Effects of copper loading on NH₃-SCR and NO oxidation over Cu impregnated CHA zeolite

Cu/CHA catalysts with various Cu loadings (0.5 wt%–6.0 wt%) were synthesized via incipient wetness impregnation. The catalysts were applied to the selective catalytic reduction (SCR) of NO with NH₃ and NO oxidation reaction. XRD and N₂ adsorption-desorption data showed that CHA structure was maintained with the incorporation of Cu, while specific surface areas decreased with increasing Cu loading. At intermediate Cu loading, 4 wt%, the highest NH₃-SCR activity was observed with ∼98% N₂ selectivity from 150 °C to 300 °C. Small amounts of water, 2%, slightly increased NO conversion in addition to the remarkable N₂O and NO₂ reduction at high temperature. Water effects are attributed to the improved Cu ion reducibility and mobility. NO oxidation results provided no relation between NO₂ formation and SCR activity. Physicochemical properties, NO conversion, N₂ selectivity, and activation energy data showed that impregnated samples’ molecular structure and catalytic activity are comparable to the conventional ion-exchanged (IE) samples’ ones.