Influence of co-cations in the selective catalytic reduction of NO by NH3 over copper exchanged faujasite zeolites

The effect of a co-cation (Cs, Ba, Ca, Sr, Ba, La, Ce, Sm, Dy, Yb) on the p roperties of Cu exchanged faujasite catalysts in the selective catalytic re duction (SCR) of NO by NH3 in an oxidising atmosphere has been studied. Tem perature programmed reduction (TPR) by H-2 of Cu-faujasite (Cu-FAU) was use d as a tool to identify and quantify the nature and location of Cu species. The 'blocking' of sodalites cages of Cu-FAU by alkali earth or lanthanide ions enhanced the SCR activity at low temperature (LT) and made the reactio n fully selective towards N-2 in the whole temperature range studied (up to 773 K). The formation of N2O in Cu-FAU zeolites results from the reaction between nitrogen monoxide and ammonia on next-nearest-neighbour (NNN) Cu io ns located in sodalite cages. (C)2000 Elsevier Science B.V All rights reser ved.