Dimerization of perfluoropropyl vinyl ether during the pyrolysis of hexafluoropropylene oxide dimer

Abstract

Dimerization of perfluoropropyl vinyl ether (PPVE) generally reduces its yield and selectivity during the pyrolysis of hexafluoropropylene oxide dimer ((HFPO)₂). However, the mechanism of PPVE dimerization is not well understood. In this paper, the PPVE dimer was obtained during the pyrolysis of (HFPO)_2. Subsequently, the chemical structure of PPVE dimer was further determined by gas chromatography-mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR). The results showed that the concentration of PPVE dimer rises in proportion to the extended reflux time of PPVE in the reaction system. Based on the experimental phenomenon, a possible generation mechanism of PPVE dimer was then proposed, and the possibility of the generation pathway was further verified in combination with density functional theory (DFT). In addition, to effectively reduce the production of PPVE dimer, crown ethers and quaternary ammonium salts were added to the reaction system as phase transfer catalysts. Among them, the phase transfer catalyst (15-crown-5) was more effective and reduced the PPVE dimer content from 1.34 % to 0.31 %. This work provides an idea to inhibit the dimerization of PPVE and increase the yield and selectivity of PPVE.