Rate constants of C ₅ F ₁₀ O decomposition reactions at temperatures of 300–3500 K

Abstract

Abstract Five-carbon perfluorinated ketone (C 5 F 10 O) has been reported as a remarkable eco-efficient replacement for SF 6 . To investigate its dielectric strength, thermodynamic properties and decomposition characteristics, accurate compositions of C 5 F 10 O discharge plasma are a prerequisite and can be studied by a chemical kinetic model considering non-equilibrium effects. Rate constants of C 5 F 10 O decomposition reactions are the basis for this model but have not been reported yet. Therefore, this paper is devoted to investigating the rate constants of C 5 F 10 O decomposition reactions at temperatures of 300–3500 K, relevant to electrical breakdown and arc-quenching in high-voltage electrical equipment. The rate constants and equilibrium constants as the function of temperature are computed using the transition state theory on the basis of energies and vibrational frequencies, calculated by the B3LYP/6-311G(d,p) method. The dominant reactions generating and/or consuming the species in C 5 F 10 O decomposition are also selected by contributions higher than 1%. The results in this paper show that (1) C 5 F 10 O decomposition reactions (except for R7) are endothermic and rate constants differ significantly between different reactions, mainly caused by activation energies; (2) at 1500 K and above, most rate constants fall in the region from 10 −15 to 10 30 cm 3 mole −1 s −1 or s −1 , making it so that the corresponding reactions cannot be neglected in C 5 F 10 O plasma models; (3) reactions R5, R11, R12, R14, R29, R32, R33 and R36 mainly contribute to the degradation of the insulating and arc-quenching performance of C 5 F 10 O; (4) reaction R2 plays the major role in C 5 F 10 O dissociation with the contribution more than 72.2% at temperatures of 300–3500 K. To verify the method adopted, thermodynamic properties (entropy, enthalpy and specific heat) of CF 2 , CF 2 CF 2 , CF 3 , CF–CF 2 and CO are compared with those from NIST-JANAF tables and a good agreement is obtained. This work is expected to provide the input data for the calculation of non-equilibrium C 5 F 10 O discharge plasma compositions employing a chemical kinetic model.