Improved low-temperature activity of V2O5-Wo3/TIO2 for denitration using different vanadium precursors

Abstract

This work tested two V2O5-WO3/TiO2 catalysts with different vanadium precursors for selective catalytic reduction (SCR) of flue gas NO using NH3 at 150–450°C. While catalyst A was prepared using ammonium metavanadate (NH4VO3) through incipient impregnation, catalyst B was made according to the solvothermal method using vanadyl acetylacetonate (VO(acac)2) as the vanadium precursor. The catalytic evaluation for denitration was in a laboratory fixed bed reactor using simulated flue gas under conditions of a gas hourly space velocity(GHSV)of40,000h-1 and an NH3/NO molar ratio of 0.8. Without SO2 and water vapor in the flue gas at 200°C, the realized NO conversion was 56% for catalyst A but 80% for B. The presence of 350 ppm SO2 and 10 vol. % water vapor in the flue gass lightly reduced the NO conversion over catalyst B, and its activity was stable in a 108-h continuous test at temperatures varying from 450°C to 220°C. Via fourier transformation infrared spectroscopy (FT-IR) and thermogravimetric (TG) analysis, it was shown that over catalyst B a dynamic balance between the formation and decomposition of ammonium sulfite or sulfate is built possibly at temperatures as low as 220°C. For this catalyst there was a higher surface atomic concentration of vanadium and a higher ratio of V4+/(V4+ + V5+), while the NH3 adsorption test revealed more acidic sites on catalyst B. The study discloses a potentially new approach to prepare a V2O5-WO3/TiO2 catalyst with good performance for SCR of flue gas NO at 220–300°C.