Effect of ash participation on the catalytic activity of as-prepared catalysts to promote diesel soot combustion

Abstract

This paper studies the effects of ash species and ash aging deposition on the physical and chemical properties of KC catalysts. By thermogravimetric analysis (TGA), the pure KC catalyst has good stability and catalytic activity at 600 °C. In the loosely contacting soot particles (PU)/ash/KC mixtures, the negative effect of ash on KC catalytic soot oxidation is relatively weak. The addition of ash makes the active site areas between PU and KC catalyst lose contact without changing the physicochemical properties of the catalyst. By contrast, the ash aging deposition on KC at 400 °C has an obviously negative effect on the soot combustion catalyzed by KC, because ash aging deposition leads to enormous changes in the chemical properties and catalytic activity of KC. This finding is consistent with characterization analyses such as XRD, SEM, XPS and Raman. Ash aging deposition destroys the KC structure and reduces the activity of KC to catalyze soot oxidation, and CaSO4 has the greatest effect on the oxidation activity. Consequently, ash aging deposition causes structural property damage of as-prepared catalysts, leading to the failure of CDPF catalytic layer. This study provides a new idea for the selection and optimization strategy of catalysts in CDPF.