Quantitative chromatographic analysis method of butadiene in butadiene production process

Abstract

The invention provides a quantitative chromatographic analysis method for butadiene in a butadiene production process. The method comprises the following steps: firstly, collecting a sample; separating the extracting agent and the hydrocarbon substances in the sample by using a first chromatographic separation column, and separating each component in the hydrocarbon substances by using a second chromatographic separation column; and respectively detecting the separated extraction agent and hydrocarbon substances, and calculating the content of each component in the sample by using a peak area normalization calculation method. According to the method for detecting the content of each component in the sample after fine separation of the sample, the detection result is more accurate and is not easily influenced by the components of the sample. A peak area normalization calculation method is adopted, detection results of multiple channels are fitted, the detection results are not prone to being affected by pressure changes, component changes, character changes and other reasons, repeatability is good, and errors are small. In addition, the method can meet the requirement for analysis of intermediate control samples in the whole process of the whole butadiene production process.

Description

Technical Field

[0001] The invention relates to the field of chemical engineering, and in particular to a quantitative chromatographic analysis method for butadiene in a butadiene production process. Background Art

[0002] In the butadiene extraction process, the alkyne flash distillation section is mainly used for the separation and removal of heavy components such as C4 alkynes and cis-butene. If the C4 alkynes are not completely removed, the product will be unqualified. If the C4 alkyne content in the product is too high, it will also cause explosions, fires and other dangers. Therefore, the accurate and effective determination of the alkyne content in the butadiene product is of great significance for actual production.

[0003] However, most samples in the alkyne flash distillation section contain a large amount of solvents, such as acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, etc., among which acetonitrile is the most common. The content of hydrocarbon components and acetonitrile in the samples can provide key references for the process, but since the composition content of acetonitrile and hydrocarbon components in the samples is unstable, it is very difficult to accurately analyze the composition of the gas phase and liquid phase in the samples.

[0004] GB / T6015-2021 "Gas Chromatographic Method for the Determination of Trace Dimers and Residual Extracting Agents in Industrial Butadiene" implemented in March 2022 provides a gas chromatography method for the determination of trace dimers and residual extracting agents in industrial butadiene. However, this method is only applicable to the detection of trace extracting agents remaining in butadiene products, and is not applicable to gas, liquid, and gas-liquid mixed samples of extracting agents mixed with C4 hydrocarbons with an extracting agent content of 1% to 85%. In addition, this method uses the external standard method for quantification, and has high requirements for sample purity and operating techniques. Some samples that do not meet the purity requirements or samples such as residual C4 cannot be determined using this method, and it is also impossible to simultaneously determine hydrocarbon components and extracting agents, and the analysis efficiency is low.

[0005] The prior art mentions the use of a central cutting system and an external standard method for the separate detection of acetonitrile and hydrocarbons. However, in actual applications, for samples with too high an extractant content, incomplete gasification and unstable sample pressure during the detection process will lead to instability in the external standard method quantification. There is no comprehensive description of the sample collection method and injection method as well as the analysis process of the system, which ultimately makes it impossible to accurately measure the exact content of each component in butadiene.

[0006] The present invention is proposed to solve the problem that the prior art is only applicable to the determination of trace residual extracting agent in finished butadiene, and cannot handle gas phase, liquid phase and gas-liquid mixed samples with high extracting agent content, as well as the problem of poor repeatability and large error of analysis results caused by changes in sample extracting agent content in the prior art. Summary of the invention

[0007] The main purpose of the present invention is to provide a quantitative chromatographic analysis method for butadiene in a butadiene production process, so as to solve the problem in the prior art that gas phase, liquid phase and gas-liquid mixed samples with high extractant content cannot be processed during the testing of components in the butadiene production process, and the problem of poor repeatability and large error of analysis results caused by changes in the extractant content of the sample in the prior art.

