Method for detecting component content of polyacrylonitrile-based carbon fiber production recovery liquid
By using potassium thiocyanate as an internal standard, a standard working curve for infrared spectroscopy was established, which solved the problem of large errors in the detection of the composition content of polyacrylonitrile-based carbon fiber recycled liquid in the existing technology, achieving rapid and accurate detection results and reducing production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHONGFU SHENYING CARBON FIBER
- Filing Date
- 2023-07-21
- Publication Date
- 2026-06-26
AI Technical Summary
Existing technologies for detecting the composition of recycled liquid from polyacrylonitrile-based carbon fiber production suffer from large errors, complex operations, and the inability to perform batch testing. In particular, they are inefficient when multiple methods are used in combination.
Potassium thiocyanate was used as an internal standard, and a standard working curve was established by infrared spectroscopy to quickly and accurately detect the content of components in the recovered liquid, including acrylonitrile and dimethyl sulfoxide.
This technology enables rapid and accurate detection of the components in the recycled liquid from the production of polyacrylonitrile-based carbon fiber, reducing production costs, improving work efficiency, and minimizing errors.
Smart Images
Figure CN116735523B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of detection and analysis technology, and in particular to a method for detecting the component content of recycled liquid from the production of polyacrylonitrile-based carbon fiber. Background Technology
[0002] Carbon fiber has been widely used in many fields due to its high performance. With the in-depth development of the carbon fiber industry and changes in market demand, higher requirements have been put forward for carbon fiber manufacturers. At present, the promotion and application of carbon fiber is still limited by high production costs. Therefore, how to reduce the production costs in the field of carbon fiber has become a key research area.
[0003] Polyacrylonitrile-based carbon fiber is mainly produced by polymerization of acrylonitrile and solvents such as dimethyl sulfoxide under a series of reaction conditions. To reduce production costs, the reaction solution can be recycled and reused. The main components of the recycled solution from polyacrylonitrile-based carbon fiber production are dimethyl sulfoxide and a small amount of acrylonitrile. To ensure the quality of the carbon fiber product, it is necessary to accurately determine the content of the main substances in the recycled solution from polyacrylonitrile-based carbon fiber production.
[0004] Currently, the main methods for detecting acrylonitrile content are titration, dimethyl sulfoxide content is detected using an Abbe refractometer, and trace component content is detected using gas chromatography. However, manual titration can cause significant errors, while gas chromatography is complex to operate, cannot perform batch testing, and has poor timeliness. Furthermore, if it is necessary to detect the content of multiple components in the recycled liquid from the production of polyacrylonitrile-based carbon fiber, at least two or more methods need to be used, further reducing work efficiency.
[0005] Therefore, it is necessary to find a method for detecting the composition of recycled liquid from the production of polyacrylonitrile-based carbon fiber. Summary of the Invention
[0006] To address the aforementioned technical problems, this application provides a method for detecting the component content of polyacrylonitrile carbon fiber production recycled liquid, which can achieve rapid and accurate detection of the component content in the polyacrylonitrile carbon fiber production recycled liquid.
[0007] This application provides a method for detecting the component content of recycled liquid from polyacrylonitrile carbon fiber production, comprising the following steps:
[0008] S1. Prepare a standard solution by using potassium thiocyanate as an internal standard and mixing the potassium thiocyanate with the standard solution at a predetermined mass ratio to obtain a series of mixed standard solutions.
[0009] S2. Perform infrared spectral scanning on the series of mixed standard solutions respectively, and record the infrared absorption spectra.
[0010] S3. Based on the infrared absorption spectrum described in S2, measure the peak height of each characteristic absorption peak in the series of mixed standard solutions, and calculate the peak height ratio and mass ratio of each component of the series of mixed standard solutions to the potassium thiocyanate, and plot the standard working curve.
[0011] S4. Mix the polyacrylonitrile-based carbon fiber production recovery liquid with the potassium thiocyanate to obtain a test solution; perform infrared spectral scanning on the test solution and record the infrared absorption spectrum; measure the peak height of each characteristic absorption peak in the test solution, calculate the peak height ratio of each component of the polyacrylonitrile-based carbon fiber production recovery liquid to the potassium thiocyanate, substitute into the standard working curve, and calculate the mass ratio of each component of the polyacrylonitrile-based carbon fiber production recovery liquid in the polyacrylonitrile-based carbon fiber production recovery liquid.
[0012] In some embodiments of this application, in step S1, the standard solution is prepared from 75-90 wt% dimethyl sulfoxide, 9.5-24.5 wt% acrylonitrile, and 0.5-1.5 wt% water.
[0013] In some embodiments of this application, in step S1, the standard solution is prepared from 75-85 wt% dimethyl sulfoxide, 14-23.5 wt% acrylonitrile, and 1-1.5 wt% water.
