Effects of preparation and structure of cerium-zirconium mixed oxides on diesel soot catalytic combustion

• Published in: Applied catalysis. A, General General, 2012-01, Vol.413, p.292-300
• Main Authors: Oliveira, Claudinei F., Garcia, Fillipe A.C., Araújo, Daniel R., Macedo, Julio L., Dias, Sílvia C.L., Dias, José A.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Ceria; Cerium-zirconium mixed oxide; Combustion; Contact; Diesel; Diesel fuels; Diesel soot combustion; Mixed oxides; Sol–gel method; Soot; Zirconia
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2011.11.020

[Display omitted] ► Preparation of nanostructured materials. ► Mixed oxides of cerium-zirconium have distorted structures from cubic ceria. ► Raman spectra confirmed cell contraction as a result of zirconium insertion. ► Ce 0.8Zr 0.2O 2 was the most acidic and had the best performance for soot combustion. ► Ce 0.8Zr 0.2O 2 can be reutilized, with no loss of activity and maintenance of structure. Mixed oxides of Ce x Zr 1− x O 2 (0.1 ≤ x ≤ 0.9) were prepared by sol–gel method, in aqueous ammonia solution with CeCl 3·7H 2O and ZrOCl 2·8H 2O as precursors, and employed in diesel soot combustion. The catalysts were characterized by XRF/EDX, nitrogen adsorption, TGA/DTG, powder XRD, FTIR/DRIFTS and Raman. In addition, the acidity was evaluated by adsorption and desorption of pyridine. XRD indicated the formation of solid solutions that progressively distorted from cubic into tetragonal lattices. Raman studies confirmed that the Ce–O bonding was stronger in the mixed oxide series because of the cell contraction, as a result of the zirconium insertion. Ce 0.8Zr 0.2O 2 was the most acidic and active material, shifting the combustion temperature ( T m) from 622 to 547 °C (loose contact) or 404 °C (tight contact). The calculated activation energy for the catalytic combustion of this optimized oxide attested that the combustion temperature was lower under all conditions, compared to the thermal process. The catalyst was utilized five times without any appreciable loss of activity and maintained its structural properties.