(233b) Various Roles of Water in the Pt-Ba/Alumina Lean Nox Trap Catalysts

The LNT (lean NOx trap) is generally considered as one of the promising solutions for the exhaust control of gasoline lean burn and diesel engine in order to meet future requirements on emission levels. In the LNT technology, an active (alkali and/or alkaline earth) oxide material takes up NOx under lean engine operation conditions and stores them as nitrates [1]. In a brief rich cycle these nitrates are released form the active oxide catalyst component, and reduced to N2 on the precious metal component of the catalyst. Water, a major component of the Diesel exhaust gas mixture, has been shown to significantly affect the NOx storage process by strongly interacting with the alumina support, and thus eliminating its NOx uptake [2]. Here we report the results of our multi-spectroscopy study in which we set out to understand the various roles of water on BaO/Al2O3 NOx storage materials and catalytic activity. To this end, we investigated the morphological changes of fresh or pre-adsorbed NO2 BaO/Al2O3 materials upon the water treatment using XRD, NO2 TPD, transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) and 27Al solid state NMR spectroscopies. Also we tried to investigate the effect of water in the NOx uptake activity especially for the thermally aged samples. In addition, we followed the effect of H2O during desulfation processes using synchrotron time resolved XRD (TR-XRD ? carried out at the National Synchrotron Light Source at Brookhaven National Laboratory) and H2 Temperature Programmed Reaction (TPRX).

[1] W.S. Epling, L.E. Campbell, A. Yezerets, N.W. Currier, J.E. Parks II, Cat. Rev.-Sci. Eng. 2004 46, 163. [2] W.S. Epling, G.C. Campbell, J.E. Parks, Catalysis Letters 2003 90(1-2), 45.