[0014] In some embodiments of this application, in step S1, the standard solution is prepared from 85 wt% dimethyl sulfoxide, 14 wt% acrylonitrile and 1 wt% water.
[0015] In some embodiments of this application, in step S1, the predetermined mass ratio is 1:30 to 1:3.
[0016] In some embodiments of this application, in step S3, the calculation of the peak height ratio of each component of the series of mixed standard solutions to potassium thiocyanate is performed, i.e., the calculation of the peak height ratio of acrylonitrile at 2230 cm⁻¹ is performed. -1 The characteristic absorption peak height and that of the potassium thiocyanate at 2067 cm⁻¹ -1 The ratio of characteristic absorption peak heights, and the dimethyl sulfoxide at 1010 cm⁻¹ -1 The characteristic absorption peak height and that of the potassium thiocyanate at 2067 cm⁻¹ -1 The ratio of the height of the characteristic absorption peak.
[0017] In some embodiments of this application, the characteristic absorption peak heights of acrylonitrile, potassium thiocyanate, and dimethyl sulfoxide are measured using the baseline method.
[0018] In some embodiments of this application, in step S4, the mass ratio of the polyacrylonitrile-based carbon fiber production recovery liquid to the potassium thiocyanate is 32:1 to 2:1.
[0019] In some embodiments of this application, in step S3, the regression equation of the standard working curve of acrylonitrile and potassium thiocyanate is: y = 0.00811 + 0.09778x, R 2 =0.99221;
[0020] Where x is the mass ratio of acrylonitrile to potassium thiocyanate, and y is the peak height ratio of acrylonitrile to potassium thiocyanate.
[0021] In some embodiments of this application, in step S3, the regression equation for the standard working curve of dimethyl sulfoxide and potassium thiocyanate is: y = 0.01484 + 0.44513x, R 2 =0.99634;
[0022] Where x is the mass ratio of dimethyl sulfoxide to potassium thiocyanate, and y is the peak height ratio of dimethyl sulfoxide to potassium thiocyanate.
[0023] The technical solutions provided by the embodiments of this application may include the following beneficial effects: This application uses potassium thiocyanate as an internal standard and establishes a model based on Lambert-Beer's law, which can quickly, accurately and easily detect the component content in the recycled liquid of polyacrylonitrile carbon fiber production, providing data support and correct guidance for the actual reuse of recycled liquid and reduction of production costs.
[0024] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description
[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.
[0026] Figure 1 This is a flowchart illustrating a method for detecting the component content of recycled liquid from the production of polyacrylonitrile-based carbon fiber according to an exemplary embodiment.
[0027] Figure 2 This is the standard working curve of absorbance ratio-mass ratio of acrylonitrile and potassium thiocyanate shown in Example 1.
[0028] Figure 3 This is the standard working curve of absorbance ratio-mass ratio of dimethyl sulfoxide and potassium thiocyanate shown in Example 1.
[0029] Figure 4 Comparative Example 1 shows the characteristic absorption peak height measured using the baseline method.
[0030] Figure 5 Comparative Example 2 shows the characteristic absorption peak height measured using the tangent method. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.
[0032] Carbon fiber has been widely used in many fields due to its high performance. With the in-depth development of the carbon fiber industry and changes in market demand, higher requirements have been put forward for carbon fiber manufacturers. At present, the promotion and application of carbon fiber is still limited by high production costs. Therefore, how to reduce the production costs in the field of carbon fiber has become a key research area.
[0033] Polyacrylonitrile-based carbon fiber is mainly produced by polymerization of acrylonitrile and solvents such as dimethyl sulfoxide under a series of reaction conditions. To reduce production costs, the reaction solution can be recycled and reused. The main components of the recycled solution from polyacrylonitrile-based carbon fiber production are dimethyl sulfoxide and a small amount of acrylonitrile. To ensure the quality of the carbon fiber product, it is necessary to accurately determine the content of the main substances in the recycled solution from polyacrylonitrile-based carbon fiber production.
[0034] Currently, the main methods for detecting acrylonitrile content are titration, dimethyl sulfoxide content is detected using an Abbe refractometer, and trace component content is detected using gas chromatography. However, manual titration can cause significant errors, while gas chromatography is complex to operate, cannot perform batch testing, and has poor timeliness. Furthermore, if it is necessary to detect the content of multiple components in the recycled liquid from the production of polyacrylonitrile-based carbon fiber, at least two or more methods need to be used, further reducing work efficiency.
