NO Adsorption and Desorption Phenomena on a Pd-exchanged Zeolite Passive NOx Adsorber
Josh Pihl, Oak Ridge National Laboratory
As combustion engine efficiency improves, exhaust temperatures will continue to decrease. In response to the difficulties of low temperature emissions control, the U.S.DRIVE government/industry partnership has issued a challenge to develop catalytic materials that can convert 90% of emissions at 150 C. While numerous efforts are underway to develop catalysts that light-off at temperatures below 150 C, trap materials, such as passive NOx adsorbers (PNAs) and hydrocarbon traps, could play a critical role in enabling high efficiency advanced combustion systems to meet emissions regulations. Since they are designed to trap regulated pollutants at low temperatures and release them at higher temperatures when conversion catalysts have lit off, modeling the performance of trap materials requires accurately capturing both storage and release processes. However, the underlying chemistry controlling the adsorption and desorption of NO on Pd-exchanged zeolite PNA materials is not well understood. This presentation will discuss work aimed at unraveling the reaction mechanisms for NO storage and release on Pd-exchanged zeolite PNAs.