Three types of supported cobalt catalysts (CoO x /SiO 2 , CoO x /TiO 2 and CoO x /Al 2 O 3 ) were prepared by incipient wetness impregnation with aqueous Co(NO 3 ) 2 AE6H 2 O solution. The phase composition and the interactions of cobalt with supports under different calcined temperatures were investigated using thermogravimetry (TG), N 2 -adsorption at )196°C, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and diffuse reflectance spectroscopy (DRS). Their catalytic activities towards the CO oxidation were further studied in a continuous flow micro-reactor. The results showed that the interaction of cobalt oxide with supports was much stronger in the kinds of Al 2 O 3 and TiO 2 , while no conclusive evidence of any interaction was found for SiO 2 . Besides the crystalline Co 3 O 4 which was formed in three supported catalysts, both high-temperature phases CoAl 2 O 4 and CoTiO 3 spinel were also detected under XRD, DRS and TPR analysis. The degree of interaction between cobalt oxide and the support not only affected the surface area and reduction behavior of the catalysts, the catalytic activity toward the CO oxidation also affected simultaneously. As the CoAl 2 O 4 and CoTiO 3 spinel formed, both the surface area and catalytic activity decreased significantly.
Three types of supported cobalt catalysts (5% as metal Co loading on SiO 2 , Al 2 O 3 and TiO 2 ) were prepared by incipient wetness impregnation with aqueous Co(NO 3 ) 2 AE 6H 2 O solution. Then, all catalysts were calcined in air at 400°C (assigned as 5Co/Si C400, 5Co/Al C400 and 5Co/Ti C400). Their catalytic activities towards the CO oxidation were studied in a continuous flow microreactor. Adsorption of carbon monoxide (CO) and the co-adsorption of CO/O 2 over cobalt oxide were further tested under in situ FT-IR. The results showed that both 5Co/Si C400 and 5Co/Al C400 had higher activity than 5Co/Ti C400. The T 50 (50% conversion) for both 5Co/Si C400 and 5Co/Al C400 was reached at temperatures as low as ambient temperature. According to the in situ FT-IR analysis, the variation in oxidation of CO was interpreted with different mechanisms, i.e., the reaction between adsorbed CO and lattice oxygen of cobalt oxide, and part of CO 2 formation via carbonates on 5Co/Si C400; both types of carbonates are formed on 5Co/Al C400 to promote the CO oxidation; while both strong adsorption of CO on TiO 2 and CO 2 on cobalt oxide for 5Co/Ti C400 leads to affect the activity.
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