[0035] Based on this, this application provides a method for detecting the component content of polyacrylonitrile-based carbon fiber production recovery liquid. Using potassium thiocyanate as an internal standard, a series of mixed standard solutions prepared by mixing potassium thiocyanate and standard solutions in a predetermined mass ratio are subjected to infrared spectral scanning to obtain infrared absorption spectra. Based on the infrared absorption spectra, the peak heights of each characteristic absorption peak in the series of mixed standard solutions are measured, and the peak height ratio and mass ratio of each component in the standard solution to potassium thiocyanate are calculated, thus plotting a standard working curve. The polyacrylonitrile carbon fiber production recovery liquid is mixed with potassium thiocyanate to obtain a test solution. The test solution is then subjected to infrared spectral scanning, and the infrared absorption spectra are recorded. The peak heights of each characteristic absorption peak in the test solution are measured, and the peak height ratio of each component in the polyacrylonitrile carbon fiber production recovery liquid to potassium thiocyanate is calculated. These values are then substituted into the standard working curve to calculate the mass ratio of each component in the polyacrylonitrile carbon fiber production recovery liquid. The method described in this application can simultaneously detect multiple components in the recycled liquid from the production of polypropylene-based carbon fiber, such as acrylonitrile and dimethyl sulfoxide. The detection method is simple, rapid, accurate, and has small errors.
[0036] In an exemplary embodiment of this application, reference is made to Figure 1 This embodiment provides a method for detecting the component content of recycled liquid from the production of polyacrylonitrile-based carbon fiber, including the following steps:
[0037] S1. Prepare standard solutions by using potassium thiocyanate as an internal standard. Mix potassium thiocyanate with the standard solutions according to a predetermined mass ratio to obtain a series of mixed standard solutions.
[0038] S2. Perform infrared spectral scanning on the series of mixed standard solutions and record the infrared absorption spectra.
[0039] S3. Based on the infrared absorption spectrum in S2, measure the peak height of each characteristic absorption peak in the series of mixed standard solutions, and calculate the peak height ratio and mass ratio of each component of the series of mixed standard solutions to potassium thiocyanate, and plot the standard working curve.
[0040] S4. Mix the polyacrylonitrile-based carbon fiber production recovery liquid with potassium thiocyanate to obtain the test solution; perform infrared spectral scanning on the test solution and record the infrared absorption spectrum; measure the peak height of each characteristic absorption peak in the test solution, calculate the peak height ratio of each component of the polyacrylonitrile-based carbon fiber production recovery liquid to potassium thiocyanate, substitute into the standard working curve, and calculate the mass ratio of each component of the polyacrylonitrile-based carbon fiber production recovery liquid in the polyacrylonitrile-based carbon fiber production recovery liquid.
[0041] This embodiment establishes a method for detecting the content of components in the recycled liquid from the production of polyacrylonitrile-based carbon fiber using a solution system. Using solid potassium thiocyanate as an internal standard, a standard working curve model is established based on Lambert-Beer's law. This method can quickly, accurately, and easily detect the content of various components in the recycled liquid from the production of polyacrylonitrile-based carbon fiber, such as acrylonitrile and dimethyl sulfoxide, so as to facilitate the reuse of the recycled liquid.
[0042] In one embodiment, in step S1, the standard solution is prepared from 75-90 wt% dimethyl sulfoxide, 9.5-24.5 wt% acrylonitrile, and 0.5-1.5 wt% water.
[0043] In the production process of polyacrylonitrile-based carbon fiber precursor, acrylonitrile monomer undergoes polymerization using dimethyl sulfoxide (DMSO) as a solvent. The resulting polymer is then separated and used to produce carbon fiber precursor. DMSO, as the solvent in the polymerization reaction, is the main component of the recycled liquid from polyacrylonitrile carbon fiber production. In addition, the recycled liquid also contains some unreacted acrylonitrile and a small amount of water. This embodiment primarily detects the content of DMSO and acrylonitrile in the recycled liquid from polyacrylonitrile-based carbon fiber production. Therefore, the standard solution is prepared by mixing DMSO, acrylonitrile, and water in a specific ratio. Since the content of each component in the recycled liquid varies depending on the production process, a standard solution prepared with 75-90 wt% DMSO, 9.5-24.5 wt% acrylonitrile, and 0.5-1.5 wt% water can meet the requirements for detecting the content of DMSO and acrylonitrile in the recycled liquid from polyacrylonitrile-based carbon fiber production under most current production processes.
[0044] For example, when the standard solution is prepared from 75-90 wt% dimethyl sulfoxide, 9.5-24.5 wt% acrylonitrile and 0.5-1.5 wt% water, it is suitable for the detection of production recovery liquids with a dimethyl sulfoxide content of 60-92 wt%, an acrylonitrile content of 8-40 wt% and a water content of 0.1-1 wt%.
[0045] Preferably, in step S1, the standard solution is prepared from 75-85 wt% dimethyl sulfoxide, 14-23.5 wt% acrylonitrile, and 1-1.5 wt% water. Further, the standard solution is prepared from 85 wt% dimethyl sulfoxide, 14 wt% acrylonitrile, and 1 wt% water.
