CN114428126A

CN114428126A - Gas phase chromatography system and method for detecting detailed composition of gasoline for vehicle

Info

Publication number: CN114428126A
Application number: CN202011187235.8A
Authority: CN
Inventors: 李长秀; 王亚敏
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2020-10-29
Filing date: 2020-10-29
Publication date: 2022-05-03

Abstract

The invention relates to a gas chromatography system and a method for detecting the detailed composition of motor gasoline, wherein the system comprises the following components: a first detection channel and a second detection channel; the first detection channel comprises a first sample inlet, a first nonpolar chromatographic column and a first detector; the first sample inlet is communicated with the inlet of the first nonpolar chromatographic column, and the outlet of the first nonpolar chromatographic column is communicated with the inlet of the first detector; the second detection channel comprises a second sample inlet, a second nonpolar chromatographic column, a central cutting assembly, a third sub-channel and a fourth sub-channel; the third sub-channel comprises a damping column and a second detector which are communicated in sequence, and the fourth sub-channel comprises a polarity chromatographic column and a third detector which are communicated in sequence. The system disclosed by the invention is compact in structure and can be used for measuring the detailed hydrocarbon composition and the content of the added components of the motor gasoline.

Description

Gas phase chromatography system and method for detecting detailed composition of gasoline for vehicle

Technical Field

The invention relates to a gas chromatography system and a method for detecting the detailed composition of motor gasoline.

Background

The motor gasoline is prepared by blending gasoline with different blending components according to a certain blending proportion, and a certain amount of oxygen-containing compounds such as methyl tert-butyl ether and the like are added to meet the national gasoline standard requirement so as to ensure the octane number of the gasoline. Meanwhile, the national gasoline quality standard also stipulates that unconventional addition components such as methylal, sec-butyl acetate, aniline, N-methylaniline and the like cannot be artificially added. Due to the complex type of blending component gasoline and the addition of various additives, blending schemes are diversified. The composition information of the molecular level of the gasoline for the vehicle is obtained by measurement, so that basic data can be provided for the optimization of a blending scheme and the development of high-end brand gasoline, and simultaneously, support is provided for the quality monitoring of gasoline products.

From the current analytical means, the GB/T30519-2014 multidimensional gas chromatography for measuring hydrocarbon group compositions and benzene in light petroleum fractions and products is adopted in the national VI gasoline standard for measuring the composition of the motor gasoline, and the multidimensional gas chromatography can measure and obtain the total amount of saturated hydrocarbon, olefin and aromatic hydrocarbon of the motor gasoline, but cannot obtain the content information of single components. Meanwhile, when the finished product of the motor gasoline is added with the added components such as the oxygen-containing compounds, the added components such as the oxygen-containing compounds or the unconventional added components must be corrected by SH/T0663-2014 gas chromatography for measuring alcohol and ether compounds in the gasoline or GB/T33649-2017 gas chromatography for measuring oxygen-containing compounds and aniline compounds in the motor gasoline. GB/T28768-2012 multidimensional gas chromatography for determining hydrocarbon composition and oxygen-containing compounds of the motor gasoline can also be used for determining the composition of the motor gasoline, components in the gasoline are separated and detected according to carbon number and type through a series of chromatographic columns of different types, but detailed monomer hydrocarbon composition information of the motor gasoline cannot be obtained. The high-resolution elastic quartz capillary chromatographic column has strong separation capacity and is particularly suitable for separation and detection of a complex mixture system such as gasoline. In SH/T0714-2002 "determination of monomeric hydrocarbon composition in naphtha (capillary gas chromatography)" in the industry standard, the determination of monomeric hydrocarbon composition in naphtha without olefin by using a non-polar capillary chromatographic column of 50m length has been widely used, but a single high-resolution capillary chromatographic column is used for analysis of finished gasoline, and when some oxygen-containing compounds or unconventional added components are added to the finished gasoline, the quantitative result has a large deviation due to overlapping with hydrocarbons.

Disclosure of Invention

The invention aims to provide a gas chromatography system and a method for detecting detailed composition of gasoline for vehicles, the system has compact structure, can realize accurate qualitative and quantitative analysis of oil components, and can accurately determine the contents of monomer hydrocarbon, oxygen-containing compound and unconventional additive components in oil.

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

the first detection channel comprises a first sample inlet, a first nonpolar chromatographic column and a first detector; the first sample inlet is communicated with an inlet of the first nonpolar chromatographic column, and an outlet of the first nonpolar chromatographic column is communicated with an inlet of the first detector;

the second detection channel comprises a second sample inlet, a second nonpolar chromatographic column, a center cutting assembly, a third sub-channel and a fourth sub-channel; the third sub-channel comprises a damping column and a second detector which are sequentially communicated, and the fourth sub-channel comprises a polar chromatographic column and a third detector which are sequentially communicated; the second sample inlet is communicated with an inlet of a second nonpolar chromatographic column, an outlet of the second nonpolar chromatographic column is communicated with an inlet of the center cutting assembly, a first outlet of the center cutting assembly is connected with an inlet of the damping column, and a second outlet of the center cutting assembly is communicated with an inlet of the polar chromatographic column.

