Fly ash-derived NaA zeolite supported cu catalysts: structure-activity relationship for NH3-SCR denitrification

To address the demand for non‑vanadium catalysts in coal-fired flue gas denitrification, NaA zeolite was synthesized from industrial solid waste (coal fly ash) via hydrothermal method and loaded with 0.5–10 wt% Cu to construct x Cu/NaA catalysts. The optimized 5Cu/NaA catalyst exhibited superior NH 3 -SCR performance, achieving >90% NO conversion and > 95% N 2 selectivity within a broad temperature window of 200–350 °C. Comprehensive characterizations (XRD, XPS, H 2 -TPR) demonstrate that at 5 wt% loading, Cu species exist as highly dispersed Cu species on the NaA surface, forming intimate contact with the NaA framework. In contrast, excessive loading (10Cu/NaA) induces severe CuO agglomeration, blocking active sites and deteriorating performance. In-situ DRIFTS and DFT calculations reveal that 5Cu/NaA activates NH 3 via Cu 2+ -Lewis acid sites to form NH 2 * intermediates, while redox-active Cu sites facilitate NO oxidation to NO 2 /NO + . The synergistically optimizes both Langmuir-Hinshelwood (L-H) and Eley-Rideal ( E -R) pathways, steering the reaction toward selective N 2 formation while suppressing N 2 O generation. The work clarifies the dispersion-activity relationship of Cu on fly ash-derived zeolites, providing a cost-effective and green route for solid waste valorization and efficient denitrification.