Cold-Start NOx Mitigation by Passive Adsorption Using Pd-Exchanged Zeolites: From Material Design to Mechanism Understanding and System Integration

It remains a major challenge to abate efficiently the harmful nitrogen oxides (NOx) in low-temperature diesel exhausts emitted during the cold-start period of engine operation. Passive NOx adsorbers (PNA), which could temporarily capture NOx at low temperatures (below 200 °C) and release the stored...

Full description

Saved in:
Bibliographic Details
Published in:Environmental science & technology 2023-03, Vol.57 (9), p.3467-3485
Main Authors: Li, Ying, Chen, Dongdong, Xu, Xin, Wang, Xinyu, Kang, Running, Fu, Mingli, Guo, Yanbing, Chen, Peirong, Li, Yongdan, Ye, Daiqi
Format: Article
Language:English
Subjects:
Atmospheric chemistry
Chemical reduction
Cold
Cold starts
Emissions
Exhaust systems
Exhausts
High temperature
Integration
Low temperature
Nitrogen oxides
Palladium
Photochemicals
Poisons
Reviews
Selective catalytic reduction
Zeolites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:It remains a major challenge to abate efficiently the harmful nitrogen oxides (NOx) in low-temperature diesel exhausts emitted during the cold-start period of engine operation. Passive NOx adsorbers (PNA), which could temporarily capture NOx at low temperatures (below 200 °C) and release the stored NOx at higher temperatures (normally 250–450 °C) to downstream selective catalytic reduction unit for complete abatement, hold promise to mitigate cold-start NOx emissions. In this review, recent advances in material design, mechanism understanding, and system integration are summarized for PNA based on palladium-exchanged zeolites. First, we discuss the choices of parent zeolite, Pd precursor, and synthetic method for the synthesis of Pd-zeolites with atomic Pd dispersions, and review the effect of hydrothermal aging on the properties and PNA performance of Pd-zeolites. Then, we show how different experimental and theoretical methodologies can be integrated to gain mechanistic insights into the nature of Pd active sites, the NOx storage/release chemistry, as well as the interactions between Pd and typical components/poisons in engine exhausts. This review also gathers several novel designs of PNA integration into modern exhaust after-treatment systems for practical application. At the end, we discuss the major challenges, as well as important implications, for the further development and real application of Pd-zeolite-based PNA in cold-start NOx mitigation.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.2c06207