[0046] When the standard solution is prepared from 85 wt% dimethyl sulfoxide, 14 wt% acrylonitrile, and 1 wt% water, it is suitable for detecting production recovery liquids with a dimethyl sulfoxide content of 60-92 wt%, an acrylonitrile content of 8-40 wt%, and a water content of 0.1-1 wt%. For example, the production recovery liquid may include 85.02 wt% dimethyl sulfoxide, 13.99 wt% and 0.99 wt% water; or, the production recovery liquid may include 90.74 wt% dimethyl sulfoxide, 8.95 wt% acrylonitrile and 0.21 wt% water; or, the production recovery liquid may include 60.02 wt% dimethyl sulfoxide, 39.01 wt% acrylonitrile and 0.97 wt% water.
[0047] In one embodiment, the predetermined mass ratio is 1:30 to 1:3.
[0048] In this embodiment, potassium thiocyanate and standard solution were weighed and mixed accurately at mass ratios of 1:30, 1:29, 1:28...1:4, 1:3 (accurate to ±0.0001g) to obtain 28 sets of series of mixed standard solutions.
[0049] In one embodiment, in step S3, the peak height ratio of each component of the series of mixed standard solutions to potassium thiocyanate is calculated, that is, the peak height ratio of acrylonitrile at 2230 cm⁻¹ is calculated. -1 Characteristic absorption peak height and potassium thiocyanate at 2067 cm⁻¹ -1 The ratio of characteristic absorption peak heights, and dimethyl sulfoxide at 10¹⁰ cm⁻¹ -1 Characteristic absorption peak height and potassium thiocyanate at 2067 cm⁻¹ -1 The ratio of the height of the characteristic absorption peak.
[0050] In one embodiment, the characteristic absorption peak heights of acrylonitrile, potassium thiocyanate, and dimethyl sulfoxide were measured using the baseline method. Compared to the tangent method, this embodiment uses the baseline method to measure the heights of each characteristic absorption peak on the infrared absorption spectrum, which has smaller errors and helps improve the accuracy of the detection results.
[0051] In one embodiment, in step S3, the regression equation for the standard working curve of acrylonitrile and potassium thiocyanate is: y = 0.00811 + 0.09778x, R 2 =0.99221;
[0052] Where x is the mass ratio of acrylonitrile to potassium thiocyanate, and y is the peak height ratio of acrylonitrile to potassium thiocyanate.
[0053] In step S3, the regression equation for the standard working curves of dimethyl sulfoxide and potassium thiocyanate is: y = 0.01484 + 0.44513x, R 2 =0.99634;
[0054] Where x is the mass ratio of dimethyl sulfoxide to potassium thiocyanate, and y is the peak height ratio of dimethyl sulfoxide to potassium thiocyanate.
[0055] The correlation coefficient R of the regression equation of the standard working curve of acrylonitrile to potassium thiocyanate absorbance ratio-mass ratio in this embodiment is... 2 The correlation coefficient R of the regression equation for the standard working curve of absorbance ratio-mass ratio of dimethyl sulfoxide and potassium thiocyanate. 2 All values are greater than 0.99, indicating that the standard working curve established by the method of this embodiment has better linear correlation and higher detection accuracy for the content of each component in the production recovery liquid.
[0056] To more clearly explain the technical solution of this application, this application provides specific embodiments of the method for detecting the component content of the recycled liquid from the production of polyacrylonitrile-based carbon fiber. The beneficial effects will be explained by providing specific experimental data through these specific embodiments.
[0057] It should be noted that the term "content" in this article refers to "mass percentage content"; the peak height of the characteristic absorption peak is also known as absorbance, and the ratio of the characteristic absorption peak height of each component in the series of mixed standard solutions to the characteristic absorption peak height of potassium thiocyanate is also known as the absorbance ratio.
[0058] Example
[0059] Example 1: A method for detecting the composition content of recycled liquid from the production of polyacrylonitrile-based carbon fiber, comprising the following steps:
[0060] (1) Preparation of standard solution: Take 85g of dimethyl sulfoxide, 14g of acrylonitrile and 1g of water, mix them evenly and prepare a standard solution.
[0061] (2) Using solid potassium thiocyanate as an internal standard, potassium thiocyanate and standard solution were weighed accurately (accurate to ±0.0001g) according to the mass ratio of 1:30, 1:29, 1:28...1:4, 1:3 to obtain 28 series of mixed standard solutions.
[0062] (3) Infrared spectral curves were scanned for 28 series of mixed standard solutions, and their respective infrared absorption spectra were recorded.