[0008] In order to solve the above problems, the present invention provides a quantitative chromatographic analysis method for butadiene in a butadiene production process, the analysis method comprising the following steps: step (1), collecting a mixed sample including an extractant and a hydrocarbon substance in the butadiene production process; step (2), separating the extractant and the hydrocarbon substance in the sample by using a first chromatographic separation column, and then separating the components in the hydrocarbon substance by using a second chromatographic separation column; step (3), respectively detecting the separated extractant and hydrocarbon substance, and calculating the content of each component in the sample by using a peak area normalization calculation method.

[0009] Furthermore, the sample collection process includes a sampling process and a sampling process; wherein the sampling method is selected according to the content of the extractant in the sample: when the content of the extractant is less than 0.1%, a ball bladder is used for sampling; when the content of the extractant is 0.1-70%, a high-pressure steel cylinder is used for sampling; when the content of the extractant is more than 70%, a glass bottle is used for sampling.

[0010] Furthermore, the method of injection is selected according to the sampling method: when using a bladder for sampling, a gas valve is used for injection; when using a high-pressure steel cylinder for sampling, a high-pressure liquid valve is used for injection; when using a glass bottle for sampling, a micro-syringe is used for injection.

[0011] Further, the extracting agent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile and dimethyl sulfoxide; preferably, the extracting agent is acetonitrile.

[0012] Furthermore, the first chromatographic separation column and the second chromatographic separation column are connected in series; preferably, the first chromatographic separation column is a strong polar chromatographic column, and the second chromatographic separation column is a weak polar chromatographic column; preferably, the first chromatographic separation column is an INNOWAX chromatographic column; preferably, the second chromatographic separation column is an alumina chromatographic column.

[0013] Furthermore, the hydrocarbon substance is one or more of isobutane, normal butane, trans-butene, normal butene, isobutene, cis-butene, 1,3-butadiene, isopentane, normal pentane, vinyl acetylene and ethyl acetylene.

[0014] Furthermore, the peak area normalization calculation method includes first using a standard substance to calculate a correction factor, and the correction factor is used to perform analytical correction on the peak area; the calculation of the correction factor is shown in Formula I: F i =c i / A i Formula I, wherein c i is the mass concentration of the corresponding component in the standard substance, A i is the peak area of ​​the corresponding component in the standard substance; F i is the correction factor for the corresponding component in the standard substance.

[0015] Furthermore, the peak area normalization calculation method is shown in Formula II: Among them, w i is the content of component i in the sample, F i is the correction factor for component i in the sample, A i is the peak area of ​​component i in the sample.

[0016] Furthermore, in step (3), the detection is to use a hydrogen flame ionization detector to simultaneously detect the extraction agent and the hydrocarbon substances.

[0017] Furthermore, steps (1) to (3) include: the first chromatographic separation column is an INNOWAX (60m×0.32mm×0.5um) chromatographic column; the second chromatographic separation column is an AL / S (25m×0.32mm×10um) chromatographic column, an empty column (9.3m×0.25mm×0.0um); and the flow rate of the first chromatographic separation column is: 1.0mL / min, the flow rate of the second chromatographic separation column is: 5.0mL / min, and the flow rate of the empty column is: 6.46mL / min; the split ratio is: 10:1, the column box temperature is: first maintained at 60°C for 10 minutes, then increased to 180°C at a rate of 20°C / min and maintained for 5 minutes; PCM flow controller event: open for 0.01 minutes and close for 12.0 minutes.

