Synchronous analysis method for contents of C4 olefin, C4 alkyne and acetonitrile

Abstract

The invention provides a synchronous analysis method for contents of C4 olefin, C4 alkyne and acetonitrile. The method comprises the following steps: sampling in a butadiene production device by using a sampling steel cylinder, and adjusting the pressure to 0.9-1.1 MPa to obtain a sample solution; respectively injecting the standard solution and the sample solution into a gas chromatograph to obtain the peak area of each component; and calculating the mass concentration wx of each component according to a formula (1) and a formula (2). According to the invention, through pressurization operation on the sampling steel cylinder, complete liquefaction of a sample to be detected can be ensured, sample nonuniformity caused by different boiling points and critical pressures of different components is eliminated, and the accuracy of sample introduction and detection is ensured; on the basis, separation and quantification of C4 olefin, ethyl acetylene, vinyl acetylene and acetonitrile can be realized on one instrument and one chromatographic column by using a strong-polarity chromatographic column, and the contents of C4 olefin, C4 alkyne and acetonitrile can be accurately and efficiently analyzed at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, and in particular to a method for synchronously analyzing the contents of C4 olefins, C4 alkynes and acetonitrile. Background Art

[0002] In butadiene production plants, accurate analysis of C4-acetylenes and acetonitrile content is crucial for product quality control and process optimization. C4-acetylenes, mainly vinylacetylene and ethylacetylene, are important by-products in the butadiene production process, and their content directly affects the purity of butadiene and the efficiency of subsequent processing. Acetonitrile, as a solvent or intermediate, is also important to control its residual content, which needs to be reasonably controlled to avoid adverse effects on the final product or the environment.

[0003] Traditional analytical methods usually require the use of two gas chromatographs with different configurations when dealing with such complex samples. This is because C4 olefins and C4 alkynes are usually analyzed using non-polar Al2O3 columns due to the non-polar nature of their molecular structures. These columns excel in separating C4 alkynes due to their high efficiency in separating non-polar molecules, but have poor separation effects on acetonitrile, which has a high polarity. The detection of acetonitrile requires the use of polar OXY-PLOT columns, which have high separation efficiency for polar molecules such as acetonitrile, but have limited separation effects on non-polar C4 alkynes due to their high polarity, and cannot meet the needs of simultaneous detection.

[0004] However, using two gas chromatographs with different configurations for separate analysis not only increases the hardware cost of equipment purchase and maintenance, but also significantly increases the energy consumption, maintenance and calibration costs of the two instruments during daily operation. In addition, this separation and analysis process will also reduce work efficiency and extend the total time of sample analysis. Especially in a production environment with high-frequency analysis requirements, this inefficient analysis process will become a key factor restricting production efficiency. In addition, acetonitrile and carbon tetraacetylenes may interfere with each other during chromatographic analysis. When using a non-polar chromatographic column for analysis, the presence of acetonitrile may cause peak distortion and affect the accurate quantification of carbon tetraacetylenes. Similarly, when using a polar chromatographic column for analysis, the residues of carbon tetraacetylenes that are not completely separated may affect the detection results of acetonitrile and reduce the accuracy and reliability of the analysis.

[0005] Therefore, developing a method that can simultaneously, accurately and efficiently analyze the content of C4 olefins, C4 alkynes and acetonitrile has become an urgent technical requirement in the butadiene production process. Summary of the invention

[0006] The main purpose of the present invention is to provide a method for synchronously analyzing the contents of four carbon olefins, four carbon alkynes and acetonitrile, so as to solve the problem in the prior art that it is difficult to simultaneously, accurately and efficiently analyze the contents of four carbon olefins, four carbon alkynes and acetonitrile.

[0007] In order to achieve the above-mentioned object, according to one aspect of the present invention, a method for synchronous analysis of the content of C4 olefins, C4 alkynes and acetonitrile is provided, comprising the following steps: step S1, sampling in a butadiene production device using a sampling cylinder to obtain a sample to be tested, the sample to be tested comprising C4 olefins, C4 alkynes and acetonitrile; the C4 olefins comprise 1,3-butadiene and C4 olefins other than 1,3-butadiene, and the C4 alkynes comprise ethyl acetylene and vinyl acetylene; step S2, adjusting the pressure of the sample to be tested to 0.9-1.1 MPa to obtain a sample solution; step S3, obtaining a standard solution, the standard solution having 1,3-butadiene as the background and containing a standard liquid of ethyl acetylene, vinyl acetylene and acetonitrile;

