CO2-reforming reactions have been studied in a plug-flow reactor with
catalysts containing less than a monolayer of Rh, Ru, or Ir deposited
from tetrametallic dodecacarbonyl clusters onto low surface area polyc
rystalline alpha-Al2O3, MgO, CeO2, La2O3, and TiO2. The catalytic reac
tions are studied in conditions at which the carbon formation quickly
deactivates Ni-based catalysts but does not deactivate noble metal bas
ed materials. Diffuse-reflectance-infrared-Fourier-transform (DRIFT) s
pectroscopy and mass spectrometry experiments inside a high-temperatur
e high-pressure (HTHP) chamber have cast light on molecular aspects of
the CO2-reforming reaction which have been embodied in a reaction mec
hanism. The formation of highly reactive oxidic species from the disso
ciation of CO2 is showed, and their role in inhibiting the production
of large carbon aggregates is discussed. (C) 1995 Academic Press, Inc.