Study on the mechanism of the effect of temperature on the decomposition reaction of SFn (n = 1–6) under discharge conditions

Abstract

The study on the mechanism of the effect of temperature on the decomposition reaction of SFn (n=1-6) under discharge conditions is very important in studying the potential fault of SF6 high voltage switch equipment and perfecting the chemical kinetic model of SFn discharge. In this paper, structural optimizations, vibrational frequency calculations, and zero-point energy calculations for the reactants and products were performed at the B3LYP/6-311++G(d,p) theory level. The single-point energies of all species were collected at the CCSD(T)/aug-cc-PVTZ level. The electric and thermal decomposition mechanism of SFn under discharge conditions of 298K-10000K were studied, respectively. The conclusion drawn was that in the temperature range of 298-10000K, the thermal decomposition homopolytic reaction △G began to decline from 200 kJ/mol, while the △G of the other two heterogenous reactions began to decrease from 1000 kJ/mol and 2000 kJ/mol, showing a downward trend of an almost similar slope. The electrolysis of SFn is related to the electron energy. When the electron energy is low, SFn + e→SFnseries reactions occur, and △G of R12, R20, R28, R36, R44 increases with temperature rise, while △G of R4 decreases with temperature. When the electron energy is high, one of SFn -→SFn−1 -+ F、 SFn -→SFn−1 + Fand SFn -→SFn−1 + F + e will occur, and the reactions that occur at various temperature ranges as the temperature rises vary. When the second electron hits the SFn -, the SFn -+ e→SFn−1 -+ F reaction will occur. The △G of this reaction slowly decreases with an increase in temperature. This study in clearer terms explains the decomposition process and mechanism of SFn at different temperatures.