NOx storage and reduction over potassium titanate nanobelt-based catalyst with high storage capacity

We have identified a new NOx storage/reduction catalyst with the composition of Pt–KNO3 supported on a K-titanate nanobelt (KTN) prepared using hydrothermal method. Isothermal NOx storage experiments at 350 °C revealed the highest storage capacity (2.27 mmol/g) ever achieved over 33 wt.% KNO3 impregnated catalyst, and lean–rich cycles could be operated for more than 15 times with maintaining its high storage capacity. The characterization of the spent catalysts revealed that addition of more than 33 wt.% KNO3 caused the gradual destruction of the nanobelt structure during the reaction and the decrease in NOx storage capacity. High temperature operation such as at 500 °C also caused the destruction of nanobelt structure. It was demonstrated that the main storage specie of NOx was potassium nitrate. Immigration of K+ from and back to K-rich layers on KTN might be the mechanism for the storage and reduction of NOx on those materials.