Researchers from MIT and the Laboratory for Energy and the Environment are using technologies at an atomic level to investigate how sulphur in vehicle emissions is causing catalytic converters to not be as good at removing noxious emissions from car engines.
The removal of sulphur from fuel is difficult and costly so it is preferential to work out how to develop a sulphur-resistant catalytic converter. The work is focussing on a catalytic converter with two components: a platinum catalyst to convert carbon monoxide and hydrocarbons in exhaust to carbon dioxide and water, and a barium oxide “trap” that captures nitrogen oxides. The converter thus controls emissions that can harm human health and contribute to the formation of smog and acid rain. The problem is that with excess oxygen present, sulphur dioxide in the exhaust reacts on the platinum catalyst to form sulphur trioxide which then coats the barium oxide trap, so it fails to work.
The goal is to stop sulphur dioxide turning to sulphur trioxide, without interfering with the reactions that clean up carbon monoxide and hydrocarbons.
By using supercomputers at the National Computational Science Alliance at the University of Illinois at Urbana-Champaign they are performing quantum mechanical calculations to determine on an atomic level the reaction process by which sulfur trioxide forms. This analysis has shown the step-by-step process whereby a single oxygen atom on a platinum surface approaches and eventually joins onto an existing sulphur dioxide molecule to form sulphur trioxide. Other calculations show the energy consumed or released at each step as chemical bonds break or form.