Metal-decorated opal-like silica catalysts: High-temperature reconstructions in cobalt-ceria active layer during simultaneous oxidation of CO and hydrocarbons

Abstract

Opal-like silica, which represents a new class of SiO₂-based nanomaterials, was used as a support for the deposition of cobalt and cerium oxides as active components. A series of samples was prepared and tested in the oxidation of CO and hydrocarbons in a prompt thermal aging regime. As revealed by a set of physicochemical methods, the initial catalytic performance of the samples is high (T₅₀ = 214 °С) due to the emergence of new catalytic sites, which appeared as a result of interaction between Co and Ce oxides located between silica nanospheres in a close proximity to each other. At 800 °C, these particles undergo agglomeration, which is expressed in a slight deactivation of the catalysts (T₅₀ ≥ 260 °С). The bulk silicate phase is formed at 900 °C, thus leading to further deactivation. Recovering of the catalytic activity (T₅₀ = 252 °С) takes place at 1000 °С.