title: Pressure-Dependent Competition among Reaction Pathways from First- and Second-O2 Additions in the Low-Temperature Oxidation of Tetrahydrofuran.
abstract: We report a combined experimental and quantum chemistry study of the initial reactions in low-temperature oxidation of tetrahydrofuran (THF). Using synchrotron-based time-resolved VUV photoionization mass spectrometry, we probe numerous transient intermediates and products at P = 10-2000 Torr and T = 400-700 K. A key reaction sequence, revealed by our experiments, is the conversion of THF-yl peroxy to hydroperoxy-THF-yl radicals (QOOH), followed by a second O2 addition and subsequent decomposition to dihydrofuranyl hydroperoxide + HO2 or to γ-butyrolactone hydroperoxide + OH. The competition between these two pathways affects the degree of radical chain-branching and is likely of central importance in modeling the autoignition of THF. We interpret our data with the aid of quantum chemical calculations of the THF-yl + O2 and QOOH + O2 potential energy surfaces. On the basis of our results, we propose a simplified THF oxidation mechanism below 700 K, which involves the competition among unimolecular decomposition and oxidation pathways of QOOH.
authors.affiliation: Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: Ivan O
authors.initials: IO
authors.lastname: Antonov
authors.affiliation: Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: Judit
authors.initials: J
authors.lastname: Zádor
authors.affiliation: Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: Brandon
authors.initials: B
authors.lastname: Rotavera
authors.affiliation: Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: Ewa
authors.initials: E
authors.lastname: Papajak
authors.affiliation: Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: David L
authors.initials: DL
authors.lastname: Osborn
authors.affiliation: Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: Craig A
authors.initials: CA
authors.lastname: Taatjes
authors.affiliation: Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: Leonid
authors.initials: L
authors.lastname: Sheps