In a second aspect, the present invention provides a method for detecting the detailed composition of an oil product by gas chromatography, which comprises:

introducing a first part of oil to be detected into a first detection channel, enabling the first part of oil to be detected to flow through a first nonpolar chromatographic column for separation and carrying out first detection to obtain a first chromatographic chart;

introducing a second part of oil to be detected into a second detection channel, and separating the oil to be detected by a second nonpolar chromatographic column to obtain a continuous outflow component;

in a preset time period, enabling target difficultly-separated components in the continuous outflow components to sequentially enter a polar chromatographic column and a third detector for third detection to obtain a third chromatographic chart;

sequentially passing the remaining set of the continuous effluent fraction from the second non-polar chromatography column into a damping column and a second detector;

and correcting the peak area of the target difficultly-separated component in the first chromatographic spectrogram according to the peak area of the target difficultly-separated component in the third chromatographic spectrogram, and determining the mass fraction of each component in the oil product to be detected by adopting a correction normalization method according to the corresponding peak area and a correction factor of each component in the first chromatographic spectrogram.

Through the technical scheme, the system can accurately analyze and detect the hydrocarbon components, the oxygen-containing compounds and other additive components in the oil products on the same gas chromatograph, has a compact structure, and can accurately and quantitatively analyze the hydrocarbon components and the additive components of the oil products.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic diagram of one embodiment of a gas chromatograph system of the present invention;

FIG. 2 is a first chromatogram of sample A and sample C of example 1, wherein a is the first chromatogram of sample A, and b is the first chromatogram of sample C;

FIG. 3 is a second chromatogram of sample C of example 1 according to the present invention;

FIG. 4 is a partial third chromatograms of sample A and sample C in example 1 of the present invention, wherein a is a partial third chromatogram of sample A, and b is a partial third chromatogram of sample C;

FIG. 5 is a third chromatograms of the remaining portions of sample A and sample C in example 1, wherein a is the third chromatogram of the remaining portion of sample A, and b is the third chromatogram of the remaining portion of sample C;

fig. 6 is an actual chromatogram of the motor gasoline of country VI-92, which is a third chromatogram obtained by the third detection, b is a first chromatogram obtained by the first detection, and c is a second chromatogram obtained by the second detection, in example 2 of the present invention.

Description of the reference numerals

1. A first sample inlet 2, a first nonpolar chromatographic column 3 and a first detector

5. Second sample inlet

7. Damping column 8, second nonpolar chromatographic column 9 and polar chromatographic column

10. Second detector 11, third detector 12, first outlet

13. Second outlet 14, microfluidic assembly 15, first carrier gas line

16. Solenoid valve 17, second carrier gas pipeline 18, damping column

19. Center cutting assembly 20, first detection channel 21 and second detection channel

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

As shown in fig. 1, according to the present invention, there is provided a gas chromatograph system in a first aspect of the present invention, the system comprising: a first detection channel 20 and a second detection channel 21;

the first detection channel 20 comprises a first sample inlet 1, a first nonpolar chromatographic column 2 and a first detector 3; the first sample inlet is communicated with the inlet of the first nonpolar chromatographic column 2, and the outlet of the first nonpolar chromatographic column 2 is communicated with the inlet of the first detector 3;

the second detection channel 21 comprises a second sample inlet 5, a second non-polar chromatography column 8, a central cutting assembly 19, a third sub-channel and a fourth sub-channel; the third sub-channel comprises a damping column 7 and a second detector 10 which are communicated in sequence, and the fourth sub-channel comprises a polarity chromatographic column 9 and a third detector 11 which are communicated in sequence; the second sample inlet 5 is communicated with the inlet of the second nonpolar chromatographic column 8, the outlet of the second nonpolar chromatographic column 8 is communicated with the inlet of the center cutting component 19, the first outlet 12 of the center cutting component 19 is connected with the inlet of the damping column 7, and the second outlet 13 of the center cutting component 19 is communicated with the inlet of the polar chromatographic column 9.

The system provided by the invention has a dual-channel sample injection detection structure, can realize accurate analysis and detection of hydrocarbons, oxygen-containing compounds and unconventional added components in oil products on the same gas chromatograph, and is compact in structure.

As shown in fig. 1, the central cutting assembly 19 of the system of the present invention may comprise: a microfluidic component 14, a carrier gas inlet, a solenoid valve 16 and a damping column 18 for ensuring flow stability;

the microfluidic assembly comprises a first port, a second port and a third port; a first port is formed as an inlet of the central cutting assembly 19, a second port is in communication with the first outlet 12, and a third port is in communication with the second outlet 13; the central cutting assembly 19 has a first working state and a second working state which can be switched; in a first working state, the electromagnetic valve is in a closed state, the carrier gas inlet is communicated with the second outlet 13 through the first carrier gas pipeline 15, and the carrier gas is used for enabling the carrier gas to flow out through the first carrier gas pipeline 15 and the second outlet 13 and then to carry the components flowing out from the second nonpolar chromatographic column 8 to enter the damping column 7; in the second working state, the electromagnetic valve is in an open state, the carrier gas inlet is communicated with the first outlet 12 through the second carrier gas pipeline 17, and the carrier gas is used for enabling the carrier gas to flow out through the second carrier gas pipeline 17 and the first outlet 12 and then to carry the components flowing out from the second nonpolar chromatographic column 8 into the polar chromatographic column 9.

The damping columns 7 are well known to those skilled in the art and may include, for example, an elastomeric quartz capillary column, examples of which include, but are not limited to, elastomeric quartz capillary columns having an inner diameter of 0.10mm and elastomeric quartz capillary columns having an inner diameter of 0.15 mm; the column resistance of the damping column 7 may be the same as the polar column 9 to further reduce detection errors.

