Experimental and density functional theory studies on Cu/Ba-coimpregnated gamma-Al2O3 for low-temperature NOx storage and adsorbent regeneration
- Authors
- Kim, Hyunwook; Jung, Hyeonjung; Han, Jeong Woo; Lee, Ki Bong
- Issue Date
- 1-2월-2022
- Publisher
- ELSEVIER SCIENCE SA
- Keywords
- NO; NO2; Lean-NOx trap; NOx storage-regeneration; Density-functional-theory calculation
- Citation
- CHEMICAL ENGINEERING JOURNAL, v.429
- Indexed
- SCIE
SCOPUS
- Journal Title
- CHEMICAL ENGINEERING JOURNAL
- Volume
- 429
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/135228
- DOI
- 10.1016/j.cej.2021.132112
- ISSN
- 1385-8947
- Abstract
- Although the lean-NOx trap (LNT) has been used to reduce NOx emissions from diesel-powered vehicles, LNT application is limited because its performance degrades at low temperatures (e.g., during cold starting). Therefore, to enhance low-temperature NO r storage and adsorbent regeneration, gamma-Al2O3 was coimpregnated with both Cu and Ba (Cu-Ba/gamma-Al2O3). The experimentally measured NOx storage capacities (NSCs) and NOx storage efficiencies (NSEs) were compared. Density-functional-theory (DFT) calculations were performed to reveal the NOx storage mechanism. The Cu/Ba-coimpregnated gamma-Al2O3 improved both NSC and NSE of NO storage and enhanced NSE of NO 2 storage at initial stage. In addition, it desorbed NOx at lower temperatures than the conventional Ba-impregnated gamma-Al2O3 (Ba/gamma-Al2O3). The in-situ diffuse reflectance infrared Fourier-transform spectroscopy analysis and DFT calculations for NO storage showed that NO adsorption was superior on the Cucompound surfaces and that stable hyponitrite was stored on the Ba-compound surfaces. In NO2 storage, Cu/Ba coimpregnation offered high preferential NO2 coverage on the CuO surface and produced the most stable ionic nitrate on the Ba-compound surfaces. The experimental and theoretical results confirmed that the Cu/Bacoimpregnated adsorbent exhibited both superior NOx storage and adsorbent regeneration compared to the conventional Ba-containing LNT adsorbent.
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