Pyrolysis of n-butane investigated using synchrotron threshold photoelectron photoion coincidence spectroscopy

Abstract

We present here the coupling of a flash pyrolysis micro-reactor with threshold photoelectron photoion coincidence (TPEPICO) spectroscopy at Hefei synchrotron to investigate thermal decomposition of n-butane. Primary products in the pyrolysis were determined with TPEPICO time-of-flight mass spectra and mass-selected threshold photoelectron spectra (TPES). Vibrational structures in the TPES of the CH₃, C₂H₅ and C₃H₆ products were observed and their ionization energies were measured and compared satisfactorily to literature data. Moreover, the potential energy surface involved in the decomposition was calculated by using high-level quantum chemistry and several transition states were recognized. Then the detailed mechanisms of the pyrolysis of n-butane have been discussed and revealed.