Abstract: The V₂O₅-WO₃/TiO₂ type catalyst was covered with a layer of black substance after 2 years of operation in a petrochemical company. The composition of the black matter was determined, and the effect of black matter on the denitration performance of catalyst was studied. The mass fraction of Cr element on the surface of the catalyst was about 12% by energy spectrum analysis, and the main composition of Cr element was Cr₂O₃ by X-ray diffraction. The overall denitrification performance of the catalyst was inferior to that of fresh catalyst, especially at higher temperatures. The results indicated that the decrease of catalyst performance was probably related to the reduction of V⁴⁺ content on the catalyst surface and the decrease of catalyst reduction performance. In conclusion, Cr element has a significant impact on V₂O₅-WO₃/TiO₂ catalyst, so the content of Cr in the flue gas should be reduced as far as possible, and the flue gas temperature should be controlled to around 350 ℃ to reduce the influence of Cr.

Key words: selective catalytic reduction, denitration, chromium element, impregnation