Propane dissociation in a non-thermal high-pressure nitrogen plasma

Abstract

Abstract. The removal and the conversion processes of propane in N 2 /C 3 H 8 mixtures (concentration of hydrocarbon molecules up to 5500 ppm) energised by a photo-triggered discharge (homogeneous plasma) are studied at 460 mbar total pressure, both experimentally and theoretically. A self-consistent 0D discharge and kinetic model is used to interpret chromatographic measurements of propane and some by-products concentrations (hydrogen and hydrocarbons with 2 or 3 carbon atoms). It is suggested, from the comparison between measurements and model predictions, that quenching processes of nitrogen metastable states by C 3 H 8 lead to the dissociation of the hydrocarbon molecule, and are the most important processes for the removal of propane. Such a result is obtained using the quenching coefficient value previously determined by Callear and Wood for the A 3 Σ + u state [19], whereas the coefficient for collisions of the singlet states with C 3 H 8 is estimated to be 3.0x10 -10 cm 3 s -1 in order to explain the measured propane disappearance in the N 2 / C 3 H 8 mixture excited by the photo-triggered discharge. The hydrogen molecule is the measured most populated by-product and, also from the comparison between experimental results and model predictions, the most probable dissociation products of propane appear to be H 2 and C 3 H 6 . The propene molecule is also efficiently dissociated by quenching processes of N 2 states, and probably leads to the production of hydrogen atoms and methyl radicals with equivalent probabilities. The kinetic model predicts that the carbon atom is distributed amongst numerous molecules, including HCN, CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 3 H 6 .

Catalytic Steam Reforming of Natural Gas over a New Ni Exsolved Ruddlesden‐Popper Manganite in SOFC Anode Conditions

“…In agreement with some other authors, high temperatures result in enhanced production of CH 4 , C 2 H 4 , C 2 H 6 and C 3 H 6 due to a significant thermal decomposition of C 3 H 8 , evidenced in the present study by individual experiments concerning propane steam reforming reaction (Table S4). In this case, the activation of C 3 H 8 first C−H bond is easier than for CH 4 and even than C 2 H 6 (C−H bond in CH 3 group 417 kJ mol −1 and C−H bond in CH 2 group 398 kJ mol −1 ); the dehydrogenation of these two kinds of bond is favored as well as the rupture of adsorbed C 3 radicals due to the weakness of the C−C bond (347 kJ mol −1 ), which improves the formation of methyl, ethyl, vinyl and propyl radicals occupying metallic Ni active sites and promotes the C 3 H 8 related propane cracking and the reforming reactions e. g . ESR, Et.SR, Pt.SR.…”

Fast gas heating in N 2 /O 2 mixtures under nanosecond surface dielectric barrier discharge: the effects of gas pressure and composition

“…The rates for these reactions were taken from [36]. Figure 13 compares the fractional electron power transferred to heat by 1 μs in a stoichiometric C 2 H 2 /air mixture and in air at 300 K and 1 atm versus the reduced electric field, E/N, at which the energy was deposited.…”

Oxidation of Propylene with Oxygen and Air in a Barrier Discharge in the Presence of Octane

“…Therefore, in addition to reaction (17) the electronically excited nitrogen molecules can cause dissociation of propylene molecules. Similar high-rate reactions are, for instance, described in [26].…”

“…According to [26], the CH bond energy for a secondary carbon atom of propylene (4.532 eV) is lower than that in the CH 2 -group (4.731 eV), which enables the propenoxy radical to rearrange into acetone more readily than into propanal. Indeed, the increase in the concentration of propylene gives rise to a higher selectivity towards formation of acetone and a lower selectivity towards formation of propylene oxide, while the selectivity towards formation of propanal remains largely unchanged.…”