Formation and decomposition of NH4HSO4 during selective catalytic reduction of NO with NH3 over V2O5-WO3/TiO2 catalysts

Abstract Based on commercial V 2 O 5 -WO 3 /TiO 2 catalysts, the formations of ammonium bisulfate (ABS) and ammonium sulfate were detected from the reactions among SO 3 , NH 3 and H 2 O in the flue gas during the process of selective catalytic reduction (SCR) of NO with NH 3 , leading to the deactivation of the catalyst and the increased number concentration of fine particles. The mechanism of formation and decomposition of ABS during SCR of NO with NH 3 was investigated through the In Situ Diffuse Reflectance Infrared Spectroscopy (DRIFTS) and the Thermo Gravimetric analyzer coupled with Fourier Transform Infrared analyzer (TG-FTIR). The results of the in situ DRIFTS showed that ABS deposited on the surface of the catalysts could be generated from the adsorption activation of NH 3 with SO 2 in presence of O 2 . It also could be produced by the direct reaction between NH 3 and the intermediate metal sulfates on the surface of the catalysts. In addition, it suggested that the reaction between NO and NH 4 + in ABS promoted ABS decomposition. TG-FTIR demonstrated that the process of ABS decomposition on the catalysts was composed of two steps. Moreover, the temperature window of the complete pyrolysis of ABS was delayed by catalysts.