含铜MFI分子筛的H_2-TPR和O_2-TPD研究

Studies on Cu-Containing MFI Zeolites by H_2-TPR and O_2-TPD

采用H2 TPR和O2 TPD手段考察了不同金属离子交换的ZSM 5分子筛催化剂上的氢还原性能和氧脱附性能 .发现Cu ZSM 5催化剂的储氧能力及氧脱附性能优于Co ZSM 5和Fe ZSM 5催化剂 ;储氧能力强、低温下氧脱附性能好的催化剂 ,对NO分解反应的催化活性就高 .铜离子是反应的活性中心 .添加Ag和Ce可使Cu ZSM 5催化剂上氧的脱附温度大大降低 .Cu ZSM 5 /堇青石整体式催化剂上Cu的存在形式与单纯的Cu ZSM 5有差异 ,整体式催化剂上的一价铜数量少 。

Different metal ion-exchanged ZSM-5 zeolites were investigated by means of H-2-temperature-programmed reduction (H-2-TPR) and O-2-temperature-programmed desorption (O-2-TPD). Pure Cu-ZSM-5 and in-situ synthesized Cu-ZSM-5/cordierite monolithic catalysts were also characterized by H-2-TPR in order to compare the oxidation states of copper ions on them. The results show that the Cu-ZSM-5 catalyst has superior oxygen storage capacity than the Co-ZSM-5 and Fe-ZSM-5. The catalyst activity for NO decomposition is closely related to this property. Copper ions are the active sites for the reaction. The addition of Ag and Ce, as promoters decreases the temperature of O-2 desorption, which indicates that adding Ag and Ce favors the O-2 desorption from the catalyst surface. The state of Cu on the Cu-ZSM-5/cordierite monolithic catalyst is different from that on the pure Cu-ZSM-5. Less Cu+ species is found on the monolithic sample but it is more stable than that on the pure Cu-ZSM-5.