Abstract
Pd/SSZ-13 catalysts after hydrothermal aging (HTA) treatment at 750°C for 25h 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 2wt% 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.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
