THE NATURE OF THE ACTIVE Cu SPECIES IN Cu/CHA MATERIALS FOR THE SELECTIVE CATALYTIC REDUCTION OF NOx WITH NH3

摘要

Metal-exchanged molecular sieves with a Chabazite (CHA) structure are of considerable current research interest due to the very recent commercial success of their application for the selective catalytic reduction (SCR) of NOx with ammonia on diesel vehicles [1]. Catalysts with outstanding SCR performance (activity, hydrothermal stability, etc.) include the aluminosilicate zeolite, SSZ-13, and the silico-alumino-phosphate, SAPO-34, with ion-exchanged Cu. Apart from the commercial success, detailed catalyst structures, reaction mechanisms, and structureactivity relationships are still lacking. In this presentation, we will describe results of more recent studies of Cu/SSZ-13 that specifically focus on the nature of the active Cu species under a variety of reaction conditions. Catalysts with varying Si/Al ratios and Cu loadings have been prepared and studied. We use a number of characterization methods including FTIR, x-ray absorption (XAS), and electron paramagnetic resonance (EPR) spectroscopies. Temperatureprogrammed reduction (TPR) experiments in the presence or absence of water are also highlighted. Besides these catalyst characterization measurements, we will also provide NH3-SCR and NH3 oxidation kinetics over these catalysts at high space velocity conditions for the development of structure-activity relationships.