2024 AIChE Annual Meeting

(110g) The Role of Radical Reactions in the Chemistry of Small Hydrofluorocarbons

Authors

Sivaramakrishnan, R. - Presenter, Argonne National Laboratory
Jasper, A., Argonne National Laboratory
Tranter, R. S., Chemistry Division, Argonne National Laboratory
Hydrofluorocarbons (HFC’s) represent an important class of molecules that find widespread usage in numerous industrial sectors ranging from polymers to refrigeration. The kinetics of these halogenated molecules received a lot of attention (primarily from experiments) in the latter half of the last century [1] with the predominant driver for these fundamental kinetics studies initiated by ozone depletion concerns in the earth’s stratosphere. In recent years, global warming concerns from HFC emissions have prompted renewed interest in understanding the kinetics of these molecules.

In recent work on CH2F2 dissociation [2], we have shown that prior literature studies [3,4] have ignored the formation of radical pathways from the self-reaction of the CHF radicals which is the main product from the thermal initiation process in this widely used HFC refrigerant. These radical pathways were shown [2] to influence interpretations of the literature initiation kinetics and subsequent product formation in CH2F2 dissociation as well as flammability in CH2F2/air mixtures. Radical driven reactions play a prominent role in the chemistry of complex systems and here we characterize the self/cross reactions of fluorinated methyl/methylene radicals and reactions between them. Lastly, we also explore the potential influence of radical driven reactions currently not considered in existing detailed kinetics models [5] for describing the flammability of small HFC molecules.

References

  1. NIST Chemical Kinetics Database, https://kinetics.nist.gov/.
  2. R. A. Shaik, A. W. Jasper, P. T. Lynch, R. Sivaramakrishnan, R. S. Tranter, In Review, ChemPhysChem, 2024.
  3. C. J. Cobos, K. Hintzer, L. Solter, E. Tellbach, A. Thaler, J. Troe, J. Phys. Chem. A 2017, 121, 7813.
  4. A. Matsugi, H. Shiina, Chem. Phys. Lett. 2018, 707, 140.
  5. D. R. Burgess Jr., R. R. Burrell, V. I. Babushok, J. A. Manion, M. J. Hegetschweiler, G. T. Linteris, Combust. & Flame 2022, 236, 111795.