Characteristics of Pt-K/MgAl2O4 NOx Storage-Reduction Catalysts

Although the lean burn engines are considered as a promising solution for obtaining high fuel efficiency, however, there are challenges in their catalytic aftertreatment system, especially due to selectively reduce nitrogen oxides (NO_x) in the net oxidizing environment.  Lean NOx trap (LNT) catalysts are generally regarded as one of the potential options for removing NO_x in the diesel engine exhaust.  In the LNT technology, alkali or alkaline earth elements (K or Ba) take up NO_x under lean operation and store them as nitrates, which are subsequently reduced during rich operation [1].  Ba is primarily used for storing NOx at low temperature, while K is at high temperature.  It was reported that MgAl₂O₄ support promotes the shift of the maximum NOx uptake toward the higher temperature.  Therefore, Pt-K/MgAl₂O₄ catalyst demonstrated the excellent activity at higher temperature [2].  However, the detailed study about the effects of K loading, thermal aging and SO₂ poisoning on the activity of MgAl₂O₄ supported catalyst is not clear yet.  In this contribution, we try to understand the characteristics of Pt-K/MgAl₂O₄ catalysts, especially focusing on the role of MgAl₂O₄ support in NOx storage-reduction processes, compared with Al₂O₃ supported one.

References

1. Roy S. and Baiker, A. Chem. Rev. 109, 4054 (2009).
2. Takahashi, N., Matsunaga, S., Tanaka, T., Sobukawa, H. and Shinjoh, H. Appl. Catal. B 77, 73 (2007).