Poisoning effects of lead species on the V2O5-WO3/TiO2 type NH3-selective catalytic reduction catalyst

Heavy metal Pb is an inevitable ingredient of coal-fired flue gas and has been proven to be a source of inhibiting effect on the selective catalytic reduction (SCR) catalyst. In this paper, two types of Pb-poisoned catalyst, prepared by the incipient wetness impregnation and solid diffusion methods, are studied to unveil the poisoning effects of lead species on the V 2 O 5 -WO 3 /TiO 2 catalyst. The activity test results showed that lead species loaded by the incipient wetness impregnation method exhibited a significant inhibiting effect on the denitrification efficiency of the catalyst although a negligible activity loss was observed on the samples from the solid diffusion method. Characterizations of fresh and Pb-poisoned catalysts from incipient wetness impregnation method were applied using comprehensive techniques such as X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray fluorescence (XRF), NH 3 -temperature programmed desorption (NH 3 -TPD), X-Ray photoelectron spectroscopy (XPS), and so forth. The analytical results indicated that a phase transformation occurred in tungsten species and the amorphous WO 3 converted into PbWO 4 , causing the accumulation and valence imbalance of active vanadium phase, which further decreased the surface acidity and activity of the V 2 O 5 -WO 3 /TiO 2 catalyst.