[0063] (4) Based on the infrared absorption spectrum in step (3), the acrylonitrile in the 28 sets of series of mixed standard solutions at 2230 cm⁻¹ was measured using the baseline method. -1 Characteristic absorption peak height, potassium thiocyanate at 2067 cm⁻¹ -1 Characteristic absorption peak height and dimethyl sulfoxide at 1010 cm⁻¹ -1Characteristic absorption peak heights were determined, and the ratios and mass ratios of the characteristic absorption peak heights of acrylonitrile and potassium thiocyanate in the 28 series of mixed standard solutions were calculated. Similarly, the ratios and mass ratios of the characteristic absorption peak heights of dimethyl sulfoxide and potassium thiocyanate in the 28 series of mixed standard solutions were also calculated. Based on the obtained data, standard working curves of acrylonitrile absorbance ratio versus mass ratio were plotted (e.g., ...). Figure 2 The standard working curves for absorbance ratio-mass ratio of dimethyl sulfoxide (as shown) and dimethyl sulfoxide (as shown) are obtained. Figure 3 (as shown);
[0064] The curve regression equation for the standard working curve of acrylonitrile absorbance ratio-mass ratio is:
[0065] y = 0.00811 + 0.09778x, R 2 =0.99221;
[0066] Where x is the mass ratio of acrylonitrile to potassium thiocyanate, and y is the absorbance ratio of acrylonitrile to potassium thiocyanate.
[0067] The standard working curve regression equation for the absorbance-mass ratio of dimethyl sulfoxide is:
[0068] y = 0.01484 + 0.44513x, R 2 =0.99634;
[0069] Where x is the mass ratio of dimethyl sulfoxide to potassium thiocyanate, and y is the absorbance ratio of dimethyl sulfoxide to potassium thiocyanate.
[0070] (5) Weigh the polyacrylonitrile-based carbon fiber production recovery liquid m1 and potassium thiocyanate m2 separately, mix them thoroughly to obtain the test solution; perform infrared spectral scanning on the test solution and record the infrared absorption spectrum; use the baseline method to measure the potassium thiocyanate concentration at 2067 cm⁻¹ in the test solution. -1 Characteristic absorption peak height A1, acrylonitrile is at 2230 cm⁻¹ -1 Characteristic absorption peak height A2, and dimethyl sulfoxide at 1010 cm⁻¹ -1 The characteristic absorption peak height A3 is calculated. The ratios of the characteristic absorption peak heights of acrylonitrile and potassium thiocyanate, and the ratios of the characteristic absorption peak heights of dimethyl sulfoxide and potassium thiocyanate are calculated respectively. These data are then substituted into the regression equations of the standard working curves of acrylonitrile absorbance ratio-mass ratio and dimethyl sulfoxide absorbance ratio-mass ratio in step (4) to calculate the mass ratios of acrylonitrile and potassium thiocyanate, and the mass ratios of dimethyl sulfoxide and potassium thiocyanate, thereby calculating the content of acrylonitrile and dimethyl sulfoxide in the polyacrylonitrile-based carbon fiber production recovery liquid.
[0071] When measuring the height of each characteristic absorption peak, the mass ratio of acrylonitrile (AN%) and dimethyl sulfoxide (DMSO%) in the polyacrylonitrile-based carbon fiber production recovery liquid can be calculated according to the following formulas (I) and (II).
[0072]
[0073]
[0074] Confirmatory test
[0075] To verify the accuracy of the method in Example 1 for detecting acrylonitrile and dimethyl sulfoxide content in the recycled liquid from the production of polyacrylonitrile-based carbon fiber, the following verification test was conducted:
[0076] Verification Experiment 1:
[0077] ①Preparation of the test solution: Take 85.02g of dimethyl sulfoxide, 13.99g of acrylonitrile and 0.99g of water, mix them evenly, and prepare the test solution A.
[0078] ②Preparation of the mixed solution to be tested:
[0079] Weigh 14.9875g of the test solution A and 1.0012g of potassium thiocyanate, and mix them thoroughly to obtain the test solution a;
[0080] Weigh 10.0129g of the test solution A and 1.0041g of potassium thiocyanate, and mix them thoroughly to obtain the test solution b.
[0081] Weigh 5.0014g of the test solution A and 9.8646g of potassium thiocyanate, and mix them thoroughly to obtain the test solution c.
[0082] Weigh 3.1421g of the test solution A and 1.0145g of potassium thiocyanate, and mix them thoroughly to obtain the test solution d.
[0083] ③ Determine the infrared absorption spectrum: Perform infrared spectral curve scanning on the mixed solution to be tested a, mixed solution to be tested b, mixed solution to be tested c and mixed solution to be tested d respectively, and record their respective infrared absorption spectra.
[0084] ④ Measurement of characteristic absorption peak height: The potassium thiocyanate in mixed solution a, mixed solution b, mixed solution c, and mixed solution d was measured at 2067 cm⁻¹ using the baseline method. -1 Characteristic absorption peak height, acrylonitrile at 2230 cm⁻¹ -1 Characteristic absorption peak height and dimethyl sulfoxide at 1010 cm⁻¹ -1The characteristic absorption peak heights were substituted into formulas (I) and (II) in Example 1, respectively, to calculate the contents of acrylonitrile and dimethyl sulfoxide in the test solution, and the errors between the contents of each component in the test solution obtained by the method of Example 1 and the contents of each component in the actually prepared test solution were calculated:
[0085] Error = (content of each component in the test solution detected by the method of Example 1 - content of each component in the actual prepared test solution) × 100%.
