| 초록 |
Passive NOx adsorber (PNA) is a practical solution to the NOx slip issue during the cold-start period. PNA adsorbs NOx at low temperatures and releases NOx at high temperatures where the other catalytic converts can fully function. Several materials, including metal oxides and zeolites, have been intensively studied as possible PNA materials. It is worth comparing different materials that can function in the same way to understand each material's pros and cons in the application. Here, we studied two representative PNA materials, Pd/CeO2 and Pd/SSZ-13, how they adsorb and desorb NOx. Temperature-programmed desorption tests were carried out under different NO/NO2 ratios. NO2 and NO competitively adsorb over Pd/SSZ-13, while NO2 promoted NO adsorption over Pd/CeO2. This phenomenon is attributed to the characteristics of their adsorption site. The effect of CO and sulfur treatments were also investigated over Pd/CeO2 and Pd/SSZ-13. |
