Effect of Pr/Ce addition on the catalytic performance and SO2 resistance of highly dispersed MnOx/SAPO-34 catalyst for NH3-SCR at low temperature

Abstract

Based on ionic polarization, a series of MeOx-MnOx/SAPO-34 (Me=Pr or Ce) catalysts were prepared by a simple solvent dispersion method and their low temperature ammonia-selective catalytic reduction (SCR) performance were tested with and without SO2. The highly dispersed MnOx/SAPO-34 catalyst was doped with Pr and showed better low temperature catalytic activity (140–280°C) than that of the Ce-modified MnOx/SAPO-34. Also, the PrOx-MnOx/SAPO-34 presented good SO2 resistance performance with 100ppm SO2 at 200°C. Additionally, the fresh and SO2-poisoned catalysts were characterized by FE-SEM, BET, XRD, XPS, H2-TPR, NH3-TPD and TG analysis. The results indicated that there was no obvious change in the crystal structure of the PrOx-MnOx/SAPO-34 sample. The MnOx/SAPO-34 catalyst was doped with Pr, which prevented the catalyst from being sulfated and inhibited the formation of ammonia sulfate on the catalyst surface. The SO2 may favor combination with PrOx over MnOx, which could form praseodymium sulfate and protect the manganese active sites to some extent, in accordance with the theory of ionic polarization. More than 80% NOx conversion was provided by PrOx-MnOx/SAPO-34 catalysts in the presence of 100ppm SO2 at 200°C.