Deactivation Mechanism of Multipoisons in Cement Furnace Flue Gas on Selective Catalytic Reduction Catalysts

Increasing numbers of cement furnaces have applied selective catalytic reduction (SCR) units for advanced treatment of NO in the flue gas. However, the SCR catalysts may face various poisons, such as acidic, alkaline, and heavy metal species, in the fly ash. In this work, we studied the deactivation mechanisms of multipoisons (Ca, Pb, and S) on the CeO2-WO3/TiO2 catalyst, using the in situ diffuse reflectance infrared Fourier transform spectroscopy method. Calcium promoted the conversion of Ce(III) to Ce(IV) and, thus, (i) suppressed the redox cycle, (ii) decreased the NO adsorption (monodentate NO3- and bridged NO2-), and (iii) enriched the Lewis acid sites. Pb(IV) blocked Ce-2(WO4)(3), aggravating the electronegativity of W6+, which inhibited (i) the binding stability of tungsten and ammonia species, (ii) bridged NO3- (bonded to tungsten), and (iii) the Bronsted acid sites. The multipoisoning processes enriched O2- by repairing partial surface oxygen defects, which suppressed O-2(2-) and O-. Sulfur occupied the surface base sites and formed PbSO4 after Ce-2(WO4)(3) was saturated.