Abstract
The water-gas shift (WGS) is an essential process in hydrogen production
from hydrocarbon and biomass fuel processing. Recently, it was shown
that the chemistry of the WGS reaction on Pt is complex and depends
critically on the oxidation of CO by adsorbed OH and H2O, mainly
via the carboxyl intermediate A.B. Mhadeshwar, D.G. Vlachos, J.
Phys. Chem. B 108 (2004) 15246. On the other hand, previous one-step
rate expressions in the literature have described experimental data
reasonably well. Here, starting from a comprehensive microkinetic
model, we derive a reduced microkinetic model consisting of elementary
reaction steps using principal component analysis and then develop
a one-step rate expression for WGS on Pt using a posteriori analysis.
It is shown that the rate-determining step of WGS on Pt is the oxidation
of CO by H2O, but the effective reaction rate constant and reaction
orders are concentration dependent. Finally, the effect of uncertainty
in reaction rate constants on the rate-determining step is discussed.
(c) 2005 Elsevier B.V. All rights reserved.
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