Researchers at the Massachusetts Institute of Technology affiliated to the Laboratory for Energy and the Environment are using atomic-level information to work out how sulphur in engine exhaust damages advanced catalytic converters.

Principal investigator Bernhardt Trout said 'removing sulphur from fuel is difficult and costly, so we need to develop a sulphur-resistant catalytic converter that will work with the lean-running engines now being designed.

'Lean-running engines operate with excess air and are highly efficient, which means low fuel consumption and low emissions.'

In particular, the scientists are looking at ways to protect one highly advanced converter, which uses a platinum catalyst to convert carbon monoxide and hydrocarbons in exhaust to water, and traps nitrogen oxides in a barium oxide 'trap'.

The presence of excess oxygen allows sulphur dioxide in the exhaust to react with the platinum and turn into sulphur trioxide, which then coats the barium oxide trap and prevents the converter from working.

'Our goal is to stop the reactions that turn sulphur dioxide to sulphur trioxide', said Dr Trout, 'but without interfering with the reactions that clean up carbon monoxide and hydrocarbons.

'That's challenging because all of those reactions involve the same process - adding an oxygen atom to an existing molecule.'

'Trial and error' experimentation is unlikely to produce a way of performing this selective oxidation, so the researchers are using quantum mechanical calculations and supercomputers.

The team has produced a series of pictures showing the formation of sulphur trioxide, and are now occupied with a means of predicting how sulphur and oxygen metals will move and react to each other, in a bid to prevent the formation of sulphur trioxide.