[0086] The test results are shown in Table 1.
[0087] Table 1. Detection of Acrylonitrile and Dimethyl Sulfoxide Contents in the Test Mixture (ad)
[0088]
[0089] As can be seen from the data in Table 1, when the test solution and potassium thiocyanate are prepared into a mixed test solution (ad) with different mass ratios, the error between the acrylonitrile and dimethyl sulfoxide content in the test solution obtained by the method of Example 1 and the actual content of the above components in the test solution is <0.05%. This indicates that when the method of Example 1 of this application is used to detect acrylonitrile and dimethyl sulfoxide in the polyacrylonitrile-based carbon fiber production recovery liquid, the error is small and the accuracy is high.
[0090] Verification Experiment 2:
[0091] ① The online recovery liquid was taken and its content was tested by gas chromatography. The contents of each component in the online recovery liquid were found to be: dimethyl sulfoxide 90.74%, acrylonitrile 8.95%, and water 0.21%.
[0092] ②Preparation of the test solution: Weigh 5.2010g of the test solution and 1.0105g of potassium thiocyanate, and mix them thoroughly to obtain the test solution e;
[0093] ③ Determine the infrared absorption spectrum: Perform infrared spectral curve scanning on the mixed solution e to be tested and record its infrared absorption spectrum.
[0094] ④ Measurement of characteristic absorption peak height: The potassium thiocyanate in mixed solution e was measured at 2067 cm⁻¹ using the baseline method. -1 Characteristic absorption peak height, acrylonitrile at 2230 cm⁻¹ -1 Characteristic absorption peak height and dimethyl sulfoxide at 1010 cm⁻¹ -1 The characteristic absorption peak heights were substituted into formulas (I) and (II) in Example 1, respectively, to calculate that the content of acrylonitrile in the online recovery solution was 8.97%, with a detection error of 0.02%, and the content of dimethyl sulfoxide in the test solution was 90.69%, with a detection error of -0.05%.
[0095] Therefore, it can be seen that the error between the content of acrylonitrile and dimethyl sulfoxide in the online recovery liquid obtained by the method of Example 1 and the content of the above components in the test solution detected by gas chromatography is ≤0.05%, indicating that when using the method of Example 1 of this application to detect acrylonitrile and dimethyl sulfoxide in the polyacrylonitrile-based carbon fiber production recovery liquid, the error is small and the accuracy is high.
[0096] Verification Experiment 3:
[0097] ①Preparation of the test solution: Take 60.02g of dimethyl sulfoxide, 39.01g of acrylonitrile and 0.97g of water, mix them evenly and prepare the test solution B.
[0098] ②Preparation of the mixed solution to be tested:
[0099] Weigh 3.7149g of the test solution B and 1.0012g of potassium thiocyanate, and mix them thoroughly to obtain the test solution f.
[0100] ③ Determine the infrared absorption spectrum: Perform infrared spectral curve scanning on the mixed solution f to be tested and record its infrared absorption spectrum.
[0101] ④ Measurement of characteristic absorption peak height: The baseline method was used to measure the potassium thiocyanate in the mixed solution f at 2067 cm⁻¹. -1 Characteristic absorption peak height, acrylonitrile at 2230 cm⁻¹ -1 Characteristic absorption peak height and dimethyl sulfoxide at 1010 cm⁻¹ -1 The characteristic absorption peak heights were substituted into formulas (I) and (II) in Example 1, respectively, to calculate the content of acrylonitrile in the test solution as 40.21% with a detection error of 1.2%, and the content of dimethyl sulfoxide in the test solution as 58.98 wt% with a detection error of -1.04%.
[0102] Therefore, it can be seen that the error between the content of acrylonitrile and dimethyl sulfoxide in the test solution obtained by the method of Example 1 and the content of the above components in the test solution actually prepared is ≤1.2%, indicating that when the method of Example 1 of this application is used to detect acrylonitrile and dimethyl sulfoxide in the polyacrylonitrile-based carbon fiber production recovery liquid, the error is small and the accuracy is high.
[0103] Combining verification experiments one and three, it can be seen that the closer the content of each component in the standard solution is to the content of each component in the actual production recovery liquid, the smaller the error in detecting the content of each component in the production recovery liquid using the method of Example 1. In actual production, corresponding standard solutions can be prepared according to different carbon fiber production processes; alternatively, by detecting the content of each component in the production recovery liquid under different production processes, a standard solution with the same component concentration can be selected, within the allowable error range, to be adapted to the production recovery liquid under different production processes.
