Effects of Ba/Ce ratio on NO_x storage performance of NSR catalyst

In order to explore the effects of Ba/Ce ratio on the NO_x storage performance of the catalyst, a series of Pt/xBa-(30-x)Ce/γ-Al₂O₃ (x=10, 15, 20, x is a mass fraction) NSR catalysts were prepared by a modified sol-gel method combined with an impregnation method, and their properties were characterized by means of X-ray diffraction (XRD), specific surface area analysis (BET), temperature programmed reduction of H₂ (H₂-TPR) and temperature programmed desorption of NO (NO-TPD). The results indicate that Ba mainly exists in the form of BaCO₃, and CeO₂ is present in the amorphous form. With the increase of x value, CeO₂ grain size decreases firstly and then increases. With the increase of Ce content, the high temperature reduction peak has a similar tendency with that of CeO₂ grain size. The NO-TPD results show that the NO_x adsorbed on the surface of the catalyst has a better thermal stability with the temperature below 350℃. The effects of Ba/Ce ratio on the NO_x storage performance were investigated by a simulated gas test platform. The results show that the NO_x storage capacity of the Pt/15Ba-15Ce/γ-Al₂O₃ catalyst has a maximum value of 47.1%, and the NO_x breakthrough time is 7 min. When the storage process completes, the NO₂/NO_x ratio of Pt/15Ba-15Ce/γ-Al₂O₃ catalyst is 28%. The NO_x storage efficiency increases firstly and then decreases, and different Ba/Ce ratios have great influences on the storage path of the catalyst. The catalyst presents excellent NO_x storage performance when the Ba/Ce ratio is 1.0. The experimental results provide a reference for the optimal design and application of NSR catalyst in the field of diesel exhaust after-treatment system.