A gas chromatography system and method for detecting detailed composition of gasoline for motor vehicles

Abstract

The present invention relates to a gas chromatography system and method for detecting the detailed composition of motor gasoline, the system comprising: a first detection channel and a second detection channel; the first detection channel comprises a first injection port, a first non-polar chromatographic column, and a first detector; the first injection port is connected to the inlet of the first non-polar chromatographic column, and the outlet of the first non-polar chromatographic column is connected to the inlet of the first detector; the second detection channel comprises a second injection port, a second non-polar chromatographic column, a heart cutting assembly, a third sub-channel and a fourth sub-channel; the third sub-channel comprises a damping column and a second detector connected in sequence, and the fourth sub-channel comprises a polar chromatographic column and a third detector connected in sequence. The system structure of the present invention is compact, and can be used to determine the detailed hydrocarbon composition of motor gasoline and the content of added components.

Description

Technical Field

[0001] The invention relates to a gas chromatography system and method for detecting the detailed composition of gasoline for automobiles. Background Art

[0002] Motor gasoline is blended from different blending component gasolines according to a certain blending ratio. At the same time, in order to meet the national gasoline standards, a certain amount of oxygen-containing compounds such as methyl tert-butyl ether will be added to ensure the octane number of gasoline. At the same time, the national gasoline quality standards also stipulate that unconventional added components such as methylal, sec-butyl acetate, aniline, and N-methylaniline shall not be added artificially. Due to the complex types of blending component gasoline and the addition of various additives, the blending schemes are diverse. The determination of the molecular level composition information of motor gasoline can provide basic data for the optimization of blending schemes and the development of high-end brand gasoline, and also provide support for gasoline product quality monitoring.

[0003] From the current analytical methods, the determination of the composition of automotive gasoline in the National VI gasoline standard adopts the GB / T30519-2014 "Multidimensional gas chromatography method for the determination of hydrocarbon composition and benzene in light petroleum fractions and products". This multidimensional chromatography method can determine the total amount of saturated hydrocarbons, olefins and aromatics in automotive gasoline, but cannot obtain the content information of a single component. At the same time, when oxygen-containing compounds and other additives are added to the finished automotive gasoline, the oxygen-containing compounds or unconventional additives must be corrected by SH / T 0663-2014 "Gas chromatography method for the determination of alcohols and ether compounds in gasoline" or GB / T 33649-2017 "Gas chromatography method for the determination of oxygen-containing compounds and aniline compounds in automotive gasoline". GB / T28768-2012 "Multidimensional gas chromatography for the determination of hydrocarbon composition and oxygenated compounds in gasoline for motor vehicles" can also be used to determine the composition of gasoline for motor vehicles. This method uses a series of different types of chromatographic columns to separate and detect the components in gasoline according to carbon number and type, but it is also unable to obtain detailed information on the monomer hydrocarbon composition of gasoline for motor vehicles. High-resolution elastic quartz capillary chromatographic columns have strong separation capabilities and are particularly suitable for the separation and detection of complex mixture systems such as gasoline. The industry standard SH / T 0714-2002 "Determination of Monomer Hydrocarbon Composition in Naphtha (Capillary Gas Chromatography)" uses a 50m long non-polar capillary chromatographic column to determine the monomer hydrocarbon composition of naphtha without olefins and has been widely used. However, when a single high-resolution capillary chromatographic column is used for the analysis of finished gasoline for motor vehicles, when some oxygenated compounds or unconventional added components are added to the finished gasoline, the quantitative results will have a large deviation due to the overlap with hydrocarbons. Summary of the invention

[0004] The purpose of the present invention is to provide a gas chromatography system and method for detecting the detailed composition of motor gasoline. The system of the present invention has a compact structure and can realize accurate qualitative and quantitative analysis of oil components. The method of the present invention can accurately determine the content of monomer hydrocarbons, oxygen-containing compounds and unconventional added components in oil products.

[0005] In order to achieve the above object, the present invention provides a gas chromatograph system in a first aspect, the system comprising: a first detection channel and a second detection channel;

[0006] The first detection channel comprises a first injection port, a first non-polar chromatographic column, and a first detector; the first injection port is connected to the inlet of the first non-polar chromatographic column, and the outlet of the first non-polar chromatographic column is connected to the inlet of the first detector;

[0007] The second detection channel includes a second injection port, a second non-polar chromatographic column, a center cutting assembly, a third sub-channel and a fourth sub-channel; the third sub-channel includes a damping column and a second detector connected in sequence, and the fourth sub-channel includes a polar chromatographic column and a third detector connected in sequence; the second injection port is connected to the inlet of the second non-polar chromatographic column, the outlet of the second non-polar chromatographic column is connected to the inlet of the center cutting assembly, the first outlet of the center cutting assembly is connected to the inlet of the damping column, and the second outlet of the center cutting assembly is connected to the inlet of the polar chromatographic column.