[0008] Step S4, injecting the standard solution into the vaporization chamber of the gas chromatograph through the carrier gas, passing through the chromatographic column and the detector, and obtaining the peak areas of 1,3-butadiene, ethylacetylene, vinylacetylene, and acetonitrile in the standard solution; calculating the relative mass correction factor F of each component in the standard solution relative to 1,3-butadiene according to formula (1) i :

[0009]

[0010] Among them, w i is the mass concentration of a component in the standard solution, in %; w s is the mass concentration of 1,3-butadiene in the standard solution, in %; A i is the corresponding peak area of ​​a component in the standard solution; A s is the peak area of ​​1,3-butadiene in the standard solution;

[0011] Step S5, injecting the sample solution into the vaporization chamber of the gas chromatograph through the carrier gas, passing through the chromatographic column and the detector, and obtaining the peak areas of C4 olefins, C4 alkynes, and acetonitrile in the sample solution; and calculating the mass concentrations w of C4 olefins, C4 alkynes, and acetonitrile in the sample solution respectively according to formula (2): x :

[0012]

[0013] Among them, A x is the corresponding peak area of ​​a component in the sample solution; X is the total mass concentration of impurities in the sample solution other than those measured by this method, in %; wherein the chromatographic column is a polar chromatographic column.

[0014] Furthermore, the elution order of the peaks of the chromatographic column is the combined peak of C4 olefins, ethylacetylene, vinylacetylene, and acetonitrile.

[0015] Furthermore, the filler of the chromatographic column is cross-linked polyethylene glycol.

[0016] Furthermore, the column length of the chromatographic column is 55 to 65 m, the diameter is 0.30 to 0.34 mm, and the liquid film coating is 0.8 to 1.2 μm.

[0017] Furthermore, the chromatographic column is an INNOWAX chromatographic column.

[0018] Furthermore, the column temperature of the chromatographic column is programmed to be kept constant at 35-40°C for 3-7 minutes and then increased to 170-190°C at a rate of 8-12°C / min.

[0019] Furthermore, the temperature of the vaporization chamber is 150-200°C; and / or the detector is a hydrogen flame ionization detector, and the temperature of the detector is 200-250°C.

[0020] Furthermore, in the standard solution, the sum of the mass concentrations of acetonitrile, ethylacetylene and vinylacetylene is 2.0 to 20.0%.

[0021] Furthermore, the injection volume of the standard solution and the sample solution is 0.2-0.5 μL, and the split ratio is 1:(20-50).

[0022] Furthermore, the carrier gas is one or more of nitrogen, hydrogen and helium, and the flow rate of the carrier gas is 2.0 to 5.0 mL / min.

[0023] By applying the technical solution of the present invention, the complete liquefaction of the sample to be tested can be ensured by pressurizing the sampling cylinder, eliminating the sample inhomogeneity caused by different boiling points and critical pressures of different components, and ensuring the accuracy of injection and detection. On this basis, a chromatographic column with strong polarity is used to achieve the separation of C4 olefins, ethylacetylene, vinylacetylene, and acetonitrile on a chromatographic column, and the detection is performed on the same detector and then the correction area is normalized for quantitative analysis, and acetonitrile does not interfere with the analysis of ethylacetylene, vinylacetylene, etc. The present invention realizes the separation of polar substances and non-polar substances on the same chromatographic column, and uses the same detector for content determination, which can reduce labor consumption, shorten analysis time, improve analysis efficiency, reduce analysis cost, and achieve simultaneous, accurate, and efficient analysis of C4 olefins, C4 alkynes, and acetonitrile content. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0025] Figure 1 A key structural flow chart of a gas chromatograph according to Example 1 of the present invention is shown; and

[0026] Figure 2 The gas chromatogram of the sample to be tested according to Example 1 of the present invention is shown.

