. In addition, there are many side reactions that interfere with the identification of hydrocarbon compounds.

[0006] Atmospheric pressure chemical ionization (APCI) sources can achieve the advantageous "soft" ionization of alkane standard compounds under solvent-assisted ionization conditions. However, when analyzing complex real-world systems, alkanes are inhibited by the ionization of other types of hydrocarbons (especially aromatic compounds) during the ionization process, resulting in low ionization efficiency and a lack of molecular composition information for low-concentration alkanes. Furthermore, the ionization products of alkanes are complex and contain excessive fragments, posing a significant challenge to the analysis of complex samples.

[0007] Existing GC-MS-based methods for alkane analysis are limited by instrument temperature and separation capabilities, and can only analyze low-carbon alkanes (usually not exceeding C35). ESI combined with UHRMS cannot directly analyze alkanes; the RICO derivatization reaction converts alkanes into alcohols, resulting in low ionization response and numerous side reactions under negative ESI mode, interfering with alkane identification. While APCI combined with UHRMS can achieve the advantageous soft ionization of alkane standards, in the analysis of complex systems, alkanes are inhibited by the ionization of their own compounds, leading to low ionization efficiency and the inability to detect low-content alkanes. Four-component group composition separation methods have low resolution, and small amounts of monocyclic aromatic hydrocarbons in the saturated fraction still inhibit the ionization of alkanes. Summary of the Invention

[0008] In view of this, the technical problem to be solved by the present invention is to provide a method for comprehensive characterization and relative quantitative analysis of the molecular composition of C10 to C150 chain alkanes in complex systems.

[0009] Specifically, an HPLC-MS (high performance liquid chromatography-tandem mass spectrometry) analytical method was developed to characterize and relatively quantify the molecular composition of C10–C150 alkanes in complex organic matter from petroleum and petrochemical industries.

[0010] This invention provides a method for detecting C10-C150 alkanes in complex organic matter from petroleum and petrochemical industries, comprising the following steps:

[0011] A) Use column chromatography or thin-layer chromatography to separate complex matrices to obtain saturated fractions;

[0012] B) After removing the solvent from the saturated fraction, redissolve the obtained saturated fraction in a nonpolar solution;

[0013] C) Perform HPLC-APCI MS or UHPLC-APCI MS analysis on the solution obtained in step B);

[0014] The conditions for the HPLC analysis and the UHPLC analysis include:

[0015] Isocratic elution is performed using a mobile phase, which includes a non-polar mobile phase and a polar mobile phase. The non-polar mobile phase includes at least one of n-heptane, n-hexane, isooctane, and petroleum ether, and the polar mobile phase includes at least one of acetone, diethyl ether, dichloromethane, and chloroform. The column temperature is 15–40 °C, and the flow rate of the mobile phase is 0.1–1.5 mL / min.

[0016] The MS analysis uses APCI mode and includes:

[0017] The automatic gain control target is 4.0–5.0e5, the maximum injection time is 100 ms, the micro-scan is 1, and the quality scan range is 100–2000.

[0018] Preferably, in step A), the complex matrix includes crude oil, petroleum distillate oil with a boiling point range of 125–750°C, petroleum products, coal tar, kerogen, source rock extracts, or coal extracts.

[0019] Preferably, in step B), the solvent is removed by evaporating the solvent with nitrogen.

[0020] Preferably, in step B), the concentration of the nonpolar solution is 0.5–10 mg / mL.

[0021] Preferably, in step C), the HPLC analysis conditions further include an injection volume of 1–20 μL.

[0022] Preferably, in step C), the chromatographic column used is a CN column;

[0023] The HPLC column has a length of 250 mm, an inner diameter of 4.6 mm, and a packing particle size of 5 μm; the UHPLC column has a length of 50–100 mm, an inner diameter of 2.1 mm, and a packing particle size of 1.7 μm.

[0024] Preferably, in step C), the high performance liquid chromatograph used is an Agilent 1200, and the ultra-high performance liquid chromatograph is an Agilent 1290.

