Toward Improved Exhaust Emission Control of Stoichiometric Engines by Intentional Oxygen Dithering

Methane emissions from the exhaust gas of stoichiometric engines can be efficiently controlled by means of three-way catalysts. In this work, we show how the activity of a fully formulated commercial three-way catalyst can be significantly enhanced by periodically varying the oxygen concentration in the feed between lean and rich phases. We also show that this pulse-based approach is valid on the same catalyst not only at the lab scale on a dedicated reactor enabling fast and controlled changes of feed but especially on an engine, demonstrating the potential for practical applications. Pd-only catalyst compositions with different oxygen storage capacity components require targeted pulse adjustments to reflect the different extent of influence on the chemistry involved in methane and nitric oxide conversion under different reaction conditions.