| Autor: |
Wu Y; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States., Ma Y; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States., Wang Y; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States., Rappé KG; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States., Washton NM; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States., Wang Y; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States.; Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99163, United States., Walter ED; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States., Gao F; Institute for Integrated Catalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99354, United States. |
| Abstrakt: |
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 (NH 3 -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 ∼0.04 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. |