[0025] The MS analysis used an APCI ionization source. The nebulizing gas, auxiliary gas, and backflush gas were all selected from at least one of nitrogen, helium, and neon. The flow rate of the nebulizing gas was 5–10 Arb, the flow rate of the auxiliary gas was 3–5 Arb, and the flow rate of the backflush gas was 0.1–2 Arb. The corona needle current was 3–6 mA, and the capillary voltage was 3000–5000 V.

[0026] Preferably, in step C), the mass spectrometer used for the MS analysis is a Thermo Fisher Scientific Orbitrap FusionMS with a resolution ≥500,000.

[0027] Preferably, in step C), the detector type used for the MS analysis is Orbitrap, RF Lens: 80%.

[0028] In this invention:

[0029] 1. Development of analytical methods for HPLC-APCI MS or UHPLC-APCI MS analysis. HPLC (High Performance Liquid Chromatography) separation uses a normal-phase column as the stationary phase. Under mobile phase elution, alkanes elute before aromatic hydrocarbons, thus achieving efficient separation of saturated hydrocarbons and aromatic hydrocarbons. HPLC is directly connected in series with UHRMS via APCI (Atmospheric Pressure Chemical Ionization Source) in online mode, using n-hexane as the solution. After HPLC separation, the sample is ionized by APCI. Because HPLC eliminates the ionization inhibition of alkanes by aromatic hydrocarbons after separating them from aromatic hydrocarbons, it greatly improves the detection sensitivity of alkanes.

[0030] 2. Relative quantitative analysis of alkanes. By eliminating the inhibition of alkane ionization by aromatic hydrocarbons, high-sensitivity and high-precision analysis of alkanes of the same type of hydrocarbons was achieved under APCI, extending its detection range to C10+. 150 .

[0031] 3. Ionization efficiency can be considered consistent, and the mass spectrum peak intensity shows a linear relationship with the concentration of alkane compounds. Therefore, the mass spectrum peak intensity can be used as a basis for relative quantification. In HPLC-UHRMS analysis, the elution time for alkanes is 5.0–5.5 min. The UHRMS mass spectra from 5.0–5.5 min are averaged, and the mass spectrum peak intensities of alkanes with different carbon numbers are extracted separately. Relative quantitative analysis of alkanes can be achieved by comparing the intensities. Attached Figure Description

[0032] Figure 1 The mass chromatogram of saturated fraction of source rock extract from Comparative Example 1, analyzed by GC-MS at m / z = 85.

[0033] Figure 2 The average mass spectrum of the saturated fraction of the source rock extract in Example 1, with a retention time of 5–5.5 min, obtained by HPLC-UHRMS.

[0034] Figure 3 This is a DBE carbon number distribution diagram of hydrocarbon compounds in the saturated fraction of the source rock extract after HPLC-UHRMS analysis in Example 1;

[0035] Figure 4 This is a diagram showing the relative abundance distribution of alkanes in the saturated fraction of the source rock extract after HPLC-UHRMS analysis in Example 1. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a method for detecting C10-C150 alkanes in complex organic matter from petroleum and petrochemical industries, comprising the following steps:

[0038] A) Use column chromatography or thin-layer chromatography to separate complex matrices to obtain saturated fractions;

[0039] B) After removing the solvent from the saturated fraction, redissolve the obtained saturated fraction in a nonpolar solution;

[0040] C) Perform HPLC-APCI MS or UHPLC-APCI MS analysis on the solution obtained in step B);

[0041] The conditions for the HPLC analysis and the UHPLC analysis include:

[0042] Isocratic elution is performed using a mobile phase; the mobile phase includes a non-polar mobile phase and a polar mobile phase; the non-polar mobile phase includes at least one selected from n-heptane, n-hexane, isooctane, and petroleum ether, and the polar mobile phase includes at least one selected from acetone, diethyl ether, dichloromethane, and trichloromethane, with a volume ratio of 94%–98%:2%–6%; the column temperature of the high-performance liquid chromatography is 15–40°C, and the flow rate of the mobile phase is 0.1–1.5 mL / min;

[0043] The MS analysis uses APCI mode and includes:

[0044] The automatic gain control target is 4.0–5.0e5, the maximum injection time is 100 ms, the micro-scan is 1, and the quality scan range is 100–2000.

