In situ X-ray absorption study of Cu species in Cu-CHA catalysts for NH3-SCR during temperature-programmed reduction in NO/NH3

Abstract Ammonia-mediated selective catalytic reduction (NH 3 -SCR) using Cu-exchanged chabazite zeolites as catalysts is one of the leading technologies for NO x removal from exhaust gases, with Cu II /Cu I redox cycles being basis reaction. The amount ions reduced by NO/NH can be quantified consumption during temperature-programmed experiments (NO-TPR). In this article, we show capabilities in situ X-ray absorption near-edge spectroscopy (XANES), coupled multivariate curve resolution (MCR) and principal component analysis (PCA) methods, following speciation after oxidation NO/O 2 at 50 °C on samples different copper loading pretreatment conditions. Our XANES results that ramp are fully to 50–290 range. number species involved process, their spectra concentration profiles a function temperature were obtained MCR PCA. Mixed ligand ammonia solvated complexes [Cu ) (X)] + (X = OH − /O or present beginning experiment, transformed into mobile ] complexes: these lose an NH become framework-coordinated above 200 °C. multiple events observed: first around 130 identified (OH/O)] moieties, while second occurs 220–240 associated ammonia-solvated Cu-NO species. nitrate found dependent zeolite applied Ammonia solvation increases sites available formation nitrates, confirmed infrared spectroscopy.