### R equest to Use an Alternate GWP for Perfluoropropyl vinyl ether (CAS Number: 1623

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Summary:

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

- GHG). The regulation requires f acilities to monitor and report 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 emission s 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 t hat 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 eviden ce exists to support such a lower value.

Table A

– 1 does not list a GWP for perfluoropropyl vinyl ether

. Perfluoropropyl 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 substantia l body of evidence in the peer

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

. T he atmospheric lifetime of perfluoropropyl vinyl ether has been estimated as 8 .077 days using the AOPWIN module of EPA’s E PI Suite TM v4.10 exposure assessment modeling tool ; the infrared spectrum of perfluoropropyl vinyl ether has been accurately estimated using ab initio quantum chemical methods recommended in the peer

- reviewed scientific literature and the GWP of perfluorop ropyl vinyl ether has been estimated as 3 relative to CO 2 with a 100

- year integration time horizon. DuPont is requesting a provisional GWP of 3 be assigned for perfluoropropyl vinyl ether

. Evidence Supporting Request :

F

- GHG Identity : Perfluoropropyl vi nyl ether Chemical Formula : C 5 O F 10 CAS Number: 1623

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Estimated GWP: 3 relative to CO 2 with a 100

- year integration time horizon

Data and analysis: A global and yearly averaged atmospheric lifetime for perfluoropropyl vinyl ether of 8.077 days was es timated using the AOPWIN module of EPA’s EPI Suite TM v4.10 exposure assessment modeling tool

. [3]

For compar ison, Mashino et al. have measured kinetic rate constants for the vapor phase reaction of the chemically very similar perfluoromethyl vinyl ether with OH. [4] 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 theknown lifetime of methyl chloroform. This approach gives an atmospheric lifetime of perf luoromethyl vinyl ether with respect to reaction with OH of 0.023 years (8 days). Thus the lifetime of 8.077 days obtained for perfluoropropyl vinyl ether using AOPWIN is reasonable. I nfrared cross

- sections of perfluoropropyl vinyl ether were obtained us ing ab initio quantum chemical methods recommended in the peer

- reviewed scientific literature. [5

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

- year integration time horizon was established.

The methods u sed 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 atmospheric lifetime

w as 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 substance to greenhou se forcing.

Based on this publication in the peer

- reviewed literature , DuPont requests that a provisional GWP of 3 be assigned for perfluoropropyl vinyl ether

.

1. "Mandatory Reporting of Greenhouse Gases: Additional Sources of Fluori nated 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. EPI Suite TM v4.10 , EPA Office of Pollution Prevention & Toxics and Syr acuse Research Corporation (2000

- 2008). 4. Mashino, M., et al., Atmospheric Degradation of CF3OCFCF2: Kinetics and Mechanism of Its Reaction with OH Radicals and Cl Atoms. The Journal of Physical Chemistry A, 2000. 104 (13): p. 2925

- 2930. 5. Blowers, P. and K. Hollingshead, Estimations of Global Warming Potentials from Computational 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. 6. H alls, M.D. and H.B. Schlegel, Comparison of the performance of local, gradient

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

- 10593. 7. Pinnock, S., et al., Radiative forcing of climate by hydrochlorofluorocarbons and hydrofluorocarbons. Journal of Geophysical Research, 1995. 100 (D11): p. 23227

- 23238.