CN-121974776-A - Method for removing impurities in tetrafluoroethylene component and improving purity

CN121974776ACN 121974776 ACN121974776 ACN 121974776ACN-121974776-A

Abstract

The invention discloses a method for removing impurities in tetrafluoroethylene components and improving purity, which comprises the following steps of (1) optimizing a rectifying filler, sequentially filling 1000Y silk screen filler and 752Y silk screen filler in a rectifying section of a tetrafluoroethylene rectifying tower from top to bottom, filling 752Y silk screen filler in a stripping section, and (2) selectively absorbing and desorbing methanol to remove impurities, namely introducing tetrafluoroethylene material gas containing difluoromethane, trifluoroethylene and trifluoromethane impurities into a methanol absorbing tower, and utilizing methanol as a strong polar solvent to realize selective absorption and separation on the solubility difference of the impurity components and tetrafluoroethylene. The invention has the beneficial effects that the invention utilizes the fundamental difference of tetrafluoroethylene and impurity molecules in polarity, realizes the targeted capturing and efficient removal of impurities based on the molecular recognition capability of the intermolecular acting force difference, and ensures that the purity of tetrafluoroethylene products is improved.

Inventors

Wang Decao
ZHOU GUANGBING
YANG HONGFEI
ZHANG CHANGQING
TAN JIAN
Yin Zhanyue
BAI SHULIN

Assignees

聊城氟尔新材料科技有限公司

Dates

Publication Date: 20260505
Application Date: 20251225

Claims (5)

1. A method for removing impurities in tetrafluoroethylene components to improve purity, comprising the steps of: (1) The rectification filler optimization, namely sequentially filling 1000Y silk screen filler and 752Y silk screen filler from top to bottom in a rectification section of a tetrafluoroethylene rectification tower, and filling 752Y silk screen filler in a stripping section; (2) The method comprises the steps of selectively absorbing and desorbing methanol to remove impurities, namely introducing tetrafluoroethylene material gas containing difluoromethane, trifluoroethylene and trifluoromethane impurities into a methanol absorption tower, utilizing methanol as a strong polar solvent to realize selective absorption and separation of impurity components and solubility difference of tetrafluoroethylene, then, conveying methanol solution with the impurities absorbed into the methanol desorption tower to carry out analysis and regeneration, discharging the removed impurity components out of the system, returning the regenerated methanol to the methanol absorption tower for recycling, and extracting the purified tetrafluoroethylene material gas from the top of the methanol absorption tower.
2. The method for removing impurities from tetrafluoroethylene composition according to claim 1, wherein in the step (2), the selective absorption of the impurity composition by methanol is based on a difference in dipole-dipole interaction and hydrogen bonding ability between a solute and methanol, wherein difluoromethane interacts most strongly with methanol due to strong polarity and good hydrogen bonding acceptor ability, trifluoroethylene is inferior, trifluoromethane is inferior again, tetrafluoroethylene interacts most weakly with methanol due to non-polarity and lack of effective interaction site, thereby achieving efficient separation of tetrafluoroethylene from impurities.
3. The method for removing impurities from tetrafluoroethylene composition according to claim 1, wherein in the step (2), the operation pressure of the methanol absorption column is controlled to about 0.5Mpa, the overhead condenser condenses with brine at-35 ℃, the material extracted from the overhead is purified tetrafluoroethylene, the purified tetrafluoroethylene is returned to the front-end production system, and the methanol solution having absorbed difluoromethane, trifluoroethylene and trifluoromethane is extracted from the bottom of the column and sent to the methanol desorption column.
4. The method for removing impurities from tetrafluoroethylene according to claim 3, wherein the operating pressure of the methanol stripping column is controlled to be about 0.05Mpa, the column bottom is heated by steam and the temperature of the column bottom is controlled to be within the range of 0-20 ℃ by a column bottom regulating valve, the methanol solution regenerated by the column bottom is conveyed by a methanol circulating pump, cooled by a methanol condenser and returned to the top of the methanol absorption column, and the liquid-gas ratio in the methanol absorption column is controlled by regulating the frequency conversion of the methanol circulating pump.
5. The method for removing impurities from tetrafluoroethylene composition according to claim 4, wherein the desorption material gas rich in difluoromethane, trifluoroethylene and trifluoromethane is taken out from the top of the methanol desorption column and sent to the waste gas disposal system through the top-outlet regulating valve.

