Reasonable design of Sm-modified Cu-based catalyst for NH3-SCO: Role of the amide intermediates.

The selective catalytic oxidation of ammonia (NH 3 -SCO) is currently the most effective method used to eliminate NH 3. However, one of the major challenges for NH 3 -SCO is the development of catalyst capable of completely converting NH 3 into harmless N 2 and water vapor. In this paper, a high N 2 selective catalyst prepared by the sol-gel method using TiO 2 as the support, Cu as the active species, and Sm as the auxiliary agent is presented. Compared to traditional Cu/TiO 2 catalyst, the 4SmCu/TiO 2 catalyst has higher catalytic activity and N 2 selectivity at low temperatures. The NH 3 conversion can reach 100%, and the selectivity of N 2 can be maintained at 100% at 275 °C. The excellent catalytic activity is attributed to the highly dispersed active species, abundant Lewis acid sites (LASs), and the generation of large amounts of surface-adsorbed oxygen. In addition, doping Sm species will cause TiO 2 lattice distortion, and at the same time load the distorted TiO 2 with more active material. Moreover, in-situ DRIFTS analysis suggests that both the 4SmCu/TiO 2 and Cu/TiO 2 catalysts follow the "internal" selective catalytic reduction (iSCR) mechanism during NH 3 -SCO reactions. The 4SmCu/TiO 2 catalyst generates more amides (-NH 2), which reduces the non-selective oxidation of the catalysts and promotes the formation of N 2. This provides a new idea and method for the selective catalytic oxidation of NH 3 to N 2 and water vapor using Cu-based catalysts. [Display omitted] • 4SmCu/TiO2 catalyst converts all NH3 into N2 and water vapor at 275 ℃. • The lattice distortion of TiO2 can support more active species. • Doping of Sm species increased the content of Lewis acid site and surface-adsorbed oxygen. • The rich amide intermediates reduce the non-selective oxidation of NH3 and O2. [ABSTRACT FROM AUTHOR]