Enhancing the K-poisoning resistance of CeO2-SnO2 catalyst by hydrothermal method for NH3-SCR reaction

It is a very challenging task to improve the anti-alkali metal poisoning ability of non-vanadium-based denitration catalysts. To address this issue, we attempt to synthesize CeO2-SnO2 catalyst by hydrothermal method (denoted as CS-HT), which uses high temperature and high pressure environment of hydrothermal process to promote the distribution of Sn4+ in CeO2 lattice and enhance the interaction between each component. For comparison, CeO2-SnO2 catalyst was also prepared by co-precipitation method (denoted as CS-CP). The denitration activity and resistance to K-poisoning performance of these prepared catalysts for the selective catalytic reduction of nitrogen oxides by ammonia (NH3-SCR) were studied. The results showed that CS-HT catalyst had better denitration activity and anti-K poisoning performance than CS-CP catalyst. The physicochemical properties of these catalysts were characterized by XRD, Raman, XPS, H2-TPR, NH3-TPD. Experimental results indicated that the enhancement of anti-K poisoning ability of CS-HT catalyst was related to the good distribution of Sn4+, excellent redox performance and surface acidity. Moreover, the Sn-O bonds could combine with the introduced K more easily, which protected the Ce-O active sites. Finally, the possible NH3-SCR reaction mechanism and K-poisoning reasons on CeO2-SnO2 catalyst were analyzed by in-situ DRIFTS experiments.