CN104730029B - Method for detecting solvent and moisture in spandex production solvent recovering system simultaneously - Google Patents
Method for detecting solvent and moisture in spandex production solvent recovering system simultaneously Download PDFInfo
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- CN104730029B CN104730029B CN201510109451.3A CN201510109451A CN104730029B CN 104730029 B CN104730029 B CN 104730029B CN 201510109451 A CN201510109451 A CN 201510109451A CN 104730029 B CN104730029 B CN 104730029B
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Abstract
The present invention relates to a kind of method for detecting solvent and moisture in spandex production solvent recovering system simultaneously, the method is comprised the following steps：One) a series of various concentrations DMAC and H are prepared2The standard liquid of O, selects enough representational calibration set samples；Two) the near infrared spectrum spectrogram of calibration set sample is determined, 12000~4000cm of spectrogram is taken‑1After wave band carries out Pretreated spectra, respectively with DMAC in standard sample and H2O content is associated, and DMAC contents and H are set up using PLS2The calibration model of O content；Three) determine testing sample near infrared spectrum spectrogram, using with step 2 identical preprocess method treatment gained spectrogram in 12000~4000cm‑1Wave band, the absorbance that will be obtained after pretreatment substitutes into the calibration model of step 2, obtains DMAC contents in testing sample.The present invention has analysis process simple and quick, strong antijamming capability, nondestructive analysis, the advantages of sampling amount is small.
Description
Technical Field
The invention relates to a method for simultaneously detecting DMAC (dimethylacetamide) and H in a DMAC recovery system of a spandex production solvent2A near infrared spectrum method of O content belongs to the field of industrial analysis.
Background
The spandex (polyurethane) fiber is a synthetic fiber which is most elastic at present, has excellent elongation at break and breaking strength, is an indispensable special textile fiber for producing high-grade elastic textiles, and has high application value and good development prospect. DMAC is a solvent which is most widely applied in spandex production, the recovery of DMAC can reduce the production cost and is beneficial to environmental protection and sustainable development, and DMAC and H in a recovery system2The O content is an important parameter for characterizing the recovery efficiency, so that DMAC and H can be rapidly and accurately determined2The O content becomes an important technology in the production process of spandex.
At present, the DMAC content is determined mainly by gas chromatography, H2The method for measuring the content of O is mainly a Karl Fischer volumetric method. Because the water content of the feed of one tower and the distillate of one tower in the DMAC recovery system is higher, the sample needs to be pretreated when the DMAC content is analyzed by adopting the gas chromatography, the DMAC in the sample is extracted, a large amount of water contained in the sample is removed, the interference to the FID detector is prevented, and the recovery rate is reduced in the extraction process. The distillate of one tower has a water content of more than 95 percent, when the water content is measured by a Karl Fischer volumetric method, the error of the result is about 3 percent, and the waste liquid generated by using the Karl Fischer reagent causes environmental problems. Another commonly used for DMAC and H2The analysis method for detecting the content of O is to establish a standard curve according to the change of the refractive index of a sample, but the method is easy to be subjected toThe environmental temperature, humidity and impurities in the sample affect, and thus the accuracy of the result is not sufficient. Therefore, the research of the method which can be used for detecting the content of the dimethylacetamide and the water in the dimethylacetamide recovery system in spandex production in time, accurately and quickly has important practical significance for determining the stability control of the DMAC recovery system.
The main information of the near infrared spectrum is represented by frequency doubling and combined frequency absorption of hydrogen-containing groups (including O-H, C-H, N-H, S-H and the like) in the internal components of the substance on near infrared light, can represent the information of the composition and molecular structure of most organic substances, and is very suitable for determining the composition property of hydrocarbon organic substances. Therefore, in recent years, near infrared spectroscopy detection techniques have been used in many fields such as agriculture, medicine, and chemistry.
Method for simultaneously determining DMAC and H in spandex DMAC recovery system by using near-infrared spectroscopy2No studies on the O content have been reported.
Disclosure of Invention
The technical problem is as follows: the invention aims to solve the defects of the prior art and provides a method for simultaneously detecting a solvent and water in a solvent recovery system for spandex production. The detection method has the advantages of simple implementation process, high precision, good repeatability and wide detection range.
