Abstract
Co3O4, Fe2O3 and a mixture of the two oxides Co–Fe (molar ratio of Co3O4/Fe2O3 = 0.67 and atomic ratio of Co/Fe = 1) were prepared by the calcination of cobalt oxalate and/or iron oxalate salts at 500 °C for 2 h in static air using water as a solvent/dispersing agent. The catalysts were studied in the steam reforming of ethanol to investigate the effect of the partial substitution of Co3O4 with Fe2O3 on the catalytic behaviour. The reforming activity over Fe2O3, while initially high, underwent fast deactivation. In comparison, over the Co–Fe catalyst both the H2 yield and stability were higher than that found over the pure Co3O4 or Fe2O3 catalysts. DRIFTS-MS studies under the reaction feed highlighted that the Co–Fe catalyst had increased amounts of adsorbed OH/water; similar to Fe2O3. Increasing the amount of reactive species (water/OH species) adsorbed on the Co–Fe catalyst surface is proposed to facilitate the steam reforming reaction rather than decomposition reactions reducing by-product formation and providing a higher H2 yield.
Highlights
There is a significant drive to move away from the use of non-renewable fossil fuels, i.e. petroleum, natural gas and coal, for energy production due to the associated environmental problems such as the production of air pollutants and greenhouse gas emissions [1]
Significant amounts of hydrogen are produced by the steam reforming of natural gas, the production of hydrogen from alternative, sustainable sources is highly desirable with one such process being the steam reforming of bioethanol which is produced via biomass fermentation processes
The hydrogen yield (H2 Y %), ethanol conversion (Ethanol conv. %) and selectivity of carbon-containing products (S %) are defined as: H2 Y % 1⁄4/(6 Â moles of ethanol fed) reduction, the temperature was lowered to 100 C and the reduced catalyst taken as a background spectrum
Summary
There is a significant drive to move away from the use of non-renewable fossil fuels, i.e. petroleum, natural gas and coal, for energy production due to the associated environmental problems such as the production of air pollutants and greenhouse gas emissions [1]. Noble metals exhibit high activity and stability towards ethanol steam reforming (ESR), their use is undesirable due to their high cost. Most of the studies investigating cobalt catalysts for ethanol steam reforming have been in the area of improving their activity and, importantly, stability while concomitantly reducing the formation of undesired by-products, in particular coke. The addition of promoters such as noble metals [5,6], Ni, Cu, Na, Mn, Cr and Fe [4,7e14] to Co catalysts has been investigated for their effect on the activity and stability for ethanol steam reforming. Unsupported Co3O4 catalysts have been reported to be active for steam reforming of ethanol [11,15e18] with 1% Fe doped onto Co3O4 showing a promoting effect with lower CH4 and CO formed compared to Co3O4. A physical mixture of Co3O4 and Fe2O3 (CoeFe-Physical) was prepared from grinding together the individual oxides and this catalyst was tested under the same reaction conditions
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