Mobility of NH3-Solvated CuII Ions in Cu-SSZ-13 and Cu-ZSM-5 NH3-SCR Catalysts: A Comparative Impedance Spectroscopy Study
Open Access
Abstract
The mobility of NH3-solvated Cu ions within the zeolite framework has been recently identified as a key factor for the kinetics of the selective catalytic reduction of NOx with NH3 (NH3-SCR) over Cu-zeolite catalysts at low temperatures. Here, we utilize in situ impedance spectroscopy to explore the mobility of NH3-solvated CuII ions, i.e., CuII(NH3)n, in Cu-SSZ-13 and Cu-ZSM-5 zeolites with varied Cu ion exchange levels, and observed that both the zeolite framework (CHA or MFI) and the Cu exchange level influence the high-frequency dielectric relaxation processes that are associated with the short-range (local) motion of CuII(NH3)n. Our results suggest that the local motion of CuII(NH3)n species is favored within the CHA framework due to the unique cage structure, and thereby contribute to the overall ion conductivity at high frequencies, which, on the contrary, is not observed for ZSM-5, where NH3-solvated Cu2+ ions do not experience a comparable constrained space for local motion. This study sheds new light on the mobility of Cu active sites under NH3-SCR related reaction conditions and may contribute to an advanced understanding of the underlying mechanism.Keywords
This publication has 30 references indexed in Scilit:
- Local Environment and Nature of Cu Active Sites in Zeolite-Based Catalysts for the Selective Catalytic Reduction of NOxACS Catalysis, 2013
- Zeolites as nanoporous, gas-sensitive materials for in situ monitoring of DeNOx-SCRBeilstein Journal of Nanotechnology, 2012
- Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction of NOx with NH3Journal of Catalysis, 2010
- The role of Brønsted acidity in the selective catalytic reduction of NO with ammonia over Fe-ZSM-5Journal of Catalysis, 2009
- The State of the Art in Selective Catalytic Reduction of NOxby Ammonia Using Metal‐Exchanged Zeolite CatalystsCatalysis Reviews, 2008
- Correlation of TPD and impedance measurements on the desorption of NH3 from zeolite H-ZSM-5Solid State Ionics, 2008
- Solvate‐Supported Proton Transport in ZeolitesChemphyschem, 2004
- Proton Mobility in Chabazite, Faujasite, and ZSM-5 Zeolite Catalysts. Comparison Based on ab Initio CalculationsThe Journal of Physical Chemistry B, 2001
- Electrical properties of nanoscaled host/guest compoundsMicroporous and Mesoporous Materials, 2000
- Proton mobility in H-ZSM5 studied by impedance spectroscopySolid State Ionics, 1999