The technical scheme is as follows: in order to achieve the aim, the invention provides a method for simultaneously detecting DMAC and H in a DMAC recovery system of a solvent in spandex production2A method for near infrared spectroscopy of O content, the method comprising the steps of:
1) preparing a series of N, N' -Dimethylacetamide (DMAC) and water H with different concentrations2O standard solution, selecting enough representative calibration set samples;
2) after the sample spectrum is pretreated, determining the near infrared spectrogram of the sample in the correction set, wherein the scanning range is 12000-4000 cm-1Wave band, and performing spectrum pretreatment, and mixing with DMAC and H in standard sample2The contents of O are correlated, and a correction model is respectively established by adopting a partial least square method;
3) measuring the near infrared spectrogram of the sample to be detected, processing the spectrogram by the same pretreatment method as the step 2), analyzing the near infrared spectrogram of the pretreated sample by using a correction model through Horizon MB analysis software of ABB company to obtain DMAC and H in the sample to be detected2And (4) the content of O.
The spectrum pretreatment method comprises the steps of uniformly mixing samples, sampling, loading into a 8mm colorimetric tube, and preheating to 50 ℃.
The number of sufficient representative calibration set samples is more than 100.
H of the sample for near-infrared scanning2The mass percent of O is 2.0-100%, and the mass percent of DMAC is 0-98%.
The method for measuring the near-infrared spectrogram is characterized in that an MB3600 Fourier transform near-infrared spectrometer manufactured by ABB company is used, a transmission mode and a special detection channel for a liquid pool are adopted, and each sample is scanned for 64 times and averaged to obtain the near-infrared spectrogram.
The pretreatment method of the near infrared spectrogram comprises the following steps: and (6) normalization and standardization.
The optimal wave band for establishing a correction model of the near infrared spectrogram of the pretreated sample is 5508-6534cm-1、7143-7976cm-1、8092-9273cm-1、9751-11602cm-1Four spectral detection ranges.
Has the advantages that: DMAC and H in a DMAC recovery system for selecting solvent in spandex production2The content of O is used as a detection target, a quantitative model is established, the method RMSECV is small, and R is2＝0.99994(H2O)、R2Correlation is good for 0.99996 (DMAC). And the result is satisfactory by predicting unknown samples. Shows that the near infrared spectrum technology is combined with the PLS method to simultaneously recover DMAC and H in a solvent recovery system in spandex production2Quantitative analysis of O content, accurate method, and specific gasThe phase chromatography and the Karl Fischer volumetric method save a great deal of time, are more accurate than a refractive index method, can obviously improve the quality control efficiency, shorten the detection period and open up a new way for a real-time analysis technology in industrial production.
Drawings
FIG. 1 is a near infrared spectroscopy model building and application process;
FIG. 2 is a graph of the original near infrared spectrum of a sample;
FIG. 3 is a graph of the number of main factors of the DMAC content correction model versus RMSECV;
FIG. 4 is H2A relation graph of the main factor number of the O content correction model and RMSECV;
FIG. 5 is a correlation curve of predicted values of spectra of a DMAC content correction set with true values;
FIG. 6 is H2The correlation curve of the predicted value and the true value of the O content correction set spectrum;
FIG. 7 is a correlation curve of predicted value of sample spectrum and true value in the prediction set of DMAC content;
FIG. 8 is H2And (4) a correlation curve between the predicted value of the O content prediction set sample spectrum and the true value.
Detailed Description
1) Preparing a series of DMAC and H with different concentrations2Selecting enough representative calibration set samples from a standard solution of O;
2) after sample pretreatment, determining the near infrared spectrogram of the sample in the correction set, wherein the scanning range is 12000-4000 cm-1Wave band, and performing spectrum pretreatment, and mixing with DMAC and H in standard sample2The contents of O are correlated, and a correction model is respectively established by adopting a partial least square method;
3) determining the near red of a sample to be testedProcessing the optimal modeling wave band in the obtained spectrogram by adopting the same preprocessing method as the preprocessing method in the step two, and analyzing the spectrum obtained after preprocessing by adopting a correction model to obtain DMAC (dimethylacetamide) and H in the recovery system to be detected2And (4) the content of O.
