Insight\ninto the Key Role of Yttrium Modification\nfor the Enhanced Hydrothermal Stability over Y‑Cu-SSZ-39 Zeolite\nCatalysts

Cu-SSZ-39 represents one of the most\npromising diesel\nselective\ncatalytic reduction (SCR) catalysts, but it has remained challenging\nto gain superior low-temperature catalytic activity and hydrothermal\nstability for meeting the stringent diesel emission regulations. In\nthis study, a diesel NO<sub><i>x</i></sub> purification\ncatalyst with excellent low temperature catalytic activity and outstanding\nhydrothermal stability was synthesized. It was found that the denitration\nactivity of fresh samples increased with increasing Y content throughout\nthe temperature interval, while it decreased when the Y content exceeded\n0.25%. Y modification can increase the proportion of ZCuOH (singly\ncoordinated with an isolated Al atom) in 8MRs and strong Lewis acid\nsites, resulting in a significant better low temperature NO<sub><i>x</i></sub> reduction activity. The moderate amount of Y ions\non the ion-exchange sites can well stabilize the framework of SSZ-39,\nwhich results in an enhancement effect on hydrothermal stability.\nMechanism studies reveal that the interplay between Y and Cu not only\nenhances the electron transfer ability from Cu to Y ions but also\ninhibits the aggregation of Cu sites. This work may pave a new way\nfor the next generation of advanced diesel NH<sub>3</sub>-SCR catalysts.