[0045] In step A):

[0046] Column chromatography or thin-layer chromatography is used to separate the complex matrix into saturated components. Specifically, column chromatography or thin-layer chromatography is used to separate the complex matrix into saturated components, aromatic components, resins, and asphaltenes.

[0047] In some embodiments of the present invention, the complex matrix includes crude oil, petroleum distillate oil with a boiling point range of 125–750°C, petroleum products (including gasoline, diesel, aviation kerosene, lubricating oil, petroleum wax, and petroleum coke, etc.), coal tar, kerogen, source rock extracts, or coal extracts. In some embodiments of the present invention, the source rock extract is obtained by extracting soluble organic matter from the source rock. Specifically, the soluble organic matter in the source rock can be extracted according to the method disclosed in the industry standard "SY / T 5118-2005 Determination of Chloroform Bituminous Pitch in Rocks".

[0048] In some embodiments of the present invention, the complex matrix is ​​separated into saturated components, aromatic components, resins and asphaltenes by column chromatography or thin-layer chromatography, which can be performed according to the methods disclosed in the industry standard "SY / T 5119-2016 Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks".

[0049] In step B):

[0050] After removing the solvent from the saturated fraction, the resulting saturated fraction is redissolved in a nonpolar solution.

[0051] The solvent in the saturated fraction is n-hexane (HPLC grade).

[0052] In some embodiments of the present invention, the solvent is removed by evaporating the solvent with nitrogen.

[0053] In some embodiments of the present invention, the nonpolar solution is a hexane solution with a concentration of 0.5–10 mg / mL, for example, 2 mg / mL. The hexane is HPLC grade.

[0054] In step C):

[0055] The solution obtained in step B) was analyzed by HPLC-APCI MS or UHPLC-APCI MS.

[0056] Specifically, the solution obtained in step B) is analyzed by HPLC-UHRMS or UHPLC-UHRMS.

[0057] In some embodiments of the present invention, the conditions for the HPLC (high performance liquid chromatography) analysis and the UHPLC analysis include:

[0058] Isocratic elution is performed using a mobile phase, which includes a non-polar mobile phase and a polar mobile phase. The non-polar mobile phase includes at least one selected from n-heptane, n-hexane, isooctane, and petroleum ether, and the polar mobile phase includes at least one selected from acetone, diethyl ether, dichloromethane, and trichloromethane. Specifically, the mobile phase comprises petroleum ether and acetone in a volume ratio of 95%:5%. The column temperature is 15–40°C, for example, 25°C; the flow rate of the mobile phase is 0.1–1.5 mL / min, for example, 1.5 mL / min.

[0059] The injection volume is 1–20 μL, for example, 20 μL.

[0060] The chromatographic columns used are CN columns, such as ZORBAX Original CN columns, Agilent Technologies, USA.

[0061] The HPLC column has a length of 250 mm, an inner diameter of 4.6 mm, and a packing particle size of 5 μm; the UHPLC column has a length of 50–100 mm, an inner diameter of 2.1 mm, and a packing particle size of 1.7 μm.

[0062] The high-performance liquid chromatograph used was an Agilent 1200, and the ultra-high performance liquid chromatograph used was an Agilent 1290.

[0063] The MS analysis used an APCI ionization source. The nebulizing gas, auxiliary gas, and backflush gas were all selected from at least one of nitrogen, helium, and neon. The flow rate of the nebulizing gas was 5–10 Arb, the flow rate of the auxiliary gas was 3–5 Arb, and the flow rate of the backflush gas was 0.1–2 Arb. The corona needle current was 3–6 mA, and the capillary voltage was 3000–5000 V.

[0064] In some embodiments of the present invention, the conditions for the UHRMS (high-resolution mass spectrometry) analysis include:

[0065] The automatic gain control target is 4.0–5.0e5, for example, 5.0e5; the maximum injection time is 100ms, the microscan is 1, and the quality scan range is 100–2000.

[0066] The mass spectrometer used was a Thermo Fisher Scientific Orbitrap FusionMS with a resolution of ≥500,000 FWHM, an Orbitrap detector, and an RF lens of 80%.