The polar column 9 according to the invention is well known to the person skilled in the art and may be, for example, a weakly polar column, a moderately polar column and a strongly polar column, preferably a moderately polar column. Stationary phase of the column is conventional to those skilled in the art, and in one embodiment, the stationary phase of the polar column 9 may be selected from at least one of 6% cyanopropylphenyl-94% dimethylpolysiloxane, 5% phenyl-methylpolysiloxane, and 50% phenyl-methylpolysiloxane; the length and the inner diameter of the polar chromatographic column 9 can be changed in a large range and selected according to actual needs, for example, the length of the chromatographic column can be 25-50 m, and the inner diameter is 0.20-53 mm; preferably, the length of the chromatographic column is 25-30 m, and the inner diameter is 0.25-0.32 mm.

According to the present invention, the stationary phases of the first non-polar chromatography column 2 and the second non-polar chromatography column 8 are conventionally employed by those skilled in the art, and may be, for example, each independently 100% methylpolysiloxane. The length and the inner diameter of the first nonpolar chromatographic column 2 and the second nonpolar chromatographic column 8 can also be changed in a large range and selected according to actual needs, for example, the length of each chromatographic column is independently 30-100 m, and the inner diameter is independently 0.20-0.53 mm; preferably, the chromatographic columns have a length of 30 to 50m and an inner diameter of 0.20 to 0.25mm, respectively.

According to the present invention, the first detector 3 and the third detector 11 may be each independently a flame ionization detector, and the second detector 10 may be a flame ionization detector or a thermal conductivity detector.

According to the invention, in order to realize synchronous sample injection analysis of the first channel and the second channel, the system further comprises a first automatic sample injector and a second automatic sample injector, wherein the first automatic sample injector is communicated with the first sample injection port 1, and the second automatic sample injector is communicated with the second sample injection port 5, so as to realize real-time simultaneous sample injection operation between the first detection channel and the second detection channel.

In a second aspect, the present invention provides a method for detecting oil composition by gas chromatography, wherein the method comprises:

enabling a first part of an oil product to be detected to flow through a first nonpolar chromatographic column for first detection to obtain a first chromatographic chart;

allowing a second part of the oil to be detected to flow through a second nonpolar chromatographic column to obtain a continuous outflow component;

in a preset time period, enabling target difficultly-separated components in the continuously-flowing components to sequentially enter a polar chromatographic column and a third detector for third detection to obtain a third chromatographic chart;

sequentially passing the remaining fractions of the continuously effluent fraction from the second non-polar chromatography column to a damping column and a second detector;

and correcting the peak area of the target difficultly-separated component in the first chromatographic chart according to the peak area of the target difficultly-separated component in the third chromatographic chart, and determining the mass fraction of each component in the oil product to be detected by adopting a correction normalization method according to the corresponding peak area and correction factors of each component in the first chromatographic chart.

According to the present invention, the target hardly-separable component section means a time section in which several target hardly-separable components having close retention times flow out. The preset time period is a time period for cutting the continuous outflow component flowing out of the second nonpolar chromatographic column according to the retention time of the target difficultly separated component so as to allow the target difficultly separated component to enter the polar chromatographic column. The sample to be tested can be divided into two parts to obtain a first oil product to be tested and a second oil product to be tested, and the first oil product to be tested and the second oil product to be tested have the same composition. The method can avoid the problems of difficult separation and inaccurate detection caused by co-outflow of oxygen-containing compounds, unconventional added components and hydrocarbons when the conventional monomer hydrocarbon analysis method is used for detecting the oil products, and can remarkably improve the accuracy and efficiency of detecting the components of the oil products.

In one embodiment, in order to determine a target difficultly-separated component, a first detection is carried out on an alkane solution such as n-nonane solution added with a certain amount of an oxygen-containing compound and an unconventional added component to obtain a first chromatographic spectrum of the alkane solution; and carrying out first detection on the finished product gasoline which does not contain the oxygenated chemicals and unconventional additive components to obtain a first chromatographic chart of the finished product gasoline. And comparing the first chromatographic chart of the finished gasoline with the first chromatographic chart of the alkane solution to determine the target difficultly-separated components. The comparison method is well known to those skilled in the art and will not be described herein.

According to an embodiment of the present invention, the method may further include: and comparing the retention time or retention index of the chromatographic peak in the first chromatographic spectrum with the retention time or retention index of the component in a known database, identifying the chromatographic peak in the first chromatographic spectrum, namely qualitatively identifying the chromatographic peak, and determining the difficultly separated component in the gasoline sample to be detected.

Illustratively, 2,3, 3-trimethylpentane has the same retention time as toluene in the first chromatogram compared to a known qualitative database according to chromatographic retention time or retention index, both of which are co-eluting, difficult to separate components.

According to an embodiment of the present invention, in a preset time period, sequentially entering a target difficultly separated component segment in a continuously flowing component into a polar chromatographic column and a third detector for third detection, so as to obtain a third chromatographic spectrum, including: performing third detection on each target difficult-to-separate group segment in the oil product to be detected within a preset time period corresponding to the target difficult-to-separate group segment; the third chromatogram contains the chromatographic peaks of all the difficult-to-separate components of interest.

For example, for a continuous stream containing a plurality of hard-to-separate group segments and other group segments, it may be switchably routed to a third subchannel and a fourth subchannel; in a preset time period corresponding to each selected difficult-to-separate component section, the component section can enter a fourth sub-channel, namely enter the polar chromatographic column to further separate difficult-to-separate components in the component section, and at the end of the preset time period, the component flowing out of the second nonpolar chromatographic column is switched to be sent into a third sub-channel, namely enter the damping column.

According to an embodiment of the invention, the method may comprise: a preset time period is determined. For example, a standard sample containing a component difficult to separate is used to determine the preset time period.

