(441e) Evaluation of Rh-Pyrochlore Coated Monolith for the Reforming of Diesel Fuel

Evaluation of Rh-Pyrochlore Coated Monolith for the
Reforming of Diesel Fuel

Daniel J. Haynes¹,
David A. Berry¹, Dushyant Shekhawat¹,Mark W.
Smith^1,2, Matthew Seabaugh³

¹National Energy Technology Laboratory/US DOE, Morgantown,
WV

² URS-Washington Division, Morgantown, WV

³NexTech Materials, Lewis Center, OH

Through its Solid State Energy Conversion Alliance (SECA)
program, the U.S. Department of Energy has been in collaboration with
industrial partners to sponsor the development of solid oxide fuel cells
(SOFCs) for clean and efficient energy production from hydrocarbon-based fuels.  While the applications for fuel cells are
numerous, auxiliary power units (APUs) for long haul diesel trucks and military
vehicles have been identified as a possible entry point to introduce the
technology into the commercial market.  On-board
hydrogen production from the reforming of diesel can be used to meet the energy
requirements of the SOFC.  However, high
levels of sulfur and aromatic compounds commonly found in diesel fuel limit the
formation of synthesis gas (H₂ + CO) because they are poisons to
traditional reforming catalysts.  The
National Energy Technology Laboratory (NETL) has been developing reforming
catalysts based on the pyrochlore crystal structure (A₂B₂O₇)
to reduce deactivation.  Pyrochlore-based
catalysts are of interest primarily due to their chemical stability in high
temperature reducing and oxidizing environments.  They also possess the ability to accommodate
the substitution of a wide variety of active and promoting metals within the oxide
framework.  This distinguishes them from traditional
supported metal catalysts, which are more prone to sintering at
high-temperatures and have less control of particle size and ?next nearest-neighbor
interactions?.  Furthermore,
oxygen-conducting supports have been shown to greatly improve hydrocarbon
reforming with substituted oxide catalysts such as pyrochlores.  In particular, the rate of deactivation is
reduced by decreasing the amount of deactivating carbon formed on the
catalytically active phase through oxygen transport from the gas phase, through
the support to react with strongly adsorbed hydrocarbon species believed to be
coke precursors.  Researchers at NETL
successfully demonstrated a Rh-substituted zirconate pyrochlore catalyst
supported onto zirconium-doped ceria (ZDC) to be active and stable for the
reforming of commercial diesel fuel for 1000 hrs under oxidative steam
reforming conditions.  Following this
test, NETL has been collaborating with NexTech Materials in order to develop an
effective process to apply the optimized pyrochlore/ZDC catalyst onto a
commercially representative form such as monolith.  A square channel alumina monolith structure
coated with an oxygen-conducting support, onto which the active pyrochlore
phase was deposited, has been fabricated. 
NETL has recently completed a successful 93 hour fuel reforming testing of
the commercially representative monolith using commercial diesel fuel.  Synthesis gas yields were stable and near
those predicted by equilibrium for the 93 hours time on stream.  No indicators of catalyst degradation (olefin
formation, pressure buildup, etc.) were observed when the run was discontinued.