In the method, near infrared spectrum data are collected in a transmission mode, spandex prepolymer solution is led into a quartz liquid pool, a special channel for the liquid pool is used for measurement, sample spectrum data are collected, and each sample is scanned at 50 ℃ for 64 times and averaged to obtain the polyurethane elastic fiber. The scanning spectrum range is 12000-4000 cm-1。
In the method, in the step 2), before the spectrogram is associated with data, a proper spectrum preprocessing method is adopted for the spectrogram so as to eliminate the interference of a base line and other backgrounds, and the optimal preprocessing method is normalization and standardization. And 3) the method for preprocessing the near-infrared spectrogram of the sample to be detected is the same as the step 2).
In the method, in the step 2), after spectrum preprocessing is carried out, cross validation root mean square deviation (RMSECV) and relative deviation (RSECV) are used as indexes, modeling parameters are optimized, and a quantitative correction model is established by a Partial Least Squares (PLS) regression method.
The criterion of applicability of the spectrum and the correction model measured in the step 3) of the invention is as follows: performing internal cross validation on a quantitative model established by a prediction set sample, determining the optimal PLS principal component number by taking a cross validation error Root Mean Square (RMSECV) as an index, and establishing a final model by taking the optimal principal component number and the selected optimal waveband as parameters; assaying the samples of the test set by predicting Root Mean Square Error (RMSEP) and correlation coefficient (R)2) To evaluate the quality of the final model. Performing data processing by PLS method in Horizon MB analysis software, selecting 40 samples as prediction sample set, performing internal cross validation by using correction sample set, wherein RMSECV of DMAC is 0.268461, H2RMSECV of 0.288993 for O. When the detection capability of the PLS model was evaluated with prediction set samples, the RMSEP of DMAC was 0.214264, H2RMSEP of O is 0.187573.
The near infrared spectral modeling and application process of the present invention is further illustrated by way of examples, which should not be construed as limiting the invention.
Example 1:
the near-infrared spectrum model establishment and application process is as shown in the attached figure 1, and specifically comprises the following steps:
1. instrument conditions and sample handling:
the instrument comprises the following steps: the near infrared spectra were collected by a Switzerland ABB MB3600 Fourier transform near infrared spectrometer equipped with Horizon MB and QA analysis software, a quartz liquid cell and an InGaAs detector. The spectra for each sample were averaged over 64 scans. The scanning range is 12000-4000 cm-1
Sample preparation: the samples used in the experiment are samples collected by feeding in a tower and distilling out in a refining and recycling system in the spandex production process.
2. And (3) near infrared spectrum measurement of a sample:
the experiment uses a quartz liquid absorption cell, samples are mixed evenly and poured into the liquid absorption cell, the liquid absorption cell is preheated to 50 +/-0.5 ℃, the liquid absorption cell is placed into a detection cell for spectrum collection of the samples, the same sample is scanned for 64 times, and a final spectrogram is obtained according to the average, as shown in figure 2.
3. And (3) prediction:
FIG. 2 shows the raw data of the spectrum, which is normalized and normalized to confirm 5508-6534cm-1、7143-7976cm-1、8092-9273cm-1、9751-11602cm-1And establishing a quantitative correction model by using a PLS method by taking the four spectral detection ranges as modeling bands. In order to avoid the phenomenon of over-fitting, a leave-one cross-validation method is adopted to reasonably select the number of main factors and cross-validate the obtained DMAC and H2The main factor numbers of O content are shown in FIG. 3 and FIG. 4, respectively, andthe number of preferred major factors is 5.
4. And (3) analysis:
140 spandex prepolymer samples are taken as a correction set, and 40 samples are taken as a prediction set. The curve obtained by fitting the predicted value and the true value of the DMAC content of the sample corresponding to the optimal number of the major factors is shown in FIG. 5, and the sample H corresponding to the optimal number of the major factors2The curve obtained by fitting the predicted value and the true value of the O content is shown in FIG. 6, and the correlation coefficient R between the predicted value and the true value of DMAC2＝0.99996，H2Correlation coefficient R of predicted value and true value of O20.99994, the specific numerical value is shown in table 2, and the modeling result is ideal and reliable.
