Theoretical Kinetic Study of SF₆ Decomposition via Reactions With H and OH Radicals

A comprehensive kinetic model for SF₆ decomposition in combustion environments has been hindered by the lack of accurate thermodynamic and kinetic data, particularly for radical-driven high-temperature chemistry. This study provides ab initio thermodynamic and kinetic data for SF₆ decomposition via reactions with H and OH radicals, key species in combustion chemistry. The thermodynamic properties of various fluorinated species are provided in NASA polynomial format, allowing direct integration into kinetic simulation packages. Three major reaction pathways are examined using density functional theory (DFT) calculations are as follows: (1) SF_n + H → SF_{n − 1} + HF, (2) SF_n + OH → SOF_{n − 1} + HF, and (3) SOF_n + OH → SO₂F_{n − 1} + HF. These reactions are key steps in forming major products, such as SO₂ and SO₂F₂. Temperature-dependent rate constants are computed, and the corresponding Arrhenius parameters are determined. The decomposition of SF_n species is more strongly promoted by OH radicals than by H radicals. SOF_n species, formed from SF_n and OH radicals, subsequently react with OH radicals to generate SO₂ and SO₂F₂. These findings provide a valuable thermodynamic and kinetic dataset that can be integrated into combustion or pyrolysis kinetic models to develop a detailed SF₆ decomposition model.