Ag/bauxite catalysts: Improved low-temperature activity and SO2 tolerance for H2-promoted NH3-SCR of NOx

• Ag/bauxite possesses much higher SCR activity below 250 °C than Ag/Al2O3.
• Ag/bauxite possesses much stronger tolerance against SO2 and H2O than Ag/Al2O3.
• The compositions of bauxite are beneficial to improve SCR performances.

A series of Ag/bauxite catalysts were applied in H2-promoted selective catalytic reduction (SCR) of NOx. In comparison with 3Ag/Al2O3, 3Ag/bauxite exhibits higher catalytic activity at low temperature, stronger resistance to SO2 poisoning and better regenerability in SCR of NOx. NOx conversion of 3Ag/bauxite at 100–200 °C is more than 60%, which is much higher than less than 7% in 3Ag/Al2O3. NH3-TPD and in situ DRIFTS studies confirm the presence of Lewis and Brønsted acid sites in Ag/bauxite, and Lewis acid sites are the major acid sites. H2-TPR, UV–vis, in situ DRIFTS and DFT calculation show that FeOx and metallic Ag clusters are main active species in SCR of NOx at low temperature.

Ag/bauxite catalysts show much higher catalytic activity at low temperature, stronger resistance against SO2 and better regenerability than Ag/Al2O3, which can serve as promising alternative for Ag/Al2O3 in selective catalytic reduction of NOx.Figure optionsDownload as PowerPoint slide