[0018] The present invention provides a quantitative chromatographic analysis method for butadiene in a butadiene production process, wherein the collected sample is first separated by a first chromatographic separation column to obtain an extractant and a hydrocarbon substance, respectively, and then the separated hydrocarbon substance is further separated by a second chromatographic separation column, and finally the separated extractant and the hydrocarbon substance after secondary separation are detected respectively, and then the content of each component in the sample is calculated by a peak area normalization calculation method. The analysis method fits the detection results of multiple channels and performs a normalized calculation method. The error caused by changes in sample pressure, components, and properties is small, and not only has good repeatability, but also has the advantage of low requirements for sample injection operations, and can meet the needs of intermediate control sample analysis throughout the entire butadiene production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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:

[0020] Figure 1 The flow path schematic diagram of the quantitative chromatographic analysis method of butadiene in the butadiene production process according to the present invention is shown, wherein the definitions of the reference numerals are as follows:

[0021] 1. First chromatographic separation column; 2. Second chromatographic separation column; 3. Empty column; 4. First hydrogen flame ionization detector; 5. Second hydrogen flame ionization detector; 6. Electronic flow controller; 7. Inlet; 8. Center cutting valve. DETAILED DESCRIPTION

[0022] 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.

[0023] As described in the background technology section, in the butadiene extraction process, incomplete removal of components such as carbon tetraacetylene may cause explosions, fires and other dangers. Therefore, accurate and effective determination of the alkyne content in the butadiene product is of great significance for actual production. The existing technology for testing samples in the butadiene production process is only applicable to the determination of trace residual extracting agents in the finished butadiene, and cannot handle the problem of gas phase, liquid phase and gas-liquid mixed samples with high extracting agent content, as well as the problem of poor repeatability and large errors in the analysis results caused by changes in the extracting agent content of the sample in the prior art.

[0024] In order to solve the above problems, the present invention provides a quantitative chromatographic analysis method for butadiene in a butadiene production process, the analysis method comprising the following steps: step (1), collecting a mixed sample containing an extractant and a hydrocarbon substance in the butadiene production process; step (2), separating the extractant and the hydrocarbon substance in the sample by using a first chromatographic separation column, and then separating the components in the hydrocarbon substance by using a second chromatographic separation column; step (3), respectively detecting the separated extractant and hydrocarbon substance, and calculating the content of each component in the sample by using a peak area normalization calculation method.

[0025] Specifically, in the quantitative chromatographic analysis method for butadiene in the butadiene production process proposed by the present invention, the collected sample is first separated by a first chromatographic separation column to obtain an extracting agent and a hydrocarbon substance, respectively, and then the separated hydrocarbon substance is further separated by a second chromatographic separation column to separate the various components in the hydrocarbon substance. Finally, the separated extracting agent and the hydrocarbon substance after the secondary separation are detected respectively, and then the content of each component in the sample including the extracting agent and the hydrocarbon substance is calculated by a peak area normalization calculation method.

[0026] In the above analysis method, a mixed sample containing an extractant and a hydrocarbon substance in the butadiene production process is first sampled, and then the characteristics of the separation column are used to separate the extractant with greater polarity and the hydrocarbon substance with relatively smaller polarity in the sample, and the hydrocarbon substance containing multiple components is further separated by the second separation column, and finally the separated extractant and the hydrocarbon substance after secondary separation are detected respectively, and then the peak area normalization calculation method is used to calculate the content of each component in the sample including the extractant and the hydrocarbon substance. The above method of finely separating the sample and then detecting the content of each component in the sample can make the test result more accurate, even if the content of a certain component in the hydrocarbon substance is very low or the content of the extractant is high, an accurate result can be obtained. Secondly, the peak area normalization calculation method is used to fit the test results of multiple channels, and the test results are not easily affected by pressure changes, component changes, property changes, etc., and the repeatability is good, the requirements for the injection operation are low, and the error caused by the sample is small. Not only that, the above method can meet the needs of the analysis of intermediate control samples in the entire process of the butadiene production process.

