Pyung Soon Kim

Fully Copper-Exchanged High-Silica LTA Zeolites as Unrivaled Hydrothermally Stable NH3-SCR Catalysts

Diesel engine technology is still the most effective solution to meet tighter CO2 regulations in the mobility and transport sector. In implementation of fuel-efficient diesel engines, the poor thermal durability of lean nitrogen oxides (NOx ) aftertreatment systems remains as one major technical hurdle. Divalent copper ions when fully exchanged into high-silica LTA zeolites are demonstrated to exhibit excellent activity maintenance for NOx reduction with NH3 under vehicle simulated conditions even after hydrothermal aging at 900 °C, a critical temperature that the current commercial Cu-SSZ-13 catalyst cannot overcome owing to thermal deactivation. Detailed structural characterizations confirm the presence of Cu2+ ions only at the center of single 6-rings that act not only as a catalytically active center, but also as a dealumination suppressor. The overall results render the copper-exchanged LTA zeolite attractive as a viable substitute for Cu-SSZ-13.

Bifunctional Ag‐based catalyst for NOx reduction with E‐diesel fuel

The excellent low‐temperature deNOx performance of Ag/AlF3/Al2O3 by simulated E‐diesel fuel has been achieved, mainly due to the multiple roles of AlF3 impregnated onto Al2O3. It increases the formation of the highly dispersed Ag ions and the catalyst surface acidity as well as the formation of the reaction intermediates such as cyanides and isocyanates. A plausible process for the formation of the surface composition of Ag/AlF3/Al2O3 has been proposed by using the results from XPS and FTIR.