A Dutch researcher takes a closer look on the new type of catalytic converter found in cars. The NOx Storage Reduction (NSR) catalytic converter the fuel is alternately combusted in the engine under oxygen-rich (lean) and fuel-rich (rich) conditions. Such diesel engines and ‘lean-burn’ petrol engines are more economical than conventional engines.

Vehicles with diesel and lean-burn petrol engines produce exhaust fumes that are particularly rich in oxygen and therefore the conventional three-way catalytic converter is not suitable for converting the generated NOx into nitrogen. The current trend is therefore to add specific components such as barium to the catalytic converter to store the NOx formed.

In this new type of NOx Storage Reduction (NSR) catalytic converter the diesel or petrol combustion in the engine takes place alternately over long oxygen-rich and short fuel-rich periods. During a long oxygen-rich period the generated NOx is stored in the barium component. When this component becomes saturated the catalyst is regenerated. This happens during the short fuel-rich period when an oxygen-poor emission gas is produced. The NOx stored is released and subsequently reduced to nitrogen over a precious metal such as platinum.

The researcher carried out experiments in a laboratory reactor containing the NSR catalyst. She studied the behavior of the catalyst, like the effect of the various forms in which barium occurs in the catalytic converter, the effect of the presence of carbon dioxide and water in the exhaust gas, and the effect of the various reducing agents, such as carbon monoxide, hydrogen, and ethylene on the NOx storage and reduction. The research has yielded important new insights with respect to the function of various components in the catalytic converter.

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