Mechanism, kinetics, and environmental assessment of CTDE during
OH-oxidation in the presence of NO and O2
Abstract
The transformation mechanism and kinetics of
2-chloro-1,1,2-trifluoroethyl-difluoromethyl-ether (CTDE, CHF2OCF2CHFCl)
triggered by OH radicals were researched by DFT methods and canonical
variational transition state theory. The computational rate constant
including small-curvature tunneling correction was in commendable
agreement with the experimental data. Two hydrogen abstraction channels
to form the alkyl radicals of C·F2OCF2CHFCl and CHF2OCF2C·FCl were
observed, and the formation of CHF2OCF2C·FCl was more favorable than
C·F2OCF2CHFCl in kinetics and thermodynamics. Subsequent evolution of
CHF2OCF2C·FCl in the presence of NO and O2 indicated that the organic
nitrate (CHF2OCF2CONO2FCl) was the stable product. The dechlorinate of
alkoxy radical (CHF2OCF2C(O·)FCl) was the most favorable degradation
channel and the estimated ozone depletion potential for CTDE relative to
CFC-11 was 0.0204, which could lead to a consequence of ozone depletion.
Computed atmospheric lifetime for CTDE was 3.69 years by considering the
combined contributions from OH radicals and Cl atoms. The total
radiative forcing and global warming potential of CTDE were respectively
0.547 W m-2 ppbv and 628.58 (100 years) at 298 K, suggesting that the
contribution of CTDE to the greenhouse effect is moderate.