New Insight into the Effect of Potassium on Commercial SCR Catalyst: Promotion of Thermal Stability

Abstract

Thermal stability is one of the most important indexes determining the practical applications of selective catalytic reduction (SCR) catalysts. The influence of typical alkali element on the thermal stability of industrial V2O5-WO3/TiO2 catalyst is first reported in this work. The activity of the sample is measured, and physicochemical properties are characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectrum, field emission scanning electron microscope (FE-SEM), N2 adsorption-desorption, temperature programmed desorption of NH3 (NH3-TPD), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). The sintering and anatase-to-rutile phase transformation at high temperature will cause deactivation of SCR catalyst, and low concentration of K can increase the thermal stability. Under the same thermal treatment, the activity (380 °C) of sample deposited by K is more than three times higher than that of the fresh sample without K. Aggregation of vanadia in conventional SCR catalyst favors the sintering and anatase-to-rutile phase transformation of catalysts. Incorporation of K can modify the structure of partial V-OH and form V-OK, which hinders the aggregation of vanadia species and further increases the thermal stability of catalysts.