Mechanistic insight into reaction behaviors of acetonitrile catalytic combustion over Cu-based catalysts with different supports

A series of Cu-based catalysts with different types of supports (TiO2, Al2O3, S-1, HZSM-5 SiO2/Al2O3 = 27 and 85) were investigated for selective catalytic combustion of acetonitrile (CH3CN). Among all catalysts, the Cu/TiO2 and Cu/Al2O3 catalysts had superior activity accompanied with the generation of massive NOx, while Cu/ZSM-5 catalysts exhibited excellent N2 selectivity. The characterization results indicated that the surface acidity of catalysts played a decisive role in reaction behavior. For the Cu/TiO2 and Cu/Al2O3 catalysts mainly with Lewis acid sites, CH3CN underwent an initial hydrolysis step with surface hydroxy group to form acetamide anion (CH3CONHad), then occurred further hydrolysis reaction to form NH3 at low temperatures, or turned to proceed oxidation reaction with numerous NOx generation at high temperatures. Whereas, the enriched Brønsted acid sites on the Cu/ZSM-5 catalysts brought abundant isolated Cu2+ ions, which guaranteed the processing of iSCR reaction, thereby promoting the occurrence of hydrolysis and oxidation reaction pathways in parallel and benefiting the improvement of N2 selectivity. These results elucidated the influence of supports with different acidic types in reaction pathway and provided precious reference for the development of high-performance NVOCs catalysts.