[0027] The above drawings include the following reference numerals:

[0028] 1. High-pressure liquid injection valve; 2. Sample inlet; 3. Sample outlet; 4. Split / splitless inlet; 5. INNOWAX chromatographic column; 6. FID detector. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] As described in the background of the present invention, there is a problem in the prior art that it is difficult to simultaneously, accurately and efficiently analyze the contents of C4 olefins, C4 alkynes and acetonitrile. In order to solve the above problems, in a typical embodiment of the present invention, a method for synchronous analysis of the contents of C4 olefins, C4 alkynes and acetonitrile is provided, comprising the following steps: Step S1, sampling using a sampling cylinder in a butadiene production device to obtain a sample to be tested, the sample to be tested includes C4 olefins, C4 alkynes, and acetonitrile; the C4 olefins include 1,3-butadiene and C4 olefins other than 1,3-butadiene, and the C4 alkynes include ethylacetylene and vinyl acetylene; Step S2, adjusting the pressure of the sample to be tested to 0.9-1.1 MPa to obtain a sample solution; Step S3, obtaining a standard solution, the standard solution uses 1,3-butadiene as the background and contains a standard liquid of ethylacetylene, vinyl acetylene and acetonitrile;

[0031] Step S4, injecting the standard solution into the vaporization chamber of the gas chromatograph through the carrier gas, passing through the chromatographic column and the detector, and obtaining the peak areas of 1,3-butadiene, ethylacetylene, vinylacetylene, and acetonitrile in the standard solution; calculating the relative mass correction factor F of each component in the standard solution relative to 1,3-butadiene according to formula (1) i :

[0032]

[0033] Among them, w i is the mass concentration of a component in the standard solution, in %; w s is the mass concentration of 1,3-butadiene in the standard solution, in %; A i is the corresponding peak area of ​​a component in the standard solution; As is the peak area of ​​1,3-butadiene in the standard solution;

[0034] Step S5, injecting the sample solution into the vaporization chamber of the gas chromatograph through the carrier gas, passing through the chromatographic column and the detector, and obtaining the peak areas of C4 olefins, C4 alkynes, and acetonitrile in the sample solution; and calculating the mass concentrations w of C4 olefins, C4 alkynes, and acetonitrile in the sample solution respectively according to formula (2): x :

[0035]

[0036] Among them, A x is the corresponding peak area of ​​a component in the sample solution; X is the total mass concentration of impurities in the sample solution other than those measured by this method, in %; wherein the chromatographic column is a polar chromatographic column.

[0037] Aiming at the analysis requirements of butadiene process equipment, especially the alkyne flash distillation section of butadiene extraction equipment for the contents of butadiene, C4 alkynes and acetonitrile, the present invention develops an analysis method for simultaneously detecting the above three items using a gas chromatograph, and uses a highly polar chromatographic column to completely separate the C4 hydrocarbon peak, ethylacetylene, vinylacetylene and acetonitrile.

[0038] Specifically, the present invention first performs sampling by using a sampling steel cylinder, the pressure resistance of the steel cylinder is not less than 6.0 MPa, and an appropriate sampling steel cylinder can be selected according to the situation of the on-site sampler to obtain the sample to be tested, and the sample to be tested includes C4 olefins, C4 alkynes, and acetonitrile; the C4 olefins include 1,3-butadiene and C4 olefins other than 1,3-butadiene, and the C4 alkynes include ethyl acetylene and vinyl acetylene.

[0039] After the sample is collected, a pressure gauge is used to detect the pressure, and the pressure of the sample to be tested is adjusted to 0.9-1.1 MPa to obtain a sample solution. The inventor unexpectedly found in the research process that C4 olefins will be completely liquefied at about 1.0 MPa, and will no longer be compressed and will be in a stable state. The main purpose of this step is to liquefy all the C4 olefins in the sample. Since acetonitrile itself is liquid, all components of the sample can form a stable mixture with acetonitrile after it is completely liquefied to ensure the accuracy of injection and detection. If the analyzed sample does not meet the condition that it is all liquid when circulating in the system pipeline, it will be due to the problem of gasification discrimination of different components with a large boiling point span, which is not suitable for the content determination method of the same gas chromatograph and the same polar chromatographic column of the present invention.