[0104] Example 2:
[0105] The difference between this embodiment and Example 1 is that the standard solution is prepared from 75 wt% dimethyl sulfoxide, 23.5 wt% acrylonitrile and 1.5 wt% water.
[0106] This embodiment follows the experimental steps in Embodiment 1 to establish the model and obtain:
[0107] The regression equation for the standard working curve of acrylonitrile and potassium thiocyanate is: y = 0.00810 + 0.09781x, R0 2 =0.99243;
[0108] Where x is the mass ratio of acrylonitrile to potassium thiocyanate, and y is the peak height ratio of acrylonitrile to potassium thiocyanate.
[0109] The regression equation for the standard working curves of dimethyl sulfoxide and potassium thiocyanate is: y = 0.01479 + 0.44517x, R 2 =0.99694;
[0110] Based on the correlation coefficient R of Examples 1 and 2 2 It can be seen that the detection accuracy of acrylonitrile and dimethyl sulfoxide in the production recovery liquid using the methods of Examples 1 and 2 is basically the same. Therefore, it can be concluded that the standard solutions prepared in this application, consisting of 75-90 wt% dimethyl sulfoxide, 9.5-24.5 wt% acrylonitrile, and 0.5-1.5 wt% water, can all establish correct test models and exhibit high detection accuracy when detecting acrylonitrile and dimethyl sulfoxide in the production recovery liquid.
[0111] Comparative Example
[0112] Comparative Example 1: This comparative example differs from Example 1 in that: potassium thiocyanate solution (0.1 mol / L) was used as the internal standard, and the baseline method (e.g.) was employed. Figure 4 (As shown) Acrylonitrile in a series of mixed standard solutions was measured at 2230 cm⁻¹. -1 Characteristic absorption peak height, potassium thiocyanate at 2067 cm⁻¹ -1Characteristic absorption peak height and dimethyl sulfoxide at 1010 cm⁻¹ -1 Calculate the characteristic absorption peak heights of acrylonitrile and potassium thiocyanate, and their mass ratios, respectively, and plot a standard working curve. Also calculate the characteristic absorption peak heights of dimethyl sulfoxide and potassium thiocyanate, and their mass ratios, and plot a standard working curve.
[0113] The curve regression equation for the standard working curve of acrylonitrile absorbance ratio-mass ratio is:
[0114] y = 0.00404 + 0.07607x, R 2 =0.91247;
[0115] Where x is the mass ratio of acrylonitrile to potassium thiocyanate, and y is the absorbance ratio of acrylonitrile to potassium thiocyanate.
[0116] The standard working curve regression equation for the absorbance-mass ratio of dimethyl sulfoxide is:
[0117] y = -0.83421 + 1.36099x, R 2 =0.93874;
[0118] Where x is the mass ratio of dimethyl sulfoxide to potassium thiocyanate, and y is the absorbance ratio of dimethyl sulfoxide to potassium thiocyanate.
[0119] As can be seen from Example 1 and Comparative Example 1, the correlation coefficient R of the standard working curve in Comparative Example 1 is... 2 The correlation coefficient R is significantly smaller than that of Example 1. 2 This demonstrates that the method of Example 1 provides higher accuracy in detecting acrylonitrile and dimethyl sulfoxide in the production recovery liquid. Therefore, it can be concluded that, in this application, the standard working curve obtained by using solid potassium thiocyanate as an internal standard is more accurate than that obtained by using potassium thiocyanate solution.
[0120] Comparative Example 2: This comparative example differs from Example 1 in that it uses the tangent method (e.g., Figure 5 (As shown) Acrylonitrile in a series of mixed standard solutions was measured at 2230 cm⁻¹. -1 Characteristic absorption peak height, potassium thiocyanate at 2067 cm⁻¹ -1 Characteristic absorption peak height and dimethyl sulfoxide at 1010 cm⁻¹ -1 Calculate the characteristic absorption peak heights of acrylonitrile and potassium thiocyanate, and their mass ratios, respectively, and plot a standard working curve. Also calculate the characteristic absorption peak heights of dimethyl sulfoxide and potassium thiocyanate, and their mass ratios, and plot a standard working curve.
[0121] The curve regression equation for the standard working curve of acrylonitrile absorbance ratio-mass ratio is:
[0122] y = 0.05338 + 0.08043x, R 2 =0.83706;
[0123] Where x is the mass ratio of acrylonitrile to potassium thiocyanate, and y is the absorbance ratio of acrylonitrile to potassium thiocyanate.
[0124] The standard working curve regression equation for the absorbance-mass ratio of dimethyl sulfoxide is:
[0125] y = 0.1164 + 0.43034x, R 2 =0.92614;
[0126] Where x is the mass ratio of dimethyl sulfoxide to potassium thiocyanate, and y is the absorbance ratio of dimethyl sulfoxide to potassium thiocyanate.
