What do you do when the oil runs out? You make it!

It's all about the very large and the very small.

Schematic representation of restructuring of α-Fe2O3 precursor

Schematic representation of restructuring of α-Fe2O3 precursor in the INS experiments on continuing exposure to a CO/ H2 mixture at elevated temperature. The reaction coordinate, η, increases from left to right of the figure. The colour scheme is as follows; chequered - α-Fe2O3, orange – Fe3O4, blue – iron carbide, black – hydrocarbonaceous overlayer, grey – amorphous carbon. Roman numerals indicate stages of the catalysts conditioning process [2].
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Neutrons have been used to understand Fischer-Tropsch chemistry, an industrial process for generating gasoline and diesel from a variety of carbon sources.

Syngas (or synthesis gas) is a mixture of carbon monoxide and hydrogen, which can be converted into clean gasoline and diesel by a process called Fischer-Tropsch catalysis.  Importantly the carbon monoxide can come from any carbon source including biomass, coal and methane, so the process is very flexible.  Sasol are pioneers and world leaders in this technology and their manufacturing plants in South Africa produce millions of litres of fuel a day, supplying about a third of the national demand.  This massive scale of production relies on mastery of materials at the nanoscale.  Scientists have been using ISIS to study Fischer-Tropsch catalysis at this molecular level, in order to better understand this vital process.  The work was done in collaboration with Sasol Technology UK Ltd. and Glasgow University.

At the heart of the process is a catalyst, and iron-based catalysts are often used as iron is widely available.  In the reactor the iron-based catalyst precursor transforms to the active catalyst in a highly complex system (see Figure 1). Amorphous carbon, metallic iron and carbides are all present, as well as a layer of hydrocarbon, and the role each plays in the catalysis process is believed to be critical.

The group first used the TOSCA instrument at ISIS to study samples from a working plant in South Africa to investigate the nature of the surface hydrocarbon layer [1].  This is very difficult to study by conventional methods, but is possible with neutron spectroscopy, which is able to characterise hydrogen-containing species.  This is the first time the technique has been used to examine the Fischer-Tropsch process on a real industrial catalyst [1].  Follow-up work has examined how the iron-based catalysts respond to different reaction conditions [2]. 

Sara Fletcher

Research date: April 2014

Further Information

References

[1]        Vibrational Analysis of an Industrial Fe-based Fischer-Tropsch Catalyst Employing Inelastic Neutron Scattering, N.G. Hamilton, I.P. Silverwood, R. Warringham, J. Kapitán, L. Hecht, P.B. Webb, R.P. Tooze, S.F. Parker and D. Lennon, Angewandte Chemie International Edition, 52 (2013) 5608-5611.

[2]          The application of inelastic neutron scattering to investigate CO hydrogenation over an iron Fischer-Tropsch synthesis catalyst, N.G. Hamilton, R. Warringham, I.P. Silverwood, J. Kapitán, L. Hecht, P.B. Webb, R.P. Tooze, W. Zhou, C.D. Frost, S.F. Parker and D. Lennon, Journal of Catalysis, 312 (2014) 221-231.

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