Issue Date: April 14, 2008
Catalyst Architecture Revealed
Researchers have assembled the first three-dimensional experimental images of cobalt-based catalysts used in Fischer-Tropsch processes to convert synthesis gas to hydrocarbon fuels and feedstocks (J. Am. Chem. Soc., DOI: 10.1021/ja710299h). A better understanding of the architecture of such metal complexes may enable efforts to design more efficient or more specific catalysts. Led by Ilke Arslan of Sandia National Laboratories, the group used scanning transmission electron tomography to study two catalyst combinations of cobalt and rhenium: 20% Co/0.5% Re on γ-alumina and 12% Co/0.5% Re on α-alumina/nickel-aluminate. In both cases the Co was oxidized to Co3O4, which is an inactive form, but the researchers expect the overall morphology would be the same for the reduced state. In the first composition, Co3O4 fills pores in the alumina matrix by forming interlocking oxide-alumina clusters. In the second system, Co3O4 forms nanocages on the surface, enclosing the Ni-aluminate component. The authors propose that the larger exposed catalytic surface area for the second catalyst may contribute to greater selectivity for producing larger hydrocarbons.
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