Predicting samples of 40 prediction sets by using a newly-established near infrared spectrum correction model, and carrying out DMAC (dimethylacetamide) and H2The correlation curves of the predicted value O and the true value are shown in fig. 7 and 8, respectively. Coefficient of correlation R20.99996, RMSEP 0.187573(H2O) and RMSEP 0.214264(DMAC) are predicted to be substantially consistent with cross-validation Root Mean Square Error (RMSECV), the values are given in table 2.
TABLE 1
Claims (4)
1. A method for simultaneously detecting solvent and water in a solvent recovery system for spandex production is characterized by comprising the following steps:
1) preparing a series of N, N' -Dimethylacetamide (DMAC) and water H with different concentrations2O standard solution, selecting enough representative calibration set samples;
2) after the sample spectrum is pretreated, determining the near infrared spectrogram of the sample in the correction set, wherein the scanning range is 12000-4000 cm-1Wave band, and performing spectrum pretreatment, and mixing with DMAC and H in standard sample2Phase of O contentCorrelating, namely respectively establishing correction models by adopting a partial least square method;
3) measuring the near infrared spectrogram of the sample to be detected, processing the spectrogram by the same pretreatment method as the step 2), analyzing the near infrared spectrogram of the pretreated sample by using a correction model through Horizon MB analysis software of ABB company to obtain DMAC and H in the sample to be detected2The content of O;
wherein,
the spectrum pretreatment method comprises the steps of uniformly mixing samples, sampling, loading into a colorimetric tube with the diameter of 8mm, and preheating to 50 ℃;
the number of the sufficient representative calibration set samples is more than 100;
h of the sample for near-infrared scanning2The mass percent of O is 2.0-100%, and the mass percent of DMAC is 0-98%.
2. The method for simultaneously detecting the solvent and the water in the solvent recovery system for spandex production according to claim 1, characterized in that the near-infrared spectrogram is obtained by using an ABB MB3600 Fourier transform near-infrared spectrometer and adopting a transmission mode and a liquid pool special detection channel, and each sample is scanned 64 times for averaging.
3. The method for simultaneously detecting the solvent and the water in the solvent recovery system for spandex production according to claim 1, wherein the method for preprocessing the near infrared spectrogram comprises the following steps: and (6) normalization and standardization.
4. The method for simultaneously detecting the solvent and the water in the solvent recovery system for spandex production according to claim 1 or 3, wherein the optimal waveband for establishing a calibration model in the near infrared spectrogram of the pretreated sample is determined to be 5508-6534cm-1、7143-7976cm-1、8092-9273cm-1、9751-11602cm-1Four spectral detection ranges.
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| WO2001061320A1 (en) * | 2000-02-15 | 2001-08-23 | Kowalski Craig R | Plural component coating analysis |
| CN101403689A (en) * | 2008-11-20 | 2009-04-08 | 北京航空航天大学 | Nondestructive detection method for physiological index of plant leaf |
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Effective date of registration: 20190826 Address after: 325206 Ruian Economic Development Zone, Dongshan Road, Zhejiang, No. 1788, No. Co-patentee after: Chongqing Huafeng spandex Co., Ltd. Patentee after: Zhejiang Huafeng Spandex Co., Ltd. Address before: 325206 Ruian Economic Development Zone, Dongshan Road, Zhejiang, No. 1788, No. Patentee before: Zhejiang Huafeng Spandex Co., Ltd. |
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Address after: No. 1788, Dongshan Economic Development Zone, Ruian, Wenzhou, Zhejiang Patentee after: Huafeng Chemical Co.,Ltd. Patentee after: HUAFON CHONGQING SPANDEX Co.,Ltd. Address before: No. 1788, Dongshan Economic Development Zone, Ruian, Wenzhou, Zhejiang Patentee before: ZHEJIANG HUAFENG SPANDEX Co.,Ltd. Patentee before: HUAFON CHONGQING SPANDEX Co.,Ltd. |