Activation of Pd/SSZ-13 catalyst by hydrothermal aging treatment in passive NO adsorption performance at low temperature for cold start application

Young Seok Ryou, Jaeha Lee, Sung June Cho, Hyokyoung Lee, Chang Hwan Kim, Do Heui Kim

Research output: Contribution to journalArticlepeer-review

141 Scopus citations

Abstract

Pd/SSZ-13 catalysts after hydrothermal aging (HTA) treatment at 750 °C for 25 h showed enhanced passive NO adsorption performance at temperature below 120 °C, which will be suitable for cold start application, although those calcined at 500 °C did not possess good NO adsorption capacity irrespective of the preparation methods such as incipient wetness impregnation, wet impregnation, ion-exchange, and solid state ion exchange. NO adsorption ability of HTA treated Pd/SSZ-13 samples increases gradually as a function of the metal content, up to 2 wt% Pd loading, and then decreased implying that there is an optimum chemistry between the metal and zeolite support. Combined H2-TPR and Pd XAFS results clearly demonstrate that PdO mainly existed over the fresh samples, whereas HTA treated samples contained ionic Pd2+ species, indicating the redistribution of PdO into highly dispersed Pd2+ species within the SSZ-13 structure arising from HTA treatment. Such phenomenon was visually confirmed by comparative STEM-EDS analysis of fresh and HTA Pd/SSZ-13 samples. DRIFT results display the formation of two nitrosyl complexes adsorbed on Pd2+ ions, which are directly related to two desorption peaks of NOx at 250 and 400 °C. All combined results provide the unambiguous evidence about the generation of Pd ions in SSZ-13 zeolite induced by HTA treatment, which play as the active sites for NO adsorption at low temperature.

Original languageEnglish
Pages (from-to)140-149
Number of pages10
JournalApplied Catalysis B: Environmental
Volume212
DOIs
StatePublished - 2017

Keywords

  • Cold start application
  • Hydrothermal aging treatment
  • Low temperature NO adsorption
  • Pd ion exchange
  • Pd/SSZ-13

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