CeO2−δ Nanoparticles Supported on SnNb2O6 Nanosheets for Selective Catalytic Reduction of NOx with NH3

This is the authors' abstract. We don't add key points for this paper.

Selective catalytic reduction with NH 3 (NH 3 -SCR) is an effective technique for purifying flue gas by removing nitrogen oxides, and the catalyst plays a key role in this technology. For the purpose of developing novel, highly efficient, green, and vanadium-free catalysts, SnNb 2 O 6 nanosheets were synthesized successfully by hydrothermal and solid reactions and confirmed by XRD and TEM. These nanosheets were first used as a support for CeO 2−δ to prepare environmentally friendly Ce/SnNb 2 O 6 catalysts for NH 3 -SCR. These Ce/SnNb 2 O 6 catalysts had more than 90% NO x conversion and 98% N 2 selectivity at 250–400 °C and a high space velocity of 120,000 mL/(g·h), which is higher than the per surface area performance of the previously reported Ce-based NH 3 -SCR catalysts. To explore the factors for this increased activity, NH 3 -TPD, H 2 -TPR, and XPS data were analyzed in detail. The results indicated that Ce/SnNb 2 O 6 nanocatalysts have more acid and oxidative sites than Ce/SnO 2 and Ce/Nb 2 O 5 . In addition, the surface of Ce/SnNb 2 O 6 contained 39.4% Sn 4+ ions, which synergize with Ce as additional redox sites. The effect of electron transfer between Sn and Ce at the interface promoted the formation of molecular oxygen and cycling of redox sites. Kinetic studies showed that Ce/SnNb 2 O 6 had a low apparent activation energy of 38.0 kJ/mol, which reduced the difficulty of the reaction. DFT studies indicated that the adsorption energy of NH 3 in SnNb 2 O 6 was 429.7 kJ/mol, which is much higher than that of other common supports, meaning that NH 3 is much easier to adsorb on SnNb 2 O 6 nanosheets, therefore showing higher catalytic performance. Moreover, in situ DRIFTS analysis showed the changes in the dominant mechanisms: the L–H and E–R mechanism coexist at 300 °C, while most of the reactions follow the E–R mechanism at 400 °C. This study can provide new insights into the development of new Ce-based NH 3 -SCR catalysts to control NO x emissions from stationary sources.