### R equest to Use a n Alternate GWP for 3,3,3
- trifluoropropene (CAS Number: 677
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- 4 ) 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 - e quivalent 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 emissions 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 th ese 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 evidence exi sts to support such a lower value.
Table A

– 1 does not list a GWP for 3,3,3

- trifluoropropene

. 3,3,3

- trifluoropropene is a s hort

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

- reviewed scientific literature has established that the GWP s of fluorinated alkenes are modest . Kinetic rate constants for the atmospheric degradation of 3,3,3

- trifluoropropene have been measured in an environmental chamber; the atmospheric life time of 3,3,3

- trifluoropropene has been estimated as 7 days; the infrared spectrum of 3,3,3

- trifluoropropene has been accurately measured and the GWP of 3,3,3

- trifluoropropene 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 3,3,3
- trifluoropropene
. Evidence Supporting Request :
F

- GHG Identity : 3,3,3

- trifluoropropene Chemical Formula : C 2 H 3 F 3 CAS Number: 677

- 21

- 4
Estimated GWP: 3 relative to CO 2 with a 100

- year i ntegration time horizon Data and analysis: Andersen et al. have measured kinetic rate constants for the vapor phase reaction of 3,3,3

- trifluoropropene with OH and O 3 . [3] OH and O 3 radicals react with 3,3,3

- trifluoropropene with rate constants of (1.36 ± 0.25) × 10 −12 cm 3 molecule −1
s −1 and (3.5 ± 0.3) × 10 −19 cm 3 molecule −1 s −1
, respectively i n 700 Torr of N 2 or N 2 /O 2 , diluent at 296 K

. Using a global weighted

- average OH concentration of 1.0 × 10 6 molecule cm −3 leads to an estimated lifetime of 3,3,3

- trifluoroprop ene with respect to reaction with OH radicals of 8.5 days. [4] The global background concentration of O 3 is approximately 35 ppb which leads to an estimated lifetime of 38.4 days. [5] Thus, the o verall global and yearly averaged lifetime of 3,3,3

- trifluoropropene is expected to be 7.0 days with removal occurring approximately 8 0% via reaction with OH and 2 0% viareaction with O 3 . I nfrared cross

- sections of 3,3,3

- trifluoropropene were obtained usi ng ab initio quantum chemical methods recommended in the peer

- reviewed scientific literature. [6

- 7] R adiative forcing calculations were performed using the approximation method developed by Pinnock et al. [8] A GWP 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 identi cal 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 was determined; (2) the infrared absorption spectrum of t he 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 greenhouse forcing.
Based on this publication in the peer
- revi ewed literature , DuPont requests that a provisional GWP of 3 be assigned for 3,3,3
- trifluoropropene
. 1. "Mandatory Reporting of Greenhouse Gases: Additional Sources 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. Andersen, M.P.S., et al., Atmospheric chemistry of C x F 2x+1 CH=CH 2 (x=1, 2, 4, 6, and 8): Kinetics of gas

- phase reactions with Cl ato ms, OH radicals, and O 3 . Journal of Photochemistry and Photobiology, A: Chemistry, 2005. 176 (1

- 3): p. 124

- 128. 4. Prinn, R.G., et al., Evidence for Substantial Variations of Atmospheric Hydroxyl Radicals in the Past Two Decades. Science, 2001. 292 (5523): p . 1882

- 1888. 5. Finlayson

- Pitts, B.J., Pitts, James N., Atmospheric chemistry : fundamentals and experimental techniques . 1986, New York: John Wiley & Sons. 6. Blowers, P. and K. Hollingshead, Estimations of Global Warming Potentials from Computational Che mistry 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, gradient

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

- 10593. 8. Pinnock, S., et al., Radiative forcing of climate by hydrochlorofluorocarbons and hydrofluorocarbons. Journal of Geophysical Research, 1995. 100 (D11): p. 23227

- 23238.