Theoretical modeling study of the reaction H + CF₄ → HF + CF₃

Abstract

The high-temperature hydrogenation of CF 4 in mixtures of CF 4 and H 2 is assumed to involve the reaction H + CF 4 → HF + CF 3 . The hydrogen atoms here are either formed by the reaction of F and CF 3 (i.e., the products of the thermal dissociation of CF 4 ) with H 2 , or by the thermal dissociation of H 2 . In the former case, a complicated chain process is started, while the reaction proceeds in a more direct way in the latter. This article determines the rate constant of the reaction H + CF 4 → HF + CF 3 , characterizing its transition state by quantum-chemical methods. Over the temperature range 1000-3000 K, the most accurate results for the rate constant can be represented in the form 1.64 × 10 14 (T/1000 K) 1.95 exp(−178.8 kJ mol -1 /RT) cm 3 mol -1 s -1 , based on coupled cluster theory extrapolated to the complete basis set limit, and incorporating vibrational anharmonicity, electron correlation through CCSDT(Q), and relativistic and non-Born-Oppenheimer effects.