Monolith or Powder: Improper Sample Pretreatment May Mislead the Understanding of Industrial V2O5-WO3/TiO2 Catalysts Operated in Stationary Resources.

Abstract

Although various characterizations are widely applied to commercial V2O5-WO3/TiO2 catalysts, the influence of the catalyst physical structure, i.e., monolith or powder, on the characterization results has not been investigated. Several important catalytic behaviors and phenomena were observed in this study using V2O5-WO3/TiO2 monolithic catalysts employed for over 5000 h in various stationary flue gases, and many of the results were only observable on monolithic catalysts, such as depth-dependent distribution of external elements, penetration of As2O3, and the formation of Tl2O-TiO2 p-n junctions. If the monolith is ground into powder states, it will alter or destroy the catalyst surface and remove important clues closely related to catalytic performance under working conditions. The redox and acidity properties of V2O5-WO3/TiO2 obtained from powder samples may be significantly different from their true state under working conditions, resulting in a misperception of catalyst performance. Therefore, a cautious pretreatment should be taken into careful consideration when analyzing commercial honeycomb V2O5-WO3/TiO2 catalysts.