Exemplary embodiments: preparing a paraffin solution containing a target component difficult to separate as a standard sample, or taking an actual typical gasoline sample containing the target component difficult to separate as the standard sample, and enabling the standard sample to sequentially flow into a second nonpolar column, a damping column and a second detector to obtain a second chromatographic chart; determining a preset time period according to the second spectrogram; wherein the chromatographic column resistance of the damping column is equal to the chromatographic resistance of the polar chromatographic column.

In a further embodiment, the standard sample may further contain a reference substance, wherein the reference substance is a component stably existing in gasoline, and the component has an independent and interference-free chromatographic peak in the first chromatographic spectrum; the reference substance is selected from one or more of 3-methyl pentane, isopentane and n-pentane. In a specific embodiment, the finished gasoline is used as a first standard sample, the first standard sample is subjected to second detection to obtain a retention time period of a reference substance, and then the alkane solution containing the target difficultly-separated component is used as a second standard sample, and the second standard sample is subjected to second detection to obtain a retention time period of the target difficultly-separated component; in another embodiment, the second test is performed using an alkane solution containing a reference substance and a target difficultly-separated component as a standard sample, and the retention time period of the reference substance and the retention time period of the target difficultly-separated component are obtained simultaneously.

In a further embodiment, determining the preset time period according to the second chromatogram may include: according to the retention time period [ T ] corresponding to the target difficult separation component section in the second spectrogram₁,T₂]Determining a preset time period [ T₃,T₄](ii) a Preferably, T₃＝T₁-ΔT₁，T₄＝T₂+ΔT₂；ΔT₁Is 10-60 seconds, preferably 5-30 seconds,. DELTA.T₂The time is 10-60 seconds, preferably 5-30 seconds, so as to further ensure that all the components which are difficult to separate enter the polar chromatographic column for separation detection, and ensure that the rest components except the components which are difficult to separate in the oil product to be detected flow into the damping column.

In further embodiments, the standard sample contains all selected target difficult-to-separate components; in the standard sample, the content of each component difficult to separate is 1-10 wt%, preferably the content of each component difficult to separate is the same. In one embodiment, the standard sample is an alkane solution, such as n-nonane solution, in which all selected target difficult-to-separate components are dissolved.

According to a specific embodiment of the present invention, the 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 includes: according to the formula (1) A_i,PONA＝(A_s,PONA/A_S,624)×A_i,624×F_iCorrecting peak areas of the target difficult-to-separate component i in the first chromatographic spectrum; in the formula (1), A_i,PONAThe corrected peak area of the group target hard separation component i in the first chromatographic spectrum is shown; a. the_s,PONAPeak area of the first peak as reference; a. the_S,624Peak area of the third spectral peak for the reference; a. the_i,624The peak area of the component i in the third spectrogram corresponding to the peak; f_iThe correction coefficient for the peak area between channels is shown.

Exemplary embodiments: obtaining the peak area of the third spectral peak of the reference substance by adopting a method comprising the following steps: in the cutting time period, enabling a reference substance in the continuously flowing components to enter a polar chromatographic column and a third detector for third detection to obtain a third chromatographic chart; determining the peak area of a third spectral peak of the reference substance according to the third spectrogram; wherein the retention time [ T ] corresponding to the reference substance in the second chromatogram is determined₅,T₆]Determining a cutting time period [ T₇,T₈]；T₇＝T₅-ΔT₅，T₈＝T₆+ΔT₆Wherein, Δ T₅Is 20 to 60 seconds, delta T₆The time is 20 to 60 seconds.

In the embodiment where the second detector is a thermal conductivity detector, in order to ensure the detection sensitivity, the second part of the oil to be detected can be detected by using hydrogen as the carrier gas, and a larger inlet gas is requiredThe sample amount and the smaller split ratio are determined, for example, the sample amount can be 0.5-2.0 muL, and the split ratio can be 10: 1-50: 1. the method may cause that when a first part of the oil product to be detected flows through the first nonpolar chromatographic column and enters the first detector and a second part of the oil product to be detected flows through the polar chromatographic column and enters the third detector, the relative mass response factors obtained by actual measurement have certain difference, and at the moment, the area correction coefficient F between channels needs to be calculated_i。

Illustratively, F according to equation (2)_i＝(f_i,624/f_i,PONA)×(f_s,PONA/f_s,624) Calculating F_i: in the formula (2), f_i,624The relative mass response factor of a component corresponding to the ith spectrum peak in the third chromatogram relative to n-heptane on the polar chromatographic column; f. of_i,PONAThe relative mass response factor of a component corresponding to the ith peak in the third chromatogram relative to n-heptane on the first nonpolar chromatographic column; f. of_s,PONAIs the relative mass response factor of the reference on the first non-polar chromatography column relative to n-heptane; f. of_s,624Is the relative mass response factor of the reference substance on a polar chromatography column relative to n-heptane.

In another embodiment, F_iIs 1.

According to one embodiment of the invention, A is according to formula (3)_k,PONA＝A_t,PONA-A_i,PONADetermining the peak area of the peak of the component k which co-flows out with the target difficult-to-separate component i in the first chromatographic spectrum; wherein A is_k,PONAThe peak area of the peak of the component k which co-flows out with the target difficult-to-separate component i in the first chromatographic spectrum; a. the_t,PONAThe total area of the peaks for target hard-to-separate component i and component k. The co-eluting component is a substance represented by a peak which is difficult to distinguish by at least partially overlapping with a peak of the target difficult-to-separate component in the first chromatogram.

