NH3-SCR performance and SO2 resistance comparison of CeO2 based catalysts with Fe/Mo additive surface decoration

• The redox capacity of CeO 2 could be improved by in situ surface deposition of Fe 2 O 3 . • CeO 2 -Fe 2 O 3 showed the high NH 3 /NO oxidation ability and strong interaction with SO 2 . • CeO 2 -MoO 3 showed excellent SCR activity due to the enhanced surface acidity by MoO 3 . • Surface MoO 3 could inhibit catalyst sulfation and ammonium sulfate deposition. • The main SO 2 deactivation reasons were different for diverse CeO 2 based catalysts. Fe 2 O 3 and/or MoO 3 surface decorated CeO 2 were designed and synthesized by in situ deposition and incipient wetness impregnation to adjust the SCR catalytic performance and SO 2 resistance of CeO 2 . The addition of iron oxide slightly improved low temperature SCR activity of CeO 2 -Fe 2 O 3 , but resulted in a fast decline of NO x removal efficiency at higher temperatures, which was due to the enhanced NH 3 oxidation by surface redox capacity improvement. Surface acidity instead of redox capacity was the main limiting factor for SCR activity of CeO 2 and CeO 2 -Fe 2 O 3 . Meanwhile, the introduction of MoO 3 increased NO x conversion of CeO 2 -MoO 3 and CeO 2 -Fe 2 O 3 -MoO 3 dramatically in a broad temperature range. The increase of catalysts surface acid sites promoted their SCR catalytic performance through Eley-Rideal mechanism. SO 2 resistance test indicated the different surface characteristics for the four catalysts resulting from the composition disparity leaded to different deactivation behaviors at 250 °C. The deposition of ammonium sulfate species accounted for the main activity loss of CeO 2 and CeO 2 -Fe 2 O 3 , while the sulfation of redox sites was main deactivation reason for CeO 2 -MoO 3 and CeO 2 -Fe 2 O 3 -MoO 3 . The interaction between SO 2 and CeO 2 /CeO 2 -Fe 2 O 3 catalysts changed the surface active sites for SCR reaction essentially and MoO 3 could inhibited surface sulfation and ammonium sulfate species deposition. The variation behavior of NO x conversion during SO 2 resistance test depended on the reaction temperature. All four catalysts show the usability in the presence of SO 2 when the reaction temperature is between 300 °C and 400 °C. Considering the complexity of preparation process, catalytic performance and SO 2 durability, CeO 2 -MoO 3 catalyst is a better choice for substituting the traditional V-Ti catalyst.