Nanocluster catalysts aim to clean up fossil fuels

Scientists from the University of Aarhus, Denmark, have developed a technique that could improve the commercial processes used to remove environmentally harmful sulphur from fossil fuels. This is currently done using a catalyst, which binds the harmful sulphur molecules to it, in much the same way as a car’s catalytic converter works.

In a paper published today in the Institute of Physics journal Nanotechnology the Danish team explain how they have studied the chemical reactions which occur when the industrial catalyst combines with sulphur-based molecules in the oil. Until now these reactions have not been properly understood as they occur on an atomic scale. The researchers overcame this problem by making a model of the catalyst and observing these nanoscale reactions using a technique called scanning tunnelling microscopy (STM).

Dr Jeppe Lauritsen, a member of the research team from the University of Aarhus, said: “Throughout the last century most catalysts have been developed by costly time-consuming trial-and-error methods. Nanotechnology is about to change this, since we can now build and view matter directly on the nanoscale.”

The commercial catalysts used to remove sulphur contain tiny metal-sulphide nanoclusters. The particular metal-suphide complex used in the team’s nanocluster model is usually fairly non-reactive. However the nanoclusters are so small that the scientists found that at the edges, the clusters behaved unexpectedly. Dr Lauritsen said: “Surprisingly, the nanocluster edges behave just like ordinary catalytically active metals. This metallic reactive behaviour is shown in the STM images as a bright brim extending around the cluster edges.”

The team’s model shows how the first and most difficult step in the catalytic process, that removes sulphur from fossil fuels, occurs. They now plan to extend their model to provide information on the rest of the process. Through their collaboration with catalyst company Haldor TopsØe A/S, the team aims to provide the basis for the manufacture of better catalysts for the production of clean transport fuels, thereby helping to solve one of our most important environmental problems.