不同钡铈比对NSR催化剂NO_x存储性能的影响

通过改进的溶胶凝胶法结合浸渍法制备了一系列Pt/x Ba-(30-x)Ce/γ-Al2O3(x=10、15、20,x为质量分数)型NSR催化剂,并利用XRD、BET、H_2-TPR和NO-TPD对其性能进行了表征。结果表明,Ba主要以BaCO_3形式存在,CeO_2晶粒粒径随着x值增大先减小后增大,且以无定型形式存在于催化剂中。随着Ce含量的增加,高温还原峰温度先降低后升高。NOTPD结果表明,吸附于催化剂表面的NO_x在低温时具有较好的热稳定性;通过NO_x完全存储实验,探究了不同Ba/Ce比对催化剂NO_x存储性能的影响。结果表明,当x=15时,催化剂的NO_x存储量最大,NO_x穿透时间达7 min,吸附稳定时NO_2/NO_x比为28%,NO_x存储效率达47.1%,具有最佳的NO_x存储性能。

Effects of Ba/Ce ratio on NOx 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.