[0027] According to different samples, the present application further optimizes the sampling and sample delivery methods. In a preferred embodiment, the sample collection process includes a sampling process and a sampling process; wherein, the sampling method is selected according to the content of the extractant in the sample: when the content of the extractant is less than 0.1%, a ball bladder is used for sampling; when the content of the extractant is 0.1-70%, a high-pressure steel cylinder is used for sampling; when the content of the extractant is more than 70%, a glass bottle is used for sampling. In the process of sampling the sample, the content of the extractant in the sample can be first estimated according to the material balance or sampling stage, and then according to the estimated range of the content of the extractant in the sample, a suitable sampling and sampling process is selected. According to the distribution of the components in the sample, the selection of a suitable sampling and sampling method can further improve the accuracy of the entire detection. Specifically, when the content of the extractant is less than 0.1%, a ball bladder is used for sampling, which is mainly beneficial to prevent the enrichment of a small amount of high-boiling point extractant in the sampling steel cylinder and reduce the impact on the sampling accuracy. In addition, after a lot of exploration and research, the inventors found that when the content of the extractant in the sample is below 0.1%, the extractant can exist in the carbon four component in gaseous form, and the above sampling method has a better match for gaseous samples; when the content of the extractant is 0.1-70%, the use of high-pressure steel cylinders for sampling can prevent sample distortion caused by gas-liquid phase separation in the sample even after pressurizing the sample during the detection process, thereby further improving the accuracy of sample detection; when the content of the extractant is above 70%, the use of glass bottles for sampling is better and more conducive to the subsequent sampling process.

[0028] The method of injection is selected according to the sampling method. In a preferred embodiment, when a bladder is used for sampling, a gas valve is used for injection; when a high-pressure steel cylinder is used for sampling, a high-pressure liquid valve is used for injection; when a glass bottle is used for sampling, a micro-syringe is used for injection. The specific method of injection can be adapted according to the sampling method. The overall principle of injection and sampling is not to change the representativeness of the sample. For example, when a high-pressure steel cylinder is used for sampling, the reason for using a high-pressure liquid valve for injection is that the boiling point of the extracting agent is usually different from that of hydrocarbon substances, and it is easy to produce gasification discrimination when it is vaporized during the detection process. The corresponding use of a high-pressure liquid valve for injection can make the sample directly vaporize instantly in the gasification chamber of the gas chromatograph and enter the chromatographic separation column, thereby minimizing the injection error. In the present invention, the sampling and injection methods are adapted in the above manner to further improve the accuracy of the detection.

[0029] The above-mentioned matching of different sampling and injection methods according to the different content ranges of the extractant will make the test results more accurate. In the actual test process, if all components in the sample to be tested are non-volatile components, glass bottles can be used for sample collection, and the accuracy of the test results can also be within a good range.

[0030] By way of example but not limitation, the extracting agent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile and dimethyl sulfoxide. The extracting agents commonly used in the butadiene production process can all be used to detect and analyze the components in the sample using the quantitative chromatographic analysis method of the present invention, and the correction factor and other parameters can be adjusted according to the actual solvent used in the production process to achieve the purpose of accurate detection. The method of the present invention is for the specific detection situation when the extracting agent is acetonitrile.

[0031] In a preferred embodiment, the first chromatographic separation column and the second chromatographic separation column are connected in series; preferably, the first chromatographic separation column is a strong polarity chromatographic column, and the second chromatographic separation column is a weak polarity chromatographic column; preferably, the first chromatographic separation column is an INNOWAX chromatographic column; preferably, the second chromatographic separation column is an aluminum oxide chromatographic column. The first separation column is used to separate the extractant and hydrocarbon substances in the sample, and the extractant and hydrocarbon substances often have greater polarity than the extractant. The first chromatographic separation column and the second chromatographic separation column are connected in series, and the sample is first passed through the first separation column with strong polarity to separate the extractant and hydrocarbon substances, two substances with a large difference in polarity, and then the separated hydrocarbon substances are passed through the second chromatographic separation column with weak polarity to separate the various components in the hydrocarbon substances, and finally the purpose of separating all the components in the sample is achieved.

[0032] In a preferred embodiment, the hydrocarbon substance is one or more of isobutane, normal butane, trans-butene, normal butene, isobutene, cis-butene, 1,3-butadiene, isopentane, normal pentane, vinyl acetylene and ethyl acetylene. The quantitative chromatographic analysis method of the present invention is for samples in the butadiene production process, so the components of the hydrocarbon substances in the sample include but are not limited to the above types, and the effect of accurate detection can be achieved.

