Mechanistic and Kinetic Investigations on Decomposition of Trifluoromethanesulfonyl Fluoride in the Presence of Water Vapor and Electric Field

Abstract

As a potential insulation gas to replace sulfur hexafluoride (SF6) due to environmental concerns, trifluoromethanesulonyl fluoride (CF3SO2F) has attracted great interests in various high-voltage electric applications. Thermal stability of CF3SO2F plays an important role in the rational design of the gas-insulated electric equipment. Unimolecular decomposition of CF3SO2F was investigated using high-level ab initio methods including the explicitly correlated RCCSD(T)-F12, the composite ROCBS-QB3, and the multireference RS2 extrapolated to complete basis set limit on the basis of M06-2X-, B2PLYPD3-, and CCSD-optimized geometrical parameters. Rate coefficients and decomposition temperatures were simulated using master equations. CF3SO2F decomposes predominantly via a simple C-S bond cleavage to form CF3 and SO2F, accompanied by a roaming induced F-abstraction detour to release CF4 and SO2, or isomerizes via CF3 migration to the more stable CF3OSFO followed by the production of CF2O and SOF2. Various characteristic decomposition products (e.g., CF4, C2F6, CF2O, SO2, SOF2, SO2F2, CF3H, and so on.) have been identified theoretically through secondary reactions and hydrolysis of CF3SO2F in the presence of water vapor. Electronic structures and stability of CF3SO2F could be affected significantly by the external electric field orientated along the S-C bond. The field-dependent electron-molecule capture rates support that CF3SO2F is superior to SF6 in dielectric strength. The present computational findings shed light on the practical use of CF3SO2F as the replacement gas for SF6.