[0040] Then obtain a standard solution, which uses 1,3-butadiene as the background and contains standard liquids of ethylacetylene, vinylacetylene, and acetonitrile. Since C4 olefins such as trans-butene, n-butene, isobutylene, and cis-butene cannot be completely separated on the chromatographic column of the present invention, it is not necessary to prepare the standard solution. For other hydrocarbons except C4 alkynes, the background correction factor can be used. The container uses a 4.0L or 8.0L standard gas cylinder with a filling pressure of 1.0MPa. The concentration of the component is selected according to the specific situation of the sample point to be analyzed. The standard solution is injected into the vaporization chamber of the gas chromatograph through the carrier gas, and the peak areas of 1,3-butadiene, ethylacetylene, vinylacetylene, and acetonitrile in the standard solution are obtained after passing through the chromatographic column and the detector; the relative mass correction factor F of each component in the standard solution relative to 1,3-butadiene is calculated according to formula (1). i The principle of the calculation formula is to use the ratio of the concentration of the component in the standard solution to the peak area of ​​the component to calculate the correction factor, which is the correction factor of the component. The purpose of calculating the relative mass correction factor is to use the correction to calculate the accurate concentration after obtaining the peak area of ​​the component in the sample to be tested.

[0041] Finally, the sample solution is injected into the vaporization chamber of the gas chromatograph through the carrier gas, and the peak areas of C4 olefins, C4 alkynes, and acetonitrile in the sample solution are obtained after passing through the polar chromatographic column and the detector. The mass concentrations of C4 olefins, C4 alkynes, and acetonitrile in the sample solution are calculated according to formula (2): x The principle of the calculation formula is that the sum of the mass percentages of all components in the sample is 100%, so the sum of the peak areas of each component is the total peak area, and the proportion of the peak area of ​​each component in the total peak area is corrected using the correction factor to obtain its mass percentage concentration in the sample.

[0042] The present invention can ensure the complete liquefaction of the sample to be tested by pressurizing the sampling cylinder, eliminate the sample inhomogeneity caused by different boiling points and critical pressures of different components, and ensure the accuracy of injection and detection. On this basis, a chromatographic column with strong polarity is used to achieve the separation of C4 olefins, ethylacetylene, vinylacetylene, and acetonitrile on a chromatographic column, and detect them on the same detector, and then use the correction area normalization for quantitative analysis, and acetonitrile will not interfere with the analysis of ethylacetylene, vinylacetylene, etc. The present invention realizes the separation of polar substances and non-polar substances on the same chromatographic column, and uses the same detector for content determination, which is conducive to reducing labor consumption, shortening analysis time, improving analysis efficiency, reducing analysis cost, and can achieve simultaneous, accurate and efficient analysis of C4 olefins, C4 alkynes and acetonitrile content.

[0043] The present invention solves the problem of gasification discrimination of different components with a large boiling point span by optimizing method parameters, changing configuration and the like, and simultaneously optimizes the quantitative method, solves the problem of inaccurate quantification caused by injection error, realizes effective separation and synchronous detection of C4 hydrocarbons and acetonitrile on a single chromatographic column, and also solves the problem of mutual interference that may occur in the analysis process, thereby ensuring the accuracy of the analysis results and providing strong support for the efficient operation, quality control and process optimization of the butadiene device.

[0044] As described above, in the method of the present invention, each component will not interfere with each other on the basis of complete liquefaction in the same strong polar chromatographic column, so the accuracy of the content determination result can be improved. In a preferred embodiment, the peak order of the chromatographic column is the combined peak of C4 olefins, ethylacetylene, vinylacetylene, and acetonitrile. Among them, trans-butene, n-butene, isobutylene, cis-butene, etc. cannot be completely separated in the polar chromatographic column and flow out of the chromatographic column in the form of a combined peak.

[0045] In a preferred embodiment, the filler of the chromatographic column is cross-linked polyethylene glycol. By using a highly polar filler, polar and non-polar compounds can be effectively distinguished, so that C4 alkynes, C4 olefins and acetonitrile form clear separation peaks on the chromatogram. Even in the face of components with a large boiling point span and significant property differences, the preferred filler combination can also promote each component to continuously peak in a preset order (merged peak of C4 olefins, ethylacetylene, vinylacetylene, acetonitrile), reduce mutual interference between components, improve the accuracy of analysis, and no longer need two gas chromatographs with different configurations, can reduce operational complexity and hardware cost, shorten the analysis cycle, and improve overall analysis efficiency.