[0008] A second aspect of the present invention provides a method for detecting the detailed composition of an oil product by gas chromatography, the method comprising:

[0009] The first portion of the oil product to be tested is introduced into the first detection channel, passed through the first non-polar chromatographic column for separation and subjected to a first detection, thereby obtaining a first chromatographic spectrum;

[0010] The second portion of the oil to be tested is introduced into the second detection channel, and is passed through the second non-polar chromatographic column for separation to obtain continuous outflow components;

[0011] Within a preset time period, the target difficult-to-separate components in the continuously eluted components are sequentially entered into the polar chromatographic column and the third detector for a third detection to obtain a third chromatographic spectrum;

[0012] Allowing the remaining component segments of the continuously eluted components obtained from the second non-polar chromatographic column to enter the damping column and the second detector in sequence;

[0013] According to the peak area of ​​the target difficult-to-separate component in the third chromatogram, the peak area of ​​the target difficult-to-separate component in the first chromatogram is corrected, and according to the corresponding peak area of ​​each component in the first chromatogram and the correction factor, a correction normalization method is adopted to determine the mass fraction of each component in the oil to be tested.

[0014] Through the above technical scheme, the system of the present invention can realize accurate analysis and detection of hydrocarbon components and added components such as oxygen-containing compounds in oil products on the same gas chromatograph. The system structure is compact, and the method of the present invention can accurately and quantitatively analyze the hydrocarbon components and added components of oil products.

[0015] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0017] Figure 1 It is a structural schematic diagram of a specific implementation mode of the gas chromatograph system of the present invention;

[0018] Figure 2 a is the first chromatogram of sample A in Example 1 of the present invention;

[0019] Figure 2 b is the first chromatogram of sample C in Example 1 of the present invention;

[0020] Figure 3 is the second chromatogram of sample C in Example 1 of the present invention;

[0021] Figure 4 a is a partial third chromatogram of sample A in Example 1 of the present invention;

[0022] Figure 4 b is a partial third chromatogram of sample C in Example 1 of the present invention;

[0023] Figure 5 a is the third chromatogram of the remaining part of sample A in Example 1 of the present invention;

[0024] Figure 5 b is the third chromatogram of the remaining part of sample C in Example 1 of the present invention;

[0025] Figure 6 is the actual chromatogram of the finished product National VI-92 gasoline for motor vehicles in Example 2 of the present invention, wherein: Figure 6 a is the third chromatogram obtained by the third detection, Figure 6 b is the first chromatogram obtained by the first detection, Figure 6 c is the second chromatogram obtained by the second detection.

[0026] Description of Reference Numerals

[0027] 1. First injection port 2. First non-polar chromatographic column 3. First detector

[0028] 5. Second injection port

[0029] 7. First damping column 8. Second non-polar chromatographic column 9. Polar chromatographic column

[0030] 10. Second detector 11. Third detector 12. First exit

[0031] 13. Second outlet 14. Microfluidic component 15. First carrier gas pipeline

[0032] 16, solenoid valve 17, second carrier gas pipeline 18, second damping column

[0033] 19. Center cutting assembly 20. First detection channel 21. Second detection channel DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0035] like Figure 1 As shown, according to the present invention, a first aspect of the present invention provides a gas chromatograph system, the system comprising: a first detection channel 20 and a second detection channel 21;

[0036] The first detection channel 20 includes a first injection port 1, a first non-polar chromatographic column 2, and a first detector 3; the first injection port is connected to the inlet of the first non-polar chromatographic column 2, and the outlet of the first non-polar chromatographic column 2 is connected to the inlet of the first detector 3;

[0037] The second detection channel 21 includes a second injection port 5, a second non-polar chromatographic column 8, a center cutting assembly 19, a third sub-channel and a fourth sub-channel; the third sub-channel includes a first damping column 7 and a second detector 10 connected in sequence, and the fourth sub-channel includes a polar chromatographic column 9 and a third detector 11 connected in sequence; the second injection port 5 is connected to the inlet of the second non-polar chromatographic column 8, the outlet of the second non-polar chromatographic column 8 is connected to the inlet of the center cutting assembly 19, the first outlet 12 of the center cutting assembly 19 is connected to the inlet of the first damping column 7, and the second outlet 13 of the center cutting assembly 19 is connected to the inlet of the polar chromatographic column 9.

[0038] The system of the present invention has a dual-channel sampling detection structure, which can realize accurate analysis and detection of hydrocarbons and oxygen-containing compounds and unconventional added components in oil products on the same gas chromatograph, and the system structure is compact.

[0039] like Figure 1As shown, the center cutting assembly 19 of the system of the present invention may include: a microfluidic assembly 14, a carrier gas inlet, a solenoid valve 16, and a second damping column 18 for ensuring flow stability;

[0040] The microfluidic component includes a first port, a second port and a third port; the first port is formed as an inlet of a center cutting component 19, the second port is connected to the first outlet 12, and the third port is connected to the second outlet 13; the center cutting component 19 has a switchable first working state and a second working state; in the first working state, the solenoid valve is in a closed state, and the carrier gas inlet is connected to the second outlet 13 through the first carrier gas pipeline 15, so that the carrier gas flows out through the first carrier gas pipeline 15 and the second outlet 13 and then carries the components flowing out from the second non-polar chromatographic column 8 into the first damping column 7; in the second working state, the solenoid valve is in an open state, and the carrier gas inlet is connected to the first outlet 12 through the second carrier gas pipeline 17, so that the carrier gas flows out through the second carrier gas pipeline 17 and the first outlet 12 and then carries the components flowing out from the second non-polar chromatographic column 8 into the polar chromatographic column 9.

[0041] According to the present invention, the first damping column 7 is well known to those skilled in the art, and may include, for example, an elastic quartz capillary column, examples of damping columns include but are not limited to an elastic quartz capillary column with an inner diameter of 0.10 mm and an elastic quartz capillary column with an inner diameter of 0.15 mm; the chromatographic column resistance of the first damping column 7 may be the same as that of the polar chromatographic column 9 to further reduce the detection error.

