Low-Temperature Oxidation Reaction Processes of Cyclopentanone Unraveled by In Situ Mass Spectrometry and Theoretical Study

Although cyclopentanone (CPO) is a promising bio-derivedfuel,thermodynamic data of its low-temperature oxidation under high-pressureconditions are lacking. In this work, the low-temperature oxidationmechanism of CPO is investigated in a flow reactor in the temperaturerange of 500-800 K and at a total pressure of 3 atm by a molecularbeam sampling vacuum ultraviolet photoionization time-of-flight massspectrometer. The electronic structure and pressure-dependent kineticcalculations are carried out at the UCCSD(T)-F12a/aug-cc-pVDZ//B3LYP/6-31+G(d,p)level to explore the combustion mechanism of CPO. Experimental andtheoretical observations showed that the dominant product channelin the reaction of CPO radicals with O-2 is HO2 elimination, yielding 2-cyclopentenone. The hydroperoxyalkyl radical((center dot)QOOH) generated by 1,5-H-shifting is easily reactedwith second O-2 and forms ketohydroperoxide (KHP) intermediates.Unfortunately, the third O-2 addition products are not detected.In addition, the decomposition pathways of KHP during the low-temperatureoxidation of CPO are further assessed, and the unimolecular dissociationpathways of CPO radicals are confirmed. The results of this studycan be used for future research on the kinetic combustion mechanismsof CPO under high pressure.