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Probing Gas-Phase Pyrolysis of C2-C4 Perfluoroalkanes with Photoionization Mass Spectrometry
Satya P Joshi1, Michael Stuhr1, Ahren W Jasper1
1Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 S. Cass Ave., Lemont, Illinois60439, United States.
The Journal of Physical Chemistry. A
|July 21, 2026
Summary
This study investigated perfluoroalkane decomposition using photoionization mass spectrometry, identifying key pyrolysis products and their formation pathways. Measured appearance energies largely agree with theoretical calculations, refining kinetic models.
Area of Science:
- Chemical Kinetics
- Physical Chemistry
- Materials Science
Background:
- Perfluoroalkanes (PFAs) are widely used but their decomposition pathways are not fully understood.
- Existing kinetic models for PFA pyrolysis require experimental validation.
- Characterizing pyrolysis products is crucial for understanding PFA environmental fate and industrial applications.
Purpose of the Study:
- To experimentally investigate the gas-phase pyrolysis of C2-C4 perfluoroalkanes (PFAs).
- To identify and characterize pyrolysis products using tunable vacuum ultraviolet photoionization mass spectrometry (PIMS).
- To compare experimental appearance energies with theoretical ionization energies and refine kinetic models.
Main Methods:
- Pyrolysis of hexafluoroethane (C2F6), octafluoropropane (C3F8), and decafluorobutane (n-C4F10) in a silicon carbide microreactor.
- Analysis of pyrolysis products using tunable vacuum ultraviolet photoionization mass spectrometry (PIMS).
- Measurement of photoionization spectra and appearance energies (AEs) for observed species.
Main Results:
- First observation of parent-ion signals for C2F6, C3F8, and n-C4F10 using PIMS.
- Identified pyrolysis products including CF, CF2, CF3, C2F4, and C2F5.
- Measured AEs showed good agreement with calculated adiabatic ionization energies (IEs), despite discrepancies with some literature values.
Conclusions:
- Pyrolysis of PFAs proceeds via C-C bond cleavage for longer chains, and radical addition/decomposition for smaller fragments.
- Experimental data provides valuable insights complementing existing theoretical kinetic models for PFA decomposition.
- The study refines understanding of PFA degradation mechanisms relevant to environmental and industrial contexts.
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