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IR spectroscopy was used to study CO adsorption on two samples of By variation of sample 5%Co/Al 2 O 3 . pretreatment, CO pressure, contact time and mode of hydrogen coadsorption, several surface species were identiÐed : CO adsorbed on cobalt ions of di †erent oxidation state, CO on metallic cobalt and polycarbonyls. Three species were distinguished which gave rise to bands in the 2050È2060 cm~1 region and could coexist on the catalyst, depending on the experimental conditions : CO linearly adsorbed on Co atoms with partial positive charge (Cod`), hydrocarbonyl and polycarbonyl The thermal stability and (Co † OE H CO) [Co(CO) n]. reactivity to hydrogen of the various species were studied and COwCo0 was found to be the most stable.

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Two-component Co-Ce samples deposited onto SiO 2 have been prepared, characterized and tested in the reaction of complete n-hexane and CO oxidation. It was established that cerium enhanced the catalytic activity of cobalt in the reaction of n-hexane oxidation, although this depended on the sequence of cobalt and cerium introduction. Co-impregnation of Co and Ce resulted in a close interaction between Co 3 O 4 and CeO 2 leading to more surface oxygen species available and, therefore, a better reactivity.

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© Versita Sp. z o.o. Received 29 June 2012; Accepted 2 October 2012 Keywords: Biogenic iron oxide materials • Sphaerotilus-Leptothrix group bacteria • Mossbauer spectroscopy • X-ray diffraction • IR spectroscopyMaterials based on biogenic iron oxides, which are a product of the metabolic activities of the neutrophilic iron-oxidizing bacteria (NIOB) from Sphaerotilus-Leptothrix group, were investigated. Natural microbial probes were collected from freshwater flow from Vitosha Mountain (Bulgaria) and cultivated under laboratory conditions in respect to select suitable cultures and conditions (nutrition media) for biomaterial accumulation of biogenic oxides. Samples were studied by physicochemical methods: X-ray diffraction, Mossbauer spectroscopy and IR spectroscopy. Their phase composition and physicochemical properties were obtained. Presence of both amorphous and crystal phase (ultra-and highly dispersed particles) was proved. Iron-containing compound in the natural biomass consists of α-FeOOH. The cultivated materials have more complex composition with iron-containing ingredients as α-FeOOH, γ-FeOOH, γ-Fe 2 O 3 and Fe 3 O 4 . The sample of natural biomass was tested in reaction of CO oxidation and it showed potential to be used as catalyst support.