Low temperature NO adsorption over hydrothermally aged Pd/CeO2 for cold start application

Pg/CeO2 catalyst hydrothermally aged at 750 degrees C for 25 h was employed for NO adsorption at low temperature (80-160 degrees C). For comparison, Pt or Pt-Pd supported on CeO2 or Al2O3 catalysts were also applied. Analysis of the hydrothermally aged catalysts clearly indicates that PGM (Pt and/or Pd) on CeO2 is more resistant to sintering than that on Al2O3 support. Reducibility test of Pd/CeO2 by H-2-TPR exhibits H-2 spillover from Pd to CeO2 support, attributed to the strong interaction between Pd and CeO2. NO adsorption/desorption results demonstrate that CeO2-based catalysts exhibit superior NO adsorption ability than Al2O3-based catalysts. In addition, PGM/CeO2 catalysts shows the desirable desorption temperature for cold start application. The influence of reactant in stream, NO adsorption time, and temperature on low temperature NO adsorption over Pd/CeO2 is also examined to advance the understanding of NO adsorption/desorption behavior. DRIFT results of adsorbed NOx species on Pd/CeO2 during NO adsorption/desorption prove that NOx desorption peaks at 250, 300, and 450 degrees C originate from weakly bound nitrite, nitro-nitrito species, and nitrate species, respectively. In Pd/CeO2 catalyst, Pd plays a role in providing additional NO adsorption site arising from the intimate interaction between Pd and CeO2 and promoting the oxidation from adsorbed nitrite to nitrate. It can be summarized that Pd/CeO2 can be a good candidate as low temperature NO adsorption catalyst for cold start application. (c) 2017 Elsevier B.V. All rights reserved.