Quantifying the Decomposition Kinetics of Linear C₂–C₄ Perfluoroalkanes

The pyrolysis of C₂-C₄ linear perfluoroalkanes was investigated using laser schlieren densitometry (LS) in a diaphragmless shock tube. Mixtures of 1, 2, and 4% perfluoroethane (PFE), perfluoropropane (PFP), and perfluorobutane (PFB) in excess krypton were shock-heated to 1400-2500 K at pressures of 60, 120, and 240 Torr. The initiation step for all perfluoroalkanes involved carbon-carbon bond fission. The rate constants for unimolecular decomposition were computed using microcanonical rate theory, and these rate constants were combined into a detailed chemical kinetic mechanism. For PFE and PFP, there was one dissociation channel, while PFB dissociated via two competing bond-fission reactions. The perfluoroalkyl radicals subsequently recombined or underwent further unimolecular decomposition. The kinetic model accurately simulated the density gradient profiles of all perfluoroalkanes.