Nickel-Iron Alloy Supported over Iron-Alumina Catalysts for Steam Reforming of Biomass Tar Model Compound

Iron-alumina-supported nickel-iron alloy catalysts were tested in a fixed-bed reactor for steam reforming of toluene as a biomass tar model compound. The influence of the calcination temperature of the iron-alumina support was also explored for the steam reforming reaction. Ni supported on an Fe2O3-Al2O3 support calcined at 500 degrees C [NFA(500)] gave superior catalytic performance in terms of activity and stability over other catalysts. NFA(500) gave a toluene conversion of more than 90% for a period of 26 h with a H-2/CO value of 4.5. According to XRD analysis, the Ni-Fe alloys were formed and stable throughout the reforming reaction. It was observed from XPS results that the surface of the reduced NFA(500) catalyst was enriched with Fe species, where the other catalysts were enriched with Ni species. These surface Fe species play the role of cocatalysts by increasing the coverage of oxygen species during the reforming reaction to enhance the reaction of toluene and suppresses coke formation. The presence of oxygen species in the reduced catalysts was confirmed by temperature-programmed surface reaction (TPSR) with toluene and water over NFA catalysts. A temperature-programmed oxidation (TPO) study on spent catalysts revealed that the NFA(500) and NFA(700) catalysts have an additional low-temperature oxidation peak at around 525 and 535 degrees C, respectively, suggesting the presence of a higher amount of amorphous carbon compared with the NFA(900) catalyst. The presence of a low-temperature oxidation peak at 525 degrees C for the NFA(500) catalyst is one of the reasons for its stable catalytic performance compared with other catalysts.