[0046] In order to further make the analysis process more efficient, reduce the analysis time, reduce the running cost, and significantly improve the accuracy and efficiency of the analysis, in a preferred embodiment, the column length of the chromatographic column is 55-65m, the diameter is 0.30-0.34mm, and the liquid film coating is 0.8-1.2μm. Under the above conditions, sufficient separation paths can be provided so that different components have enough time to be effectively separated in the column, especially for compounds with similar boiling points, such as C4 olefins and C4 alkynes, it is possible to ensure the formation of clear peak shapes and improve the accuracy and reliability of the analysis. Moreover, the moderate inner diameter maintains a higher column efficiency while improving the separation efficiency, reduces peak broadening, and further enhances the separation effect of the components. This preferred chromatographic column design can ensure that the combined peaks of C4 olefins, ethylacetylene, vinylacetylene, and acetonitrile are sequentially peaked in a preset order, reducing the analysis error caused by mutual interference between components.

[0047] In a preferred embodiment, the chromatographic column is an INNOWAX chromatographic column. The above chromatographic column has a strong polar separation ability and can effectively distinguish compounds of different polarities, such as simultaneously analyzing acetonitrile (polar compound) and C4 olefins and C4 alkynes (non-polar and weakly polar compounds). This chromatographic column can separate the peaks of each component in a preset order according to its polarity and boiling point characteristics, further reduce mutual interference between molecules, and improve the reliability of the analysis results.

[0048] In order to further improve the accuracy of the analysis, significantly shorten the analysis time, and improve the efficiency of the analysis, in a preferred embodiment, the column temperature of the chromatographic column uses a program temperature rise, first at 35-40 ° C for 3-7 minutes, and then at a rate of 8-12 ° C / min to 170-190 ° C. The optimized column temperature can further balance the vaporization rate and separation efficiency of each component, ensuring that the separation of different compounds in complex samples reaches the best state. As the column temperature gradually increases, each component flows out of the chromatographic column in turn according to its boiling point and polarity difference, forming a clear chromatographic peak, effectively avoiding peak overlap. By dynamically adjusting the column temperature, this preferred solution can accurately control the separation window of each component, even in the face of complex samples with a large boiling point span and significant polarity differences, it can ensure the separation effect of each component.

[0049] In a preferred embodiment, the temperature of the vaporization chamber is 150-200°C; and / or the detector is a hydrogen flame ionization detector, and the temperature of the detector is 200-250°C. The optimized vaporization chamber temperature can promote rapid and complete vaporization of the sample, further reducing injection discrimination, which is particularly important for compounds with large boiling point differences. The higher temperature can prevent the sample from partially condensing before entering the chromatographic column, ensuring the uniformity and integrity of the injection, thereby improving the accuracy of subsequent separation and detection. The control of the hydrogen flame ionization detector (FID) and its temperature can further improve the stability and response speed of the detector, so that when different components pass continuously, the signal can be captured quickly and accurately, reducing the peak broadening or peak tailing during the detection process. By accurately controlling the temperature of the vaporization chamber and the detector, combined with the efficient separation ability of the strong polarity chromatographic column, the present invention not only realizes the rapid separation and detection of multi-components, but also ensures the high accuracy of the analysis results. At the same time, due to the use of a single detector and optimized temperature control, the analysis process is simplified, the efficiency is improved, and the cost is effectively controlled, which is conducive to the simultaneous, accurate and efficient analysis of the content of carbon four olefins, carbon four alkynes and acetonitrile.

[0050] In order to match various process conditions and increase the application scope of the present invention, in a preferred embodiment, in the standard solution, the sum of the mass concentrations of acetonitrile, ethylacetylene and vinylacetylene is 2.0-20.0%.

[0051] In a preferred embodiment, the injection volume of the standard solution and the sample solution is 0.2-0.5 μL, and the split ratio is 1:(20-50). An appropriate injection volume can avoid chromatographic overload, reduce peak broadening, and ensure the sharpness of the peak shape of each component and the clarity of the separation effect. Especially for compounds with large differences in boiling points, such as C4 olefins and acetonitrile, an appropriate injection volume helps to maintain the separation window of each component and avoid mutual interference. The optimized split ratio further reduces injection discrimination while increasing the depth of sample analysis, and even low-content components in high-concentration samples can be accurately detected. By adjusting the split ratio, the amount of sample entering the chromatographic column can be effectively controlled, thereby stabilizing the detector signal, improving the linear range and sensitivity of the analysis, and further improving the data reliability during the entire analysis process.

