Fluorine-atom initiated oxidation of CF₃CF₂H (HFC-125) studied by FTIR spectroscopy: product yields and kinetic modelling

Abstract

A comprehensive study has been carried out of the oxidation of CF₃CF₂H (HFC-125). Reaction was initiated by continuous photolysis of F₂ in the near-UV. The F atoms produced abstracted a hydrogen atom from CF₃CF₂H initiating oxidation in gas mixtures containing variable amounts of O₂ and made up to a total pressure of 700 Torr with N₂. Product yields were measured as a function of time using FTIR spectroscopy. Experiments were performed at room temperature and in mixtures containing different ratios of [F₂] to [CF₃CF₂H]. The major products were COF₂, CF₃O₃CF₃ and CF₃O₃C₂F₅, consistent with C–C bond scission being the dominant loss process for CF₃CF₂O radicals and with previous studies which used chlorine atoms toinitiate oxidation. Attempts to match the experimental results with predictions using the FACSIMILE chemical modelling pro-gram were moderately successful and confirmed recent results regarding the equilibrium constant for: F+O₂(+M)=FO₂(+M).

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