Thermal Aging Behavior of Pt-only TWC Converters Under Simulated Exhaust Conditions: Effect of Rare Earths (CeO2, La2O3) and Alkali (Na) Modifiers

• Published in: Topics in catalysis Vol. 54; no. 16-18; pp. 1124 - 1134
• Main Authors: Matsouka, V., Konsolakis, M., Yentekakis, I. V., Papavasiliou, A., Tsetsekou, A., Boukos, N.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.11.2011
• Subjects: Catalysis; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Industrial Chemistry/Chemical Engineering; Original Paper; Pharmacy; Physical Chemistry; Simulated exhaust conditions; Na; Thermal aging; Catalyst promotion; TWCs; La; Platinum; FT-IR; CeO; DRIFT; O
• ISSN: 1022-5528; 1572-9028
• DOI: 10.1007/s11244-011-9734-6

In the present work, the feasibility to design monometallic (Pt-only), low metal loading (0.1 wt% Pt) three-way catalytic converters (TWCs), with comparable catalytic efficiency and thermostability to that of commercial bimetallic Pt/Rh TWCs has been explored. It is shown that this can be accomplished by modifying Pt/γ-Αl 2 O 3 washcoat of TWC via two different methods of promotion: support-mediated promotion by modifying the γ-Al 2 O 3 support with rare earth structure-modifiers (CeO 2 –La 2 O 3 ) and surface-induced promotion by directly modifying the Pt surface with alkalies (e.g., Na), producing a doubly-promoted Pt(Na)/Al 2 O 3 -(CeO 2 –La 2 O 3 ) TWC. The catalytic performance of as prepared TWCs in comparison to that of a commercial bimetallic (Pt–Rh) TWC, under simulated exhaust conditions at the stoichiometric point appears to be superior, even after severe thermal treatment at 900 °C for 5 h in air and despite the fact that the latter contain 4.5-fold higher noble metals loading. Moreover, the evolution of structural, textural and surface behavior of aged catalysts was identified by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and diffuse reflectance infrared Fourier transform spectroscopy and appropriately correlated with the catalytic performance and thermostability of TWCs.