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 measured according to the peak areas in the first chromatogram and the third chromatogram may be a calibration normalization method. In one embodiment, the composition is characterized by comparing chromatographic peaks in the first chromatogram to a known database. For a certain difficultly separated component, the chromatographic peak area of the difficultly separated component in the third chromatogram is converted into the chromatographic peak area of the difficultly separated component on the first nonpolar chromatographic column, and the same conversion is carried out on all difficultly separated components. And calculating the mass fraction of each component by adopting a correction normalization method according to the peak area of the chromatographic peak of each component and the corresponding relative mass correction factor.

Illustratively, the mass fraction of each component is calculated according to formula (4):

wherein ω is_iIs the mass fraction of the component i,%; a. the_iIs the peak area of the chromatographic peak of the component i in the first chromatographic spectrogram; f. of_iIs the relative mass correction factor for component i on the first chromatogram.

According to one embodiment of the present invention, examples of the oil to be tested include, but are not limited to, motor gasoline; the oil to be tested may contain additives, the additives include oxygen-containing compounds, the oxygen-containing compounds include methyl tert-butyl ether, ethyl tert-butyl ether, methyl tert-amyl ether, diisopropyl ether and C₁～C₄One or more of alcohol. In one embodiment, the oil to be tested contains an unconventional additive component, which is a non-hydrocarbon component other than the above-mentioned oxygen-containing compound and not added by human beings specified in the motor gasoline standard, such as dimethoxymethane, sec-butyl acetate, ethyl acetate, dimethyl carbonate, aniline, N-methylaniline, o-methylaniline, m-methylaniline, p-methylaniline, etc.

According to one embodiment of the invention, the lower limit of detection of the additive is 0.1% by weight; the lower limit of the detection of the hydrocarbons in the oil product to be detected is 0.01 wt%.

In a preferred embodiment of the invention, the method comprises: enabling a first part of an oil product to be detected to flow through a first nonpolar chromatographic column for first detection to obtain a first chromatographic chart; determining target difficultly-separated components in the gasoline sample to be detected according to the obtained first chromatographic spectrum; preparing a standard sample containing target components difficult to separate and a reference substance, enabling the standard sample to sequentially flow into a second nonpolar column, a damping column and a second detector to obtain a second chromatographic chart, and determining a preset time period and a cutting time period according to the second chromatographic chart;

enabling a second part in the oil product to be detected to continuously flow through a second nonpolar chromatographic column to obtain a continuous outflow component; according to a preset time period, enabling target difficultly-separated component sections in the continuous outflow components flowing out of the second nonpolar chromatographic column to sequentially enter the polar chromatographic column and a third detector for third detection in the preset time period to obtain a third chromatographic chart; the remaining set of the continuously flowing components exiting the second non-polar chromatography column are staged to enter the damping column and the second detector in sequence.

And correcting the spectral peak area of the target difficultly-separated component in the first chromatogram according to the inter-channel peak area correction coefficient and the peak area of the target difficultly-separated component in the third chromatogram, and determining the mass fraction of each component in the oil product to be detected by adopting a correction normalization method according to the peak area of each component in the first chromatogram.

The invention is further illustrated by the following examples, but is not to be construed as being limited thereto.

Example 1

The structure of the gas chromatograph system of the embodiment is as follows:

as shown in fig. 1, the first detection channel 20 includes a first sample inlet 1, a first nonpolar chromatography column 2 (HP-PONA chromatography column of agilent corporation, stationary phase is 100% methyl polysiloxane, column length is 50m, inner diameter is 0.20mm), a hydrogen flame ionization detector. The inlet of the first nonpolar chromatographic column 2 is communicated with the first sample inlet 1, and the outlet of the first nonpolar chromatographic column 2 is communicated with the inlet of the first hydrogen flame ionization detector.

The second detection channel 21 comprises a second sample inlet 5, a second non-polar chromatography column 8 (HP-PONA chromatography column of agilent, with a stationary phase of 100% methyl polysiloxane, a column length of 50m and an inner diameter of 0.20mm), a central cutting assembly 19, a third sub-channel and a fourth sub-channel. Wherein, the third sub-channel comprises an elastic quartz capillary column (the column length is 0.76m, and the inner diameter is 0.1mm) and a thermal conductivity detector which are communicated in sequence. The fourth sub-channel comprises a middle-polarity chromatographic column (DM-624 chromatographic column of Decoma, the stationary phase of which is 6% cyanopropylphenyl-94% dimethylpolysiloxane, the column length is 30m, the inner diameter is 0.25mm and a second hydrogen flame ionization detector, a second injection port 5 is communicated with the inlet of a second nonpolar chromatographic column 8, the outlet of the second nonpolar chromatographic column 8 is communicated with the inlet of a central cutting assembly 19, the central cutting assembly 19 comprises a first outlet 12, a second outlet 13, a microfluidic assembly 14, a carrier gas inlet, a damping column 18 and an electromagnetic valve 16, the microfluidic assembly comprises a first port, a second port and a third port, the first port is formed as the inlet of the central cutting assembly 19, the second port is communicated with the first outlet 12, the third port is communicated with the second outlet 13, the central cutting assembly 19 has a first working state and a second working state which can be switched, when the electromagnetic valve is in a closed state, the carrier gas inlet is communicated with the second outlet 13 through the first carrier gas pipeline 15, so that the carrier gas enters the damping column 7 together with the carrier gas and the components flowing out of the second nonpolar chromatographic column 8 through the first carrier gas pipeline 15 and the second outlet 13; in the second operating state, the solenoid valve is in an open state, and the carrier gas inlet is in communication with the first outlet 12 via the second carrier gas line 17 for passing carrier gas through the second carrier gas line 17, the first outlet 12, and into the polar chromatography column 9 along with carrier gas and components exiting the second non-polar chromatography column 8.

