Chain Reaction Mechanism in Hydrogen/Fluorine Combustion

Vibrationally excited species have
been considered to play significant
roles in H2/F2 reaction systems. In the present
study, in order to obtain further understanding of the chain reaction
mechanism in the combustion of mixtures containing H2 and
F2, burning velocities for H2/F2/O2/N2 flames were measured and compared to that obtained
from kinetic simulations using a detailed kinetic model, which involves
the vibrationally excited species, HF­(ν) and H2(ν),
and the chain-branching reactions, HF­(ν > 2) + F2 = HF + F + F (R1) and H2(ν = 1) + F2 = HF + H + F (R2). The results indicated that reaction R1 is not
responsible for chain branching, whereas reaction R2 plays a dominant
role in the chain reaction mechanism. The kinetic model reproduced
the experimental burning velocities with the presumed rate constant
of k2 = 6.6 × 10–10 exp­(−59 kJ mol–1/RT) cm3 s–1 for R2. The suggested chain-branching
reaction was also investigated by quantum chemical calculations at
the MRCI-F12+CV+Q/cc-pCVQZ-F12 level of theory.