Initiation and Carbene Induced Radical Chain Reactions in CH₂F₂ Pyrolysis

High temperature dissociations of organic molecules typically involve a competition between radical and molecular processes. In this work, we use a modeling, experiment, theory (MET) framework to characterize the high temperature thermal dissociation of CH₂F₂, a flammable hydrofluorocarbon (HFC) that finds widespread use as a refrigerant. Initiation in CH₂F₂ proceeds via a molecular elimination channel; CH₂F₂→CHF+HF. Here we show that the subsequent self-reactions of the singlet carbene, CHF, are fast multichannel processes and a facile source of radicals that initiate rapid chain propagation reactions. These have a marked influence on the decomposition kinetics of CH₂F₂. The inclusion of these reactions brings the simulations into better agreement with the present and literature experiments. Additionally, flame simulations indicate that inclusion of the CHF+CHF multichannel reaction leads to a noticeable enhancement in predictions of laminar flame speeds, a key parameter that is used to determine the flammability of a refrigerant.