A team of researchers led by University of Amsterdam (UvA) chemists has developed new Fischer-Tropsch catalysts—consisting of ultra-thin cobalt shells surrounding inexpensive iron oxide cores—that can be used to produce synthetic fuels from natural gas and biomass. The method used to produce the catalysts is based on an approach previously optimized for preparing magnetic tape for audio cassettes in the 1960s.
France-based energy major Total, which was part of the research team, has patented the new catalysts and the method for their preparation, naming the UvA researchers as co-inventors. The research has just been published online as a VIP (very important paper) communication in the journal Angewandte Chemie.
The Fischer-Tropsch process is used for producing fuels from synthesis gas, which in turn is made from natural gas, biomass or coal. Large reserves of shale gas and natural gas currently changing the world energy market have increased interest in F-T technology. However, F-T reactors are huge, and typically use hundreds of tons of catalyst.
Cobalt-based catalysts are the optimal choice for synthesizing middle distillate fuels such as diesel and kerosene with F-T technology. But cobalt is also expensive. In 2009 the Total Gaz & Power company contacted the Heterogeneous Catalysis and Sustainable Chemistry group (Van ‘t Hoff Institute for Molecular Sciences) at UvA to develop a new F-T catalyst together.
Roberto Calderone, Raveendran Shiju and Gadi Rothenberg from the group took up the challenge to design a less-expensive catalyst that can be prepared on a very large scale, yet performs at least as well as pure cobalt.
To gain an economic advantage would require engineering of the particles at single-nanometer resolution, yet in a manner that can be scaled up to multi-ton scale. This rules out all chemical procedures that require high sophistication, extreme temperatures, or expensive chemicals.
The UvA team sought to meet these restraints with the surface nucleation of a cobalt phase onto iron oxide colloids. They were inspired by the method that companies such as TDK used in the 1960s for producing magnetic tapes for audio cassettes. The standard recording materials in these cassettes were polymer-based tapes containing cigar-shaped cobalt-doped iron oxide particles.
After two years of hard work they achieved a cheap, reliable, efficient and, most importantly, scalable method for synthesizing spherical core-shell catalyst particles. The particles have an average diameter of 10 nanometer (nm) and consist of a 8 nm magnetite (iron oxide) core with a cobalt oxide shell of only 1 nm.
The new catalysts were then tested in collaboration with research groups in Lille. The catalysts proved to be excellent Fischer-Tropsch catalysts, giving good diesel fractions.
V.R. Calderone, N.R. Shiju, D. Curulla Ferré, S. Chambrey, A. Khodakov, A. Rose, J. Thiessen, A. Jess and G. Rothenberg. (2013) De novo design of nanostructured iron-cobalt Fischer-Tropsch catalysts. Angew. Chem. Int. Ed. doi: 10.1002/anie.201209799