Journal
ACS CATALYSIS
Volume 9, Issue 7, Pages 6137-6145Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.9b00759
Keywords
selective catalytic reduction; Cu/SSZ-13; transient kinetics; mechanism; DRIFTS
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Funding
- national key research and development program of China [2017YFC0211300, 2016YFE0126600]
- China Postdoctoral Science Foundation [2017M620800]
- US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office
- DOE's Office of Biological and Environmental Research
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A Cu/SSZ-13 catalyst containing predominately Z(2)Cu sites is prepared. Using FTIR spectroscopy, two nonsteady-state measurements, (1) continuous NO titration of an NH3 saturated catalyst and (2) intermittent NO on/off cycles during quasi-steady state (i.e., NO perturbation), are conducted to shed light on active sites, reaction intermediates, and possible reaction mechanisms. During continuous NO titration, a strong NH3 inhibition effect is found, where Cu active sites containing NH3 ligands are less active than Cu sites depleted of NH3 ligands. In the NO perturbation experiments, it is demonstrated that NO+NH3 interactions lead to formation of Bronsted acid sites, which further interact with NH3 to form NH4+. Perturbation measurements, using ND3 to replace NH3 in order to distinguish ammonia and nitrate vibrations, further show that NH4NO3 and other surface nitrates are not involved in the SCR process under typical low-temperature quasi-steady-state conditions.
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