Direct Observation of the Ethyl Radical in the Pyrolysis of Ethane

Abstract

We report the first direct detection of ethyl radical in the pyrolysis of ethane. Observation of this vital intermediate was made possible in this extremely reactive environment by the use of a microreactor coupled with synchrotron radiation and photoelectron photoion coincidence (PEPICO) spectroscopy, despite its short lifetime and low concentration. Together with ab‐initio master equation‐calculated rates and fully coupled computational fluid dynamics simulations, our measurements show that even under the low pressures and short residence times in our experiment, ethyl formation can only be explained by bimolecular reactions; the most important is the catalytic attack of ethane by H atoms, which are then regenerated by decomposition of the nascent ethyl radicals. Our results complete the observation of all hypothesized intermediates in this industrially important process and highlight the need for further studies under additional conditions using similar methods to improve existing models and optimize process chemistries.

The elusive phenylethynyl radical and its cation: synthesis, electronic structure, and reactivity

“…33 This suite of techniques 34 allows to unravel reaction mechanisms relevant in combustion, 35,36 astrochemistry 37–39 and catalysis. 40,41 In addition, experimental vibrational information of the ground and excited states, and in some cases the singlet–triplet energy splitting (Δ E ST ), has been obtained for the ethyl, 42 vinyl, 43 phenyl, 44 and benzyl cations. 45 In particular, the ethynyl cation in its triplet ground state was unveiled via direct photoionization of the ethynyl radical.…”