The detection method of the oil product comprises the following steps:

3 samples were prepared: the sample A is a national No. V-92 finished gasoline sample; the sample B is the finished product gasoline of the national No. V-92, a certain amount of oxygen-containing compounds and unconventional additive components are added to prepare a sample to be detected, and the types and the addition amounts of the oxygen-containing compounds and the unconventional additive components are shown in a table 4; sample C was a formulated n-nonane solution containing about 2% of oxygenates and unconventional additives. Wherein, the types of the oxygen-containing compound and the unconventional additive components in the n-nonane solution are the same as those of the oxygen-containing compound and the unconventional additive components added into the national finished gasoline V-92. The determination steps are as follows:

(1) the parameters of the gas chromatography system were set according to the conditions of table 1. Injecting a sample A into a first detection channel by a first automatic sample injector, carrying components in the sample by carrier gas (nitrogen), flowing through a first nonpolar chromatographic column 2, separating according to a boiling point sequence, carrying out first detection by a flame ionization detector to obtain a first chromatographic chart (see figure 2a), and carrying out integration treatment on the first chromatographic chart to obtain chromatographic peak retention time and a chromatographic peak area. Sample C was analyzed by the first sample injector under the same conditions to obtain a separation chromatogram of the components on the first non-polar column (see fig. 2 b).

(2) And determining target difficultly-separated components needing to be cut and reference substances in the gasoline sample to be detected according to the obtained first chromatographic chart (figure 2), and referring to table 2.

(3) Respectively sampling a sample A and a sample C, injecting the samples by a second automatic sample injector, enabling the components in the samples to sequentially flow into a second nonpolar column, a damping column and a second detector to obtain second chromatographic spectrums of the two samples, wherein the second chromatographic spectrum of the sample C is shown in figure 3, and determining the cutting time period of the cutting reference substance and all preset time periods of cutting all target components difficult to separate according to the second chromatographic spectrums, which are shown in table 2.

(4) Samples A and C are respectively taken again, the oil to be detected is injected into the second detection channel by the second automatic sample injector, and the components in the samples are carried by carrier gas (hydrogen) to enter the second nonpolar chromatographic column 8 and are separated according to the boiling point sequence to obtain the continuous outflow components.

The time the solenoid valve was opened and closed was controlled according to table 2: in the preset time period and the cutting time period, the electromagnetic valve 16 is in an open state, at this time, the carrier gas entering the electromagnetic valve flows through the second carrier gas pipeline 17 and the first outlet 12, then flows through the second port and the first port of the microfluidic component 14, and carries the target component which is difficult to separate and flows out of the chromatographic column 8 together with the carrier gas flowing out of the nonpolar chromatographic column 8, enters the middle-polarity chromatographic column for further separation, and is detected by the flame ionization detector for third detection, so that a third chromatographic chart is obtained. The third chromatograms for sample a and sample C are shown in fig. 4 and 5. In the non-preset time period and the non-cutting time period, the electromagnetic valve 16 is in a closed state, at this time, the carrier gas entering the electromagnetic valve flows through the third port and the first port of the microfluidic component 14 after flowing through the first carrier gas pipeline 15 and the second outlet 13, and the carrier gas flowing out of the nonpolar chromatographic column 8 carry other components flowing out of the chromatographic column 8 together to enter the damping column 7 for second detection through the thermal conductivity detector.

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

FIG. 5a is a third chromatogram of sample A, and FIG. 5b is a third chromatogram of sample C, wherein 1 is aniline; 2 is N-methylaniline; 3 is o-methylaniline and p-methylaniline; 4 is m-methylaniline.

As can be seen from fig. 4 and 5, the oxygenates and unconventional additive components cut onto the polar chromatography column are well separated from the hydrocarbon components in the gasoline.

(5) Determination of sample B: dividing the sample B into two parts, placing the two parts on a first sample injector and a second sample injector, starting a chromatographic instrument, simultaneously introducing the sample into a first detection channel and a second detection channel by the first sample injector and the second sample injector, and operating according to the chromatographic conditions in the table 1 and the valve-cutting time table in the table 2 to obtain a first spectrogram and a third spectrogram of the sample B.

And (4) performing qualitative determination according to the retention time of the components, and calculating the relative response factors of the oxygen-containing compound and the unconventional added component on the nonpolar chromatographic column and the polar chromatographic column according to the content of each component in the sample C and the chromatographic peak areas of the first chromatographic spectrum and the third chromatographic spectrum, which are shown in Table 3.

(6) Calculating the content of each component in the sample B:

obtaining a first peak of 3-methylpentane in the first chromatogram of sample B, obtaining a third peak of 3-methylpentane in the third chromatogram, and then obtaining the first peak and the third peak according to formula A_i,PONA＝(A_s,PONA/A_S,624)×A_i,624×F_iCalculating the peak area of a third chromatographic peak after correction of each target difficultly-separated component in the third spectrogram; wherein, F_iAccording to formula F_i＝(f_i,624/f_i,PONA)×(f_s,PONA/f_s,624) The calculations were performed and the results are shown in table 3.

Comparing each spectral peak in the first chromatogram with a known database for qualitative determination, and determining the peak value according to formula A_k,PONA＝A_t,PONA-A_i,PONADetermining peak areas of peaks of components which co-flow out with target components difficult to separate in the first chromatographic spectrum, and performing a correction normalization method on all the peaks in the first chromatographic spectrum according to a formula

The mass fractions of the components were calculated to obtain the measurement results of the oxygen-containing compound and the aniline compound added to the gasoline, which are shown in table 4.

