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. SO2, which is inevitably included in the diesel engine emissions, acts as a poisoning element by transforming the barium species into the more stable barium sulfates, which eventually leads to the decrease in the NOx storage. Therefore, the regeneration step by applying reductants (e.g. H2) at high temperature enough to convert barium sulphate into BaO/BaCO3 is required to desulfate the catalyst. Here we report the results of our multi-techniques in which we set out to understand the desulfation steps on sulfated Pt-BaO/Al2O3 NOx storage materials. To this end, we primarily used synchrotron time resolved XRD (TR-XRD), in situ S K-edge XANES spectroscopy (both are carried out at the National Synchrotron Light Source at Brookhaven National Laboratory) and H2 TPRX (temperature programmed reaction with H2). These in situ techniques allow us to understand the changes in the morphology and oxidation states of sulfur species during desulfation processes.

[1] W.S. Epling, L.E. Campbell, A. Yezerets, N.W. Currier, J.E. Parks II, Cat. Rev.-Sci. Eng. 2004 46, 163.

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