Chemical kinetics analysis of two C5-perfluorinated ketone (C5 PFK) thermal decomposition products: C₄F₇O and C₃F₄O

SF₆ has been designated as a greenhouse gas by the Kyoto Protocol because of its high global warming potential. C5-perfluorinated ketone (C₅F₁₀O or C5-PFK) has excellent insulation properties and environmental characteristics, and has been chosen as an alternative gas to SF₆. Calculation of thermal decomposition is usually based on local thermodynamic equilibrium (LTE) and local chemical equilibrium assumptions. However, the composition may not reach chemical equilibrium, particularly at lower temperatures and high rates of temperature increase. In order to compare the chemical non-equilibrium and local thermodynamic equilibrium compositions, a chemical kinetic model is used to calculate time evolution of composition; this considers the effects of the energy barrier in chemical reactions. To obtain the required data for the model, which is necessary because of the limited research on reaction rates in C5-PFK decomposition, the methods of computational chemistry are used to calculate transition states and reaction rates. The LTE composition is calculated using Gibbs free energy minimization. Calculations are presented for two possible C5-PFK thermal decomposition products, C₄F₇O and C₃F₄O. The result indicates that chemical kinetics is required to calculate the dissociation of C5-PFK at low temperatures, such as occur during arc ignition and near the arc boundary.