Gas phase degradation of trifluoromethyl peroxynitrate and trifluoromethyl nitrate in presence of water vapour

Abstract

Trifluoromethyl peroxynitrate (CF3O2NO2) and trifluoromethyl nitrate (CF3ONO2) could be formed in the degradation of chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons and hydrofluoroethers, from the reaction of CF3Ox radicals and NO2. In the present work, the role of gas-phase water in the degradation of CF3O2NO2 and CF3ONO2 was evaluated for the first time. The study has included experiments with and without water, theoretical calculation and kinetics mechanism modelling. Concentration of fluorinated species in different experimental systems He, He/H2O, N2, and N2/H2O were monitored by infrared spectroscopy. Results indicated that water vapour does not affect the peroxynitrate stability. On the other hand, nitrate degrades quickly in presence of water forming HNO3, CF2O and HF, while, in absence of water, the products are NO2 and CF2O. Kinetics mechanism was proposed and modelled to corroborate the experimental results. Theoretical calculations show that the formation of Van der Waals complexes CF3O2NO2·(H2O)n, CF3ONO2·(H2O)n is unfavourable. Mechanism for CF3ONO2 degradation in the presence and absence of water are discussed.