Steel wool-based microreactors with nanostructured iron oxide films for the catalytic CO oxidation

Abstract

Microreactors based on iron oxide films formed on common steel wool substrates were developed to be employed in the carbon monoxide oxidation. It is shown that a simple and short oxidation treatment in air at 600 ºC produced films firmly anchored to the surface of strands, consisting of micrometric layers of magnetite on which a nanometric layer of hematite grew. This hematite layer exhibited a preferential crystallographic orientation along the (110) planes and also developed whisker-shape and plate-shape nanocrystals. FexOy-based microreactors exhibited an outstanding catalytic performance, becoming one of the most efficient simple iron oxide catalysts reported to date. Full conversion at 275 °C was achieved with high stability under reaction conditions, withstanding consecutive catalytic cycles and retaining their activity for more than 50 h at high conversion levels. The activity, stability and recyclability was due to the thin hematite layer with oriented (110) planes which was immobilized at the surface of the steel wool strands with an intricate geometry. These efficient microreactors offer advantages for potential applications in emission control and sustainable oxidation processes, meeting a green criteria such as the use of a very low-cost substrate, a catalytic phase based on a non-noble metal and the utilization of a simple, environmentally friendly preparation methodology.