Enhancing resistance to CaO&PbO poisoning of CeO2/TiO2 NH3-SCR catalyst via hybrid with SO42−/ZrO2: Dual functions of SO42−/ZrO2

Abstract

Catalyst deactivation caused by the co-poisoning of alkaline earth metals (CaO) and heavy metals (PbO) is still a problem in the NH3 selective catalytic reduction (SCR) of NOx in flue gas. In this work, a hybrid catalyst (Hybrid-CT) was being synthesized by grinding CeO2/TiO2 (CT) catalyst and SO42−/ZrO2 to evaluate the poisoning tolerance. It shown that Hybrid-CT exhibited a higher tolerance against CaO&PbO poisoning compared with CT. Under the co-poisoning of 2.5 wt% CaO and 2.5 wt% PbO, the NOx conversion of Hybrid-CT catalyst could approach to 100 % at 350 °C. Whereas, the NOx conversion of CT was only 66.3 % under the same condition. A series of characterizations suggested that the SO42−/ZrO2 could inhibit the CaO&PbO poisoning. Once the CaO&PbO present on the surface of Hybrid-CT catalyst, SO42− could convert CaO&PbO into CaSO4&PbSO4 with less toxic, which could protect the redox site and acid site of the CeO2/TiO2. Furthermore, the ZrO2 released from SO42−/ZrO2 could serve as a promoter, enhancing the acid performance of CeO2/TiO2 catalysts. Moreover, SO42−/ZrO2 could also reduce the passive effect of CaO&PbO on nitrate oxide. This work provides a simple and novel way to improve the resistance to CaO&PbO of Ce-based SCR catalysts.