TABLE 1

TABLE 2

TABLE 3

TABLE 4

Example 2

The finished product of the national gasoline VI-92 was analyzed and measured under the same conditions as in example 1, and the actual chromatogram of the finished product of the national gasoline VI-92 was shown in FIG. 6 by controlling the opening and closing of the solenoid valve according to the preset time shown in Table 2 (wherein a is the third chromatogram obtained by the third detection, b is the first chromatogram obtained by the first detection, and c is the second chromatogram obtained by the second detection). Comparing the retention time of the component on the chromatographic peak of the medium polarity chromatographic column of the second detection channel, confirming that the component contains methyl tert-butyl ether, correcting the peak area of the methyl tert-butyl ether on the first chromatogram according to the chromatographic peak areas of the methyl tert-butyl ether and the 3-methylpentane on the third chromatogram and the chromatographic peak area of the 3-methylpentane on the first chromatogram, and calculating to obtain the mass fraction results of the methyl tert-butyl ether and the hydrocarbon component shown in Table 5.

TABLE 5

Example 3

The ethanol gasoline for the actual country VI-92 vehicle was used, and analyzed and measured under the same conditions as those in Table 1 by the method of example 1, and the opening and closing of the solenoid valve were controlled at the preset times shown in Table 2. The measurement was carried out 6 times in succession. Because the ethanol component is well separated from the hydrocarbon component on the first nonpolar chromatographic column of the first detection channel, the chromatographic peak area of the ethanol on the first detection channel is directly adopted to calculate the content of the ethanol. Comparing the retention time of the component on the chromatographic peak of the medium-polarity chromatographic column in the second channel, confirming that the component does not contain other oxygen-containing compounds and unconventional added components, correcting the toluene peak area on the first chromatogram according to the chromatographic peak areas of toluene and 3-methylpentane on the third chromatogram and the chromatographic peak area of 3-methylpentane on the first chromatogram, simultaneously obtaining the chromatographic peak area of 2,3, 3-trimethylpentane co-flowing out with toluene on the first chromatogram, and adopting a correction normalization method to calculate the content of the hydrocarbon component according to the first chromatographic peak area and the relative response factor, wherein the result is shown in Table 6.

TABLE 6

The method can accurately detect the contents of hydrocarbons, oxygen-containing compounds and unconventional additives in the oil product.

The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A gas chromatography system for detecting the detailed composition of motor gasoline, the system comprising:

a first detection channel (20) and a second detection channel (21);

the first detection channel (20) comprises a first sample inlet (1), a first nonpolar chromatographic column (2) and a first detector (3); the first sample inlet is communicated with the inlet of the first nonpolar chromatographic column (2), and the outlet of the first nonpolar chromatographic column (2) is communicated with the inlet of the first detector (3);

the second detection channel (21) comprises a second sample inlet (5), a second non-polar chromatography column (8), a central cutting assembly (19), a third sub-channel and a fourth sub-channel; the third sub-channel comprises a damping column (7) and a second detector (10) which are communicated in sequence, and the fourth sub-channel comprises a polarity chromatographic column (9) and a third detector (11) which are communicated in sequence; the second sample inlet (5) with the entry intercommunication of second non-polar chromatographic column (8), the export of second non-polar chromatographic column (8) with the entry intercommunication of center cutting subassembly (19), first export (12) of center cutting subassembly (19) with the entry of damping post (7) links to each other, the second export (13) of center cutting subassembly (19) with the entry intercommunication of polarity chromatographic column (9).

2. The system according to claim 1, wherein the central cutting assembly (19) further comprises: a microfluidic component (14), a carrier gas inlet, a damping column (18) and a solenoid valve (16);

the microfluidic assembly (14) comprises a first port, a second port and a third port; the first port being formed as an inlet of the central cutting assembly (19), the second port communicating with the first outlet (12), the third port communicating with the second outlet (13); the center cutting assembly (19) has a first working state and a second working state which can be switched; in the first operating state, the solenoid valve is in a closed state, the carrier gas inlet communicates with the second outlet (13) through a first carrier gas line (15) for allowing carrier gas to enter the damping column (7) through the first carrier gas line (15), the second outlet (13) together with the components exiting the second non-polar chromatography column (8); in the second operating state, the solenoid valve is in an open state, the carrier gas inlet communicates with the first outlet (12) via a second carrier gas line (17) for the carrier gas to enter the polar chromatography column (9) via the second carrier gas line (17), the first outlet (12) together with the components exiting the second non-polar chromatography column (8).

3. The system according to claim 1, wherein the damping column (7) is an elastomeric quartz capillary column; the column resistance of the damping column (7) is the same as the polar column (9);

the stationary phase of the polar chromatographic column (9) is selected from at least one of 6% cyanopropylphenyl-94% dimethylpolysiloxane, 5% phenyl-methylpolysiloxane and 50% phenyl-methylpolysiloxane;

the length of the polar chromatographic column (9) is 25-50 m, and the inner diameter is 0.20-0.53 mm;

the stationary phases of the first non-polar chromatography column (2) and the second non-polar chromatography column (8) are each independently 100% methylpolysiloxane;

the first nonpolar chromatographic column (2) and the second nonpolar chromatographic column (8) have column lengths of 30-100 m respectively and independently;

the inner diameters of the first nonpolar chromatographic column (2) and the second nonpolar chromatographic column (8) are respectively 0.20-0.25 mm.

4. The system according to claim 1, wherein the first detector (3) and the third detector (11) are each independently a flame ionization detector, and the second detector (10) is a flame ionization detector or a thermal conductivity detector.