[0033] In a preferred embodiment, the peak area normalization calculation method includes first using a standard substance to calculate a correction factor, which is used to analyze and correct the peak area. In the quantitative analysis process, since the response values ​​of the same detector to different substances are different, in this case, using the peak area to reflect the content of the component to be measured will result in errors, so it is necessary to introduce a correction factor to achieve the ability to use the peak area to accurately reflect the content of the component to be measured. The calculation of the correction factor is shown in Formula I: F i =c i / A i Formula I, wherein c i is the mass concentration of the corresponding component in the standard substance, A i is the peak area of ​​the corresponding component in the standard substance; F iIt is the correction factor of the corresponding component in the standard substance. In the actual test process, three standard substances were selected according to the different contents of the extractant in the sample to detect their correction factors, namely: 0.1% of the mass content of the extractant and 99.99% of the mass content of hydrocarbons; 20% of the mass content of the extractant and 80% of the mass content of hydrocarbons; 85% of the mass content of the extractant, 10% of the mass content of water and 5% of the mass content of hydrocarbons.

[0034] In a preferred embodiment, the peak area normalization calculation method is shown in Formula II:

[0035]

[0036] Among them, w i is the content of component i in the sample, Fi is the correction factor of component i in the sample, and Ai is the peak area of ​​component i in the sample. The present invention adopts the peak area normalization calculation method to analyze samples in the butadiene production process, and the test results are more accurate and have better repeatability.

[0037] It should be further explained here that the selection of standard substances can be adjusted according to the actual content of the extractant in the butadiene production process and the degree of saturation of butadiene, which will be more conducive to the accuracy of the test results.

[0038] In a preferred embodiment, the detection in step (3) is to detect the extraction agent and the hydrocarbon material simultaneously using a hydrogen flame ionization detector. Detecting each component in the separated hydrocarbon material and the extraction agent simultaneously is conducive to the subsequent unified calculation of the detection results.

[0039] According to the quantitative chromatographic analysis method of butadiene in the butadiene production process, it is characterized in that steps (1) to (3) include: the first chromatographic separation column is an INNOWAX (60m×0.32mm×0.5um) chromatographic column; the second chromatographic separation column is an AL / S (25m×0.32mm×10um) chromatographic column, an empty column (9.3m×0.25mm×0.0um); and the flow rate of the first chromatographic separation column is: 1.0mL / min, the flow rate of the second chromatographic separation column is: 5.0mL / min, and the flow rate of the empty column is: 6.46mL / min; the split ratio is: 10:1, the column box temperature is: first maintained at 60°C for 10min, then increased to 180°C at a rate of 20°C / min and maintained for 5min; PCM flow controller event: open for 0.01 minutes and close for 12.0 minutes.

[0040] The flow path diagram of the chromatographic analysis method is as follows Figure 1As shown, the sample (SS) is first passed into the injection port 7, and then the extractant and hydrocarbon substances in the sample are separated through the first chromatographic separation column 1. Then, the separated extractant and hydrocarbon substances are passed through the center cutting valve 8, and the separated hydrocarbons are passed through the second chromatographic separation column 2 to separate the various components in the hydrocarbon substances in sequence, and the separated extractant is passed through the empty column 3 for further detection. The electronic flow controller 6 supplies carrier gas to the center cutting valve 8 in this process. Then, the first hydrogen flame ionization detector 4 is used to detect the extractant flowing out of the empty column 3, and the second hydrogen flame ionization detector 5 is used to detect the various components in the hydrocarbon substances separated by the second chromatographic separation column 2. Finally, the peak area normalization method is used to calculate the content of each component in the sample, including the extractant. The empty column 3 in the flow path schematic diagram of the analysis method can balance the pressure of the detection system and prevent the system flow from fluctuating when the center cutting valve 8 is in operation. The quantitative chromatographic analysis method for butadiene in the butadiene production process provided by the present invention can meet the needs of intermediate control sample analysis throughout the entire butadiene production process, and the test result has small error and good repeatability, and has practical application significance.

