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3 Comparison of Catalytic Reduction of NO by Propene on Zeolite-Based and Clay-Based Catalysts Ion-Exchanged by Cu ´ JOSE L. VALVERDE, FERNANDO DORADO, PAULA SANCHEZ, ISAAC ASENCIO, and AMAYA ROMERO University of Castilla–La Mancha, Ciudad Real, Spain I. INTRODUCTION Selective catalytic reduction (SCR) of NO with hydrocarbons has been a subject of extensive study due to its potential for the effective control of NO emission in oxidant environments [1–11]. Hydrocarbons would be the preferred reducing agents over NH3 because the practical problems associated with its use: handling and slippage through the reactor. Although many types of catalysts have been studied for this purpose, only. | 3 Comparison of Catalytic Reduction of NO by Propene on Zeolite-Based and Clay-Based Catalysts Ion-Exchanged by Cu JOSE L. VALVERDE FERNANDO DORADO PAULA SANCHEZ ISAAC ASENCIO and AMAYA ROMERO University of Castilla-La Mancha Ciudad Real Spain I. INTRODUCTION Selective catalytic reduction SCR of NO with hydrocarbons has been a subject of extensive study due to its potential for the effective control of NO emission in oxidant environments 1-11 . Hydrocarbons would be the preferred reducing agents over NH3 because the practical problems associated with its use handling and slippage through the reactor. Although many types of catalysts have been studied for this purpose only a few copper-loaded zeolites have been demonstrated as adequate and among them Cu-ZSM-5 gives good yields and seems to be one of the most active ones 3 5 12-15 . The majority of these catalysts are ion-exchanged zeolites including H forms. Metal oxides supported on alumina have also been studied. Shimuzu et al. 16 17 recently reported that Cu-aluminate catalysts containing highly dispersed Cu2 ions in the aluminate phase showed high de-NOx activity comparable to Cu-ZSM-5 and higher hydrothermal stability. The activity of copper-loaded zeolites was found to depend on the Cu content. Iwamoto et al. 18 observed that the activity of Cu-ZSM-5 increased with the increment of the Cu exchange level. On the other hand the concentration of O2 in the NO-containing stream plays an important role in the reaction rate and product selectivity of the SCR reaction. It has been suggested that the roles of the O2 in this reaction are to activate NO and hydrocarbons 19 to oxidize NO to NO2 20 to maintain a Cu Cu2 site balance 21 and to react with carbonaceous deposits on Cu-ZSM-5 20 22 . Copyright n 2003 by Marcel Dekker Inc. All Rights Reserved. The majority of Cu ions in copper-exchanged zeolites are found as single cations located in structural cationic sites. Besides these atomically dispersed single Cu ions in .