5. The system according to claim 1, wherein the system further comprises a first auto-injector in communication with the first sample inlet (1) and a second auto-injector in communication with the second sample inlet (5).

6. A method for detecting the detailed composition of oil products by gas chromatography comprises the following steps:

7. The method of claim 6, wherein the method further comprises: and comparing the retention time or retention index of the chromatographic peak in the first chromatographic spectrum with the retention time or retention index of the component in a known database, identifying the chromatographic peak in the first chromatographic spectrum, and determining the difficultly separated component in the gasoline sample to be detected.

8. The method of claim 6 or 7, wherein the step of sequentially allowing the target difficultly separated component segment in the continuous effluent component to enter a polar chromatographic column and a third detector for third detection within a preset time period to obtain a third chromatographic spectrum comprises:

performing the third detection on each target difficult-to-separate group segment in the oil product to be detected within a preset time period corresponding to the target difficult-to-separate group segment;

the third chromatogram comprises chromatographic peaks of all of the target hard-to-separate components.

9. The method of claim 7, wherein the method further comprises:

preparing a standard sample containing the target difficultly-separated component, or taking an actual typical gasoline sample containing the target difficultly-separated component as the standard sample, and enabling the standard sample to sequentially flow into the second nonpolar chromatographic column, the damping column and the second detector to obtain a second chromatographic chart;

determining the preset time period according to the second spectrogram;

wherein the column resistance of the damping column is equal to the column resistance of the polar column.

10. The method of claim 9, wherein the standard sample contains all of the target hard-to-separate component; in the standard sample, the content of each target difficultly-separated component is 1-5 wt% respectively.

11. The method of claim 9, wherein determining the preset time period from the second chromatogram comprises:

according to the retention time period [ T ] corresponding to the target difficult separation component section in the second spectrogram₁,T₂]Determining the preset time period [ T₃,T₄]；

Wherein, T₃＝T₁-ΔT₁，T₄＝T₂+ΔT₂；ΔT₁Is 5 to 30 seconds, Delta T₂The time is 5 to 30 seconds.

12. The method of claim 6, wherein correcting the peak area of the target hard-to-separate component in the first chromatogram from the peak area of the target hard-to-separate component in the third chromatogram comprises:

calculating a corrected peak area of a target difficult-to-separate component i in the first chromatogram according to formula (1):

A_i,PONA＝(A_s,PONA/A_S,624)×A_i,624×F_iformula (1);

in the formula (1), A_i,PONAThe corrected peak area of the target difficult-to-separate component i in the first chromatogram;

A_s,PONA(ii) peak area being a first spectral peak of the reference;

A_S,624peak area of the third spectral peak for the reference;

A_i,624peak areas of component i in the third spectrogram corresponding to spectral peaks;

F_ithe correction coefficient for the peak area between channels is shown.

13. The method of claim 12, wherein F_iIs 1, or F is calculated according to the formula (2)_i：

F_i＝(f_i,624/f_i,PONA)×(f_s,PONA/f_s,624) Formula (2);

in the formula (2), f_i,624A relative mass response factor on the polar chromatography column relative to n-heptane for a component corresponding to the ith peak in the third chromatogram;

f_i,PONAthe relative mass response factor of a component corresponding to the ith peak in the third chromatogram relative to n-heptane on the first nonpolar chromatographic column;

f_s,PONAis the relative mass response factor of the reference on the first non-polar chromatography column relative to n-heptane;

f_s,624is the relative mass response factor of the reference to n-heptane on the polar chromatography column.

14. The method according to claim 12, wherein the standard sample further contains a reference substance, wherein the reference substance is a component stably existing in gasoline and having an independent and non-interference chromatographic peak in the first chromatographic spectrum; the reference substance is selected from one or more of 3-methyl pentane, isopentane and n-pentane;

obtaining the peak area of the third spectral peak of the reference substance by adopting a method comprising the following steps:

allowing a reference substance in the continuous outflow component to enter the polar chromatographic column and the third detector for third detection in a cutting time period to obtain a third chromatographic spectrum;

determining the peak area of a third spectral peak of the reference substance according to the third spectrogram;

wherein the retention period [ T ] corresponding to the reference in the second chromatogram is determined₅,T₆]Determining said cutting time period [ T₇,T₈]；

T₇＝T₅-ΔT₅，T₈＝T₆+ΔT₆Wherein Δ T₅Is 20 to 60 seconds, delta T₆The time is 20 to 60 seconds.

15. The method according to claim 12, wherein the peak area of the peak of the component k co-eluting with the target difficult-to-separate component i in the first chromatogram is determined according to equation (3):

A_k,PONA＝A_t,PONA-A_i,PONAformula (3)

Wherein A is_k,PONAThe peak area of the peak of the component k which co-flows out with the target difficult-to-separate component i in the first chromatographic spectrum; a. the_t,PONAIs the total area of the peaks of the target difficult-to-separate component i and the component k.

16. The method of claim 6, wherein the oil to be tested is motor gasoline; the oil product to be detected contains an additive, wherein the additive comprises one or more of an oxygen-containing compound, aniline and methylaniline; the oxygen-containing compound comprises methyl tert-butyl ether, ethyl tert-butyl ether, methyl tert-amyl ether, diisopropyl ether and C₁～C₄One or more of alcohol, methylal, sec-butyl acetate, ethyl acetate and dimethyl carbonate.

17. The method of claim 6, wherein the additive has a lower detection limit of 0.1 wt%; the lower limit of the detection of the hydrocarbons in the oil product to be detected is 0.01 wt%.