[0041] The present application is further described in detail below in conjunction with specific examples, which should not be construed as limiting the scope of protection claimed in the present application. The method of the present invention is based on a sample when the extracting agent is acetonitrile, and the flow path diagram of the chromatographic analysis method is as follows Figure 1 shown.

[0042] Example 1

[0043] 1. Gas chromatography conditions:

[0044] The first chromatographic separation column: INNOWAX (60m×0.32mm×0.5um) chromatographic column;

[0045] Second chromatographic separation column: AL / S (25m×0.32mm×10um);

[0046] Empty column (9.3m×0.25mm×0.0um);

[0047] First chromatographic separation column flow rate: 1.0 mL / min;

[0048] Second chromatographic separation column flow rate: 5.0 mL / min;

[0049] Detector: Hydrogen flame ionization detector

[0050] Empty column flow rate: 6.46 mL / min;

[0051] Split ratio: 10:1;

[0052] Column box temperature: 60℃ for 10 min, then increase the temperature to 180℃ at a rate of 20℃ / min and maintain for 5 min;

[0053] PCM flow controller events: 0.01 minutes open, 12.0 minutes closed.

[0054] 2. Calculate the correction factor:

[0055] According to the formula shown in Formula I, the correction factors of each compound in the three standard substances corresponding to the three cases are calculated respectively: F i =c i / A i Formula I, wherein c i is the mass concentration of the corresponding component in the standard substance, A i is the peak area of ​​the corresponding component in the standard substance; F i is the correction factor of the corresponding component in the standard substance. Case 1: acetonitrile content is 0.1% and hydrocarbon content is 99.99%, Case 2: acetonitrile content is 20% and hydrocarbon content is 80% and acetonitrile content is 85%, Case 3: acetonitrile content is 85% and hydrocarbon content is 5%, and the remaining 10% is water. The results are shown in Table 1:

[0056] Table 1

[0057]

[0058] 3. Detection steps

[0059] The method comprises the following steps: taking samples by high-pressure steel cylinders and injecting samples by high-pressure liquid valves to realize sample collection; separating the extractant and hydrocarbon substances in the sample in a first chromatographic separation column, and separating the components in the separated hydrocarbon substances in a second chromatographic separation column; detecting the extractant flowing out of the first chromatographic separation column and the hydrocarbon flowing out of the second chromatographic separation column respectively by a hydrogen flame ionization detector, recording the peak areas, correcting the peak areas by using correction factors, and performing peak area normalization calculation on the corrected peak areas of the components to obtain the content of the components.

[0060] 4. Sample analysis

[0061] The content of each component in the sample was calculated using the peak area normalization calculation formula shown in Formula II: Among them, w i is the content of component i in the sample, Fi is the correction factor of component i in the sample, and Ai is the peak area of ​​component i in the sample. The sample analysis results are shown in Table 2:

[0062] Table 2

[0063] Isobutane n-Butane Trans-Butene n-Butene Isobutylene Cis-Butene 1,3-Butadiene Acetonitrile Actual content / % 2.58 2.61 15.47 21.06 20.48 10.55 28.66 2.90 Test content / % 2.64 2.53 15.38 20.80 20.90 10.28 27.47 2.88 Accuracy / % 102.25 97.11 99.44 98.78 102.04 97.41 95.86 99.31

[0064] Example 2

[0065] The difference from Example 1 is that when the content of the extractant in the sample is 50%, a glass bottle is used for sampling and a micro syringe is used for injection. The sample analysis results are shown in Table 3.

