Reaction-driven Ion Exchange of Copper into Zeolite SSZ-13
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We have used several techniques to characterize Cu-SSZ-13 before and after exposure to reaction conditions relevant for NO reduction by NH3-SCR to address the increase in NH3-SCR activity observed as a function of time on stream. Specifically, we focus on characterizing copper species in samples prepared with solid state ion exchange (SSIE) having varying Cu loadings from 0.7 to 5.2 wt %. X-ray diffraction shows that CuO species that likely remain from the SSIE synthesis on the outside of the zeolite crystallites are significantly reduced by exposure to reaction conditions. High-resolution X-ray diffraction (HR-XRD) further reveals a corresponding increase of Cu2O species. X-ray photoelectron, Auger electron, and ultraviolet -visible spectroscopy show an increase in both Cu(II) and Cu(I) species inside the zeolite pores, with a preserved long-range order of the zeolite structure as revealed by HR-XRD.