Improved low temperature removal of NOX from lean-burn exhaust via adsorption on TiO2-modified Ag–alumina

Authors:  Toshiyuki Tanaka, Chika Ando, Tsuyoshi Hamaguchi, Yasuhiro Ikuta

Abstract:
TiO₂-modified Ag–alumina was studied as an NOX trapping material with the aim of improving the removal of NOX from lean-burn exhaust at low temperatures. This trapping material, in which both Ag and TiO₂ were finely dispersed throughout the alumina support on a nanometre scale, effectively adsorbed NOX at temperatures as low as 150^◦C. The TiO₂-modification of Ag–alumina improved the NOX trapping performance of the material by enhancing NO adsorption in the presence of other gases, including CO, hydrocarbons, CO₂ and H₂O. This modified material also exhibited less deterioration resulting from sulfur poisoning as compared to either conventional NOX storage and reduction (NSR) catalysts or unmodified Ag–alumina. TiO₂ was shown to be dispersed throughout the alumina in an octahedral structure, and spectroscopic analyses along with DFT calculations demonstrated that this dispersion is effective at stabilizing Ag in the material. It was also determined that Ag supported on octahedral TiO₂ formed active sites at which the redox reaction between Ag⁰ and Ag⁺ proceeded, and that NO was effectively oxidized and adsorbed as nitro and nitrite species on the active surface composed of the dispersed Ag and TiO₂.

Keywords:
Nitric oxide
Ag
TiO₂
Al₂O₃
Adsorption
Reduction

Published in: Applied catalysis A: General  (Volumes 464–465, Pages 1-384, 15 August 2013)

Publisher: Elsevier  

ISSN Information: 0926-860X

Improved low temperature removal of NOX from lean-burn exhaust via adsorption on TiO2-modified Ag–alumina

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