[0067] The present invention does not impose any special restrictions on the source of the raw materials used above, and they can be commercially available.

[0068] To further illustrate the present invention, the following detailed description of C10-C150 chain alkanes in complex organic matter of petroleum and petrochemical industries provided by the present invention is provided in conjunction with embodiments, but it should not be construed as limiting the scope of protection of the present invention.

[0069] Comparative Example 1

[0070] 1) Sample pretreatment:

[0071] Sample: Hydrocarbon source rock sample;

[0072] Soluble organic matter in source rocks was extracted according to the method disclosed in the industry standard "SY / T 5118-2005 Determination of Chloroform Bituminous Pitch in Rocks" to obtain source rock extracts;

[0073] According to the column chromatography method disclosed in the industry standard "SY / T 5119-2016 Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks", the source rock extract was separated into saturated components, aromatic components, resins and asphaltenes.

[0074] After removing the solvent n-hexane (HPLC grade) from the saturated fraction by nitrogen evaporation, the resulting saturated fraction was redissolved in n-hexane (HPLC grade) solution with a concentration of 2 mg / mL, and then analyzed by GC-MS.

[0075] 2) GC-MS analysis:

[0076] Instrument model: Agilent 7890 gas chromatograph and 5975C mass spectrometer detector coupled together; gas chromatograph column: HP-5MS fused silica capillary column; carrier gas: helium; flow rate: 1 mL / min; split ratio: 50:1; injection port temperature: 280℃; injection volume: 1 μL.

[0077] The gas chromatography temperature program was as follows: hold at 80℃ for 2 min, then heat to 300℃ at a rate of 10℃ / min, hold at 300℃ for 20 min, and set the solvent delay time to 10 min. The ion transfer tube temperature was 280℃, the mass spectrometry ion source was an EI ionization source with an electron impact voltage of 70 eV and an ion source temperature of 250℃.

[0078] Figure 1 The image shows a GC-MS mass chromatogram of the saturated fraction of the source rock extract from Comparative Example 1 at m / z = 85. Figure 1 As can be seen, GC-MS can detect C 14 ~C 33 n-Alkanes.

[0079] Example 1

[0080] 1) Sample pretreatment:

[0081] Sample: Hydrocarbon source rock sample;

[0082] Soluble organic matter in source rocks was extracted according to the method disclosed in the industry standard "SY / T 5118-2005 Determination of Chloroform Bituminous Pitch in Rocks" to obtain source rock extracts;

[0083] According to the column chromatography method disclosed in the industry standard "SY / T 5119-2016 Analysis of Soluble Organic Matter and Crude Oil Group Components in Rocks", the source rock extract was separated into saturated components, aromatic components, resins and asphaltenes.

[0084] After removing the solvent n-hexane (HPLC grade) from the saturated fraction by nitrogen evaporation, the resulting saturated fraction was redissolved in a n-hexane (HPLC grade) solution with a concentration of 2 mg / mL, and then analyzed by HPLC-UHRMS.

[0085] 2) HPLC-UHRMS analysis:

[0086] The conditions for the HPLC analysis include:

[0087] The high-performance liquid chromatograph used was an Agilent 1200; the column type was a ZORBAX OriginalCN (4.6×250mm, 5μm) column (Agilent Technologies, USA); isocratic elution was performed using a mobile phase consisting of petroleum ether and acetone in a volume ratio of 95%:5%; the flow rate was 1.5 mL / min; the injection volume was 20 μL; and the column oven temperature was 25℃.

[0088] The ionization source used is APCI. The atomizing gas, auxiliary gas and backflush gas are all selected from nitrogen. The flow rate of the atomizing gas is 5-10 Arb, the flow rate of the auxiliary gas is 3-5 Arb, and the flow rate of the backflush gas is 0.1-2 Arb. The corona needle current is 3-6 mA and the capillary voltage is 3000-5000 V.

[0089] The conditions for the UHRMS analysis include:

[0090] Mass spectrometer model: Thermo Fisher Scientific Orbitrap Fusion MS, resolution 500,000 (FWHM), detector type: Orbitrap, RF Lens: 80%, automatic gain control target: 5.0e5, maximum injection time: 100ms, microscan: 1, mass scan range: 100~2000.

