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The use of low-sulfur fuel is known to improve the performance of the three-way catalytic converter (TWC). However, in this work we report how low-sulfur operation of commercial TWC also favors formation of N 2 O and NH 3 as by products. We found that low-sulfur rich operation above 300°C increases the production of NH 3 , inhibiting the formation of N 2 O characteristic of high-sulfur operation. During lean operation, the production of N 2 O near the stoichiometric point is not significantly affected by the sulfur level. The large production of N 2 O observed during light-off is not affected by SO 2 when the operation is lean, but under rich conditions N 2 O is produced up to 575°C. The increased production of NH 3 and N 2 O in TWC as a result of the introduction of low-sulfur gasoline is an area that requires further analysis because of its implication upon public health in large urban settings.

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