Reaction Pathways and Site Requirements for the Activation and Chemical Conversion of Methane on Ru−Based Catalysts

Abstract

Kinetic and isotopic tracer and exchange measurements were used to determine the identity and reversibility of elementary steps required for CH4 reforming reactions on Ru-based catalyst. These studies provide a simple mechanistic picture and a unifying kinetic treatment for CH4/CO2 and CH4/H2O reforming reactions and CH4 decomposition. Forward kinetic rates were measured from net rates by correcting for the approach to equilibrium, after ruling out transport artifacts using pellet and bed dilution tests. The kinetic processes involved are exclusively limited by C−H bond activation, and CH4 reaction rates are unaffected by the identity or the concentration of co-reactants (H2O, CO2). Similar normal kinetic isotopic effects (kC-H/kC-D = 1.40−1.51) were measured for CO2 reforming, H2O reforming, and CH4 decomposition, consistent with kinetically relevant C−H bond activation steps. The ratio of CH4/CD4 cross-exchange to methane chemical conversion rates during the reaction of CO2 reforming with CH4−CD4 mixtur...