Description

Method for removing impurities in tetrafluoroethylene component and improving purity Technical Field The invention relates to the technical field of chemical impurity purification, in particular to a method for removing impurities in tetrafluoroethylene components and improving purity. Background In industrial production of Tetrafluoroethylene (TFE) by pyrolysis of difluoromethane (R22), the process path is long and the control is complex, and the generation and separation of impurities are core challenges throughout the process. The raw material R22 is subjected to non-catalytic homogeneous phase gas phase reaction in a high-temperature cracking furnace under steam dilution, the process is essentially free radical chain reaction, and the reaction path has the characteristics of strong selectivity and difficult control. In addition to the formation of the target product TFE, side reactions such as dechlorination, disproportionation, carbon-carbon bond cleavage and deep cleavage which occur in parallel are difficult to completely inhibit, resulting in the inevitable production of trifluoroethylene (TrFE), difluoromethane (R32), trifluoromethane (R23) and various chlorofluorocarbon trace impurities. These impurity components are very close to the boiling point of the main product TFE and have very similar physicochemical properties, e.g., TFE boiling point-76.3 ℃ and TrFE boiling point-53 ℃, R32 boiling point-51.6 ℃ and R23 boiling point-82.1 ℃ to form a near boiler system which is difficult to separate. In the subsequent rectification and purification working section, the characteristic of similar physical properties forms a fundamental separation barrier. Conventional multistage rectification relies on differences in relative volatilities between components, but for mixtures with very small boiling point differences, the separation efficiency is very low, requiring very high theoretical plate numbers to very large reflux ratios, which directly results in a sharp rise in energy consumption and separation efficiency that may still not meet the polymeric grade purity requirements (typically requiring TFE purity >99.99%, critical impurity content in ppm). More seriously, some impurities such as TrFE have a vinyl double bond structure similar to TFE and can enter the polymer chain as a comonomer or chain transfer agent during subsequent polymerization, disrupting the regularity of Polytetrafluoroethylene (PTFE), leading to broadening of the molecular weight distribution of the polymer, degradation of crystallinity, deterioration of thermal stability, and significant degradation of the mechanical (e.g., tensile strength, creep resistance) and dielectric properties of the article. While the low-boiling impurities such as R32, R23 and the like do not directly participate in polymerization, the accumulation of the low-boiling impurities in a rectification system can influence the balance of gas and liquid phases in a tower and the operation stability, so that the pressure fluctuation of the rectification tower is caused, entrainment which is difficult to remove can be formed in a product TFE, and the isotacticity of a polymerization reaction and the pressure abnormality of a system are also damaged. Therefore, the nature of the impurity problem is the double coupling of the complexity of the side reaction path of the reaction source and the separation limit of the near-boiling-point object system at the separation end, which not only restricts the final purity of TFE products, but also forms a key bottleneck restricting the quality and efficiency of the whole industrial chain by influencing the stability of the downstream polymerization process and the performance of the final polymer material. Disclosure of Invention The invention aims to overcome the defects that in the process of rectifying tetrafluoroethylene, components such as difluoromethane, trifluoroethylene, trifluoromethane and the like appear to influence the purity of tetrafluoroethylene, and impurity components such as trifluoroethylene, difluoromethane and the like influence the product quality of a polymerization user; There is provided a method for removing impurities in tetrafluoroethylene components to enhance purity, comprising the steps of: (1) The rectification filler optimization, namely sequentially filling 1000Y silk screen filler and 752Y silk screen filler from top to bottom in a rectification section of a tetrafluoroethylene rectification tower, and filling 752Y silk screen filler in a stripping section; (2) The method comprises the steps of selectively absorbing and desorbing methanol to remove impurities, namely introducing tetrafluoroethylene material gas containing difluoromethane, trifluoroethylene and trifluoromethane impurities into a methanol absorption tower, utilizing methanol as a strong polar solvent to realize selective absorption and separation of impurity components and solubility difference of tetrafluoroethylene, then, co