Low-Temperature NOx Removal Using Cu-Hierarchical SAPO-34 Catalysts with High Hydrothermal Stability

Cu-hierarchical SAPO-34-based catalysts are targeted to allow an efficient gas diffusion through mesopores, improving NOx abatement efficiency at low temperature. A downside of mesopores, however, is that they could eventually reduce hydrothermal stability. To demonstrate the potential of novel catalytic systems, the NH3-SCR catalytic activity of fresh and hydrothermally treated (HT, in air with 10 % H2O at 750 degrees C for 16 h) hierarchical catalysts was evaluated and compared with a Cu-microporous catalyst. As expected, the catalytic performances of the hydrothermally treated Cu-hierarchical catalysts did not surpass that of the microporous one at high temperatures. Nevertheless, their NH3-SCR catalytic activity at low temperature overcame that of the microporous catalyst, which could be assigned to both: the increase of Cu2+ active sites after HT and the enhanced diffusion of reactants through the mesopores. This reduction of diffusion resistance by the formation of mesopores was further confirmed by the estimated effectiveness factor.