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CN-121994950-A - Vinyl chloride product produced by ethylene method and trace impurity detection method

CN121994950ACN 121994950 ACN121994950 ACN 121994950ACN-121994950-A

Abstract

The invention belongs to the technical field of analytical chemistry, and particularly relates to a chloroethylene product produced by an ethylene method and a trace impurity detection method. The method ensures that the liquid vinyl chloride sample is completely vaporized and integrally transferred to a gas chromatograph in an instant manner through flash evaporation sample introduction, ensures that the liquid vinyl chloride sample is completely vaporized and integrally transferred, ensures volume quantification by entering a gas chromatograph 1mL sample introduction six-way valve after flash evaporation, effectively separates the vinyl chloride and impurities through the separation effect of a gas chromatographic column, only monitors 1-3 characteristic ions of target impurities in a SIM mode through the advantages of high sensitivity and low detection limit of a four-level mass spectrum detector, eliminates the interference of other ions in a matrix, greatly improves the signal-to-noise ratio, realizes high-sensitivity and high-selectivity quantitative analysis of trace or even trace level (mu g/g or lower) impurities in the vinyl chloride, realizes quick screening and identification process abnormality of the vinyl chloride product, and has universality.

Inventors

  • BO ZHENHAI
  • ZHAO JIANHAO
  • SHI JIE
  • JI MENGFAN
  • XU KE
  • XUE XIAOLEI

Assignees

  • 青岛海湾科技产业研究院有限公司

Dates

Publication Date
20260508
Application Date
20260120

Claims (10)

  1. 1. A vinyl chloride product produced by an ethylene method and a trace impurity detection method are characterized by comprising the following steps: s1, sample flash evaporation and sample injection, namely evaporating a liquid vinyl chloride sample through a flash evaporation sample injector, and transferring the evaporated sample to a gas six-way sample injection valve of a gas chromatograph; S2, gas chromatographic separation, namely, enabling a sample to enter a vaporization chamber through the gas six-way sample injection valve, and then entering a chromatographic column for separation; S3, mass spectrum detection, namely sequentially entering the components subjected to chromatographic separation into a four-stage rod mass spectrometer, and ionizing under an electron bombardment ion source, wherein the detection comprises the following steps: (a) Collecting a total ion flow chromatogram and a mass spectrum of each component by adopting a full scanning mode for qualitative analysis; (b) Adopting a selective ion monitoring mode to monitor characteristic ion signals aiming at specific target impurities for quantitative analysis; S4, data processing: (a) Qualitative analysis, namely comparing a mass spectrogram of each chromatographic peak in the total ion flow chromatograms obtained in the full scanning mode with a standard mass spectrogram library, and qualitatively identifying a main peak of vinyl chloride and each impurity peak by combining the retention time of a standard substance; (b) And (3) quantitatively analyzing, namely under the selected ion monitoring mode, establishing a standard working curve by analyzing the standard gas of the target impurity by adopting an external standard method, and calculating the concentration of the target impurity characteristic ions in the vinyl chloride sample according to the response value of the target impurity characteristic ions.
  2. 2. The method for detecting vinyl chloride products and trace impurities produced by an ethylene method according to claim 1, wherein before detection, a flash evaporation sample injector, a gas chromatograph and a four-stage rod mass spectrometer are sequentially started, parameters are set and preheated, the temperature of the flash evaporation sample injector is set to be 100 ℃, and the flash evaporation sample injector is preheated and stabilized for at least 20 minutes; setting the temperature of a gas chromatograph sample inlet or a vaporization chamber to be 200 ℃, setting the temperature of a gas six-way valve to be 100 ℃, setting the temperature of a transmission line to be 120-150 ℃ and setting the temperature of a chromatographic column Wen Chushi to be 45 ℃; The ion source temperature of the four-stage rod mass spectrometer is set to be 200 ℃ and the interface temperature is set to be 250 ℃.
  3. 3. The method for detecting vinyl chloride products and trace impurities produced by an ethylene method according to claim 1, wherein in the step S1, after the sample is vaporized, the pipeline is purged through the sample, and the purging time is 1-2 min.
  4. 4. The method for detecting vinyl chloride products and trace impurities produced by an ethylene method according to claim 1, wherein in the step S2, the gas injection six-way valve is a 1mL gas injection six-way valve, the injection time is 1min, and the auxiliary carrier gas pressure of the gas six-way valve during injection is set to be 40.0kPa.
  5. 5. The method for detecting vinyl chloride product and trace impurities according to claim 4, wherein said chromatographic column is a capillary column packed with 100% divinylbenzene porous polymer, having a specification of 30m x 0.32mm x 10 μm, and a column flow rate of 2 mL/min.
  6. 6. The method for detecting vinyl chloride products and trace impurities according to claim 5, wherein the chromatographic column is heated to an initial temperature of 45 ℃ for 3 min ℃ and then heated to 180 ℃ at a rate of 5 ℃/min for 10-15 min.
  7. 7. The method for detecting vinyl chloride products and trace impurities according to claim 1, wherein in step S4, the electron energy of said ion source is 70 eV, and the mass range of scanning is in the range of m/z 35-400 in the full scanning mode.
  8. 8. The method for detecting vinyl chloride products and trace impurities produced by ethylene method according to claim 1, wherein in step S4, a full scanning mode is adopted for qualitative analysis, mass spectrograms of each chromatographic peak in the obtained total ion chromatogram are compared with a standard mass spectrogram library such as NIST and the like, and the main peak of vinyl chloride and each impurity peak are qualitatively identified by combining the retention time of a standard substance, wherein the identified impurities comprise ethylene, acetylene, ethane, propylene, methyl chloride, propyne, vinyl chloride, isobutane, 1-butene, vinyl acetylene, 1, 3-butadiene, vinyl chloride, 1-butyne, 2-butene, vinyl bromide, 1-dichloroethylene, trans-1, 2-dichloroethylene, 1-dichloroethane, cis-1, 2-dichloroethylene, 1, 2-dichloroethane and 1, 2-trichloroethane.
  9. 9. The method for detecting vinyl chloride products and trace impurities produced by ethylene process according to claim 1, wherein in step S4, quantitative analysis adopts a selective ion monitoring mode, quantitative analysis adopts an external standard method, standard gas containing target impurities is subjected to standard working curve establishment under the analysis condition identical to that of the sample, and the concentration of the standard gas in the sample is calculated according to the response value of the target.
  10. 10. The method for detecting a vinyl chloride product and a trace impurity by using a vinyl chloride process according to claim 1, wherein the detection limit is determined by repeating the analysis 7 times under the same conditions as the sample analysis with a concentration corresponding to a signal-to-noise ratio of 3 as the detection limit of the method using a mixed standard gas containing the target component at a concentration of 5 times or more than the expected detection limit.

