Furan formation pathways exploration in low temperature oxidation of 1,3-butadiene, trans-2-butene, and cis-2-butene

Abstract

Furan is one of the smallest organic compounds with heterocycle ring. With this particular molecular structure, furan is considered as a highly toxic and carcinogenic combustion pollutant, and furan may contribute to the formation of oxygenated soot. In this work, furan formation pathways from 1,3-butadiene, trans-2-butene and cis-2-butene were comprehensively explored. The potential energy surfaces, reaction rate coefficients, and thermodynamics were calculated by quantum chemistry using high level of theories including the CCSD (T) and G3 methods. The proposed reaction pathways were then implemented into the AramcoMech 3.0 model uniformly or independently to examine the model performance with the experimental data. The oxidation experiments of 1,3-butadiene, trans-2-butene and cis-2-butene were performed in a jet stirred reactor (JSR) in the low temperature regime (500–830 K). The JSR is coupled with time-of-flight molecular beam mass spectrometry (ToF-MBMS) using synchrotron radiation as photon ionization source for species identification and quantification. Compared with experiments, both updated models (the independent and uniform model) showed better prediction of furan than the base AramcoMech 3.0 model, which highlighted the contribution of the proposed pathways. Reaction pathway analyses reveal that in the proposed reaction pathway, both reactions C 4 H 6 + OH ⇌ S1–4 (H 2 C CH-ĊH CH 2 OH, but‑1-en-3-yl-4-ol) and C 4 H 6 + HO 2 ⇌ C 4 H 6 1–3OOH4 (H 2 C CH-ĊH CH 2 OOH, but‑1-en-3-yl-4-peroxide) not only contribute to furan formation, but also to fuel consumption. Furthermore, the kinetic uncertainty from activation energy calculated by the CCSD series methods, CBS-ANPO, and G4 methods was evaluated for reaction C 4 H 6 + HO 2 ⇌ C 4 H 6 1–3OOH4. Instead of developing a new kinetic model, this work aims at proposing and validating new reaction pathways to advance the understanding of furan formation chemistry in low temperature oxidation, and provide guidance for future model development.