Abstract: The de-NOx catalysts with different operation-time were adopted. The comparative analysis on properties of the catalysts was made. The test and the analysis of SCR with different catalysts of 10 080, 25 145, 30 288 and 40 368 h were carried out. The results show that the last two ones, 30 288 （C3） and 40 368 h （C4）, have unsatisfactory denitration rate which is lower than 60 % after 30 000 hours operation. Their performances cannot meet designed demand of the power plant. Moreover, the techniques of XRD, SEM, BET, FT-IR, IC and ICP-MS were used to characterize the objectives with different operation-time. The results indicate that the aggregations cannot be found remarkably, and the crystal form of carrier maintains the anatase style. However, the data from SEM show that the active compound on the surface of the catalyst runs off along with the operation-time, which is consistent with the analysis obtained from FT-IR. In the meantime, the channels and mesopores of catalysts are influenced badly with the long operation-time. Besides, there are also some water-soluble ions and trace heavy metals deposited on the surface of the catalysts.

Key words: coal fired power plant, flue gas denitrification, selective catalyst reduction (SCR), catalyst