Approaches to low-temperature emission control using multifunctional reactor beds

Pranaw  Kunal, Oak Ridge National Laboratory

Recent automotive research has focused on increasing the overall efficiency of automobile engines while also meeting the increasingly stringent emissions standards. Thus, the automotive industry issued a 150 °C challenge, which requires > 90% conversion of criteria pollutants at low exhaust temperature that is expected with more fuel-efficient vehicles.  With current catalysts typically requiring 200 °C to light off, significant improvements in emissions control technology is needed. This project aims to address these concerns through the synthesis, characterization and evaluation of passive NOx adsorbers (PNA), hydrocarbon traps (HCT), and diesel oxidation catalysts (DOC). The evaluations were performed both on an individual basis and in combined systems.

For the PNA portion of the research, Pd/SSZ-13 was the primary focus.  It was synthesized at ORNL and evaluated employing protocols defined by US-DRIVE.  An important component of the PNA work described is its durability and reproducibility under these protocol conditions. For HCT materials, both metal exchanged (Ag, Pd) and unexchanged zeolites are being studied.  The DOC research investigates a novel core@shell support of SiO2@ZrO2 with Pd and/or Pt as the active catalyst.  Each of these components is evaluated individually prior to combining and testing them as a 2- or 3-component system.  Results will be presented on the overall reactivity of these catalytic materials along with the percentage of CO/NOx/THC removed during the fast temperature ramp.  Additionally, we aim to distinguish between the nature of active sites on these supports under industrially relevant conditions, and also study any changes with aging.