Characterisation of the active copper species for the NOx removal on Cu/Mg/Al mixed oxides derived from hydrotalcites: an in situ XPS/XAES study

In situ X-ray photoelectron spectroscopy was used to characterise Cu/Mg/Al mixed oxides derived from hydrotalcites (catalyst used for the NOx removal reaction). The active sites are the copper centres: (i) Cu(0) for NO decomp osition and (ii) Cu(0) and/or Cu(I) for NO reduction with a hydrocarbon. Th e ability of these materials to redisperse the copper active sites without destroying the structure of the material makes them different from other ca talysts such as zeolites, and is essential for suitable catalytic behaviour at high temperatures.