[0091] Figure 2The average mass spectrum of the saturated fraction of the source rock extract in Example 1, with retention times of 5–5.5 min, obtained by HPLC-UHRMS.

[0092] Figure 3 This is a DBE carbon number distribution diagram of hydrocarbon compounds in the saturated fraction of the source rock extract after HPLC-UHRMS analysis in Example 1.

[0093] Figure 2 and Figure 3 The images show the average mass spectrum over 5-5.5 minutes and the DBE carbon number distribution of hydrocarbon compounds obtained after data processing. Figure 2 and Figure 3 As can be seen, HPLC-UHRMS can achieve C 10 ~C 150 Detection of alkanes (DBE=0).

[0094] Relative quantitative analysis of alkanes was performed based on the peak intensities in the UHRMS mass spectra, such as... Figure 4 As shown, Figure 4 This is a diagram showing the relative abundance distribution of alkanes in the saturated fraction of the source rock extract after HPLC-UHRMS analysis in Example 1. It can be seen that C... 35 The distribution characteristics of alkanes were similar to those in the GC-MS results, showing no carbon number dominance, while at C... 50 ~C 110 They exhibit a clear advantage in even carbon distribution.

[0095] The descriptions of the above embodiments are merely illustrative of the methods and core ideas of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for detecting C10-C150 alkanes in complex organic matter from petroleum and petrochemical industries, comprising the following steps: A) Use column chromatography or thin-layer chromatography to separate complex matrices to obtain saturated fractions; B) After removing the solvent from the saturated fraction, redissolve the resulting saturated fraction in a nonpolar solution; C) Perform HPLC-APCI MS or UHPLC-APCI MS analysis on the solution obtained in step B); The conditions for the HPLC analysis and the UHPLC analysis include: Isocratic elution was performed using a mobile phase comprising a nonpolar mobile phase and a polar mobile phase. The nonpolar mobile phase comprised at least one of n-heptane, n-hexane, isooctane, and petroleum ether, while the polar mobile phase comprised at least one of acetone, diethyl ether, dichloromethane, and chloroform. The volume ratio of the nonpolar to polar mobile phase was 94%–98%:2%–6%. The column temperature was 15–40°C, and the flow rate of the mobile phase was 0.1–1.5 mL / min. A CN column was used. The HPLC column has a length of 250 mm, an inner diameter of 4.6 mm, and a packing particle size of 5 µm; the UHPLC column has a length of 50-100 mm, an inner diameter of 2.1 mm, and a packing particle size of 1.7 µm. The MS analysis uses APCI mode and includes: The automatic gain control target is 4.0~5.0 e5, the maximum injection time is 100 ms, the micro-scan is 1, and the quality scan range is 100~2000. The mass spectrometer used for the MS analysis was a Thermo Fisher Scientific Orbitrap Fusion MS with a resolution ≥500,000; the detector used for the MS analysis was an Orbitrap, and the RF lens was 80%. The MS analysis used an APCI ionization source. The nebulizing gas, auxiliary gas, and backflush gas were all selected from at least one of nitrogen, helium, and neon. The flow rate of the nebulizing gas was 5-10 Arb, the flow rate of the auxiliary gas was 3-5 Arb, and the flow rate of the backflush gas was 0.1-2 Arb. The corona needle current was 3-6 mA, and the capillary voltage was 3000-5000 V.

2. The detection method according to claim 1, characterized in that, In step A), the complex matrix includes crude oil, petroleum distillate oil with a boiling point range of 125~750℃, petroleum products, coal tar, kerogen, source rock extracts or coal extracts.

3. The detection method according to claim 1, characterized in that, In step B), the solvent is removed by evaporating it with nitrogen.

4. The detection method according to claim 1, characterized in that, In step B), the concentration of the nonpolar solution is 0.5~10 mg / mL.

5. The detection method according to claim 1, characterized in that, In step C), the HPLC analysis conditions also include an injection volume of 1~20 μL.

6. The detection method according to claim 1, characterized in that, In step C), the high performance liquid chromatograph used is an Agilent 1200, and the ultra-high performance liquid chromatograph used is an Agilent 1290.

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