FY2010 - Oak Ridge National Laboratory

Director’s R&D Fund—
Systems Biology and the Environment
enhances yield and selectivity, although the origin of this enhancement is unclear. By understanding and
controlling confinement effects, significant advances could be made in ethanol formation and other
reactions such as Fischer-Tropsch synthesis and formation of longer chain alcohols. The overarching goal
of this project is to understand and control the confinement effects on catalysis by transition-metal
nanoclusters confined in porous supports. We will pursue three specific aims. First, how can we achieve
and control the confinement where the monodisperse catalytic particles are confined in a well-defined
porous environment? Second, how does the confinement by the porosity of the support affect activity and
selectivity of the metal nanoclusters to catalytically convert syngas to ethanol? Third, how can we control
the catalyst’s performance to achieve desirable targets of activity and selectivity of syngas to ethanol?
The knowledge generated from this project will help achieve high-yield ethanol formation from syngas
and benefit other energy-relevant reactions, thereby attracting applied funding sources such as the DOE
Office of Energy Efficiency and Renewable Energy (EERE) Biomass Program and the joint DOE–U.S.
Department of Agriculture (USDA) program on biofuels.
Mission Relevance
Catalysis is core to DOE’s missions. The proof-of-principle study of this project could potentially attract
future funding from DOE’s highly successful catalysis program. The novel method to prepare the support
and the confinement effect by the hybrid support will increase the knowledge base of heterogeneous
catalysis for studying other energy-relevant reactions such as Fischer-Tropsch synthesis and the formation
of longer chain alcohols. Therefore, this project will position us to attract new funding from DOE such as
EERE’s Biomass Program. For example, President Barack Obama announced on May 5 that DOE plans
to invest $786.5 million in American Resource and Recovery Act Funds in biofuels, including
$130 million in biofuels research and development. Moreover, several funding agencies have current and
future programs to fund biofuels research. For example, USDA has a joint program with DOE to fund
biofuels research (Biomass Research and Development Initiative, DE-PS36-09GO99016, issued on
1/30/2009; program funding: $25 million). The catalyst developed in this project is promising for the
thermochemical route of converting biomass-derived syngas to ethanol, thereby benefiting this program.
Results and Accomplishments
The deliverable for the first year was a reliable protocol to load rhodium nanoparticles into the carbon
support. We met this goal by testing various conditions to load rhodium nanoparticles into nanopores of
mesoporous carbons, which we have in great quantity. The final sample was characterized by a
combination of secondary electron (SE), bright field transmission electron, and high-angle annular dark
field images (z-contrast). The results showed that we achieved the goal of loading rhodium nanoparticles
inside the channels. On average, rhodium particle size is 2 ~ 4 nm. With this gained experience, we
started making zeolitic carbons by depositing carbon-forming precursors (cations of special ionic liquids)
into the cages and channels of a crystalline inorganic zeolite, NaX. We used two salts for the ion
exchange process. Followed by filtration, washing, drying, and carbonization at 800°C, the zeolitc carbon
was obtained. We then analyzed the carbon content in the two zeolitic carbons by performing
thermogravimetric analysis (TGA) in air to oxidize the carbon. We found that carbon was successfully
formed in both samples. The deliverable for the first year for our computational effort was a basic
understanding of the reaction mechanisms of syngas-to-alcohol catalyzed by rhodium. We met this goal
in the sense that we focused on the key reaction steps, since the complete reaction network is rather
complicated. By using supercomputers, we first determined the reaction path of the CO dissociation step
on a model rhodium nanoparticle surface. We found a quite large barrier (53 kcal/mol), indicating the
difficulty for pure rhodium to activate CO and the necessity of adding promoter elements. We applied a
monolayer of manganese atoms on the rhodium surface and found that the barrier for CO dissociation is
dramatically reduced to 25 kcal/mol. This implies to our experimental effort that coating a layer of
manganese atoms on the rhodium particles may greatly help CO conversion and oxygenate selectivity.
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