Explorations into the Nature of Cu2+ Ions in SSZ-13 Zeolites for the Selective Catalytic Reduction of NOx with NH3 (NH3¬-SCR)
- Arthur Shih (Purdue University, USA)
- Wednesday 1 April 2020
- Hotel NH Noordwijk Conference Centre Leeuwenhorst
Arthur J. Shiha, Ishant Khuranaa, Atish A. Parekha, Christopher Paoluccib, Sichi Lib, Hui Lib, John R. Di Iorioa, Jonatan D. Albarracin-Caballeroa, Aleksey Yezeretsc, Jeffrey T. Millera, W. Nicholas Delgassa, William F. Schneiderb, Rajamani Goundera, Fabio H. Ribeiroa
a Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA
b Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
c Cummins Incorporated, 1900 McKinley Avenue, MC 50183, Columbus, IN 47201, USA
Zeolites are porous silica frameworks with localized aluminum anionic sites throughout its crystalline framework. Loose cations (often H+ or metals) charge balance these anionic sites. Due to these unique properties, zeolites have been used in ion-exchange, gas separation, and catalysis technologies . The SSZ-13 zeolite used in this work is used in the automotive industry for NOx pollution abatement and has promise in the petrochemical industry for hydrocarbon and oxygenate conversion to fuels and chemicals - particularly partial methane oxidation [2-4].
The overall goal of this work is to understand the active site requirements for and the mechanistic details of NH3-SCR by combining operando X-ray absorption spectroscopy (XAS) measurements with other in-situ and ex-situ characterization techniques and density functional theory (DFT) calculations. We elucidate the presence of two types of Cu2+ ions and molecular details on how Cu2+ ions undergo a reduction-oxidation catalytic cycle dependent on the spatial density of Cu2+ to reduce NOx [5-6]. These discoveries compel us to reconsider the turnover rate (catalytic reaction rate normalized per active site), which are traditionally used to characterize single-site heterogenous catalysts, independent of the spatial density of active sites. This study also opens avenues to better understand the nature of Cu2+ sites for various reactions, and to strategically synthesize Cu-zeolites tailored for a broad range of chemistries.
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