Rate constants of C5F10O decomposition reactions at temperatures of 300-3500 K

Abstract

Five-carbon perfluorinated ketone (C5F10O) has been reported as a remarkable eco-efficient replacement for SF6. To investigate its dielectric strength, thermodynamic properties and decomposition characteristics, accurate compositions of C5F10O discharge plasma are a prerequisite and can be studied by a chemical kinetic model considering non-equilibrium effects. Rate constants of C5F10O 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 C5F10O 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 C5F10O decomposition are also selected by contributions higher than 1%. The results in this paper show that (1) C5F10O 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 1030 cm3 mole-1 s-1 or s-1, making it so that the corresponding reactions cannot be neglected in C5F10O 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 C5F10O; (4) reaction R2 plays the major role in C5F10O 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 CF2, CF2CF2, CF3, CF-CF2 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 C5F10O discharge plasma compositions employing a chemical kinetic model.