Grabow, Lars C.Vempatti, Veera Venkata RamprajwalRahman, Bhuiyan Md2021-02-112021-02-112020-09-29https://hdl.handle.net/10657/7502Vehicles are the source of a large portion of worldwide NOx (NO and NO2) emissions that have far-reaching ramifications on climate, ecological balance and human health. Although vehicles are presently equipped with catalytic converters that significantly reduce NOx at high temperatures (> 200°C) before emission, the majority of the NOx escapes during the cold-start period of an engine – the time taken by the converter to reach its required operating temperature (> 200°C). Passive NOx Adsorbers (PNA) have shown potential to prevent cold-start NOx emissions. Specifically, Pd/ZSM-5 - medium pore ion-exchanged zeolite - can act as a PNA by trapping NOx at lower temperatures (< 200°C) and releasing it at higher temperatures (> 200°C) for catalytic reduction. Density Functional Theory (DFT) simulations of passive NOx adsorption to Pd/ZSM-5 were performed to identify active sites in ZPd and calculate the binding free energies (BFE) of adsorbates – NO, NO2, O2 and CO - at different temperatures. BFE data revealed that adsorbate binding becomes weaker with increasing temperature. Comparison of BFE data for Pd/ZSM-5 with corresponding data for Pd/SSZ-13 (small pore zeolite PNA) showed that the former is a stronger adsorbent.en-USThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).Poster