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Probing QOOH-Mediated Reactions in Cyclohexene Oxidation using Photoionization Mass Spectrometry

Alanna Koritzke
Alanna Koritzke
Department of Chemistry
University of Georgia
Chemistry Building, Room 400
Analytical Seminar

Combustion research aims to produce fundamental science that enables the development of advanced technologies for cleaner-burning and more-efficient energy conversion, including next-generation internal combustion engines. One primary target is understanding complex chemistry at low-temperature oxidation conditions (< 1200 K) where the formation of NOx is avoided. The chemistry at lower temperature is driven by organic peroxy radicals (ROO), for which isomerization into carbon-centered hydroperoxyalkyls radicals (QOOH) is a critical reaction step. Our role is to investigate reaction mechanisms and probe QOOH chemistry at low-temperature oxidation conditions.

Multiplexed photoionization mass spectrometry (MPIMS) was utilized in the present work to examine reaction mechanisms of QOOH radicals derived from cyclohexene, a primary intermediate formed in cyclohexane oxidation. The goal was to assess the influence of a single C=C bond in a cyclic hydrocarbon on reactions relevant to low-temperature oxidation and chain-branching. The experiments were conducted using Cl-initiated oxidation at 10 Torr and from 500 to 700 K. The results confirm that cyclohexene undergoes complex QOOH-mediated chemistry [1] involving radical ring-opening and ketohydroperoxide formation, which are facilitated by resonance-stabilization. The reactions discovered from these experiments provide more rigorous targets for numerical chemical kinetics modeling.

This seminar will cover the functional details of the MPIMS instrument, including the photolysis technique, photoionization source, and mass detector. Additionally, I will explain the unique types of data the experiment produces and what information can be extracted. Further, I will discuss how this data is used to produce fundamental insight that enables an understanding of reaction mechanisms of peroxy radicals.

 

[1] A Koritzke, J. Davis, R.L Caravan, D.L. Osborn, C.A. Taatjes, B. Rotavera, Proceedings of the Combustion Institute, 2017, in press.

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