A mechanistic and kinetic study on the decomposition of morpholine

J Phys Chem A. 2012 Jul 26;116(29):7703-11. doi: 10.1021/jp303463j. Epub 2012 Jul 11.

Abstract

The combustion chemistry of morpholine (C(4)H(8)ONH) has been experimentally investigated recently as a representative model compound for O- and N-containing structural entities in biomass. Detailed profiles of species indicate the self-breakdown reactions prevailing over oxidative decomposition reactions. In this study, we derive thermodynamic and kinetic properties pertinent to all plausible reactions involved in the self-decomposition of morpholine and its derived morphyl radicals as a crucial task in the development of comprehensive combustion mechanism. Potential energy surfaces have been mapped out for the decomposition of morpholine and the three morphyl radicals. RRKM-based calculations predict the self-decomposition of morpholine to be dominated by 1,3-intramolecular hydrogen shift into the NH group at all temperatures and pressures. Self-decomposition of morpholine is shown to provide pathways for the formation of the experimentally detected products such as ethenol and ethenamine. Energetic requirements of all self-decomposition of morphyl radicals are predicted to be of modest values (i.e., 20-40 kcal/mol) which in turn support the occurrence of breaking-down reactions into two-heavy-atom species and the generation of doubly unsaturated four-heavy-atom segments. Calculated thermochemical parameters (in terms of standard enthalpies of formation, standard entropies, and heat capacities) and kinetic parameters (in terms of reaction rate constants at a high pressure limit) should be instrumental in building a robust kinetic model for the oxidation of morpholine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomass
  • Biomimetic Materials / chemistry*
  • Free Radicals / chemistry
  • Hydrogen / chemistry*
  • Kinetics
  • Models, Molecular
  • Morpholines / chemistry*
  • Nitrogen / chemistry*
  • Oxidation-Reduction
  • Pressure
  • Quantum Theory
  • Temperature
  • Thermodynamics

Substances

  • Free Radicals
  • Morpholines
  • Hydrogen
  • morpholine
  • Nitrogen