Study on impregnation process optimization for regenerating the spent V2O5-WO3/TiO2 catalysts

Abstract

It is of great economic value and environmental significance to extend the service life of commercial SCR catalysts. Water and acid wash as well as thermal regeneration were often used to remove toxic substances (such as dust, metal sulfates and metal chlorides) residual on catalyst surface so as to reduce the replacement frequency of catalyst, but easily lead to the loss of active components. In this paper, impregnation method was used to supplement the lost active components of the spent honeycombed V2O5-WO3/TiO2 (labeled as VW/Ti) catalyst, and the effects of drying duration and impregnation solution concentration on NH3-SCR performance of catalyst were studied. The results showed that the catalyst dried for 6 h at 110 °C exhibited the best deNOx activity and sulfur/water resistance. Further prolonging or shortening drying duration reduced the catalytic activity instead. It can be attributed that proper drying duration constructs abundant pore channels inside catalyst, optimizes active components dispersion, reduces diffusion resistance of reactants into the inner surface and provides more effective active sites on catalyst surface for adsorption and oxidation of reactants. With rise of V content in impregnation solution from 1.06 wt.% to 3.61 wt.%, deNOx activity as well as SO2/H2O resistance of catalyst improves at 150–300 °C. Besides, key influence factors are also discussed based on reaction kinetics analysis.