[0042] According to the present invention, the polar chromatographic column 9 is well known to those skilled in the art, for example, it can be a weak polar chromatographic column, a medium polar chromatographic column and a strong polar chromatographic column, preferably a medium polar chromatographic column. The stationary phase of the chromatographic column is conventionally used by those skilled in the art. In a specific embodiment, the stationary phase of the polar chromatographic column 9 can be selected from at least one of 6% cyanopropylphenyl-94% dimethylpolysiloxane, 5% phenyl-methylpolysiloxane and 50% phenyl-methylpolysiloxane; the chromatographic column length and inner diameter of the polar chromatographic column 9 can vary within a large range and be selected according to actual needs, for example, the chromatographic column length can be 25 to 50m, and the inner diameter is 0.20 to 53mm; preferably, the chromatographic column length is 25 to 30m, and the inner diameter is 0.25 to 0.32mm.

[0043] According to the present invention, the stationary phases of the first non-polar chromatographic column 2 and the second non-polar chromatographic column 8 are conventionally used by those skilled in the art, for example, they can be 100% methyl polysiloxane independently. The column length and inner diameter of the first non-polar chromatographic column 2 and the second non-polar chromatographic column 8 can also vary within a large range and be selected according to actual needs, for example, the column length is independently 30 to 100 m, and the inner diameter is independently 0.20 to 0.53 mm; preferably, the column length is independently 30 to 50 m, and the inner diameter is independently 0.20 to 0.25 mm.

[0044] According to the present invention, the first detector 3 and the third detector 11 can be flame ionization detectors independently, and the second detector 10 can be a flame ionization detector or a thermal conductivity detector.

[0045] According to the present invention, in order to realize synchronous sampling analysis of the first channel and the second channel, the system also includes a first automatic sampler and a second automatic sampler, the first automatic sampler is connected to the first injection port 1, and the second automatic sampler is connected to the second injection port 5, so as to realize real-time simultaneous sampling operation between the first detection channel and the second detection channel.

[0046] A second aspect of the present invention provides a method for detecting the composition of an oil product by gas chromatography, wherein the method comprises:

[0047] Allowing a first portion of the oil product to be tested to flow through a first non-polar chromatographic column for a first test to obtain a first chromatographic spectrum;

[0048] Allowing the second portion of the oil product to be tested to flow through a second non-polar chromatographic column to obtain a continuous effluent component;

[0049] In a preset time period, the target difficult-to-separate components in the continuously eluted components are sequentially entered into the polar chromatographic column and the third detector for a third detection to obtain a third chromatographic spectrum;

[0050] Allowing the remaining component segments of the continuously eluted components obtained from the second non-polar chromatographic column to enter the damping column and the second detector in sequence;

[0051] According to the peak area of ​​the target difficult-to-separate component in the third chromatogram, the peak area of ​​the target difficult-to-separate component in the first chromatogram is corrected, and according to the corresponding peak area of ​​each component in the first chromatogram and the correction factor, the correction normalization method is used to determine the mass fraction of each component in the oil to be tested.

[0052] According to the present invention, the target difficult-to-separate component segment refers to the time period during which several target difficult-to-separate components with similar retention times flow out. The preset time period refers to the time period set according to the retention time of the target difficult-to-separate component to cut the continuously eluted components flowing out of the second non-polar chromatographic column to allow the target difficult-to-separate component segment to enter the polar chromatographic column. The sample to be tested can be divided into two parts to obtain a first portion of oil to be tested and a second portion of oil to be tested, and the first portion of oil to be tested and the second portion of oil to be tested have exactly the same composition. The method of the present invention can avoid the problems of separation difficulties and inaccurate detection caused by the co-elution of oxygen-containing compounds and unconventional added components with hydrocarbons when conventional monomer hydrocarbon analysis methods are used to detect oil products, and can significantly improve the detection accuracy and efficiency of oil product components.

[0053] In one embodiment, in order to determine the target difficult-to-separate component, an alkane solution, such as a n-nonane solution, to which a certain amount of oxygen-containing compounds and unconventional added components are added is subjected to a first test to obtain a first chromatogram of the alkane solution; a finished gasoline without oxygen-containing compounds and unconventional added components is also subjected to a first test to obtain a first chromatogram of the finished gasoline. The first chromatogram of the finished gasoline is compared with the first chromatogram of the alkane solution to determine the target difficult-to-separate component. The comparison method is well known to those skilled in the art and will not be described in detail herein.

[0054] According to a specific embodiment of the present invention, the method may also include: comparing the retention time or retention index of the chromatographic peak in the first chromatogram with the retention time or retention index of the components in a known database, identifying the chromatographic peak in the first chromatogram, that is, qualitatively identifying the chromatographic peak, and determining the difficult-to-separate components in the gasoline sample to be tested.

[0055] For example, in the first chromatogram, the chromatographic retention time or retention index is compared with a known qualitative database, and 2,3,3-trimethylpentane and toluene have the same retention time, and the two are co-eluting components that are difficult to separate.

