MULTIPHOTON IONIZATION DETECTION OF METHYL RADICALS FROM CATALYTIC-OXIDATION OF METHANE

A catalytic microreactor coupled with a multiphoton ionization time-of-flight mass spectrometer (MPI TOF) is used to directly observe stable and unstable reaction products from oxidative coupling of methane. Production of gas-phase methyl radicals from 10:1 mole ratio methane/oxygen mixture over CaO/Al2O3 and 1% Sr/La2O3 catalysts as a function of temperature is studied. At low methane conversion, ethane production can be accounted for by gas-phase coupling of methyl radicals produced by the catalytic reaction. Apparent energies of activation for methyl radical production of 41.6 and 30.0 kcal/mol for CaO/Al2O3 and 1% Sr/La2O3 catalysts, respectively, were determined by Arrhenius analysis of relative methyl radical production rates measured at low methane conversion. © 1990 American Chemical Society.