Impact of copper loading on the copper species and SCR reactions over Cu-SAPO-34

Kirsten  Leistner, Chalmers University of Technology

The copper-exchanged silicoaluminophosphate Cu/SAPO-34 and zeolite Cu/SSZ-13 are used for selectively converting NOx to N2 from the exhaust gases of diesel engines, with NH3 as a reductant. The above Cu/CHA catalysts have shown remarkable hydrothermal stability (Wang et al. 2013). A significant amount of studies, dealing with preparation and characterization, have been published and are being pursued on Cu/SSZ-13 catalysts, however such studies were limited on Cu/SAPO-34 catalysts. In this study, the impact of the ion-exchanged copper in Cu/SAPO-34 on NH3-SCR reactions was characterized. The Cu/SAPO-34 catalysts were prepared by aqueous ion exchange with Cu(NO3)2 solutions with different concentrations. The catalysts were characterized by XRD, UV-vis, NH3-TPD and NH3-SCR activity evaluations. The impact of Cu loading on the standard and rapid SCR reactions in presence of water was studied.

Cu/SAPO-34 catalysts with high copper loading resulted in high NOx conversion. Higher copper loadings also increased NH3 oxidation activity, leading to lower NOx conversion from 400°C. Apart from copper loading, the catalyst pre-treatment temperature was found to have impact on the NOx conversion (Ma et al. 2013). The UV-vis characterization indicated that catalysts with a higher concentration of Cu-O complexes were more active for NO and NH3 oxidation. Cu-O complexes were present in relatively low concentrations in catalysts treated at 750°C compared with those which had undergone 500°C treatment. In the presentation, several observations made from characterization of Cu/SAPO-34, together with its catalytic performance in various reactions will be discussed.