[0066] Table 3

[0067]

[0068] Example 3

[0069] The difference from Example 1 is that the content of the extractant in the sample to be tested is less than 0.1%, a ball bladder is used for sampling, and a gas injection valve is used for injection. The sample analysis results are shown in Table 4:

[0070] Table 4

[0071]

[0072]

[0073] Example 4

[0074] The difference from Example 1 is that the content of the extractant is more than 70%, a high-pressure steel bottle is used for sampling, and a high-pressure liquid valve is used for injection. The sample analysis results are shown in Table 5:

[0075] Table 5

[0076] Acetonitrile Ethyl acetylene Vinyl Acetylene 1,3-Butadiene Actual content / % 99.7112 0.0304 0.2188 0.0396 Test content / % 99.7095 0.0298 0.2205 0.0402 Accuracy / % 99.9983 98.03 100.78 101.51

[0077] Comparative Example 1

[0078] The test was performed using conventional detection methods.

[0079] 1. Chromatographic conditions

[0080] Chromatographic column: AL / S (25m×0.32mm×10um);

[0081] Column flow rate: 3.0 mL / min;

[0082] Detector: Hydrogen flame ionization detector

[0083] Split ratio: 20:1;

[0084] Column box temperature: 60℃ for 5 min, then increase the temperature to 120℃ at a rate of 10℃ / min and maintain for 5 min; increase the temperature to 160℃ at a rate of 20℃ / min and maintain for 5 min;

[0085] 2. Detection steps

[0086] Since the above test conditions cannot detect samples with high acetonitrile content, the samples need to be placed in a bladder, which is heated to vaporize the hydrocarbons. The vaporized hydrocarbon mixture is then introduced into the chromatograph through a six-way injection valve to detect the hydrocarbon content, and then quantified by normalization of the correction area to calculate the content of each hydrocarbon substance in the sample. The test content results in the table are expressed in a manner that does not take into account the content of the extractant.

[0087] 3. Sample analysis

[0088] The sample analysis results are shown in Table 6:

[0089] Table 6

[0090]

[0091]

[0092] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0093] Embodiment 1, embodiment 3 and embodiment 4 adopt the quantitative chromatographic analysis method of butadiene described in the present invention, and select the appropriate sampling and injection method according to the content of the extracting agent in the sample. The detected content of each component in the sample to be tested is relatively close to the actual content, and the accuracy error range is within 3%; Embodiment 4 adopts the quantitative chromatographic analysis method of butadiene described in the present invention, but does not adopt the sampling and injection method described in the present invention that best matches the content of the extracting agent. Since there are no volatile hydrocarbon substances in the sample, the detected content of each component in the sample to be tested is also relatively close to the actual content, and the accuracy error range is within 5%, which is within the normal range.

[0094] The test method in Comparative Example 1 does not adopt the quantitative chromatographic analysis method of butadiene described in the present invention. Not only can the content of the extractant therein be not measured, but the detected content of hydrocarbon substances is also far from the actual content, and the test results cannot be evaluated with accuracy.

[0095] From the above results, it can be seen that the present invention first separates the collected samples through the first chromatographic separation column to obtain the extractant and hydrocarbon substances respectively, and then further separates the separated hydrocarbon substances through the second chromatographic separation column, and finally detects the separated extractant and the hydrocarbon substances after secondary separation respectively, and then calculates the content of each component in the sample by the peak area normalization calculation method. The quantitative chromatographic analysis method of butadiene proposed by the present invention by applying the heart cutting system solves the analysis problem of the hydrocarbon content in the acetonitrile rich solvent at the bottom of the butadiene unit extraction tower, and the analysis method can meet the needs of the whole process of intermediate control sample analysis of the entire butadiene production process.

[0096] 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 quantitative chromatographic analysis method for butadiene in a butadiene production process, characterized in that: The analytical method comprises the following steps: Step (1), collecting a mixed sample including an extractant and hydrocarbon substances in a butadiene production process; Step (2), using a first chromatographic separation column to separate the extractant and hydrocarbon substances in the sample, and then using a second chromatographic separation column to separate the components in the hydrocarbon substances; Step (3), respectively detecting the separated extracting agent and the hydrocarbon substance, and calculating the content of each component in the sample using a peak area normalization calculation method.

