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) of 40,000 h−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 gas slightly 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.
Highlights
Nitrogen oxides (NOx ) including NO, NO2 and N2 O remain as one of the major sources of air pollution, which greatly contribute to the greenhouse effect, ozone depletion, and formation of photochemical smog, acid rain, and particulate matters [1]
selective catalytic reduction (SCR) catalysts forcatalysts denitration, denitration, but we can see that the temperature window enabling the steady conversion was but we can see that the temperature window enabling the steady NO conversion was 250–400 ̋ C C 200–400
The study showed that the solvothermal method using VO(acac)2 as vanadium precursor resulted in a NH3 -SCR catalyst with stable performance for removing NO from flue gas containing SO2 and water vapor at temperatures of 240–400 ̋ C, even potentially 220–450 ̋ C
Summary
Nitrogen oxides (NOx ) including NO, NO2 and N2 O remain as one of the major sources of air pollution, which greatly contribute to the greenhouse effect, ozone depletion, and formation of photochemical smog, acid rain, and particulate matters [1]. VO(acac) deposited on TiO2 , TiO2 -SiO2 , Al2 O3 -SiO2 , and SBA-15 by liquid or gas phase dispersion techniques has been well studied [22,23,24,34], but there has been little reporting on the use of VO(acac) as a vanadium precursor and WO3 -TiO2 used as support for the NO reduction catalyst made by the solvothermal method This work attempts such an idea and is concerned with testing the potential denitration catalyst by the solvothermal preparation method, using VO(acac) as the vanadium precursor to realize a wide working-temperature window of, for example, 220–450 ̋ C for NO reduction by NH3 in flue gases containing SO2 and water vapor
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