Deactivation Mechanism in NOx Reduction Zeolite Catalysts Revealed by Atom Probe Tomography
Reconstructed APT results (Cu-Al atom maps) for aged Cu-ZSM-5 (left) and Cu-SSZ-13 (right). Extensive Cu-Al affinity observed in Cu-ZSM-5 after aging, consistent with the formation of CuAl2O4 phase leading to rapid catalyst deactivation and performance loss. (hi-res image)
Atom-level distributions in two aged industrial zeolite catalysts are revealed by atom probe tomography (APT), yielding the first direct observations of the chemical redistributions responsible for catalyst deactivation.
Significance and Impact
APT acquired after aging show catalyst deactivation occurs via Cu-Al clustering in Cu-SSZ-13 vs. severe Cu-Al aggregation in Cu-ZSM-5 forming deleterious CuAl2O4, which correlates with observed catalyst activity loss.
– Zeolite chabazite (Cu-SSZ-13) was recently commercialized for catalytic NOx reduction and exhibited superior performance compared to the industry standard zeolite catalyst (Cu-ZSM-5).
– Both zeolites were exposed to aging protocol that simulated 135,000 miles of vehicle use.
– The single-atom sensitivity of APT was integral towards identifying deactivation mechanisms of the two zeolites.
J. E. Schmidt, R. Oord, W. Guo, J. D. Poplawsky, B. M. Weckhuysen, "Nanoscale tomography reveals the deactivation of automotive copper-exchanged zeolite catalysts," Nature Communications 8, 1666 (2017). DOI: 10.1038/s41467-017-01765-0