Theoretical and experimental investigation on decomposition mechanism of eco-friendly insulation gas HFO1234zeE

Decomposition experiments under corona discharge and theoretical calculations using the density functional theory (DFT) method were accomplished to clarify the dissociation behavior and decomposition mechanism of HFO1234zeE (trans-1,3,3,3-tetrafluoropropene), an eco-efficient SF6 alternative gas. The discharge decomposition products of HFO are mainly fluorocarbon, unsaturated hydrocarbon and saturated hydrocarbons, which are containing no more than three carbons. Free radicals, CF3·, F· and H·, generated via bond-cleavage reaction are important structures to promote the decomposition, and HFO is more likely to dissociate with them by abstraction reaction to form CF4 and CF3H. Long-chain radicals, such as CF3CHCF·, CF3CHCH· and CF3CCHF·, will be decomposed into CF3CCH and CF3CCF, and small intermediates would be easier to combine to form HF, C2F6, C2F4, C2HF5, CF3HCF3H and C3F8. It is also likely to be converted to Z-isomer. Due to the high discharge intensity and ion bombardment, solid by-products appeared on the electrode surface may contain carbon dust and metal compounds. The solid attached to the surface has little effect on the electric field distribution, and most gas decomposition products still maintain the insulation strength, so the air-gap breakdown voltage only dropped by about 6.2% after long-term corona discharge. The obtained results not only reveal the decomposition mechanism in a comprehensive way, but also present useful reference for exploring the application potentials of HFO1234zeE. [Display omitted] •A theoretical and experimental study of decomposition mechanism of HFO1234zeE under corona discharge.•CF3·, F· and H· radicals dominate decomposition process.•The mechanism relies on changes of reaction energies and barriers.•Gaseous and solid products have little effect on insulation strength.