[0056] According to one embodiment of the present invention, within a preset time period, the target difficult-to-separate component segments in the continuously eluted components are sequentially entered into the polar chromatographic column and the third detector for a third detection to obtain a third chromatographic spectrum, including: for each target difficult-to-separate component segment in the oil product to be tested, a third detection step is performed within a preset time period corresponding to the target difficult-to-separate component segment; the third chromatographic spectrum contains chromatographic peaks of all target difficult-to-separate components.

[0057] For example, for a continuous material flow containing multiple difficult-to-separate component segments and other component segments, it can be made to switchably enter the third subchannel and the fourth subchannel; within the preset time period corresponding to each selected difficult-to-separate component segment, the component segment can enter the fourth subchannel, that is, enter the polar chromatographic column to further separate the difficult-to-separate components therein, and at the end of the preset time period, the component flowing out of the second non-polar chromatographic column is switched to enter the third subchannel, that is, enter the damping column.

[0058] According to one embodiment of the present invention, the method may include: determining a preset time period. For example, the preset time period is determined using a standard sample containing a difficult-to-separate component.

[0059] An exemplary implementation method is as follows: an alkane solution containing a target difficult-to-separate component is prepared as a standard sample, or an actual typical gasoline sample containing a target difficult-to-separate component is used as a standard sample, and the standard sample is made to flow into a second non-polar column, a damping column and a second detector in sequence to obtain a second chromatogram; a preset time period is determined based on the second chromatogram; wherein the chromatographic column resistance of the damping column is equal to the chromatographic column resistance of the polar chromatographic column.

[0060] In a further embodiment, the standard sample may also contain a reference substance, which is a component that exists stably in gasoline and has an independent and non-interfering chromatographic peak in the first chromatogram; the reference substance is selected from one or more of 3-methylpentane, isopentane and normal pentane. In a specific embodiment, the finished gasoline is used as the first standard sample, and the first standard sample is subjected to a second test to obtain the retention time period of the reference substance, and then the alkane solution containing the target difficult-to-separate component is used as the second standard sample, and the second standard sample is subjected to a second test to obtain the retention time period of the target difficult-to-separate component; in another specific embodiment, the alkane solution containing the reference substance and the target difficult-to-separate component is used as the standard sample for a second test, and the retention time period of the reference substance and the retention time period of the target difficult-to-separate component are obtained simultaneously.

[0061] In a further embodiment, determining the preset time period according to the second chromatogram may include: determining the preset time period [T3, T4] according to the retention time period [T1, T2] corresponding to the target difficult-to-separate component segment in the second chromatogram; preferably, T3 = T1-ΔT1, T4 = T2+ΔT2; ΔT1 is 10-60 seconds, preferably 5-30 seconds, and ΔT2 is 10-60 seconds, preferably 5-30 seconds, so as to further ensure that all difficult-to-separate components enter the polar chromatographic column for separation and detection, and at the same time ensure that the remaining components in the oil product to be tested, except for the difficult-to-separate components, flow into the damping column.

[0062] In a further embodiment, the standard sample contains all selected target difficult-to-separate components; in the standard sample, the content of each difficult-to-separate component is 1 to 10% by weight, preferably the content of each difficult-to-separate component is the same. In a specific embodiment, the standard sample is an alkane solution, such as a n-nonane solution, in which all selected target difficult-to-separate components are dissolved.

[0063] According to a specific embodiment of the present invention, the peak area of ​​the target difficult-to-separate component in the first chromatogram is corrected according to the peak area of ​​the target difficult-to-separate component in the third chromatogram, including: according to formula (1) A i,PONA =(A s,PONA / A S,624 )×A i,624 ×F i The corrected peak area of ​​the target difficult-to-separate component i in the first chromatogram; in formula (1), A i,PONA A is the corrected peak area of ​​the target difficult-to-separate component i in the first chromatogram; s,PONA A is the peak area of ​​the first peak of the reference; S,624 A is the peak area of ​​the third peak of the reference; i,624 is the peak area of ​​the peak corresponding to component i in the third chromatogram; F i is the peak area correction factor between channels.

[0064] An exemplary implementation method: The peak area of ​​the third spectral peak of the reference object is obtained by a method comprising the following steps: within a cutting time period, the reference object in the continuously eluted component enters a polar chromatographic column and a third detector for a third detection to obtain a third chromatographic spectrum; the peak area of ​​the third spectral peak of the reference object is determined according to the third chromatographic spectrum; wherein the cutting time period [T7, T8] is determined according to the retention time period [T5, T6] corresponding to the reference object in the second chromatographic spectrum; T7=T5-ΔT5, T8=T6+ΔT6, wherein ΔT5 is 20 to 60 seconds, and ΔT6 is 20 to 60 seconds.

[0065] In the specific implementation where the second detector is a thermal conductivity detector, in order to ensure the detection sensitivity, hydrogen can be used as a carrier gas for detecting the second part of the oil product to be tested, and a larger injection volume and a smaller split ratio need to be used. For example, the injection volume can be 0.5-2.0 μL, and the split ratio can be 10:1-50:1. This may cause a certain difference in the relative mass response factor actually measured when the first part of the oil product to be tested flows through the first non-polar chromatographic column into the first detector and the second part of the oil product to be tested flows through the polar chromatographic column into the third detector. In this case, the inter-channel area correction factor F needs to be calculated. i .

