Study on Catalytic Soot Oxidation over Spinel Type ACo2O4 (A = Co, Ni, Cu, Zn) Catalysts
Aerosol and Air Quality Research
In this study, a series of spinel type ACo 2 O 4 (A = Co, Ni, Cu, Zn) catalysts were synthesized via a citric acid complex method for catalytic soot oxidation. The effects of A sites on the removal of soot particles and CO 2 selectivity was investigated. The best performances for soot oxidation was achieved over ZnCo 2 O 4 with the T 50 of 569°C. The textural and redox properties of the ACo 2 O 4 catalysts were tested using BET, XRD, H 2 -TPR, O 2 -TPD, XPS. The substitution of A site caused
... change of Co 3+ /(Co 2+ + Co 3+ ) ratios as well as the oxygen mobility in the spinel structure. Both Co 2+ and Co 3+ species were observed on the surface of ACo 2 O 4 catalyst, and Co 3+ species were more easily to be reduced to lower states, thus improved the catalytic performance. Compared to other catalysts, the interactions between Zn and Co species led to larger surface area, higher relative concentration of surface active Co 3+ and more chemisorbed oxygen species. Additionally, the activity of the catalysts on soot oxidation were inhibited in the presence of sulfur dioxide and water vapor, while nitric oxide facilitated the catalytic activity.