Theoretical Characterizations on Novel Eco-friendly Dielectric Gas: Trifluoromethyl Carbonofluoridate

Although natural and synthetic esters have been employed as insulating fluids for transformers due to their biodegradability, one of the perfluorinated esters, namely, trifluoromethyl carbonofluoridate, CF
3
OCFO, has been identified to be a viable gaseous dielectric to be useful for insulation as replacement gas for SF
6
. Global warming potential, dielectric strength with respect to SF
6
, and the boiling point of CF
3
OCFO was estimated to be 1700, 2.0, and -37
^o
C, respectively, which even outperforms the well-established perfluoronitrile (C
4
F
7
N) gaseous dielectric. Chemical stability of CF
3
OCFO is assessed by the mechanistic study of unimolecular decomposition and bimolecular hydrolysis using various high-level ab initio methods. CF
3
OCFO decomposes predominantly via an isomerization of the F atoms of CF
3
accompanied by the simultaneous C-C bonds breaking to form two CF
2
O molecules. The corresponding activation energy is as high as 57.1 kcal/mol, as indicative of its good thermal stability. Hydrolysis of CF
3
OCFO proceeds dominantly via four types of the addition/elimination routes to generate various characteristic products including CF
3
OH, FCOOH, HF, CF
3
OCOOH, and CF
2
O. The lowest barrier height for hydrolysis is 38.3 kcal/mol. However, all the hydrolysis paths could be catalyzed efficiently by even a single water molecule to reduce the critical barriers considerably. Therefore, great attentions should be paid to the effect of the inevitable water impurity on the performance of CF
3
OCFO in electrical equipment. The present theoretical work might stimulate experimental tests on the CF
3
OCFO gas as a potential SF
6
-free technique.