[0066] For example, according to formula (2) F i =(fi,624 / f i,PONA )×(f s,PONA / f s,624 ) Calculate F i :In formula (2), f i,624 is the relative mass response factor of the component corresponding to the i-th peak in the third chromatogram on the polar chromatographic column relative to n-heptane; i,PONA is the relative mass response factor of the component corresponding to the i-th peak in the third chromatogram on the first non-polar chromatographic column relative to n-heptane; s,PONA f is the relative mass response factor of the reference substance on the first non-polar chromatographic column relative to n-heptane; s,624 is the relative mass response factor of the reference substance on the polar chromatographic column relative to n-heptane.

[0067] In another specific embodiment, F i is 1.

[0068] According to a specific embodiment of the present invention, according to formula (3) A k,PONA =A t,PONA -A i,PONA Determine the peak area of ​​the peak of component k that co-elutes with the target difficult-to-separate component i in the first chromatogram; wherein A k,PONA A is the peak area of ​​the peak of component k that co-elutes with the target difficult-to-separate component i in the first chromatogram; t,PONA is the total area of ​​the spectral peaks of the target difficult-to-separate component i and component k. The co-eluting component refers to the substance represented by the spectral peak that at least partially overlaps with the peak of the target difficult-to-separate component in the first chromatogram and is difficult to distinguish.

[0069] According to a specific embodiment of the present invention, the method for determining the mass fraction of each component in the oil product to be tested according to the peak area in the first chromatogram and the third chromatogram can be a correction normalization method. In a specific embodiment, the components are qualitatively characterized by comparing the chromatographic peaks in the first chromatogram with a known database. For a certain difficult-to-separate component, the peak area of ​​the chromatographic peak of the difficult-to-separate component in the third chromatogram is converted into the peak area of ​​the chromatographic peak of the difficult-to-separate component on the first non-polar chromatographic column, and the same conversion is performed on all difficult-to-separate components. Then, according to the peak area of ​​the chromatographic peak of each component and the corresponding relative mass correction factor, the mass fraction of each component is calculated using the correction normalization method.

[0070] For example, the mass fraction of each component is calculated according to formula (4):

[0071]

[0072] where ω i is the mass fraction of component i, %; A iis the chromatographic peak area of ​​component i in the first chromatogram; f i is the relative mass correction factor of component i in the first chromatogram.

[0073] According to a specific embodiment of the present invention, examples of oil products to be tested include but are not limited to gasoline for motor vehicles; the oil products to be tested may contain additives, the additives include oxygen-containing compounds, and the oxygen-containing compounds include one or more of methyl tert-butyl ether, ethyl tert-butyl ether, methyl tert-amyl ether, diisopropyl ether and C1-C4 alcohols. In a specific embodiment, the oil products to be tested contain unconventional added components, which refer to non-hydrocarbon components other than the above-mentioned oxygen-containing compounds and are not allowed to be artificially added in the gasoline standards for motor vehicles, such as dimethoxymethane, sec-butyl acetate, ethyl acetate, dimethyl carbonate, aniline, N-methylaniline, o-methylaniline, m-methylaniline, p-methylaniline, etc.

[0074] According to a specific embodiment of the present invention, the lower limit of detection of the additive is 0.1 wt %; the lower limit of detection of hydrocarbons in the oil product to be tested is 0.01 wt %.

[0075] In a preferred specific embodiment of the present invention, the method comprises: allowing a first portion of the oil product to be tested to flow through a first non-polar chromatographic column for a first detection to obtain a first chromatographic spectrum; determining a target difficult-to-separate component in the gasoline sample to be tested based on the obtained first chromatographic spectrum; preparing a standard sample containing the target difficult-to-separate component and a reference, allowing the standard sample to flow into a second non-polar column, a damping column, and a second detector in sequence to obtain a second chromatographic spectrum, and determining a preset time period and a cutting time period based on the second chromatographic spectrum;

[0076] The second part of the oil product to be tested is made to flow continuously through the second non-polar chromatographic column to obtain a continuously effluent component; according to a preset time period, within the preset time period, the target difficult-to-separate component segments in the continuously effluent components flowing out of the second non-polar chromatographic column are sequentially entered into the polar chromatographic column and the third detector for a third detection to obtain a third chromatographic spectrum; the remaining component segments in the continuously effluent components flowing out of the second non-polar chromatographic column are sequentially entered into the damping column and the second detector.

[0077] According to the inter-channel peak area correction coefficient and the peak area of ​​the target difficult-to-separate component in the third chromatogram, the peak area of ​​the target difficult-to-separate component in the first chromatogram is corrected, and the mass fraction of each component in the oil to be tested is determined by the correction normalization method based on the peak area of ​​each component in the first chromatogram.

[0078] The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

[0079] Example 1

[0080] The structure of the gas chromatograph system of this embodiment is as follows:

[0081] like Figure 1 As shown, the first detection channel 20 includes a first injection port 1, a first non-polar chromatographic column 2 (Agilent's HP-PONA chromatographic column, with a stationary phase of 100% methyl polysiloxane, a column length of 50m, and an inner diameter of 0.20mm), and a hydrogen flame ionization detector. The inlet of the first non-polar chromatographic column 2 is connected to the first injection port 1, and the outlet of the first non-polar chromatographic column 2 is connected to the inlet of the first hydrogen flame ionization detector.

