Physicochemical properties and NH₃-SCR catalytic performance of intercalated layered aluminosilicates

The representative of natural layered clays, bentonite, was modified according to two routes and tested as a new catalyst for selective catalytic reduction of nitrogen oxides with ammonia (NH₃-SCR). The natural acid-activated clay was ion-exchanged with Na⁺ or remained in H-form and pillared with metal oxides. In order to limit the number of synthesis steps, iron as an active phase was introduced simultaneously with Al₂O₃ during the intercalation procedure. Additionally, the samples were doped with 0.5 wt% of copper to promote low-temperature activity. It was found that the performed modifications resulted in disorganization of the ordered layered arrangement of bentonite. Nevertheless, acid activation and pillaring improved structural and textural parameters. The results of catalytic tests indicated that the samples containing Fe₂O₃ pillars promoted with Cu exhibited the highest NO conversion of 85% at 250 °C (H-Bent-AlFe-Cu) and 75% at 300 °C (Na-Bent-AlFe-Cu). What is important, activity of the protonated samples in the high-temperature region was noticeably affected by the side reaction of ammonia oxidation, correlated with the production of NO and resulting in N₂O emission during the process comparing to Na-Bentonite catalysts.