[0052] For the purpose of more effectively reducing peak broadening so that all components are separated and detected under optimal conditions, in a preferred embodiment, the carrier gas is one or more of nitrogen, hydrogen and helium, and the flow rate of the carrier gas is 2.0-5.0 mL / min. The choice of carrier gas affects the sensitivity, selectivity and analysis speed of chromatographic analysis. The above-mentioned carrier gas types are suitable for the separation and high-sensitivity detection of complex samples, can provide a stable detection environment and accelerate the analysis speed, optimize the separation effect according to the characteristics of different components, improve the response speed of the detector, and ensure the accuracy of the analysis results. The control of the carrier gas flow rate within the above range can better balance the efficiency and resolution of chromatographic separation, which is conducive to improving the separation degree, ensuring the sharp peak shape, and accelerating the analysis speed.

[0053] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0054] Example 1

[0055]

sampling

[0056] Take the reflux material of the alkyne flash tower of the butadiene extraction unit as the sample to be tested. The main components of the sample are 1,3-butadiene, ethylacetylene, vinylacetylene, acetonitrile and some other C4 olefins. Use a sampling cylinder for sampling. The pressure resistance of the cylinder is not less than 6.0MPa. The appropriate sampling cylinder can be selected according to the situation of the on-site sampler.

[0057]

Sample solution preparation

[0058] After the sample is collected, a pressure gauge is used to test the pressure. When the sample pressure is lower than 1.0 MPa, pressurization operation is performed. Fixed pressure nitrogen can be used for pressurization, and the pressure is set at 1.0 MPa.

[0059]

Preparation of standard solution

[0060] Using 1,3-butadiene as the background, the standard liquid containing ethylacetylene, vinylacetylene and acetonitrile is used. The container is a 4.0L standard gas cylinder with a filling pressure of 1.0MPa. The sum of the mass concentrations of ethylacetylene, vinylacetylene and acetonitrile is 10.0%, and the sum of the mass concentrations of 1,3-butadiene, trans-butene, n-butene, iso-butene and cis-butene is 90.0%.

[0061]

Gas chromatography analysis

[0062] Chromatographic conditions:

[0063] Vaporization chamber: temperature is 180℃.

[0064] Chromatographic column: INNOWAX chromatographic column, the filler is cross-linked polyethylene glycol, the column length is 60m, the diameter is 0.32mm, the liquid film coating is 1.0μm, the column temperature is kept at 40℃ for 5 minutes, and then increased to 180℃ at a rate of 10℃ / min.

[0065] Detector: Hydrogen flame ionization detector, temperature is 230℃.

[0066] Carrier gas: nitrogen, flow rate 3.5 mL / min.

[0067] Injection volume: 0.35 μL, split ratio: 1:35.

[0068] Analysis process:

[0069] The key structural flow chart of gas chromatograph is as follows Figure 1 As shown, the standard solution and the sample solution are respectively introduced into the chromatograph from the sample inlet 2 of the high-pressure liquid injection valve 1 (the excess sample flows out from the sample outlet 3), brought into the vaporization chamber by the continuous flow of nitrogen, and then vaporized through the split / splitless injection port 4 and the vaporization chamber, and then flow into the highly polar INNOWAX chromatographic column 5, in which 1,3-butene and other C4 hydrocarbons (trans-butene, n-butene, isobutylene, cis-butene, etc.), ethyl acetylene, vinyl acetylene, and acetonitrile flow out of the chromatographic column in sequence, and after being detected by the FID detector 6, the correction area is normalized and calculated by the peak area:

[0070] According to formula (1), the relative mass correction factor F of each component in the standard solution relative to 1,3-butadiene is calculated. i .

[0071] According to formula (2), the mass concentrations of C4 olefins, C4 alkynes and acetonitrile in the sample solution were calculated as w x , report the results of each component, repeat the measurement 11 times, calculate the precision as shown in Table 1, the gas chromatogram of the sample to be tested (vinyl acetylene extraction) is as follows Figure 2The results are reported to the nearest 0.01%. Other C4 components are reported using the correction factor for 1,3-butene.

[0072] Table 1

[0073]

[0074] As shown in Table 1, when the same sample was determined using this method and the determination was repeated 11 times, the repeatability limit r was less than 0.15%. The method had good precision and could accurately determine the content of each component at the same time.

[0075] Depend on Figure 2 It can be seen that when this method is used to analyze such samples, the separation degrees of acetonitrile, ethylacetylene, vinylacetylene (butyne), and other C4 olefins all satisfy R≥1.5, and each component can be well separated under the chromatographic conditions of the present invention.

