Direct incorporating small amount of Ce (III) in Cu-SAPO-18 catalysts for enhanced low-temperature NH3-SCR activity: Influence on Cu distribution and Si coordination

The reduction of NOx emission during the cold start period of diesel vehicles requires special attention in accordance with the emission regulations. In this work, the direct incorporation of cerium and copper in SAPO-18 catalyst with AEI type framework structure (CuCe-SAPO-18) resulting in a substantial enhancement of the performance in the low-temperature NH3-SCR reaction (< 200 celcius). A small amount of cerium (0.13-0.31 wt%) broadened the reaction temperature range of use and increased the hydrothermal stability of the catalyst considerably. The cerium species was introduced in the ion-exchange sites of Cu-SAPO-18 in the form of Ce3+ ions even with high loading (3.15 wt%). The Ce3+ ions were found to affect the distribution of silicon and aluminum atom coordination (Si-29 NMR, Al-27 MAS NMR) in the AEI-type skeleton structure leading to an increase of both the amount of active Cu2+ species and the acidity of the CuCe-SAPO-18 catalysts that are beneficial for the NH3-SCR reaction.