Wenig Mirjam, Khare Rachit, Jentys Andreas, Lercher Johannes A
Department of Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstraße 4, 85748, Garching, Germany.
Institute for Integrated Catalysis, Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354, USA.
Angew Chem Int Ed Engl. 2025 Jan 27;64(5):e202416954. doi: 10.1002/anie.202416954. Epub 2024 Dec 8.
Combining operando X-ray absorption spectroscopy (XAS) and computational modelling shows unequivocally the distribution of active species in fresh and hydrothermally aged Cu-CHA and Cu-AEI zeolites during NH-assisted selective catalytic reduction of NO. Four principal species co-exist: (i) Cu cations coordinated to NH, (ii) Cu cations coordinated to the zeolite framework, (iii) solvated Cu cations, and (iv) framework-coordinated Cu species (Cu ) formed upon hydrothermal ageing of the zeolite sample. The Cu species were only observed in the hydrothermally aged zeolite samples and are formed upon the interaction of hydrated Cu cations with extra-framework Al (EFAl) generated during the hydrothermal treatment. These sites are inactive for NO reduction, leading to a decrease in the catalytic performance of the hydrothermally aged zeolites. Cu formation was higher in Cu-CHA (46 %) than in Cu-AEI (28 %). The better hydrothermal stability of Cu in the AEI framework is attributed to the tortuous channel structure of AEI that hinders the migration of hydrated Cu cations during hydrothermal ageing.
将原位X射线吸收光谱（XAS）与计算模型相结合，明确显示了在NH辅助的NO选择性催化还原过程中，新鲜的和水热老化的Cu-CHA和Cu-AEI沸石中活性物种的分布。存在四种主要物种：（i）与NH配位的Cu阳离子，（ii）与沸石骨架配位的Cu阳离子，（iii）溶剂化的Cu阳离子，以及（iv）沸石样品水热老化时形成的骨架配位Cu物种（Cu ）。仅在水热老化的沸石样品中观察到Cu 物种，它是由水合Cu阳离子与水热处理过程中产生的骨架外Al（EFAl）相互作用形成的。这些位点对NO还原无活性，导致水热老化沸石的催化性能下降。Cu-CHA中Cu 的形成率（约46%）高于Cu-AEI（约28%）。AEI骨架中Cu具有更好的水热稳定性，这归因于AEI曲折的孔道结构，它在水热老化过程中阻碍了水合Cu阳离子的迁移。