[0076] Example 2

[0077]

sampling

[0078] Take the reflux material of the alkyne flash tower of the butadiene extraction unit as the sample to be tested. The main components of the sample are 1,3-butadiene, ethylacetylene, vinylacetylene, acetonitrile and some other C4 olefins. Use a sampling cylinder for sampling. The pressure resistance of the cylinder is not less than 6.0MPa. The appropriate sampling cylinder can be selected according to the situation of the on-site sampler.

[0079]

Sample solution preparation

[0080] After the sample is collected, a pressure gauge is used to test the pressure. When the sample pressure is lower than 1.0MPa, pressurization operation is performed. Fixed pressure nitrogen can be used for pressurization, and the pressure is set at 0.9MPa.

[0081]

Preparation of standard solution

[0082] Using 1,3-butadiene as the background, the standard liquid containing ethylacetylene, vinylacetylene and acetonitrile is used. The container is a 4.0L standard gas cylinder with a filling pressure of 1.0MPa. The sum of the mass concentrations of ethylacetylene, vinylacetylene and acetonitrile is 2.0%, and the sum of the mass concentrations of 1,3-butadiene, trans-butene, n-butene, iso-butene and cis-butene is 98.0%.

[0083]

Gas chromatography analysis

[0084] Chromatographic conditions:

[0085] Vaporization chamber: temperature is 150℃.

[0086] Chromatographic column: INNOWAX chromatographic column, the filler is cross-linked polyethylene glycol, the column length is 55m, the diameter is 0.30mm, the liquid film coating is 1.2μm, the column temperature is constant at 35℃ for 7 minutes, and then increased to 170℃ at a rate of 8℃ / min.

[0087] Detector: Hydrogen flame ionization detector, temperature is 200℃.

[0088] Carrier gas: nitrogen, flow rate 2.0 mL / min.

[0089] Injection volume: 0.2 μL, split ratio: 1:20.

[0090] The analysis process is the same as in Example 1.

[0091] Example 3

[0092]

sampling

[0093] Take the reflux material of the alkyne flash tower of the butadiene extraction unit as the sample to be tested. The main components of the sample are 1,3-butadiene, ethylacetylene, vinylacetylene, acetonitrile and some other C4 olefins. Use a sampling cylinder for sampling. The pressure resistance of the cylinder is not less than 6.0MPa. The appropriate sampling cylinder can be selected according to the situation of the on-site sampler.

[0094]

Sample solution preparation

[0095] After the sample is collected, a pressure gauge is used to test the pressure. When the sample pressure is lower than 1.0MPa, pressurization operation is performed. Fixed-pressure nitrogen can be used for pressurization, and the pressure is set at 1.1MPa.

[0096]

Preparation of standard solution

[0097] Using 1,3-butadiene as the background, the standard liquid containing ethylacetylene, vinylacetylene and acetonitrile is used. The container is a 4.0L standard gas cylinder with a filling pressure of 1.0MPa. The sum of the mass concentrations of ethylacetylene, vinylacetylene and acetonitrile is 20.0%, and the sum of the mass concentrations of 1,3-butadiene, trans-butene, n-butene, iso-butene and cis-butene is 80.0%.

[0098]

Gas chromatography analysis

[0099] Chromatographic conditions:

[0100] Vaporization chamber: temperature is 200℃.

[0101] Chromatographic column: INNOWAX chromatographic column, the filler is cross-linked polyethylene glycol, the column length is 65m, the diameter is 0.34mm, the liquid film coating is 0.8μm, the column temperature is kept at 40℃ for 3 minutes, and then increased to 190℃ at a rate of 12℃ / min.

[0102] Detector: Hydrogen flame ionization detector, temperature is 250℃.

[0103] Carrier gas: nitrogen, flow rate 5.0 mL / min.

[0104] Injection volume: 0.5 μL, split ratio: 1:50.

[0105] The analysis process is the same as in Example 1.

[0106] The measurement results of Example 2 and Example 3 are shown in Table 2.

