Abstract
A leading method of hydrogen production that is free of carbon oxides is catalytic methane decomposition. In this research, Fe supported catalysts produced by wet impregnation method were employed in the methane decomposition. The effect of doping ZrO2 with La2O3 and WO3 on the catalytic performance was studied. Different techniques were used to characterize the catalysts. It was discovered that support doped with WO3 gave the best performance in terms of CH4 conversion, H-2 yield and stability at the test condition (800 C, 4000 ml/hgcat space velocity). The initial H-2 yield was found to be 58%, 81% and 92% on Fe/ZrO2, Fe/La2O3-ZrO2 and Fe/WO3-ZrO2 catalysts, respectively. These values were significantly decreased to reach 20% and 25% over the Fe/ZrO2 and Fe/La2O3-ZrO2 catalysts after running for 240 min. On the contrary, the Fe/WO3 -ZrO2 catalyst maintained its catalytic activity and stability within the reaction time. The BET results showed remarkable increase in the specific surface area of Fe/La2O3+ZrO2 and Fe/WO3+ZrO2 compared to Fe/ZrO2 catalyst. TPR profiles revealed progressive change in the valency of Fe in its combined form to the zero valence free metal. The Fe/WO3 -ZrO2 catalyst showed the highest reduction temperature among the tested catalysts, probably due to the strong metal support interaction. The Fe/WO3-ZrO2 gave the best performance and maintained stability during the time on stream. Its stability was attributed to the higher dispersion and stabilization of iron nanoparticles on the surface of WO3-ZrO2 support. TEM and TPO results indicated that the deposited carbon was multi-walled carbon nanotubes with tabular structure. (C) 2020 Elsevier Ltd. All rights reserved.