[0082] The second detection channel 21 includes a second injection port 5, a second non-polar chromatographic column 8 (Agilent's HP-PONA chromatographic column, with a stationary phase of 100% methyl polysiloxane, a column length of 50m, and an inner diameter of 0.20mm), a heart cutting assembly 19, a third sub-channel and a fourth sub-channel. The third sub-channel includes an elastic quartz capillary column (column length of 0.76m, inner diameter of 0.1mm) and a thermal conductivity detector connected in sequence. The fourth subchannel includes a mid-polar chromatographic column (DM-624 chromatographic column of Dicoma, with a stationary phase of 6% cyanopropylphenyl-94% dimethylpolysiloxane, a column length of 30m, an inner diameter of 0.25mm and a second hydrogen flame ionization detector connected in sequence. The second injection port 5 is connected to the inlet of the second non-polar chromatographic column 8, and the outlet of the second non-polar chromatographic column 8 is connected to the inlet of the center cutting component 19. The center cutting component 19 includes: a first outlet 12, a second outlet 13, a microfluidic component 14, a carrier gas inlet, a second damping column 18 and a solenoid valve 16; the microfluidic component includes a first port, a second port and a third port; the first port is formed as the inlet of the center cutting component 19, and the second port is connected to the first The outlet 12 is connected, and the third port is connected to the second outlet 13; the center cutting assembly 19 has a switchable first working state and a second working state; in the first working state, the solenoid valve is in a closed state, and the carrier gas inlet is connected to the second outlet 13 through the first carrier gas pipeline 15, which is used to allow the carrier gas to pass through the first carrier gas pipeline 15 and the second outlet 13, and enter the first damping column 7 together with the carrier gas and components flowing out of the second non-polar chromatographic column 8; in the second working state, the solenoid valve is in an open state, and the carrier gas inlet is connected to the first outlet 12 through the second carrier gas pipeline 17, which is used to allow the carrier gas to pass through the second carrier gas pipeline 17 and the first outlet 12, and enter the polar chromatographic column 9 together with the carrier gas and components flowing out of the second non-polar chromatographic column 8.

[0083] The oil testing method is as follows:

[0084] Prepare 3 samples: Sample A is a National V-92 finished gasoline sample; Sample B is the aforementioned National V-92 finished gasoline, with a certain amount of oxygen-containing compounds and unconventional added components added to prepare the test sample, the types and addition amounts of oxygen-containing compounds and unconventional added components are shown in Table 4; Sample C is a prepared n-nonane solution containing about 2% oxygen-containing compounds and unconventional added components. Among them, the types of oxygen-containing compounds and unconventional added components in the n-nonane solution are the same as the types of oxygen-containing compounds and unconventional added components added to the National V-92 finished gasoline. The determination steps are as follows:

[0085] (1) The parameters of the gas chromatography system are set according to the conditions in Table 1. The sample A is injected into the first detection channel by the first automatic sampler, and the components in the sample are carried by the carrier gas (nitrogen) through the first non-polar chromatographic column 2 and separated according to the order of boiling points. The first detection is performed by the flame ionization detector to obtain the first chromatogram (see Figure 2 a), integrate the first chromatogram to obtain the chromatographic peak retention time and chromatographic peak area. Take sample C under the same conditions, inject and analyze through the first injector, and obtain the separation chromatogram of these components on the first non-polar chromatographic column (see Figure 2 b).

[0086] (2) According to the first chromatogram obtained ( Figure 2 ) Determine the target difficult-to-separate components and reference materials that need to be cut in the gasoline sample to be tested, see Table 2.

[0087] (3) Sample A and sample C are taken respectively, and the samples are injected through the second automatic sample injector, so that the components in the samples flow into the second non-polar column, the damping column and the second detector in sequence, and the second chromatograms of the two samples are obtained. The second chromatogram of sample C is as follows: Figure 3 As shown, the cutting time period for cutting the reference object and all the preset time periods for cutting all the target difficult-to-separate components are determined according to the second chromatogram, see Table 2.

[0088] (4) Sample A and sample C are taken again, and the oil to be tested is injected into the second detection channel by the second automatic sampler. The components in the sample are carried into the second non-polar chromatographic column 8 by the carrier gas (hydrogen) and separated in the order of boiling points to obtain continuous outflow components.

[0089] The opening and closing time of the solenoid valve is controlled according to Table 2: within the preset time period and the cutting time period, the solenoid valve 16 is placed in an open state, at which time the carrier gas entering the solenoid valve flows through the second carrier gas pipeline 17 and the first outlet 12 and then flows through the second port and the first port of the microfluidic component 14, and together with the carrier gas flowing out of the non-polar chromatographic column 8, carries the difficult-to-separate target components flowing out of the chromatographic column 8 into the medium-polar chromatographic column for further separation, and is detected by a flame ionization detector for a third detection to obtain a third chromatogram. The third chromatograms of sample A and sample C are shown in FIG. Figure 4 and Figure 5 During the non-preset time period and the non-cutting time period, the solenoid valve 16 is placed in a closed state. At this time, the carrier gas entering the solenoid valve flows through the first carrier gas pipeline 15 and the second outlet 13 and then flows through the third port and the first port of the microfluidic component 14. Together with the carrier gas flowing out of the non-polar chromatographic column 8, it carries other components flowing out of the chromatographic column 8 into the first damping column 7 for second detection through the thermal conductivity detector.

[0090] Figure 4 a is the third chromatogram of sample A, Figure 4 b The third chromatogram of sample C, wherein 1 is methanol, 2 is methylal, 3 is tert-butanol, 4 is MTBE, 5 is DIPE, 6 is sec-butanol, 7 is ethyl acetate, 8 is DMC; 9 is n-butanol; 10 is SBA; 11 is 3-methylpentane, and 12 is toluene.

