Sol-Gel Derived CeO2/alpha-Al2O3 Bilayer Thin Film as an Anti-Coking Barrier and Its Catalytic Coke Oxidation Performance

摘要

A CeO2/-Al2O3 bilayer was coated on a high temperature alloy (Incoloy 800H) by sol-gel dip-coating and was evaluated for its potential as an anticoking barrier and coke oxidation catalyst. The bilayer effectively functioned as a barrier to metal surface catalyzed coking. The film prevented filamentous catalytic coking via blocking surface active metallic sites on the Incoloy substrate. Furthermore, the bilayer reduced the oxidation temperature of pyrolytic coke deposited on the film surface as compared to a bare oxidized Incoloy substrate, mostly owing to the oxidation catalytic activity of the CeO2 layer. Finally, it is demonstrated that the presence of the alpha-Al2O3 buffer layer is critically important to the overall performance. Without the alpha-Al2O3 layer, a CeO2 layer nearly completely lost both its barrier and oxidation catalytic functions. It is presumed that metallic species migrating from the substrate during high temperature treatments are responsible for the CeO2 deactivation, likely by blocking catalytic sites on the CeO2 surface. (C) 2018 American Institute of Chemical Engineers