Effect of sulfate-modified CeO2 with different morphologies on NH3-SCR

Three CeO2 catalysts with different morphologies (Rod, Spindle and Cube) were modified by SO42− (dented as S–CeO2) and used for NH3-SCR reaction. The results showed that the order of the NO conversion over different catalysts were in the following sequence: S–CeO2-Rod > S–CeO2-Spindle > S–CeO2-Cube (>80 %) at 300–450 °C, the NO conversion of the S–CeO2 catalyst was affected by the morphologies. A series of characterizations (TEM, H2-TPR, NH3-TPD, N2 adsorption-desorption, XPS, Raman and in situ DRIFTS) were used to investigate the physicochemical properties of catalysts with different morphologies. It showed that the active CeO2 (1 1 1) facets was exposed except CeO2-Cube, and the highly active CeO2 (2 0 0) and (2 2 0) facets were shown in CeO2-Cube and CeO2-Rod, respectively. The order of the temperature of H2 reduction peak was in the following sequence: S–CeO2-Rod (544 °C) < S–CeO2-Spindle (576 °C) < S–CeO2-Cube (612 °C). The order of the ratio of ID/IF2g and the amount of total acid of the catalysts were the same as NO conversion, showed the following sequence: S–CeO2-Rod (0.09) > S–CeO2-Spindle (0.05) > S–CeO2-Cube (0.03), S–CeO2-Rod (18.3 μmol/g) > S–CeO2-Spindle (9.69 μmol/g) > S–CeO2-Cube (9.40 μmol/g), respectively. The NH3-SCR reaction over the three S–CeO2 with different morphologies (Rod, Spindle, Cube) followed the Eley-Rideal and Langmuir-Hinshelwood mechanism. The S–CeO2-Rod was more suitable for NH3-SCR reaction.