[0091] Figure 5 a is the third chromatogram of sample A, Figure 5 b is the third chromatogram of sample C, in which 1 is aniline; 2 is N-methylaniline; 3 is o-methylaniline+p-methylaniline; and 4 is m-methylaniline.

[0092] Depend on Figure 4 and Figure 5 It can be seen that the oxygen-containing compounds and unconventional added components cut onto the polar chromatographic column are well separated from the hydrocarbon components in gasoline.

[0093] (5) Determination of sample B: Divide sample B into two parts, place them on the first injector and the second injector, start the chromatographic instrument, and the first injector and the second injector simultaneously introduce the sample into the first detection channel and the second detection channel and operate according to the chromatographic conditions of Table 1 and the valve cutting time table of Table 2 to obtain the first chromatogram and the third chromatogram of sample B.

[0094] The components were qualitatively characterized based on their retention time. The relative response factors of oxygen-containing compounds and unconventional added components on non-polar and polar columns were calculated based on the content of each component in sample C and the chromatographic peak areas in the first and third chromatograms. See Table 3.

[0095] (6) Calculate the content of each component in sample B:

[0096] The first peak of 3-methylpentane is obtained in the first chromatogram of sample B, and the third peak of 3-methylpentane is obtained in the third chromatogram. Then, according to formula A i,PONA =(A s,PONA / A S,624 )×A i,624 ×F i Calculate the corrected peak area of ​​the third chromatographic peak for each target difficult-to-separate component in the third spectrum; where Fi According to formula F i =(f i,624 / f i,PONA )×(f s,PONA / f s,624 ) were calculated, and the results are shown in Table 3.

[0097] Each chromatographic peak in the first chromatogram is compared with the known database for qualitative analysis. According to formula A k,PONA =A t,PONA -A i,PONA Determine the peak area of ​​the component co-eluting with the target difficult-to-separate component in the first chromatogram, and use the correction normalization method for all chromatographic peaks in the first chromatogram according to the formula The mass fraction of each component was calculated to obtain the determination results of oxygen-containing compounds and aniline compounds added to gasoline, as shown in Table 4.

[0098] Table 1

[0099]

[0100] Table 2

[0101]

[0102]

[0103] Table 3

[0104]

[0105] Table 4

[0106]

[0107]

[0108] Example 2

[0109] The finished product of National VI-92 motor gasoline was analyzed and measured under the same conditions as in Example 1, and the switch of the solenoid valve was controlled according to the preset time in Table 2. The actual chromatogram of the finished product of National VI-92 motor gasoline was shown in FIG. Figure 6 (in, Figure 6 a is the third chromatogram obtained by the third detection, Figure 6 b is the first chromatogram obtained by the first detection, Figure 6c is the second chromatogram obtained by the second detection). By comparing the retention time of the chromatographic peak of the component on the medium polarity chromatographic column of the second detection channel, it is confirmed that methyl tert-butyl ether is contained. According to the chromatographic peak area of ​​methyl tert-butyl ether and 3-methylpentane on the third chromatogram and the chromatographic peak area of ​​3-methylpentane on the first chromatogram, the peak area of ​​methyl tert-butyl ether on the first chromatogram is corrected, and the mass fractions of methyl tert-butyl ether and hydrocarbon components are calculated and shown in Table 5.

[0110] Table 5

[0111]

[0112]

[0113] Example 3

[0114] Take the actual National VI-92 ethanol gasoline for vehicles, adopt the method of Example 1, analyze and determine under the same conditions as Table 1, and control the switch of the solenoid valve according to the preset time of Table 2. Continuously measure 6 times. Since the ethanol component is well separated from the hydrocarbon component on the first non-polar chromatographic column of the first detection channel, the chromatographic peak area of ​​ethanol on the first detection channel is directly used to calculate the content of ethanol. Compare the retention time of the chromatographic peak of the component on the medium polar chromatographic column of channel two, confirm that there are no other oxygen-containing compounds and unconventional added components, according to the chromatographic peak area of ​​toluene and 3-methylpentane on the third chromatogram and the chromatographic peak area of ​​3-methylpentane on the first chromatogram, the toluene peak area on the first chromatogram is corrected, and the chromatographic peak area of ​​2,3,3-trimethylpentane co-eluted with toluene on the first chromatogram is obtained at the same time. The hydrocarbon component content is calculated by the correction normalization method according to the first chromatographic peak area and the relative response factor. The results are shown in Table 6.

[0115] Table 6

[0116]

[0117]

[0118] The method of the invention can accurately detect the contents of hydrocarbons, oxygen-containing compounds and unconventional additives in oil products.

