Abstract
A thermodynamically consistent C-1 microkinetic model is developed
for methane partial oxidation and reforming and for oxygenate (methanol
and formaldehyde) decomposition on Rh via a hierarchical multiscale
methodology. Sensitivity analysis is employed to identify the important
parameters of the semiempirical unity bond index quadratic exponential
potential (UBI-QEP) method and these parameters are refined using
quantum mechanical density functional theory. With adjustment of
only two pre-exponentials in the CH4 oxidation subset, the Q mechanism
captures a multitude of catalytic partial oxidation (CPOX) and reforming
experimental data as well as thermal decomposition of methanol and
formaldehyde. We validate the microkinetic model against high-pressure,
spatially resolved CPOX experimental data. Distinct oxidation and
reforming zones are predicted to exist, in agreement with experiments,
suggesting that hydrogen is produced from reforming of methane by
H2O formed in the oxidation zone. CO is produced catalytically by
partial oxidation up to moderately high pressures, with water-gas
shift taking place in the gas-phase at sufficiently high pressures
resulting in reduction of CO selectivity.
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