Nature of Cu Active Centers in Cu-SSZ-13 and Their Responses to SO2 Exposure

The effect(s) of SO2 on the two types of active sites on Cu-SSZ-13 NH3–SCR catalysts, Z2Cu and ZCuOH, were investigated. Two Cu-SSZ-13 catalysts with Si:Al ratios of 6 and 30 were synthesized, and they provide very different distributions of these two active sites. Inductively coupled plasma optical emission spectroscopy (ICP-OES), H2 temperature-programmed reduction (H2-TPR), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were utilized to characterize catalyst samples and quantify the amounts of total Cu, Z2Cu and ZCuOH. In situ DRIFTS results show that Z2Cu and ZCuOH responses to low-temperature (550 °C). Therefore, compared with Z2Cu, ZCuOH sites are more susceptible to severe low-temperature SO2 poisoning because of the formation of more stable bisulfite and ultimately bisulfate species.