Removal of NO by absorption and the subsequent reduction method using YBa₂CU₃O(y) and Ce-ZSM-5

The effectiveness of the ab(ad)sorption and the subsequent reduction (abbreviated as ASR hereafter) system for the removal of highly dilute NO has been examined using a flew-type reaction system. The ASR system comprises two serial processes: first, NO is absorbed into (and/or adsorbed on) the system in the presence of O₂ until saturation, and then the absorbed NO is decomposed, for example, by reduction at a higher temperature in the presence of propene and oxygen. YBa₂Cu₃O(y) (YBC) and Ce-ZSM-5 were chosen in this study as materials for absorption and reduction, respectively. Efficient removal of NO was attained when the first layer consisting of a mixture of YBC and Ce-ZSM-5 was combined with the second layer of Ce-ZSM-5, and propene was additionally introduced between the two layers during the reductive decomposition. By this ASR system, the amount of NO absorption reached 1.5 mol per mole of YBC at 573 K and 60% of the NO absorbed was selectively decomposed to N₂ at 623 K in 9 h (N balance, 75%; N₂ selectivity, 79%).