Formation of Organic Acids and Carbonyl Compounds in n ‐Butane Oxidation via γ‐Ketohydroperoxide Decomposition

Denisia Popolan-Vaida (1) , Arkke Eskola (2) , Brandon Rotavera (3) , Jessica Lockyear , Zhandong Wang , S. Mani Sarathy , Rebecca Caravan , Judit Zádor , Leonid Sheps , Arnas Lucassen , Kai Moshammer , Philippe Dagaut (4) , David Osborn , Nils Hansen , Stephen Leone , Craig Taatjes

1 UCF - University of Central Florida [Orlando]
2 Helsingin yliopisto = Helsingfors universitet = University of Helsinki
3 University of Georgia [USA]
4 ICARE - Institut de Combustion, Aérothermique, Réactivité et Environnement

A crucial chain-branching step in autoignition is the decomposition of ketohydroperoxides (KHP) to form an oxy radical and OH. Other pathways compete with chain-branching, such as “Korcek” dissociation of γ-KHP to a carbonyl and an acid. Here we characterize the formation of a γ-KHP and its decomposition to formic acid+acetone products from observations of n-butane oxidation in two complementary experiments. In jet-stirred reactor measurements, KHP is observed above 590 K. The KHP concentration decreases with increasing temperature, whereas formic acid and acetone products increase. Observation of characteristic isotopologs acetone-d3 and formic acid-d0 in the oxidation of CH3CD2CD2CH3 is consistent with a Korcek mechanism. In laser-initiated oxidation experiments of n-butane, formic acid and acetone are produced on the timescale of KHP removal. Modelling the time-resolved production of formic acid provides an estimated upper limit of 2 s−1 for the rate coefficient of KHP decomposition to formic acid+acetone.

Mots clés: hydrocarbon oxidation; Butane; Autoignition; Ketohydroperoxides; Photoionization mass spectrometer; Synchrotron; Jet-stirred reactor; Mass spectrometry

Domaines: Milieux fluides et réactifs

Denisia Popolan-Vaida, Arkke Eskola, Brandon Rotavera, Jessica Lockyear, Zhandong Wang, et al.. Formation of Organic Acids and Carbonyl Compounds in n ‐Butane Oxidation via γ‐Ketohydroperoxide Decomposition. Angewandte Chemie International Edition, 2022, 61 (42), pp.9168. ⟨10.1002/anie.202209168⟩. ⟨hal-03783203⟩