期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 144, 期 22, 页码 9734-9746出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.2c01933
关键词
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资金
- US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office
- DOE's Office of Biological and Environmental Research
- US DOE
- Tsinghua University
This study investigates the key factors controlling the low-temperature NH3-SCR reaction using Cu/SSZ-13 catalysts. The kinetics of Cu loading and the dynamics of Cu ions are found to strongly affect the SCR reaction. Operando EPR spectroscopy reveals a strong correlation between Cu-ion dynamics and SCR kinetics.
A series of seven Cu/SSZ-13 catalysts with Si/Al = 6.7 are used to elucidate key rate-controlling factors during low-temperature standard ammonia-selective catalytic reduction (NH3-SCR), via a combination of SCR kinetics and operando electron paramagnetic resonance (EPR) spectroscopy. Strong Cu-loading-dependent kinetics, with Cu atomic efficiency increasing nearly by an order of magnitude, is found when per chabazite cage occupancy for Cu ion increases from similar to 0.04 to similar to 0.3. This is due mainly to the release of intercage Cu transfer constraints that facilitates the redox chemistry, as evidenced from detailed Arrhenius analysis. Operando EPR spectroscopy studies reveal strong connectivity between Cu-ion dynamics and SCR kinetics, based on which it is concluded that under low-temperature steady-state SCR, kinetically most relevant Cu species are those with the highest intercage mobility. Transient binuclear Cu species are mechanistically relevant species, but their splitting and cohabitation are indispensable for low-temperature kinetics.
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