Determining the Nature of the Active Sites of Cu-Beta Zeolites for the Selective Catalytic Reduction (SCR) of NOxby Using a Coupled Reaction-XAES/XPS Study

The present work reports a XPS and XAES study of Cu-Beta zeoliteswith different Cu loadings, coupled with anin situtype ofcatalytic experiments conducted in a high-pressure gas cell installedin the preparation chamber of the spectrometer. It has been foundthat the most active Cu-Beta zeolites for SCR ofNO x are those in which the conversion betweenCu+2and Cu+1species is quicklyproduced under reaction conditions. This conversion between bothoxidation states is easier in over-exchanged Cu-Beta samples. Whenexposed to the reaction conditions, the over-exchanged Cu-Betazeolites show a high level of dispersed Cu+1species,and a correlation between the ratio of Cu+1to totalCu on the surface in the working catalyst and catalytic activity hasbeen found.