Venkata D. B. C. Dasireddy*1, Darko Hanzel2, Krish Bharuth-Ram3 and Blaž Likozar1
1Laboratory of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry Slovenia, Hajdrihova 19, SI-1001 Ljubljana, Slovenia
2Jozef Stefan Institute, Jamova 39, SI-1001 Ljubljana, Slovenia
3 School of Chemistry and Physics, University of KwaZulu-Natal, Durban, South Africa
Selective CO oxidation was studied over Cu, Fe and Co supported carbon nanotubes which were prepared by wet impregnation along with Cu-Fe and Cu-Co supported carbon nanotubes via co-impregnation methods. These catalysts were characterised via various characterisation techniques. The application of Mössbauer spectroscopy for characterising the fresh and used catalysts showed that CuFe2O4 phase formed during the reaction is responsible for the high activity towards CO oxidation. Optimized bimetallic Cu-Fe/CNT catalyst can preferentially oxidize dilute CO in a H2-rich stream at a wide temperature window of 120-220 °C. The activities are compared as follows on T50 (the temperatures where 50 % CO conversion is achieved): Cu-Fe/CNT (120 °C) > Cu-Co/CNT (140 °C) > Cu/CNT (140 °C) > Co/CNT and Fe/CNT. The high selectivity towards CO2 can be attributed to the presence of CuFe2O4 on Cu-Fe/CNT and the synergistic effect between Cu and Co on Cu-Co/CNT catalysts. The Cu-Fe/CNT catalyst showed a high rate of CO conversion (with and without H2O and CO2) with compared to Cu/CNT and Fe/CNT catalysts. In situ FTIR under CO studies along with Mössbauer spectroscopy, show that the copper and iron metallic species are the active species for CO oxidation, along with Cu+/Cu0, a redox couple Fe2+/Fe0 plays an important role in the CO oxidation. Mössbauer measurements on the spent catalysts give an insight about the phase changes and the oxidation state change of iron during the reaction. The effect of Fe particle size on these reactions has been investigated.
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