DETERMINING THE NATURE OF THE ACTIVE-SITES OF CU-BETA ZEOLITES FOR THE SELECTIVE CATALYTIC REDUCTION (SGR) OF NOX BY USING A COUPLED REACTION XAES XPS STUDY/

The present work reports a XPS and XAES study of Cu-Beta zeolites with different Cu loadings, coupled with an in situ type of catalytic expe riments conducted in a high-pressure gas cell installed in the prepara tion chamber of the spectrometer, It has been found that the most acti ve Cu-Beta zeolites for SCR of NOx are those in which the conversion b etween Cu+2 and Cu+1 species is quickly produced under reaction condit ions, This conversion between both oxidation states is easier in over- exchanged Cu-Beta samples. When exposed to the reaction conditions, th e over-exchanged Cu-Beta zeolites show a high level of dispersed Cu+1 species, and a correlation between the ratio of Cu+1 to total Cu on th e surface in the working catalyst and catalytic activity has been foun d. (C) 1997 Academic Press.