Production of hydrogen-rich syngas and multiwalled carbon nanotubes by biogas decomposition over zirconia supported iron catalysts

Abstract

A set of Fe/ZrO2 catalysts were successfully synthesized by a facile urea-assisted solid-state combustion method, and their catalytic test was evaluated for the thermal decomposition of undiluted-biogas into hydrogen-rich syngas and multiwalled carbon nanotubes (MWCNTs). The as-prepared catalysts were characterized by X-Ray diffraction (XRD), Scanning and Transmission electron microscopy (SEM and TEM), Nitrogen-physisorption, X-ray photoelectron spectroscopy and Temperature programmed reduction analyses. The iron was found in the form of hematite and metallic-iron in the fresh and reduced catalysts respectively. A suitable metal-support interaction due to the fine surface dispersion of iron species on ZrO2 was observed in the catalysts. The N2-physisorption analysis indicated the reduced surface area of the catalysts after iron loading. However, it does not influence the catalytic efficiency since the metal amount and metal-support interaction was determined to play the main role. The Fe/ZrO2 catalysts exhibited improved catalytic efficiency. With increasing the amount of iron and increasing the reaction temperature, the CH4 and CO2 conversions were increased significantly. A highest CH4 and CO2 conversions of 92% and 89% respectively, with an H2/CO ratio of ∼2.25 were obtained for the 50%Fe/ZrO2 catalyst at 900°C. The enhanced catalytic performance could be attributed to the fine-surface dispersion of iron-nanocrystals on ZrO2. Moreover, the MWCNTs were characterized by XRD, SEM, TEM and Raman analyses for their structural properties.