2. The quantitative chromatographic analysis method of butadiene in the butadiene production process according to claim 1, characterized in that: The sample collection process includes a sampling process and a sampling process; wherein the sampling method is selected according to the content of the extractant in the sample: when the content of the extractant is less than 0.1%, a ball bladder is used for sampling; when the content of the extractant is 0.1-70%, a high-pressure steel cylinder is used for sampling; when the content of the extractant is more than 70%, a glass bottle is used for sampling.

3. The quantitative chromatographic analysis method of butadiene in the butadiene production process according to claim 2, characterized in that: The injection method is selected according to the sampling method: when the bladder is used for sampling, a gas valve is used for the injection; when the high-pressure steel cylinder is used for sampling, a high-pressure liquid valve is used for the injection; when the glass bottle is used for sampling, a micro-syringe is used for the injection.

4. The quantitative chromatographic analysis method for butadiene in the butadiene production process according to any one of claims 1 to 3, characterized in that: The extracting agent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile and dimethyl sulfoxide; Preferably, the extracting agent is acetonitrile.

5. The quantitative chromatographic analysis method for butadiene in the butadiene production process according to any one of claims 1 to 3, characterized in that: The first chromatographic separation column and the second chromatographic separation column are connected in series; Preferably, the first chromatographic separation column is a strong polar chromatographic column, and the second chromatographic separation column is a weak polar chromatographic column; Preferably, the first chromatographic separation column is an INNOWAX chromatographic column; Preferably, the second chromatographic separation column is an aluminum oxide chromatographic column.

6. The quantitative chromatographic analysis method for butadiene in the butadiene production process according to any one of claims 1 to 3, characterized in that: The hydrocarbon substance is one or more of isobutane, normal butane, trans-butene, normal butene, isobutene, cis-butene, 1,3-butadiene, isopentane, normal pentane, vinyl acetylene and ethyl acetylene.

7. The quantitative chromatographic analysis method for butadiene in a butadiene production process according to any one of claims 1 to 6, characterized in that: The peak area normalization calculation method includes first using a standard substance to calculate a correction factor, wherein the correction factor is used to perform analytical correction on the peak area; The calculation of the correction factor is shown in Formula I: F i =c i / A i Formula I, Among them, c i is the mass concentration of the corresponding component in the standard substance, A i is the peak area of ​​the corresponding component in the standard substance; F i is the correction factor for the corresponding component in the standard substance.

8. The quantitative chromatographic analysis method of butadiene in the butadiene production process according to claim 7, characterized in that: The peak area normalization calculation method is shown in Formula II: Among them, the w i is the content of component i in the sample, the F i is the correction factor of component i in the sample, and the A i is the peak area of ​​component i in the sample.

9. The quantitative chromatographic analysis method for butadiene in a butadiene production process according to any one of claims 1 to 6, characterized in that: The detection in step (3) is to detect the extraction agent and the hydrocarbon substance using a hydrogen flame ionization detector.

10. The quantitative chromatographic analysis method of butadiene in the butadiene production process according to claim 1, characterized in that: The steps (1) to (3) include: the first chromatographic separation column is an INNOWAX (60m×0.32mm×0.5um) chromatographic column; the second chromatographic separation column is an AL / S (25m×0.32mm×10um) chromatographic column, an empty column (9.3m×0.25mm×0.0 u m); and the flow rate of the first chromatographic separation column is: 1.0 mL / min, the flow rate of the second chromatographic separation column is: 5.0 mL / min, and the empty column flow rate is: 6.46 mL / min; the split ratio is: 10:1, and the column box temperature is: first 60°C for 10 min, then increased to 180°C at a rate of 20°C / min and maintained for 5 min; PCM flow controller event: open at 0.01 minutes and close at 12.0 minutes.

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