Kinetics and modeling of the thermal reaction of propene at 800 K. Part iii. Propene in the presence of small amounts of oxygen

Abstract

The thermal reaction of propene was examined around in the presence of 800 K less than 20% oxygen. At initial time, the production of H 2 , CH 4 , C 2 H 4 , C 2 H 6 , allene, C 3 H 8 , 1,3-butadiene, butenes, 3-and 4-methylcyclopentene, a mixture of 1,4-and 1,5-hexadienes, methylcyclopentane (or dimethylcyclobutane), 4-methylpent-1-ene, and hex-1-ene, was observed along with hydrogen peroxide, CO, and small quantities of ethanal and CO 2 . Oxygen increases the initial production of hydrogen and of most hydrocarbons and, particularly, that of C 6 dienes and of cyclenes. However, the production of allene, methylcyclopentane (or dimethylcyclobutane), and 4-methylpent-1-ene is practically not affected. A kinetic study confirms the mechanism proposed for the thermal reaction of propene. Formation of allene, thus, involves a four-center-unimolecular dehydrogenation of propene, that of 4-methylpent-1-ene is explained by an ene bimolecular reaction while methylcyclopentane (or dimethylcyclobutane) probably arises from a bimolecular process involving a biradical intermediate. Other products arise from a conventional chain radical mechanism.A kinetic scheme is proposed in which chains are primarily initiated by the bimolecular step:which competes with the second-order initiation of propene pyrolysis. Since allene production is not affected by oxygen, it is concluded that allyl radicals are not dehydrogenated by oxygen; but they oxidize in a branching step involving allylperoxyl radicals; r. radicals other than methyl, and allyl are dehydrogenated according to the conventional process:r· ϩ O !: unsaturated ϩ HO · 2 2

Direct H abstraction by molecular oxygen from unsaturated C3–C5 hydrocarbons: A theoretical study

“…al. 40 and Stothard and Walker, 41 and the recommendation 42 The present results computed with the UCCSD(T)-F12 energies closely agree with the previous ones. At 800 K, our calculations underestimate the experimental rate constants by 9-12%, whereas the difference is somewhat larger at 700 K, 71%.…”

Quantum Chemical Molecular Dynamics Simulations of 1,3-Dichloropropene Combustion

“…Although this reaction is endothermic (ΔH(G3MP2B3) = 30.3 kJ/mol), the same initiation reaction mechanism has been observed for non-chlorinated analogues. 54,55,59 Kinetic parameters for this process for a temperature range of 300−3000 K, provided in Table 1, are also consistent with experimental and theoretical results for the analogous H abstraction in propene (A = 3.2 × 10 −12 cm 3 mol −1 s −1 ; E a = 164 kJ/mol) between 600 and 1000 K. 58,75 1,3dichloropropene-1-peroxol is formed via radical recombination of the derived radical intermediate and HO 2 . We note that unimolecular C−Cl bond scission at the allylic carbon atom is more kinetically favorable compared with allylic H abstraction, and this is consistent with observations made for many QM/ MD trajectories calculated in this work.…”

A chemical kinetic perspective on the low-temperature oxidation of propane/propene mixtures through experiments and kinetic analyses

“…The formation of the allyl radicals through H-atom abstraction from propene by molecular oxygen has been optimized. The reaction rate from Zhou et al [49] matches the experimental measurements from Stothard et al [50] and Barbe et al [51] in the temperature range from 600-900 K (Fig. 5(a)).…”