[0127] As can be seen from Example 1 and Comparative Example 2, the method of Example 1 provides higher accuracy in detecting acrylonitrile and dimethyl sulfoxide in the production recovery liquid. Therefore, in this application, the baseline method for measuring the characteristic absorption peak height is more accurate, and the resulting standard working curve is more precise.
[0128] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0129] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. A method for detecting the component content of recycled liquid from the production of polyacrylonitrile-based carbon fiber, characterized in that, Includes the following steps: S1. Prepare a standard solution by using potassium thiocyanate as an internal standard and mixing the potassium thiocyanate with the standard solution at a predetermined mass ratio to obtain a series of mixed standard solutions. S2. Perform infrared spectral scanning on the series of mixed standard solutions respectively, and record the infrared absorption spectra. S3. Based on the infrared absorption spectrum described in S2, measure the peak height of each characteristic absorption peak in the series of mixed standard solutions, and calculate the peak height ratio and mass ratio of each component of the series of mixed standard solutions to the potassium thiocyanate, and plot the standard working curve. S4. The polyacrylonitrile-based carbon fiber production recovery liquid is mixed with the potassium thiocyanate to obtain a test solution; the test solution is subjected to infrared spectral scanning, and the infrared absorption spectrum is recorded; the peak height of each characteristic absorption peak in the test solution is measured, and the peak height ratio of each component of the polyacrylonitrile-based carbon fiber production recovery liquid to the potassium thiocyanate is calculated. Substitute these values into the standard working curve to calculate the mass ratio of each component of the polyacrylonitrile-based carbon fiber production recovery liquid in the polyacrylonitrile-based carbon fiber production recovery liquid. In step S1, the standard solution is prepared from 75-90 wt% dimethyl sulfoxide, 9.5-24.5 wt% acrylonitrile, and 0.5-1.5 wt% water. In step S3, the peak height ratio of each component of the series of mixed standard solutions to potassium thiocyanate is calculated, that is, the peak height ratio of acrylonitrile at 2230 cm⁻¹ is calculated. -1 The characteristic absorption peak height and that of the potassium thiocyanate at 2067 cm⁻¹ -1 The ratio of characteristic absorption peak heights, and the dimethyl sulfoxide at 1010 cm⁻¹ -1 The characteristic absorption peak height and that of the potassium thiocyanate at 2067 cm⁻¹ -1 The ratio of the height of characteristic absorption peaks; In step S4, measuring the peak height of each characteristic absorption peak in the mixed solution to be tested, and calculating the peak height ratio of each component of the polyacrylonitrile-based carbon fiber production recycled liquid to potassium thiocyanate, includes: The potassium thiocyanate in the test solution was measured at 2067 cm⁻¹. -1 Characteristic absorption peak height, the acrylonitrile at 2230 cm⁻¹ -1 Characteristic absorption peak height, and the dimethyl sulfoxide at 1010 cm⁻¹ -1 The characteristic absorption peak heights are calculated, and the ratios of the characteristic absorption peak heights of acrylonitrile and potassium thiocyanate, as well as the ratios of the characteristic absorption peak heights of dimethyl sulfoxide and potassium thiocyanate, are calculated respectively.
2. The detection method according to claim 1, characterized in that, In step S1, the standard solution is prepared from 75-85 wt% dimethyl sulfoxide, 14-23.5 wt% acrylonitrile, and 1-1.5 wt% water.
3. The detection method according to claim 2, characterized in that, In step S1, the standard solution is prepared from 85 wt% dimethyl sulfoxide, 14 wt% acrylonitrile and 1 wt% water.
4. The detection method according to claim 1, characterized in that, In step S1, the predetermined mass ratio is 1:30 to 1:
3.
5. The detection method according to claim 1, characterized in that, The characteristic absorption peak heights of acrylonitrile, potassium thiocyanate, and dimethyl sulfoxide were measured using the baseline method.
6. The detection method according to claim 1, characterized in that, In step S4, the mass ratio of the polyacrylonitrile-based carbon fiber production recovery liquid to the potassium thiocyanate is 32:1 to 2:
1.
7. The detection method according to claim 1, characterized in that, In step S3, the regression equation for the standard working curve of acrylonitrile and potassium thiocyanate is: y = 0.00811 + 0.09778x, R 2 =0.99221; Where x is the mass ratio of acrylonitrile to potassium thiocyanate, and y is the peak height ratio of acrylonitrile to potassium thiocyanate.
8. The detection method according to claim 1, characterized in that, In step S3, the regression equation for the standard working curve of dimethyl sulfoxide and potassium thiocyanate is: y = 0.01484 + 0.44513x, R 2 =0.99634; Where x is the mass ratio of dimethyl sulfoxide to potassium thiocyanate, and y is the peak height ratio of dimethyl sulfoxide to potassium thiocyanate.