Development of deNOx Catalyst Based on Ag/Al2O3 Catalyst for Diesel Applications

Ag/Al₂O₃ was studied as a HC-SCR (Hydrocarbon - Selective Catalytic Reduction) catalyst for diesel application[1, 2 and 3]. Performance required of (or from) this catalyst is high NOx conversion with high thermal durability and sulfur resistance. Also low HC slip is desired. The Ag/Al₂O₃ system was improved by addition of additives.

In the diesel 13-mode (Japan) evaluation, improved Ag/Al2O3 catalyst showed higher de-NOx activity (>50%) compared to the original when fresh. Improved Al2O3 catalyst showed smaller hysteresis of de-NOx activity between ramping up and down the temperature and smaller amount of HC slip.

To study the improvement effect, interactions between the HC and catalyst were investigated by TG/DTA-MS (define) and FT-IR (define). TG/DTA measurement results showed that HC/O₂ reaction was restrained in the improved catalyst. These results suggest that there was sufficient of HC for NOx reduction on the improved catalyst.