Architecture of core-shell Ce-OMS-2@CeO2 catalyst and its SCR activity and SO2+H2O tolerance performance at low-temperature
-
-
Abstract
It is a challenge to develop highly sulfur dioxide and water (SO2+H2O) resistance for the low-temperature selective catalytic reduction (SCR) catalysts of nitrogen oxide (NOx) in the non-electric-power industry. In this paper, core-shell and loaded type of Ce-OMS-2 complexes (Ce-OMS-2@CeO2 and CeO2/Ce-OMS-2) were successfully prepared. Their textural properties were characterized and catalytic performance were carried out. The results showed that the core-shell Ce-OMS-2@CeO2 material could maintain the mesoporous structure and significantly improve the mass transfer and adsorption of the reaction gas NO, thus improving the SCR efficiency. On the contrary, for the loaded CeO2/Ce-OMS-2 catalyst, large amounts of CeO2 deposited on the surface of Ce-OMS-2 and blocked the mesoporous structure. Furthermore, SO2 reacted with CeO2/Ce-OMS-2 to form lots of metal sulfate (manganese sulfate or cerium sulfate), which led to the deactivation of the active Mn sites. Therefore, the CeO2/Ce-OMS-2 catalyst exhibited the low SCR activity and poor SO2+H2O tolerance during the SCR reaction. We also clarify the reason for the anti-sulfur of core-shell Ce-OMS-2@CeO2 catalyst. In the presence of SO2 and H2O, SO2 could easily react with NH3 and H2O to produce ammonium bisulfate (NH4HSO4, ABS) on the surface of the Ce-OMS-2 and CeO2/Ce-OMS-2 catalysts. Then ABS can be physically deposited on the surface of the catalysts, thus blocking the active Mn sites to participate in the SCR reaction. Interesting, for the core-shell Ce-OMS-2@CeO2 catalyst, the formed ABS could significantly decomposed at low temperature, leading to the exposure of surface active Mn sites of the catalyst. Herein, it could maintain the efficient SCR performance over the Ce-OMS-2@CeO2 catalyst. A dynamic balance of ABS formation and decomposition was achieved over Ce-OMS-2@CeO2 even at low temperatures, which hindered the SO2 poisoning during the NH3-SCR reaction. As expected, the core-shell Ce-OMS-2@CeO2 catalyst showed excellent SCR performance and SO2+H2O resistance (~100% NO conversion in the temperature range of 100−200 ℃ without SO2, ~80% NO conversion for 4 h in the presence of SO2). This work provides an effective strategy for the development of efficient and stable Mn-based low-temperature SCR catalysts.
-
-