[0119] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0120] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0121] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for detecting the detailed composition of an oil product by gas chromatography, the method comprising: The first portion of the oil product to be tested is introduced into the first detection channel, passed through the first non-polar chromatographic column for separation and subjected to a first detection, thereby obtaining a first chromatographic spectrum; The second portion of the oil to be tested is introduced into the second detection channel, and is passed through the second non-polar chromatographic column for separation to obtain continuous outflow components; Within a preset time period, the target difficult-to-separate components in the continuously eluted components are sequentially entered into the polar chromatographic column and the third detector for a third detection to obtain a third chromatographic spectrum; Allowing the remaining component segments of the continuously eluted components obtained from the second non-polar chromatographic column to enter the damping column and the second detector in sequence; According to the retention time or retention index of the chromatographic peak in the first chromatogram, the retention time or retention index of the component in the known database is compared to identify the chromatographic peak in the first chromatogram, and determine the difficult-to-separate component in the oil product to be tested; according to the peak area of ​​the target difficult-to-separate component in the third chromatogram, the peak area of ​​the target difficult-to-separate component in the first chromatogram is corrected; and according to the corresponding peak area of ​​each component in the first chromatogram and the correction factor, the mass fraction of each component in the oil product to be tested is determined by a correction and normalization method; Wherein, the first detection channel and the second detection channel adopt synchronous sampling analysis; The method further includes: Prepare a standard sample containing the target difficult-to-separate component, or use an actual typical gasoline sample containing the target difficult-to-separate component as a standard sample, and make the standard sample flow into the second non-polar chromatographic column, the damping column and the second detector in sequence to obtain a second chromatographic spectrum; determine the preset time period according to the second chromatographic spectrum; wherein the chromatographic column resistance of the damping column is equal to the chromatographic resistance of the polar chromatographic column; Determining the preset time period according to the second chromatogram includes: determining the preset time period [T3, T4] according to the retention time period [T1, T2] corresponding to the target difficult-to-separate group segment in the second chromatogram; wherein T3=T1-ΔT1, T4=T2+ΔT2; ΔT1 is 5 to 30 seconds, and ΔT2 is 5 to 30 seconds; Correcting the peak area of ​​the target difficult-to-separate component in the first chromatogram according to the peak area of ​​the target difficult-to-separate component in the third chromatogram comprises: The corrected peak area of ​​the target difficult-to-separate component i in the first chromatogram is calculated according to formula (1): A i,PONA =(A s,PONA / A S,624 )×A i,624 ×F i Formula (1); In formula (1), A i,PONA is the corrected peak area of ​​the target difficult-to-separate component i in the first chromatogram; A s,PONA is the peak area of ​​the first peak of the reference; A S,624 is the peak area of ​​the third spectrum peak of the reference; A i,624 is the peak area of ​​the peak corresponding to component i in the third chromatogram; F i is the peak area correction factor between channels; F i = 1, or, according to formula (2), calculate F i : F i =(f i,624 / f i,PONA )×(f s,PONA / f s,624 ) Formula (2); In formula (2), f i,624 is the relative mass response factor of the component corresponding to the i-th peak in the third chromatogram on the polar chromatographic column relative to n-heptane; f i,PONA is the relative mass response factor of the component corresponding to the i-th peak in the third chromatogram on the first non-polar chromatographic column relative to n-heptane; f s,PONA is the relative mass response factor of the reference substance relative to n-heptane on the first non-polar chromatographic column; f s,624 is the relative mass response factor of the reference substance relative to n-heptane on the polar chromatographic column; The standard sample also contains a reference substance, which is a component that exists stably in gasoline and has an independent and non-interfering chromatographic peak in the first chromatogram; the reference substance is selected from one or more of 3-methylpentane, isopentane and n-pentane; The peak area of ​​the third spectrum peak of the reference object is obtained by a method comprising the following steps: During the cutting time period, the reference substance in the continuously eluting component enters the polar chromatographic column and the third detector for a third detection to obtain the third chromatographic spectrum; Determine the peak area of ​​the third spectral peak of the reference object according to the third chromatogram; wherein the cutting time period [T7, T8] is determined according to the retention time period [T5, T6] corresponding to the reference substance in the second chromatogram; T7=T5-ΔT5, T8=T6+ΔT6, where ΔT5 is 20~60 seconds, and ΔT6 is 20~60 seconds.

2. The method according to claim 1, wherein: The method of causing the target difficult-to-separate component in the continuously effluent components to enter the polar chromatographic column and the third detector in sequence for a third detection within a preset time period to obtain a third chromatographic spectrum comprises: For each of the target difficult-to-separate component segments in the oil product to be tested, performing the third detection step within a preset time period corresponding to the target difficult-to-separate component segment; The third chromatogram contains chromatographic peaks of all the target difficult-to-separate components.

3. The method according to claim 1, wherein: The standard sample contains all the target difficult-to-separate components; in the standard sample, the content of each of the target difficult-to-separate components is 1 to 5% by weight.

4. The method according to claim 1, wherein: The peak area of ​​the peak of component k co-eluting with the target difficult-to-separate component i in the first chromatogram is determined according to formula (3): A k,PONA =A t,PONA -A i,PONA Formula (3) Among them, A k,PONA A is the peak area of ​​the peak of the component k co-eluting with the target difficult-to-separate component i in the first chromatogram; t,PONA is the total area of ​​the spectral peaks of the target difficult-to-separate component i and the component k.

5. The method according to claim 1, wherein: The oil product to be tested is automotive gasoline; the oil product to be tested contains additives, and the additives include one or more of oxygen-containing compounds, aniline and methylaniline; the oxygen-containing compounds include one or more of methyl tert-butyl ether, ethyl tert-butyl ether, methyl tert-amyl ether, diisopropyl ether, C1~C4 alcohol, methylal, sec-butyl acetate, ethyl acetate and dimethyl carbonate.

6. The method according to claim 5, wherein: The lower limit of detection of the additive is 0.1% by weight; the lower limit of detection of hydrocarbons in the oil product to be tested is 0.01% by weight.

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