Description

Vinyl chloride product produced by ethylene method and trace impurity detection method Technical Field The invention belongs to the technical field of analytical chemistry, and particularly relates to a chloroethylene product produced by an ethylene method and a trace impurity detection method. Background Vinyl Chloride (VCM) is a monomer for synthesizing polyvinyl chloride (PVC), and is industrially produced mainly by a calcium carbide method and an ethylene method (ethylene post-chlorination cracking process). The purity and impurity content of vinyl chloride are key indicators for determining the quality and the post-processing performance of the polyvinyl chloride resin. In the process of producing vinyl chloride by an ethylene method, trace impurities remain in the product due to factors such as incomplete reaction, side reaction, raw material introduction and the like, and mainly comprise unreacted raw materials (ethylene), byproducts (acetylene, chloromethane, 1-butene, vinyl acetylene, 1, 3-butadiene, chloroethane, 2-butene, bromoethylene, 1-dichloroethylene, trans-1, 2-dichloroethylene, 1-dichloroethane, cis-1, 2-dichloroethylene, 1, 2-dichloroethane and the like). The existence of the impurities not only can influence the polymerization degree and the post-processing performance of the polyvinyl chloride product, but also can cause equipment corrosion and potential process safety hazards. Therefore, the accurate detection of the chloroethylene products and impurities is a core link for guaranteeing the production quality and optimizing the process. The vinyl chloride is typically detected by conventional gas chromatography, by sample vaporization into a hydrogen flame ionization detector for analysis. These methods have mainly the following drawbacks: Firstly, sample injection discrimination exists, namely, in the traditional method, a sample is directly injected into liquid or directly released to a sample injection interface of a gas chromatograph through a sampling steel cylinder, obvious sample injection discrimination effect exists on chloroethylene and impurities which are instantaneously released to normal pressure to form gas-liquid mixture, and the main components and the impurities are inaccurately quantified; Secondly, the sensitivity and the anti-interference capability are poor, namely the main peak (the content is more than 99.9%) of chloroethylene in the sample is extremely high, the impurity separation effect is poor, and the detection limit is high in the traditional method; The traditional hydrogen flame ionization detector cannot accurately and qualitatively determine unknown impurities, the qualitative accuracy only depends on standard substances, the unknown impurities are not identified, and the impurities with similar structures such as isomers are difficult to effectively separate and identify; The method has lower sensitivity and higher detection limit, and the detection limit of the traditional vinyl chloride detection method is more than 10-20 mug/g level, so that the detection requirement of high-end PVC production on trace impurities (mug/g level or even lower) cannot be met. The gas chromatography-quadrupole mass spectrometry technology is the most advanced and popular detection method at present, but few reports are made for detecting vinyl chloride products and trace impurities produced by an ethylene method. Therefore, there is an urgent need to develop a method for accurately, directly and comprehensively analyzing the contents of vinyl chloride products and trace impurities generated by the ethylene process. Disclosure of Invention The invention aims to solve the technical problem of providing a vinyl chloride product produced by an ethylene method and a trace impurity detection method, and provides a more comprehensive and superior analysis guarantee for quality control and process optimization of the vinyl chloride product by the ethylene method by adopting a flash evaporation sample injection-gas chromatography-four-stage rod mass spectrometry combined method. The technical scheme adopted is as follows: a vinyl chloride product produced by an ethylene method and a trace impurity detection method comprise the following steps: s1, sample flash evaporation and sample injection, namely, instantly vaporizing a liquid vinyl chloride sample through a flash evaporation sample injector, and transferring the vaporized sample to a gas six-way sample injection valve of a gas chromatograph; S2, gas chromatographic separation, namely, enabling a sample to enter a vaporization chamber through the gas six-way sample injection valve, and then entering a chromatographic column for separation; S3, mass spectrum detection, namely sequentially entering the components subjected to chromatographic separation into a four-stage rod mass spectrometer, and ionizing under an electron bombardment ion source, wherein the detection comprises the following steps: (a) Collecting a total ion f