Ignition of the butene isomers: An experimental and kinetics study

X. L. Zheng, H. Y. Sun, Chung King Law

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

There is considerable interest to understand the influence of the molecular structure on the ignition of alkenes, particularly that of the position of the double bond. The present study selected the smallest set of the alkene isomers, namely the butene isomers, and determined their ignition temperatures under identical experimental conditions. Specifically, experiments were conducted in a counterflow with heated air impinging onto the fuel flow consisting of nitrogen-diluted butene isomers for various strain rates and system pressures up to 5 atmospheres. The relative order of ignitability is that 1- butene is the easiest, cis- and trans-2-butenes are similar, and isobutene is the hardest. To further understand the observed trend, kinetic analysis on three reaction paths important for ignition was performed using enthalpies calculated by the ab initio CBS-QB3 method. One is the chain initiation by O2 abstraction, i.e., C4H8 + O2= C4H7 + HO2, and the calculated reaction rate constants for different isomers exhibit a similar trend as that of the experiment. This trend is consistent with the bond strength of the allylic C-H bond and the number of equivalent H atoms in the different isomers. The calculated rate constants for the second reaction path, HO2 addition to the double bond, show the opposite trend with the experiment. This could be ascribed to the formation of oxiranes from the butene-OH adduct, which converts fuel to stable species and therefore inhibits ignition. The third reaction path is the OH addition and subsequent O2 addition followed by intramolecular H transfer. Four butenes isomers were found to be similar in both the well depth and the rate constants for the isomerization.

Original languageEnglish (US)
Title of host publicationFall Technical Meeting of the Western States Section of the Combustion Institute 2005, WSS/CI 2005 Fall Meeting
PublisherWestern States Section/Combustion Institute
Pages106-126
Number of pages21
ISBN (Electronic)9781617827921
StatePublished - Jan 1 2005
EventFall Technical Meeting of the Western States Section of the Combustion Institute 2005, WSS/CI 2005 - Stanford, United States
Duration: Oct 17 2005Oct 18 2005

Publication series

NameFall Technical Meeting of the Western States Section of the Combustion Institute 2005, WSS/CI 2005 Fall Meeting
Volume1

Other

OtherFall Technical Meeting of the Western States Section of the Combustion Institute 2005, WSS/CI 2005
CountryUnited States
CityStanford
Period10/17/0510/18/05

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Physical and Theoretical Chemistry
  • Mechanical Engineering

Keywords

  • Butene isomers
  • H abstraction
  • HO addition
  • Ignition temperature

Fingerprint Dive into the research topics of 'Ignition of the butene isomers: An experimental and kinetics study'. Together they form a unique fingerprint.

  • Cite this

    Zheng, X. L., Sun, H. Y., & Law, C. K. (2005). Ignition of the butene isomers: An experimental and kinetics study. In Fall Technical Meeting of the Western States Section of the Combustion Institute 2005, WSS/CI 2005 Fall Meeting (pp. 106-126). (Fall Technical Meeting of the Western States Section of the Combustion Institute 2005, WSS/CI 2005 Fall Meeting; Vol. 1). Western States Section/Combustion Institute.