### R equest to Use an Alternate GWP for Perfluoromethyl vinyl ether (CAS Number: 1187

- 93

- 5 )

Summary:

EPA recently promulgated a mandatory reporting regulation for Fluorinated Greenhouse Gases ( F

- GHG). The regulation requires f acilities to monitor and repor t CO 2 - equivalent F

- GHG process vent emissions, if those emissions exceed a threshold of 10,000 metric tons CO 2 - equivalent per year. [1] Estimated CO 2 - equivalent emissio ns are obtained by multiplying the F

- GHG mass emissions by the Global Warming Potential for the individual fluorinated gases that comprise the flow. EPA has provided a t able of 100

- year time horizon GWP values for about 70 individual F

- GHG

, and specifies that these values are to be used for the purpose of computing CO 2 - equivalent emissions

. [2] A default GWP value of 2,000 is to be used for any F

- GHG not listed in Table A

- 1. T he regulation allows a facility to request a lower provisional GWP when clear scientific evide nce exists to support such a lower value.

Table A

– 1 does not list a GWP for perfluoromethyl vinyl ether

. P erfluoromethyl vinyl ether is a s hort

- lived fluorinated vinyl ether . T he default GWP value of 2,000 is inappropriate for such gases and a substanti al body of evidence in the peer

- reviewed scientific literature has established that the GWP s of fluorinated vinyl ethers are modest

. Kinetic rate constants for the atmospheric degradation of perfluoromethyl vinyl ether have been measured in an environment al chamber; the atmospheric lifetime of perfluoromethyl vinyl ether has been estimated as 8 days; the infrared spectrum of perfluoromethyl vinyl ether has been accurately measured and the GWP of perfluoromethyl vinyl ether has been estimated as 2 relative to CO 2 with a 100

- year integration time horizon. DuPont is requesting a provisional GWP of 2 be assigned for perfluoromethyl vinyl ether

. Evidence Supporting Request :

F

- GHG Identity : Perfluoromethyl vinyl ether Chemical Formula : C 3 O F 6 CAS Number: 1187

- 93

- 5

Estimated GWP: 2 relative to CO 2 with a 100

- year integration time horizon

Data and analysis: Mashino et al. have measured kinetic rate constants for the vapor phase reaction of perfluoromethyl vinyl ether with OH. [3] OH radicals react with perfluoromethyl vinyl ether with a rate constant of ( 2.6 ± 0. 3 ) × 10 −12 cm 3 molecule −1 s −1 at 296 K in 700 Torr of air

. The global and yearly averaged atmospheric lifetime of perfluoromethyl vinyl ether was estimated by scaling to the known lifetime of methyl chloroform. This approach gives an atmospheric lifetime of perf luorom ethyl vinyl ether with respect to reaction with OH of 0.023 years (8 days). Quantitative infrared cross

sections of perfluoromethyl vinyl ether were obtained at 298 K in the region 5 00

- 40 00

cm - 1 , and r adiative forcing calculations were performed usi ng the approximation methoddeveloped by Pinnock et al.

. [4] The GWP of perfluoromethyl vinyl ether was estimated to be 4.57 × 10 - 4 relative to CFC

- 11 fo r a 100 year time horizon. The GWP of CFC

- 11 relative to CO 2 with a 100 year time horizon is 4,750. [5] Thus, the Mashino et al. estimate of the GWP of perfluorome thyl vinyl ether relative to CO 2 with a 100 year time horizon is 4.57 × 10 - 4 x 4,750 = 2. A s a further check, we used the global and yearly averaged lifetime of 8 days measured by Mashino et al. and i nfrared cross

- sections of perfluoromethyl vinyl ether o btained using ab initio quantum chemical methods recommended in the peer

- reviewed scientific literature. [6

- 7] R adiative forcing calculations were again performed using the approximation method developed by Pinno ck et al. [4] Using this approach, a GWP for perfluoromethyl vinyl ether of 3 relative to CO 2 with a 100

- year integration time horizon was established.

The methods used in determining this GWP value are essentially identical to those used for the values obtained for the gases listed in Table A

- 1: (1) the kinetic rate constants for reaction with critical atmospheric oxidants were measured and an atmosph eric lifetime was determined; (2) the infrared absorption spectrum of the substance was measured ; and (3) the atmospheric lifetime and infrared absorption spectrum were incorporated into a radiative transfer model to estimate the contribution of the substa nce to greenhouse forcing.

Based on this publication in the peer

- reviewed literature , DuPont requests that a provisional GWP of 2 be assigned for perfluoromethyl vinyl ether

.

1. "Mandatory Reporting of Greenhouse Gases: Additional So urces of Fluorinated GHGs; Final Rule" , Federal Register 75:230 (December 1, 2010) p.74774. 2. "Table A

- 1 to Subpart A of Part 98

— Global Warming Potentials" : Table A

- 1 in 40 CFR part 98, subpart A. 3. Mashino, M., et al., Atmospheric Degradation of CF3OCFC F2: Kinetics and Mechanism of Its Reaction with OH Radicals and Cl Atoms. The Journal of Physical Chemistry A, 2000. 104 (13): p. 2925

- 2930. 4. Pinnock, S., et al., Radiative forcing of climate by hydrochlorofluorocarbons and hydrofluorocarbons. Journal of Geophysical Research, 1995. 100 (D11): p. 23227

- 23238. 5. IPCC, Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. [Solomon, S., D. Qin, M. Mann ing, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)] 2007, Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. 996 pp. 6. Blowers, P. and K. Hollingshead, Estimations of Global Warming Potentials from Computatio nal Chemistry Calculations for CH2F2 and Other Fluorinated Methyl Species Verified by Comparison to Experiment. The Journal of Physical Chemistry A, 2009. 113 (20): p. 5942

- 5950.7. Halls, M.D. and H.B. Schlegel, Comparison of the performance of local, grad ient

- corrected, and hybrid density functional models in predicting infrared intensities. The Journal of Chemical Physics, 1998. 109 (24): p. 10587

- 10593.