[0107] Table 2

[0108]

[0109] As can be seen from the above, each embodiment of the present invention can ensure the complete liquefaction of the sample to be tested by pressurizing the sampling cylinder, eliminate the sample unevenness caused by the different boiling points and critical pressures of different components, and ensure the accuracy of sampling and detection. On this basis, a chromatographic column with strong polarity is used to achieve the separation of ethylacetylene, vinylacetylene, and acetonitrile on a chromatographic column, and the detection is carried out on the same detector and then the correction area is normalized for quantification, and acetonitrile will not interfere with the analysis of ethylacetylene, vinylacetylene, etc. The present invention realizes the separation of polar substances and non-polar substances on the same chromatographic column, and uses the same detector for content determination, which can reduce labor consumption, shorten analysis time, improve analysis efficiency, reduce analysis costs, and realize simultaneous, accurate, and efficient analysis of C4 olefins, C4 alkynes, and acetonitrile content.

[0110] In addition, it can be seen that when each process parameter is within the preferred range of the present invention, the overall effect is better.

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for simultaneous analysis of the contents of C4 olefins, C4 alkynes and acetonitrile, characterized in that: The following steps are involved: Step S1, sampling in a butadiene production device using a sampling cylinder to obtain a sample to be tested, wherein the sample to be tested includes C4 olefins, C4 alkynes, and acetonitrile; the C4 olefins include 1,3-butadiene and C4 olefins other than 1,3-butadiene, and the C4 alkynes include ethylacetylene and vinylacetylene; Step S2, adjusting the pressure of the sample to be tested to 0.9-1.1 MPa to obtain a sample solution; Step S3, obtaining a standard solution, wherein the standard solution has 1,3-butadiene as the background and contains standard liquids of ethylacetylene, vinylacetylene, and acetonitrile; Step S4, injecting the standard solution into a vaporization chamber of a gas chromatograph through a carrier gas, passing through a chromatographic column and a detector, and obtaining the peak areas of 1,3-butadiene, ethylacetylene, vinylacetylene, and acetonitrile in the standard solution; According to formula (1), the relative mass correction factor F of each component in the standard solution relative to 1,3-butadiene is calculated respectively. i : Among them, w i is the mass concentration of a component in the standard solution, in %; w s A is the mass concentration of 1,3-butadiene in the standard solution, in %; i is the corresponding peak area of ​​a component in the standard solution; A s is the peak area of ​​1,3-butadiene in the standard solution; Step S5, injecting the sample solution into the vaporization chamber of the gas chromatograph through the carrier gas, passing through the chromatographic column and the detector, obtaining the peak areas of the C4 olefins, the C4 alkynes, and the acetonitrile in the sample solution; and calculating the mass concentrations w of the C4 olefins, the C4 alkynes, and the acetonitrile in the sample solution according to formula (2). x : Among them, A x is the corresponding peak area of ​​a component in the sample solution; X is the total mass concentration of impurities in the sample solution other than those measured by this method, in %; Wherein, the chromatographic column is a polar chromatographic column.

2. The method according to claim 1, characterized in that The peak elution order of the chromatographic column is the combined peak of C4 olefins, ethylacetylene, vinylacetylene and acetonitrile.

3. The method according to claim 1 or 2, characterized in that: The filler of the chromatographic column is cross-linked polyethylene glycol.

4. The method according to any one of claims 1 to 3, characterized in that The column length of the chromatographic column is 55-65m, the diameter is 0.30-0.34mm, and the liquid film coating is 0.8-1.2μm.

5. The method according to any one of claims 1 to 4, characterized in that The chromatographic column is an INNOWAX chromatographic column.

6. The method according to any one of claims 1 to 5, characterized in that The column temperature of the chromatographic column is programmed to be kept constant at 35-40°C for 3-7 minutes, and then heated to 170-190°C at a rate of 8-12°C / min.

7. The method according to any one of claims 1 to 6, characterized in that The temperature of the vaporization chamber is 150-200°C; And / or the detector is a hydrogen flame ionization detector, and the temperature of the detector is 200-250°C.

8. The method according to any one of claims 1 to 7, characterized in that In the standard solution, the sum of the mass concentrations of acetonitrile, ethylacetylene and vinylacetylene is 2.0-20.0%.

9. The method according to any one of claims 1 to 8, characterized in that The injection volume of the standard solution and the sample solution is 0.2-0.5 μL, and the split ratio is 1:(20-50).

10. The method according to any one of claims 1 to 9, characterized in that The carrier gas is one or more of nitrogen, hydrogen and helium, and the flow rate of the carrier gas is 2.0 to 5.0 mL / min.

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