Comparative analysis of the catalytic behaviour in CO oxidation of iron containing materials obtained by abiotic and biotic methods and after thermal treatment

This work concerns synthesis of iron oxide containing materials by biotic and abiotic methods and comparison of their properties aimed at finding a common point of intersection that may determine a possible replacement of abiotic materials. Biosynthesis comprised Leptothrix genus of bacteria cultivation in growth medium of Adler. Thermal treatment of biomass samples was used in order to approximate synthesis conditions of the biogenic iron oxide material to those of abiotically obtained hematite. The catalytic activity of the samples was measured in the reaction of CO oxidation by two ways: in situ infrared spectroscopy using a diffuse-reflectance measuring chamber of Nicolet 6700 spectrometer high-temperature vacuum accessory and a flow-type glass reactor. Biomass showed low CO conversions up to 200°C but an increase at 250°C was registered by both used methods. This increase was accompanied by phase transformation. Initial catalytic activity was a result of predominant work of lepidocrocite, whereas a higher activity at 250°C was due to formed maghemite. Abiotic hematite was a bit more active below 240°C than a thermally treated biomass sample in flow-type glass reactor experiments. At higher temperatures, both materials demonstrated the same CO conversion. Spent samples did not show any changes of composition. Although the studied samples were synthesized by different methods, which resulted in different original iron oxide phases, their catalytic performance was very close. Thermally treated biomass samples (obtained by cultivation in Adler’s medium) could replace chemically obtained iron oxide as a catalyst in the studied reaction.